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Bank and slope morphology as an indicator of Arctic terrain stability : (field studies along the rivers… Miles, Michael J. 1980

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BANK AND SLOPE MORPHOLOGY AS AN INDICATOR OF ARCTIC TERRAIN STABILITY ( F i e l d S t u d i e s A l o n g The R i v e r s and C o a s t s o f Banks I s l a n d , N.W.T.) by MICHAEL JOHN MILES B . S c , U n i v e r s i t y o f B r i t i s h C olumbia, 1972 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Department o f Geography) We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA August, 19 80 ©.Michael John M i l e s , 1980 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e -ments f o r an advanced degree a t t h e U n i v e r s i t y o f B r i t i s h C o lumbia, I agree t h a t t h e l i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by the Head o f my Department o r h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f Geography The U n i v e r s i t y o f B r i t i s h Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date: flpyyf ^ ; t ? 8 Q ABSTRACT F i e l d s t u d i e s were u n d e r t a k e n on Banks I s l a n d , N.W.T., t o i n v e s t i g a t e the. f e a s i b i l i t y o f u s i n g bank o r s l o p e morphology as an i n d i c a t o r o f t h e l a t e r a l s t a b i l i t y o f c o a s t a l and r i v e r i n e a r e a s l o c a t e d i n r e g i o n s o f p e r m a f r o s t . The s t u d y i n v e s t i g a t e d t h e m a t e r i a l c h a r a c t e r i s t i c s and n a t u r a l l y o c c u r r i n g e r o s i o n r a t e s ' a s s o c i a t e d w i t h the range o f bank o r s l o p e forms o c c u r r i n g w i t h i n the s t u d y a r e a . M o r p h o l o g i c f e a t u r e s w h i c h were s t u d i e d i n c l u d e d repose banks, s o l i f l u c t i o n s l o p e s , s k i n f l o w s , r e t r o -g r e s s i v e thaw f l o w s l i d e s , t h e r m o - e r o s i o n a l n i c h e s , o r g a n i c d e p o s i t s and d e f l a t i o n f e a t u r e s . The i n v e s t i g a t i o n i n d i c a t e d t h a t t h e morphology o f a bank o r slope' composed o f u n l i t h i f i e d sediments i s r e l a t e d t o the t e x t u r e and i c e c o n t e n t o f t h e a s s o c i a t e d m a t e r i a l s , and t o t h e r e l a t i v e e x posure o f t h e s i t e t o f l u v i a l o r l i t t o r a l p r o c e s s e s o f sediment r e m o v a l . Each m o r p h o l o g i c type was found t o have a c h a r a c t e r i s t i c range o f v a l u e s f o r each o f t h e s e p a r a m e t e r s . M a t e r i a l g e n e s i s was a l s o an i m p o r t a n t f a c t o r as i t a f f e c t s g r a i n s i z e , t o p o -g r a p h i c p o s i t i o n and t h e a v a i l a b i l i t y o f pore w a t e r . N i v a t i o n p r o c e s s e s , i c e wedges, v e g e t a t i o n c o v e r and e o l i a n p r o c e s s e s were o b s e r v e d t o m o d i f y morphology i n v a r y i n g d e g ree. Rates o f e r o s i o n as d e t e r m i n e d from f i e l d measurements, a i r photograph i n t e r p r e t a t i o n and l i t e r a t u r e r e v i e w were found t o v a r y w i t h bank o r s l o p e form. O b s e r v a t i o n s on t h e t i m i n g o f sediment movement i n d i c a t e t h a t t h e peak p e r i o d o f suspended sediment t r a n s p o r t o c c u r s d u r i n g s p r i n g snow m e l t r u n o f f . However sediment p r o d u c t i o n from t h e r m o k a r s t and n i v a t i o n p r o c e s s e s was observed to continue throughout most of the summer. As the post spring peak discharges are generally incompetent to transport t h i s material, s i g n i f i c a n t amounts of within channel sediment storage occur on an annual basis. Thus the seasonal timing of erosion does not d i r e c t l y correspond to the annually observed pattern of suspended sediment transport. The d i s t i n c t i v e bank and slope forms i d e n t i f i e d i n t h i s thesis are generally of s u f f i c i e n t size to be i d e n t i f i e d on e x i s t i n g a e r i a l photography. As each morphologic 1 type was observed to have a t y p i c a l range i n material c h a r a c t e r i s t i c s and erosion rates, a i r photograph interpretation of the d i s t r i b u t i o n of these features has p r a c t i c a l application i n the reconnais-sance l e v e l analysis of a r c t i c t e r r a i n s t a b i l i t y . i v TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS i v -LIST OF FIGURES v i LIST OF TABLES v i i i LIST OF PLATES i x ACKNOWLEDGEMENTS x i SECTION ONE INTRODUCTION 1.1 I n t r o d u c t i o n and O b j e c t i v e s 1 1.2 P r e v i o u s S t u d i e s 4 1.3 L o c a t i o n o f the Study Ar e a 7 1.4 The P h y s i c a l S e t t i n g 10 1.5 C l i m a t e 19 1.6 H y d r o l o g i c Regime 35 SECTION TWO MORPHOLOGIC CLASSIFICATION AND . REGIONAL DISTRIBUTION 2.1 I n t r o d u c t i o n 46 2.2 C l a s s i f i c a t i o n and Geometry 47 2.3 R e g i o n a l D i s t r i b u t i o n o f C l a s s i f i e d M o r p h o l o g i e s 5 3 SECTION THREE GEOTECHNICAL CHARACTERISTICS AND ENVIRONMENTAL SETTING OF REPRESEN-B.TATIVE BANKEOROSBOBEOM0RPHOLOGIES 3.1 Methodology 59 3.2 P r i m a r y F a c t o r s A f f e c t i n g Bank o r Slope Morphology 65 3.2.1 M a t e r i a l Genesis 65 3.2.2 T e x t u r e 73 3.2.3 I c e C o n t e n t 77 3.2.4 Exposure t o P r o c e s s e s o f Sediment Removal 90 3.2.5 Summary 93 Page 3.3 The E f f e c t o f M o d i f y i n g F a c t o r s .... 102 3.3.1 L o c a l i z e d Snow A c c u m u l a t i o n ... 102 3.3.2 I c e Wedges 112 3.3.3 V e g e t a t i o n 114 3.3.4 D e f l a t i o n 114 3.4 R e c o g n i t i o n o f R e p r e s e n t a t i v e M o r p h o l o g i e s /: 116 SECTION FOUR STABILITY OF REPRESENTATIVE MORPHOLOGIES 4.1 T y p i c a l Rates o f R e c e s s i o n 126 4.1.1 -l!^phodQlQ.gyja3\^fi^:Q^r.^\v-i-.»\ . .. 126 4.1.2 R e s u l t s 129 4.2 Ti m i n g o f Sediment P r o d u c t i o n 147 4.3 Assessment o f T e r r a i n S t a b i l i t y on The B a s i s o f Bank o r S l o p e Morphology 153 SECTION FIVE SUMMARY, CONCLUSIONS AND FUTURE STUDIES 5.1 Summary and C o n c l u s i o n s 156 5.2 F u t u r e S t u d i e s 159 BIBLIOGRAPHY 161 ( w i t h Addendum) vi'.-LIST OF FIGURES Page 1. L o c a t i o n o f the s t u d y a r e a 8 2. G e n e r a l i z e d bedrock g e o l o g y o f Banks I s l a n d 11 3a. G l a c i a l l i m i t s on Banks I s l a n d 13 3b. L o c a t i o n o f g r a i n s i z e samples d i s c u s s e d i n S e c t i o n 3.2.1 T 14 4. S e a s o n a l v a r i a t i o n i n r a d i a t i o n a t Sachs Harbour and Mould Bay 20 5. S e a s o n a l v a r i a t i o n i n mean d a i l y a i r temperature a t Sachs Harbour, Holman and Mould Bay 22 6. Frequency a n a l y s i s o f the obser v e d d a i l y maximum and, average mean d a i l y a i r t e m p e r a t u r e s a t Moula'^Bayf- Holman and Sachs Harbour d u r i n g the month o f J u l y 2 3 7. Average monthly s o i l t e m p e r a t u r e s r e c o r d e d a t Mould Bay A i r p o r t 25 8. S e a s o n a l d i s t r i b u t i o n and c o m p o s i t i o n o f mean monthly p r e c i p i t a t i o n 2 7 9. S e a s o n a l v a r i a t i o n i n t h e maximum 2 4 hour p r e c i p i t a t i o n and r a i n f a l l a t Sachs Harbour and Holman 2 8 10. Frequency a n a l y s i s o f the g r e a t e s t 24 hour p r e c i p i t a t i o n 29 11. S e a s o n a l v a r i a t i o n i n snow c o v e r a t Mould Bay, Sachs Harbour and Cape P a r r y 30 12. H y d r o m e t e o r o l o g i c a l d a t a , Thomsen R i v e r , 1975 36 13. M a x i m u m u o B s e r v e d e u n i t i d i s c h rc b a s i n a r e a f o r r i v e r s on Banks I s l a n d 39 14. Observed r i v e r t e m p e r a t u r e s on Banks I s l a n d , 1975 .. 41 15. C r o s s - s e c t i o n a l s u r v e y s o f r e p r e s e n t a t i v e bank o r s l o p e m o r p h o l o g i e s 48 16. M o d i f i e d p h y s i o g r a p h i c r e g i o n s o f Banks I s l a n d .... 54 17. P l a c e names and l o c a t i o n s o f f i e l d s i t e s 55 18. C u m u l a t i v e g r a i n s i z e p l o t s from r e t r o g r e s s i v e thaw f l o w s l i d e s i t e s l o c a t e d w i t h i n the b o u n d a r i e s o f t h e Amundsen G l a c i a t i o n 6 8 19. C u m u l a t i v e g r a i n s i z e p l o t s from r e t r o g r e s s i v e thaw f l o w s l i d e s i t e s l o c a t e d beyond the b o u n d a r i e s o f the Amundsen G l a c i a t i o n 70 v i ' i Page 20. R e l a t i v e p e r c e n t a g e s o f g r a v e l , sand and f i n e s a s s o c i a t e d w i t h banks o r s l o p e s o f v a r y i n g morphology 74 21. R e l a t i v e p e r c e n t a g e s o f sand, s i l t and c l a y i n m a t e r i a l s f o r m i n g s o l i f l u c t i o n s l o p e s , s k i n f l o w s and r e t r o g r e s s i v e thaw f l o w s l i d e s 76 22. T h e o r e t i c a l p o t e n t i a l f o r the growth o f s e g r e g a t e d i c e as a f u n c t i o n o f g r a i n s i z e ( a f t e r Penner, 1968) ~. 78 23. I c e c o n t e n t v e r s u s t h e p e r c e n t a g e o f g r a v e l , sand and f i n e s 79 24. I c e c o n t e n t v e r s u s the p e r c e n t a g e o f sand, s i l t and c l a y 81 25. I c e c o n t e n t v e r s u s i n d i v i d u a l p e r c e n t a g e s o f g r a v e l , sand and f i n e s 82 26. I c e c o n t e n t v e r s u s i n d i v i d u a l p e r c e n t a g e s o f s i l t and c l a y 83 27. Observed water c o n t e n t s and a c t i v e l a y e r depths on t h e o p p o s i n g s l o p e s o f an a s y m e t r i c v a l l e y ... 106 28. Observed w a t e r c o n t e n t s a d j a c e n t t o a s k i n f l o w s i t e 108 29 . S e a s o n a l v a r i a t i o n i n d i s c h a r g e and suspended sediment t r a n s p o r t i n r e l a t i o n to w a t e r temperature and p o t e n t i a l h e a t f l u x o b s e r v e d on D i s s e c t i o n Creek 148 v i i d \ LIST OF TABLES Page I Summary o f average wind speed and d i r e c t i o n a t Sachs Harbour and Mould Bay 32 I I D i r e c t i o n a l f r e q u e n c y o f monthly winds e q u a l t o or e x c e e d i n g 31.5 km/hr (17 kno t s ) a t Sachs Harbour, 1957-1966 34 I I I Observed maximum annua l mean d a i l y d i s c h a r g e s f o r r i v e r s on Banks I s l a n d 38 IV Exposure c l a s s i f i c a t i o n used i n t h i s s t u d y 6 3 V G e n e t i c o r i g i n and s t r a t i g r a p h y o f m a t e r i a l s f o r m i n g r e p r e s e n t a t i v e bank o r s l o p e m o r p h o l o g i e s 66 VI I c e c o n t e n t s i n banks o r s l o p e s o f d i f f e r e n t morphology^ based on 5 0 p e r c e n t ranges i n p e r c e n t g r a v e l , sand and f i n e s 85 V I I Types o f ground i c e o b s e r v e d i n banks and s l o p e s o f d i f f e r e n t morphology 87 V I I I Summary o f exposure r a t i n g f o r f i e l d s i t e s o f d i f f e r e n t morphology 91 IX Bank o r s l o p e morphology as a f u n c t i o n o f i c e c o n t e n t , g r a i n s i z e and exposure 9 4 X R e q u i r e d average a n n u a l r e c e s s i o n n e c e s s a r y f o r d i s c r i m i n a t i o n o f n e t r e t r e a t a t v a r y i n g s c a l e s o f photography and p e r i o d between s u c c e s s i v e a i r photo coverage 130 XI Observed r e t r e a t a t r e t r o g r e s s i v e thaw f l o w s l i d e s i t e s T ' -.. 139 X I I R e l a t i v e o r d e r o f magnitude f o r annual r a t e s o f r e c e s s i o n o r downslope movement a s s o c i a t e d w i t h banks o r s l o p e s o f v a r y i n g morphology 146 X I I I Summary t a b l e showing the r e l a t i o n s h i p between morphology and t e r r a i n s t a b i l i t y 155 i x LIST OF PLATES Page 1. The e f f e c t o f i n c r e a s i n g i c e c o n t e n t on the morphology o f banks o r s l o p e s composed o f f i n e t e x t u r e d m a t e r i a l s and l o c a t e d i n low exposure environments 95 2. The e f f e c t o f i n c r e a s i n g i c e c o n t e n t on the morphology o f banks o r s l o p e s composed of f i n e t e x t u r e d m a t e r i a l s and l o c a t e d i n moderate exposure environments 96 3. The e f f e c t o f i n c r e a s i n g i c e c o n t e n t on the morphology o f banks o r s l o p e s composed o f f i n e t e x t u r e d m a t e r i a l s and l o c a t e d i n h i g h exposure environments 9 7 4. The e f f e c t o f exposure and i c e c o n t e n t on the morphology o f sand t e x t u r e d d e p o s i t s 98 5. The e f f e c t o f exposure t o f l u v i a l a t t a c k on the morphology o f banks composed o f low i c e c o n t e n t g r a v e l s ? 99 6. The m o d i f y i n g e f f e c t o f n i v a t i o n p r o c e s s e s on morphology 10 4 7. V a r i a t i o n s i n snow c o v e r a t a s k i n f l o w s i t e on t h e P a r k e r R i v e r 109 8. The e f f e c t o f i c e wedges on bank morphology 113 9. An example o f v e g e t a t i o n p r o t e c t i n g a r i v e r bank from l a t e r a l e r o s i o n 115 10. An example o f d e f l a t i o n m o d i f y i n g t h e appearance o f an a n g l e o f repose bank 115 11. The appearance o f r e p r e s e n t a t i v e bank o r s l o p e 11-8-.-m o r p h o l o g i e s on a i r photographs 124 12. S e q u e n t i a l a i r photographs o f t h e 1913-1918 Canadian A r c t i c E x p e d i t i o n ' s base camp l o c a t e d 8 km e a s t o f Cape K e M e t t 134 13. S e q u e n t i a l a i r photographs o f a r e t r o g r e s s i v e thaw f l o w s l i d e l o c a t e d on the south-west c o a s t , 2 0 km n o r t h o f Masik R i v e r 141 i X Page 14. An e x c e p t i o n a l c o n c e n t r a t i o n o f wind blown sand a s s o c i a t e d w i t h l o c a l i z e d d e p o s i t s o f snow 144 15. S e a s o n a l v a r i a t i o n i n r i v e r bank morphology, D i s s e c t i o n Creek .. . ; 150 16. An example i n the use o f bank morphology as an i n d i c a t o r o f s u r f i c i a l s t r a t i g r a p h y 154 ACKNOWLEDGEMENTS The f i e l d work f o r t h i s t h e s i s was un d e r t a k e n as p a r t o f an i n v e n t o r y program sponsored by the T e r r a i n S c i e n c e s D i v i s i o n o f the G e o l o g i c a l Survey o f Canada. T h i s s u p p o r t i s g r a t e f u l l y acknowledged, and i n p a r t i c u l a r , Dr. T. Day, the p a r t y manager, d e s e r v e s r e c o g n i t i o n f o r h i s c o o p e r a t i o n and a s s i s t a n c e . F i n a n c i a l s u p p o r t f o r the s t u d y was p r o v i d e d by b o t h the A r c t i c and A l p i n e Research Committee and the Summer F e l l o w s h i p Program a t t h e U n i v e r s i t y o f B r i t i s h C olumbia. The a u t h o r would l i k e t o tak e t h i s o p p o r t u n i t y t o thank W. Gorman f o r h e r a s s i s t a n c e d u r i n g the f i e l d work and B. McLean f o r a i d i n g i n the d a t a c o m p i l a t i o n . B. Mordaunt and B. C o l l i n s a s s i s t e d w i t h the d r a f t i n g and the f i n a l t e x t was t y p e d by E. G o l d s w o r t h y . The a d v i s o r y committee composed o f Dr. M. Church, Dr. J . Ross Mackay and Dr. W. Mathews o f f e r e d a d v i c e and encouragement t h r o u g h o u t t h e p r o j e c t and t h i s a s s i s t a n c e was g r e a t l y a p p r e c i a t e d . 1 SECTION ONE INTRODUCTION 1.1 INTRODUCTION AND OBJECTIVES Given t h e c u r r e n t i n t e r e s t i n A r c t i c development, t h e r e i s an o b v i o u s need f o r a r e c o n n a i s s a n c e l e v e l p r o c e d u r e t o e v a l u a t e the g e o t e c h n i c a l c h a r a c t e r i s t i c s o f p o t e n t i a l development s i t e s and t r a n s p o r t a t i o n c o r r i d o r s . The e x t r e m e l y e x p e n s i v e c h a r a c t e r o f f i e l d o p e r a t i o n s i n the remote a r e a s o f n o r t h e r n Canada d i c t a t e s t h a t i n i t i a l s t u d i e s s h o u l d be based p r i m a r i l y on e x i s t i n g g e o l o g i c a l d a t a and a i r photo a n a l y s i s , w i t h o n l y a l i m i t e d amount o f f i e l d c h e c k i n g . E x p e r i e n c e g a i n e d on b o t h the A l y e s k a o i l p i p e l i n e and the Mackenzie V a l l e y P i p e l i n e Study i n d i c a t e t h a t w i t h i n r e g i o n s o f p e r m a f r o s t , r i v e r and c o a s t a l p r o c e s s e s can pose s i g n i f i c a n t g e o t e c h n i c a l and e n v i r o n m e n t a l problems. I n p a r t i c u l a r , work by a u t h o r s such as B r i c e (1971) , McDonald and Lewis (1973) , Outhet (1974), and C h i l d e r s (1975), i n d i c a t e t h a t r a t e s o f e r o s i o n can be s p e c t a c u l a r l y h i g h under t h e a p p r o p r i a t e ground i c e c o n d i t i o n s , m a t e r i a l t e x t u r e and e n v i r o n m e n t a l l o c a t i o n . Numerous s t u d i e s i n t h e Mackenzie V a l l e y by a u t h o r s such as Mackay (1966), Rampton and Mackay (1971), Hughes (1972), I s a a c s and Code (1972), Code (1973), and McRoberts and M o r g e n s t e r n (1973, 1974a, 1974b) a l s o i n d i c a t e the p r e s e n c e o f l a r g e s c a l e i n s t a b i l i t y f e a t u r e s such as s k i n f l o w s and r e t r o g r e s s i v e thaw f l o w s l i d e s , w h i c h o c c u r as a r e s u l t o f p e r m a f r o s t c o n d i t i o n s . As one s t e p i n the development o f a methodology f o r the e v a l u a t i o n o f such h a z a r d s , t h e p r e s e n t i n v e s t i g a t i o n seeks t o det e r m i n e the f e a s i b i l i t y o f u s i n g c o a s t a l and r i v e r b a n k : 2 morphology as an i n d i c a t o r o f the l a t e r a l s t a b i l i t y o f r i v e r i n e and c o a s t a l f e a t u r e s l o c a t e d w i t h i n a r e g i o n o f p e r m a f r o s t . I n a d d i t i o n , r i v e r and c o a s t a l e r o s i o n f r e q u e n t l y p r o v i d e v e r t i c a l e xposures o f m a t e r i a l w h i c h would o t h e r w i s e be u n a v a i l a b l e w i t h -o u t e x t e n s i v e s u b s u r f a c e d r i l l i n g . Thus bank o r s l o p e morphology may a l s o p r o v i d e an i n e x p e n s i v e i n d i c a t i o n o f the s t a b i l i t y o f t h e a d j a c e n t t e r r a i n . W i t h i n t h e c o n t e x t o f t h i s s t u d y , the terms "bank" and " s l o p e " a r e t h e r e f o r e d e f i n e d t o i n c l u d e r i v e r banks, t e r r a c e s c a r p s , and v a l l e y w a l l s , as w e l l as n o n - d e p o s i t i o n a l c o a s t a l f e a t u r e s . I n o r d e r t o l i m i t the scope o f t h e p r o j e c t , "banks" o r " s l o p e s " formed o f l i t h i f i e d m a t e r i a l s have been e x c l u d e d from the s t u d y . These m a t e r i a l s t e n d t o be c o m p a r a t i v e l y s t a b l e , as d i s c u s s e d by H a r t w e l l ( 1 9 7 3 ) and S h o r t and Wright- (1974), and a r e t h e r e f o r e o f l e s s i n t e r e s t . The i n i t i a l s t a g e s o f t h e s t u d y i n v o l v e d the i d e n t i f i c a t i o n o f a f i n i t e number o f t y p i c a l bank o r s l o p e forms w h i c h encom-passed the range o f m o r p h o l o g i c e x p r e s s i o n o c c u r r i n g w i t h i n the s t u d y a r e a ( S e c t i o n 2 ) . One o f t h e c r i t e r i a i n c h o o s i n g t h e s e morphologie-.rfea.tur.es was t h a t they s h o u l d g e n e r a l l y be-of s u f f i c i e n t s i z e t o be i d e n t i f i a b l e on e x i s t i n g a e r i a l photography. A r e p r e s e n t a t i v e number o f t h e s e s i t e s was then sampled t o d e t e r m i n e the range i n i c e c o n t e n t , t e x t u r e , and g e n e s i s a s s o c i a -t e d w i t h each morphology ( S e c t i o n 3 ) . F a c t o r s such as the r e l a -t i v e exposure t o p r o c e s s e s o f sediment r e m o v a l , v e g e t a t i o n c o v e r , e f f e c t o f n i v a t i o n , and ground i c e o c c u r r e n c e were a l s o i n v e s t i -g a t e d , as t h e s e c o n d i t i o n s were o b s e r v e d t o have a s i g n i f i c a n t e f f e c t on the o b s e r v e d bank o r s l o p e form. Thus t h i s a n a l y s i s p r o v i d e s q u a n t i t a t i v e d a t a on the r e l a t i o n s h i p between "form and 3 process", w h i c h a u t h o r s such as F r e n c h (1976) suggest "are u r g e n t l y r e q u i r e d " f o r an u n d e r s t a n d i n g o f p e r i g l a c i a l p r o c e s s e s . Net s e a s o n a l e r o s i o n was m o n i t o r e d a t a number o f s i t e s w i t h i n each m o r p h o l o g i c c a t e g o r y ( S e c t i o n 4 ) , i n o r d e r t o q u a n t i f y the r e l a t i v e magnitude and t i m i n g o f sediment p r o d u c t i o n . As r e p r e s e n t a t i v e r a t e s o f e r o s i o n a r e d i f f i c u l t t o d e t e r m i n e from one season's measurements, c o m p a r a t i v e a i r photo a n a l y s i s was u n d e r t a k e n f o r s i t e s w i t h r e p e a t e d coverage. Due t o the s m a l l s c a l e o f most of t h e a v a i l a b l e photography (1:100,000) , t h e s e s t u d i e s were g e n e r a l l y n o t as u s e f u l as was o r i g i n a l l y e x p e c t e d ; however i n a few cases o f e x c e p t i o n a l l y r a p i d r e c e s s i o n , t h e y p r o v i d e d i n t e r e s t i n g r e s u l t s . The o b s e r v e d c h a r a c t e r i s t i c s o f each bank o r s l o p e form were then summarized ( S e c t i o n 5) t o a l l o w an assessment o f t e r r a i n s t a b i l i t y under b o t h n a t u r a l and d i s t u r b e d c o n d i t i o n s . As the m o r p h o l o g i c f e a t u r e s are g e n e r a l l y o f s u f f i c i e n t s i z e t o be i d e n t i f i e d from a e r i a l p h otography, t h e s t u d y t h u s a l l o w s an i n i t i a l q u a n t i f i c a t i o n o f f a c t o r s p e r t a i n i n g t o t e r r a i n s t a b i l i t y , s o l e l y on the b a s i s o f a i r photograph i n t e r p r e t a t i o n . 4 1.2 PREVIOUS STUDIES I n t e r e s t i n t h e p r o c e s s e s a f f e c t i n g r i v e r and c o a s t a l s t a b i l i t y i n t h e A r c t i c e x t e n d s back a t l e a s t as f a r as the e a r l y 1 9 0 0 f s . K e e l e (1910), L e f f i n g w e l l (1919),and O ' N e i l l (1924) documented the exposure o f ground i c e i n r e c e n t cut-banks and d i s c u s s e d examples of r a p i d e r o s i o n r e s u l t i n g from slumps and wave a c t i o n . E a r d l e y (1938) p r o v i d e d q u a n t i t a t i v e measurements o f r a t e s o f r e c e s s i o n on Yukon R i v e r and d i s c u s s e d the v a r y i n g b e h a v i o u r a s s o c i a t e d w i t h banks composed o f f r o z e n , sand, s i l t and "muck 11. The p e r i o d b e g i n n i n g i n t h e l a t e 1940's and e x t e n d i n g t h r o u g h t o t h e 1960's saw an i n c r e a s i n g amount o f work u n d e r t a k e n i n the A r c t i c and r e s u l t e d i n a l a r g e number o f papers d e s c r i b i n g the s e a s o n a l regime o f h y d r o l o g i c p r o c e s s e s and t h e i r r e s u l t a n t e f f e c t on r i v e r and c o a s t a l s t a b i l i t y . P r o c e s s e s unique t o p e r m a f r o s t c o n d i t i o n s , such as "ground i c e slumps" o r ".thermo-e r o s i o n a l n i c h i n g " and subsequent b l o c k f a l l s , were d e s c r i b e d by a u t h o r s such as Yefimov and S o l o v ' e v (1951), W i l l i a m s (1952, 1955), MacCarthy (1953) , K u z n e t s o v a and K a p l i n a (1960) , Henoch (1961) and T o l s t o v (1962) . D u r i n g t h i s p e r i o d a l a r g e number o f r e g i o n a l s t u d i e s were c a r r i e d o u t , such as t h o s e i n the v i c i n i t y o f V i c t o r i a I s l a n d (Washburn, 1947) and R e s o l u t e (Cook, 1959, 1963, 1967), i n t h e Mackenzie D e l t a a r e a (Mackay, 1963a), a l o n g t h e A l a s k a n N o r t h S l o p e (Rex, 1964), and C o l v i l l e R i v e r (Walker and Morgan, 1964; Walker and McCloy, 1969), on Lena R i v e r (Yefimov, 1964), w i t h i n t h e Queen E l i z a b e t h I s l a n d s ( S t . Onge, 1965, 1969), on Blow R i v e r D e l t a (McCloy, 1970) and on t h e sandurs on B a f f i n I s l a n d (Church, 1972) . These s t u d i e s p r o v i d e d o b s e r v a t i o n s on 5 the f a c t o r s i n f l u e n c i n g t e r r a i n s t a b i l i t y o v e r a wide range o f e n v i r o n m e n t s , w i t h papers by Mackay (1963b), Walker and A r n b o r g (1966) , K e r f o o t (1969) and Czudek and Demek (1970) s p e c i f i c a l l y d i s c u s s i n g the e f f e c t s o f p e r m a f r o s t on t h e morphology and s t a b i l i t y o f r i v e r b a n k s and c o a s t a l a r e a s . The 1970's saw t h e development o f " e n v i r o n m e n t a l geomor-p h o l o g y " as d i s c u s s e d by P o s e r ( i n Rapp, 1975) and J o p l i n g (1975) . T h i s e n v i r o n m e n t a l awareness r e s u l t e d i n a l a r g e number o f s t u d i e s b e i n g o r i e n t e d towards t h e i d e n t i f i c a t i o n o f t e r r a i n c o n d i t i o n s o r p r o c e s s e s a s s o c i a t e d w i t h r i v e r and c o a s t a l s t a b i l i t y w h i c h might r e s u l t i n g e o t e c h n c i a l o r e n v i r o n m e n t a l problems f o r p r o -posed development a c t i v i t i e s , such as the Mackenzie V a l l e y gas p i p e l i n e (see papers by Church, 1971; Dingman e t a l . , 1971; Cooper and H o l l i n g s h e a d , 1973; N e i l , 1973; MacKay, 1973; Newbury, 1974; and Day and E g g i n t b n , 1976) . Many o f t h e s e s t u d i e s were c a r r i e d o ut by s c i e n t i s t s w i t h a background i n c i v i l e n g i n e e r i n g or s u r f i c i a l g e o l o g y and t h i s r e s u l t e d i n a number o f papers r e l a t i n g bank and s l o p e s t a b i l i t y t o s o i l mechanics ( C h y u r l i a , 1973; Code, 1973; McRoberts and M o r g e n s t e r n , 1973, 1974a and 1974b) and t o the s u r f i c i a l g e o l o g y and Q u a t e r n a r y h i s t o r y (Hughes, 1972; Rampton and MacKay, 1971; McDonald and L e w i s , 1973; K u r f u r s t , 1973; Rampton, 1973; Hughes e t a l . , 1974. ; S k i n n e r 1974; and Lewis and F o r b e s , 1975) . The 1970's a l s o saw g e o m o r p h o l o g i s t s u n d e r t a k i n g d e t a i l e d s t u d i e s o f the p r o c e s s e s i n v o l v e d i n the f o r m a t i o n o f s p e c i f i c r i v e r b a n k and s l o p e m o r p h o l o g i e s (see McCloy, 1970; F r e n c h , 1971; Kennedy and M e l t o n , 1972; G i l l , 1972; MacKay, F o g a r a s i and S p i t z e r , 1973; F r e n c h and E g g i n t o n , 1973; McCann and C o g l e y , 1973; McCann e t a l . , 1974; Outhet, 1974; and H a r p e r , 1978a). 