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Factors influencing the sedimentary environments of the Squamish River delta in southwestern British… Bell, Leonard Montague 1975

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FACTORS INFLUENCING THE SEDIMENTARY ENVIRONMENTS OF THE SQUAMISH RIVER DELTA IN SOUTHWESTERN BRITISH COLUMBIA by LEONARD MONTAGUE BELL B.A. B.A.I., D u b l i n U n i v e r s i t y , 1949 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n the Department of G e o l o g i c a l S c i e n c e s We a c c e p t thxs t h e s i s r as c o n f o r m i n g t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1975 In present ing th is thes is in p a r t i a l fu l f i lment of the requirements for an advanced degree at the Un ivers i ty of B r i t i s h Columbia, I agree that the L ibrary sha l l make it f ree ly ava i l ab le for reference and study. I fur ther agree that permission for extensive copying of th is thes is for scho la r ly purposes may be granted by the Head of my Department or by h is representa t ives . It is understood that copying or p u b l i c a t i o n of th is thes is fo r f i n a n c i a l gain sha l l not be allowed without my wri t ten permission. Department The Un ivers i ty of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 i i ABSTRACT The Squamish River Delta located at the head of Howe Sound, a glacial fjord, in southwestern British Columbia, is being formed by the deposition of sediments carried by the Squamish River and i t s main tributaries the Cheakamus and Mamquam Rivers. The river system drains an area of 1428 square miles generally underlain by granitic rocks. River flow is seasonal resulting in the intermittent deposition of sediments on the delta front. River training works constructed in 1972 have changed the hydrology of the river and influenced sediment transport and deposition. Channelization has resulted in increased deposition off the mouth of the west channel, and a marine transgression of 'the intertidal zone of the central channel. Hydrologic and oceano-graphic factors are the most significant of the natural processes influencing the sedimentary environments of the Delta. Estuarine circulation varies in relation to the dominance of river and t i d a l currents. Wind conditions are an important factor relating to the wave regime of the delta front. A comparison of bathymetric surveys made in 1930 and 1973 shows the delta front advancing at a rate of 21 feet per year, in the west and central sectors. Erosion is occurring at the head of the Mamquam Submarine Channel on the east flank of the central sector. A seismic profile survey in 1973 recorded the presence of large slump structures on the steep upper slopes of the delta front. These records indicate that the present delta is being built on a series of deformed and unstable sediments. i i i S u r f i c i a l sediment sampling of the delta front was carried out during and after the freshet of 1973. On the west sector, sands tend to dominate. These are fine to medium grained with large admixtures of s i l t s and clays. The effect of flocculation on the differential settling of the suspended sediment may be an important factor contributing to the presence of clays on the delta front. The effect of port and industrial development on the aquatic ecosystem i s currently being studied by research scientists from the Department of the Environment. Land f i l l and dredging has resulted in the loss of vegetation and benthic algal mats. Habitats of the benthic invertebrates, the primary source of food for juvenile salmon, have been disrupted and are threatened by future development. The need for inter-disciplinary studies combined with a continuing program of data collecting, i s necessary to f u l l y understand the factors influencing the formation of the Squamish River Delta and to evaluate the effect of future development. iv TABLE OF CONTENTS PAGE ABSTRACT i i TABLE OF CONTENTS iv LIST OF TABLES v i i i LIST OF FIGURES . . . x ACKNOWLEDGEMENTS . , . . . . . . x i i i CHAPTER I INTRODUCTION . . . . . . 1 Purpose of Study 1 Geographical Location of Study Area . . . . . . 1 History of Development of Study Area 2 Previous Work 5" II REGIONAL GEOLOGY 7 General 7 Pleistocene Geology . . . . . 9 River and Delta Morphology . . . . . . . . . . . 10 Comparison of changes from aerial photographs . . . . . . . . . 10 III LOCAL CONDITIONS INFLUENCING THE ENVIRONMENT . . . . 24 Hydrology . 24 Climatology . . . . . . . . . . . . . . . . . . 33 Climatological stations . . . 35 Winds 35 Northerly outflow winds . . . . 37 Southerly inflow winds . . . . . . . . . . . 40 V TABLE OF CONTENTS (Continued) PAGE Diurnal sea-breeze circulations . . . . . 40 Temperature and precipitation . . . . . . 41 Oceanography . . . . . . . . 43 Wave regime 43 Internal waves 47 Tides and currents . . . . . . . . . . . 47 Salinity and temperature . . . . . . . . 52 Turbidity 55 Estuarine circulation . 56 IV STRUCTURE OF THE DELTA 61 Factors Influencing Deltaic Sedimentation . . 61 Physiographical Regions 63 Submarine Topography . . . . 66 Source of data 66 Description of physical" features . . . . 67 Squamish delta 67 Mamquam submarine channel 76 Prodelta basin 77 Internal Structure of the Delta . . . . . . . 78 Description of profiles . 79 Slope st a b i l i t y 84 Rate of growth 86 Rate of vertical acretion 89 v i TABLE OF CONTENTS (Continued) PAGE V SEDIMENTARY ENVIRONMENTS . 92 River Mouth Bars 92 Tidal Flats ...... 94 Ripple marks 102 Tidal Marshes 107 Sediments . . . . . . . » • • • 111 Sampling 111 Colour . .,, 114 Composition . . . . . . . . 114 Distribution . . . . . . . . . . . . . . . 116 Clay mineralogy 118 Mineral identification . 120 VI ENGINEERING ASPECTS 122 Man-made Changes 122 Effects of Development 123 Short-term changes . . . . 124 Long-term changes 124 Hydrological changes . . . . . . . . . . . 126 Sedimentological changes . . . . . . . . . 127 Biological changes . . . . . . . . . . . . 129 Investigation of Geological and Engineering Parameters . . . . . . . . . . • . 130 VII CONCLUSIONS . . . . . . . . . . . . . . . . . . . 134 SELECTED REFERENCES . . . . . . . . . . . . . . . 136 v i i TABLE OF CONTENTS (Continued) PAGE APPENDIX I Calculations for Discharge through Culverts in Training Dyke 142 Ila Calculations for Wave height and period off mouth of Squamish River -September 29, 1973 . . . . 143 l i b Graph used for wave height calculations . 144 III Calculations for tide phase difference (Howe Sound) . . . . . . . . . . . . . . 145 v i i i LIST OF TABLES TABLE - PAGE 1 Aerial Photographs used to Determine Changes in River and Delta Morphology 11 2 Squamish Drainage Basin Areas 25 3 Geographical Locations of River Gauging Stations . . 28 4 Squamish River - Monthly and Mean Annual Discharge 29 5 Mamquam River - Monthly and Mean Annual Discharge . . . . . . . . 29 6 Cheakamus River - Monthly and Mean Annual Discharge 30 7 Stawamus River - Monthly and Mean Annual Discharge . . . . . . . . . . 30 8 Squamish River - Maximum and Minimum Flows Recorded at Brackendale Gauging Station 34 9 Geographical Locations of Weather Stations and Available Data 36 10 Temperature and Precipitation Normals 1941-1970 Squamish Station 42 11 Frequency and Occurrence of Wind Speeds -Howe. Sound 44 12 Wind Directions and Velocities for Figures 15 and 16 ... 45 13 Tide Heights - Squamish and Vancouver . 50 14 Squamish River Velocities 53 15 Squamish River - Salinities and Temperatures . . . . 55 16 Factors Influencing Deltaic Sedimentation 62 17 Delta Front Slopes - 1930 and 1973 74 18 Seismic Survey Tidal Conditions 79 ix LIST OF TABLES (Continued) TABLE PAGE 19 Squamish Delta - Rate of Annual Advance 87 20 Comparative Rates of Advance - Squamish, Lillooet and Fraser Deltas . . 88 21 Squamish Delta - Rate of Vertical Acretion . . . . 90 22 Sediment Colour 115 23 Mineralogy of the Squamish Delta Sand . . . . . . . . 119 24 Effects of Development on the Deltaic Environment . . . . . 125 X LIST OF FIGURES FIGURE PAGE 1 Study Area Location Map . . . . . . 3 2 Regional Geology of the Squamish Area . 8 3aa Aerial Photograph - Squamish Delta - 1930 15a 3b Sketch from Aerial Photograph - 1930 16 4a Aerial Photograph - Squamish River - 1946 . . . . . 17a 4b Sketch from Aerial Photograph - 1946. . . . . . . . 18 5a Aerial Photograph - Squamish River - 1963 19a 5b Sketch from Aerial Photograph - 1963 20 6a Aerial Photograph - Squamish Delta - 1972 . . . . . 21a 6b Sketch from Aerial Photography - 1972 . 22 6c Aerial Photograph - Meander on Squamish River . . . 23 7 Squamish Drainage Basin . 26 8 Locations of River Gauging Stations 27 9 Graph of Squamish River Mean Annual Discharge -1966 to 1973.. . 31 10 Graph of Squamish River Mean Monthly Discharge -1922 to 1973 . . . 31 11 Graph of Mamquam River Mean Monthly Discharge -1967 to 1973 32 12 Graph of Cheakamus River Mean Monthly Discharge - 1967 to 1973 . . . . . . . . . . . . . 32 13 Squamish Wind Rose - 1972 38 14 Squamish Wind Rose - 1973 39 15 Wave Front - Squamish Delta - September 1973 .. . . 46 16 Wave Front - Squamish Delta - October 1973 . . . . 46 x i LIST OF FIGURES (Continued) FIGURE . PAGE 17 Typical Tide Records - Vancouver 48 18 Aerial Photograph showing Estuarine Circulation 51 19 Model of Estuarine Sedimentation 57 20 Conditions Typical of a Highly Stratified Estuary . . . . . . . . . . . . . 58 21 Conditions Typical of a Partly Mixed Estuary . . . 58 22 Angle of Discharge of Squamish River -1930 and 1972 . 60 23 Physiographical Regions of the Squamish River Delta . . 64 24 Bathymetry of the Squamish River Delta -1930 \ • . - t ) - ' - . mecp CRloiM&t" 25 Bathymetry of the Squamish River Delta -1973 *> j ; . ' . * • • rnftp^.cfttMMeJr • 26-31 Profiles of the Squamish River Delta . . . . . . . 68-73 32 Seismic Profile - Line S-2 . . . . . . . . . . . . 80 33 Seismic. Profile - Line S-3 81 34 Location of Seismic Profiles 82 35 Aerial photograph of River Mouth Bars -May 1968 93 36 Area of Bar Build-up - West Channel 1972 95 37 Squamish River - Jet Flow Discharge . . . . . . . 96 38 Tidal Flats - West Sector 97 39 River Bank Erosion - West Channel . 99 40 Layering of Sediments on Tidal Flats . . . . . . . 99 41 Location of D r i l l Holes - West Channel Intertidal Zone 100 x i i LIST OF FIGURES (Continued) FIGURE PAGE 42 D r i l l Hole Data . 101 43 Asymmetrical Current Ripples . . . . . 104 44 Bifurcation Ripples . . ' 104 45 Ladder Back Ripples . . . . . . . . . . . . . . . 105 46 Burial of Ripples 105 47 Mud Boils - West Sector Tidal Flats 106 48 Mud Boil Bed Forms 106 49 Tidal Channel - West Sector Tidal Flats . . . . . 109 50 Sediment Sampling Locations - Intertidal Zone . . 112 51 Sediment Sampling Locations - Sublittoral • Zone 113 52 Composition of Sediments . . . . . 117 53=54 River Bank Erosion - Tidal Marshes -West Channel , 128 55 Simplified Structure Diagram for Analysis of River Systems 133 x i i i ACKNOWLEDGEMENTS S p e c i a l thanks a r e due to Dr. C o l i n L e v i n g s o f the P a c i f i c Environment I n s t i t u t e f o r h i s encouragement i n i n i t i a t i n g t h i s s t u d y , and h i s c o o p e r a t i o n and a s s i s t a n c e i n a d i f f i c u l t problem o f t r a n s p o r t a t i o n l o g i s t i c s . My many d i s c u s s i o n s w i t h him of problems o f mutual i n t e r e s t were b o t h p l e a s a n t and r e w a r d i n g . A c c e s s t o the i n t e r t i d a l zones o f the west and c e n t r a l s e c t o r s o f the d e l t a was made p o s s i b l e by the use of a p o r t a b l e rubber boat g e n e r o u s l y p r o v i d e d by the P a c i f i c Environment I n s t i t u t e . O f f s h o r e sediment sampling and c o n t i n u o u s s e i s m i c p r o f i l i n g was c a r r i e d out from the Department o f the Environment Research V e s s e l " A c t i v e L a s s " . The c o o p e r a t i o n and a s s i s t a n c e o f h e r - s k i p p e r , Sandy Matheson, was much a p p r e c i a t e d . The a s s i s t a n c e o f M e s s r s . R.D. Macdonald, T.M. McGee and J.M. Kennedy i n o b t a i n i n g and i n t e r p r e t i n g the s e i s m i c p r o f i l e r e c o r d s o f the d e l t a was v e r y much a p p r e c i a t e d . D e t a i l e d b a t h y m e t r i c c h a r t s ( f i e l d s h e e t s ) were g e n e r o u s l y s u p p l i e d by the Canadian H y d r o g r a p h i c S e r v i c e . I am e s p e c i a l l y g r a t e f u l t o Dr. R.L. Chase f o r h i s guidance and sym p a t h e t i c approach t o a mature s t u d e n t f a c e d w i t h the t r i a l s and t r i b u l a t i o n s o f U n i v e r s i t y l i f e a f t e r a l o n g s o j o u r n i n i n d u s t r y . L a s t , b u t by no means l e a s t , t o Dr. J.W. Murray go my s i n c e r e thanks f o r t a k i n g on the r o l e o f s u p e r v i s o r o f t h i s p r o j e c t . H i s g r e a t e n t h u s i a s m and i n t e r e s t i n work o f t h i s n a t u r e p r o v i d e d j u s t the r i g h t i n s p i r a t i o n t o t a c k l e the p r o j e c t . F unding o f the p r o j e c t was p r o v i d e d through the g e n e r o s i t y o f the U n i v e r s i t y o f B r i t i s h Columbia's R e s e a r c h Committee and the N a t i o n a l R e search C o u n c i l o f Canada. 1 CHAPTER I INTRODUCTION Purpose of the Study Today, more so than ever before, maa'-s attention i s being focussed on his natural environment. The impact of industrial or recreational development on the environment has produced the realization for the need of multi-disciplinary studies prior to development. A thorough understanding of the regional environment and ecology is essential to determine f u l l y the effect of the development on the region, as well as the suitability of the region for development. The purpose of this study was therefore, to examine the hydrologic, climatic and oceanographic conditions influencing the sedimentary environments of the west and central sectors.of the Squamish Delta in an effort to relate them to: (a) changes in the delta between 1930 and 1973 (the f i r s t detailed hydro-graphic survey of the Squamish Delta and Estuary was made in 1930) (b) the sta b i l i t y of the delta (c) their influence on the present aquatic eco-system (d) their relationship to environmental changes on the delta resulting from the construction of the Squamish River training works. Geographical Location of Study Area The Squamish River Delta, classified as a bayhead delta (Mathews, Murray et_ a i , 1966), i s located at the head of Howe Sound, 2 f o r t y m i l e s northwest o f the c i t y o f Vancouver ( F i g u r e 1 ) . I t s i L a t i t u d e i s 49° 42' N o r t h and L o n g i t u d e 123° 10' West. A c c e s s t o the i n t e r t i d a l zone of the west and c e n t r a l s e c t o r s of the d e l t a i s d i f f i c u l t . L i m i t e d a c c e s s can be ga i n e d from the B.C. Railway T r a i n i n g dyke and the Squamish F o r e s t P r o d u c t s T e r m i n a l . A c c e s s to the t i d a l f l a t s on the V e s t s i d e o f the Squamish R i v e r i s o n l y p o s s i b l e by b o a t . A Government dock on the Mamquam Channel i n the town o f Squamish p r o v i d e s l a u n c h i n g f a c i l i t i e s f o r s m a l l b o a t s . However, a c c e s s from the seaward s i d e of the d e l t a can be d i f f i c u l t d u r i n g p e r i o d s of s t r o n g winds, and can p r e s e n t problems when s c h e d u l i n g f i e l d work i n the i n t e r t i d a l zone. T h i s can o n l y be c a r r i e d out a t p e r i o d s o f low, low water, which o n l y occur d u r i n g the d a y l i g h t hours i n the summer months and a t n i g h t d u r i n g the w i n t e r months. H i s t o r y o f Development of the Study A r e a L i t t l e i s known o f the h i s t o r y o f the Squamish r e g i o n p r i o r to 1873. In t h a t y e a r a s u r v e y p a r t y s e t out to e x p l o r e a r o u t e f o r a t r a i l from Squamish t o B u r r a r d I n l e t . By 1875 a c a t t l e t r a i l was completed through t o B u r r a r d I n l e t , and i n 1877 the f i r s t s e t t l e r s came to the Squamish V a l l e y ( S t a t h e r s , 1958). Squamish soon became known as a good a g r i c u l t u r a l a r e a and much i n t e r e s t was develop e d i n the f e r t i l e and open l a n d b o r d e r i n g the Squamish and Mamquam R i v e r s . The f i r s t dykes on the d e l t a were b u i l t i n the e a r l y 1900's, P a r t o f th e s e dykes s t i l l e x i s t today. Up t o now the 3 40' 20' 123° 00' FIGURE11. L o c a t i o n Map. delta had been used primarily for agricultural purposes, however with the construction of a railroad into the hinterland, for logging purposes, the delta was soon opened up for booming grounds. For the next forty years l i t t l e development was undertaken. Then in 1949 the Premier of British Columbia formed the Squamish Valley Development Committee. In 1955 a dyking requirement study was carried out by the Provincial Government, and in 1957 Premier W.A.C. Bennett announced a government plan to promote the development of the Squamish area as a seaport. With the completion of the Pacific Great Eastern's railway line from Squamish to North Vancouver inl3>956, Squamish was already in a favourable position with respect to r a i l location. Ten years later in 1967, B.C. Railway announced i t s plans, to construct a coal loading port at Squamish. Then, in 1971, they received the Provincial Government's approval to commence the design and construction of the f i r s t phase of the proposed coal handling f a c i l i t i e s . Phase I consisted of river training works designed to channel the entire flow of the Squamish River down i t s western arm. By June 1972, a 3 mile long training dyke.had been constructed, and the west channel of the Squamish River widened and deepened for a distance of 5400 feet north of the river mouth. In the f a l l of 1972, Premier W.A.C. Bennett's Social Credit Government was defeated by Mr. D. Barrett of the New Democratic Party and subsequently Phase II of the coal handling f a c i l i t i e s at Squamish was deferred indefinitely. 