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Lineament control on drainage basin development, large rock landslides and mountain slope deformation… English, Russell Richard 1998

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L I N E A M E N T C O N T R O L O N D R A I N A G E BASIN D E V E L O P M E N T , L A R G E R O C K LANDSLIDES A N D M O U N T A I N SLOPE D E F O R M A T I O N IN T H E SOUTHWEST COAST M O U N T A I N S , BRITISH C O L U M B I A , C A N A D A . by R U S S E L L RICHARD ENGLISH B.Sc.(hons), Imperial College, University of London, 1993 A THESIS SUBMITTED IN PARTIAL F U L F I L L M E N T OF THE REQUIREMENTS FOR T H E D E G R E E OF M A S T E R OF SCIENCE  in THE F A C U L T Y OF G R A D U A T E STUDIES Department of Earth and Ocean Sciences  THE UNIVERSITY OF BRITISH C O L U M B I A April 1998 © Russell Richard English, 1998  In  presenting  degree  this  at the  thesis  in  partial  fulfilment  of  University  of  British  Columbia,  I agree  freely available for copying  of  department publication  this or of  reference  thesis by  this  for  his thesis  and  study.  scholarly  or  her  for  I further  purposes  gain shall  It not  permission.  Department  of  /~C"~&,  The University of British Vancouver, Canada  Date  DE-6 (2/88)  Oc<2cn Columbia  requirements that  agree  may  representatives.  financial  the  5c*'Q,*%g J  be is  that  the  Library  permission  granted  by  understood be  for  an  advanced  shall make for  the that  allowed without  it  extensive  head  of  my  copying  or  my  written  ABSTRACT  This research describes lineaments in the southwestern Coast mountains of British Columbia and their effect on landscape evolution and contemporary geomorphic processes. Lineaments mapped on air photographs are reflective of bedrock structure. Three regional trends are evidenced: a Cretaceous, northwest trend; a Tertiary norhteast trend; and an east-west trend which may represent recent crustal convergence between the North American and Juan de Fuca plates. Field and air photo evidence suggests lineaments should be interpreted primarily as either faults or large-scale regional joints. Lineament control of basin axial position is demonstrated. The spatial correlation between stream segments and lineaments is determined using the IDRISI GIS. On average 66% of the stream network overlies lineaments and 51% of lineaments in a basin are overlain by streams. The relationship of lineament length to basin morphometry is assessed by linear regression and compared to the relation between stream length and basin morphometry, Stream length is a better predictor of basin morphometry but lineament length is a good predictor of many parameters and becomes more important as basin area increases. It is speculated that lineaments become more important than streams in determining mean topography as landscape scale increases. 20 sites of large rock landslides and mountain slope deformation are identified in the study area. Rock avalanches and mountain slope deformation are the most common features, other failure types include rockfalls and landslides in surficial materials adjacent to rivers. Lineaments influence these features in three ways: 1) forming landslide headscarps; 2) providing locations about which slope deformation occurs; 3) forming rockfaces capable of shedding large rockfalls.  ii  Debris flow and avalanche initiation points are examined in the Seymour watershed north of Vancouver, British Columbia.  These are almost twice as likely to occur where streams and  lineaments intersect as where a stream only is present. This study suggests that the morphometry of drainage basins in the southwest Coast Mountains and some of the processes operating within them are a consequence of the underlying, tectonically emplaced bedrock structure. It is argued that processes operating at tectonic scales influence, and are reflected in, the landscape patterns around us.  iii  TABLE OF CONTENTS  ABSTRACT  ii  TABLE OF CONTENTS  iv  LIST OF TABLES  viii  LIST OF FIGURES  x  ACKNOWLEDGEMENTS CHAPTER ONE  xiv  INTRODUCTION  1  1.1 Background  1  1.2 Research synopsis and contributions.  2  1.3 Thesis structure  2  CHAPTER TWO  LITERATURE REVIEW  4  2.1 Introduction  4  2.2 The relations between lineaments and bedrock structure  5  2.3 Relations between lineaments and drainage basin morphometry  7  2.4 Relations between lineaments and landslides  12  2.5 Conclusions  18  CHAPTER THREE  REGIONAL PHYSIOGRAPHY AND GEOLOGY  19  3.1 Physiography  19  3.2 Climate  22  3.3 Local rock types  23  3.4 Tectonic evolution and regional structure  25  3.5 Glaciation and Quaternary deposits  26  CHAPTER FOUR  THE LINEAMENT INVENTORY  iv  28  4.1 Introduction  28  4.2 Air photo interpretation of lineaments  28  4.3 The lineament inventory  29  4.3.1 Processing  29  4.3.2 The scale affect  31  4.3.3 Lineament trends  31  4.4 Field and air photo observations  42  4.5 Conclusions  52  CHAPTER FIVE  DRAINAGE BASIN ANALYSIS  54  5.1 Background and methodology  54  5.2 Terminology  55  5.3 Sample set basins  56  5.3.1 Mapping of sample set basins  :  5.3.2 Description of sample set basins  57 58  5.4 Basin and fan morphometry  60  5.5 Lineament control on drainage basin location  63  5.5.1 Method  64  5.5.2 Results  66  5.5.3 Discussion  74  5.6 Lineament control on drainage pattern  75  5.6.1 Method  76  5.6.2 Results  79  5.6.3 Discussion  83  5.6.4 Directional correlation of lineament and stream trend datasets  v  86  5.6.5 Stream incidence angles  92  5.6.6 Comparison of visual assessment and automatic evaluation of lineament control on streams  94  5.7 Regression analysis of lineament control on basin morphometry  95  5.7.1 Method  95  5.7.2 Results of regression analysis  97  5.7.3 Discussion  113  5.8 Investigation into sediment yield from drainage basins  115  5.8. J Regression analysis of morphometric parameters related to sediment yield. 5.8.2 Results of regression analysis  117  5.8.3 Discussion  129  5.9 Summary and conclusions CHAPTER SIX  117  130  LINEAMENTS AND LANDSLIDES  6.1 Introduction  134 134  6.1.1 Large rock landslides and mountain slope deformation  135  6.2 Airphoto identification of landslides and mountain slope deformation  135  6.3 The landslide and slope deformation inventory  136  6.3.1 Examples of lineament control on large rock landslides and mountain slope deformation  138  6.3.2 Discussion  152  6.4 Investigation into lineament control on small surficial landslides  156  6.4.1 Method of investigating the correlation between lineaments and small surficial landslides  157  6.4.2 Results  161  vi  6.4.3 Discussion  171  6.5 Small surficial landslides as sediment sources and contributors of materials to fans  175  6.6 Conclusions  179  CHAPTER SEVEN  DISCUSSION AND CONCLUSIONS  REFERENCES APPENDIX I  183 195  Frequency tables for lineament trend data  205  APPENDIX II Statistical methods  208  APPENDIX III Location and description of sample set basins  212  APPENDIX IV Tabulated sample set data  216  APPENDIX V Results of spatial correlation between lineaments and streams  220  APPENDIX VI Lineament and stream trend data for the sample set Basins  230  APPENDIX VII Matrices of R values for regression analysis  236  APPENDIX VIII Diskette containing regression results (included in back pocket)  246  2  APPENDIX IX Additional details of landslide and slope deformation inventory sites not discussed in the main text  248  APPENDIX X Results of overlay of streams on lineaments for the seymour watershed  vii  253  LIST OF TABLES Table 4.1. Comparison of lineament parameters mapped on high and low altitude air photos. The basin number corresponds to numbers reported in Chapter 5, and the percentage lineament increase in the final column is the increase seen on the lower altitude air photos 31 Table 4.2. Summary information for lineaments. (*) A more realistic value is 0.677 because approximately 2,500 km of this block resides in the developed Fraser Lowland  36  Table 5.1. Parameters investigated in the morphometric analysis of the basin - fan system  62  Table 5.2. Assessment of lineament control on basin axis and headwalls  67  2  Table 5.3. Showing the spatial correlations of streams and lineaments for basin #2 overlying lineaments  80  Table 5.4. Strength of correlations for all stream orders  81  Table 5.5. Showing the average percentages of streams in the sample set basins overlaying lineaments at the two pixel acceptance level, (s.d. = standard deviation) 83 Table 5.6. Orientation data for lineament and stream segment trends in the sample set basins. (* indicates no preferred trend in the data) 89 Table 5.7. Summary data for the two streams in the cited example  93  Table 5.8. Summarizing the correlation results from GIS analysis as compared to visual assessment.94 Table 5.9. Showing the regression analysis of basin area and lineament length variables  96  Table 5.10 Regression equations for relations between lineaments and stream length with other morphometric variables 101 Table 5.10 (Continued) Regression equations for relations between lineaments and stream length with other morphometric variables 102 Table 5.11 Regression equations resulting from sediment yield investigations  118  Table 5.11 (Continued) Regression equations resulting from sediment yield investigations  119  Table 6.1. The large rock landslide and slope deformation inventory  139  Table 6.1. (Continued) The large rock landslide and slope deformation inventory  140  Table 6.2. Results of overlay of landslide initiation points on 20 m buffer zones around lineament pixels. 21 landslide pixels are omitted from the results (see text). Each pixel represents 400 m .163 2  vin  Table 6.2 (Continued). Results of overlay of landslide initiation points on 20 m buffer zones around lineament pixels. 21 landslide pixels are omitted from the results (see text). Each pixel represents 400 m 164 2  Table 6.3. Results of overlay of landslide initiation points on 20 m buffer zones around stream pixels. 21 landslide pixels are omitted from the results (see text). Each pixel represents 400 m 165 2  Table 6.3 (Continued). Results of overlay of landslide initiation points on 20 m buffer zones around stream pixels. 21 landslide pixels are omitted from the results (see text). Each pixel represents 400 m 166 2  Table 6.4. Results of overlay of landslide initiation points on 20 m buffer zones around pixels at the intersection of streams and lineaments. 21 landslide pixels are omitted from the results (see text). Each pixel represents 400 m 172 2  Table 6.4. (Continued). Results of overlay of landslide initiation points on 20 m buffer zones around pixels at the intersection of streams and lineaments. 21 landslide pixels are omitted from the results (see text). Each pixel represents 400 m 173 2  ix  LIST OF FIGURES Figure 3.1. The location of the study area in southwest British Columbia, Canada  20  Figure 3.2. Detailed geography of the study area: CaR = Capilano Reservoir, SR = Seymour Reservoir, CoR = Coquitlam Reservoir  21  Figure 4.1. Rose diagram showing all lineaments in the inventory  32  Figure 4.2. The lineament inventory map. The inset shows the breakdown of this area into the blocks discussed in the text. The distinction between lineaments and faults indicates features mapped by the GSC from Roddick (1965) 33 Figure 4.3. Rose diagrams for each of the blocks described in the text  35  Figure 4.4. Lineament distribution in the GVRD watersheds. The approximate location of key field sites is also shown: AC = Appian Creek; OC = Orchid Creek; CC = Camp Creek 37 Figure 4.5. Simplified map of northeastern block geology and lineaments: FLG = Fire Lake Group; TIG = Twin Island Group; M = Migmatite; Qdio = Quartz diorite; Gdio = Granodiorite; Al = Alluvium; I = Ice. (Adapted from Roddick 1965) 39 Figure 4.6. A schematic diagram showing the orientation of the maximum principle stress (ai) and the conjugate fault pattern which may develop as a result of this 41 Figure 4.7. Suspected lineaments in alluvium at the mouth of Widgeon Creek near the confluence with Pitt River. These lineaments can be followed into bedrock. (Photo: 30BCB92018 #122) 43 Figure 4.8a. Stereophoto (30BCB92018:134,135) of the Camp Creek basin showing debris cones building from "canyons" in the cliff face, (note also the NE trending lineaments responsible for the cliff face on the lower photograph) 45 Figure 4.8b. The Camp Creek basin viewed from the west side of Coquitlam reservoir: The arrows indicates the lineaments mentioned above 45 Figure 4.9. Lineament controlled creek in the Coquitlam watershed (facing east from Coquitlam mainline) 46 Figure 4.10. A large gully (lineament) bisecting the Orchid Creek basin headwall (facing east: This gully is approximately 8 m across) 47 Figure 4.11. Two views of a large lineament behind the Orchid creek headwall of the Seymour watershed: a) facing west from the ridge above the lineament (arrows indicate the lineament), b) the view along the lineament as photographed from the top left of Fig. 4.1 la 48 Figure 4.12. Joints in the eastern headwall of the Appian Creek basin in the Capilano watershed...49 x  Figure 4.13. Weathered rock material in situ on the Appian Creek headwall (lens cap indicates scale)  49  Figure 5.1. Distribution of sample set basins  59  Figure 5.2. Stereophoto (BC87098:175,176) showing lineament control of the basin axis and the northern wall in basin #1. Basin #26 is adjacent to the northeast 65 Figure 5.3. Air photo (BC87098:139) showing a laterally persistent lineament controlling the axis of three basins including basin #15 68 Figure 5.4. Stereophoto (BC87098:206,207) showing lineaments on the back and northern walls of basin #22. Note also the major north trending lineament and associated cone 69 Figure 5.5. Stereophoto (BC87098:165,166) showing lineament control in basin #14. Lineament numbers correspond to those mentioned in the text 70 Figure 5.6. Stereophoto(BC87098:178,179) showing basin #16. This basins axis is not attributed lineament control however the southern basin wall appears to be lineament controled. Note how the stream changes course as it reaches this basin wall 72 Figure 5.7. Stereophoto(BC87098:185,186) showing lineament bounding of basin #2. Basin #10 is located adjacent and to the southwest of this basin 73 Figure 5.8. IDRISI image of sample set basin #2 showing streams overlying the lineaments and their surrounding buffer zone 78 Figure 5.9. Orientation of visually assessed lineament controlled streams for the entire dataset and for igneous and metamorphic streams individually 87 Figure 5.10. Plot of Stream length versus lineament length  103  Figure 5.11. Plot of Drainage density versus lineament length  103  Figure 5.12. Plots of basin area versus a) lineament length, and b) stream length  104  Figure 5.13. Plots of basin width versus a) lineament length, and b) stream length  105  Figure 5.14. Plots of basin length versus a) lineament length, and b) stream length  106  Figure 5.15. Plots of maximum basin elevation versus a) lineament length, and b) stream length. 107 Figure 5.16. Plots of maximum basin relief versus a) lineament length, and b) stream length  108  Figure 5.17. Plots of relief ratio versus a) lineament length, and b) stream length  109  Figure 5.18. Plots of basin relief versus a) lineament length, and b) stream length  110  xi  Figure 5.19. Plots of basin gradient versus a) lineament length, and b) stream length  111  Figure 5.20. Plot of fan area versus basin area  120  Figure 5.21. Plot of fan gradient versus basin area  120  Figure 5.22. Plot of basin area versus relief ratio  121  Figure 5.23. Plot of fan area versus relief ratio  121  Figure 5.24. Plot of fan area versus fan gradient  122  Figure 5.25. Plot of fan gradient versus relief ratio  122  Figure 5.26. Plots of fan area versus a) lineament length and b) stream length  123  Figure 5.27. Plots of fan gradient versus a) lineament length and b) stream length  124  Figure 5.28. Plot of relief ratio versus drainage density  125  Figure 6.1. Showing sites identified in the landslide and slope deformation inventory: l=Dickson Lake; 2=West Norrish Creek; 3=Lower Coquitlam River; 4=Lower Seymour Valley; 5=The Lions; 6=Chehalis River; 7=Bivouac Mountain; 8=Anne Lake; 9=Stave River I; 10=Stave River II; 1 l=Mount Bonnycastle; 12=Winslow Lake; 13=Winslow Creek; 14=Goat Ridge; 15=Mamquam River; 16=Shale Creek; 17=Bremner Creek; 18=Cheekye Ridge; 19=Rubble Creek; 20=Mount Mason 137 Figure 6.2. Stereophoto (15BC87098:156,157) showing Dickson lake landslide and the west Norrish Creek site. Notice the northeast trending lineament influencing both sites. Additional interpretation of this stereophoto is shown in Figure 6.3 141 Figure 6.3. Interpretation of Dickson Lake landslide and West Norrish Creek mountain slope deformation. Note: traced from airphoto 15BCB87098-156  143  Figure 6.4. The southern slope of the west Norrish Creek site showing the major lineament described in the text. The location of Figure 6.5 is indicated 144 Figure 6.5. An opening (extension joint) along the course of the major lineament at the West Norrish Creek site 145 Figure 6.6. Stereophoto (30BCB92019:41,42) showing The Lions in the Capilano Watershed. Notice the east trending lineament 147 Figure 6.7. Possible interpretation of mountain slope deformation on the southern face of The Lions in the Capilano watershed. The current state of activity at the site is unknown 148 Figure 6.8. Stereophoto (30BCB92019:196,198) showing Bivouac Mountain in the Seymour watershed. Major features of interest are indicated... xii  149  Figure 6.9. Stereophoto (BC87098:232,233) showing Goat Ridge above Britannia Creek where prominant cracks are indicated 150 Figure 6.10. Stereophoto (15BC87096:20,21) showing a large section of the slope above Mamquam River identified as deforming by mass rock creep (Scalia 1995) 151 Figure 6.1 la. Antislope scarp and graben feature at site #15 above Mamquam River (photograph used by permission) 153 Figure 6.1 lb. High angle jointing at site #15 above Mamquam River (photograph used by permission)  153  Figure 6.12. Stereophoto (BC87089:60,61,62) showing Cheekye ridge: several features described in the text are indicated 154 Figure 6.13. The Seymour watershed showing streams and landslide initiation points (from images supplied by the GVRD) 158 Figure 6.14. The Seymour watershed showing streams, landslide initiation points and lineaments  159  Figure 6. 15. The Jamieson Creek landslide, an example of the type of feature included in the GVRD landslide inventory of the Seymour watershed 162 Figure 6.16. Graph showing the distribution of landslides away from target features  167  Figure 6.17. The northern Seymour watershed showing the 0 - 40 m stream buffer, the "intersecting lineament and stream" pixels and landslide initiation points 169 Figure 6.18. The southern Seymour watershed showing the 0 - 40 m stream buffer, the "intersecting lineament and stream" pixels and landslide initiation points 170 Figure 6.19. The view down a landslide track in the Camp Creek Basin, Coquitlam watershed. The slide track is about 6-7m wide 177 Figure 6.20. A small cone at the site where this landslide enters Camp Creek. The distance across the foreground of this photograph is about 2m 178  xiii  ACKNOWLEDGMENTS For the completion of this thesis, and for the last two and a half years of my studies I am indebted to a number of people. I should like to express to my supervisor Dr. K. Wayne Savigny, my sincere thanks for inspiration, guidance, and patience. Also thanks to Dr. Lisel Currie, and Dr. M . Journeay of the GSC, for long discussions, valuable guidance, and for motivation over the last year. Thanks also to Dr. Currie, Dr. R. Beckie and Dick Chase for sitting on my committee and Ken Rood of Northwest Hydraulics for guidance at various stages during this work. Grateful thanks are extended to Matt Boucher who assisted with fieldwork and other thesis related activities last summer. Financial support was provided by the Watershed Management Division of the Greater Vancouver Regional District under the direction of Dr. T. Griffing (grant #554741) and NSERC Operating Grant to Dr. Savigny (#581923). Thanks to Lome Gilmour (GVRD) for providing data and to all GVRD watershed staff who assisted during field activities in particular Dennis, Armond and the two Johns. Bruce Geotechnical Consultants Inc. provided hardware, software, and high altitude air photos for the work conducted during this thesis. I would like to thank my family and friends still in England for all of their encouragement and support over the years that I have been studying and working. Thanks also are extended to friends and colleagues (past) at the Royal School of Mines, Imperial College and in the Geological Sciences Department at the University of British Columbia (present), especially to Dan Walker for hours of discussion, praise, criticism and suggestion, and to the office staff for making the university a little easier to deal with. Special personal thanks are due to Teresa Delvecchio and her family who have been there for me since my first day in Vancouver, and Mark Mauthner for unerring friendship, without these people this would all have been very much harder. Final thanks go to Lynda for getting me this far in thefirstplace.  xiv  Introduction  Chapter 1  CHAPTER 1  INTRODUCTION  1.1 Background  This study relates bedrock structure to contemporary process in drainage basins in the southwest Coast Mountains, British Columbia, Canada. Three large drainage basins in the mountains north of Vancouver supply water to the metropolitan areas in their vicinity. These basins are: the Capilano, Seymour, and Coquitlam rivers. Each basin is managed by the GVRD (Greater Vancouver Regional District). Erosion within the basins influences water quality, a prime concern of the GVRD and Vancouver residents.  Above-  normal levels of sediment in the water supply typically result from landslide activity during heavy rain storms. Structural control is evident in drainage basins of the region. Bedrock structure (described by lineaments) controls drainage patterns, the distribution of large rock landslides, and possibly influences location of debris flow and torrent activity. Establishment of a drainage network in this area requires bedrock incision which occurs preferentially in zones of bedrock weakness such as faults and joints and is primarily due to debris flow activity in steep, high elevation, mountain watersheds.  This study  quantifies structural control on the drainage pattern, demonstrates its relation to basin geometry, and shows that landslide activity occurs preferentially in structurally controlled areas.  1  Chapter 1  Introduction  1.2 Research synopsis and contributions  Research is presented in three parts: a regional lineament inventory; the effect of lineaments on drainage basins; and the affects of lineaments on landslides. The lineament inventory is compiled from air photos.  The occurrence of lineaments is  described and an attempt made to explain their origins and significance in interpreting regional structure.  That lineaments play a major role in the evolution of individual drainage basins is  demonstrated by positional relations between lineaments and important basin features, and by regression analysis of allometric relations between lineaments and basin morphometry. Lineament control on both large rock landslides and mountain slope deformation, and debris flows and avalanches are examined. A regional inventory of the former is complemented by a smaller scale study of the latter in the Seymour watershed using a database compiled by the GVRD and a PC (Personal Computer) based GIS (Geographic Information System), IDRISI. The major contributions of this research are: the presentation of a regional lineament inventory and identification of a previously unrecognized regional structural trend; the quantification of lineament control on the drainage partem; presentation of the idea that bedrock structure influences basin morphometry; the presentation of a regional large rock landslide and mountain slope deformation inventory; and the investigation of lineament control on landslides.  1.3 Thesis structure  The first chapter details research aims and thesis structure.  The second details relevant  literature. Chapter three describes physiography, geology, and climate of the regional study area. Chapter four examines lineaments. In Chapter five, analysis of individual basins is described to 2  Introduction  Chapter 1  elucidate relationships between lineaments and drainage basin evolution. The effect of lineaments on landslides is examined in Chapter six.  Chapter seven summarizes the research and presents  conclusions along with suggestions for further research. Supplemental information, and data whose volume would interrupt the flow of text are presented in appendices. Additionally, a diskette is included which contains the results of regression analysis. The volume of this data is too large for inclusion as a printed appendix.  3  Literature review  Chapter 2  CHAPTER 2  LITERATURE REVIEW  2.1 Introduction  A review of literature posed three questions that act as a framework about which this thesis is constructed. Firstly: Do lineaments reflect bedrock structure? If this is proven, it can be shown that the regional stresses responsible for bedrock structure can be linked to present day processes influenced by lineaments. Secondly: Is there a direct relation between lineaments and drainage basin morphometry? If this is proven it will show that the fundamental landscape unit is controlled by the rock mass and its inherent properties. Finally: Is there a relation between lineaments and landslides in the study area? Demonstrating such a relation for large rock landslides will show that bedrock structure controls large-scale catastrophic landscape mass wasting processes. Small surficial landslides are the most common, point sourced, mass wasting events in the region today and are responsible for the redistribution of significant quantities of surficial materials. It is interesting to speculate to what extent structural control influences the initiation of these contemporary processes. This chapter is divided into three sections based on the questions presented above and is written to show how each question evolved from previous research.  4  Literature review  Chapter 2 2.2 The relations between lineaments and bedrock structure  The literature suggests that lineaments are ubiquitous and typically representative of bedrock structure. This section defines the term lineament, reviews existing literature on lineaments and states conclusions drawn from the literature specifically relating to the first of the questions posed above. The term lineament is well established in the literature. In Wertz (1968) lineaments are used to aid in the search for ores in the Basin and Range province in southeast Arizona. The same author later reported lineaments in the northern Cordillera that are described as more significant planes of weakness in the earth's crust than faults (Wertz 1974). It is important, therefore, to clarify use of the term lineament. The most formal definition found in the literature appears inadequate to properly describe the features examined in this research. Mollard (1988) presented a review of fracture lineament research and applications on the western Canadian plains with case studies illustrating lineament mapping applications in geological, hydrogeological and geotechnical investigations. As seen on air photos, a fracture lineament is defined as a composite linear topographic, drainage, vegetation, moisture, and tonal feature (Mollard 1988). Other investigators have used the terms fracture trace, fractures, lineament, surface lineament, and photolineament interchangeably (Mollard 1988). Cronin et al. (1990, p. 232) define a [drainage] lineament as a "...laterally persistent trend of sub-parallel drainage segments." While Mollard's (1988) definition forms a good basis for defining the features examined in this research, lineaments need not necessarily represent fractures. It is preferable to use the term lineament alone as being non-genetic. Hence a formal definition of the term lineament, as it applies in this research is: a non-genetic term describing a feature recognizable on an air photo, or other remotely sensed image, that is essentially linear, and comprises a contiguous set of topographic, drainage, vegetation, moisture and/or tonal features. Other terms used are: lineament pattern, describing the 5  Literature review  Chapter 2  overall distribution of lineaments, and lineament set that describes a group of lineaments with similar orientation. It has become a common practice to analyze lineaments in terms of regional patterns. This has been facilitated by high altitude airborne and spaceborne remote sensing platforms and tools. Burdick and Speirer (1980) reported the detection of faults and other linear features from LANDSAT imagery. Field checking of approximately 31 lineaments in south-central Wyoming revealed that the lineaments mapped could not safely be considered faults without field investigation. However, features that proved not to be faults were anthropogenic such as roads or buried pipelines. LANDSAT was also used to map lineaments and propose a neotectonic model for the Nicoya Peninsula, Costa Rica by Hare and Gardner (1985). These authors considered lineaments to represent structural breaks. As a further example, Harris (1991) used remotely sensed lineaments to assist with interpretation of regional tectonics in gold exploration in Nova Scotia. In studies that bear comparison with pattern analysis of drainage networks it is recognized that fractal geometry is well suited to the analysis of fracture systems, e.g., Hestir et al. (1990) and Barton et al. (1990). Hestir et al. noted that the iterated function system, a standard means of producing fractal images, provided a means of generating "geologically realistic" fracture patterns. The evolution of natural fracture patterns is an iterative process dependent upon the presence of pre-existing fractures (Barton et al. 1990). Barton et al. (1990) showed that fracture networks from dissimilar settings of lithology, age, and tectonic setting evolve fractal dimensions in the range of 1.6 -1.8. Quart and Sen (1994) identified one of the most important implications of a fracture pattern as the flow of fluids through the fractured media. In southwestern Saudi Arabia the natural fracture pattern exhibits significant anisotropic permeability and maps of fracture density were used to show potential groundwater recharge locations and provide large-scale rock quality zonations.  6  Literature review  Chapter 2  Fracture pattern research has also helped reveal the connection between drainage patterns and lineaments. Cronin et al. (1990) analyzed drainage segments mapped from LANDSAT to identify structural trends extending across multiple watersheds. Subsequent comparison with drainage segments showed that a number of drainage segments had been initiated along high-angle faults, joint sets or lithologic discontinuities. Birdseye and Christians (1988) examined drainage lineaments in late Pleistocene and Holocene sediments in Louisiana. Linear physiographic features included: "...stream channels, natural levees, stream valleys, rectangular drainage patterns and terrace scarps" (Birdseye and Christians 1988, p. 1109). They further state that the orientations of mapped joint systems are similar to the orientations of the lineaments suggesting an underlying structural control. They conclude that joints "...may provide paths of weakness along which surface drainage might develop preferentially. Thus, joints probably exert an important control on the geomorphology of the region" (Birdseye and Christians 1988, p. 1109). In conclusion, lineaments reflect underlying regional structure, and can be used to aid interpretation of both prehistoric and neotectonic stress regimes. Lineaments have typically been identified as either faults, joints (both reflecting bedrock structure) or as anthropogenic features. In areas remote from human development, however, a structural interpretation appears reasonable.  2.3 Relations between lineaments and drainage basin morphometry  It is not classically recognized that bedrock structure may be a controlling factor in drainage basin morphometry. However, examination of the literature suggests that it is possible to infer this. Geological structure can play an important part in the evolution of topography. Even where structure is not visible it may be responsible for landform features. Geomorphology has been used to 7  Literature review  Chapter 2  characterize the structure of the lithosphere at three scales: continental; regional; and local. At the continental scale it is now recognized that tectonic and geomorphic processes in landscape evolution are strongly coupled (Howard et al. 1994). Much work in this field has been done in New Zealand on the Southern Alps (e.g., Adams 1985, Kamp  1988) where surface geomorphology is considered  representative of differing modes of subduction below the Hikurangi Margin. At a regional scale the Basin and Range province in the United States provides a good example of a structurally controlled landscape. Fault scarps, and folds, provide examples of smaller scale geomorphic features. Currently work is underway at the Geological Survey of Canada (GSC) in Vancouver to investigate the evolution of the landscape pattern of southern British Columbia with respect to large-scale crustal features such as fault blocks (Journey and Currie, pers. comm. 1995, 1996). Recent modeling developments have demonstrated the importance of the mechanical behavior of the lithosphere in evolution of topography in collisional mountain systems (e.g., Koons 1995). Modeling mean topography resulting from collisional stresses and strains has been successful in generating gross approximations of the landscape at the wavelength of mean topography. Although erosional processes modify the landscape at lower wavelengths they are often dependent on mechanical properties of the rock mass, in particular heterogeneity's caused by structural patterns. Structural control of topographic features has been identified in the form of entrainment of rivers by growing fault blocks or by preferential incision along fault planes (Bloom 1991). Koons (1995) described the particular conditions that must be met for the entrainment of rivers by growing structures explaining how a ridge valley system parallel to the dominant fault and orogen strike will result where tectonic, rather than erosional processes, are primarily responsible for topography. The drainage basin is recognized as a fundamental landscape unit, the morphology of which has classically been interpreted as a function of the drainage pattern. If erosional processes concentrate near the drainage pattern which, in turn, develops in areas of bedrock weakness, then the drainage 8  Literature review  Chapter 2  pattern may reflect the nature of the structural trends inherent in the bedrock. This could be interpreted as evidence that landscape morphology is influenced by bedrock structure. Horton (1945) formulated laws explaining drainage composition of a basin and initiation of the channel network. Later workers have concentrated on refining Horton's laws applying them to their studies; for example Strahler (1952), Woldenberg (1969), and Nikora (1994). Researchers recognize a need to accurately define drainage paths in a network. One reason for this is that catchment flood properties are predictable from catchment geomorphology. Rinaldo et al. (1994) investigate the relation between basin geometry and hydrologic response attempting to extract salient geomorphic parameters of a basin by measuring the hydraulic response. Results indicate the hydraulic response is "imprinted" in the shape of the basin. Many properties of the hydrologic response can be predicted from the width function (W(x)), the relative proportion of basin area at distance V from the basin outlet. Further examples are presented by Helmlinger et al. (1993), e.g., mean channel length is used to predict time of concentration of a basin and mean annual flood is often related to basin area. The arrival of GIS technologies as a watershed management tool should prove invaluable in rapid characterization of a drainage network and estimation of hydrologic parameters. The GVRD is currently formulating a GIS database for detailed watershed modeling. The state-of-the-art in drainage pattern extraction is currently performed using DEMs (Digital Elevation Models). Drainage patterns derived from DEMs are typically more detailed than those mapped by conventional means. Concavity and slope of the topography are examined to postulate the presence of a stream channel, or potential for initiation of such. Helmlinger et al. (1993) review the use of DEM data for the extraction of channel networks. The scale of available topographic maps often prohibits the mapping of lower order streams. Attempts have been made to relate properties of a drainage pattern, and/or basin, to parameters such as sediment yield and measures of river discharge. Church et al. (1989) analyze suspended 9  Literature review  Chapter 2  sediment load from basins in British Columbia and reported a relationship between specific sediment yield ("the quantity of sediment passing a monitored river cross section per unit area drained upstream of that section per unit time" Owens and Slaymaker 1992, p. 147) and basin area, and basin area and main stream length. This suggests that in British Columbia the specific sediment yield of a basin is related to the length of the major stream. Basins studied ranged upwards of 10 km . It was found that 2  to a threshold area of approximately 30,000 km the specific sediment yield increased with increasing 2  basin area. This is opposite to conventional thinking that specific sediment yield should decrease as sediment is returned to storage along the river course. Owens and Slaymaker (1992) subsequently refined the limits of this study showing that sediment yield increases with area in basins over one square kilometer. Below this, sediment yield increases with decreasing elevation, consistent with the idea of low sediment yields in small alpine basins (Owens and Slaymaker 1992). Recently, fractal geometry has been used to investigate drainage patterns and drainage basin properties (Nikora 1994). Fractal structure of drainage patterns is demonstrated by La Barbera and Rosso (1989), Robert and Roy (1990) and Karlinger and Troutman (1992). La Barbera and Rosso show natural channel networks have fractal dimensions between 1.5 - 2.0 with average values between 1.6 - 1.7. The fractal dimension approaches two when maturity is reached "...in the absence of geologic, topographic or hydrologic constraints" (Karlinger and Troutman 1992, p. 1975). A fractal dimension of two suggests that the pattern is space filling. This is consistent with the requirement that every point in a basin be drained (Karlinger and Troutman 1992). It has been shown that fractal dimensions of a basin can be estimated using Horton's laws (e.g., Helmlinger et al. 1993). Considering the multi-scale nature of drainage basin morphology, Nikora (1994) examined drainage basin shape from the perspectives of self-similarity and self-affinity. Results indicated that self-affinity is a more likely solution to drainage basin morphology because the process of basin formation is directionally controlled by gravity (Nikora 1994). 10  Literature review  Chapter 2  Workers have looked for the optimal arrangements of drainage patterns (e.g., Sun et al. 1994) and basins (e.g., Woldenberg 1969). Drainage area is organized into a "...spatial structure that has a power law distribution of drainage basin areas, self-similar fractal basin boundaries, and a self-similar network structure" (Sun et al. 1994b, p. 2599). Sun et al. (1994) used principles derived from optimal basin modeling to relate mean annual discharge of a basin to its length-width ratio. The structure of river networks obtained by optimization modeling are similar to those obtained from DEMs. Two key conclusions are drawn from the literature to this point. First, while there is a long history of relating certain topography to structural control it is only recently that geomorphology has been used to infer the tectonic history of an area. This fact has significant implications for landscape studies in active tectonic regions and for studies in areas in which tectonic activity has ceased within one landscape cycle. Second, the characters of a single drainage basin and a network of drainage basins are typically similar suggesting that there may be some underlying, and regionally uniform, controlling factor. This may be bedrock structure. Basin parameters such as length, width, and parameters of the stream network are interrelated and additionally relate to values of mean annual discharge and specific sediment yield. Drainage basin morphologic parameters are easily measured from topographic or digital format maps. With this information it should be possible to make predictions about the hydrological properties of a basin. One potential drawback is that much existing research has been conducted on homogeneous basins or models that take little account of variability in lithology or structure. Studies of real data are likely to provide more reliable results. In summation it seems that topography resulting from fluvial erosion can be controlled by structure in the underlying bedrock. Lineaments are seen as a reflection of this structure. Much work in drainage basin research has demonstrated the close relation between the drainage network and basin  11  Literature review  Chapter 2  morphometry. If the drainage network is proven to mirror bedrock structure (lineaments) then it should be possible to demonstrate a more direct relationship between lineaments and basin morphometry.  2.4 Relations between lineaments and landslides  Besides providing pathways for drainage development, a plane or zone of weakness in the bedrock may provide a structural discontinuity sufficient to focus catastrophic failure or deformation of the rock mass. This may be particularly true if the slope is oversteepened or has some other internal or external condition which might make the slope susceptible to failure. Evans and Savigny (1994) review landslide occurrence in the Vancouver-Fraser ValleyWhistler region. Characteristic landslide activity in British Columbia includes rock avalanches from high mountain slopes, and volcanic debris avalanches from Quaternary volcanics, (Evans 1992). A brief description of these common landslide events is presented here. Rock avalanches, the most frequent of known historic landslides, are relatively common in certain geomorphic, and geologic environments (Evans 1992). They result from rockslides or falls and involve the rapid downslope movement of bedrock fragments shattered during transport (Evans and Savigny 1994). High magnitude events of this type show high mobility, whereas lower magnitude events behave as rockfalls. Detachment of rock avalanches is favored on steep rock slopes where structural elements combine to form a detachment surface (Evans 1991, for example the 1965 Hope Slide). Volcanic debris avalanches may be initiated on the flanks of volcanoes in the Garibaldi volcanic belt, or on the high margins of lava flows a distance from the source vent. The Rubble Creek landslide is an example (Moore and Mathews 1978).  12  Literature review  Chapter 2  Rock slopes adjacent to glaciers seem particularly susceptible to failure (Cruden et al. 1989, Evans and Clague 1988). A recent example is the Kshwan Glacier rock avalanche (Mauthner 1996). A significant amount of non-catastrophic mountain slope deformation is also reported in the Cordillera. Evans and Savigny (1994) reported non-catastrophic mountain slope deformation as having an important impact on Civil Engineering Structures because of the uncertainty of their future behavior. It is thought that slopes may become increasingly unstable with time and ultimately fail catastrophically.  The southwest Coast Mountains show much evidence of such deformation for  example the Affliction Creek site, about 100 km north of Squamish, is currently evolving and is reported in (Bovis 1982, 1990, and Bovis and Evans 1995). Most landslide events in British Columbia have occurred in remote areas but several have impacted the infrastructure of the province.  