6 A l l o f t h e above s t u d i e s a r e r e l e v a n t t o the p r e s e n t i n v e s t i -g a t i o n , as t h e y i n d i c a t e t h a t t h e r e a r e r e l a t i o n s h i p s amongst p r o c e s s , g e o t e c h n c i a l c h a r a c t e r i s t i c s and bank o r s l o p e morphology. S p e c i f i c r e s u l t s o f t h e r e l e v a n t s t u d i e s w i l l be d i s c u s s e d i n subsequent s e c t i o n s o f the d i s s e r t a t i o n . However i t i s w o r t h w h i l e t o draw a t t e n t i o n t o the t h e s i s by Outhet (1974) d e a l i n g w i t h e r o s i o n a l p r o c e s s e s i n the f i n e t e x t u r e d f l u v i a l sediments o f the s o u t h e r n Mackenzie D e l t a . H i s s t u d i e s i n d i c a t e t h a t e r o s i o n r a t e s can be c o r r e l a t e d w i t h ground i c e c o n t e n t and t h a t r i v e r b a n k s u n d e r g o i n g d i f f e r e n t r a t e s o f r e t r e a t have c h a r a c t e r i s t i c m o r p h o l o g i e s . These r e s u l t s a r e l i m i t e d t o a s i n g l e g e n e t i c m a t e r i a l . However i f i t were p o s s i b l e t o d e t e r m i n e s i m i l a r r e l a t i o n s h i p s f o r a range o f m a t e r i a l s and p r o c e s s e s o c c u r r i n g w i t h i n a r e g i o n o f r e l a t i v e l y homogeneous e n v i r o n m e n t a l c o n d i t i o n s , i t might t h e n be p o s s i b l e t o use morphology as an i n d i c a t o r upon which t o a s s e s s p o t e n t i a l e r o s i o n r a t e s and g e o t e c h n i c a l c h a r a c -t e r i s t i c s . Thus the t h e s i s o b j e c t i v e o f d e v e l o p i n g a methodology f o r e v a l u a t i n g r i v e r o r c o a s t a l s t a b i l i t y on the b a s i s o f r e l a t i o n -s h i p s between form, p r o c e s s and g e o t e c h n i c a l o r e n v i r o n m e n t a l c h a r a c t e r i s t i c s can be seen t o be r e l a t e d t o t r a d i t i o n a l p r o c e s s -s p e c i f i c s t u d i e s and t o the more r e c e n t t r e n d of u s i n g geo-morphology as a t o o l f o r r e s o u r c e management. 7 1.3 LOCATION OF THE STUDY AREA The f i e l d s t u d i e s were c a r r i e d out i n the summer o f 1975 on Banks I s l a n d , the southwesternmost member o f t h e A r c t i c A r c h i -p e l a g o ( F i g u r e 1 ) . Banks I s l a n d i s one o f t h e l a r g e r o f the h i g h 2 A r c t i c i s l a n d s w i t h an a r e a o f a p p r o x i m a t e l y 64,000 km ; w h i c h i s comparable i n s i z e w i t h t h a t o f the p r o v i n c e o f New B r u n s w i c k o r about t w i c e the a r e a o f Vancouver I s l a n d . W i t h i n t h i s l a r g e r e g i o n , the s t u d y a r e a was d e f i n e d by t h e a v a i l a b i l i t y o f t r a n s p o r t . Through s u p p o r t by a c o m b i n a t i o n o f h e l i c o p t e r and b o a t , a l l o f t h e c o a s t a l r e g i o n s and much o f the a r e a d r a i n e d by t h e major westward and n o rthward f l o w i n g r i v e r s were s u r v e y e d . The l o c a t i o n o f f i e l d s i t e s and p l a c e names are shown on F i g u r e 17 . The s u r v e y s were u n d e r t a k e n w i t h a number o f o t h e r s c i e n t i s t s , and thus the s e l e c t i o n and number o f sample s i t e s were d e t e r m i n e d t o a l a r g e e x t e n t by t h e i r r e l e v a n c e t o s t u d i e s u n d e r t a k e n by t h e s e c o - w o r k e r s . W i t h i n t h e s e l i m i t a t i o n s , a p p r o x i m a t e l y 100 s i t e s were i n v e s t i g a t e d o v e r the summer. The l o c a t i o n s a t w h i c h n e t s e a s o n a l r e c e s s i o n was m o n i t o r e d ( a l s o shown on F i g . 17) were s e l e c t e d such t h a t t r a n s p o r t t o t h e s e a r e a s was f r e q u e n t l y a v a i l a b l e from the r e l a t i v e l y i s o l a t e d base camp s i t u a t e d i n c e n t r a l Banks I s l a n d . Thus the m a j o r i t y o f e r o s i o n s i t e s on r i v e r i n e l o c a t i o n s were e s t a b l i s h e d i n t h e v i c i n i t y o f a s u b s i d i a r y f l y camp l o c a t e d near the j u n c t i o n o f " I v i t a r u k " and Thomsen R i v e r s . S t u d i e s by Stephen (1976) on beach p r o c e s s e s i n v o l v e d two f l i g h t s c i r c u m n a v i g a t i n g the i s l a n d and p r o v i d e d t h e o p p o r t u n i t y t o examine a number o f c o a s t a l s i t e s a t w h i c h the n e t e r o s i o n c o u l d be o b s e r v e d o v e r th e c o u r s e o f the summer. Figure 1= Location of the study area 9 Background information on the physical setting and regional climatic conditions i s presented i n the following sections, p r i o r to the r e s u l t s of the study. 1.4 THE PHYSICAL SETTING 10 1.4.1 Bedrock Geology The bedrock g e o l o g y o f Banks I s l a n d was o r i g i n a l l y mapped a t a s c a l e o f 1:1,000,000 by T h o r s t e i n s s o n and T o z e r (1962) i n c o o p e r a t i o n w i t h R. C h r i s t i e and J.. F y l e s . M i a l l (1976, 1979) and V i n c e n t (19 78a) have r e c e n t l y completed more d e t a i l e d s t u d i e s w h i c h i n c l u d e g e o l o g i c a l mapping o f the s t u d y a r e a a t a s c a l e o f 1:250,000. As i l l u s t r a t e d by t h e g e n e r a l i z e d bedrock j g e o l o g y map shown on F i g u r e 2, o v e r 80% o f t h e s u r f a c e a r e a o f Banks I s l a n d i s u n d e r l a i n by u n l i t h i f i e d o r p o o r l y l i t h i f i e d sediments o f M e s o z o i c and T e r t i a r y age. The B e a u f o r t F o r m a t i o n , the youngest o f the T e r t i a r y d e p o s i t s , i s composed o f u n c o n s o l i d a t e d f l u v i a l g r a v e l s and sands w i t h minor i n c l u s i o n s o f o r g a n i c m a t t e r . W i t h the e x c e p t i o n o f the sand d e p o s i t s o f t h e H a s s e l and I s a c h s e n Forma-t i o n s , t h e r e m a i n i n g T e r t i a r y d e p o s i t s are p r i m a r i l y composed o f s i l t s and c l a y s w i t h v a r y i n g degrees o f l i t h i f i c a t i o n , as i n d i -c a t e d on t h e map l e g e n d . S u r f a c e e x p r e s s i o n o f P a l e o z o i c and P r o t e r o z o i c d e p o s i t s i s l i m i t e d i n d i s t r i b u t i o n t o the n o r t h - e a s t e r n "Devonian P l a t e a u " , and t h e n o r t h e r n and s o u t h e r n e x t r e m i t i e s o f t h e i s l a n d . These o l d e r , g e n e r a l l y l i t h i f i e d d e p o s i t s are composed o f s a n d stone, s i l t s t o n e , s h a l e , l i m e s t o n e , d o l o m i t e and c h e r t , w i t h gabbro i n t r u s i o n s o c c u r r i n g a l o n g the s o u t h e r n c o a s t . Thus the bedrock g e o l o g y o f much o f Banks I s l a n d i s com-posed o f u n l i t h i f i e d o r p o o r l y l i t h i f i e d sediments which a r e r e a d i l y s u s c e p t i b l e t o p r o c e s s e s o f e r o s i o n . F i g u r e 2. G e n e r a l i z e d b e d r o c k g e o l o g y o f Banks I s l a n d . (after M i a l l , 1979) . LEGEND FOR BEDROCK GEOLOGY MAP ERA PERIOD TERTIARY U H O tsj O W C J MAP SYMBOL Tb Te2 FORMATION B e a u f o r t F o r m a t i o n E u r e k a Sound F o r m a t i o n c y c l i c member MATERIALS u n l i t h i f i e d g r a v e l , sand and minor o r g a n i c m a t t e r d e p o s i t e d i n a f l u v i a l e n v i r o n m e n t m a i n l y u n l i t h i f i e d s a n d s , s i l t s , c l a y s and c o a l d e p o s i t e d i n m a r i n e and t e r r e s t r i a l e n v i r o n m e n t s CRETACEOUS H o csi O CO T e l Kk Kch K i E u r e k a Sound F o r m a t i o n " s h a l e " member Kanguk F o r m a t i o n C h r i s t o p h e r and H a s s e l F o r m a t i o n s I s a c h s e n F o r m a t i o n m a i n l y u n l i t h i f i e d s i l t s and c l a y s o f non-marine o r i g i n m a i n l y p o o r l y l i t h i f i e d s i l t s and c l a y s o f marine o r i g i n w i t h an upper sand member and a b a s a l b i t u m i n o u s member w i t h b e n t o n i t e beds H a s s e l : r a r e o u t c r o p s o f g l a u c o n i t i c sand w i t h minor s i l t and c l a y o f n e a r s h o r e o r i g i n C h r i s t o p h e r : u n l i t h i f i e d , v e r y s t i c k y s i l t s and c l a y s o f marine o r i g i n u n l i t h i f i e d q u a r t z o s e sands o f f l u v i a l o r i g i n w i t h minor s i l t and l i g n i t e DEVONIAN Dm2 Upper Map U n i t o H o CSI O W < O H o N o Pi w EH O Cd CM Dml NEOHELIKIAN- P g 2 HADRYNIAN P9i P r e Mercy Bay Member G l e n e l g F o r m a t i o n (Upper Map U n i t ) G l e n e l g F o r m a t i o n (Lower Map U n i t ) Mercy Bay Member: l i m e s t o n e Younger s t r a t a : s a n d -s t o n e , s i l t s t o n e , s h a l e s a n d s t one, s i l t s t o n e and s h a l e sandstone w i t h m i n o r s i l t s t o n e , s h a l e d o l o m i t e , c h e r t 1.4.2 G l a c i a l H i s t o r y and S u r f i c i a l M a t e r i a l s As a r e s u l t o f a r e c e n t s u r f i c i a l g e o l o g y mapping program, V i n c e n t (1978a, b and c) has r e c o g n i z e d a t l e a s t t h r e e main g l a c i a t i o n s and two l o c a l g l a c i a l readvances on Banks I s l a n d , as i l l u s t r a t e d on F i g u r e 3a. I n a d d i t i o n , a number o f g l a c i a l l a k e s and e x t e n s i v e a r e a s o f marine i n u n d a t i o n have been i d e n t i f i e d . The f o l l o w i n g summary i s based on V i n c e n t ' s work and the i n t e r e s -t e d r e a d e r i s r e f e r r e d t o the c i t e d r e f e r e n c e s f o r a d e t a i l e d d e s c r i p t i o n o f the Q u a t e r n a r y h i s t o r y o f the s t u d y a r e a . The o l d e s t r e c o g n i z e d g l a c i a l e v e n t , d e f i n e d as the "Banks G l a c i a t i o n " ( V i n c e n t , 1978c) appears t o have c o v e r e d a l l o f Banks I s l a n d w i t h the p o s s i b l e e x c e p t i o n o f t h e n o r t h - w e s t e r n c o r n e r . The a s s o c i a t e d t i l l d e p o s i t s a r e c l a y e y i n t e x t u r e and are m a i n l y d e r i v e d from t h e u n d e r l y i n g f i n e t e x t u r e d C r e t a c e o u s and T e r t i a r y F o r m a t i o n s . Two g l a c i a l l a k e s have been r e c o g n i z e d as b e i n g a s s o c i a t e d w i t h t h e "Banks G l a c i a t i o n " . "Lake E g i n a " , w i t h an a r e a o f 2 a p p r o x i m a t e l y 1,000 km , was l o c a t e d n o r t h o f B e r n a r d R i v e r and i m m e d i a t e l y west o f Musk-ox R i v e r . " G l a c i a l Lake Storkerson'! was 2 s i g n i f i c a n t l y s m a l l e r ( w i t h an a r e a o f a p p r o x i m a t e l y 15 0 km ) , and was l o c a t e d n o r t h o f S t o r k e r s o n R i v e r . The age o f t h e "Banks G l a c i a t i o n " and a s s o c i a t e d l a c u s t r i n e d e p o s i t s i s p r e s e n t l y unknown. P r e s t e t a l . (1968) has d e s c r i b e d the t i l l d e p o s i t s i n t h i s r e g i o n as b e i n g " p r e - W i s c o n s i n " i n age, w i t h V i n c e n t ' s more r e c e n t work i n d i c a t i n g t h a t t h e s e sediments a r e s u f f i c i e n t l y o l d t h a t they "are thought t o be o v e r l a i n by d e p o s i t s o f a t l e a s t two f u l l i n t e r g l a c i a t i o n s " ( V i n c e n t , 1978c, p. 56) . F i g u r e 3 a : G l a c i a l l i m i t s on B a n k s I s l a n d ( f r o m V i n c e n t , 1 9 7 8 c ) figure 3b. Location of grain s i z e samples discussed i n Section 3.2.1. The "Thomsen G l a c i a t i o n " o v e r r o d e the s o u t h e r n and e a s t e r n r e g i o n s o f Banks I s l a n d , w i t h a major l o b e o c c u p y i n g the Thomsen R i v e r V a l l e y as f a r n o r t h as M'Clure S t r a i t . T i l l d e p o s i t s a s s o c i a t e d w i t h t h i s g l a c i a l e v e n t a r e more sandy i n t e x t u r e t h a n t h o s e o f t h e e a r l i e r "Banks G l a c i a t i o n " . D u r i n g t h e "Thomsen G l a c i a t i o n " , a marine t r a n s g r e s s i o n o c c u r r e d w i t h i n the w e s t e r n , c e n t r a l and e a s t e r n r e g i o n s o f Banks I s l a n d . A l o n g t h e west c o a s t , the l i m i t s o f marine i n u n d a t i o n ( d e f i n e d by V i n c e n t (1978c) as "The B i g S e a " ) , c o r r e s p o n d t o p r e s e n t e l e v a t i o n s o f o v e r 60 m a s i . , w i t h e x t e n s i v e r e g i o n s o f the B e r n a r d , S t o r k e r s o n and B i g R i v e r d r a i n a g e s b e i n g i n u n d a t e d t o e l e v a t i o n s o f up t o 215 m a s i . M arine t r a n s g r e s s i o n s a l s o o c c u r r e d w i t h i n the Thomsen V a l l e y and a l o n g e x t e n s i v e r e g i o n s o f the e a s t c o a s t d u r i n g d e g l a c i a t i o n and r e s u l t e d i n the w i d e s p r e a d d e p o s i t i o n o f deep w a t e r marine s e d i m e n t s . Amino a c i d d a t i n g o f marine s h e l l s o c c u r r i n g w i t h i n t h e s e d e p o s i t s s u g g e s t s t h a t they are pre-Sangamonian i n age and thus t h e "Thomsen G l a c i a t i o n " appears t o p r e d a t e t h e " C l a s s i c a l W i s c o n s i n " . Two l a r g e g l a c i a l l a k e s were a s s o c i a t e d w i t h the "Thomsen G l a c i a t i o n " . " G l a c i a l Lakes P a r k e r " and " D i s s e c t i o n " o c c u p i e d much o f t h e n o r t h - e a s t e r n p o r t i o n o f t h e i s l a n d and r e s u l t e d i n the d e p o s i t i o n o f f i n e t e x t u r e d g l a c i o - l a c u s t r i n e d e p o s i t s w i t h i n many o f the v a l l e y s i n t h i s r e g i o n . The t h i r d major g l a c i a l e v e n t has been d e f i n e d as the "Amundsen G l a c i a t i o n " , w h i c h o c c u p i e d the e a s t e r n r e g i o n o f Banks I s l a n d . The " T h e s i g e r Lobe" o f t h i s i c e sh e e t i s thought t o have extended westward i n t o Amundsen G u l f t o impinge on the s o u t h -w e s t e r n c o a s t o f t h e i s l a n d . T h i s g l a c i a l advance r e s u l t e d i n 16 t h e d e p o s i t i o n o f a g e n e r a l l y t h i n s i l t y t i l l , p r i m a r i l y d e r i v e d from f i n e t e x t u r e d marine s e d i m e n t s . T h i s t i l l v eneer i s f r e -q u e n t l y a s s o c i a t e d w i t h t h e pr e s e n c e o f h i g h c e n t e r e d p o l y g o n s and numerous t h e r m o k a r s t l a k e s . In t h e n o r t h e r n r e g i o n s o f Banks I s l a n d the " V i s c o u n t M e l v i l l e G l a c i a t i o n " o r "M'Clure Lobe" d e p o s i t e d a sandy t i l l a l o n g the n o r t h - w e s t c o a s t and w i t h i n Mercy Bay. These d e p o s i t s were o r i g i n a l l y d e s c r i b e d by P r e s t e t a l . (1968) as b e i n g o f the same age as t h o s e o f t h e s u b s e q u e n t l y d e f i n e d "Amundsen G l a c i a t i o n " . However, t h e more r e c e n t work o f V i n c e n t (1978c) n e i t h e r c o n f i r m s n o r d i s p r o v e s t h i s h y p o t h e s i s . Two minor readvances have a l s o been t e n t a t i v e l y i d e n t i f i e d . A deformed r i d g e o f f i n e t e x t u r e d marine (?) sediments on t h e n o r t h - e a s t c o r n e r o f Banks I s l a n d may have been d e p o s i t e d by the " R u s s e l Readvance" o f " V i s c o u n t M e l v i l l e " o r "Amundsen" i c e . S i m i l a r l y , young l o o k i n g moraine topography l o c a t e d on t h e south-west c o a s t . e a s t o f Sachs Harbour i s tho u g h t t o have r e s u l t e d from a l o c a l "Sands H i l l s Readvance" o f the "Amundsen G l a c i a t i o n " ( V i n c e n t , 1978c) . V i n c e n t (1978c) has r e c o g n i z e d a number o f i c e dammed l a k e s w h i c h d e v e l o p e d a l o n g the ma r g i n o f t h e "Amundsen G l a c i a t i o n " . Two s m a l l l a k e s (the " S a r f a r s s u k Lakes") o c c u r r e d w i t h i n the n o r t h - e a s t e r n r e g i o n o f t h e i s l a n d and r e s u l t e d i n the l o c a l i z e d d e p o s i t i o n o f l a c u s t r i n e s e d i m e n t s . S i m i l a r l y " G l a c i a l Lakes R a d d i " , "Masik", "Rufus", "De S a l i s " and " C a r d w e l l " o c c u r r e d a l o n g t h e s o u t h e r n c o a s t . 17 A w e l l d e f i n e d break i n s l o p e a l o n g the e a s t c o a s t i n d i c a t e s t h a t marine o r g l a c i o l a c u s t r i n e submergence a s s o c i a t e d w i t h the "Amundsen G l a c i a t i o n " g e n e r a l l y o c c u r r e d t o a h e i g h t o f 120 m above p r e s e n t sea l e v e l . T h i s e v e n t has been d e f i n e d by V i n c e n t (1978c) as t h e "East Coast Submergence". H i g h e r e l e v a t i o n s t r a n d l i n e s o c c u r w i t h i n the C a r d w e l l Brook and De S a l i s R i v e r d r a i n -ages as a r e s u l t o f g l a c i a l dammed l a k e s . " G l a c i a l Lake C a r d w e l l " appears t o have reached"'an e l e v a t i o n o f 245 "m a s l and to.-have d r a i n e d i n t o " G l a c i a l Lake De S a l i s " ( e l e v a t i o n 200 m a s l ) , w h i c h i n t u r n d r a i n e d i n t o the headwaters o f B i g R i v e r . ( T h i s d r a i n a g e p a t t e r n l i k e l y e x p l a i n s t h e r e l i c c h a n n e l s c a r s and e x t e n s i v e outwash d e p o s i t s w h i c h p r e s e n t l y occupy much o f t h e B i g R i v e r d r a i n a g e . ) A l o w e r s t r a n d l i n e a l s o o c c u r s a l o n g the e a s t c o a s t a t an e l e v a t i o n o f 25 m a s l and has been d e f i n e d as r e s u l t i n g from the "Schuy t e r P o i n t Sea". The "Schuyter P o i n t Sea" sediments o v e r l i e those o f t h e "Amundsen G l a c i a t i o n " and thus V i n c e n t (197 8c) i n d i c a t e s t h a t t h i s marine t r a n s g r e s s i o n p r o b a b l y d i d n o t abut a g a i n s t i c e o c c u p y i n g P r i n c e o f Wales S t r a i t . Thus the "Schuyter P o i n t Sea" may r e p r e s e n t " e i t h e r a l a t e r phase o f t h e 'East C o a s t Submergence• o r i t may be a t o t a l l y s e p a r a t e e v e n t r e s u l t i n g from g l a c i o - i s o s t a t i c d e p r e s s i o n by l a t e W i s c o n s i n i c e t h a t d i d n o t r e a c h Banks I s l a n d " ( V i n c e n t , 1978c, p. 6 1 ) . Two major g l a c i a l dammed l a k e s were a s s o c i a t e d w i t h t h e " V i s c o u n t M e l v i l l e G l a c i a t i o n " . " G l a c i a l Lake B a l l a s t " i n u n d a t e d p o r t i o n s o f t h e B a l l a s t Brook d r a i n a g e b a s i n t o an e l e v a t i o n o f 90 m a s l . " G l a c i a l Lake I v i t a r u k " a l s o r e a c h e d a s i m i l a r e l e -v a t i o n and r e s u l t e d i n the i n u n d a t i o n o f e x t e n s i v e p o r t i o n s o f t h e n o r t h c o a s t between " G l a c i a l Lake B a l l a s t " and Mercy Bay, as w e l l as f l o o d i n g much o f the Thomsen R i v e r d r a i n a g e b a s i n . M a r ine submergence a l o n g t h e west c o a s t , subsequent t o t h a t o f t h e " B i g Sea", l o c a l l y r e a c h e d 20 m a s l . The age o f t h i s i n u n d a t i o n i s not known p r e c i s e l y , however, V i n c e n t (1978c) has t e n t a t i v e l y c o r r e l a t e d t h i s e v e n t , d e f i n e d as the "Meek P o i n t Sea w i t h the "East Coast Submergence" a s s o c i a t e d w i t h the "Amundsen G l a c i a t i o n " . From t h i s d i s c u s s i o n of t h e g l a c i a l h i s t o r y i t can be seen t h a t t h e s u r f i c i a l s t r a t i g r a p h y o c c u r r i n g w i t h i n the s t u d y a r e a can f r e q u e n t l y be v e r y complex. F or example, s i t e s sampled on t h e e a s t c o a s t o f Banks I s l a n d c o n t a i n d e p o s i t s o f t i l l r e f l e c t i n g e i t h e r t h r e e o r f o u r g l a c i a l e v e n t s ( s e e V i n c e n t , 1978b). These sediments are s e p a r a t e d by i n t e r g l a c i a l d e p o s i t s o f b o t h marine and t e r r e s t r i a l o r i g i n , w i t h t h e ground s u r f a c e b e i n g composed o f c o l l u v i a t e d d e p o s i t s from m a r i n e , g l a c i a l and bedrock s o u r c e s . W i t h i n c e n t r a l and w e s t e r n Banks I s l a n d , t h e u p l a n d s u r f a c e s have g e n e r a l l y a s i m p l e r s t r a t i g r a p h y , w i t h c o l l u v i u m o r e o l i a n sediments o v e r l y i n g a t i l l v e neer w h i c h o v e r l i e s bedrock. However near the c o a s t o r w i t h i n t h e v a l l e y s , the s e d i m e n t a r y s t r a t i -graphy can a g a i n become more c o m p l i c a t e d as m a r i n e , l a c u s t r i n e , f l u v i o - g l a c i a l , r e c e n t f l u v i a l sediments and c o l l u v i u m d e r i v e d from e i t h e r t h e u n d e r l y i n g s u r f i c i a l m a t e r i a l s o r bedr o c k , o c c u r l o c a l l y . 1.5 CLIMATE 19 The c l i m a t e o f the w e s t e r n Canadian A r c t i c has been d e s -c r i b e d by numerous a u t h o r s , i n c l u d i n g Thompson (1967), F o g a r s i (1972) , and r e c e n t l y Burns (1973 and 1974) . M i l l e r (1975) and Anderson (1978) have p r e s e n t e d a summary o f c l i m a t i c normals f o r Banks I s l a n d and have compared the s e averages w i t h t h e c o n -d i t i o n s o c c u r r i n g d u r i n g the 1975 f i e l d s e a s o n . T h i s s e c t i o n i s t h e r e f o r e o n l y i n t e n d e d t o p r o v i d e a g e n e r a l i n t r o d u c t i o n t o t h e c l i m a t e o f t h e s t u d y a r e a and t h e i n t e r e s t e d r e a d e r i s a g a i n r e f e r r e d t o the c i t e d r e f e r e n c e s f o r a more comprehensive d i s -c u s s i o n . However, a r e l a t i v e l y d e t a i l e d a n a l y s i s o f snow c o v e r , p r e c i p i t a t i o n and t e m p e r a t u r e d a t a i s p r o v i d e d as t h e s e t o p i c s a r e p a r t i c u l a r l y r e l e v a n t t o a s t u d y o f s l o p e p r o c e s s e s . R a d i a t i o n The s e a s o n a l v a r i a t i o n i n g l o b a l r a d i a t i o n a t Sachs Harbour and Mould Bay i s shown on F i g u r e 4. The t o t a l a n n u a l v a l u e a t Mould Bay i s a p p r o x i m a t e l y 6% l e s s than t h a t o b s e r v e d a t Sachs 2 Harbour (10 3.7 v e r s u s 110.7 MJ/m ) . Peak monthly v a l u e s o f g l o b a l r a d i a t i o n can be seen t o o c c u r i n May and June, w i t h 2 v a l u e s a p p r o a c h i n g 25 MJ/m . However the s e a s o n a l v a r i a t i o n i n n e t r a d i a t i o n a t Mould Bay, a l s o shown on F i g u r e 4, i n d i c a t e s t h a t t h e maximum n e t r a d i a t i o n o c c u r s i n June and J u l y . T h i s d i f f e r e n c e i n t i m i n g i s thought to o c c u r due t o a h i g h e r a l b e d o i n May, r e f l e c t i n g t h e snow c o v e r e d c o n d i t i o n s . c 0 • H 4J 03 • H T> nj CN S H E 03 r H 0 a cn r H 03 . Q 0 i H CJ 25 20 15 10 5 0 max. annual 110.7 MJ/nu mean annual 104.0 MJ/iru min. annual 99.5 MJ/m 4-1 M M T - 1 , J J A S 0 — ' — i i N D C O • H +J 03 • H T3 03 rj ~ CN u a 03 \ r H r j O S cn ^ 03 o r H G l o b a l s o l a r r a d i a t i o n - Sachs Harbour, E l . 84 m (1970-1977) 25 20 A 15 H 10 5 0 max. annual 103.7 MJ/nu mean annual 96.7 MJ/rru min. annual 91.6 MJ/m J F ' M ' A ' M ' J ' J ' A ' S 0 G l o b a l s o l a r r a d i a t i o n - Mould Bay, E l . 