5 P r e v i o u s Work S t a t h e r s ' (1958) M.A. T h e s i s , U.B.C. Department o f Geography, i s e n t i t l e d "A G e o g r a p h i c a l I n v e s t i g a t i o n o f Development P o t e n t i a l i n the Squamish V a l l e y Region, B.C.". I t c o v e r s the h i s t o r y o f development and geography o f the town o f Squamish and i t s h i n t e r l a n d t o 1958 i n good d e t a i l . I n c l u d e d i s : a b r i e f d e s c r i p t i o n o f t h e Squamish D e l t a as i t e x i s t e d then, and the Squamish R i v e r d r a i n a g e b a s i n . Whereas Howe Sound has a c o n s i d e r a b l e h i s t o r y o f oc e a n o g r a p h i c s t u d i e s ( C a r t e r , 1932 u n p u b l i s h e d d a t a ; P a c i f i c Oceanographic Group, 1953; P i c k a r d , 1961; Waldichuk e t a l , 1968; Crean and Ages, 1971; B e l l , 1973; and Pond, 1973 u n p u b l i s h e d d a t a ) , l i t t l e d e t a i l e d oceano-graphy has been un d e r t a k e n i n the v i c i n i t y of the d e l t a and r i v e r e s t u a r y . P i c k a r d (1961) i n c l u d e d Howe Sound i n a stud y o f 21 i n l e t s on the southwest c o a s t o f B r i t i s h Columbia and d e s c r i b e s i n g e n e r a l terms the c h a r a c t e r i s t i c s o f the i n l e t w i t h r e g a r d t o wind and wave c o n d i t i o n s , t i d e s , t emperatures, s a l i n i t y and t u r b i d i t y . Recent i n t e r e s t i n the e f f e c t s o f man-made changes and i n d u s t r i a l p o l l u t i o n on the p r o d u c t i v i t y o f Howe Sound has i n i t i a t e d m o n i t o r i n g o f p h y s i c a l o c e a n o g r a p h i c parameters (Waldichuk e_t a l , 1958), water c i r c u l a t i o n s t u d i e s (Crean and Ages, 1969) and c u r r e n t o b s e r v a t i o n s and measurements ( B e l l , 1973; Pond and B u c k l e y , 1973 u n p u b l i s h e d d a t a ) . Mathews, Murray e_t a l (1966) p r e p a r e d an u n p u b l i s h e d r e p o r t on the g r o s s l i t h o l o g y o f the bottom sediments o f Howe Sound and the Squamish D e l t a . 6 Recently much effort has been put into research on the biological parameters of the delta and estuary. Research on the benthic community of the estuary was started by Levings in 1972, and is s t i l l in progress. One of the most abundant organisms on the t i d a l flats i s the amphipod, Anisogammarus confervicolus, a prime source of food for juvenile salmon feeding in the estuary. It has been selected for a long term study of i t s habitat, and i t s adaptability to man-made changes in i t s natural environment. In conjunction with the research by Levings, investigations into fish u t i l i z a t i o n of the inner estuary (Goodman and Vroom, 1972), studies of primary production and zooplankton (C l i f f and Stockner, 1973), distribution of benthic algae, a primary food source for amphipods, and the distribution and biomass of intertidal plants on the delta, have a l l played an important role in the overall assessment of environmental and ecological conditions of the delta. Feeney (1950) prepared a report for the Department of Public Works, regarding flood control and bank protection on the Squamish River and included a proposal forpport development on the delta front. Reports on the planning and growth of Squamish, including industrial development, have been prepared by Minshall (1958), and the School of Community and Regional Planning, University of British Columbia (1964). 7 CHAPTER II REGIONAL GEOLOGY General The geology of the area underlying the drainage basins of the Squamish, Cheakamus and Mamquam Rivers has been described by Mathews (1958). Figure 2 shows the major features of the area and the divisions of the plutonic, metavolcanic and metasedimentary formations. The latter, exposed in the drainage basin of the Mamquam River, consist of massive greenstones, breccias, conglomerates, slaty a r g i l l i t e , limestone and green schists. No information on the age of these rocks i s available, other than that they antedate the pre-upper Cretaceous quartz-diorites of the area (Mathews, 1958). Plutonic rocks of the pre and post Upper Cretaceous can be seen in the exposures of cloudburst quartz-diorites visible in the Cheakamus Canyon, and in the granodiorites and quartz-diorites of the Squamish batholith and Castle Towers batholith. A notable character-i s t i c of these rocks i s the absence of potassium feldspar, which was also observed in the clay mineralogy of the delta sediments. Biotite occasionally converted to chlorite, and hornblende are also characteristic of these quartz-diorites. Mineralogical analyses of these plutonic rocks show plagioclase and quartz as the predominant minerals (Mathews, 1958). The mineralogy of the Squamish Delta sand (Table 23), as 8 FIGURE 2. R e g i o n a l Geology. 9 determined by Mathews, Murray and McMillan (1966) reflects the strong influences of the granitic rocks of the drainage basin in their contribution to the alluvium of the Squamish River flood plain. Pleistocene Geology Peacock (1935) stated that the fjords of British Columbia are pre-glacial valleys, whose troughed and basined forms are due to powerful glacial excavations. During the glacial period the previously existing Squamish Valley was f i l l e d with moving ice to an altitude which corresponds roughly to the present 6,400 foot level (Mathews, 1952). Armstrong and Brown (1954) discussed the regional Pleistocene geology of British Columbia and reached the conclusion that, during this period, a r Codilleran glacial complex at least 7,500 feet thick over the valleys, extended from south of the Canada-United States boundary 1200 miles northwest to the Yukon Territory and Alaska. The average direction of the ice movement as indicated by striae and transported boulders was S 20° W. As the ice retreated, at the end of the Sumas Stade of the Fraser Glaciation approximately 9,000 years ago, the present day topo-graphy of the Squamish Valley and Howe Sound evolved. A l l u v i a l , deltaic, estuarine and marine sediments were deposited in the flood plains, delta and estuary of the Squamish River. North of the Mamquam River, fluvio-glacial deposits observed close to the 400 foot contour provide evidence that these deposits accumulated to depths of 300 to 400 feet above the valley floor (Mathews, 1952). 10 River and Delta Morphology B.C. Department of Lands and Forests and Energy, Mines and Resources aerial photographs taken between 1930 and 1973 (Table 1), were examined for comparative changes in the morphology of the Squamish River and Delta. A selected group was used to best i l l u s t r a t e the changes over the years. Figures 3a, 3b to 6a, 6b ill u s t r a t e the main changes in the Squamish River and Delta occurring between the years 1930 and 1973. The most significant change prior to 1930 was the relocation of the Mamquam River, which after the great flood of 1921 altered i t s course from a southerly to a westerly direction and joined up with the Squamish River about two miles north of the town of Squamish. In 1930 a small southerly flowing tributary of the Mamquam River s t i l l remained, but by 1946 i t had completely dried up. A prominent feature of the lower reaches of the Squamish River is a large meander (Figure 3b), which, as can be seen in a comparison of the aerial photographs, i s a key factor in the migration of the main channel of the river from the central sector to the western sector of the delta. Comparison of changes from aerial photographs The photographs used to describe comparative changes were selected from those taken during the years 1930, 1946, 1963 and 1972, and w i l l be discussed in this order. The photographs have been taken from slightly varying altitudes and consequently direct scaling of the features for a comparison of physical dimensions is not possible. 11 TABLE 1 AERIAL PHOTOGRAPHS USED TO DETERMINE CHANGES IN RIVER AND DELTA MORPHOLOGY YEAR FLIGHT LINE NO YEAR FLIGHT LINE NO 1930 A 2658 - 1/3 1963 BC 5073 - 176/178 1946 BC 262 - 95/97 1964' BC 5099 - 117 BC 866 - 80/82 BC 5105 - 083/084 A 4425 - 15/18 1967 BC 5226 - 167/170 1950 BC 1060 - 40/43 1968 BC 5279 - 174/175 1951 A 13250 - 54 1969 BC 5316 - 037/039 BC 1634 - 45/48 BC 5342 = 033/034 1957 BC 2349 - 70/72 1972 BC 5469 - 116/119 BC 2358 - 69/71 1973 A 23128 - 1/78 1958 BC 5005 - 50/53 AA 30627 - 1/78 1959 BC 5007 - 18/22 12 To m i n i m i z e the s c a l e d i s t o r t i o n i n comparing photographs o n l y those w i t h minor s c a l e d i f f e r e n c e s were used. An approximate s c a l e was dete r m i n e d u s i n g the s t r e e t s i n the town o f Squamish on B.C. Department o f Lands and F o r e s t s photograph B.C. 5469 ( L e v i n g s , 1973). T h i s s c a l e as determined from the l e n g t h o f a c i t y b l o c k i s a p p r o x i m a t e l y 1 i n c h to 960 f e e t . 1930 ( F i g u r e s 3a and 3b) - As th e s e s e r v e as the b a s i s f o r comparison o f changes i n subsequent y e a r s , the f o l l o w i n g f e a t u r e s a r e impo r t a n t t o n o t e : (a) the l a r g e meander i n the main c h a n n e l o f the Squamish R i v e r (b) the s t a t u s o f t h e west c h a n n e l - a t t h i s s t a g e i t o n l y has one c o n n e c t i o n w i t h the main, or c e n t r a l c h a n n e l (c) the l o c a t i o n o f the P a c i f i c G r e a t E a s t e r n R a ilway (P.G.E.) barge and passenger l o a d i n g docks (d) the p o s i t i o n o f the seaward edge of the s u b a e r i a l s e c t i o n of the e a s t and c e n t r a l d e l t a . 1946 ( F i g u r e s 4a and 4b) - Development o f tne township o f D e n t v i l l e i s now v i s i b l e on the e a s t e r n bank on the l a r g e meander i n the Squamish R i v e r . The west c h a n n e l o f t h e r i v e r has now been connected to the main r e a c h o f the r i v e r by a man-made c h a n n e l a p p r o x i m a t e l y h a l f a m i l e l o n g (Mathews - p e r s o n a l communication). T h i s c h a n n e l was exc a v a t e d t o a l l e v i a t e the f l o w i n the main c h a n n e l and so m i n i m i z e t h e r i s k o f f l o o d i n g the newly devel o p e d a r e a on the e a s t bank o f the r i v e r . The west c h a n n e l , as a r e s u l t o f t i d a l a c t i o n , was a l r e a d y back c u t t i n g to the n o r t h . By e x t r a p o l a t i n g the r a t e of p r o g r e s s s i n c e 1930, i t would appear t h a t the two ch a n n e l s may have j o i n e d n a t u r a l l y by the 1960's. 13 In the main (central) channel, point bars have developed to the stage that a major portion of the river flow has been diverted to the west channel, subsequently to become the main channel. In the west channel sedimentation has occurred resulting in i n f i l l i n g of secondary channels on the t i d a l f l a t s . 1963 (Figures 5a and 5b) - It i s now evident that the west channel has become the main channel of the Squamish River. The flow of fresh water to the central channel has been greatly impeded by the further advance of the point bar building up at itsjjunction with the main river channel. A notable feature of the bar i s the amount of vegetation that has grown since'1946. This i s also evident on the second bar, which has now become part of the meander island. The confluence of the Mamquam and Squamish Rivers i s visible at the l e f t hand side of Figures 5a and 5b. The course of the Mamquam River prior to 1921 shows up in Figure 5a as a dark line to the north of the town of Squamish. 1972 (Figures 6a and 6b) - These show the extent and delineation of the B.C.. Railway training dyke completed in June 1972. Figure 6c, a low level aerial photograph of the large meander on the river, shows how effectively the flow of water to the central channel has been cut off by both natural and man-made processes. The junction of the central channel and the main channel of the river has been almost entirely sealed off by the growth,of the point bar at the north end of the meander. A decision to maintain some flow of fresh water to the central 14 channel was made after the construction of the training dyke (personal communication - C. Levings). This entailed the installation of 2 24" dia. culverts at the southern end of the meander. Calculations (Appendix I) show that, assuming an average head of 4 feet, the two culverts would only pass a maximum quantity of 60 cusecs. This i s a relatively insignificant volume when related to the average maximum and minimum daily flows for the Squamish River (max. 40,000 c f . s . and min. 1,200 c.f.s.). However, i t is not known how much of. this flow was carried by the central channel and how much by the west channel prior to the construction of the training dyke. n Figures 6a and 6b also show the major man-made changes that have taken place since 1960; these are: (1) The area of approximately 46 acres of the eastern sector of the delta reclaimed for the construction of the F.M.C. Chemicals Plant ' and loading docks. The present location of the loading docks i s comparable with the southern limit of the barge loading dock built-in 1930 (Figures 3a and 3b). (2) The area of approximately 43 acres of the lower tida l flats of the central sector of the delta f i l l e d for the construction of the Squamish Forest Products Terminal. (3) The Squamish River training dyke and channel straightening of the lower reaches of the west channel. Squamish R i v e r D e l t a - 1930 (view l o o k i n g e a s t ) . Upper R i g h t - P a c i f i c G r e a t E a s t e r n p assenger and barge u n l o a d i n g docks, b u i l t i n 1910 and 1930. Lower L e f t - Main c h a n n e l o f the Squamish R i v e r . Figure 3 b SQUAMISH D E L T A - 1930 (From Aerial Photograph A 2 6 5 8 - 2 ) Approx. Scale. I inch = 1000 feet ON FIGURE 4a. Squamish R i v e r - 1946 (view l o o k i n g e a s t ) . P o i n t b a r s a r e b u i l d i n g on the main ( c e n t r a l ) c h a n n e l o f the Squamish R i v e r . West c h a n n e l i s connected t o the main c h a n n e l by a man-made c a n a l . Figure 4b SQUAMISH R I V E R - 1946 (From Aerial Photograph BC 2 6 2 - 9 5 ) Approx. scale I inch = IOOO feet. oo FIGURE 5a. Squamish River - 1963 (view looking east). The main flow of the river i s through the west channel. Flow through the central channel i s restricted by the growth of point bars. rox. Scale I inch = 750 Feet Course of Mamquam River Prior to flood of 1921 N / Dentville Township' Pacific Great Eastern^ Railway-Point Bar s<7uam/sh R j v e r Figure 5b SQUAMISH RIVE"R - 1963 (From Aerial Photograph BC 5 0 7 3 - 1 7 7 ) Cho»«e/ Tidal Marshes, fSand. Bar FIGURE 6a. Squamish Delta - 1972. Aerial photograph looking east, showing the river training dyke and industrial development on the lower tida l flats of the central sector of the delta. 23 FIGURE 6c. Aerial photograph (1972) looking east at meander on Central channel of the Squamish River, approximately 3 miles north of river mouth. Culverts connecting the west and central channels are located i n the training dyke at south end of meander (lower right). 24 CHAPTER III LOCAL CONDITIONS INFLUENCING THE ENVIRONMENT Three local conditions directly affect the formation of the Squamish River Delta. These are: (1) the hydrology of the rivers discharging on the delta front; (2) the climatology of the area, especially wind conditions and precipitation; (3) the oceanography of the estuary and delta area. The data used to describe the prevailing hydrologic and climatic conditions on the delta were obtained through the courtesy of Mr. G. Tofte, Inland Waters Directorate, Pacific Region, and Mr. G. Schaefer, Atmospheric Environment Services. Additional local observations were made during f i e l d v i s i t s in 1973 and 1974. The influence of these three local conditions as they affect deltaic sedimentation is discussed further in Chapter IV. Hydrology The Squamish River, with i t s two main tributaries the Cheakamus and Mamquam Rivers, carries almost the entire runoff of the Squamish drainage basin, discharging i t through a single channel (since 1972) on to the western side of the delta. The Stawamus River, draining an area of 24 square miles, and Shannon Creek are the only sources of fresh water discharging in to the eastern sector of the delta. The Squamish drainage basin covers an area of 1428 square 25 miles (Figure 7). The drainage areas for the main rivers;-in the drainage basin are shown in Table 2. TABLE 2 SQUAMISH DRAINAGE BASIN AREAS (¥ater Survey of Canada 1973) River Drainage Area - Sq. Mis. Squamish 904 Cheakamus 371 Mamquam 129 Stawamus 24 Total Area 1428 The locations of the main Water Survey of Canada river flow gauging stations in the Squamish drainage basin are shown in Figure 8 and Table 3. River discharge quantities have been compiled from Water Survey of Canada records for the following years: Squamish River 1922— 26, 1955-59, 1960-69, 1970-73 (Table 4), Mamquam River 1967-73 (Table 5), Cheakamus River 1967-73 (Table 6), and the Stawamus River 1972-73 (Table 7). Discharge records for the Squamish and Mamquam Rivers show that the maximum flowsboccur during the months of June and July, with the minimum discharge occurring generally in February and March, but occasionally in January and April (Figures 9, 10 and 11). The same discharge pattern occurs for the Cheakamus River (Figure 12). Records 26 Figure 7 Squamish Drainage Basin (After Stathers — 1 9 5 8 ) i !j ~: P e , 7 T i a n e n t ice f' e |d ~f C (Data incomplete) 123° 15' I23°00' FIGURE 8. Locations of River Gauging Stations. TABLE 3 GEOGRAPHICAL LOCATIONS OF RIVER GAUGING STATIONS RIVER LOCATION Squamish Near Brackendale Lat. 49 47' 40" N Long. 123 12' 00" W Mamquam Cheakamus Above Mashiter Creek Lat. 49 43' 53" N Long. 123 06' 19" W Near Brackendale Lat. 49 48' 58" N Long. 123° 08' 54" W Stawamus Below Ray Creek Lat. 49° 48' 58" N Long. 123° 08' 54" W T A B L E 4 SQUAMISH RIVER - MONTHLY AND MEAN ANNUAL DISCHARGE ( c . f . s . ) - FOR YEARS 1922-26, 1955-59, 1960-69 and 1970-73 (Canadian I n l a n d W a t e r s D i r e c t o r a t e ) YEAR JAN FEB MAR APR MAY JUN J U L AUG SEP OCT NOV DEC MEAN 1922/ 1969 3030 3260 2560 4950 10900 17300 17400 13900 10000 8770 5190 4230 8570 1970 1840 2150 1990 2970 8440 18200 15400 12700 7370 5640 4520 2040 6970 1971 3240 4960 2250 4340 14000 17000 20700 18300 10800 '7310 4210 2010 9120 1972 1630 1960 6900 4810 13500 19500 21200 15800 7080 3610 3200 4110 9290 1973 3370 2050 2570 3160 11000 13900 16000 12700 7920 7760 3850 3790 7390 MEAN 2625 2876 3254 3974 11568 17180 18140 14680 8634 6618 4194 3236 8268 T A B L E 5 MAMQUAM RIVER - MONTHLY AND MEAN ANNUAL DISCHARGE ( c . f . s . ) - 1967 TO 1973 (Canadian I n l a n d W a t e r s D i r e c t o r a t e ) YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MEAN 1967 685 563 534 377 1380 2580 1530 971 601 1850 897 686 1060 1968 1480 910 1040 496 1380 1920 1580 711 631 1390 1100 698 1110 1969 415 384 474 958 2240 2380 1260 625 1240 803 695 681 1010 1970 417 447 409 534 827 1570 633 239 265 386 658 470 571 1971 604 845 490 - 625 1880 1970 2030 867 687 662 690 324 973 1972 320 512 1490 830 1940 2240 2160 796 658 380 981 1120 1119 1973 808 478 461 467 1620 1740 1350 -•• - - - 801 958 -MEAN 676 591 695 612 1709 2057 1506 601 583 781 832 705 974 TABLE 6 CHEAKAMUS RIVER. - MONTHLY AND MEAN ANNUAL DISCHARGE ( c . f . B . ) - 1967 TO 1973 (Canadian I n l a n d Waters D i r e c t o r a t e ) YEAR JAN FEB MAR APR MAY J U N . JUL . AUG SEP OCT NOV DEC MEAN 1967 681 570 482 372 864 5680 2830 1290 599 1950 1170 1010 1460 1968 1670 980 1030 664 1290 3140 3980 1180 783 - 785 1969 601 581 717 998 2710 4680 1610 612 1040 617 593 592 1280 1970 406 451 467 535 589 2930 918 501 496 457 545 526 733 1971 659 736 541 563 1770 2610 3100 1840 734 630 • - ' - -1972 -' ' - - • 3340 - 500 419 530 725 -1973 713 508 486 432 1490 2070 2590 912 446 868 615 829 996 MEAN 788 638 620 594 1452 4075 2505 1056 766 823 575 744 1117 TABLE 7 STAWAMUS RIVER - MONTHLY AND MEAN ANNUAL DISCHARGE ( c . f . B . ) - 1972 AND 1973 ( C a n a d i a n I n l a n d Waters D i r e c t o r a t e ) YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MEAN 1972 - - -. 