The Fraser transportation corridor has on several  occasions been affected (Evans and Savigny 1994, Savigny 1996). Large landslides can impact structures great distances from their source and are prone to producing secondary effects such as landslide dams (see Clague and Evans 1994, and Evans 1986). Lineament and landslide distributions have been correlated in the lower Fraser Valley (Savigny 1996, Leir et al. 1994, and Leir 1995). Typically in the literature the occurrence of a landslide at a given locality may be partly attributed to structure, however lateral persistence of the feature responsible is rarely described unless there remains obvious potential for further failure. Savigny (1996) has shown that often landslide occurrence is related to the presence of a laterally persistent lineament which is mappable on an air photo. Leir (1995) showed that when compared to factors such as the presence of certain rock types, proximity to a plutonic contact, and certain slope classes, proximity of a lineament was a high predictor in landslide occurrence at a locality. Initiation of a drainage pattern in the southwest Coast Mountains requires bedrock incision. The two primary eroding agents capable of this are: surface water flow; and debris flows. Fluvial 13  Literature review  Chapter 2  erosion of channels is dependent on the ability of the stream to scour or pluck bedrock materials. This is a function of drainage area and stream slope (Howard et al. 1994). Horton (1945) stated that erosion on a surface occurs when rainfall intensity exceeds infiltration capacity and the erosive force of overland flow is greater than surface resistance to erosion. The erosive force is a shear stress exerted parallel to the slope by water that increases downslope as more water is added until a threshold value is reached where erosive force becomes larger than surface resistance. This value is dependent on the size of the slope material (Ritter et al. 1995) and is effected by type and density of vegetal cover. Where no vegetation exists soil surfaces form a hard crust that provides a high initial resistance that is progressively destroyed during a precipitation event. Erosion by overland flow is therefore a threshold process (Ritter et al. 1995) which Horton (1945) used to explain the initiation of the drainage system. Horton's model is invoked on a sloping surface as a series of sub-parallel rills, parallel to the slope gradient, form where variations in topography lead to a greater depth of flow and therefore an increase in erosive forces. In humid temperate regions rills develop first near the base of the slope and extend gradually upslope by headward erosion.  As rills develop, one "master rill" will become deeper capturing others by  destruction of the divides between them. The original pattern is obliterated as downcutting continues until a small stream develops. Ultimately the original slope, parallel to the master channel, is replaced by slopes on either side sloping toward the main drainage line. These side slopes then develop rills and the process is repeated (Horton 1945). Seidl and Dietrich (1992) found scour by debris flows to be the dominant erosional agent on steep, first order channels in the Oregon Coast Range. They demonstrate a change in bedrock erosion processes when stream gradient reaches 0.2. Below this gradient, erosion is primarily due to abrasion and dissolution varying linearly with stream power. Above this, debris flow scour takes over and  14  Chapter 2  Literature review  contributing area becomes less important. This has important implications for stream channels that, it appears, will preferentially erode in areas susceptible to debris flow activity. Debris flows and avalanches represent active wasting processes on high elevation slopes in British Columbia. Events in the early nineteen eighties in the Howe Sound area prompted studies into debris flows resulting in a report by Thurber Engineering Ltd. (1983) and several studies by others into various aspects of these features. In addition to presenting a hazard, debris flows deliver large volumes of sediment to catchments. Van Dine (1984, p.44) defines a debris torrent as a mass movement involving water charged, dominantly coarse grained, inorganic, and organic material flowing rapidly down a steep pre-existing confined channel. This is distinct from a debris flow, which occurs on a planar, unconfined slope. Despite the introduction of this distinction early in the literature many authors exclusively use the term debris flow, even for events and studies confined to gullies (for example, Takahashi (1993)). Popular opinion in B.C., argues for the use of the term debris flow only and the term torrent is not used subsequently in this work. Local studies include: Van Dine (1984), Buchanan and Savigny (1990), Fanin and Rollerson (1990), and Jordan (1994). Additionally, Kellerhals and Church (1990) review hazard management on fans in southern British Columbia with special reference to Howe Sound. Costa (1984) provides a comprehensive review of literature prior to 1984. Davies et al. (1992) report on three landscape units involved in a debris flow: the actively eroding gully wall, a steep narrow degrading gully, and a less steep, wider, alluvial-bedded channel or valley. These also represent the transition from a zero order basin through the first order channel to a second or higher order channel. Dietrich et al. (1987) report periodic evacuation of zero order basins by small surficial landslides. Buchanan and Savigny (1990) report that studies in Japan show events on convergent slopes are more common than those on planar or divergent slopes. Hence these events are typically associated 15  Literature review  Chapter 2  with creeks and gullies. Events in southern British Columbia often occur in gully sidewalls and move into gullies where they will flow in the confined channel. Only one third of events studied by Fannin and Rollerson (1990) initiated and terminated on open slopes. There is a consensus about the factors required for a creek to be a suitable site for debris flow initiation. The creek must have a drainage area within a critical range, be sufficiently steep, and contain debris for mobilization. The critical area identified in the Howe Sound is between 0.4 and 7.0 km (Van Dine 1984). Jordan (1994) reports 0.1 to 10 km in the Squamish - Lillooet river areas. 2  2  This latter figure is in line with those reported in Japan by Van Dine (1984). The steep profiles required are reported at between 20° and 57° for Howe sound (Thurber Engineering Ltd. 1983). Most authors cite extreme precipitation as a common triggering mechanism, (e.g., Van Dine (1984), Buchanan and Savigny (1990) and Fannin and Rollerson (1990)), although snowmelt and antecedent precipitation can be major contributing factors. Snowmelt played a major part in the large number of debris flows on the Wasatch Front, Utah during the springs of 1983 and 1984 (Wieczorek et al. 1989). Johnson and Sitar (1990) review in detail the hydrologic conditions leading to debris flow initiation. Other possible triggering mechanisms are mentioned by Fannin and Rollerson (1990) such as rockfalls, planar translational slides or sidewall collapse. However, for proper classification as debris flows or avalanches the materials involved must be saturated. Once mobilized debris flows may flow between 100 and 1000 m, depositing when the gradient becomes insufficient for continued motion, or when the flow becomes unconfined. In studies in the Queen Charlotte Islands, Fannin and Rollerson (1990) showed that slightly more than 50% of events traveling in a gully finally deposited outside that gully. The remainingflowsdeposited within the gully. The physical properties of debris flows in motion have been extensively studied. Examples include Costa (1984), Bovis and Dagg (1988) Takahashi (1993), and Jordan (1994).  16  The slope of the  Literature review  Chapter 2  transport and erosion zone is typically larger than 10° and in Howe Sound ranges from 13 - 35° (Van Dine 1984). In southern British Columbia debris flow deposition typically occurs on fans.  Thurber  Engineering Ltd. (1983) analyzed hazards on fans in Howe Sound. Kellerhals and Church (1990) report on the major findings. Whipple (1993) attempted to interpret debris flow hazard from fan morphology, citing critical factors as the number and spacing of abandoned channels, texture and irregularity of interfluves, form of channel-margin levees, and degree of cross fan convexity. However, Whipple's studies were conducted on unvegetated fans where measurement of such features is easily made from remote sensing imagery. In British Columbia fans are typically well vegetated. Debris flow paths are often easily identifiable for several years and may stay visible for a maximum 50 - 100 years, if recolonizing vegetation is different to surrounding vegetation (Kellerhals and Church 1990). The sedimentology of deposits from these events is variable, and reported by most authors for their own areas. Debris composition depends on the nature of the bedrock and overburden. Deposits typically have a uniform size distribution up to boulders of several meters. These are supported in a matrix of fine grained debris (Costa 1984) that can be winnowed from the deposit leaving it clast supported. Deposits can be extremely variable from creek to creek and Van Dine (1984) reports that three creeks, less than six kilometers apart in Howe Sound produced widely diverse debris. Van Dine (1984) concluded that occurrence of debris flows appears to be unrelated to geology but Davies et al. (1992) report that gullies exhibiting debris flows are typically unstable and may be associated with faulting and crush zones. Several key conclusions are drawn from the above review. Debris flow activity is a primary eroding mechanism in stream channels in mountain watersheds. Although it is traditionally believed that there is little relation between bedrock geology and debris flow activity, it appears that their  17  Literature review  Chapter 2  occurrence may be related to structure as suggested by Davies et al. (1992) in symbiotic relation with structurally emplaced stream channels. Most debris flows initiate in the sidewalls of gullies containing stream channels, material is moved to the channel and either flushed to the fan or deposited in the channel where it may later be remobilized. In either case there is the potential for fine materials to be winnowed from the deposit. These may proceed farther into the hydrological system and cause sediment problems in the water supply. It is therefore important to determine how closely the occurrence of debris flow activity is related to the location of stream channels known to be structurally controlled.  2.5 Conclusions  It is shown by a review of the literature that lineament mapping provides a means of evaluating the structure of an area and can be used to infer a region's tectonic history. It is also established that structure influences topographic evolution of the landscape, including development of the drainage network. In the literature the drainage network is generally attributed responsibility for basin and fan morphometry and conventional views of drainage basin development are typically presented for homogeneous surfaces with little regard for inhomogeneity that may be caused by bedrock structure. Lineaments have been related to landslides in the neighboring Fraser River Valley. Typically a lineament may provide the structural control at a site necessary for catastrophic failure or provide a focus for slope deformation. It is therefore important to try to ascertain whether lineaments control landslide occurrence in the study area. As a contemporary process, debris flows are revealed as the primary force of erosion in steep, low order channels and transport large amounts of sediment to the fan. The location of debris flow and debris avalanche activity may also be related to lineament occurrence. 18  Regional physiography and geology  Chapter 3  CHAPTER 3  REGIONAL PHYSIOGRAPHY AND GEOLOGY  3.1 Physiography  The study area, located in the southwest Coast Mountains, British Columbia, Canada (Fig. 3.1), comprises most of the 92G, NTS (National Topographic System), 1:250,000 scale map sheet east of Howe Sound and Squamish River and north of the North and West Vancouver urban areas and the north shore of Fraser River. The eastern boundary lies near Harrison Lake and the northern boundary is in Garibaldi Park. Detailed geographical information is shown in Figure 3.2. The following physiographic description is based on the authors' field and airphoto experience. In the south, moderately steep slopes lead to frontal ridges of mountains with summit elevations upward of 1400 m. Several slopes are developed for housing and three of the higher slopes are utilized for ski resorts. Behind these are a series of flat-topped ridges and peaks separated by narrow, northwest trending river valleys. Several valleys open southward to wide flat bottomed, alluvial valleys, e.g., Pitt River, others are directed through narrow bedrock canyons, e.g., Capilano River. Two coastal fjords, Howe Sound and Indian Arm, are respectively west and east of Vancouver. The GVRD watersheds lie in this southern region. Summit elevations and terrain ruggedness increase northward. Northwest trending ridges and valleys persist to central parts of the study area where most rivers are sourced in high, glaciated,  19  Regional physiography and geology  Chapter 3  1/1  Legend Study  Area  Vancouver FL  Fraser  SG  Strait  VIR  Lowland of  Gerogia  Vancouver Ranges  Figure 3.1. The location of the study area in southwest British Columbia, Canada. 20  Island  Regional physiography and geology  Chapter 3  50 N  10 M o r v t r r t  0  49 N_^_  _j 4 9 N  123° 25' W  122° V  Figure 3.2. Detailed geography o f the study area: CaR = Capilano Reservoir, SR = Seymour Reservoir, CoR = Coquitlam Reservoir.  21  Regional physiography and geology  Chapter 3  mountain valleys. Numerous icefields, moraine dammed and glacial fed lakes exist north of about 49° 35'N. The northwest is dominated by the Mount Garibaldi volcanic center (elevation approximately 2680 m) from which extend numerous, well-defined lava flows. The northeastern part of the study area contains the northwest trending Harrison Lake-Pemberton Valley. Over the entire area, slopes are moderate to steep and largely till mantled except for the steepest slopes and ridge-tops. Valley glaciers extend short distances down valleys radiating from the icefields. Logging is ubiquitous especially, but not exclusively, in valleys with access from the south and west where the major transport and urban infrastructure exists. Some northern valleys are logged by boat access, for example the northern Pitt River valley.  3.2 Climate  Climate information is derivedfromthe GVWD (Greater Vancouver Water District) watershed ecological inventory pilot study, final report (1993) and from Ryder (1981). The climate of the region is controlled by location and topography. A complex relationship exists between amounts of precipitation (both rain and snow), and distance and elevation up the major valleys. Westerly trade winds are responsible for warm and moist Pacific air. Barometric pressure changes frequently are associated with Arctic to sub-tropic air masses into the region resulting in variable weather. Winter frontal systems are associated with cyclonic storms in the Gulf of Alaska. Frontal system precipitation is enhanced orographically. Precipitation increases with elevation from 2500 mm on the coast to 5000 mm at higher elevations (Ryder 1981). The mountains produce a rain  22  Regional physiography and geology  Chapter 3 shadow effect with precipitation decreasing to the northeast.  The Fraser lowland channels coastal  weather systems inland. Rain storms are frequent and data collected by the GVRD show the one-hour, 100 year storm can be expected to yield 50 mm per hour. The one day, 100 year storm yields precipitations of about 12.5 mm per hour and can be expected to provide about 300 mm of precipitation, and the five day, 100 year storm about 640 mm. Both values were exceeded in November 1990. The maximum temperature range for the southern parts of the study area is 32°C. The mean temperature range for Vancouver is 2 - 18°C with a mean January temperature between 1 - 5°C (Roddick 1965). Temperatures decrease inland from the coast. Two seasons are recognized, winter extends from late September through March. Winter storms have a large areal extent and temperature variations in the air mass lead to rainfall at low elevations and snow accumulation in high areas. Transient snowpacks, resulting from fluctuating freezing levels, form and disappear at elevations between 200 and 1000 m. Near Vancouver mean annual snowfall increases at approximately 660 cm per km of elevation. Snow accumulations in Seymour valley have been measured at 2.5 - 4.6 m. Water equivalents at high elevation range from 1-2 m. The regional snowline rises, and snowfall decreases, eastwards as the climate becomes more continental. Semi-arid conditions exist at low elevations on the lee side of the Coast Mountains.  3.3 Local rock types  Rocks of the Coast Plutonic Complex occupy 85 - 90% of the study area. Precise lithologies are described by Roddick (1965). The complex comprises mid-Jurrasic to middle Cretaceous granites, granodiorites, quartz diorite, diorite, gabbro and migmatite dated at 167 - 91 Ma (Monger and Journeay 1994). 23  Regional physiography and geology  Chapter 3  The Coast Plutonic Complex was intruded into regionally metamorphosed, greenschist facies, Triassic and Jurrasic stratified strata of the Wrangellia and Harrison terranes (see Section 3.4). These metamorphic rocks now occur as fault bounded pendants or septa and are, from oldest to youngest: Twin Island Group; Bowen Island Group; Cultus Formation; Harrison Lake Formation; Fire Lake Group; Helm Formation; occasional Tertiary deposits and extrusives; and Quaternary, Garibaldi Group volcanics. The pre-Tertiary volcanic and sedimentary rocks typically contain more rocks of sedimentary than volcanic origin. Outcrops are often aligned with the dominant northwesterly structural trend. Within these rocks structure typically trends northwesterly with moderate to steep dips. Some smaller pendants of Twin Island Group rocks seem unrelated, structurally, to others and exhibit a northeasterly trend (Roddick 1965). Late Cretaceous to early Tertiary stratified rocks occur in small exposures on the southern slopes of the mountains north of Vancouvers. These southerly dipping rocks represent continental deposits with minor volcanics deposited in Georgia Depression below Fraser lowland. These materials underlie Vancouver but are largely buried below Quaternary deposits (Roddick 1965). The Garibaldi volcanics represent part of a belt trending for 110 km northwest of Mount Garibaldi. Including pre-glacial, intra- and post-glacial deposits these range in age from 3.8 Ma to 1340 yBP (Lawrence et al. 1984). Rocks comprise flows and pyroclastics of varying composition from basalt through andesite and dacite, to rhyodacite (Roddick 1965).  24  Regional physiography and geology  Chapter 3 3.4 Tectonic evolution and regional structure  The geological history of the Vancouver area is influenced by the interaction of three crustal blocks, the Coast Mountains, the Vancouver Island Ranges and the Cascade Range mountains. These are separated by two lowland depressions, Strait of Georgia and Fraser Lowland. The recent tectonic evolution of the Canadian Cordillera is best described as a series of accretion events. The local history is separated into three phases (Monger and Journeay 1994). A pre-accretionary stage saw the joined Vancouver Island Ranges and southwestern Coast Mountains separated from North America by basins now forming the southeastern Coast Mountains. By about 100 Ma these blocks had accreted to the continental margin causing crustal thickening and associated uplift and erosion in the Coast Mountains.  The syn-, and post-accretion stage lasted until  approximately 40 Ma when the continental Cascade Arc (see Fig.4.6) formed as the present subduction regime evolved. Presently, the Cascadia subduction zone lies about 100 km west of Vancouver Island. The subducting plate is at an estimated depth of 70 km below Vancouver (Monger and Journeay 1994, after Rogers and Horner 1991). Strait of Georgia represents the forearc depression and is subsiding at about 1 mm.a' (Monger and Journeay 1994). The Garibaldi Volcanics are a part of the Cascade 1  magmatic arc. Regional physiography is believed to have formed mainly in the last ten million years, and is thought to be related to stresses on the plate margin and thermal expansion of the Cascade arc (Monger and Journeay 1994). Further details of the tectonic evolution of the Canadian Cordillera can be found in Gabrielse and Yorath (1991). The dominant regional structure is a northwesterly trending fabric formed when plate motions switched from an orthogonal sense, to dextral relative motions between approximately 85 Ma and the early Tertiary. This occurred contemporaneous with, and following closure of the basins separating 25  Chapter 3  Regional physiography and geology  the Coast Mountain and Vancouver Island crustal blocks from North America.  At this time a  compressional and transpressional regime existed in the southeastern Coast Mountains. In the southwest, deformation was concentrated on northwest-trending, and west- to southwest-vergent dextral shear zones. One, the Harrison Fault Zone, cuts the northeast corner of the study area. This zone separates two distinct tectonostratigraphic terranes, the Wrangellia and Harrison terranes, respectively west and east of the fault zone. The fault zone extends to the base of the crust and at surface forms the Harrison Lake - Pemberton valley (Monger and Journeay 1994). The youngest dated structures in the area are northeast trending, dextral transcurrent faults with associated northwest striking high angle reverse faults (Journeay 1990). These are possibly associated with the eastward subduction of the Juan de Fuca plate and perhaps recording northeastsouthwest crustal shortening. These are thought to have been active between 25 and 14 Ma (Journeay 1990).  3.5 Glaciation and Quaternary deposits  At the climax of each of three major glaciations in the Quaternary ice covered most of British Columbia. The last glaciation, the Fraser, mantled slopes with till and filled valley floors with glaciofluvial and glaciolacustrine sediments collectively known as Vashon drift. These are overlain in places by Capilano sediments (Hicock and Armstrong 1984). Materials deposited prior to the last glaciation which remained unconsolidated, were extensively scoured and reworked from the valleys and slopes to form the outwash deposits that underlie much of Vancouver and, in places, the Vashon drift. These are the Quadra sands. The southwestern section of the Wisconsinan ice sheet began to decay at about 14 ka and parts of coastal areas were ice-free by 13 ka. Ice had completely withdrawn from the area by 10 ka (Clague 26  Regional physiography and geology  Chapter 3  1989). At this time mass wasting and fluvial processes began to redistribute glacial deposits. A period of valley aggradation was followed by downcutting as sediment supplies diminished. By mid to late Holocene times many streams flowed near their present levels. The main depositional areas have since been lake and sea floors, fans and deltas (Clague 1989).  27  The lineament inventory  Chapter 4  CHAPTER 4  THE LINEAMENT INVENTORY  4.1 Introduction  The focus of the chapter is an inventory of lineaments compiled from air photos of the study area. A discussion of the air photo identification of lineaments is followed by presentation of the lineament inventory. Details of inventory production and interpretation are combined with presentation of the data.  Field observations of selected lineaments are described along with suggested  interpretations for the features identified.  4.2 Air photo interpretation of lineaments  Lineament identification on air photos relies on the observer's ability to detect a combination of features defining the lineament. This imparts a bias on interpretation which might imply automatic detection by computer would be preferable. Although subjective, visual inspection tends to reveal a larger number of features than automated detection (Leir 1995). For photo detection of lineaments a sun angle that allows utilization of shadows revealing subtle differences in relief and textural patterns is preferred (Lillesand and Kiefer 1979). In mountainous terrain the sun must be high enough to illuminate the valleys. A mid-morning or mid-afternoon flight during early summer when the ground is free of snow cover is optimal because the presence of snow and ice will obscure ground detail. 28  The lineament inventory  Chapter 4  Certain landscape features enhance lineament detection; straight stream segments and rock walls can be used as guidelines for lineament mapping because these morphological features may be part of a more persistent lineament. Some anthropogenic features may be confused with naturally occurring lineaments: Abandoned logging roads and pipelines may be difficult to identify through a dense tree cover, but have a visible photo expression. During field studies the author found one overgrown logging road that had been mapped as a lineament. Other landscape features, such as alluvial valley fill, and alluvial and colluvial fans and cones, may mask the surface expression of lineaments unless the feature has been recently active. In summary a lineament was mapped if it showed a variation in photo tone and is: straight or nearly straight; persistent over a length which may be reasonably mapped at the scale of the study; and if partly formed by a morphological feature such as a stream segment, continuous beyond the expression of that feature on the photograph. To facilitate further processing curvilinear features were mapped as a series of successive straight lineaments.  4.3 The lineament inventory  The lineament inventory described below was compiled for two reasons: firstly, to gain an appreciation of regional structure and secondly to provide a framework within which to study the effects of lineaments on individual drainage basins and landslide events.  4.3.1 Processing The lineament inventory was prepared by air photo investigation of stereo air photos (approximate scale 1:60,000). Lineaments were drawn directly onto each photograph and checked 29  The lineament inventory  Chapter 4  twice over a period of three months to ensure identification of all features before transfer to a 1:250,000 scale topographic map for subsequent digitization. Despite easy identification in areas of bare rock, lineaments less than 300 m (5 mm photo-length) in length, were not included in the inventory because of the difficulty in transfering these to the basemap. Photos were examined in stereo during transfer to a basemap and mapping accuracy depends on the certainty with which the endpoints of the lineament can be fixed with respect to topographic features. Placement of lineaments on a map in open terrain, such as a hillslope, is difficult where no distinguishing features exist. There is a maximum placement error of + 250 m (within two pixels in subsequent analysis (see Section 5.6.1.)) in the location of lineaments on the map. This represents a map distance of between 0 - 250 m (0 - 1 mm) on a 1:250,000 scale map. This inaccuracy represents the largest probable ground error. In practice persistent lineaments, intersecting a number of topographic features, can be easily placed in comparison with shorter features visible on a single hillslope. When the accuracy of placement was examined features in the Seymour watershed were found to have a maximum placement error of 150 m (see Section 6.4.1). Lineaments were digitized and UTM (Universal Transverse Mercator) grid referenced in AUTOCAD 12 for WINDOWS (ACAD). A total of 4215 lineaments were transferred to ACAD and exported to IDRISI by way of a data exchange (dxf) file. In IDRISI, a rastorized image file and a vector file was generated. The vector file was processed in a FORTRAN program "TREND" to determine lineament orientations. TREND calculates the angle between the first and last points of each line. The output is distributed between 0 and 179°. To construct a rose diagram of lineament data the output file from trend is saved as a TEXT file in windows then displayed graphically by ROSE 1.02. Details of ACAD and IDRISI may be found in the user manuals, Autodesk Inc. (1993) and Eastman (1993) respectively. TREND was written by Leir (1994) for in-house use at the University of  30  The lineament inventory  Chapter 4  British Columbia, Geological Sciences Department. Rose 1.02 is shareware software available from Thompson and Thompson, Indiana, USA.  4.3.2 The scale effect When mapping on lower altitude (larger scale) air photos the number of lineaments detectable increases. Table 4.1 shows the result of remapping lineaments in sample set basins for which 1:60,000 and 1:20,000 scale photographs were available and compares number, and length of lineaments mapped at both scales. There is an average threefold increase in the length of lineaments mapped on the larger scale photos. Lineament length is calculated in IDRISI by multiplying the number of lineament pixels by the length of one side of one pixel. In the field the number of lineaments detectable in all ground conditions but bare rock exposure drops appreciably (see Section 4.4).  1:20,000 scale air photo mapping  1:60,000 scale air photo mapping Basin # # of lins. 1 16 25 26 Average  14 5 6 9  Lin. length (m) 8300 2440 1680 4900  Lin. density (/m ) 0.00752 0.00326 0.00614 0.00903  # of Lins.  2  36 17 18 20  Lin. length (m) 16593 11466 5034 8371  Lin. density (/m ) 0.01503 0.01533 0.01839 0.01542  % lin. increase  2  199.9 469.9 299.6 170.8 285.05  Table 4.1. Comparison of lineament parameters mapped on high and low altitude air photos. The basin number corresponds to numbers reported in Chapter 5, and the percentage lineament increase in the final column is the increase seen on the lower altitude air photos.  4.3.3 Lineament trends Figure 4.1 is a rose diagram representation of the lineament data with the calculated statistics and Figure 4.2 shows the lineament map derived from the study.  31  Chapter 4  The lineament inventory  Arithmetic Plot Number of Points Class Size Maximum Percent Vector Mean Vector Magnitude Consistency Ratio  4215 5 6 17.43 1344.61 0.3190  Figure 4.1. Rose diagram showing all lineaments in the inventory. 32  Chapter 4  The lineament inventory 122 W  122 25 W 50" N  50 N  10 Ktocyettrs  0  I  49 N  V  ^  ^  I.  NE  \  ^9  Leoend  122 25  /  Lineaneni; Fault  Figure 4.2. The lineament inventory map. The inset shows the breakdown o f this area into the blocks discussed in the text. The distinction between lineaments and faults indicates features mapped by the GSC from Roddick (1965). 33  The lineament inventory  Chapter 4  The rose diagram (Fig. 4.1) shows a preferred trend of 17.43 ± 3.73° (see below) and peaks in the data representing east-west and northwest-southeast trends. The data is grouped in five degree classes and tabulated in Appendix I. Statistics were compiled in ROSE 1.02 using standard techniques for evaluating directional data (see Davis (1986), and summary examples in Appendix II). The vector mean is the direction of the resultant vector if all lineaments are placed end to end in classical "head to tail" fashion. Standard error is calculated according to Davis (1986, p.325) at the 95% confidence interval. The magnitude of the resultant vector is its length assuming each vector (lineament) is of unit length.  Consistency ratio is a means of standardizing the vector magnitude and measuring the  distribution of the data and varies from zero to one. A value near one implies the data is tightly grouped. The data is tested for randomness to determine whether a preferred trend exists. Calculation of the standard error is detailed in Appendix II. From Figure 4.2 several observations are made: There is a higher lineament density in the region between approximately 49° 23' N . and 49° 45' N . This region contains many of the longer lineaments in particular several large east-west trending lineaments. North of 49° 45' N., the map area can be split into two regions, east and west of 122° 35' W. To the west the density of mapped lineaments is reduced by numerous ice fields and glaciers. Farther east is a proliferation of northwest trending lineaments following Harrison Lake - Pemberton Valley. Lineament density is lower in the Southern area because of the presence of several wide, flat bottomed, alluvial filled valleys, e.g., those of Pitt, and Stave rivers. Figure 4.3 shows the lineament trend data for the four blocks discussed and Table 4.2 summarizes lineament data for the regional study and these areas. The GVRD watersheds represent a subset of the regional study area and the field area used in this study.  34  Chapter 4  The lineament inventory  Southern Block  Central Block  Arithmetic Plot Number of Points Class Size Maximum Percent Vector Mean Vector Magnitude Consistency Ratio  Arithmetic Plot Number of Points Class Size Maximum Percent Vector Mean Vector Magnitude Consistency Ratio  487 5 7 23.08 209.20 0.4296  2546 5 7 22.66 895.45 0.3517  Northeast Block  Northwest Block  Arithmetic Plot Number of Points Class Size Maximum Percent Vector Mean Vector Magnitude Consistency Ratio  Arithmetic Plot Number of Points Class Size Maximum Percent Vector Mean Vector Magnitude Consistency Ratio  614 5 7 10.59 218.92 0.3565  Figure 4.3. Rose diagrams for each of the blocks described in the text. 35  625 5 5 346.01 184.34 0.2949  The lineament inventory  Chapter 4  The number of lineaments calculated for the individual blocks totals 4272 (57 (1.35%) of the lineaments are repeated). Lineaments were separated in ACAD by selecting the required block and deleting all others before export to IDRISI. In doing this some overlapping lineaments may be included in two sections. A visual assessment of each block was made and the most apparent overlapping lineaments removed. The data confirms the visual assessment of lineament distribution. The central block has the highest lineament density and the southern block the lowest. GVRD watersheds overlap the southern and central blocks and visual assessment of the lineament distribution within the watersheds reveals a slightly higher lineament concentration in the northern parts of the basins (Fig. 4.4).  Average length (km.) 1.961  Lineament density (/km ) 1.319  Mean Trend Orientation  Regional area  10,900  4215  Total length of lins. (Km.) 8266.3  Southern block  4000  487  1015.84  2.086  0.001*  23.08±7.95°  Central Block  4000  2546  5303.06  2.083  1.326  22.66±4.34°  Northeast block  1160  625  1010.38  1.617  0.871  166.01±10.52°  Northwest block  1740  614  1080.8  1.760  0.621  10.59±8.5°  GVRD watersheds  596  474  794.36  1.676  0.751  30.2±8.46°  Area (km )  Site  2  #of lins.  2  17.43±3.73°  Table 4.2. Summary information for lineaments. (*) A more realistic value is 0.677 because approximately 2,500 km of this block resides in the developed Fraser Lowland. 2  The larger the sample size the more constrained is the mean trend. The standard error for the entire data set is sufficient to capture all but the mean of the northeastern block and GVRD watersheds.  36  The lineament inventory  Chapter 4  123  15 U  122  40  V  49 40 N  49 20 N  123' 15 v  Scale  0  Capilano y ' )/ River Seymour River in k i l o m e t e r s  10  7  122 40  v  Coqui t l a m River : 20  Figure 4.4. Lineament distribution in the GVRD watersheds. The approximate location of key field sites is also shown: AC = Appian Creek; OC = Orchid Creek; CC = Camp Creek.  37  The lineament inventory  Chapter 4  The GVRD watershed dataset contains the means of both the southern and central blocks. A more rigorous comparison of data is made by testing for equivalence of the mean directions statistically. This is done using the two-sample test of Watson and Williams (Mardia 1972, Davis 1986). Only results of these tests are detailed here, an example calculation is found in Appendix II. The south and central blocks derive from the same statistical population but the two northern blocks differ significantly both from those in the two southern blocks (which were joined for the purposes of analysis) and from each other. The GVRD sample set cannot be tested in the same fashion because it is not independent from the south-central dataset. The primary difference between the two northerly blocks is the presence of long, northwesterly trending lineaments in Harrison Lake-Pemberton Valley, the distribution of which corresponds with the outcrop of the Jurassic Fire Lake Group and other metamorphic rocks in the area (Fig. 4.5). Statistical similarities and differences between areas and variations in structural style may be due to either variable rock type response to a particular lineament generating stress field or, more likely, to differences in the stress history of particular rocks. As an example, the northwesterly trend of the major rivers dates from the Jurassic (Journey pers. comm. 1995). This trend is not particularly evident anywhere on the lineament map except where Jurassic and pre-Jurassic rocks occur. It is reasonable to conclude that the these rocks have retained an older structural trend while the younger rocks of the Coast Plutonic Complex have only been subjected to younger stress fields. This younger stress field has imprinted itself over the Jurassic and pre-Jurassic trend as is demonstrated by the additional presence of a northeasterly trend in the northeastern block. This trend is likely to be representative of the Tertiary trend identified by Journeay (1990). Details of the origin and nature of these trends were presented in Chapter 3, Section 3.4.  38  The lineament inventory  Chapter 4  Figure 4.5. Simplified map of northeastern block geology and lineaments: F L G = Fire Lake Group; TIG = Twin Island Group; M = Migmatite; Qdio = Quartz diorite; Gdio = Granodiorite; A l = Alluvium; I = Ice. (Adapted from Roddick 1965). 39  The lineament inventory  Chapter 4  The northeastern block is the only block underlain by significant amounts of metasedimentary rock. The northwestern block contains areas of pre-Jurassic rocks which, when combined with the presence of numerous icefields are sufficient to disrupt the lineament patterns away from trends seen in the dominantly crystalline igneous, remaining area. Other areas of metasedimentary rocks do exist, notably on the eastern flanks of Howe Sound but these are areally small. The east-west trend visible in the central and southern blocks may represent the youngest regional trend.  This trend does not correlate with a recognized structural trend.  The present  convergence vector of the Juan de Fuca and the North American plate is oriented at approximately (060°) northeast-southwest (Fig. 4.6). If it is assumed that the convergence vector represents the axis of maximum principal stress then the angle at which faulting is expected is given by:  0 = 45°-(|>/2  Where < > | = tan'u, and u. is the coefficient of sliding friction. For most rocks at the large-scale < > | is taken as 30°, hence dextral faulting can be expected oriented at approximately 030° (north-northeast) and sinistral faulting oriented approximately 090° (east-west). The presence of north-northeast faults in this region would be obscured by the Tertiary trend already identified above, however, east-west oriented lineaments dominate the area southwest of the Harrison Lake - Pemberton Valley. It is suggested that the east-west trend may be a young, previously unrecognized structural trend in the southwest Coast Mountains. These lineaments are laterally extensive and cross-cut both  40  Chapter 4  The lineament inventory  Figure 4.6. A schematic diagram showing the orientation of the maximum principle stress (<J\) and the conjugate fault pattern which may develop as a result of this. 41  The lineament inventory  Chapter 4  metamorphic and igneous rocks. Additionally there is evidence that this trend may be expressed in Quaternary fill and alluvium. Figure 4.7 shows features identified in alluvium at the southern end of Widgeon Creek (see figure 3.2, Page 22). The persistence of the lineaments in both the soft sediment of the valley fill and the adjacent bedrock suggests they are related. Whether the features represent movement in the valley fill or an induced surface expression of a bedrock feature below (possibly hydraulic discharge from the adjacent slope concentrated along the subsurface lineament) cannot be verified from air photographs. Field investigation is necessary to properly understand these features. These lineaments are currently being investigated by Thurber Engineering Ltd. under contract from the GVRD.  4.4 Field and air photo observations  While lineaments are ubiquitous in the study area, many are difficult to detect, or are undetectable in the field. They typically express themselves as gullies suggesting that they represent a zone of weakness in the rock mass. Often these gullies are the focus of groundwater and surface flow. On air photos major creeks are easily visible on vegetated slopes because the presence of debris, typically broken rock, produces a high reflectance (whiteness) if the channel width is sufficient that tree crowns do not meet across it. Creeks are deeply incised into the hillsides forming very steep, rockwalled gullies often impossible to access. This suggests that these creeks may be exploiting preexisting fractures. On vegetated slopes lineaments visible on air photos area rarely detectable with certainty. Where represented by gullies, lineaments are often filled with large organic debris and may have trees and other growth within them. Recent clearcuts may reveal small gullies but in older clearcuts vegetation is typically too thick to traverse easily and ground observation is impossible. 42  Chapter 4  The lineament inventory  The lineament inventory  Chapter 4  In areas of bedrock exposure, common in the upper elevations of drainage basins, lineaments manifest themselves as cracks in the rock mass. These range in magnitude from steep sided "canyons" in a cliff face or ridge top to small cracks visible in a single rock face. Field examples of lineaments are shown in figures 4.8 to 4.13. Figure 4.8 shows the Camp Creek basin in the Coquitlam watershed. Lineaments have eroded deep canyons in the cliff faces that are interpreted as faults. The features are up to 10 m wide and have a central zone exhibiting epidote and chlorite mineralization suggesting fluid movement in the zone. Rock fragments with slickensides were found in the canyon, but not in situ.  Small debris cones  composed of talus from the canyon walls, and of till and soil that has fallen from the walls and cliff top, have built out from these features. Material from the fault zone is removed only with the aid of a hammer however this does not preclude removal offinematerial from the zone because the zone is wet and solution processes may be operating. These features appear capable of headward erosion of the basin because freeze - thaw and shattering processes presumably operate in the canyon walls. The back of the Camp Creek basin is an amphitheater floored entirely with broken, angular rock fragments up to 5 - 6 m across. Figure 4.9 shows a creek in the Coquitlam watershed following a straight path for some distance and cutting deeply into bedrock. The creek is interpreted as lineament controlled. Figure 4.10 shows a deep, steep sided gully traversing the drainage divide of the Orchid Creek basin. Photographed in the same area, Figure 4.11 shows a major lineament at a high elevation behind Orchid Creek in the Seymour watershed (located in the Capilano watershed). This feature is easily detectable on 1:60,000 scale air photos. Figure 4.12 shows joints at the back of the Appian Creek basin in the Capilano watershed. From the same locality, Figure 4.13 shows weathered rock material in situ on the flat ridgetop. This  44  The lineament inventory  Chapter 4  Figure 4.8a. Stereophoto (30BCB92018:134,135) of the Camp Creek basin showing debris cones building from "canyons" in the cliff face, (note also the N E trending lineaments responsible for the cliff face on the lower photograph).  Figure 4.8b. The Camp Creek basin viewed from the west side of Coquitlam reservoir: The arrows indicates the lineaments mentioned above. 