15 m (1965-1977) N D CN e a c o • H +J 03 • H T S 03 U • P CD 2 20 15 10 5-1 0 -5 max. annual 2 7.9 MJ/m^ mean annual 2 0.8 MJ/mZ min. annual 13.7 MJ/m 1 1 1 — — J F M A — — I 1 — i 1 M J J A S 0 N D Net r a d i a t i o n - Mould Bay, E l . 15 m (1968-1977) Note: The graphs i n d i c a t e the maximum monthly, the average monthly and the minimum monthly v a l u e s F i g u r e 4. Seasonal v a r i a t i o n i n r a d i a t i o n a t Sachs Harbour and Mould Bay (data p r o v i d e d by the Atmospheric Environment S e r v i c e ) . A i r Temperature A i r t e mperature d a t a from Sachs Harbour, Mould Bay and Holman (shown on F i g u r e 5) i n d i c a t e t h a t the average d a i l y a i r t e m p e r a t u r e s a re above 0°C d u r i n g the months o f June, J u l y and August, w i t h the month o f J u l y h a v i n g t h e h i g h e s t average mean d a i l y a i r t e m p e r a t u r e . A f r e q u e n c y a n a l y s i s o f J u l y a i r tempera-t u r e s i s shown on F i g u r e 6 and i n d i c a t e s t h a t extreme maximum temper a t u r e s may range from 20 t o 30°C. I t i s i n t e r e s t i n g t o note t h a t the average mean d a i l y a i r t e m p e r a t u r e s r e c o r d e d a t Holman a r e , on t h e a v e r a g e , 2°C warmer t h a n t h o s e a t Sachs Harbour and are l i k e l y more r e p r e s e n t a t i v e o f the te m p e r a t u r e s o c c u r r i n g on the e a s t s i d e o f Banks I s l a n d . T h i s o b s e r v a t i o n i s s u p p o r t e d by t h e s h o r t term c l i m a t i c d a t a c o l l e c t e d a t Johnson P o i n t and a n a l y s e d by Anderson (1978) . S i m i l a r l y , t e m p e r a t u r e s a t Mould Bay are a p p r o x i m a t e l y 2°C c o l d e r than those r e p o r t e d a t Sachs Harbour and are thought t o be more t y p i c a l o f the n o r t h e r n c o a s t o f Banks I s l a n d ( F r e n c h , 1970) . Sachs Harbour, Mould Bay and Holman a r e a l l s i t u a t e d on the c o a s t and t h e r e f o r e c o u l d be e x p e c t e d t o u n d e r e s t i m a t e summer temp e r a t u r e s i n i n l a n d a r e a s . A i r temperature d a t a c o l l e c t e d d u r i n g t h e 1975 f i e l d season s u p p o r t t h i s h y p o t h e s i s and i n d i c a t e t h a t t h e average mean d a i l y a i r t e m p e r a t u r e s a t t h e base camps i n c e n t r a l Banks I s l a n d were 0.5 t o 2.5°C warmer, and the extreme maximum d a i l y a i r t e m p e r a t u r e s were 4 t o 5°C warmer, t h a n those r e c o r d e d a t the c o a s t a t Johnson P o i n t (Anderson, 1978) . +10T 22 cu u + J n3 U CU e CU 4-1 - io H -20 1 - 3 0 1 u _40 < / Annual average v . 'z'Daily maximum -10.5°C\\"--V Mean d a i l y -13.7°C \ ; D a i l y minimum -16.9°C _L M A M J J A S O Sachs Harbour - E l . 84 m N D cu u 4-1 CCS u (U CU 6 cu 4-> +10 - i -10 1 -20 1 -30 T / / D a i l y max ' / Mean d a i l y Annual average imum -14.6^CvN D a i l y minzmum - 1 7 . 8 ° C < N -21.1°C *^ u -4 0 •H M A M J J A S Mould Bay - E l . 1 5 m 0 N D U (U i - i 4J 03 u CU cu s cu 4-1 U •H < +10 -10 -20 F i g u r e 5 -30 4 -40 Note: M A M J J A S Holman - E l . 9 m mean d a i l y maximum temperature mean d a i l y temperature mean d a i l y minimum temperature Seasonal v a r i a t i o n i n mean d a i l y a i r temperature a t Sachs Harbour, Holman and Mould Bay (data pro-v i d e d by the Atmospheric Environment S e r v i c e ) . 23 1 0 . 5 2 3 4 5 1 0 20 50 100200 Return p e r i o d (years) Note: The s t r a i g h t l i n e s have been f i t t e d by eye. Data from Mould Bay have been p l o t t e d t o i n d i c a t e the t y p i c a l range i n v a l u e s about the f i t t e d l i n e . The l e n g t h o f the l i n e c orresponds to the e x t e n t of data coverage. maximum temperatures average mean d a i l y temperatures F i g u r e 6. Frequency a n a l y s i s o f the observed d a i l y maximum and average mean d a i l y a i r temperature a t Mould Bay, Holman and Sachs Harbour d u r i n g the month of J u l y (data p r o v i d e d by the Atmospheric Environment S e r v i c e ) . Ground Temperature Mean a n n u a l a i r t e m p e r a t u r e s i n t h e s t u d y a r e a a r e i n the range o f -12 t o -18°C. The mean an n u a l ground t e m p e r a t u r e a t the d e p t h o f z e r o mean an n u a l a m p l i t u d e can be e x p e c t e d t o be a p p r o x i m a t e l y 3°C (6°F) warmer. Thus the mean an n u a l ground t e m p e r a t u r e s are s i g n i f i c a n t l y below the v a l u e o f -5°C w h i c h i s t h o u g h t t o be t h e boundary between the zones o f c o n t i n u o u s and d i s c o n t i n u o u s p e r m a f r o s t (see Brown, 1966, 1967). The o n l y l o n g term ground t e m p e r a t u r e d a t a a v a i l a b l e f o r t h i s r e g i o n i s t h a t r e c o r d e d a t Mould Bay. The average monthly ground t e m p e r a t u r e s a t t h i s s t a t i o n are shown on F i g u r e 7. These d a t a i n d i c a t e an average a n n u a l ground t e m p e r a t u r e o f a p p r o x i m a t e l y -14.3°C, which c o r r e s p o n d s q u i t e n i c e l y w i t h the mean an n u a l a i r temperature o f -18°C. The maximum average ground s u r f a c e t e m p e r a t u r e s o c c u r i n J u l y , w i t h a f t e r n o o n v a l u e s e x c e e d i n g 7.0°C, a t a depth o f 5 cm. S o i l t e m p e r a t u r e d a t a c o l l e c t e d on Banks I s l a n d by Tedrow and Douglas (1964), F r e n c h (1970) and M i l l e r (1975) i n d i c a t e t h a t i n w e l l d r a i n e d , c o a r s e t e x t u r e d m a t e r i a l s , s u r f a c e t e m p e r a t u r e s can exceed 19°C. Thus t h e r e i s a c o n s i d e r -a b l e p o t e n t i a l f o r t h e t h a w i n g o f t h e u n d e r l y i n g m a t e r i a l . A c t i v e l a y e r depths depend on the t h e r m a l p r o p e r t i e s o f t h e ground, v e g e t a t i o n c o v e r and a s p e c t , w i t h maximum depths o f o v e r 1 m b e i n g o b s e r v e d i n n o n - v e g e t a t e d , w e l l d r a i n e d sands and g r a v e l s . P e r m a f r o s t t h i c k n e s s i s not w e l l d e l i n e a t e d ; however, o i l w e l l l o g s i n d i c a t e t h a t depths o f a p p r o x i m a t e l y 500 m can be e x p e c t e d ( T a y l o r and Judge, 1974). 25 Ground t e m p e r a t u r e (°C) -30 -20 -10 0 +10 Note: Data p r o v i d e d by t h e A t m o s p h e r i c E n v i r o n m e n t S e r v i c e . V a l u e s a r e n o t a v a i l a b l e f o r June o r September. F i g u r e 7. Average m o n t h l y s o i l t e m p e r a t u r e s r e c o r d e d a t Mould Bay A i r p o r t . P r e c i p i t a t i o n The s e a s o n a l p a t t e r n o f p r e c i p i t a t i o n , shown on F i g u r e 8, i n d i c a t e s t h a t on the a v e r a g e , r a i n f a l l a c c o u n t s f o r n e a r l y one-h a l f o f the mean an n u a l p r e c i p i t a t i o n . Peak v a l u e s o f 24 hour p r e c i p i t a t i o n ( F i g . 9) o c c u r as r a i n ' i n the p e r i o d o f June th r o u g h September, w i t h the extreme v a l u e s r e f l e c t i n g i n c r e a s e d c y c l o n i c a c t i v i t y i n J u l y and August. I n t e n s i t y - d u r a t i o n -f r e q u e n c y d a t a are n o t a v a i l a b l e f o r t h i s r e g i o n . However, the d i s t r i b u t i o n a n a l y s i s o f t h e g r e a t e s t 24 hour p r e c i p i t a t i o n e v e n t s ( F i g . 10) i n d i c a t e s t h a t t h e magnitude o f extreme r a i n e v e n t s approaches 5 cm. T h i s v a l u e i s s i m i l a r i n magnitude t o t h a t o f t h e average o b s e r v e d t o t a l snow c o v e r , shown on F i g u r e 11. I t i s i n t e r e s t i n g t o note the s i g n i f i c a n t l y l a r g e r 24 hour p r e c i p i t a t i o n v a l u e s o b s e r v e d a t Holman. Three y e a r s o f p r e c i p i -t a t i o n d a t a c o l l e c t e d a t Johnson P o i n t s u g g e s t t h a t t h e e a s t c o a s t o f Banks I s l a n d may have s i m i l a r l y h i g h v a l u e s as the maximum ob s e r v e d 24 hour p r e c i p i t a t i o n o f 2.64 cm i s somewhat g r e a t e r t h a n the l a r g e s t r e c o r d e d v a l u e a t Sachs Harbour (2.18 cm) d e s p i t e a 2 0 y e a r p e r i o d o f r e c o r d . Snow Cover The r e p o r t e d s e a s o n a l v a r i a t i o n i n snow c o v e r i s shown i n F i g u r e 11. Snow b e g i n s a c c u m u l a t i n g i n September o r October and pe s i s t s u n t i l l a t e May or- J u n e , w i t h . t h e average w a t e r e q u i v a l e n t o f the t o t a l a c c u m u l a t i o n b e i n g r e p o r t e d as 5 t o 7 cm. However the r e c e n t work conducted near R e s o l u t e by Woo and Heron (1979) i n d i c a t e s t h a t the t o t a l snow a c c u m u l a t i o n may be t w i c e t h a t r e c o r d e d by the A t m o s p h e r i c Environment S e r v i c e , due t o r e d i s t r i -b u t i o n o f the snow c o v e r by wind a c t i o n and snow d e n s i t i e s b e i n g 3.0 2 .OH 1.0 0 5.6 4 .6 10 .2 J F M A M J J A S O N D Sachs Harbour - E l . 84 m 3 .OH 2 .0 1.0 J F M A M J J A S O N D Cape P a r r y A - E l . 16 m cu a J F M A M J J A S O N D Holman - E l . 9 m 3 .0 2.0 i l . o H o o .0 o .0 o .0 N i c h o l s o n P e n i n s u l a -E l . 98 m Mean snow, water e q u i v a l e n t (cm) Mean r a i n (cm) Mean p r e c i p i t a t i o n (cm) Rain Snow (water e q u i v a l e n t ) 0 N D Mould Bay - E l . 15 m Note: The r e l a t i v e l y s m a l l e r amount of snow observed a t N i c h o l s o n P e n i n s u l a may be a r e s u l t o f the d i f f i c u l t y i n o b t a i n i n g a c c u r a t e measurements due to the r e d i s t r i b u t i o n of snow c o v e r by wind a c t i o n F i g u r e 8. Seasonal d i s t r i b u t i o n and c o m p o s i t i o n o f mean monthly p r e c i p i t a t i o n (data p r o v i d e d by the Atmospheric Environment S e r v i c e ) . 2 8 ©-mm • • M M •€> Ra i n f a 11 C )nly 0 Q T o t a l p r e c i p i t a t i o n - A * X \ 7 V J F M A M J J A S O N D Sachs Harbour (1956-1961, 1963-1976) 0-—••—-O R a i n f a l l o n l y Q 0 T o t a l / ' p r e c i p i t a t i o n / • 1 Q / ' j of' J V J F M A M J J A S O N D Holman (1950, 1952-1956, 1959-1962, 1964-1968) Seasonal v a r i a t i o n i n the maximum 2 4 hour p r e c i p i t a t i o n and r a i n f a l l a t Sachs Harbour and Holman (data p r o v i d e d by the Atmospheric Environment S e r v i c e ) . 2 Frequency (percent larger) .3 .2 J 1 1 1 I I I 1 I I I I I 2 3 4 5 10 25 50 100 200 Return period (years) Note: The s t r a i g h t l i n e s have been f i t t e d by eye. Data from Sachs Harbour have been p l o t t e d to indicate the t y p i c a l range i n values about the f i t t e d l i n e . The length of the s o l i d l i n e corresponds to the extent of data coverage. Figure 10. Frequency analysis of the greatest 2 4 hour p r e c i p i t a t i o n (data provided by the Atmospheric Environment S e r v i c e ) . 30 o C O a) > CD •H > 3 O CT U i> H o d) c •P cn s M-l o , c o H > <D •H > 3 0 cu n o CU c -P cn (0 s CH o + J e* c u <u — rH i-l > 0 ) •H > 3 O CT o CL) M O 1) c -U cn (0 15 .0 12 .0 9.0 6 .0 • 3 .0 0.0 15.0 • 12.0 9.0 • 6.0 • 3.0 • 0.0 15.0 • 12.0 -9.0 -6.0 -3 .0. -0.0 • Note: M M A O N D Mould Bay - E l . 15 m ( p e r i o d o f r e c o r d : 1966/67 t o 1976/77; M M N Sachs Harbour - E l . 84 m ( p e r i o d o f r e c o r d : 1964/65 t o 1976/77) M M 0 N F i g u r e 11. Cape P a r r y - E l . 1 6 m ( p e r i o d o f r e c o r d : 1964/65 t o 1976/77) The t h r e e l i n e s i n d i c a t e the maximum o b s e r v e d , average and minimum o b s e r v e d snow c o v e r on the f i r s t and 15th day o f e a c h month o v e r the p e r i o d o f r e c o r d . S e a s o n a l v a r i a t i o n i n snow c o v e r a t Mould Bay, Sachs Harbour and Cape P a r r y (data p r o v i d e d by the A t m o s p h e r i c E n v i r o n m e n t S e r v i c e ) . g r e a t e r t h a n the s t a n d a r d i z e d f a c t o r employed by the At m o s p h e r i c Environment S e r v i c e . S i m i l a r r e s u l t s have a l s o been r e c o r d e d by Cook (1960) and Hare and Hay (1971). A comparison o f t h e snow c o v e r d a t a from Sachs Harbour and Mould Bay i n d i c a t e s t h a t the snow f r e e p e r i o d ranges from 2% t o 3h months, b u t may be 2 weeks t o a month l o n g e r a t t h e more s o u t h e r l y s t a t i o n . T h i s i s s u p p o r t e d by f i e l d o b s e r v a t i o n s d u r i n g 1975 whi c h i n d i c a t e d t h a t snow c o v e r p e r s i s t e d s i g n i f i -c a n t l y l a t e r i n t o the season on t h e n o r t h c o a s t o f t h e i s l a n d . Snowmelt proceeds q u i c k l y once the snow pack i s r i p e . Woo and Heron (1979) r e p o r t t h a t a t R e s o l u t e , a d r a i n a g e b a s i n w h i c h i s c o m p l e t e l y snow c o v e r e d can be l a i d bare i n l e s s than 10 days. T h i s i s comparable w i t h o b s e r v a t i o n s on Banks I s l a n d , w i t h the e x c e p t i o n o f snow a c c u m u l a t i o n s i n n i v a t i o n h o l l o w s w h i c h may p e r s i s t f o r some t i m e . Wind Wind i s an i m p o r t a n t c l i m a t i c f a c t o r w h i c h may a f f e c t p e r i -g l a c i a l p r o c e s s e s t h r o u g h the r e d i s t r i b u t i o n o f snow c o v e r ( F r e n c h , 1971),by a f f e c t i n g ground temperature t h r o u g h t h e a d v e c t i o n o f s e n s i b l e h e a t o r the promotion o f e v a p o r a t i o n ( F r e n c h , 1970), by the g e n e r a t i o n o f waves ( W i l l i a m s , 1952; and B a r r y e t a l . , 1975) o r sto r m surges (Lewis and F o r b e s , 1975; and Henry, 1975) , and th r o u g h the d i r e c t e r o s i o n and t r a n s p o r t a t i o n o f m a t e r i a l ( P i s s a r t e t a l . , 1977) . Tab l e I p r e s e n t s a summary o f the average wind d i r e c t i o n s and v e l o c i t i e s r e c o r d e d a t Sachs Harbour and Mould Bay. I t can be seen t h a t d u r i n g the w i n t e r the predominant wind d i r e c t i o n s a t Sachs Harbour a re from t h e E a s t and S o u t h - e a s t , w h i l e t h o s e a t P e r i o d 1955 - 72 He i g h t o f Anemometer 43' JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC YEAR PERCENTAGE FREQUENCY N 25 20 25 19 18 14 9 12 20 18 23 22 19 NE 9 8 10 12 14 14 10 15 14 11 11 10 12 E 7 7 9 •8 7 7 4 8 9 10 9 8 8 SE 6 7 6 8 7 6 4 7 8 10 8 7 • 7 S 8 9 8 13 13 14 19 16 9 10 9 10 12 SW 3 4 4 5 6 11 15 12 5 5 4 4 6 W 7 7 7 5 8 13 13 10 10 9 7 7 8 NW 26 21 17 19 23 20 25 18 22 21 22 22 21 Calm 9 17 14 11 4 1 1 2 3 6 7 10 7 AVERAGE WIND SPEED IN KILOMETERS PER HOUR N 16.7 17.7 14.3 13.5 17.2 20.0 19.2 19.5 17 .2 14 .2 13 .7 16.4 16.6 NE 11.6 10.1 14 .6 15.0 17.7 19.0 20 .4 20.4 18 .8 15 .4 11 .7 11.3 15 .4 E 6.3 5.1 8.7 6.1 15.4 19.2 21.1 19 .0 17 .4 13 .2 8 .0 6.9 12 .2 SE 12.2 11.3 10.6 11.3 12.6 14.3 16.9 14.8 15.6 14.5 11 .9 11.4 13 .2 S 20.0 20.0 15.3 17 .5 18 .0 16 .7 16 .7 16.1 17 .9 16 .3 18 .3 16 .7 17 .5 SW 21.1 18 .8 16 .7 15 .6 15.3 14.3 14 .2 15 .3 20.3 18 .5 19 .6 17 .1 17 .2 W 22.0 17.5 14.3 13.7 14 .5 18 .7 16.9 18.0 21.4 22.4 17 .2 16.9 17 .9 NW 23.7 19.3 17.4 17.4 19.8 21.4 21.9 21.2 23.7 20.0 19 .0 20.8 20.4 A l l D i r e c t i o n s 16 .3 13 .5 12 .2 12.7 16 .6 18 .3 18 .2 18 .2 18 .8 15 .8 13.8 14.2 15 .8 SACHS HARBOUR, N. .W.T. P e r i o d 1955 - 70 Height o f Anemometer 33 • JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC YEAR PERCENTAGE FREQUENCY N 16 14 13 14 15 16 15 14 13 11 13 14 14 NE 10 11 12 12 14 12 7 12 13 15 15 9 12 E 14 20 17 18 15 13 7 10 17 25 20 18 16 SE 23 25 29 28 22 18 21 22 18 16 16 21 22 S 10 11 8 11 10 13 16 13 12 7 8 12 11 SW 3 3 3 3 4 6 10 5 3 4 4 4 4 W 8 6 7 5 7 7 8 7 9 13 11 8 8 NW 14 8 8 8 13 15 16 16 14 9 12 12 12 Calm 2 2 3 1 0 0 0 1 1 0 1 2 1 AVERAGE WIND SPEED IN KILOMETERS PER i HOUR N 18.5 17.2 18.5 21.2 20.6 23.3 22.9 22.7 21 .7 19.5 18 .2 20 .4 20 .4 NE 18.0 17.9 19.6 22 .4 20 .6 20.8 22.4 23 .2 22 .2 22 .9 20.1 19 .6 20 .8 E 17.7 19.8 20.9 21.2 19.2 21.7 20.1 20.9 23 .7 24 .9 20 .9 19 .2 20 .9 SE 19.8 20.4 20.0 23 .5 23 .8 24.8 23.2 24.1 27 .0 30.3 24 .0 22 .2 23 .7 S 17.9 15.8 14 .6 16 .6 17.9 15.6 15.4 18 .2 23 .7 24 .9 20.3 19 .2 18 .3 SW 14.5 13.2 13.2 11.9 18 .3 15.4 16 .7 17.7 18 .2 22 .5 16.1 15 .3 16 .1 W 16.6 16.7 17.4 16.7 18.5 19.6 23.7 22.0 22 .2 23 .8 20.3 17 .1 19 .6 NW 24.1 18.7 20.1 20.9 22.5 21.7 23.3 22.7 24 .9 22.7 20.8 24 .8 22 .2 A l l D i r e c t i o n s 18.7 18 .0 18.7 20.9 20.8 20.9 21.1 21.7 23 .5 24.3 20.3 20 .0 20 .8 TABLE I : Summary o f average wind speed and d i r e c t i o n a t Sachs Harbour and Mould Bay (data p r o v i d e d by the A t m o s p h e r i c Environment S e r v i c e ) . Mould Bay are from t h e N o r t h and No r t h - w e s t . In the summer Sachs Harbour winds are from t h e E a s t , S o u t h - e a s t and So u t h , w h i l e Mould Bay r e p o r t s v a r i e d w ind d i r e c t i o n s w i t h E a s t and S o u t h -e a s t e r l y o r i e n t a t i o n s b e i n g t h e l e a s t f r e q u e n t . S h o r t term d a t a from Johnson P o i n t , a n a l y s e d by Anderson (1978) , i n d i c a t e a p r i m a r y E a s t and N o r t h - e a s t wind o r i e n t a t i o n and Anderson s u g g e s t s t h a t t h i s "may be i n d i c a t i v e o f a b a c k i n g o r c o u n t e r c l o c k w i s e s h i f t o f the p r e v a i l i n g winds as one p r o g r e s s e s northwards a c r o s s Banks I s l a n d " . Wind o r i e n t a t i o n and d i r e c t i o n p l a y a major r o l e i n d e t e r -m i n i n g t h e d i s t r i b u t i o n o f i c e i n t h e e a s t e r n B e a u f o r t Sea. sou t h and e a s t e r l y winds tend t o d r i v e the i c e o f f s h o r e , w h i l e w e s t e r l y winds guide t h e i c e landward (Burns, 19 74) . Wind v e l o c i t y a l s o p l a y s an i m p o r t a n t r o l e i n d e t e r m i n i n g wave h e i g h t , w i t h o r i e n t a t i o n and f e t c h b e i n g the o t h e r c o n t r o l l i n g f a c t o r s . B e r r y e t a l . y (1975) have a n a l y s e d the d i r e c t i o n a l f r e q u e n c y and magnitude o f the wind a t Sachs Harbour, and a summary o f t h e i r a n a l y s i s i s p r e s e n t e d i n T a b l e I I . Wind speeds e q u a l t o o r e x c e e d i n g 31.5 km/hr (17 k n o t s ) can be seen t o i n c r e a s e i n f r e q u e n c y d u r i n g the l a t e summer and f a l l , r e f l e c t i n g an i n c r e a s e i n c y c l o n i c a c t i v i t y . The p r e f e r r e d o r i e n t a t i o n o f th e s e h i g h v e l o c i t y winds i s from the e a s t and s o u t h - e a s t , and can be e x p e c t e d t o r e s u l t i n on-shore wave a c t i o n on the s o u t h e r n c o a s t d u r i n g c o n d i t i o n s o f open w a t e r . T h i s i s i n agreement w i t h the o b s e r v e d c o a s t a l morphology and the r e s u l t s o f a c o m p a r a t i v e s t u d y o f beach p r o f i l e s u n d e r t a k e n by Stephen (19 76) . Wind D i r e c t i o n P e r c e n t D i r e c t i o n a f r E q e q u e n c y June J u l y August September October NNE .79 .44 .89 .67 .85 NE 1.63 .44 2.02 1.13 2 .74 " : ENE . 46 .32 .73 1.30 2 .18 E 1.25 .20 .85 3 .08 4 .19 : : ?, ESE 1.92 .85 1.33! 2 .80 3 .43 SE 3 .21 3 .19 2 .82 5 .42 5 .16 SSE .71 .85 1.21 1.54 1.45 S .54 .20 .08 1.13 .89 SSW .04 .04 .04 .21 .24 SW .13 .24 .32 .04 .48 WSW .08 .16 .40 .17 .60 W .38 1.09 .93 .96 1.69 WNW .38 1.13 .69 1.17 1.69 NW 1.34 1.37 1.49 2 .42 1.17 NNW .92 1.33 1.45 1.58 .52 N 2 .63 2.26 1.61 1.46 .60 TOT. PC. 16.4 14.1 . 16 .9 24 .1 2 7.8 n o t e : d a t a from B e r r y e t a l . , 1975 TABLE I I : D i r e c t i o n a l f r e q u e n c y o f monthly w i n d s e q u a l t o • o r e x c e e d i n g 31.5 km/hr (17 Knots) a t Sachs Harbour, 1957-1966. 35 1.6 HYDROLOGIC REGIME  R i v e r s S y s t e m a t i c h y d r o l o g i c measurements w i t h i n the A r c t i c I s l a n d s have been i n i t i a t e d o n l y r e c e n t l y (Environment Canada, 1978), and d a t a from Banks I s l a n d i s c o n s e q u e n t l y l i m i t e d . A s t u d y o f the upper Thomsen R i v e r d r a i n a g e b a s i n was u n d e r t a k e n i n 1975 by the G l a c i o l o g y D i v i s o n o f Environment Canada (see Anderson and D u r r a n t , 1976; and Anderson, 1978). I n a d d i t i o n , a c o n t i n u o u s stream g a u g i n g program on B i g R i v e r i n s o u t h - w e s t e r n Banks I s l a n d was i n i t i a t e d by t h e Water Survey o f Canada i n 1975 . The f i n a l r e p o r t by Anderson (1978) : p r e s e n t s a good a n a l y s i s o f t h e a v a i l a b l e d a t a and the r e a d e r i s r e f e r r e d t o t h i s paper f o r a d e t a i l e d d i s c u s s i o n . The h y d r o l o g i c regime on Banks I s l a n d i s c l a s s i f i e d as " A r c t i c N i v a l " , as t h e a n n u a l hydrograph i s dominated'by a snow-m e l t peak i n the s p r i n g o r e a r l y summer and i s c h a r a c t e r i z e d by the absence o f w i n t e r f l o w (Church, 19 74) . A t y p i c a l hydrograph i s shown i n F i g u r e 12, a l o n g w i t h the c o r r e s p o n d i n g meteoro - r l o g i c a l c o n d i t i o n s . A n a l y s i s by A l l e n and C u d b i r d (1971) , Anderson (1978) and A l l e n (1978) i n d i c a t e s t h a t t h e r i v e r s on Banks I s l a n d g e n e r a l l y can be e x p e c t e d t o break-up w i t h i n the p e r i o d between e a r l y June and e a r l y J u l y , w i t h l a k e s becoming c o m p l e t e l y i c e f r e e d u r i n g the p e r i o d between e a r l y J u l y and the f i r s t o f August. Freeze-up i s n o t w e l l documented, b u t appears t o commence i n l a t e August and t o be completed p r i o r t o the 15th o f O c t o b e r , w i t h l a k e s becoming c o m p l e t e l y i c e c o v e r e d d u r i n g the month o f September. The t o t a l p e r i o d o f open w a t e r on r i v e r s i s t h e r e f o r e a p p r o x i -m a t e l y 3h months. However, as i n d i c a t e d by t h e hydrograph 500 36 400 9 THOMSEN RIVER AT THOMSEN FLY 1975 « 3 0 0 CD tn U n 200 •<-i a 100 CD u 3 4J (0 S-l CD Cu E CD En 0 30 25 20 15 10 5 0 -5 p 1 \ 1 \ 1 I f \ 1 \ 1 \ • mean discharge for the day A instantaneous discharge measurement , \ I o estimated maximum discharge 1 \ 1 A « T i l i i ' A i A • A " f > I A / / / 11 tan i i i i i i i i i i i i 1 1 i i • • • • • •••••• " i 1 1 II II 1 1 II 1 1 1 i 1 1 1 i t m i l rtmfrPimfA > 10 15 20 25 30 10 15 20 25 30 10 d a i l y p r e c i p i t a t i o n d a i l y maximum and minimum a i r temperatures, Thomsen F l y camp I I I i 11 I I i I M an i I i i i I I I 10 30 Note: Figure 12 15 20 June From Anderson, 1978. 10 15 20 July 30 5 10 August 7 6 i 5 c 4.2 -p f0 -P •H a, •rH o CD 0 ft Hydrometeorological data,• Thomsen River, 1975 . shown on F i g u r e 12, the p e r i o d i n wh i c h a c t i v e e r o s i o n and s e d i -ment t r a n s p o r t c o u l d be e x p e c t e d i s o n l y lh t o 2 months as ;, e x c e p t d u r i n g i n f r e q u e n t heavy r a i n s t o r m s , d i s c h a r g e s a r e g e n e r a l l y low t o n e g l i g i b l e a f t e r m i d - J u l y . I c e t h i c k n e s s e s o f over 2 m have been r e c o r d e d and,except i n the deepest p o o l s , r i v e r s are g e n e r a l l y f r o z e n t o t h e i r bed d u r i n g the w i n t e r . ( D a y and Anderson, 1976) . A c o m p i l a t i o n o f the a v a i l a b l e maximum an n u a l d i s c h a r g e v a l u e s o b s e r v e d on Banks I s l a n d i s p r e s e n t e d i n T a b l e I I I , w i t h u n i t d i s c h a r g e s b e i n g p l o t t e d a g a i n s t b a s i n a r e a on F i g u r e 13. Snow m e l t peaks can be seen t o produce the l a r g e s t o b s e r v e d 2 d i s c h a r g e s w i t h u n i t v a l u e s r a n g i n g from 30 t o 320 1/sec/km . I n comparison w i t h maximum u n i t d i s c h a r g e s o b s e r v e d w i t h i n b a s i n s o f comparable s i z e i n B r i t i s h C o l u m b i a , t h e s e v a l u e s a re s l i g h t l y h i g h e r t h a n t h o s e r e c o r d e d i n the r e g i o n o f t h e I n t e r i o r P l a t e a u (Environment Canada, 1972). However, w i t h the p o s s i b l e e x c e p t i o n o f t h e d a t a from Environment Canada, a l l o f the a v a i l a b l e peak d i s c h a r g e v a l u e s from Banks I s l a n d are e s t i m a t e s based on e x t r a -p o l a t i o n s o f s t a g e - d i s c h a r g e r e l a t i o n s h i p s . Such e x t r a p o l a t i o n s are p o t e n t i a l l y u n r e l i a b l e as a t l e a s t some o f the c r o s s - s e c t i o n s were s u b j e c t t o i c e c o n d i t i o n s a t the time o f peak d i s c h a r g e (see Day and Anderson, 1976; and F o r b e s , 1979) . Thus t h e s e d a t a must be r e g a r d e d w i t h some u n c e r t a i n t y . I n a d d i t i o n , the r e p o r t e d v a l u e s r e p r e s e n t o n l y one o r two y e a r s o f o b s e r v a t i o n and thus the maximum d i s c h a r g e v a l u e s can be e x p e c t e d to i n c r e a s e as a l o n g e r p e r i o d o f r e c o r d becomes a v a i l a b l e . The h y d r o l o g i c response t o the i n t e n s e r a i n e v e n t s d i s c u s s e d i n S e c t i o n 1.7 appears t o v a r y w i t h b o t h p h y s i o g r a p h y and s e a s o n a l t i m i n g . O b s e r v a t i o n s a t R e s o l u t e on August 12, 1960 (Thomas and L o c a t i o n B a s i n a r e a km^ P e r i o d o f r e c o r d Maximum mean d a i l y 3 / m /sec ann u a l d i s c h a r g e o 1/sec/km Date R e f e r e n c e " G a l l o i s R i v e r " 221 1975 30-70 (est) 136-317 June 16, 1975 Anderson, 1978 D i s s e c t i o n Creek 1060 1975 120 (est) 113 June 16, 1975 Anderson, 1978 "Chebyshev R i v e r " 1670 1975 50 (est) 30 June 16, 1975 Anderson,,1978 Thomsen^River above "Chebyshev R i v e r " 3610 1975 380 ( e st) 105 June 16, 1975 Anderson, 1978 B i g R i v e r above Egg R i v e r 3652 1976-1977 250 68 June 06, 1976 Environment Canada 19 76 & 1977 ( r e f . no. lOTBOOl) Thomsen R i v e r above D i s s e c t i o n Creek 5280 1975 430 (est) 81 June 16, 1975 Anderson, 1978 n o t e : u n o f f i c i a l names are shown i n q u o t a t i o n marks TABLE I I I : Observed maximum and mean d a i l y d i s c h a r g e s f o r r i v e r s on Banks. I s l a n d . u> 00 3 9 0 ? " 3a l i e ) i s •er it < r Tl lomse n Rive r 0 Dis C >se :re c t ek i c n "Ch€ ar sbysh ove ev R i v e r " O 1 J i g R abc i v e r ve Egg R i v e r 0 Thomsen R i v e r 1 above 1 1 it Disss >cti on Cr ee k" "C he Ri ^shev sr" 200 300 400 600 800 1000 1500 2000 4000 60 00 80 00 B a s i n area (km ) Note: - u n o f f i c i a l names are i n i t a l i c s . -data sources and p e r i o d o f r e c o r d s are shown on Table I I I . F i g u r e 13. Maximum observed u n i t d i s c h a r g e p l o t t e d a g a i n s t b a s i n a r e a f o r r i v e r s on Banks I s l a n d . 