293 262 210 34 76 2 1 . 130 169 -1973 113 72 51 66 260 215 111 34 39 135 116 157 114 MEAN - - - 276 238 160 34 57 78 123 163 -31 *s.. 1966 1967 I96B 1969 1970 1971 1972 1973 Figure 9 SQUAMISH RIVER - MEAN ANNUAL DISCHARGE (1966-1973) o o o <0 0 Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Figure 10 SQUAMISH RIVER- MEAN MONTHLY DISCHARGE (1922-1973) 32 o o <0 Vi Jan. . Feb. Mar. Apr. May June July Aug. Sept. Oct. No*. Dec. Figure 11 MAMQUAM RIVER - MEAN MONTHLY DISCHARGE (1967- 1973) o Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. . Figure 12 CHEAKAMUS RIVER - MEAN MONTHLY DISCHARGE (1967- 1973) 33 for the Stawamus River have only been kept since May 1972. These indicate that the spring runoff may be one month earlier than for the Squamish River. The maximum discharge for the Stawamus occurred in the month of May for both 1972 and 1973, and was only one per cent of the maximum monthly discharge for the Squamish River. The Squamish River has an annual mean discharge of 8,268 c.f.s., with monthly flows usually reaching a maximum in July (27,000 c.f.s.) and a minimum in March (2,500 c.f.s.). The highest annual mean discharge recorded to date is 10,300 c.f.s. and the lowest 6,700 c.f.s. (Table 8). Anomalously high winter discharges were recorded in 1968, with flows of 3-4 times normal being recorded during the months of January, February and March. The recorded monthly flows of 9,030, 5,180 and 6,100 c.f.s., respectively, were well above the seasonal average. The annual mean discharge for 1968 was 10,000 c.f.s. An examination of the temperatureaand precipitation records for these three months showed them to be well above the seasonal average, and a probable cause of the high winter discharges recorded. Climatology Squamish experiences a modified maritime climate which is common to many of the bayhead deltas at the heads of the fjords of the south-western coast of British Columbia. Due to i t s distance from the Strait of Georgia i t is subject to continental as well as marine influence, and therefore experiences a somewhat wider range of extremes than maritime areas more directly on the coast. Winters are generally dull and cool, with frequent intrusions 34 TABLE 8 SQUAMISH RIVER - MAXIMUM AND MINIMUM FLOWS RECORDED AT BRACKENDALE GAUGING STATION (Water Survey o f Canada) Maximum d a i l y f l o w Minimum d a i l y f l o w Maximum mean monthly f l o w Minimum mean monthly f l o w H i g h e s t mean a n n u a l f l o w Lowest mean annua l f l o w c . f . s . DATE 78,600 Sept. 6 1957 388 Feb. 12 1923 26,200 June 1967 859 February 1923 10,300 1967 6,770 1923 35 of cold arctic air from the interior, accompanied by strong northerly winds known locally as the "Squamish". Summers are generally dry and hot, with a predominance of strong southerly winds with maximum velocities occurring around mid-day. Precipitation i s at a minimum in the summer, and reaches a maximum in the f a l l and winter. Climatological stations Weather records for wind, precipitation and temperature have been available since 1960, from stations at Squamish Townsite, Squamish > F.M.C. Chemicals and Woodfibre. Long term records of temperature and precipitation are available from the station at Britannia Beach, 6 miles south of Squamish, where reporting commenced in 1913. The geographic locations of the existing recording stations, and type of data recorded, i s summarized in Table 9. Winds Wind records for the Squamish d i s t r i c t have only been kept since May 1965. Early attempts to record winds at the Squamish delta began with the installation of a Type 45B Anemograph in 1967, at the F.M.C. Chemicals Plant located on the delta one mile south of the town.of Squamish. However the records were of poor quality, often missing, and have not been used by the Atmospheric Environment Service. In December 1969 a Type U2A Anemometer was installed on a 30 foot mast on the grounds of the Squamish F.M.C. Chemicals Plant. The 36 TABLE 9 GEOGRAPHICAL LOCATION OF WEATHER STATIONS AND AVAILABLE DATA (Atmospheric Environment Service) Squamish 49° 42' N 123° 09' W 5 1 asl (above sea level) Precipitation October 1959 - January 1960 Temperature and Precipitation February 1960 - February 1970 Wind Mileage May 1965 - May 1966 Squamish F.M.C. Chemicals 49° 41' N 123° 10' W 10' asl Precipitation November 1968 - Continuing Wind Mileage April 1971 - Continuing Britannia Beach 49° 37' N 123° 12' W 160' asl Temperature and Precipitation December 1913 - Continuing Woodfibre 49° 39' N 123° 16' W 20' asl Precipitation April 1960 - Continuing 37 exposure i s unobstructed in the north-south direction, the nearest building being 300 feet to the east-southeast. Wind speed and direction have been abstracted from monthly records and used to compile wind roses for the years 1972 and 1973 (Figures 13 and 14). The records prior to 1972 are suspect in regard to the directions of the wind, and therefore have not been used. However, even with a relatively short period of records a f a i r l y clear picture i s emerging of the wind patterns in the delta area. Records now exist which document persistent "Squamish" outflow winds and southerly inflow winds during the winter months, with a diurnal sea breeze circulation during the summer months. As i s expected in a mountainous coastal area the configuration of topography and land-water boundaries exert a marked control over the surface wind patterns. Northerly outflow winds During the colder winter months (primarily December and January) extensive masses of cold arctic air commonly build up over the interior of British Columbia. Strong flows of cold dense air from these high pressure cells then spread towards the coast seeking the path of least resistance through passes and valleys, including those to the north of Squamish. Northerly outflow winds occur on an average of 5 to 6 days per month or about 16 per cent of the time. Windyvelocities commonly reach values of 35 to 40 miles per hour, with gusts ranging from 50 to 70 miles per hour. A mean wind speed of 45 miles per hour, with gusts reaching 74 miles per hour was recorded on January 25, 1972 (G. Schaefer -38 Figure 13 WIND ROSE-FM.C CHEMICALS SQUAMISH B. C - 1972 Figure 14 WIND ROSE - FM.C CHEMICALS SQUAMISH B. C - 1973 AO personal communication). Southerly inflow winds During the winter season (approximately October to March), the B.C. coast i s in the direct path of Pacific storms approaching the mainland in the prevailing westerly upper-air flow. Frontal disturbances issuing from the lows associated with these storms are preceded by southeasterly winds that are often of gale force. The configuration of mountain barriers around Howe Sound are such that these winds are channeled towards Squamish resulting in strong south to south west winds. Inflow winds in excess of 20 miles per hour are recorded on about 10 days each month or about 30 per cent of the time. The strongest wind to have been recorded to date at Squamish was from the south, and occurred on February 27, 1972 (G. Schaefer - personal communication). Winds increased dramatically over a period of three to four hours, changing from light northerly to south 55 m.p.h. with gusts to 9A miles per hour. Diurnal Sea-Breeze Circulations. During the summer period (May to August) the frequency of low pressure ridges i s much reduced, and the coast is largely protected by the northward extensions of the Pacific anti-cyclone, or region of high pressure. During this season thermal heating i s strong thereby giving rise to land breeze-sea breeze dirculations along the coastlines. .41 During a typical summer day at Squamish light winds blow from the north from midnight u n t i l about 9 a.m. These then switch to light southerly increasing i n velocity, u n t i l , between noon and 6 to 8 p.m., gusty southwest winds often reach velocities of 25 miles with gusts to 35 miles per hour. Following the strong afternoon winds, velocities drop off after sunset reverting to light northerly about midnight to complete the cycle. During the period of available records, i t appears that sea-breezes occur on almost half of the summer days at Squamish, or about 50 per cent of the time. As i s discussed later, under the section on oceanography, these sea-breezes are of major importance in the determination of the wave energy at the delta front. The longer fetch of the southerly winds compared with the limited fetch of the northerlies i s especiably noticeable in the size of the waves observed on the delta i n September and October, 1973 (Figures 15 and 16). The wind direction and velocities at the time of observationaare shown in Table 12. Temperature and Precipitation Temperature extremes at Squamish have ranged.from a high of 99° F in July to a low of 05° F in January. The mean daily temperature for a 29 year average (1941-1970) ranges from 33° F in January to 62° F in July (Table 10). The mean annual r a i n f a l l is 75 inches, which, with a mean annual snowfall of 57 inches, gives a total mean annual precipitation reading of 81 inches (Table 10). TABLE 10 TEMPERATURE AND PRECIPITATIONS NORMALS, 1941-1970 SQUAMISH STATION (Lat. 49° 42' N Long. 123° 09' W) (Atmospheric Environment Service) ; JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC YEAR Mean daily temp. (Deg. F) 33 38 41 47 54 58 62 62 57 49 41 36 48 Mean daily max. temperature 38 45 49 56 63 67 72 71 66 56 46 41 56 Mean daily min. temperature 27 31 33 39 44 49 53 52 47 42 35 31 40 Mean r a i n f a l l (inches) 9 8 6 5.5 2.8 2.7 2.1 2.1 4.7 10.8 11 11 75.4 Mean snowfall 25 7 4 0 0 0 0 0 0 0 3 18 57.3 Mean Total :Precipitation 111.5 8.7 6.4 5.5 2.8 2.7 2.1 2.1 4.7 10.8 11.3 12.8 ' 81.T 43 Generally the months of October, November, December and January each receive in excess of 10 inches of precipitation (rain and snow), whereas the summer months of May, June, July and August usually record less than 3 inches of precipitation. Oceanography Pickard studied 21 inlets on the northern and southern coast-line of the British Columbia mainland during a 3-month summer cruise in 1951, and visited again some of the southern inlets during the period 1951 and 1960. His research showed Howe Sound to be a highly stratified estuary with a surface water layer about 10 fathoms or 60 feet deep, with average salinity measurements of 10 parts per thousand at the head to 25-30 parts per thousand at the mouth. More detailed measurements in the vi c i n i t y of the Squamish Delta are discussed under the section on temperature and salinity. To review the oceanographical features that play an important role in the formation of the delta the following breakdown has been used: • 1. wave regime 2. tides and currents 3. salinity, temperature and turbidity 4. estuarine circulation Wave regime Waves may be divided into two categories: (a) wind generated surface waves; and (b) internal waves. While surface waves predominate 44 and p r o b a b l y p l a y the more im p o r t a n t r o l e i n the distribution°and r e d i s t r i b u t i o n o f the sediment b u i l d i n g the d e l t a , i n t e r n a l waves a r e p r e s e n t , though t h e i r e f f e c t on sediment t r a n s p o r t i s not known. Wind c h a r a c t e r i s t i c s f o r the d e l t a a r e a have a l r e a d y been d i s c u s s e d and a p a r t from t h e i r i n f l u e n c e on the motion o f t h e water s u r f a c e l a y e r , w i l l not be f u r t h e r d i s c u s s e d . T a b l e 11, a f t e r P i c k a r d (1961), r e l a t e s wave h e i g h t t o wind speed, and i s r e p r e s e n t a t i v e o f the average wave c o n d i t i o n s found i n Howe Sound. S i m i l a r r e l a t i o n s h i p s o f wave h e i g h t and wind speed were observed i n the v i c i n i t y o f the d e l t a ( T a b l e 12 - F i g u r e s 15 and 16). TABLE 11 FREQUENCY OF OCCURRENCE OF WIND SPEEDS AND WAVE HEIGHTS IN BRITISH COLUMBIA INLETS FOR SUMMER MONTHS FROM 1951 TO 1959 INCLUSIVE (Percentage of 1653 o b s e r v a t i o n s between 0600 and 2000 hours) Wind speed (m.p • h.) Wave-height Wave height 0-4 5-14 15-28 29+ frequency (feet) (Percent frequency of occurrence) totals Calm 27 4 0 0 31 8 to i 14 28 5 0 47 1 to 3 1 5 14 20% 33to 5 0 0 1 h ik Wind speed frequency totals 42 32 20 1 100 TABLE 12 WIND DIRECTIONS AND VELOCITIES -FIGURES AND SQUAMISH DELTA - SEPTEMBER 29 AND OCTOBER 14 1973 TIME VELOCITY DIRECTION COMMENTS 11.00 hrs. 18 m.p.h. S.W. September 29, 1973 (Figure 12.00 > 18 " S.W. 13.00 17 " S.W. gusts to 20 m.p.h. 14.00 22 11 S. gusts to 25 m.p.h. 14.00 27 " S. highest velocity for day 11.00 hrs. • 4 m.p.h. N.N.E. October 14, 1973 (Figure 12.00 9 " N.N.E. gusts to 12-16 m.p.h. 13.00 14 " N.E. to gusts to 20 m.p.h. 14.00 14 11 E.N.E. 46 FIGURE 15. Wave front, mouth of Squamish River (west channel) September 29th, 1973 (1300 hrs). Wind from SW, 17 m.p.h. with gusts to 20 m.p.h. Wave heights estimated at 2-3 feet. FIGURE 16. Wave front, mouth of Squamish River (central channel) October 14th, 1973 (1300 h r s ) . Wind from NE, 14 m.p.h. with gusts to 20 m.p.h. Wave heights estimated at 6-8 inches. 47 Hindcasting of wave heights and periods requires the wind direction and velocity to be known. The heights of wind generated waves are limited by fetch and duration of blow. In Howe Sound and most estuaries the waves are fetch limited. The significant wave height (h 1/3) and significant wave period (T 1/3) were calculated for the waves observed on the delta front on September 29, 1973 (Appendix I l a and l i b ) . The Calculated wave height of 3.3/2 feet and period of 2.9 seconds.compares well with the estimated height and period (Figure 15). (b)! Internal Waves Pickard (1961) observed internal waves at the heads of most B.C. coastal inlets. The waves occurred in the upper water layers (15-60 feet) with a period of oscillation of 1 to 3 minutes. The waves are generated as a shear flow between low salinity surface water layers and the deeper more saline waters. They are further complicated by estuarine and t i d a l currents. While i t i s quite probable that internal waves do occur in the vi c i n i t y of the Squamish Delta, their effect on sediment transport i s not known and i s probably quite minimal when compared to the effect of wind generated surface waves (P. Le Blond -oral communication). Tides and currents Giving rise to a t i d a l circulation in the estuary is a mixed, mainly semi-diurnal tide (MSD) - two complete t i d a l oscillations da'ilyy with inequalities both in height and time (Figure 17). Superimposed on the t i d a l flow i s an "estuarine circulation" resulting from a pattern of surface outflow and sub-surface inflow. The fresh, less dense water 48 Vancouver Point Atkinson N P o LEGEND © O O new moon first quarter full moon last quarter N c A — moon in apogee P — moon in perigee E — moon on equator N — moon farthest north of equator S — moon farthest south of equator FIGURE 17. Typical t i d a l records for Vancouver and Point Atkinson showing the mixed, mainly diurnal nature typical of tides on the Pacific Coast of North America. (From Canadian Tide and Current Tables, 1974, Volume 5: Juan de Fuca and Georgia Straits.) 49 entering the estuary at the head, flows seawards on top of the incoming, more dense seawater. The result of this unidirectional flow is to decrease the speed of the flood tide and increase the speed of the ebb tide. This then could be an important factor when assessing the net movement of the sediments on the delta. Table 13, compiled from the Canadian Hydrographic Services tide and current tables, illustrates the range of tides that can occur at the Squamish Delta. Pickard (1961) observed that there i s an approximate difference of 10 minutes at high or low water between the head and the mouth of west coast inlets. Calculations for Howe Sound show a difference of 9 minutes between the mouth and the Squamish Delta (Appendix I I I ) . The difference in t i d a l range at the head is from 1 to 10 per cent greater than at the mouth (Pickard, 1961). Recent studies of surface currents in the v i c i n i t i e s of the Squamish Delta and Britannia Beach (Pond and Buckley, unpublished, 1973) show a surface current circulation pattern for the Squamish estuary similar to the path of the sediment plume visible in Figure 18. Pond and Buckley (1973), tracking marker floats by radar, observed that the southward flowing surface currents in the Squamish estuary tend to follow the eastern shoreline to Watts Point before turning sharply to the west and thence remaining on the western side of the Sound to the v i c i n i t y of Britannia Beach. Associated with this general circulation pattern are occasionally circular or clockwise gyres. TABLE 13 TIDE HEIGHTS - SQUAMISH AND VANCOUVER (Canadian H y d r o g r a p h i c S e r v i c e 1973) LOCATION LOCATION HEIGHT ABOVE DATUM OF SOUNDINGS H E LARGE A.TIDE S AVERAGE TIDES MEAN WATER LEVEL HIGHER H.W. LOWER L.W. HIGHER H.W. - LOWER L.W. SQUAMISH CAULFIELD COVE (West Vancouver) F e e t Metres 15.8 4.8 16.3 5.0 F e e t Metres -0.9 -0.3 0.4 0.1 '* F e e t Metres 13.4 4.1 14.4 4.4 F e e t Metres 3.0 0.9 4.1 1.3 F e e t Metres 9.1 2.8 10.0 3.0 H.W. = H i g h Water L.W. = Low Water FIGURE 18. A e r i a l photograph o f the Squamish E s t u a r y , June 1964, showing sediment plume d u r i n g p e r i o d o f h i g h r i v e r d i s c h a r g e (25,350 c . f . s . ) . Plume i l l u s t r a t e s the s u r f a c e p a t t e r n o f the e s t u a r i n e c i r c u l a t i o n , and shows the e f f e c t o f suspended sediment on the o p t i c a l t u r b i d i t y o f the upper l a y e r s o f the s u r f a c e w a t e r s . 