45  Chapter 4  The lineament inventory  Chapter 4  The lineament inventory  Figure 4.10. A large gully (lineament) bisecting the Orchid Creek basin hcadvvall (facing east: This gully is approximately 8 m across). 47  The lineament inventory  Chapter 4  a  Figure 4.11. Two views of a large lineament behind the Orchid creek headwall of the Seymour watershed: a) facing west from the ridge above the lineament (arrows indicate the lineament), b) the view along the lineament as photographed from the top left of Fig. 4.1 la. 48  The lineament inventory  Chapter 4  Figure 4.12. Joints in the eastern headwall of the Appian Creek basin in the Capilano watershed.  Figure 4.13. Weathered rock material in situ on the Appian Creek headwall (lens cap indicates scale). 49  The lineament inventory  Chapter 4  was the only locality where such fine breakdown of material was observed. This may be because the wide, flat ridgetop does not facilitate removal of shattered rock material which usually falls from the slopes before the material can be this finely weathered. In the field it was clear that lineaments recognized on air photos may be one of several things reflecting either primary or secondary features. Lineaments themselves are primary features and may be identified as faults, joints, dykes or the expressions of lithologic contacts. Secondary features associated with lineaments are gullies, including small bedrock canyons, straight stream courses, scarps and rock walls. The distinction between faults and large joints is difficult to judge in the absence of movement indicators. In an area such as this, which has experienced repeated glaciations with consequent isostatic response, and larger amounts of tectonic uplift, movement would probably have occurred on these joints. Additionally many slopes will have undergone differential stress release over their length due to unloading during deglaciation. This would suggest that existingfractures,such as joints and faults, may have responded with movement. For the purposes of this study, the distinction between faults and large joints is unimportant because most of the features in question can be said to have "moved" at some point in time. On air photos small joints occur in parallel sets with a defined spacing that are not (visually) persistent into the vegetation. Large-scale, regional joints and faults may be persistent features forming small bedrock scarps, gullies or rockwalls and crossing multiple drainage divides. Dykes are numerous in the study area. There are many small dykes visible in the granodiorite and some larger features visible in the pendant rocks. In granodiorite at the back of the Orchid Creek basin several small dykes were observed ranging between 15 and 200 cm in width striking approximately east-west. A larger dyke was found intruding a fault in pendant rocks on the Coquitlam mainline (the main road through the Coquitlam watershed). Dykes represent a contrast in lithology that 50  The lineament inventory  Chapter 4  may show up as lineaments on air photos, however those observed in the field were small and none of the major lineaments examined represented dykes. Some dykes represent more resistant features and are not likely to form gullies or be eroded as a stream course. However they may form scarps or control a stream course as water flows adjacent to them. No examples were found. Contacts between different rock types may appear as lineaments on air photos. Typically geological maps can be examined to determine the location of these features, however it was noted during fieldwork that the existing GSC are not sufficiently detailed to show the distribution of the pendant rocks accurately. Many contacts are known to be faulted and regular lithologic contacts are likely to be responsible for only a small number of mapped lineaments. In conclusion, field evidence and air photo investigation suggests that persistent lineaments crossing multiple divides and detectable through a vegetation cover should be interpreted as faults, or large scale regional joints.  Smaller features, seen only in areas of bedrock exposure, with no  persistence into vegetal cover, and, occurring in parallel sets are likely to be joints. Dykes and lithologic contacts represent only a small number of the lineaments mapped on air photos. Many lineaments detected on air photos are only detectable on the ground in areas of bedrock exposure, where they have captured stream courses, or where vegetation is insufficient to obscure their topographic detail, for example in new clearcuts. On vegetated slopes the features are rarely detected with certainty. Finally, while important for headward erosion in drainage basins, lineaments do not seem to be directly responsible for the input of fine sediment to the basin. They do provide rock walls from which material is weathered, gullies in which material can accumulate, and creeks along which material can be mobilized.  51  The lineament inventory  Chapter 4 4.5 Conclusions  This investigation has shown the value of a regional lineament inventory. Once lineament mapping is completed investigation of trends can be used to characterize the structural style of the region. By this method the stress history of the northeast study block is inferred to differ from the other blocks in that metamorphic rocks in this block have retained the oldest (northwest) structural trend in the region. If lineaments are interpreted as faults, three phases of lineament inducing stress are proposed for this region: 1)  The oldest phase, associated with dextral shear in the Cretaceous has produced northwest  trending lineaments, is responsible for the trends of the major river valleys and the dominant northwest trend into which rocks of the Coast Plutonic Complex were later intruded, and is most clearly developed in the metasedimentary rocks of the study area. The trend is also seen in the younger, igneous rocks, and this could represent reactivation of this trend at a later time. 2)  A Tertiary trend which probably represents northeast-southwest crustal shortening. This phase  has emplaced a northeast trending lineament set on both the igneous and metamorphic rocks in the area. 3)  A more recent east-west trend with lineaments persistent for tens of kilometers and cutting both  igneous and metamorphic rocks. The age of this trend is unknown however there is evidence that it may be recent, for example its visibility in recent alluvium (see discussion, page 42 and Figure 4.6). These lineaments are oriented in a manner conducive to the transmittal of stresses from the present convergence directions of the North American and Juan de Fuca plates (Journeay, pers. comm. 1996). It is suggested that the majority of lineaments be interpreted as either faults or large regional joints. Field evidence suggests that lineaments represent zones of weakness in the rock mass and lineaments examined in the Camp Creek basin show evidence of faulting. Weakness in the rock mass is evidenced by gullies and deeply incised streams following lineament courses. Other features that 52  The lineament inventory  Chapter 4  may express themselves as lineaments on air photos are dykes, contacts between rock types, and anthropogenic features. It is suggested that investigation of lineament trends provides a relatively fast means of analyzing the structural style of an area, after which field studies may be initiated to evaluate the hypotheses formulated. Visual inspection of the lineament trends in the study area allowed the division of the region into four blocks which were investigated for statistical variations.  53  Chapter 5  Drainage basin analysis  CHAPTER 5  DRAINAGE BASIN ANALYSIS  5.1 Background and methodology  This chapter describes investigations into the relationship between lineaments and drainage basin, and fan, systems. A sample set of basins is selected to analyze. Four analysis sections describe the process and results of investigating lineament control on basin position, drainage pattern, basin/fan morphometry, and sediment yield. Research was initiated in response to the observation that large fans were built into the valleys of major rivers in the southern Coast Mountains. It appeared that these fans developed from basins aligned with major lineaments crossing the valleys. That basins seem to align themselves with lineaments suggests some structural control in their formation. This hypothesis is tested visually by air photo interpretation, and by mathematical analysis. It was proposed that the lineaments may in some way be responsible for the large volumes of material in the fans, perhaps by direct weathering of the lineaments (Dr. K.W. Savigny, pers. comm. 1994). Visual interpretation of air photos allows inference of spatial relations between lineaments and basin features such as the drainage network and location of the basin axis. Knowledge of processes operating in basins, combined with a knowledge of existing literature, allows the proposal of allometric relations. Spatial correlations are established using a GIS while mathematical relations are tested using regression analysis. Both methods are described in subsequent sections. With the  54  Chapter 5  Drainage basin analysis  exception of a visual assessment of lineament control on drainage basin location (Section 5.5) each analysis employed the following steps in establishing relations: 1)  Either examination of air photos allows the formulation of a hypotheses to be tested, or presence of a mathematical relation is proposed based on previous knowledge;  2)  parameters from either topographic maps or digital representations of the features in question are measured;  3)  the strength of hypothesized relationships is tested either spatially or mathematically; and,  4)  physical reasons are proposed for the relations found. Lineament length and density are determined to be the parameters most useful in establishing  the relation of basin morphometry to bedrock structure. Both reflect the structural character of the rock mass and are easily measured, or calculated, from topographic maps. Parameters such as lineament gradient, or persistence (a possible measure of overall lineament length) were deemed unnecessary for initial research purposes. Additionally, the linear nature of lineaments suggests comparison with drainage parameters which are also linear and whose most critical measurements are stream length and drainage density.  5.2 Terminology  The terms fan and cone describe sediment deposition/storage zones at the mouth of a drainage basin. The distinction is largely one of slope with cones being the steeper features at angles above 15° (Ministry of Environment 1988). For convenience in this text, the term fan is used when discussing either fans or cones where both are implied. The term cone is used where it properly applies for specific description of a particular feature e.g. "cone #4 has a slope of 47°". The term basin is used both for general discussion of the sample set, and for specific discussion where it  55  Chapter 5  Drainage basin analysis  relates to the drainage basin and excludes the fan. The term system refers to both the basin and fan when usage is related to processes operating both in the basin, and on the fan, or to describe the movement of materials through the basin and onto the fan or beyond. Additionally drainage basins developed on igneous and metamorphic rocks are henceforth referred to as igneous basins and metamorphic basins in order to simplify reference to these features.  5.3 Sample set basins  Because of the large number of drainage basins identified in the study area (over 600) only a representative sample set was selected for study. This section describes random selection of this set and describes some of their more important characteristics. The data collected from the sample set represented as many variables within the study area as possible. The physiography of the study area, while broadly similar, has some variations which were considered in sample set selection. In particular some areas are currently, or have recently been, affected by valley glaciers. A set with as many variations in aspect, lithology and elevation range as possible was used. The size of the sample set was determined by the data. An initial set of twenty five basins was considered for analysis. Trial analysis were conducted and when it was established that relations among variables were apparent the sample size was accepted. If relations had been shown then five more basins would have been added and the process repeated. The 1:60,000 scale air photos were re-examined and drainage basins identified by the presence of a fan. This process allowed inclusion of small alpine basins, but excluded larger basins whose rivers empty into lakes or the coastal fjords. It became apparent during mapping that a more stringent selection criteria was required.  56  Chapter 5  Drainage basin analysis  Where a fan was determined to be solely the result of rockfall it was ignored. This again implies a scale factor problem in the analysis because larger scale air photos would reveal subtler drainage patterns than the 1:60,000 photos employed. Small fans, developed from first order streams that were obviously part of a larger drainage system were ignored since it is possible the feature might represent a single mass movement event. These requirements led to identification of 2nd to 5th order basins. Each fan detected was numbered on the air photo and its location later recorded on a topographic map. 639 fans were identified in the regional study area. To randomly select basins random numbers were generated between 1 and 639 using QUATTRO PRO for windows (QPRO). The first 25 of these random numbers were taken for consideration as a sample set. From this point on, reference to the basins is made by their assigned number after random generation, i.e., numbers range from 1 to 29 (11 - 13, and 23, are missing because they did not fit the original criteria for selection). These numbers have been used throughout the study and in the text. The mapped numbers appear after the assigned number in Appendix III.  5.3.1 Mapping of sample set basins Lineaments mapped at the regional 1:250,000 scale (Chapter 4) were insufficient to properly characterize lineament distribution at the individual basin scale. Consequently lineaments were remapped on 1:20,000 scale air photos for each sample set basin. The fans and drainage divides were mapped on air photos, transferred to topographic basemaps, and digitized in ACAD. lineaments, and streams.  Three ACAD files were created; basin and fan polygons,  Streams segments were digitized according to Strahler (1952) orders.  Where a lake exists in a basin (e.g. basin #19) the lake is treated as a stream of the highest order  57  Chapter 5  Drainage basin analysis  entering the lake "since there would then necessarily be a stream of the highest order traversing the lake bed" (Horton 1945 p.289). Filled polygons were produced for the basin and fan. Resolution of the initial IDRISI image determines the thickness of the rastorized lineaments and streams in IDRISI. Each lineament or stream automatically assumes one pixel width. The selected resolution (20 m) is based on the largest mapped sample set basin and the maximum number of rows and columns displayed in the IDRISI image.  5.3.2 Description of sample set basins The distribution of sample set basins is shown in Figure 5.1. Appendix III details basin localities, with a short description of the character of each basin and its fan. Sample set basins are distributed over much of the area although none occur north of 49°50' N or in the Mamquam River basin. There is little lithologic diversity between sample set basins. Nineteen are developed on crystalline igneous rocks: Fifteen comprise quartz diorite and four granodiorite. One basin each is developed in migmatite (#5), Twin Island group (#14), Fire Lake Group (#19) and Gambier Group (#21) rocks. Only basin #29 contains appreciable geologic diversity. This basin is made up, in order of decreasing importance, of migmatite, quartz diorite, Harrison Lake Formation, and Twin Island Group rocks. The size distribution of the basins range from approximately 0.2 (#6) to 100 (#19 and #29) square kilometers. The three largest basins are grouped on a diagonal between Pitt and Harrison rivers. Each is characterized by the presence of subdrainages. Excluding major rivers these appear to be among the largest basins in the area. Minimum basin elevations range from sea level (0 m asl. (above sea level)) for fan #14 to 1110m asl. for cone #20. Fan #14 builds into Indian Arm, a coastal fjord at the mouth of the Indian River. Cone #20 lies in the high mountains northeast of Mamquam Lake. Cone #20 ranks third in 58  Chapter 5  Drainage basin analysis  Figure 5.1. Distribution of sample set basins.  59  Drainage basin analysis  Chapter 5  terms of maximum basin elevation. Elevations in Basins #19 and 29 reach 2260 m asl. Located just north of basin #20, #24 has the highest basin elevation at 2320 m asl. In general northern basins are higher, more rocky, and alpine in nature while southern basins tend to be less steep and more heavily forested.  Basin distribution in terms of aspect is relatively even. Aspect is considered the  direction of flow of the major stream. These are grouped into the following ranges, 316-045°; east, 046-135°; south, 136-225°; west, 226-316°. Five basins each face north and south, eight face east and seven face west. The sample set appears to fulfill the aims of selection. Lack of lithological diversity might be cause for concern but crystalline igneous rocks are by far the dominant rock type in the region. To introduce more basins of variable lithology might bias results. Another feature by which basins may be distinguished is whether the fan builds directly into a large body of still water (a lake or fjord), e.g., fans #10, 14, 16, 17 and 28. This may effect measurement of fan related parameters in particular fan area because only the area above water level can be measured from a topographic map. This will effect investigation results by some amount but a sensitivity analysis determined this to be minor probably because only 20% of fans are affected. Attempting to rigorously determine likely loss in area measurement (loss of material to river erosion or submerged fan area) is beyond the scope of this research.  5.4 Basin and fan morphometry  Drainage basins possess a set of geometric properties that define the characteristics of the basin in certain ways (Ritter et al 1995). Taken collectively, these describe basin morphometry. All basin parameters that were easily obtained from topographic and thematic maps were measured or recorded for use. This removed the need to evaluate parameters for consideration,  60  Chapter 5  Drainage basin analysis  instead allowing the relations to show themselves during regression analysis. Table 5.1 defines the parameters measured which belong to four classes, areal, linear, relief, and physical. Linear parameters include lineament, stream, basin, and fan length, and basin width. Lineament and stream length are the primary focus of the following investigations. Measuring lineament length allows assessment of the significance of lineament control in the basins. Stream length is classically recognized as being related to many of a basins morphometric parameters. Basin length and width measurements allow calculation of a shape parameter (see below) and length is critical for calculating basin slope. Fan length is measured, where possible, along the line on which basin length is measured from fan apex to fan edge. This is not necessarily the line of the stream course across the fan. Directly measurable relief parameters are minimum basin elevation, maximum fan elevation and maximum basin elevation. Additional parameters can be calculated including basin relief, maximum basin relief, and relief ratio. The first two differ depending upon whether fan apex elevation or minimum elevation is considered. Other parameters calculated include lineament and stream density, basin shape, and basin and fan gradient. Basin shape has been described in different ways, by various authors with varying degrees of success (see Thorn (1988) pp. 100-107 for a discussion). Here, an attempt is made to quantify basin shape by producing a number between zero and one by using the width to length ratio. This provided values in the desired range with a few exceptions where measured basin width exceeded the length.  In general, measuring basin shape in this fashion yielded values which  correlated poorly with other basin parameters (see regression tables in Appendix VII). However the same parameter has been successfully related to basin area by Nikora (1994) for different shaped basins (wide basins, pear-shaped basins and narrow basins).  61  Drainage basin analysis  Chapter 5  Parameters investigated in morphometric analysis of the basin-fan system  Fan Area:  The planimetric area of the fan.  Basin Area:  The planimetric area of the basin.  Lineament length:  The total length of lineaments measured within the boundaries of the drainage divide.  Lineament Density:  The lineament length divided by the basin area.  Stream Length:  The total length of all streams mapped within the basin.  Drainage Density:  The stream length divided by the basin area.  Minimum Basin Elevation:  The elevation at which the main stream enters a river or would enter a river if one were present at the base of the fan  Maximum Basin Elevation:  Maximum elevation on the drainage divide.  Basin Relief:  Maximum basin elevation minus fan apex elevation.  Maximum Basin Relief:  Maximum basin elevation minus minimum basin elevation.  Relief Ratio:  The maximum basin elevation divided by the basin length.  Basin Length:  Longest horizontal distance in the basin measured parallel to the major stream.  Basin Width:  Maximum width of the basin measured perpendicular to the line of basin length.  Basin Shape:  An attempt to quantify the shape of the basin by dividing the width by the basin length.  Fan Length:  Length of the fan measured along the line of the major stream, with some exceptions where uncharacteristic shapes occur.  Fan Apex Elevation:  Elevation of the fan at its' apex.  Basin Gradient:  Maximum basin elevation minus cone apex elevation, divided by basin length.  Fan Gradient:  Apex elevation minus minimum cone elevation and divided by cone length.  Apical Angle:  As closely as possible, the angle formed by lines connecting the cone apex to the furthest points or corners of the cone.  Geology:  The bedrock geology of the basin/cone system characterized from GSC maps.  Aspect:  The direction of flow of the major stream.  Table 5.1. Parameters investigated in the morphometric analysis of the basin - fan system.  62  Drainage basin analysis  Chapter 5  Basin and fan gradient are important because these influence a number of basin characteristics not necessarily measurable as morphometric parameters including likelihood of debris flow activity and runout characteristics of such flows. Additionally stream power is related to slope and this relates to erosion related parameters. Physical attributes recorded for each basin are aspect and geology. Neither are used in regression analysis. Measurement of parameters were made from digital representations or directly from 1:50,000 scale topographic maps. Areal properties were measured by ACAD and lengths of digitized features were measured in IDRISI with a 20m resolution. Elevations were recorded in meters where necessary converting feet to meters to be recorded to the nearest 10 m. The resulting data are presented in Appendix IV.  5.5 Lineament control on drainage basin location  In order to fully evaluate lineament effects on drainage basins it is first necessary to assess lineament control on basin location, i.e., to determine whether the basin is preferentially located about a lineament. If this is proven it can be used as a basis for subsequent investigation. For example, assuming the main stream flows at the basin axis and is lineament controlled it can be hypothesized that the remaining drainage pattern may also exhibit lineament control. This is investigated in Section 5.6. When the extent to which lineaments influence the drainage pattern is known the correlation between lineaments and other drainage basin parameters can be analyzed and compared to the correlations between streams and these parameters. analysis in Section 5.7.  63  This is done by regression  Drainage basin analysis  Chapter 5 5.5.1 Method  To determine whether the basin axis is positionally controlled by a lineament, the basin axis was located. Typically this was the line of the major stream and was approximately straight. The axis was carefully followed to determine whether a lineament was present beyond the limit of the stream and its persistence to the drainage divide and beyond assessed. Ideally the lineament should also persist beyond the basin mouth however lineaments are often masked by the fan and other valley fill materials. It is therefore considered adequate to find evidence of the axial lineament over as great a length as possible. If a lineament is found fulfilling the above criteria it is seen as strong evidence that the basin is preferentially located about this lineament. The extent to which a basin is bounded by lineaments is also viewed as evidence for structural control. For example, the drainage divides may be contiguous with, or associated with recognized lineaments. Although typically representing zones of weakness where gullies form, if one side of a lineament is more resistant to erosion, a ridge may be formed. An example is the northern wall of basin #1 (Fig. 5.2), where the axial lineament appears responsible for the steep basin wall. This basin also appears to be lineament bounded at the rear. The number of basin walls where lineament bounding is observed was recorded. An inspection was also conducted to visually assess the extent to which the drainage pattern of each basin is lineament controlled. Each basin was assigned a rating of poor (P), where little or no visual correlation occurs, moderate (M), or high (H), where the correlation is visually striking. In order to interpret lineament control on a stream the lineament should be persistent beyond the steam segment at one or both of its ends. A comparison is later made between this visual interpretation and the results of a more rigorous, spatial correlation (Section 5.6.6.).  64  65  Chapter 5 f/  Drainage basin analysis  lt  5.5.2 Results Table 5.2 shows the results of these examinations. The orientation of the basin axis generally corresponds to the trend of the axial lineament except in basins #16, 24 and 29 where no lineament control is reported. Several examples of basins showing lineament control are presented in stereophotos in figures 5.3 to 5.8. Although each basin is unique these illustrate a variety relations between controlling lineaments and basin axes. Figure 5.3 shows a lineament that is persistent across the photograph and controls the axis of three separate basins including sample set basin #15. The lineament/stream correlation in basin #15 is visually assessed as high while in Basin #1 (Fig. 5.2) it is moderate. In basin #22 a number of lineaments are visible on the rear and northern basin walls (Fig. 5.4) which trend parallel to the axis of the basin. Some of those visible on the rear wall disappear (and are possibly masked) on the basin floor at its axis. The establishment of lineament control is not as clear as in the two previous examples but these lineaments do appear to be correctly located and oriented and it is suggested that one of these was probably responsible for early capture of the master channel (see discussion below). Basin #14 (Fig. 5.5) appears to have at least three lineaments controlling the basin axis. The main stream is bounded by two lineaments in the upper parts of the basin. In the middle of the basin the course of the stream changes abruptly, probably to conform to some feature not immediately visible, and trends at about 40° to its original course. It then follows a trend corresponding to a third lineament. This stream course is obviously controlled by these lineaments but because of the irregular shape of the basin it is difficult to tell which of the lineaments is responsible for the basin axis. It seems likely that streams initiated higher in the basin about lineaments #1 and 2 were subsequently captured by lineament #3.  66  Chapter 5  Drainage basin analysis  Sample set #  lineament control  Lineament bounded on 'X' number of sides  1  2  3  Visually assessed Lin/stream correlation  Axial trend  Moderate  NW  High  NE  High  NW  High  NW  4  •  1  yes  2  yes  3  yes  4  yes  5  yes  Poor  E-W  6  yes  High  NE  7  yes  Moderate  NW  8  yes  High  NW  9  yes  Moderate  NE  10  yes  High  NW  14  yes  Moderate  NW  15  yes  High  E-W  16  no  Moderate  NW  17  yes  High  NW  18  yes  Moderate  NW  19  yes  Moderate  NW  20  yes  High  N-S  21  yes  High  NE  22  yes  Moderate  E-W  24  no  Moderate  NE  25  yes  High  NW  26  yes  High  NE  27  yes  High  NE  28  yes  Moderate  E-W  29  no  Poor  N-S & E-W  • • •  •  •  •/  V  •  Table 5.2. Assessment of lineament control on basin axis and headwalls.  67  Chapter 5  Drainage basin analysis  Chapter 5  Drainage basin analysis  Chapter 5  Drainage basin analysis  Chapter 5  Drainage basin analysis  In basin #16, (Figure 5.6) the main stream flows at the base of the southern wall of the basin. This wall is lineament controlled but the basin axis does not follow the line of the major stream, instead the axis trends northwest-southeast while the main stream trends approximately east-west. Basin #16 is not attributed axial lineament control. Lineament bounding is exhibited by basin #2 (Figure 5.7). To the north the basin empties into a lineament controlled valley. Both basin sidewalls are contiguous with lineaments and the basin headwall coincides with the steep, lineament controlled sidewall of basin #10. In basin #24, there is insufficient evidence of persistent lineaments, and no lineament control is ascribed. Basin #29, has two distinct drainage limbs, the distal portion of the easterly limb appears to be developed about a lineament trend but the northern limb shows no such evidence. In the case of the other large basin (#19), the basin axis corresponds closely to the trend of a syncline whose axis is near the valley floor. In summary, 20 of the 25 basins (80%) have a single clearly defined lineament controlling the position of the basin axis which is visible beyond the drainage divide. Although two of the basins (#14 and #17) have basin floors that are bounded by lineaments that do not persist beyond the confines of the basin both are included in the lineament controlled set. With this inclusion, a total of 22 of the 25 basins studied (88%) exhibit lineament control on their axis. Two basins (#16 and #24), show no lineament control and in basin #29 lineament control is limited to the end of one of the two main valleys. Many of the basins are lineament bounded on at least one side, and several on two sides. In most cases basins can be approximated by a roughly elongate, elliptical to rectangular shape. Two side walls and a headwall generally exist. The fourth possibility for lineament bounding occurs in the valley into which the basin empties. This is the case in basin #2, as shown in Figure 5.7.  71  72  Chapter 5  Drainage basin analysis  Chapter 5  Drainage basin analysis  Twelve of the sample set basin axes (48%) are oriented about a northwest-southeast axis and eleven of these are lineament controlled. Seven (28%) are developed about a northeast-southwest trend and six are lineament controlled. Four (16%) and one (4%) of the basins respectively are developed about east-west and north-south axes. One basin (#29) has two arms a north-south and an east-west arm. It was additionally determined that three basins share a drainage divide with basins developed about the same axial lineament (#'s 4, 7 and 8).  5.5.3 Discussion Visual examination of the sample set basins revealed a strong correlation between the location of the basin axis and lineaments. In total 22 (88%) of the sample set basins, appeared to have a major lineament controlling the position of the basin axis and/or the position of the major stream. Lineament control on a basin axis was inferred if there is a lineament detectable beyond the limits of the basin and conforming approximately to the basin axis. The more laterally persistent the lineament the greater the certainty that it is responsible for basin position because these lineaments tend to control other basins and are likely to represent more significant planes of weakness in the rock mass than shorter lineaments. The implication of this is that early in the formation of the drainage network the lineament fixed the position of the master channel. This may have occurred as early as the rill development stage. It has been shown (Horton 1945, Ritter et al. 1995) that the erosive force of water on a slope increases downslope where more water is available. More water also becomes available where flow is concentrated in a depression. A threshold shear strength must be reached by the water to begin plucking the rock mass and this required stress will be lower when the rock material is weaker. A lineament may provide both a small depression for concentration of flow, and a weakened zone in the  74  Chapter 5  Drainage basin analysis  rock mass, both of which make the lineament an ideal site for capture of the master channel. Once a master channel is captured by a lineament the rest of the drainage basin will initiate about this lineament. For a lineament to be a candidate for capturing an early channel the lineament should trend perpendicular to the initial slope. Lineaments capturing channels obliquely on a slope will transmit water to a lineament trending perpendicular to the slope and the flow will move preferentially to this course. This may be the case in basin #14 (Fig. 5.5). While it is likely that the more laterally persistent the lineament, the greater the weakness in the rock mass, and hence the greater the likelihood of basin development about it, structurally, the lineament controlling the basin need not persist far. In particular there is no reason why the initiating lineament should persist across the major valley which may, in itself, represent a structural feature. Considering the scale at which initial channel development occurs, it is impossible to say for sure that the lineament now seen as controlling the basin axis is that responsible for its initiation. However, whether by initiation or subsequent capture the location of the present basin axis is likely to have been lineament controlled for much of the basins existence. Dykes may represent zones of stronger rock and their added strength may steer stream channels during early stages of development causing them to run parallel to the dyke. In this sense these have the same effect as a weaker zone exploited by water.  5.6 Lineament control on drainage pattern  Howard (1967) reported on the structural control of drainage patterns and presented diagrams showing its effects. The pattern which most closely reflects that seen in small, steep basins in the study area is that of the parallel arrangement which Howard attributes to the presence of  75  Chapter 5  Drainage basin analysis  moderate to steep slopes. However, a variety of the stream patterns are seen in the sample set basins, despite their similarity in lithology. Roddick (1965, p. 140) observed locally that a number of creeks were aligned "in a manner suggesting that they follow faults". It seems intuitive that if the position of the basin axis is lineament controlled then this should also be the case for at least some of the associated drainage network. The classical view of drainage development argues for a series of streams developed parallel to the master channel by the evolution of sideslopes, and the natural tendency for water to flow downhill perpendicular to the strike of the slope. If the stream network were developed more as a function of a pre-existing component of the rock mass/landscape (i.e., a lineament) such a relationship would not necessarily develop unless lineaments were perpendicular to each other and only two lineament sets existed.  5.6.1 Method There are two means by which one can investigate the control of lineaments on the drainage pattern. A spatial correlation of lineaments and streams provides information on how closely the lineament and stream pattern in a basin are related. Alternatively, or as a supplement, the incidence angles of streams could be investigated. In the past spatial correlations between datasets were performed by time consuming map overlay techniques. The advent of GIS technology has afforded a much more effective, and simple method. The analysis described below was conducted entirely in IDRISI. The lineament image file was subjected to a distance operator that calculates the Euclidean distance between any pixel in the image and a set of target features (Eastman 1993). In this case the target feature is the lineament set. Distances are assigned to each pixel in meters. Once this is complete it is possible to manually 76  assign a color value to any given pixel based on a specified range of distances. Since the pixel resolution is 20 x 20 m, distances were classed in the following way: 0 - 20 m  (Lineament pixel)  20-40 m  (1 pixel distant)  40 - 60 m  (2 pixels distant)  In this way a buffer zone is set up around the lineaments in the IDRISI image file. An example showing the initial lineament file, and the buffer zone is shown in Figure 5.8 for basin #2. On the ground this means that distances of up to 60 m from a lineament may be included in this buffer zone since each lineament is one pixel wide. The first step in determining the spatial correlation between the two features of interest is to overlay their respective image files. Because it is assumed that the lineaments are inherent in the rock mass on which the basin is developed, it was decided to overlay the streams on the lineaments. The overlay process in IDRISI combines two images by adding their pixel values together for identical pixels in each image. One resultant image is produced with new pixel values which may be examined to determine which combination of pixel values from the two separate images exist at a particular location. For example, a stream pixel overlaying a lineament buffer zone 2 (40 - 60 m distant) will have a different pixel value in the resultant image than a stream pixel directly overlaying a lineament pixel. When the user determined values are known for each combination of overlays then the extent of the correlation may be calculated in terms of the percentages of stream pixels lying in each of four classes; Class one:  Stream pixel in isolation  Class two:  Stream pixel on a lineament pixel  Class three:  Stream pixel on a buffer zone 1 pixel  Class four:  Stream pixel on a buffer zone 2 pixel 77  Chapter 5  Drainage basin analysis  Chapter 5  ^  ^  Drainage basin analysis  the results of this analysis provide a means of determining the extent to which lineaments and streams are spatially correlated in any given basin.  5.6.2 Results Table 5.3 shows example data for one of the sample set basins (basin #2). The first column shows the four classes described above further separated into stream orders. The second column shows the stream length (in meters) of each class. To obtain the number of pixels in each class simply divide the length by 20. For example 2780 m of the stream network directly overlie lineaments. These numbers are shown as a percentage of the stream network in the next column i.e., 2780 m represents 49% of the total stream network of 5660 m. This column is again subdivided according to each class, hence 500 m of second order streams which lie within 20 m of a lineament represents 9% of the total stream network. The remaining three columns show the percentage breakdown for each stream order. For example the 1920 m of first order streams which directly overlie lineaments represent 52% of all first order steams. At the bottom of the table are the totals in terms of percentages of the entire stream network in each class. Also shown are the total lengths of each of the stream orders and the percentage of the lineament network overlain by streams. Table 5.4 shows the summarized results of the spatial correlation between streams and lineaments for all stream orders, for all of the sample set basins. Appendix V shows the results for individual basins and for individual stream orders. In each case the correlation strength cited is the percentage of the total length of, either, all stream lengths (Table 5.4), or of the total length of streams of a given order overlaying lineaments (Appendix V). For example when all stream orders for basin #2 are considered there is an overall correlation of 49%, therefore basin #2 is listed in the 40 - 49% correlation band along with five other basins which share this strength of correlation.  79  Chapter 5  Drainage basin analysis  Cone #2 Stream order/class 1st 2nd 3rd 4th Isolated lst/lin 2nd/lin 3rd/lin 4th/lin Overlying Lineaments lst+40 2nd+40 3rd+40 4th+40 Within 40 m lst+60 2nd+60 3rd+60 4th+60 Within 60 m Total stream length % on lins. % within 40m % within 60m % isolated streams % occupied lineaments  Length (m) 0 0 420 0 420 1920 860 0 0 2780 1800 500 120 0 2420 0 0 40 0 40 5660 49 92 93 7 56.47  %  0.00 0.00 7.42 0.00 7.42 33.92 15.19 0.00 0.00 49.12 31.80 8.83 2.12 0.00 42.76 0.00 0.00 0.71 0.00 0.71  %of 1st. 0.00  %of 2nd  %of 3rd  0.00 72.41  51.61 63.24 0.00  48.39 36.76 20.69  0.00 0.00 6.90  3720  1360  580  Table 5.3. Showing the spatial correlations of streams and lineaments for basin #2 overlying lineaments.  80  Chapter 5  Drainage basin analysis  Direct overlay of streams on lineaments Correlation 40-49 30-39 20-29 10-19 0-9  Basin #'s 2,3,4,6,9,20 7,18,21,25,28 1,10,14,22,26 5,15,17,24,27,29 8,16,19  Frequency 6 5 5 6 3  % 24 20 20 24 12  Cumulative Frequency 6 11 16 22 25  % 24 44 64 88 100  Frequency 1 2 4 7 5 0 1 3 2  % 4 8 16 28 20 0 4 12 8  Cumulative Frequency 1 . 3 7 14 19 19 20 23 25  % 4 12 28 56 76 76 80 92 100  Frequency 2 6 6 4 2 0 3 1 1  % 8 24 24 16 8 0 12 4 4  Cumulative Frequency 2 8 14 18 20 20 23 24 25  % 8 32 56 72 80 80 92 96 100  Within 40m (1 pixel buffer zone) Correlation 90-100 80-89 70-70 60-69 50-59 40-49 30-39 20-29 10-19  Basin #'s 2 20,25 6,4,26,28 1,3,9,10,15,17,27 7,14,18,21,22 8 5,24,29 16,19  Within 60m (2 pixel buffer zone) Correlation 90-99 80-89 70-79 60-69 50-59 40-49 30-39 20-29 10-19  Basin #'s 2,25 4,6,10,17,20,26 1,3,9,15,27,28 7,14,18,21 8,22 5,24,29 19 16  Table 5.4. Strength of correlations for all stream orders.  81  Chapter 5  Drainage basin analysis  When all stream orders are considered and a direct overlay is required for acceptance of the lineament control hypothesis, six (24%) of the sample set basins show a > 40% correlation. This increases substantially when streams within the one pixel acceptance level are taken. Then, 76% of the basins show a > 40% correlation and 56% of the basins show a > 60% correlation. Basins #2, 20 and 25 have a greater than > 80% correlation. These values again increase in the two pixel acceptance level: 72% of the basins show a > 60% correlation and 56% of the basins show correlation's at the > 80% level. When only first order streams are considered there is an improvement in the strengths of the correlations. Again six (24%) of the sample set basins show a > 40% correlation with the direct overlay, but now three (12%) of the basins are at the > 50% level with one at the > 60% level. Within one pixel, 84% of the sample basins lie above the > 40% correlation level. Basin #2 shows 100% correlation offirstorder streams and lineaments and six (24%) of the basins show a correlation of > 80%+. Within the two pixel zone, two basins show 100% correlation (Basins #2 and 4). Eight of the basins are now at the > 80% correlation level. Second order streams show an initial decrease in the strength of correlations. Only four (16%) of the basins show a correlation at the > 40% level when direct overlay is required. This number rises to 17 (68%) when the one pixel zone is used. In this class one of the basins (#2) shows a 100% correlation and 12 (48%) of the basins show a correlation at the > 60% level. At the same level 16 (64%) of the basins show a correlation at the two pixel acceptance level and three basins show 100% correlation. All of the sample set basins have first and second order streams. Only 10 of the 25 samples have third and two of the samples have fourth order streams (basins #19 and 29). For third order streams only basin #18 shows a > 40% correlation for streams directly overlying lineaments. Within the one pixel acceptance level five (20%) of the basins show correlation at the same (> 40%) level.  