40 Thompson, 1962) and a t Vendom F i o r d , E l l e s m e r e I s l a n d on J u l y 22, 1973 (Cogley and McCann, 1976) i n d i c a t e t h a t i n r e l a t i v e l y s t e e p , p o o r l y v e g e t a t e d b a s i n s , 24 hour p r e c i p i t a t i o n e v e n t s i n the o r d e r o f 50 mm ( r e p o r t e d r e c u r r e n c e i n t e r v a l o f 10-20 y e a r s i n the e a s t e r n A r c t i c ) can r e s u l t i n o v e r l a n d f l o w , e x t e n s i v e f l o o d i n g and mass movement. However i n the more subdued topography a d j a c e n t t o Mould Bay, o b s e r v a t i o n s on August 19, 1960 (Thomas and Thompson, 1962) i n d i c a t e t h a t a s i m i l a r amount o f p r e c i p i t a t i o n (48 mm, r e c u r r e n c e i n t e r v a l a p p r o a c h i n g 500 y e a r s from F i g u r e 1 0 ) , r e s u l t e d i n o n l y an i n c r e a s e i n w a t e r l e v e l , w i t h no f l o o d i n g b e i n g o b s e r v e d . A d m i t t e d l y t h i s d i f f e r e n c e i n response may p a r t i a l l y r e f l e c t f a c t o r s such as c h a n n e l morphology and v e g e t a t i o n c o v e r , b u t the a u t h o r s a s c r i b e the p r i m a r y i n f l u e n c e t o p h y s i o -graphy . O b s e r v a t i o n s made by Holocek and V o s a h l o (1975) on Devon I s l a n d i n d i c a t e t h a t s e a s o n a l - t i m i n g i s a l s o . i m p o r t a n t , as summarized below: " I t was o b s e r v e d towards the end o f the r u n o f f season t h a t t h e r e sponse o f t h e w a t e r s h e d t o even a h i g h i n t e n s i t y p r e c i p i t a t i o n , w hich a few weeks e a r l i e r would have r e s u l t e d i n c o n s i d e r a b l e r u n o f f , was n e g l i g i b l e o r n i l f o r b o t h y e a r s of r e c o r d . There-f o r e i t can be c o n c l u d e d t h a t t h e b u i l d u p o f s u b s u r f a c e s t o r a g e o c c u r s m a i n l y d u r i n g the l a t t e r p a r t o f August and i n September.!,', (p. 456) . Thus the e f f e c t o f p r e c i p i t a t i o n e v e n t s w i l l depend upon b a s i n c h a r a c t e r i s t i c s and a n t e c e d e n t m o i s t u r e c o n d i t i o n s . Much o f Banks I s l a n d i s q u i t e s i m i l a r t o P r i n c e P a t r i c k I s l a n d and thus peak d i s c h a r g e v a l u e s r e s u l t i n g from i n t e n s e r a i n e v e n t s are more l i k e l y t o resemble th e documented response a t Mould Bay t h a n t h a t o f t h e c e n t r a l and e a s t e r n A r c t i c I s l a n d s . The a v a i l a b l e w a t e r temperature d a t a from Banks I s l a n d a r e p l o t t e d on F i g u r e 14. Temperatures can be seen t o r i s e s t e a d i l y 41 U I I l l l I i i M I I I I I I i i I i i I i i i i-i i I I i i i i i i i i i i i i i i i I.I i i n I i i i I i i i i i i 10 15 20 June 25 30 ID 15 20 Jul y 25 30 5 ID August 0) u 3 u 0) Cu E <u 30 25 20 15 10 5 0 -5 d a i l y p r e c i p i t a t i o n d a i l y maximum and minimum a i r temperatures, Thomsen F l y camp 1 7 _6 -5 4 5 10 15 20 25 30. 5 June 10 15 2 0 July 2 5 30 5 10 August Symbol River Location Basin area km2 Source O Thomsen R. above D i s s e c t i o n Cr. 73°14 ' N 119°32• W S280 Anderson, 1978 O Thomsen R. above "Chebyshev R." 73°14 • N 119°32 ' H 3610 Anderson, 1978 A • D i s s e c t i o n Cr. near the mouth "Chebyshev R." near the mouth 73°16 73°14 • N ' N 119°35' 119°32 • W W 1060 1670 Anderson, 1978 & pers. obs. Anderson, 1978 V " G a l l o i s R." near the mouth 73°17 ' N 119°41' W 221 Anderson, 1978 O Parker River 73°28 ' N 116°15' W pers. obs. .< Bernard River 73°25 • N 122°18' W pers. obs. .» Bernard River near the mouth 73°35 ' N 124°01' W pers. obs. a "Murchison R." near the mouth 74°04 • N 124°23' W pers. obs. © Thomsen R. above D i s s e c t i o n C r . 73°14 • N 119°32• W pers. obs. Note: a i r temperature data from Anderson, 1978. Figure 14. Observed r i v e r temperatures on Banks Island, 19 75 o v e r the p e r i o d between i n i t i a l m e l t and 10 t o 15 days f o l l o w i n g th e snowmelt peak, w i t h maximum te m p e r a t u r e s b e i n g i n the range o f 13 t o 16°C. S u b s e q u e n t l y t e m p e r a t u r e s are v a r i a b l e w i t h v a l u e s o f 6°C b e i n g commonly o b s e r v e d near t h e end o f J u l y . A comparison o f d a t a from " G a l l o i s " , D i s s e c t i o n and Thomsen R i v e r s i n d i c a t e s t h a t the s m a l l e r b a s i n s t e n d t o have h i g h e r w a t e r t e m p e r a t u r e s d u r i n g the i n i t i a l p e r i o d s u r r o u n d i n g break-up, p o s s i b l y r e f l e c t i n g l o w e r w a t e r t e m p e r a t u r e s a s s o c i a t e d w i t h l a k e s t o r a g e on Thomsen R i v e r o r l e s s e x t e n s i v e o c c u r r e n c e s o f snow and i c e d e p o s i t s w i t h i n the c h a n n e l s o f t h e s m a l l e r r i v e r s . The t h r e e a v a i l a b l e water temperature measurements on B e r n a r d and "Murchison" R i v e r s appear t o i n d i c a t e r e l a t i v e l y h i g h e r v a l u e s t h a n on the Thomsen d r a i n a g e and may r e f l e c t t h e lower e l e v a t i o n of t h i s r e g i o n and t h e s h a l l o w e r w a t e r depths i n t h e s e wide b r a i d e d c h a n n e l s . These d a t a i n d i c a t e r e g i o n a l v a r i a t i o n s i n w a t e r t e m p e r a t u r e , b u t i n a l l c a s e s t h e v a l u e s are s u f f i c i e n t l y h i g h t o r e s u l t i n s i g n i f i c a n t t h a w i n g o f f r o z e n m a t e r i a l i n t h e immediate v i c i n i t y o f t h e c h a n n e l bed and banks. However, t h e p a t t e r n o f i n c r e a s i n g summer w a t e r t e m p e r a t u r e s i s a s s o c i a t e d w i t h a d e c l i n e i n d i s -charge and thus the d i s t r i b u t i o n o f water w i t h i n the c h a n n e l i s an i m p o r t a n t f a c t o r i n d e t e r m i n i n g t h e r e s u l t i n g e f f e c t on the near c h a n n e l t h e r m a l regime, as w i l l be d i s c u s s e d i n S e c t i o n 4.2. C o a s t a l Regions The c i r c u l a t i o n p a t t e r n o f t h e B e a u f o r t Sea i s dominated by a l a r g e c o u n t e r - c l o c k w i s e f l o w o f s u r f a c e w a t e r (the " B e a u f o r t Gyre") d e s c r i b e d by H e r l i n v e a u x and de Lange Boom (1975), and 43 Walker (19 75) . T h i s g y r e r e s u l t s i n a g e n e r a l southward f l o w o f wate r a l o n g t h e west c o a s t o f Banks I s l a n d and a n o r t h - w e s t e r l y f l o w a l o n g t h e s o u t h - w e s t e r n c o a s t , as d e s c r i b e d by Burns (1974) . The r e g i o n a l o r i e n t a t i o n o f s p i t s w i t h i n t h e s e r e g i o n s c o n f i r m s t h i s f l o w p a t t e r n and i n d i c a t e s v a r y i n g c u r r e n t d i r e c t i o n s i n response t o l o c a l c o n d i t i o n s w i t h i n P r i n c e o f Wales S t r a i t . H i s t o r i c r e c o r d s o f sea i c e c o n d i t i o n s i n the s t u d y a r e a have been c o m p i l e d by t h e Canada Department o f T r a n s p o r t (1964-1972), Markham (1975), Ramseier e t a l . , (1975), Marko (1975), and r e c e n t l y by L i n d s a y (1975, 1977), and the r e a d e r i s r e f e r r e d t o thes e a u t h o r s f o r a d e t a i l e d d e s c r i p t i o n . Numerous summaries o f the o b s e r v e d range i n i c e c o n d i t i o n s have a l s o been p r e p a r e d (see S w i t h i n b a n k , 1960; Canada Department o f Energy Mines and Res o u r c e s , 1968, 1974; Bu r n s , 1974; and E n v i r o n m e n t a l P r o t e c t i o n S e r v i c e , 1978) . These s t u d i e s i n d i c a t e t h a t i n y e a r s w i t h minimum i c e c o v e r , open water may be found i n b o t h Amundsen G u l f and o f f the west c o a s t o f Banks I s l a n d by May. I c e f r e e c o n d i t i o n s may o c c u r a l o n g the e a s t c o a s t o f Banks I s l a n d by June and p r o g r e s s n o r t h w a r d t h r o u g h P r i n c e o f Wales S t r a i t i n J u l y and August. However, even i n y e a r s o f maximum open w a t e r , o n l y p o r t i o n s o f M'Clure S t r a i t can be e x p e c t e d t o become i c e f r e e . I n e x c e p t i o n a l y e a r s t h e s e i c e f r e e c o n d i t i o n s may p e r s i s t u n t i l October. I n c o n t r a s t , d u r i n g y e a r s o f maximum i c e c o v e r , l i m i t e d e x t e n t s o f open water may n o t o c c u r a l o n g t h e s o u t h c o a s t o f Banks I s l a n d u n t i l J u l y . P a r t i a l i c e c o v e r can p e r s i s t a l o n g b o t h the e a s t e r n and w e s t e r n c o a s t s t h r o u g o u t J u l y and August, w i t h the n o r t h e r n p o r t i o n o f P r i n c e o f Wales S t r a i t and M'Clure S t r a i t r e m a i n i n g c o m p l e t e l y i c e f a s t . Few o r no ar e a s o f open water may o c c u r by l a t e September o r Oc t o b e r . The c o m p o s i t i o n o f t h e sea i c e c o v e r a d j a c e n t t o Banks I s l a n d r e f l e c t s t h e p a t t e r n o f i c e c o n d i t i o n s d i s c u s s e d above, and c o n s e -q u e n t l y i s g e n e r a l l y composed o f s i n g l e y e a r i c e , w i t h second and m u l t i - y e a r i c e o c c u r r i n g a l o n g t h e n o r t h e r n c o a s t . A n a l y s i s by Burns (1974) i n d i c a t e s t h a t the average t h i c k n e s s o f s i n g l e year i c e i n the v i c i n i t y o f Sachs Harbour and Holman i s r o u g h l y 190 and 200 cm r e s p e c t i v e l y . H i s t o r i c a l r e p o r t s o f e a r l y e x p l o r e r s (such as M i e r t s c h i h g : , . 185.4 and M ' C l u r e , 1854), and more r e c e n t e x p e d i t i o n s by'Manning (1953, 1956) i n d i c a t e s i g n i f i c a n t movement o f the n e a r s h o r e w i n t e r i c e c o v e r may o c c u r and r e s u l t i n s i z e -a b l e p r e s s u r e r i d g e s and i c e push f e a t u r e s a l o n g the c o a s t . A n a l y s i s o f the p o t e n t i a l magnitude o f wave h e i g h t s f o r v a r y i n g r e c u r r e n c e i n t e r v a l s and w a t e r depths i n the s o u t h e r n B e a u f o r t Sea has r e c e n t l y been conducted by B e r r y e t a l . (1975) . The p u b l i s h e d r e s u l t s i n d i c a t e t h a t extreme wave h e i g h t s o f 2.0 m and 4.6 m may o c c u r i n 10 m water d e p t h s , a t a r e c u r r e n c e i n t e r v a l o f two and f i f t y y e a r s r e s p e c t i v e l y . These r e s u l t s are based on an a n a l y s i s o f o f f s h o r e winds o n l y , and, as i n d i c a t e d by the d a t a p r e s e n t e d i n S e c t i o n 1.5, the onshore winds can be e x p e c t e d t o be o f a h i g h e r v e l o c i t y d u r i n g t h e p e r i o d o f open w a t e r . Thus,when t h e s h a l l o w e r w a t e r depths i n the n e a r s h o r e a r e a a r e a l s o c o n s i d e r e d , the wave h e i g h t s p r e d i c t e d by B e r r y e t a l . a r e l i k e l y an u n d e r e s t i m a t i o n o f t h e p o t e n t i a l magnitude o f wave h e i g h t s w h i c h c o u l d be e x p e c t e d t o impinge on t h e s o u t h c o a s t o f Banks I s l a n d . T i d a l a c t i o n can a l s o a f f e c t c o a s t a l morphology. Burns (1974) and d a t a p u b l i s h e d by F i s h e r i e s and E n vironment Canada (1978) i n d i c a t e t h a t t h e average t i d a l range i n the s t u d y a r e a i s a p p r o x i m a t e l y 1 m. Thus t h i s s m a l l t i d a l v a r i a t i o n w i l l r e s u l t 45 i n the c o n c e n t r a t i o n o f wave energy w i t h i n a r e l a t i v e l y s m a l l range i n e l e v a t i o n . Wind can be e x p e c t e d t o cause some v a r i a -b i l i t y d u r i n g major s t o r m s j however a t p r e s e n t t h e r e are no d a t a upon which t o q u a n t i f y p o t e n t i a l wind t i d e e f f e c t s . S u r f a c e water temperature d a t a from t h e s o u t h e r n B e a u f o r t Sea are l i m i t e d . A summary, a g a i n p r e s e n t e d by Burns (1974), i n d i c a t e s t h a t the average J u l y w a t e r t e m p e r a t u r e s a d j a c e n t t o Banks I s l a n d range from 0°C t o h i g h s o f 3.3°C (38°F) a d j a c e n t t o t h e s o u t h e r n a r e a s and 1.1°C (34°F) midway up the w e s t e r n c o a s t . By comparison the maximum s u r f a c e water t e m p e r a t u r e s o f f t h e n o r t h e r n m a i n l a n d are somewhat h i g h e r a t 4.4°C (40°F). Average September t e m p e r a t u r e s remain p o s i t i v e a l o n g the s o u t h c o a s t , w i t h a v a l u e o f 1.1°C (34°F). Thus t h e s u r f a c e w a t e r t e m p e r a t u r e s a d j a c e n t t o s o u t h e r n Banks I s l a n d are p o s i t i v e o v e r much o f t h e summer and a r e , t h e r e f o r e , c a p a b l e o f i n d u c i n g t h e r m a l e r o s i o n i n s u s c e p t i b l e m a t e r i a l s . 46 SECTION TWO MORPHOLOGIC CLASSIFICATION AND REGIONAL DISTRIBUTION 2.1 INTRODUCTION P e r i g l a c i a l t e r m i n o l o g y has been d e s c r i b e d by Hamelin and Cook (1967) as b e i n g " i r r a t i o n a l , i m p r e c i s e , i n c o m p l e t e and non-d e f i n e a s i n g l e phenomenon o r p r o c e s s , and i n many ca s e s t h e same d i s s i m i l a r forms". D e s p i t e t h e d i s c u s s i o n s o f t e r m i n o l o g y i n r e c e n t papers by a u t h o r s such as McRoberts and M o r g e n s t e r n (1974a) and E g g i n t o n (1976) , the c l a s s i f i c a t i o n o f i n s t a b i l i t y f e a t u r e s i n r e g i o n s o f p e r m a f r o s t i s s t i l l n o t u n i v e r s a l l y a c c e p t e d . The handbook o f p e r m a f r o s t t e r m i n o l o g y r e c e n t l y completed by Brown and Kupsch (1974) p r e s e n t s a c o m p i l a t i o n o f recommended d e f i n i t i o n s and when a v a i l a b l e t h e s e a r e used i n t h i s s t u d y . However, i n c i r c u m s t a n c e s where d e f i n i t i o n s are n o t i n c l u d e d i n t h i s r e f e r e n c e and when nomenc l a t u r e v a r i e s between a u t h o r s o r d i s c i p l i n e s one t e r m i n o l o g y has been a r b i t r a r i l y chosen and an i n d i c a t i o n o f e q u i v a l e n c e has been g i v e n . The c l a s s i f i c a t i o n o f ground i c e forms f o l l o w s the usage o f Mackay (1972), and Brown and Kupsch s y s t e m a t i c " w i t h "many d i f f e r e n t terms [ibe i n g used] t o term [ b e i n g used] by d i f f e r e n t w o r k ers t o d e s c r i b e (1974) . 2.2 CLASSIFICATION AND GEOMETRY Banks and s l o p e s formed i n u n c o n s o l i d a t e d sediments were c l a s s i f i e d on t h e b a s i s o f morphology and i n f e r r e d p r o c e s s . A f t e r i n i t i a l a i r photograph i n t e r p r e t a t i o n and a p e r i o d o f h e l i c o p t e r r e c o n n a i s s a n c e , t h e f o l l o w i n g f e a t u r e s (or c o m b i n a t i o n o f f e a t u r e s i n p o l y g e n e t i c forms) were r e c o g n i z e d as b e i n g r e p r e -s e n t a t i v e o f t h e c o n d i t i o n s o c c u r r i n g w i t h i n the s t u d y a r e a . S o l i f l u c t i o n F e a t u r e s S o l i f l u c t i o n i n c l u d e s " p h y s i o g r a p h i c f e a t u r e s o f v a r y i n g s c a l e produced by the .... p r o c e s s o f slow g r a v i t a t i o n a l , down-s l o p e movement o f s a t u r a t e d , n o n f r o z e n e a r t h m a t e r i a l , b e h a v i n g a p p a r e n t l y as a v i s c o u s mass o v e r a s u r f a c e o f f r o z e n m a t e r i a l " (Brown and Kupsch, 1974). I n t h i s usage, s o l i f l u c t i o n i s e q u i v a l e n t t o t h e t e rm " g e l i f l u c t i o n " as d e f i n e d by B a u l i g (1956) and recommended by Washburn (1973) t o d i s t i n g u i s h " s o l i f l u c t i o n " o c c u r r i n g w i t h i n a p e r m a f r o s t e n v i r o n m e n t . S o l i f l u c t i o n s l o p e s ( F i g . 15a) f r e q u e n t l y have a concave h e a d w a l l ( g e n e r a l l y a t r a n s v e r s e n i v a t i o n h o l l o w ) and an e s s e n -t i a l l y l i n e a r s l o p e . The t o e o f t h e s e f e a t u r e s i s f r e q u e n t l y composed o f one o r more r i d g e s r e s u l t i n g from the downslope movement o f m a t e r i a l . Repose F e a t u r e s Repose f e a t u r e s i n c l u d e banks and s l o p e s which a r e p r e d o m i -n a n t l y r e c t i l i n e a r i n form. Those f e a t u r e s a t or near t h e i r a n g l e o f r epose a r e d e f i n e d as "repose banks", w h i l e t h o s e w i t h , s h a l l o w e r s l o p e s , and not e x h i b i t i n g o b v i o u s i n d i c a t i o n s o f 20 H g 1 5 H 80 sol i f luct ion H o p * average slope 12.5° repose bank location ol snow In eariy June average (lop* 4 2 ° / / / ^ 1 » 48 r-20 15 1 H o i a e 5 * 70 60 50 40 30 20 l e n g t h m) a) S o l i f l u c t i o n S l o p e 10 0 0 10 20 b ) R e p o s e Bank 40 35-30-25-20 15-10-5-o-l— sol i f luct ion slops with skin flow average s lop* 9° _ l 10 transverse nivation hollow ' and repose bank location of snow In early Juno 20 I 30 40 50 60 70 length (m) C) S k i n F l o w 80 90 100 110 120 30-25-- 20 6 | ' M a l 10-| 5 0 -alluvial fan 10 20 • Incised gully Inactive mud deposits exposed frozen sediments active head-debrla flow wall retrogressive thaw flow sl ide 30 40 50 60 70 length (m) d)R e t r o g r e s s i v e Thaw Flow S l i d e 8 0 90 100 110 5 0 sloughed sediments oversteepened face ! thermo-erosional J f nlcha 0 5 10 length (m) e ) T h e r m o - e r o s i o n a l N i c h e 40-35-30 - 2 H E ' 20i 10-5-0 • alluvial fan -Incised gully headwal I ^ _ oversteepened by nivation 20 30 40 50 6 length (m) f) N i v a t i o n Hol low / location of snow In early June 80 90 100 15-10-5 10 * 5 S 0 20 30 40 length (m) g) E o l i a n F e a t u r e 0 5 length (m) H ) O r g a n i c F e a t u r e repose blow-out — bank feature -*" 50 60 70 F i g u r e 15 • C r o s s - s e c t i o n a l s u r v e y s of r ep resen ta t i ve bank or s l o p e m o r p h o l o g i e s movement by s o l i f l u c t i o n , a r e d e f i n e d as "low a n g l e s l o p e s " . Repose banks, as i l l u s t r a t e d by F i g u r e 15b, a r e s i m i l a r i n form t o t h e i r temperate c o u n t e r p a r t , w i t h the a n g l e of repose g e n e r a l l y i n c r e a s i n g w i t h d e c r e a s i n g g r a i n s i z e . S k i n Flows " S k i n f l o w s i n v o l v e the detachment o f a, t h i n veneer o f v e g e t a t i o n and m i n e r a l s o i l and i t s subsequent movement o v e r a p l a n a r , i n c l i n e d s u r f a c e . They a r e commonly a c t i v e i n r i b b o n -l i k e forms and may c o a l e s c e i n t o broad s h e e t s o f i n s t a b i l i t y . T h i s c a t e g o r y o f f l o w s i s s h a l l o w i n comparison w i t h i t s length.;", (McRoberts and M o r g e n s t e r n , 1974a) . S k i n f l o w s are e q u i v a l e n t t o some o f the " e a r t h f l o w s " d i s c u s s e d by B i r d (1967) , the " d e t a c h -ment f a i l u r e s " o b s e r v e d by Hughes (1972), " a c t i v e l a y e r g l i d e s " r e p o r t e d by Mackay and Mathews (19 7 3 ) , and the " a c t i v e l a y e r detachment f a i l u r e s " documented by V i n c e n t (1978a). S i t e s s u b j e c t t o s k i n f l o w s ( F i g . 15c) are s i m i l a r i n appearance t o s o l i f l u c t i o n s l o p e s . The s l o p e a n g l e i n the r e g i o n of i n i t i a t i o n was o b s e r v e d -to be as low as 8 d e g r e e s , and examples o f l o w e r a n g l e f a i l u r e s l i k e l y e x i s t . S k i n f l o w s can f r e q u e n t l y be o f c o n s i d e r a b l e l e n g t h , w i t h a l a r g e f l o w on A b l e Creek e x c e e d i n g 700 m i n l e n g t h , and h a v i n g an average w i d t h o f 20 m. R e t r o g r e s s i v e Thaw Flow S l i d e s These f e a t u r e s are d e f i n e d as "a s l i d e t h a t c o n s i s t s o f a s t e e p h e a d w a l l , c o n t a i n i n g i c e o r i c e r i c h s e d i m e n t s , w h i c h r e t r e a t s i n a r e t r o g r e s s i v e f a s h i o n t h r o u g h m e l t i n g , and a d e b r i s f l o w formed from t h e m i x t u r e o f thawed sediment and i c e , w h i c h s l i d e s down the f a c e o f the h e a d w a l l t o i t s base.", (Brown and Kupsch, 19 74) . R e t r o g r e s s i v e thaw f l o w s l i d e s a r e one o f a num-*1 b e r o f f e a t u r e s caused by " t h e r m o k a r s t " o r the " m e l t i n g o f ground i c e and subsequent s e t t l i n g o r c a v i n g o f t h e ground" ( M u l l e r , 1947). The term " r e t r o g r e s s i v e thaw f l o w s l i d e " i s e q u i v a l e n t t o the term " t h e r m o c i r q u e " as used by Czudek and Demek (1970), "ground i c e slump" as used by Rampton and Mackay (1971) , "bi-modal f l o w " as d e f i n e d by McRoberts and Morgenstern (1974a), "ground i c e mud slump h o l l o w " as used by Fre n c h and E g g i n t o n (1973), and " r e t r o g r e s s i v e s e m i c i r c u l a r ground i c e slump" as d i s c u s s e d by Fr e n c h (19 76) . R e t r o g r e s s i v e thaw f l o w s l i d e s ( f i g . 