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Terrain mapping and regional slope stability evaluation in the Fraser Canyon, British Columbia Bell, Alison 1980

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TERRAIN MAPPING AND REGIONAL SLOPE STABILITY EVALUATION IN THE FRASER CANYON, BRITISH COLUMBIA by ALISON BELL B.Sc,  McGill University,  1977  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES Department of Geography  We accept t h i s t h e s i s as conforming to the r e q u i r e d  standard  THE UNIVERSITY OF BRITISH COLUMBIA J u l y , 1980  (£) A l i s o n B e l l ,  1980  .  :  \  '%  In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library shall make i t freely available for reference and study. I further agree that permission for extensive copying of this  thesis  for scholarly purposes may be granted by the Head of my Department or by his representatives.  It is understood that copying or publication  of this thesis for financial gain shall not be allowed without my written permission.  Department nf  Geography  The University of B r i t i s h Columbia 2075 wesbrook Place Vancouver, Canada V6T  n.tp  1W5  July  17 . 1 9 8 0 .  A B S T R A C T  Terrain  a n a l y s i s o f the 22-mile  Canyon between C h i n a B a r and Y a l e , theme o f t h i s variables  Micro-,  are d i f f e r e n t i a t e d  evaluation. scale  research.  a t t r i b u t e s only  S u r f i c i a l materials ELUC t e r r a i n  Fraser  Columbia,  i s the  meso-, and m a c r o - s c a l e  as a b a s i s  f o r slope failure  stability and meso-  a r e examined i n d e t a i l .  are c l a s s i f i e d  classification  according  t o the  s y s t e m i n terms o f t e x t u r e ,  f o r m , and s u r f a c e - m o d i f y i n g  a r e mapped units  British  R e l a t i o n s h i p s between s l o p e  slope  genesis,  (32.5 km)  processes.  t o an e l e v a t i o n o f 1500 f e e t  The m a t e r i a l s  (6 40 m)  as  terrain  on an a i r p h o t o m o s a i c a t t h e a p p r o x i m a t e s c a l e o f  1:25,000.  The t e r r a i n map  i s the f i r s t  a p p l i c a t i o n o f t h e ELUC c l a s s i f i c a t i o n  example o f t h e scheme i n t h e F r a s e r  Canyon. Twelve meso-scale s l o p e and  bedrock geology,  are  evaluated  railway  lines  at sites on b o t h  maintenance r e c o r d of slope  slope  failure  attributes describing  g e o m e t r y , and a n t h r o p o g e n i c  a t 0.1 m i l e  (0.16 km)  s i d e s o f the canyon.  along  data.  surficial  the eastern An A u t o m a t i c  effects  intervals A 20-year  along railway  canyon s i d e i s t h e  source  Interaction-Detector  (AID3) p r o g r a m i s u s e d t o d e t e r m i n e w h i c h a t t r i b u t e s c o n t r i b u t e most t o t h e e x p l a n a t i o n incidence  along  most i m p o r t a n t modifying  of variation  the e a s t e r n contributors:  slopes.  i n slope  S i x a t t r i b u t e s are the  surficial  process.(es) , s l o p e h e i g h t  failure  material(s), surface-  above and d i s t a n c e  away  from the r a i l w a y t r a c k s , angle, of e x c a v a t i o n .  and the presence or absence  Together the v a r i a b l e s e x p l a i n 41.4%  t o t a l v a r i a t i o n of f a i l u r e i n c i d e n c e .  The most  of  the  significant  variable i s s u r f i c i a l material. Colluvium comprising  i s the most common s u r f i c i a l m a t e r i a l ,  60.5%  of a l l slope s i t e s .  Bedrock u n i t s along  the e a s t e r n slopes e x h i b i t the h i g h e s t mean i n c i d e n c e of f a i l u r e with  3.0 3 events per s i t e over the 20-year p e r i o d ,  f o l l o w e d by c o l l u v i a l u n i t s a t 1.95 and  fluvio-glacial  f a i l u r e , w i t h 0.24  sites and  events per s i t e .  show the lowest mean i n c i d e n c e of  0.4 8 events per s i t e , r e s p e c t i v e l y .  S i t e s where the slope has been excavated d u r i n g construction  Fluvial  railway  (80% of the t o t a l number) experience  above-  average f a i l u r e i n c i d e n c e , where the average f o r a l l s i t e s i s 1.84  events per s i t e .  Where the t r a c k s i d e slope  i s g r e a t e r than 41° i n u n c o n s o l i d a t e d  m a t e r i a l , and  than 70° i n bedrock, above-average f a i l u r e (3.03  and  2.15  angle greater  incidence  occurs  events per s i t e , r e s p e c t i v e l y ) .  Guttmannv- Lingoes  multi-dimensional  scalogram a n a l y s i s  (MSA-T)and a c l u s t e r i n g program (HCLUS) are used to group the s i t e s on the b a s i s of the s i x most i n f l u e n t i a l attributes. icantly  The  r e s u l t a n t c a t e g o r i e s do not d i s p l a y s i g n i f -  d i f f e r e n t f a i l u r e means.  Classification  the b a s i s of s u r f i c i a l m a t e r i a l only y i e l d s broad c a t e g o r i e s , i n which bedrock and high and  slope  intermediate  colluvial sites  classes, respectively.  of s i t e s hazard fall'into  on  iv  The value of t h i s r e s e a r c h i s t h a t i t p r o v i d e s a method f o r r e g i o n a l slope s t a b i l i t y e v a l u a t i o n a t the reconnaissance  stage of a development p r o p o s a l .  V  CONTENTS Page ABSTRACT  .  ACKNOWLEDGEMENTS . .  i i xi  CHAPTER 1 - INTRODUCTION  1  Introduction Objectives  1 6  CHAPTER 2 - THE FRASER CANYON STUDY AREA Introduction Physiographic Description Drainage Geology Hozameen Group Custer Gneiss Spuzzum I n t r u s i v e s Yale I n t r u s i v e s Scuzzy P l u t o n Regional F a u l t i n g Ouarternary H i s t o r y S u r f i c i a l Materials Climate V e g e t a t i o n and S o i l s H i s t o r y and Economic Development CHAPTER 3 - TERRAIN CLASSIFICATION AND SLOPE STABILITY Introduction Terrain Classification Slope S t a b i l i t y M i c r o - S c a l e Concepts Surrogate V a r i a b l e s a t Meso- and Micro-Scales Case Studies CHAPTER 4 - METHODS  9 9 9 18 20 23 24 25 26 26 27 29 33 34 35 36 . 41 41 41 48 48 51 57 68  Introduction 68 Mapping o f the T e r r a i n 68 The ELUC T e r r a i n C l a s s i f i c a t i o n 69 F i e l d V e r i f i c a t i o n and S i t e I n v e s t i g a t i o n . 72 Fieldwork 72 Slope A t t r i b u t e s as Surrogate V a r i a b l e s . 72 Analysis 80 Objectives 80 H i s t o r i c a l Slope F a i l u r e Records . . . . 81 Descriptive S t a t i s t i c s . . . 85 Numerical S i t e C l a s s i f i c a t i o n 86  vi Page CHAPTER 5 - RESULTS . ,  8 9  Introduction T e r r a i n C l a s s i f i c a t i o n Mapping and Fieldwork Topographic P r o f i l e s S u r f i c i a l Materials ^ Mass Movement 10 Analysis l 5 Frequency D i s t r i b u t i o n s o f the Slope Attributes Slope A t t r i b u t e s and A s s o c i a t e d F a i l u r e . I l l -Relative Importance o f the Slope Attributes S t a b i l i t y C l a s s i f i c a t i o n of Sites . . . . 120 A l t e r n a t e Means o f S i t e C l a s s i f i c a t i o n . . I 8  9  8  9  8  9  9  2  y  1  0  6  1  1  5  2  CHAPTER 6 - CONCLUSIONS  REFERENCES  1  2  3  8  Overview  I  I m p l i c a t i o n s o f the R e s u l t s  1  3  0  1  3  4  . . . . . . .  2  8  APPENDIX I.  II. III. IV. V. VI. VII. VIII.  C l i m a t i c Data f o r L y t t o n , H e l l ' s Gate, and Hope  140  The ELUC T e r r a i n C l a s s i f i c a t i o n  142  Methods of A n a l y s i s  146  Types o f Slope F a i l u r e  15 8  Frequency D i s t r i b u t i o n s o f the Slope Attributes  I  Mean Slope F a i l u r e Incidence  170  6  AID3 Tree Diagram  1  7  2  MSA-I Scalograms  1  7  4  2  vii  LIST OF TABLES Table 2.1  2.2. 2.3  Page Monthly discharge (1912-1976) and suspended sediment l o a d (1965-1976) f o r the F r a s e r R i v e r measured a t Hope  19  G l a c i a l episodes Columbia  30  i n southwestern B r i t i s h  Stages o f g l a c i a l development and the a s s o c i a t e d landforms  3.1 '3.2  The h i e r a r c h y o f t e r r a i n  31 information  43  System o f slope p r i o r i t y r a t i n g s employed along the Canadian P a c i f i c  Railway l i n e  64  4.1  A e r i a l photography used i n the study  69  4.2  Slope  74  4.3  Relevance o f slope a t t r i b u e s measured  5.1  Modes o f f a i l u r e encountered on the F r a s e r Canyon slopes Mean f a i l u r e i n c i d e n c e on slopes o f the p r i n c i p a l s u r f i c i a l materials Summary o f the frequency o f occurrence o f principal s u r f i c i a l materials.  5.2 5.3  a t t r i b u t e s considered  i n the study  75  106 10 8  5.4  F a i l u r e i n c i d e n c e of the p r i n c i p a l materials  5.5  S u r f i c i a l m a t e r i a l types showing the h i g h e s t and lowest mean i n c i d e n c e o f f a i l u r e s  112  A s s o c i a t i o n between c u t s l o p e and f a i l u r e incidence  114  A s s o c i a t i o n between slope h e i g h t and d i s t a n c e from the t r a c k with f a i l u r e i n c i d e n c e  114  A s s o c i a t i o n o f t r a c k s i d e slope angle f a i l u r e incidence  116  5.6 5.7 5.8 5.9  surficial  10 4  112  with  S u r f i c i a l m a t e r i a l s , slope angles, and f a i l u r e incidence  116  viii  Table 5.10  Page ETA values of the twelve independent slope a t t r i b u t e s  .5.11 5.12 5.13  H8  R e s u l t s o f the c l a s s i f i c a t i o n methods . . . . . . . I C l a s s i f i c a t i o n of s i t e s along the e a s t e r n slopes C l a s s i f i c a t i o n of s i t e s along the e a s t e r n and western slopes  5.14  General  slope f a i l u r e hazard  categories  5.15  Slope f a i l u r e hazard c a t e g o r i e s based on the s u r f i c i a l m a t e r i a l v a r i a b l e a t the t h r e e - d i g i t level  l  2  2  I  2  4  I  2  4  ^  2  i  2  6  ix LIST OF FIGURES Figure  Page  1.1  L o c a t i o n o f the study area  3  1.2  O r g a n i z a t i o n o f the r e s e a r c h  7  2.1  Map o f the study  2.2  Aspects of p o s t - g l a c i a l l a n d s l i d e s  15  2.3  Geology of the F r a s e r Canyon area  22  ;3.1  Examples o f the morphological technique  47  3.2  3.3  area  10  mapping  Mean monthly temperature and p r e c i p i t a t i o n and t o t a l monthly i n c i d e n c e o f r o c k f a l l s (1933-1970)  5  5  S e a s o n a l i t y o f movement on rock slopes a t Ferabee B l u f f s (near H e l l ' s Gate)  56  3.4  I n t e r - r e l a t i o n o f micro-, meso-, and macros c a l e slope s t a b i l i t y .-variables  58  3.5  S e l e c t i o n o f slope treatment a t a s i t e  67  4.1  Slope  76  4.2  T y p i c a l t r a c k s i d e slope c o n d i t i o n s encountered i n the F r a s e r Canyon  .4.3  4.4  5.1  a t t r i b u t e s considered  i n the study  Number o f slope f a i l u r e s per 0.1 m i l e (0.16 km) of t r a c k as recorded by the Canadian N a t i o n a l Railway from 1948 t o 196 8 Number o f slope f a i l u r e s p e r 0.1 m i l e (0.16 km) of t r a c k as recorded by the Canadian P a c i f i c Railway from 19.74 t o 1978 . . Four topographic F r a s e r Canyon  ^8  8  2  8  4  p r o f i l e s encountered i n the  Accomp&v^uAta«.|X  90 ^£o~Xi^.  _ -  -  -  .  -  -  -  . . .  . m Specia,!  X  LIST OF PHOTOGRAPHS Photo  Page  2.1  Extensive  I  4  2.2  F l u v i a l T e r r a c e : on. both s i d e s o f the canyon  I  7  2.3  The Cariboo Wagon Road near Black Canyon  3  8  5.1  Blocky  9  3  5.2  R e t a i n i n g w a l l t o prevent d r y r a v e l l i n g m a t e r i a l from r e a c h i n g the t r a c k E l e c t r i c warning fence beneath a steep rock slope  5.3  c o l l u v i a l slope  c o l l u v i a l m a t e r i a l i n a f i n e matrix  5.4  Loosened j o i n t - b l o c k s beside  5.5  Fluvio-glacial Bridge  5.6 5.7 5.8  . . . .  the t r a c k s  9f> 9  ^  t e r r a c e near the Alexandra  Dipping and c o n t o r t e d s t r a t a i n f l u v i o - g l a c i a l material Blocky f a i l u r e material  ->  9  i n cemented  9  8  9  9  9  9  fluvio-glacial  View o f a f l u v i o - g l a c i a l exposure along the e a s t e r n slope  100  5.9  Poorly sorted f l u v i o - g l a c i a l material  100  5.10 5.11  Steeply d i p p i n g g r a v e l - a n d - f i n e s s t r a t a . . ... . 101 Unsorted f l u v i o - g l a c i a l m a t e r i a l along the e a s t e r n slope  101  5.12  Fluvial  10 3  5.13  T r a c k s i d e slope c u t i n t o f l u v i a l m a t e r i a l o f the Spuzzum a l l u v i a l f a n  t e r r a c e a t Stout  10  3  xi  A C K N O W L E D G E M E N T S  I am i n d e b t e d at  a l l stages  of  terrain  in  the e a r l y  t o a number o f p e o p l e  of this  research.  for their  help  D i s c u s s i o n and i n f o r m a t i o n  c o n d i t i o n s i n t h e F r a s e r Canyon a r e a were stages  of this  r e s e a r c h b y D. W y l l i e ,  provided  CO.  B r a w n e r , a n d D.R. P i t e a u . My f a m i l i a r i t y w i t h resulted and  the t e r r a i n  from s e v e r a l days spent  classification  working with  t h e s t a f f o f t h e mapping d i v i s i o n  system  Dr. June  Ryder  o f t h e Resource  A n a l y s i s Branch i n V i c t o r i a . Mr.  N.H. P r i c e  engineering  and Mr. E.N.A. (Ted) S e w e l l  department a t t h e Vancouver o f f i c e  Pacific  R a i l w a y were v e r y  granted  access  this  co-operative with  Abrahamson a t C a n a d i a n N a t i o n a l R a i l w a y . railway  lines  arranged  to less  o f Canadian  t h e r e s e a r c h and  to the railway right-of-way.  r e s e a r c h was shown b y Mr. W.E. J u b i e n  of the  Interest i n and Mr. W.A.  Transport  along the  a c c e s s i b l e p a r t s o f t h e c a n y o n was  b y Mr. J.M. McAree, t h e C.P.R. r o a d m a s t e r a t N o r t h  Bend, and Mr. A. Van Dyke, t h e C.N.R. weekend r o a d m a s t e r a t Hope. Assistance with Flynn  and M r s .  methods o f a n a l y s i s was g i v e n by Mr. F.  V. G r e e n a t t h e F a c u l t y o f A r t s c e n t e r f o r  c o m p u t i n g and d a t a . a n a l y s i s . Mr.  P. Wong gave a d v i c e  the  final  a i r photo mosaic.  was  reproduced  at Burnett  and i n s t r u c t i o n The t e r r a i n  o f assembly o f  c l a s s i f i c a t i o n map  Resource Surveys L i m i t e d , i n  xii  Burnaby,  B.C.  Comments on the manuscript made by Dr. M.J. greatly The  Bovis were  appreciated. t h e s i s was  typed by C. Mackenzie.  F i n a n c i n g f o r t h i s r e s e a r c h was  provided by the N a t i o n a l  Research C o u n c i l , o p e r a t i n g grant number 67-7073, and by a summer grant from the Youth Employment Program of the  British  Columbia P r o v i n c i a l Government. I am e s p e c i a l l y g r a t e f u l to my Slaymaker, f o r h i s encouragement and project.  s u p e r v i s o r , Dr. H. support  throughout  Olav the  1  CHAPTER 1 I N T R O D U C T I O N  Introduction The  i d e n t i f i c a t i o n o f landforms and o f t h e i r r e l a t i v e  and d i s t r i b u t i o n p l a y s an important d e s c r i p t i o n of t e r r a i n .  size  r o l e i n the geomorphologic  Landform morphology i s dependent  upon s p a t i a l and temporal v a r i a b i l i t y  i n geologic, climatic,  p h y s i o g r a p h i c , and h y d r o l o g i c c o n d i t i o n s , as w e l l as human activity.  V a r i a t i o n i n a l l o f these  interdependence  f a c t o r s and t h e i r complex  leads t o a wide range o f landforms,  which can be the t o p i c o f separate  each o f  research.  T e r r a i n may be d e s c r i b e d a c c o r d i n g t o c o n s t i t u e n t m a t e r i a l s , form, and/or dominant geomorphologic p r o c e s s e s .  The  o r g a n i z a t i o n o f t h i s i n f o r m a t i o n c o n s t i t u t e s geomorphologic terrain classification.  Information w i t h i n the  c l a s s i f i c a t i o n system can be r e t r i e v e d by engineers,  o r environmental  geomorphologists,  p l a n n e r s , and a p p l i e d i n t e r r a i n  analysis. The purpose o f t h i s study i s t o c l a s s i f y and t o map the t e r r a i n of a s t e e p - s i d e d canyon i n order t o p r o v i d e a d e t a i l e d d i s c u s s i o n o f s u r f i c i a l m a t e r i a l i n terms o f t e x t u r e , form, genesis,;,  and s u r f a c e - m o d i f y i n g p r o c e s s e s .  S e v e r a l measured  a t t r i b u t e s are used t o c h a r a c t e r i z e the canyon slopes i n a d d i t i o n t o geomorphologic a t t r i b u t e s d e r i v e d from the t e r r a i n classification. A p o r t i o n o f the F r a s e r R i v e r V a l l e y i n southwestern  2  B r i t i s h Columbia has been chosen f o r t h i s t e r r a i n study  classification  ( F i g . 1.1). The w e l l - d e f i n e d v a l l e y i s p a r t i c u l a r l y  s t e e p - s i d e d i n the s e c t i o n between Yale and Petch Creek, a 22-mile  (35 km) s t r e t c h which trends d i r e c t l y  north-to-south.  T h i s area i s here c a l l e d the F r a s e r Canyon, a r e s t r i c t e d p a r t of the commonly d e f i n e d canyon between L y t t o n and Y a l e .  In  t h i s area, the upper slopes e x h i b i t much steep, bare bedrock with  some coarse  colluvial material.  With i n c r e a s e d  p r o x i m i t y t o the r i v e r , the p r o p o r t i o n o f c o l l u v i u m i n c r e a s e s , and a t the base o f the canyon slopes a r e some f l u v i a l and f l u v i o - g l a c i a l deposits.  As i t i s the p r i n c i p a l passageway  through the Coast Mountains t o the I n t e r i o r P l a t e a u , the canyon houses both the Canadian N a t i o n a l Railway and the Canadian P a c i f i c Railway, as w e l l as the Trans Canada Highway. Slope  i n s t a b i l i t y i s a constant  concern t o engineers  r e s p o n s i b l e f o r the maintenance o f slopes along these The  slope a t t r i b u t e s d e r i v e d from a i r photo  reconnaissance  routes.  and f i e l d  o f the F r a s e r Canyon are mapped, and then used  i n an i n v e s t i g a t i o n o f slope f a i l u r e i n the r e g i o n .  This i s  an example o f a p p l i c a t i o n o f i n f o r m a t i o n s t o r e d i n a t e r r a i n c l a s s i f i c a t i o n to a geomorphologic a n a l y s i s o r slope The  hypothesis  t o be c o n s i d e r e d  failure.  i s t h a t the l o c a l i z a t i o n o f  slope f a i l u r e s along the r a i l w a y t r a c k s can be r e l a t e d . t o upslope s u r f i c i a l geology and t o t e r r a i n a t t r i b u t e s o f slopes adjacent t o the t r a c k s . While slope s t a b i l i t y t r a d i t i o n a l l y i s estimated  after  intensive research a t - a - s i t e , i t i s i m p r a c t i c a l to extrapolate  3  4  r e s u l t s of such an i n v e s t i g a t i o n to the r e g i o n a l s c a l e of F r a s e r Canyon. a t t r i b u t e s and  the  Thus, to i s o l a t e s e v e r a l geomorphologic slope t o evaluate  t h e i r a s s o c i a t i o n with  ure i s a more manageable means of assessment.  slope  fail-  A study o f  t h i s k i n d l o g i c a l l y precedes s i t e - s p e c i f i c g e o t e c h n i c a l work performed by c o n s u l t i n g engineers companies.  f o r the r a i l w a y and  highway  I t i s a r e g i o n a l - s c a l e geomorphic i n v e n t o r y  slope c h a r a c t e r and  s t a b i l i t y along  at t h i s s c a l e i s of use  the canyon s i d e s .  i n p r e l i m i n a r y stages  of  of Inquiry  geotechnical  or environmental p r o j e c t s . The First,  reasons f o r choosing  t h i s study area are s e v e r a l .  i t i s the most c o n s t r i c t e d p a r t of the r i v e r v a i l e y .  I t e x h i b i t s both a c t i v e and r e l i c t f e a t u r e s o f  instability.  Secondly, though the canyon has been of major use p o r t c o r r i d o r f o r over a century,  as a t r a n s -  no t e r r a i n a n a l y s i s or  hazard c l a s s i f i c a t i o n has been made.  Since both r a i l w a y  companies are c o n s i d e r i n g i n c r e a s e d t r a f f i c l o a d and track f a c i l i t i e s  through the canyon area,  i t i s of i n t e r e s t to  i d e n t i f y s p e c i f i c t e r r a i n c o n d i t i o n s a s s o c i a t e d with f a i l u r e incidence.  F i n a l l y , the presence of the  companies, t h e i r p o t e n t i a l c o - o p e r a t i o n  upgraded  high  railway  with t h i s p r o j e c t ,  t h e i r source of f a i l u r e i n c i d e n c e data p r o v i d e d  and  early incentive  to work i n .this r e g i o n . Information and  gathered i n t h i s study i s from three  i s used i n combination to achieve  A i r photo i n t e r p r e t a t i o n and  sources  the o b j e c t i v e s o u t l i n e d .  subsequent c l a s s i f i c a t i o n  mapping of the canyon slopes i n t o t e r r a i n u n i t s i s the  and first  5  data source. f i e l d season.  Second i s slope a t t r i b u t e s c o l l e c t e d d u r i n g The  i n c i d e n c e of slope f a i l u r e , d e r i v e d from  maintenance records, comprises the t h i r d data In generating  source.  a t e r r a i n c l a s s i f i c a t i o n map  f o r the  Fraser  Canyon, a d i s t i n c t i o n must be made between t e r r a i n u n i t s s u r f i c i a l geology.  the  The  and  l a t t e r term r e f e r s t o m a t e r i a l s exposed  a t the s u r f a c e of a land area; t h i s may  be bedrock or a  d e p o s i t of u n c o n s o l i d a t e d  i s largely  m a t e r i a l , and  responsible  f o r f e a t u r e s of m i c r o - r e l i e f . Methods of d e s c r i p t i o n of s u r f i c i a l geology u s u a l l y i n c l u d e genesis and l i t h o l o g i c content of the m a t e r i a l .  specific  Terrain units define  w i t h i n which the s u r f i c i a l geology, geomorphic form, genesis The  areas  and  are homogeneous. slope a t t r i b u t e s d e s c r i b e the geometry and  m a t e r i a l s of the canyon s l o p e s .  Other f a c t o r s which a f f e c t  slope s t a b i l i t y are c l i m a t e , hydrology, anthropogenic a c t i v i t y .  constituent  s e i s m i c i t y , and  While these aspects are not  i n d e t a i l i n t h i s p r o j e c t , they present slope s t a b i l i t y r e s e a r c h .  considered  a l t e r n a t e avenues f o r  For example, the i n c r e a s e d  of r o c k f a l l s along the west s i d e of the canyon  incidence  (Canadian  P a c i f i c Railway l i n e ) s i n c e 19 74 has been l i n k e d t o the i n t r o d u c t i o n of the u n i t t r a i n concept a t t h a t time. t r a i n s c o n s i s t of more than one hundred u n i f o r m l y  These  loaded boxcars  and are r e s p o n s i b l e f o r i n i t i a t i n g s t r o n g resonance i n adjacent bedrock.  The  p r a c t i c a l i m p l i c a t i o n s of t h i s  mation r e l a t e to remedial the appropriateness  infor-  slope work and to the e v a l u a t i o n of  of concrete  r a i l w a y t i e s c u r r e n t l y being  used to r e p l a c e o l d wooden ones i n the area  (CO.  Brawner,  6  p e r s . comm.).  B e t t e r understanding  of a l l f a c t o r s a f f e c t i n g  slope s t a b i l i t y i s demanded. The present  study has evolved  f l o w c h a r t i n F i g u r e 1.2.  i n stages presented  I d e n t i f i c a t i o n of the study  f o l l o w e d by i n v e s t i g a t i o n o f t e r r a i n c l a s s i f i c a t i o n and an e v e n t u a l  s e l e c t i o n o f one scheme.  Fieldwork  in a theme was  techniques was  e f f e c t e d t o v e r i f y c l a s s i f i c a t i o n on a e r i a l photography and to e v a l u a t e  slope a t t r i b u t e s along the r a i l w a y l i n e s .  Using  f a i l u r e i n c i d e n c e data f o r the e a s t s i d e of the canyon, s t a t i s t i c a l a n a l y s i s was performed, exposing r e l a t i o n s h i p s between f a i l u r e and slope a t t r i b u t e s .  L a s t l y , methods o f  r e c l a s s i f i c a t i o n of the slopes i n t o groups o f s i m i l a r  terrain  a t t r i b u t e s were employed and e v a l u a t e d .  OBJECTIVES  The  primary o b j e c t i v e s o f t h i s p r o j e c t a r e :  i ) to generate a t e r r a i n c l a s s i f i c a t i o n map a t an approximate s c a l e of 1:25,000, ii) iii)  The  t o i n v e s t i g a t e the i n c i d e n c e of slope and,  failure,  t o i d e n t i f y the slope a t t r i b u t e s which c o n t r i b u t e most t o the e x p l a n a t i o n of v a r i a t i o n i n the i n c i d e n c e of slope f a i l u r e . secondary o b j e c t i v e s i n c l u d e :  i ) t o i d e n t i f y g e n e r a l i n t e r - r e l a t i o n s h i p s between slope a t t r i b u t e s , ii) iii)  t o catalogue area, and  types of f a i l u r e o c c u r r i n g i n the  t o e v a l u a t e the methodology.  A l s o , methods of generating  a c l a s s i f i c a t i o n of slope  sites  7  identification o f t h e study theme  a i r photo interpretation and t e r r a i n mapping.  fieldwork  ~1  slope data  failure  analysis  descriptive statistics and f r e q u e n c y distributions f o r slope attributes  identification o f t h e most significant attributes  relationships between s l o p e attributes  classification of s i t e s w i t h respect t o slope a t t r i b u t e s and f a i l u r e tendency  I  evaluation of methodology and r e s u l t s  conclusions  F i g . 1.2  Organization of the research.  recommendations for further study  8  adjacent  to the two  railway l i n e s  of such a c l a s s i f i c a t i o n r e f l e c t slope f a i l u r e .  are e v a l u a t e d .  i s measured by how The  The  w e l l the  success categories  s i t e c a t e g o r i e s then i n d i c a t e zones  of s i m i l a r f a i l u r e tendency assuming t h a t the slope a t t r i b u t e s are r e s p o n s i b l e f o r , or are reasonable failure.  indices of,  slope  9  CHAPTER 2 T H E  F R A S E R  C A N Y O N  S T U D Y  A R E A  INTRODUCTION Terrain  a n a l y s i s involves the i n t e r a c t i o n  characteristics operating bles  of t e r r a i n with  i n the study  i s necessary  area.  before  environmental v a r i a b l e s  An u n d e r s t a n d i n g  a link  o f the v a r i a -  c a n be made between  from t h e t e r r a i n  classification  In t h i s  the physiography o f the study  chapter,  described,  and h i s t o r i c a l  which i s d i r e c t l y  of physical  information  and mass movement on s l o p e s .  and e n v i r o n m e n t a l  area i s  information  r e l a t e d to evolution of the t e r r a i n i s  presented.  PHYSIOGRAPHIC DESCRIPTION The  Fraser  River  follows a straight,  v a l l e y between Hope and L y t t o n , B r i t i s h Yale,  and f r o m P e t c h  w i d e and t h e r i v e r ' s study  It  tributaries the  the v a l l e y  grade moderate.  The a r e a  south  Generally  and l i e s  and e a s t  i s relatively  chosen f o r Creek  0  the Fraser  Canyon  f a u l t - d e f i n e d v a l l e y with  ( F i g . 2.1).  no m a j o r  between t h e C a s c a d e M o u n t a i n complex t o  and t h e C o a s t M o u n t a i n complex t o t h e w e s t .  t h e v a l l e y - s i d e s a r e c h a r a c t e r i z e d by s t e e p  f a c e s on t h e u p p e r s l o p e s w i t h the  From Hope t o  (121 26'W; 49°34'N) t o P e t c h  49°49'N) and i s c a l l e d  i s a steep-sided,  Columbia.  Creek t o L y t t o n ,  extends from Y a l e  (121°26'W;  north-trending  base, o c c a s i o n a l f l u v i a l  large accumulation  and f l u v i o - g l a c i a l  rock  of talus at deposits,  large  10  11  p r e - h i s t o r i c l a n d s l i d e b a s i n s , and s t e e p - s i d e d t r i b u t a r y notches. The  canyon slopes r i s e 3000 t o 4000 f e e t (1000 t o 1200 m)  though t o the west mountain peaks reach a height o f 7000 f e e t (2100  m). Within  and  the canyon the F r a s e r R i v e r i s bedrock c o n t r o l l e d ,  i n some p l a c e s , has i n c i s e d a notch i n t o the base o f the  g l a c i a l l y - r o u n d e d v a l l e y (Camsell,  1911, p. 108).  I t i s not improbable t h a t the a c t u a l v a l l e y of the F r a s e r be due c h i e f l y t o i t s own a c t i o n of ' c o r r a s i o n ' while the p r e d i s p o s i n g hollow depends on the o r i g i n a l f l e x u r e s o f the rocks . . . (Dawson, 1879, p. 9 8). C u r r e n t l y i t i s thought t h a t i n the T e r t i a r y p e r i o d , the r i v e r occupied and  a wide v a l l e y w e l l above i t s present  level,  t h a t i n response t o major u p l i f t i n the P l i o c e n e epoch,  the r i v e r has c u t the p r e s e n t  canyon.  The l a t t e r has s i n c e  been smoothed d u r i n g P l e i s t o c e n e g l a c i a t i o n , and subsequently notched i n the Recent epoch (Holland, 19 76).  Davis and  Mathews C1944) a t t r i b u t e t h i s type o f v a l l e y c r o s s - s e c t i o n t o m u l t i p l e g l a c i a t i o n s , thereby d a t i n g the form as P l e i s t o c e n e . T h i s seems u n l i k e l y a t the s c a l e o f the F r a s e r Canyon. The  n a t u r a l steepness o f the canyon s i d e s has been l o c a l l y  m o d i f i e d by c o n s t r u c t i o n o f the two r a i l w a y s and the highway. E a r l y d e s c r i p t i o n s o f the u n a l t e r e d v a l l e y r e f l e c t  great  d i f f i c u l t y i n i t s penetration: The view Csouth o f Boston Bar) changes from the grand t o the t e r r i b l e . Through t h i s gorge, so deep and narrow i n many p l a c e s t h a t the rays o f the sun h a r d l y enter i t , the black and f e r o c i o u s waters o f the g r e a t r i v e r f o r c e t h e i r way (Canadian P a c i f i c Railway Company, 1893).  12  E a r l y t r a v e l l e r s were f o r c e d t o use t r a i l s and a s m a l l  road  along the v a l l e y slope as the r i v e r i s impassable f o r any  form  of v e s s e l . North of Petch Creek the v a l l e y i s r e l a t i v e l y wide, the r i v e r channel i s smooth-sided and mile  (0.75m/km) ( P i t e a u , 1977,  p. 86).  g l a c i a l d e p o s i t s are continuous a l l u v i a l fans, and  the g r a d i e n t i s 4 f e e t per F l u v i a l and  fluvio-  along the r i v e r as t e r r a c e s or  l o c a l l y form a narrow zone of g e n t l y s l o p i n g  t e r r a i n along which the road and  railway  run.  At Petch Creek, the r i v e r becomes c o n s t r i c t e d between steep rock w a l l s , i t s channel i r r e g u l a r i n width and  rough-sided.  T h i s d i f f e r e n c e i s a t t r i b u t e d to a s i g n i f i c a n t change i n l i t h o l o g y at t h i s p o i n t , between s o f t P a l e o z o i c sediments to the n o r t h and younger c r y s t a l l i n e rocks t o the south. here and Y a l e , a l l u v i a l fans and i n f r e q u e n t and  Between  f l u v i o - g l a c i a l deposits  are  o f t e n d i s s e c t e d , and only near Spuzzum Creek  i s there any e x t e n s i v e  flat  land.  