82  Chapter 5  Drainage basin analysis  This figure is constant for the two pixel acceptance level but the correlation for basin #18 increases from 68% to 76%. Table 5.5 shows the average percentages of streams in the sample set basins overlaying lineaments. An average of 66% of stream pixels per basin are correlated with lineaments. When broken down by lithology 71% of stream pixels correlate with lineaments in igneous basins while 46% correlate in metamorphic basins. On average for the sample set basins 51% of all lineaments correlate with stream pixels.  These numbers are respectively 57% and 28% for igneous and  metamorphic basins.  All basins Igneous basins Metamorphic basins  All si ream Ore ers mean s.d. 65.71 20.99 70.74 19.17 45.57 18.11  1st Order mean 68.47 73.21 49.52  s.d. 22.45 21.35 15.74  2nd Order mean 63.25 66.75 49.26  s.d. 26.57 26.29 22.81  3rd Order mean 37.71 51.24 17.41  s.d. 24.51 22.13 18.85  Table 5.5. Showing the average percentages of streams in the sample set basins overlaying lineaments at the two pixel acceptance level, (s.d. = standard deviation). 5.6.3 Discussion The results appear to indicate that there is a high correlation between streams and lineaments in the sample set basins. The correlation is significantly better in the igneous basins. For the whole sample set an average of 51% of the lineament length within a basin is within the two pixel acceptance level for correlation with streams (for reasons described below this is likely to be a minimum value). In other words about half of the lineament length in each basin is occupied by stream channels. This generalization is more reliable in igneous basins and less so in metamorphic basins.  83  Chapter 5  Drainage basin analysis  Nearly 73% of first order streams in igneous basins correlate with lineaments and 67% of second order channels do likewise. In metamorphic basins these numbers decrease to 49% for both first and second order streams. In igneous basins 50% of third order streams lie in lineaments. This evidence seems consistent with the hypothesis that lineaments exert a significant control on the drainage pattern. In particular this seems true of lower order streams. While it would seem initially that correlation within two pixels is imprecise, it is acceptable within limits of mapping accuracy of ± 50 m. In the field lineaments can be many meters wide, for example see Figure 4.10. When mapped on the computer differences in the selection of digitized points for streams and lineaments can be sufficient to cause the two to separate over part of their course even if they are obviously related. Neither streams nor lineaments were intentionally digitized to follow the same path in cases where this appeared to be the case. There are two problems with this means of analysis.  The main problem with the  methodology is that some pixels representing streams which should be included are missed due to sinuosity of the stream of greater amplitude than is included in the two pixel acceptance level. This is not a major problem in this analysis because few of the streams in the study area exhibit much sinuosity except where a stream meanders between two lineaments as is the case of Basin #14. Higher order streams in the larger basins present a greater risk for this kind of error but these streams are generally not well correlated with lineaments. These streams tend to be incised in glacial and alluvial deposits that mask the effects of lineaments in the rock mass. An additional error is the inclusion of pixels which should not be added to the results of the analysis. This results from locations where lineaments intersect streams obliquely. In this case the lineament has no effect on the stream in question in terms of controlling orientation. In general when a stream/lineament crossover occurs a total of five stream pixels will be counted which should not be included in the results. To solve this problem a visual assessment is made of the number of crossover 84  Chapter 5  Drainage basin analysis  points in a basin. For each crossover five pixels were subtracted from the results for the appropriate stream order. The reported correlations (Table 5.4) are best considered as a minimum correlation strength because there are a number of streams in basins which parallel lineament trends but which are not themselves seen as being lineament controlled because of the restrictions imposed on lineament mapping (Section 4.2). This appears to be the case for 15 additional stream segments from seven basins. Five basins (#5, 16, 19, 24 and 29) consistently show low correlation's between streams and lineaments. Basins #5, 19 and 29 are the largest basins in the study set and each of these basins is developed on metamorphic rocks (Basins #5 and #19) or has variable lithologies (Basin #29). Two other basins developed on metamorphic rocks (basins #14 and 21) consistently appear in the middle range of correlation values. There is, therefore, some evidence for concluding that lineament control is not as prevalent in metamorphic basins. A more compelling reason for the low correlation is the larger size and greater (inferred) maturity of these three basins. In a larger basin it may be expected that there would be a much greater variability in the possible stream courses since every point in the basin must be drained and if a suitable lineament is not available the stream must make its own course. Larger basins also tend to have flatter bottoms where streams will incise alluvial, colluvial and glacial deposits, much more so than in the high basin walls therefore, a larger proportion of the stream network will be flowing in areas where lineament effects are masked. A further possible explanation is that the metamorphic rocks on which the larger basins are developed are, softer rocks than the crystalline igneous rocks of the other basins. These, in addition to being more easily erodable, may have primary structures which obscure lineament effects. In basin #16 the main stream appears lineament controlled but it plots poorly in the correlation tables because of the location of the lineament. The lineament is mapped at the top of the 85  Chapter 5  Drainage basin analysis  divide but the entire southern wall of the basin is likely to be lineament controlled. The stream flows at its base. Unfortunately this places the stream at a considerable distance from the mapping of the lineament. This kind of error could be remedied by subjectively mapping lineaments, however the controlling effect on the stream is interpretive only (although strongly suggested), and is not known for sure. Basin #24 plots here probably because of the low number of lineaments in the basin, one of which does control, in part, the course of the major stream. In basin #24 the major stream does not follow the basin axis.  5.6.4 Directional correlation of lineament and stream trend datasets In order to separate the orientation data for lineament controlled streams it was necessary to visually determine the orientations of lineaments that controlled streams and manually separate them from the rest of the data. This could not be done automatically. 153 lineaments were visually interpreted as controlling stream segments. A rose plot (Fig. 5.9) shows the orientations of lineament controlled streams. Three notable peaks occur, approximately north-south, northeast-southwest, and east-west.  The northwest-  southeast trend occupied by the major river valleys (Fig. 3.2) appears rarely paralleled in the sample set basins. When this plot is divided between basins developed on igneous and metamorphic rocks the mean trends are broadly similar although, statistically, there is no preferred trend in the metamorphic basins. The statistical relations between the data for stream trends and lineament trends in the sample set basins were analyzed by the same statistical methods described in Chapter 4, and Appendix II. Table 5.4 shows the mean directions for the data sets relevant to this analysis. Summary data for calculations and vector statistics are presented in Appendix VI.  86  Chapter 5  Drainage basin analysis A l l lineament controlled streams  Arithmetic Plot Number of Points Class Size Maximum Percent Vector Mean Vector Magnitude Consistency Ratio igneous basins  Arithmetic Plot Number of Points Class Size Maximum Percent Vector Mean Vector Magnitude Consistency Ratio  153 5 8 21.94 26.97 0.1763  N  metamorphic basins  Arithmetic Plot Number of Points Class Size Maximum Percent Vector Mean Vector Magnitude Consistency Ratio  85 5 7  22.90 15.33 0.1803  68 5 10 20.68 11.66 0.1715  Figure 5.9. Orientation o f visually assessed lineament controlled streams for the entire dataset and for igneous and metamorphic streams individually. 87  Chapter 5  Drainage basin analysis  The overall trend of lineaments in these basins can be accommodated within that of the entire regional study site (17.43 ± 3.73°). When tested for equivalence of means the sample set lineaments are shown to come from the same lineament population as the regional data set (described in Section 4.6.3). As well as demonstrating that the sample set is representative of the overall lineament pattern in the region this shows that remapping of the lineaments in these basins at 1:20,000 scale does not alter observer bias in the orientations of lineaments mapped from the photographs. Stream segments in general show no preferred trend and neither do lineaments that control streams in metamorphic basins (Table 5.4). Neither first, nor second order streams show a preferred trend until they are split into datasets indicative of their geology (Table 5.4). Third order streams do show a preferred trend. When all stream segments are considered one might account for the lack of a preferred trend by recognizing that any particular order of stream might bias the data against a preferred trend by being randomly oriented. The distribution of the number of streams of a given order in a basin is controlled by a power law (Ritter et al. 1995). One would expect to see a relation between lineaments and streams more strongly evidenced in the lower order streams because first order streams are typically higher on the slopes (where there is little surface cover) and are more likely to have trends closely reflecting bedrock structure. Intermediate slopes containing second order streams typically show thickening surficial deposits which may mask the effects of some lineaments and allow for a more random distribution of stream orientations. Analysis revealed that second order streams have no preferred orientation, while the first and third order streams do. The trend of third order streams may be explained by lineament control of the position of the basin axis, i.e., although these streams may not flow on a lineament, or within the two  88  Chapter 5  Drainage basin analysis  # of lineaments/ segments  Mean trend + standard deviation  Lineament trends  509  11.31+17.44  Igneous basins  195  28.8±24.13  Metamorphic basins  314  0.15±20.10  Stream segment trends*  882  150.33+52.05  Igneous basins  230  20.79+43.31  Metamorphic basins  652  167.1±39.87  Lineaments visually controlling stream orientations  153  21.94+35.74  Igneous basins  85  22.9±47.42  Metamorphic basins*  68  20.68+55.98  First order stream segments*  559  147.22+56.49  Igneous basins  171  24.42±30.27 (NNE)  Metamorphic basins  388  176.37±43.98 (N-S)  Second order stream segments*  168  342.88±101.09  Igneous basins*  52  346.6+105.79 (NNW)  Metamorphic basins*  116  338.49+181.77 (NNW)  Third order stream segments  96  172.35±25.69  Igneous basins  15  200.84±30.32 (NNE)  Metamorphic basins  81  163.7+27.04 (NNW)  Description of dataset  Table 5.6. Orientation data for lineament and stream segment trends in the sample set basins. (* indicates no preferred trend in the data).  89  Chapter 5  Drainage basin analysis  pixel acceptance level (Section 5.6.1), the orientation of these streams may be closely constrained by lineaments. An alternate explanation for the apparent random orientation of all first and second order streams is the bias in the number of these streams occurring in the larger metamorphic basins. In each instance there are more than double the number of segments in the metamorphic basins. Since these basins have apparently been subject to at least two phases of lineament inducing stress (see Section 4.5) one would expect the lineaments and hence streams to have a random orientation. This also explains the lack of a preferred trend in the lineaments visually controlling streams in the metamorphic basins. When the lineaments controlling stream segments in both igneous and metamorphic basins are compared there is an equivalence which suggests a preferred lineament orientation of 21.94 ± 35.74° occupied by streams in both subsets of basins. This is from a population comprising almost entirely first order streams with an approximately 55% in igneous basins. When the trends for all first order streams in the sample set basins are compared with the trends for all lineaments in igneous basins it is found that the mean trends agree closely. This is also true of comparing all igneous basin, first order streams with igneous basin lineaments but is not true of the same comparison within metamorphic basins. This might imply that lineament control is preferred in igneous basins. There is no evidence for equivalence of means in any of the second or third stream order datasets. When the numbers are generalized to compass directions (shown selectively in Table 5.6) we see that first and third order streams in igneous basins tend to trend to the NNE whereas second order streams have a mean NNW trend (although this is not a statistically preferred direction). In metamorphic basins first order streams trend approximately north-south, and second and third order  90  Chapter 5  Drainage basin analysis  streams trend northwesterly. It is known that a northeast trend is in agreement with the Tertiary structural trend in the region whereas a northwest trend agrees with the older trend in the region. The statistical evidence suggests that there is a preferred direction for the stream segments which are visually assessed to be lineament controlled however this dataset comprises only 18% of all mapped stream segments in the sample set basins. The data suggests that the preferred direction is 21.94 ± 35.74°, and this is close to the mean trend of lineaments in the regional inventory (Chapter 4). There is no preferred trend in the data for all sample set basins. There is a preferred trend for each subset divided on lithology. The mean orientation for all stream segments in the igneous basins (20.79 ± 43.31°) is similar to that in the metamorphic basins (167.1 ± 39.87°) but these datasets cannot be shown to derive from the same statistical population. The conclusion to be drawn from this is that in the igneous basins the orientation of stream segments is strongly controlled by lineaments.  In the metamorphic basins where at least two different lineament sets have been  imprinted on one another the orientation of stream segments is consequently more varied. While the average orientations seem to agree well there is sufficient statistical variation in the samples that a test for the equivalence of means does not show a good correlation. The calculated resultant magnitude is 0.0876 and the pooled value is 0.0527. This is a difference of 0.0349 whereas other similar calculations show better correlations. Although it cannot be statistically proven it does seem that there is a preferred orientation for lineament controlled streams in the area and that this is a NNE trend which is similar to the Tertiary structural trend experienced by the region. This trend is found dominantly in first order streams and suggests that the orientation of the main streams was fixed by the Tertiary probably along the northwest structural fabric and that the lower order streams, which are responsible for headward erosion of the basins, are influenced by the more recent lineament trends (Tertiary and later).  91  Chapter 5  Drainage basin analysis  5.6.5 Stream incidence angles The spatial correlation, and the similarities in trends between stream channels and lineaments is compelling reason for accepting the hypothesis that many stream channels are lineament controlled. However, the question of natural flow paths on the hillslopes should not be ignored. One means of determining whether a stream is following the expected (i.e. due to gravity alone) path down a hillslope is to examine the junction angles of the streams to determine whether they match those predicted by the topography. To do this Horton (1945, p. 349) established the following geometric relation: Cos z = tan s /tan s c  c  s  Where z is the angle between two streams; s is the slope of the parent stream and s is the ground c  c  s  slope or the slope of the tributary stream. While this formula was found by Horton to reasonably predict stream entrance angles it was found to be too sensitive for practical use with the data collected here. The problem is the sensitivity of the formula to small variations in the measurements of the gradients in question.  This is  compounded by the fact that small changes in the ratio on the right hand side of the equation cause large changes in the angle produced on the left. This meant that when the errors in measuring the gradients of the two streams making up a single junction are accounted for, the range of angles predicted is very large, easily encompassing both the angle of incidence measured on the map and that predicted by the formula. The errors in measuring the gradient of the stream lie in the correct assignment of elevation and length. The elevation is taken as accurate to within half a contour interval and the length to within one half of a millimeter (it is customary to measure to within one half of the lowest gradation on the measuring device) which represents 25 m. As an example the junction at the western end of  92  Chapter 5  Drainage basin analysis  basin #2 is considered, (see Fig. 5.9). Both streams are judged to be lineament controlled. The data for each stream is summarized in Table 5.7. Upper elevation (m) Northern stream Southern stream  Lower elevation (m)  Maximum slope  Minimum slope  1320+20  Stream length (m) 375125  1120+20  34°  25°  1400+20  550+25  1120120  31°  17°  Table 5.7. Summary data for the two streams in the cited example.  The 'worst case scenario' that will result in the greatest range of predicted values occurs when the two most varied and the two most similar gradients are placed into the formula. These result in predicted angles of between 0 and 65°. This range encompasses the measured angle of 28°. While it is recognized that errors will be reduced over longer length streams, where a length variation of 1 25 m is less consequential, analysis of all stream intersections in basin #2 showed little improvement on the use of the formula. Additionally many streams that are lineament controlled along their entire length to the junction with a higher order stream are not long, but rather short first order features. In conclusion, while measurement of incidence angles is valuable in determining for certain whether natural flow laws are being observed or whether some other control is in effect, the sensitivity of the predicting formula is too great for the measurements made in this analysis. Accuracy could perhaps be improved by the utilization of a DEM. This would improve the accuracy of measures and could automatically calculate gradients. However it is felt that the results of the spatial overlay and of the analysis of trend data are sufficient evidence to accept the hypothesis that stream paths are lineament controlled.  93  Chapter 5  Drainage basin analysis  5.6.6 Comparison of visual assessment and automatic evaluation of lineament control on streams In order to compare the accuracy of visual assessment of lineament control on streams, the assessment reported in Table 5.2 is compared to the calculated percentage of streams that correlate with lineaments reported in Appendix V. The range of values assigned to those basins in each of the three classes in Table 5.2 is evaluated. The results are presented in Table 5.8.  Visual classification Poor Moderate High  number of basins  mean of stream/lin. correlation 33.5 55.1 78.7  2 10 13  standard deviation. 3.5 20.13 10.77  Table 5.8. Summarizing the correlation results from GIS analysis as compared to visual assessment. In order to establish the typical values for each class resulting from visual inspection the overlap of the standard deviations from each class was bisected and class ranges drawn at the midpoints. This resulted in the following classification: Poor visual correlation:  0 - 36 % of streams correlate with lineaments  Moderate visual correlation:  37 - 72 % of streams correlate with lineaments  High visual correlation:  73 - 100 % of streams correlate with lineaments  This provides an indication of the range of values that may be expected from a visual interpretation of structural control conducted on 1:60,000 scale air photos in this environment. Comparison of the data will show that basin #16, is assigned a moderate lineament control whereas the actual amount of correlation is only 19%. This is largely due to the placement error described in Section 5.6.3 (page 85). Note that basin #2, has the highest correlation at 93% (see also Figure 5.7).  94  Chapter 5  Drainage basin analysis  5.7 Regression analysis of lineament control on basin morphometry  It has been shown (Section 5.6.2) that an average 66% of the stream network is a reflection of the lineament pattern inherent in the underlying rock mass. It is, therefore, reasonable to speculate that basin morphometric parameters might also be connected to the underlying structural pattern. In order to assess the validity of this hypothesis the relation between the geometry of the basin, and the lineaments is examined by regression analysis. If the drainage network of a basin is controlled by the lineament pattern then the parameters that describe the lineament characteristics of a basin should exhibit similar relations to basin geometry as the drainage pattern.  5.7.1 Method Each morphometric parameter measured is tested against each of the other parameters by means of regression analysis performed in QPRO. The results of the analysis provide the values necessary for a regression line through the data. An example of regression output is presented in Table 5.9 (for details of linear regression see Ferguson 1976). The R value may be thought of as an assessment of the strength of the correlation, or fit, of 2  the predicted line through the data, its value is used as a guideline for further investigation. It is important to note that it is only a guideline since it is possible for R values to be dramatically 2  influenced by outliers in the data. If the R value is high, near one, then the graph is examined for the 2  presence of outliers. It is also often the case that each of the relations checked: linear; log-linear; and log-log have similar R values. In this case a graphical examination of the data is necessary to 2  correctly determine the nature of the relation. In order to investigate the data it was grouped into three datasets:  95  Chapter 5 Independent variable (X) Basin Area. Lin. Length Log(Basin A.) Lin. Length Basin Area. Log(Lin. Length) Log(Basin A.) Log(Lin. Length)  Drainage basin analysis Dependent variable (Y)  Constant  Lin. Length Basin Area. Lin. Length Log(Basin A.) Log(Lin. Length) Basin Area. Log(Lin. Length) Log(Basin A.)  4709.86 -2318010.58 -341303.51 5.92 3.64 -114485550.8 -1.23 2.31  Standard. Error of Y Estimate. 9395.06 5445861.71 25878.33 0.38 0.44 19563204.19 0.27 0.30  R  2  0.96 0.96 0.73 0.73 0.54 0.54 0.83 0.83  X Coefficient  1.69E-03 569.21 58639.89 1.24E-05 1.65E-08 32729578.9 0.81 1.02  Standard Error of Coefficient 6.80E-05 569.21 7454.04 1.58E-06 3.18E-09 6309561.4 0.08 0.10  Table 5.9. Showing the Regression Analysis of Basin Area and Lineament Length Variables.  Set one:  All data  Set two:  Basins larger than one square kilometer  Set three:  Basins smaller than one square kilometer  Matrices were compiled (Appendix VII) showing the R values for each of the data sets tested. 2  It was found that three broad groups of data showed high R values. First, sets of variables 2  related to the areal and dimensional character of the basin such as basin area, and basin width, and length in general returned high correlations, as did those of relief.  Second, there were high  correlations between parameters describing the drainage network and key aspects of the basin morphometry. Finally there were high correlations between parameters describing the lineament patterns and the same key aspects of basin morphology. A certain number of relations may be thought of as primary mathematical relations. That is where one of the attributes directly contributes to the calculation of the other. An example is the lineament density parameter, where both lineament length and basin area are required to calculate the density. In this case the lineament length should be proportional to basin area and lineament density. The former should show up as a positive correlation and the latter a negative correlation in the regression analysis. When the regression correlations for all of the sample set basins are examined 96  Chapter 5  Drainage basin analysis  (Appendix VII), it will be seen that lineament density does not correlate well with either basin area or lineament length. This is because the simple linear regression assumes that the two variables are related by a single explanatory variable (Ferguson  1976). Where the value of the independent  variable (lineament density) is dependent upon more than one dependent variable then multiple regression is required to show the relationship. No multiple regression was conducted during this research. In the case of the primary mathematical relations the influence of each factor on the other is already established by its mathematical formulation. Examination of Table 5.2. shows which of the variables are directly related mathematically. Secondary mathematical relations also exist. It is possible to rewrite some of the relations to deduce unknown values if all other values are known for example, it is possible to relate basin length and cone apex elevation in the following manner: Basin Length = (Maximum Basin Elevation - Cone Apex Elevation)/Basin Gradient However in this case all other parameters must be known by observation, since basin length is required to calculate the basin gradient. Hence many parameters can be related mathematically.  5.7.2 Results of regression analysis Before examination of individual relationships between variables, two conclusions were drawn from this analysis. First, there is a significant difference in the strength of the relations, as expressed by their variance (R ), between each of the three datasets considered. 2  With a few  exceptions the correlations are better in basins larger than one square kilometer than in either of the other datasets. Second, log-log relations are more useful because outliers bias the data in linear relationships. This is particularly the case with basins #19 and 29 which cause regression lines for linear relationships to be drawn between two groups of data points (a cluster of data at one end of the  97  Chapter 5  Drainage basin analysis  graph and two data points at the other). A trend derived from two clustered data points lacks the credibility of the log-log graphs which show a developed trend including all points. This section is split into two sub-sections the first describes general relations found by the analysis and the second compares the significant relations between the lineament and stream length and density, and other morphometric parameters of the basins.  Examination of the matrices  presented in Appendix VII will show that there are a large number of relations that have been tested (209 sets of variables for each matrix). Only a small number of variables are related. The relations between parameters which might relate directly to sediment yield are described in detail in Section 5.8: These are fan gradient and area, and basin area and relief ratio. Discussion of basin area and relief ratio is also found below. Throughout the following discussions R values are reported for the larger basins and refer to 2  log-log relationships unless otherwise indicated.  5.7.2.1 General relations There is a weak positive relation between basin area and fan area (R = 0.57) indicating that 2  as the size of the basin increases, the amount of material in the fan also increases. This is expected since the fan is the deposition site for material moving from the basin. The larger the area of the basin the larger the drainage network, and the more extensive the erosion and deposition on the fan. Basin length and basin width are strongly, positively correlated (R = 0.94) suggesting that there is a 2  tendency for basins to get wider as they become longer. Maximum basin relief and basin relief are both positively correlated with basin area (R = 2  0.63 and R = 0.69) because smaller basins tend to occur higher in the mountains. Conversely there 2  is a negative relation between the relief ratio (indicating overall steepness of the basin) and basin areal properties. Relief ratio will begin to decrease as soon as erosion begins, either by headward 98  Chapter 5  Drainage basin analysis  erosion (increasing basin length) or by relief lowering (decreasing maximum basin elevation). Hence a mature basin will have a lower relief ratio than a more youthful basin. Because of the sensitivity of relief ratio to changes in basin length or height this parameter is probably the most useful in determining the amount of erosion that has been undergone by a basin. As such we may expect a negative correlation between this parameter and the fan area. Unfortunately in each of the three datasets the relations are too poorly correlated to say this for sure but the regression indicated relation is negative (R = 0.42, 0.39, and 0.08, respectively for the entire 2  dataset, large and small basins). This is discussed more fully in Section 5.8. Basin gradient is negatively correlated with basin length (R = 0.87) and width (R = 0.82) 2  2  because increasing the area of the basin decreases its slope. Basin gradient is positively correlated with relief ratio (R = 0.99) because gradient is dependent on basin length and height. 2  In summary these observations show that increasing the areal parameters of a basin by erosion will decrease the relief ratio. This will also necessitate the removal of material from the basin which appears to increase the area of the fan. Hence these parameters (areal and relief) may be seen as a measure of the amount of material depleted from the basin. Interpreting these relations in the context of accepted landscape models it is demonstrated that as a basin increases in size, by headward erosion, the length and width of the basin increase. Headward erosion continues until the divide is reached at which point basin length and the width become fixed and erosion continues by relief lowering. This process is most clearly expressed by the relief ratio of the basin and is consistent with the Davisian model of landscape evolution. While a decrease in the relief of the basin probably occurs throughout the period of headward erosion it is only when the basin reaches the divides that it becomes the dominant process. Because of the lack of plateaus in the study area it is inferred that at the present time all basins probably have their areal parameters fixed and are only undergoing relief lowering.  99  Chapter 5  Drainage basin analysis  5.7.2.2 Relations between lineament and stream, and other morphometric parameters The hypothesis being tested is that basin morphometry is related to lineaments.  These  relations are examined in this section by comparison with the relations between the stream length and basin morphometry.  Stream length is the more classically accepted control of drainage basin  morphometry. Results of regression analysis show high R values when stream length and lineament 2  length are regressed against certain morphometric variables, these are: fan area; basin area; maximum basin relief; relief ratio; basin length; basin width; fan gradient; basin relief; and basin gradient (see figures 5.11 - 5.19). Regression equations for all relations described below are presented in Table 5.10. The log-log relationship between stream length and lineament length (R2 = 0.82) is shown in Figure 5.10. Drainage density is less clearly related to lineament length (Fig, 5.11). The two parameters are negatively correlated suggesting that a larger lineament length in a basin does not increase the length of the stream network. This is initially surprising but might be accounted for by the fact that in large basins significantly more of the basin area is taken up by surficial, valley filling materials which mask the effects of lineaments on the lower slopes and at the valley floors. Therefore the majority of the lineament length visible and available for exploitation by streams is confined to a small area of the basin on the upper slopes, hence, even if every lineament in this area is occupied by a stream the effect on the overall drainage density will be minor. In the larger basins drainage density and lineament density are strongly correlated (R = 0.89). 2  The relations between basin area and lineament length (R2 = 0.83) and stream length (R = 2  0.97) is shown in Figure 5.12. When lineament length is compared to basin area two outliers are seen in the smaller basins (basins #24, and 27). These basins are also among those with the lowest lineament density values as are basins #19 and 29 which also deviate from the major trend. When  100  Chapter 5  Drainage basin analysis  Regression equations showing the relations between lineament and stream length, and other mornhometric variables Stream length versus lineament length All basins;  Log (Stream length) = 0.72.Log (lineament length) + 0.96  (R = 0.82)  Large basins;  Log (Stream length) = 0.90.Log (lineament length) + 0.23  (R = 0.78)  Small basins;  2  2  (R = 0.0) 2  Drainage densitv versus lineament length All basins;  Log (Drainage density) = 1.02.Log (lineament length) + 2.3  (R = 0.66)  Large basins;  Log (Drainage density) = 1.36.Log (lineament length) + 0.89  (R = 0.71)  Small basins;  Log (Drainage density) = 0.19.Log (lineament length) + 2.24  (R = 0.07)  2  2  2  Basin area versus lineament length All basins;  Log (Basin area) = 1.02.Log (lineament length) + 2.3  (R = 0.83)  Large basins;  Log (Basin area) = 1.36.Log (lineament length) + 0.89  (R = 0.97)  Small basins;  Log (Basin area) = 0.19.Log (lineament length) + 2.24  (R = 0.02)  2  2  2  Basin area versus stream length All basins; Large  Log (Basin area) = 1.39.Log (stream length) + 1.05  (R = 0.97)  basins: Small  Log (Basin area) = 1.47.Log (stream length) + 0.67  (R = 0.96)  basins:  Log (Basin area) =1.31 .Log (stream length) +1.32  (R = 0.74)  2  2  2  Basin length versus lineament length All basins; Large  Log (Basin length) = 0.49.Log (lineament length) + 1.35  (R = 0.68)  basins Small  Log (Basin length) = 0.67.Log (lineament length) + 0.60  (R = 0.92)  basins::  Log (Basin length) = -0.1 .Log (lineament length) + 3.33  (R = 0.03)  2  2  2  Basin length versus stream length All basins; Large  Log (Basin length) = 0.71.Log (stream length) +0.61  (R = 0.88)  basins; Small  Log (Basin length) = 0.74.Log (stream length) + 0.49  (R = 0.91)  basins:  Log (Basin length) = 0.90.Log (stream length) - 0.01  (R = 0.03)  2  2  2  Basin width versus lineament length All basins; Large  Log (Basin width) = 0.59.Log (lineament length) + 0.82  (R = 0.88)  basins: Small  Log (Basin length) = 0.76.Log (lineament length) + 0.12  (R = 0.97)  basins:  Log (Basin length) = 0.17.Log (lineament length) + 2.21  (R = 0.23)  2  2  2  Basin width versus stream length All basins; Large  Log (Basin width) = 0.77.Log (stream length) + 0.22  (R = 0.94)  basins: Small  Log (Basin width) = 0.82.Log (stream length) - 0.01  (R = 0.95)  basins:  Log (Basin width) = 0.41.Log (stream length) +1.41  (R = 0.27)  2  2  2  Maximum basin elevation versus lineament length All basins; Large  Log (Maximum basin elevation) = 0.08.Log (lineament length) + 2.89  (R = 0.22)  basins: Small  Log (Maximum basin elevation) = 0.17.Log (lineament length) + 2.47  (R = 0.75)  basins:  2  2  (R = 0.0) 2  Table 5.10 Regression equations for relations between lineaments and stream length with other morphometric variables. 101  Chapter 5  Drainage basin analysis  Maximum basin elevation versus stream lensth All basins; Large  Log (Maximum basin elevation) = 0.lO.Log (stream length) + 2.81  (R = 0.24)  basins: Small  Log (Maximum basin elevation) = 2.48.Log (stream length) + 0.18  (R = 0.67)  basins:  2  2  (R = 0.0) 2  Maximum basin relief versus lineament length All basins; Large  Log (Maximum basin relief) = 0.12.Log (lineament length) + 2.60  (R = 0.40)  basins: Small  Log (Maximum basin relief) = 0.22.Log (lineament length) + 2.19  (R = 0.66)  basins:  2  2  (R = 0.0) 2  Maximum basin relief versus stream length All basins; Large  Log (Maximum basin relief) = 0.8.Log (stream length) + 2.42  (R = 0.53)  basins: Small  Log (Maximum basin relief) = 0.25.Log (stream length) + 2.09  (R = 0.74)  basins:  Log (Maximum basin relief) = 0.21 .Log (stream length) + 2.32  (R = 0.10)  2  2  2  Relief ratio versus lineament lensth All basins; Large  Log (Relief Ratio) = -0.37.Log (lineament length) + 1.25  (R = 0.64)  basins: Small  Log (Relief Ratio) = -0.46.Log (lineament length) + 1.59  (R = 0.80)  basins:  Log (Relief Ratio) = 0.12.Log (lineament length) - 0.36  (R = 0.06)  2  2  2  Relief ratio versus stream lensth All basins; Large  Log (Relief Ratio) = -0.53.Log (stream length) +1.80  (R = 0.82)  basins: Small  Log (Relief Ratio) = -0.48.Log (stream length) + 1.60  (R = 0.74)  basins:  Log (Relief Ratio) = -0.68.Log (stream length) + 2.33  (R = 0.40)  2  2  2  Basin relief versus lineament length All basins; Large  Log (Basin relief) = 0.17.Log (lineament length) + 2.35  (R = 0.46)  basins: Small  Log (Basin relief) = 0.26.Log (lineament length) + 1.93  (R = 0.72)  basins:  2  2  (R = 0.0) 2  Basin relief versus stream lensth All basins; Large  Log (Basin relief) = 0.25.Log (stream length) +2.07  (R = 0.64)  basins: Small  Log (Basin relief) = 0.30.Log (stream length) + 1.82  (R = 0.79)  basins:  Log (Basin relief) = 0.60.Log (stream length) + 1.05  (R = 0.40)  2  2  2  Basin gradient versus lineament lensth All basins; Large  Log (Basin Gradient) = -0.33.Log (lineament length) + 1.01  (R = 0.66)  basins: Small  Log (Basin Gradient) = -0.41.Log (lineament length) + 1.33  (R = 0.76)  basins:  Log (Basin Gradient) = -0.46.Log (lineament length) +0.12  (R = 0.12)  2  2  2  Basin gradient versus stream length All basins; Large  Log (Basin Gradient) = -0.46.Log (stream length) +1.46  (R = 0.81)  basins: Small  Log (Basin Gradient) = -0.43.Log (stream length) + 1.33  (R = 0.69)  basins:  Log (Basin Gradient) = -0.34.Log (stream length) + 1.06  (R = 0.20)  2  2  2  Table 5.10 (Continued) Regression equations for relations between lineaments and stream length with other morphometric variables.  102  Chapter 5  Drainage basin analysis  Stream length vs. Lineament length (R = 0.82) 2  1E6 £  1E5  ^ c  1E4  Ar-j,  (L>  -4—»  | 1000  < 1 km : R = 0.0 2  03  •a  2  100  i—i  10  I i 11 n |  10  Mill  100  1 1 I I I I III  1 1 I I III l|  1000 1E4 Stream length (m)  1 1 I I I III  '1E5  1E6  Log (S.L.) = 0.72.Log(L.L.)+0.96  Figure 5.10. Plot of Stream length versus lineament length. Drainage Density V s . Lineament Length (R = 0.66) 0.1 2  C  0.01  ^  ^-  P  C*  <D DO 03  —  m  < 1 km : R = 0.07 2  •  ~  2  • i 0.001  _  Q  .....^x^..*  -Zsy  > 1 km2; R = 0.71 2  1E-4 10  1—1 1 1 1 H-H  100  1 1IH| 1—1 1 1 1 UN 4 11—  1 1 1 MINI  1 h-H-H-H  1000 1E4 1E5 Lineament Length (m)  Log(D.D.) = -0.3.Log(L.L.) - 1.34  Figure 5.11. Plot of Drainage density versus lineament length.  103  1E6  Chapter 5  Drainage basin analysis  Basin Area Vs. Lineament Length (All Data: R 2 - 0 . 8 3 ) 1E9 1E8 1E7  < 1 km2; R2 = 0.19  1E6 CO  m  1E5 1E4 1000  —f  I—1-H-H+t  100  10  1—H-H-HHf-  I 11 III  1—I  I I I I l+j  1000 1E4 1E5 Lineament Length (m)  1-  1E6  Log(B.A.) = 1.02Log(L.L.) + 2.3  Basin Length V s . Stream Length (R = 0.88) 2  1E5 1E4 c 1000 c 100 10 100  -t  1—I I I I l+t  1000  t  1—I—H-H+f-  -4—1 I I I I — |  1E4 1E5 Stream Length (m)  1E6  Log(B.L.) = 0.71.Log(S.L.)+0.61  Figure 5.12. Plots of basin area versus a) lineament length, and b) stream length. 104  Chapter 5  Drainage basin analysis  Basin Width Vs. Lineament Length (R 2 - 0 . 9 0 ) 1E5 > 1 km : R = 0.97 2  2  1E4  3  1000  I  100  < 1 kiii2 R = 0.23 2  :  10 1  -i—I-H++H|  1—t-M-H-H)  10  F—+-H++H)  1—i  MINI]  i—i i i  100 1000 1E4 Lineament Length (m)  H  Hi  1E5  1—i 11111+  1E6  LogfB.W.) = 0.59.Log(L.L) + 0.82  Basin Width V s . Stream Length (R =0.94) 2  1E5  10  -+— t - H - H - H  1  1  |_)H-H ^ H  (—  -+++i  100  1000  1—I—i—I M i l l  1E4 1E5 Stream Length (m)  1E6  LogfB.W.) = 0.77Log(S.L.)+0.22  Figure 5.13. Plots o f basin width  versus a) lineament length, and b) stream length. 105  Chapter 5  Drainage basin analysis  Basin Length V s Lineament Length (All Data:R =0.76)  a  2  1E5  S  1E4  to  Cm  g 1000  > 1 kni : R =0.93 z  c |  /  < 1 km : R = 0.03 2  2  100 10  1—t—1-H-H+l  10  H  100  1—l-H-H-M-  1 1--+-H-H+I  1 1 1 1 1 1 III  1 1—I-H-H+  1000 1E4 1E5 Lineament Length (m)  1E6  Log(B.L) - 0.49.Log(L.L.) + 1.35  Basin Length V s . Stream Length ( R = 0.88) 2  1E5 S  1E4 > 1 km2 R = 0.91 2  :  g 1000 H-l c 8 100 10 100  < I km : R2 = 0.42 2  -i—i--i--t-t-i-t-|  1000  f—i—i-i-H-H-  -f—M-H-H-  1E4 1E5 Stream Length (m)  1E6  Log(B.L.) = 0.71.Log(S.L.)+0.61  Figure 5.14. Plots of basin length versus a) lineament length, and b) stream length. 106  Chapter 5  Drainage basin analysis  a  M a x . Basin Elevation V s . L i n . Length (R 2= 0.22)  10  100  1000 1E4 1E5 Lineament Length (m)  1E6  — Log(MBE) = 0.08.Log(L.L.) + 2.89  M a x . Basin Elev. V s . Stream Length (R2 = 0.24) 1E4  >  .£ 1000 in  > 1 km : R = 0.67 2  < 1 km ; R = 0.0 2  100 100  -)—H-H-H  1000  2  1 I I I II|  1—1  1  1  2  1 I I I IH  1—I  1E4 1E5 Stream Length (m)  1 I I I II  1E6  Log(M.B.E.) = 0.1 .Log(S.L)+2.81  Figure 5.15. Plots o f maximum basin elevation  versus a) lineament length, and b) stream length.  107  Chapter 5  Drainage basin analysis  M a x . Basin Relief Vs. L i n . Length (R =0.40) 2  1E4  10  100  1000 1E4 1E5 Lineament Length (m)  1E6  Log(M.B.R.) = 0.12.Log(L.L.) + 2.6  M a x . Basin Relief Vs. Stream Length ( R = 0,53) 2  1E4  § 1000 } > 1km : R = 0.74 2  2  < lkni : R = 0.10 2  B  2  Vi  m X  100  10 100  1000  1E4 1E5 Stream Length (m)  1E6  Log(MBR) = 0.18.Log(S.L.) + 2.42  Figure 5.16. Plots of maximum basin relief versus a) lineament length, and b) stream length.  108  Chapter 5  Drainage basin analysis  Relief Ratio V s . Lineament Length ( R = 0.64) 2  10 1km : R = 0. 06 2  2  > lkni : R = 0.80 2  *  2  -1  IB  0.1  -i—i  10  i Mini  100  1—i i M i n i  1—i—i—t-H-++f  1—i i i 1111|  1—i  1000 1E4 1E5 Lineament Length (m)  i i 1111-  1E6  — Log(RR) = -0.37.Log(LL)+l .25  Relief Ratio V s . Stream Length ( R =0.82) 2  10  Log(R.R.) = -0.53.Log(S.L.) + 1.80  Figure 5.17. Plots of relief ratio versus a) lineament length, and b) stream length. 109  Drainage basin analysis  Chapter 5  Basin Relief Vs. L i n . Length  (R = 0.46) 2  1E4T  10  H I M l+H  10  1 1—t—H-H+)  100  1 1 I I i I ll|  1000  1 1 I I I l+H  1E4  1 1—H  1E6  1E5  Lineament Length (m) Log(B.R.) = 0.17.Log(L.L.) + 2.35  Basin Relief V s . Stream Length  (R2=0.64)  1E4i  )  -|  100  1  1 l-t-H-H-)  1  1 H-M+H  1000  1  1 1 I I III |  1E4  1  1 l-H-H+l  1E5  1E6  Stream Length (m) — Log(B.R.) = 0.25.Log(S.L.) + 2.07  Figure 5.18. Plots of basin relief versus a) lineament length, and b) stream length.  110  Chapter 5  Drainage basin analysis  Basin Gradient V s . Lineament Length (R2 = 0.66) 10 < 1 kni2 r2 = 0.12 :  c3  o .S  1  S3 0.1  H-H+t  10  1 1 ! II  100  1 1 I I Mil  1 i I I 1 I III  1000 1E4 Lineament Length (m)  1E6  1E5  Log(B.G.) = -0.33.Log(L.L.)