15d) have a c h a r a c t e r i s -t i c s t e e p h e a d w a l l , which a t times may be alm o s t v e r t i c a l . Mud f l o w d e p o s i t s a d j a c e n t t o t h e base o f t h i s s c a r p form a t a s i g n i f i c a n t l y s h a l l o w e r a n g l e w h i c h i s dependent upon the under-l y i n g s t r u c t u r a l c o n t r o l , exposure t o sediment r e m o v a l , and w a t e r c o n t e n t . R e t r o g r e s s i v e thaw f l o w s l i d e s can be i n i t i a t e d on v e r y low a n g l e s l o p e s , w i t h the h e i g h t o f the r e s u l t i n g h e a d w a l l i n -c r e a s i n g w i t h the i c e c o n t e n t , the t h i c k n e s s o f the u n d e r l y i n g i c e r i c h m a t e r i a l and the a b i l i t y o f the thawed sediment t o move away from t h e a c t i v e f a c e (see Mackay, 1966, f o r a d e t a i l e d d i s c u s s i o n ) . v e r s u s " t h e r m a l e r o s i o n " i n w h i c h ground i c e i s m e l t e d p r i m a r i l y as a r e s u l t o f h e a t t r a n s f e r r e d from f l o w i n g w a t e r . T h e r m o - e r o s i o n a l N i c h e s As d i s c u s s e d by Gusev (1952), Walker and A r n b o r g (1966), and Czudek and Demek (1970) , t h e r m o - e r o s i o n a l n i c h e s a r e formed as a r e s u l t o f t h e r m a l l y enhanced f l u v i a l u n d e r c u t t i n g o f r i v e r banks o r c o a s t a l a r e a s . G r i g o r y e v (1966; in_ F r e n c h , 1976) r e p o r t s t h a t the w i d t h o f t h e s e u n d e r c u t s can r e a c h 2 0 m. F a i l u r e o f t h e o v e r -l y i n g f r o z e n sediments can r e s u l t i n e i t h e r s u r f i c i a l s l o u g h i n g o r b l o c k f a l l s i f t h e u n d e r c u t m a t e r i a l b r e a k s o f f i n l a r g e p i e c e s . T h e r m o - e r o s i o n a l n i c h e s f r e q u e n t l y have near v e r t i c a l f a c e s i n s i t e s u n d e r g o i n g a c t i v e u n d e r c u t t i n g . As i l l u s t r a t e d on F i g u r e 15e, s u r f i c i a l s l o u g h i n g can reduce t h e s l o p e a n g l e ; however, i f b l o c k f a i l u r e o c c u r s , p a r t i c u l a r l y i f a l o n g an i c e wedge, a near v e r t i c a l p r o f i l e can a g a i n form. A t h e o r e t i c a l a n a l y s i s r e l a t i n g bank h e i g h t t o the depth o f u n d e r c u t t i n g r e q u i r e d f o r b l o c k f a i l u r e i s p r e s e n t e d i n Harper (1978a). N i v a t i o n H o l l o w s " N i v a t i o n h o l l o w s a r e s h a l l o w , c i r q u e l i k e b a s i n s found on s l o p e s and u p l a n d s u r f a c e s . When a c t i v e they a r e o c c u p i e d by semi-permanent o r permanent snowbanks t h a t never grow i n t o g l a c i e r s . Three t y p e s are r e c o g n i z e d : a) t r a n s v e r s e , w i t h t h e major a x i s l y i n g t r a n s v e r s e t o the l i n e o f d r a i n a g e ; b) l o n g i -t u d i n a l , e l o n g a t e d downslope; and c) c i r c u l a r , w h i c h , though-t r a n s i t i o n a l between t h e o t h e r two, i n ground P l a n i s - f r e q u e n t l y o f f a r g r e a t e r d i m e n s i o n s " (Hamelin and Cook, 1967). N i v a t i o n h o l l o w s , as shown on F i g u r e 1 5 f , have a concave up p r o f i l e w i t h a marked break, i n s l o p e i n the r e g i o n o f a c t i v e n i v a t i o n s a p p i n g . Large a l l u v i a l f a n s f r e q u e n t l y form downslope o f t h e s e f e a t u r e s and r e s u l t i n a c h a r a c t e r i s t i c p r o f i l e . N i v a t i o n h o l l o w s can be q u i t e l a r g e , w i t h complex forms c o v e r i n g a r e a s as 2 l a r g e as 0.4 km , as i l l u s t r a t e d on P l a t e 6 i n S e c t i o n 3.3. E o l i a n F e a t u r e s Blow-out f e a t u r e s composed o f " s a u c e r - , cup- o r t r o u g h -shaped h o l l o w s " , formed by the w i n d , a r e found a l o n g many o f the l a r g e r r i v e r s w i t h i n the s t u d y a r e a , and, as s u c h , form a r e c o g -n i z e a b l e bank morphology ( a f t e r , American G e o l o g i c a l I n s t i t u t e , 1962) . A s shown on F i g u r e 15g, thes e f e a t u r e s a re g e n e r a l l y a s s o c i a t e d w i t h repose banks. Blow-outs have a c h a r a c t e r i s t i c s h arp break i n s l o p e a t the s i t e o f a c t i v e e r o s i o n , w h i c h can be up t o one t o two meters i n h e i g h t . Such f e a t u r e s have been o b s e r v e d w i t h a c o n t i n u o u s l i n e a r e x t e n t o f w e l l o v e r a k i l o m e t e r . O r g a n i c F e a t u r e s O r g a n i c f e a t u r e s a re s u p e r f i c i a l l y q u i t e s i m i l a r i n ap-^ . pearance t o t h e p r e v i o u s l y d e f i n e d "repose banks". However the i n c l u s i o n o f a h i g h p e r c e n t a g e o f o r g a n i c m a t e r i a l , the g e n e r a l l y low h e i g h t ( f r e q u e n t l y l e s s than 1 t o 2 m) and the common a s s o c i a -t i o n w i t h i c e wedges i n d i c a t e t h a t t h e s e f e a t u r e s s h o u l d be c o n -s i d e r e d a s e p a r a t e m o r p h o l o g i c u n i t . As i l l u s t r a t e d by F i g u r e 15h, o r g a n i c f e a t u r e s f r e q u e n t l y have a near v e r t i c a l p r o f i l e a t s i t e s u n d e r g o i n g a c t i v e e r o s i o n . 2.3 REGIONAL DISTRIBUTION OF CLASSIFIED MORPHOLOGIES F y l e s (1962) r e c o g n i z e d s i x p h y s i o g r a p h i c r e g i o n s on Banks I s l a n d w h i c h c o r r e s p o n d e d c l o s e l y w i t h the bedrock geology and g l a c i a l h i s t o r y as known a t the time o f mapping. On the b a s i s o f t h e more d e t a i l e d i n f o r m a t i o n now a v a i l a b l e ( S e c t i o n 1.3), as w e l l as o b s e r v a t i o n s u n d e r t a k e n i n c o n j u n c t i o n w i t h t h i s p r o j e c t , a somewhat m o d i f i e d p h y s i o g r a p h i c map has been p r e p a r e d ( F i g . 16) i n w h i c h each r e g i o n has a c h a r a c t e r i s t i c range o f c o a s t a l o r r i v e r b a n k morphology. As some o f t h e d e f i n e d r e g i o n s have .not been e x t e n s i v e l y s u r v e y e d (see F i g . 17) and complete a i r p h o t o -graph coverage o f t h e i s l a n d . w a s n o t a v a i l a b l e t o the a u t h o r , the u n i t b o u n d a r i e s must be c o n s i d e r e d as o n l y f i r s t a p p r o x i -m a t i o n s . N o n e t h e l e s s the map does a l l o w the p r e s e n t a t i o n o f i m p o r t a n t r e g i o n a l v a r i a t i o n . A l o n g t h e e a s t e r n c o a s t , w i t h i n the " E a s t e r n M o r a i n a l B e l t " , r e t r o g r e s s i v e thaw f l o w s l i d e s o c c u r f r e q u e n t l y , p a r t i c u l a r l y on the c o a s t and a l o n g t h e edges o f r i v e r s and l a k e s . The h e a d w a l l s o f t h e s e f e a t u r e s g e n e r a l l y have a h e i g h t o f 1 t o 3 meters i n t h i s r e g i o n and can be a s s o c i a t e d w i t h the f o r m a t i o n o f thermo-k a r s t l a k e s . . Repose banks, s o l i f l u c t i o n s l o p e s and n i v a t i o n h o l l o w s o c c u r l o c a l l y , w i t h t h e r m o - e r o s i o n a l n i c h e s b e i n g o b s e r v e d t o o c c u r e x t e n s i v e l y a l o n g t h e s o u t h e r n c o a s t i n t h i s r e g i o n . The "Devonian P l a t e a u " i n the n o r t h - e a s t e r n c o r n e r o f t h e i s l a n d i s c h a r a c t e r i z e d by d e e p l y i n c i s e d v a l l e y s w h i c h a r e f r e q u e n t l y asymmetric i n c r o s s - s e c t i o n . The v a l l e y w a l l s a r e n o r m a l l y c o v e r e d by a c . o l l u v i a l v eneer d e r i v e d from b o t h t h e u n d e r l y i n g , g e n e r a l l y l i t h i f i e d , sediments and the more r e c e n t 733 NORTH—WESTERN COAST l i t * iko* NORTHERN?. NORTHERN CRETACEOUS COrfPtEJC Bernard Island SrSMSH-WESfi KaQtMST SOUTHERN CftEfA£EOUS COMPLE*** 7I« Key location of field sites location of field sites where net seasonal erosion was measured (numerical superscripts indicate the number of sites monitered within the area covered by the solid circle) Note: Figure 16 unofficial place names are shown in quotation marks Modified physiographic regions of Banks Island. Figure 17= Place names and location of field sites g l a c i a l , l a c u s t r i n e and marine d e p o s i t s . S o l i f l u c t i o n s l o p e s , s k i n f l o w s and n i v a t i o n h o l l o w s o c c u r t h r o u g h o u t t h i s r e g i o n , w i t h the e x c e p t i o n o f t h e n o r t h e r n c o a s t which i s formed o f s t e e p l y s l o p i n g c o n s o l i d a t e d bedrock. The " N o r t h e r n and S o u t h e r n C r e t a c e o u s Complex" a r e c h a r a c t e r i z e d by r e l a t i v e l y wide v a l l e y s w h i c h are a g a i n f r e q u e n t asymmetric. M o d e r a t e l y s l o p i n g v a l l e y w a l l s a r e c o v e r e d i n c o l l u -vium, f r e q u e n t l y d e r i v e d from t h e p o o r l y l i t h i f i e d sediments o f t h e C h r i s t o p h e r and Kang.uk Fo r m a t i o n s w h i c h u n d e r l i e much o f t h i s r e g i o n . The s t e e p e r s i d e s o f t h e asymmetric v a l l e y s a r e g e n e r a l l y composed o f bedrock exposures and f r e q u e n t l y c o n t a i n w e l l d e v e l o p e d n i v a t i o n f e a t u r e s . S o l i f l u c t i o n s l o p e s and e x t e n s i v e s k i n f l o w f a i l u r e s commonly o c c u r on t h e o p p o s i n g o r lower a n g l e v a l l e y w a l l s . Repose., banks , o r g a n i c d e p o s i t s e o l i a n ; f e a t u r e s and the o c c a s i o n a l t h e r m o - e r o s i o n a l n i c h e o c c u r w i t h i n the v a l l e y bottoms. R e t r o g r e s s i v e thaw f l o w s l i d e s were obse r v e d l o c a l l y on t h e u p l a n d s u r f a c e s , a g a i n b e i n g most common a l o n g the edges o f v a l l e y s , r i v e r s and l a k e s . These t h e r m o k a r s t f e a t u r e s ar e p a r t i c u l a r l y w e l l d e v e l o p e d i n t h i s r e g i o n and can f r e q u e n t l y have h e a d w a l l s 3 m o r more i n h e i g h t . The "Southern U p l a n d s " i s a r e g i o n o f l i t h i f i e d bedrock and the c o a s t s i n t h i s r e g i o n a r e c o n s e q u e n t l y formed o f near v e r t i c a l s l o p e s , g e n e r a l l y a s s o c i a t e d w i t h e x t e n s i v e t a l u s a c c u m u l a t i o n s . The " N o r t h e r n U p l a n d s " i s c o m p r i s e d o f a number of bedrock t y p e s and c o n s e q u e n t l y e x p r e s s e s a range o f c h a r a c t e r i s t i c s . A l o n g the c o a s t , near v e r t i c a l sea c l i f f s o c c u r i n the a r e a s u n d e r l a i n by l i t h i f i e d Devonian s e d i m e n t s . However th e s u r r o u n d i n g a r e a i s composed o f u n c o n s o l i d a t e d sediments o f C h r i s t o p h e r , Kang.uk and E u r e k a Sound F o r m a t i o n s and would thus be ^expected t o have m o r p h o l o g i e s s i m i l a r t o t h a t o c c u r r i n g i n the "Cretaceous Complex". R i v e r s f l o w i n g t h r o u g h the r e g i o n o f t h e " B e a u f o r t P l a i n " t y p i c a l l y have wide b r a i d e d c h a n n e l s w i t h i n t h e i r l o wer r e a c h e s , and g e n e r a l l y have a n g l e o f repose banks. S m a l l t h e r m o k a r s t l a k e s o c c u r e x t e n s i v e l y on the a s s o c i a t e d l o w - l y i n g wide f l u v i a l t e r r a c e s . The upper s e c t i o n s o f t h e s e r i v e r s have anastomosing o r s i n g l e t h r e a d c h a n n e l s and t h e r m o - e r o s i o n a l n i c h e s o c c u r l o c a l l y . The west c o a s t i s g e n e r a l l y composed o f a n g l e o f repose banks and l o w - l y i n g d e l t a i c d e p o s i t s . However c o a s t a l r e c e s s i o n and v a l l e y submergence have r e s u l t e d i n the e x t e n s i v e development o f b a r r i e r beaches. A l o n g the "North-western C o a s t " , r e t r o g r e s s i v e thaw-flow s l i d e s a r e v e r y common. These f e a t u r e s a r e s h a l l o w e r i n depth t h a n those o c c u r r i n g w i t h i n the "Cretaceous Complex" and t h e " E a s t e r n M o r a i n a l B e l t " as the h e a d w a l l s a re g e n e r a l l y l e s s t h a n one meter i n h e i g h t . Angle o f repose banks and s o l i f l u c t i o n s l o p e s a l s o commonly o c c u r i n t h i s r e g i o n . The "Western Lowland" r e g i o n i s s i m i l a r t o the " B e a u f o r t P l a i n " i n t h a t the lower r e a c h e s o f t h e r i v e r s i n t h i s a r e a a g a i n have wide b r a i d e d c h a n n e l s and are a s s o c i a t e d w i t h numerous s h a l l o w t h e r m o k a r s t l a k e s . R i v e r banks t y p i c a l l y have an a n g l e o f repose form and may have a s s o c i a t e d eold,an f e a t u r e s . The c o a s t a l a r e a s e x h i b i t a much w i d e r range o f morphology. The l o w - l y i n g a r e a s , f r e q u e n t l y l o c a t e d a d j a c e n t t o the mouths o f the major r i v e r s , a r e g e n e r a l l y c o m p r ised o f low e l e v a t i o n a n g l e o f repose banks o r o r g a n i c f e a t u r e s . S o l i f l u c t i o n s l o p e s , h i g h e r r e l i e f a n g l e o f repose banks, n i v a t i o n h o l l o w s and r e t r o g r e s s i v e thaw f l o w s l i d e s a l l o c c u r i n a s s o c i a t i o n w i t h the major i s l a n d s and h i g h e r e l e v a t i o n h e a d l a n d s . T h e r m o - e r o s i o n a l n i c h e s were obs e r v e d t o o c c u r a l o n g t h e s o u t h e r n s e c t i o n o f t h i s c o a s t , i n the a r e a i m m e d i a t e l y t o t h e n o r t h o f Cape K e l l e t t . The "South-western C o a s t " r e g i o n i s composed o f two d i s t i n c t a r e a s . The t e r r a i n i m m e d i a t e l y e a s t o f Sachs Harbour i s formed by a r e l a t i v e l y l e v e l t e r r a c e thought t o be o f f l u v i a l o r i g i n ( V i n c e n t , 1978a) . Thermokarst l a k e s , e o l i a n f e a t u r e s and thermo-e r o s i o n a l n i c h e s o c c u r t h r o u g h o u t t h i s s e c t i o n o f c o a s t . F u r t h e r e a s t , a s e r i e s o f subdued h i l l s ( c o r r e s p o n d i n g t o t h e l o c a t i o n o f the Sand H i l l s Readvance o f the Amundsen G l a c i a t i o n ) abut a g a i n s t t h i s t e r r a c e . S o l i f l u c t i o n s l o p e s and l a r g e r e t r o g r e s s i v e thaw f l o w s l i d e s , w i t h h e a d w a l l s o b s e r v e d t o exceed 4 meters i n h e i g h t , t y p i c a l l y o c c u r w i t h i n t h i s r e g i o n . 59 SECTION THREE GEOTECHNICAL CHARACTERISTICS AND ENVIRONMENTAL SETTING OF REPRESENTATIVE BANK OR SLOPE MORPHOLOGIES 3.1 METHODOLOGY Sampling P r o c e d u r e As d i s c u s s e d i n S e c t i o n 1.3, t h e f i e l d program was t o a l a r g e e x t e n t dependent on h e l i c o p t e r t r a n s p o r t . Weight l i m i t a -t i o n s p r e c l u d e d t h e c a r r y i n g o f d r i l l i n g equipment, and thus s a m p l i n g f o r m a t e r i a l t e x t u r e and i c e c o n t e n t was unde r t a k e n m a n u a l l y . Hand augers p r o v e d e s s e n t i a l l y u s e l e s s due t o b o t h the time n e c e s s a r y t o complete a h o l e and t h e i r p r o p e n s i t y f o r becoming s t a l l e d on p e b b l e s o r c o b b l e s . The b e s t compromise was e v e n t u a l l y o b t a i n e d t h r o u g h the use o f an e n t r e n c h i n g t o o l and an i c e axe . A t f i e l d s i t e s w hich were a c t i v e l y r e t r e a t i n g , the. a c t i v e , l a y e r was f r e q u e n t l y r e d u c e d o r a b s e n t , and samples o f n e a r - s u r f a c e f r o z e n m a t e r i a l s were r e a d i l y a v a i l a b l e . I n s i t e s u n d e r g o i n g slow r a t e s o f e r o s i o n , a c t i v e l a y e r depths were o c c a s i o n a l l y o v e r 1 m i n t h i c k n e s s and thus s a m p l i n g f o r i c e c o n t e n t p r o v e d d i f f i c u l t o r i m p o s s i b l e . I n such c i r c u m s t a n c e s , the de p t h o f the h o l e ( p e r p e n d i c u l a r t o the s l o p e ) was extended as f a r below t h e f r o s t t a b l e as time p e r m i t t e d , i n o r d e r t o ensure t h a t the i c e c o n t e n t was r e p r e s e n t a t i v e o f t h e u n d e r l y i n g c o n d i t i o n s , r a t h e r t h a n t h a t o f t h e i n c r e a s e d i c e c o n c e n t r a t i o n s f r e q u e n t l y o b s e r v e d a t the base o f the a c t i v e l a y e r (see Mackay, 1971b; G e l l , 1974) . A t s i t e s where t e x t u r e o r i c e c o n t e n t v a r i e d o v er t h e h e i g h t o f t h e bank o r s l o p e , c h a n n e l samples were t a k e n o f each s t r a t i g r a p h i c u n i t , w i t h one o r more samples b e i n g i n d i c a t e d on the f i e l d n o t e s 60 a s r e f l e c t i n g t h e d o m i n a n t c h a r a c t e r i s t i c s o f t h e s i t e . S a m p l e s i z e w a s g e n e r a l l y i n t h e r a n g e o f 1 t o 2 k g , b u t w a s i n c r e a s e d u p t o 5 k g i n g r a v e l s o r i n c a s e s o f r e t i c u l a t e d i c e d e p o s i t s ( s e e M a c k a y , 1 9 7 4 ) . W h e n m a s s i v e i c e w a s e n c o u n t e r e d d u e t o t h e p r e s e n c e o f i c e w e d g e s o r i c e l e n s e s , r e p r e s e n t a t i v e s a m p l e s w e r e t a k e n o f t h e a d j a c e n t m a t e r i a l , a n d t h e p r e s e n c e o f m a s s i v e i c e i n d i c a t e d o n t h e f i e l d n o t e s . I c e C o n t e n t I c e c o n t e n t , a s a p e r c e n t a g e o f s a m p l e d r y w e i g h t , w a s d e t e r m i n e d a t t h e m a i n f i e l d c a m p . D r y i n g f a c i l i t i e s c o n s i s t e d o f t h e c o o k s o v e n a n d a n i m p r o v i s e d " s a m p l e c o o k e r " , c o n s i s t i n g o f a s m a l l k e r o s e n e h e a t e r a n d a n e m p t y 4 5 g a l l o n f u e l d r u m . . T e m p e r a -t u r e c o n t r o l s i n t h e " c o o k e r " w e r e p r i m i t i v e a n d t h u s o n r a r e o c c a s i o n s t e m p e r a t u r e r o s e s u f f i c i e n t l y h i g h t o c h a r o r g a n i c m a t t e r . S u c h t e m p e r a t u r e s w o u l d b e e x p e c t e d t o a f f e c t t h e s t r u c -t u r e o f c l a y m i n e r a l s ( L a v k u l i t c h , p e r s . c o m m . ) ; h o w e v e r t h i s e x c e s s i v e h e a t h a s b e e n a s s u m e d t o b e o f m i n o r c o n s e q u e n c e a s f a r a s t h e i c e c o n t e n t d e t e r m i n a t i o n s a r e c o n c e r n e d . O r g a n i c m a t t e r i n c l u s i o n s ( a s l a t e r d e t e r m i n e d b y h y d r o g e n p e r o x i d e t r e a t m e n t ) w e r e g e n e r a l l y n e g l i g i b l e i n a l l s a m p l e s o f f r o z e n m a t e r i a l e x c e p t t h o s e f r o m o r g a n i c d e p o s i t s s u c h a s p e a t . T h u s , d e h y -d r a t i o n o f o r g a n i c m a t e r i a l d i d n o t s i g n i f i c a n t l y a f f e c t t h e i c e c o n t e n t d e t e r m i n a t i o n s . A p o t e n t i a l l y m o r e s e r i o u s c o n c e r n a r i s e s f r o m t h e f a c t t h a t t h e s a m p l e s w e r e s t o r e d i n h e a v y g a u g e p l a s t i c b a g s . I n s o m e c a s e s , w a t e r w a s f o u n d a d j a c e n t t o t h e b a g s a n d i t w a s i m p o s s i b l e t o d e t e r m i n e i f i t o r i g i n a t e d f r o m c o n d e n s a t i o n o r l e a k a g e t h r o u g h t h e s e c u r i n g s t r i n g . T h e n u m b e r o f s a m p l e s w h i c h m a y h a v e b e e n a f f e c t e d i s t h o u g h t t o b e r e l a t i v e l y s m a l l . I n f u t u r e , however, a b e t t e r f i e l d p r o c e d u r e would be t o use s o i l s a m p l i n g t i n s o r o t h e r such l a r g e m e t a l c o n t a i n e r s w i t h screw l i d s . A comparison o f i c e c o n t e n t s measured e a r l y i n t h e season w i t h t h o s e from th e l a t e r p a r t o f the summer was conducted f o r s i t e s u n d e r g o i n g slow r a t e s o f e r o s i o n . The e f f e c t o f v a r y i n g sample l o c a t i o n s was d i f f i c u l t t o a s s e s s ; however v a l u e s were g e n e r a l l y i n c l o s e agreement, w i t h t h e d i f f e r e n c e s i n i c e c o n t e n t f r e q u e n t l y b e i n g o n l y a few p e r c e n t and o c c a s i o n a l l y a g r e e i n g t o w i t h i n a t e n t h o f a p e r c e n t . N o t w i t h s t a n d i n g , where p o s s i b l e , i c e c o n t e n t s o b t a i n e d l a t e ..in the season were used i n a l l a n a l y s e s , due t o t h e s m a l l e r l i k e l i h o o d o f s a m p l i n g m a t e r i a l from w i t h i n the a c t i v e l a y e r . T e x t u r a l A n a l y s i s G r a i n s i z e d e t e r m i n a t i o n was u n d e r t a k e n a f t e r r e t u r n i n g from t h e f i e l d . Wet and d r y s i e v e a n a l y s i s was conducted on a 100 t o 200 g s p l i t sample, d e f l o c c u l a t e d i n t h e .old f o r m u l a "Calgon" ( c o n t a i n i n g hexametaphosphate). " P l a t e s " o f p o o r l y l i t h i f i e d , f i n e t e x t u r e d sediment were s u b j e c t e d t o m e c h a n i c a l s t i r r i n g i n the d e f l o c c u l a n t and m i l d a b r a s i o n w i t h a p a i n t b r u s h d u r i n g wet s i e v i n g , b u t were n o t o t h e r w i s e p h y s i c a l l y b r o k e n up, as s i m i l a r p l a t e s were e v i d e n t i n t h e f i e l d . Dry s i e v i n g was u n d e r t a k e n a t one p h i i n t e r v a l s from 0.0625 t o 8 mm on a l l samples. The r e l a t i v e p e r c e n t a g e s o f sand, s i l t and c l a y were d e t e r m i n e d f o r a r e p r e s e n t a t i v e number of samples from bank o r s l o p e forms t y p i c a l l y found i n f i n e t e x t u r e d m a t e r i a l s . Hydro-meter a n a l y s i s was u n d e r t a k e n on a 50 g s p l i t sample o f t h e under 2mm s i z e f r a c t i o n , a f t e r d e f l o c c u l a t i o n i n 5 p e r c e n t metaphosphate 62 w i t h m e c h a n i c a l s t i r r i n g . E x p o s u r e t o P r o c e s s e s o f S e d i m e n t R e m o v a l E v e n f r o m c a s u a l o b s e r v a t i o n , i t i s o b v i o u s t h a t t h e f o r m t a k e n b y a r i v e r b a n k , a s l o p e o r a c o a s t a l a r e a i s p a r t i a l l y d e p e n d e n t u p o n t h e r a t e a t w h i c h s e d i m e n t i s r e m o v e d b y p r o c e s s e s o f e i t h e r m a s s w a s t a g e o r e r o s i o n . A t a s i m p l e l e v e l , t h i s " r e l a t i v e e x p o s u r e t o p r o c e s s e s o f s e d i m e n t r e m o v a l " c a n b e c o r r e l a t e d d i r e c t l y w i t h p l a n i m e t r i c p a t t e r n , a s i l l u s t r a t e d b y a c o a s t a l h e a d l a n d w h i c h w o u l d h a v e a h i g h e r e x p o s u r e t h a n a s h e l t e r e d b a y , o r e v e n m o r e s i m p l y , t h e u n d e r - c u t s i d e o f a m e a n d e r b e n d v e r s u s t h e s l i p - o f f s l o p e . A m o r e r i g o r o u s q u a n t i f i c a t i o n o f e x p o s u r e i s n o t a s i m p l e u n d e r t a k i n g d u e t o t h e l a r g e n u m b e r o f t e r r a i n o r s i t e c h a r a c -t e r i s t i c s w h i c h h a v e b e e n o b s e r v e d t o b e i m p o r t a n t i n p e r i g l a c i a l e n v i r o n m e n t s . A d e t a i l e d c o n s i d e r a t i o n o f f a c t o r s s u c h a s o r i e n t a t i o n t o w i n d a n d s u n , w a t e r t e m p e r a t u r e a n d v e l o c i t y , f e t c h , v e g e t a t i o n c o v e r , t h e o c c u r r e n c e o f i c e r e l a t e d p h e n o m e n a a n d s o i l p o r e w a t e r p r e s s u r e s i s b e y o n d t h e s c o p e o f t h i s p r o j e c t , a s s t u d i e s b y O v i t h e t ( 1 9 7 4 ) i n d i c a t e t h e d i f f i c u l t y o f q u a n t i f y i n g t h e e f f e c t o f e v e n a l i m i t e d n u m b e r o f t h e s e v a r i a b l e s . T h u s t h e " L o w , " M o d e r a t e " a n d " H i g h " c l a s s i f i c a t i o n o f e x p o s u r e u s e d i n t h i s s t u d y i s e s s e n t i a l l y s u b j e c t i v e a n d b a s e d p r i m a r i l y o n t h e a u t h o r ' s i m p r e s s i o n o f h o w e x p o s e d a s i t e i s t o a n y o n e o f a n u m b e r o f p r o c e s s e s . P l a n i m e t r i c c o n f i g u r a t i o n , a s i n d i c a t e d o n a i r p h o t o g r a p h s , p r o v i d e d t h e b a s i s f o r t h e c l a s s i f i -c a t i o n , b u t f a c t o r s s u c h a s r e l a t i v e r e l i e f , f e t c h a n d t h e o n - s i t e i m p r e s s i o n o f h o w f a s t s e d i m e n t w a s b e i n g r e m o v e d w e r e a l s o c o n -s i d e r e d , a s s u m m a r i z e d o n T a b l e I V . EXPOSURE H i g h Moderate TYPICAL LOCATION RIVERS COASTS AND LAKES Are a s undergoing a c t i v e under-^ c u t t i n g , such as on t h e o u t s i d e o f meander bends o r o t h e r a r e a s where the r i v e r i s a c t i v e l y im-p i n g i n g on the r i v e r bank or v a l l e y w a l l (e.g., on the s t e e p s i d e o f an asymmetric v a l l e y , a d j a c e n t t o major b a r s i n a b r a i d e d r e a c h , e t c . ) A r e a s a d j a c e n t t o r e l a t i v e l y s t r a i g h t s t r e t c h e s o f r i v e r Areas f u l l y exposed t o wave o r c u r r e n t a c t i o n due t o o r i e n -t a t i o n , a v a i l a b l e f e t c h and i c e . c o n d i -t i o n s Areas n o t f u l l y exposed t o wave o r c u r r e n t a c t i o n due t o e i t h e r o r i e n t a -t i o n , a v a i l a b l e f e t c h o r p e r s i s t e n t i c e c o v e r A reas undergoing a g g r a d a t i o n , P r o t e c t e d l o c a t i o n s such as on t h e i n s i d e o f a such as b e h i n d l a r g e meander bend o r a d j a c e n t t s p i t s and b a r s , t o a s l o p e which i s undergoing a r e a s w i t h l i t t l e o r movement due t o s o l i f l u c t i o n no f e t c h , o r i n r e g i o n s g e n e r a l l y s u b j e c t t o c o n r i r . t i n u o u s i c e c o v e r TABLE IV: Exposure c l a s s i f i c a t i o n used i n t h i s s t u d y . RELATIVE RELIEF. AND SEDIMENT TRANSPORT Ar e a i s o f s u f f i c i e n t r e l i e f , o r s u f f i c i e n t l y c l o s e t o a s i t e o f a c t i v e e r o s i o n , t h a t i n most y e a r s , sediment p r o -duced by t h e r m o k a r s t , mass wastage o r e r o s i o n a l p r o -c e s s e s w i l l be removed from the p l a c e o f o r i g i n A r e a i s o f s u f f i c i e n t r e l i e f f o r mass w a s t i n g , thermo-k a r s t o r e r o s i o n a l p r o c e s s e s t o o c c u r ; however the m a t e r i a l so produced i s f r e -q u e n t l y r e - d e p o s i t e d b e f o r e r e a c h i n g a s i g n i f i c a n t stream o r the ocean (on r i v e r s and c o a s t s , r e s p e c -t i v e l y ) A r e a s o f low r e l a t i v e r e l i e f o r s u f f i c i e n t l y g e n t l e s l o p e s t h a t i n most y e a r s , m a t e r i a l produced by mass w a s t i n g , e r o s i o n o r thermo-k a r s t p r o c e s s e s i s g e n e r a l l y n o t t r a n s p o r t e d any s i g n i f i -c a n t d i s t a n c e from i t s p l a c e o f o r i g i n M a t e r i a l G e n e s i s The g e n e t i c o r i g i n o f the m a t e r i a l s a t each f i e l d s i t e was d e t e r m i n e d from a c o m b i n a t i o n o f a i r photograph i n t e r p r e t a t i o n , f i e l d o b s e r v a t i o n and subsequent a n a l y s i s o f c u m u l a t i v e g r a i n s i z e p l o t s . I n some ca s e s t h e a v a i l a b l e f i e l d time o r n a t u r a l l y o c c u r r i n g e x posures were i n s u f f i c i e n t t o d i s t i n g u i s h between p o t e n t i a l l y s i m i l a r u n i t s , such as t i l l , m arine washed t i l l o r c r y o t u r b a t e d m a t e r i a l o r i g i n a l l y d e p o s i t e d i n a marine e n v i r o n m e n t . F o r t u n a t e l y V i n c e n t (1978a) has p u b l i s h e d the p r e l i m i n a r y r e s u l t s o f h i s s u r f i c i a l g e o l o g y mapping program and t h i s a l l o w e d an independent check on t h e o r i g i n a l d e s c r i p t i o n , as w e l l as the b e n e f i t o f h i s much w i d e r f i e l d e x p e r i e n c e i n those c a s e s o f u n c e r t a i n c l a s s i f i c a t i o n . 