Scuzzy Creek j o i n s the F r a s e r R i v e r through a narrow gorge and a t i t s mouth i s evidence trending d i r e c t l y north.  of the major Hope and Yale  Opposite Scuzzy Creek is.<: an o l d  l a n d s l i d e s c a r whose base seems to l i e w e l l above the river level.  Though t h i s and  a t t r i b u t e d to p o s t - g l a c i a l (Read, 1960; s c a r s may  faultline  current  other l a n d s l i d e s c a r s are commonly  (Recent) adjustment o f the  slopes  P i t e a u , 19 77), the w r i t e r b e l i e v e s t h a t some such  be r e l a t e d to e a r l i e r l a n d s l i d e a c t i v i t y i n response  to l a t e T e r t i a r y f l u v i a l  incision.  South to Chapmans, the canyon w a l l s are r e l a t i v e l y  uniform,  13  comprising steep rock and c o l l u v i u m extending t o the r i v e r (Photo 2.1).  H e l l ' s Gate i s the narrowest p o i n t i n the  o r i g i n a l l y l e s s than 100  feet  (30m)  canyon,  i n width from bank t o bank.  Since c o n s t r u c t i o n of the two r a i l w a y s , many m o d i f i c a t i o n s t o the n a t u r a l c o n s t r i c t i o n have been made, i n c l u d i n g narrowing of the r i v e r immediately upstream a l a r g e anthropogenic l a n d s l i d e i n 1913,  and  accidental  from the gate by subsequent  b u i l d i n g o f salmon l a d d e r s i n the channel. Black Canyon i s a s t r a i g h t s e c t i o n of the r i v e r where the Recent r o c k - f a c e d notch i s e v i d e n t .  From Black Canyon  south t o the Alexandra B r i d g e , both s i d e s o f the canyon are c h a r a c t e r i z e d by r o c k s l i d e s c a r s . western s i d e , the Teequaloose mile  (.2 km)  i n width.  A p r e - h i s t o r i c scar on the  l a n d s l i d e , i s g r e a t e r than  one  T h i s bowl-shaped s c a r e x h i b i t s steep  headwalls, a c t i v e l y f a i l i n g  i n some p l a c e s , a more g e n t l y  s l o p i n g and d i s s e c t e d base, and prominent bedrock mounds of 30Q  feet  C 1 0 0 m)  i n h e i g h t a t the r i v e r ' s e d g e . ( F i g . 2.2 a ) .  The same c o n f i g u r a t i o n i s seen a t the l a r g e r K u t h l a t h l a n d s l i d e o p p o s i t e Y a l e , where some f l u v i a l g r a v e l s are c l e a r l y adjacent t o the rock mounds.  exposed  T h i s evidence suggests t h a t the  present landform d e r i v e s from a l a n d s l i d e whose base was away and/or reworked  by f l u v i a l p r o c e s s e s .  cut  I t seems that the  r i v e r flowed i n the bowl of the s l i d e a t one time, but has s i n c e cut a more d i r e c t route a c r o s s the mouth of the bowl (Fig.  2.2 b , c ) .  On the b a s i s of subsequent  i n c i s i o n , these l a n d s l i d e events may  Fraser River  have been p r e - P l e i s t o c e n e .  From the Alexandra Bridge south t o Stout the canyon i s  Photo 2.1 Extensive c o l l u v i a l slope above mile 11.6 (18.6 km) on the western side of the canyon. Note a l s o the steep t r a c k s i d e slope of bedrock i n the foreground.  15  x  headscarp  ,,^,~7 fluvial  r o ck  I  LANDSLIDE  SCAR  I  ROCK MOUND  ©  ©  ©  Fig  2.2  Aspects of p o s t - g l a c i a l l a n d s l i d e s . a) Cross-section b) P l a n view o f the h y p o t h e s i z e d channel c o n f i g u r a t i o n i n the l a n d s l i d e bowl s h o r t l y a f t e r the f a i l u r e event c) P l a n view o f the p r e s e n t channel configuration  16  marked by o c c a s i o n a l benches of f l u v i a l and m a t e r i a l on both s i d e s up t o the 1000 (Photo 2.2).  foot  fluvio-glacial (300 m)  level  The r i v e r channel here i s smooth-sided  than t o the n o r t h or south.  and  At Stout, the l a r g e f l u v i o - g l a c i a l  l e v e l ends and the canyon becomes c o n s t r i c t e d a g a i n . western  wider  On  the  slope the a l l u v i a l fan of Spuzzum Creek has been  deeply d i s s e c t e d by the creek and t r u n c a t e d by the F r a s e r R i v e r , and i s graded t o the t e r m i n a l s u r f a c e of the glacial  fluvio-  levels.  Signs of a e o l i a n d e p o s i t i o n occur throughout  the  study  area and the most e x t e n s i v e capping of windblown sand and s i l t occurs on the south s i d e of the Spuzzum Creek f a n . The area south of Stout i s the most p r e c i p i t o u s of the e n t i r e canyon, having steep rock faces up to 1500 in  e l e v a t i o n , and r e l a t i v e l y l i t t l e  area o f t a l u s accumulation.  The  feet  (460  m)  g e n t l y s l o p i n g land or  r i v e r i s of v a r i a b l e  and has an i r r e g u l a r channel boundary.  width  Some prominent rock  i s l a n d s and r a p i d s occur i n t h i s s t r e t c h , ending w i t h the bedrock c o n s t r i c t i o n i n the r i v e r near Y a l e .  last  The grade of the  F r a s e r R i v e r over the e n t i r e canyon s e c t i o n i s 8 f e e t per m i l e (1.5 m/km)  (Camsell, 1911,  p. 108;  P i t e a u , 1977,  p.  86).  The K u t h l a t h l a n d s l i d e bowl, on the e a s t e r n s i d e of the canyon j u s t upstream from Y a l e , i s roughly 115 m i l e s diameter  and i s s i m i l a r to the Teequaloose  (3 km)  in  bowl mentioned  previously. South of Y a l e , the v a l l e y widens, steep rock faces are l e s s p r e v a l e n t and s e t back from the r i v e r , and t e r r a c e s of  Photo 2.2 F l u v i a l terraces at mile 18.0 (29.0 km) of the eastern side and mile 20.0 (32.2 km) of the western side of the canyon. Photo looks southeast.  18  f l u v i a l and f l u v i o - g l a c i a l m a t e r i a l are common along i t s length.  The g r a d i e n t o f the r i v e r i n t h i s s e c t i o n i s 3.5 f e e t  per mile  (0.65 m/km)  ( P i t e a u , 1977, p. 86).  DRAINAGE While no major t r i b u t a r i e s j o i n the F r a s e r R i v e r w i t h i n the study area, s e v e r a l streams e n t e r from the western s l o p e s : Scuzzy, Spuzzum and Sawmill creeks  [ F i g . 2.1). Only one of  e q u i v a l e n t s i z e t o these, Siwash Creek, e n t e r s from the e a s t . T r i b u t a r y creeks enter the F r a s e r R i v e r v i a steep bedrock notches, and flow through rounded v a l l e y s hanging w e l l above the p r e s e n t r i v e r l e v e l .  Spuzzum Creek alone  flows  conformably  i n t o the F r a s e r R i v e r through i t s a l l u v i a l f a n d e p o s i t s . The  F r a s e r R i v e r d r a i n s an area o f 83,500 square m i l e s 2  (.216,300 km ) upstream from Hope. and  Average monthly  discharge  suspended sediment l o a d measured a t the Hope s t a t i o n are  shown i n Table  2.1.  bedrock-controlled,  Because t h i s p o r t i o n o f the r i v e r i s changes i n i t s channel morphology are slow,  and only i n s e v e r a l p l a c e s can any a l t e r a t i o n i n the r i v e r ' s course be d e t e c t e d .  Rather, the r i v e r has degraded i t s channel  i n Recent time, and t h i s process  i s ongoing.  claims t h a t l a t e r a l e r o s i o n i s as important i n c i s i o n , but t h i s i s not evidenced  Piteau  (1977)  as v e r t i c a l  i n the canyon r e g i o n .  long p r o f i l e o f the r i v e r i s r e l a t i v e l y s t r a i g h t ,  The  with  s t e p - l i k e breaks o c c u r r i n g near Scuzzy Creek, H e l l ' s Gate, and  i n s e v e r a l l o c a t i o n s upstream from Y a l e . The seasonal nature o f d i s c h a r g e and sediment l o a d i s a l s o  19  Discharge  (1912-76)  Suspended Sediment Load  (1965-76)  Period  ffvsec  nr/sec  tons/day  January  32600  923  3370  February  30400  861  3110  March  28700  813  7050  April  58500  1656  55700  May  171000  1927  240000  June  252000  7136  221000  July  200000  5663  94000  August  128000  3625  43800  September  86000  2135  18200  October  70500  1996  16500  November  56200  1487  9720  December  40400  1144  3320  Annual  96900  2744  59400  Table 2.1  Mean monthly discharge and suspended sediment load f o r the Fraser River, measured at Hope, B.C. (Water Survey o f Canada, H i s t o r i c a l Streamflow Summary, 1977, and H i s t o r i c a l Sediment Data Summary, 1978).  20  noted i n Table 2.1. the  May,  June and J u l y t y p i c a l l y experience  h i g h e s t d i s c h a r g e s , and the annual d i s c h a r g e maximum occurs  most f r e q u e n t l y i n the second week of June. 250,000 t o 350,000 c u b i c f e e t per second l(.Muir, 1969, p. 9 ) . the  T h i s peak averages  (7079 t o 9911  m /s) 3  The f r e s h e t i s caused by snowmelt r u n o f f ,  c o n t r i b u t i o n by r a i n f a l l a t t h a t time b e i n g s m a l l .  peak f l o o d c o n d i t i o n s t o develop, t h e r e must be c o o l and at l e a s t average s n o w f a l l , f o l l o w e d by a sudden continued temperature r i s e  (Quick, 1965, p. 62).  For  weather and  Such a f l o o d  o c c u r r e d i n 189 4 when the F r a s e r R i v e r rose more than 70  feet  (20 m) and washed out the f i r s t Alexandra Suspension Bridge north o f Spuzzum.  The d i s c h a r g e has been e s t i m a t e d a t 620,000 3 c u b i c f e e t per second (.17,556 m /s) compared to t h a t of 3 520,000 c u b i c f e e t per second  major f l o o d i n 1948  (Muir, 1969, p . 6 ) .  h i g h water, the l e v e l may C.60 m)  (.14,725 m /s) d u r i n g another At H e l l ' s Gate  r i s e t o a t o t a l depth of 200  during feet  or more.  GEOLOGY I n t e r e s t on the p a r t of Canadian P a c i f i c Railway i n a r a i l passage through the C o r d i l l e r a sparked many s t u d i e s o f the t e r r a i n and geology o f major r i v e r v a l l e y s through the mountains. The f i r s t r e p o r t on the geology o f the F r a s e r R i v e r V a l l e y was made t o the G e o l o g i c a l Survey o f Canada by A.R.C. Selwyn i n 1872  CSelwyn, 1872).  George Dawson, who in  The most complete r e p o r t was made by  d e t a i l e d aspects of physiography and geology  southwestern B r i t i s h Columbia  (Dawson, 1879).  Reginald  21  Daly  (1912) was the f i r s t t o r e p o r t f u l l y , and name, rock u n i t s  i n the v i c i n i t y  o f the F r a s e r Canyon.  Since the 19 40's,  f u r t h e r work i n southwestern  British  Columbia and northwestern Washington State comprises g e o l o g i c mapping i n c l u d i n g the F r a s e r Canyon area  (Cairnes, 1944;  McTaggart and Thompson, 1967; Monger, 1970) and s t u d i e s o f the s t r u c t u r a l r e l a t i o n s h i p s between rock u n i t s (Morris, 1955; Read, 1960; McTaggart and Thompson, 1967; Roddick and Hutchinson, 1969; Monger, 1970; Wheeler, 1970). complete l i s t i n g s Misch  o f work i n surrounding  (.1966) , and Monger (.1970) .  areas, see Read  (1960),  Of the v a r i o u s g e o l o g i c  maps mentioned p r e v i o u s l y , t h a t by Monger (19 70) adopted f o r use i n t h i s study  F o r more  has been  s i n c e i t i s the most r e c e n t  v e r s i o n c o v e r i n g the whole study area a t a s c a l e o f 1:250,000. F i v e rock u n i t s a r e found exposed i n the v a l l e y w a l l s of the F r a s e r Canyon between Yale and China Bar (Monger, 19 70, Hope map sheet, west h a l f ) . i) ii)  Scuzzy P l u t o n  These are the (Late Eocene t o Miocene)  Yale I n t r u s i v e s (Late Cretaceous o r E a r l y Tertiary)  iii) iv) v)  Spuzzum I n t r u s i v e s (Late Cretaceous o r older) Custer Gneiss  (Late Permian o r older)  Hozameen Group (Devonian?  Carboniferous?  and  Permian?) They w i l l be d e s c r i b e d i n c h r o n o l o g i c a l sequence  ( F i g . 2.3).  22  23  Hozameen The  Group Hozameen Group r e p r e s e n t s t h e o l d e s t  stratified  and  largest  bedrock type exposed i n t h e F r a s e r Canyon.  Itis  r e p r e s e n t e d by f o u r u n i t s o f L a t e P a l e o z o i c (?) s e d i m e n t a r y volcanic  rocks o f g r e a t magnitude, a s i n g l e u n i t  much a s 10,000 f e e t 1967,  p . 1201).  units,  (3000 m)  Most l i k e l y  approximately  i n depth  a c h i e v i n g as  ( M c T a g g a r t and Thompson,  i t i s t h e uppermost o f t h e s e  7000 f e e t  (2100 m)  i n thickness, that i s  e x p o s e d a l o n g t h e e a s t bank o f t h e F r a s e r R i v e r , e x t e n d i n g miles  (4 km)  and  n o r t h and 3.7 m i l e s  (.6 km)  south  2.5  of Stout  ( M c T a g g a r t and Thompson, 1967, p . 1201) . The and by  some  Hozameen Group c o m p r i s e s limestone,  the greenstone  being  chert,  pelite,  i n t r u d e d near  Stout  y o u n g e r g r a n i t e s and g r a n o d i o r i t e s (Monger, 19 7 0, p . 3 ) .  Greenstone r e f e r s this The  greenstone,  case,  t o somewhat a l t e r e d b a s i c v o l c a n i c s , i n  andesitic basalt  original  composition  subsequent s h e a r i n g Chert  volcanic  sequences  Lineations,  and t e x t u r e has b e e n o b l i t e r a t e d by  (Monger, 1970, p . 4 ) .  folds,  the  form  Generally  and j o i n t s  occur  i n particular,  of close joints  and f a u l t s  i n t h e Hozameen  rocks,  minor s t r u c t u r e takes  ( M c T a g g a r t and Thompson,  They u s u a l l y a r e o r i e n t e d n o r t h w e s t  the greenstones  i s weak.  i n t h e Hozameen  i s i n f r e q u e n t and o c c u r s w i t h i n t h e  i n the greenstones  p . 120 3 ) .  p. 4 ) .  ( M c T a g g a r t and Thompson, 1967, p . 12Q2).  and  chert  (Monger, 19 70,  i s t h e most common s e d i m e n t r e p r e s e n t e d  Group, a s l i m e s t o n e  196 7,  and s p i l i t e  to southeast.  a r e h i g h l y competent w h i l e t h e  24  To  the  south  Group i s c l e a r l y  of the p r e s e n t in fault  study  area,  contact with  the  the  Hozameen  younger C u s t e r  t o the west, whereas near S t o u t  this  Near the  grade i s r e l a t i v e l y  the  gneiss  raetamorphic  grainsize of constituent minerals  ( M c T a g g a r t and The Jurassic north with  the  Thompson, 196 7,  p.  Hozameen F a u l t s e p a r a t e s rocks  from the  t o the  east.  The  high,  correspondingly  and  larger  t h e Hozameen Group f r o m fault  t r a c e can  be  the  followed  t o L y t t o n , where i t merges  faults.  Gne1ss  The  Custer  Gneiss  named by  o f t h e Hozameen Group and western  s i d e of the  has  Daly  (1912) l i e s  ( F i g . 2.3).  faulting  Thompson p o s t u l a t e d t h a t t h e  of the  ( M c T a g g a r t and  p.  (McTaggart, The  1970,  gneiss  138  p.  dark  the  unit  and  individual mineral  crystals  by  Misch). belt  1968) .  in biotite  Toward Y a l e  in color,  after  layers rich  layers rich  35).  appears p a l e  "light  formed  a McTaggart  S k a g i t metamorphic  a f t e r Misch,  comprises  alternating with (Monger, 1970,  p.  of  was  o l d e r Hozameen Group  1208,  i s a c o n t i n u a t i o n of the  the  Formation  shearing.  g n e i s s was  metamorphism and m i g m a t i z a t i o n Thompson, 1967,  and  west  along  v i a metamorphic a l t e r a t i o n  granodiorite b a t h o l i t h during  gneiss  to the  sporadic occurrence  F r a s e r Canyon  t h o u g h t t o have o c c u r r e d  The  i s gradational  12 0 3 ) .  i n t e r n a t i o n a l border  o t h e r major  Custer  and  relation  Gneiss  in plagioclase . . . and/or  hornblende"  and  northwards to  Stout  friable,  s h a t t e r e d and  jointed,  are  sheared,  or  mylonitized.  25  This  lightened  color  results  o f t h e m a f i c m i n e r a l s and on  t h e many s m a l l j o i n t  Thompson, 1967, Minor  to accumulation  and  structures  of a l t e r a t i o n  p. 1205).  folds  the  near  their  junction  possible  Orientation of lineations  t o the west  the a l t e r a t i o n  adjoining gneiss resulted schists  (McTaggart  vicinity Yale  at Saddle  Spuzzum The  and  into  t h e Hozameen u n i t  small  p.  and p.  in  36) of  and i t the  shearing of 1210).  In  through  fault-  these  the  younger  t o t h e e a s t ; however,  directly  i n Hozameen r o c k s .  Intrusives Spuzzum I n t r u s i v e  from  t h e same s i d e o f t h e r i v e r  side o f the r i v e r  predominant  rock extends  rock type  i t extends  t h a n by b i o t i t e  Rock t o  a t the H e l l ' s  and  i s darkened  (Monger, 1970,  t h e F r a s e r Canyon, and  p.  toward  small  at China Bar.  On  f r o m o p p o s i t e Spuzzum Gate a r e a .  i s quartz d i o r i t e ,  b l a c k and w h i t e  Saddle  t h e w e s t bank, w i t h a n o t h e r  t o C h i n a B a r , w i t h a gap  in  lies  disintegration  folding  Rock t h e g n e i s s g r a d e s  o c c u r r e n c e on  appears  and  Thompson, 1967,  t h e A l e x a n d r a B r i d g e on  east  from  (Monger, 1970,  o f Y a l e , the C u s t e r Gneiss grades  Intrusives  and  and  northwest.  schists that  to  (McTaggart  In t h e F r a s e r Canyon a r e a , t h e C u s t e r G n e i s s  is  and  t h e Hozameen Group, i n c l u d i n g i n t e n s e  Thompson, 1967,  contact with  products  s u r f a c e s (McTaggart  i n the Custer Gneiss are s i m i l a r  and m y l o n i t i z a t i o n  i s toward  fracture  and b l e a c h i n g  p . 1206) .  t h o s e e x h i b i t e d by shearing  from a l t e r a t i o n  40).  The  China Bar  Creek  The  or t o n a l i t e , more by  the  which  hornblende  tonalite  i s gneissoid  i s very coarse-grained.  26  F o l d i n g and high-grade  metamorphism along a northwest  axis  p a s s i n g through Spuzzum i s a s s o c i a t e d with the emplacement of t h i s i n t r u s i v e rock  (McTaggart,  1970,  p.  146).  Yale I n t r u s i v e s The Yale i n t r u s i v e s occur as s i l l s , on the western continuous  dykes, and s m a l l masses  edge of the Hozameen Group.  from 8 m i l e s  (12.9 km)  They are more or l e s s  south of Hope northwards t o  Saddle Rock and occur mostly on the e a s t s i d e of the F r a s e r River.  These i n t r u s i o n s comprise  a p l i t e and quartz d i o r i t e .  g r a n o d i o r i t e with minor  The rocks e x h i b i t graded j u n c t i o n s  with the Spuzzum t o n a l i t e and the Custer g n e i s s , and c o n t a i n i n c l u s i o n s of the l a t t e r rocktype Thompson, 1967,  p. 1215;  Monger, 1970,  may  (McTaggart and  p. 41).  The  Yale  I n t r u s i o n s are s t r o n g l y sheared and f o l i a t e d , and of i n t e r mediate competence.  The Hozameen and Custer u n i t s are cut  by dykes and s i l l s of Yale I n t r u s i v e m a t e r i a l which has  taken  on the m i r r o r s t r u c t u r e of the host rock.  Scuzzy  Pluton  E x t e n s i v e g r a n i t i c rocks i n the:..northern end of the area are a t t r i b u t e d to m i d - T e r t i a r y i n t r u s i o n by the Pluton. in  T h i s l a t t e r was  study  Scuzzy  one of three major b a t h o l i t h s  appearing  t h a t p e r i o d ; the Needle Peak and C h i l l i w a c k p l u t o n s occur  f u r t h e r south.  The rock u n i t appears  on the e a s t bank i n the  v i c i n i t y of H e l l ' s Gate, and on the west bank from Creek northward p a s t China Bar.  Tsileuh  At H e l l ' s Gate the g r a n o d i o r i t e  27  i s considerably finer-grained, less obviously f o l i a t e d ,  and  more massive than toward Scuzzy Mountain but i s considered of the same i n t r u s i v e event  (Monger, 1970,  comprises f i n e - g r a i n e d b i o t i t e and and  p. 42).  i s o t r o p i c and  rock  c o a r s e r quartz and f e l d s p a r ,  i s of c o n s i d e r a b l y lower mafic m i n e r a l content  main body of Scuzzy P l u t o n .  The  part  J o i n t i n g and  than the  fracture i s r e l a t i v e l y  coarse, g i v i n g the g r a n o d i o r i t e much h i g h e r  competence than other g r a n i t e s i n the  region.  REGIONAL FAULTING At the r e g i o n a l s c a l e , f a u l t s run predominantly  north-south,  with s m a l l e r s p l i n t e r - f a u l t s as the s i g n a t u r e of l o c a l s t r e s s release  CFig. 2.3).  F a u l t s are important  s t r u c t u r a l h i s t o r y and  i n terms, of  r e s u l t a n t physiography of the  area,  and i n f l u e n c e r o c k s l o p e s t a b i l i t y along the canyon. McTaggart and Thompson (1967, p. 1223)  recognize  main f a u l t contacts i n the F r a s e r Canyon area. i)  between the Custer gneiss and Hozameen u n i t ,  three  These are:  the  ii)  the Hozameen F a u l t , between Hozameen rock and J u r a s s i c - C r e t a c e o u s u n i t s to the e a s t  iii)  w i t h i n the Custer g n e i s s , Hozameen Group and Spuzzum I n t r u s i o n s , forming the south e a s t end of the F r a s e r R i v e r F a u l t Zone.  In the F r a s e r Canyon, the boundary between the gneiss the Hozameen rock i s a g r a d a t i o n a l , metamorphosed band probably  i s not f a u l t - c o n t a c t .  Two  major f a u l t l i n e s  and  and  called  the Hope and Yale f a u l t s together  d e f i n e the F r a s e r R i v e r F a u l t  Zone (Duffel 1 and McTaggart, 1952;  McTaggart, 1970,  p.  146).  28  This  fault  fault,  zone i s t h o u g h t t o s t a r t  a possible extension  northwards  Thompson,  1967,  most one,  and  along  its  1224).  p.  faults,  Hope f a u l t  It parallels  the  the  the  probably continued lithic is  and  be  beyond  108;  traced  the  McTaggart  Hozameen f a u l t  The  fault  River, fault  and  i s the  eastern-  The  two  At  p.  Yale.  Bridge,  this  1225),  Hozameen f a u l t by  point  (1977,  Piteau  t r e n d o f the  faults  cuts  near  evidence  the  Hope and  Fraser  f o r p e r i o d i c movement a l o n g  ceous t h r o u g h t o Recent t i m e s  the  lithology. Yale  faults have  i n t o l a t e T e r t i a r y time i n response to nearby North o f the  p.  across  i n E o c e n e e p o c h t h o u g h movement may  emplacement.  to  though i s  seem t o have c o a l e s c e d  northward t r e n d o f the  the  north  t r e n d i n g Hozameen f a u l t  1967,  1224)  east.  t o w e s t bank a t  ( F i g . 2.3).  Thompson,  faults  west o f  to the Alexandra  l a s t m a j o r movement a l o n g occurred  s t e e p l y t o the  slightly  and p.  f r o m Hope a l o n g  from e a s t  again  of rupture,  Thompson, 1967,  dips  trends  rock  zone i s a- s e r i e s o f  north  and  northeast  from the  northwest s t r u c t u r a l The  km)  ( M c T a g g a r t and  river  the  C e r t a i n l y the  N o r t h Bend.  The  River  ( M c T a g g a r t and  mapped s e p a r a t e l y 87).  p.  t h e Hope f a u l t n o r t h  merge w i t h  east  Yale  Fraser  where i t c r o s s e s may  1966,  runs d i r e c t l y  Fraser  N o r t h o f Hope, t h e crosses  (3 20  fault,  r a t h e r than a s i n g l e plane  west s i d e o f the  and  miles  S t r a i g h t Creek  e x h i b i t s a n a r r o w band o f s e r p e n t i n i z e d  trace often unclear The  it  (Misch,  most o f i t s l e n g t h .  parallel  of the Yale  f o r more t h a n 200  i n t e r n a t i o n a l border  a t the  (Duffell  batho-  Canyon, however, the  and  faults  from  McTaggart,  there  Creta-  1952,  p.  29  QUATERNARY In State,  HISTORY  southwest four  (Armstrong  major et  p.14)(Table tion  which  of  States"  the form  of  Washington  been  drift,  1969,  was t h e F r a s e r  Wisconsin  Valley,  documented  Ryder,  Interglaciation  (Armstrong  Fraser  have  Crandell;  these  "the classical  United  i n  after  the Olympia  In the lower i s  recent  and northwest  glaciations  1965, p . 3 2 3 , Most  with  mid-western  stades  a l .  2.2)  Columbia  Pleistocene  followed  correlated  F l i n t ) .  British  et  Glacia-  and has  glaciation a l .  been  of  the  1965, p . 3 2 6 ,  stratigraphic  glacio-marine  after  evidence  and  for  fluvial  sediments. Ice  spread  south  and east  Mountain  Range.  North  of  west  and crossed  25).  In the Fraser  yet  i c e i s  valley  (Prest,  nature,  It  Canyon  of  occurred  1944, seems  River  area,  i n  four  valley  evidence  moved  from  contains  importance  of  erosion  p.  (Table  404)  that  the Fraser  experienced  the second  sharp-faced  nunatak  stage  peaks  Coast  was from (Ryder,  movement  the north of  down  i t s  is  p.  sparse,  the  British underlying  determining  and deposition  1969,  material.  southwestern the  the  constricted  glacial  i n which i n  the  axis  l i t t l e  i n  stages,  glacial  in  i c e movement  the glaciers  had varying  consequent  Mathews,  t o have  the Fraser  topography and  Canyon  centers  1970, m a p 1253 A ) . B e c a u s e  Development Columbia  Lytton,  the Fraser  thought  from  ice  (Davis  movement and  2.3) Canyon of  area  may o n l y  glaciation,  nearby,  rounded  as  have  evidenced  hilltops,  the  by steep  30  GLACIAL EPISODE  SUBSTAGE  TIME lOOO's years B.P.  IV  FRASER GLACIATION  Sumas Stade  J. X  Everson Interstade  Vashon Stade  STRATIGRAPHIC EVIDENCE IN THE FRASER LOWLAND  NATURE OF THE ICE IN THE COAST MOUNTAINS  Sumas D r i f t  extension of Cordilleran i c e to the eastern Fraser Lowland uncertain e f f e c t of the interstade on the extent of ice i n the mountains  Capilano Sediments  ± j — ±H Surrey D r i f t  1  in.  Evans Creek Stade  OLYMPIA INTERGLACIATION III SALMON SPRINGS GLACIATION PUYALLUP INTERGLACIATION II STUCK GLACIATION ALDERTON INTERGLACIATION I  ORTING GLACIATION  Table 2.2  continental i c e sheet up to 7500 feet (2300 m) thick large alpine glaciers; i n i t i a l development of the C o r d i l l e r a n ice sheet  - o—o~  Quadra Sediments  3b? Semiamu Drift non-glacial •sediments unnamed d r i f t ?  unnamed d r i f t  G l a c i a l episodes i n southwestern B r i t i s h Columbia ( a f t e r Armstrong et a l . , 1965; Ryder. 1969).  31  PHYSIOGRAPHIC CHARACTER  GLACIAL CHARACTER  CONTROL ON GLACIAL MOVEMENT  1  r e l i e f much greater than i c e thickness  alpine glaciers  2  r e l i e f just exceeds Ice thickness  3  4  STAGE  ASSOCIATED LANDFORMS  GLACIAL EROSIVITY  tOpO; graphic  cirques, horns, U-shaped v a l l e y s , hanging t r i b u t a r y v a l l e y s , overdeepened g l a c i a l channels ( a l l of southwestern B.C.)  strong  branching glacier systems, extensive Ice f i e l d s  topographic  heavily g l a c i a t e d trunk v a l l e y s , zones of l a t e r a l flow of i c e between major v a l l e y s ( a l l of southwestern B.C.)  moderate  i c e thickness j u s t exceeds the r e l i e f  continuous i c e sheet, sometimes _ thin  topographic and climatic  glaciated valley f l o o r s , domed summits, rounded ridges (western Coast Mountains and Georgia Stralt-Puget Sound depression only)  limited except at ridge tops and peaks  i c e thickness much greater than r e l i e f  continuous i c e sheet of great thickness  climatic  small, undrained depressions, rounded h i l l s and v a l l e y s (Georgia Strait-Puget Sound depression only)  negligible  Table 2.3  Stages o f g l a c i a l development and the associated landforms Davis and Mathews, 1944).  (after  32  U-shaped F r a s e r Since has  and  hanging t r i b u t a r y  Pleistocene glaciers  several notable  processes.  channels. the  area  These  are:  i)  The f o r m a t i o n o f p a r a - g l a c i a l a l l u v i a l f a n s , p r i m a r i l y a t t h e c o n f l u e n c e s o f Spuzzum and Yale creeks w i t h the F r a s e r R i v e r . The c h a r a c t e r o f s i m i l a r f a n s i s w e l l documented, p a r t i c u l a r l y i n the u p p e r F r a s e r R i v e r V a l l e y and i n o t h e r l o c a t i o n s i n B r i t i s h C o l u m b i a by R y d e r ( 1 9 6 9 ) . They a r e f o r m e d a l o n g m a j o r r i v e r v a l l e y s i n response to r a p i d t r a n s p o r t and d e p o s i t i o n o f g l a c i a l m a t e r i a l s by t r i b u t a r y streams. I n t h e F r a s e r Canyon, t h e r e was l i m i t e d s p a c e f o r t h e d e v e l o p m e n t o f fans w i t h the r e s u l t t h a t m a t e r i a l from t r i b u t a r y s t r e a m s has b e e n t r a n s p o r t e d by t h e F r a s e r R i v e r t o t h e F r a s e r L o w l a n d and d e p o s i t e d there.  ii)  The o c c u r r e n c e o f e x t e n s i v e p o s t - g l a c i a l l a n d s l i d i n g a l o n g the F r a s e r R i v e r i n response t o u n l o a d i n g o f t h e s l o p e s and d o w n - c u t t i n g by t h e main r i v e r . Some o f t h e s e a p p e a r t o h a v e b e e n r e l a t i v e l y s h a l l o w f a i l u r e s , as i n the v i c i n i t y of H e l l ' s Gate. Closer examination of s e v e r a l of the s l i d e s c a r s suggests t h a t t h e y may be o l d e r , p e r h a p s P l i o c e n e o r i n t e r glacial . C o n t i n u e d i n c i s i o n by t h e F r a s e r R i v e r i n response to P l i o c e n e - P l e i s t o c e n e u p l i f t , r e s u l t i n g i n d i s s e c t i o n o f g l a c i a l l y d e r i v e d m a t e r i a l and bedrock.  iv)  I n c i s i o n by t h e t r i b u t a r y s t r e a m s , i n r e s p o n s e t o d o w n c u t t i n g by t h e t r u n k s t r e a m .  v)  J o i n t i n g and s p a l l i n g o f b e d r o c k e x p o s e d i n n e a r v e r t i c a l f a c e s a l o n g the canyon i n response t o t h e r e l e a s e o f v e r t i c a l and l a t e r a l p r e s s u r e , and t o m e c h a n i c a l s t r e s s i m p o s e d by s e a s o n a l i c e , producing l o c a l i z e d t a l u s accumulations.  result  although in  r e t r e a t of the  b e e n a f f e c t e d by  iii)  The  the  River valley,  the  i s t h a t the  i t is likely  canyon d e r i v e s  Glaciation.  glacial history is difficult t h a t most o f from the  the  latest  glacial  to ascertain,  material  phase o f the  found  Fraser  33  SURFICIAL MATERIALS Colluvium of  the  Fraser  i s the Canyon.  sometimes i n t h e On  p r e d o m i n a n t s u r f i c i a l m a t e r i a l on The  colluvial  form o f c o a l e s c i n g  bare and/or a c t i v e s l o p e s  very  coarse,  ranges feet  angular  fragments.  from s e v e r a l f e e t  (several metres),  t h a n .that a t t h e  the  slopes fans  The  often  surface.  or aprons  depth  i n the  but  t h i s was  not  measured.  Fluvial  and  f l u v i o - g l a c i a l materials the  comprise  may  at depth i s be  quite  of the  canyon t o  erosion.  M o s t o f t h i s m a t e r i a l was  M o u n t a i n g l a c i e r s were w a n i n g a t t h e epoch.  At  t h a t time  effected transport  the  river  Recent bedrock notch form o f  localized  Exceptions  have e s c a p e d deposited end  as  of the  The  and  d e p o s i t i o n of  deposits  i n c i s e d by  patches or  Fluvio-glacial material  are the  have  the  Coast  Pleistocene  glacial  released  debris  in  f o u n d h a n g i n g above Fraser  truncated  River  and  have  the the  levels.  characteristically  in size  occur  subsequent  l a r g e v o l u m e s o f m e l t w a t e r were  and  valleys.  m).  