52 Surface currents (top 2 metres) of 1.5 to 2 knots were measured by Pond and Buckley (1973) in the v i c i n i t y of the Squamish Delta. These currents are seasonally affected by the discharge velocities of the Squamish River (Table 14). Velocities range from a low of less than 1 knot in the winter to a high of about 3 knots during the spring freshet. Flash floods during the winter months can also produce high velocities, as was the case in 1974 when a velocity of 2.65 knots was recorded on January 16th. The direction and strength of the wind and state of the tide also play a prominent role in the movement of the surface waters. Strong north-easterly winds and an ebb tide tend to force the river discharge to the western side of the estuary. Visual observations have been made of sediment plumes moving southwards along the western shore-line under such conditions. Conversely, with strong southwesterly winds and a flood tide, the surface waters tend to get compressed to the centre and eastern side of the delta. Salinity and temperature Pickard (1961) classifies Howe Sound as one of a group of inlets on the B.C. coast with low surface salinity at the head. This he attributes to the higher fresh water discharge associated with the rivers, whose runoff comes mainly from glaciers and snowfields. In general this i s true, as is the overall picture of salinity and temperature distribution with depth and time, drawn by Tully (1949) for Alberni Inlet on Vancouver Island and by Pickard (1961) for a group of inlets on the mainland coast of British Columbia. TABLE 14 SQUAMISH RIVER VELOCITIES (Canadian Inland Waters Directorate) V e l o c i t y D i s c h a r g e 1973 f . p . s . k n o t s c . f . s . J a n . 23 1.58 0.94 2,520 May 1 2.57 1.52 5,420 Jun. 6 4.79 23.84 19,300 Sep. 17 2.66 1.57 5,680 Nov. 13 3.08 1.83 7,430 V e l o c i t i e s measured a t Squamish R i v e r gauging s t a t i o n near B r a c k e n d a l e %Lat. 49° 47' N, Long. 123° 12' W) f . p . s . = f e e t p e r second c . f . s . = c u b i c f e e t p e r second 54 There can, however, be a marked s e a s o n a l v a r i a t i o n i n s a l i n i t y and temperature as d e s c r i b e d f o r Bute I n l e t by Tabata and P i c k a r d (1957). They noted an annua l c y c l e of change e v i d e n t t o a depth of 60 f e e t i n s a l i n i t y and 150 f e e t i n temperature. Such changes can be i m p o r t a n t when c o n s i d e r i n g d e p o s i t i o n o f c l a y s on the upper l e v e l s o f the Squamish D e l t a , namely the i n t r a d e l t a and d e l t a f r o n t . Dyer (1972) s t a t e s t h a t w i t h adequate p a r t i c l e c o n c e n t r a t i o n s , f l o c c u l a t i o n o f i l l i t e and k a o l i n i t e i s complete above a s a l i n i t y o f about 4%0. A d e c r e a s e i n water temperature can a l s o r e s u l t i n an i n c r e a s e i n sediment t r a n s p o r t ( G r a f , 1971). S t u d i e s on the C o l o r a d o R i v e r , where the f l o w r a t e remains f a i r l y c o n s t a n t over seasons and over y e a r s , showed t h a t a c o n s i d e r a b l e v a r i a t i o n i n sediment l o a d s c o u l d be c o r r e l a t e d w i t h v a r i a t i o n s i n water temperature. Whitehouse e^t a l (1958) s t u d i e d the d i f f e r e n t i a l s e t t l i n g t e n d e n c i e s o f c l a y m i n e r a l s i n s a l i n e water, as an im p o r t a n t parameter i n the u n d e r s t a n d i n g o f t i d a l h y d r a u l i c s and s e d i m e n t a t i o n . They n o t e d d e c r e a s i n g temperatures over, the range 26° to 6° C (79° to 43° F) d e c r e a s e d s e t t l i n g r a t e s of sediments p r o g r e s s i v e l y , up to 40%, f o r a l l c l a y t y p e s . Water temperatures f o r the Squamish R i v e r range from 34° t o 51° F, f o r s i x t y - e i g h t o b s e r v a t i o n s made by the Water Survey of Canada, between 1955 and 1971. L e v i n g s (1974) n o t e d t h a t the water s u r f a c e temperature a t the mouth o f the Squamish R i v e r ranged from 39.7° F i n the w i n t e r t o 51.4° F i n the summer, w i t h temperatures i n the c e n t r a l c h a n n e l b e i n g s l i g h t l y h i g h e r i n the summer ( T a b l e 15). 55 TABLE 15 SALINITY AND TEMPERATURE - SQUAMISH DELTA (After Levings, 1973) MAY-AUGUST 1973 Temperature Range °F Salinity Range %o Squamish River mouth (west channel) 43.2 to 47.8 0.0 to 16.8 Central Channel (intertidal zone) 41.0 to 62.1 1.0 to 19.8 The higher upper limits of both temperature and salinity in the central channel is most l i k e l y a result of the recent training of the river to the west channel. This resulted in a flow of only a few hundred cusecs of the colder fresh water in the central channel during the spring freshet and less at other times of the year. Turbidity Pickard (1961) points out that a conspicuous feature of the British Columbia coastalninlet waters i s the colour and turbidity of the top 3 meters of the water layer. appearance.due to a high concentration of "rock flour". This turbid sediment laden water is clearly v i s i b l e on the surface water layer of the Squamish Delta and Upper Howe Sound. Secchi-disc depths for Howe Sound recorded during the period May to September 1957 (Pickard, 1961) were 0.5 m (1.6 ft) at the head, High turbidity spring freshet runoff i s often milky-white in 56 1.5 m (4.9 f t ) a t the m i d d l e of the i n l e t and 3.0 m (9.8 f t ) a t the mouth. E s t u a r i n e C i r c u l a t i o n S c h u b e l (1971) l i s t s and compares t e n d e f i n i t i o n s of an e s t u a r y . He chose P r i t e h a r d ' s 1967 d e f i n i t i o n as the most r e p r e s e n t a t i v e , namely "an e s t u a r y i s a s e m i - e n c l o s e d body of water which has a f r e e c o n n e c t i o n w i t h the open s e a and w i t h i n which s e a water i s measurably d i l u t e d w i t h f r e s h water d e r i v e d from l a n d d r a i n a g e " . Burns (1973), d i s c u s s i n g marine i n f l u e n c e s on e s t u a r i n e s e d i m e n t a t i o n ( F i g u r e 19), shows the i n f l u e n c e of e s t u a r i n e c i r c u l a t i o n on sediment d e p o s i t i o n and t r a n s p o r t . The e s t u a r i n e c i r c u l a t i o n , J however, v a r i e s ? i n r e l a t i o n t o the dominance of the r i v e r o r t i d a l c u r r e n t ( P r i t e h a r d , 1971; Bowden, 1967). T h i s makes i t d d i f f i c u l t to f i t one p a r t i c u l a r model to any system f o r a l l seasons. I f , as i s the case a t Squamish, the r i v e r f l o w dominates d u r i n g t h e s p r i n g f r e s h e t , the e s t u a r y may be c l a s s i f i e d as h i g h l y s t r a t i f i e d or as a salt-wedge e s t u a r y ( F i g u r e 20). C o n v e r s e l y , d u r i n g p e r i o d s of low r i v e r f l o w the e s t u a r y may become a partl-ylmixedx: J. e s t u a r y ( F i g u r e 21). The c l a s s i f i c a t i o n can be determined by c a l c u l a t i n g the M i x i n g Index (M.I.) ( S c h u b e l , 1971), d e f i n e d as, the r a t i o of the volume of f r e s h water e n t e r i n g d u r i n g a h a l f - t i d a l p e r i o d to the volume o f water e n t e r i n g d u r i n g a f l o o d t i d e ( T i d a l P r i s m ) . I f M.I. =s 1, the e s t u a r y w i l l p r o b a b l y be h i g h l y s t r a t i f i e d . I f M.I.<3<1, the e s t u a r y i s SEDIMENT SOURCE REMOVAL FROM ESTUARY TRANSPORTATION WITHIN ESTUARY TEMPORARY DEPOSITION WITHIN ESTUARY PERMANENT DEPOSITION WITHIN ESTUARY IMPULSE OR INITIAL SETTING IN MOTION OF SEDIMENTARY PARTICLE ORIGINALLY AT REST WITHIN ESTUARY REDEPOSITION WITHIN ESTUARY FIGURE 19. Model of Estuarine Sedimentation (After Burns, 1973) 58 F R E S H W A T E R <9> S A L T W A T E R FIGURE 20. Conditions typical of Shoaling i s localized (After a highly stratified estuary, at tip of salt water wedge. Simmons and Hermann, 1972) FIGURE 21. Conditions typical of a partly mixed estuary. Arrows indicate current reverseswith tide. Predominant current indicated by length of arrow. (After Simmons, 1955) 59 c o n s i d e r e d t o be p a r t l y mixed. An example o f changing c i r c u l a t i o n p a t t e r n s i s d e s c r i b e d by Simmons and Hermann (1972) f o r the Savannah R i v e r . P e r i o d s o f peak f l o w s o f 60 t o 70,000 c u s e c s produced a s a l t wedge type of c i r c u l a t i o n . When the r i v e r f l o w dropped t o 5 to 10,000 c u s e c s the c i r c u l a t i o n e x h i b i t e d t h e c c h a r a c t e r i s t i c s of a p a r t l y mixed e s t u a r y . By comparison, the maximum and minimum f l o w s o f the Squamish R i v e r a r e i n the o r d e r of 20,000 and 2,000 c u s e c s r e s p e c t i v e l y . In a d d i t i o n t o t i d a l and r i v e r c u r r e n t s , d e n s i t y and wind in d u c e d c u r r e n t s i n f l u e n c e e s t u a r i n e c i r c u l a t i o n ( H o r r e r , 1967). T r a n s -p o r t and m i x i n g of the top s i x f e e t o r so o f s u r f a c e water can r e s u l t from wind i n d u c e d c u r r e n t s caused by d i r e c t wind s t r e s s e x e r t e d on the s u r f a c e water, or by wind g e n e r a t e d s u r f a c e waves. I n Howe Sound, where winds o f h i g h v e l o c i t i e s change p e r i o d i c a l l y from u p - i n l e t t o d o w n - i n l e t , the e f f e c t on t h e e s t u a r i n e c i r c u l a t i o n can be s i g n i f i c a n t when r e l a t e d to sediment t r a n s p o r t i n the s u r f a c e waters o f Upper Howe Sound. P i c k a r d and Rodgers (1959), i n a stud y o f K n i g h t I n l e t , B.C., found t h a t a wind of 20 kn o t s b l o w i n g up the i n l e t caused the normal seaward c u r r e n t of 0.38 kn o t s t o be r e v e r s e d t o a c u r r e n t o f 0.97 kn o t s upstream i n the first few meters o f water depth. I n Howe Sound up-inletXfjwihdscof • 20 k n o t s a r e a common o c c u r r e n c e i n the summer months. The volume and a n g l e o f r i v e r d i s c h a r g e may a l s o i n f l u e n c e the e s t u a r i n e c i r c u l a t i o n p a t t e r n . F i g u r e 22 shows the change i n a n g l e o f d i s c h a r g e f o r the Squamish R i v e r between 1930 and 1973, as a r e s u l t o f development on the i n t e r t i d a l zone o f the e a s t and c e n t r a l s e c t o r s of the d e l t a . FIGURE 22. Angle.of Discharge of Squamish River - 1930 and 1972. 61 CHAPTER IV S STRUCTURE OF THE DELTA  Factors Influencing Deltaic Sedimentation The structure of the delta depends to a large extent on the amount of sediment deposited or eroded in the intradelta and on the delta front. This i s in turn controlled by three major factors -oceanographic, climatic and hydraulic (Bates, 1953; Morgan, 1970; Silvester and La Cruz, 1970; Coleman and Wright, 1971). Morgan (1970) adds one more factor influencing deltaic -sedimentation, namely, structural behaviour with relation to sea-level datum. This he breaks down into three categories: (i) stable areas, ( i i ) subsiding areas, and ( i i i ) elevating areas. Table 16, modified from Morgan (1970), summarizes the three main factors and their influence on deltaic sedimentation. For the Squamish Delta, the most important factor appears to be the river regime. It i s the prime source of the sediments building the delta, and i s greatly influenced by marine processes and climatic changes. Fluctuating volumes of river discharge result in intermittent deposition of sediment on the delta front. High quantities of non-cohesive sediments deposited rapidly can lead to delta ins t a b i l i t y and localized minor slumping. Such conditions are evident from the interpretation of bathymetry and seismic profiles. An engineering approach to the factors influencing the formation TABLE 16 FACTORS INFLUENCING DELTAIC SEDIMENTATION RIVER FLOOD SEDIMENT LOAD Quantity of suspended load and bad load (that i s , stream capacity) increases during flood STAGE PARTICLE SIZE Particle size of suspended load and bed load (that i s , stream competence) increases during flood • REGIME LOW RIVER-STAGE SEDIMENTKEOAD Stream capacity diminishes during low river stage PARTICLE SIZE Stream competence diminishes during low river stage MARINE WAVE ENERGY High wave energy" with resulting turbulence and currents, erode, rework and winnow deltaic sediments PROCESSES TIDAL RANGE High tida l range creates tid a l currents and influences deposition in the intertidal zone CURRENTS Currents generated by waves and tides, density and turbidity currents provide mechanism for sediment transport CLIMATIC SEASONAL EFFECTS Quantity of fresh water supplied by the river varies with amount of run^off from rain or melting snow. Water temper-ature variations affect settling rate of suspended sediment FACTORS WET HOT OR WARM High temperature and humidity yield dense vegetative cover which aids in trapping sediment transport by f l u v i a l or tid a l currents AREA COOL OR COLD Seasonal character of vegetative growth is less effective in sediment trapping - cool winter temperature allows seasonal accumulation of plant debris to form delta plain peats Modified from Morgan, 1970. 63 of deltas has been taken by Silvester and La Cruz (1970). They studied the pattern forming forces in deltas keeping in mind man's interest in maintaining navigable channels, inhibiting salt wedge intrusion, building land areas above flood levels, and studying strata for load , bearing capabilities. They divided the overall system into three basic components, a catchment area, a river system and a receiving body of water. The dependent variables associated with the delta such as area, topography, vegetation, climatology and oceanography, are correlated with the independent variables associated with the catchment area, therriver and the sea. Physiographical Regions For easy reference the delta has been divided into three physio-graphical regions (Figure 23): 1. The west sector - an area bounded by Squamish valley rock bluffs to the west, and by the B.C. Railway training dyke to the east. 2. The central sector - extending from the east side of the training dyke to the eastern limits of the Squamish Forest Products Terminal. 3. The east sector - the' area between the eastern limits of the Squamish Forest Products Terminal and the eastern shoreline of the estuary. Each.of these regions i s further sub-divided into three basic units, or sedimentary environments: ( (i) the intradelta ( i i ) the delta front ( i i i ) the prodelta 64 Contours in \ cen\re \ A p p r o x . Scale 0.5 1.0 Mi Figure 23- Physiographicol Regions of the Squamish River Delta ( modi f ied from Levings - 1972 ) .65 ' These terms were originally defined by the American Geological Institute glossary of geology (1972), but have been modified to f i t the geometry of the Squamish Delta environment, as follows: Intradelta: Generally referred to as the intertidal zone, is the land-ward part of the delta, largely subaerial, extending from the low water level (L.W.L.) to an elevation of 15 feet above sea level. It i s characterized by three main sedimentary environments - (i) river mouth bars, ( i i ) ti d a l f l a t s , and ( i i i ) t i d a l marshes. Levings (1972) arbitrarily divided the vertical profile of the intertidal zone into three zones (Figure 23): (i) The lower intertidal zone - t i d a l f l a t s extending from low water level to about 8 feet above sea level. • ( i i ) The middle or intermediate zone - t i d a l f l a t s between 8 and 12 feet above sea level, including most of the t i d a l marshes, ( i i i ) The upper intertidal zone - the. area between 10 and 15 feet above sea level. This zone marks the transition from marsh to shrub or forest vegetation. Delta front: A narrow zone where deposition in the delta i s most active; includes the delta-front platform and delta-front slope. The delta-front platform i s a generally sandy, f l a t area, approximately 1000 feet wide, extending from the low water level to the break in slope of the delta front, which occurs in the vi c i n i t y of the 10 fathom level. The delta-front slope i s the steep seaward face of the delta front, extending from the seaward limit of the delta-front platform to the toe of the slope at about 80 fathoms. Prodelta: The part of the delta that i s below the effective depth of wave erosion, lying beyond the delta front and sloping gently down the floor of the basin into which the delta is advancing and where clastic river sediment ceases to be a significant part of the basin floor deposits. Submarine Topography Source of data The general submarine topography of the Squamish Delta and associated harbour area for the years 1930 and 1973 i s shown in Figures 24 and 25 (map pocket). These are the only two years for which detailed data are available. Periodical corrections and additions to the hydrographic charts for thisaarea were made between 1944 and 1972. The bathymetry for the year 1930 is based on the Canadian Hydrographic Services f i e l d sheet number 2313-2, enlarged from a scale of 1:24,300 to 1:8000, for comparison with the 1973 bathymetry. Enlarging was done with the aid of a Saltzman photographic enlarger at the Department of Geography, University of British Columbia. The bathymetry for the year 1973 is based on the Canadian Hydrographic Services f i e l d sheets numbers ,2235-S (Squamish Harbour) drawn to a scale of 1:8000, and 2278-L (Northern Howe Sound) enlarged, from a scale of 1:30,000 to 1:8000. Bottom contours were plotted from soundings shown on the 67 f i e l d sheets i n fathoms. The soundings were reduced by the Canadian Hydrographic Services to a sounding datum referenced to Geodetic BM 1274 J at Squamish. Description of physical features Three main features comprise the submarine topography of the Squamish Estuary and Harbour area: ( i ) the sub-aqueous section of the Squamish Delta, ( i i ) the prodelta basin, and ( i i i ) the Mamquam Channel extension. The extent and l i m i t s of these features are outlined i n •.. Figure 25 (map pocket). (i). Squamish Delta The sub-aqueous section of the Squamish Delta i s confined at i t s western extremity by the rock b l u f f s of the Squamish Batholith, adjacent to the west channel of the Squamish River, and at i t s eastern extremity by the Mamquam Blind Channel and adjacent shoreline. I t i s 1.26 miles wide at i t s northern l i m i t and extends i n a southwesterly d i r e c t i o n , reaching i t s maximum widthoof 1.5 miles at the base of slope of the delta front, at approximately the 80 fathom contour. The break i n slope of the delta front occurs at about the 