+1.01  Basin Gradient V s . Stream Length (R = 0.81) 2  10  < 1 km2;  O c  R2=0.19  1  0.1  —i 1—I—l-t-H-j—  100  1000  I II I I  I  1 1—  I  I  H  1E4 1E5 Stream Length (m)  1E6  Log(B.G.) = -0.46.Log(S.L.) + 1.46  Figure 5.19. Plots of basin gradient versus a) lineament length, and b) stream length.  Chapter 5  Drainage basin analysis  Figure 5.11 is examined these outliers are not apparent suggesting that even where no significant lineament network is developed, as is the case in basins #24 and 27, a drainage network develops that is sufficient to fully drain the basin. This implies that a lack of lineaments in a basin does not inhibit the formation a stream network. Increases in basin area are matched by an increases in the stream length (Fig. 5.12) however, an increase in the lineament length relies on the pre-existence of lineaments in the rock mass into which the basin expands. Lineaments may allow preferential basin growth along their course but the evidence suggests that although basin area and lineament length are strongly correlated (R = 0.83) 2  there is no required lineament length necessary for the development of a particular basin area. The typical elongate shape of a drainage basin shows that basins develop preferentially in one direction. Basin width is more accurately predicted by both stream length (R = 0.94) and 2  lineament length (R = 0.90) than is basin length (R = 0.88, and 0.76 respectively). This is shown by 2  2  comparison of figures 5.13, and 5.14. The data shows lineament length (R = 0.75) to be a better predictor of maximum basin 2  elevation than stream length (R = 0.67). These relations are shown in Figure 5.15. The regression 2  line relating maximum basin elevation and stream length is slightly biased by basins #19 and 29 which are significantly outlying from the other data. Maximum basin elevation in the entire dataset is not well predicted by either lineament length (R = 0.0) or stream length (R = 0.0) in the smaller 2  2  basins. Maximum basin relief is better predicted by stream length (R = 0.74) than lineament length 2  R = 0.66) as shown in Figure 5.16. The two largest basins (#19 and 29) may again be biasing the 2  equation of the regression line although their removal from the dataset does not significantly improve the strength of the correlation.  112  Chapter 5  Drainage basin analysis  Stream length better predicts relief ratio (R = 0.82 for all data) than does lineament length 2  (R = 0.64 all data) however in the larger basins lineament length has the higher R value (0.80 as 2  2  compared to 0.74, Fig. 5.17). The spread of data about the regression line for small basins in both plots suggests that stream length is again the better predictor although R values in both cases are low 2  (0.06 for lineaments and 0.40 for stream length). Basin relief is negatively correlated with lineament and stream length and is better predicted by lineament length in the larger basins (R = 0.72, Fig. 5.18) although the value for stream length is 2  similar (R = 0.64). Stream length is the better predictor than lineament length of basin gradient (R 2  2  = 0.81 compared to R = 0.66) in the entire data (Fig. 5.19). 2  In general lineament density does not correlate well with basin. Drainage density shows good correlation with relief ratio (R = 0.79), basin length (R = 0.82), width (R = 0.81), and 2  2  2  gradient (R = 0.79). There are no relations between either lineament density or drainage density in 2  the small basins. Where relations do exist the associated relation is invariably stronger when the linear properties are considered as opposed to the density parameters.  5.7.3 Discussion Stream length is the best predictor of basin areal parameters (basin area, basin length and basin width) when the entire data set is considered. Lineament and stream length show very similar strength correlations in the larger basins where lineament length is the better predictor of all areal parameters. Maximum basin elevation and maximum basin relief are poorly predicted in the entire data set but are reasonably predicted (by lineament length for the former and by stream length for the latter) in the larger basins. Relief ratio and basin relief are both better predicted by stream length except in larger basins where relief ratio is better predicted by lineament length. Basin gradient is  113  Chapter 5  Drainage basin analysis  better predicted by stream length except in the larger basins. It appears that while lineament length is not a better predictor than stream length of basin morphometry it is a reasonable predictor in many cases. The drainage network in a basin is developed in response to external factors, specifically climate. Although a suitable lineament will preferentially locate channels and the consequent drainage pattern is a function of the lineament network in the basin, channel network will always evolve regardless of bedrock structure and lithology. This is the primary reason why the lineament length of a basin may not be a good indicator of the morphometry of the basin. The presence of a developed stream network in the absence of lineaments is likely to bias correlations away from the lineament length and toward the stream length in places where suitable lineaments do not exist. On average only 66% of the stream network is lineament controlled the remaining amount probably has a significant affect on the strength of correlations. The stream network is a self contained, isolated network within the basin whereas the lineament network is not isolated at the drainage basin scale but persistent beyond the drainage divides and may only be isolated at the much larger scale regional scale. For example it is known that different structural patterns exist in the crustal blocks adjacent to that containing the study area (Journeay, pers. Comm. 1996). It is speculated here that small basins are likely to have their morphometry controlled by the stream pattern in the fashion classically recognized by geomorphologists. As the size of the basin increases it is more likely to be influenced by lineaments in the rock mass, hence in basins between one and approximately one hundred square kilometers, lineament length becomes more of a controlling factor and is often at least of equivalent importance as stream length. It is possible that if larger basins than these are considered (up to the scale of the major rivers) lineaments will be found to be even more important in controlling topography and morphometry.  114  Chapter 5  Drainage basin analysis  Finally there is no apparent distinction in the data examined between igneous and metamorphic basins. This is true of all of the relations examined in this section suggesting that the areal and relief parameters of drainage basins in the study area are not significantly controlled by rock type at this scale.  5.8 Investigation into sediment yield from drainage basins  One research aim was to determine whether morphometric parameters can be used to make inferences about the nature of landslide activity within the basin or if any correlations can be drawn between these morphometric parameters and sediment yield from the basin. The former is best judged from air photos. Recent debris flow and avalanche activity in a basin is apparent on these and has been noted for the sample set in Appendix III. It is recognized that not all debris flow or avalanche deposition occurs on the fan (Fannin and Rollerson 1990), some material may go into storage in the basin. However, over a long time scale much of this material should ultimately reach the fan. If sediment yield from the basin can be linked to basin or fan morphometry then only select parameters are required from a topographic map to estimate annual sediment yield. Schumm (1954) demonstrated that relief ratio could be used to estimate sediment yield. Ryder (1971a) suggested that the gradient of upper one fourth of the fan as an indicator of sediment yield from basins. Church et al. (1989) examined sediment yield from large basins in British Columbia (> 10 km ) and formulated the following expression relating basin area to sediment yield: 2  Specific Sediment Yield (Mg km" day" ) = Basin Area ( k m ) 2  1  2  115  06  Chapter 5  Drainage basin analysis  This formula provides an indirect means of calculating specific sediment yield by manipulation of the value of basin area. For this reason it was decided to investigate the relationship between basin area and other morphometric parameters that might be related to sediment yield. No attempt was made to convert basin areas to sediment yield values by the above formula. The primary obstacle in attempting a study of sediment yield in this area is the lack of calibrating data. Three studies are known on sediment yield from drainage basins in southwest British Columbia These are: Church et al (1989); Owens and Slaymaker (1992); and Millard (1986). Owens and Slaymaker (1992) provide sediment yield estimates for three small alpine basins each of drainage area less than one square kilometer. Millard (1986) provides sediment yield estimate for gullies in the Coquitlam watershed, but his study is too limited to be widely applied over the sample set basins. Although the study performed by Church et al. (1989) was conducted in British Columbia evidence in the literature suggests that relationships between morphometric parameters may vary regionally, especially where climatic changes are important, and that relations may change in basins above and below one square kilometer. The latter point is consistent with the idea that at time scales of 10° to 10 years (i.e. since deglaciation) sediment yield may not accurately measure erosion and 4  primary denudation rates in small basins but that in larger basins sediment yield will tend toward being a measure for denudation of the land surface (see Owens and Slaymaker 1993, p. 153 for a discussion). The basins examined in Church et al. (1989) study appear to be high order drainage basins, hence the basins examined in this thesis may be comparatively considered subdrainages. No basins higher than fourth order are included in the sample set. This suggests that the relationship identified by Church et al. (1989) may need modification for "sub"-drainage basins in the southwest Coast Mountains. Unfortunately there is a lack of sediment yield data with which to make these modifications.  116  Chapter 5  Drainage basin analysis  Previous literature has identified three parameters that might reflect sediment yield from a basin: fan gradient (Ryder 1971a); basin area (Church et al. 1989); and relief ratio (Schumm 1954). Although Ryder (1971a) has pointed out that fan area is not a good indicator of sediment yield because of subsequent erosion it is considered here because an initial observation of this study was the large size of the fans building into the valleys in the study area. It was initially suggested that fan area might reflect the amount of sediment output from the basin. Additionally Bull (1964) has shown basin area and fan area to be related in California for basins developed over mudstone, shale and sandstone.  5.8.1 Regression analysis of morphometric parameters related to sediment yield To investigate sediment yield in the absence of sediment yield data it is necessary to accept one parameter as definitely related to the amount of sediment leaving the basin. This parameter is chosen to be the basin area since area must depend on the amount of material removed by primary erosion (the direct weathering of the bedrock) and because previous authors have correlated basin area and sediment yield (e.g., Church et al (1989)). In this examination basin area is compared to fan area, gradient, and relief ratio. If it can be demonstrated that these parameters relate well to basin area then it can be inferred that they should also be valid measures of sediment yield. This will provide an alternative to measurement of basin area for estimation of sediment yield.  5.8.2 Results of regression analysis This section is divided into five parts based on the investigated comparisons between the parameters described above. Regression data for each analysis is presented in Appendix VIII and graphical analysis is presented in figures 5.20 to 5.28. Table 5.11 shows the regression equations resulting from these analysis.  117  Chapter 5  Drainage basin analysis Regression equations resulting from sediment vield investigations  Fan area versus Basin area All basins;  Log (Fan area) = 0.39.Log (Basin area) + 2.96  (R = 0.58)  Large basins;  Log (Fan area) = 0.38.Log (Basin area) + 3.08  (R = 0.57)  Small basins;  Log (Fan area) = -0.18.Log (Basin area) + 6.6  (R = 0.03)  2  2  2  Fan area versuslineament length All basins;  Log (Fan area) = 0.45.Log (lineament length) + 3.65  (R = 0.62)  Large basins:  Log (Fan area) =1.11 Log (lineament length) - 1.94  (R = 0.58) .  Small basins:  Log (Fan area) = 0.38.Log (lineament length) + 1.41  (R = 0.07)  2  2  2  Fan area versus stream length All basins;  Log (Fan area) = 0.56.Log (stream length) + 3.29  (R = 0.48)  Large basins  Log (Fan area) = 1.05.Log (stream length) - 1.79  (R = 0.62)  Small basins::  Log (Fan area) = -0.13.Log (stream length) + 4.02  (R = 0.04)  2  2  2  Fan area versusfan gradient All basins;  Log (Fan area) = -0.62.Log (Fan gradient) +5.01  (R = 0.46)  Large basins;  Log (Fan area) = -1.02.Log (Fan gradient) + 4.84  (R = 0.55)  Small basins:  Log (Fan area) = 0.19.Log (Fan gradient) - 1.36  (R = 0.06)  2  2  2  Fan gradient versus basin area All basins;  Log (Fan gradient) = -0.44.Log (Basin area) + 2.11  (R = 0.60)  Large basins:  Log (Fan gradient) = -0.46Log (Basin area) + 2.28  (R = 0.45)  Small basins:  Log (Fan gradient) = -0.67.Log (Basin area) + 5.44  (R = 0.29)  2  2  2  Fan gradient versus lineament lensth All basins;  Log (Fan gradient) = -0.44.Log (Lineament length) + 1.07  (R = 0.48)  Large basins:  Log (Fan gradient) = -0.73.Log (Lineament length) + 3.71  (R = 0.47)  Small basins:  Log (Fan gradient) = 0.22.Log (Lineament length) + 3.43  (R = 0.14)  2  2  2  Fan gradient versus stream lensth All basins;  Log (Fan gradient) = -0.62.Log (Stream length) + 1.73  (R = 0.61)  Large basins:  Log (Fan gradient) = -0.67.Log (Stream length) + 3.56  (R = 0.48)  Small basins:  Log (Fan gradient) = -0.49.Log (Stream length) + 2.16  (R = 0.35)  2  2  2  Fan srdadient versus relief ratio All basins;  Log (Fan gradient) = 0.1.04.Log (Relief ratio) - 0.42  (R = 0.58)  Large basins:  Log (Fan gradient) = 0.37.Log (Relief ratio) - 0.09  (R = 0.45)  Small basins:  Log (Fan gradient) = 0.24.Log (Relief ratio) + 0.53  (R = 0.35)  2  2  2  Basin area versus relief ratio All basins;  Log (Basin area) = -0.39.Log (Relief ratio) + 2.24  (R = 0.88)  Large basins:  Log (Basin area) = -0.35.Log (Relief ratio) + 1.95  (R = 0.86)  Small basins:  Log (Basin area) = -0.53.Log (Relief ratio) + 3.05  (R = 0.52)  2  2  Table 5.11 Regression equations resulting from sediment yield investigations.  118  2  Chapter 5  Drainage basin analysis  Fan area versus lineament densitv All basins;  Log (Fan area) = -1.8.Log (Lineament density) -0.11  (R = 0.02)  Large basins:  Log (Fan area) = -OALog (Lineament density) - 0.18  (R = 0.43)  Small basins:  Log (Fan area) = 0.04.Log (Lineament denstiy) - 5.19  (R = 0.12)  2  2  2  Fan area versusdrainage densitv All basins;  Log (Fan area) = -0.41 .Log (Drainage density) - 0.29  (R = 0.41)  Large basins:  Log (Fan area) = -0.46.Log (Drainage density) - 0.03  (R = 0.38)  Small basins:  Log (Fan area) = 0.04.Log (Drainage density) - 2.57  (R = 0.01)  2  2  2  Fan area versusrelief ratio All basins;  Log (Fan area) = 0.13.Log (Relief ratio) + 2.66  (R = 0.42)  Large basins:  Log (Fan area) = 0.18.Log (Relief ratio) + 2.25.  (R = 0.39)  Small basins:  Log (Fan area) = - 1.01.Log (Relief ratio) + 0.20  (R = 0.08)  2  2  2  Fan gradient versus lineament densitv All basins;  Log (Fan gradient) = -2.22.Log (Lineament density) + 0.28  (R = 0.14)  Large basins:  Log (Fan gradient) = -0.73.Log (Lineament density) + 3.71  (R = 0.47)  Small basins:  Log (Fan gradient) =..0.88 Log (Lineament denstiy) - 2.01  (R = 0.18)  2  2  2  Fan gradient versus drainage densitv All basins;  Log (Fan gradient) = -2.26.Log (Drainage density) + 0.38  (R = 0.43)  Large basins:  Log (Fan gradient) = -2.37.Log (Drainage density) + 0.31  (R = 0.31)  Small basins:  Log (Fan gradient) = 0.18.Log (Drainage density) - 2.29  (R = 0.06)  2  2  2  Relief ratio versus lineament densitv All basins;  Log (Basin relief) = 0.53.Log (Lineament density) - 2.3  (R = 0.29)  Large basins:  Log (Basin relief) = 0.74.Log (Lineament density) - 2.13  (R = 0.81)  Small basins:  Log (Basin relief) = 1.45.Log (Lineament density) - 2.4  (R = 0.40)  2  2  2  Relief ratio versus drainage densitv All basins;  Log (Basin Gradient) =1.13 .Log (Drainage density) + 2.64  (R = 0.79)  Large basins:  Log (Basin Gradient) = 0.96.Log (Drainage density) - 2.25  (R = 0.92)  Small basins:  Log (Basin Gradient) = 0.4.Log (Drainage density) - 2.37  (R = 0.27)  2  2  2  Basin area versus lineament densitv All basins;  Log (Basin area) = -0.19.Log (lineament density) -1.23  (R = 0.21)  Large basins:  Log (Basin area) = -0.28.Log (Lineament density) - 0.53  (R = 0.84)  Small basins:  Log (Basin area) = -0.81 .Log (Lineament density) - 2.24  (R = 0.23)  2  2  2  Basin area versus drainage densitv All basins;  Log (Basin area) = -0.3.Log (Drainage density) - 0.61  (R = 0.84)  Large basins:  Log (Basin area) = -0.35.Log (Drainage density) - 0.27  (R = 0.87)  Small basins:  Log (Basin area) = -0.12.Log (Drainage density) - 0.43  (R = 0.58)  2  2  2  Table 5.11 (Continued) Regression equations resulting from sediment yield investigations.  119  Chapter 5  Drainage basin analysis Fan Area Vs. Basin A r e a (R = 0.58) 2  1E7,  1E4 -1000 1E4  1E5  -H-H-H  H-t+|-  -(—\— i-H H-H+l-  1E6 1E7 Basin Area ( m )  1—i-H-mi I  1E8  1E9  2  Log(C.A.) = 0.39.Log(B.A.)+2.96  Figure 5.20. Plot of fan area versus basin area.  Fan Gradient V s . Basin A r e a (R = 0.60) 2  10 c  <D  -3  cd i-,  O c  cd  ^  < 1  0.1  km : R = 0.29 2  2  0.01 0.001  n—i-H-m|-  1E4  1E5  -H-H|  ;—i—in-m-H  -t—I-I-H+I4  1E6 1E6 1E7 Basin Area (m )  1E8  2  L o g ( F . C ) = -0.44.Log(B.A.)+2.11  Figure 5.21. Plot of fan gradient versus basin area. 120  1 — H + H #  1E9  Drainage basin analysis  Chapter 5  Basin Area Vs. Relief Ratio (R = 0.87) 2  1E9 1E8  > I km : R =0.77 2  <a CD  2  1E7 1  *—'  < 1  km : R = 0.52 2  2  <  .S 1E6 cd CQ  1E5 1E4 0.1  1 Relief Ratio  10  Log(B.A.)=-2.25.Log(R.R.)+5.82  Figure 5.22. Plot o f basin area  versus relief ratio.  Fan Area Vs. Relief Ratio (R = 0.42) 2  1E7 1E6 o3  < C HH  1E5 > I km : R =0.39 2  2  < 1 km : R =0.08 2  2  1E4 1000  i-  H  0.1  H  1 Relief Ratio Log(F.A.)=-0.79.Log(R.R.) + 5.24  Figure 5.23. Plot o f fan area 121  versus relief ratio.  1  1—I—(-  10  Drainage basin analysis  Chapter 5  Fan Area Vs. Fan Gradient (R = 0 . 4 6 ) 2  1E7-j  1E4 1000  "I  0.001  ' —  -H  1—  0.01  1 1 i i i iII|  -H  0.1 Fan Gradient  1—(-H-m-H-l  1  10  — Log(F.A.) = -0.62.Log(F.G.)+5.01  Figure 5.24. Plot of fan area versus fan gradient.  Fan Gradient Vs. Relief Ratio (R = 0.58) 2  10  c •3 O c IX,  < I km : R =0.35 2  2  0.1 > 1 km : R =0.45 2  1  0.01 0.001 0.1  -f—i—i—i—t—  1 Relief Ratio Log(C.G.)= 1.04.Log(RR)-0.42  Figure 5.25. Plot of fan gradient versus relief ratio. 122  10  Chapter 5  Drainage basin analysis  a  Fan Area Vs. Lineament length (R =0.62) 2  1E7i  1E4 f 1 000  T  1  1  I I I ll+l  10  \—f-H-H+|  1  100  t  l-HHH+ll  1  1 I I I I l-H  1  1 I I I III  1000 1E4 1E5 Lineament Length (m)  1E6  Log(F.A.) = 0.45.Log(L.L.)+3.65  Fan A r e a V s . Stream Length (R =0.48) 2  1E71E6> 1 km : 2  2  < I  1E5< 1 km : 2  R  2  =  R  2  =  0.62  0.04  1E41000 100  -i  1—I  I I  l+H  1000  1  1— 1~  -I—I  I I 111  1—I—I I I 1 1 1  1E4 1E5 Stream Length (m)  1E6  Log(F.A.) = 0.56.Log(S.L.)+3.29  Figure 5.26. Plots of fan area versus a) lineament length and b) stream length. I23  Drainage basin analysis  Chapter 5  Fan Gradient V s . Lineament Length (R = 0.48)  a  2  10 l  c cd  o [1  0.1 0.01 0.001 ^ — — • 100 10  •  H—M-H+H H-4+Hn 1000 1E4 1E5 Lineament Length (m)  1—i  i i i in|  1E6  •Log(F.G.) = -0.44.Log(L.L.)+1.07  Fan Gradient V s . Stream Length ( R = 0.61) 2  10  0.001  1  -I  100  h-l-MH-H-H  1000  -t—I I I I I M I  1 I I I I H-H  1—<  1E4 1E5 Stream Length (m)  I  1E6  — Log(F.G.) = -0.62.Log(S.L.)+l .73  Figure 5.27. Plots of fan gradient versus a) lineament length and b) stream length. 124  Drainage basin analysis  Chapter 5  Relief Ratio V s . Drainage Density (R =0.79) 2  10  Figure 5.28. Plot of relief ratio versus drainage density.  125  Drainage basin analysis  Chapter 5 5.8.2.1 Fan area as a measure of sediment yield  The hypothesis that fan area indicates sediment yield from a basin is based on an assumption that a constant proportion of the material eroded from the basin is ultimately stored in the fan and similarly a constant proportion of eroded material is transported beyond the fan.  A constant  proportion of material is also returned to storage within the basin. If this were true these values would be comparable across the region and a 100% regression correlation between basin and fan area would result. The relationship between fan area and basin area is shown in Figure 5.20. It is seen that larger basins tend to build larger fans. R = 0.58, however, this relation appears unreliable in the 2  smaller basins where there is a significantly lower correlation and identification of a trend would be difficult. The apparent increased variability in the amount of material deposited on the fans by smaller basins may be due to variation of the slope gradients on which the fans are deposited. Two fans of the same area may have different volumes. For example cones #8 and 20 are highlighted in Figure 5.20. The area of each is comparable (176,000 and 167,000 m respectively) but basin area is very 2  different. Basin #20 is twice the size of basin #8. Using the slope of the basin as an indicator of the gradient upon which the cones are built it is seen that cone #8 (slope 27°) rests at 37° and cone #20 (slope 22°) rests at 50°. For this reason in steep mountain watersheds fan area may not be a reliable indicator of sediment production. Larger fans building into flat bottomed valleys may be better for deducing relations since the depositional slope is less variable. Ideally the volume of each fan should be determined.  126  Chapter 5  Drainage basin analysis  5.8.2.2 Fan gradient as a measure of sediment yield There is a general increase in fan gradient with decreasing basin area (Fig. 5.21) Basin area and fan gradient correlate are moderately correlated (R = 0.60). This relation is best developed in 2  the larger basins. The two largest basins (#19 and 29) are the greatest outliers and have very different fan gradients. These gradients are 0.0074 (0.42°) and 0.1517 (8.63°) respectively. Fan #29 is a large fan with multiple stream channels which are capable of reworking material and lowering fan gradient. Fan #19 has a single channel building from a narrow valley. Both are fourth order basins with similar basin slopes (8° and 9° respectively). Ryder (1971a) suggested that only the top one fourth of the fan gradient may accurately predict sediment yield. There is insufficient accuracy on the topographic maps chosen for this study to better evaluate fan gradient.  5.8.2.3 Relief ratio as a measure of sediment yield Basin area and relief ratio show excellent overall correlation with relief ratio increasing as basin area decreases. R = 0.87 for the entire data set (Figure 5.22). This suggests that relief ratio is 2  a good predictor of sediment output from both large and small basins and is consistent with the observations of Schumm (1954). There are no significant outliers in the data.  5.8.2.4 Relations between fan area, fan gradient, and relief ratio All relations between fan area (R = 0.0.42 for the entire dataset), fan gradient (R2 = 0.58 for 2  the entire dataset) and relief ratio are poor reinforcing the idea that fan area is not a good indicator of sediment yield (Figures 5.23 and 5.24). Figure 5.25 shows fan gradient vs. relief ratio (R = 0.58 for 2  the entire data set). The graph indicates that as relief ratio decreases, in larger basins, the fan gradient also decreases, consistent with the view that large basins build gentle fans.  127  Chapter 5  Drainage basin analysis  5.8.2.5 Lineament length and stream length as predictors of sediment yield Lineament and stream length were examined in comparison with fan area and gradient. Fan area shows moderate correlation with lineament length (R = 0.62, for the entire data set) but the 2  relation is weaker with stream length (R = 0.48, for the entire data set) as shown in Figure 5.26. If 2  fan area were a reliable indicator of sediment yield a good relation would be expected since both parameters correlate extremely well with basin area (R = 0.83 and 0.97 for the entire data set, for 2  lineament length and stream length respectively). However, fan area appears the least successful indicator of sediment yield except at a gross scale (a large fan generally indicates large sediment output from the basin). It is therefore difficult to explain this high correlation. It may be that the larger the stream length in a basin the more power the major stream has to remove material from the basin to the fan. Additionally larger stream channels on the fan are likely to be less susceptible to avulsion, characteristic of small, and sometimes debris flow dominated fans. Lineament length is highly correlated with the stream length (R = 0.82 for all basins and 0.97 in the larger basins, see 2  section 5.7.2.2) largely due to the extent to which the stream network occupies the lineament pattern in a basin. It is likely that a larger lineament network provides more localities for erosion. This is consistent with the hypothesis that lineaments are zones of weakness in the rock mass which provide sites for erosive and wasting processes such as freeze-thaw and rockfall (see Section 4.4) and thus increase the rate of primary erosion in a basin. Hence the larger the lineament network the larger the stream network may be and the more opportunities that may exist for sediment to be introduced to the stream network. Although fan area is thought not to be a good sediment yield indicator it does seem to correlate well with lineament length and reasonably so with stream length. Lineament and stream length are compared to fan gradient in Figure 5.27. Stream length is the stronger correlating parameter because a larger developed stream network in a basin is likely to 128  Chapter 5  Drainage basin analysis  develop a larger, alluvially dominated, low gradient fan. In the smaller basins processes other than alluvial may be responsible for deposition on the fan. In particular the fan may be dominated by debris flow activity and such fans have been shown to be generally smaller and steeper than alluvially dominated fans (for example Kochel 1990, Stanistreet and McCarthy 1993). The initially surprising relation is that fan gradient decreases as lineament length increases. This obscures the fact that although there is a greater potential for erosion and possibly more potential for debris flow and avalanche activity in small basins (see Chapter 6) there is also less likelihood of these reaching the fan and being responsible for primary deposition on the fan, which will be alluvially dominated. Fan area; fan gradient; relief ratio; and basin area, were examined in relation to both lineament and drainage density, only the relation between relief ratio and drainage density showed a strong correlation (R = 0.92 in the large basins, Fig. 5.27). This is consistent with the findings of 2  Schumm (1954). In general the drainage density is highest in basins with a higher relief ratio.  5.8.3 Discussion This analysis was based on the assumption that sediment yield is related to basin area. In the absence of available sediment yield data for the sample set basins the parameters of fan area, fan gradient, and relief ratio were compared to basin area. Additionally described were the relations between these parameters and stream and lineament length. A good correlation with basin area would suggest that a parameter provides an alternative to measuring basin area for estimation of sediment yield. If the hypothesis that basin area is a predictor of sediment yield is accepted then the following conclusions can be inferred from the analysis described in this section: 1)  Fan area is not a good predictor of sediment yield;  2)  Fan Volume might prove a better predictor;  129  Chapter 5 3)  Drainage basin analysis  Fan gradient is a slightly better predictor of basin area than fan area and may be improved if the assertion of Ryder (1971a) can be investigated;  4)  Relief ratio appears to be the best predictor of basin area and by inference sediment yield (R  2  = 0.86 for all basins); 5)  Sediment yield is perhaps best predicted by relief ratio for basins larger than 1 km (R = 2  2  0.88). Lithology may have implications for the sediment yield from a basin (for example see Schumm 1954) however since almost half of the larger basins are metamorphic there is insufficient data to separate lithologic effects in this analysis. Additionally these analysis do not permit identification of factors which would identify a basin's potential for increased sediment yield due to debris flow or avalanche activity. They also do not permit identification of the amount of each parameter due to contemporary process (as opposed to early post glacial increased process rates). For this reason for accurate prediction of sediment yield relations must be calibrated for the present with field measures of sediment yield as attempted in the study by Church et al. (1989).  5.9 Summary and conclusions  Analyses were conducted into the effect of lineaments on drainage basin position, the drainage pattern, basin morphometry and sediment yield. A sample set of 25 basins was used for these investigations. In 22 of the sample set basins the position of the basin axis was found to be lineament controlled. This result is interpreted as indicating that during initial development of the drainage basin a lineament provided the necessary topographic depression for concentration of surface water flow into a master rill and subsequently a main stream channel. These have deeply  130  Chapter 5  Drainage basin analysis  incised the lineament in question forming a basin. This has been facilitated by the fact that lineaments are zones of weakness in the rock mass. A spatial correlation was performed in IDRISI to determine the extent to which the drainage pattern mirrored the lineament pattern in a basin. An average 66% of streams are found to overlay lineaments in the sample set basins. These values were respectively 71% in igneous basins and 46% in metamorphic basins.  Additionally the directional correlation between lineament and stream  segment trends was investigated. Preferred trends were found for stream segments in each subgroup (igneous and metamorphic) of basins and streams occupying lineaments have a preferred trend of 22 ± 36°. This value is close to the preferred lineament trend in the sample set basins 11 ± 17°. Both trends approximate the orientation of the Tertiary structural trend developed in the region. It was found that the preferred trend of third order stream segments (172 ± 26°) trends agree well with the dominant lineament trend consistent with the idea that lineaments control basin axis position. It is speculated that low order streams are concentrated primarily in the younger lineaments since major drainages probably initiated along the oldest lineaments (Cretaceous, northwest trending lineaments) for example, the major rivers in the area. It is concluded from these investigations that lineaments strongly influence the stream network developed in the study area. The reason for this is that lineaments represent a network of weakened zones emplaced in the rock mass by tectonic stresses operative since the Cretaceous. Water has provided the forces necessary to exploit this network. Regression analysis of allometric relations between morphometric parameters showed that while stream length is often the better predictor of morphometric parameters, the lineament length is also a good predictor. This is especially true in basins larger than one square kilometer in area. Investigation was conducted separately into the entire data set and then two subsets: large and small basins. This was based on the observation of Owens and Slaymaker (1992) that sediment yield 131  Chapter 5  Drainage basin analysis  characteristics of basins larger and smaller than this area are different. The evidence of this study seems to support this in that in many cases relations are poor in the small basins while in larger basins good correlations are observed. The relations between basin morphometry and sediment yield were reported. In the absence of suitable sediment yield data for the study area it was necessary to assume that the parameter of basin area was related to sediment yield. This assumption is supported by the relation established by Church et al. (1989), however it is likely that this relation would need to be refined with sediment yield data taken from within the study area. This is because it has been shown in the literature that relations vary regionally especially where climate is variable. It appears from this investigation that relief ratio is a good predictor of basin area. This is true for both the large and small basins and appears consistent with the idea that in small basins sediment yield increases with lower elevation (Owens and Slaymaker 1992). Fan gradient is also a reasonable predictor of basin area but fan area proved inappropriate. The area of the fan was initially believed representative of the volume of material leaving the basin. Fan area is well predicted by both lineament length and stream length as is basin area.  Examination of lineament effects on drainage basins leads to the proposal of the  following hypothesis: The lineament network is not isolated at the scale of individual (1st through 4th order basins) but may be at the regional scale. Because small basins may not be large enough to include a significant proportion of the regional lineament network it is likely that streams play a much more important role in drainage basin development than lineaments at this scale. When basins with areas between one and one hundred square kilometers are examined it is found that lineaments and streams reveal approximately equivalent correlation strengths when compared to other morphometric parameters of the drainage basin. Significantly at this scale much more of the regional lineament pattern is included in the basins.  132  Chapter 5  Drainage basin analysis  Finally, although not investigated, it appears that at the regional scale the lineament network may be more responsible for topography than the drainage network in the southwest Coast Mountains. For example, the trends of the major rivers seen in Figure 3.2 follows the northwest lineament trend. Convenient boundaries for the regional scale exist locally in the form of a number of joined, but distinct crustal blocks. Additionally, it has been recognized that "strain concentration along a series of strain-weakening zones in an orogen produces the first harmonic pattern of ridges and valleys in the complete absence of erosion" (Koons 1995, p. 399). It is inferred that the major valleys in the study area are developed along major lineaments. Although these are not visible on air photo because of the dominance of surflcial materials, it is likely that mapping from higher altitude imagery would reveal these as lineaments on the basis of the nearly straight alignment of the river network. It is concluded that the proposed hypothesis is consistent with the latest ideas on the topographic evolution of collisional belts. The evidence suggests that lineaments provide a focus for the development of the drainage network. As well as being zones of weakness in which water will preferentially erode they appear to have provided topographic low points for initiation of drainage basins. It is possible that lineaments quickly captured the master rills that will have developed on slopes from the divide soon after these slopes formed by tectonic means. The paths of the major drainages in the study area follow the regions oldest developed structural trend. It is also the pattern predicted by Koons (1995) of a ridge valley system parallel to the dominant fault and orogen strike. It seems clear that the drainage pattern and the consequent basin forms have developed as a result of the structural patterns tectonically emplaced on the landscape of the southwest Coast Mountains.  133  Lineaments and landslides  Chapter 6  CHAPTER 6.  LINEAMENTS AND LANDSLIDES  6.1 Introduction  Savigny (1996) and Leir (1995) have demonstrated a relationship between lineaments, large rock landslides, and mountain slope deformation in southwestern British Columbia. Chapter five has shown that relationships exist between lineaments and contemporary geomorphic processes. One such process may be small surficial landslides (specifically debris flows and debris avalanches) which are ubiquitous in the study area. This chapter examines these relationships further by presentation and investigation of two landslide inventories; Large rock landslides were identified on 1:60,000 scale air photos as part of this work. Small surficial landslides were identified in an area of 132 km located in 2  the southern portion of the study area by a study commissioned by the GVRD and conducted by Dr. J.M. Ryder of J.M. Ryder and Associates, Vancouver, B.C. This chapter begins with presentation of the large rock landslide and mountain slope deformation inventory and description of key sites then reports the investigation of small surficial landslides. Conclusions are presented about the nature of landslide activity in the study area along with a comparison of findings with those in the neighboring Fraser Valley where similar studies have previously been conducted, e.g., Savigny (1996) and Leir (1995).  134  Lineaments and landslides  Chapter 6 6.1.1 Large rock landslides and mountain slope deformation  It is important to study landslides and mountain slope deformation in the region because it is known that lineaments play a major role in the evolution of landslides in the adjacent Fraser River valley (Savigny 1996, Leir 1995). Lineaments are the primary focus of this thesis and it is desirable to know if similar relations operate in this study area. The primary benefit of a landslide inventory for this area is that it allows the assessment of hazard distribution in the area which has potential implications for regional hazard zonation. For example, areas where slope deformation is suspected may yield future failures. In conjunction with lineament mapping, described in Chapter 4, each air photo was investigated for landslide activity and slope deformation. These were recorded in an inventory style complementing the Fraser River valley study by Dr. K.W. Savigny (Savigny 1996), only failed slopes and slopes exhibiting evidence of gravity induced deformation are included.  6.2 Airphoto identification of landslides and mountain slope deformation  The air photo identification of landslides is described in Leir (1995). In this study air photos were examined for landslide scars, and rubble filling valley bottoms. Slope deformation is harder to identify. Uphill facing (antislope) scarps are characteristic of this type of deformation. These scarps have been described as "...typically between 1 and 6 m high..." and being "...located downslope of anomalous ridge-top troughs" (Bovis 1982, p. 804). These troughs are thought to represent either infilled tension cracks, small graben like structures, or small faults. Tension cracks and downslope scarps are also common. Scarps will typically trend either parallel to the ridge crest or transverse to a mountain flank. Additionally some slopes may exhibit bulging near the toe of the slope. This again indicatives slope deformation. 135  Chapter 6  Lineaments and landslides  6.3 The landslide and slope deformation inventory  Landslides were inventoried in the area extending from approximately 122° W. to 123° 25' W. and from 49° N . to 50° N . an area of approximately 10,900 km . Rock avalanches were the 2  features most commonly identified in the inventory along with mountain slope deformation. Further large landslide types include landslides in surficial deposits adjacent to major rivers and large rockfalls. Twenty sites were identified in the inventory, the site density is therefore 0.0018 sites/km if 2  all features are considered.  Considering only bedrock features the landslide density is 0.0017  landslides/km . Further, considering only bedrock failures the density is 0.001 landslides/km . 2  2  All landslides are assumed to have occurred postglacially, i.e., in the last 10,000 years because glaciation would have removed evidence of pre-glacial landslide activity. Assuming equal temporal distribution of bedrock failure one landslide will have occurred every 910 years however this figure does not take into account repeated failures from a single site or the possibility that a single triggering mechanism such as an earthquake might have simultaneously induce a number of failures. This has been shown to be the case with a number of rock avalanches in neighboring Washington State (Schuster et al. 1992). Failures in Quaternary sediments are more common often with many small failures producing a single large failure zone. The twenty sites highlighted in the study area are shown in Figure 6.1. Six of these have been previously reported and are only briefly mentioned here with references for further investigation. These are: Site #l:Dickson Lake landslide (Evans 1986); Site #3: lower Coquitlam River (Thurber Engineering Ltd  1985); Site #14:Goat Ridge (currently monitored by Thurber  Engineering Ltd., Vancouver); Site #18: Cheekye Ridge (Thurber Engineering Ltd. and Golder  136  Chapter 6  Lineaments and landslides  122  123 2 5 V  50 N  V  50 N  10 Kllemeters  0  10  20  30  40  49 N  49 N 0  /  123 25 W  122 W  Figure 6.1. Showing sites identified in the landslide and slope deformation inventory: l=Dickson Lake; 2=West Norrish Creek; 3=Lo\ver Coquitlam River; 4=Lower Seymour Valley; 5=The Lions; 6=Chehalis River; 7=Bivouac Mountain; 8=Anne Lake; 9=Stave River I; 10=Stave River II; ll=Mount Bonnycastle; 12=Winslow Lake; 13=Winslow Creek; 14=Goat Ridge; 15=Mamquam River; 16=Shale Creek; 17=Bremner Creek; 18=Cheekye Ridge; 19=Rubble Creek; 20=Mount Mason. 137  Chapter 6  Lineaments and landslides  Of the remaining fourteen sites, three represent prehistoric, and now well vegetated, landslides. Six appear as fresh rock avalanche or rockfall debris, four sites exhibit evidence of rock mass deformation and one is the site of slides in surficial materials adjacent to a river. The inventory is presented in Table 6.1. Exact locations and air photo numbers are shown in this table along with a brief description of the feature. Of the sites previously reported all but one (Site #20: Mount Mason) is near human development.  While logging is ubiquitous throughout the area urban growth and transportation  networks are restricted to the western and southern margins of the region. Accordingly known landslides lie mostly in the these areas. One site (the Cheekye, #18) was discovered by development investigations.  6.3.1 Examples of lineament control on large rock landslides and mountain slope deformation Discussion of five of the sites from the inventory is presented below. These sites were chosen to best illustrate the relationship between lineaments and landslides and mountain slope deformation. They also illustrate the variety of ways in which lineament control on large rock landslides and mountain slope deformation is manifested.  Appendix IX provides additional  discussion of some of the sites. Dickson Lake (site #1, Fig. 6.1) is the site of a landslide dam caused by a rock avalanche reported in Evans (1986) and Clague and Evans (1994). This slide is shown in Figure 6.2. The area of the slide is 971,280 m and the estimated volume is 25.59xl0 m (Evans 1986). The slide 2  6  3  occurred in granodiorite of the Coast Plutonic Complex and has not been accurately dated. The material forming the dam is large, blocky, and has been only partially revegetated, the main scarp is clearly visible.  A discussion of the stability and draining characteristics of landslide dams in  different materials are found in Evans (1986) and Clague and Evans (1994).  