an  c a n y o n where t h e s e m a t e r i a l s  t o a c c u m u l a t e and  (300  found  i n wider  opportunity  feet  are  1000  an  finer  deep,  a l t i t u d e of approximately  had  of  large p o s t - g l a c i a l landslides,  lower s l o p e s  l o c a t i o n s i n the  2.1).  of.colluvium  the m a t e r i a l  particularly  o c c a s i o n a l l y along  (Fig.  metre) t o t e n s •  Some d e p o s i t s  bowls o f  extensive,  m a t e r i a l tends to  ( l e s s t h a n one  and  are  slopes  rounded p a r t i c l e s  ranging  from g r a v e l s  interspersed with  accumulations of s t r a t i f i e d  It occasionally exhibits steeply dipping  and  comprises to  boulders,  s a n d and contorted  silt. strata.  34  The  f a b r i c of f l u v i a l m a t e r i a l s i s s i m i l a r , although  grainsize d i s t r i b u t i o n i s smaller. and  W e l l - s o r t e d beds o f sand  rounded g r a v e l c h a r a c t e r i z e f l u v i a l A e o l i a n sand and s i l t  the  deposits.  forms a veneer over f l u v i a l  and  f l u v i o - g l a c i a l d e p o s i t s i n s e v e r a l spot l o c a t i o n s i n the canyon.  CLIMATE Between Hope and L y t t o n there i s a s t r o n g  climatic  g r a d i e n t from marine west coast to sub-humid c o n t i n e n t a l conditions  (Appendix I ) .  The  F r a s e r Canyon i s seen to e x h i b i t  a c l i m a t i c c h a r a c t e r i n t e r m e d i a t e between t h a t of Hope and Lytton.  T h i s i s most e v i d e n t i n p r e c i p i t a t i o n t r e n d s .  There  i s c o n s i d e r a b l y l e s s p r e c i p i t a t i o n at Boston Bar  than at Y a l e ,  and t h i s i s r e f l e c t e d by the sparse  there.  H e l l ' s Gate, 75%  of the annual p r e c i p i t a t i o n occurs  winter months (October snow.  f o r e s t cover  to March) of which roughly  At  i n the  16%  f a l l s as  Large d a i l y temperature ranges, p a r t i c u l a r l y i n the  winter months r e s u l t i n up t o f i f t e e n freeze-thaw c y c l e s i n each of December, January and February  ( P i t e a u , 1973,  Because of the l a r g e p o r t i o n of steep rock  p.  26).  faces i n the  F r a s e r Canyon, much of the bedrock s u r f a c e i s d i r e c t l y exposed, from l a c k of snowcover, to frequent wintertime  freeze-thaw  cycles.  progressive  These c o n t r i b u t e to rock f r a c t u r e and  l o s s of s t r e n g t h .  Piteau  (.1973) found t h a t 86%  f a i l u r e s recorded by Canadian N a t i o n a l Railway slides) occurred  i n the winter months.  of  slope  ( i n c l u d i n g snow-  35  VEGETATION AND The the  SOILS  s l o p e s o f the  Interior  F r a s e r Canyon o f f i c i a l l y  D o u g l a s F i r b i o g e o c l i m a t i c zone, b u t  characteristics  timber  stands  1954). via  s p a r s e and (British  hastily  near  forest  Spuzzum C r e e k .  western white  has  two  Map,  i s accessible  l o g g i n g has  Many o f t h e  not yet reached  forests  comprise  lower  occurred,  s l o p e s were  railway lines,  maturity  and  (Duncan W y l l i e ,  D o u g l a s f i r , m o u n t a i n hemlock  hemlock p r e d o m i n a n t l y ,  spruce,  of the  and  with  secondary  western  some P o n d e r o s a p i n e t o w a r d s t h e  canyon.  The  forest  owing t o deep s h a d e , m o s t l y  comprising  A n n a s , 19 7 8) .  Cleared areas  shrubs  and  b e r r y bushes.  Toward t h e n o r t h e r n end  cactus  forms f o u n d  species inhabit  i n the  podzols. soil  litter  few  of the  slopes.  canyon,  Most p l a n t  and  i s sparse.  are broadly c l a s s i f i e d  However, on most o f t h e  and  moss  c a n y o n have s h a l l o w r o o t s y s t e m s , a l l o w i n g  Canyon s o i l s  i s thin  and  are grassy with  the dry  them t o s u r v i v e i n l o c a t i o n s where s o i l Fraser  larch,  northern  fern,lichen  and  occasional  and  undergrowth i s g e n e r a l l y sparse  (Jones  the  are  non-productive  timber  commercial  c o n s t r u c t i o n of the  regrowth  forests  comm.). The  end  immature o r  Coastal  Columbia F o r e s t S e r v i c e Inventory  constructed roads,  burned d u r i n g the  pers.  canyon's  I n s e v e r a l l o c a t i o n s where t h e  especially  the  comprise  The  into  show  o f t h e n e a r b y M o u n t a i n Hemlock and  W e s t e r n Hemlock z o n e s as w e l l . relatively  fall  as  humo-ferric  steeper p o r t i o n s of the  p o o r l y developed  t h i n m i n e r a l h o r i z o n s and  comprising i s more  a thick  correctly  slopes, organic  36  c l a s s i f i e d as a r e g o s o l .  Where the podzols  have developed  more f u l l y , the s o i l s e c t i o n i s made up of l i t t e r ,  ferric  humic o r g a n i c l a y e r s , a l i g h t - c o l o r e d e l u v i a l h o r i z o n , a moderately t o h e a v i l y cemented m i n e r a l h o r i z o n .  and  and  Where the  parent m a t e r i a l i s c o l l u v i u m , the s o i l s are u s u a l l y w e l l - d r a i n e d . F l u v i a l and  f l u v i o - g l a c i a l parent m a t e r i a l s can g i v e r i s e to  poorly-drained s o i l p r o f i l e s . c o l o r , coarse-grained,  HISTORY- AND  The  and a c i d i c  (Jungen and Lewis, 19 7 8) .  ECONOMIC DEVELOPMENT  Simon F r a s e r was  the f i r s t white man  F r a s e r Canyon area, i n 1808. the n o r t h , he was  to penetrate  the  Having approached by canoe from  f o r c e d to abandon use: of h i s v e s s e l s i n the  canyon, and to t r a v e l o v e r l a n d remained l a r g e l y unexplored was  s o i l i s o f t e n red-brown i n  (Downs, 1960,  p. 9 ) .  Company at the uppermost  l i m i t o f navigable water on the F r a s e r R i v e r .  the f a u l t l i n e above and  area  u n t i l a t r a d i n g post, F o r t Y a l e ,  e s t a b l i s h e d by the Hudson's Bay  had been cut extending  The  By 1858,  a  trail  northwards from Yale to Spuzzum along to the west of the r i v e r , across  the  r i v e r and along the east bank to Chapman's Bar, whence i t l e f t the canyon and Valley  f o l l o w e d an o v e r l a n d route to the Anderson R i v e r  (Lindsay, 1958,  p. 13; Howay, 1910,  p. 7 ) .  This  was  the route by which s u p p l i e s were packed, a t g r e a t expense, to Kamloops, and t o miners opening up the Cariboo In the 1850's, p l a c e r g o l d was d e p o s i t s along the F r a s e r R i v e r i n 1859  and 1860,  country.  discovered i n Pleistocene  (Monger, 1970,  p. 28).  Later,  the Quesnel R i v e r and A n t l e r Creek g o l d s t r i k e s  37  sparked northward movement o f miners and goods, u s u a l l y bypassing the F r a s e r Canyon by the H a r r i s o n L a k e - L i l l o o e t o r Coquihalla River t r a i l s .  A l s o i n 1859,  surveyed by the Royal Engineers,  the town of Yale  and i n 1860  a t r a i l was  by them from Y a l e to Spuzzum along the F r a s e r Canyon. the Royal Engineers was  was built  In  1861,  commissioned to survey f o r the  c o n s t r u c t i o n of a wagon road from Yale northward to C l i n t o n , to was  serve the developing mining begun on the road  community, and by 1862,  (Howay, 1910,  work  p. 8) .  The f i r s t s i x m i l e s northward from F o r t Yale had to be b l a s t e d from the face of the c l i f f s and some s e c t i o n s were even b u i l t r i g h t over the r i v e r on s t i l t s and c r i b b i n g (Downs, I960, p. 2 4 ) . By 1863,  the road had been b u i l t through the F r a s e r Canyon,  and the Alexandra  Suspension  north of Spuzzum. i n width and  Bridge spanned the r i v e r a mile  When completed the road was  390 m i l e s  (6 30 km)  long, and was  18 f e e t  (5 m)  r e f e r r e d to as  the e i g h t h wonder of the world, B r i t i s h Columbia's Appian Way  (Laut, 1916, In 1872,  p. 101)  (Photo  2.3).  i n v e s t i g a t i o n by the G e o l o g i c a l Survey of Canada  began i n connection w i t h r o u t i n g the Canadian P a c i f i c through  the mountains (Cairnes, 19 25, p. 5 ) .  Railway  While s e v e r a l  routes were proposed, t h a t along the west s i d e o f the F r a s e r Canyon was  r e c o g n i z e d as b e s t o v e r a l l f o r i t s grade,  rock b l a s t i n g was Smith, 1878, r a i l w a y was  r e q u i r e d along i t s l e n g t h (Fleming,  p. 44).  The work was  completed i n 1886.  though much 1874; The  b u i l t q u i c k l y and w i t h l i t t l e c o n s i d e r a t i o n of the  e x t e n s i v e rock s h a t t e r i n g e f f e c t of the b l a c k powder b l a s t i n g  Photo 2.3  The C a r i b o o  Wagon Road n e a r B l a c k  Canyon  (courtesy o f Vancouver C i t y  Archives)  39  employed In  (J. 1915,  occupying Edgar,  1933,  Hell's  this  portion  remove  the  the  from  pers.  of  Trans  Rock  resulted the  blocks Canada  The  highway  follows  Spuzzum,  to  Lytton.  where The  to  the  west  is  to  the  (Thompson  the  upstream 1913.  Along  required  the  Road  from  from  in  is  along  east  and  to  track.  Cariboo bank  upslope  Canyon  rockwork  built  the  completed,  landslide  maintain was  was  immediately  major  time  crosses  highway  Fraser  continual  which  i t  a  Highway  at  the  Railway  blasting  and  19 5 0 ' s ,  to  of  in  line,  late  use.  National  slope  p.225). Gate  comm.).  Canadian  eastern  loosened  The the  McAree,  was  Yale  bank  the  canyon put  .  out  of  northward  and  r a i l  in  continues  lines  at  a l l  locations. At  the  end  of  the  Cariboo  experienced  depopulation  realization  as  a  scenic  moderate  recreation  have  recreational  low  and  gold  rush  economic  area.  Land  capability,  canyon  depression  adjacent  while  capability  the  the  (Canada  to  area  u n t i l  the  upper Land  its  river  canyon  is  of  slopes  Inventory,  1971) . The or  canyon  agricultural  three  main  of  slopes  been  of  private  the  cannot  measures  along  too  routes  canyon  changed  logging  activity  are  development.  transport  steepening has  slopes  be the  The is  walls. locally  roads.  Slope  balanced entire  precipitous effect  major  and  the  natural  poorly  planned  adequately  by  Rather,  commercial  construction  oversteepening  canyon.  allow  alteration  Also, by  of  to  the  over-  state  of  construction  through  remedial only  of  those  human  stabilization locations  40  are t r e a t e d where slope f a i l u r e occurs most f r e q u e n t l y and i s hazardous t o the road and r a i l w a y s .  41  CHAPTER 3 T E R R A I N AND  C L A S S I F I C A T I O N  S L O P E  S T A B I L I T Y  INTRODUCTION While the bedrock geology has been mapped i n the F r a s e r Canyon, the d i s t r i b u t i o n and form o f s u r f i c i a l m a t e r i a l s not been i n v e s t i g a t e d . organizing Canyon.  have  T e r r a i n c l a s s i f i c a t i o n i s a means o f  and s t o r i n g geomorphic a t t r i b u t e s o f the F r a s e r  The a t t r i b u t e s a r e subsequently r e t r i e v e d and analyzed  with respect  t o slope  stability.  T h i s chapter comprises an overview o f t e r r a i n c l a s s i f i c a t i o n methods f o l l o w e d by a d i s c u s s i o n concepts. analysis  o f t h e o r e t i c a l slope  The s c a l e dependence o f v a r i a b l e s i s d i s c u s s e d , and s e v e r a l  i n slope  case s t u d i e s  stability stability  i n which  t e r r a i n a t t r i b u t e s have been r e l a t e d t o a c t i v e geomorphic processes are reviewed.  TERRAIN CLASSIFICATION T e r r a i n u n i t s are i d e n t i f i e d by "the c h a r a c t e r i s t i c s o f the observed landform elements i n the area s t u d i e d , of a p a r t i c u l a r array  o f a t t r i b u t e s and a p a r t i c u l a r  c l a s s i f i c a t i o n procedure"  (Speight, 1976, p. 155).  or t e r r a i n f a c t o r s , are c r i t i c a l  units.  Attributes,  landform d e s c r i p t o r s  form, geometry, s u r f i c i a l m a t e r i a l , evaluation  by the use  such as  e t c . , o f which the  determines the q u a l i t y and boundaries of t e r r a i n  Terrain  f a c t o r s may be q u a l i t a t i v e o r q u a n t i t a t i v e .  42  The closely  study  of terrain  inter-related.  analysis,  considered  evaluated  number  1976, p . 1 6 2 ) .  w h i c h f a c t o r s and l a n d f o r m s  f o r each u n i t  initial  o f the study  should a l l  a r e a and l i m i t e d i n  f o r e a s e i n s u b s e q u e n t a n a l y s i s and i n t e r p r e t a t i o n .  system reduces  stored within a  the p r a c t i c a l  nature  of classification  d e p e n d e n t on t h e e n v i s a g e d Classifications for military,  prevalent.  o f the t e r r a i n  terrain  to detailed  sets of terrain classification engineering  units i s  purposes each  information with  attributes. and a n a l y s i s as a  s t u d i e s i s b e c o m i n g more  S u c h work r e c e n t l y h a s b e e n u s e f u l i n t h e p r o p o s e d  r o u t i n g of the Alaska o i l p i p e l i n e , northern B r i t i s h  Columbia.  geotechnical engineering mass movement  and i n highway d e s i g n i n  A summary  of terrain  o f the importance t o  a n a l y s i s i n understanding  and i n e v a l u a t i n g s l o p e s t a b i l i t y  and H e n d r o n  i s g i v e n by  (19 74)  A h i e r a r c h y o f i n f o r m a t i o n which i s l i n k e d analysis  unit.  use o f t h e i n f o r m a t i o n .  e n g i n e e r i n g and g e o g r a p h i c  use o f t e r r a i n  forerunner  Attributes  h a v e b e e n made f o r s t o r a g e o f t e r r a i n  e m p h a s i s on d i f f e r e n t The  o f these  A  classification  use o f t h e system.  s h o u l d be f u n d a m e n t a l t o t h e d e s c r i p t i o n  Patton  The  a r e t o be  chosen t o c h a r a c t e r i z e the t e r r a i n  l a r g e number o f a t t r i b u t e s  The  components  i n the c l a s s i f i c a t i o n .  Attributes be  identification,  and e v a l u a t i o n o f t e r r a i n  1977, p . 28; S p e i g h t ,  task i s determining  stages which a r e  These a r e the d e t e c t i o n ,  classification  (Verstappen,  involves five  i s shown i n T a b l e  3.1.  to terrain  A t t r i b u t e s a r e used t o i d e n t i f y  43  ORDER  1  high  generalization and internal variability  HIERARCHICAL COMPONENTS  EXAMPLES IN THE TERRAIN  RECURRENT LANDSCAPE PATTERN or TOPOSEQUENCE  1. rock scarp: c o l l u v i a l f l u v i a l terrace  TERRAIN UNIT  2. g u l l y : a l l u v i a l fan: f l u v i a l terrace: f l u v i a l p l a i n 1. c o l l u v i a l  apron  2. f l u v i a l terrace 3. a l l u v i a l fan  low  Table 3.1  ATTRIBUTE or TERRAIN FACTOR The hierarchy of t e r r a i n  apron:  1. slope  angle  2. material texture 3. material genesis Information.  44  and d e f i n e the t e r r a i n u n i t s , which commonly occur i n characteristic associations. r e l a t i o n s and patterns  These may  be l i n e a r or a r e a l  are c a l l e d toposequences, or r e c u r r e n t landscape  (Speight, 1968,  1976;  Beckett and Webster, 1965) .  At b e s t , those a t t r i b u t e s chosen to d e f i n e t e r r a i n u n i t s can only be a subset of the t o t a l number of f a c t o r s landform  configuration.  determining  D i f f i c u l t y a r i s e s i n s e l e c t i n g the  a t t r i b u t e s which c o n t r i b u t e most s i g n i f i c a n t l y t o the d e f i n i t i o n of the t e r r a i n u n i t .  The  development of  terrain  c l a s s i f i c a t i o n systems f o r uses other than geographic i n f o r m a t i o n storage d e r i v e s from two major  sources:  - the problem of choosing a t t r i b u t e s which adequately d e f i n e t e r r a i n c h a r a c t e r and g i v e s p e c i f i c i n f o r m a t i o n t o the user, simultaneously, and - the i n a b i l i t y of the c l a s s i f i c a t i o n designer to s p e c i f y and i s o l a t e the c r i t i c a l requirements of the user. In a geographic sense, t e r r a i n c l a s s i f i c a t i o n has been developed and used to s t o r e s p a t i a l r e l a t i o n s of u n i t s , p r i m a r i l y c a t e g o r i z e d by morphometric, g e n e t i c , l i t h o l o g i c ,  and  hydrologic variables. Where the user's  requirements are s t r a i g h t f o r w a r d t e r r a i n  c l a s s i f i c a t i o n i s most s u i t a b l e . evaluated  Desert t e r r a i n has  been  f o r m i l i t a r y v e h i c l e t r a f f i c a b i l i t y , u s i n g slope  as the major c r i t e r i o n  (Beckett and Webster, 1965).  angle  In  e n g i n e e r i n g p r a c t i c e , however, the demand f o r d e t a i l e d i n f o r mation has o f t e n demonstrated the inadequacies classification. engineer  of  terrain  T h i s p a r t l y stems from the i n a b i l i t y of  the  to d e f i n e h i s requirements i n q u a n t i t a t i v e form w i t h i n  45  a c l a s s i f i c a t i o n framework.  Also.,-  " i t must not be  assumed  t h a t , because a t e r r a i n c l a s s i f i c a t i o n e x i s t s as an  apparently  l o g i c a l s u b d i v i s i o n i n nature, i t n e c e s s a r i l y have any : s i g n i f i c a n c e to an engineer" The  ( A i t c h i s o n and  storage of t e r r a i n i n f o r m a t i o n  Grant, 1968,  p.  40).  via a classification  system i s most f u n c t i o n a l when the number of c l a s s e s i s reasonable f o r data p r o c e s s i n g  and  subsequent assessment,  and  when, f o r each category, a wide range of g e n e r a l i z a t i o n s  can  be made (Speight,  The  1968,  p. 162;  M i t c h e l l , 1973,  p. 27).  number o f c l a s s e s i s determined by the complexity o f  the  t e r r a i n and by the a t t r i b u t e s chosen t o c h a r a c t e r i z e  it.  The  i d e a l r e s u l t i s a small number of c l a s s e s with i n t e r n a l homogeneity  and minimal o v e r l a p  T h i s perhaps shows the for engineering  use:  (Speight,  1976,  p. 162) .  l i m i t a t i o n s of t e r r a i n c l a s s i f i c a t i o n s  that generalized  t e r r a i n c l a s s e s do  not  n e c e s s a r i l y i s o l a t e s p e c i f i c v a r i a b l e s necessary f o r an assessment of s u i t a b i l i t y f o r a p a r t i c u l a r land use. this generalized important f i r s t  Rather,  s u b d i v i s i o n of t e r r a i n should be viewed as step i n e n g i n e e r i n g  (and other)  studies,  f a c i l i t a t i n g p r e c i s e f o c u s s i n g of subsequent g e o t e c h n i c a l For  an  example, The budget f o r b u i l d i n g or m a i n t a i n i n g (a t r a n s p o r t a t i o n route) must be spread t h i n l y . I t w i l l be q u i t e unusual f o r a p a r t i c u l a r l o c a t i o n to be the s u b j e c t o f . . . a thorough study...Under these circumstances d e a l i n g w i t h rock slopes on t r a n s p o r t a t i o n routes i s as much an a r t as a s c i e n c e . . . g e o t e c h n i c a l competence tempered with common sense and experience must be combined with a r e a l i s t i c a p p r a i s a l of economics to p r o v i d e an a c c e p t a b l e l e v e l of s a f e t y to the u s e r . . . (Peckover and Kerr, 1977, p. 488) . -  studies.  46  S e v e r a l approaches to t e r r a i n c l a s s i f i c a t i o n have emerged w i t h changes i n technology and s p e c i f i c a t i o n s of usage.  Terrain  u n i t s u s u a l l y r e f l e c t n a t u r a l l y o c c u r r i n g elements d e f i n e d by t h e i r geomorphic  character.  A l t e r n a t i v e l y , u n i t may  be  superimposed onto the t e r r a i n w i t h i n which a p a r t i c u l a r a t t r i b u t e , o r s u i t a b i l i t y f o r a s p e c i f i c l a n d use, i s d e f i n e d . In the s o - c a l l e d landscape approach, the t e r r a i n  unit,  i d e n t i f i e d v i s u a l l y as b e i n g separate from i t s n e i g h b o r i n g u n i t s , i s the b a s i s o f the c l a s s i f i c a t i o n system  (Mabbutt, 196 8).  The u n i t i s i d e n t i f i e d on the b a s i s of form and m a t e r i a l a t t r i b u t e s , and w i t h i n i t the v a r i a t i o n i n these a t t r i b u t e s i s small.  These are then c l a s s i f i e d i n t o a c o m b i n a t o r i a l h i e r a r c h y  of groups w i t h i n c r e a s i n g g e n e r a l i z a t i o n and  internal  variability. T h i s approach has come about as a r e s u l t of i n t e r e s t i n t e r r a i n at r e g i o n a l and l o c a l s c a l e s , not c o n t i n e n t a l and g l o b a l ones, and o f improved methodology measuring landform c h a r a c t e r .  with respect to  In p a r t i c u l a r , the use o f a i r  photographs and t h e i r i n t e r p r e t a t i o n i n g i v i n g an overview o f the area o f i n t e r e s t , and from which s p e c i f i c s p a t i a l and morphometric  i n f o r m a t i o n may  p o p u l a r i z e t h i s approach.  be e a s i l y a c q u i r e d , has s e r v e d t o  The p r a c t i c a l outcome has been maps  of the morphologic c h a r a c t e r o f t e r r a i n at the l o c a l and r e g i o n a l s c a l e s , the c l a s s i f i c a t i o n t y p i c a l l y based on the process o f landform development  attributes  ( F i g . 3.1 a,b).  The p a r a m e t r i c approach t o c l a s s i f i c a t i o n has been  promoted  by engineers whose demand i s f o r s i t e - s p e c i f i c , r a t h e r than  47  MORPHOLOGICAL  MAPPING  SYMBOLS (a)  "V  V  V~ Angular convex break of slope  v  v  v  Angular concave break of Mope  ~V  V  V~  Smoothly convex change of slope  V  V  v_  Smoothly concave change of slope  6  Angle of slope (degrees) Cliffs (bedrock, 40* or more)  TTl l l II IT 11 M Breaks of slope  TT  I  T T~ Changes of slope  ^  |  Convex and concave too close together to allow the use of separate symbols  » . Convex slope unit  «*• Concave slope unit  (b) MORPHOLOGY Steepness of slope (degrees)  BREAKS OF SLOPE  -tj  ^  ^- C o n v e x Concave  C H A N G E S OF SLOPE -V---V--V- C o n v e x  S m a l l scarp w-w- Free face Incised g u l l e y  dkm  Fig.  3.1  (a) I l l u s t r a t i o n o f symbols used i n m o r p h o l o g i c a l mapping (from Cooke and Doornkamp, 197^, p . 3 5 8 ) . (b) M o r p h o l o g i c a l map o f an area near Johannesburg (from Cooke and Doornkamp, 1 9 7 ^ , p . 3 5 9 ) .  48  general, t e r r a i n information.  A c c o r d i n g l y , the c l a s s i f i c a t i o n  o f t e n depends on a narrow range o f chosen f a c t o r s , such as ;  s o i l c l a y content, size.  slope angle, o r s u r f a c e m a t e r i a l p a r t i c l e  While t h i s approach i s s u i t a b l e f o r some s i t u a t i o n s i t s  p r a c t i c a l use i s narrower and l e s s f l e x i b l e than other methods of  classification. The  landscape approach to t e r r a i n c l a s s i f i c a t i o n  storage o f a wide range o f geomorphic v a r i a b l e s .  permits  Little  attempt has been made, however, t o examine the r e l a t i o n s h i p of geomorphic t e r r a i n a t t r i b u t e s t o slope f a i l u r e  incidence.  T h e o r e t i c a l slope s t a b i l i t y concepts address the l i k e l i h o o d o f f a i l u r e i n s m a l l l a b o r a t o r y samples o f m a t e r i a l , or a t particular locations.  Parameters determining  s t r e n g t h a t t h i s s m a l l s c a l e (or m i c r o - s c a l e ) stood.  A t the r e g i o n a l s c a l e , surrogates  the m a t e r i a l are w e l l under-  f o r the m i c r o - s c a l e  parameters are necessary.  SLOPE STABILITY Micro-Scale The  Concepts  e a r l i e s t equation  m a t e r i a l was presented  d e s c r i b i n g the s t r e n g t h o f dry  by Coulomb i n 1776, and had the form,  s = c + CT tan 0 ,  where s i s the m a t e r i a l shear s t r e n g t h , c i s the cohesion,& i s the normal s t r e s s component o f weight, W o f the m a t e r i a l o v e r l y i n g the f a i l u r e plane, and 0 i s the angle o f s h e a r i n g r e s i s t a n c e  49  (Coulomb, 17 76).  When groundwater i s present  i n f i s s u r e s or  pores i n the m a t e r i a l , an o m n i d i r e c t i o n a l h y d r o s t a t i c jU., i s exerted  on the s o l i d components  s u r f a c e s ) , which serves  pressure,  (rock faces or p a r t i c l e  t o reduce the shear s t r e n g t h .  The  new  form of the equation i s  s = c  1  = c  where  LCf-JLL)  1943), and  = 0"  c' and  1  +  (CT  +  tan 0  -JUL)  CV tan 0  1  1  ,  i s the e f f e c t i v e normal s t r e s s  tan 0  1  (Terzaghi,  are the e f f e c t i v e cohesion  and  e f f e c t i v e angle of i n t e r n a l f r i c t i o n , of which the values changed from the dry c o n d i t i o n due The  preceding  have  t o the e f f e c t of water.  equations were developed f o r s o i l and  of which the s t r e n g t h has been t e s t e d by a r t i f i c i a l imposed along a h o r i z o n t a l f a i l u r e s u r f a c e .  rock  shearing  In s l o p i n g s i t u a t i o n s ,  the normal s t e s s component, (X , i s not e q u i v a l e n t  t o the weight  of the o v e r l y i n g m a t e r i a l as d i s c u s s e d p r e v i o u s l y , but i s reduced by a f a c t o r determined by the slope angle  itself:  CT = W cos oc  where oc i s the angular d e v i a t i o n of the f a i l u r e plane from the horizontal.  The  o v e r a l l shear s t r e n g t h equation becomes,  s = c' +  (W cos oc  -JUL)  tan ^  1  50  i n moist c o n d i t i o n s , whereby (W cos oc -JUL) = CS ' i s the e f f e c t i v e normal s t r e s s . The  s t r e n g t h o f m a t e r i a l i s i n t e r p r e t e d as the upslope  force counterbalancing  downslope d i s t u r b i n g f o r c e s .  i s termed the shear s t r e s s , T  This  latter  , and i s p r o p o r t i o n a l t o the  weight, W, of the u n d e r l y i n g m a t e r i a l , and t o the i n c l i n a t i o n of the f a i l u r e  plane:  X  = W s i n oc  The m a t e r i a l remains s t a b l e when the shear s t r e n g t h , s, exceeds the shear s t r e s s , *"C / and becomes l e s s s t a b l e as s t r e n g t h decreases and X—•  s.  Parameters i n the t h e o r e t i c a l s t r e n g t h equation widely  i n nature,  and are measured i n l a b o r a t o r y or f i e l d t e s t s  on very s m a l l samples. micro-scale The due  vary  Here, they are c o n s i d e r e d  t o be  variables.  cohesion  term, c, i s a measure o f m a t e r i a l  t o a t t r a c t i v e f o r c e s o r chemical  bonding.  strength  In unconsolidated  m a t e r i a l s c o n t a i n i n g c l a y - s i z e d p a r t i c l e s , t h i s component o f shear s t r e n g t h i s seen t o i n c r e a s e with porewater content  to a  s p e c i f i c maximum p o i n t , and then decrease d r a s t i c a l l y as i n t r a - p a r t i c u l a r e l e c t r o c h e m i c a l bonds are broken. the cohesion  component i n c o a r s e r - g r a i n e d  s m a l l , r e g a r d l e s s o f water content. cohesiveness r e s u l t s from chemical i s very  high.  The value o f  materials i s relatively  I t i n t a c t bedrock, bonding and cementation, and  51  Both rock and u n c o n s o l i d a t e d m a t e r i a l s are seen t o have c h a r a c t e r i s t i c f r i c t i o n components d i c t a t e d by t h e i r nature, or by s i z e and g r a d a t i o n of p a r t i c l e s ,  crystalline  respectively.  For shear f a i l u r e to occur, c r y s t a l s i n rock and g r a i n s i n s o i l must move past one another. immediately friction,  Two  aspects of f r i c t i o n  are  recognized; the i n t e r - c r y s t a l l i n e or i n t e r - g r a n u l a r  and the " f r i c t i o n " of volume i n c r e a s e necessary  e f f e c t shear.  Together  shearing resistance, $  these f a c t o r s determine  to  the angle of  , which i s dependent on p a r t i c l e shape,  s o r t i n g , packing, d e n s i t y , water content, and normal s t r e s s i n u n c o n s o l i d a t e d m a t e r i a l , and on c r y s t a l s t r u c t u r e , and cementation  jointing,  i n bedrock.  F u r t h e r d i s c u s s i o n of s t r e n g t h of rock s l o p e s i s found i n Hoek and Bray Peck  (1974), and of s o i l s t r e n g t h i n T e r z a g h i and  (1967).  Surrogate V a r i a b l e s a t Meso- and M i c r o - S c a l e s Of the many f a c t o r s known t o a f f e c t slope s t a b i l i t y , some may  be measured reasonably w e l l a t a s i t e w h i l e others may  Problems a r i s e a t a given sampling  not.  l o c a t i o n when,  i ) data must be e x t r a p o l a t e d from t h a t p o i n t t o r e p r e s e n t a l a r g e r area, ii) iii) Although  a t t r i b u t e s vary c o n s i d e r a b l y over time seasonal, h i s t o r i c , g e o l o g i c ) ,  (diurnal,  r e l e v a n t a t t r i b u t e s are i n c o r r e c t l y measured or are o v e r l o o k e d . the geomorphologic and e n g i n e e r i n g emphasis has been  on q u a n t i t a t i v e measurements and c a l c u l a t i o n s , T e r z a g h i notes that,  52  I f a s t a b i l i t y computation i s r e q u i r e d under these c o n d i t i o n s , i t i s n e c e s s a r i l y based on assumptions which have l i t t l e i n common w i t h reality. Such computations do more harm than good because they d i v e r t the d e s i g n e r ' s a t t e n t i o n from the i n e v i t a b l e b u t important gaps i n h i s knowledge o f the f a c t o r s which determine the s t a b i l i t y o f s l o p e s . ( T e r z a g h i , 1962, p. 252) The forementioned f a c t o r s o f normal  stress,  porewater  pressure, angle o f s h e a r i n g r e s i s t a n c e , and cohesion, are the b a s i c m i c r o - s c a l e components o f s t r e n g t h o f m a t e r i a l a g a i n s t shearing.  I t i s c o s t l y and time-consuming  parameters  throughout  large areas.  t o e v a l u a t e these  Some o f the many q u a l i t a t i v e  aspects o f t e r r a i n which i n f l u e n c e the shear s t r e n g t h and can be used i n s t a b i l i t y a n a l y s i s o f m a t e r i a l i n s l o p e s a t the r e g i o n a l or me_so-scale  are b r i e f l y reviewed below.  1.  Bedrock geology, s t r u c t u r e and metamorphic history; the m i n e r a l o g i c components o f rock, i t s d i p and s t r i k e , l o c a l f o l d i n g , i n t r a - and i n t e r - c r y s t a l l i n e s h e a r i n g , displacement a l o n g s t r a t a , degree o f metamorphic a l t e r a t i o n and weakening, nature o f weathering p r o d u c t s  2.  F a u l t i n g and j o i n t i n g ; degree o f displacement along f a u l t s , nature o f the f a u l t z o n e , d e n s i t y o f p r i n c i p a l and " s p l i n t e r " f a u l t s , c l o s e n e s s o f j o i n t i n g , a t t i t u d e o f p r i n c i p a l and secondary j o i n t s e t s , i n t e r l o c k i n g o f j o i n t b l o c k s , degree o f i n - f i l l i n g o f j o i n t s by d e b r i s , a c t i o n o f groundwater i n j o i n t s i n i n c r e a s i n g j o i n t spacing, f i s s u r e s , t e n s i o n cracks  3.  