10 fathom contour. P r o f i l e s of the west and central sectors of the delta front (Figures 26 to 31) show the foreslopes characterized by a steep upper section between 10 and 40 fathoms, with a much f l a t t e r slope between 40 fathoms and the base of the slope at about 80 fathoms. A comparison of the maximum and minimum in c l i n a t i o n s for the upper and lower sections of the foreslopes i s shown i n Table 17 . A maximum Fathoms Feet O O 10 60 20 120 -1 30 180 H 40 240 -\ 50 300 —| 60 360 -i 70 420 H so <?so H 50 540 Figure 26 SQUAMISH DELTA PROFILE-LINE 1 (WEST SECTOR) HORIZONTAL SCALE' 1 inch* 500 feet VERTICAL SCALE' 1 inch= 120 feet 500 1000 1500 3000 4000 4500 5OO0 6000 6500 7000 7500 8000 8500 9000 Feet £>9 Fathoms Feet O O 10 60 H 20 120 -\ 30 180 ~\ 40 240 H 50 300 H 60 360 —i 70 420 —| 80 480 H 90 540 -\ Figure 27 SQUAMISH DELTA PROFILE-LINE 2 (WEST SECTOR) HORIZONTAL SCALE' 1 inch* 500 feet VERTICAL SCALE- 1 inch-120 feet 1000 1500 4000 7000 7500 8000 8500 9 OOO Feet 7P Fathoms Feet O C I -IO 60 2 0 1 2 0 -30 180 -40 240 — J 50 300 -i 60 360 -i 70 420 80 480 -\ 90 540 H SQUAMISH DELTA PROFILE- LINE 3 {CENTRAL SECTORJ HORIZONTAL SCALE- 1 inch = 500 feet VERTICAL SCALE' 1 inch* 120 feet 1000 1500 3000 4000 8000 9000 Feet Fathoms Feet O O 10 60 H 20 120 -i 30 180 —\ 40 240 -\ .50 300 H 60 360 70 420 —\ 80 480 90 540 Dredged area Figure 29 SQUAMISH DELTA PROFILE-LINE 4 (CENTRAL DELTA) HORIZONTAL SCALE' 1 inch* 500 feet VERTICAL SCALE- 1 inch* 120 feet 1930 Mamquam Submarine Channel 500 1000 — I — 1500 2000 2500 3O00 3500 1 4000 4500 5000 5500 I 6000 6500 7000 7500 r— 800O 8500 9000 Feet 12. Fathoms Feet O O -| 10 60 20 120 -30 180 ~ 40 240 — 50 300 60 360 -70 420 -80 480 -90 540 I O Dredged area 500 1000 1500 2000 2500 3000 Figure 30 SQUAMISH DELTA PROFILE-LINE S2 (WEST SECTOR) HORIZONTAL SCALE' 1 inch = 500 feet VERTICAL SCALE' 1 inch = 720 feet 3500 I 4000 4500 5000 5500 6000 6500 — r ~ 7000 7500 8000 8500 9000 Feet 73 Fathoms Feet 80 480 H 90 540 -• 1 — i — i : 1 1 : 1 1 1 1 1 n 1 1 1 1 1 1 r O 500 . • 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 9000 Feet 74 TABLE 17 DELTA FRONT SLOPES 1930 AND 1973 LINE LOCATION UPPER SLOPES LOWERSSLOPES-*' NO 1930 1973 1930 1973 MAX. MIN. MAX. MIN. MAX. MIN. MAX. MIN. 1 WEST SECTOR 11° 6° 13,5° 5° 3° 3° 3° 3° 2 I I I I 10° 4° 20° 8°: 4° 1.5° 3.5° 2° S-2 n it 8.5° 6° 9.5° 8.5° 4.5° 2° 3° 2° 3 CENTRAL SECTOR 10° 5° 12° 6° 3° 3° 3° 3° S-3 it I I 11° 3° 7.5° 6° 3° 2° 3.5° 2.5° 4 ti it 13.5° 3° 10.5° 6° 3° 2° 3° 2° AVERAGE WEST AND CENTRAL SECTORS 10.5° 4.5C 8.5° 6.5° 3.5° 2° 3° 2° UPPER SLOPES 10TT40 FATHOMS (60-240 FEET) LOWER SLOPES 40-80 FATHOMS (240-480 FEET) 75 i n c l i n a t i o n o f 20° has been measured f o r the upper s l o p e s , compared to a maximum of 3.5° f o r the lower s l o p e s . Slumping on the upper s l o p e s between 20 and 40 fathoms can be seen i n the d e l t a f r o n t p r o f i l e s and s e i s m i c r e c o r d s . The p r o b a b l e causes of slumping i n t h e s e r e g i o n s i s d i s c u s s e d l a t e r under t h e s s e c t i o n on s l o p e s s t a b i l i t y . On the e a s t e r n f l a n k of the c e n t r a l s e c t o r of the d e l t a , the d e l t a f r o n t i s i n c i s e d w i t h a s e r i e s o f g u l l i e s s i m i l a r t o t h o se d e s c r i b e d by Mathews and Shepard (1962) o f f the mouth of the F r a s e r R i v e r . The Squamish D e l t a g u l l i e s , n o n - e x i s t e n t i n the 1930 bathymetry of the d e l t a ( F i g u r e 24), o c c u r s o u t h - e a s t of the Squamish F o r e s t P r o d u c t s T e r m i n a l Wharf. They a r e most l i k e l y an e r o s i o n f e a t u r e r e s u l t i n g from the i n f i l l i n g o f the t i d a l f l a t s t o the northwest which d i s r u p t e d the sediment s u p p l y o r i g i n a l l y t r a n s p o r t e d to t h i s a r e a by the c e n t r a l c h a n n e l of the Squamish R i v e r . The g u l l i e s , about 200 f e e t l o n g , a r e 10 to 20 f e e t deep, and o c c u r i n two rows on the 15 and 20 fathom c o n t o u r s a t the head of the Mamquam Canyon, where the f o r e s l o p e s of the d e l t a f r o n t range from 7° to 22°. Mathews and Shepard (1962) compare the F r a s e r d e l t a g u l l i e s w i t h the l a n d s l i d e g u l l i e s o f f the M i s s i s s i p p i D e l t a documented by Shepard (1956). Van S t r a a t e n (1959) observed s i m i l a r g u l l i e s o f f the mouth of the Rhone R i v e r a a n d proposed t h r e e p o s s i b l e e x p l a n a t i o n s f o r t h e i r o r i g i n : ( i ) E x c e s s i v e d e p o s i t i o n of sediment on the r i d g e s between g u l l i e s from l o c a l i z e d c o n c e n t r a t i o n o f suspended m a t e r i a l i n the s u r f a c e w a t e r s . ( i i ) P e r i o d i c s c o u r by s l i d i n g o f s e d i m e n t s a a l o n g the bottom. 76 ( i i i ) The i n f l u e n c e of t u r b i d i t y c u r r e n t s . A d d i t i o n a l e r o s i o n o f t h i s a r e a o f the Squamish d e l t a f r o n t w i l l almost c e r t a i n l y r e s u l t from t h e e x t r a d r e d g i n g now r e q u i r e d t o keep n a v i g a t i o n c h a n n e l s open f o r the wharves s e r v i c i n g the F o r e s t P r o d u c t s T e r m i n a l and F.M.C. Chemicals P l a n t , and from the t r a i n i n g o f the S.quamish R i v e r t o the west s i d e o f the d e l t a . ( i i ) ' Mamquam Submarine Channel / Commencing a t the 15 fathom co n t o u r on the e a s t e r n s i d e o f the c e n t r a l s e c t o r of the d e l t a , the Mamquam Submarine Channel extends i n a s o u t h w e s t e r l y d i r e c t i o n f o r almost 2 m i l e s b e f o r e t e r m i n a t i n g a t the 85 fathom c o n t o u r . W h i l e t h e p o s i t i o n o f the Canyon r e l a t i v e to i t s l o n g i t u d i n a l a x i s has n o t changed s i n c e 1930, an a n a l y s i s o f the bottom c o n t o u r s i n d i c a t e s a s o u t h w e s t e r l y m i g r a t i o n a t a r a t e comparable w i t h t h e g e n e r a l advance of the d e l t a . T h i s can be c l e a r l y seen i n a comparison o f the r e l a t i v e p o s i t i o n s o f the Channel i n 1930 and 1973 on a p r o f i l e o f the d e l t a f r o n t ( F i g u r e 30). The Channel p i c k e d up on the s e i s m i c p r o f i l e l i n e number S-3 ( F i g u r e 33) ranges i n de p t h from 30 t o 40 f e e t a t i t s n o r t h e r n l i m i t t o o n l y 10 to 15 f e e t a t i t s s o u t h e r n e x t r e m i t y . S i d e s l o p e s measured from s i e s m i c p r o f i l e s appear t o be q u i t e s t e e p , i n the o r d e r o f 15° to 18°. The mechanism r e s p o n s i b l e f o r k e e p i n g the Channel open i s not-known, and to determine i t , a d d i t i o n a l s t u d i e s o f the s u r f a c e and sub-s u r f a c e c u r r e n t s , water temperatures and d e n s i t i e s ' , bottom sediments and o t h e r r e l a t e d f a c t o r s would have to be c a r r i e d o u t . The Channel f o l l o w s c l o s e l y the a x i s o f the c i r c u l a t i o n p a t h o f the r i v e r d i s c h a r g e . S u r f a c e 77 c u r r e n t s , , w i t h v e l o c i t i e s o f 1.5 t o 2 k n o t s , f l o w i n g i n a s o u t h w e s t e r l y d i r e c t i o n i n the g e n e r a l v i c i n i t y o f t h e Channel have been measured by Pond and B u c k l e y of the U n i v e r s i t y o f B r i t i s h Columbia (1973, u n p u b l i s h e d d a t a ) . V a n . S t r a a t e n (1959), d e s c r i b i n g the submarine morphology o f the Rhone D e l t a , r e f e r s t o the p r e s e n c e of a l a r g e c h a n n e l on the d e l t a f r o n t d i r e c t l y seaward of the r i v e r b a r . He proposes the h y p o t h e s i s of low v e l o c i t y t u r b i d i t y c u r r e n t as the mechanism f o r the p r e s e n c e o f t h e c h a n n e l , and s u g g e s t s t h a t the c u r r e n t s may be i n d u c e d by the change i n f l o w of the r i v e r o r by wave a c t i o n . I t i s most l i k e l y t h a t f o r the Mamquam Channel, the mechanism k e e p i n g i t open i s a c o m b i n a t i o n of s u b s u r f a c e t i d a l c u r r e n t s and sediment l a d e n d e n s i t y or t u r b i d i t y c u r r e n t s p r o d u c i n g a h y p e r p y c n a l f l o w ( B a t e s , 1960). * ( i i i ) , P r o d e l t a B a s i n The p r o d e l t a b a s i n i s the seaward e x t e n s i o n of the d e l t a , e x t e n d i n g a p p r o x i m a t e l y 2% m i l e s southwest from the base o f the d e l t a f r o n t f o r e s l o p e s , a t about 80 fathoms, to the 120 fathom c o n t o u r a t the harbour l i m i t between Watts P o i n t and Woodfibre. The b a s i n , almost 2 m i l e s wide, s l o p e s seaward to i t s s o u t h e r n l i m i t a t 1° to 2°, w i t h g e n e r a l l y l i t t l e v a r i a t i o n i n the bottom topography. There i s , however, a l o c a l i z e d a r e a e a s t of White Rock a t l a t i t u d e 49° 39.5' n o r t h and l o n g i t u d e 123° 12.5' west where a major a c c u m u l a t i o n of f i n e sediment i s b u i l d i n g up and s l o p i n g northwest a t a n g l e s a p p r o a c h i n g 30°. E v i d e n c e of c o n t i n u o u s slumping of f i n e g r a i n e d c o h e s i v e sediments a t t h e base of 78 this ridge at a depth of 70 to 80 fathoms i s seen in the seismic profile for line S-3.(Figure 33). Internal Structure of the Delta A continuous,seismic profile (C.S.P.) survey of the delta front and prodelta area was made in September 1973. The survey was made using custom built equipment designed and built by the U.B.C. Department of Geological Sciences, and provided an opportunity to f i e l d test the equipment in a brackish water environment. The profiles were obtained using a "boomer" transducer sonar source as described by Edgerton and Hayward (1964), and a custom built 50 foot long hydrophone array (U.B.C. MP 17 x 25). A portable 110/4000 volt generator supplied the power to the "boomer", set for 400 joule pulses at a 1 second f i r i n g rate. A custom built amplifier provided the pre-amplification. Pulse waves were fil t e r e d from 3000 to 5000 hz to get the best balance of penetration and definition. The use of low frequencies results in good penetration but poor definition (Macdonald 1974 - personal communication). An EPC GraphierRecorder Model 4100 displayed the profile information in i t s f i n a l form. Two major factors affecting the quality of the records were noise interference and a vari a b i l i t y in the water density. Noise inter-ference from ship t r a f f i c in the area shows up on the profile in the form of patches of vertical lines, and i s clearly visible on the profile for line S-3 (Figure 33). It,- plus the interference from on-rboard auxiliary equipment, tended to affect the signal to noise ratio, on which the quality of the records depends. 79 Variability in water density caused problems in equipment grounding and also affected the quality of the records. In order to minimize the effect of the fresh water discharge from the Squamish River, an attempt was. made to run the survey lines during the flood stage of the tide. Table 18 shows the t i d a l conditions and river discharge during the survey. Date Sept. 11 1973 Time (P.S.T.) 1020 1705 TABLE 18 Tide L.W.L. H.W.L. Height (ft) 5.2 14.1 River Discharge (cusecs) 13,400 Sept- 12 1973 Sept. 12 1973 1105 1725 L.W.L. H.W.L. 5.7 14.2 13,000 The high river discharge produced a three foot surface layer of fresh water on the eastern side of the estuary. This resulted in weak signals when profiling in this area. A noticeable increase in the quality of the records was observed when the fresh water-salt water boundary was crossed for profiling on the west side of the estuary. Description of profiles A total of 8 lines were surveyed, representing 8.5 nautical miles of profiles. Lines S-2 and S-3 (Figures 32.and 33) have been selected as the most representative of the structure of the west and central sectors of the delta. Locations are shown in Figure 34. 1" • hi FIGURE 33. Seismic Profile - Line S-3. Heavy black lines (upper l e f t and right) represent noise interference from ship t r a f f i c . Vertical exaggeration 4:1. CO • rO FIGURE 34. Location of Seismic Profile Lines S-2 and S-3. 83 Line S-2, approximately 1.7 nautical miles long, was run along the north-south axis of the west sector of the delta, from White Rock in the south to the B.C. Railway training dyke at the northern extremity. The profile commencing in a water depth of 95 fathoms shows the delta sloping uniformly at approximately 1 ° toaa depth of 78 fathoms. At this point the slope changes abruptly to 6 ° , increasing to 8.5° between 50 and 24 fathoms. Generally, a layer of recent sediments varying from 5 to 10 feet thick and characterized by a series of horizontal reflectors, over-li e s an extensive zone of sheared and slumped sediments characterized by a series of parabolic reflectors. Two major features show up on the profile: (a) a slump structure on the upper slopes at a depth of 24 fathoms, and (b) a structure believed to be a mudlump, occurring at a depth of 52 fathoms. Line S-3, approximately 1.5 nautical miles, was run on the north-south axis of the central delta starting from the central channel of the Squamish River and finishing to the northeast of White Rock (Figure ,3'3)),. Three major features are evident on this profile: (a) a slump Structure between 28 and 38 fathoms similar to the one on the upper delta slopes of line ST-2, (b) the Mamquam Channel at 62 fathoms, and (c) an area of highly deformed sediments between the depths of 74 and 90 fathoms. Again, as in line S-2, the parabolic reflectors indicate the areas of slumped and deformed sediments, occasionally overlain by shallow horizontal layers of sediment. 84 Slope Stability The west and central sectors of the delta front, being areas of intermittent deposition and rapid accumulation of both cohesive and non-cohesive sediments, provide a basic environment for slope instability and the inherent probability of slumping. Evidence of slumping on the upper slopes of the delta front can be seen in the seismic profile records (Figures 32 and 33) and in the bathymetric cross-sections (Figures 26 to 31). Generally, slumping appears to occur between depths of 20 to 40 fathoms on the steeper and less consolidated slopes of the delta front. An area' susceptn.V1. " - . slumping i s outlined in Figure Terzaghi (1956) divides submarine slope failures into three major categories: (i). Failures involving downward movement of patches of cohesive sediments perched on the steep slope of cohesionless material, ( i i ) Spontaneous mass movements of short duration, involving large quantities of sediments, ( i i i ) Continuous slumping on gentle slopes. Slumping on the Squamish River delta front reflects the characteristics of the f i r s t category. In the prodelta basin, in the vic i n i t y of White Rock, seismic profiles show evidence of continuous slumping on gentle slopes. A slope failure, of the type described under the f i r s t category, occurred at the northern end of Howe Sound on August 22, 1955, 85 and was i n v e s t i g a t e d and documented by T e r z a g h i (1956). A warehouse and dock b e l o n g i n g to the Woodfibre Paper M i l l , i n c l o s e p r o x i m i t y t o the mouth o f M i l l Creek, c o l l a p s e d and f e l l i n t o the water. T e s t b o r i n g s c a r r i e d out d u r i n g the i n v e s t i g a t i o n o f the f a i l u r e showed t h a t the d e l t a f o r m i n g o f f the mouth o f the c r e e k c o n s i s t e d o f c l e a n sand and g r a v e l t o a depth o f 120 f e e t . The a n g l e of s l o p e o f the d e l t a f r o n t to a depth o f 100 fathoms was q u i t e s t e e p , r a n g i n g from 26.5° to 28°, thus a p p r o a c h i n g the c r i t i c a l s l o p e o r i n t e r n a l a n g l e o f f r i c t i o n f o r d r y sand and g r a v e l . A body of s i l t y sediments o f a more c o h e s i v e n a t u r e , b u i l t up on top o f t h e c o a r s e r n o n - c o h e s i v e sediment and when the h e i g h t o f the steep s l o p e o f the u n c o n s o l i d a t e d s i l t y sediment r e a c h e d a c r i t i c a l v a l u e , the s l o p e f a i l e d . S l o p e s up t o a maximum o f 22° have been measured on t h e upper s l o p e s o f t h e Squamish D e l t a f r o n t p r o f i l e s . C ontinuous slumping on g e n t l e s l o p e s , d e s c r i b e d by T e r z a g h i (1956), i s n o t i c e a b l e i n the p r o d e l t a submarine topography n o r t h o f White Rock. The u n d u l a t i n g form of the bottom p r o f i l e a t the s o u t h e r n end of the s e i s m i c . l i n e S-3 ( F i g u r e 33) and the p i l i n g up o f the sediments beyond the t o e o f the s l o p e s u g g e s t s p r o g r e s s i v e slumping. Continuous slumping o c c u r s i n c l a y d e p o s i t s as a r e s u l t o f the l a g between s e d i m e n t a t i o n and c o n s o l i d a t i o n o f the sediments ( T e r z a g h i , 1956). The s o u t h e r n end o f l i n e S-3 i s 3 m i l e s from the i n t e r f a c e of the f r e s h water o f the Squamish R i v e r and the marine waters o f t h e e s t u a r y , and i s t h e r e f o r e l i k e l y an a r e a o f d e p o s i t i o n o f c l a y s and f i n e s i l t s . A zone o f "mounds" on a g e n t l e s l o p e o f u n s t a b l e sediments i n the d i s t a l r e g i o n o f the L i l l o o e t D e l t a were observed by G i l b e r t (1973). 