138  Lineaments and landslides  Chapter 6 B--2  oo .5 e  3  1J  e  •o -°  i -3 5  C  DO  *5.s „ .3 § S  E  u 3-2 ^, ~ >*.ts oo  IS  a§ s e-  •a u S oo = oo •= .S  " .s .s b  g .o >< c in « - ° rSw  3 «, 3 £ "5 K S3 2 'C . -P C  £ 2  o  8 3 |  5  U  u  .s 1. •2 »3 c  •a s  U  3  E  o  <u "S3  «*  ^  ft  6S CO  U  1 E  8  3  O § o  1  1 § Uo cr S  1  o § O or  a g,  H 3  5 e » a  oo »o  00  to =tt  01  5t  CJ  aa  2  0\  00  CQ  *  oo os  <7v CQ  %  CQ %  aa 52  o  139  aa %  aa 5t  s  o  I  «a c5S  Lineaments and landslides  Chapter 6  ,3 § • ? h€ 1 8. « S "5  1 «  "  I  !  a  S" 8  c  o  «  >  •- a Jc S > P  s -5  1-1  3  2  I  Is  U  s  d>  3 -S - 5 2  « w ^ t« -o o  5  <u  T3  <U  -5>  s£ at  2 » 2 » .2 -S  £ o .2 o  tU  8 :•§ •= S» »  1 ""53 L3 is I E  5 J3  o  a  > \3  .3  I 3 JCe re  irt  w O  S  CQ  l « a .2  O —  0\  u  •s « £^E e« se  •i 8  —  i "2 c  | §c 1 «  U  S o *  P -5 5  •i * a0 0 o  £ -3 • < '  Kir  111  in "S <^ . C QO 3 •  5 M  « .5 E  §i  < -5  O 1»  1 ^1 2u  s o 5=  M-l  o  W  U a-  3 O  1 DO  £  U  a-  o g  U a-  js -aI O •£  ll  J ^ 5 S <» 2 §• s 2 o o c a- a co 1? »i  —  c  o S  •- u « § £-c ti  iu  1 ^  <J a0  -J H 3  sc  00  o 00  ^ a  (S  00  r>  00  w-i  CQ  at  00  3*  11  00  140  00  03 5t  o  CN  is => 00 < 5t  CC as  MS DO 5t  Chapter 6  Lineaments and landslides  Chapter 6  Lineaments and landslides  This landslide and the adjacent site at West Norrish Creek (discussed below) show clear evidence of lineament association. The headscarp of the Dickson lake slide appears to be lineament controlled with the landslide being located at the intersection of a north-northwesterly trending and a northeast trending lineament. The northeast trending lineament is persistent to the West Norrish creek site where it appears to be influencing slope deformation. The proximity of these two features indicates that landslides and mountain slope deformations can occur in the same area and that mass movement features are not always isolated events. Additionally this site demonstrates the potential of following lineaments to locate landslides. This technique yielded good results during inventory mapping. Having identified the Dickson Lake landslide the two lineaments contributing to its headscarp were traced and the second site discovered. To clarify the air photo interpretation of the stereophoto in Figure 6.2, an additional map of the features is included in Figure 6.3. The West Norrish Creek site (site #2) occurs 1-2 km west of the Dickson Lake slide. Two prominent antislope scarps are seen on the southwest face of the peak in question. The lower scarp is contiguous with the northeast trending lineament described above. It is possible that the preexistence of this lineament was responsible for focusing of slope deformation at the site. This lineament forms approximately half of the headscarp of the Dickson lake landslide. Further evidence of deformation was found at the site. Figure 6.4 shows the side of the mountain with the major lineament indicated. Close examination revealed evidence of extension including the presence of open joints and apparently down faulted blocks (Figure 6.5). This slope is deforming toward the southeast but appears presently inactive. Site #5 is on the slopes below The Lions in the Capilano watershed. The southern flank of the eastern Lion is cut by three antislope scarps bisecting the ridge and trending parallel to the main  142  Lineaments and landslides  Chapter 6  Creek  1 km approx.  Figure 6.3. Interpretation of Dickson Lake landslide and West Norrish Creek mountain slope deformation. Note: traced from air photo 15BCB87098-156. 143  Chapter 6  Lineaments and landslides  Figure 6.4. The southern slope of the west Norrish Creek site showing the major lineament described in the text. The location of Figure 6.5 is indicated. 144  Chapter 6  Lineaments and landslides  Figure 6.5. An opening (extension joint) along the course of the major lineament at the West Norrish Creek site. 145  Chapter 6  Lineaments and landslides  ridge (Fig. 6.6). They also form a part of a more persistent lineament seen trending eastwards. It appears that the slope is peeling away in a toppling motion. A possible interpretation is shown in Figure 6.7. The rear scarp is actively shedding sediment backward onto the slope although whether this suggests current deformation or is simply due to increased exposure due to opening is unknown. Each of the other two antislope scarps is shedding some material to the sides of the ridge but not in the quantities of the third. It may be significant that the uppermost scarp appears active since this would be the most recently opened. These lineaments also control headward erosion of first order streams. These accelerate removal of material from the lineament zone and may be affecting the stability of the feature by increasing hydrostatic pressure in the lineament zones. Site #7 (Fig. 6.8) also occurs within the GVRD watersheds. Bivouac mountain appears to be the site of a prehistoric landslide that may once have dammed the Seymour River. The headscarp appears to be still shedding material to the slope below. A portion of the base of the slide is still vegetation free. Seymour River dramatically narrows as it passes through the debris and significantly alters its course upon reaching the debris limits. Of significance are a number of lineaments shown above the headwall and the presence of some antislope scarps. Goat Ridge above Britannia Creek (Site #14) is currently being monitored by Thurber Engineering Ltd. of Vancouver (Hungr pers. comm. 1996). A large number of lineaments cross the ridgetop and some antislope scarps are visible on the slopes above the confluence of Britannia Creek and the tributary from Sky Pilot Mountain (Fig. 6.9). Site #15, on the Mamquam River northeast of Squamish is a large-scale feature approximately 2 km of the hillslope appears to be slumping into the valley (Fig. 6.10). After discovery of this site it became the subject of a directed studies project by Mr. Phil Scalia at the Geological Sciences Department, University of British Columbia, Vancouver, Canada, (Scalia 1995)  146  Chapter 6  Lineaments and landslides  147  Lineaments and landslides  Chapter 6  Figure 6.7. Possible interpretation of mountain slope deformation on the southern face of The Lions in the Capilano watershed. The current state of activity at the site is unknown. 148  Chapter 6  Lineaments and landslides  Chapter 6  Lineaments and landslides  151  Lineaments and landslides  Chapter 6  under the supervision of Dr. K.W. Savigny. Mr. Scalia concluded that the slope had moved by mass rock creep as defined by Chigara (1992).  Figures 6.11a and 6.11b are two of Mr. Scalia's  photographs showing an antislope scarp and graben, and high angle jointing in the rock mass, both features typical of this kind of deformation. Site #18 is the Cheekye Ridge. The headwaters of Cheekye River are sourced in a large amphitheater-shaped excavation into the western flank of Mount Garibaldi (Figure 6.12). This large feature represents a massive landslide scar created by multiple failure events (Evans  1991).  Cheekye fan at the confluence of the Cheekye and Squamish rivers is known to be the deposition site for the rubble resulting from the collapse of the mountain flank in a series of volcanic debris avalanches (Evans 1991, Evans and Savigny 1994). The potential for further movement appears to exist, and this possibility has been investigated in a joint report by Thurber Engineering Ltd. and Golder Associates Ltd. (1993).  Modeling of potential run out from a future failure has been  conducted by Hungr (1995). Several features are highlighted in Figure 6.12. Attention is drawn to the northern front of the ridge which shows a feature that may represent slumping. Scarps reveal where sagging may be occurring. There is no obvious accommodation of this feature near the toe of the slope, however, in most cases early movement is accommodated by compression and bulging in the rock mass (Hutchinson 1988). Additionally a cracks visible near the ridge top and are indicated by the arrows.  6.3.2 Discussion Two of the twenty sites examined in the inventory are recognized for their potential hazard by the geotechnical community in Vancouver. These are the Cheekye Ridge and Goat Ridge sites. It is sometimes believed that at sites where failure has previously occurred the risk of further failures is  152  Chapter 6  Lineaments and landslides  Chapter 6  Lineaments and landslides  Chapter 6  Lineaments and landslides  reduced. This is not necessarily the case on slopes where further deformation features such as tension cracks and antislope scarps are visible behind or near the existing headscarp. Such evidence is traditionally recognized as representing the possibility of further retrogressive failure at a site. Sites where evidence of slope deformation is found are particularly difficult to assess on air photos. Bovis (1982) cites local factors such as structure, lithology, and seismicity as being controls on the amount of deformation that a slope will experience. He also reports that "...many antislope scarps do not appear to be actively evolving at present" (Bovis  1982, p. 804), however such  interpretation is difficult from air photo and it is likely that many sites in the southwest Coast Mountains have not received ground investigation. It is suggested that the removal of glacial ice reduces support for the valley walls allowing relaxation to occur post deglaciation. Apparent inactivity may imply that the slopes have reatained an equilibrium condition however while the initial disequilibriating effects of deglaciation may have been naturally remediated it is likely that cyclic reactivation of these features occurs by seismic shaking (Savigny, pers. comm. 1996) There is obvious relation between lineaments and landslides at several sites in the area, most notably the headwall of the Dickson Lake slide. One of the two lineaments that converge at this locality is traceable to the area of deformation at the West Norrish Creek site. The antislope scarps below the Lions are also a part of a major lineament traceable for some distance beyond the affected slope. A lineament is also found in the headscarp of the small rock avalanche in the Seymour watershed. It seems that lineaments can both cause and result from slope deformation and landsliding. In the case of Dickson lake it is suggested that the lineaments have controlled the headscarp position. This is similar to findings in the Fraser Valley where lineaments have also been shown to control  155  Chapter 6  Lineaments and landslides  failure position (see Savigny 1992, and Leir 1995). At the west Norrish creek site the lineament seems to be the focus about which deformation is occurring. If the lineament represents a fault, or a large joint plane at the site of the Dickson Lake slide it represents a plane of weakness subsequently occupied by the headscarp. At the West Norrish Creek site gravity induced extension is apparently focused about the lineament. Gravitational displacement alone can account for some lineaments such as those in the wall above Winslow Creek where antislope scarps are mapped as small lineaments. Also at the Cheekye Ridge and Britannia Creek sites ridgetop cracks and antislope scarps have produced mappable lineaments. At Rubble Creek the columnar jointing provided a headwall for the volcanic debris avalanche.  These features are joints not apparent on 1:60;000 scale air photos but which do  represent small lineaments which would be detectable in the field.  6.4 Investigation into lineament control on small surficial landslides  It has been recognized (Seidl and Deitrich 1992) that debris flows and debris avalanches (defined earlier as small surficial landlsides) are a primary erosive agent in steep mountain stream channels. It has also been pointed out (Davies et al. 1992) that debris flows are typically associated with unstable gully sidewalls, and that these may represent fault crush zones.  It has been  demonstrated in the previous section that large rock landslides and slope deformation are commonly associated with lineaments. Results of the following investigation indicate that there may be a relation between lineaments and small surficial landslides. Many debris flows and avalanches in the southwest Coast Mountains occur at the impermeable interface between the lodgment and basal layers in the vashon till. This surface also presents a limit to root penetration. Some events also occur at the till/bedrock interface.  156  Chapter 6  Lineaments and landslides  While lineaments clearly influence bedrock failure, their relation to surficial landslides is less obvious. Small surficial landslides may be related to lineaments for the following reasons: 1)  Lineaments form gullies in which surface and subsurface water can concentrate;  2)  Bedrock weakness in lineament zones often leads to oversteepened gully walls;  3)  Small bedrock failures caused by bedrock weakness often occur on oversteepened gully  walls and can trigger debris flows. Once initiated, small surficial landslides move preferentially into the nearest gully. Here, they either continue to flow as a torrent or exhaust their momentum and fill the gully with debris which remains in situ until flushed by a subsequent event or re-mobilized by water. Often such an event will dam a creek and subsequently become re-mobilized under a larger hydraulic load. Because debris flows are a primary erosive force they are themselves responsible for exposing deeper portions of the lineament and steepening gully sidewalls, thus the process of gully erosion by means of landsliding is likely to periodically repeat itself.  6.4.1 Method of investigating the correlation between lineaments and small surficial landslides An inventory of surficial landslides was compiled for the GVRD by J.M. Ryder and Associates, Vancouver, BC, as a part of the watershed ecological inventory currently underway in the three GVRD watersheds. A total of 1203 landslides were mapped on air photos from 1957 onward. A DBASE (database software from Borland) catalogue of slide attributes contains information on the terrain polygons (mapped according to the terrain classification system for British Columbia, MOE Manual 10 1988) in which the landslides have initiated, and on the aspect of each polygon. Figure 6.13 shows the Seymour watershed with streams and landslides, geographic localities mentioned in the text are indicated. Figure 6.14 shows lineaments added to this map. The stream network was supplied by the GVRD.  157  Lineaments and landslides  Chapter 6 Loch Lomond  Dam  Figure 6.13. The Seymour watershed showing streams and landslide initiation points (from images supplied by the GVRD). 158  Lineaments and landslides  Chapter 6 Loch  Figure 6.14. The Seymour watershed showing streams, landslide initiation points and lineaments. 159  Chapter 6  Lineaments and landslides  The spatial correlation between lineaments and landslide initiation points, and streams and landslide initiation points, was investigated in the same manner as described in Chapter 5. An investigation of lineament control on streams in the Seymour watershed was also conducted and the results presented in Appendix X. Stream order was not considered in this investigation. Lineaments used were those mapped in the initial 1;60,000 scale air photo inventory and hence include only the major features evident in the watershed. Lineaments were not re-mapped at 1:20,000 scale because the threefold increase in the expected number of lineaments (Section 4.3.2) would dramatically increase the area of buffer zones around lineaments and might obscure any reasonable assessment of relations by including too much of the land area in these zones. Use of the 1:60,000 scale lineaments, however, did present a problem in that the mapping accuracy of the two datasets is significantly different. Lineaments were mapped to within ± 259 m (see section 4.3.1.) which theoretically results in a positional uncertainty of over half a kilometer. A comparison was made between lineament position in the IDRISI image used for analysis, and the original air photo mapping. The maximum positional error observed was about 150 m: most features were accurately placed. Particularly accurate were features located near major streams. Mapping accuracy of the GVRD inventory is assumed to be within ± 10 m. Stream data is also generated at 1 ;20,000 scale. Airphoto mapping was completed at 1:20,000 scale and assuming errors similar to those in this study positional error of approximately ± 10 m is likely. A 20 m pixel resolution was chosen to investigate the Seymour watershed. The 140 m resolution of the original lineament data is too coarse for the landslide features examined and a 10 m resolution is too fine for display in IDRISI for this size basin. Additionally this scale is comparable to that used to investigate sample set basins. All data supplied by GVRD was converted to IDRISI image and vector files and IDRISI's spatial analysis capabilities were used for investigation. When incorporated in the IDRISI database 160  Chapter 6  Lineaments and landslides  1199 pixels were identified as landslide initiation points indicating that 4 small surficial landslides occurred at, or very close to preexisting initiation points (within 20m) and hence could not be distinguished independently. 21 landslide initiation points occurred outside of the boundary of the Seymour watershed as digitized by the author for this study. All were very close to the boundary and their omission is due to a small error in digitizing the basin outline. The landslide omissions represent 2 % of the data and are likely to be insignificant in the results. Figure 6.15 shows the Jamieson Creek landslide in the Seymour Watershed: an example of the type of small surficial landslide included in the GVRD inventory. The portion of the Seymour watershed examined extends northward from approximately Seymour Falls dam. The IDRISI calculated area is 131.53 km , the lineament and stream density are 2  respectively 1.417 (km/km ) and 3.583 (km/km ). 2  2  The sole purpose of the investigation was to determine if there was any significant structural control on landslide initiation points. No other landscape attributes were included in the analysis except for the stream network which is believed to be in part related to bedrock structure.  6.4.2 Results The results of analysis do not clearly indicate a relation between either lineaments and landslide initiation points or between streams and landslide initiation points.  However, the  probability of a small surficial landslide occurring is increased when the two features are coincident in an area. Table 6.2 shows the results of spatial correlation between lineaments and landslide initiation points. Table 6.3 shows the results for streams and landslide initiation points. Figure 6.16 shows a graphical representation of the results. The largest number of landslides were initiated between 20 and 40 m from each of the investigated features (lineaments and streams).  161  Lineaments and landslides  Chapter 6  Figure 6. 15. The Jamieson Creek landslide, an example of the type of feature included in the GVRD landslide inventory of the Seymour watershed.  162  Lineaments and landslides  Chapter 6  Buffer zone Distance in m 0-20 20-40 40-60 60-80 80-100 100-120 120-140 140-160 160-180 180-200 200-220 220-240 240-260 260-280 280-300 300-320 320-340 340-360 360-380 380-400 400-420 420-440 440-460 460-480 480-500 500-520 520-540 540-560 560-580 580-600 600-620 620-640 640-660 660-680 680-700 700-720 720-740 740-760  number of pixels in buffer  Percentage of watershed  Cumulative percentage  9322 26619 25850 17514 16959 23481 15361 17189 16590 13723 12202 10589 11689 11258 8977 7890 7573 7316 6678 5985 5205 5630 4332 3959 3779 3661 3106 2464 2263 2361 1885 1874 1476 1455 1289 1089 1143 969  2.83% 8.10% 7.86% 5.33% 5.16% 7.14% 4.67% 5.23% 5.05% 4.17% 3.71% 3.22% 3.55% 3.42% 2.73% 2.40% 2.30% 2.22% 2.03% 1.82% 1.58% 1.71% 1.32% 1.20% 1.15% 1.11% 0.94% 0.75% 0.69% 0.72% 0.57% 0.57% 0.45% 0.44% 0.39% 0.33% 0.35% 0.29%  2.83% 10.93% 18.79% 24.11% 29.27% 36.41% 41.08% 46.31% 51.36% 55.53% 59.24% 62.46% 66.01% 69.44% 72.17% 74.57% 76.87% 79.10% 81.13% 82.95% 84.53% 86.24% 87.56% 88.76% 89.91% 91.03% 91.97% 92.72% 93.41% 94.13% 94.70% 95.27% 95.72% 96.16% 96.55% 96.88% 97.23% 97.53%  Number of slide initiation pixels 36 108 106 71 57 87 56 70 68 54 54 40 38 41 34 23 32 20 21 20 18 14 12 13 13 12 9 7 4 6 5 3 3 5 1 5 1 1  Percentage of total slides  Cumulative number of slides  Cumulative percentage of slides  3.06% 9.17% 9.00% 6.03% 4.84% 7.39% 4.75% 5.94% 5.77% 4.58% 4.58% 3.40% 3.23% 3.48% 2.89% 1.95% 2.72% 1.70% 1.78% 1.70% 1.53% 1.19% 1.02% 1.10% 1.10% 1.02% 0.76% 0.59% 0.34% 0.51% 0.42% 0.25% 0.25% 0.42% 0.08% 0.42% 0.08% 0.08%  36 144 250 321 378 465 521 591 659 713 767 807 845 886 920 943 975 995 1016 1036 1054 1068 1080 1093 1106 1118 1127 1134 1138 1144 1149 1152 1155 1160 1161 1166 1167 1168  3.06% 12.23% 21.23% 27.25% 32.09% 39.48% 44.23% 50.17% 55.95% 60.53% 65.11% 68.51% 71.74% 75.22% 78.10% 80.05% 82.77% 84.47% 86.25% 87.95% 89.48% 90.67% 91.68% 92.79% 93.89% 94.91% 95.67% 96.27% 96.61% 97.12% 97.54% 97.80% 98.05% 98.48% 98.56% 98.99% 99.07% 99.16%  Table 6.2. Results of overlay of landslide initiation points on 20 m buffer zones around lineament pixels. 21 landslide pixels are omitted from the results (see text). Each pixel represents 400 m . 2  163  Chapter 6  Buffer Zone Distance in m 760-780 780-800 800-820 820-840 . 840-860 860-880 880-900 900-920 920-940 940-960 960-980 980-1000 1000-1020 1020-1040 1040-1060 1060-1080 1080-1100 1100-1020 1120-1140 1140-1160 1160-1180 1180-1200 1200-1220 1220-1240 1240-1260 1260-1280 1280-1300 1300-1320  Lineaments and landslides number of pixels in buffer 1072 796 617 607 509 492 413 390 384 330 369 301 316 300 244 284 206 195 79 57 46 33 25 20 17 10 6 2 328825  Percentage of watershed 0.33% 0.24% 0.19% 0.18% 0.15% , 0.15% 0.13% 0.12% 0.12% 0.10% 0.11% 0.09% 0.10% 0.09% 0.07% 0.09% 0.06% 0.06% 0.02% 0.02% 0.01% 0.01% 0.01% 0.01% 0.01% 0.00% 0.00% 0.00% 100.00%  Cumulative percentage  97.85% 98.09% 98.28% 98.47% 98.62% 98.77% 98.90% 99.01% 99.13% 99.23% 99.34% 99.44% 99.53% 99.62% 99.70% 99.78% 99.85% 99.91% 99.93% 99.95% 99.96% 99.97% 99.98% 99.98% 99.99% 99.99% 99.99% 100.00% 100.00%  Number of slide initiation pixels 4 3 0 1 0 0 0 0 1 0 0 0 1 -  Percentage of total slides  Cumulative number of slides  Cumulative percentage of slides  0.34% 0.25% 0.00% 0.08% 0.00% 0.00% 0.00% 0.00% 0.08% 0.00% 0.00% 0.00% 0.08% -  1172 1175 1175 1176 1176 1176 1176 1176 1177 1177 1177 1177 1178 -  99.49% 99.75% 99.75% 99.83% 99.83% 99.83% 99.83% 99.83% 99.92% 99.92% 99.92% 99.92% 100.00%  1178  100.00%  1178  -  -  100.00%  Table 6.2 (Continued). Results of overlay of landslide initiation points on 20 m buffer zones around lineament pixels. 21 landslide pixels are omitted from the results (see text). Each pixel represents 400 m . 2  164  Chapter 6  Buffer zone Distance in m 0-20 .20-40 40-60 60-80 80-100 100-120 120-140 140-160 160-180 180-200 200-220 220-240 240-260 260-280 280-300 300-320 320-340 340-360 360-380 380-400 400-420 420-440 440-460 460-480 480-500 500-520 520-540 540-560 560-580 580-600 600-620 620-640 640-660 660-680 680-700 700-720 Totals  Lineaments and landslides  number of pixels in buffer  Percentage of watershed  Cumulative percentage  23566 53392 46866 30263 26270 30713 18985 19025 16407 12276 10424 7563 7106 5653 3971 3129 2333 2057 1577 1202 900 759 573 492 447 414 339 260 225 213 194 166 137 137 103 79 328825  7.17% 16.24% 14.25% 9.20% 7.99% 9.34% 5.77% 5.79% 4.99% 3.73% 3.17% 2.30% 2.16% 1.72% 1.21% 0.95% 0.71% 0.63% 0.48% 0.37% 0.27% 0.23% 0.17% 0.15% 0.14% 0.13% 0.10% 0.08% 0.07% 0.06% 0.06% 0.05% 0.04% 0.04% 0.03% 0.02% 100.00%  7.17% 23.41% 37.66% 46.86% 54.85% 64.19% 69.97% 75.75% 80.74% 84.47% 87.64% 89.94% 92.11% 93.82% 95.03% 95.98% 96.69% 97.32% 97.80% 98.16% 98.44% 98.67% 98.84% 98.99% 99.13% 99.25% 99.36% 99.44% 99.51% 99.57% 99.63% 99.68% 99.72% 99.76% 99.79% 99.82% 99.82%  Number of slide initiation pixels 93 214 193 148 125 122 77 56 46 40 19 11 14 3 6 2 2 2 3 0 2 -  1178  Percentage of total slides  Cumulative number of slides  Cumulative percentage of slides  7.89% 18.17% 16.38% 12.56% 10.61% 10.36% 6.54% 4.75% 3.90% 3.40% 1.61% 0.93% 1.19% 0.25% 0.51% 0.17% 0.17% 0.17% 0.25% 0.00% 0.17%  93 307 500 648 773 895 972 1028 1074 1114 1133 1144 1158 1161 1167 1169 1171 1173 1176 1176 1178 -  7.89% 26.06% 42.44% 55.01% 65.62% 75.98% 82.51% 87.27% 91.17% 94.57% 96.18% 97.11% 98.30% 98.56% 99.07% 99.24% 99.41% 99.58% 99.83% 99.83% 100.00%  -  -  100.00%  -  -  -  -  1178  100.00%  -  -  Table 6.3. Results of overlay of landslide initiation points on 20 m buffer zones around stream pixels. 21 landslide pixels are omitted from the results (see text). Each pixel represents 400 m . 2  165  Chapter 6  Buffer zone Distance in m 720-740 740-760 760-780 780-800 800-820 820-840 840-860 860-880 880-900 900-920 920-940 940-960 960-980 980-1000 1000-1020 Totals  Lineaments and landslides number of pixels in buffer  Percentage of watershed  Cumulative percentage  67 67 63 61 56 51 51 46 40 35 32 18 12 7 3 328825  0.02% 0.02% 0.02% 0.02% 0.02% 0.02% 0.02% 0.01% 0.01% 0.01% 0.01% 0.01% 0.00% 0.00% 0.00% 100.00%  99.84% 99.86% 99.88% 99.90% 99.91% 99.93% 99.94% 99.96% 99.97% 99.98% 99.99% 100.00% 100.00% 100.00% 100.00% 100.00%  Number of slide initiation pixels 1178  Percentage of total slides  Cumulative number of slides  -  -  -  Cumulative percentage of slides  _  _  -  -  -  100.00%  1178  -  -  -  100.00%  Table 6.3 (Continued). Results of overlay of landslide initiation points on 20 m buffer zones around stream pixels. 21 landslide pixels are omitted from the results (see text). Each pixel represents 400 m. 2  166  Lineaments and landslides  Chapter 6  Number of landslides versus distance from target feature  250 200  Landslides at distance "X" from a stream  T3  •° 150  Landslides at distance "X" from a lineamenent  0 0  200  400  600  800  1000  1200  Distance from target feature  Figure 6.16. Graph showing the distribution of landslides away from target features.  167  Chapter 6  Lineaments and landslides  No landslides are initiated more than 420 m from a stream and 75 % of features are initiated within 100 m of a stream. 144 (12.23 %) landslides are initiated within 40 m of a lineament, 32% are initiated within 100 m of a lineament. A consideration in assessing the results is the area of the watershed which lies within the buffer zones created. This is shown in each table. For example when lineaments are considered 8% of the Seymour watershed lies within the 0 - 40 m buffer zone and, 12 % of landslides lie within this 8%> of the watershed (Table 6.2). 18 %> of landslides lie in the 23 % of the watershed delineated as being within 40 m of a stream (Table 6.3). These results do not clearly reveal a relationship between either lineaments and landslide initiation points or streams and landslide initiation points. For example, Table 6.3 indicates that all landslides are initiated within a distance of about 400 m from a stream. The 0 - 400 m buffer around streams includes 99 % of the watershed. This indicates that 100 % of landslides occur within 99 % of the watershed. This result is meaningless except in indicating a maximum length a landslide can travel before entering a stream if it moves by the shortest possible route to a stream. (Landslide events may be longer because this analysis does not include the effects of topography). An additional investigation was conducted when the buffer zones containing the greatest number of landslides (i.e., the modal classes) for each of the above investigations were found. In each case this distance was determined to be between 0 - 40 m from either a lineament or stream pixel. The effect of a lineament within the 0 - 40 m stream buffer on landslide distribution was examined by identifying pixels that are both within 40 m of a stream and 40 m of a lineament as target cells and constructing distance buffer zones about them. This allowed the investigation of localities where streams are intersected by lineaments as well as locations where lineaments may control stream sections (Figs. 6.17 and 6.18).  168  Chapter 6  Lineaments and landslides  Figure 6.17. The northern Seymour watershed showing the 0 - 40 m stream buffer, the "intersecting lineament and stream" pixels and landslide initiation points. 169  Lineaments and landslides  Chapter 6  Gibbens Creek  Stream buffer zone 1 (0 - 20 m)  Stream buffer zone 2 (20 - 40 m)  Stream/lineament target zone 1 (0 - 20 m)  Landslide initiation point  Stream/lineament target zone 2 (20 - 40 m)  2 km  Figure 6.18. The southern Seymour watershed showing the 0 - 40 m stream buffer, the "intersecting lineament and stream" pixels and landslide initiation points. 170  Chapter 6  Lineaments and landslides  Table 6.4 shows the results of this analysis. The occurrence of lineaments and streams together is a better predictor of landslide initiation location than either of them independently. It is seen that in the 0 - 40 m from a stream zone (23 % of the watershed) 307 (26 %) slides occur. 102 (9 % of all landslides) occur within 40 m of a lineament intersecting this zone. This indicates that about one third of the slides in the "0 - 40 m from a stream" buffer zone occur in 19% of this zone (7 % of the watershed). The landslide density of the entire zone is 10.0 (landslides/km ), the landslide 2  density of the lineament/stream intersection zone is 17.5 (landslides/km ), a significant increase. 2  Extending the investigation to the 60 m buffer zone revealed approximately constant densities. 159 (32 %) of the 500 landslides in the 0 - 60 m from a stream buffer zone occur within the 17 % of this zone which also contains a lineament. This suggests that a slide is 1.75 times as likely to occur in an area where a lineament intersects or controls a stream as in an area without a lineament. The overall landslide density for the watershed area examined and considering 1178 slides is 8.9561 slides/km : 2  0.0036 slides/pixel.  Although it is difficult to determine the effects of lineaments on landslide  distribution in isolation it is seen that where their occurrence corresponds with the occurrence of a stream there is an increased likelihood of a landslide initiation. It is recognized that there are many other factors contributing the occurrence of small surficial landslides. These have been described in Chapter 2.  6.4.3 Discussion It is apparent that careful interpretation of the data generated by spatial correlation analysis is necessary to obtain geologically valid results from these investigations. Analysis of lineament and landslide distribution alone proved insufficient to determine if a relation existed between the two. However when the presence of a lineament and stream are combined in analysis the results suggest that the presence of a lineament in association with a stream at a location provides a site favorable  171  Chapter 6  Buffer zone Distance in m 0-20 20-40 40-60 60-80 80-100 100-120 120-140 140-160 160-180 180-200 200-220 220-240 240-260 260-280 280-300 300-320 320-340 340-360 360-380 380-400 400-420 420-440 440-460 460-480 480-500 500-520 520-540 540-560 560-580 580-600 600-620 620-640 640-660 660-680 680-700 700-720 720-740  Lineaments and landslides  number of pixels in buffer  Percentage of watershed  Cumulative percentage  14375 8473 12624 11388 13526 14226 12360 14659 14714 14028 12829 11558 13599 12312 11649 10329 10292 9941 9414 9019 7605 7905 6468 5776 6055 5342 4883 3950 3594 3696 3065 3142 2558 2555 2231 1872 1868  4.37% 2.58% 3.84% 3.46% 4.11% 4.33% 3.76% 4.46% 4.47% 4.27% 3.90% 3.51% 4.14% 3.74% 3.54% 3.14% 3.13% 3.02% 2.86% 2.74% 2.31% 2.40% 1.97% 1.76% 1.84% 1.62% 1.48% 1.20% 1.09% 1.12% 0.93% 0.96% 0.78% 0.78% 0.68% 0.57% 0.57%  4.37% 6.95% 10.79% 14.25% 18.36% 22.69% 26.45% 30.91% 35.38% 39.65% 43.55% 47.06% 51.20% 54.94% 58.49% 61.63% 64.76% 67.78% 70.64% 73.39% 75.70% 78.10% 80.07% 81.83% 83.67% 85.29% 86.78% 87.98% 89.07% 90.19% 91.13% 92.08% 92.86% 93.64% 94.32% 94.89% 95.45%  Number of slide initiation pixels 58 44 57 58 59 48 55 70 69 50 56 47 49 42 37 33 37 35 25 29 20 26 20 17 11 22 13 8 8 9 5 13 5 5 5 1 5  Percentage of total slides  Cumulative number of slides  Cumulative percentage of slides  4.92% 3.74% 4.84% 4.92% 5.01% 4.07% 4.67% 5.94% 5.86% 4.24% 4.75% 3.99% 4.16% 3.57% 3.14% 2.80% 3.14% 2.97% 2.12% 2.46% 1.70% 2.21% 1.70% 1.44% 0.93% 1.87% 1.10% 0.68% 0.68% 0.76% 0.42% 1.10% 0.42% 0.42% 0.42% 0.08% 0.42%  58 102 159 217 276 324 379 449 518 568 624 671 720 762 799 832 869 904 929 958 978 1004 1024 1041 1052 1074 1087 1095 1103 1112 1117 1130 1135 1140 1145 1146 1151  4.92% 8.66% 13.49% 18.42% 23.43% 27.50% 32.17% 38.11% 43.97% 48.21% 52.97% 56.96% 61.12% 64.68% 67.82% 70.62% 73.77% 76.74% 78.86% 81.32% 83.02% 85.23% 86.92% 88.37% 89.30% 91.17% 92.27% 92.95% 93.63% 94.39% 94.82% 95.92% 96.35% 96.77% 97.20% 97.28% 97.70%  Table 6.4. Results o f overlay o f landslide initiation points on 20 m buffer zones around pixels at the intersection o f streams and lineaments. 21 landslide pixels are omitted from the results (see text). Each pixel represents 400 m . 2  172  Chapter 6  Buffer zone Distance in m 740-760 760-780 780-800 800-820 820-840 840-860 860-880 880-900 900-920 920-940 940-960 960-980 980-1000 1000-1020 1020-1040 1040-1060 1060-1080 1080-1100 1100-1020 1120-1140 1140-1160 1160-1180 1180-1200 1200-1220 1220-1240 1240-1260 1260-1280 1280-1300 1300-1320 1320-1340 1340-1360 1360-1380 1380-1400 1400-1420 1420-1440 Totals  Lineaments and landslides  number of pixels in buffer  Percentage of watershed  Cumulative percentage  1467 1440 1249 1045 1031 911 844 688 623 608 526 546 466 467 463 383 389 298 257 202 180 156 133 113 98 91 69 56 42 36 27 20 12 7 2 328825  0.45% 0.44% 0.38% 0.32% 0.31% 0.28% 0.26% 0.21% 0.19% 0.18% 0.16% 0.17% 0.14% 0.14% 0.14% 0.12% 0.12% 0.09% 0.08% 0.06% 0.05% 0.05% 0.04% 0.03% 0.03% 0.03% 0.02% 0.02% 0.01% 0.01% 0.01% 0.01% 0.00% 0.00% 0.00% 100.00%  95.90% 96.34% 96.72% 97.04% 97.35% 97.63% 97.88% 98.09% 98.28% 98.47% 98.63% 98.79% 98.93% 99.08% 99.22% 99.33% 99.45% 99.54% 99.62% 99.68% 99.74% 99.78% 99.82% 99.86% 99.89% 99.92% 99.94% 99.95% 99.97% 99.98% 99.99% 99.99% 100.00% 100.00% 100.00% 100.00%  Number of slide initiation pixels 4 2 3 2 4 4 2 1 1 1 2 1 -  Percentage of total slides  Cumulative number of slides  Cumulative percentage of slides  1155 1157 1160 1162 1166 1170 1172 1173 1174 1175 1177 1178  98.04% 98.21% 98.47% 98.64% 98.98% 99.32% 99.49% 99.57% 99.66% 99.74% 99.91% 100.00%  -  0.34% 0.17% 0.25% 0.17% 0.34% 0.34% 0.17% 0.08% 0.08% 0.08% 0.17% 0.08% -  1178  100.00%  -  _ _  -  _  -  -  -  -  1178  100.00%  _  _  Table 6.4 (Continued). Results of overlay of landslide initiation points on 20 m buffer zones around pixels at the intersection of streams and lineaments. 21 landslide pixels are omitted from the results (see text). Each pixel represents 400 m . 2  173  Chapter 6  Lineaments and landslides  for landslide initiation. The addition of streams indicates that the pixels identified in this analysis are at the topographic low points and field experience in this area suggests that they are likely to be in the vicinity of steep gully walls. The presence of a lineament intersecting or paralleling these walls may be sufficient to initiate a failure. This will likely be either a failure in structurally weakened bedrock (which may have been undercut by rapid bedrock incision in these zones) or the result of concentration of ground and surface waters sufficient to cause a precipitation initiated event. Additionally in the event of seismic activity shaking in these weakened zones may cause rockfalls capable of triggering debris flows. The proximity of these failures to the streams suggests that they will move directly into the stream, at which point they typically flow down the confined stream channel and ultimately deposit on the fan. This a the primary mechanism for sediment transfer from the basin to the fan. Only major lineaments identified on 1;60,000 scale air photos were considered in this analysis therefore only more significant structural features were used to correlate with landslides. Examination of Figure 6.14 shows that several of these major lineaments control streams, e.g., Gibbens Creek and Burwell Creek. Fannin Creek is fault controlled and has been identified as a fault zone by the GSC (Roddick 1965). This fault was not visible on 1:60,000 scale air photos. The fault extends for great length up Seymour Valley (see Fig. 4.2). A number of smaller creeks on both the eastern and western flanks of the valley are also lineament controlled. There is no apparent increase in landslide activity in these creeks as compared to others. Landslide activity seems concentrated near lower order streams.  There are some  concentrations of landslides about lineaments and stream intersection points easily visible in Figure 6.14, as an example the northern side of Clipper Creek shows a large number of landslides in close proximity to the lineament which successively intersects several subsidiary creeks. As well as this, many areas exist where landslides appear to be initiated preferentially at a particular distance from a  174  Chapter 6  Lineaments and landslides  creek or at a uniform elevation above it, e.g., the northern side of Orchid Creek. Therefore more analysis of other attributes is required to determine whether lineaments are at all responsible for landslide activity in these areas. It is likely that increasing the number of lineaments by increasing lineament mapping scale would increase the strength of correlation between lineaments and landslides. Care should be taken that this is not due to the increase in the area of the buffer zones around lineaments. There is likely to be a threshold point at which such analysis would prove counterproductive for this reason.  6.5 Small surficial landslides as sediment sources and contributors of materials to fans  The GVRD have found that stream bank erosion and landsliding in gully walls are primary sources of sediment in the Seymour watershed (GVWD watershed ecological inventory pilot study, Final report, March 1993). The GVRD study estimated the amount of material yielded by each sediment source in a basin in the Seymour watershed. Values calculated in the report were based on average annual stream bank retreat rates and the amount of (field) observed material resulting from landslide activity. Identification of landslide initiation sites is of primary importance to the GVRD. Lineaments do not appear directly responsible for the introduction of fine sediment to the water supply (Section 4.4).  However it appears that there is a relation between lineaments and the location of landslide  initiation points. This suggests an indirect relation between the lineaments and fine sediment. The GVRD assume a fines content of about 20% in landslides (GVRD ecological inventory final report, March 1993). The fine sediment content of a landslide deposit is typically winnowed from the deposit and flushed into the primary river. Fans in the GVRD watersheds typically comprise large quantities of gravel to small boulder size materials with fine materials concentrated in  175  Chapter 6  Lineaments and landslides  naturally occurring sediment traps such as behind boulders and large organic debris. Larger materials are common higher in the creeks where boulders of several meters are often encountered. The movement of sediment from the basin to the water supply is a complex process. Upon mobilization in a landslide sediment will move from the initiation point to the nearest stream or gully, which is typically very close (within a few hundred meters), here the materials may be deposited or continue to flow as a torrent until deposition when the gradient of the slope is insufficient for further movement. Sediment will reside at the deposition site until winnowed from the deposit, the last remaining fines are typically those caught in sediment traps which may be obliterated by subsequent debris flow events. Figure 6.19 shows the view down a landslide track in the Camp Creek basin, Coquitlam watershed which has moved directly to the nearest gully. The slide has deposited material in Camp Creek (Fig. 6.20) where it will reside until re-mobilized. The landslide was initiated about 60 m from the creek and has built a small cone into the creek, just visible in the foreground of Figure 6.20 is a small debris levee. It has been pointed out in south-central British Columbia that valley degradation probably ceased around 3-4,000 years after deglaciation (Ryder 1971b). Since this time major erosion has been concentrated in small point sourced landslide events. It is likely that the fans seen in the southwest Coast Mountains have continued to build throughout the last 10,000 years by the process described above with considerable amounts of material being deposited on them by debris flows.  176  Chapter 6  Lineaments and landslides  Chapter 6  Lineaments and landslides  Chapter 6  Lineaments and landslides  6.6 Conclusions  An inventory of large rock landslides and mountain slope deformation was conducted in the regional study area from 1;60,000 scale air photos. Besides allowing an assessment of regional hazard distribution this allowed the relation between lineaments and landslides to be investigated. Landslides were identified on air photos by the presence of landslide scars and rubble filling the valley bottoms. Slope deformations were identified by the presence of antislope scarps and slope bulging. Landslides and slope deformations were inventoried over an area of approximately 10,900 km and twenty sites identified. Six of these have been previously reported. Rock avalanches and 2  slope deformations are the commonest features locally. Other failure types include large rockfalls and surficial slides in Quaternary sediments adjacent to major rivers. The density of bedrock failures in the area is 0.001 failures/km and the density of mountain slope deformations is 0.0006 2  deformations/km . Because all features have occurred postglacially the temporal distribution of 2  failures is assessed at one every 910 years although this does not preclude the possibilities of repeated failures at a single site or a single triggering mechanism initiating multiple events, for example an earthquake. Lineaments are clearly related to many of the inventory features.  The best example  presented is the Dickson Lake landslide and associated West Norrish Creek site. Lineaments appear related to inventory features in three ways: 1)  Lineaments may form the headscarp of major landslides, for example Dickson Lake;  179  Chapter 6 2)  Lineaments and landslides  Lineaments may either provide locations about which slope deformation may occur, for  example the West Norrish Creek site, or be caused by slope deformation as is probably the case at Goat Ridge; 3)  Lineaments may form rock faces capable of shedding large rockfalls, for example Stave  River I (Table 6.1). Mountain slope deformation accounts for seven inventory sites.  