Texture o f s u r f i c i a l geology; p a r t i c l e s i z e , g r a d a t i o n , a n g u l a r i t y , mode o f d e p o s i t i o n , degree o f s t r a t i f i c a t i o n , cementation, p o r o s i t y , permeability, i n f i l t r a t i o n rate, susceptability to expansion by water or i c e  4.  Slope geometry; o v e r a l l angle and aspect o f the s l o p e , v a r i a t i o n s i n angle over the s l o p e ,  53  breaks o f s l o p e , c o n v e x i t y - c o n c a v i t y , u n d e r c u t t i n g of the slope base by f l u v i a l or anthropogenic forces 5.  Drainage c h a r a c t e r ; p a t t e r n and d e n s i t y o f stream channels, presence o f i n f i l t r a t i o n zones on upper s l o p e s , p o o r l y d r a i n e d areas  6.  Anthropogenic i n f l u e n c e ; changes i n many o f the forementioned f a c t o r s as a r e s u l t o f Man's activities  The  s t a t u s o f slopes i s a t t r i b u t e d t o a d e l i c a t e balance  s t r u c k amongst the f a c t o r s a l r e a d y mentioned.  Some f l u c t u a t i o n  i n micro- and meso-scale f a c t o r s f r e q u e n t l y occurs w i t h i n a slope with no outward change i n i t s form.  Alternatively, a  very small change i n one (or more) o f these a t t r i b u t e s might suddenly e f f e c t slope f a i l u r e , t h r e s h o l d i n the balance been a t t a i n e d .  i n d i c a t i n g t h a t a geomorphic  o f slope-determining  f a c t o r s had  T h i s type o f t h r e s h o l d may be c r o s s e d whether  o r not f a c t o r s e x t e r n a l t o the slope v a r i a b l e s ) are f l u c t u a t i n g .  ( i . e . macro-scale  When f a i l u r e occurs due t o s t i m u l u s  by a macro-scale v a r i a b l e , an e x t r i n s i c t h r e s h o l d has been exceeded. ...the t h r e s h o l d e x i s t s w i t h i n the system but w i l l not be crossed and change w i l l n o t occur without the i n f l u e n c e of an e x t e r n a l variable (Schumm, 19 73). Superimposed on the meso- and m i c r o - s c a l e  f a c t o r s are  c o n t i n u a l l y v a r y i n g macro-scale v a r i a b l e s ; c l i m a t e and s e i s m i c activity.  The long-term c r e d i b i l i t y o f q u a l i t a t i v e and q u a n t i -  t a t i v e s t a b i l i t y assessments, based s o l e l y on i s o l a t e d measurements o f slope s t r e n g t h a t t r i b u t e s , must t h e r e f o r e be questioned.  54  The  e f f e c t of c l i m a t e i s exerted v i a temperature  precipitation.  The  and  l a t t e r c o n t r o l s the amount of groundwater  available for i n f i l t r a t i o n  i n t o s o i l or bedrock s l o p e s .  F a i l u r e s occur most f r e q u e n t l y d u r i n g p e r i o d s of h i g h groundwater recharge,  e s p e c i a l l y f o l l o w i n g snowmelt i n s p r i n g  heavy r a i n s i n autumn (Dunne and Leopold, 1976,  p. 290;  Bjerrum and J o r s t a d , 1968,  zones, these p e r i o d s are a s s o c i a t e d with i n temperature about the f r e e z i n g p o i n t Bjerrum and J o r s t a d , 1968, b u i l d u p of i n t e r s t i t i a l unconsolidated  p. 2 ) .  fluctuation  ( P i t e a u , 1977,  p.  103;  These c y c l e s cause the  along j o i n t s and  Bjerrum and  J o r s t a d , 1968,  rock  faces  fissures p.  f o r the F r a s e r Canyon, as w e l l as  monthly t o t a l number of r o c k f a l l s recorded  by  (Carson  2).  shows the average monthly temperature  p r e c i p i t a t i o n curves  Luckman,  In temperate  frequent  m a t e r i a l by i t s expansion, and  and Kirkby, 1972;  p. 566;  i c e which i s thought to weaken  i n c r e a s i n g outward p r e s s u r e  F i g u r e 3.2  p. 2 ) .  1978,  and  and the  along the Canadian  N a t i o n a l Railway.  F i g u r e 3.3  events at Ferrabee  B l u f f s between Black Canyon and H e l l ' s Gate  i n the F r a s e r Canyon.  The  d e p i c t s the s e a s o n a l i t y of  i n c i d e n c e of events i s seen to be  h i g h e s t when mean temperature i s roughly and p r e c i p i t a t i o n i s h i g h . interstitial to  T h i s i s due  a t the f r e e z i n g l e v e l , to the b u i l d u p  of  i c e i n rock j o i n t s d u r i n g freeze-thaw c y c l e s leading  a high t o t a l water content,  and to the c o n t i n u i n g supply  water v i a p r e c i p i t a t i o n to feed the p r o c e s s .  Scandinavia.  of  Similar d i s t r i -  b u t i o n and e x p l a n a t i o n appears i n a study by Rapp (19 61) northern  failure  in  55  80  r  X •70  (T60  UJ 0_  CO 50  ^ 3 0  o z  20r-  10  2 p 10  P i g . 3.2  II  12  Mean monthly temperature and p r e c i p i t a t i o n , and t o t a l monthly i n c i d e n c e o f r o c k f a l l s , between 1933 and 1970 (from Peckover and K e r r , 1 9 7 7 , p . 4 9 0 ) .  56  1966  Fig.  3.3  1967  1968  1969  1970  S e a s o n a l i t y o f movement on rock slopes at Ferabee B l u f f s , near H e l l ' s Gate, between 1966 and 1971 (from Peckover and K e r r , 1 9 7 7 , P. 4 9 0 ) .  57  The r o l e of s e i s m i c shock i n t r i g g e r i n g slope has been documented e x t e n s i v e l y .  failure  In North America, where  s e i s m i c a c t i v i t y i s r e l a t i v e l y low, the e f f e c t has been noted i n a l a n d s l i d e i n 1959 at Madison Canyon, Montana, i n the 196 5 Hope l a n d s l i d e , B r i t i s h Columbia, and i n m u l t i p l e  smaller  l a n d s l i d e s on Vancouver I s l a n d f o l l o w i n g an earthquake i n 1946 (Hadley, 1978; Skermer, 1976; Mathews and McTaggart, 1969,  1978;  Mathews, 1979). C o a s t a l B r i t i s h Columbia experiences moderate activity.  seismic  S e v e r a l major quakes have o c c u r r e d i n the Queen  C h a r l o t t e I s l a n d s t o Puget Sound trough (Skermer, 19 76, p. 6, a f t e r Gutenberg and R i c h t e r ) .  Zones e a s t of the Coast  Mountains are found t o be of minor s e i s m i c i t y .  Thus; the F r a s e r  Canyon, l y i n g a t the j u n c t i o n o f these two r e g i o n s , i s thought to experience r e l a t i v e l y l i t t l e  significant activity.  While  the canyon i s l o c a t e d along a major f a u l t system, i t l i k e l y has not been s u b j e c t e d t o major movement s i n c e the l a t e Eocene epoch (Monger, 1970, p. 54), though may have been a c t i v e more r e c e n t l y  ( D u f f e l l and McTaggart, 1952, p. 89).  In S c a n d i n a v i a where s e i s m i c a c t i v i t y i s low a l s o , the e f f e c t of c l i m a t i c v a r i a b l e s i s assumed t o be of much g r e a t e r importance  (Rapp, 1961, p. 109).  The i n t e r - r e l a t i o n o f micro-, meso- and macro-scale v a r i a b l e s as reviewed p r e v i o u s l y i s shown i n F i g u r e  3.4.  CASE STUDIES The micro-, meso-, and macro-scale a t t r i b u t e s p r e v i o u s l y  58  SEISMICITY]  Texture of Unconsolidated Material  Lithology^  Slope Geometry  Jointing, Faulting  Anthropogenic Influence  I  shear  stress Jj e f f e c t i v e * cohesion effective normal stress hydrostatic pressure  angle of shearing resistance K  p  i £ . 3 . H | I n t e r - r e l a t i o n of_ micro-,'meso-, and macro-scale slope s t a b i l i t y variables .  59  d e s c r i b e d have been used i n many s t u d i e s o f g e o g r a p h i c a l , g e o l o g i c a l , and g e o t e c h n i c a l nature, here.  some o f which are reviewed  In p a r t i c u l a r cases, h i s t o r i c records have been used  to extend the data base.  For example, i n f o r m a t i o n on g l a c i a l  advance and r e t r e a t i n the Mont Blanc  area has been  from h i s t o r i c a l t i t h e records maintained century  gathered  s i n c e the s i x t e e n t h  (Grove, 1966, p. 129). While i t i s r a r e t o d i s c o v e r  so long a r e c o r d , i t i s not unusual to f i n d obscure but sound documentation o f c l i m a t i c o r geomorphic phenomena from which an i d e a o f the dynamics o f the system may be  gleaned.  For n e a r l y t h i r t y y e a r s , Anders Rapp has been i n v e s t i g a t i n g geomorphic processes range o f methods. and  frequency  on slopes i n Scandinavia  u s i n g a wide  The o b j e c t i v e i n r e c o r d i n g type,  o f slope f a i l u r e i s the q u a n t i t a t i v e  of mass movement i n mountainous t e r r a i n .  location, understanding  T h i s i s approached  by the d e t a i l e d q u a l i t a t i v e and q u a n t i t a t i v e d e s c r i p t i o n o f rockfalls,  l a n d s l i d e s and d e b r i s movement.  A f t e r c a r e f u l t e r r a i n mapping and i n v e n t o r y o f f a i l u r e events,  Rapp (1961) i n v e s t i g a t e d , i ) the r o l e o f temperature f l u c t u a t i o n s on material strength,  ii) iii)  the r a t e o f r e t r e a t o f rock w a l l s , the geomorphic e f f e c t o f s l u s h and snow avalanches  iv) d e b r i s movement, and v) slow downslope movement o f t a l u s and s o i l . In order t o extend the f a i l u r e frequency  r e c o r d beyond the  scope o f h i s own i n v e s t i g a t i o n s , Rapp used maintenance  records  60  from s e v e r a l nearby r a i l w a y l i n e s which add as much as years t o h i s own  observational data.  thirty  From these he noted  s p a t i a l d i s t r i b u t i o n of s l o p e s with frequent i n s t a b i l i t y as w e l l as the temporal factors  the events,  r e l a t i o n of f a i l u r e s to c l i m a t i c  (Rapp, 1961, p. 104-106) .  The d i s t r i b u t i o n of r o c k f a l l s i n Norway has been mapped and r e l a t e d t o bedrock and p o s t - g l a c i a l unloading e f f e c t s ; i t i s found t h a t v a l l e y s i n metamorphic rock have experienced oversteepening d u r i n g g l a c i a l p e r i o d s and c u r r e n t l y the h i g h e s t r o c k f a l l frequency p. 1 ) .  Although  exhibit  (Bjerrum and J o r s t a d , 19 68,  the bedrock i s g e n e r a l l y competent i t exper-  iences j o i n t i n g and s p a l l i n g where i t i s exposed along the steep v a l l e y w a l l s , as w e l l as o c c a s i o n a l deepseated of  large extent.  Thus the r e g i o n a l i z a t i o n of f a i l u r e events i s  r e l a t e d t o geology,  slope morphology and g l a c i a l  In North America,  history.  most work on rock slope s t a b i l i z a t i o n  has been connected w i t h a r t i f i c i a l l y mines.  landslides  cut slopes i n open-pit  Steep mountain t e r r a i n i n Canada i s s p a r s e l y populated  and has not commanded the c o n c e n t r a t e d i n t e r e s t t h a t i t has i n Norway.  However, s t u d i e s have been made of s p e c i f i c  locations,  g e n e r a l l y a s s o c i a t e d w i t h t r a n s p o r t r o u t e s , o f which s e v e r a l have been c a r r i e d out i n the F r a s e r Canyon. The t r a c k of the Canadian N a t i o n a l Railway bank of the F r a s e r R i v e r Canyon.  Because i t was  f o l l o w s the e a s t the  second  r a i l w a y c o n s t r u c t e d along t h i s r o u t e , i t occupies the more d i f f i c u l t and p r e c i p i t o u s s i d e of the canyon. R e l a t i v e l y sound records have been maintained of the l o c a t i o n and  frequency  61  of slope  f a i l u r e s which i n some way  have a f f e c t e d the  company's  right-of-way. In 1972,  a c o n s u l t i n g engineer was  retained  "to determine  the c o n t r o l l i n g f a c t o r s which l e a d to i n s t a b i l i t y of the along the C.N.R. and  slopes  to e v a l u a t e the q u a n t i t a t i v e as w e l l  as  q u a l i t a t i v e s i g n i f i c a n c e of these f a c t o r s i n terms o f p o t e n t i a l i t y of f u t u r e s t a b i l i t y problems" Ensuing work between Hope and l o c a t i n g and be  Lytton,  mapping landforms and  l i n k e d i n a slope  ( P i t e a u , 1973,  B r i t i s h Columbia;,  slope  conditions  s t a b i l i t y assesment.  Piteau  p. 1) . included  that  could  investigated:  i ) aspects of slope morphology; mean slope of the canyon w a l l s , i n d i c a t i o n of mass movement i n the form o f l a n d s l i d e s c a r s , d e b r i s s l i d e s , avalanche t r a c k s , a l l u v i a l fans, abandoned r i v e r channels i i ) F r a s e r R i v e r channel geometry and form; l a r g e s c a l e bends, anomalous bulges i n the plan-form of the channel iii)  slope and f l u v i a l process i n d i c a t o r s ; l a t e r a l and v e r t i c a l e r o s i o n , degradation, aggradation  i v ) e m p i r i c a l slope f a i l u r e i n f o r m a t i o n ; l o c a t i o n o f events Other aspects which were considered  date  and  but not used i n the  final  s t a t i s t i c a l a n a l y s i s were r e g i o n a l f a u l t i n g , s t r u c t u r a l geology, l i t h o l o g y and  s u r f i c i a l material, g l a c i a l e f f e c t s , climatic  v a r i a b l e s , groundwater e f f e c t s and Using the i n f o r m a t i o n t h a t slope  anthropomorphic changes.  mentioned above, P i t e a u  f a i l u r e occurrence was  determined  c l o s e l y r e l a t e d to dynamic  aspects of r i v e r channel c o n f i g u r a t i o n .  Where the channel  been c o n s t r i c t e d by a p o s t - g l a c i a l l a n d s l i d e or f o r c e d the opposite  bank by  had  against  impingement o f a t r i b u t a r y a l l u v i a l  fan,  62  the  incidence  This  was  slopes  of  attributed  by  the  changed.  outside  bank  The  of  the  River  a  as  the  the  and  bends  railway  was  s t a t i s t i c a l  was  high.  oversteepening  l a t e r a l  undercutting  river  of  along  undercutting  Similar  results  position  on  slopes  of  of  these  i t s  above  the  suggested. analysis  of  f a i l u r e  frequency  were, i)  that  between  the fa the v a areas river ii)  that  86%  failures occurred iv)  associated  with  the  planation  i s  controlled. b i l i t y ,  and  Hope,  66%  of  a l l  of  of  oston Bar and Y a l e (roughly) t h e c u r r e n t s t u d y a r e a ) , 6 4% occurred along the 3 8% o f the opposite a l l u v i a l fans and  the  t o t a l  number  of  slope  recorded (these included snowslides) i n the w i n t e r months, and  t h a t the e f f e c t o f a l l u v i a l f a n and river b e n d l o c a t i o n on t h e f r e q u e n c y of slope f a i l u r e s was c o n s i d e r a b l y l e s s i n the reach between Boston Bar and Y a l e than to the north or south.  explanation  In  Lytton  ilure incidents occurred along 31% lley length, s p e c i f i c a l l y i n those opposite a l l u v i a l f a n s and outside bends,  that between B equivalent to of a l l events canyon length river bends,  i i i )  No  failures  to  Fraser  channel  data  slope  the  the  canyon,  100  feet  and  a c t i v i t y  (30  was  made  of  a l l u v i a l  canyon  events  fans  between  or  river though  large  does  not  v e r t i c a l  m)  i n  of  a l l u v i a l  river  Boston  u n s a t i s f a c t o r y as Despite  occurring  Bar  the  load  fans  i n  time. the  has  slopes  i s  high  canyon  the are  to  ex-  bedrock-  erosion  l a t e r a l  occurred  Also,  1977).  Piteau's  channel and  not  (Piteau,  Yale,  prominent  scouring  p o s t - g l a c i a l  and  river  sediment exhibit  bends  on  capa-  erosion  i n  a  of  depth  number,  extent  small,"and  i n  the  63  ease o f the two l a r g e s t (at Spuzzum and Y a l e ) , the r i v e r shows l i t t l e  s i g n o f constriction., or d e f l e c t i o n .  channel  The i n f l u e n c e  of channel c o n f i g u r a t i o n on s t a b i l i t y o f these s l o p e s , even c o n s i d e r i n g the lag-time  f o r slope response, seems t o have been  over-emphasized. Due  to a l t e r a t i o n o f the slopes d u r i n g r a i l w a y  the f a i l u r e  construction  f r e q u e n c i e s may not be i n d i c a t i v e o f n a t u r a l  f a i l u r e , but r a t h e r o f t h a t induced s l o p e s o r oversteepening  by a r t i f i c i a l l y  c o l l u v i a l slopes.  cutting, rock  The r e l a t i o n o f  these i n c i d e n t s t o f l u v i a l c o n t r o l s a t the base o f the slope i s not d i r e c t , e s p e c i a l l y over the f i f t y - y e a r time span A l s o , the f a i l u r e records  comprise only those events which  have d i r e c t l y a f f e c t e d the r a i l w a y right-of-way, incomplete.  considered.  and thus i s  These aspects must be taken i n t o account both i n  the P i t e a u study and i n t h i s p r o j e c t .  HAZARD CLASSIFICATION In 19 76 a r e p o r t was made by Colder A s s o c i a t e s t o Canadian P a c i f i c Railway i n which t r a c k s i d e slopes were c l a s s i f i e d according  t o t h e i r hazard t o safe passage o f t r a i n s .  Recommendations as t o the type and amount o f remedial work were i n c l u d e d , based on geology, s u r f i c i a l m a t e r i a l and past bility.  insta-  The r e p o r t was not made a v a i l a b l e t o the w r i t e r but  a s i m i l a r study performed between North Bend and Savona was released.  The c l a s s i f i c a t i o n scheme c o n s i s t e d o f a s e r i e s o f  p r i o r i t y ratings f o r preventive (Table 3.2  a,b);  o r f a i l u r e warning systems  Slopes o r i g i n a l l y c l a s s i f i e d i n t o the most  64  a. PRIORITY RATINGS A  Moderate p r o b a b i l i t y of f a i l u r e of s u f f i c i e n t volume i n the near future to r e s u l t i n derailment  B  i f f a i l u r e undetected.  Some p r o b a b i l i t y of f a i l u r e i n s u f f i c i e n t volume i n the near future to r e s u l t i n derailment  C  i f f a i l u r e undetected.  Moderate p r o b a b i l i t y of f a i l u r e of small volumes which might reach the t r a c k .  D  Moderate p r o b a b i l i t y o f l o c a l i z e d rocks or r o c k f a l l s occurring from extreme c l i m a t i c conditions - very heavy r a i n f a l l or run-off, extreme freeze-thaw c y c l e s .  E  S l i g h t p o s s i b i l i t y of l o c a l i z e d f a i l u r e s under extreme c l i m a t i c conditions.  Note:  Locations with warning fences have been rated 'B'. b. EXAMPLES  Mile*  Rating  99.7  E  Local boulder  99.9 100.1  B  Numerous r o c k f a l l s  -Scale, shotcrete  A  Large wedge f a i l u r e  100.9  D  Boulder f a l l  101.1  C  Local f a l l . One large block  -Scale, deepen d i t c h , remove wedge -Scale boulders, deepen ditches -Dowels, scale  Table 3.2  a) P r i o r i t y r a t i n g s employed by Golder Associates f o r trackside slopes i n the Thompson s u b d i v i s i o n of the Canadian P a c i f i c Railway (Golder Associates, 1976, p.8) b) P r i o r i t y c l a s s i f i c a t i o n applied to slopes, with corresponding remedial s t a b i l i z a t i o n recommendations. •Mileages are measured westward from Savona, B.C. (Golder Associates, 1976, p.3 of Table 2 ) .  P o t e n t i a l Problem fall  Stabilization -Maintain deep d i t c h  65  hazardous category hazard category  'A' a r e r e c l a s s i f i e d i n t o a moderately  lower  'B' as soon as any remedial work i s performed.  The success o f t h i s c l a s s i f i c a t i o n system, which stems from a s u b j e c t i v e assessment o f slopes by experienced engineers, was demonstrated the f o l l o w i n g y e a r .  rock  Of twelve  f a i l u r e s along rock s l o p e s , f i v e o c c u r r e d on slopes i n category  'A', s i x i n 'B , and one i n ' C . 1  u n c o n s o l i d a t e d slopes were not reviewed 1976,  Ten f a i l u r e s on (Colder A s s o c i a t e s ,  p. 6 ) . A study o f rock slopes along t r a n s p o r t a t i o n l i n e s i n  B r i t i s h Columbia was made by Peckover and Kerr  (1977).  They  e v a l u a t e d rock slope s t a b i l i t y and remedial programs and i n c l u d e d a c o s t - b e n e f i t a n a l y s i s o f s a f e t y measures. s t a t i c pressure i n rock j o i n t s  and f r o s t s h a t t e r i n g are  presented as the two most s i g n i f i c a n t slope i n s t a b i l i t y .  Hydro-  f a c t o r s l e a d i n g t o rock-  The paper r e f e r s t o slopes along the  Canadian N a t i o n a l Railway  as w e l l as those adjacent t o highways.  S i m i l a r r e p o r t s have been made i n c o r p o r a t i n g the Canadian P a c i f i c Railway  s l o p e s , by Brawner and W y l l i e (1976), and  Brawner (.197 8) .  Remedial s t a b i l i z a t i o n measures f o r v a r i o u s  types o f slope problem are reviewed. Suggested  forms o f r e m e d i a l work are o f three t y p e s :  - those which would i n c r e a s e the s t a b i l i t y o f the slope - those designed t o p r o t e c t the right-of-way a g a i n s t o b s t r u c t i o n o r damage by f a l l i n g m a t e r i a l , and, - those designed t o g i v e e a r l y warning t o v e h i c l e s approaching an o b s t r u c t i o n caused by a slope failure.  66  The  f o r m e r two  termed p a s s i v e  are a c t i v e measures w h i l e  warning systems  (Peckover  p.  and  Kerr,  1977,  493).  The  effectiveness of preventive  s l o p e work i s d e p e n d e n t  e c o n o m i c and  safety policy,  planning,  of  the  s l o p e s by  size  o f an  unstable  as a s i n g l e will and  not  r e s p o n s i b l e agents,  rock  slope  can  i s not  c a u s e an  n e c e s s a r i l y occur  Kerr,  1977,  e v a l u a t i o n and  p.  504).  expert  and  a good c r i t e r i o n  locations  interaction  routes As  the maintenance o f rock  involves several processes  o u t l i n e d by I)  study  ii)  detailed route,  iv)  study  process  study  formation addresses  a t the  slopes  3.5. along  (1977), t h e s e  of slopes  transport  acquisition.  are:  protions  adjacent  to  the  of conditions at s p e c i f i c  first  attribute  records  of suggestions the  (Peckover  remedial  of information  i n a c c e s s b i l e upper  investigation  v)  Kerr  of maintenance  a p p r a i s a l of of slopes,  iii)  This  P e c k o v e r and  rockfalls  of slope  j u d g e m e n t i n d e c i d i n g on  "the  o f i t s ' danger  "that  s t a b i l i z a t i o n measures i s d e p i c t e d i n F i g u r e Planning  maintenance  recognizing that  at expected The  on  continuous  a c c i d e n t " , and  are  for slope  three  stages  r e g i o n a l , or meso-scale,  sites,  treatment. of the  level.  planning  67  Site  conditions  A n g l e , height, and condition of slopes Size, shape, and soundness of rock Path of rock fall to track Maintenance required  Engineering judgement and economics  Stabilization methods  •  Protection methods  Warning methods  r  •  Scaling, trimming Slope modification Drainage Shotcrete Buttress Rock bolts or dowels Anchored cables or nets Anchored mesh  Fig. 3.5  Roadway relocation Wire mesh blanket Shaped ditch Catchment area Catch net or fence Catch wall Rock shed or tunnel  Electric fence Electric wire Combination with protection  S e l e c t i o n of slope treatment at a s i t e (from Peckover and K e r r , 1 9 7 7 , p . 5 0 5 ) .  68  CHAPTER 4 M E T H O D S  INTRODUCTION The  terrain  Canyon i n v o l v e d i)  field  iii)  o f s l o p e s i n the  Fraser  three stages:  mapping o f t h e  ii)  The  classification  terrain,  verification  and  site  investigation,  and  analysis  methods u s e d  i n a l l three stages are d i s c u s s e d i n t h i s  chapter.  MAPPING OF Air  THE  TERRAIN  photography  and N o r t h Bend was 1:40,000.  The  n o t be  available  o f t h e ! F r a s e r Canyon between Y a l e a t two  1:20,000 p h o t o s  f o r the t e r r a i n to delineate  coverage  1:20,000  were most e x t e n s i v e l y  classification;  large  scales,  t h e 1:40,000 frames  and used were  used  l a n d f o r m s whose b o u n d a r i e s o t h e r w i s e w o u l d  clear.  Because of the g r e a t r e l i e f  exhibited  s e t s were f o u n d t o h a v e c o r r e c t e d  i n the  the  two  and  1:36,000, m e a s u r e d a t a mean e l e v a t i o n o f 1000  above s e a l e v e l . project  are l i s t e d  The Heerbrugg  i n t e r p r e t a t i o n was  The  latter  used  feet  (300  m)  in this  4.1. done w i t h t h e a i d o f a W i l d  d e s k - t o p m i r r o r s t e r e o s c o p e and  stereoscope.  s c a l e s o f 1:19,000  C a t a l o g u e numbers o f p h o t o s i n Table  canyon,  o f f e r s b o t h two-  an Abrams CB-1 and  four-power  pocket  69  scale  flight number  frame numbers  1:20,000  BC7468 BC7470 BC7471 BC7474 BC7475 BC7476 BC7477  J u l y 1973 36-38 16-18; 123-126; 164-167; 228-291 " 14-17; 141-144 " 142-144; 264-266 " " 26-28; 147-149; 200-202 " 270-272 " " 104-107; 139-142; 252-255 " "  .1:20,000  BC5169  188-194 148-154  BC5212  Table 4.1  date  Sept. 1964 II  A e r i a l photography used i n the study.  m a g n i f i c a t i o n and was used i n labwork and i n f i e l d w o r k when increased d e t a i l i n c l a s s i f y i n g  or delineating  surficial  m a t e r i a l was n e c e s s a r y . After i n i t i a l  i n s p e c t i o n o f the a e r i a l photography, the  f i n a l boundaries o f the study area were s e t , extending from the  town o f Yale t o the mouth o f Petch Creek, a d i s t a n c e o f 22  miles  (35 km).  a.s.l.  An a r b i t r a r y a l t i t u d i n a l l i m i t o f 1500 f e e t  (46 0 m) was adopted f o r the t e r r a i n mapping.  from very low-frequency, h i g h magnitude  Except  events, i t i s u n l i k e l y  t h a t m a t e r i a l would be c o n t r i b u t e d t o the t r a c k area from above t h i s  level.  The ELUC T e r r a i n  Classification  A new system o f t e r r a i n d e v i s e d f o r B r i t i s h Columbia.  c l a s s i f i c a t i o n has r e c e n t l y  been  The system, developed i n 1976  by the Environment and Land Use Committee (ELUC) i n V i c t o r i a ,  II  70  was proposed  t o i n c o r p o r a t e t e r r a i n types encountered i n  mountainous and p l a t e a u r e g i o n s o f the p r o v i n c e .  I t was  designed f o r use i n a i r photo i n t e r p r e t a t i o n a t a s c a l e o f 1:50,000 and by i t s nature can e a s i l y be extended t e r r a i n types as w e l l .  I t s intended use i s as "a data base  s u i t a b l e t o land-use p l a n n i n g and management" intro.).  t o other  (ELUC, 1976,  Due t o i t s r e c e n t i n t r o d u c t i o n the ELUC c l a s s i f i c a t i o n  has been a p p l i e d t o a r e l a t i v e l y s m a l l p r o p o r t i o n o f B r i t i s h Columbia  t o date.  The use o f the ELUC c l a s s i f i c a t i o n ranges  from  c o l l e c t i n g and s t o r i n g data f o r i n t e r p r e t a t i o n o f i t s s p a t i a l d i s t r i b u t i o n , t o a s s e s s i n g the t e r r a i n with r e s p e c t t o a s p e c i f i c environmental c h a r a c t e r i s t i c o r t o a p a r t i c u l a r land use (Appendix it  I I ) . An advantage o f the system  i n c l u d e s both morphologic  and g e n e t i c i n f o r m a t i o n , and  allows f o r i n d i c a t i o n o f on-going w i t h i n each mapping u n i t .  i s that  slope and f l u v i a l  These aspects together  processes "generate  an e m p i r i c a l l y - s u p p o r t e d q u a l i t a t i v e g e o l o g i c a l data base f o r both g e o l o g i c a l and m u l t i p l e resource i n t e r p r e t a t i o n s " 19 76,  (ELUC,  intro.). The ELUC system o f t e r r a i n c l a s s i f i c a t i o n was chosen f o r  use i n t h i s study o f the F r a s e r Canyon f o r s e v e r a l reasons. F a m i l i a r i t y with the c l a s s i f i c a t i o n system and w i t h the t e r r a i n i t s e l f maximizes e f f i c i e n c y i n a i r photo i n t e r p r e t a t i o n and minimizes  the need f o r f i e l d v e r i f i c a t i o n .  While  originally  designed f o r use a t a s c a l e of 1:50,000, the system has been found u s e f u l , a t the s c a l e o f 1:20,000 chosen  f o r the F r a s e r  71  Canyon s t u d y . with  The s y s t e m i s f l e x i b l e  which t e r r a i n  terrain properties cation  i s described. described  i n t h e amount o f d e t a i l  Resolution  o f a l l of the  previously within  the  system i s enhanced a t t h e l a r g e r s c a l e .  Two a d d i t i o n s were made t o t h e c l a s s i f i c a t i o n its  usefulness  within  occurring within  The  first  the Fraser  o f these  (-X) s i g n i f i e s  o r road  routes,  f o r m and n a t u r e have b e e n a l t e r e d .  i) ii) iii)  h a s one o f t h r e e  in  f o r slope  modifying  terrain  u n i t s which  and o f which t h e o r i g i n a l  The c o n s t r u c t i o n o f t h e s e  e f f e c t s on s l o p e s :  oversteepening o f the rock s l o p e by i t s e x c a v a t i o n ,  and/or  colluvial  augmentation o f the n a t u r a l slope f i l l , or  by  artificial  c o m b i n a t i o n o f ( i ) and ( i i ) above.  Augmentation o f the slopes support  both  II) .  t r a v e r s e d by r a i l  rights-of-way  t o expand  Canyon s t u d y a r e a ,  the d e s c r i p t i v e terminology  processes,(Appendix  are  classifi-  i s the l e a s t  the Fraser  f o r the purpose o f r a i l w a y  track  common o f t h e s e e f f e c t s o f c o n s t r u c t i o n  Canyon b e c a u s e o f t h e s t e e p  terrain  encountered  there. Secondly, t e r r a i n deforested  u n i t s w h i c h have b e e n  f o r c o n s t r u c t i o n o r l u m b e r i n g p u r p o s e s a r e marked (-Y).  This  i s considered  also  t r a v e r s e d by r o a d s  is  i m p o r t a n t , e s p e c i a l l y where t h e s e (-X) s i n c e t h e e f f e c t  t o reduce the s t r e n g t h  likelihood  artificially  of failure  of deforestation  of surface materials,  (0'Loughlin,  19 7 2 ) .  slopes are  and i n c r e a s e  Because o f t h e  s t e e p n e s s and v e h i c u l a r i n a c c e s s a b i l i t y o f many o f t h e c a n y o n  72  s l o p e s , r e l a t i v e l y few t e r r a i n u n i t s bear t h i s  symbol.  FIELD VERIFICATION AND SITE INVESTIGATION Fieldwork With the photo i n t e r p r e t a t i o n and t e r r a i n  classification  complete, a d d i t i o n a l i n f o r m a t i o n was needed f o r a f u l l d i s c u s s i o n o f slopes i n the study  area.  A f i e l d program was  designed  i n which s e m i - q u a n t i t a t i v e t e r r a i n a t t r i b u t e s were  gathered  from t r a c k s i d e s i t e s a t 0.1 m i l e  (0.16 km)  intervals  along both the Canadian N a t i o n a l Railway and the Canadian P a c i f i c Railway l i n e s .  The spacing o f the sampling p o i n t s i s  c o n s i s t e n t w i t h t h a t used i n t r a c k maintenance records by both r a i l w a y companies.  