3.2 PRIMARY FACTORS AFFECTING BANK OR SLOPE MORPHOLOGY 65 3.2.1 M a t e r i a l G e n e s i s The g e n e t i c o r i g i n o f m a t e r i a l s o b s e r v e d a t each o f the f i e l d s i t e s i s summarized on Ta b l e V. S o l i f l u c t i o n S l o p e s S o l i f l u c t i o n s l o p e s o c c u r u b i q u i t o u s l y a l o n g b o t h the v a l l e y w a l l s and u p l a n d a r e a s . I n u p l a n d r e g i o n s t h e m a t e r i a l f o r m i n g t h e s e f e a t u r e s i s g e n e r a l l y t i l l o r c o l l u v i a t e d t i l l , w i t h d i s t i n c t t e x t u r a l v a r i a t i o n s as d e s c r i b e d i n S e c t i o n 1.4. A l o n g the v a l l e y w a l l s o r c o a s t a l a r e a s , m a t e r i a l s c o u l d be d e s c r i b e d as c o l l u v i u m , g e n e r a l l y d e r i v e d from m i x t u r e s o f b o t h t i l l and the u n d e r l y i n g p r e - Q u a t e r n a r y s e d i m e n t s , b u t l o c a l l y c o n t a i n i n g i n c l u s i o n s o f l a c u s t r i n e and marine m a t e r i a l s . S k i n Flows S k i n f l o w s were o b s e r v e d o n l y on i n c l i n e d t e r r a i n , b e i n g most common a l o n g the s i d e s o f v a l l e y s . S l o p e s formed o f c o l -l u v i u m d e r i v e d from the s i l t s and c l a y s o f t h e C h r i s t o p h e r f o r m a t i o n were o b s e r v e d to be p a r t i c u l a r l y s u s c e p t i b l e t o s k i n f l o w f a i l u r e . However c o l l u v i a t e d s l o p e s formed o f v a r y i n g m i x t u r e s o f t i l l , l a c u s t r i n e and marine s e d i m e n t s , w i t h i n c l u s i o n s o f the u n d e r l y i n g "bedrock m a t e r i a l s " ( i n c l u d i n g s i l t s , c l a y s , sands and sandstones) were a l s o o b s e r v e d t o be s u b j e c t t o s k i n f l o w f a i l u r e . R e t r o g r e s s i v e Thaw Flow S l i d e s R e t r o g r e s s i v e thaw f l o w s l i d e s were obse r v e d i n the near CENOZOIC MORPHOLOGY # OF SITES QUATERNARY MATERIAL GENESIS S o l i f l u c t i o n S l o p e s S k i n f l o w s 10 R e t r o g r e s s i v e thaw f l o w s l i d e s Repose f e a t u r e s 41 N i v a t i o n h o l l o w s T h e r m o - e r o s i o n a l n i c h e s E o l i a n f e a t u r e s 13 M L M K .1; 1; M Dm, M Kk 1; 1; Cv Kc — = 1-Cv Dm, = 1 M Tb = 4-Kc 4 ' CV Kc/Dm = 1; Cv/m/w K i = 1; 1 Cv/Lv Te, = 1 Cv/m Dmn = 3; = 1 J * = 3-Kk M T e 2 o r W o r ? o r Kc = 4 _ _ Wv WV/MV = 1 ; g-L Lv/Wv  M Tb o r Kk = 3; Lv/Wv M = 2; Tb W = 2; Fv/Lv = 1; Lv M =•- 2 K o r Kc F = 24; A = 3; Tb = 6; W = 1; K i = 1; 1 = 1 ; Kk o r K = 5; Kk = 2; Kc = 1; T e 0 = 2 ; Dm = 2 - = 1 • - = 1 • Tb = 3 • K = 1 • Kc L l W L ' 1 D 6 ' ' K i = 1; F = 1; M = 1; Tb = 2; 6 _ 6; RIVER DEPOSITS w L F I M Tb Te ALLUVIAL DEPOSITS: s t r a t i f i e d g r a v e l , sand and s i l t d e p o s i t e d by r i v e r s . A. Terraced f l u v i a l d e p o s i t s and minor fans. A: A c t i v e f l o o d p l a i n or fan d e p o s i t s . WIND DEPOSITS EOLIAN DEPOSITS: f i n e sand and l o e s s ; d e p o s i t e d or reworked by wind; mainly on f l u v i a l and outwash t e r r a c e s . E_: Areas of a c t i v e d e f l a t i o n and e o l i a n d e p o s i t i o n SLOPE DEPOSITS COLLUVIAL DEPOSITS: t h i c k sequences o f l o c a l l y d e r i v e d sediments accumulating as aprons and blankets on slopes by mass movement o r p e r i g l a c i a l processes. MARINE DEPOSITS LITTORAL, SUBLITTORAL, and OFFSHORE DEPOSITS: sediments deposited i n a marine environment; t h i c k marine d e p o s i t s u n d e r l y i n g morainal d e p o s i t s on the east coast are b e d d e d ^ s i l t s with minor c l a y and sand s u b j e c t to d i s s e c t i o n and thermokarst processes. W. Thin sandy and s i l t y marine d e p o s i t s b l a n k e t i n g o l d e r u n i t s . W: Sandy and g r a v e l l y a c t i v e beach and s p i t d e p o s i t s . GLACIAL DEPOSITS GLACIOLACUST RI NE DEPOSITS: mainly f l a t - l y i n g bedded s i l t s d e p o s i t e d i n a pro-g l a c i a l lake environment; commonly found as a veneer on o l d e r d e p o s i t s . FLUVIOGLACIAL DEPOSITS: s t r a t i f i e d sand and g r a v e l deposited by g l a c i a l melt-water streams and/or other o l d e r sand and g r a v e l d e p o s i t s reworked and redeposited by g l a c i a l meltwaters; occur as outwash p l a i n s , t e r r a c e s , and fans. ICE-CONTACT DEPOSITS: s t r a t i f i e d sand and g r a v e l and minor t i l l d e posited i n contact with melting g l a c i e r i c e ; i n c l u d e s moraine r i d g e s , eskers, and kames. MORAINAL DEPOSITS: t i l l s of varying t e x t u r e and age deposited by an i c e sheet d u r i n g i t s advance or r e t r e a t ; i n c l u d e s areas o f i c e - c o n t a c t d e p o s i t s too small to be mapped as separate u n i t s ; u s u a l l y occur as t i l l p l a i n b l a n k e t i n g ' o l d e r d e p o s i t s . BEAUFORT FORMATION: u n l i t h i f i e d g r a v e l , sand, and minor organic matter deposited i n a f l u v i a l environment; occurs as t h i c k sequences on o l d e r formations, e i t h e r as a f l a t f l u v i a l l y d i s s e c t e d p l a i n i n the northwest or as mainly low h i l l y topography elsewhere. Tb* Areas o f post d e p o s i t i o n a l f l u v i a l reworking o f Beaufort. EUREKA SOUND FORMATION: Te, C y c l i c Member: mainly u n l i t h i f i e d sands, s i l t s , c l a y s and c o a l deposited i n marine and t e r r e s t r i a l environments; g e n e r a l l y h o r i z o n t a l l y bedded; occur as a g e n t l y undulating s u r f a c e ; s u b j e c t to intense "badland" type e r o s i o n i n c e r t a i n areas. Te, "Shale" Member" mainly h o r i z o n t a l l y bedded u n l i t h i f i e d s i l t s and c l a y s of nonmarine o r i g i n ; occurs as a g e n t l y u n d u l a t i n g s u r f a c e . MESOZOIC CRETACEOUS Kk Kh Kc Ki K KANGUK FORMATION: mainly poorly l i t h i f i e d s i l t and c l a y or marine o r i g i n with an upper sand member and a ba s a l bituminous member with bentonite beds; s u r f a c e g e n e r a l l y u n d u l a t i n g with steep s l o p e s . HASSEL FORMATION: r a r e outcrops of h o r i z o n t a l l y bedded g l a u c o n i t i c sand with minor s i l t and c l a y o f nearshore o r i g i n . CHRISTOPHER FORMATION: u n l i t h i f i e d , h o r i z o n t a l l y bedded, very s t i c k y , s i l t s and c l a y s o f marine o r i g i n ; surface g e n e r a l l y u n d u l a t i n g with slopes s u b j e c t to a c t i v e l a y e r detachment f a i l u r e s . ISACHSEN FORMATION: u n l i t h i f i e d h o r i z o n t a l l y bedded quartzose sands o f f l u v i a l o r i g i n with minor s i l t and l i g n i t e ; s u r f a c e g e n e r a l l y undulating and s u b j e c t to d i s s e c t i o n . UNDIFFERENTIATED CRETACEOUS FORMATIONS: used f o r areas where i n s u f f i c i e n t data are u n a v a i l a b l e f o r s u b d i v i s i o n i n t o i n d i v i d u a l formations. PALEOZOIC DEVONIAN , n m POST-MERCY BAY MEMBER: h o r i z o n t a l l y bedded sandstone, s i l t s t o n e , and shale; 3 f r o s t s h attered and weathered i n outcrops; deeply i n c i s e d by streams. Dm, MERCY BAY MEMBER: t a b u l a r outcrops of r e s i s t a n t biohermal and bi o s t r o m a l limestone. O r g a n i c d e p o s i t s F = 2; A = 1; n o t e : numerals d e s c r i b e t h e number o f o c c u r r e n c e s o f bank forms w i t h i n each g e n e t i c u n i t TABLE V: G e n e t i c o r i g i n and s t r a t i g r a p h y o f m a t e r i a l f o r m i n g r e p r e s e n t a t i v e bank o r s l o p e m o r p h o l o g i e s Q r y j PRE-MERCY BAY MEMBER: h o r i z o n t a l l y bedded sandstone, s i l t s t o n e , and shale; I f r o s t s h attered and weathered i n outcrops; deeply i n c i s e d by streams. Note: A h o r i z o n t a l bar i s used to separate l i t h o l o g i c u n i t s which are M arranged i n s t r a t i g r a p h i c o r d e r . F or example ^ c represents morainal d e p o s i t s o v e r l y i n g C h r i s t o p h e r Formation and an ob l i q u e l i n e such as i - n W ^ M — represents a marine veneer and/or a morainal veneer o v e r l y i n g Beaufort Formation. "v" a s s o c i a t e d with u n i t s E,W,L,F, and M i n d i c a t e s that the p a r t i -c u l a r u n i t i s found as a veneer o f g e n e r a l l y l e s s than 1 metre t h i c k . Mv For example ^ represents t h i n m o r a i n a l d e p o s i t s o v e r l y i n g C h r i s t o p h e r Forma t i o n . The d e s c r i p t i o n of the s u r f i c i a l and bedrock u n i t s i s from Vincent (1978a). s u r f a c e sediments a t l o c a t i o n s w h i c h were g l a c i a l l y c o v e r e d a t some p o i n t i n t h e i r h i s t o r y and were a l s o s u b j e c t t o e i t h e r marine o r l a c u s t r i n e i n u n d a t i o n . C u m u l a t i v e g r a i n s i z e p l o t s f o r samples t a k e n from t h e a p p a r e n t l y u n d i s t u r b e d m a t e r i a l s f o r m i n g the h e a d w a l l s o f t h e s e f e a t u r e s show a c h a r a c t e r i s t i c a l l y poor degree o f s o r t i n g , as i l l u s t r a t e d on F i g u r e s 18 and 19. The shape o f t h e s e c u m u l a t i v e g r a i n s i z e p l o t s i s thought t o i n d i c a t e t h a t the r e t r o g r e s s i v e thaw f l o w s l i d e s a re formed i n the g l a c i a l l y d e r i v e d sediments ( p o s s i b l y w i t h some marine o r f l u v i a l w a s h i n g ) ; w i t h the s u b s e q u e n t l y d e p o s i t e d marine o r l a c u s t r i n e m a t e r i a l s b e i n g l i m i t e d t o a s u r f a c e v e neer. However Mackay (1963a) has i n d i c a t e d t h a t r e w o r k i n g o f m a t e r i a l by t h e r m o k a r s t p r o c e s s e s can r e s u l t i n t h e f o r m a t i o n o f t i l l - l i k e m a t e r i a l and thus the g r a i n s i z e p l o t s a r e not c o n c l u s i v e e v i d e n c e . One r e t r o g r e s s i v e thaw f l o w s l i d e n o t d i r e c t l y a s s o c i a t e d w i t h g l a c i a l sediments o c c u r r e d near the mouth o f P a r k e r R i v e r (see P l a t e 3) i n an a r e a where a t i l l v eneer o v e r l i e s - ^ f i n e t e x t u r e d sediments . mapped-by V i n c e n t (1978a) as o f l a c u s t r i n e . ' o r i g i n . T h i s l a c u s t r i n e d e p o s i t was obse r v e d t o c o n t a i n t h i n v e i n s o f s e g r e g a t e d i c e and a h i g h l y deformed d e p o s i t o f massive i c e o f unknown g e n e s i s . Good s t r a t i g r a p h i c e x posures o f t h e sediments u n d e r l y i n g r e t r o g r e s s i v e thaw f l o w s l i d e s o c c u r a l o n g t h e e a s t e r n and s o u t h e r n c o a s t w i t h i n the b o u n d a r i e s o f the Amundsen G l a c i a t i o n . H e l i c o p t e r r e c o n n a i s s a n c e and f i e l d s a m p l i n g i n d i c a t e t h a t the numerous r e t r o g r e s s i v e thaw f l o w s l i d e s i n t h i s a r e a a r e c h a r a c t e r i s t i c a l l y u n d e r l a i n by w e l l s o r t e d , medium t e x t u r e d sand, as i n d i c a t e d by t h e g r a i n s i z e d a t a shown on F i g u r e 18. V i n c e n t (19 78a) has mapped t h e s e sand t e x t u r e d m a t e r i a l s as b e i n g .001 C l a y D i a m e t e r (mm) 10.0 S i l t Sand Gran. P e b b l e s F i g u r e 18. C u m u l a t i v e g r a i n s i z e p l o t s from r e t r o g r e s s i v e thaw f l o w elite cH 4 - « c l o c a t e d w i t h i n the b o u n d a r i e s o f t h e Amundsen G l a c L t l ™ . ^ o o o f marine o r i g i n a l o n g the e a s t c o a s t and o f f l u v i a l o r i g i n i n the r e g i o n e a s t o f Sachs Harbour. However the s i m i l a r g r a i n s i z e c h a r a c t e r i s t i c s may i n d i c a t e a common g e n e s i s . S e g r e g a t e d i c e exposures o f up t o 5 meters i n h e i g h t were o b s e r v e d t o o c c u r a t or near the c o n t a c t w i t h t h e s e u n d e r l y i n g s e d i m e n t s . S u i t a b l e s t r a t i g r a p h i c e x posures a re n o t common w i t h i n o t h e r r e g i o n s o f t h e s t u d y a r e a . However h i g h i c e c o n t e n t m a t e r i a l r e s u l t i n g i n r e t r o g r e s s i v e thaw f l o w s l i d e f o r m a t i o n was obser v e d t o o c c u r i m m e d i a t e l y above the c o n t a c t w i t h t h e g r a v e l l y sandy t e x t u r e d B e a u f o r t F o r m a t i o n a t a number o f s i t e s on the n o r t h and west c o a s t s . S i m i l a r l y sandy f l u v i a l d e p o s i t s were obse r v e d t o u n d e r l i e r e t r o g r e s s i v e thaw f l o w s l i d e s a t a number o f s i t e s w i t h i n the Thomsen R i v e r d r a i n a g e . R e p r e s e n t a t i v e g r a i n s i z e d i s -t r i b u t i o n s a r e shown on F i g u r e 19. The o b s e r v a t i o n t h a t s e g r e g a t e d i c e d e p o s i t s f r e q u e n t l y o c c u r a t o r near the c o n t a c t between an o v e r l y i n g f i n e t e x t u r e d m a t e r i a l and an u n d e r l y i n g sand d e p o s i t i s s i m i l a r t o t h a t documented i n the Mackenzie D e l t a a r e a by Mackay (19 73) . T h i s l e n d s s u p p o r t t o the t h e o r y t h a t t h e s e u n d e r l y i n g permeable sediments may have a c t e d as an a q u i f e r t h rough w h i c h pore water was a b l e t o move towards a r e l a t i v e l y s t a t i o n a r y f r e e z i n g p l a n e . S i m i l a r l y , t h e o b s e r v a t i o n t h a t r e t r o g r e s s i v e thaw f l o w s l i d e s a r e f r e q u e n t l y a s s o c i a t e d w i t h g l a c i a l l y d e r i v e d sediments s u p p o r t s Rampton's (1973) h y p o t h e s i s t h a t the pr e s e n c e o f g l a c i a l m e l t water may be an i m p o r t a n t f a c t o r i n p r o v i d i n g the n e c e s s a r y pore water p r e s s u r e s r e q u i r e d f o r t h e growth o f e x t e n s i v e d e p o s i t s o f s e g r e g a t e d i c e . However i t i s i n t e r e s t i n g t o note t h a t marine (and p o s s i b l y l a c u s t r i n e ) i n u n d a t i o n may a l s o c o n t r i b u t e t o the presence o f h i g h pore water p r e s s u r e s as r e t r o g r e s s i v e thaw f l o w s l i d e s have 100 .001 1.0 10 .0 D i a m e t e r (mm) 100 90 80 70 60 50 40 30 20 10 C l a y S i l t T Sand |Gran. P e b b l e s F i g u r e 19. C u m u l a t i v e g r a i n s i z e p l o t s from r e t r o g r e s s i v e , thaw f l o w s l i d e s i t e s l o c a t e d beyond t h e b o u n d a r i e s o f t h e Amundsen G l a c i a t i o n . been o b s e r v e d t o o c c u r i n e n t i r e l y marine sediments d e p o s i t e d on the A r c t i c I s l a n d s w i t h i n the Sv e r d r u p B a s i n (see Hodgson, 1978; Hodgson and E d l u n d , 1978; and Woodward-Clyde C o n s u l t a n t s , 1980) . Repose F e a t u r e s and N i v a t i o n H o l l o w s Repose f e a t u r e s were most commonly ob s e r v e d i n f l u v i a l d e p o s i t s , b u t a l s o o c c u r r e d i n marine s e d i m e n t s , the sands and g r a v e l s o f the B e a u f o r t f o r m a t i o n and the s i l t s and c l a y s o f the Kanguk f o r m a t i o n . W e l l d e v e l o p e d n i v a t i o n h o l l o w s o c c u r r e d i n m a t e r i a l s s i m i l a r t o t h o s e o f repose f e a t u r e s , w i t h the e x c e p t i o n o f f l u v i a l s e d i m e n t s , which may be t o o c o a r s e t e x t u r e d , t o o r e c e n t l y d e p o s i t e d , o r l a c k i n g i n s u f f i c i e n t r e l i e f f o r the development o f t r a n s v e r s e or c i r c u l a r f e a t u r e s . N i v a t i o n h o l l o w s were a l s o o b s e r v e d i n the s i l t s and c l a y s o f the C h r i s t o p h e r F o r m a t i o n , the u n l i t h i f i e d sediments o f t h e Eureka Sound F o r m a t i o n and i n the weathered sediments d e r i v e d from t h e Pre-Mercy Bay Member. However as the s l o p e s w h i c h comprise a n i v a t i o n h o l l o w c o u l d g e n e r a l l y be d e s c r i b e d as a "repose f e a t u r e " , t h e d i f f e r e n c e i n o b s e r v e d g e n e s i s o f m a t e r i a l s f o r m i n g t h e s e two m o r p h o l o g i c t y p e s r e f l e c t s the c l a s s i f i c a t i o n p r o c e d u r e and s a m p l i n g program as much as any s u b s t a n t i v e d i f f e r e n c e i n g e n e t i c o r i g i n . T h e r m o - e r o s i o n a l N i c h e s T h e r m o - e r o s i o n a l n i c h e s were o b s e r v e d t o o c c u r i n the f l u v i a l o r marine sediments l o c a t e d : i n the c o a s t a l l o w l a n d a r e a i m m e d i a t e l y e a s t o f Sachs Harbour, i n the sand o f t h e B e a u f o r t F o r m a t i o n , i n t i l l and i n the u n l i t h i f i e d sands o f the I s a c h s e n F o r m a t i o n . W h i l e t h e r m o - e r o s i o n a l n i c h e s were n o t obser v e d i n f l u v i a l sediments a l o n g any o f t h e major r i v e r s , F r e n c h (1976) p u b l i s h e d a photograph o f a t h e r m o - e r o s i o n a l n i c h e i n what are l i k e l y f l u v i a l sediments a d j a c e n t t o B a l l a s t Brook r i v e r on n o r t h e r n Banks I s l a n d . E o l i a n F e a t u r e s and O r g a n i c D e p o s i t s As would be e x p e c t e d , e o l i a n f e a t u r e s o c c u r i n wind blown sand d e p o s i t s , o r i g i n a l l y o f f l u v i a l o r i g i n . S i m i l a r l y , o r g a n i c d e p o s i t s were o n l y o b s e r v e d i n a s s o c i a t i o n w i t h f l u v i a l sediments o f b o t h contemporary and Q u a t e r n a r y age. 3.2.2 T e x t u r e The range i n t e x t u r a l c o m p o s i t i o n a s s o c i a t e d w i t h each o f 8 m o r p h o l o g i c c l a s s e s i s shown on F i g u r e 20. These t r i a x i a l p l o t s i n d i c a t e the r e l a t i v e p e r c e n t a g e o f g r a v e l (2 t o l e s s than. 8 mm), sand (0 .063 t o l e s s t h a n 2 mm), and f i n e s ( l e s s t h a n 0 .063 mm) . Samples w h i c h a r e thought t o r e f l e c t the dominant c h a r a c t e r o f a s i t e a re i n d i c a t e d by s q u a r e s , w h i l e those from l e s s i m p o r t a n t s t r a t a have been i n c l u d e d t o i n d i c a t e the o b s e r v e d range i n g r a i n s i z e and are shown as s m a l l c i r c l e s . (A s i m i l a r a n a l y s i s was conducted u s i n g d a t a which i n c l u d e d the g r e a t e r than 8 mm s i z e f r a c t i o n and e s s e n t i a l l y t h e same r e s u l t s were o b t a i n e d . ) I t can be seen t h a t s l o p e s w h i c h are u n d e r g o i n g s o l i f l u c 1 -t i o n movement o r are s u b j e c t t o e i t h e r s k i n f l o w s o r r e t r o g r e s s i v e thaw f l o w s l i d e s c o n t a i n c o m p a r a t i v e l y h i g h e r p e r c e n t a g e s o f f i n e t e x t u r e d m a t e r i a l s . S k i n f l o w s i n p a r t i c u l a r o c c u r i n sediments c o n t a i n i n g h i g h p r o p o r t i o n s o f s i l t s and c l a y s . Banks o r s l o p e s s u b j e c t t o t h e r m o - e r o s i o n a l n i c h i n g were ob s e r v e d t o c o n t a i n l e s s t h a n 15 p e r c e n t g r a v e l and may be composed a l m o s t e n t i r e l y o f e i t h e r f i n e s o r sands. However the sample s i z e i s r e l a t i v e l y s m a l l and may n o t be e n t i r e l y r e p r e s e n -t a t i v e , as the p r e v i o u s l y mentioned t h e r m o - e r o s i o n a l n i c h e on B a l l a s t Brook R i v e r shown i n F r e n c h (1976) appears t o c o n t a i n g r e a t e r than 15% g r a v e l s . A n gle o f repose banks and n i v a t i o n h o l l o w s can b o t h be seen t o o c c u r o v e r a wide range o f t e x t u r a l c o m p o s i t i o n , w i t h n i v a t i o n h o l l o w s b e i n g somewhat l e s s f r e q u e n t l y o b s e r v e d i n m a t e r i a l s c o n t a i n i n g a. high, p e r c e n t a g e o f 2 t o l e s s t h a n 8 mm s i z e d m a t e r i a l . 100% <0.063 mm 100% <0.063 mm 100% <0.063 mm 100% <0.063 mm R e t r o g r e s s i v e Thaw Flow S l i d e s 100% 2-<8 mm 100% <0 .063 mm 100% <0 .063 mm 100% <0.06 3 mm 100% 100% 0.063-<2 mm <0.063 mm Ang l e o f Repose F e a t u r e s 10 Of 2-<8 mm Note: 100% 0.063-<2 mm F i g u r e 2 0 a samples r e p r e s e n t i n g the dominant t e x t u r a l c o m p o s i t i o n • samples from l e s s s i g n i f i c a n t d e p o s i t s i n d i c a t i n g the range i n t e x t u r a l c o m p o s i t i o n R e l a t i v e p e r c e n t a g e s o f g r a v e l , sand and f i n e s a s s o c i a t e d w i t h banks o r s l o p e s o f v a r y i n g morphology. As would be e x p e c t e d , s i t e s e x h i b i t i n g w e l l d e v e l o p e d e o l i a n f e a t u r e s a r e composed p r i m a r i l y o f sands, w i t h some minor i n c l u s i o n s o f g r a v e l , g e n e r a l l y as a l a g d e p o s i t . Banks c o n t a i n i n g a h i g h p e r c e n t a g e o f o r g a n i c m a t t e r were found t o c o n t a i n l i t t l e o r no g r a v e l , w i t h the dominant samples c o n t a i n i n g a r e l a t i v e l y h i g h p e r c e n t a g e o f f i n e s . Hydrometer a n a l y s i s t o determine t h e r e l a t i v e p e r c e n t a g e o f sand, s i l t and c l a y was u n d e r t a k e n f o r a number o f dominant , samples from s i t e s u n d e r g o i n g s o l i f l u c t i o n movement o r s u b j e c t t o e i t h e r s k i n f l o w s o r r e t r o g r e s s i v e thaw f l o w s l i d e s . The r e s u l t s are shown on F i g u r e 21 and i n d i c a t e t h a t t h e c o l l u v i a l m a t e r i a l s f o r m i n g s k i n f l o w s f r e q u e n t l y c o n t a i n a h i g h e r p e r c e n t a g e o f s i l t and c l a y than the m a t e r i a l s f o r m i n g e i t h e r r e t r o g r e s s i v e thaw f l o w s l i d e s o r s o l i f l u c t i o n s l o p e s . However the t e x t u r e o f f o u r samples from s k i n f l o w s i t e s i s s i m i l a r t o t h a t o f the m a t e r i a l commonly f o r m i n g s o l i f l u c t i o n s l o p e s o r r e t r o g r e s s i v e thaw f l o w s l i d e s , and t h u s g r a i n s i z e a l o n e appears i n s u f f i c i e n t t o ^ d i s -c r i m i n a t e between t h e s e f e a t u r e s . 76 Clay <0.004 mm R e t r o g r e s s i v e Thaw Flow S l i d e s Sand 0.063 — 2 mm S o l i f l u c t i o n Slopes Sand 0.063 — 2 mm A T i l l - Amundsen G l a c i a t i o n • " T i l l " - Thomsen G l a c i a t i o n • " T i l l " V i s c o u n t M e l v i l l e G l a c i a t i o n • " T i l l " - Banks G l a c i a t i o n ° l a c u s t r i n e i n d i c a t e s samples are from the same l o c a t i o n Slit 0.004-<0.063 mm c o l l u v i a t e d " T i l l " Amundsen G l a c i a t i o n c o l l u v i a t e d " T i l l " Thomsen G l a c i a t i o n c o l l u v i a t e d " T i l l " Banks G l a c i a t i o n Sand 0.063 — 2 mm Silt 0.004-<0 063 mm c o l l u v i u m d e r i v e d from: ° C h r i s t o p h e r Formation • Eureka Sound Formation O T i l l o v e r l y i n g , the p r e -Mercy Bay Member O t i l l and marine d e p o s i t s o v e r l y i n g Isachsen Formation Slit 0.004- <0.063 mm F i g u r e 21. R e l a t i v e percentages of sand, s i l t and c l a y i n m a t e r i a l s forming s o l i f l u c t i o n s i o p e s , s k i n flows and r e t r o g r e s s i v e thaw flow s l i d e s . 