These features may  represent a re-equilibriating response to deglaciation and many may be currently inactive however the state of activity is difficult to assess on air photos. The antislope scarps on the Lions in the Capilano watershed are shedding materials suggesting at least active weathering processes. These features represent possible hazards because their future behavior is uncertain. Mountain slope deformation may ultimately result in catastrophic failure. When the inventory features are compared to landslides and mountain slope deformation in the adjacent Fraser River Valley, it appears that these features are less common in this study area. The inventory compiled by Savigny (1996) identified 58 sites of instability in a 40 km wide corridor centred on Fraser River. Leir (1995) investigated factors that might influence landslide distribution including; rock type, slope, proximity to a (known) fault, proximity to a (mapped) lineament. Using a weights of evidence modelliing technique it was determined that the top five predictors of large rock landslide occurance in his study area were: 1) presence of Custer Gneiss; 2) within 1300 m of a fault trace; 3) within 1200 m of a lineament; 4) presence of Cultus Formation; 5) presence of Chiliwack Formation (Leir 1995, p. 74). It is clear that rock type strongly influenced landslide distribution however the importance of faults and lineaments is also clear. The primary difference between the two study sites is the presence of several major, pervasive fault zones: the Hope, Yale and Vedder. It is likely that these faults are strongly influencing the landslide characteristics of the  180  Chapter 6  Lineaments and landslides  Fraser River Valley and that comparison of the two study areas shows that landslides are less frequent farther from major fault zones (Savigny, pers. comm. 1996). Although one major fault zone is present in the study area, the Harrison Fault Zone, examination of Figure 6.1 (showing distribution of inventory sites) does not appear to show a decrease in sites away from this fault zone. It should be noticed however that only a small portion of this fault zone intersects the study area. Other faults mapped in this area (shown on figure 4.2) are smaller features than those seen in the Fraser River Valley study. Although small surficial landsliding is ubiquitous in the regional study it was not reported in the regional inventory. Instead the occurrence of these features was investigated in the Seymour watershed north of Vancouver. The GVRD have found that stream bank erosion and landslides in gully walls to be the primary sources of sediment input to the water supply. As such landslide initiation points represent points of high erosion and sediment supply. An inventory supplied by the GVRD was used to determine the relation between landslide initiation points and lineaments. A total of 1178 small surficial landslide initiation points were used in spatial correlations between lineaments and landslides and streams and landslides. In each case the greatest numbers of landslides were initiated between 20 and 40 m from the feature in question. Analysis of landslide distribution compared to sites where both a lineament and a stream existed showed that a landslide is almost twice as likely to occur in these zones than in a zone occupied.by a stream alone. An average of 10 slides per kilometer were found within 40 m of a stream and 17.5 slides per kilometer were found within 40 m of a lineament/stream intersection. It is concluded that while many other factors may influence landslide distribution in the Seymour watershed there is a correlation between landslide distribution and locations where lineaments intersect streams. These zones are likely to represent areas where lineaments focus surface and ground water into the creeks or where rapid incision of creeks into structurally weakened  181  Chapter 6  Lineaments and landslides  bedrock has oversteepened slopes sufficiently to cause bedrock failure capable of initiating debris flow activity. In conclusion lineaments influence landslides of all scales. Following lineaments on an air photo will often lead to identification of landslide or slope deformation features and as such lineament mapping is an important tool in hazard investigation. Additionally it has been previously reported (GVWD watershed ecological inventory pilot study, Final report 1993) that small surficial landslides are a major source of sediment in the Seymour watershed. As such these represent a contemporary process capable of moving materials from a drainage basin to its fan. Fine sediment is often winnowed from deposits on the fan and flushed into the primary river system.  182  Chapter 7  Discussion and conclusions  CHAPTER 7  DISCUSSION AND CONCLUSIONS  This study was undertaken to evaluate the importance of structure as a control on drainage basin development in the southwest Coast Mountains, British Columbia, Canada. Lineaments mapped from air photos were used to assess the structure of the regional study area and then to investigate the effects of this structure at the smaller, drainage basin, scale. The influence of lineaments on drainage basin position, stream network pattern and basin morphometry was investigated either by assessment of spatial correlations or by regression analysis of variables. Also investigated was the possibility of determining sediment yield from basin morphometric parameters. Lineament influence on large scale geomorphic process was assessed by examining lineament control on large rock landslides and slope deformations. Finally an investigation into lineament control on debris flow and avalanche activity in the Seymour watershed was conducted using an inventory compiled by the GVRD. The term lineament as applied in this research is defined as a non-genetic term describing a feature recognizable on an air photo or other remotely sensed image, that is essentially linear, and comprises a contiguous set of topographic, drainage, vegetation, moisture and tonal features. An inventory of 4215 lineaments was compiled from air photos of the regional study area in order to obtain an understanding of regional structure and to provide the necessary framework for drainage basin studies. Lineaments used in this research were mapped on 1 ;60,000 scale air photos before transfer to topographic maps. Lower altitude photos were used to assist with field work. It was determined that 183  Chapter 7  Discussion and conclusions  mapping lineaments on 1;20,000 scale air photos produced an approximately threefold increase in the number of features detectable on 1;60,000 scale air photos. Orientation data for mapped lineaments was provided by a FORTRAN77 program TREND. A preferred orientation of 17.43 ± 3.73° was found for the inventory data. Peaks were also found representing northwest and east-west trends. Two of these trends correlate with known structural trends in the region. The northwest trend is related to the oldest developed (Cretaceous) structural trend. This trend is particularly developed in Jurassic rocks in the northeast corner of the study along the Harrison Lake Fault zone. The northeast trend is probably related to a Tertiary trend developed in the region between 25 and 14 Ma. The east-west trend has not been previously reported and it is suspected that this is the youngest regionally developed trend for three reasons: 1)  These lineaments are numerous and persist for tens of kilometers throughout the central and  southern study area cutting the youngest rocks in these areas. 2)  They appear to cut Quaternary valley fill in parts of the southern map area and some are  visible in recent alluvium. (This assertion is currently the subject of further investigation by Thurber Engineering Ltd. under contract from the GVRD). 3)  They are correctly oriented to have resulted from stresses induced by the current convergence  vector of the Juan de Fuca and North American plates. Investigation of the regional lineament trends demonstrated that it is possible to infer regional structure from lineament mapping. Additionally variations in structural styles can be found by looking for statistical differences between different areas. For example the lineament pattern visible in the northeastern corner of the study is significantly different from that in the rest of the area.  184  Chapter 7  Discussion and conclusions  Lineament mapping and analysis in the manner described has suggested that rocks in the study area have been subjected to three phases of lineament inducing stress. These are summarized as follows: 1)  Phase one: associated with dextral shear in the Cretaceous produced northwest trending  lineaments and is responsible for the trends of the majorrivervalleys; 2)  Phase two: associated with northeast-southwest crustal shortening in the Tertiary which  emplaced a northeast trending lineament se; 3)  Phase three: a more recent east-west trend with lineaments of unknown age which may  represent present convergence between the North American and Juan de Fuca plates. Field investigations determined that it is difficult to detect lineaments on the ground in this area because of the nature of the topography and vegetal cover. Where detected they were found to be represented by gullies of various forms including narrow bedrock "canyons" in cliff faces, deep cuts in the ridgetops, steep-sided, deeply incised creeks, and small topographic lows traversing hillslopes. Although lacking in situ evidence of movement, it is suspected that many of these features are faults or large scale regional joints. Field investigation also concluded that it is unlikely that these features are directly responsible for fine sediment yield in drainage basins. Instead they contribute to headward erosion of drainage basins by exposing bedrock directly to weathering processes such as freeze-thaw. In order to investigate lineament effects on drainage basins a sample set of 25 were randomly selected from the study area. The basins selected were determined to be representative of a number of variables in the area such as aspect, basin order, elevational ranges and lithology. Drainage divides for sample set basins were mapped from 1:50,000 scale topographic maps. It was possible to transfer additional lineaments from 1:60,000 scale air photos to this map scale, specifically smaller features identifiable on air photos that were not transferable to the original 1:250,000 scale topographic map. It was also determined that hydrology mapped on the 1:50,000 scale topographic maps represented only 185  Chapter 7  Discussion and conclusions  higher order streams. In order to represent first order streams in the analysis it was necessary to map these on air photo and transfer them to the map sheets. 19 morphometric parameters were measured for each basin and 2 physical attributes, aspect and geology, were recorded. Lineament control on drainage basin position was investigated by determining how many of the sample set basins were located about an axial lineament. It was determined that 22 (88%) of the basins studied could be shown to have a major lineament controlling either the axial line of the basin, the path of the main stream, or (typically) both. The presence of a lineament at the center of a basin suggests that the lineament was either responsible for the positioning of the master rill early in the development of a surface flow regime or captured the master rill very shortly after its conception. A lineament cutting a sloping surface may have provided the topographic low point necessary for concentration of surface water flow. A lineament also provides the zone of weakness in the rock mass necessary for rapid incision of the bedrock. A spatial correlation analysis was conducted to determine to what extent the stream pattern in a basin mirrored the lineament pattern. This was done by creating buffer zones around lineaments and overlaying the stream network to determine the extent of correlation. When all sample set basins and all stream orders were considered an average of 66% of the stream network was found to overlay lineaments. An average of 51% of the lineament network is overlain by streams. In igneous basins the average correlation was 71% and in metamorphic basins 46%. When separated to individual stream orders first order streams showed the highest correlations. Poor correlations were observed for third order and higher (fourth order) streams because these tended to flow in Quaternary sediments which mask the effects of lineaments. Despite this, the orientations of third order streams tended to agree well with lineament trends presumably because these often flow on a basin floor which is controlled by a major lineament.  186  Chapter 7  Discussion and conclusions  A directional analysis of lineaments and lineament controlled streams was conducted for the sample set basins. It was found that preferred lineament trends existed and were different in both igneous and metamorphic basins. The average lineament orientation in igneous basins was found to be 28.8 ± 24.13° and in metamorphic basins 0.15 ± 20.10°. Stream segment trends for these sets were determined to be 20.79 ± 43.31° and 167.1 ± 39.87° respectively. Statistically, the data for igneous and metamorphic basins cannot be shown to derive from the same population. Although not statistically proven by these investigations it appears that the overall preferred lineament trend for lower order streams in the sample set basins is approximately north-northeast, similar to the Tertiary emplaced structural trend. Both lineament and stream segment trends are more varied in metamorphic basins, consistent with the idea that these rocks have a longer history and have been subjected to more varied lineament inducing stress conditions. When the results of spatial and directional data on lineaments and streams for the sample set basins are compared it can be concluded that significant evidence exists to state that the drainage pattern in these basins is largely controlled by the distribution of lineaments in the underlying bedrock. The implication of this is that lineaments not only capture the master rill early in the formation of a drainage network on a sloping surface but also will capture rills and channels on the sideslopes as well. This supports the idea that at surface lineaments are expressed as topographic low points, and that they are likely to represent zones of weakness in the rock mass which may be easily eroded. It is also interesting to speculate on die extent to which these lineaments influence groundwater flow. The creeks formed in these zones are very deeply incised and it is likely that the zone has permeability at depth. Having established a connection between bedrock structure and the stream network it was decided to investigate the correlation between lineaments and basin morphometry. Classically the morphometry of a basin has been attributed to the stream pattern and measured in terms of stream  187  Chapter 7  Discussion and conclusions  length and drainage density, as well as other parameters of the drainage network. If the stream pattern mirrors structure in the bedrock then there should be a connection between lineaments and basin morphometry. Lineament length and density were chosen to be the most representative measures of bedrock structure because they are most easily measured and the linear nature of lineaments suggests comparison with stream length and drainage density. The sample set basins were examined as a group and were also separated into basins larger than one square kilometer and smaller than this threshold value.  Morphometric parameters were linearly regressed against one another and all possible  combinations of analysis performed. Three groups of data showed high strength relations: 1)  Sets of variables related to the areal and dimensional character of the basin such as basin area  and basin width and length returned high correlations with each other as did relief parameters. 2)  High correlations (measured in terms of Revalues) existed between stream length and drainage  density and certain basin morphometric parameters (typically areal and relief parameters). 3)  High correlations existed between lineament length and the same parameters as for stream  length. In the entire sample set stream length was found to be a better predictor of basin morphometry than lineament length in many cases.  However correlations between lineament length and basin  morphometric parameters compared well with those between stream length and the same parameters typically being within a few percent of those found for stream length. Strong correlations (typically R  2  > 75%) existed between lineament length and basin area, length, width, maximum basin elevation, maximum basin relief, relief ratio, basin relief, and basin gradient. In most cases the best correlations were returned in the larger basins.  188  Chapter 7  Discussion and conclusions  The strength of most correlations in the smaller basins is poor (R < 0.40). Although it was 2  not satisfactorily determined why this should be it may be related to the processes operating in these basins. Sediment yield characteristics are known to be different in small alpine basins than in the larger basins, increased elevation plays a more important role because many of these basins are more rugged and less forested than the larger basins. Previous research indicated that it basins should be examined according to whether they were larger or smaller than one square kilometer (e.g. Owens and Slaymaker 1992). Typically relations are very poor (R < 0.4) in the smaller basins but stream length is generally 2  a better predictor of any given parameter than lineament length. In larger basins the strength of nearly all relations is similar when stream length and lineament length are jointly compared to other parameters.  It is speculated that in the larger basins lineament influences are more evident. It is  possible that one reason why the stream network is a controlling factor in drainage basin development is that the stream network within a basin is a complete and almost isolated network (the only connection to a larger network is by way of the basin mouth) therefore the stream network is responsible for the movement of all materials out of the basin. The lineament network in a basin is not an isolated network. Links exist in this network to multiple basins by lineaments traversing the divides. Lineaments are places where erosion concentrates and sediment is stored, they therefore exert some control on basin processes. The larger a basin becomes the more likely it is to include a connected lineament network. This can be extended to the regional scale where it is possible that an isolated (i.e., distinct) lineament network exists. It is speculated that at the regional scale the lineament network may become more significant than the stream network in morphometric control of the landscape. Some evidence for this hypothesis is found in Koons (1995) where it is demonstrated that a ridge valley system develops parallel to the main orogen strike in a structurally controlled landscape.  189  Chapter 7  Discussion and conclusions  A possible explanation for the fact that stronger correlations exist between stream length and basin morphometry than between lineament length and basin morphometry is that a stream network must develop in a basin regardless of the presence of lineaments, in order to satisfy the natural law that every point in a basin be drained. Hence if no lineament exists on a slope a stream must make its own course on that slope. The effect of this is that in a drainage basin without lineaments morphometry will be due to the stream network. In a basin with a very high lineament density morphometry is likely to be more heavily related to the lineament network because of the erodability of the lineaments. In other words, if two identical basins (developed on the same rock under the same climatic conditions) evolve, one with no lineaments and one with a high lineament density, in the basin without lineaments morphometry will be related to the stream network. In the basin with the high lineament density the erodability of the lineaments will more strongly influence morphometry and there will be relations between lineament length and basin morphometry.  The relations between stream length and the  morphometry of this second basin will no longer be the same. Sediment yield from the sample set drainage basins was investigated for two reasons; first because it provides a means of investigating contemporary process in these basins and secondly, because sediment input to the water supply is a primary concern of the GVRD and the local population. Several morphometric parameters have been previously identified as related to sediment yield from drainage basins for example, basin area (Church et al 1989), fan area (Bull 1962), fan gradient (Ryder 1971) and relief ratio (Schumm 1954). Because sediment yield has not been measured directly for basins in the study area basin area was chosen as reflecting sediment yield from a basin. Church et al. (1989) have identified a relationship between basin area and sediment yield for basins in southwest British Columbia. It was determined that fan area is not a good predictor of basin area (hence sediment yield). If it can be measured fan volume might prove more useful. Relief ratio is the best predictor of sediment 190  Chapter 7  Discussion and conclusions  yield because it correlates very well with basin area (R = 0.88). Both lineament and stream length 2  correlate well with basin area (R = 0.83 and 0.97 respectively). 2  Landslide events of all types represent contemporary landscape processes. An inventory of post-glacial, large rock landslides and mountain slope deformation was completed from 1:60,000 scale air photos over a total area of approximately 10,900 km . Twenty sites were identified providing a site 2  density of 0.0018 sites/km . Rock avalanches were found to be the most frequent event locally (8 total) 2  with slope deformations being almost equally distributed (7 total). When only sites representing bedrock failures are considered the event density is 0.001 landslides/km . Other types of landslide 2  occurring locally are rockfalls and surficial slides adjacent to major rivers. Large rock landslides and mountain slope deformation were inventoried to assess regional hazard and the effects of lineaments on these features. Landslides were identified on air photos by the presence of landslide scars and rubble filling valley bottoms. Slope deformations were identified by the presence of antislope scarps and sometimes slope bulging. It was determined that lineaments influence landslides in three ways: 1)  Lineaments may form the headscarps of major landslides;  2)  Lineaments may either provide locations about which slope deformation can occur or may be  the result of slope deformation; 3)  Lineaments may form rockfaces capable of shedding large rockfalls. Mountain slope deformations are important to evaluate because of the uncertainty of their  future behavior. It is believed that many of these sites in the southwest Coast Mountains may represent a re-equilibrating response to deglaciation and as such many may be currently inactive. However, seismicity may periodically reactivate sites in the study area (Savigny pers. comm. 1996). Small surficial landslides represent a contemporary process of sediment evacuation from drainage basins. An inventory of landslide initiation points in the Seymour watershed was obtained 191  Chapter 7  Discussion and conclusions  from the GVRD.  1178 landslide initiation points were considered in the analysis and these were  investigated to determine the correlation between their distribution and the distribution of streams and major lineaments in the watershed. Using the lineaments mapped in the original lineament inventory and streams extracted from the GVRD's database it was determined that 11% of landslides were initiated within 40 m of a lineament and 23% of landslides were initiated within 40 m of a stream. However the area of the watershed included in these buffer zones was extensive and introduced a lack of confidence in the results of the analysis. The intersection points of streams and lineaments were investigated in order to determine whether the presence of a lineament and a steam at the same locality influenced landslide distribution. It was found that a landslides was almost twice as likely to occur within 40 m of a lineament/stream intersection as within 40 m of either a lineament or stream alone. The landslide density within the "40 m from a stream" and the "40 m from a lineament" buffer zones was 10 landslides/km in both cases whereas the landslide density within the "40 m from a lineament/stream 2  intersection" buffer zone was found to be 17.5 landslides/km . The result is considered reasonable 2  because where a lineament intersects a stream the location represents either a site where the lineament controls stream position (in which case rapid incision into the lineament zone oversteepens gully walls to the point of instability), or the lineament is likely to a focus surface flow and groundwater flow to the creek (if the lineament is oblique to the stream). The concentration of water in what is likely to represent a topographic low point may be sufficient to cause a small surficial landslide along the lineament. Once mobilized these small landslides will move preferentially to the nearest creek where they will either continue to flow or will deposit until later remobilized by subsequent landslide events or saturation by water. Ultimately the material contained in the landslide will be deposited on the fan where fine material may be winnowed from the deposit and flushed into the primary stream. Therefore 192  Chapter 7  Discussion and conclusions  debris flows and avalanches represent a contemporary means of moving materials from the drainage basin and there is some evidence that their occurrence may be related to lineament and stream interaction. It is recognized that a large number of other factors may contribute to landslide initiation at a given point. Further investigation is recommended into the landslide distribution in the Seymour watershed using the GVRD inventory. If lineament mapping were conducted at 1:20,000 scale it is possible that the correlation between small surficial landslides and lineaments would be improved. In the analysis described only the larger lineaments were included. Additionally it would be beneficial to include other landscape attributes in the analysis such as slope, aspect, and surface material type. If the groundwater flow in these lineaments could be properly investigated the flow patterns around a lineament might be useful in predicting landslide initiation points. Additional groundwater investigations could include the effect of lineaments on regional groundwater flow patterns. For example, is there a regional anisotropy developed in the flow pattern due to the presence of lineaments? Investigation into the depths at which water flows in lineament controlled creeks might also be beneficial. It is likely that creeks developed on lineaments transmit water along their course at some depth below the surface. This could account for the fact that many of the creeks appear dry except during times of heavy rain. Subsurface flow in these zones could have implications for tunneling operations. Investigation into the east-west lineament trend identified in the lineament inventory would hopefully ascertain the age and nature of movement (if any) on these features and would assist with regional structural interpretation. Field investigations and examination of the seismic record could determine the current state of activity on these features. It would also be interesting to see if lineament/stream correlations could be improved by field examination. More work could be conducted on the preferred orientations of stream segments to see if 193  Chapter 7  Discussion and conclusions  there if any temporal information can be obtained from structurally controlled stream courses. For example, was there a change in the flow paths of the streams in response to the initiation of phase two deformation. Further investigations into the relation between lineaments and landslides would include rigorous field examination and description of the inventory sites, investigations into other possible causes for the features examined and proper identification of the current state of activity at the sites of mountain slope deformation. It would also be interesting to try to separate the effects of lineaments of different orientations (and thus inferred age) on the inventory features. For example, are all sites of mountain slope deformation associated with one particular lineament trend and what is its age. In conclusion it has been demonstrated that lineament mapping can be used to investigate the structural trends of a region. It has also been shown that lineaments strongly influence the location of drainage basins, and the stream network pattern developed in them. The evidence suggests that the stream pattern is largely a reflection of the underlying bedrock structure. The biggest problem in analyzing the relation between streams and lineaments is that, by necessity, a stream network must form in a basin even in the absence of lineaments. This fact probably obscures, to some extent, the degree to which bedrock structure influences basin morphometry. By demonstrating lineament control on large rock landslides and mountain slope deformations and the suspected influence on debris avalanche and flow locations it is shown that lineaments influence contemporary basin processes. This study suggests that the morphometry of the drainage basins in the southwest Coast Mountains and the processes operating within them are a consequence of the underlying bedrock structure that has been emplaced by tectonic stresses. It is therefore argued that processes operating at tectonic scales influence and are reflected in the landscape patterns around us.  194  REFERENCES  195  Adams, J. 1985. Large-scale tectonic geomorphology of the Southern Alps, New Zealand. In Tectonic Geomorphology, M. Morisawa, and J.T. Hack (eds.), Boston: Allen & Unwin, pp. 105-128. Armstrong, J.E. 1984. Environmental engineering applications of the surficial geology of the Fraser Lowland, British Columbia. Geological Survey of Canada paper 83-23. 54 pps. Autodesk Inc. 1993. AUTOCAD release 12: user's guide. 562 pps. Bagnold, R.A., 1973. The nature of saltation and "bed-load" transport in water. Proceedings of the Royal Society of London, Series A. 332, pp. 473-504. Barton, C.C., Channer, D.DeR., and Cande, S. 1990. Fractal scaling of fracture networks in rock. American Geophysical Union 1990 fall meeting, Eos Transactions, AGU 71 (43), p.1595. Birdseye, R.U., and Christians, G.L. 1988. Structural control of drainage in late Pleistocene and Holocene sediments, Ascension Parish, Louisiana. Gulf Coast Association of Geological Societies and Gulf Coast Section SEPM meeting; abstracts, AAPG-Bulletin, 72. (9). p. 1109. Bloom, A.L. 1991. Geomorphology, a systematic analysis of Late Cenozoic landforms. Prentice Hall, 2nd edition. 532 pps. Bovis, M.J. 1982. Uphill-facing (antislope) scarps in the Coast Mountains, southwest British Columbia. Geological Society of America Bulletin, Vol. 93, pp. 804-812. Bovis, M.J. 1990. Rock-slope deformation at Affliction Creek, southern Coast Mountains, British Columbia. Canadian Journal of Earth Sciences, Vol. 27. pp. 243-254. Bovis, M.J., and Dagg, B.R. 1988. A model for debris accumulation and mobilization in steep mountain streams. Hydrological Sciences Journal, Vol. 33, pp. 589-604. Bovis, M.J and Evans, S.G. 1995. Large-scale mountain slope deformation, upper Lillooet Valley, British Columbia. 48th Canadian Geotechnical Conference, September 25-27, 1995, Vancouver BC. pp. 901-908.  Buchanan, P. and Savigny, K.W. 1990. Factors controlling debris avalanche initiation. Canadian Geotechnical Journal, Vol. 27, pp. 659-675.  196  Bull, W.B. 1964. Erosion and sedimentation in a semiarid environment: geomorphology of segmented alluvial fans in western Fresno County, California. United States Geological Survey, Professional Paper 352 - E. pp. 89-129. Burdick, R.G., and Speirer, R.A. 1980. Development of a method to detect geologic faults and other linear features from LANDSAT images. United States Bureau of Mines, Report of Investigations 8413, 74 pps. Chigira, M . 1992. Long-term gravitational deformation of rocks by mass rock creep. Engineering Geology, 32, pp. 157-184. Church, M . , Kellerhals, R., and Day, T.J. 1989. Regional clastic sediment yield in British Columbia. Canadian Journal of Earth Sciences, Vol. 26, pp. 31-45. Clague, J.J. (compiler) 1989. Quaternary geology of the Canadian Cordillera, Chapter 1 in Quaternary Geology of Canada and Greenland, R.J. Fulton (ed.), Geological Survey of Canada, Geology of Canada, no. 1, pp. 15-96. Clague, J.J. and Evans, S.G. 1994. Formation and failure of natural dams in the Canadian Cordillera. Geological Survey of Canada, Bulletin 464, 35 pps. Costa, J.E. 1984. Physical geomorphology of debris flows. Chapter 9 in Developments and applications of geomorphology, J.E. Costa and P.J. Fleisher (eds.), Springer-Verlag, Berlin, Heidelberg, pp. 267-317. Cronin, V.S., Sverdrup, K.A., and Schurter, G.J. 1990. LANDSAT drainage lineaments, seismicity and uplift of the Nanga Parbat-Haramosh Massif, northwest Himalaya. Geological Society of America, 1990 annual meeting, Abstracts with Programs, 22 (7). p. 232. Cruden, D.M., Thompson, S., Bornhold, B.D., Chagnon, J.-Y., Locat, J., Evans, S.G., Heginbottom, J.A., Moran, K., Piper, D.J.W., Powell, R., Prior, D., and Quigley, R.M. 1989. Landslides: extent and economic significance in Canada; in Brabb and Harrod (eds.) Landslides: extent and economic significance. 1989 Balkema, Rotterdam, pp. 1-23. Davies, T.R., Phillips, C.J., Pearce, A.J., and Zhang, X.B. 1992. Debris flow behaviour - an integrated overview, in Erosion, Debris Flows and Environment in Mountain Regions (Proceedings of the Chengdu Symposium, July 1992), IAHS Publication no. 209, 1992, pp. 217-225.  Davis, J.C. 1986. Statistics and data analysis in geology. 2nd edition, John Wiley and Sons, 646 pps.  197  Dietrich, W.E., Reneau, S.L., and Wilson C.J. 1987. Overview: "Zero-order basins" and problems of drainage density, sediment transport and hillslope morphology. Erosion and sedimentation in the Pacific rim (Proceedings of the Corvallis Symposium, August, 1987). IAHS publication no. 165, pp. 27-37. Eastman, J.R. 1993. IDRISI: A raster based Geographic Information System, Users Guides, Version 4.1, rev. 0, Graduate School of Geography, Clark University, Worcester, Massachusetts, USA. 177 pps.  Evans, S.G. 1984. The 1880 landslide dam on Thompson River, near Ashcroft, British Columbia; in Current Research, Part A; Geological Survey of Canada, Paper 84-1 A, pp. 655-658. Evans, S.G. 1986, Landslide damming in the Cordillera of western Canada. Landslide dams: processes, risk and mitigation, (ed.) R.L. Schuster; American Society of Civil Engineers, Geotechnical Special publications, No. 3, pp. 111-130. Evans, S.G. 1992. High magnitude - low frequency catastrophic landslides in British Columbia, in Geological hazards in British Columbia, Proceedings of the Geologic Hazards Workshop, 1991, British Columbia Geological Survey Branch 1992 - 15, pp. 71-98. Evans, S.G., and Clague, J.J. 1988. Catastrophic rock avalanches in glacial environments. Proceedings, Vth International Symposium on Landslides, Vol. 2, pp. 1153-1158. Evans, S.G., and Savigny, K.W. 1994. Landslides in the Vahcouver-Fraser Valley-Whistler region, in Geology and Geological Hazards in the Vancouver Region, Southwestern British Columbia, (ed.) J.W.H. Monger, Geological Survey of Canada, Bulletin 481, pp. 251-286. Fanin, R.J., and Rollerson, T.P. 1993. Debris Flows: some physical characteristics and behaviour. Canadian Geotechnical Journal, Vol. 30, pp. 71-81. Ferguson, R. 1976. Linear regression in geography. Concepts and techniques in modern geography No. 15, 44 pps.  Foley, M. 1980. Bed-rock incision by streams. Geological Society of America Bulletin, Part II, 91, pp. 2189-2213. Gaile, G.L., and Burt, J.E. 1980. Directional Statistics. Concepts and techniques in modern geography No. 25, 39 pps.  198  Gabrielse, H. and Yorath, C.J. 1991. Tectonic synthesis, Chapter 18 in Geology of the Cordilleran Orogen in Canada, H. Gabrielse and C.J. Yorath (ed.), Geological Survey of Canada, Geology of Canada, no. 4, pp. 677-705.  GVWD Watershed Ecological Inventory Pilot Study (Jamieson-Orchid-Elbow Drainage) Final Report, 18 March 1993, Prepared by Acres International Limited, B.A. Blackwell and Associates, Northwest Hydraulic Consultants, Oikos Ecological Consulting, Phero Tech Inc. Remtec Inc.  Hare, P.W., and Gardner, T.W. 1985. Geomorphic indicators of vertical neotectonism along converging plate margins, Nicoya Peninsula, Costa Rica. Tectonic Geomorphology, M . Morisawa and J.T. Hack (eds.) pp. 75-104. Harris, J.R. 1991. Mapping of regional structure of eastern Nova Scotia using remotely sensed imagery: Implications for regional tectonics and gold exploration. Canadian Journal of Remote Sensing, Vol. 17, No. 2, pp. 122-135. Helmlinger, K.R., Kumar, P., and Foufoula-Georgiou, E. 1993. On the use of digital elevation model data for Hortonian and fractal analysis of channel networks. Water Resources Research, 29. (8). p. 2599-2613.  Hestir, K., Martel, S.J., and Long, J.C.S. 1990. Generation of fracture patterns using self-similar iterated function systems. American Geophysical Union 1990 fall meeting, Eos Transactions, AGU 71 (43), p. 1595. Hicock, S.R., and Armstrong, J.E. 1984. Vashon Drift: definition of the formation in the Georgia Depression, southwest British Columbia. Canadian Journal of Earth Sciences, Vol. 22, pp. 748-757.  Horton, R.E. 1932. Drainage basin characteristics. Union, Vol. 13, pp. 350-361.  Transactions of the American Geophysical  Horton, R.E. 1945. Erosional development of streams and their drainage basins; hydrophysical approach to quantitative morphology. Bulletin of the Geological Society of America, Vol. 56, pp. 275-370, March 1945.  Howard, A.D. 1967. Drainage analysis in geologic interpretation: a summation. Association of Petroleum Geologists Bulletin, Vol. 51, pp. 2246-2259.  American  Howard, A.D., Dietrich, W.E., and Seidl, M.A. 1994. Modeling fluvial erosion on regional to continental scales. Journal of Geophysical Research, Vol. 99, No. 13, pp. 971-986.  199  Howes, D.E. and Kenk, E. (Contributing eds.) 1988. MOE Manual 10, Terrain classification system for British Columbia (revised edition). Recreational Fisheries Branch, Ministry of Environment and Surveys and Resource Mapping Branch, Ministry of Crown Lands, Province of British Columbia, 90 pps.  Hutchinson, J.N. 1988. General report: Morphological and geotechnical parameters of landslides in relation to geology and hydrology. Proceedings, Vth International Symposium on Landslides, Vol. 1, pp. 3-35. Johnson, K.A., and Sitar, N . 1990. Hydrologic conditions leading to debris-flow initiation. Canadian Geotechnical Journal, Vol. 27, No. 6, pp. 789-801. Jordan, R.P. 1994. Debris flows in the southern Coast Mountains, British Columbia: dynamic behaviour and physical properties. Unpublished Ph.D. thesis, Department of Geography, the University of British Columbia, Vancouver, Canada, 258 pps. Journeay, J.M. 1990. A progress report on the structural and tectonic framework of the southern Coast Belt, British Columbia. Geological Survey of Canada, Paper 90-1E, pp. 183-195. Kamp, P.J.J. 1988. Tectonic geomorphology of the Hikurangi Margin: surface manifestations of different modes of subduction. Z. Geomorph, N.F., Suppl. -Bd. 69, pp. 55-67. Karlinger, M.R. and Troutman, B.M. 1992. Fat fractal scaling of drainage networks from a random spatial network model. Water Resources Research, Vol. 28, No. 7, pp. 1975-1981, July 1992.  Kellerhals, R., and Church, M . 1990. Hazard management on fans, with examples from British Columbia. Chapter 17 in Alluvial Fans: a field approach, A.H. Rachocki, and M . Church (eds.), John Wiley and Sons Ltd, pp. 335-354.  Kochel, R.C. 1990. Humid fans of the Appalachian Mountains. Chapter 6 in Alluvial fans: a field approach. A.H. Rachocki and M . Church (eds.), John Wiley & Sons Ltd. pp. 109-129 Koons, P.O. 1995. Modeling the topographic evolution of collisional belts. Annual Review of Earth and Planetary Sciences, 1995, 23, pp. 375-408. La Barbera, P., and Rosso, R. 1989. On the fractal dimensions of stream networks. Resources Research, Vol. 25, No. 4, pp. 735-741.  Water  Lawrence, R.B., Armstrong, R.L., and Berman, R.G. 1984. Garibaldi Group volcanic rocks of the Salal Creek area, southwestern British Columbia; Alkaline lavas on the fringe of a 200  predominantly calc-alkaline Garibaldi (Cascade) Volcanic Arc. Journal of Volcanology and Geothermal Research. Vol. 21, 3-4, pp. 255-276. Leir, M.C. 1994. TREND, a FORTRAN77 program for calculating lineament trends from coordinate endpoint ASCII data. Unpublished computer code, Department of geological Sciences, The University of British Columbia, Vancouver, British Columbia, Canada. Leir, M.C. 1995. Airborne Synthetic Aperture Radar, Digital Terrain Models, and Geographic Information Systems: Tools for mapping and managing large landslide hazards in southwestern British Columbia. Unpublished M.A.Sc. thesis, Geological Engineering Program, Department of Geological Sciences, The University of British Columbia, Vancouver, Canada, 102 pps.  Leir, M . C , English, R.R., and Savigny, K.W. 1994. Statistics and GIS: Tools for landslide prediction in the lower Fraser Valley, southwestern British Columbia. Canadian Geotechnical Conference Lillesand, T.H., and Kiefer, R.W. 1994. Remote Sensing and Image Interpretation. John Wiley and Sons Inc. Toronto, Canada, 612 pps. Lubowe, J.K. 1964. Stream junction angles in the dendritic drainage pattern. American Journal of Science, Vol. 262, March 1964, pp. 325-339. Mardia, K.W. 1972. Statistics of directional data. Academic Press, 357 pps. Mauthner, T.E. 1996. Kshwan Glacier rock avalanche, southeast Stewart, British Columbia, in Current Research 1996-A; Geological Survey of Canada, pp. 37-44. Millard, T.H. 1986. Sediment in forested and logged gullies, Coastal British Columbia. Unpublished M.Sc. thesis, Department of Geography, University of British Columbia. 217 pps.  Mollard, J.D. 1988. First R.M. Hardy Memorial Lecture: Fracture lineament research and applications on the western Canadian plains. Canadian Geotechnical Journal, Vol. 25, pp. 749-767. Monger, J.W.H. and Journeay, J.M. 1994. Basement geology and tectonic evolution of the Vancouver region, in Geology and Geological Hazards in the Vancouver Region, Southwestern British Columbia, (ed.) J.W.H. Monger, Geological Survey of Canada, Bulletin 481, pp. 3-25.  201  Moore, D.P., and Mathews, W.H. 1978. The Rubble Creek landslide, southwestern British Columbia. Canadian Journal of Earth Sciences, Vol. 15, No. 7, pp. 1039-1052. Nikora, V.I. 1994. On self-similarity and self affinity of drainage basins. Research, Vol. 30, No. 1, pp. 133-137, January 1994.  Water Resources  Owens, P., and Slaymaker, O. 1992. Late Holocene sediment yields in small alpine and subalpine drainage basins, British Columbia, in Erosion, Debris Flows and Environment in Mountain Regions (Proceedings of the Chengdu Symposium, July 1992), IAHS Publication no. 209, 1992. pp. 147-154. Price, N.J., and Cosgrove, J.W. 1990. Analysis of geological structures. Cambridge University Press, 502 pps. Quari, M.Y.H.T., and Sen, Z. 1994. Remotely sensed fracture patterns in southwestern Saudi Arabia and qualitative analysis. Bulletin of the International Association of Engineering Geology, No. 49, pp. 63-72, April 1994. Rinaldo, A., Vogel, G.K., Rigon, R., and Rodriguez-Iturbe, I. 1995. Can one gauge the shape of a basin? Water Resources Research, Vol. 31, No. 4, pp. 1119-1127, April 1995. Ritter, D.F., Kochel, R.C., and Miller, J.R. 1995. Process Geomorphology, 3rd edition. Wm. C. Brown Publishers, 546 pps. Robert, A., and Roy, A.G. 1990. On the fractal interpretation of the mainstream length-drainage area relationship. Water Resources Research, Vol. 26, No. 5, pp. 839-842. Roddick, J.A. 1965. Vancouver North, Coquitlam, and Pitt Lake map-areas, British Columbia with special emphasis on the evolution of the plutonic rocks. Geological Survey of Canada, Memoir 335, 276 pps. plus maps.  Ryder, J.M. 1971a. The stratigraphy and morphology of para-glacial alluvial fans in south-central British Columbia. Canadian Journal of Earth Sciences, Vol. 8, pp. 279-298. Ryder, J.M. 1971b. Some aspects of the morphometry of paraglacial alluvial fans in south-central British Columbia. Canadian Journal of Earth Sciences, Vol. 8, pp. 1252-1264. Ryder, J.M. 1981. Geomorphology of the southern part of the Coast Mountains of British Columbia. Z. Geomorph. N.F., Suppl. -Bd. 37, pp. 120-147.  202  Savigny, K.W. 1996. Engineering geology of large landslides in the lower Fraser Valley transportation corridor southwestern Canadian Cordillera. Canadian Geotechnical Journal (in press).  Scalia, P.R. 1995. Terrain analysis: Squamish area. Unpublished Directed Studies Report supervised by Dr. K.W. Savigny, Department of Geological Sciences, University of British Columbia, Vancouver, Canada. 17 pps. Schuster, R.L., Logan, R.L., and Pringle, P.T. 1992. Prehistoric rock avalanches in the Olympic Mountains, Washington. Science, Vol. 258. pp. 1620-1621. Schumm, S. 1954. The relation of drainage basin relief to sediment loss. International Association of scientific Hydrology(?) 