kept  V e r i f i c a t i o n o f the boundaries  of t e r r a i n u n i t s and s t r a t i g r a p h i c d e t a i l was achieved a t t h a t time.  Slope A t t r i b u t e s as Surrogate The  Variables  slope a t t r i b u t e s were chosen f o r two purposes.  a systematic  First,  i n v e s t i g a t i o n o f slope p r o p e r t i e s i n the f i e l d  y i e l d s r e l i a b l e data on the d e t a i l e d nature  o f the s l o p e s .  For  example, the j o i n t i n g o f bedrock or the e f f e c t o f e x c a v a t i o n of a slope i s not c l e a r from a i r photos. occurrence  The frequency o f  and the d i s t r i b u t i o n " o f slope a t t r i b u t e s augment  i n f o r m a t i o n s t o r e d i n the t e r r a i n  classification.  Second, s i n c e the p r e c i s e e v a l u a t i o n o f m i c r o - s c a l e parameters c o n t r i b u t i n g t o slope form and s t a b i l i t y c o u l d not be measured w i t h i n the scope o f t h i s p r o j e c t , some v i s i b l y  73  a c c e s s i b l e surrogate  a t t r i b u t e s were s e l e c t e d .  The a t t r i b u t e s  were chosen because they are i n d i c a t i v e of slope and  stability,  c o u l d be e v a l u a t e d e a s i l y over the r e g i o n of t h i s  T h e i r value as s t a b i l i t y v a r i a b l e s a t the meso-scale  study. was  investigated. The  complete l i s t of t e r r a i n a t t r i b u t e s , the slope to  which they p e r t a i n , and  t h e i r data sources  appear i n Table  4.2.  Some a t t r i b u t e s are r e t r i e v e d from the t e r r a i n  classification,  and one,  of t h i s  The  bedrock geology, has a..source''outside  study.  a t t r i b u t e s a c q u i r e d i n the f i e l d were s u b d i v i d e d i n t o  v a r i o u s value ranges, some dichotomous, others with m u l t i p l e o p t i o n s , or l e v e l s . angle were used  For example, f i v e c a t e g o r i e s o f  (Table 4.3).  slope  A g e n e r a l i z e d p i c t u r e of the  s p a t i a l r e l a t i o n o f the slope a t t r i b u t e s appears i n F i g u r e The  a t t r i b u t e " c u t s l o p e " was  of the slope adjacent steepening  determined by examination  to the t r a c k f o r s i g n s of b a s a l  by b l a s t i n g , b u l l d o z i n g , or e x c a v a t i o n .  or not the slope was  4.1.  over-  Whether  cut, the m a t e r i a l exposed along the upslope  and downslope s i d e of the t r a c k was  recorded  as the v a r i a b l e  "material". A wide range of maximum s t a b l e slope angles has been p u b l i s h e d f o r slopes i n bedrock and u n c o n s o l i d a t e d  material.  Slopes  i n randomly j o i n t e d c r y s t a l l i n e rock are unstable  angles  g r e a t e r than 70°  may  (Terzaghi, 196 2), though t h i s  at  value  decrease s i g n i f i c a n t l y where j o i n t i n g i s more r e g u l a r  roughly p a r a l l e l to the slope f a c e .  The  bedrock of the  Canyon i s s i m i l a r to t h a t d e s c r i b e d by T e r z a g h i , and the  and  Fraser value  74  Slope A t t r i b u t e  1.  f a i l u r e incidence  2. material  genesis  3.  modifying  k.  bedrock geology  processes  Relevant  trackside and t e r r a i n unit  historical a i r photos a i r photos  t e r r a i n unit  map (Monger, 1970) f i e l d observation  7.  trackside  trackside  S. height of the slope  trackside  9. distance from the track  trackside  f i e l d observation f i e l d observation f i e l d observation f i e l d observation  trackside  f i e l d observation f i e l d observation  trackside  12. seepage  trackside  13. remedial measures  trackside or t e r r a i n unit  Table .4.2  records  t e r r a i n unit  trackside  10. j o i n t i n g 11. fines  Data Source  t e r r a i n unit  5. cutslope 6. material of the cutslope angle  Slope  Slope a t t r i b u t e s considered i n the  study.  f i e l d observation f i e l d observation  75  Slope Attribute  Level  -rock • unconsolidated •rock plus unconsolidated  material exposed alongside the track corresponding to the t e r r a i n unit c l a s s i f i c a t i o n and (or) the e f f e c t of CUTSLOPE angle of the slope adjacent to the track. In rock cuts, 70 i s the angle above which slopes are unstable (Terzaghi, 1 9 6 2 ) . In unconsolidated slopes, 410 i s the maximum slope angle f o r loose material (Evans, 1 9 7 2 ) .  ANGLE  HEIGHT-  study  whether the t e r r a i n unit had been cut into f o r the purpose of construction and thus oversteepened  CUTSLOPE  MATERIAL  Relevance to t h i s  •critical -non-critical • critical  whether material from the upper parts of the slope might be contributed to the track by mass movement  non-critical  whether the trackside slope i s close enough at i t s base to contribute material to the track by mass movement  coarse intermediate fine intact not applicable  degree of f r a c t u r i n g i n the rock faces: "coarse" denotes j o i n t spacing of roughly 20 feet (6 m) , while " f i n e " denotes small blocks and shards (not applicable to unconsolidated slopes)  FINES-  -present •absent not a p p l i c a b l e  whether fine ( s i l t - c l a y ) material was present (not applicable to rock slopes)  SEEPAGE-  -present •absent  whether groundwater seepage was on the slope above the track  DISTANCE"  JOINTING  present REMEDIAL MEASURES absent  seen  whether a c t i o n had been taken to prevent or warn of future f a i l u r e s ( e l e c t r i c warning fences, shotcrete, cement walls, b o l t s , t e r r a c i n g , grading, catchditch, scaling)  Table 4.3 Relevance of slope a t t r i b u t e s measured i n the f i e l d  study.  76  TERRAIN UNIT AIR PHOTO AND MAP SOURCES FIELD SURVEY SOURCE  material genesis, modifying processes, bedrock geology seepage, m a t e r i a l , J o i n t i n g , angle,fines TRACKSIDE SLOPE  r  F i g . 4.1  1  Slope a t t r i b u t e s considered i n the study.  TERRAIN| UNIT  L_  of 70° i s used to segregate ones i n t h i s The  s t a b l e bedrock slopes from unstable  study.  s u r f a c e angle of u n c o n s o l i d a t e d d e p o s i t s depends on  p a r t i c l e s i z e , genesis and s u r f a c e - m o d i f y i n g p r o c e s s e s . underlain  by u n c o n s o l i d a t e d m a t e r i a l s were d i v i d e d i n t o  three c a t e g o r i e s :  those g r e a t e r than  and  l e s s than  41°, and those  30°.  41°, those between  unless there i s  F a i l u r e i n slopes g r e a t e r than 41° r e q u i r e s a  d i s t u r b i n g f o r c e g r e a t e r than the cohesive  Csee Chapter 3, p. 50).  material  (Evans,  197 6, p.  s t r e n g t h of the  Forty-one  maximum angle of p a r t i c l e accumulation material  30°  In u n c o n s o l i d a t e d m a t e r i a l ,  slopes g r e a t e r than 41° are not maintained cohesion.  Slopes  degrees i s the  f o r non-cohesive  79).  Loose u n c o n s o l i d a t e d m a t e r i a l on slopes becomes r e d i s t r i buted  at angles ranging from 30° to 41°, where 30° i s an  approximate lower l i m i t f o r the angle of repose of the m a t e r i a l (Evans,  19 76).  The mean angle of repose f o r t a l u s s l o p e s , f o r  example, i s approximately the angle i s l e s s than  35°.  30° are  G e n e r a l l y , slopes of which stable.  Angles of slopes adjacent to the t r a c k s were measured with an Abney h a n d - l e v e l from the base to the top of the exposure. T y p i c a l t r a c k s i d e slope c o n d i t i o n s are d e p i c t e d i n F i g u r e Where the o r i g i n a l slope had not been cut or excavated, where the t r a c k was  b u i l t on f i l l ,  the slope angle was  4.2.  or not  recorded. The hazard,  due  to slope geometry, of f a i l e d m a t e r i a l  being c o n t r i b u t e d to the right-of-way  was  estimated  i n terms  78  UNCONSOLIDATED MATERIALS W  cutslope  no  cutslope  track  BEDROCK SLOPES  cutslope  "  1  no  cutslope  X  >70Wtrack  <70 Atrack  SLOPE AT A DISTANCE FROM THE  Fig.  4.2  T y p i c a l trackside slope conditions t h e j F r a s e r Canyon.  TRACK  encountered i n  79  of  two dichotomous v a r i a b l e s , the slope h e i g h t above, and  b a s a l d i s t a n c e from, the t r a c k i t s e l f .  These e s t i m a t i o n s are  s e m i - q u a n t i t a t i v e and are made on the b a s i s o f p a r t i c l e  size  and range, angle of the n a t u r a l s l o p e , and degree o f b a s a l excavation  i n the case o f u n c o n s o l i d a t e d  slopes and of steepness  arid degree o f overhang i n bedrock s l o p e s .  The t r a j e c t o r y o f  rock- or d e b r i s - f a l l from the s l o p e s t o the t r a c k was v i s u a l l y assessed.  When the hazard o f o b s t r u c t i o n to the t r a c k s i s  high because o f the "height" and/or " d i s t a n c e " , the a t t r i b u t e ( s ) i s s a i d t o be a t the c r i t i c a l  level.  Where the s l o p e i s  g e n t l e o r removed from the t r a c k , i t s h e i g h t and d i s t a n c e are n o n - c r i t i c a l , and the hazard The  i s low.  degree o f j o i n t i n g o f rock slopes adjacent t o the  r i g h t s - o f - w a y was recorded.  C o a r s e l y j o i n t e d f a c e s were those  wherein spacing between j o i n t s was g r e a t e r than about 20 f e e t (6 m).  T h i s a t t r i b u t e was chosen as a meso-scale  surrogate  f;or.. the rock cohesion parameter a t the m i c r o - s c a l e . comprising  j o i n t e d dr f a u l t e d bedrock, cohesion  zero across j o i n t  In slopes  i s effectively  planes.  ...the cohesion even o f a moderately j o i n t e d rock i s very much s m a l l e r than the cohesion... of the same rock i n an i n t a c t s t a t e . . . t h e i n f l u e n c e o f cohesion on the s t a b i l i t y o f slopes on j o i n t e d rock i s r e l a t i v e l y unimportant... we could not determine i t s value by any other p r a c t i c a b l e means (Terzaghi, 1962, p. 257) Weakening of rock by j o i n t i n g i s aggravated  by upward and outward  groundwater pressure and by the 9% volume expansion  of this  water upon f r e e z i n g . Slopes i n u n c o n s o l i d a t e d m a t e r i a l were examined f o r the  80  presence of f i n e s as an i n d i c a t i o n of t h e i r cohesion. cases was  evidence  considered one  of s i l t or c l a y found.  study.  Groundwater seepage v i s i b l e on the face of recorded,  though t h i s was  observed during the f i e l d study.  The  few  This a t t r i b u t e i s  of the l e a s t r e l i a b l e i n the  and rock slopes was  In  unconsolidated  not  frequently  seepage v a r i a b l e  was  chosen as the i n d i c a t o r o f h y d r o s t a t i c p r e s s u r e .  A  i n c i d e n c e of observed seepage does not adequately  reflect  groundwater c o n d i t i o n s ; at the base of one  low  recent s l i d e  scar  which appeared dry a t the s u r f a c e , a weephole d r i l l e d i n t o the slope was  l e t t i n g water under c o n s i d e r a b l e  pressure.  Where steps had been taken to s t a b i l i z e slopes or warning systems along the right-of-way, work was  recorded  as the  the nature  of  install the  "remedial measures" v a r i a b l e .  i n c l u d e d t e r r a c i n g , grading,  This  s c a l i n g , b o l t i n g , and s h o t c r e t i n g  of s l o p e s , i n s t a l l a t i o n of a cement r e t a i n i n g w a l l , c a t c h d i t c h , or e l e c t r i c fence, or i n the most severe beneath the n a t u r a l s l o p e s .  F u r t h e r d i s c u s s i o n o f these methods  i s made by P i t e a u and Peckover recorded  cases, t u n n e l l i n g  (1978) .  to r e i n f o r c e slope f a i l u r e  This information  was  data.  ANALYSIS Objectives The  aims of the a n a l y t i c a l p o r t i o n of the p r o j e c t were  several: i) to h i g h l i g h t i n t e r - r e l a t i o n s h i p s between slope a t t r i b u t e s u s i n g frequency d i s t r i b u t i o n and basic s t a t i s t i c s ,  81  i)  t o measure t h e amount o f " e x p l a n a t i o n " o f t o t a l v a r i a t i o n i n the i n c i d e n c e o f s l o p e f a i l u r e c o n t r i b u t e d by t h e t w e l v e s l o p e attributes considered,  ii)  to e v a l u a t e the c o n t r i b u t i o n o f each o f the slope a t t r i b u t e v a r i a b l e s t o the v a r i a t i o n i n t h e i n c i d e n c e o f s l o p e f a i l u r e and t o e l i m i n a t e the l e a s t i n f l u e n t i a l ones,  iii)  t o group t h e samples i n t o character i s similar,  iv)  t o c h e c k w h e t h e r t h e c a t e g o r i e s g e n e r a t e d on t h e b a s i s o f t h e p r i n c i p a l a t t r i b u t e s have s i g n i f i c a n t l y d i f f e r e n t s l o p e f a i l u r e i n c i d e n c e and t h u s a r e d i s t i n c t , and  v)  t o compare a s l o p e c l a s s i f i c a t i o n b a s e d on f a i l u r e i n c i d e n c e w i t h t h a t b a s e d on attributes.  Historical The Fraser  Slope  Failure  incidence  R i v e r has  of  and  slope  in  this  p u b l i s h e d by  from r e c o r d s The sources, the  and  are  While these  the  The  information  data  recorded are  s e t has  as  failure  released for  frequency  used i n t h i s  i s taken (0.16  t o be  d e b r i s and  insignificant  events have use  soil  derive  ( F i g . 4.3) .  different  intervals  t h r e e main l i m i t a t i o n s . rock,  Railway  an  study  from t h r e e km)  the  histograms  t h e p e r i o d 194 8 t o 196 8  mile  as w e l l as  suspected  compiled  104-5) h a v e b e e n u s e d as  during  s u p p l i e d a t 0.1  Canadian N a t i o n a l  t h e y were n o t  Frequency data  maintained  t h e e a s t bank o f  A l t h o u g h such r e c o r d s  failure  (.1977, p .  source.  frequency  track.  slides  These are  years  Instead,  Piteau  data  along  been d e t e r m i n e d u s i n g  f o r over f o r t y  study.  indirect  failure  d i s r u p t t r a i n movement.  been kept  solely slope  Records  t r a c k maintenance r e p o r t s . occur  c a t e g o r i e s whose  along F i r s t , snow slides.  i n terms o f  volume  701  0 ,20 4 failure incidence including snowslides  mile 6.4 km  0: 1  201 1 2 P-9.3  20 32.2  Pig.  4 . 3  7  11.3  • -ra 13  20.9  21 3 3 . 8  =1— 14 2 2 . 5  T 22 3 5 . 4  15  24  •A-  8  9  1 2 . 9  1 4 . 5  1  .1  16 2 5 . 1  17 2 7 . 3  4-  10 16.1  18 29.0  11 1 7 . 7  T 19  30.6  end of the study area  25  26  4 0 . 2  4 1 . 8  Number of slope f a i l u r e s per 0 . 1 mile ( 0 . 1 6 km) of t r a c k as recorded by the Canadian N a t i o n a l Railway from 1 9 4 8 to 1 9 6 8 ( a f t e r P i t e a u , 1 9 7 7 , p. 1 0 4 - 1 0 5 ) . Mileages ( k i l o m e t r e s ) are measured southward from Boston Bar, B.C. Refer to the t e r r a i n c l a s s i f i c a t i o n map enclosed i n t h i s volume.  83  o r damage, t h e i r debris  failures  relative i s not  frequency  known.  i s removed by  the  respect  Secondly,  s m a l l amounts o f d e b r i s o r r o c k material  with  may  train  to rock  failures  n o t be  and  contributing  recorded  as  the  engine or p a t r o l c a r s .  Only  3  failures are  i n v o l v i n g more t h a n one  recorded,  t h o u g h an  tracks  is rarely  affect  the  is  Finally,  until  data  The  and  slope  the  Canadian P a c i f i c instability  19 74,  accuracy  not  record  record i s  subject  f a i l u r e s may  not  occurrence.  be  While  used t o i n d i c a t e  not maintained  the w e s t bank t o t h e  slope  the  areas  i n a p r e d i c t i v e sense.  about f a i l u r e s  r e p o r t s on  The  be  R a i l w a y has  along  debris  so t h a t t h e  of the  their  i t may  though not  ) of  f a i l u r e s w h i c h do  recorded,  reporter(s).  s e t i s incomplete,  thus i n f o r m a t i o n  Since  not  s e v e r a l weeks a f t e r  prone to i n s t a b i l i t y ,  of  are  (1 m  o f volume o f m a t e r i a l on  T h i r d l y , slope  d i l i g e n c e of the  recorded this  given.  right-of-way  incomplete.  t o the  estimate  cubic yard  i s very  failures  records  same  sparse  extent,  there.  have b e e n made where more  3  than roughly The  1 cubic yard  l e n g t h of the  record  ) has  i s s h o r t and  effected track  the  Their value  i n s u b s e q u e n t a n a l y s i s , e x c e p t as  failing  number o f e v e n t s r e p o r t e d  slopes,  i s so  t o h a v e an  failure  Because the  on  the  eastern  work has and  s i d e o f the  been c a r r i e d  subsequently  out  projected  record of  the  failures  small.  side.  the  slope is  initial  Canadian N a t i o n a l  to the western  not  i n d i c a t o r of  inadequate r e c o r d of  canyon, a l l o f the on  an  i s very  s m a l l t h a t the west s i d e of  canyon i s c o n s i d e r e d ( F i g . 4.4).  blockage.  snow a v a l a n c h e s were  considered;  actively  total  Cl m  longest statistical  Railway  data,  20\  0 20 4 mile 6 . 4 km  failure Incidence excluding snowslides  0 20 12 19.3  20 32.2 Fig.  4.4  5 8.0  1113  20.9  —i  21 33.8  6 9.7  14  22.5  — i —  22 35.4  -P-  JZL  7 11.3  8 12.9  14.5  10 16.1  11 17.7  15  16 25.7  17 27.3  18 29.0  19 30.6  24.1  23 37.0  24  38.6  9  — i —  25  40.2  JZL  n  end o f the study area 26 41.8  Number of slope f a i l u r e s per 0 . 1 mile ( 0 . 1 6 km) of t r a c k as recorded by the Canadian P a c i f i c Railway from 1974 to 1 9 7 8 . Mileages ( k i l o m e t r e s ) are measured southward from North Bend, B.C Refer to the t e r r a i n c l a s s i f i c a t i o n map enclosed i n t h i s volume.  85  Descriptive The terrain  Statistics  data  classification  t r e a t m e n t by of  c o l l e c t e d during  failure  field  study  semi-quantitative  and  and  from  are  dichotomous.  interval variable.  nominal v a r i a b l e s , Because of  The  and  The  incidence  other twelve  five  of  them  t h e i r aggregated nature,  slope  are the  a t t r i b u t e s were s u b j e c t e d  to b a s i c  treatment  A  and  B).  f o r each of  the  t w e l v e a t t r i b u t e s were  (Appendix I I I .  Histograms generated to  indicate  attributes'  levels.  was  reveal  used to  attributes. generated The  slope  is  obtained.  on  the  i n performing  a more c o m p l e t e The  degree of  Slope A t t r i b u t e  influence  slope  failure of  the  the  variables  slope  failure  were  attributes. descriptive  statistics  observed t e r r a i n c h a r a c t e r i s t i c s ,  image o f  level  the  of  the  of  slopes the  i n the  statistics  o f measurement o f  i n t e r a c t i o n between t h e  Fraser  Canyon  i s dependent the  attributes,  attributes.  Evaluation  purpose of  number o f  of  credibility  sample s i z e , t h e  slope  between  the  augment d e s c r i p t i o n  The  some o f  f o r each l e v e l of  that  in  common a s s o c i a t i o n s  objective  the  of  incidence  so  the  Crosstabulation  statistical  occurrence of  the  to  on  frequency of  Mean v a l u e s o f  was  and  the  descriptive  the  require  n o n - p a r a m e t r i c s t a t i s t i c a l methods.  i s an  attributes  are  the  t h i s stage of  the  analysis  a t t r i b u t e s necesary  frequency. twelve slope  The  to  in explaining  i n d i v i d u a l and  attributes  was  reduce variation  combined  in explaining  the  86  v a r i a t i o n i n f a i l u r e was e n t i t l e d UBC I I I . C)'. wherein  determined  AID3, Automatic  using a computer program  I n t e r a c t i o n Detector  (Appendix  The e a s t e r n slope data were s u b j e c t e d t o the a n a l y s i s ,  the importance  of the twelve a t t r i b u t e s was  evaluated.  In AID3 a n a l y s i s , the dependent v a r i a b l e i s assumed t o be normally d i s t r i b u t e d w i t h no extreme cases.  The  slope  f a i l u r e data along the e a s t e r n s l o p e , however, i s c o n s i d e r a b l y skewed to the r i g h t . log-transformed.  To combat t h i s , the f a i l u r e data  A l l v a l u e s were i n c r e a s e d by one  e l i m i n a t e the l a r g e zero- i n c i d e n c e c l a s s which c o u l d not be  was  to  otherwise  log-transformed.  The AID3 program s p l i t s the data i n t o d i s c r e t e groups on the b a s i s of c r i t i c a l v a r i a b l e s , i n t h i s case, the slope attributes.  The aim i s t o reduce  i n t e r n a l v a r i a t i o n of the  groups w h i l e maximizing  the i n t e r - g r o u p v a r i a t i o n .  The  program output then may  be used t o decide which of the i n d e -  pendent v a r i a b l e s are l e a s t u s e f u l i n c o n t r i b u t i n g to v a r i a t i o n i n the dependent v a r i a b l e , and t o see where i n t e r a c t i o n between the independent  Numerical Two  Site  variables i s present.  Classification  methods have been employed t o i n v e s t i g a t e the  order, or s t r u c t u r e , of the data; c l u s t e r i n g and a l scalogram a n a l y s i s  (Appendix  I I I . D).  internal  multi-dimension-  These analyses were  made to c a t e g o r i z e the canyon s l o p e s u s i n g those  attributes  which c o n t r i b u t e most t o the e x p l a n a t i o n o f v a r i a t i o n i n f a i l u r e incidence.  87 The  d e s i r e d endproduct of c l u s t e r i n g and  a n a l y s i s i s a number of slope may  scalogram  s i t e c l a s s e s , each of which  be p h y s i c a l l y d i s c r i m i n a t e d  from the o t h e r s .  In order  f o r these c l a s s e s to serve as a means of f a i l u r e as w e l l , the should be  incidence  of slope  f a i l u r e f o r the  classification site  significantly different.  Cluster analysis involves  the c o l l a p s i n g of n  i n t o one-dimensional space; then the d i f f e r e n c e or between cases, or s i t e s , i s a l i n e a r d i s t a n c e measured. and  classes  Modes o f combining and  similarity  which can  c o l l a p s i n g the  of measuring the r e s u l t a n t d i s t a n c e s  variables  variables  vary and  are  to i l l u m i n a t e d i f f e r e n t aspects of the data s t r u c t u r e . t h i s study, the aim  be  used In  i s to maximize i n t e r - c l u s t e r ..distances  i n t r a - c l u s t e r homogeneity.  The  and  method of c l u s t e r development  used i s c a l l e d complete l i n k a g e , where " d i s t a n c e s "  between  c l u s t e r s i s maximized. Because the mechanical one,  c l u s t e r i n g procedure i s l a r g e l y a assumptions of randomization and  of samples, or s i t e s , are r e l a x e d .  In f a c t , i t i s  t h a t the systematic choice of data p o i n t s on  independence stressed  i s encouraged, e i t h e r  the b a s i s of i n c l u d i n g a r a r e type or of emphasizing a r e a l  a s s o c i a t i o n between types: . . . i f the s e l e c t i o n of some data u n i t s promotes the candidacy of o t h e r s , the e f f e c t should be e x p l o i t e d f o r the evidence of a s s o c i a t i o n r a t h e r than n e u t r a l i z e d i n deference to independence (Anderberg, 1973, p. 11). Thus the way  l i n e a r pattern  i n the F r a s e r  of s i t e s along the r a i l r o a d r i g h t s - o f -  Canyon does not i n v a l i d a t e the  numerical  88  taxonomy g e n e r a t e d by t h i s method. A difficulty on  o f t h i s c l a s s i f i c a t i o n method i s i n d e c i d i n g  t h e r e s u l t a n t number  of clusters or classes.  d i s c r e t i o n of the researcher suitable and  t o h i s p u r p o s e , and t o e v a l u a t e them  statistically  analysis In  that  study.  scalogram a n a l y s i s  were u s e d on d a t a f o r t h e e a s t e r n ,  combined s l o p e s  o f the canyon.  facilitated respect,  o f groups  intuitively  i f possible.  The m u l t i - d i m e n s i o n a l analysis  t o c h o o s e a number  I t i s a t the  Results  and c l u s t e r  w e s t e r n , and  of the c l u s t e r  i n t e r p r e t a t i o n of the scalogram  plots.  t h e two methods a r e c o m p l e m e n t a r y i n t h i s  89  CHAPTER 5 R E S U L T S  INTRODUCTION A t e r r a i n map  o f t h e F r a s e r Canyon, e n c l o s e d i n  volume, i s t h e most i m p o r t a n t  result  of t h i s  study.  t h e b a s i s f o r d i s c u s s i o n o f t h e m a t e r i a l s and slopes.  Within  the  c o n t e x t of the  s u r f i c i a l material refers form  the  It is of  the  system,  to a l l types of m a t e r i a l which  s u r f a c e o f the t e r r a i n  and  t h e r e f o r e i n c l u d e s bedrock fluvial,  and  fluvio-  deposits.  This  chapter  characteristic  comprises  form  w i t h e m p h a s i s on to  slope f a i l u r e .  in  the  a detailed  description of  and m a t e r i a l s o f t h e  these An  statistics  canyon  i n v e n t o r y of the types  and  t o c h a r a c t e r i z e the  Finally, numerical  the  slopes  f a c t o r s w h i c h r e l a t e most  canyon i s p r e s e n t e d .  descriptive used  form  classification  as w e l l as u n c o n s o l i d a t e d c o l l u v i a l , glacial  this  directly  o f mass movement  results  of  the  classification  techniques  slopes with respect to f a i l u r e  are  discussed.  TERRAIN CLASSIFICATION, MAPPING, AND Topographic Several  FIELDWORK  Profiles characteristic  topographic p r o f i l e s ,  s e q u e n c e s , have b e e n i d e n t i f i e d While  steep rock  inate  i n the  s c a r p s and  canyon, t h e i r  during this  colluvial relation  terrain  c o n e s and  to other  or  topoanalysis.  aprons  surficial  predom-  90  f e e t metres 6000RS  4000-  i.  -1000 ar^h / arCh o r \ ^ / sgFl\ ^ . 0- •o — •  2000-  6000ii.  Rs=arCv  40002000«  •  1  0  0  a  R s / a r C ^ ^ " ^  0- • 0 6000' iii.  4000•1000  Rs//arCv ^ ^ ^ ^  20000" .Q S  V e r t i c a l exaggeration =  0.82  6000'  iv.  4000•1000 20000-  Fig.  5. 1  Spuzzum a l l u v i a l sgFl\  arCv(b)»Rs^^^^*^'^ fan  ^ —  Four t o p o g r a p h i c p r o f i l e s encountered i n the F r a s e r Canyon, i ) A s s o c i a t e d w i t h p o s t - g l a c i a l landsliding. i i ) Predominantly c o l l u v i a l slope. i i i ) .Steep r o c k w i t h some c o l l u v i u m . i v ) A s s o c i a t e d w i t h a l l u v i a l f a n s . (Appendix I I )  91  materials  results  Beginning  with  as  ii)  iii)  iv)  Surficial As this  uppermost  i n Figure  p o r t i o n s , these  are  5.1.  described  Predominantly c o l l u v i a l uplands breaking i n t o s t e e p r o c k y s c a r p s up t o 2000 f e e t (600 m) in h e i g h t , o f t e n showing t r a c e s o f r e c e n t f a i l u r e . A t t h e s c a r p b a s e i s an a c c u m u l a t i o n o f c o l l u v i a l m a t e r i a l o f v a r y i n g e x t e n t and sloping toward the r i v e r . I n two c a s e s a s s o c i a t e d w i t h p o s t - g l a c i a l landslides, there i s a prominent r o c k k n o l l near the r i v e r ' s edge; elsewhere t h e c o l l u v i a l s l o p e s a r e t r u n c a t e d by t h e downward i n c i s i o n o f t h e r i v e r i n t o t h e underlying bedrock. Mixed b e d r o c k and c o l l u v i a l uplands g i v i n g way t o s t e e p e r r o c k and c o l l u v i a l canyon s l o p e s . T h e m a t e r i a l may appear uniformly d i s t r i b u t e d . o r may appear banded i n t o steps of c o l l u v i u m s e p a r a t e d by s t e e p r o c k w a l l s . There i s a steep rock w a l l descending to the r i v e r . The a r e a l e x t e n t o f the c o l l u v i a l p o r t i o n s , and thus the steepness o f the o v e r a l l p r o f i l e , i s q u i t e v a r i a b l e oh t h i s t y p e o f s l o p e . Steep rocky faces from river, with relatively accumulation.  the uplands to the little colluvial  M i x e d c o l l u v i a l and s t e e p r o c k s l o p e s a b u t t i n g suddenly onto a g e n t l y s l o p i n g , t e r r a c e d a l l u v i a l f a n t r u n c a t e d a t i t s base by the main river. T h i s i s most o b v i o u s a t the l a r g e s t fan accumulations but occurs at s e v e r a l of the s m a l l e r t r i b u t a r y c o n f l u e n c e s w i t h the main r i v e r as w e l l .  Materials  i s seen  volume,  surficial  and  their  depicted  follows: i)  of  i n four profiles  the  on  the  slopes  materials.  colluvium the colluvial  terrain  slopes  exhibit  Where  slopes  classification  are  exhibit  variable  they  are  most  uniform.  an  map  complexity  predominantly  intricate  enclosed  The  regarding comprised  steeper  terrain  in  unit  bedrock pattern  92  and are c o n s i d e r a b l y more complex.  T h i s complexity  of the  slopes w i t h i n the t e r r a i n c l a s s i f i c a t i o n i s sometimes artificially  i n c r e a s e d by the s u p e r i m p o s i t i o n  of roads  and  r a i l w a y l i n e s onto the n a t u r a l s l o p e s . The  canyon slopes comprise steep rock faces and  slopes o f v a r y i n g extent, d e p o s i t s a t t h e i r base.  and  some f l u v i a l and  colluvial  fluvio-glacial  On upper slopes where the  steep  rock i s p r e v a l e n t , there are f r e q u e n t s i g n s of r o c k f a l l d e b r i s - f l o w , as w e l l as snow a v a l a n c h i n g . is  Material  and  which  contained w i t h i n p r e - e x i s t i n g stream or d e b r i s - f l o w  channels appears to be t r a n s p o r t e d downslope great d i s t a n c e s , w h i l e t h a t from s p o r a d i c a l l y f a i l i n g f u r t h e r away than the accumulation the s c a r p .  r o c k w a l l s may  zone f o r c o l l u v i u m beneath  Presumably the d i s t a n c e t r a v e l l e d by  m a t e r i a l i s dependent upon i t s own u n d e r l y i n g slope  not move  falling  mass, the nature  (angle, c o n v e x i t y / c o n c a v i t y ,  of  the  roughness,  v e g e t a t i o n ) , and the presence or absence of a channel f o r the c o n c e n t r a t i o n of  flow.  Along the rights-of-way  where c o l l u v i a l d e p o s i t s have  been cut d u r i n g t r a c k c o n s t r u c t i o n there are many oversteepened s l o p e s , sometimes i n the order of 50°. angular  The  and coarse a t the s u r f a c e , but may  f i n e r matrix  at depth  (Photo 5.1).  grade i n t o a  Remedial measures, such  as c a t c h d i t c h e s , t e r r a c i n g , grading  and r e t a i n i n g w a l l s , are  found i n some of these l o c a t i o n s to prevent m a t e r i a l from r e a c h i n g  the t r a c k s  N e a r - v e r t i c a l slopes adjacent  colluvium i s  (Photo  dry  ravelling  5.2).  to the t r a c k commonly r e s u l t  P h o t o 5.1 m a t e r i a l m i l e 20.5 e a s t e r n  Blocky c o l l u v i a l i n a f i n e matrix at (32.8 km) on the s l o p e .  94  from n o t c h i n g These s l o p e s  o f the bedrock t o form the r a i l w a y tower over t h e t r a c k ,  arid i n c a s e s where  is  a history of recurring  failure,  an  e l e c t r i c warning  (Photo 5 . 3 ) .  