86 He concluded that on1 the basis of his shear strength measurements of the lake bottom sediments, slopes as low as 1.6° are unstable in remoulded sediment. Moore (1961), discussing submarine slumps, emphasizes the importance of shear strength as a property of marine sediments to measure for an analysis of slope s t a b i l i t y . The st a b i l i t y of a sedi-mentary deposit on a given slope i s dependent on i t s shear strength, and the rate of increase of the strength with burial. These two factors are in turn controlled by grain size distribution, rate of accumulation of sediments, degree of consolidation, uniformity and pore pressure conditions. Shear strength tests carried out on sediments of the Mississippi Delta for foundation studies showed that the rapidly deposited fine sediments on the delta front are extremely unstable. Rate of Growth A comparison of the 1930 and 1973 bathymetric surveys reveals that the delta front -in the west and central sectors of the delta has advanced about 900 feet or about 21 feet per year. Delta front advances measured from profiles of the delta front for the years 1930 and 1973 (Figures 26 to 31) show advances in the west sector ranging from a maximum of 23.3 feet to a minimum of 2.3 feet, and advances in the central sector ranging from a maximum of 30.2 feet to a minimum of 7.0 feet. The mean annual advance for the delta front for the 43 years between 1930 and 1973, at depths of 60 to 360 feet (10 to 60 fathoms), is summarized in Table 19. A gradual decrease in the rate of advance 87 TABLE 19 SQUAMISH DELTA - RATE OF ANNUAL ADVANCE (1930 TO '1973) LINE LOCATION DEPTH IN FEET BELOW L0.WN- WATER LEVEL NO 60 120 180 240 .300 360 DELTA ADVANCE - FEET PER YEAR 1 WEST SECTOR 23.3 14.0 - 2.3 12.8 5.8 2 II 19.8 21.0 16.3 8.2 17.4 16.4 S-2 II 22.0 21.0 15.,2 12.8 14.0 23.3 3 CENTRAL SECTOR 20.4 19.8 21.0 30.2 11.6 18.6 S-3 II 15.7 18.6 19.8 10.5 7.0 9.3 '4 II 15.2 18.6 16.4 15.2 - 11.6 MEAN • 19.4 18.8 14.8 13.2 12.6 14.1 88 TABLE 20 COMPARATIVE RATES OF ADVANCE - SQUAMISH, LILLOOET AND FRASER DELTAS DELTA YEARS OF NO. OF DEPTH ADVANCE COMPARISON YEARS FT. rPER YR. FT. 60 19,4 SQUAMISH 1930-•1973 43 120 18.8 180 14 .8 1859- 1913 54 D e l t a 2 3 . 0 f r o n t 1914- 1948 34 from 26 .2 LILLOOET a e r i a l 1948- 1953 5 p h o t o - 9 8 . 0 graphs 1953- 1969 16 6 9 . 0 FRASER - 10 .0 ^Jo'hnston- - 1859- 1919 60 1921 180 2 6 . 0 20 7 .5 Mathews and Shepard' - 1929- 1959 30 120 15 .0 1962 (main arm o f 300 2 8 . 0 F r a s e r R i v e r ) 89 is noticeable with an increase in depth to the 360 foot (60 fathom) level. From 360 to 600 feet (60 to 100 fathoms) in the prodelta region, the rate of advance increases again. Advances of 18.6 to 23.3 feet per year were measured in the prodelta area by comparing the positions of contours on the 1930 and 1973 bathymetric surveys. A comparison of the mean annual rate of advances for the Squamish Delta, with the Lillooet Delta one of the fastest growing fresh water deltas in North America, and the Fraser Delta, i s made in Table 20. The wide range of rates of advance for the Lillooet Delta have been attributed to man-made changes in the river watershed, such as channel improvements for navigation and denudation of forested slopes (Gilbert, 1973). Recent research by Murray and Luternauer (1972) on the Fraser Delta indicates an average advance for the northern section of the delta (Sturgeon Banks) of 10 feet per year, comparable to the average rate of advance calculated by Johnson (1921). More recent work by Mathews and Shepard (1962) shows a faster rate of advance, but relatesoonlycto^a.two mile wide section across the river mouth off the Main Arm. Rate of vertical acretion Rates of vertical growth of the west and central sectors of-the delta front, summarized in Table 21, show the average rate of growth between 60 and 360 feet (10 to 60 fathoms) to be in the order of l£2 feet per year. Between 60 and 180 feet (10 to 30 fathoms) there appears to 90 TABLE 21 SQUAMISH DELTA - RATE OF VERTICAL ACRETION (1930-1973) LINE DELTA GROWTH - VERTICAL ACRETION PER YEAR NO LOCATION DEPTH IN FEET - BELOW LOW WATER LEVEL 60 120 180 240 300 360 1 WEST SECTOR 1.4 2.5 - 0.3 009 0.6 2 II 1.4 2.5 2.1 0.6 1.0 0.7 S-2 it - 2.0 2.5 1.4 1.4 0.8 , 3 CENTRAL . SECTOR - 1.4 2.5 1.4 .0.7 0.8 S-3 ti - 1.4 2.4 0.8 0.6 1.1 4 II - 1.4 2.5 1.5 - 0.4 MEAN VERT. ANNUAL ACRETION 1.4 1.9 2.4 0.8 0.9 0.7 be a slightly faster rate of acretion than from 180 to 360 feet (30 to 60 fathoms). Below 360 feet (60 fathoms) the vertical acretion appears to decrease. Measurements from profiles in the v i c i n i t y of the 80 fathom (480 feet) contour show the annual rate of acretion varying from 0.4 to 1.1 feet per year, with an average of 0.7 feet per year for the six profiles measured. 92 CHAPTER V SEDIMENTARY ENVIRONMENTS The i n t r a d e l t a , or i n t e r t i d a l zone as i t i s more f r e q u e n t l y r e f e r r e d t o , extends from low water l e v e l t o an e l e v a t i o n o f 15 f e e t above sea l e v e l . I t i s i n t h e i n t e r t i d a l zone t h a t the g r e a t e s t e f f e c t s , ' of s h o r t term changes i n s e d i m e n t a t i o n a r e t a k i n g p l a c e . Changes i n the p a t t e r n o f d e p o s i t i o n w i t h i n t h i s a r e a r e s u l t from b o t h n a t u r a l causes such as changes i n the r i v e r morphology, and u n - n a t u r a l causes such as ch a n n e l improvements, f i l l i n g o f t i d a l f l a t s f o r i n d u s t r i a l development and r e l a t e d phenomena. Three sedimentary environments c h a r a c t e r i z e the i n t e r t i d a l zone o f t h e Squamish D e l t a . These a r e : ( i ) r i v e r mouth b a r s , ( i i ) t i d a l f l a t s , and ( i i i ) t i d a l marshes. R i v e r mouth ba r s . R i v e r mouth sand b a r s p r e v i o u s l y b u i l d i n g o f f the west and c e n t r a l c h a n n e l s o f t h e r i v e r ( F i g u r e 35) a r e now s o l e l y c o n f i n e d t o the west c h a n n e l . S k r i p t u n o v (1969), d e s c r i b i n g h y d r o l o g i c a l p r o c e s s e s i n o f f i n g s ( a r e a o f f t h e r i v e r mouth) and t h e i r r o l e i n the f o r m a t i o n o f a d e l t a f r o n t , s t a t e s t h a t " t h e mouth b a r i s one of the s p e c i f i c elements of the d e l t a f r o n t " . S i n c e b o t h the h y d r o l o g y and morphology of the o f f i n g i s c o n t r o l l e d t o a c o n s i d e r a b l e degree by the streamflow, s i g n i f i c a n t changes i n the mouth b a r s can take p l a c e i n a r e l a t i v e l y s h o r t p e r i o d o f time. S i n c e the c o m p l e t i o n o f d r e d g i n g of the r i v e r c h a n n e l i n March 1972, a l a r g e submerged b a r has been b u i l d i n g o f f the 93 FIGURE 35. Aerial photograph (May 1968) showing river mouth Bars off the west and central channels of the Squamish River. 94 mouth of the west channel of the Squamish River. The extent of build-up can be seen in Figure 36, reproduced from a sounding survey of the river mouth carried out between July 28 and August 1, 1972, by Swan Wooster Engineering for B.C. Railway. A profile along the center-line of the river mouth showed a build-up of up to 40 feet of material, between the -10 and -90 foot contours. A second sounding survey in February 1974 showed additional build-up in the same area. Bates (1953), discussing jet flow in the process of delta formation, makes the point that the distance at which lateral bar formation starts off a river mouth is dependent on whether the jet of turbid water is of the axial or plane type. Figure 37 illustrates the axial jet flow discharging from the west channel of the river, after training and deepening, and during a period of high river discharge in * June 1972 (mean flow 25,000 c.f.s.). Tidal Flats Tidal f l a t s of the lower intertidal zone extend from low water level to approximately 8 feet above sea level. This elevation marks the point at which the f i r s t vegetation is found on the t i d a l f l a t s (Figure 38) and has been used to delineate the boundary between ti d a l f l a t s and t i d a l marshes. The s u r f i c i a l sediment distribution and composition of the ti d a l flats of the west and central sectors of the delta varies considerably, and can be related to the different modes of sediment transport and deposition resulting from the construction of the river - West Channel River Mouth, 1972. FIGURE 37. (From aerial photograph BC 5469-119) Sediment discharge (jet flow), off the mouth of the west channel of the Squamish River, June 18, 1972. River discharge 15,700 c.f.s. FIGURE 38. Tidal flats of the lower intertidal zone of the west sector of the delta. The transition from t i d a l flats to t i d a l marshes occurs at approximately 8 feet above sea level. West channel of Squamish River in background. 98 training works. Unfortunately, there i s a paucity of knowledge relating to the distribution of sediments on the ti d a l flats prior to the construction of the training dyke in 1972, and consequently comparative changes with the sedimentary environments as they now exist are d i f f i c u l t to assess. On the westsside of the mouth of the Squamish River (that i s , the west channel), a bar of well washed, coarse to fine grained sand is separated by a ti d a l channel from the fine sandy s i l t s of the lower t i d a l f l a t s . On the east side of the river there is a sand bar of fine to medium grained sand adjacent to the training dyke and extending 200 feet south of the row of dolphins at the southern limit of the dyke. This bar, containing layers of black sands and muds (Figures 39 and 40) is subjected to considerable wavererosion and.river scour, which cause re-working and re-deposition of these sediments (Kestner, 1961). Seven test holes were d r i l l e d to a depth of -20 feet in the tid a l flats and ti d a l marshes of the west sector of the delta in March 1971, prior to the construction of the Squamish River training works. The location of holes numbers D.H.I, D.H.2, D.H.3 and D.H. 4 on the ti d a l f l a t s , is shown in Figure 41. Test hole data compiled from information supplied by Cooke Pickering and Doyle, Vancouver, B.C., is shown in Figure 42. In the ti d a l flats of the central sector of the delta, coarse s u r f i c i a l sediments are noticeably absent. Amounts of s i l t s and clays greater than 70% were not uncommon in samples from this area. A large zone of silty-clay was found to occur on the eastern side of the training dyke at i t s southern extremity. This build-up might be the result of the construction of the training dyke, which almost eliminates the fresh 99 FIGURE 40. L a y e r i n g of sediments on lower t i d a l f l a t s , west c h a n n e l i n t e r t i d a l zone ( l o o k i n g n o r t h e a s t ) . FIGURE 41. Location of D r i l l Holes - West Channel Intertidal Zone. o o ELEVATION (A.S.L.) D.H.4 + 1 0 - 1 0 — - 2 0 D.H.I SILTY SAND-FINE SAND SOME SILT COARSE SAND SOME FINE GRAVEL D.H.2 * -~ i. . y o , t * (, A 1 ' i. , < o ' *) SAND TRACE. OF SILT FINE SAND SOME SILT GRAVELLY VERY COARSE SAND VERY COARSE TO COARSE SAND GRAVELLY SOME GRAVEL TRACE SILT D.H.3 SILTY SAND SANDY GRAVEL TRACE OF SILT COARSE SAND MED-COARSE SAND TRACE OF SILT ! CLAYEY SILT SAND TRACE OF SILT SAND LOWER TIDAL FLATS TIDAL MARSH FIGURE 4 2 . D r i l l hole data f o r test holes i n the i n t e r t i d a l zone of the west channel. (Data courtesy B.C. Railway.) 102 water flow through the central channel, thus allowing the transgression of seawater up the channel. Evidence of this can be seen in the patches of blue mussels (Mytilus edulis dinnaeus) now colonizing the upper limits of the tida l f l a t s . The t i d a l f l a t s of the central sector extend approximately 2,000 feet north from low water level and end abruptly at a small sandy platform, where a 4 foot vertical bank, covered with a rhizome mat, marks the sudden change from t i d a l flats to t i d a l marshes. In summary, three main factors appear to control the deposition and distribution of the sediments of the lower intertidal zone of the west and central sectors of the delta: 1. An increase in volume of fresh water discharge in the west channel of the Squamish River and a substantial decrease in fresh water discharge in the central channel, as a result of river training. 2. Changes in salinity distribution in the west and central channels and the intrusion of, the salt water wedge as a result of deepening of the west channel. 3. Changes in the wave energy environments at the mouths of the west and central channels, resulting.from the breakwater effect of the training dyke during periods of strong southerly winds. Ripple Marks Ripple marks as indicators of bottom energy environments are visible on the lower tida l f l a t s of the west and central sectors of the delta. 103 R i p p l e s o b served on the t i d a l f l a t s o f the west and c e n t r a l s e c t o r s i n d i c a t e two d i f f e r e n t energy environments e a s t and west of the t r a i n i n g dyke. E a s t o f the dyke, wave a n d c c u r r e n t formed l i n e a r a s y m e t r i c a l r i p p l e s ( F i g u r e 43) were predominant, i n d i c a t i n g a low energy environment. West of the dyke t h r e e types of r i p p l e marks a s s o c i a t e d w i t h h i g h energy environments were observed ( F i g u r e s 44 to 46): ( i ) R i p p l e s w i t h b i f u r c a t i o n s , from which wind and wave v e l o c i t i e s may be determined, ( i i ) Ladder back r i p p l e s formed by changes i n c u r r e n t d i r e c t i o n d u r i n g the d i f f e r e n t s t a g e s of the t i d e , ( i i i ) I s o l a t e d r i p p l e s i n the base o f a d e p r e s s i o n caused by bottom s c o u r i n the v i c i n i t y o f an immovable o b j e c t . O b s e r v a t i o n s of s i m i l a r o c c u r r e n c e s of t h e s e r i p p l e marks on the t i d a l f l a t s o f the Maine Coast (U.S.A.) have been d e s c r i b e d by T r e f e t h e n and Dow (1960). The use of r i p p l e mark i n d i c e s d e r i v e d from t h e r i p p l e mark geometry has been used to i d e n t i f y the environment o f sediment accumula-t i o n (Tanner, 1967). To the two main parameters, r i p p l e i n d e x (R.I.) and r i p p l e symmetry i n d e x ( R . S . I . ) , Tanner added f i v e a d d i t i o n a l parameters i n c l u d i n g the b i f u r c a t i o n i n d e x , d e f i n e d ast'the b i f u r c a t i o n of i n d i v i d u a l c r e s t s per u n i t c r e s t l e n g t h . T h i s b i f u r c a t i o n may v a r y w i t h the f e t c h and f r e q u e n c y o f waves ( T r e f e t h e n and Dow, 1960). Another f e a t u r e i n d i c a t i v e o f the energy environment of sediment d e p o s i t i o n a r e the mud-boils ( F i g u r e 47) observed on the lower t i d a l f l a t s o f the west s e c t o r of the d e l t a , and i n c l o s e p r o x i m i t y t o FIGURE 44. B i f u r c a t i o n o f r i p p l e s . Lower t i d a l f l a t s , n e a r r i v e r mouth west c h a n n e l , June 1974. 105 FIGURE 45. Ladder back r i p p l e s . Lower t i d a l f l a t s , near r i v e r mouth, west channel, June 1974. FIGURE 46. B u r i a l of r i p p l e s . Lower t i d a l f l a t s , near r i v e r mouth, west channel, June 1974. FIGURE 48. Relict mud-boils. Lower tidal f l a t s , west channel, June 1974. 107 the t r a i n i n g dyke a t the r i v e r mouth. These f e a t u r e s o c c u r i n an a r e a where t h e r e i s e v i d e n c e of t h e r e - w o r k i n g of sediments d u r i n g t i d a l c y c l e s . The m u d - b o i l s , v o l c a n o - l i k e i n appearance, a r e from 6-8 i n c h e s i n d i a meter and 2-3 i n c h e s i n h e i g h t . TThey a r e r e l a t i v e l y u n s t a b l e and when p l a n e d o f f by bottom c u r r e n t s they l e a v e a d i s t i n c t i v e mark on the sediment s u r f a c e ( F i g u r e 48). T i d a l Marshes T i d a l marshes occupy the g r e a t e s t a r e a of the i n t e r t i d a l zone. They c o v e r a p p r o x i m a t e l y 55 a c r e s of the west s e c t o r and 25 a c r e s of the c e n t r a l s e c t o r of the i n t e r t i d a l zone. T h e . s e c t i o n s o f marshes l y i n g between 8 and 12 f e e t above sea l e v e l ( i n t e r m e d i a t e i n t e r t i d a l zone) a r e s u b j e c t e d to c y c l i c a l i n n u n d a t i o n s of b o t h f r e s h and s a l t water. They a r e g e n e r a l l y c h a r a c t e r i z e d by v a r i o u s s p e c i e s of sedge ( C y p e r a c e a e ) , and a r e r e f e r r e d to l o c a l l y as the sedge marshes of the d e l t a . Between 10 and 15 f e e t above sea l e v e l (upper i n t e r t i d a l z o n e ) , the marshes a r e o n l y i n t e r m i t t e n t l y c o v e r e d by water and a t r a n s i t i o n from marsh to shrub or f o r e s t v e g e t a t i o n i s e v i d e n t . On the w e s t e r n s e c t o r o f the d e l t a the d e m a r c a t i o n l i n e between the t i d a l f l a t s and the t i d a l marshes can be s p o t t e d v e r y e a s i l y by an a b r u p t end to the marsh v e g e t a t i o n a t an e l e v a t i o n of about'.. 7 t o 8 f e e t above sea l e v e l . The a r e a of t i d a l f l a t s d e v o i d of v e g e t a t i o n , between the edge of the marshes and the low water l e v e l , has been d e s c r i b e d by Hedgepeth (1957) as an u n s t a b l e r e g i o n where the g r e a t e s t r u n o f f d u r i n g ebb o c c u r s , and e r o s i o n p r e v e n t s the e s t a b l i s h m e n t of r o o t e d v e g e t a t i o n . 108 On the c e n t r a l s e c t o r o f the d e l t a t h e marshes a t t h e i r s o u t h e r n l i m i t end a b r u p t l y a t an e l e v a t i o n o f about 9 f e e t above sea l e v e l , w i t h a v e r t i c a l drop of 3 to 4 f e e t t o a sandy l e d g e . Exposed on t h i s v e r t i c a l f a c e a t low t i d e s a r e the sedge r o o t s f o r m i n g a sedge rhizome o r " r o o t mat". Under these mats l i v e l a r g e c o l o n i e s of amphipods, the main s o u r c e of f o o d f o r the j u v e n i l e salmonids which f e e d i n t h i s a r e a f o r a p p r o x i m a t e l y two y e a r s b e f o r e m i g r a t i n g to t h e sea. L e v i n g s (1972) e s t i m a t e s t h a t the rhizome h a b i t a t s of the c e n t r a l and e a s t d e l t a s p r o v i d e a p p r o x i m a t e l y f o u r times as much amphipod biomass as i s found i n the west d e l t a , w hich i s d e v o i d of t h i s h a b i t a t . Log d e b r i s s u p p l i e s the o n l y c o v e r f o r the amphipods i n h a b i t i n g t h e west d e l t a . The marshes of b o t h the west and c e n t r a l d e l t a s a r e c r i s s -c r o s s e d w i t h t i d a l c h a n n e l s , w i t h depths r a n g i n g f r o m ' l to 6 f e e t and w i d t h s of 2~h f e e t . The c h a n n e l s d r a i n e d of water a t low t i d e s s t a r t f o r m i n g i n the t i d a l f l a t s ( F i g u r e 49) and c u t northward i n t o the sedge marshes. The c h a n n e l s appear t o be deepened by an u n d e r c u t t i n g a c t i o n of the t i d a l c u r r e n t s . S e v e r a l c h a n n e l s were o b s e r v e d to have c u t through the marshes and j o i n e d up w i t h the Squamish R i v e r , thus p r o v i d i n g a two-way f l o w f o r f r e s h and s a l t water. C o n s i d e r a b l e l a t e r a l m i g r a t i o n of channels i s n o t i c e a b l e , w h i c h P e s t r o n g (1965) a t t r i b u t e s p r i m a r i l y t o the more r e s i s t a n t S a l i c o r n i a sp. banks i n s a l t marshes. P o s s i b l y the type of v e g e t a g i v e c o v e r i s a l s o a key f a c t o r i n c h a n n e l m i g r a t i o n i n p r e d o m i n a n t l y f r e s h water marshes. While no sediment samples were taken from the c r e e k beds i t was o b s e r v e d t h a t the sediment i n the c e n t e r of the beds was g e n e r a l l y FIGURE 49. Formation of t i d a l channel at junction of ti d a l flats and tida l marshes, west sector of delta. 