36 (1), International Union of Geodesy and Geophysics, 10th General Assembly, Rome, Transactions 1, pp. 216-219. Seidl, M.A., and Dietrich, W.E. 1992. The problem of channel erosion in bedrock, in Catena Supplement 23 (ed.), pp. 101-124. Stanistreet, I.G., and McCarthy, T.S. 1993. The Okavango fan and the classification of subaerial fan systems. Sedimentary Geology, 85, pp. 115-133. Strahler, A.N. 1952. Dynamic basis of geomorphology. Geological Society of America Bulletin, 63, pp. 923-938. Sun, T., Meakin, P., and Jossang, T. 1994b. The topography of optimal drainage basins. Water Resources Research, Vol. 30, No. 9, pp. 2599-2610, September 1994. Takahashi, T. 1993. Debris flow initiation and termination in a gully. Hydraulic Engineering 1993 Hsieh wen Shen and others (eds.). Vol. 2, pp. 1756-1761. Thurber Engineering Ltd. 1983. Debris torrent and flooding hazards, Highway 99, Howe Sound. Report to British Columbia Ministry of Transportation and Highways. 25 pps. + appendices. Thurber Engineering Ltd. and Golder Associates Ltd. 1993. Cheekye River terrain hazard and land use study; Final Report, Volume 1. 146 pages + Tables, Plates and Figures. Thurber Engineering Ltd. 1985. Westwood Plateau area escarpment and gravel study - phase 2: report to Ministry of Lands, Parks and Housing Land Development Branch. Thorn, C.E. 1988. Introduction to theoretical geomorphology. Allen & Unwin, Inc., 247 pps.  203  VanDine, D.F. 1984. Debris flows and debris torrents in the Southern Canadian Cordillera. Canadian Geotechnical Journal, Vol. 22, pp. 44-68.  Wertz, J.B. 1968. Structural elements of ore search in the Basin and Range province, southeast Arizona: domes and fracture intersections. American Society of Mining Engineers, Transactions, Vol. 241. pp. 276-291, September 1968. Wertz, J.B. 1974. Detection and significance of lineaments and lineament intersections in parts of the northern Cordillera. Proceedings of the First International Conference on the New Basement Tectonics, A. Robert, S. Hodgson, Parker Gay Jr., and J.Y. Benjamins (eds.), Salt Lake City, Utah, June 3-7, 1974, pp.42-53. Whipple, K.X. 1993. Interpreting debris-flow hazard from study of fan morphology. Hydraulic Engineering '93, Hsieh Wen Shen and others (eds.). Vol. 2, pp. 1302-1307. Wieczorek, G.F., Elliott, W.L., and Ellen, S.D. 1989. Debris Flows and hyperconcentrated floods along the Wasatch Front, Utah, 1983 and 1984. Bulletin of the Association of Engineering Geologists, Vol. XXVI, No. 2, 1989, pp. 191-208. Woldenberg, M.J. 1969. Spatial order in fluvial systems: Horton's laws derived from mixed hexagonal hierarchies of drainage basin areas. Geological Society of America Bulletin, Vol. 80, pp. 97-112, January 1969.  204  APPENDIX I  Frequency Tables for Lineament Trend Data  205  Distribution 0-4 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89 90-94 95-99 100-104 105-109 110-114 115-119 120-124 125-129 130-134 135-139 140-144 145-149 150-154 155-159 160-164 165-169 170-174 175-179 Total  Frequency 156 244 272 277 251 242 212 151 164 122 99 92 69 55 56 62 72 84 107 82 65 72 44 55 55 74 85 102 89 88 90 87 91 106 125 118 4215  % 3.70 5.79 6.45 6.57 5.95 5.74 5.03 3.58 3.89 2.89 2.35 2.18 1.64 1.30 1.33 1.47 1.71 1.99 2.54 1.95 1.54 1.71 1.04 1.30 1.30 1.76 2.02 2.42 2.11 2.09 2.14 2.06 2.16 2.51 2.97 2.80 100.00  Frequency - distribution for all lineaments in the study area.  206  Frequency Distribution 0-4 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89 90-94 95-99 100-104 105-109 110-114 115-119 120-124 125-129 130-134 135-139 140-144 145-149 150-154 155-159 160-164 165-169 170-174 175-179 Total  Southern Block 19 28 36 34 27 37 30 25 35 11 12 7 10 6 5 3 7 8 14 8 8 11 5 7 8 2 4 5 5 5 5 7 7 13 20 13 487  Central Block 90 166 171 184 164 162 136 100 100 74 69 62 42 39 32 36 49 60 68 62 45 41 27 32 23 37 39 49 46 36 44 28 52 53 69 59 2546  Northeast Block 18 27 29 25 26 18 26 10 12 16 11 11 7 6 7 11 7 4 10 4 8 15 6 7 21 26 30 33 28 34 21 29 22 23 16 21 625  Northwest Block 33 32 40 43 38 27 24 17 17 22 10 12 9 6 11 12 9 12 15 8 4 7 6 8 3 9 14 15 11 13 22 25 13 21 22 24 614  Frequency - distribution for lineaments in the sample blocks.  207  APPENDIX II  Statistical Methods  208  Test for randomness We must assume a Von Mises distribution. The null hypothesis and its alternative are therefore: Ho:k=0 H,:k>0 The value of R is calculated using either ROSE 1.02 or methods described in Davis (1986). This is compared to a critical value at the desired level of significance obtained from table 5.7 in Davis (1986, pp. 324). If R is greater than the critical value the null hypothesis is rejected and the observations are assumed to come from a population with a preferred orientation (Davis 1986). In the case of large values of 'n' the critical value is distributed as chi-square with 2 degrees of freedom and is approximated by 2nR (Mardia 1972). 2  Example calculation: For the southern block of lineaments described on page 36. The sample size V is 487. R=0.4296.  2nR = 2.487 x 0 x 4296 2  =179.76 The critical value from tables of Chi-square is found to be 5.99. Because 179.76 is greater than 5.99, the null hypothesis is rejected and a preferred trend is implied.  209  Calculation of standard error A confidence angle about the mean direction of the sample data can be calculated based on the standard error of the estimate of mean direction. In this fashion both the size of the sample and the dispersion are taken into account.  First R is calculated and K estimated from tables (e.g. Davis 1986, p.323). Then the standard error is calculated according to the following formula; Se = l/(nRK)  ,/2  This gives a result in radians which must be converted to degrees. The calculated value is a measure of the chance variation expected in the sample in estimates of the mean direction.  Assuming the  estimation errors are normally distributed;  6>±Za.Se  should capture the true population mean a % of the time. Za is determined from standard normal distribution tables. The value is 1.96 for the 95% confidence level. Example calculation: For the entire lineament dataset n = 4215, R = 0.319 and K is estimated to be 0.67587. Hence:  Se= 1/(4215 x0.319x0.67587)  m  = 0.0331722 rads. = 1.9°  Thus Za.Se = 3.725°.  210  Test for equality of two sets of directional data The equality of two mean directions can be tested by comparing the vector resultants of the two groups to that produced when the two groups are combined. If the two groups are drawn from the same population the resultant of the pooled sample should be approximately equal to the sum of their two resultants (Davis 1986). If the mean directions are significantly different then the pooled resultant will be shorter than the sum of their resultants. R is calculated using the following formula: R = (R, + R )/n 2  The hypothesis being tested is: Ho^AuUrv,) =  (XTHIVJ)  .HI:(AI/*,V,) *  Q.^i v ) 2  2  Example calculation: To test the equality of the southern and central blocks described on page 35. R = 209.2 (for the t  southern data) and R = 895.45 (for the central data), n = 3033; the sample size of the pooled dataset. 2  R =.(209.2 + 895.45)/3033 = 0.3642 This value is compared to that calculated by ROSE 1.02 for the pooled dataset. This value is 0.3642. Since the two values are equal it is concluded that they are from the same population.  More rigorous testing is provided by the Watson - Williams test described by Mardia (1972).  211  APPENDIX III  Location and Description of Sample Set Basins  212  u  O  C  •GO  E  cj fc  o  S o  I s?  J3 4s  —;  O  >,3  c  .2!  2 w > E T3 «  tf  ag  •s > -e a  S3  2 «f "c ^ n - " i on «J  >  en  wi  —  0.3  a ««c CJ  O0(«  ° ? "£  S <u *  s «  »« 1 "  °  x. §  1 •o c wo  1  «E _ 1 -a Q O « ^  4)  CQ  1  JS S  8"  c  « S*  tt  «• -s  •» -o c <u c (A *-> o o 00  .E  .£  Eg  S o * t  r.  be  O- to «J  CJ  3  V  •3 S  " 8  >  •u il o 55 <2 Xj  X) u « XI 2 3  S -2 c .£  •d  CJ e s — o. c <o  « x: o  2 § 2 -S  1  £ u  > •-  2  se flariking  >• £  2 & o >  :epl icti Undi;  3 E  00  >  c  Cone mostly coll may be avalanch been logged.  a.  W  Large colluvial c one vegetation would SU| avalanche.  *S  -if  6  al, littl latedc  ._  lack of usceptible to  «5  '5,3 xi ca  C  S 6 'J  CU-—  --5  = £? o c« 2 « S o c « S S  3  —-'5  SI, « S  fc  f2  •s  f  .5  3  £2  S  c  ed  3 8s > rt 3 > £ it  E  « -  &  -s I Jj "O  3  o o  .  JO '  X) « l  in «  -c -d 2 -S  C5  c xi : 1  l ' ~ "O x: <J  Cu,  11  a.  t  S o  •°S3 3a, E  c o  c  <U  O  > E T3T3  e C  o  o  CO  H D  o  -1  CQ 5t  vaa 2»  oa %  aa *  ON  3 c'C o C  aa *  oa %  a  se  OS  1?  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O  bo .•2 >. i~ a.  00  O  CQ =tt  o  o s; <N o  3 o  3  X>  Hi  C  I  IS £. 1  c 2 H c  & 60 T3  .2  1-5  <U  .5 •£  3  e  0  0 0 * ^ 0  _ o  " "3 " •c  "  oo  «  '  c  •a *e a s  K * •- a a .a « -  E S  o. •= Kg  3 -6  00 ™ —  " S>  3  S3  u  «  J3d  cj  t i  •a <o  •S -2 5  G O CJ  C XL  -d  * -s P 0  ti5 E  2i  GO  O  >  4i  1>  2^  -C  "8 « E .2  f  •S 8 U  «  XJ  oo <D  o —  —  t  to  O C3 c D a O CO *-• ra  .—  r  -  c  O  3  o  «i  ^  CQ at  CQ at  CQ at  o CO o o  ON  E  -5  g  O i_ rj  3 5  3 > J  3 L  O  O  6  J;  ^  6 0  "  l«  « 3  Q oo  3 p  «  inc  o ej H O oo O  3  O "oo C 73  > .S3  >  ^  u  o  <L)  <o  u S« <u g  CO c - g o . </> a oo i 2  M  3 <£! o) .2 -5 o a Jj a s ^ c o > ° c<U 60 •— t4_ o o •a c o «  •= 2 8" «  ™  o .2 > ? -ao  .«  o  u  e  00 ON  U CQ at  w  I- «  OO  £ C  CQ at  —  < / > — « = "  C  OO  oo oo  aCTJ ^No ! ^SO *-«»  "  03  ON  60  > a •« ^  C C  T3 T3 C  OO  <j  s£ y 5 35 <u o. 03 oo J=! - y I—  __  ± I  2  3  §8*;  il.fi  = K  o p c  o w  1 •• o  -o .S  3 2  ^  *  H o, <g *  11  sz 5  1  S3  c  -  r-  X) o  o  «  3 > oo CJ  E o •o x: H 2  '> 5 "> 5 2 c c  C  o o cx, (/)  £  o TO  -a c  on - C  z i2 5 £ 2  215  APPENDIX I V  Tabulated Sample Set Data  216  CI  o  o  i S  o  3  i« o  2  2 Q  I- g  U  •a S«  u  OS D  15  It  Q  u <  u o t/3  217  c o  «2 c. n. E  •S 8. 8 9S b o o o  £ J!  o a. I—  00  o o. o — f  US "s „ |« « ~  O  I -a £  'CL O H  O H  < < 4!  s I-i OH  | —  T3  3 "£j  c o U  10 2  03  3 O  a  .S II S3 o O  \< i  D.  "a  O H  E  t> —  I O H  •"  9- on M  2 Q  •SS2  en  •a n  o  o  85 E  o  3 5  O H  05 «  < O o  o  1= ?  D 3  <  o  3  < -a c o oo _o u  3  o on  218  1 2 3 4 5 6 7 8 9 10 14 15 16 17 18 19 20 21 22 24 25 26 27 28 29  Cone U 453 174 205 248 281 639 221 470 314 162 41 18 45 445 53 285 305 186 484 303 89 99 153 71 229  SOURCE  Aspect  Geology Granodiorite. Quartz diorite. Quartz diorite. Granodiorite. Migmatite Quartz diorite. Granodiorite. Granodiorite. Quartz diorite. Quartz diorite. Twin Island/Gambier Groups Quartz diorite. Quartz diorite. Quartz diorite. Quartz diorite. Fire Lake Group Quartz diorite. Gambier Group Quartz diorite. Quartz diorite. Quartz diorite. Granodiorite. Quartz diorite. Quartz diorite. Migmatite, quartz diorite, Harrison Lake Formation, and Twin Island Group GEOLOGIC MAP  east-southeast northeast northwest northwest west south-southwest southeast southeast north-northeast west-northwest southeast east-southeast southeast southwest east-southeast southeast north northeast west southwest northwest northeast southwest west south-southwest TOPOGRAPHIC MAP  Thematic Information for sample set basins.  219  APPENDIX V  Results of spatial correlation analysis between lineaments and streams  220  DATA FOR A L L S T R E A M ORDERS Overlying lineaments Correlation Basins %  40-49 30-39 20-29 10-19 0-9  2,3,4,6,9,20 7,18,21,25,28 1,10,14,22,26 5,15,17,24,27,29 8,16,19  Within 40m Correlation Basins %  90-99 80-89 70-79 60-69 50-59 40-49 30-39 20-29 10-19  2 20,25 6,4,26,28 1,3,9,10,15,17,27 7,14,18,21,22 8 5,24,29 16,19  Within 60m Correlation Basins %  90-99 80-89 70-79 60-69 50-59 40-49 30-39 20-29 10-19  2,25 4,6,10,17,20,26 1,3,9,15,27,28 7,14,18,21 8,22 5,24,29 19 16  Frequency  %  6 5 5 6 3  24% 20% 20% 24% 12%  Frequency  %  1 2 4 7 5 0 1 3 2  4% 8% 16% 28% 20% 0% 4% 12% 8%  Frequency  %  2 6 6 4 2 0 3 1 1  8% 24% 24% 16% 8% 0% 12% 4% 4%  Cumulative Frequency 6 11 16 22 25  Cumulative Frequency 1 3 7 14 19 19 20 23 25  Cumulative Frequency 2 8 14 18 20 20 23 24 25  Results of overlay of streams on lineaments: All stream orders. 221  %  24% 44% 64% 88% 100%  %  4% 12% 28% 56% 76% 76% 80% 92% 100%.  %  8% 32% 56% 72% 80% 80% 92% 96% 100%  DATA FOR 1ST. ORDER STREAMS Correlation Basins %  60-69 50-59 40-49 30-39 20-29 10-19 0-9  6 2,4 3,20,25 9,21,28 1,7,10,14,18,22,26 5,8,15,17,24,27,29 16,19  Within 40m Correlation Basins %  100 90-99 80-89 70-79 60-69 50-59 40-49 30-39 20-29 10-19  2 4,25 6,20,26 3,17,28 1,8,10,15,22 7,21,27 9,14,18 5 19,24,29 16  Within 60m Correlation Basins %  100 90-99 80-89 70-79 60-69 50-59 40-49 30-39 20-29 10-19  2,4 25 6,10,17,20,26 1,3,22,27,28 7,8,14,15,21 9,18 5 19 24,29 16  Frequency  %  1 2 3 3 7 7 2  4% 8% 12% 12% 28% 28% 8%  Frequency  %  1 2 3 3 5 3 3 1 3 1  4% 8% 12% 12% 20% 12% 12% 4% 12% 4%  Frequency  %  2 1 5 5 5 2 1 1 2 1  8% 4% 20% 20% 20% 8% 4% 4% 8% 4%  Cumulative Frequency 1 3 6 9 16 23 25  Cumulative Frequency 1 3 6 9 14 17 20 21 24 25  Cumulative Frequency 2 3 8 13 18 20 21 22 24 25  Results of overlay of streams on lineaments: First order streams. 222  %  4% 12% 24% 36% 64% 92% 100%  %  4% 12% 24% 36% 56% 68% 80% 84% 96% 100%  %  8% 12% 32% 52% 72% 80% 84% 88% 96% 100%  DATA FOR 2ND. ORDER STREAMS Overlying lineaments Correlation Basins %  60-69 50-59 40-49 30-39 20-29 10-19 0-9  2 7,9,20 18,21,26 3,6,10,14,15,17,25,27,28 1,24,29 4,5,8,16,19,22  Within 40m Correlation Basins %  100 90-99 80-89 70-79 60-69 50-59 40-49 30-39 20-29 10-19 0-9  2 1,9 20 25,28 6,7,15,17,18,27 10,14,26 21,29 3,24 4 19,5,22 8,16  Within 60m Correlation Basins %  100 90-99 80-89 70-79 60-69 50-59 40^J9 30-39 20-29 10-19  1,2,9 15,25 17,20 6,7,14,18,26,27,28 10,21 29 3 4,5,24 8,22 16,19  Frequency  %  1 3 0 3 9 3 6  4% 12% 0% 12% 36% 12% 24%  Frequency  %  1 2 1 2 6 3 2 2 1 3 .2  4% 8% 4% 8% 24% 12% 8% 8% 4% 12% 8%  Frequency  %  3 2 2 7 2 1 1 3 2 2  12% 8% 8% 28% 8% 4% 4% 12% 8% 8%  Cumulative Frequency 1 4 4 7 16 19 25  Cumulative Frequency 1 3 4 6 12 15 17 19 20 23 25  Cumulative Frequency 3 5 7 14 16 17 18 21 23 25  Results of overlay of streams on lineaments: Second order streams. 223  %  4% 16% 16% 28% 64% 76% 100%  %  4% 12% 16% 24% 48% 60% 68% 76% 80% 92% 100%  %  12% 20% 28% 56% 64% 68% 72% 84% 92% 100%  DATA FOR 3RD. ORDER STREAMS Overlying lineaments Correlation Basins %  40-49 30-39 20-29 10-19  0-9  18 14 1,10 2,5,16,19,22,29  Within 40m Correlation Basins %  18 10 40-49 ; 1,14,22 30-39 2 20-29 16 10-19 5,19,29 0-9 60-69 50-59  Within 60m Correlation Basins %  70-79 60-69 50-59 40-49 30-39 20-29 10-19 0-9  18 10 14,22 1 16 2 5,19,29  Frequency  %  1 0 1 2 6  10% 0% 10% 20% 60%  Frequency  %  1 1 3 0 1 1 3  10% 10% 30% 0% 10% 10% 30%  Frequency  %  1 1 2 1 1 1 0 3  10% 10% 20% 10% 10% 10% 0% 30%  Cumulative Frequency 1 1 2 4 10  Cumulative Frequency 1 2 5 5 6 7 10  Cumulative Frequency 1 2 4 5 6 7 7 10  Results of overlay of streams on lineaments: Third order streams. 224  %  10% 10% 20% 40% 100%  %  10% 20% 50% 50% 60% 70% 100%  %  10% 20% 40% 50% 60% 70% 70% 100%  Basin « 1 Stream Order lot 2nd 3rd 4lh Isolated 1st/lin 2nd/lln 3rd/1in 4th/lin Overiyinq L i n t . 1«1*40 2nd«40 3rdi-40 41h*40 W i t h i n 40 m 1st««0 2nd*«0 3rd*60 4lh>«0 W i t h i n 60 m Stream Length S o n Una. H w i t h l n 40m S w r t h i n 60m %occupied lins.  Basin # 3 Stream O r d e r 1st 2nd 3rd 4th Isolated 1st/I in 2ndflin 3rdflin 4th/lin Overiyinq L i n s . 1st«40 2nd*40 3rd . 4 0 4th«40 W i t h i n 40 m 1.1.60 2nd«60 3rd . 6 0 4th*«0 W i t h i n 60 m Stream L e n g t h %on line. % w r t h i n 40m % w i t h i n 60m %occupied lins.  Basin # 5 Stream Order 1st 2nd 3rd 4th Isolated 1st/lin 2ndflin 3rd/lin 4th/lin Overiyinq Lins. 1st«40 2nd*40 3rd . 4 0 4th«40 W i t h i n 40 m 1st»«0 2nd<«0 3rd»«0 4th*60 W i t h i n 60 m Stream L e n g t h V o n lins. %w«hln 40m % w f t h l n 60m %occupi«d l i n s .  Length 920 0 4*0 0 1400 940 100 120 0 1160 1360 620 320 0 2300 600 40 20 0 560 5420 21*. 64% 74% 48%  Length 1080 540 0 0. 1620 2060 240  •o  0 2300 1240 160 0 0 1400 220 100 0 0 320 5640 41% 66% 71% 47%  Length 5460 2200 2340 0 10000 1900 120 0 0 2020 1760 500 60 0 2320 880 500 100 0 1480 15820 13% 27% 37% 15%  % 16.97% 0 00% 886% 0.00% 25.83% 17.34% 1.85% 2.21% 0.00% 21.40% 25.09% 11.44%| 5.90% 0.00% 42.44% 9.23% 0.74%| 0.37% 0.00% 10.33%  1«t_ 24.73%  25 2 7 %  36.56% 61.83%  13.44% 75.27%  3720  % 19.15% 9.57% 0.00% 0.00% 28.72% 36.52% 4.26% 0.00% 0.00% 40.78% 21.99% 2.84%| 0.00% 0.00% 24.82% 3.90% 1.77%| 0.00% 0.00% 5.67%  1st. 23.48%  44.78%  26,96% 71.74%  4.78% 76.52%  4600  % 34.51% 13.91% 14.79% 0.00% 63.21% 12.01% 0.76% 0.00% 0.00% 12.77% 11.13% 3.16%| 0.38% 0.00% 14.66% 5.56% 3.16%| 063% 000% 9 36%  1st 54.60%  19.00%  17.60% 36.60%  8 80% 45.40%  10000  2nd  B a s i n tt 2 Stream Order 1st 2nd 3rd 4th Isolated 1at/lin 2nd/1in 3rd/lin 4tti/lin Overiyinq Lins. 1*1*40 2nd*40 3rd+40 4th+40 W i t h i n 40 m 1st*«0 2nd*60 3rd«60 4th«60 W i t h i n 60 m Stream Length % o n line. S w H h l n 40m S w r t h i n 60m % o c c u p i e d line.  3rd  0.00%  13.16%  81.58% 94 7 4 %  5.26% 100.00%  760  51.06%  12.77%  34 0 4 % 4681%l  2.13% 48.94%|  940  Basin #4 Stream Order 1st 2nd 3rd 4th Isolated 1st/lin 2nd/lin 3rd(lin 4tWlin Overiyinq Lins. 1«t*40 2nd«40 3rd»40 41h*40 W i t h i n 40 m 1st*60 2nd*60 3rd . 6 0 4th*60 W i t h i n 60 m Streem Length %on lins. S w K h i n 40m % w i t h i n 60m % o c c u p i e d line.  2nd 51.92%  23.08%  15.38% 38.46%|  9.62% 48.08% I  1040  2nd 66.27%  3.61%  15.06% 18.67%  15.06% 3373%  3320  Basin # 6 Stream O r d e r 1st 2nd 3rd 4th Isolated 1st/1in 2ndflin 3rd/lin 4thflin Overiyinq Lins. 1sH40 2nd*40 3rd*40 4th«40 W i t h i n 40 m 1st . 6 0 2nd.60 3rd . 6 0 4th«60 W i t h i n 60 m Stream Length %on lins. %wHhin40m % w i t h i n 60m %occupied lins.  3rd  93.60%  0.00%  2.40% 2.40%  4.00% 6.40%  2500  Length  0 0 420 0 420 1920 860 0 0 2780 1800 500 120 0 2420 0 0 40 0 40 5660 49% 92% 93% 56%  Length  0 280 0 0 280 620 20 0 0 640 400 80 0 0 480 60 40 0 0 100 1500 43% 75% 81% 36%  Length 120 260 0 0 380 580 220 0 0 800 200 400 0 0 600 40 100 0 0 140 1920 42% 73% 80% 84%  % IKL 0.00% 0.00% 0.00% 7.42% 0.00% 7.42% 33 9 2 % 51.61% 15.19% 0 00% 0.00% 49.12% 31.80% 48.39% 8.83% | 100.00% 2.12% 0.00% 42.76% 0.00% 0.00% 0.00% | 100.00% 0.71% 0.00% 0.71% 3720  % 1st 0.00% 0.00% 18.67% 0.00% 0.00% 18.67% 41.33% 57.41% 1.33% 0.00% 0.00% 42.67% 26.67% 37.04% 5.33% | 94.44% 0.00% 0.00% 32.00% 4.00% 5.56% 2.67% | 100.00% 0.00% 0.00% 6.67% 1080  %  6.25% 13.54% 0.00% 0.00% 19.79% 30.21% 11.46% 0.00% 0.00% 41.67% 10.42% 20.83% | 0.00% 0.00% 31.25% 2.08% 5.21%| 0.00% 0.00% 7.29%  1st 12.77%  61.70%  21.28% 82.98%  4.26% 87.23%  940  2nd  3rd  0.00%  63.24%  36.76% 100.00%  0.00% 100.00%  1360  72.41%  0.00%  20 6 9 % 20.69% I  6.90% 27.59%l  580  2nd 66.67%  4.76%  19.05% 23 81%)  9.52% 33.33% I  420  2nd 26.53%  22.45%  40.82% 63.27%  10.20% 73.47%  980  Results of spatial correlations between lineaments and streams for individual basins. (lins. = lineaments) 225  Basin « 7 Stream Order 1«t 2nd 3rd 4th Isolated 1st/lin 2nd/1in 3rd/lin 4th/lin Overlyinq L i n * . 1e1*40 2nd«40 3rd«40 41h*40 W i t h i n 40 m 1et»80 2nd.60 3rd*«0 4th*60 W i t h i n 60 m Stream L e n g t h V o n lins. Swithin40m S w i t h i n 60m % o c c u p ( e d lins.  6 . .in « i length 620 380 0 0 1000 360 700  0  0 1060 460 240  0  0 700 160 60 0 0 220 2980 3614 5914 6614 3714  %  2081% 1275% 000% 000% 33 5 6 % 12 0 8 % 2349% 0 00%  1«t 38.75%  22.50%  Stream O r d e r let 2nd 3rd 4th Isolated 1*1/lln 2nd/1in 3rd/1in 4th/1in Overlyinq U n a . 1st . 4 0 2 n d *40 Jrf»40 4th<40 W i t h i n 40 m 1st««0 2nd-60 3rd««0 4thf«0 W i t h i n 60 m Stream Length % o n Una. %w i t h i n 40m S w i t h i n 60m %occupied lins.  2nd 27.54%  50.72%  000%  35.57% 1544% 8.05% | 0 00% 0.00% 23.49% 5.37% 2.01%| 000% 000% 7.38%  28 7 5 % 51.25%  1000% 61.25%  1600  17.39% 68.12%l  4 35% 72.46%|  1380  Length % 18.42% 1720 5.57% 520 9.64% 900 0.00% 0 3140 33.62% 1100 11.78% 5.14% 480 360 3.85% 0.00% 0 1940 20.77% 1380 14.78% 10.28%| 960 480 5.14% 0.00% 0 2820 30.19% 920 9.85% 4.93% | 460 0 64% 60 0 0 00% 15,42% 1440 9340 200 0 0 % 21% 51% 66% 48%  1st 33.59%  21.48%  26.95% 48.44%  17.97% 66.41%  5120  2nd 21.49%  19.83%  39.67% 59,50%  19.01% 78,51%  2420  15 6 3 % 34 38%  640 60  0 00% 50 0 0 % 6.25%  0 0 0 0 0  80 340 60  0 0  400 40 120  %  1st 30.30%  2nd 70.97%  000%  0.00%  0.00% 0.00% 6.25% 26.56% 4.69% 0.00%  12.12%  51 5 2 % 63.64%  000%  31.25% 3.13% 9.38% 0 0.00% 0 0.00% 160 12.50% 1280 200.00% 6% 38% 50% 42%  606% 69.70%  660  000%  9.68% 9.68% I  19.35% 29 0 3 % |  620  B a s i n tt 10 Stream Order Length % 1st 2nd 3rd 1st 1540 9.99% 13.87% 2nd 680 4.41% 31.78% 3rd 740 4.80% 33.94% 4th 0 0.00% Isolated 2960 19.20% 1et/lin 2780 18.03% 25.05% 2nd/lin 620 4.02% 28.97% 3rd/lin 240 1.56% 11.01% 4th/1in 0 000% Overlyinq Lins. 3640 2361% 1st*40 4620 29.96% 41.62% 2nd»40 640 4.15% 66.67% 29.91% 3rd*40 880 5.71% 58.88% 40.37% 4th*40 0 0.00% 51.38% W i t h i n 40 m 6140 39.82% 1st*60 2160 14.01% 19.46% 2nd*«0 200 1.30% 86.13% 9.35% 3rd 460 320 2.08% 68.22% 14.68% 41h460 0 0.00% 66.06% W i t h i n 60 m 2680 17.38% Stream L e n g t h 15420 200.00% %on lins. 24% S w i t h i n 40m 63% 11100 2140 2180 S w i t h i n 60m 81% %occupied lins. 56%  Basin #9 1st 2nd Length Stream O r d e r % 780 29.77% 46.99% 1st 0 00% 0.00% 0 2nd 0 0.00% 3rd 0 0.00% 4th 29.77% 780 isolated 600 19.08% 30.12% 1st/lin 540 20.61% 56.25% 2nd/lin 0.00% 3rdnin 0 0.00% 0 4th/lin 39.69% Overlyinq Lins. 1040 300 11.45% 18,07% 1st*40 41.67% 15.27% 48.19% 2nd«40 400 0.00% 97.92% 0 3rd*40 0.00% 4th*40 0 W i t h i n 40 m 700 26.72% 4.82% 1st*«0 so 3.05% 0.76% 53.01% 2.08% 20 2nd*«0 100.00%| 3rd*60 0 0.00% 0 0.00% 4th»60 W i t h i n 60 m 100 3.82% 2620 200.00% Stream L e n g t h %on lins. 40% 66% 1660 960 % w i t h i n 40m % w i t h i n 60m 70% 100% ^ o c c u p i e d lins. B a s i n # 14 Stream Order 1st 2nd 3rd 4th Isolated 1st/lin 2ndflin 3rd/lin 4th/)in Overlyinq Lins. 1st*40 2nd*40 3rd*40 4th«40 W i t h i n 40 m 1st«60 2nd*60 3rd»«0 4th4«0 W i t h i n 60 m Stream L e n g t h V o n lins. % w f t h i n 40m % w t t h i n 60m % o c c u p i e d line.  Length 200 440  Basin #15 Stream O r d e r 1st 2nd 3rd 4th Isolated 1 st/lin 2nd/lin 3rd/lin 4th/lin Overlyinq Line. 1ai*40 2 n d 440 3rd 440 4th»40 Within 40 m 1et*60 2nd««0 3rd.60 4th460 W i t h i n 60 m Stream L e n g t h %on lins. %wrthin40m X w i t h l n «0m % o c c u p i e d line.  3rd  50.00%  20.00%  2667% 4667%|  3.33% 50 0 0 % |  1800  % Length 1040 18.18% 220 3.85% 0 0.00% 0 0.00% 1260 22.03% 640 11.19% 460 8.04% 0 0.00% 0 0.00% 1100 19.23% 1460 25.52% 940 16.43%| 0 0.00% 0 0.00% 2400 41.96% 280 4.90% 680 11.89%| 0 0.00% 0 000% 960 16.78% 5720 200 00% 19% 61% 78% 58%  1st 30.41%  18.71%  42.69% 61.40%  8,19% 69.59%  3420  2nd 9.57%  20.00%  40,87% 60.87% |  29.57% 90.43% |  2300  Results of spatial correlations between lineaments and streams for individual basins (Continued). (lins. = lineaments)  226  B a s i n U 16 Stream O r d e r 1at 2nd 3rd 4th Isolated 1et/lin 2nd/lin 3rd/lin 4tMin Overiyinq Line. 1st+40 2nd+40 3rd+40 4th+40 Within 40 m 1st+80 2nd+60 3rd+60 4th+60 W i t h i n 60 m Stream L e n g t h S o n line. S w i t h i n 40m S w i t h i n 60m S o c c u p i e d lins.  Length 1260 800 440 0 2500 20 0 20 0 40 100 20 100 0 220 140 100 80 0 320 3080 1% 8% 19% 24%  B a s i n # 18 Stream Order 1st 2nd 3rd 4th Isolated Istyiin 2nd/lin 3rd/lin 4th/lin Overiyinq Lins. 1st+40 2nd+40 3rd+40 4th+40 W i t h i n 40 m 1st+80 2nd+60 3rd+60 4th+60 W i t h i n 60 m Stream L e n g t h S o n tins. S w i t h i n 40m S w i t h i n 60m S o c c u p i e d lins.  Length S 2700 26.01% 6.74% 700 460 4.43% 0 0.00% 3860 37.19% 14.26% 1480 8.67% 900 7.51% . 780 0.00% 0 30.44% 3160 13.10% 1360 6.74%| 700 5.01% 520 0.00% 0 2580 24.86% 460 4.43% 1.54%| 160 1.54% 160 0 0.00% 780 7.51% 10380 200.00% 30% 55% 63% 55%  B a s i nft20 Stream Order 1st 2nd 3rd 4th isolated 1st/lin 2nd/1in 3rdflin 4th/lin Overiyinq Lins. 1st440 2nd+40 3rd . 4 0 41h+40 W i t h i n 40 m 1st+60 2nd+60 3rd»60 41h»60 W i t h i n 60 m Stream L e n g t h S o n tins. S w i t h i n 40m S w i t h i n 60m S o c c u p i e d lins.  Length 140 180 0 0 320 320 520 0 0 840 320 300 0 0 620 20 20 0 0 40 1820 46% 80% 82% 77%  % 40.91% 25.97% 14.29% 0.00% 81.17% 0.65% 0.00% 0.65% 0.00% 1.30% 3.25% 0.65%| 3.25% 0.00% 7.14% 4.55% 3.25% | 2.60% 0.00% 10.39% 200.00%  1st 82.89%  1.32%  6 58% 7.89%  9.21% 17.11%  1520  S 7.69% 9.89% 0.00% 0.00% 17.58% 17.58% 28.57% 0.00% 0.00% 46.15% 17 5 8 % 16.48%| 0.00% 0.00% 34.07% 1.10% 1.10%| 0.00% 0.00% 2.20% 200.00%  1st 45.00%  24.67%  22.67% 47.33%  7.67% 55.00%  6000  1st 17.50%  40.00%  40.00% 80.00%  2.50% 82.50%  800  2nd 86.96%  0.00%  217% 2.17%  10.87% 13.04%  920  2nd 28.46%  36.59%  28.46% 65.04%  6.50% 71.54%  2460  2nd 17.65%  50.98%  29.41% 80.39%|  1.96% 82.35% |  1020  3rd  68.75%  3.13%  15.63% 18.75%l  1250% 31.25%|  640  3rd  23.96%  40.63%  27.08% 67.71%|  8.33% 76.04%|  1920  B a s i n # 17 Length Stream Order 200 1st 140 2nd 0 3rd 4th 0 reolated 340 1st/tin 320 2nd/lin 260 Srdflin 0 4th/1ln 0 Overiyinq U n s . 580 1st +40 1020 520 2nd+*0 3rd*40 0 0 4th+40 Within 40 m 1540 1st+60 340 2nd+60 260 0 3rd+60 4th+60 0 W i t h i n 60 m 600 Stream Length < 3060 %on line. 19% S w i t h i n 40m 69% S w i t h i n 60m 89% S o c c u p i e d lins. 62%  % 6.54% 4.58% 0.00% 0.00% 11.11% 10.46% 8.50% 0.00% 0.00% 18.95% 33.33% 16.99% | 0.00% 0.00% 50.33% 11.11% 8.50% | 0.00% 0.00% 19.61% 200.00%  let 10.64%  17.02%  54.26% 71.28%  18.09% 89.36%  1880  B a s i n * 19 Stream O r d e r 1st 2nd 3rd 4th Isolated 1st/lin 2nd/1in 3rdflin 4th/iin Overiyinq Lins. 1et+40 2nd+40 3rd+40 4th+40 W i t h i n 40 m 1st+60 2nd+60 3rd+60 4th+60 W i t h i n 60 m Stream Length S o n lins. S w i t h i n 40m S w i t h i n 60m S o c c u p i e d lins.  Length S 34560 39.89% 9080 10.48% 10940 12.63% 9360 10.80% 63940 73.80% 3460 399% 680 0.78% 40 0.05% 40 0.05% 4220 4.87% 11280 13.02% 520 0.60% | 280 0.32% 240 0.28% 12320 14.22% 5380 6.21% 340 0.39% | 260 0.30% 180 0.21% 6160 7.11% 86640 200.00% 5% 19% 26% 15%  B a s i n #21 Stream O r d e r 1st 2nd 3rd 4th Isolated 1st/lin 2nd/lin 3rd/lin 4th/lin Overiyinq Line. 1st+40 2nd+40 3rd+40 4th+40 Within 40 m 1st+60 2nd+60 3rd.60 4th+60 W i t h i n 60 m Stream L e n g t h S o n lins. S w i t h i n 40m S w i t h i n 60m S o c c u p i e d lins.  Length 1560 600 0 0 2160 1580 520 0 0 2100 1360 240 0 0 1600 560 400 0 0 960 6820 31% 54% 68% 49%  S 22.87% 8.80% 0.00% 0.00% 31.67% 23.17% 7.62% 0.00% 0.00% 30.79% 19.94% 3.52% | 0.00% 0.00% 23.46% 8.21% 5.87% | 0.00% 0.00% 14.08% 200.00%  2nd 11.86%  22 0 3 %  44.07% 66.10%  22 0 3 % 88.14%  1180  1st 63.20%  6.33%  20.63% 26.96%  9.84% 36.80%  54680  1st. 30.83%  31.23%  26.88% 58.10%  11.07% 69.17%  5060  10620  11520  2nd 34.09%  29.55%  13.64% 43.18%  22.73% 65.91%  1760  Results of spatial correlations between lineaments and streams for individual basins (Continued) (lins. = lineaments) 227  B e . I n « 22 Stream Order 1.1 2nd 3rd 4th Isolated let/tin 2nd/1in 3rd/lin 4th/lin Ov.ftyinq Line. 1.1-»0 2nd»40 3rd . 4 0 4th<40 WHhin40m 1et««0 2nd««0 3td»60 4th.60 W i t h i n 60 m Stream L e n g t h V o n line. V w r t h i n 40m V w i t h i n 60m V o c c u p i e d line.  B a s i n # 25 Stream Order 1st 2nd 3rd 4th Isolated 1st/lin 2nd/lin 3rdflin 4th/lin Overlyinq L i n s . 1.1*40 2nd*40 3rd*40 4th*40 W i t h i n 40 m 1st»60 2nd*60 3rd*60 41hi60 W i t h i n 60 m Stream L e n g t h V o n lins. V w i t h i n 40m V w i t h i n 60m V o c c u p i e d lins.  B a s i n 0 27 Stream Order 1st 2nd 3rd 4th Isolated IstTlin 2nd/1in 3rd/lin 4th/lin Overlyinq L i n s . 1st M O 2nd . 4 0 3rd»40 4th»40 W i t h i n 40 m 1st«60 2nd»60 3rd*60 41h«60 Within 60 m Stream L e n g t h V o n line. V w r t h i n 40m V w i t h i n 60m V o c c u p i e d lins.  Length 2400 2700 280 0 5380 2540 60 60 0 2660 3060 420 220 0 3700 660 340 100 0 1100 12840 21V 50V 58% 32%  Length  0 120 0 0 120 340 140 0 0 480 420 260 0 0 680 0 100 0 0 100 1380 35% 84% 91V 75%  Length 620 240 0 0 860 340 240 0 0 580 1040 500 0 0 1540 460 100 0 0 560 3540 16% 60% 76V 100%  V 1869% 21.03% 2 18% 000% 41.90% 1978% 0.47% 0.47% 0.00% 20.72% 23.83% 3.27%| 1.71% 000% 28.82% 5.14% 2.65%| 0.78% 0.00% 8.57%  1st 27.71%  29.33%  35.33% 64.67%  7.62% 72.29%  8660  % 1st, 0.00% 0.00% 8.70% 0.00% 0.00% 8.70% 24.64% 44.74% 10.14% 0.00% 0.00% 34.78% 30.43% 55.26% 18.84%| 100.00% 0.00% 0.00% 49.28% 0.00% 0.00% 7.25%l 100.00% 0.00% 0.00% 7.25% 760  V 17.51% 6.78% 0.00% 0.00% 24.29% 9.60% 6.78% 0.00% 0.00% 16.38% 29.38% 14.12%| 0.00% 0.00% 43.50% 12.99% 2.82%| 0.00% 0.00% 1582%  1st. 25.20%  13.82%  42.28% 56.10%  1870% 74.80%  2460  3rd  2nd 7670%  1.70%  11.93% 13 6 4 %  966% 23.30%  3520  2nd 19.35%  22.58%  41.94% 64.52% |  16.13%  SO.65%1  620  42.42%  909V  33 3 3 % 42.42VI  15.15% 57.58% |  660  B a a l n * 24 Stream Order 1st 2nd 3rd 4th Isolated 1st/lin 2ndflin 3rrJ/1in 4thAin Overlyinq Lins. 1st*40 2nd*40 3rd«40 4th*40 W i t h i n 40 m 1st«60 2nd»60 3rd*60 4th*eo W i t h i n 60 m Stream Length V o n lins. Vwrthin 40m V w r t h i n 60m V o c c u p i e d lins.  B a s i n « 26 Stream Order 1st 2nd 3rd 4th Isolated IstTlin 2nd/lin 3rd/lin 4th/lin Overlyinq Lins. 1st«40 2nd*40 3rd»40 4th*40 W i t h i n 40 m 1st*60 2nd»60 3rd*60 4th*60 W i t h i n 60 m Stream Length V o n lins. V w i t h i n 40m V w i t h i n 60m V o c c u p i e d lins.  B a s i n # 28 Stream O r d e r 1st 2nd 3rd 4th Isolated 1st/lin 2nd/1in 3rd/lin 4th/Iin Overlyinq Lins. 1st t 4 0 2nd«40 3rd»40 4th*40 W i t h i n 40 m 1st««0 2nd*60 3rd*60 4th»<0 W i t h i n 60 m Stream Length V o n line. V w i t h i n 40m V w r t h i n 60m V o c c u p i e d lins.  2nd 22.22%  22.22%  46.30% 68.52%|  9.26% 77.78% |  1080  Length 880 760 0 0 1640 120 180 0 0 300 180 200 0 0 380 60 20 0 0 80 2400 13V 28% 32V 70%  26 Length 220 220 0 0 440 520 240 0 0 760 940 180 0 0 1120 100 160 0 0 260 2580 29% 73% 83% 44%  Length 280 200 0 0 480 400 240 0 0 640 520 360 0 0 880 60 40 0 0 100 2100 30% 72V 77% 29%  2nd  V 1st 36.67% 70.97% 31.67% 0.00% 0.00V 68.33% 5.00% 9.68% 7.50% 0.00% 0.00% 12.50% 7.50% 14.52% 8 . 3 3 V | 24.19% 0.00% 0.00% 15.83% 2.50% 4.84% 0.63% | 29.03% 0.00% 0.00% 3.33V 153.23%  167.24V  1240  1160  V 8.53% 8.53% 0.00% 0.00% 17.05% 20.16% 9.30% 0.00% 0.00% 29.46% 36.43% 6.98%| 0.00% 0.00% 43.41% 3.88% 6.20% | 0.00% 0.00% 10.08%  1st. 12.36%  29.21%  52.81% 82.02%  5.62% 67,64%  1780  V 13.33% 9.52% 0.00% 0.00% 22.86% 19.05% 11.43V 0.00% 0.00% 30.48% 24.76% ,17.14%| 0.00% 0.00% 41.90% 2.86% 1.90%| 0.00% 0.00% 4.76%  1st 22.22%  31.75%  41.27% 73.02%  4.76% 77.78%  1260  65.52%  15.52%  17.24% 32.76%  1.72V 34.48%  2nd 27.50%  30.00%  22.50% 52.50% |  20.00% 72.50% |  800  2nd 23.81%  28.57%  42.86% 71.43%  4 76% 76.19%  840  Results of spatial correlations between lineaments and streams for individual basins (Continued). (lins. = lineaments)  228  B a s i n # 29 Stream O r d e r 1st 2nd 3rd 4th Isolated 1st/lin 2nd/lin 3rd/lin 4th/1in Overlyinq t i n s . 1st+40 2nd«40 3rd*40 41h*40 W i t h i n 40 m 1st+60 2nd+60 3rd»60 4tht60 Wrthin 60 m Stream L e n g t h %on lins. %wrthin40m % w i t h t n 60m V o c c u p i e d lins.  Length 50780 8760 7620 11340 78500 8980 3400 120 0 12500 8960 5260 280 900 15400 3620 1480 280 640 6020 112420 11% 25% 30% 17%  1st. % 45.17% 70.20% 7.79% 6.78% 10.09% 69.83% 7.99% 12.41% 3.02% 0.11% 0.00% 11.12% 757% 12.39% 4.68%| 24.80% 0.25% 0.80% 13.70% 3.22% 5.00% 1.32%| 29.80% 0.25% 0.57% 5.35% 72340  2nd 46.35%  17.99%  27.83% 45.82%  7.83% 53.65%  18900  3rd  91.81%  1 45%  3.37% 4,82%  3.37% 8.19%  8300  4th  88 0 4 %  0.00%  6 99% 6.99%l  4.97% 11.96%l 12880  Results o f spatial correlations between lineaments and streams for individual basins (Continu (lins. = lineaments)  229  i  APPENDIX V I  Lineament and stream trend data for the sample set basins  230  Freauency Distribution 0-4 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89 90-94 95-99 100-104 105-109 110-114 115-119 120-124 125-129 130-134 135-139 140-144 145-149 150-154 155-159 160-164 165-169 170-174 175-179 Total  Entire Sample Set 17 30 37 25 16 16 19 < 18 22 16 13 9 5 5 7 9 6 15 19 14 9 10 10 6 11 12 19 14 15 8 8 12 8 15 17 17 509  Igneous Basins 6 8 11 10 7 6 8 9 11 7 6 5 4 0 3 3 5 9 10 8 2 3 4 3 3 1 4 0 3 4 3 3 3 7 8 8 195  Metamorphic Basins 11 22 26 15 9 10 11 9 11 9 7 4 1 5 4 6 1 6 9 6 7 7 6 3 8 11 15 14 12 4 5 9 5 8 9 9 314  Frequency - distribution of lineaments in the sample set basins  231  Frequency Distribution 0-4 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89 90-94 95-99 100-104 105-109 110-114 115-119 120-124 125-129 130-134 135-139 140-144 145-149 150-154 155-159 160-164 165-169 170-174 175-179 Total  Igneous Basins 5 10 7 1 6 12 5 9 7 12 6 9 8 6 4 3 5 6 5 3 5 8 3 11 2 4 9 1 5 3 10 4 6 7 11 12 230  Entire Sample Set 25 32 27 17 22 34 20 27 25 39 23 25 22 28 15 26 23 30 35 21 32 26 24 32 19 20 27 16 21 18 22 17 15 21 29 27 882  Metamorphic Basins  Frequency - distribution of stream segments in the sample set basins  232  20  22 20  16 16 22 15 18 18 27 17 16 14  22 11  23 18  24 30 18 27 18 21 21 17 16 18 15 16 15 12 13  9 14 18 15  652  Frequency Distribution  A l l lineaments controlling streams  Igneous Basins  Metamorphic Basins  0-4 5-9 10-14 15-19 20-24 25-29 30-34  145-149 150-154 155-159 160-164 165-169 170-174 175-179  5 13 7 5 2 0 6 7 10 5 6 3 1 1 4 4 2 6 9 2 2 3 3 3 5 3 4 2 0 1 2 3 6 4 7 7  2 6 4 3 1 0 ,3 3 5 4 4 3 1 0 2 2 1 4 3 1 0 2 3 3 2 1 4 0 0 1 1 1 2 3 4 6  3 7 3 2 1 0 3 4 5 1 2 0 0 1 2 2 1 2 6 1 2 1 0 0 3 2 0 2 0 0 1 2 4 1 3 1  Total  153  85  68  35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89 90-94 95-99 100-104 105-109 110-114 115-119 120-124 125-129 130-134 135-139 140-144  Frequency - distribution of lineament controlled stream segments in the sample set basins  233  Frequency Distribution 0-4 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85-89 90-94 95-99 100-104 105-109 110-114 115-119 120-124 125-129 130-134 135-139 140-144 145-149 150-154 155-159 160-164 165-169 170-174 175-179 Total  1st. order 16 20 21 8 16 24 11 17 14 26 14 15 14 19 10 16 15 17 25 11 22 16 18 20 9 12 15 11 13 14 12 11 9 12 17 19 559  Ig-  Meta.  4 9 6 1 5 11 4 7 6 10 3 7 5 5 4 2 5 4 5 2 2 4 2 6 1 3 5 1 5 2 7 1 4 4 9 10 171  12 11 15 7 11 13 7 10 8 16 11 8 9 14 6 14 10 13 20 9 20 12 16 14 8 9 10 10 8 12 5 10 5 8 8 9 388  2nd. order 5 6 4 4 2 5 5 2 6 4 6 4 6 4 1 5 6 4 5 3 3 6 4 5 5 4 8 3 4 1 6 6 5 6 9 6 168  Ig  Mcta.  1 1 2 0 1 1 1 2 1 2 3 2 2 1 0 1 0 1 1 0 2 3 1 3 0 1 3 0 0 0 3 3 3 3 3 1 52  4 5 2 4 1 4 4 0 5 2 3 2 4 3 1 4 6 3 4 3 1 3 3 2 5 3 5 3 4 1 3 3 2 3 6 5 116  3rd. order 2 2 0 3 2 4 0 4 3 5 2 4 2 4 3 3 2 6 5 7 7 2 1 5 2 3 1 3 2 0 0 1 1 1 1 96  Ig 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 1 0 2 1 1 0 3 1 0 2 0 0 1 0 0 0 0 0 1 15  Meta. 2 2 0 3 2 4 0 4 3 5 2 3 1 4 3 3 2 5 5 5 6 1 1 2 1 3 1 1 3 1 0 0 1 1 1 0 81  Frequency - distribution of stream segments in the sample set basins (Ig. = Igneous basins; Mcta. = Metamorphic basins)  234  Dataset Lineament trends Igneous basins Metamorphic basins Stream segment trends Igneous basins Metamorphic basins Lins visually controlling stream orientations Igneous basins Matamorphic basins First order stream segments Igneous basins Metamorphic basins Second order stream segments Igneous basins Metamorphic basins Third order stream segments Igneous basins Metamorphic basins  11.31 28.80 .015 150.33 20.79 167.10 21.94  Vector Magnitude 101.54 45.81 69.19 46.47 27.82 49.43 26.97  Consistency Ratio 0.1995 0.2349 0.2203 0.0527 0.1209 .00758 0.1763  Vector Mean  509 195 314 882 230 652 153  Maximum percent 7 5 8 4 5 4 8  85 68 559  10 4  22.90 20.68 147.22  15.33 11.66 35.89  0.1803 0.1715 0.0588  171 388 168  6 5 5  24.42 176.37 342.88  33.71 36.08 10.27  0.1972 0.0930 0.0611  52 116 96  5 5 7  346.60 338.49 172.35  5.61 4.76 29.30  0.1078 0.0411 0.3052  15 81  20 7  200.84 163.70  9.05 25.52  0.6034 0.3151  Sample size  Summary vector statistics for lineament and stream trend data from the sample set basins  235  APPENDIX VII  Matrices of R values for regression analysis 2  (  236  237  238  -3 c  < - ^ 2» 2? 2? 2? J»  * ° ' ' .J '7 ^1  £ c « ^ ^ J" _c *c oo — oc « •*» "*  ^  55 .» j ; s; s; s; us £  £  S ' s ' ^ S ^ s ^ s s ' S S S  ^  ca 5? ^ oo r- v-i — rTJ 1  -Nl -vf  V)  ^  c—  CO  "6  C~  £  • <.  .°  >°  •?  >~ '.'  .° ^ ';V ... ... ... ...  „~  ...  ^"  S  ^?  <i'  :  o X!  •c  239  ^01 ?r] o ] o ] ©J  oo]  «0 00 —" f*> (*1 f  -  O  tr «  r-~ ci y- ^\ o- « n M « ^ n <-i OS o> o .  M  «"v  >o o\ <o i  i-- c i oi <•*"» r - v-i  S t £ * « c J 2? ^  CO h W "TO  2? S? ^  -fl * M M Ov  l*i  • — 1 \r, oo O in D rt ON eer2 «C i-  J  ,5? ^  5?  J2 <;*- v-ic--q-oom<no.«-i  ^  VO CO  1< — c  "O — 1  ST 2? ,5? 25 S? ^ r- tr-i o O r» CM  c n  E g "  u c  CIS  00  S o  —•  —  a  i  M  «  c <--* r-  t--  T  r~  0° 0° ^ o- 0° o- o- i>(  ^ K >o ct U,  «^  r~ -  -  -  -  * it S S sf  ^  r  S S c-- — r s r< n  N  —> T  <»% T  N« S°  «-l >©  S i*  • ^  o<  £ -  V-  - o o o ^> .» -.0 2? ^ ^ ^ x  ^  x  i* .<•  S  M  J? J? s  Si?  I~1  5 - £ S 5 3 S> 2  h22~  5  u  ICQ irt  ~ " ~ *"*  ~  ~~  "ir^^roc-t — v~> — *r » •© c- 0 0 <7>  0 3  —. f-J "-I — «J f J O. M  J  *  7 1^ r i w o . o c o > > o c o o o o c ~ t t 5 ^  — r-  £ c r~ - SSSSSSSS;SS«;S w-| ON T Ov (N £- f~) «™ j«j «i <n oO-  ^ T r - - -  ,  o  i  o  i  c « M ' N i ' 0 ^ ^ « w ^ ^  t~ ^> 00  0° 0° 0° 0° -O (? «  v  2S  1  C2  M t  -,fNi„kir-<rir-  *r ^ ^  "O «  E t I £S  ^  03  ^  _  241  -  «  £ £  S j!  S £ * S g J! £ £ S g * £ * g  * * * 3; g * M * M o  j; *  j I: = Is = a H - H - s F « ' ' - r M*H3 s  CO  X  .  r- xo»- v-.-Tr^r^t-'Oor~6. )  l  •  O — t  — r . — h> v% ^ -«T »-> -<r — ^ 1 »-i  v-> v-, t>, o  ifi i n 1^1 o r-*(~-t~-e>. O i i ^ - O C - s O > — • ON t t (\| — * "O <0 I—r«"i >© t~- f l fM *0  00 ©  O  ^  a. ' <  OO 1^ OO vo T  O.  •srv-,^rr-tr^v^i'5(--j<-i -'  u"i 'Or< -r  t  * *  N N M  O. —  « I"-  v.  IS  £ £ S £  o"- o- o- ^  o- o  M N fJf*"'  — -»  i? j?  s  i-  gggg*  « o « o « c -= u.[.j)uj|-j|ca|.j|.j  242  * i* £  gg  v  o-  S  80%  Estimated Fan Area = •  Stream Length Log(Srream Length) Drainage Density Log (Drainage Density) Minimum Fan Elevation Log (Minimum Fan Elevation) Maximum Basin Elevation Log (Maximum Basin Elevarlo Maximum Basin Relief Log (Maximum Basin Relief) Relief Ratio !  Fan Area Log (Fan Area) Estimaled Fan Area Log(Esrlmared Fan Area) Basin Area Log (Basin Area) Lineament Length Loc (Lineament Length) Lineament Density  i ss*$mm- •  •  I II- •  1 • •  !!••  j i i i ! Mill i i i  lliliffliiillliiWiHiN  244  j  •« *  Sf s * * s *, g o  °  —  * ** *.  o m £ =5  c  t/3 . £  R  "  S  M O . ' 0 ' C  03  re  O  — n 1  y  ^  — ' O ^ ^ ^ r , ^ ^  1  ° * <--(  i t-~  r~t r*^ r-~  — — «—i r*-\  T  <r-J <~-« —  § 2  S j; S S °  S5  o  245  " o -  H  g; g  —  APPENDIX  VIII  Diskette containing regression results (included in back pocket)  246  The Diskette contains three spreadsheet files containing regression data for analysis conducted on the sample set basins. The files are: Allkmr.wbl (289030 bytes) overlkmr.wbl (285035 bytes) undlkmr.wbl (290542 bytes) These are formatted in QUATTRO PRO For Windows.  247  APPENDIX DC  Additional details of landslide and slope deformation inventory sites not discussed in the main text  248  Additional details of landslides and mountain slope deformations in the regional inventory  In order to preserve text flow in the main document additional discussion of eleven inventory sites is included here. Only sites significant to the establishment of the relations between lineaments and landslides are described in section 6.3. Two additional stereopairs are presented. Site #3 in the lower Coquitlam River valley shows evidence of a number of slides. The west side of the valley is extensively quarried in Middle Wisconsin and earlier deposits. The east side is largely Fraser River sediments. The stability of the sediments on the western side has been investigated by Thurber Consultants Ltd. (Thurber Engineering Ltd. 1985). The eastern side of the valley at the margin of the Coquitlam Upland is heavily dissected with numerous bowl shaped hollows, and many scarps. The hollows appear to be vegetated with younger trees than those on the corresponding ridges. Landslides in the Coquitlam and Port Moody area are described in Armstrong (1984) and by Eisbacher and Clague (1981). Surficial slides are also seen at Site #6 on Chehalis river where small slides are apparent in terraces of Chehalis river and on Maisal Creek. A small rock avalanche in the lower Seymour valley (Site #4) is shown in Figure 1. This appears to be the result of the detachment of a rock block from the slope. The headscarp is 120m long and the deposition zone extends about 400 m-downslope. The limit of deposition is well defined and the slide is relatively recent. The headwall may be controlled by the lineament shown. In such a case there remains the possibility of failures in the immediate vicinity and this potential should be investigated. Site #8, at Anne lake, is just outside the northern end of the Coquitlam watershed. A small prehistoric rockslide has occurred here leaving a large square shaped rockmass missing from the ridge. There seems insufficient volume of deposits on the slope below the slide to account for all of the apparently missing material.  249  Sites #9, and #10 are on, and near, Stave river respectively. These rockfalls are large enough for inclusion in the inventory. Material has been shed directly to the valley below with no apparent mobilization. Site # 12 is similar, a large talus cone is formed by rockfall in the valley west of Winslow lake. Site #13 shows a number of antislope scarps on the valley wall above Winslow Creek. No other movement features are obvious. The scarps are particularly obvious on small ridges protruding from the valley sides and give the impression that the rock mass is peeling away from the slopes as described at site #5 (Section 6.3). Site #16 is on the Pitt River near the confluence with Shale creek. This feature is an ancient, possibly early post glacial, slump. It has the appearance of a rotational failure and several major antislope scarps are visible. This feature is shown in Figure 2. Site #19 the Rubble Creek slide is well documented in Moore and Mathews (1978). The slide occurred in winter 1855/56 and is an example of a debris avalanche from the quaternary volcanics of the Garibaldi group. An estimated 25x10 m of rock detached from a late glacial dacite lava flow and 6  3  traveled down rubble Creek at a velocity of >20m/s (72 km/h). The headwall of the slide comprised steep columnar joints within the cooled lava. The base of the slide corresponded closely to an unconformity surface (Moore and Mathews 1978) and it is likely that groundwater flow at this surface contributed to failure. There remains the potential for further failure at the site. The Mount Mason Slide (site #20) is briefly described in Evans (1986) and in Clague and Evans (1994). The slide has an estimated area of 450,000 m and an estimated volume of 10.5 xl0 m 2  6  3  (Evans 1986). The slide has not been accurately dated and occurs on or near the contact between coast plutonic migmatite and quartz diorite.  250  251  252  APPENDIX X  Results of overlay of streams on lineaments for the Seymour watershed  253  Buffer zone distance in m  Number of stream pixels  Percentage of total stream pixels  Cumulative percentage of stream pixels  0-20  676  2.87%  2.87% 10.81%  20-40  1871  7.94%  40-60  1786  7.58%  18.39%  60-80  1277  5.42%  23.81%  80-100  1210  5.13%  28.94%  100-120  1599  6.79%  35.73% 40.21%  120-140  1056  4.48%  140-160  1195  5.07%  45.28%  160-180  1208  5.13%  50.40%  180-200  973  4.13%  54.53%  200-220  907  3.85%  58.38%  220-240  758  3.22%  61.60%  240-260  783  3.32%  64.92%  260-280  712  3.02%  67.94%  280-300  530  2.25%  70.19%  300-320  555  2.36%  72.55%  320-340  557  2.36%  74.91%  340-360  491  2.08%  76.99%  360-380  468  1.99%  78.98%  380-400  406  1.72%  80.70%  400-420  391  1.66%  82.36%  420-440  445  1.89%  84.25%  440-460  327  1.39%  85.64%  460-480  287  1.22%  86.86%  480-500  292  1.24%  88.09%  500-520  306  1.30%  89.39%  520-540  260  1.10%  90.50%  540-560  188  0.80%  91.29%  560-580  185  0.79%  92.08%  580-600  192  0.81%  92.89%  600-620  166  0.70%  93.60%  620-640  145  0.62%  94.21%  640-660  117  0.50%  94.71%  660-680  153  0.65%  95.36%  680-700  150  0.64%  96.00%  700-720  107  0.45%  96.45%  720-740  83  0.35%  96.80%  740-760  82  0.35%  97.15%  760-780  101  0.43%  97.58%  780-800  65  0.28%  97.85%  800-820  59  0.25%  98.10%  820-840  65  0.28%  98.38%  840-860  49  0.21%  98.59%  860-880  51  0.22%  98.80%  880-900  53  0.22%  99.03%  900-920  39  0.17%  99.20%  Results of overlay of streams on lineaments for the Seymour Watershed. 254  920-940 940-960 960-980 980-1000 1000-1020 1020-1040 1040-1060 1060-1080 1080-1100 1100-1020 1120-1140 1140-1160 1160-1180  0.13% 0.11% 0.13% 0.06% 0.07% 0.04% 0.04% 0.05% 0.08% 0.03% 0.03% 0.03% 0.02% 100.00%  31 26 31 15 17 9 9 11 18 7 6 6 4 23566  99.33% 99.44% 99.57% 99.63% 99.70% 99.74% 99.78% 99.83% 99.90% 99.93% 99.96% 99.98% 100.00%  Results of overlay of streams on lineaments for the Seymour Watershed (Continued)  255  

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