jointed  coarsely,  fence  The r o c k i s o f t e n  seem p r e c a r i o u s l y b a l a n c e d above t h e t r a c k the rock s h a t t e r i n g along  of  careless  of  the railways,  "black  pattern superimposed bedrock. exhibit  coarse  the r i v e r  angle o f the p r i n c i p a l j o i n t i n g  the  susceptibility  and  o f rock slopes  the j o i n t i n g  high.  Elsewhere the j o i n t i n g  blocks  a r e n o t as e a s i l y  The deposited sorted It  differentiation  deposited  and be  to failure.  deposits  i s difficult found  is  that  fluvially  i n the Fraser  Canyon.  f u r t h e s t u p s l o p e was  c o n d i t i o n s , whereas t h e  are l o c a l l y  origin.  derive  toward t h e t r a c k  i c e f r o n t , from  Their  variable i n their surface  used as a d i s t i n g u i s h i n g f a c t o r s i n c e  like  I n some  of fluvio-glacial material,  under f l u v i o - g l a c i a l  fluvio-glacial  planes p a r t l y determines  i s i r r e g u l a r and l o o s e n e d  such m a t e r i a l  lower-slope materials  slopes  disturbed.  f i n e s and g r a v e l s , that  jointing  The a t t i t u d e  onto the right-of-way  a t or near a g l a c i a l  i s likely  construction  and on t h e u p p e r  planes d i p steeply  the l i k e l i h o o d o f r o c k f a l l  Some  coarsely-fractured  jointing patterns.  and  locations  (Photo 5 . 4 ) .  tends t o r e s u l t i n a f i n e r  along  blocks  i s a direct result  on t h e p r e - e x i s t i n g  Rock s l o p e s similarly  the tracks  joint  powder" b l a s t i n g e f f e c t e d d u r i n g  and t h i s  there  a r e sometimes g u a r d e d b y  and i n some l o c a t i o n s , l a r g e  of  right-of-way.  expression  fluvial cannot  levels or terrace-  from e i t h e r form o f d e p o s i t i o n  (Photos  P h o t o 5.2 Retaining w a l l to prevent dry r a v e l l i n g c o l l u v i a l m a t e r i a l from r e a c h i n g the t r a c k a t m i l e 10.7 ( 1 7 . 1 km) on t h e e a s t e r n s i d e o f the canyon.  P h o t o 5.3 Electric warning fence beneath a steep rock slope a t m i l e 1 1 . 5 ( 1 8 . 4 km) on t h e c a n y o n ' s west side.  96  Photo 5 . 4 Loosened j o i n t - b l o c k s beside the t r a c k s at mile 7 . 5 ( 1 2 . 0 km) on the western s i d e o f the canyon.  97  5.5 a n d 2 . 2 ) . F l u v i o - g l a c i a l m a t e r i a l comprises sized particles,  which u s u a l l y are p o o r l y  exposures the overburden pressure sand i n t o p r e s s u r e  ridges within  a p p e a r as bands o f v a r y i n g deposit the  east  16.9  km)  Within  of fluvio-glacial material  origin  (W.H. Mathews, p e r s .  comm.).  the eastern  m i g h t have s i m i l a r  origin  deposits  are  slopes  the  present  ( P h o t o s 5.8 t h r o u g h  those  remaining,  along  i t s high  most d e p o s i t s  only  material  fluvio-glacial 13.3 (21.4 km)  5.11). River  t h e c a n y o n , and c o m p r i s e  and b o u l d e r s .  under p r e v i o u s  river, with  for this  of mile  o u t o f t h e canyon a r e a .  material deposited  appearing  end o f the exposure.  basis,  south  unsorted  and sandy  a t t r i b u t e d t o the current Fraser  o f beaches o f cobbles transported  On t h i s  blocks.  south-dipping  and s i l t y  i s suggested  r e g i m e a r e n o t i c a b l y uncommon bars  colluvial  i s of variable thickness,  A possible jokulhlaup  along  10.1 and 10.5 (16.2 and  a veneer over bedrock a t the northern  Fluvial  i s exposed  and g r a v e l , some zones o f c o m p l e t e l y  The d e p o s i t  along  along  (Photo 5 . 7 ) .  from g r a v e l - t o b o u l d e r - s i z e d ,  interbeds.  These  compacted and cemented, and  and i s o v e r l a i n b y a v e n e e r o f c o a r s e  particles  s i l t and  a r e exposed  i t a r e some w e l l - s o r t e d b u t s t e e p l y  deposits  fine  and o r i e n t a t i o n w i t h i n t h e  s i d e o f t h e c a n y o n between m i l e  s t r a t a of cobbles  as  thickness  i n large intact blocks  large deposit  In s e v e r a l  the coarser m a t e r i a l s .  (Photo 5 . 6 ) . Where s u c h d e p o s i t s  may f a i l  the  sorted.  has squeezed  t r a c k s i d e , the m a t e r i a l i s often  A  s i l t - t h r o u g h to boulder-  Most f i n e r  particles  Much o f t h e f l u v i a l  r e g i m e s h a s b e e n removed b y  discharge derive  and s t e e p  grade.  f r o m a p e r i o d when  Of  98  P h o t o 5.5 F l u v i o - g l a c i a l t e r r a c e a t m i l e 15.0 ( 2 4 . 1 km) a l o n g t h e w e s t s i d e o f t h e c a n y o n . Photo l o o k s southward from the A l e x a n d r a B r i d g e .  P h o t o 5.6 D i p p i n g and c o n t o r t e d s t r a t a i n f l u v i o - g l a c i a l m a t e r i a l found at m i l e 13.4 (21.4 km) on t h e west s i d e o f t h e c a n y o n . The pen i s v e r t i c a l .  P h o t o 5.7 B l o c k y f a i l u r e o f cemented fluviog l a c i a l m a t e r i a l on t h e w e s t e r n c a n y o n s i d e a t m i l e 10.5 (16.9 km).  100  Photo 5.8 View o f a f l u v i o - g l a c i a l exposure along the e a s t e r n slope at mile 10.1 (16.2 km). Note the r e l a t i v e l y g e n t l e c o l l u v i a l slope above the t r a c k , and the steep rock notch below.  Photo 5.9 Poorly s o r t e d f l u v i o - g l a c i a l m a t e r i a l at mile 10.1 (16.2 km) on the east s l o p e . Note s t r a t i f i e d sands between the rounded b o u l d e r s , center o f photo.  101  Photo 5.10 Steeply dipping gravel-and-fines s t r a t a a t m i l e 1 0 . 5 ( 1 6 . 9 km) on t h e e a s t e r n s l o p e . The pen i s v e r t i c a l .  Photo 5.11 Unsorted f l u v i o - g l a c i a l m a t e r i a l at m i l e 13.5 (21.7 km) . Note t h e v e r t i c a l nature of t h i s cutface.  102  g l a c i a l l y deposited m a t e r i a l s throughout the r e g i o n were r e a d i l y a v a i l a b l e f o r reworking by the F r a s e r R i v e r and The most s i g n i f i c a n t are the Yale and  i t s tributaries.  Spuzzum a l l u v i a l  fans  mentioned p r e v i o u s l y . F l u v i a l m a t e r i a l comprises sand, g r a v e l and cobbles,  always rounded and  occasional  sorted into near-horizontal  In some l o c a t i o n s , d i p p i n g s t r a t a are evidence of an b r a i d e d channel regime.  and  classification  5.13).  F i n e sand and are found very  earlier  Some d e p o s i t s e x h i b i t a wide range i n  g r a i n s i z e and pose a c o n t i n u i n g problem i n t h e i r (Photos 5.12  strata.  s i l t y capping m a t e r i a l of a e o l i a n o r i g i n  l o c a l l y , on p a r t of the Spuzzum a l l u v i a l  fan  and a t o c c a s i o n a l p o i n t l o c a t i o n s elsewhere along the canyon. While i t may  have been more e x t e n s i v e  of t h i s f i n e capping has wind and water. 5 f e e t (1.5 m)  At one  i n e a r l i e r times,  little  s u r v i v e d subsequent reworking by s i t e , the a e o l i a n m a t e r i a l i s roughly  i n t h i c k n e s s , and  Most l i k e l y i t s source was  appears r e l a t i v e l y  f r e s h g l a c i a l and  sediments i n the surrounding  unstratified.  fluvio-glacial  uplands, s u b j e c t e d  to wind e r o s i o n  in a drier, post-glacial period.  Mass Movement The  types of slope f a i l u r e encountered i n the  Canyon are presented i n Appendix IV.  i n Table  5.1  and  Fraser  i l l u s t r a t e d by photos  C o l l u v i a l dry r a v e l l i n g and  rockfall  activity  were evidenced on a l l p a r t s of the s l o p e s , but were most concentrated  along the slopes adjacent  to the t r a c k s .  Failures  103  P h o t o 5.12 F l u v i a l terrace at Stout, mile 18.1 ( 2 9 . 0 km) on t h e e a s t s i d e o f t h e c a n y o n .  Photo 5 . 1 3 T r a c k s i d e s l o p e cut i n t o f l u v i a l m a t e r i a l o f t h e Spuzzum a l l u v i a l f a n , a t m i l e 1 7 . 3 ( 2 7 . 7 km) on t h e west s i d e o f t h e c a n y o n . A capping of aeolian f i n e s i s roughly 5 feet ( 1 . 5 m) t h i c k h e r e .  10 4  in  fluvial,  f l u v i o - g l a c i a l , and  a e o l i a n m a t e r i a l s were not  seen, except where these had been excavated d u r i n g track construction. m a t e r i a l was  In g e n e r a l ,  very l o c a l i z e d  f a i l u r e i n the  and took the  railway  unconsolidated  form of slow d i s i n -  t e g r a t i o n of the t r a c k s i d e slope angle to the angle of repose of the m a t e r i a l .  M O D E S  OF  F A I L URE  Surficial Material  undisturbed  bedrock  post-glacial landslide  rockfall  rockfall  slow d i s i n t e g r a t i o n  slab  rock- and  bedrock p l u s colluvial colluvial  fluvio-glacial  slopes  failure  trackside  dry  ravelling  debris  slide  dry  ravelling  debris  flow  debris  slide  debris  fall  debris  fall  N.A.  Table  N.A.  5.1  The  fall  ravelling  earth  fall  earth  fall  Modes of f a i l u r e encountered on the F r a s e r Canyon s l o p e s . Those which are underscored are thought to be the most s i g n i f i c a n t i n c o n t r i b u t i n g m a t e r i a l to the r a i l w a y rights-of-way (terminology a f t e r Varnes, 197 8) . ......  contents  of Table  s t a b i l i t y of f l u v i a l and turbed  dry  : N.A.  fall  ravelling  earth  aeolian  debris  r o c k - 1 r i gge re d co11uvi a1 slides  dry fluvial  slopes  state.  5.1  r e f l e c t the  comparative  f l u v i o - g l a c i a l m a t e r i a l s i n the  More c a t a s t r o p h i c events occur by sudden  undisfailure  105  of rock and c o l l u v i a l s l o p e s and may stem from the t r a c k s i d e slope alone, or from h i g h e r e l e v a t i o n s on the s l o p e . types are thought  t o c o n t r i b u t e m a t e r i a l t o the r a i l w a y  rights-of-way most f r e q u e n t l y , and are underscored 5.1.  These  i n Table  Slopes e x h i b i t i n g modes of f a i l u r e which occur more  slowly are cleaned up b e f o r e any hazardous amount o f m a t e r i a l accumulates  near the t r a c k s .  ANALYSIS  The  g e n e r a l context o f the numerical analyses was  o u t l i n e d i n Chapter  4.  Reference  to s p e c i f i c  analyses i s made  i n t h i s chapter i n c o n j u n c t i o n w i t h the p r e s e n t a t i o n o f t h e i r results.  The analyses which i n v o l v e slope f a i l u r e are  performed  on data f o r the e a s t e r n s l o p e s f o r which a twenty-  year r e c o r d i s a v a i l a b l e .  The s t a t i s t i c a l a n a l y s i s c o n s i d e r s  only t h a t p o r t i o n o f the canyon which i s t r a v e r s e d by the railway l i n e s ,  and thus i s r e p r e s e n t a t i v e o f the lower  slopes below approximately  1000 f e e t  (300 m) i n e l e v a t i o n .  C r o s s t a b u l a t i o n o f s u r f i c i a l m a t e r i a l w i t h slope f a i l u r e shows t h a t s l o p e s comprising bedrock,  which u s u a l l y  occurs 'as- steep s c a r p s , f a i l most f r e q u e n t l y .  The r e s u l t s  appear i n Table 5.2 and s e t the stage f o r f u r t h e r d i s c u s s i o n of  slope a t t r i b u t e s and a s s o c i a t e d f a i l u r e .  106  Number of Cases  Mean number of f a i l u r e s i n the 20-. year p e r i o d  Surficial Material  colluvial  1.95  125  bedrock  3.03  36  fluvio-glacial  0.48  21  fluvial  0 .24  17 absent  aeolian 1.84  total Table 5.2  199  Mean f a i l u r e i n c i d e n c e on slopes of the p r i n c i p a l s u r f i c i a l m a t e r i a l s found i n the F r a s e r Canyon  Frequency D i s t r i b u t i o n of the Slope A t t r i b u t e s I n i t i a l l y there were 220 (0.16  km.)  and  230  sample s i t e s at 0.1  mi  i n t e r v a l s along the r a i l w a y t r a c k s of the e a s t e r n  and western slopes r e s p e c t i v e l y . At each s i t e , each of the t h i r t e e n v a r i a b l e s was  determined d u r i n g the a i r photo i n t e r -  p r e t a t i o n of f i e l d w o r k s e s s i o n S i t e s at which a rock t u n n e l was  ( r e f e r to Table 4.2,  page 74).  p r e s e n t were e l i m i n a t e d from  the a n a l y s i s , reducing the number of s i t e s along the e a s t e r n l i n e to 199,  and along the western s i d e , to  216.  At each s i t e along the t r a c k s , each of the twelve a t t r i b u t e s was generated  determined.  slope  Frequency d i s t r i b u t i o n s have been  f o r the western and e a s t e r n slopes s e p a r a t e l y and f o r  the combined data.  These are presented  i n Appendix V.  For ease i n computer h a n d l i n g , the a l p h a b e t i c t e r r a i n c l a s s i f i c a t i o n has been n u m e r i c a l l y recoded  resulting in  107  c h a r a c t e r s t r i n g s of one through seven d i g i t s i n l e n g t h .  The  s u r f i c i a l m a t e r i a l s and t h e i r q u a n t i t a t i v e and p o s i t i o n a l r e l a t i o n s t o one another was r e t a i n e d ; t e x t u r e and s u r f a c e e x p r e s s i o n were not c o n s i d e r e d .  E v e n t u a l l y the s e v e n - d i g i t  numeric s t r i n g s were t r u n c a t e d t o three d i g i t s so t h a t the number of s u r f i c i a l m a t e r i a l c l a s s e s was reduced t o twenty. This t r u n c a t i o n r e t a i n e d the two most s i g n i f i c a n t m a t e r i a l s w i t h i n a t e r r a i n u n i t , and t h e i r r e l a t i v e a r e a l r e l a t i o n s h i p . G e n e r a l i z e d s t a t i s t i c s were performed with t h i s v a r i a b l e t r u n c a t e d t o one d i g i t so t h a t the predominantly rock,  colluvial,  f l u v i o - g l a c i a l and f l u v i a l u n i t s c o u l d be compared. In frequency  t a b l e s of the s u r f i c i a l m a t e r i a l s i t i s  seen t h a t the west s i d e of the canyon occupied by the Canadian P a c i f i c Railway i s c o n s i d e r a b l y more g e n t l y s l o p i n g than the other bank.  The eastern slopes comprise more  steep  rock, w h i l e western slopes show n e a r l y twice the percentage of the more s t a b l e f l u v i o - g l a c i a l and f l u v i a l  materials  (Table 5.3). In Appendix V. (A) a more d e t a i l e d breakdown o f the f  occurrence  of s u r f i c i a l m a t e r i a l s i s g i v e n .  are encountered most f r e q u e n t l y , w i t h those  Colluvial  slopes  c l a s s e s where  c o l l u v i u m i s a r e a l l y predominant over steep rock b e i n g the most common (C/Rs p l u s C//Rs = 27.7%). bedrock-dominated s l o p e s , those i s predominant are most frequent  S i m i l a r l y , of the  c a t e g o r i e s where steep  rock  (Rs/C p l u s Rs//C = 14.0%)  The p a r t of the t e r r a i n c l a s s i f i c a t i o n which i n d i c a t e s slope modifying  processes  was r e t a i n e d and considered as  108  Surficial Material  Eastern Slopes (199 cases)  Western Slopes (216 cases)  Combined Slopes (415 cases)  % of t o t a l :  % of t o t a l :  %'.. o f t o t a l :  colluvial  62.7 (125)  58.2 (126)  60 .5 (251)  bedrock  18.0 (36)  6.5 (14)  12 .1 (50)  fluvio-glacial  10 .5 (21)  17.2 (37)  14.0 (58)  fluvial  8.5 (17)  17.1 (37)  13.0 (54)  aeolian  nil  0.9 (2)  0.5 (2)  Table 5.3  Summary of the frequency o f occurrence o f p r i n c i p a l s u r f i c i a l m a t e r i a l s . The number of cases i n each category i s shown i n brackets.  a separate slope a t t r i t u b e from the m a t e r i a l i t s e l f . definition,  By  a l l s i t e s were m o d i f i e d by being c r o s s e d by the  railway rights-of-way.  Each s i t e may have one o r more  a d d i t i o n a l s l o p e - m o d i f y i n g process symbols.  The western  slopes  e x h i b i t a s m a l l e r range o f modifying c o n d i t i o n s than the e a s t bank.  The occurrence o f g u l l i e d  h i g h e s t slope f a i l u r e s i d e than the e a s t . processes appears  s l o p e s , a s s o c i a t e d with the  f r e q u e n c i e s , i s a l s o s m a l l e r on the west Frequency o f occurrence o f slope modifying  i n Appendix V (B), .  Along both r a i l  lines,  77.6% o f the s l o p e s adjacent t o  the t r a c k have been excavated  and thus oversteepened.  On the  e a s t e r n s i d e o f the canyon, the s l o p e s ' h e i g h t above the d i s t a n c e from the t r a c k are estimated t o be c r i t i c a l r e g a r d i n g  109  hazard at a m a j o r i t y of s i t e s .  The hazard was  determined  by o b s e r v a t i o n of the probable t r a j e c t o r i e s of f a l l i n g  rock  and d e b r i s from the slope above, and the a s s o c i a t e d l i k e l i h o o d of t r a c k o b s t r u c t i o n . geometric  a t t r i b u t e s -isj n o n - c r i t i c a l a t the m a j o r i t y of  s i t e s along the western The  The hazard due to both of these  slopes (Appendix  V('G, D, E) I .  frequency d i s t r i b u t i o n of t r a c k s i d e slope angles  again shows the predominance o f steep s l o p e s i n bedrock  and  u n c o n s o l i d a t e d m a t e r i a l along the e a s t e r n canyon s i d e .  The  western  of  s l o p e s e x h i b i t a c o n s i d e r a b l y h i g h e r percentage  slopes i n the 30° t o 41° range and i n the unmeasured c l a s s , presumably due  t o a h i g h e r occurrence there of f l u v i a l  and  f l u v i o - g l a c i a l d e p o s i t s , and to the b u i l d i n g - u p of the t r a c k onto f i l l . appears  The  frequency d i s t r i b u t i o n of slope angle c l a s s e s  i n Appendix V  (F) .  M a t e r i a l exposed along the t r a c k s i d e , a separate v a r i a b l e from the s u r f i c i a l m a t e r i a l a t a s i t e , again shows the r o c k i e r nature of the e a s t e r n canyon s l o p e s (Appendix  V (G)),.  Roughly 40% of a l l s i t e s are c h a r a c t e r i z e d by  steep  rock adjacent t o the right-of-way whether or not rock i s a component of the corresponding t e r r a i n u n i t . (or 25.1% category.  Of these,  62.7%  of the t o t a l number) f a l l i n t o the c o a r s e l y j o i n t e d The  frequency of occurrence of the j o i n t c l a s s e s  i s found i n Appendix V  (H) ,  Of the f i v e l i t h o l o g i e s found i n the study area, the Spuzzum i n t r u s i v e quartz d i o r i t e i s the most common, t y p i f y i n g 44.1%  of a l l s i t e s .  The o l d e s t u n i t , the Hozameen  sedimentary  110  and v o l c a n i c group,  i s absent from the western  s i d e of the  canyon, w h i l e the Custer g n e i s s does not occur along the e a s t e r n slopes.  Appendix V (I) g i v e s the frequency of occurrence of  the bedrock  types.  The occurrence of remedial measures a t s i t e s along the r i g h t s - o f - w a y were s i m i l a r f o r both s i d e s of the canyon IV  (J)) . While the o b s e r v a t i o n of these was  (Appendix  relatively  s t r a i g h t f o r w a r d , s e v e r a l s i t u a t i o n s have been s y s t e m a t i c a l l y overlooked: i) occurrence of rock s c a l i n g a t l e v e l s w e l l above the t r a c k s and i n areas where subsequent weathering has obscured the evidence, and ii)  r e m e d i a l work performed below the l e v e l of the t r a c k s , such as b u t t r e s s i n g , r e t a i n i n g w a l l s , weepholes, e t c .  The presence of f i n e s and seepage were recorded f o r a l l s i t e s but t h e i r occurrence i s sparse  (Appendix V, (K, L) ),.  Subsequent SPSS i n v e s t i g a t i o n s of the occurrence of slope f a i l u r e s f o r s p e c i f i c l e v e l s of each a t t r i b u t e were u s i n g the Canadian N a t i o n a l Railway twenty-year thus a p p l i e s to the e a s t e r n s l o p e s o n l y .  r e c o r d and  Observations  on these data are assumed to be t r u e on the western well.  performed  based  s i d e as  Although e x t e r n a l v a r i a b l e s e f f e c t i n g slope f a i l u r e  seem t o be the same from s i d e to s i d e of the canyon, f a c t o r s which may  vary i n c l u d e subsurface drainage, p a t t e r n , date  r a t e of the s p r i n g thaw, and l i t h o l o g i c s t r u c t u r e . f a c t o r s were not i n v e s t i g a t e d i n t h i s  study.  These  and  Ill  Slope A t t r i b u t e s and A s s o c i a t e d F a i l u r e Bedrock and/or c o l l u v i a l t e r r a i n h i g h e s t number o f s l o p e f a i l u r e s  u n i t s experience the  (Table 5.2). A more d e t a i l e d  c r o s s t a b u l a t i o n o f s u r f a c e m a t e r i a l with slope f a i l u r e shows that 94.0% o f a l l of the s i t e s has experienced six f a i l u r e s . colluvium-are  fewer than  The remainder occur i n u n i t s where steep rock and present  .(Table 5 v,4 ;)••-.- -A .very small number o f . f a i l u r e s  occurs on both f l u v i a l and f l u v i o - g l a c i a l m a t e r i a l s . S e v e r a l combinations o f rock and c o l l u v i a l m a t e r i a l s e x h i b i t high mean i n c i d e n c e o f f a i l u r e , while fluvio-glacial  f l u v i a l and  c l a s s e s have the lowest occurrence  A complete l i s t o f mean f a i l u r e  (Table 5.5).  i n c i d e n c e f o r the study  s u r f i c i a l m a t e r i a l groups appears i n Appendix VI (A),. Slopes which are both c r o s s e d by the r a i l w a y l i n e (X) and a c t i v e l y f a i l i n g  (F) are a s s o c i a t e d with higher  o f f a i l u r e , those which a d d i t i o n a l l y are g u l l i e d the h i g h e s t occurrence deforested lowest  of f a i l u r e s .  (Y), avalanched  f a i l u r e occurrence  Table  incidence  (V) having  Those s i t e s which are  (A), o r c h a n n e l l e d  (E) show the  (Appendix VI (B)).  5.6 shows the a s s o c i a t i o n of c u t s l o p e w i t h  i n c i d e n c e on the e a s t e r n s l o p e s .  failure  Only 19.1% o f a l l the s i t e s  have not been excavated, and a l l o f these have three or fewer recorded  f a i l u r e events.  difference i n failure  Colluvial  frequency  slopes e x h i b i t the l a r g e s t  between excavated and non-  excavated s l o p e s , presumably due t o d e s t a b i l i z a t i o n and dry ravelling  o f the base o f the s l o p e s which are c u t . The e f f e c t  of u n d e r c u t t i n g  c o l l u v i a l slopes i s c o n s i d e r a b l y more d r a s t i c  112  NUMBER OF FAILURES IN THE 20-YEAR RECORD Surficial Material  percent w i t h : zero $1 ?$2  $5  Number o f Cases  colluvial  38.4  56.8  72.8  95.2  125  bedrock  30.6  50.0  63.9  83.4  36  fluvio-glacial  76.2  90.5  90.5 100.0  21  fluvial  76.5  100.0 100.0 100.0  17  number o f cases Table 5.4  88  125  150  187  199  F a i l u r e i n c i d e n c e o f the p r i n c i p a l s u r f i c i a l m a t e r i a l s , given i n percentage of the t o t a l number of, cases per category.  Surficial Material  Mean F a i l u r e Incidence  Rs // C  3.94  C / Rs  3.85  20  Rs  3.17  6  F R  0.00  G  HIGH  LOW  Number o f Cases !7  4  F F o r |  0.19  16  Rs / F  0.50  2  Table 5.5  S u r f i c i a l m a t e r i a l types showing the h i g h e s t and lowest mean i n c i d e n c e o f f a i l u r e s .  113  than of  that  of  colluvium  and  height  limited  is  and  the  to  is  failure The  that  the  latter  track  (Table  whose  three  height  times  noticably,  or  the  highest  those  greater  than  fluvio-glacial colluvial  than  do  sites  material than  failures  occur  different slope (>70°)  in  A l l  in  the  of  the  cases  each  occur,  colluvial  and  and  can  the  of  second  was  failure The  for  of  highest more  The  steep  mean than  >70°  categories.  s u r f i c i a l  material  f l u v i a l  fact  their  failures.  especially  of  demonstrated  relation  with  the  maintain  reason  shows  the  >41°  within  may  5.8  the  incidence  exhibits  sites  classes  the  is  of  contains  5.2).  and  in  material,  higher  (Table  is  frequency  i t  much  cohesive  Table  to  failures.  ones  colluvium  incidence.  ( >70°)  is  than  class  however,  experience  fluvio-glacial  categories  of  sites;  This  slope  distance  fluvio-glacial  41°.  materials.  general,  height  the  category  in  In  greater  when  two and  5.7).  exhibiting  and  points:  often  times.  category  angles  are  4.6  angle  several  former  increased  slope  At  f l u v i a l  is  failure  slope  the  incidence  slope-angles  incidence  in  prevalence  of  c r i t i c a l  lower  rock  is  the  the  between'failure  slopes  Most  fluvio-glacial  higher  than  extent  be  that  frequency  on  in  of  to  are  colluvial earlier  cases.  slope  failures  the  c r i t i c a l  estimated  cuts  higher  from  Because  vertical  association  failures be  non-critical slope  and  strong  of  bedrock.  deposits,  distance  number  estimated  two  and  extensive  There  the  into  fluvio-glacial  much more  the  cutting  of  steep  units.  This  five  category rock exemplifies  114  Surficial  MEAN FAILURE INCIDENCE  Material  on uncut slopes  colluvial bedrock fluvio-glacial Fluvial total Table 5.6  Multiplication  on cut slopes  0.21 (24) 0.50 (2) 0.25 (4) 0.25 (8) 0.24 (38)  2.37 3.18 0.53 0.22 2.22  (101) (34) (17) (9) (161)  Factor  11.3 6.4 2.1 0.9 9.3  A s s o c i a t i o n between cutslope and f a i l u r e incidence. The number of cases i n each category appears i n brackets.  MEAN INCIDENCE OF FAILURE  MEAN INCIDENCE OF FAILURE  Surficial  on slopes whose height i s :  Material  non-critical  critical  on slopes whose distance i s : non-critical critical  colluvial  1.03  (39)  2.36 ( 8 7 )  1.12  (50)  2 . 5 1 (75)  bedrock  1.00  (1)  3.09 (35)  0.50  (2)  3.18 (34)  fluvio-glacial  0.14 (7)  0.64 (14)  0.63  (16)  0.00 ( 5 )  fluvial  0.13  (15)  1.00 ( 2 )  0.19  (16)  1.00 ( 1 )  total  0.70  (61)  2.35 (138)  0.83  (84)  2 . 5 8 (115)  Table 5.7  Association between slope height and distance from the track with f a i l u r e incidence. The number of cases i n each category appears i n brackets.  115  i) t h a t i n c l a s s i f y i n g s u r f i c i a l m a t e r i a l on a i r photo imagery there i s an i n h e r e n t m i n i m i z a t i o n of the importance o f v e r t i c a l rock f a c e s , and ii)  Table  t h a t the t h i c k n e s s o f u n c o n s o l i d a t e d d e p o s i t s i s v a r i a b l e such t h a t , i n some l o c a t i o n s , bedrock i s encountered i n c u t s l o p e s w i t h i n non-bedrock terrain units.  5.9 i l l u s t r a t e s the v a r i o u s slope angles  and t h e i r  a s s o c i a t e d f a i l u r e i n c i d e n c e encountered w i t h i n s e v e r a l mixed s u r f i c i a l material categories. From the f o r e g o i n g d i s c u s s i o n i t i s apparent t h a t s i t e s with a bedrock component e x h i b i t the h i g h e s t frequency o f failure. nature.  T h i s i s a r e s u l t o f i t s steep and s t r o n g l y j o i n t e d Bedrock i s s u s c e p t i b l e t o weakening by i c e accumulation  i n t h e j o i n t s , expansion and c o n t r a c t i o n d u r i n g ;  freeze-thaw  c y c l e s , and the b u i l d - u p o f groundwater pressure behind a f r o z e n plane p a r a l l e l t o the rock face i n the w i n t e r . C o l l u v i a l s l o p e s , while probably  l e s s i n f l u e n c e d by i c e - r e l a t e d  processes,  f a i l when t r i g g e r e d by r o c k f a l l s from the bedrock  scarps above, o r i n response t o oversteepening f a i l u r e frequency  o f a base.  Low  i n f l u v i a l and f l u v i o - g l a c i a l m a t e r i a l s i s  a t t r i b u t e d t o t h e i r g e n t l e slope and good  drainage.  R e l a t i v e Importance o f the Slope A t t r i b u t e s The  importance o f the twelve slope a t t r i b u t e s i n e x p l a i n i n g  v a r i a t i o n i n slope f a i l u r e was i n v e s t i g a t e d using the AID3 program (Appendix I I I , C ) . An e a r l y run of the program on the e a s t e r n slope data r e s u l t e d i n a confused t r e e - s t r u c t u r e , so t h a t a l l subsequent analyses were made on  log-transformed  1 1 6  Slope Angle Ml  NUMBER OF FAILURES IN THE 20 - YEAR RECORD percent with zero ^1 ^2 $5  Mean F a i l u r e Incidence  0  3.03 1.20  30.6  50.0  3 0 ° - 41°  57.1  <30°  0.25  83.3  >70° >70°  2.15 1.17 1.45  63.6  unmeasured Table 5.8  89.0  36  80.0  63.9 80.0  97.2  95.8  95.8  100.0  35 24  29.9  50.6  66.7  71.3 83.4  93.1 100.0  87  66.7  72.2  81.8  90.9  11  6  Association of trackside slope angle with f a i l u r e incidence along the eastern canyon slopes.  SURFICIAL MATERIALS: Mean Failure R//C Incidence C/R  Slope Angle angles associated with unconsolidated material angles associated with bedrock  >4l°  17.6?  10.0  30°-4l°  5.9*  4.0  <30°  —  >70°  76.5%  <70°  — —  angles not measured Table 5 . 9  Number of Cases  —  15.9?  Mean Failure Incidence  F  6.2?  1.0  31.2?  0.2  50.0?  0.1  12.5?  0.0  10.3  —  —  Mean Failure Incidence  75.0?  . 2.8  —  5.0?  2.0  —  —  —  5.0?  2.0  —  —  2.5  S u r f i c i a l materials , slope angles, and f a i l u r e incidence.  117  failure done  incidence  values  for  the  descriptive  variable  was  truncated  was  using  made  variable  and  slope  the  as  outlined  statistics,  to  three  failure  twelve  in the  The  program  slope  two  groups  largest  sites.  difference  two  groups  for  each  or  of  is  the  group  internal  tree-like The  the  That  (19 (10 (5 (2 (3 (6 (2 (2 (5 (3 (2 (2  basis  until  of  the  variation.  entire slope  between  data  l l l l l l l l l l l l  e e e e e e e e e e e e  set  attribute  the  mean  the  s p l i t .  s p l i t t i n g The  genesis  f i r s t  the  was  AID3  run  dependent  process  e e e e e e e e e e e e  ls) ls) ls) ls) ls) ls) ls) ls) ls) ls) ls) ls)  and  The  process  be  by  i t  into  effects  incidence  limited  may  splits  which  failure  is  v v v v v v v v v v v v  of  is  the  repeated  group  presented  the  size  as  a  structure. amount  the  twelve  the  t o t a l .  of  This  generalized  of  the  tree  were  size.  The  could  is  prevented others not  There  was  notably  distance,  be  slope  considered  s p l i t  failure 17  being  explained  times  was  reasonable  attributes.  from  were  some  in  splitting  predictor  provided. of  after  figure  the  variation  variation  attributes  of  small  with  as  As  attributes:  measures  begins  The  occurrence  4.  material  digits.  material genesis modifying processes bedrock cutslope material angle height distance jointing fines seepage remedial  Chapter  Ten  further  of  "unexplained",  and  further  of  interaction  modifying  on  any  between  processes,  55.8%  in  the  the  s p l i t  by  endgroups their  internal  variables  variables,  remedial  of light  18  their the  by  most  measures,  118  and  j o i n t i n g , with material genesis In  of  Table  5.10, t h e " e x p l a n a t o r y power o f t h e f u l l  each p r e d i c t o r " ,  or ETA-statistic  the p r o p o r t i o n o f the t o t a l each a t t r i b u t e twelve greater  alone,  a c o a r s e way,  such  variation  those  that those  detail  This value i s  s i x w h i c h have ETA  Of t h e values  showed t h e maximum  They a r e v a r i a b l e s w h i c h d e s c r i b e , i n  the s u r f i c i a l  The r e s u l t  I I I . C).  