110 coarser than the black organic muds at the sides of the channel beds. Lim and Levings (1973) identified twenty-four species of plants on the tidal marshes. Most were species of sedge (Cyperaceae sp.), grasses (Gramineae sp.) and rushes (Juncaeae sp.). Spike rush (Eleocharis  palustris) favoured regions near the mouth of the Squamish River, and provide the demarcation line between the marshes and lower t i d a l f l a t s . Members of the sedge family are the dominant plants on the delta, Carex lyngbyei being widespread throughout the delta. Large clouds df dust blowing off the marshes at low tide on hot sunny days during the summer months are indicative of a considerable amount of entrapment of suspended sediment by the marsh sedges. Suspended sediment loads in the river reach a maximum (May-July) at about the same time as the sedges are at their maximum height of 3 to 4 feet, thus provising an effective trap. Water-logged timbers lying on the marshes were observed to be covered with a layer of fine sediment (mud) 1/8 to 3/8 of an inch thick. Timbers such as these, i f cleaned off and marked, could be used as indicators of the rate of accumulation of suspended sediment on the marshes. Pomeroy and Stockner (1973), investigating the distribution and production of benthic algae on the tidal flats and marshes, found that the maximum algal growth occurred on the west delta and was restricted to wood surfaces in the lower zone (tidal flats) and to the sediment surface in an area of short deltaic vegetation in the intermediate zone (sedge marshes). The distribution pattern for the central delta was also restricted to these two zones. They also point out that the training of 111 the Squamish River has been a prime factor in establishing recent algal growth patterns. The algal habitats oh the west delta have been subjected to increases in current velocity and sediment load. This has resulted i n the development of unstable substrates. Sediments Sampling Surficial sediment sampling of the tida l flats and t i d a l marshes of the west and central sectors of the delta was carried out in June, 1973 i n conjunction with a biological sampling program initiated by the Fisheries Research Board of Canada (Levings, 1974)". Sediment samples in the intertidal zone were obtained at low tide, at 14 stations in the central sector and at 9 stations in the west sector. The location of the transects and sampling stations i s shown in 2 Figure 50. At each location the sediment within a 0.06 m quadrat was-collected with a trowel to a depth of 2 cm. An additional 6 samples were collected from the sand bar at the southern end of the training dyke. Sublittoral grab samples were obtained at 16 locations on the delta front i n June and September 1973 (Figure 51). An additional 12 • samples taken by the Fisheries Research Board (Pacific Environment Institute) in July 1972 were analyzed for comparison. Sampling was carried out from the Fisheries Research Vessel "Active Lass" using Van Veen and Dietz La Fond grab samplers. Sample locations were fixed by radar and plotted on a hydrographic chart. Location depths on the chart were correlated with those recorded at the time of sampling. FIGURE 50. L o c a t i o n o f Sediment Samples - I n t e r t i d a l Zone. FIGURE 51. Location of Sediment Samples - Delta Front. 114 Colour The colours of the wet sediments were obtained by comparison with a rock colour chart (Geol. Soc. Am. 1963). Delta front sediments ranged in colour from light olive gray (5Y 5/2) to olive gray (5Y 4/1), to greenish gray (5GY 6/1). Reddish-brown iron staining was noticeable in samples JO-2 and JO-7 (June 1973). Both these samples are south of the central channel, where prominent iron staining occurred in the samples taken in the intertidal zone. Sediment samples from the intertidal zone ranged in colour from light olive gray (5Y 5/2) to olive black (5Y 3/1) and grayish'black (N2), depending on the percentage of organic matter. In the central channel at stations C-l, C-2, and C-7A the sediment had a strong yellowish brown coloration (10YR 4/2), due to iron staining. A summary of the sediment colours for the sediments of the intertidal and offshore zones is shown in Table 22. Composition Sediments were analyzed for grain size distribution in accordance with the following procedure modified from Folk (1963) and Royse (1970): 1. Frozen samplesthawed. 2. Soluble salts removed - sediments agitated in 600 ml beakers f i l l e d 2/3 f u l l with d i s t i l l e d water for approximately % hour. Then centrifuged at 2000 r.p.m. for % hour and liquid decanted. 3. Sediments wet sieved through a U.S. Standard Sieve Mesh # 35 (1 fy). > Coarse fraction retained on sieve air dried and weighed. TIDAL MARSHES I ' 1 WEST CENTRAL light olive gray (5Y 5/2) to olive gray (5Y 3/2) Occasional traces of reddish-brown iron oxide staining and black patches of organic matter olive gray (5Y 3/2) to olive black (5Y 2/1) heavy brown iron oxide staining v i s i b l e in sediments in upper elevations of marshes C-2 C-7, 7a, 7b TABLE 22 SEDIMENT COLOUR ZONE OFFSHORE 1 ' TIDAL FLATS 1 1 10-20 20-40 1 40 1 1 FATHOMS FATHOMS FATHOMS WEST CENTRAL olive gray (5Y olive gray light olive olive gray 4/1) to greenish 5Y 4/1 gray (5Y (5Y 3/2) to gray (5GY 6/1) iron 5/2) to grayish black sediments close . staining olive gray (N2). to intertidal. JO-7 (5Y 3/2) Sediments zone heavy in 46 fathoms with reddish- high in organic black organic brown iron ma 11 er (mar ine material oxide influence?) iron staining staining C-15 seaweed (reddish brown) evident in macoma wood JO-2 26 fathoms the samples bark", from the upper t i d a l f l a t s . Sediments generally low in organic matter. Occasional macoma and wood bark 116 4. Fine fraction from # 35 mesh sieve wet sieved through a U.S. Standard Sieve Mesh # 230 (4 <f>) . Coarse fraction air dried and weighed. Fine fraction collected in 1000 ml bottles and allowed to settle. Liquid poured off, sediment transferred to !>00 ml beakers, ovenAlried, weighed and retained for analysis of s i l t s and clays by hydrometer or pipette. The composition of the sediments obtained from the grain size analysis was plotted on a compositional triangle (Shepard, 1954) with sand, s i l t and clay as the end members (Figure 52).. Distribution The tid a l marshes of the intertidal zone are dominated by a silty-clay facies with small percentages of sand. The numerous ti d a l creeks crossing the marshes provide the means for the transportation and distribution of the sand fraction. S i l t s and clays carried in suspension by the river are trapped by the sedge grasses on the marshes. The t i d a l flats of the lower intertidal zone are dominated by medium to fine grained sands in the west sector of the delta, with occasional areas of coarse gravel and cobbles in the v i c i n i t y of the river mouth. A sand-bar of medium to fine grained sands with small amounts of s i l t and clay divides the west and central channels of the Squamish River, in the v i c i n i t y of the river mouth. An area of black muds occupies most of the tid a l f l a t s on the west side of the central sector. The tid a l f l a t s to the east of t h i s " area have been disturbed byddredging for the Squamish Forest Products Terminal. Sediment samples from the lower tida l f l a t s occasionally FIGURE 52. Composition of Sediments. 118 contained large quantities of wood bark, moved around by tid a l currents from the log booming grounds. The delta front i s covered by a sandy-silty facies. On the west sector sands tend to dominate. According to Mathews, Murray and McMillan (1966), these sands are primarily Recent d e t r i t a l , but some residual and Pleistocene materials are also present. This sand i s fine to coarse grained, generally poorly sorted, with large admixtures of s i l t , but only limited amounts of clay. A summary of the mineralogy of the Squamish Delta sand i s shown in Table 23. Sediments of the central and eastern sectors of the delta front have a higher portion of s i l t and clay than those of the western sector. This may be partially attributable to flocculation, when at periods of river discharge, the sediment plume follows the surface pattern of the estuarine circulation. (Figure 18).. Clay Mineralogy X-ray analyses to determine the clay mineralogy of a random selection of sediment samples were made using a Philips PW 1010-75 x-ray diffractometer with a Philips PM 8000 strip chart recorder. Sixteen of a total of sixty-five samples collected from the intertidal and sub-aqueous sectors of the delta were used to perform the analyses. Eight of the samples represent the sediments of the intertidal zone and the other eight represent the sediments of the offshore zone. Sample locations are shown in Figures 50 and 51. Processing of the samples to obtain the<2_psize fraction was TABLE 23 MINERALOGY OF THE SQUAMISH DELTA SAND (after Mathews, Murray and McMillan, 1966) 119 Mineral %_ Rock fragments 35 Quartz 25 Plagioclase 14 Hornblende 6 Orthoclase 5 Biotite 4 Mineral % Magnetite and Ilmenite 3 Chlorite' 1 Epidote 2 Muscovite 1 Pyroxene 2 The mineralogy of the sand i s based on a point count of the fraction greater than U.S. Standard Sieve Mesh No. 170. 120 done using the procedure for preparation of soils for mineralogical analysis (Kittrick and Hope, 1963) with modifications by Lavkulich and Harris (1972). The procedure included the removal of carbonates, organic matter and soluble iron. Potassium and magnesium saturation of the clays was done following the procedure of Lavkulich and Harris (1972). Oriented mounts of the<2>sfraction were prepared for x-ray analysis. Three slides were made for each sample, one saturated with potassium, one with magnesium and one with magnesium and glycerol. X-ray diffractograms for mineral identification were obtained for the following combination of slides for each sample: (1) Potassium saturated; (2) Potassium saturated and heated to 300° C for 2 hours; (3) Potassium saturated and heated to 500° for 2 hours; (4)-Magnesium saturated with the addition of glycerol. Mineral Identification Identification of diagnostic peaks by comparison with standard tables (Lavkulich and Harris, 1972; Carroll, 1970; Rich and Kunz, 1964) indicated the presence of the following minerals: MONTMORILLONITE - identified by the expansion of the (001) spacing of 14 1 to 17.7 X after glycerol solvation of the Mg-saturated mounts. CHLORITE - predominant in a l l samples and indicated by the presence of four orders of diagnostic peaks, with a strong second order peak at a basal spacing of 7.07 A. On heating the K-saturated sample to 500° C the 7 X peak noticeably weakened. A diagnostic indicator (Rich and Kunz, 1964, p.255). Weak f i r s t and third order peaks at 14 A* and 4.72 X 121 r e s p e c t i v e l y and s t r o n g second and f o u r t h o r d e r peaks a t 7.07 X and 3.54 X r e s p e c t i v e l y , i n d i c a t e d the p r e s e n c e o f i r o n r i c h c h l o r i t e s . VERMICULITE - d i f f i c u l t t o i d e n t i f y because i t s d i a g n o s t i c peak, 14.4 X ( R i c h and Kunz, 1964), i s so c l o s e to t h e f i r s t o r d e r peak o f c h l o r i t e . D e f i n i t i o n o f peaks was n o t g e n e r a l l y s h a r p . Broadening t o ' t h e 10 X peak i n d i c a t e d the c o n t i n u i n g a l t e r a t i o n o f the micas t o v e r m i c u l i t e , m o n t m p r i l l o n i t e and c h l o r i t e . MICAS and/or ILLITES - w e l l d e f i n e d by a sh a r p , narrow c h a r a c t e r i s t i c peak w i t h a b a s a l d s p a c i n g o f 10 X. The peak i n c r e a s e d and sharpened when the K - s a t u r a t e d samples were heated to 300° C and 500° C. The peaks d e c r e a s e d n o t i c e a b l y w i t h M g - s a t u r a t i o n and g l y c e r o l a t i o n . AMPHIBOLE (HORNBLENDE) - i d e n t i f i e d by a s i n g l e peak w i t h a b a s a l d s p a c i n g o f 8.42 X. Amphiboles g i v e peaks i n the r e g i o n 8.40 X to 8.48 X ( R i c h and Kunz, 1964). QUARTZ - i d e n t i f i e d from a s i n g l e s t r o n g peak a t 3.31 to 3.35 X. The second d i a g n o s t i c peak a t 4.26 X. i n d i c a t i n g more than 10 per c e n t q u a r t z ( R i c h and Kunz, 1964) was n o t p r e s e n t . FELDSPAR (PLAGIOCLASE) - i d e n t i f i e d by a peak a t 13.8 X, as compared t o a d i a g n o s t i c peak o f 3.24 X f o r o r t h o c l a s e ( R i c h and Kunz, 1964; C a r r o l l , 1970). 122 CHAPTER VI ENGINEERING ASPECTS Man-Made Changes P r i o r t o 1971 a l l man-made changes a s s o c i a t e d w i t h t h e Squamish Harbour development were l o c a t e d on the e a s t e r n s e c t o r o f the d e l t a , i n the v i c i n i t y o f the Mamquam R i v e r . The f i r s t major s t r u c t u r e to be b u i l t on the d e l t a was a r a i l -head and u n l o a d i n g dock f o r barges and passenger b o a t s . The r a i l h e a d , c o n s t r u c t e d i n 1909 by the Howe Sound and N o r t h e r n R a i l w a y Company, extended 15 m i l e s northward from t i d e - w a t e r i n t o the Cheakamus v a l l e y . I t was b u i l t p r i m a r i l y t o t r a n s p o r t timber from t h e i n t e r i o r t o t h e booming grounds on the d e l t a , b u t a l s o p r o v i d e d a main t r a n s p o r t a t i o n l i n k between Vancouver and Squamish p r i o r t o the c o n s t r u c t i o n o f a highway. The u n l o a d i n g dock, b u i l t between 1910 and 1912, was l o c a t e d i n t h e i n t e r t i d a l zone, a p p r o x i m a t e l y 1500 f e e t e a s t o f the Mamquam R i v e r Channel. I t was b u i l t on timber p i l e s e x t e n d i n g 3000 f e e t i n a s o u t h w e s t e r l y d i r e c t i o n and t e r m i n a t e d a t the low water l e v e l . I n 1921 i t was washed out by the c a t a s t r o p h i c f l o o d t h a t changed the c o u r s e o f the Mamquam R i v e r , and was s u b s e q u e n t l y abandoned i n 1939. I n 1930, the P a c i f i c G r e a t E a s t e r n R a i l w a y , f o r m e r l y the Howe Sound and N o r t h e r n R a i l w a y , c o n s t r u c t e d a second.dock t o t h e e a s t o f t h e f i r s t o n e . ( F i g u r e 24). The dock, o r i g i n a l l y b u i l t on p i l e s , was s u b s e q u e n t l y connected t o the mainland by a f i l l causeway. I t i s now an i n t e g r a l p a r t o f the a r e a o f the t i d a l f l a t s f i l l e d f o r the c o n s t r u c t i o n o f the F.M.C. Chemicals P l a n t . The p l a n t , b u i l t f o r the 123 p r o d u c t i o n o f b l e a c h i n g agents f o r the p u l p and paper i n d u s t r y , commenced o p e r a t i o n i n December, 1965. The f i r s t s t r u c t u r e t o be b u i l t on the c e n t r a l s e c t o r o f the d e l t a was the Squamish F o r e s t P r o d u c t s T e r m i n a l warehouse and s h i p l o a d i n g f a c i l i t i e s . By 1971, 45 a c r e s of the lower t i d a l f l a t s were f i l l e d t o p r o v i d e a s i t e f o r the t e r m i n a l and d o c k i n g f a c i l i t i e s f o r s h i p s up t o 12,000 t o n s , f o r the e x p o r t of lumber ( F i g u r e 25). D r e d g i n g to a d e p t h o f 40 f e e t was c a r r i e d out f o r s h i p s l o a d i n g a t the wharf on t h e e a s t s i d e of t h e t e r m i n a l , and f o r a 600,000 square f o o t t u r n i n g b a s i n f o r barges l o a d i n g on the west s i d e . A p l a n o f t h e t e r m i n a l s and e x t e n t o f the d r e d g i n g i s shown on the Canadian H y d r o g r a p h i c S e r v i c e s F i e l d Sheet Number 2240-S. A l s o i n 1971, work commenced on the f i r s t s t a g e o f a c o a l l o a d i n g p o r t and f a c i l i t i e s on the w e s t e r n s e c t o r of the d e l t a . T h i s f i r s t s t a g e , c o n s i s t i n g of a 3 m i l e longer t r a i n i n g dyke and t h e r e - a l i g n m e n t .-' and deepening o f the lower r e a c h e s o f the west c h a n n e l of the Squamish R i v e r , was completed i n June, 1972. The second s t a g e , c o n s t r u c t i o n o f the harbour and c o a l l o a d i n g f a c i l i t i e s , i s c u r r e n t l y under r e v i e w by the P r o v i n c i a l and F e d e r a l Governments, and has been d e f e r r e d i n d e f i n i t e l y . E f f e c t s o f Development . When c o n s i d e r i n g the e f f e c t s o f development on a d e l t a i c or e s t u a r i n e environment, i t i s i m p o r t a n t t o d i f f e r e n t i a t e between the e f f e c t s o f s h o r t - t e r m and l o n g - t e r m changes on the n a t u r a l regime of the a r e a ( C a l d w e l l , 1950; I n g l i s and K e s t n e r , 1958; K e s t n e r , 1961; Simmons, 1965; Meade, 1969; Simmons and Hermann, 1972). 