3.2.3 I c e Co n t e n t Mackay (1971a) f o l l o w i n g the work o f E v e r e t t (1961) and W i l l i a m s (1967), has shown t h a t the p o t e n t i a l f o r s e g r e g a t e d i c e growth i s r e l a t e d t o t h e overbu r d e n w e i g h t , the pore; water p r e s s u r e a t t h e p e n e t r a t i n g f r o s t l i n e , the i n t e r f a c i a l i c e - w a t e r t e n s i o n and the r a d i u s o f t h e l a r g e s t c o n t i n u o u s pore openings o r c h a n n e l s . Both pore water p r e s s u r e (as a f u n c t i o n o f p e r m e a b i l i t y ) and pore r a d i u s can be e x p e c t e d t o v a r y w i t h g r a i n s i z e and thus t e x t u r e a l o n e forms the b a s i s f o r many r u l e s - o f - t h u m b i n d i c e s o f f r o s t s u s c e p t i b i l i t y (see Casagrande, 1932; T e r z a g h i , 1952; and K a p l a r , 1971) . C o a r s e ' t e x t u r e d m a t e r i a l s have such l a r g e pore spaces t h a t the p o t e n t i a l f o r s e g r e g a t e d i c e growth i s reduc e d , w h i l e v e r y f i n e t e x t u r e d samples have a s u f f i c i e n t l y low permea-b i l i t y t h a t pore;water p r e s s u r e and w a t e r movement i s r e s t r i c t e d . M a t e r i a l s o f a * L i n t e r m e d i a t e t e x t u r e , h a v i n g a c o m b i n a t i o n o f r e l a t i v e l y s m a l l pore s i z e and h i g h p e r m e a b i l i t y , . , a r e tho u g h t t o p r o v i d e the optimum c o n d i t i o n s f o r the growth o f s e g r e g a t e d i c e . I n t h i s c i r c u m s t a n c e , t h e c o n t r o l l i n g f a c t o r s a r e then reduced t o the overburden w e i g h t , the r a t e o f f r e e z i n g and t h e a v a i l a b i l i t y o f w a t e r . T h i s g e n e r a l r e l a t i o n s h i p between the p o t e n t i a l f o r s e g r e g a t e d i c e growth and t e x t u r e i s i l l u s t r a t e d i n F i g u r e 22. The o b s e r v e d r e l a t i o n s h i p between i c e c o n t e n t and m a t e r i a l t e x t u r e f o r 187 samples c o l l e c t e d i n t h e c o u r s e o f t h i s s t u d y i s shown on F i g u r e 23. These t r i a x i a l graphs show the average i c e c o n t e n t , t h e s t a n d a r d d e v i a t i o n about the average , the c o e f f i c i e n t o f v a r i a t i o n , and the number o f samples f o r 2 0 p e r c e n t ranges i n p e r c e n t g r a v e l ( g r e a t e r t h a n 2::.mm) > sand (0.063 t o 2 mm) and f i n e s ( l e s s t h a n 0.063 mm). Both the average i c e c o n t e n t and the s t a n d a r d d e v i a t i o n about the average can be seen t o i n c r e a s e as the 78 u 3 cn cn l) u cu fj> c • H > Coarse g r a i n e d Medium F i n e g r a i n e d S o i l Texture F i g u r e 22. T h e o r e t i c a l p o t e n t i a l f o r the growth of se g r e g a t e d i c e as a f u n c t i o n o f g r a i n s i z e ( a f t e r Penner,1968) 100% S i l t and clay « 0 .063 mm) 100% Gravel 100% Sand ( >2 mm) (0 .063-<2 mm) Figure 23. Observed ice content versus the percentage -of gravel, sand and fines p e r c e n t a g e o f f i n e s i n c r e a s e s t o a p p r o x i m a t e l y 80 p e r c e n t . Above t h i s p o i n t a s l i g h t r e d u c t i o n i n t h e average i c e c o n t e n t o c c u r s . However the s t a n d a r d d e v i a t i o n and c o e f f i c i e n t o f v a r i a t i o n c o n t i n u e s t o i n c r e a s e , r e f l e c t i n g a number o f v e r y h i g h i c e c o n t e n t samples. When the i c e c o n t e n t i s compared t o the p e r c e n t a g e o f sand (0.063 t o l e s s than 2 mm), s i l t (0.004 t o l e s s than 0.063 mm) and c l a y ( l e s s t h a n 0.004 mm), shown on F i g u r e 24, a s i m i l a r t r e n d appears i n whi c h t h e mean i c e c o n t e n t , the s t a n d a r d d e v i a t i o n and the c o e f f i c i e n t o f v a r i a t i o n g e n e r a l l y i n c r e a s e w i t h d e c r e a s i n g p e r c e n t a g e s o f sand. The maximum i c e c o n t e n t and g r e a t e s t c o e f f i c i e n t o f v a r i a t i o n o c c u r s i n samples c o n t a i n i n g a p p r o x i m a t e l y a f i f t y p e r c e n t m i x t u r e o f s i l t and c l a y . However the number o f samples i s i n s u f f i c i e n t t o i n d i c a t e c o n c l u s i v e l y whether t h i s r a t i o p r o v i d e s t h e optimum b a l a n c e between pore s i z e and permea-b i l i t y o r o n l y r e f l e c t s l o c a l c o n d i t i o n s a s s o c i a t e d w i t h m a t e r i a l of t h i s t e x t u r a l c o m p o s i t i o n . F u r t h e r i l l u s t r a t i o n o f the r e l a t i o n s h i p between i c e c o n -t e n t and g r a i n s i z e i s shown by t h e p l o t s o f average i c e c o n t e n t v e r s u s i n c r e a s i n g p e r c e n t a g e s o f g r a v e l , sand, f i n e s , s i l t and c l a y shown on F i g u r e s 25 and 26. The obs e r v e d range i n s t a n d a r d d e v i a t i o n a g a i n i n c r e a s e s w i t h i c e c o n t e n t and p r o v i d e s an i n d i c a t o r o f t h e p o t e n t i a l f o r s e g r e g a t e d i c e growth. Maximum i c e c o n t e n t s and g r e a t e s t c o e f f i c i e n t s o f v a r i a t i o n c a n a g a i n be seen t o o c c u r i n samples c o n t a i n i n g 0 t o 10% sand, 40 t o 50% c l a y and 50 t o 60% s i l t . The p r e c e d i n g a n a l y s i s i n d i c a t e s t h a t i n o r d e r t o p r o v i d e a m e a n i n g f u l c o m p a r i s o n o f t h e r e l a t i v e o c c u r r e n c e o f s e g r e g a t e d i c e i n banks o f d i f f e r e n t m o r p h o l o g i e s , i t i s n e c e s s a r y t o 100% Clay K0.004 mm) 100% Sand 100% S i l t (0 .063-<2 mm) (0 .004-<0 .063 mm) Figure 24. Observed ice content versus the percentage of sand, s i l t and clay . -p - f l cn •H (D -p A CU -p H 0 O ^ 0 Q) O +J H fl cu 0 u CU Cu 4-) x: Cn -H <U -P fl <U >i -P M fl 0 0 <W 0 0) u 4J M fl CU o U CU Cu -P . f l Cn -H CU -p 3 fl CU >i -p S-l C T 3 0 O 0 (1) o -P M C (U o CU Q 4 100 90 8 0 70 60 50 40 30 - • 2 0 10 0 0 10 20 30 40 50 60 70 80 90 10( Percentage of fines (< 0 .063 mm) 10 20 30 40 50 60 70 80 90 100" Percentage of sands (0 .063-<2 mm) -.2 .0 1.8 1.6 1.4 1.2 1.0 -|0 .8 0.6 0.4 0 .2 o fl •P o fl -H 0) -P •H rd O -H •H S-l m rd M-4 > (U o u 10 20 30 40 50 60 70 80 90 10 Percentage of gravel (>2 mm) Note: Ice content has been overaged for samples grouped on the basis of 10% ranges i n t e x t u r a l composition, except i n the gravel p l o t where two 5% increments have been included. Figure 25 . Observed i c e content versus i n d i v i d u a l percentages of gravel, sand and f i n e s . 82 ® mean standard deviation about mean coefficient of variation -\2 .0 1.8 4-1 1 . 6 ° 1.4 c - P o G -H 1 2 ® 1 0 ° -H 0.8 £ * 0.6 g 0.4 U 0.2 0 10 20 30 40 50 60 70 80 90 100 P e r c e n t a g e o f c l a y «0.004 mm) Note; F i g u r e 26. 12 .0 1 1 1 1 1 8 4-1 o , o ,4 ,2 ,0 70 80 90 10 P e r c e n t a g e o f s i l t (0.004 -<0 . 063 mm) 0.8 0.6 0 .4 0.2 8 c • P o QJ +J •H rd U -H •H ! - l 4-1 rs 4-1 > CD O CJ - t h e r e a r e o n l y 2 samples i n t h e 10-20% s i l t c l a s s . One c o n t a i n s 52% c l a y and has an i c e c o n t e n t o f 71.4%. The o t h e r sample has 0% c l a y and an i c e c o n t e n t o f 4.7%. - t e x t u r e i s e x p r e s s e d as a p e r c e n t a g e o f t h e o r i g i n a l sample l e s s t h a n 2 mm i n d i a m e t e r . - i c e c o n t e n t has been a v e r a g e d f o r samples grouped on t h e b a s i s o f 10% ranges i n t e x t u r a l c o m p o s i t i o n . Observed i c e c o n t e n t v e r s u s i n d i v i d u a l p e r c e n t a g e s o f s i l t and c l a y . 84 compare s i t e s w i t h s i m i l a r t e x t u r e s . However, due t o the l i m i t e d number o f s i t e s sampled, d a t a comparison has had t o be made on the b a s i s o f r e l a t i v e l y l a r g e ranges i n t e x t u r e . T a b l e VI p r o v i d e s a summary o f i c e c o n t e n t i n banks o r s l o p e s o f d i f f e r e n t m o r p h o l o g i c c l a s s e s . T e x t u r a l c o m p o s i t i o n has been grouped on the b a s i s o f f i f t y p e r c e n t ranges i n g r a v e l , sand and f i n e c o n t e n t . The r e s u l t s o f t h i s c o m p i l a t i o n i n d i c a t e s u b s t a n t i a l d i f f e r e n c e s i n i c e c o n t e n t between some c l a s s e s . Repose banks, tho s e s u b j e c t t o e o l i a n p r o c e s s e s and n i v a t i o n h o l l o w s a l l have s i m i l a r l y low i c e c o n t e n t s . The s l i g h t l y h i g h e r v a l u e s g e n e r a l l y a s s o c i a t e d w i t h n i v a t i o n h o l l o w s l i k e l y r e f l e c t t h e i n c o r p o r a t i o n and r e f r e e z i n g o f s u r f a c e w a t e r , r a t h e r than an i n c r e a s e i n s e g r e g a t e d i c e c o n t e n t a t d e p t h . S o l i f l u c t i o n s l o p e s and t h e r m o - e r o s i o n a l n i c h e s have somewhat l a r g e r i c e c o n t e n t s , w i t h s l o p e s s u b j e c t t o s k i n f l o w s h a v i n g s t i l l h i g h e r v a l u e s . I t i s i n t e r e s t i n g t o note t h a t the average water c o n t e n t measured d u r i n g t h e h e i g h t o f the s p r i n g thaw was h i g h e r w i t h i n the thawed p o r t i o n o f the a c t i v e l a y e r t h a n w i t h i n t h e u n d e r l y i n g f r o z e n m a t e r i a l . T h i s t o p i c w i l l be d i s c u s s e d f u r t h e r i n S e c t i o n 3.3.1. The i c e c o n t e n t w i t h i n o r g a n i c r i c h d e p o s i t s was ob s e r v e d t o be h i g h , i n the range o f 100 p e r c e n t o f t h e sample d r y w e i g h t . However these f i g u r e s a r e s u b j e c t t o some u n c e r t a i n t y due t o the e f f e c t o f d e h y d r a t i o n on the o r g a n i c c o n t e n t d u r i n g the d r y i n g p r o c e s s . S i t e s r e p r e s e n t a t i v e o f r e t r o g r e s s i v e thaw f l o w s l i d e s were o b s e r v e d t o have the h i g h e s t i c e c o n t e n t s , w i t h r e c o r d e d v a l u e s r a n g i n g up t o 104 p e r c e n t o f t h e sample d r y w e i g h t . However i c e c o n t e n t s a s s o c i a t e d w i t h samples o f massive i c e 85 " ICE CONTENT" "Low" MORPHOLOGY Repose banks TEXTURE g r a v e l ( > 2 nun) sand (0.063-<2 nun) <50% s i + c , s, g s i l t and c l a y (<0.063 mm) sand (0 .06 3-<2 mm) g r a v e l ( >/ 2 mm) sand (0.063-<2 mm) <50% s i + c , s, g s i l t and c l a y (< 0 .063 mm) "Moderate" S o l i f l u c t i o n s l o p e s <50% s i + c , s, g, s i l t and c l a y (< 0 .063 mm) E o l i a n f e a t u r e s N i v a t i o n h o l l o w s T h e r m o - e r o s i o n a l n i c h e s S k i n f l o w s f r o z e n m a t e r i a l f r o z e n m a t e r i a l a c t i v e l a y e r sand (0.063-<2mm) <50% s i + c , s, g s i l t and c l a y «0.063 mm) sand (0.063-<2mm) s i l t and c l a y «0.063 mm) s i l t and c l a y (<0.063 mm) O r g a n i c d e p o s i t s s i l t and c l a y «0.063 mm) "High" R e t r o g r e s s i v e thaw f l o w s l i d e s <50% s i + c , s, g s i l t and c l a y (<0.063 mm) ICE CONTENT AS A PERCENTAGE OF DRY WEIGHT # o f samples maximum average minimum s t a n d a r d d e v i a t i o n c o e f f i c i e n t o f v a r i a t i o n 6 17 1 7.8 19.7 • • • 5.4 12.3 44.7 3.7 3.6 • • • 1.5 5.6 • • • 0 .28 0.46 5 38.3 30.6 23.3 7.0 0.23 4 21.6 8.1 5.4 2.8 0 .34 1 • • • 5.9 • • • • • • 11 3 12 38.8 14.7 49 .3 19 .5 9.5 34 .2 9.9 4.7 13.4 8.6 5.0 10.4 0.44 0.53 0.30 1 • • • 10 .0 • • • • • • 4 57.3 36.8 16.8 18.1 0.49 3 1 28.1 • • • 23.8 47.4 17.4 • • • 5.7 • • • 0.24 2 37.7 35.0 32 .2 3.9 0.11 1 • • • 31.6 • • • 8 5 123.4 89 .2 46.8 54.5 24.3 40.8 32.4 19.7 0.69 0.36 2 147.3 117 .5 87.6 42 .2 0.36 3 13 46.9 104.0 40.1 53 .5 32 .3 19.4 7.4 25.5 0.18 0.48 f l o w s l i d e s do n o t i n c l u d e v a l u e s from samples o f massive i c e TABLE V I : I c e c o n t e n t s i n banks o r sloDes nf r i i f f p ^ f u -. f i n e s . S l ° P e S ° f d l f f e r e n t morphology, based on 50 p e r c e n t ranges i n p e r c e n t g r a v e l , sand and 86 from e i t h e r i c e l e n s e s o r i c e wedges (which f r e q u e n t l y o c c u r a t t h e s e s i t e s ) a r e not i n c l u d e d i n T a b l e VI and t h e r e f o r e t h e l i s t e d f i g u r e s s i g n i f i c a n t l y u n d e r e s t i m a t e the average i c e c o n t e n t f o r t h i s m o r p h o l o g i c c l a s s . Thus w i t h i n the l i m i t a t i o n s o f the d a t a , e o l i a n f e a t u r e s , a n g l e o f r epose banks and n i v a t i o n h o l l o w s appear t o have g e n e r a l l y low i c e c o n t e n t s . S o l i f l u c t i o n s l o p e s , s k i n f l o w s and t h e r m o - e r o s i o n a l n i c h e s have somewhat h i g h e r v a l u e s , and s i t e s s u b j e c t t o r e t r o g r e s s i v e thaw f l o w s l i d e s have the h i g h e s t average i c e c o n t e n t s , d e s p i t e the e x c l u s i o n o f samples o f massive i c e . I c e D i s t r i b u t i o n The p r e s e n c e and r e l a t i v e abundance o f v a r i o u s t y p e s o f ground i c e o c c u r r i n g w i t h i n the d i f f e r e n t m o r p h o l o g i c c l a s s e s i s summarized i n T a b l e V I I . E o l i a n f e a t u r e s , repose banks and n i v a t i o n h o l l o w s c o n t a i n e d v a r y i n g amounts o f pore i c e . S e g r e g a t e d i c e d e p o s i t s i n t h e form o f f r e e z e - b a c k - i c e , r e t i c u l a t e d i c e o r o c c a s i o n a l t h i n d e p o s i t s o f l e n s i c e were i n f r e q u e n t l y o b s e r v e d i n the near s u r f a c e m a t e r i a l s a t repose and n i v a t i o n s i t e s . S o l i f l u c t i o n s l o p e s and s k i n f l o w s i t e s commonly c o n t a i n e d f r e e z e - b a c k i c e d e p o s i t s and e x t e n s i v e o c c u r r e n c e s o f pore i c e . Lenses o f s e g r e g a t e d i c e were commonly o b s e r v e d i n t h e n e a r s u r f a c e m a t e r i a l s , w i t h t h e m a j o r i t y o f d e p o s i t s b e i n g l e s s than 1 cm i n t h i c k n e s s . The u n d i s t u r b e d s u r f a c e m a t e r i a l a d j a c e n t t o a n o t a b l y wide s k i n f l o w s i t e , formed i n c o l l u v i u m o v e r l y i n g and p a r t i a l l y d e r i v e d from t h e E ureka Sound F o r m a t i o n , was o b s e r v e d t o c o n t a i n an a p p r o x i m a t e l y 10 cm t h i c k d e p o s i t o f f r e e z e - b a c k Observed i c e o c c u r r e n c e Morphology Freeze-back i c e Pore i c e R e t i c u l a t e d i c e Wedge i c e T h i n l e n s o f se g r e g a t e d s?<s->>,r.'7-~ice:A;. T h i c k l e n s o f s e g r e g a t e d i c e E o l i a n f e a t u r e s o c c a s i o n a l common absent a b s e n t absent a b s e n t Repose banks o c c a s i o n a l common o c c a s i o n a l common o c c a s i o n a l a b s e n t N i v a t i o n h o l l o w s o c c a s i o n a l common o c c a s i o n a l _ y.common o c c a s i o n a l a b s e n t S o l i f l u c t i o n s l o p e s common common absent ( o c c a s i o n a l ? ) common ( o c c a s i o n a l ? ) S k i n f l o w s common common absent ( o c c a s i o n a l ? ) common o c c a s i o n a l T h e r m o - e r o s i o n a l n i c h e s o c c a s i o n a l common abs e n t common o c c a s i o n a l o c c a s i o n a l O r g a n i c d e p o s i t s o c c a s i o n a l common absent common common abs e n t R e t r o g r e s s i v e thaw f l o w s l i d e s o c c a s i o n a l common absent noeommon common common Note: - l e n s e s o f seg r e g a t e d i c e l e s s than 1 cm i n t h i c k n e s s have been d e f i n e d as b e i n g " t h i n " . -the "absent", " o c c a s i o n a l " and "common" c l a s s i f i c a t i o n i s o n l y i n t e n d e d t o i n d i c a t e the r e l a t i v e f r e q u e n c y o f occurrence and...has no q u a n t i t a t i v e s i g n i f i c a n c e . -the presence and abundance o f s e g r e g a t e d i c e appears t o be the main d i s c r i m i n a t o r o f ; t o t a l i c e content, over the m o r p h o l o g i c t y p e s . TABLE V I I : Types o f ground i c e observed i n banks and s l o p e s o f d i f f e r e n t morphology. 00 88 i c e . T h i s m a t e r i a l had a w a t e r c o n t e n t o f 485 p e r c e n t o f the sample d r y w e i g h t , and i s o b v i o u s l y o f s u r f a c e o r i g i n . I n a r e a s where t h e r m a l e r o s i o n o r t h e r m o k a r s t p r o v i d e d v e r t i c a l e x p osures o f t h e sediments u n d e r l y i n g s o l i f l u c t i o n s l o p e s and s k i n f l o w s i t e s , t h e c o n c e n t r a t i o n o f l e n s i c e was g e n e r a l l y o b s e r v e d t o d e c r e a s e w i t h d e p t h . S i m i l a r l y , s k i n f l o w s o c c u r r i n g i n the C h r i s t o p h e r F o r m a t i o n f r e q u e n t l y removed t h e s u r f a c e c o l l u v i u m down to the s i l t s and c l a y s o f the unweathered p a r e n t m a t e r i a l . These u n d e r l y i n g d e p o s i t s had few o r no i n c l u s i o n s o f s e g r e g a t e d i c e and l i k e l y i n d i c a t e t h a t the i c e d e p o s i t s o b s e r v e d i n t h e o v e r l y i n g c o l l u v i u m a r e a r e s u l t o f w a t e r d e r i v e d from a s u r f a c e o r i g i n . I c e wedges were g e n e r a l l y n o t o b s e r v e d on s o l i -f l u c t i o n s l o p e s o r s k i n f l o w s i t e s . However downslope movement o f c o l l u v i u m as a r e s u l t o f s o l i f l u c t i o n p r o c e s s e s makes the i d e n t i f i c a t i o n o f such d e p o s i t s / ' d i f f i c u l t w i t h o u t s u b s u r f a c e e x p o s u r e s . Pore i c e was t h e most e x t e n s i v e form o f ground i c e o b s e r v e d a t s i t e s s u b j e c t t o t h e r m o - e r o s i o n a l n i c h i n g . I c e wedges were commonly found a l o n g r e c e n t e x p o s u r e s , w i t h t h e presence o f s e g r e g a t e d i c e b e i n g l i m i t e d t o f r e e z e - b a c k d e p o s i t s and o c c a s i o n a l t h i n i c e l e n s e s , g e n e r a l l y .as i n c l u s i o n s w i t h i n minor beds o f f i n e t e x t u r e d s e d i m e n t s . O r g a n i c f e a t u r e s were f r e q u e n t l y a s s o c i a t e d w i t h pore i c e d e p o s i t s and t h i n s e g r e g a t e d i c e l e n s e s . I ce wedges were a l s o commonly exposed a t t h e s e s i t e s . R e t r o g r e s s i v e thaw f l o w s l i d e s were o b s e r v e d t o o c c u r as a r e s u l t o f i n c l u s i o n s o f p o r e , wedge and s e g r e g a t e d i c e . S i t e s l o c a t e d w i t h i n t h e b o u n d a r i e s o f t h e Amundsen and Thomsen G l a c i a t i o n s were f r e q u e n t l y o b s e r v e d t o c o n t a i n i c e l e n s e s ; o f 1 t o over 3 meters i n t h i c k n e s s . I n c o n t r a s t , r e t r o g r e s s i v e thaw f l o w s l i d e s l o c a t e d w i t h i n the b o u n d a r i e s o f the V i s c o u n t M e l v i l l e and Banks G l a c i a t i o n s were g e n e r a l l y composed o f t h i n n e r e xposures o f r e l a t i v e l y lower i c e c o n t e n t m a t e r i a l s / f r e q u e n t l y b e i n g l i m i -t e d t o t h i n - l e n s e s o f s e g r e g a t e d i c e and pore i c e . Wedge i c e c o n t r i b u t e d t o the f o r m a t i o n o f t h e r m o k a r s t f e a t u r e s t h r o u g h o u t the s t u d y a r e a , b u t was most f r e q u e n t l y o b s e r v e d w i t h i n the b o u n d a r i e s o f t h e Amundsen G l a c i a t i o n , and appears t o be l e a s t common w i t h i n the b o u n d a r i e s o f the Banks and V i s c o u n t M e l v i l l e G l a c i a t i o n s . 3.2.4 Exposure t o P r o c e s s e s o f Sediment Removal The exposure r a t i n g s f o r each o f t h e d i f f e r e n t m o r p h o l o g i u n i t s a re summarized i n Table V I I I . S o l i f l u c t i o n s l o p e s can be seen t o o c c u r i n environments w i t h a low t o medium e x p o s u r e , r e f l e c t i n g t h e i r c h a r a c t e r i s t i c a l l y low a n g l e s l o p e s , which a r e f r e q u e n t l y p r o g r a d i n g . A l l s k i n f l o w s i t e s were g i v e n a medium exposure r a t i n g i n d i c a t i n g t h a t t h e s e f e a t u r e s were s i t u a t e d on s l o p e s s t e e p e r than some o f tho s e on wh i c h o n l y s o l i f l u c t i o n was o c c u r r i n g . R e t r o g r e s s i v e thaw f l o w s l i d e s p r e f e r e n t i a l l y o c c u r i n medium o r h i g h exposure environments i n wh i c h t h e r e i s s u f f i c i e n t r e l a t i v e r e l i e f t h a t the thawed sediment can be removed from the exposed h e a d w a l l . W i t h i n low exposure s e t t i n g s , h i g h i c e c o n t e n t m a t e r i a l i s g e n e r a l l y c o v e r e d b y . c o l l u v i u m o r f l u v i a l sediments and t h u s i n s u l a t e d . I n s i t u a t i o n s where t h i s o v e r l y i n g m a t e r i a l i s d i s t u r b e d ( f o r example by e r o s i o n a l o n g an i c e wedge), thermo-k a r s t can cause t h e i n i t i a t i o n o f r e t r o g r e s s i v e thaw f l o w s l i d e s ; p a r t i c u l a r l y i n c a s e s where the volume l o s s due t o t h e m e l t i n g o f i c e i s s u f f i c i e n t t o m a i n t a i n t h e f l o w o f sediment from t h e h e a d w a l l . However, as l o n g as t h i s sediment i s n o t removed from t h e s i t e , t h e s e r e t r o g r e s s i v e thaw f l o w s l i d e s r e m a i n compara-t i v e l y p o o r l y d e v e l o p e d and t h e s h a l l o w "thaw l a k e s " w h i c h a r e f r e q u e n t l y produced w i l l e v e n t u a l l y r e s t a b i l i z e , as d i s c u s s e d by B i r d (1967) . Repose f e a t u r e s o c c u r i n each o f the t h r e e exposure c l a s s e s w i t h a n g l e o f repose banks b e i n g found i n the more exposed e n v i r o n m e n t s . N i v a t i o n h o l l o w s o c c u r i n o n l y medium and h i g h exposure e n v i r o n m e n t s , as a d i s t i n c t break i n s l o p e appears t o be needed t o i n i t i a t e t h e p r e f e r e n t i a l a c c u m u l a t i o n o f snow. Morphology #,of- . s i t e s s r . # i n each of s i t e s exposure c l a s s o "o i n each o f s i t e s exposure c l a s s Low Medium High Low Medium High S o l i f l u c t i o n s l o p e s 6 4- 4 2 0 67 33 0 S k i n f l o w s 11 0 11 0 0 100 0 R e t r o g r e s s i v e f l o w s 18 0 9 9 0 50 .50 Repose f e a t u r e s 41 4 20 17 19 49 41 N i v a t i o n h o l l o w s 14 0 10 4 0 71 29 T h e r m o - e r o s i o n a l niches. 5 0 0 5 0 0 100 E o l i a n f e a t u r e s 6 0 6 0 0 100 0 O r g a n i c d e p o s i t s 3 0 2 1 0 67 33 Note: exposure c l a s s e s are d e f i n e d on T a b l e I V . TABLE V I I I : Summary o f exposure r a t i n g s f o r f i e l d s i t e s o f d i f f e r e n t morphology. 92 As would be expected, a l l of the thermo-erosional niches occurred i n areas of active erosion, such as on the outside of r i v e r bends or along exposed sections of the southern coast, which are subject to high winds and wave action. Eolian features were located on banks of medium exposure in situations with enough of a break i n slope for d e f l a t i o n to occur, but having a suf-f i c i e n t l y slow rate of recession that this c h a r a c t e r i s t i c bank form could develop. Only three s i t e s t y p i c a l of organic accumulation were v i s i t e d and the observed medium and high exposure ratings l i k e l y r e f l e c t more on the choice of f i e l d s i t e s that any under-l y i n g causative mechanism. 