t h a t i s e x p l a i n e d by  0.1 were r e t a i n e d as t h e y  d i s c r i m i n a t o r y power.  slope.  i s given.  considering a l l i t s levels.  slope a t t r i b u t e s , than  and a n g l e , ( A p p e n d i x  m a t e r i a l and g e o m e t r y o f t h e  i s a logical  attributes  division  concerning  o f the v a r i a b l e s  the i n t e r n a l  character  of  the slope m a t e r i a l are r e j e c t e d .  of  inconsistency of observation or sparsity of occurrence,  thought  t o be  They a r e , f o r r e a s o n s  unreliable.  .201  jointing  .065  .154  fines  .056  distance  .139  bedrock  .047  angle  .132  r e m e d i a l measures  .044  cutslope  .130  material  .0 40  height ,  .110  seepate  :oio  material  genesis  modifying  Table  In  5.10  ETA v a l u e s o f t h e t w e l v e s l o p e a t t r i b u t e s u s e d i n t h e i n i t i a l r u n o f AID3.  t h e s e c o n d  v a r i a b l e s  were  i n d e p e n d e n t p e r c e n t  processes  r u n o f t h e AID3 p r o g r a m ,  used.  T h e r e  t h e s i x h i g h - E T A  w a s a r e d u c t i o n i n t h e number o f  v a r i a b l e s o f 50% a n d a c o r r e s p o n d i n g d r o p  o fv a r i a t i o n  e x p l a i n e d o f 14.4% t o 41.4%.  i nt h e  A f t e r  n i n e  119  s u c c e s s f u l s p l i t s there were t e n endgroups of which four were l i m i t e d by s i z e , and the r e s t unexplained. number of s p l i t s achieved  The  reduction i n  i n d i c a t e s t h a t there i s more  i n t e r n a l v a r i a t i o n w i t h i n the endgroups, r e s u l t i n g from fewer predictor variables.  The  r e s u l t a n t t r e e appears i n Appendix V I I .  In the t r e e there i s a tendency toward upward  branching,  i n d i c a t i n g some p o s i t i v e skewness i n the dependent v a r i a b l e . Wide angles between subgroups r e s u l t from l a r g e v a r i a t i o n i n the parent group from which the s p l i t was  made.  m a t e r i a l genesis and angle are the prominent  splitting  variables.  While h e i g h t was  Overall,  i n c l u d e d i n the a n a l y s i s on  the b a s i s of i t s previous ETA-value, i t was  not used as an  active s p l i t t i n g variable i n this tree. The  o v e r a l l v a r i a t i o n e x p l a i n e d i s thought to be  acceptable with r e s p e c t to the g e n e r a l i z e d nature data.  Frequency i s not 44.1%  of the  caused by the l e v e l s o f the  s i x p r e d i c t o r s ; r a t h e r there i s an a s s o c i a t i o n between the  value  of slope f a i l u r e i n c i d e n c e .and ;the. values' of: the s i x . a t t r i b u t e s . E f f e c t i v e l y no i n t e r a c t i o n occurs between v a r i a b l e s i n the second t r e e . When m a t e r i a l genesis was  t r u n c a t e d to one  digit  (thus  reducing the number of l e v e l s of t h i s v a r i a b l e from 19 to 4), and run i n the AID3 program, there was of the t o t a l v a r i a t i o n to 37.8%.  The ETA  a t t r i b u t e dropped as w e l l , from .201 i n t e r a c t i o n between modifying  another  3.6%  value o f t h a t  to .127.  processes  loss of  There i s  and d i s t a n c e ,  amongst m a t e r i a l genesis, angle, and d i s t a n c e .  and  There are  120  e l e v e n endgroups o f which t e n are e x p l a i n e d .  C l e a r l y the  e f f e c t o f f u r t h e r aggregation o f the m a t e r i a l genesis v a r i a b l e has been t o decrease The twelve  the e x p l a i n i n g power o f t h a t v a r i a b l e .  r e s u l t s o f the AID3 runs i n d i c a t e t h a t a drop from  t o s i x independent v a r i a b l e s , m a i n t a i n i n g m a t e r i a l  genesis a t nineteen l e v e l s i s the best compromise f o r the available predictors.  Subsequent c l a s s i f i c a t i o n and a n a l y s i s  t h e r e f o r e makes use o f s i x p r e d i c t o r s t o generate  groups o f  s i t e s with s i m i l a r character.  S t a b i l i t y C l a s s i f i c a t i o n of Sites Each time t h a t the c l u s t e r i n g program was employed a corresponding m u l t i - d i m e n s i o n a l scalogram  a n a l y s i s was made,  and t h e i r r e s u l t s i n each case w i l l be c o n s i d e r e d t o g e t h e r . In these analyses the data were o r g a n i z e d i n t o groups o f s i t e s on the b a s i s o f the s i x slope a t t r i b u t e s by the AID3 program.  identified  When the data are w e l l - s e p a r a t e d  into  groups, the c o e f f i c i e n t o f c o n t i g u i t y o f the MSA-I program approaches +1 (Appendix I I I , D). These two programs simply s o r t out s t r u c t u r e i n the d a t a . Whether r e s u l t a n t groups, or c l u s t e r s , are meaningful i n t e r p r e t e d by the u s e r . to generate  must be  Since these methods are being used  a framework w i t h i n which t o c l a s s i f y the s i t e s  along the s l o p e s , the i n t e r n a l v a r i a b i l i t y o f the groups generated by HCLUS and MSA-I should be s m a l l i n order t o be most e f f e c t i v e and p r a c t i c a l . The  f a i l u r e i n c i d e n c e v a r i a b l e was not employed i n the  121  c l a s s i f i c a t i o n o p e r a t i o n , though i t was used i n one way a n a l y s i s o f v a r i a n c e t o check the s t a t i s t i c a l s i g n i f i c a n c e o f the c l a s s e s so generated.  R e s u l t s o f the four HCLUS and  MSA-I runs are summarized i n Table 5.11.  The scalogram  plots  appear i n Appendix V I I I . In a l l f o u r runs o f the HCLUS and MSA-I programs, an a r b i t r a r y l i m i t o f s i x t e e n c l u s t e r s was adopted, w i t h subsequent r e d u c t i o n to fewer groups were a p p r o p r i a t e . r e s u l t a n t c l u s t e r s vary widely variability.  The  i n s i z e and e x h i b i t h i g h  internal  When t h e i r s i g n i f i c a n c e w i t h r e s p e c t t o s l o p e  f a i l u r e was t e s t e d w i t h a n a l y s i s o f v a r i a n c e , the groups were m a r g i n a l l y s i g n i f i c a n t or b e t t e r .  However, a c l o s e r  i n s p e c t i o n i n d i c a t e s t h a t the s i g n i f i c a n t l y d i f f e r e n t mean f a i l u r e i n c i d e n c e s occur only between s e v e r a l o f t h e groups, the others having means o f z e r o .  While dropping  of c l u s t e r s from s i x t e e n t o s i x o r four improves  the number their  s i g n i f i c a n c e , there was an a s s o c i a t e d i n c r e a s e i n the groups' internal  variability.  The b e s t r e s u l t s o f these analyses were obtained when the m a t e r i a l genesis v a r i a b l e was t r u n c a t e d from three t o one digit,  l e a v i n g each s i t e r e p r e s e n t e d only by the a r e a l l y  predominant s u r f i c i a l m a t e r i a l p r e s e n t .  The s i g n i f i c a n c e o f  the r e s u l t a n t c l u s t e r s was improved over t h a t o f other  runs,  though a c o n s i d e r a b l e amount o f i n f o r m a t i o n was f o r f e i t e d . The r e d u c t i o n i n c o n t r i b u t i o n (ETA) o f the t r u n c a t e d m a t e r i a l genesis v a r i a b l e t o the e x p l a n a t i o n o f t o t a l v a r i a t i o n i n the f a i l u r e i n c i d e n c e i n the AID3 program ( r e f e r t o page 119) i s  METHOD OP ANALYSIS: I  DUPLICATE SEARCHING  dataset  number of sites  number of unique cases  Eastern Slopes  199  90  HCLUS and MSA-I percent sites i n largest cluster  percent clusters of only one s i t e  percent clusters  with<10 sites  MSA-I coeff. of contiguity after 2 5 iterations  UBC S P S S ; 8 subprogram ONEWAY F-statistic  0.9999  for  1 6 clusters  51.7  50.0  68.7  1.673  for  6 clusters  93.5  50.0  83.3  0.545  Eastern Slopes *  | 199  for  1 6 clusters  for  6  for  I  Slopes  18.7  68.7  3.978  76.9  33.3  50.0  2.162  77.9  nil  16.7  4.175  33.8  I 216  |  415  1.52 1.72 1.88 2.26 1.97 2.42  0.9857  90  for -16 c l u s t e r s E a s t e r n and Western Slopes  45.2  4 clusters  Western  1.52 1.72 1.88 2.26  0.9992  63  clusters  =0.10 «=0.05  o e  F-ratio  25.0  56.2  157  N.A  N.A  N.A.  N.A.  0.9910 71.8  31.2  43.7  for1 6 clusters T a b l e 5 . 1 1 R e s u l t s o f the c l a s s i f i c a t i o n methods. An a r b i t r a r y number o f 1 6 f i n a l c l u s t e r s was c h o s e n . A s t e r i s k (*) i n d i c a t e s the case w h e r i n the m a t e r i a l g e n e s i s v a r i a b l e was t r u n c a t e d from t h r e e t o one d i g i t .  123  evidence variable.  of the importance of the t h r e e - d i g i t l e v e l of t h i s Thus, d e s p i t e improved s i g n i f i c a n c e , the t r u n c a t e d  o n e - d i g i t form was abandoned i n f u r t h e r a n a l y s i s .  A l t e r n a t e Means of S i t e  Classification  Two a l t e r n a t i v e methods of c l a s s i f y i n g the s l o p e s of the study area were c o n s i d e r e d , i n which c a t e g o r i e s were formed on the b a s i s of only one of the slope a t t r i b u t e s . first,  the s i t e s along the e a s t e r n slopes were grouped  a c c o r d i n g t o f a i l u r e frequency in  In the  alone.  T h i s method r e s u l t s  a c l e a r image o f the d i s t r i b u t i o n of slope f a i l u r e  the right-of-way, isolated  along  from which a c t i v e l y f a i l i n g s i t e s can be  easily.  However, t h e r e are s e v e r a l disadvantages of t h i s scheme. F i r s t , the c l a s s i f i c a t i o n i s dependent upon a reasonably long slope f a i l u r e r e c o r d .  These are r a r e l y  available.  Second, w i t h i n t h i s c l a s s i f i c a t i o n there i s no i n d i c a t i o n of the p h y s i c a l nature of the slopes., L a s t , t h i s  classification  cannot be extended t o other s l o p e s o r t o other areas.  While  t h i s c l a s s i f i c a t i o n may be of i n t e r e s t t o Canadian N a t i o n a l Railway, i t i s o f l i t t l e p r a c t i c a l use as a g e n e r a l l y a p p l i c a b l e method. The  second c a t e g o r i z a t i o n of the slopes was made u s i n g  the m a t e r i a l genesis v a r i a b l e a l o n e .  In t h i s case, the  v a r i a b l e was t r u n c a t e d t o one d i g i t so t h a t s i t e s were  initially  grouped a c c o r d i n g t o t h e i r predominant s u r f i c i a l m a t e r i a l . One-way a n a l y s i s of v a r i a n c e shows t h a t there are s i g n i f i c a n t  124  DESCRIPTION OF THE CATEGORIES: Mean Number of Failures Per S i t e  Surficial Material  Number of Cases  colluvial bedrock  125 36  fluvio-glacial fluvial  21  0.48  17  total  199  1.95 3.03  Maximum Number of F a i l u r e s at One S i t e  Standard Deviation  2 . 76 4.49  0.24  17 21 4 1  1.84  21  3.03  1.08  0.44  ANALYSIS OF VARIANCE: Source  Degrees of Freedom  between within  3 195 198  total Table 5 . 1 2  Sum of Squares  Mean Squares  135.19 1671.96 1812.16  45.06 8.60  F-ratio  5 .24  F-statistic  ( <* = 0 . 0 1 ) 3.88  C l a s s i f i c a t i o n and analysis of variance of s i t e categories based on s u r f i c i a l materials encountered along the eastern slopes of the canyon.  DESCRIPTION OF THE CATEGORIES: Surficial Material  Number of Cases  colluvial bedrock  251 50  fluvio-glacial fluvial  58  total  Mean Number of Failures Per S i t e  Maximum Number of F a i l u r e s at One S i t e  Standard Deviation  1.04  17 21  4.01  4 1  0.70  54  2.28 0.22 0.07  413  0.95  21  2.29  2.17  0.26  ANALYSIS OF VARIANCE: Source  Degrees of Freedom  Sum of Squares  Mean Squares  between within  3 409  162.64  33.47  1998.35  4.95  total  412  2161.00  Table 5 . 1 3  F-ratio  11.09  F-statistic ( « = 0.01)  3.32  C l a s s i f i c a t i o n and analysis of variance of s i t e categories based on s u r f i c i a l materials encountered along the eastern and western slopes.  125  d i f f e r e n c e s between t h e mean number o f f a i l u r e s category.  Table  Analysis  5.12  o f v a r i a n c e was  dataset of s i t e s canyon.  The  different, western of  along  result  s l o p e s was  with  s i d e s of  t h a t the g r o u p s were s t i l l  A broad  into  i n Table  drastically  The  outcome o f  5.13.  groups t o a  hazard  classification  Surficial Material  to  intermediate  colluvial  low  fluvio-glacial and f l u v i a l  this  made  5.14.  bedrock  A problem with  i n Tables  c a t e g o r i e s can be  high  Table  the  t o a l a r g e number o f  g r a d a t i o n o f the r e s u l t s  failure  H a z a r d Due Failure  combinations  i n Table  the  of the s h o r t p e r i o d  to reduce  due  the  significantly  along  incidence of f a i l u r e .  the v a l u e of these  5.13  failures  effect  s i d e was  i s presented  scheme i s s e e n .  as o u t l i n e d  An  occurrence  z e r o o r low  Clearly  and  t h e e a s t e r n and w e s t e r n  the western  the a n a l y s i s  5.12  combined  sparse.  v a l u e s o f mean s l i d e  analysis.  f o r the  was  repeated  even though the r e c o r d o f  r e c o r d on  sites  i s a summary o f t h e  i n each  5.14  form  General slope f a i l u r e hazard c a t e g o r i e s .  of c l a s s i f i c a t i o n  i s that  certain  of m a t e r i a l s are m i s l e a d i n g l y assigned w i t h i n i t .  F o r e x a m p l e , on  the e a s t s i d e o f the  where c o l l u v i u m p r e d o m i n a t e s o v e r  canyon the t e r r a i n  steep bedrock  units  (C/Rs) have  126  a mean, i n c i d e n c e 0.1 m i l e  of failure  o f 3.85 e v e n t s p e r s i t e  o r 0.16 km segment o f t r a c k )  Although t h i s surficial  i s the second h i g h e s t  hazard  category  incidences.  groups c o n t a i n i n g intuitive  i n Table  5.14.  the t h r e e - d i g i t m a t e r i a l  5.15.  This  b e t w e e n them. the eastern  i s several  classification  data  into  appears i n  i s t h e combined r e s u l t o f  a t a l l stages  photo i n t e r p r e t a t i o n , f i e l d  no  A possible  slope  c a t e g o r i e s o f m a t e r i a l types  gathered  a range  unrelated materials with  from s p l i t t i n g  incidence  information  survey,  of this  research:  and n u m e r i c a l  air  analysis.  Hazard Due t o Failure  Surficial  high  Rs  2 .00-2 .99  intermediate  C C=R; G  1.00-1.99  low  C; C//Rs ; § ; § ; F//C  0.00-0.99  v e r y low  F |  Failure : Incidence  3  Table  It  into the  However, t h e r e s u l t  pattern o r connection  scheme r e s u l t i n g  Table  somewhat  period.  amongst t h e  and t o generate c a t e g o r i e s each c o m p r i s i n g  o f mean f a i l u r e  failure  incidence  presented  An a l t e r n a t i v e i s t o r e t a i n genesis  over the r e c o r d  m a t e r i a l c a t e g o r i e s , i t would f a l l  intermediate  ( i . e . per  5.15  Materials  ; Rs//C ; C/Rs  F  ; Rs/C  G  ; C=F  G ; R/F ; F  ; F  S l o p e f a i l u r e h a z a r d c a t e g o r i e s b a s e d on t h e s u r f i c i a l m a t e r i a l v a r i a b l e a t the threedigit level.  i s justified  on t h e b a s i s o f t h e r e s u l t s  o f those  stages  127  and on i n t u i t i o n . surficial  The f a i l u r e  m a t e r i a l s c a n be a p p l i e d t o  f o r w h i c h t h e y were g e n e r a t e d . outside tested  of  ranges and t h e i r  the  further.  study area,  associated  the e a s t e r n  slopes  F o r the western slopes  these hazard  levels  need t o  or be  128  CHAPTER 6 C O N C L U S I O N S  OVERVIEW Despite  i t s heavy use as a t r a n s p o r t c o r r i d o r , the F r a s e r  Canyon has been overlooked hazard  as f a r as t e r r a i n a n a l y s i s and  e v a l u a t i o n are concerned.  T h i s study was designed t o  c l a s s i f y t h e t e r r a i n and i n v e s t i g a t e the d i s t r i b u t i o n o f slope f a i l u r e s along the r a i l w a y rights-of-way.. drawn from the r e s u l t s presented  Conclusions  i n Chapter 5 f a l l i n t o three  r e l a t e d , but d i s t i n c t , c a t e g o r i e s , namely: i) ii)  iii)  the nature  o f t e r r a i n i n the F r a s e r Canyon  the r e l a t i o n o f meso-scale t e r r a i n v a r i a b l e s to slope f a i l u r e i n c i d e n c e along the r a i l w a y l i n e s , and the implementation o f slope a t t r i b u t e s i n c l a s s i f y i n g t e r r a i n with r e s p e c t t o slope f a i l u r e incidence.  On the b a s i s o f a i r photo a n a l y s i s , f i e l d w o r k , and slope a t t r i b u t e frequency  d i s t r i b u t i o n s , the f o l l o w i n g g e n e r a l  c o n c l u s i o n s are made: i) ii)  F r a s e r Canyon slopes are dominated by c o l l u v i a l and steep bedrock t e r r a i n , f l u v i a l and f l u v i o - g l a c i a l m a t e r i a l s a r e found s p o r a d i c a l l y along the lower canyon s i d e s ,  iii)  the nature o f the western s i d e o f the canyon i s c o n s i d e r a b l y g e n t l e r than the e a s t e r n s i d e ,  iv)  steep rock slopes e x h i b i t the h i g h e s t i n c i d e n c e or slope f a i l u r e , f o l l o w e d by c o l l u v i a l s l o p e s ,  v) vi)  f l u v i a l and f l u v i o - g l a c i a l m a t e r i a l s have very low f a i l u r e i n c i d e n c e , and 80% o f the slopes have been excavated (and oversteepened) d u r i n g r a i l w a y c o n s t r u c t i o n  129  The  two r a i l w a y routes make maximum use o f the more s t a b l e  unconsolidated  d e p o s i t s by m a i n t a i n i n g  low e l e v a t i o n along the  canyon s l o p e s , and where rock and c o l l u v i a l t e r r a i n t r a v e r s e d , the hazard  due t o slope f a i l u r e i s i n c r e a s e d .  R e s u l t s o f the numerical following  u n i t s are  analyses g i v e r i s e t o the  conclusions:  i ) t h a t m a t e r i a l genesis (derived from the t e r r a i n u n i t terminology) i s the s i n g l e most u s e f u l index o f slope f a i l u r e , ii)  iii) iv)  t h a t the most s i g n i f i c a n t slope a t t r i b u t e s i n e x p l a i n i n g f a i l u r e i n c i d e n c e are m a t e r i a l genesis, modifying processes, c u t s l o p e , angle, h e i g h t above the right-of-way, and d i s t a n c e from the track. t h a t the v a r i a b l e s l i s t e d i n ( i i ) account f o r 41.4% of the v a r i a n c e i n slope f a i l u r e i n c i d e n c e , t h a t v a r i a b l e s chosen as surrogates f o r micros c a l e parameters are i n e f f e c t i v e i n adding t o the e x p l a n a t i o n of v a r i a n c e i n f a i l u r e occurrence, and  v) t h a t c l u s t e r s generated on the b a s i s of v a r i a b l e s l i s t e d i n ( i i ) were i n a p p r o p r i a t e as a means of s i t e c l a s s i f i c a t i o n with r e s p e c t t o f a i l u r e incidence. Information  contained  i n the t e r r a i n  i s the best index of f a i l u r e a t i n d i v i d u a l specific  failure  classification, sites,  f r e q u e n c i e s cannot be attached  conclusion contests Piteau's claim that r i v e r and a l l u v i a l f a n impingement alone along the right-of-way 1973,  1977).  though  to i t . This  channel  influence failure  o f the e a s t e r n canyon slopes  plan-form incidence  (Piteau,  The importance o f the b e d r o c k - c o n t r o l l e d  R i v e r i n determining  upslope f a i l u r e occurrence  t h i s author t o be s m a l l .  Fraser  i s thought by  Rather, slope m a t e r i a l and l o c a l  geometry, i n c l u d i n g a l t e r a t i o n  then,  of the n a t u r a l slope  during  130 r a i l w a y c o n s t r u c t i o n , are a t r r i b u t e d major d i r e c t i n f l u e n c e on slope f a i l u r e d i s t r i b u t i o n along the t r a c k s .  IMPLICATIONS OF THE The  RESULTS  c l a s s i f i c a t i o n scheme e f f e c t s storage of t e r r a i n  c h a r a c t e r i s t i c s f o r u s e f u l r e t r i e v a l by engineers, and environmental  planners.  geomorphologists, As w e l l as a s e r i e s of  e a s i l y d i s t i n g u i s h e d topographic p r o f i l e s , s p e c i f i c geomorphol o g i c i n f o r m a t i o n r e s u l t i n g from t h i s study i n c l u d e s : i) the a r e a l extent and d i s t r i b u t i o n of t e r r a i n u n i t s i n a l a t e r a l and v e r t i c a l sense, ii)  iii)  d e t a i l e d c l a s s i f i c a t i o n of the s u r f i c i a l m a t e r i a l , by i t s t e x t u r e , g e n e s i s , s u r f a c e e x p r e s s i o n , and modifying processes, an i n v e n t o r y of past and present slope processes as evidenced i n the canyon,  failure  iv) an i n v e n t o r y of s e m i - q u a n t i t a t i v e slope a t t r i b u t e s , and v) the a s s o c i a t i o n of slope f a i l u r e i n c i d e n c e w i t h m a t e r i a l genesis and other slope a t t r i b u t e s . The r e g i o n a l or meso-scale t e r r a i n c l a s s i f i c a t i o n map the F r a s e r Canyon and the a s s o c i a t e d slope f a i l u r e t i c s are complementary to the engineers' f a m i l i a r i t y with slopes along the t r a c k s .  of  characteris-  site-specific As such, they m e r i t  c o n s i d e r a t i o n i n p l a n n i n g and a l l o c a t i o n of funds f o r remedial work, and w i l l be u s e f u l i n the l i g h t of plans to i n c r e a s e r a i l w a y t r a f f i c and f a c i l i t i e s i n the canyon area p e r s . comm.).  (Duncan W y l l i e ,  A d d i t i o n a l c o n s t r u c t i o n along the s l o p e s w i l l  i n c r e a s e hazard due  to f a i l u r e by c r i t i c a l l y a l t e r i n g f o u r of  the v a r i a b l e s c o n s i d e r e d i n t h i s p r o j e c t ; c u t s l o p e , angle,  131  d i s t a n c e and The  height.  aim o f t h i s p r o j e c t was  the reconnaissance  of  F r a s e r Canyon t e r r a i n with r e s p e c t to s u r f i c i a l m a t e r i a l s slope f a i l u r e .  There were three  photo i n t e r p r e t a t i o n and f i c a t i o n , and  numerical  and  stages w i t h i n the work; a i r  terrain classification, a n a l y s i s o f the data.  field  veri-  From w i t h i n  framework, there are s e v e r a l recommendations f o r the  this  design  of s i m i l a r s t u d i e s . Two  aspects  of the F r a s e r Canyon study which might be  improved i n o t h e r r e g i o n a l - s c a l e s t u d i e s , and which a f f e c t a l l stages  of the i n v e s t i g a t i o n are: i ) Slope a t t r i b u t e s e l e c t i o n . V a r i a b l e s which d e s c r i b e meso-scale slope p r o p e r t i e s (eg. m a t e r i a l g e n e s i s , slope geometry) prove to be more c l o s e l y r e l a t e d to slope f a i l u r e i n c i d e n c e at the r e g i o n a l s c a l e o f i n v e s t i g a t i o n than surrogates of m i c r o - s c a l e v a r i a b l e s . The purpose of the reconnaissance w i l l d i c t a t e some or a l l of the slope a t t r i b u t e s to be considered. ii)  Slope f a i l u r e r e c o r d s . Recording of the type and extent of f a i l u r e s should be improved. I d e a l l y , the r e c o r d i n g of f a i l u r e events should be c o n t r o l l e d by the designers of the reconnaissance, but t h i s i s u s u a l l y at the expense of the d u r a t i o n of the r e c o r d p e r i o d . G e n e r a l l y , such records d e r i v e from secondary sources, and thus are u n c o n t r o l l e d .  When no r e c o r d of slope f a i l u r e h i s t o r y i s a v a i l a b l e , a method f o r determining  the ranking  tendencies  o f the p r i n c i p a l  surficial  m a t e r i a l s with r e s p e c t to p o t e n t i a l f a i l u r e i s necessary. In mountainous t e r r a i n s i m i l a r to t h a t found i n the F r a s e r Canyon r e g i o n , v a r i a b l e importance of f a i l u r e i n bedrock, colluvial, to hold.  f l u v i a l and  f l u v i o - g l a c i a l s l o p e s can be assumed  However, t h e i r f a i l u r e behavior  undoubtedly changes  132  \  where v a r i a b l e s which were i n s i g n i f i c a n t a t the s c a l e of t h i s analysis  (such as l i t h o l o g y ) take on g r e a t e r  Where the t e r r a i n i s c o n s i d e r a b l y  importance.  d i f f e r e n t and no h i s t o r i c  r e c o r d i s a v a i l a b l e , the p o t e n t i a l f o r f a i l u r e i n the p r i n c i p a l m a t e r i a l types can be estimated by ( i n decreasing  order  of e f f e c t i v e n e s s ) : i) ii) iii) iv)  comparison o f o l d and c u r r e n t a i r photos f o r v i s u a l evidence o f slope f a i l u r e , field  investigation  laboratory  t e s t s on m a t e r i a l  strength,  evidence of f a i l u r e behavior o f s i m i l a r m a t e r i a l s i n other l o c a t i o n s , or  v) i n t u i t i v e  evaluation.  The methods of numerical analyses used were i d e a l f o r the s e m i - q u a n t i t a t i v e  F r a s e r Canyon slope data.  A wide range  of s i m i l a r methods i s a v a i l a b l e , those i n c l u d i n g q u a n t i t a t i v e parameters y i e l d i n g the most r e l i a b l e r e s u l t s . Where f e a s i b l e , a p i l o t study i n v o l v i n g the measurement and  a n a l y s i s o f slope v a r i a b l e s and i t s subsequent a n a l y s i s  would be u s e f u l i n determining the s u i t a b i l i t y o f the v a r i a b l e s s e l e c t e d , t h e i r i n t e r a c t i o n s , and t h e i r power i n e x p l a i n i n g the d i s t r i b u t i o n of slope The  failures.  most important c o n t r i b u t i o n of t h i s t h e s i s i s the  i d e n t i f i c a t i o n o f a method f o r r a p i d i n v e n t o r y  and assessment  of t e r r a i n c a p a b i l i t y t o support routeways i n the face of n a t u r a l slope hazards.  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New  York:  TERZAGHI, K a r l , 1962, " S t a b i l i t y o f S t e e p S l o p e s on H a r d Unweathered R o c k , " G e o t e c h n i q u e . V o l . 12. pp.251-270. TERZAGHI, K a r l , and R.B. PECK, 1967, S o i l M e c h a n i c s i n E n g i n e e r i n g P r a c t i c e . 2nd. ed. New Y o r k ; W i l e y . 729pTHOMPSON, N. and J.H. EDGAR, 1933, C a n a d i a n R a i l w a y from the E a r l i e s t Times. M a c m i l l a n o f Canada.  Development  VARNES, D . J . , 1978, " S l o p e Movement T y p e s and P r o c e s s e s , " L a n d s l i d e s : A n a l y s i s and C o n t r o l , e d i t e d by R.L. S c h u s t e r and R..J. K r i z e k . N a t i o n a l Academy o f S c i e n c e . 234p. VERSTAPPEN,H.T., 1977, Remote S e n s i n g i n G e o m o r p h o l o g y . E l s e v i e r S c i e n t i f i c Pub. Co. WATER SURVEY OF CANADA, 19 78, H i s t o r i c a l S e d i m e n t D a t a Summary, B r i t i s h Columbia. F i s h e r i e s and E n v i r o n . Canada, O t t a w a . WATER SURVER OF CANADA, 1977, H i s t o r i c a l S t r e a m f l o w Summary, B r i t i s h Columbia. F i s h e r i e s and E n v i r o n . Canada, O t t a w a . WHEELER, J.O. ( e d i t o r ) , 1970, " S t r u c t u r e o f t h e S o u t h e r n •{'•. C a n a d i a n C o r d i l l e r a , " G e o l . A s s o c . Can., S p e c i a l R e p o r t No. 6. 166p.  140  Appendix I .  CLIMATIC DATA FOR  LYTTON,  HELL'S GATE, AND HOPE, B.C. . in  o\ cr.  5?  VO  m  m  cn -=r  m vo 00 . . . vo in t—  ni  m fl-  c— r— co  o  o\  3-  oj  rH  rH rH  co  o rH  ON .  VO VO . .  rH  rH rH  vo  CO  in in  01 OJ  »"3  rn vo o rn  i n -a-  .=T  -=T  CM  co 3  CM  3  in M  o  rH  m  m  -=r  vo  t— VO  in  OJ rH CM CM  OJ  rH  OJ  OJ CM  CT\ CO rH rH  o  vo -=r  o\  rn c—  co  in  m  o\  rH O  c_> in -=r i n O M  J3-  CM -=3"  3  rH  CM  X • * ' En  rn  < X v o aW • CLi rn  S  i  E-i  CM  l  vo l  O  O  s O vo s • M O X  <  5H  cu •p  X  M  o  M  ta  Q C o <  -P  g  J  w >>  ~  1  a o a  2 <  .  o  rH  0  OJ  1  a>  O -P -P  U >> S J  t— t—  H  (J\  O  rH . 0  vo i n  O  rH I  rH rH I I  o\  co  vo  m  rH  m  I  s  in co  vo  CM  S as t—  2 • MVO 2 1 H 2 X  ij  M  ca  a 0c  O. O  x x  H  « o\  I  CM  EH < C3  vo m  cn t—  m  m  vo  rn co  o •a-  CO  C— .  m  m  o  co  o  vo  m-  m  m  vo  a• a-  • c-  o  rH OV . .  vo vo CM  o  o\  ' " «) M 3 •P rd  • m  a-  o\  co  a-  m  oj  U  x  o.  « ecu  2  EH  S  rH et)  E f. O c  cd  2 <  -P -P  w >> _ J  EH  co  vo  vo  m  cn I  o  vo co oj CM  m I  m  m  O  rn  O  0  .  1  OJ • 0  . .  VO  OJ  a-  m  1  1  rn oj  o  cn •  ON •  *  rH  ^co 0  0  0  •  S in =3 rH  s H X  CD •P ed  CM I  in  CM CM  m  .  •a• ON •rH  VO  rH CM I  O  0  c— •  0  0  ™ 1  rH  ON  ^ c—  rH rH  m rH  2 D  trn  S 1  M  z s  CU  •p  H  —to  CO  s c w 0 05 - P  _ c w 0  X  X >> CU 0 W J ac X  a 0  EH 40  cd 0  rH H  cu  a  m I  rH  < S  CO rH rH 01  T3  H  O  <C  Ct)  CM  ON  CO  0 0  O  rH rH CD  m  _r  O  CM  CM CM I I  in  co  =3- m  _r  rH a f-  m I  co  t— o  in N  G\  •P ed  < C Q  cu  CM  O * _• in in  a-  t-  •a: -H  m  CO  -=r  o  o\  CM  rH  LH CM . .  vo co  I  t— co  . o. -.=r  VO -=JCM CM  CM  aCM I  rn  co  o\  VO r H . .  r n rn  o  o  OV CM  OJ  rH  i n vo  t— OJ I  i-t  t—  CM  o 00  O  vo  O  co  rH  vo  CM  rH CM  in  ro .  CM rH  CM  00 o co  O  O  .  O a-  cn co  Cr. CO  in vo  *r  CM  O -=r  rH  I  m  CM  _r  I  in vo 3  I  O  . vo. .m  D \ CO  H  I  m  m. m . . n <  in  rH  c\j  rH  in  4  t— m co m CM o  o I  CM r H . .  CO .  co co cr\ . . . H • H m  o  1  •P  m . . m _r  -=r  EH - P  X rd  c  cd  C—  VO CVI rH I I  • rH CM  rH " rH OJ  1  1 co  • aCM  • CM OJ  1  1  CU  cu E C >H o PC u  <  CO  •  <  •  X  CO  rH rH  c  H  ed CJ3  —  o  MM  1-1  rn c—  CU  a  X >> CU 0 Cd J X X  •H T3 C CU  a  0.  <  •H >  c  Station  Jan. Feb. Mar. Apr. May  June  July  MEAN RAINFALL (mm.) Lytton  30.5 29.7 20.3 18.3 14.7 20.6 12.2  H e l l ' s Gate  119.1 98.6 108.0 59-9 38.4  34.3 24.4  Hope  165.6 149.6 125.0 107.2 6 1 . 5 55.1 35.6  MEAN SNOWFALL (cm.) Lytton  50.822.4 8.4  1.0  H e l l ' s Gate  5 5 . 92 3 . 4 8 . 1  1.5  Hope  6 6 . 82 7 . 41 1 . 9  1.0  7 4 . 9 5 1 . 1 2 8 . 4 1 9 . 1 14.7 2 0 . 6  H e l l ' s Gate  175.3  121.9  116.1  Hope  227.3 177.0  136.9  61.538.434.3 108.2  18.8  2 3 . 4 49.5 51.6  27.9  69.6 140.2 153.4 152.7 1026.8  6 1 . 55 5 . 1  45.0 334.6  46.0 104.4 181.9 204.2 212.3 1448.4  0.8  17.8 40.4 141.6  1.3  18.5 40.1 148.8 13.7  MEAN TOTAL PRECIPITATION (mm.) Lytton  Aug. Sept. Oct. Nov. Dec. Year  41.1 161.9  18.8 23.4 50.3 68.6 80.8 462.9 12.2 27.9 69.6 141.5 172.0 192.8 1175.7 24.4 46.0 104.4 181.9 217.7 249.4 1601.1 35.6  GREATEST RAINFALL IN 24 HOURS (mm.) Lytton  42.2 6 9 . 9 2 1 . 1 2 2 . 9 3 1 . 0 1 8 . 8 1 9 . 3 24.9 24.6 7 6 . 7 5 1 . 8 3 2 . 5  7 6 . 7  H e l l ' s Gate  8 8 . 6 9 3 - 5 3 6 . 