124 Short-term changes Short-term changes usually occur in the intertidal zone and may best be observed at periods of extreme low water. Short-term changes in the Squamish Delta have generally resulted from a partial interference in the natural regime of the environment by man-made structures. These structures, as i n the case of the recent channelization of the Squamish River, may also result in long-term changes in the offshore environment, namely the delta front and prodelta. Long-term changes Long-term changes in the sedimentary environments of the Squamish Delta have resulted from both natural and un-natural causes. While insufficient data is available to assess the total impact of the natural diversion of the Mamquam River in 1921, i t is known that the sediment supply transported by the river was diverted from the eastern sector of the delta front to the central sector. I n f i l l i n g of the ti d a l f l a t s of the east and central sectors of the delta, and the recent training of the Squamish River to the west channel, has resulted in a change in sediment distribution on the delta front, and may in the long-term cause slumping and slope instability on the western sector of the delta and erosion on the central and eastern sectors. Evidence of this is already visible in the comparison of the 1930 and 1973 bathymetry. A summary of the short-termaand long-term effects of develop-ment on the Squamish Delta i s shown in Table 24. From this table i t i s apparent that the major effects of development are related to the hydrology, sedimentology, and biology of the deltaic environment. TABLE 24 EFFECTS OF DEVELOPMENT ON THE DELTAIC ENVIRONMENT STRUCTURE EFFECTS OF DEVELOPMENT SHORT-TERM CHANGES LONG-TERM CHANGES P.G.E. passenger and barge unloading docks No changes Re-distribution of sediment trapped on west side of causeway linking dock to mainland F.M.C. Chlor-Alkali Plant Water quality and fish management problems related to effluent disposal Loss of primary production of tidal flats f i l l e d in for construction Squamish Harbour Forest Products Terminal and Wharves Change in direction of angle of discharge for central channel of the Squamish River Loss of primary production from land f i l l Stability of delta front affected by dredging of new ship channels Squamish River Improve-ments - training dyke - channelization - dredging Rapid build-up of river mouth bars. Non-equilibrium of river flow regime resulting in bank erosion and slumping, river-bed gradient changes Change in distribution pattern of suspended sediment on delta front. Erosion,of eastern sector of delta front. Change in delta vegetation and benthos habitats 126 Hydrological changes The prime causes of changes in the hydrology of the delta are river channel improvement and dredging. The effects are: (a) re-distribution of river flows; (b) re-distribution of river transported sediments; (c) river bank failure and slumping; .(d) loss or re-distribution of vegetation and the associated benthic organisms. The f i r s t major hydrological change associated with the Squamish Delta occurred in 1921, when, after a major flood, the Mamquam River changed i t s course and diverted i t s waters into the Squamish River. This added another 1000 cusecs (average monthly flow) and i t s associated sediment load to that of the Squamish River discharging onto the west and central sectors of the delta. At the same time the Mamquam River discharge to the eastern sector of the delta was reduced to almost zero. The second major change in hydrology affecting the structure of the delta occurred in 1945 when the main channel of the Squamish River was connected by a man-made canal to the western arm of the river. This had a long-term effect of gradually decreasing the flow in the central channel of the river, and increasing the flow in the new west channel, with the subsequent re-distribution of sediments at the delta front. The third and most recent change occurred in 1972 with the completion of the river training works for port development. This resulted in a considerable sediment build-up off the mouth of the west channel of the river. A noticeable effect of the channel improvements in the lower 127 reaches of the river i s the attempt by the river to establish a new natural equilibrium. A survey by Swan Wooster Engineering Limited in 1974 showed an acretion of 9.12 inches of new sediment in the river bed and a natural widening of the channel by bank erosion on both the east and westssides of the channel. Bank erosion of the tid a l marshes on. the^west side of the river can be seen in Figures 53 a n d 54. Laury (1971) relatesbbank erosion to an unbalanced condition between the bank profile and river channel, caused by a rise in water-level. Leopold et a l (1964) suggested that bank failure, assuming equilibrium prior to a rise in water-level, results from: (1) an increase in the weight of bank material due to the absorption of water; (2) decreased shear strength within the bank sediments due to increasing pore water pressure; or (3) increased depth and intensity of river scouring, creating an unstable, over steepened bank. Sedimentological changes Changes in sediment distribution in river, deltas and the estuarine environment following harbour construction, channel improvements and dredging operations have been studied i n the eastern United States by Simmons,and Hermann (1972), Meade (1969) and Caldwell (1950); on the west coast of the United States, in the San Francisco Bay area, by Pestrong (1972) and Trask and Rolston (1951); and in England by Inglis and Kestner (1958). Simmons and Hermann (1972), describing dredging and channel improvements in Mississippi River entrances, identify two major effects of channel deepening as: (1) the problem of increasing the salt water 128 129 intrusion in the river during stages of low river flow; and (2) the problem of recurring shoaling that develops as the river attempts to restore i t s e l f to i t s natural equilibrium. Studies of dredging on the Savannah and Santee Rivers by Meade (1969) and Simmons (1965) confirmed that dredging of river mouth bars allowed the ti d a l prism to move . landwards trapping river sediments formerly carried to the sea. The rapid build-up of sediment off the mouth of the west channel of the Squamish River, described in Chapter V, is most l i k e l y related to the landward movement of the tida l prism and the resulting occurrence of shoaling at the tip of the salt water wedge described by Simmons (1972). Caldwell (1950), analyzing the sedimentation problems associated with harbour locations in an estuarine environment, suggests that off-river harbours, generally located in channels with l i t t l e or no inflow, may have problems with s i l t and clay brought in by the inter-change of waters in the harbour arid the river. Short-term changes in the sedimentation pattern of the ti d a l f l a t s of the central channel of the Squamish River between 1972 and 1974 may be the result of the reduction of the fresh water inflow into the channel and the subsequent marine transgression of the lower reaches of the channel. Biological changes Lim and Levings (1973) have documented some of the changes caused by port development that affect the vegetation of the intradelta. Successional shifts in vegetation have resulted from changes in the pattern of fresh water flows. A complete loss of vegetation has resulted 130 from heavy coverage by f i l l and by dredging. Levings (1973) estimates that about 100 acres of marsh vegetation and benthic a l g a l habitat have already been l o s t to port construction and r i v e r t r a i n i n g . In the west and central deltas the largest biomass of the amphipod (A. confervicolus), a primary source of food for juvenile salmonids, are found i n the sedge rhizome habitat of the intermediate zone of the central delta. This i s the area of proposed port develop-ment, which i f constructed would destroy one of the main habitats of the amphipods, resulting i n turn i n losses of f i s h . There i s a p o s s i b i l i t y that they may recolonize elsewhere, such as i n the undeveloped regions of the east and central deltas, but at present there i s i n s u f f i c i e n t data available to predict their movements. On the west sector of the delta the increased scouring of the sand substrate, resulting from the construction of the r i v e r t r a i n i n g works, may lead to the destruction of the amphipod colonies i n t h i s area.-Investigation of Geological and Engineering Parameters Trask and Rolston (1951), i n a study of the engineering characteristics of the geology of San Francisco Bay, concluded that individual sequences of sediments have characteristics of their own, which either are constant or vary with respect to the environmental condition of deposition and subsequent geologic history. Assuming t h i s hypothesis to be v a l i d , i t follows that a study of the sedimentary environment and the factors and processes r e l a t i n g to 131 their transportation and deposition, along with a brief review of the geologic history of the area, should be made in order to determine which environments should be sampled for engineering characteristics. It may be important to know theeengineering characteristics of sediments outside the development area that later may be subjected to environ-mental changes brought about by construction. "Propegrdesign of commercial harbours, offshore loading f a c i l i t i e s and coastal protection works, should "be based on reliable coastal engineering data, collected over a period of time of sufficient length to cover a l l thessignificant changes taking place in the coastal environment concerned',"1 (Zwamborn, Russell and Nicholson, 1972). Based on this philosophy an extensive program of f i e l d measurements were carried out over a period of three years prior to the development of Richards Bay as a major South African coal handling port. As many of the significant changes in the coastal and estuarine environment are of a seasonal nature, data should be collected over a period of time of not less than one natural cycle, usually one year. Guidelines should be established to determine the minimum amount of data required to assess the impact of a proposed development plan on the environment, based on i t s size, i t s nature and i t s estimated cost. . ., Inaa deltaic and estuarine environment, such as Squamish, an integrated program to obtain hydrological, oceanographical, sediment-ological, biological and engineering data would (a) establish the dominant • characteristics of the environment, (b) provide a data bank for research and (c) provide the best possible basis for Governmental decisions 132 relating to future development. At the present time many Government Agencies are collecting sc i e n t i f i c data relevant to the development and management of the Coastal zone. It would therefore seem expedient to establish a uniform system for the collection, storage and retrieval of data pertaining to the development of the coastal area. Coleman and Wright (1971) established a uniform system and set of procedures for the analysis of major river systems and their deltas. A simplified structure diagram of the system is shown in Figure 55. The advantages of this system are: (a) i t is readily adaptable for computerization; (b) i t integrates data on an interdisciplinary basis; (c) data categories can be added or deleted. For example, for port development, categories could be added to cover engineering, economic and social aspects; (d) the system is readily adaptable to any deltaic or coastal environment. RIVER SYSTEMS LEVEL I "SYSTEMS" DRAINAGE BASIN ALLUVIAL VALLEY DELTAIC PLAIN RECEIVING BBASM MARGINAL COASTS MAP GEO- GEOMORPHO- CLIMATO- PEDO- HYDRO-LOCATION LITERATURE COVERAGE LOGICAL LOGICAL LOGICAL LOGICAL BBIOLOGICAL LOGICAL 1 1 1 1 1 1 1 1 A B C D E F G N 1 1 1 1 1 1 1 A B C D E F G N LEVEL II "COMPO-NENTS" LEVEL III "DATA CATEGORIES" LEVEL IV "PARAMETERS" LEVEL V "SUB-PARAMETERS" FIGURE 55. Simplified structure diagram for organizing the data tabulated for each river system (After Coleman and Wright, 1971) u> 134 CHAPTER VII CONCLUSIONS The impact of development on the present eco-system of the Squamish River Delta is v i s i b l e in both the intradelta and delta front. Land f i l l in the intertidal zone has eliminated t i d a l f l a t s and t i d a l marshes, thus reducing the primary productivity of the area. River training has affected the hydrology of the river system, and in turn the transportation and distribution of sediments in the intradelta and on the delta front. Recent shoaling off the mouth of the west channel of the river and in the central channel, may present problems for future development on the central sector of the delta. Studies of the marine and f l u v i a l processes associated with sediment transport within the estuary are required to better understand their inter-relationship, and to predict their effect on proposed development. To do this additional data must be collected relating to the river flow regime and effect of the salt water wedge•(tidal prism), and to the oceanography of the estuary, including both chemical and biological aspects. In the offshore zone the west sector of the delta front i s rapidly prograding, while erosion i s evident in specific areas of the central sector, mainly at the head of the Mamquam Submarine Channel. The possibility of the relationship between dredging for navigation channels and erosion in this section of the delta should be investigated. Slump structures recorded on the upper slopes of the delta 135 front by seismic profiles indicate a general area of instability in the central sector of the delta between 20 and 40 fathoms. Interpretation of the seismic profile records suggests a history of slumping on both the upper and lower slopes of the delta front. Coring of selected areas and in situ measurements of sediment shear strengths would substantiate' the validity of this interpretation, and determine whether slope s t a b i l i t y analyses should be carried out in the event of future harbour development. Inter-layering of cohesive and non-cohesive sediments has been proposed, as a possible cause of slope in s t a b i l i t y . Flocculation of clay minerals may be a major factor contributing to the deposition of clays on the delta front, and demands further investigation. 136 SELECTED REFERENCES American G e o l o g i c a l I n s t i t u t e . 1972. G l o s s a r y o f Geology. K i n g s p o r t P r e s s , Tennessee, 805 p. Armstrong, J . E . and W.L. Brown. 1954. L a t e W i s c o n s i n Marine D r i f t and a s s o c i a t e d sediments o f the Lower F r a s e r V a l l e y , B r i t i s h Columbia, Canada. B u l l . G e o l / Soc. Am., 65_, pp. 340-364. Atmospheric Environment S e r v i c e . Wind, temperature and p r e c i p i t a t i o n d a t a f o r the Squamish A r e a . Atmos. E n v i r o n . Serv. Vane, ( u n p u b l i s h e d d a t a ) . . 1971. C l i m a t e of B r i t i s h Columbia. C l i m a t i c normals 1941-1970. B.C. Dept. A g r i c . V i c t o r i a . B a t e s , C C . 1953. R a t i o n a l t h e o r y o f D e l t a f o r m a t i o n . B u l l . Am. A s s . P e t r o l . G e o l . , 37, pp. 2119-2162. B e l l , W.H. 1973. The exchange o f deep water i n Howe Sound b a s i n . Mar. S c i . D i r e c t . , Pac. Reg.; Pac. Mar. S c i ; Rept., 73-13, 35 p. Bowden, K.F. 1967. C i r c u l a t i o n and D i f f u s i o n . I n : E s t u a r i e s (G.H. L a u f f , e d i t o r ) , Amer. A s s o c . Adv. S c i . , 83, pp. 15r-16. Burns, R.E. 1963. Importance of marine i n f l u e n c e s i n e s t u a r i n e s e d i m e n t a t i o n . I n : P r o c . o f Fed. I n t e r - A g e n c y Sed. Conf. a. 1963: U.S. Dept. A g r i c . M i s c . Pub. 970, pp. 593-598. C a l d w e l l , J.M. 1950. S e d i m e n t a t i o n i n Harbours. I n : A p p l i e d S e d i m e n t a t i o n ( P a r k e r D. T r a s k , e d . ) , John W i l e y and Sons, I n c . , New York, 707 p. Canadian H y d r o g r a p h i c S e r v i c e . 1973(a) Howe Sound, Woodfibre t o Squamish, F i e l d Sheet 2213-S, S c a l e 1:24,300, Surveyed 1930. . 1973(b). N o r t h e r n Howe Sound, F i e l d Sheet 2278-L, S c a l e 1:30,000, Surveyed 1973. . 1973(c). Squamish Harbour, F i e l d Sheet 2235-S, S c a l e 1:8,000, Surveyed 1973. . 1973(d). Canadian T i d e and C u r r e n t T a b l e s , V o l . 5, Juan de Fuca and G e o r g i a S t r a i t s . Queen's P r i n t e r , Ottawa. C a r r o l l , D. 1970. C l a y m i n e r a l s : A gui d e t o t h e i r X-ray i d e n t i f i c a t i o n . G e o l . Soc. Am. Sp. Paper 126, 80 p. C a r t e r , N.M. 1932. The oceanography o f the f j o r d s o f ' s o u t h e r n B r i t i s h Columbia. F i s h . Res. Bd. Can. P r o g . 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In: Proc. 8th Texas Conf. on s o i l mechanics and foundation engineering, 40 p. Trask, P.D. and J.W. Rolston. 1951. Engineering geology of San Francisco Bay, C a l i f o r n i a . B u l l . Geol. Soc. Am. 62, pp. 1079-1110. Trefethen, J.M^ and R.L. Dow. 1960. Some features of modern beach sediments. J . Sed. Pet. 30, pp. 589-602. 141 Tully, J.P. 1949. Oceanography and prediction of pulp m i l l pollution in Alberni Inlet, British Columbia. Fish. Res. Bd. Can. 83, 169 p. University of British Columbia. 1964. A development plan for Squamish, B.C. Community Regional Planning. Student project 2, 108 pp. Waldichuk, M; J.R. Markert and J.H. Meikle. 1968. Fraser River Estuary, Howe Sound and Malaspina Strait: physical and chemical oceanographic data 1957-1966. Fish. Res. Bd. Can. MS. Rept. 939. Water Survey of Canada. 1970. Historical stream flow summary, British Columbia. Inland Waters Directorate, Dept. of Environ., Ottawa. 393 pp. . 1973. Flow data for the Squamish, Cheakamus, Mamquam and Stawamus Rivers. (Unpublished data.) Wiegel, R.L. 1964. Oceanographical engineering. Prentice-Hall Inc., Englewood C l i f f s , N.J. Whitehouse, V.G.; L.M. Jeffrey and J.D. Debbrecht. 1958. Differential settling tendencies of clay minerals in saline waters. In: Proc. 7th Conf. Clays and Clay Min. 5, pp. 1-79. ZwambornTj. J.A.; K.S. Russell and J. Nicholson. 1972. Coastal engineering measurements. In': Proc. 13th Int. Conf. Coast. Eng., Vancouver, B.C., Canada. APPENDIX I Calculations for discharge through 2 - 2 4 inch diameter culverts located in the Squamish River training dyke Q = discharge in cubic feet per second C = discharge coefficient d = diameter of culvert a = cross sectional area ofcculvert h = average head of water For discharge through one culvert: Q = Ca \|2gh. Assume C = 0.6 and h = 4 feet a = 3.14 sq. f t . Q = 0.6 x 3.14 ^ 64 x 4 = 30.2 c.f.s. For two culverts: Discharge =2% = 60.4 c.f.s. APPENDIX H a Calculations for hindcasting wave height and period at the mouth of the west channel of the Squamish River at 1400 hours on September 29, 1973 Wind direction - south Wind velocity — 22 m.p.h. (35.4 km/hr) (Atmospheric Environment Service). From Hydrographic Chart 3586 (Howe Sound) Fetch (F) = 14 naut. miles (25.9 km) Wind velocity (U) = 35.A km/hr (10 m/sec) gF 9.81 x 25.9 x 103 2 2 i r ( io ) z = 2.54 x 10 3 From graph (Appendix lib) - Wiegel (1961) g H l / 3 = 0.1 H. = significant wave height 2 " 1 / 3 H l / 3 — ^ " " 9 7 8 1 I * 0 2 m or, Significant wave height = 3.32 feet. Also from graph (Appendix l i b ) , 3 x 9.81 ^ 3 T = wave period T = 10 or, Wave period = '2.9 seconds. APPENDIX l i b Relationships among fetch, wind velocity and wave height, period and velocity (after Wiegel, 1961) 10,000 "wo° *°OT 100,000 '°°'aB APPENDIX I I I C a l c u l a t i o n s f o r t i d e phase d i f f e r e n c e between the head and mouth of Howe Sound L e n g t h o f Howe Sound = 40 km Average depth = 250 m Wave v e l o c i t y C = ^| gD D = depth (m) ( f o r s h a l l o w waves) g = 9.81 m/sec C = NJ9.81 x 250 = 49.5 m/sec =2278 km/hour 40 T i d e phase d i f f e r e n c e = -=-=^- x 60 = 9 mins. 

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