8 5 5 . 6 2 1 . 6 3 7 . 1 2 9 . 2 2 1 . 1 42.2 8 6 . 1 8 6 . 9 6 6 . 8  9 3 . 5  Hope  9 7 . 7105.7  6 9 . 96 8 . 6 38.1  41.1 3 9 . 1 2 9 . 7 6 6 . 3 1 0 1 . 3  8 5 . 98 6 . 4  Appendix I. B. SUMMARY OF PRECIPITATION DATA FOR LYTTON, HELL'S GATE, AND HOPE, B.C. (Environment Canada, Canadian Normals: P r e c i p i t a t i o n , 1 9 4 1 - 1 9 7 0 ) .  105.7  142  APPENDIX I I T H E E L U C T E R R A I N C L A S S I F I C A T I O N Terrain units basis of t h e i r normally  are  form  are c l e a r l y  i s o l a t e d by  and  visible,  but  shadow o r v e g e t a t i v e c o v e r .  is  then  a s s i g n e d t o the u n i t .  are  The  in  this  P r o p e r t i e s o f the  Their  and  :  unit  texture  (lower  case)  level  of  to which  are  represented  A  i i ) '• g e n e s i s o f t h e m a t e r i a l (upper iii)  surface expression  iv)  qualifying  v) m o d i f y i n g full  list  page 14 3 prepared The  and by  process  of t e r r a i n  (upper  (upper  attributes  ELUC  case s u p e r s c r i p t )  case preceded and  their  by  a hyphen)  symbols a p p e a r on  classification  handbook  (1976) . descriptor  properties.  i s used  f o r those  material  units  i n f o r m a t i o n as t o g l a c i a l ,  T h e s e a r e i n d i c a t e d by  f o l l o w i n g the m a t e r i a l o r p r o c e s s  water-deposited  case)  case)  each i s e x p l a i n e d i n the  qualifying  or process  (lower  descriptor  which there i s a d d i t i o n a l  letters  case  sequence: i-) c l a s t i c  The  i f obscured  attribute  terrain  the  o f a l p h a b e t i c symbols  order the  on  boundaries  inferred  A string  t h e a l p h a b e t i c components s p e c i f y refer.  interpreter  material types.  by  they  the  upper  symbols.  (F) a s s o c i a t e d w i t h g l a c i a l  for  organic, case Thus meltwater  Q  ( ) i s written,  while are  inactive  labeled  ( ) colluvial  slopes  (C)  in a landslide  area  143  I.  TEXTURE  Specific b k p s 4 c II.  Clastic  Terms  bouldery cobbly pebbly sandy silty clayey  Common C l a s t i c Terms  Org; a n i c Terms e flbric m mesic h humic  a blocky r rubbly g gravelly f fines  GENESIS A C E P I L M  III.  0  anthropogenic colluvial aeolian fluvial ice lacustrine morainal  R S V W  u  organic bedrock saprolite volcanic marine undifferentiated  m r s t v  subdued ridged steep terraced veneer  SURFACE EXPRESSION a b f h 1  IV.  apron blanket fan hummocky level  QUALIFYING DESCRIPTORS  Clastic  Organic  Process  G  A glacial 1  active inactive  B  S  V.  bog  F fen swamp  MODIFYING PROCESSES -A -B -C -D -E  avalanched bevelled cryoturbated deflated channelled  -F -H -K -N -P  falling kettled karst modified nivated piping  -S -V -W * -X * -Y  D e s c r i p t i v e t e r m i n o l o g y o f the ELUC t e r r a i n c l a s s i f i c a t i o n A s t e r i s k (*) denotes a d d i t i o n s made by the w r i t e r .  soliflucted gullied washed road, railway deforested scheme.  144  c  .  1  F i n a l l y , where f i e l d o b s e r v a t i o n shows t h a t the s u r f i c i a l geology i s more complex than i n d i c a t e d by i t s surface  e x p r e s s i o n , s t r a t i g r a p h i c r e l a t i o n s between  may be shown.  materials  F o r example, where a t h i n l a y e r o f b l o c k y  colluvium  o v e r l i e s gravelly f l u v i a l deposits,  described  as,  the u n i t i s  arCv gFl When s e v e r a l  s u r f i c i a l materials  occur w i t h i n  a single  t e r r a i n u n i t , t h e i r a r e a l p r o p o r t i o n s may be i n d i c a t e d by e q u a l i t y o r s l a s h symbols.  I f one type of m a t e r i a l  occupies  90 t o 100% o f the area, i t alone r e p r e s e n t s t h a t u n i t .  In  a u n i t wherein a c o l l u v i a l apron i s much more e x t e n s i v e than steep bedrock, the c l a s s i f i c a t i o n i s , arCa // Rs A r e a l p r o p o r t i o n s of m a t e r i a l s  on v e r t i c a l l y - t a k e n photography  i s not t o be confused with t h e i r r e l a t i v e predominance i n l a t e r a l viewing o f the t e r r a i n .  This applies p a r t i c u l a r l y  to steep rock slopes o f which the a c t u a l v e r t i c a l extent i s hidden i n a e r i a l photographs.  Symbols f o r a r e a l  used i n composite u n i t s appear i n the f o l l o w i n g  relationships table:  145  symbol  secondary material (% cover)  dominant material (% cover)  proportional relation  55  i s equivalent to  =  45  70 - 55  i s greater  /  30 - 45  90 - 70  i s much g r e a t e r  //  10 - 30  - 45  than  D e s c r i p t i v e terminology  than  - 55  f o r t e r r a i n u n i t s i n the  F r a s e r Canyon i s i l l u s t r a t e d i n the f o l l o w i n g examples:  descriptive terminology  terrain unit characteristics  arCa - FA  Blocky and rubbly c o l l u v i a l apron, showing r e c e n t f a i l u r e scars and avalanche t r a c k s .  arC h(r)  Blocky, rubbly c o l l u v i u m d e r i v e d from i n a c t i v e r o c k f a l l or l a n d s l i d e processes whose s u r f a c e appears hummocky and s l i g h t l y r i d g e d , and which i s t r a v e r s e d by a road and/or r a i l w a y t r a c k .  I  fgCv(b)  - X  F i n e and g r a v e l l y c o l l u v i a l veneer o r blanket.  r  gF l ( t )  Gravelly f l u v i o - g l a c i a l  sgFt  Sand and g r a v e l f l u v i a l t e r r a c e .  •" -FX  F i n e i n a c t i v e a e o l i a n veneer o v e r l y i n g a sand and g r a v e l f l u v i a l t e r r a c e .  ,E  l e v e l or terrace.  146  APPENDIX I I I M E T H O D S APPENDIX I I I . A  0 F  A N A L Y S I S  DESCRIPTIVE STATISTICS  A computer program s e t c a l l e d UBC SPSS:8, Package f o r the S o c i a l S c i e n c e s " , was used.  "Statistical  I t i s a large  program designed t o do d e s c r i p t i v e analyses on large-volume data, accommodating both parametric and non-parametric statistics.  The SPSS program was chosen i n the study t o handle  the s e m i - q u a n t i t a t i v e a t t r i b u t e s used t o c h a r a c t e r i z e the slopes a d j a c e n t t o the t r a c k s . Frequency  o f occurrence o f each o f the s l o p e a t t r i b u t e s  was generated by SPSS subprogram FREQUENCIES i n both t a b u l a r and histogram form.  J o i n t frequency t a b l e s o r c r o s s t a b u l a t i o n s ,  i n v o l v i n g two o r more slope a t t r i b u t e s s i m u l t a n e o u s l y , are a v a i l a b l e i n SPSS u s i n g subprogram CROSSTABS.  The s t a t i s t i c a l  s i g n i f i c a n c e o f the CROSSTABS d i s t r i b u t i o n i s t e s t e d by the chi-square s t a t i s t i c , and measures o f a s s o c i a t i o n between v a r i a b l e s are a l s o  available.  SPSS subprogram BREAKDOWN p r o v i d e s a c r o s s t a b u l a t i o n o f independent v a r i a b l e s w i t h r e s p e c t t o a dependent one.  In t h i s  study a BREAKDOWN o f s u r f i c i a l geology by slope angle r e s u l t s i n a mean slope f a i l u r e i n c i d e n c e f o r each p o s s i b l e of  those a t t r i b u t e s .  combination  An example o f the SPSS FREQUENCIES,  CROSSTABS, and BREAKDOWN subprograms i s found i n Appendix  III(B).  F u r t h e r i n f o r m a t i o n on the SPSS programs i s found i n N i e e t a l . ..(2nd ed., 1975) and i n K i t a  (.1978) .  147  Appendix  III.Bi  Sample SPSS P r o g r a m  SPSS BATCH SYSTEM HTS/SPSS, VERSION H , RELEASE 8.0, DECEMBER  17, 1979  DEFAULT SPACE ALLOCATION.. WORKSPACE 71630 BYTES TRANSPACE 10240 BYTES  ALLOWS FOR.. 102 TRANSFORMATIONS 409 RECOOE VALUES • LAG VARIABLES 1641 IF/COMPUTE OPERATIONS  PAGESIZE VARIABLE LIST  5 6 INPUT MEDIUM 7 INPUT FORMAT  NOEJECT MILE FREQ SURFGEOL MODI TO M0D6 BR1 3R20 BR24 BRCUS CUTSLOPE MATROCK MATUN ANGLE 1 TO ANGLES HEIGHT 01 STANCE JOINTNGl TO JOINTNG4 SILTPRES SILTABS SEEPAGE FIXED MEASURE 1 TO MEASURE9 DISK FIXED(F4.0,1X,F2.0,IX,F7.0,10F1.0» 1K,F1.0,IX,2F1.0.1X,5F1.0, 1X,F1.0,1X,F1.0,1X,4F1.0,1X,2F1.0, IX.F1.0,IX,F1.0,IX,9F1.0I  ACCORDING TO YOUR INPUT FORMAT, VARIABLES ARE TO BE READ AS FOLLOWS VARIABLE FORMAT RECORD COLUMNS MILE F 4. 0 FREQ F 2. 0 SURFGEOL F 7. 0 MODI F 1. 0 MOD 2 F 1. 0 MO 03 • F 1. 0 MQD4 F 1. 0 M0D5 F 1. 0 M0D6 F 1. 0 BR1 F' 1. 0 BR20 F 1. 0 BR24 F 1. 0 BRCUS F 1. 0 CUTSLOPE F 1. 0 HATROCK F 1. 0 MATUN <"F 1. 0  I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1  16916171819202122232425272930-  4 7 15 16 17 18 19 20 21 22 23 24 25 27 29 30  148  ANGLE 1 ANGLE2 ANGLE3 ANGLE4 ANGLES HEIGHT DISTANCE J0INTNG1 J0INTNG2 J0INTNG3 J0INTNG4 SILTPRES SILTABS SEEPAGE FIXED MEASURE I MEASURE2 MEASURE3 MEASURE4 MEASURES MEASURE6 MEASURE? MEASURE8 MEASURE"?  F F F F F F F F F F F F F F F F F F F F F F F F  9 N OF CASES 10 COMPUTE 11 RECODE 12 13 14 15 COMPUTE 16 COMPUTE 17 COMPUTE 18 19 20 21 22 23 24  COMPUTE COMPUTE COMPUTE COMPUTE COMPUTE COMPUTE COMPUTE  25 26 27 28  COMPUTE COMPUTE COMPUTE COMPUTE  29 30 31 32 33  COMPUTE COMPUTE COMPUTE COMPUTE COMPUTE  1. 0 1. 0 1. 0 1. 0 1. 0 1. 0 1. 0 I. 0 1. 0 1. 0 1. 0 1. 0 1. 0 1. 0 1. 0 1. 0 1. 0 1. 0 1. 0 1. 0 1. 0 1. 0 1. 0 1. 0  1 l 1 X 1 1 1 1 1 1 1 1 1 1 l l 1 1 1 1 1 1 i 1  32333435363 8404243444547485052545556575859606162-  32 33 34 35 36 38 40 42 43 44 45 47 48 50 52 54 55 56 57 58 59 60 61 62  UNKNOWN SURFGEOL=TRUNC(SURFGEOL/100001 SURFGEOL!400=1)(415,514=2»I 416 = 3)(417=4) (425=51(435=6) (495=7)(496=8)(497=9)(500,515=10)(517=11) 1524=12) (527=13)(534=14)(600=15)(634=16)(695=17) (700,795=18)(734=19)(897=20) NSURF=SURFGEOL NFREQ=FREQ>1 M0DIFIER=l*M0Dl+2*M0D2«-4*M0D3*8*M0D4<-16*M0D5 •32*M0D6 NMOD=MODIFIER+1 BEDROCK=1*BR1*2*BR20+3*BR24*4*BRCUS NR0CK=BEDR0CK+1 NCUT=CUTSL0PE+1 MATERIAL=1*MATR0CK+2*MATUN NMAT=MAT£RIAL»1 ANGLE=1*ANGLE1+2*ANGLE2*3*ANGLE3+4*ANGLE4* 5*ANGLE5 NANGLE=ANGLE+1 NHEIGHT=HEIGHT*1 NDIST=DISTANCE+l J0INTNG=l*J0INTNGl*2*J0INTNG2«-3*J0INTNG3* 4*J0INTNG4 NJ0INT=J0INTNG+1 SILT=1«SILTPRES+2*SILTABS NSILT=SILT*l NSEEP=SEEPAGE*l NFIX=FIXED+l  149  MEASURES=1*MEASURE1+2*NEASURE2+4*NEASURE3* 8*MEASURE4+ 16*MEASURE5*32*MEASURE6*64*MEASURE7* 35 128*MEASURE8+256*MEASURE9 36 RECODE MEASURES (1=1)(2=2)(4=3)(8=4)(16 = 5)(32=6) (64=7)(128=8)(256=9) 37 COMPUTE NMEAS=MEASURES+l 38 RECODE NMODI 2=1 M 4 = 2 ) ( 6 = 3 M 8=4) (10=5 )(12=6) (18=7) 122=81 39 (26=9)(34=10) 40 FREQUENCIES INTEGER=NCUT(1,2) NANGLE!l?6I 41 STATISTICS ALL AFTER READING 199 CASES FROM SUBFILE NONAME , END OF DATA WAS ENCOUNTERED ON LOGICAL UNIT # 8  34 COMPUTE  SPSS BATCH SYSTEM FILE  NONAME  (CREATION DATE = 06/23/80)  NCUT CATEGORY LABEL CODE uncut  VALID CASES  RELATIVE ADJUSTED CUMULATIVE FREQUENCY FREQUENCY ADJ FREQ (PERCENT)(PERCENT) (PERCENT)  1  33  19.1  19.1  2  161  80.9  100.0  TOTAL  199  100.0  cut  MEAN MODE KURTOSIS MINIMUM  ABSOLUTE FREQUENCY  1.809 2.000 0.516 1.000  199  STO ERR STD DEV SKEWNESS MAXIMUM  0.028 0.394 -1.585 2.000  MISSING CASES  MEDIAN VARIANCE RANGE  1.882 0.155 1.000  150  NANGLE CODE  ABSOLUTE FREQUENCY  RELATIVE FREQUENCY IPERCENT)  ADJUSTED FREQUENCY (PERCENT)  CUMULATI ADJ FR (PERCEN  NA. 1  11  5.5  5.5  5.5  > 70° 2  87  43. 7  43.7  49.2  <70°3  6  3.0  3.0  52.3  <30°4  24  12.1  12.1  64.3  30°41°5  35  17.6  17.6  81.9  36  18.1  18.1  100.0  199  100.0  100.0  TOTAL MEAN MODE HURTOSIS (MINIMUM MEDIAN VARIANCE RANGE VALID CASES  43 CROSSTAB'S 44 45 OPTIONS 46 STATISTICS  3.467 2.000 -1.513 1.000 2.750 2.907 5.000 199  STD ERR STD DEV SKEWNESS MAXIMUM  MISSING CASES  0.121 1 .705 0.282 6.000  0  -  VARIABLES=FREQI0,22 ) NCUT(1,2) NANGLE(1*61/ TABLES=NCUT BY NANGLE/ 9 1,3,7  151  * *  C R O S S T A B U L A T I O N OF NCUT BY NANGLE  * *  NANGLE COUNT ROM PCT COL PCT  2  <70" 3  uncut 54.5 I 1.1  TOT PCT N.A. 1  *CUT  1  I>70  6 15.8  I  1 2.6  3.0  1  0.5  2 5.3 33.3 1.0  2  5 3.1 45.5 2.5  1  86 53.4 98.9 43.2  4 2.5 66.7 2.0  1 0.6 4.2 0.5  COLUMN TOTAL  11 5.5  6 3.0  24 12.1  cut  1  I<30° 4 -I  87 43.7  *A* CHI SQUARE = SIGNIFICANCE =  126.08058 HITH  I30^f5  23 60.5 95.8 11.6  5 13.2 14.3 2.5 I I I I  30 18.6 85.7 15.1 35 17.6  I  I I I I  1  > 0 ° 6  38 1 2.6 19.1 2.8 0.5 161 35 21.7 80.9 97.2 17.6 36 199 18.1 100.0  5 DEGREES OF FREEDOM.  0.0000  CONTINGENCY COEFFICIENT = 0.62277 KENDALL'S TAU C = -0.01717 SIGNIFICANCE  47 BREAKDOWN 48 49 STATISTICS  ROW TOTAL  I2-TAILEDJ>= 0.8047  VARIABLES=FREQ(0,22) NCUT(1,2) NANGLEt1,6)/ CROSSBREAK=FREQ BY NANGLE BY NCUT/ ALL  152  *  *  *  *  *  *  *  * *  VARIABLE  C R O S *  *  *  *  *  *  S *  *  AVERAGED...  B R E A K D O W N NANGLE BY NCUT * * * * * * * * * *  O F *  *  * *  *  FREQ  NCUT MEAN COUNT SUM STO D E V  uncut  l  MANGLE  N.A.  I  1.45 11 16.00 3.01  2.17 I 86 I 187.00 I 2.81 I 1 1.75 I 4 I 7.00 I 2.36 I 1 0.0 I 1 I 0.0 I 0.0 I  2.15 87 187.00 2.81  1.20 35 42.00 2.14  1.00 0.0  1.33 I 30 1 40.00 I 2.28 I 1 3.09 I 35 I 108.00 I 4.58 I  0.24 38 9.00 0.59  2.22 161 358.00 3.24  6 0.0 0.0  >70°  <70  0.0 2 0.0 0.0  <30"  2  3.20 I 5 I 16.00 I 3.96 I  o.o  0.0 1 0.0 0.0  u  CUt  ROW TOTAL  0.26 23 6.00 0.69  1  0.40 3CP-41°  5  2.00 0.55 1.00  >«1°  COLUMN  TOTAL  1  1.17 6 7.00 2.04 0.25 24 6.00 0.68  3.03 36 109.00 4.53  — I  1.84 199 367.00 3.03  *  * *  *  *  *  *  *  153  RAW CHI SQUARE = 126.08058 WITH 5 DEGREES OF FREEDOM. SIGNIFICANCE = 0.0000 CRAMER'S V = 0.79597 CONTINGENCY COEFFICIENT = 0.62277 LAMDA (ASYMMETRIC) = 0.19643 WITH NANGLE DEPENDENT. = 0.60526 WITH NCUT DEPENDENT. LAMDA (SYMMtTRIC) = 0.30000 JNCERTAINTY COEFFICIENT (ASYMMETRIC) =0.19160 WITH NANGLE DEPENDENT. 0.58840 WITH NCUT DEPENDENT. UNCERTAINTY COEFFICIENT (SYMMETRIC) = 0.28907 KENDALL'S TAU B = -0.01812. SIGNIFICANCE = 0.3520 KENDALL'S TAU C = -0.01717. SIGNIFICANCE = 0.3594 GAMMA = -0.02938 SOMERS'S D (ASYMMETRIC) = -0.02779 WITH NANGLE DEPENDENT. = -0.01181 WITH NCUT DEPENDENT. SOMERS'S D (SYMMETRIC) = -0.01658 ETA = 0.00155 WITH NANGLE OEPENDENT. = 0.63358 WITH NCUT DEPENDENT. =  50 FINISH NORMAL END OF JOB. 50 CONTROL CARCS WERE PROCESSED. 0 ERRORS WERE OETECTED.  154  APPENDIX  I I I . C  An was  SLOPE  "Automatic  used  t o  e x p l a i n i n g  t h i s  t h a t i s  study,  The  AID3 p r o g r a m  m a x i m i z e d .  t h e  was o f  s e a r c h i n g  s e t o f p r e d i c t i n g e n t i f i e s those which a r c h e r ' s a b i l i t y t o c e o f a d e p e n d e n t 2). s l o p e  t e r r a i n c l a s s i f i c a t i o n  d e s i g n e d  t h e  f o r l a r g e  map  p a t t e r n  s o  t h a t  o f  a n d  o v e r a l l v a r i a n c e  o f  batches s o  t h e e a s t e r n b y  p r o c e d u r e  s l o p e  r e s t r i c t i n g  d a t a  t h e power  r e s u l t a n t endgroups a r e n o t  t h e  d i s c u s s i o n o f  d a t a  s p l i t t i n g / r e s p l i t t i n g  i s j u s t i f i e d  importance  i n t r i c a c i e s  t h e a t t r i b u t e s i n  f a i l u r e .  I t s a p p l i c a t i o n t o  199 c a s e s  F u r t h e r  (AID3)  i n v e s t i g a t i o n .  t h e r e l i a b i l i t y  e x p l a i n i n g  e t  from  f i e l d  The  a i d s e a n p.  o f  p r o g r a m  t h e p r e d i c t i n g c h a r a c t e r i s t i c sa r e  t h e  s m a l l .  i n f l u e n c e  a r c h e s among e r i s t i c s a n d c r e a s e t h e r e f o r t h e v a r i e ( L e , 19 75,  d e r i v e d  c o m p r i s i n g the  t h e  t h e v a r i a t i o n i n s l o p e  a t t r i b u t e s from  EVALUATION  I n t e r a c t i o n D e t e c t o r "  determine  AID3 s e c h a r a c t b e s t i n account v a r i a b l In  ATTRIBUTE  i n d i v i d u a l v a r i a b l e s  i s  o f  t o o  i n  s t r e s s e d .  t h e n a t u r e  o f AID3 o u t p u t  i t s i n t e r p r e t a t i o n a r e p r e s e n t e d  b y  a n d  t h e  S o n q u i s t  a l . ,1974). B e g i n n i n g  v a r i a b l e  w i t h  c l a s s e s  t h e complete  a r e f i r s t  d e p e n d e n t  v a r i a b l e , s l o p e  s p l i t s  each  on  i s chosen.  i n  a r e l e s s  c l a s s  o r d e r e d f a i l u r e  The than  o r  s e t , t h e  b y  a mean  i n c i d e n c e .  v a r i a b l e i s e v a l u a t e d  s i g n i f i c a n t , one  d a t a  s p l i t e q u a l  a n d  v a l u e  s o  o f  t h e  A number  t h e b e s t ,  i s made t o  p r e d i c t o r  t h a t  a l lm e a n s  o r  o f m o s t  a l l . means  i n t h e  o t h e r  155  class.  Subsequently, each subgroup undergoes the same t r e a t -  ment u n t i l the t o t a l v a r i a t i o n i s reduced as much as p o s s i b l e . The AID3 user imposes  l i m i t s on the analyses which  terminate the s p l i t t i n g procedure.  These a r e ,  i) the minimum v a r i a n c e e x p l a i n e d i n each group, s e t i n these a n a l y s e s t o 2% o f the t o t a l variance, ii) iii)  the minimum number o f cases i n each group, s e t here t o f i v e , and t o maximum number o f s p l i t s allowed, s e t here to an a r b i t r a r i l y h i g h value o f 89.  A t r e e diagram showing the s u c c e s s i o n o f s p l i t groups may be generated and i t s form used as an i n d i c a t i o n of v a r i a b l e i n t e r a c t i o n and d i s t r i b u t i o n . F i n a l groups r e s u l t i n g from the s p l i t t i n g process may be o f three t y p e s .  Small groups cannot be s p l i t f u r t h e r as the  r e s u l t a n t groups c o n t a i n fewer cases than the minimum number s e t by the programmer. E x p l a i n e d groups c o n t a i n more than the minimum number of. cases but have l i t t l e  internal  variation,  so t h a t f u r t h e r s p l i t t i n g on the independent v a r i a b l e s cannot occur.  Irt unexplained groups, though the i n t e r n a l v a r i a t i o n i s  l a r g e , a f u r t h e r s p l i t cannot be made on the independent v a r i a b l e s used i n the a n a l y s i s . I n c o n s i s t e n c y i n the s t r u c t u r e o f the t r e e i s evidence of i n t e r a c t i o n between v a r i a b l e s . Where no i n t e r a c t i o n o c c u r s , the v a r i a n c e i s s p l i t on the same v a r i a b l e a t c o r r e s p o n d i n g l e v e l s , o r branches, o f t h e , t r e e . When there i s i n t e r a c t i o n between s e v e r a l v a r i a b l e s the r e s u l t i s a skewed, asymmetric  tree  structure.  156  APPENDIX III.D.  CLUSTER ANALYSIS AND SCALOGRAM ANALYSIS  MULTI-DIMENSIONAL  A h i e r a r c h i c a l c l u s t e r i n g program, HCLUS,  developed  by Frank Flynn a t the U n i v e r s i t y o f B r i t i s h Columbia, was used on the F r a s e r Canyon slope data.  I t employs an  agglomerative  method by which a nested t r e e i s c o n s t r u c t e d from the i n d i v i d u a l cases, or branches, t o the r o o t .  The data are  organized i n t o groups w i t h i n which v a r i a b l e s used t o d e s c r i b e each datum are s i m i l a r .  In t h i s study, s i t e s along the  r a i l w a y l i n e s are d e s c r i b e d i n terms o f slope The  attributes.  s i m i l a r i t y between cases and/or c l u s t e r s i s  e v a l u a t e d on the b a s i s o f a pre-determined  linkage  procedure.  S e v e r a l o f the merging sequences are between - c l o s e s t members ( s i n g l e linkage) - most d i s t a n t members (complete linkage) - average d i s t a n c e w i t h i n o r between members (average l i n k a g e ) . The  complete l i n k a g e method was employed i n t h i s study as i t  i n c r e a s e s the d i f f e r e n c e between r e s u l t a n t c l u s t e r s . d i s c u s s i o n o f HCLUS i s made by F l y n n Although procedure, the groups.  Further  (1976).  slope f a i l u r e was not c o n s i d e r e d i n the c l u s t e r i n g  i t has been used i n the s t a t i s t i c a l  j u s t i f i c a t i o n of  SPSS subprogram ONEWAY, the a n a l y s i s o f  v a r i a n c e , was employed i n the cases along the e a s t e r n where the f a i l u r e h i s t o r y i s known. t e s t i n g o f c l u s t e r s generated  slopes  R e s u l t s o f the s t a t i s t i c a l  with the e a s t e r n slope a r e ;-•..<•.:' •" v  t e n t a t i v e l y . e x t r a p o l a t e d t o the western slopes as w e l l . A second method used t o group the s i t e s was the GuttmannLingoes m u l t i d i m e n s i o n a l  scalogram  a n a l y s i s , MSA-I.  In t h i s  157  a n a l y s i s , data d e s c r i b e d by n v a r i a b l e s f a l l s i n t o a m-dimensional E u c l i d e a n framework.  W i t h i n t h i s each case  occupies a d i s t i n c t p o s i t i o n determined by the n v a r i a b l e s . A c o e f f i c i e n t o f c o n t i g u i t y i s generated, ranging from -1 t o +1, which i n d i c a t e s the degree o f s p a t i a l a s s o c i a t i o n o f the data i n the m-dimensional  space.  The c o e f f i c i e n t has a  value of +1 when the a s s o c i a t i o n i s p e r f e c t . cannot be separated i n m-dimensional  When the data  space on the b a s i s o f  the v a r i a b l e s used, the c o e f f i c i e n t has a value o f -1. F i r s t the data are p l a c e d i n an o r t h o g o n a l c o - o r d i n a t e system from which the i n i t i a l E u c l i d e a n d i s t a n c e s are calculated.  A p r e - s e t number of i t e r a t i o n s ensues by which  the c o e f f i c i e n t o f c o n t i g u i t y i s maximized m u l t i p l i e r f o r the i t e r a t i o n s .  using a s c a l a r  F i n a l l y the m-dimensional  c o - o r d i n a t e s o f the data are l i s t e d and a p l o t ( s ) showing  two dimensions a t a time.  produced  The data may be separated  i n t o groups o f s i m i l a r c h a r a c t e r by (m-1)-dimensional cutting surfaces.  F u r t h e r d i s c u s s i o n o f the Guttmann-Lingoes  MSA procedure i s made by Lingoes (19 7 3 ) . Before HCLUS and MSA-I were used, the data were s u b j e c t e d t o a d u p l i c a t e - s e a r c h i n g program, which i s o l a t e d cases w i t h unique combinations o f the v a r i a b l e s employed. i n order t o save computing  T h i s was done  time i n the lengthy search  procedures w i t h i n the two c l a s s i f i c a t i o n o p e r a t i o n s .  The  d u p l i c a t e d s i t e s were r e i n s t a t e d a f t e r the programs were complete.  158  Appendix IV. Appendix  IV.  TYPES OF SLOPE FAILURE IN THE FRASER CANYON A.  MODES OF FAILURE IN ROCK SLOPES Undisturbed  Slopes  (above) K u t h l a t h post-glacial landslide upslope from mile 25.0 (40.2 km) on the east s i d e o f the canyon. Steep rock scarps extend up t o 2000 f e e t (600 m) i n h e i g h t . (below) Recent r o c k f a l l s i t e s on the upper slope and i n the bedrock notch i n c i s e d by the F r a s e r R i v e r . Photo taken o f mile 9.6 (15.4 km) on the east s i d e o f the canyon.  159  Trackside  Slope  Site of o r i g i n of a r e c e n t r o c k f a l l onto t h e t r a c k s . Note t h e j o i n t i n g and f r a c t u r i n g p a t t e r n at the r o c k f a l l s c a r . Photo taken at m i l e 1 6 . 7 ( 2 6 . 9 km) on t h e e a s t s i d e o f the canyon.  ti.  FAILURES IN ROCK-AND-COLLUVIAL Undisturbed  Slopes  F a i l u r e o f a b e d r o c k - a n d - c o l l u v i a l s l a b above t h e T r a n s Canada H i g h w a y , u p s l o p e f r o m m i l e 13.0 ( 2 0 . 9 km) on t h e e a s t e r n s l o p e .  SLOPES  160  Rock-triggered colluvial slide above m i l e 19.2 (30.9 km) on the western s l o p e .  Trackside  Slope  Debris f a l l of c o l l u v i a l material o v e r l y i n g bedrock exposed i n the t r a c k s i d e slope at m i l e 13.9 (22.4 km) on the western s l o p e .  161 C. MODES OF FAILURE ON COLLUVIAL  SLOPES.  Undisturbed  Slopes  D e b r i s s l i d e from the upper slope at m i l e 6.4 ( 1 0 . 3 km) on t h e eastern slope.  Trackside  Slope  Dry r a v e l l i n g o f a c o l l u v i a l slope oversteepened at i t s base d u r i n g r a i l w a y c o n s t r u c t i o n . Photo t a k e n on t h e e a s t s i d e o f t h e canyon at m i l e 1 1 . 4 ( 1 8 . 3 km).  162  Appendix  V.  FREQUENCY DISTRIBUTIONS OF THE SLOPE ATTRIBUTES  The upper f i g u r e r e p r e s e n t s the percentage o f s i t e s i n that c l a s s o f the t o t a l number o f s i t e s ( = 1 9 9 ) . The a c t u a l number of s i t e s appears'in b r a c k e t s below. A. Material  Genesis  Eastern Slopes  Western Slopes  Eastern Western  predominantly colluvial: C  8.5 (17)  8.3 (18)  8.4 (35)  C=R  8.0 (16)  7.9 (17)  8.0 (33)  3.7 (8)  1.9 (8)  C=F° C=F  4.0  __  1.9 (8)  C/R  10.1 (20)  10.6 (23)  10.4 (43)  C//R  17.6 (35)  20.8 (45)  19.3 (80)  C R  4.0 (8)  4.6 (10)  4.3 (18)  3.0 (6)  1.4 (3)  2.2 (9)  V r  7.5 (15)  0.9 (2)  4.1  total colluvial slopes  62.7 (125)  58.2 (126)  60.5 (25D  C F  G  C  (8)  (17)  163  Appendix Material  V.  A.  Genesis  cont. Eastern Slopes  Western Slopes  E a s t e r n and Western S l o p e s  predominantly bedrock 3.0  R  (6)  R=F  R/C  —  5.5 (11)  2.3 (5)  2.7 (11)  0.9  (2)  0.5 (2)  1.9  3.6  (4)  (15)  R/F  1.0 (2)  R//C  8.5 (17)  1.4 (3)  4.8 (20)  t o t a l bedrock slopes  18.0  6.5 (14)  12.1 (50)  5.6  7.0  (12)  (29)  (36)  0.5 (2)  predominantly fluvio-glacial F  G  8.5 (17)  F //C  _ — _  F R  2.0 (4)  9.3 (20)  5.8 (24)  total fluviog l a c i a l slopes  10.5 (21)  17-2 (37)  14 .0 (58)  G  G  . 2.3 (5)  1.2 (5)  164  Appendix  V.  A.  cont. Eastern Slopes  Western Slopes  E a s t e r n and Western Slopes  8.0  13.9 (30)  11.1  3.2 (7)  1.9  17.1 (37)  13.0  E  0.9  0.5  F  (2)  (2)  M a t e r i a l Genesis predominantly fluvial F  (16)  F//C total fluvial slopes  0.5  (1) 8.5  (17)  (46)  (8)  (54)  a e o l i a n capping present  1 6 5  Appendix V.  B. Eastern Slopes  Western Slopes  58.3 (116)  58.3 (126)  (242)  XF  22.6 (45)  32.4 (70)  27.7 (115)  XA  2.5 (5)  1.9 (4)  2.2 (9)  XFA  2.5 (5)  2.3 (5)  2.4 (10)  XV  1.5 (3)  0.7 (3)  XFV  4.5 (9)  2.2 (9)  XY  4.5 (9)  2.2 (9)  XAY  1.5 (3)  0.7 (3)  M o d i f y i n g Processes X  XVY  E a s t e r n and Western Slopes 58.3  2.3 (5)  1.2 (5)  2.0 (4)  2.8 (6)  2.4 (10)  Cutslope  Eastern Slopes  Western Slopes  E a s t e r n and Western Slopes  uncut  19.1  25.5  22.4  (38)  (55)  (93)  80.9  74.5 (161)  77.6 (322)  XE  Appendix V.  cut  C.  (161)  166  Appendix V .  D. Eastern Slopes  Western Slopes  E a s t e r n and Western Slopes  30.7 (61)  56.5 (122)  44.1  69.3 ( 1 3 8 )  43.5 (94)  55.9 (232)  Eastern Slopes  Western Slopes  E a s t e r n and Western Slopes  non-critical  42.2 (84)  64.8  54.0  (140)  (224)  critical  57.8  35.2  46.0  Height non-critical critical  Appendix V. Distance  ( 1 8 3 )  E.  (115)  (76)  (19D  167  Appendix  V.  F. Eastern Slopes  Western Slopes  E a s t e r n and Western S l o p e s  5.5 (11)  15.7 (34)  10.8 (45)  70°  43.7 (87)  35.2 (76)  39.3 (163)  70°  3.0 (6)  1.9 (4)  2.4 (10)  30°  12.1 (24)  7.4  9.6 (40)  17.6 (35)  29.2 (63)  23.6  18.1 (36)  10.6 (23)  14.2 (59)  Material  Eastern Slopes  Western Slopes  E a s t e r n and Western S l o p e s  bedrock and unconsolidated  2.5 (5)  0.9 (2)  1.7 (7)  bedrock  46.7 ((93)  36.6  (79)  41.4 (172)  unconsolidated  50.8 (101)  62.5 (135)  56.9 (236)  Angle not a p p l i c a b l e  30°  -  41°  1*1°  Appendix  V.  (16)  (98)  G.  168  Appendix  V.  H. Eastern Slopes  Western Slopes  E a s t e r n and Western Slopes  not a p p l i c a b l e  54.3 (108)  63.0  (136)  58.8 (244)  coarse  24.6 (49)  25.5 (55)  25.1 (104)  intermediate  12.6 (25)  5.1 (11)  8.7  fine  7.0 (14)  6.0 (13)  6.5 (27)  intact  1.5 (3)  0.5 (1)  Eastern Slopes  Western Slopes  E a s t e r n and Western Slopes  12.1  20.8 (45)  16.6 (69)  18.1 • (39)  20.7 (86)  35.8 (99)  44.1  15.3 (33)  8.0  Jointing  Appendix V .  Pluton  Yale I n t r u s i v e s  (24) 23.6 (47)  Spuzzum I n t r u s i v e s Custer  1.0 (4)  I.  Bedrock Scuzzy  (36)  42.2  (84)  Gneiss  Hozameen Group  22.1 (44)  (183)  (33) 10 .6 (44)  169  Appendix V.  J. Eastern Slopes  Western Slopes  E a s t e r n and Western Slopes  absent  81.4 (162)  81.9 (177)  81.7 (339)  present  18.6 (37)  18.1 (39)  18.3 (76)  Pines  Eastern Slopes  Western Slopes  E a s t e r n and Western Slopes  not  48.2  36.6 (79)  42.2  Remedial Measures  Appendix V.  applicable  (96)  (175)  absent  46.2 (92)  58.3 (126)  52.5 (218)  present  5.5 (11)  5.1 (11)  5.3 (22)  Seepage  Eastern Slopes  Western Slopes  E a s t e r n and Western Slopes  absent  94.0  94.4  (187)  (204)  94.2 (391)  present  6.0 (12)  5.6 (12)  (24)  Appendix V.  9  K.  L.  5.8  170  Appendix VI. MEAN SLOPE FAILURE INCIDENCE FOR CATEGORIES OF SURFICIAL MATERIALS AND OF MODIFYING PROCESSES (Eastern slope data only) Appendix VI. surficial material  A. mean f a i l u r e incidence  number of cases  C  1.06  17  C=R  2.38  16  C=F  0.75  8  C/R  3.85  20  C//R C R C F C F R  1.71  35  1.50  8  2.00  6  3.17  6  R/C  2.00  11  R/F  0.50  2  R//C  3.94  17  F  G  0.59  17  F R F  G  0.00  4  G  1.40  0.19  F//C  1.00  total  1.54  15  •  16  1 199  171  Appendix  V I . B.  modifying  mean f a i l u r e  number of  processes  incidence  cases  X  1.36  116  XF  2.91  45  XA  0.40  5  XFA  3.00  5  XV  2.67  3  XFV  5.00  9  XY  0.56  9  XAY  0.67  3  XE  0.25  4  total  1.84  199  172  Appendix  VII.  A I D 3 TREE  AID3 was u s e d w i t h log-transformed variable,  DIAGRAM  the eastern  slope  failure  and t w e l v e o r f e w e r  slope  data,  as t h e dependent slope  a t t r i b u t e s as  independent v a r i a b l e s . T h i s appendix tree  diagram r e s u l t i n g  s i x most I m p o r t a n t with  ETA v a l u e s  Key  were  contains the  f r o m an A I D 3 r u n where t h e  slope a t t r i b u t e s  ( i e . those  g r e a t e r than 0.1), i n c l u d i n g  the m a t e r i a l g e n e s i s level,  using  v a r i a b l e at the t h r e e - d i g i t  used.  t o the Diagram:  mean f a i l u r e incidence (log-transformed) parent group  number o f s i t e s i n t h i s group ( a s t e r i s k denotes endgroups).  .354  62  .217 48  Appendix  VII.  174  Appendix V I I I . MSA-I  SCALOGRAMS.  A.  E a s t e r n slope data i n c l u d i n g  B.  E a s t e r n s l o p e data i n c l u d i n g 199 s i t e s and with the m a t e r i a l genesis v a r i a b l e t r u n c a t e d t o one d i g i t .  C.  Western slope data i n c l u d i n g  D.  Combined e a s t e r n and western slope i n c l u d i n g 415 s i t e s .  Key  199 s i t e s .  216 s i t e s . data  t o the Scalograms  O  1-4  sites  O  5-9  sites  #  10-24 25 +  sites  sites  S i x slope a t t r i b u t e s are used to d e s c r i b e each s i t e , and d e f i n e i t s p o s i t i o n i n s i x - d i m e n s i o n a l space. For ease i n i n t e r p r e t a t i o n , the scalogram data i s presented  o f the  i n two-dimensions, represented  by v e c t o r s 1 and 2.  175  176  rH  U  O -P o  o  «  >  O °  n 0° fc °  ° o  <  o o ° o o vector  °  2  O Cr O  o O  0  o  o o 3  o  #  0  ° o  1  o o o  ©  o  % * ° o o  0 °  o °  O 9§ co ° o o  °o ° o O® o  o  vector  0  8  n  %  ^  1  O o  o  ct  o ro  O  Appendix V I I I .  C.  <8  o  O  8 ° 0  o  8  (  M  D O  o o  to  o o  o  o o c£9ooo@  ©  S  " ©  o o  o r— -j CO 1  o  o vector  1  

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