93 3.2.5 Summary The p r e c e d i n g d i s c u s s i o n i n d i c a t e s t h a t the morphology o f a bank o r s l o p e i s t o a v a r y i n g degree dependent upon i t s t e x t u r e , i c e c o n t e n t and exposure o r e n v i r o n m e n t a l s e t t i n g . M a t e r i a l g e n e s i s i s i m p o r t a n t as i t a f f e c t s i c e c o n t e n t ( t h r o u g h t h e a v a i l a b i l i t y o f water a t t h e t i m e o f f r e e z i n g ) , g r a i n s i z e (as some g e n e t i c m a t e r i a l s would be e x p e c t e d t o c o n t a i n a l a r g e r p e r c e n t a g e o f f i n e s ) and exposure (as m a t e r i a l s o f d i f f e r e n t o r i g i n can be e x p e c t e d t o o c c u r i n d i f f e r e n t t e r r a i n l o c a t i o n s ) . When the i n t e r a c t i o n s amongst i c e c o n t e n t , g r a i n s i z e and exposure a r e c o n s i d e r e d , a number o f o b v i o u s g e n e r a l t r e n d s become a p p a r e n t . V a r i a t i o n s i n g r a i n s i z e a f f e c t i c e c o n t e n t as f i n e t e x t u r e d m a t e r i a l s have a h i g h e r p o t e n t i a l f o r s e g r e g a t e d i c e growth, which i n t u r n i n c r e a s e s the p o t e n t i a l f o r t h e development o f t h e r m o k a r s t f e a t u r e s . The e f f e c t o f sediment removal i s i m p o r t a n t as i n low exposure environments a l l c o m b i n a t i o n s o f i c e c o n t e n t and g r a i n s i z e t e n d t o r e s u l t i n the f o r m a t i o n o f r e l a -t i v e l y s i m i l a r , low a n g l e s l o p e s o r s o l i f l u c t i o n f e a t u r e s . I t i s o n l y i n environments w i t h medium o r h i g h exposures t h a t the p o t e n t i a l l y d i s t i n c t i v e b e h a v i o u r o f the exposed m a t e r i a l i s f u l l y d i s p l a y e d . An i d e a l i z e d summary d f t h e bank o r s l o p e morphology which o c c u r s w i t h v a r y i n g c o m b i n a t i o n s o f i c e c o n t e n t , g r a i n s i z e and exposure i s p r e s e n t e d i n T a b l e I X , and i l l u s t r a t e d i n P l a t e s 1 t h r o u g h 5. F e a t u r e s such as n i v a t i o n h o l l o w s , e o l i a n forms and o r g a n i c d e p o s i t s have been o m i t t e d as they a r e s t r o n g l y a f f e c t e d by a d d i t i o n a l m o d i f y i n g p r o c e s s e s , as w i l l be d i s c u s s e d i n S e c t i o n 3.3 . ICE C O N T E N T GRAVEL LOW Low angle slopes Angle ol Repose banks Angle of Repose banks SAND EXPOSUR E ICE C O N T E N T T E X T U R E MEDIUM HIGH LOW MEDIUM HIGH Low angle s lopes Angle of Repose banks Low angle s lopes Angle of Repose banks I LOW MEDIUM HIGH Angle of Q S o l if 1 uct ion S o l i f 1 uct ion Sol i f luct ion Repose banks Thermo-erosional _J s lopes s l o p e s s l o p e s niches (Thaw lakes) S ^) Sol i f luc l ion Sol i f l u c l i o n Ret rogressive a slopes s lopes f lows UJ + + SILT AND CLAY 2 (Skin f l o w s ? ) Skin f lows HIGH Repose T h e r m o - n i c h e s Retrogressive flows banks (Retrogressive flows) (Thermo-niches) note: -f e a t u r e s i n b r a c k e t s are p o t e n t i a l a l t e r n a t i v e forms. ma t r i x l o c a t i o n s w i t h o u t l i s t e d m orphologies i n d i c a t e t h a t no s i t e s were observed w i t h these i c e c o n t e n t v a l u e s . TABLE IX: Bank or sl o p e morphology as a f u n c t i o n o f i c e c o n t e n t , g r a i n s i z e and exposure. a) A t y p i c a l s o l i f l u c t i o n slope l o c a t e d i n a r e l a t i v e l y low i c e c o ntent m a t e r i a l . Parker R i v e r (Devonian Plateau) 95 73° 21' N, 117 30'W c) b) A more a c t i v e s o l i f l u c t i o n s l o pe composed of h i g h e r water content m a t e r i a l . D i s s e c t i o n Creek (Northern Cretaceous Complex) A moderately h i g h i c e content s i t e i l l u s t r a t i n g the r e c u r -r i n g c y c l e o f thermokarst a c t i v i t y . Note the p o s i t i o n of the a c t i v e thaw face i n r e l a t i o n t o the p o l y g o n a l p a t t e r n of i c e wedges. Adjacent t o "Chebyshev R i v e r " ? v (Northern Cretaceous Complex) 73° 13' N, P l a t e 1. The e f f e c t o f i n c r e a s i n g i c e content on the morphology of banks or s l o p e s composed of f i n e t e x t u r e d m a t e r i a l and l o c a t e d i n low exposure environments. 96 a) The low angle s o l i f l u c t i o n slopes adjacent to this stream are t y p i c a l of areas containing r e l a t i v e l y low ice contents. "Ivitaruk River" (Northern Cretaceous Complex) Details of a single r e t r o -gressive thaw flow s l i d e . Note the ice wedges exposed in the headwall. Adjacent to "Ivitaruk River" (Northern Cretaceous Complex) 73° 23 ' N, 120° 18 1 W Plate 2. The e f f e c t of increasing ice content on the morphology of banks or slopes composed of fine textured material and located i n moderate exposure environments. a) The steeper face of t h i s asym-m e t r i c v a l l e y i s composed of low i c e content s i l t and c l a y of the C h r i s t o p h e r and Kanguk Formations. The w e l l vege-t a t e d s o l i f l u c t i o n slope i s prograding i n t o the stream r e s u l t i n g i n u n d e r c u t t i n g of the steeper f a c e . Able Creek t r i b u t a r y (Northern Cretaceous Complex) 73° 35' N, 120° 20' W c) A moderately h i g h i c e c o n t e n t bank i l l u s t r a t i n g f a c i a l s l o u g h i n g of sediment. Deep snow accumulations p r o t e c t e d t h i s bank from u n d e r c u t t i n g d u r i n g the s p r i n g f l o o d . D i s s e c t i o n Creek (Northern Cretaceous Complex) 73° 16 ' N, 119° 30' W b) A t h e r m o - e r o s i o n a l niche formed i n moderate i c e con-t e n t m a t e r i a l c o n t a i n i n g a s i g n i f i c a n t p o r t i o n o f f i n e t e x t u r e d sediment. Note the mud flow i n the foreground. "Murchison R i v e r " (Beaufort P l a i n ) 74° 08 « N, 118° 38 ' W d) A r e t r o g r e s s i v e thaw flow s l i d e formed i n h i g h i c e content m a t e r i a l . Note t h a t the s u r f a c e m a t e r i a l has a c o m p a r a t i v e l y lower i c e c o n t e n t . Parker R i v e r (Eastern M o r a i n a l B e l t ) 73° 40 ' N, 115° 46 1 W P l a t e 3. The e f f e c t of i n c r e a s i n g i c e content on the morphology of banks or slopes composed of f i n e t e x t u r e d m a t e r i a l and l o c a t e d i n h i g h exposure environments. 98 a ) A l o w i c e c o n t e n t r e p o s e b a n k i n a l o w e x p o s u r e e n v i r o n m e n t B e r n a r d R i v e r c ) A l o w i c e c o n t e n t r e p o s e b a n k i n a h i g h e x p o s u r e e n v i r o n m e n t . P l a t e 4. T h e e f f e c t o f e x p o s u r e a n d i c e c o n t e n t o n t h e m o r p h o l o g y o f s a n d t e x t u r e d d e p o s i t s . a) A low exposure environment. Thomsen River (Northern Cretaceous Complex) 73° 04' N, 119° 30' W c) A high exposure environment. Big River (Western Lowlands) W 72° 27 ' N, 125° 05' Note the remnants of the surface vegetation. b) A moderate exposure environ ment. Bernard River (Western Lowlands) 73° 28' N, 122° 40* W Plate 5. The e f f e c t of exposure to f l u v i a l attack on the morphology of repose banks composed of low ice content gravels. 100 The s c a l e o f "low", "medium" and " h i g h " i c e c o n t e n t s r e f e r t o the d a t a p r e v i o u s l y shown i n T a b l e V I . I t s h o u l d be n o t e d t h a t the q u a n t i t a t i v e v a l u e s a s s o c i a t e d w i t h t h i s s c a l e a r e dependent upon g r a i n s i z e , as a "low" i c e c o n t e n t i n f i n e t e x t u r e d m a t e r i a l c o n t a i n s a h i g h e r p e r c e n t a g e o f water t h a n a "low" v a l u e i n g r a v e l . The i l l u s t r a t e d t r e n d s i n morphology r e f e r t o s i t u a t i o n s o f u n i f o r m t e x t u r a l c o m p o s i t i o n . I n c l u s i o n s o f f i n e t e x t u r e d m a t e r i a l i n an o t h e r w i s e c o a r s e t e x t u r e d d e p o s i t s i g n i f i c a n t l y i n c r e a s e the p o t e n t i a l f o r i c e s e g r e g a t i o n and can r e s u l t i n a m o r p h o l o g i c e x p r e s s i o n s i m i l a r t o t h a t o c c u r r i n g i n a f i n e r t e x t u r e d d e p o s i t . By way o f example, s k i n f l o w s and r e t r o g r e s s i v e thaw f l o w s l i d e s , w h i c h t y p i c a l l y o c c u r i n f i n e t e x t u r e d s e d i m e n t s , were o b s e r v e d i n m a t e r i a l s i n w h i c h over 30 p e r c e n t o f . t h e d r y w e i g h t was composed o f sands and g r a v e l s . A l t e r n a t e bank o r s l o p e forms (shown i n b r a c k e t s on T a b l e IX) r e f l e c t the p o t e n t i a l i n t e r a c t i o n o f a number o f e x t e r n a l f a c t o r s . H i g h i c e c o n t e n t m a t e r i a l s i n low exposure environments g e n e r a l l y t a k e the form o f s o l i f l u c t i o n s l o p e s . However "thaw l a k e s " o r t h e r m o k a r s t f e a t u r e s can o c c u r i n s i t u a t i o n s where the s u r f a c e c o v e r i s d i s t u r b e d . The o c c u r r e n c e o f s k i n f l o w s i n b o t h low and medium i c e c o n t e n t m a t e r i a l s r e f l e c t s the u n c e r t a i n t y i n the mechanism r e s p o n s i b l e f o r t h e i r development, as i t i s p r e s e n t l y unknown whether the h i g h pore w a t e r p r e s s u r e s w h i c h a r e t h o u g h t t o r e s u l t i n t h e s e f e a t u r e s o c c u r due t o thaw c o n s o l i d a -*1 t i o n o f ground i c e (McRoberts and M o r g e r n s t e r n , 1974a) o r from Thaw c o n s o l i d a t i o n i s d e f i n e d as "the p r o c e s s by which a r e d u c -t i o n i n volume and an i n c r e a s e i n d e n s i t y o f a s o i l mass o c c u r s , f o l l o w i n g thaw, i n response t o the escape o f water under the w e i g h t o f the s o i l . . i t s e l f and/or an a p p l i e d l o a d " (Brown and Kupsch, 1974 , p. 39) . external sources such as r a i n (French, 1976), or snowmelt. In high exposure environments layer i c e contents generally r e s u l t i n an increased thermokarst a c t i v i t y , as indicated by the progression of repose banks, to thermo-erosional niches, to retrogressive thaw flow s l i d e s . However i n situations of high ice content and low thermal input from either radiation or advection of sensible heat, thermo-erosional niche development could occur. S i m i l a r l y i n medium ice content material, high thermal input could r e s u l t i n retrogressive thaw flow s l i d e development as long as f l u v i a l erosion continued to remove the thawed sediments from the base of the receding headwall. 102 3.3 THE EFFECT OF MODIFYING FACTORS 3.3.1 L o c a l i z e d Snow A c c u m u l a t i o n N i v a t i o n F e a t u r e s N i v a t i o n p r o c e s s e s , r e s u l t i n g from the l o c a l a c c u m u l a t i o n o f wind blown snow, can have a s i g n i f i c a n t e f f e c t on bank o r s l o p e morphology. As i n d i c a t e d i n the d a t a p r e s e n t e d i n S e c t i o n 3.2, d i s t i n c t n i v a t i o n f e a t u r e s were obser v e d t o o c c u r i n f i n e t o g r a v e l l y sandy t e x t u r e d m a t e r i a l s o f low t o moderate i c e c o n t e n t . P o o r l y d e v e l o p e d t r a n s v e r s e n i v a t i o n h o l l o w s commonly o c c u r r e d a l o n g c o a r s e t e x t u r e d r i v e r banks and c o a s t a l b l u f f s , and r e s u l t e d i n minor s a p p i n g o r u n d e r m i n i n g o f t h e s e e s s e n t i a l l y a n g l e o f repose banks. More c l a s s i c a l l y d e v e l o p e d t r a n s v e r s e f e a t u r e s o c c u r r e d a l o n g b r e a k s o f s l o p e f r e q u e n t l y c o r r e s p o n d i n g to the upper l i m i t o f r e g i o n a l i n u n d a t i o n as d e l i n e a t e d by V i n c e n t (1978a) . These f e a t u r e s encompassed a wide v a r i e t y o f t e x t u r a l c o m p o s i t i o n , i n c l u d i n g p o o r l y l i t h i f i e d s h a l e s and s a n d s t o n e s . I n c o n t r a s t , l o n g i t u d i n a l and c i r c u l a r n i v a t i o n f e a t u r e s were g e n e r a l l y b e s t d e v e l o p e d i n f i n e o r medium t e x t u r e d uncon-s o l i d a t e d m a t e r i a l s , o r p o o r l y l i t h i f i e d sediments which weather t o f i n e t e x t u r e d m a t e r i a l s , as d i s c u s s e d by S t . Onge (1969) . M u l t i f a c e t e d c i r c u l a r n i v a t i o n h o l l o w s such as shown on P l a t e 6a were o n l y o b s e r v e d a d j a c e n t t o a r e a s where a r i v e r c h a n n e l was c o n f i n e d by the v a l l e y w a l l s . The s t e e p s l o p e s w h i c h would have a t one time o c c u r r e d a t such s i t e s l i k e l y r e s u l t e d i n the o r i g i n a l p r e f e r e n t i a l a c c u m u l a t i o n o f snow n e c e s s a r y f o r n i v a t i o n development. Such s i t e s were commonly ob s e r v e d t o have 103 a w e l l d e v e l o p e d p a t t e r n o f i c e wedges i n the s u r f a c e m a t e r i a l , w hich may e x p l a i n the i n i t i a l p r e s e n c e o f more than one a c t i v e n i v a t i o n " f a c e " , i n much the same manner as F r e n c h and E g g i n t o n (1973) d e s c r i b e the development o f b a y d j a r a k h - l i k e t e r r a i n . However, the p r e s e n t s i z e and d e n s i t y o f the component f a c e s , even i n l e s s complex examples such as shown on P l a t e 6b, do not appear t o be r e l a t e d t o the p r e s e n t d i s t r i b u t i o n o f i c e wedges and . must have some o t h e r e x p l a n a t i o n . Cook ( i n Hamelin and Cook, 1967) has p r e v i o u s l y o b s e r v e d t h a t : "Measurements [_of the p h y s i c a l s i z e ] o f n i v a t i o n h o l l o w s w i t h i n a l i m i t e d a r e a appear t o f a l l w i t h i n a v e r y s m a l l range, s u g g e s t i n g t h a t they d e v e l o p a c c o r d i n g t o some geomorphic p r o c e s s o r law" ( p . 7 5 ) . The a u t h o r c o n c u r s w i t h t h i s v i e w . G r a i n s i z e (and a s s o c i a t e d v a r i a t i o n s i n the a n g l e o f repose) appears t o be an i m p o r t a n t parameter , w i t h t h e d e n s i t y o f n i v a t i o n f e a t u r e s (as t h e number o f h o l l o w s p e r u n i t l e n g t h ) g e n e r a l l y i n c r e a s i n g w i t h d e c r e a s i n g g r a i n s i z e . R e l a t i v e r e l i e f a l s o appears t o p l a y a r o l e a s , w i t h i n a p a r t i c u l a r m a t e r i a l , s l o p e s w i t h h i g h e r r e l i e f were g e n e r a l l y o b s e r v e d t o have a s m a l l e r number o f l a r g e r d i a m e t e r f e a t u r e s . E f f e c t s oh Thermokarst N i v a t i o n a l s o i n f l u e n c e s t h e development o f bank o r s l o p e forms t y p i c a l l y o c c u r r i n g i n h i g h e r i c e c o n t e n t m a t e r i a l s . D u r i n g t h e e a r l y p a r t o f the summer, m e l t water o r i g i n a t i n g from l o c a l a c c u m u l a t i o n s o f snow was f r e q u e n t l y o b s e r v e d t o r e s u l t i n *1 B a y d j a r a k h i s a Y a k u t i a n term "used t o d e s c r i b e s i l t y o r p e a t y mounds .... formed due t o p r e f e r e n t i a l thawing and s u b s i d e n c e " a l o n g i c e wedge po l y g o n s ( F r e n c h , 1976) . a) A multi-faceted c i r c u l a r nivation hollow formed i n low i c e content s i l t s and clays. Un-named River (Northern Cretaceous Complex) 73° 55' N, 119° 25 1 W c) P r e f e r e n t i a l snow accumulation associated with the develop-ment of an asymmetric v a l l e y . Un-named River (Devonian Plateau) 73° 45" N, 118° 20' W 104 b) A series of nivation hollows formed i n low ice content sands and gravels of the Beaufort Formation. Bernard Island (Western Lowlands) 73° 35' N, 124° 20 ' W d) The common rel a t i o n s h i p between nivation hollows and skin flows. Thomsen River (Northern Cretaceous Complex) 73° 20' N, 119° 40 ' W 6. The modifying e f f e c t of nivation processes on morphology. 105 the s a t u r a t i o n and e r o s i o n o f m a t e r i a l d e p o s i t e d below the h e a d w a l l o f r e t r o g r e s s i v e • ; thaw f l o w s l i d e s . The subsequent exposure o f the u n d e r l y i n g h i g h i c e c o n t e n t m a t e r i a l i s thought t o p l a y an i m p o r t a n t r o l e i n the s e a s o n a l r e a c t i v a t i o n o f many such f e a t u r e s , as o b s e r v a t i o n s i n the l a t t e r p a r t o f t h e summer i n d i c a t e d t h a t , w i t h the d i s a p p e a r a n c e o f t h i s a d d i t i o n a l m e l t w a t e r , t h e h e a d w a l l was f r e q u e n t l y c o v e r e d w i t h c o l l u v i u m and s t a b i l i z e d . T h i s p a t -term i s thought t o o c c u r on an an n u a l b a s i s . E f f e c t s on S o l i f l u c t i o n The i m p o r t a n t r o l e w hich a c c u m u l a t i o n s o f snow on l e e s l o p e s p l a y s i n t h e development o f asymmetric v a l l e y s has been d e s c r i b e d p r e v i o u s l y by French (1971) . The h i g h e r c o n c e n t r a t i o n s o f m e l t w a t e r and a s s o c i a t e d i n c r e a s e d s o l i f l u c t i o n a c t i v i t y downslope o f thes e d e p o s i t s a re w e l l i l l u s t r a t e d i n P l a t e 6c. T h i s u n e q u a l d i s t r i b u t i o n o f s o i l w a ter may p e r s i s t i n t o m i d -J u l y as i n d i c a t e d by t h e water c o n t e n t measurements p r e s e n t e d i n F i g u r e 27. However, on c a s u a l o b s e r v a t i o n , s o i l . .- . -w i t h i n the a c t i v e l a y e r g e n e r a l l y appears t o be u n i f o r m l y d r y by the m i d d l e o f August. E f f e c t s on S k i n Flows The p r e f e r e n t i a l a c c u m u l a t i o n o f snow can a l s o a f f e c t the d i s t r i b u t i o n o f s k i n f l o w s as t h e s e f e a t u r e s were commonly observ e d below n i v a t i o n h o l l o w s , as i l l u s t r a t e d i n P l a t e 6d. However the p r o c e s s by which t h i s i n f l u e n c e o c c u r s i s not c o m p l e t e l y u n d e r s t o o d . McRoberts and M o r g e n s t e r n (1974a) have suggested t h a t t h e h i g h pore water p r e s s u r e s which a re thought t o o c c u r i n s k i n f l o w f a i l u r e s a r e a r e s u l t o f t h a w - c o n s o l i d a t i o n dominant w i n t e r wind d i r e c t i o n from t h e n o r t h Sample # Water c o n t e n t - % A c t i v e V e g e t a t i o n c o v e r F r o s t t a b l e t o s u r f a c e S u r f a c e o f f r o s t t a b l e l a y e r d e p t h cm 314 32 .8 48 d i s c o n t i n u o u s 315 18 .1 c o v e r a s s o c i a t e d w i t h " s t r i p e d 316 45 .5 44 ground" 317 20 .1 318 34 c o n t i n u o u s 319 45.3 c o v e r o f g r a s s and moss 320 57 .8 33 321 32 .0 Note: measurements t a k e n on J u l y 29, 1975. F i g u r e 27. Observed w a t e r c o n t e n t s and a c t i v e l a y e r d e p t h s on o p p o s i n g s l o p e s o f an asymmetric v a l l e y . 107 p r o c e s s e s due t o the m e l t i n g o f ground i c e w i t h i n the a c t i v e l a y e r . I n the e n s u i n g d i s c u s s i o n the e f f e c t o f r a i n f a l l and n i v a t i o n i s d e s c r i b e d as f o l l o w s : " W h i l e summer r a i n f a l l o r snowmelt may i n c r e a s e the r a t e o f thaw o r i n c r e a s e s t r e s s imbalance i n a th a w i n g s l o p e , the dominant i n f l u e n c e o f wet summer c o n d i t i o n s i s t o c o n t r i b u t e t o s a t u r a t e d c o n d i t i o n s a t the o n s e t o f f r e e z e b a c k . These s a t u r a t e d c o n d i t i o n s , t h e r e f o r e , e nsure an adequate w a t e r s u p p l y f o r f r o s t h e a v i n g " ( p . 459). Two f a c t o r s appear t o be i m p o r t a n t . The f i r s t i s the water s o u r c e f o r i c e growth w i t h i n the a c t i v e l a y e r , and the second c o n c e r n s t h e r o l e w hich t h i s i c e p l a y s i n the f o r m a t i o n o f s k i n f l o w s . Measurements t a k e n a t a s k i n f l o w s i t e on P a r k e r R i v e r ( F i g . 28) i l l u s t r a t e t he s e a s o n a l p a t t e r n o f s o i l w a ter concen-t r a t i o n downslope o f a p o o r l y d e f i n e d l o n g i t u d i n a l n i v a t i o n h o l l o w . On June 16 ( P l a t e 7a) snow m e l t was a c t i v e l y o c c u r r i n g and the wa t e r c o n t e n t i n t h e a c t i v e l a y e r was o b s e r v e d t o be h i g h e r than i n the u n d e r l y i n g f r o z e n m a t e r i a l (44.5% v e r s u s 33.3%.of the sample d r y w e i g h t ) . By June 29 ( P l a t e 7b) the s u r f a c e c o n d i t i o n s a t t h e s i t e were g e n e r a l l y much d r i e r . However c o n c e n t r a t i o n s o f m e l t w a t e r due t o the snow accumulated i n the n i v a t i o n h o l l o w r e s u l t e d i n s i g n i f i c a n t l o c a l v a r i a t i o n s i n b o t h water c o n t e n t s and d e p t h o f thaw. Downslope o f the n i v a t i o n h o l l o w , the a c t i v e l a y e r was o b s e r v e d t o have a water c o n t e n t o f 82.9%, r o u g h t l y 2.5 t i m e s t h a t o f t h e m a t e r i a l r e - d e p o s i t e d w i t h i n the s k i n f l o w s c a r , which was obser v e d t o be near i t s l i q u i d l i m i t w i t h a water c o n t e n t o f 34.0%. Three o t h e r s i t e s l o c a t e d a t v a r y i n g d i s t a n c e s from t h e a r e a o f n i v a l a c c u m u l a t i o n had s i g n i f i c a n t l y l o w e r water c o n t e n t s r a n g i n g from 30.6 t o 52.3% and a c t i v e l a y e r s w h i c h were 18 t o 31 cm deeper, r e f l e c t i n g the r e t a r d i n g i n f l u e n c e o f t h e m e l t w a t e r . l o c a l i z e d a c c u m u l a t i o n o f snow t r a n s v e r s e n i v a t i o n h o l l o w w i t h i n a ( p o o r l y d e f i n e d ) l o n g i t u d i n a l n i v a t i o n h o l l o w sample o f s a t u r a t e d sample o f d r i e d m a t e r i a r i v e r edge f l o w s c a r Sample # Date Water c o n t e n t - % A c t i v e l a y e r d e p t h cm F r o s t t a b l e t o s u r f a c e S u r f a c e o f f r o s t t a b l e 142 June 16 34 .0 143 June 16 44 .5 144 June 16 33 .3 173 June 2 9 19 .7 38, 38, 37 174 June 29 89.2 27, 27, 27 175 June 29 52 .3 52 (average) 176 June 29 30 .6 58, 53, 52 177 June 29 32 .7 49, 45, 50 Note: s i t e i l l u s t r a t e d on P l a t e 7. F i g u r e 28. Observed w a t e r c o n t e n t s a d j a c e n t t o a s k i n f l o w s i t e a) June 16th, 1975. 109 b) June 29th, 19 75. c) J u l y 29th, 1975. (note - l i g h t toned "pools" are r e f l e c t i o n s from the s u r f a c e of sediment d e p o s i t s ) P l a t e 7. V a r i a t i o n s i n snow cover a t a s k i n flow s i t e on the Parker R i v e r (73° 28' N, 116° 15' W). W h e n t h i s s i t e w a s r e v i s i t e d i n l a t e J u l y ( P l a t e 7 c ) a l l o f t h e a c c u m u l a t e d s n o w h a d m e l t e d a n d t h e s l o p e b e l o w t h e n i v a t i o n h o l l o w w a s o b s e r v e d t o b e m u c h d r i e r . U n f o r t u n a t e l y i t w a s u n f e a s i b l e t o v i s i t t h i s s i t e i n A u g u s t , b u t c a s u a l o b s e r v a t i o n a t s i m i l a r l o c a t i o n s i n d i c a t e s t h a t s o i l m o i s t u r e c o n t e n t s w o u l d b e m u c h l o w e r t h a n i n t h e s p r i n g , a n d g e n e r a l l y s i m i l a r t o t h a t o c c u r r i n g i n t h e s u r r o u n d i n g t e r r a i n . N i v a t i o n h o l l o w s w o u l d b e e x p e c t e d t o h a v e l i t t l e o r n o e f f e c t o n t h e d i s t r i b u t i o n o f w a t e r r e c h a r g e r e s u l t i n g f r o m f a l l r a i n s t o r m s w h i c h , a s d e s c r i b e d i n S e c t i o n 1 . 5 , p r o v i d e o v e r a q u a r t e r o f t h e a n n u a l p r e c i p i t a t i o n , a n d a s d i s c u s s e d b y H o l o c e k a n d V a s a h l o ( 1 9 7 5 ) ( S e c t i o n 1 . 6 ) o c c u r d u r i n g t h e p e r i o d o f " b u i l d u p o f s u r f a c e s t o r a g e w h i c h o c c u r s d u r i n g t h e l a t t e r p a r t o f A u g u s t a n d i n S e p t e m b e r " . T h u s t h e a v a i l a b l e o b s e r v a t i o n s i n d i c a t e t h a t t h e p r i m a r y e f f e c t o f l o c a l i z e d a c c u m u l a t i o n s o f s n o w a p p e a r s t o b e a g r e a t l y i n c r e a s e d s u p p l y o f m e l t w a t e r i n t h e s p r i n g . T h e o b s e r v a t i o n s u n d e r t a k e n i n t h i s r e c o n n a i s s a n c e p r o j e c t a r e i n s u f f i c i e n t t o d e t e r m i n e t h e r e l a t i v e r o l e o f t h a w c o n s o l i -d a t i o n p r o c e s s e s i n t h e f o r m a t i o n o f s k i n f l o w s . T h e t h i c k d e p o s i t s o f f r e e z e - b a c k i c e w h i c h o c c u r r e d a t a s k i n f l o w s i t e n o t a s s o c i a t e d w i t h n i v a t i o n f e a t u r e s m a y i n d i c a t e t h a t t h a w c o n s o l i d a t i o n i s l o c a l l y i m p o r t a n t . H o w e v e r , t h e o b s e r v e d h i g h w a t e r c o n t e n t s w i t h i n t h e a c t i v e l a y e r ( r e s u l t i n g f r o m t h e m e l t i n g o f l o c a l i z e d a c c u m u l a t i o n s o f s n o w ) i n r e l a t i o n t o t h e l o w e r i c e c o n c e n t r a t i o n s w i t h i n t h e u n d e r l y i n g f r o z e n m a t e r i a l a t t h e P a r k e r R i v e r s k i n f l o w s i t e , a n d o b s e r v a t i o n s b y M a c k a y a n d M a t h e w s ( 1 9 7 3 ) a n d F r e n c h ( 1 9 7 6 ) t h a t s k i n f l o w s m a y b e g e n e r a t e d b y h e a v y r a i n s t o r m s , i n d i c a t e t h a t o t h e r p r o c e s s e s m a y b e e q u a l l y I l l i m p o r t a n t , and t h a t f u r t h e r s t u d y i s r e q u i r e d . E f f e c t s on Repose Banks S i g n i f i c a n t a c c u m u l a t i o n s o f snow f r e q u e n t l y o c c u r a l o n g r i v e r banks. As t h i s snow d e p o s i t g e n e r a l l y p e r s i s t s t hroughout the p e r i o d o f maximum d i s c h a r g e , i t o f f e r s c o n s i d e r a b l e p r o t e c t i o n a g a i n s t d i r e c t f l u v i a l e r o s i o n . However,in some s m a l l e r s t r eams, t h e s e d e p o s i t s o f snow may c o m p l e t e l y b l o c k the c h a n n e l c a u s i n g upstream p o n d i n g o f water / and an i n c r e a s e i n peak d i s c h a r g e when the dam i s e v e n t u a l l y o v e r - t o p p e d . The e f f e c t s o f one such e v e n t were observed - a n d w h i l e n o t a p p e a r i n g t o r e s u l t i n any s i g n i f i c a n t l a t e r a l e r o s i o n , l o c a l s c o u r d i d o c c u r a d j a c e n t t o snow b l o c k s w h i c h were eroded d u r i n g the peak f l o w and s u b s e q u e n t l y d e p o s i t e d downstream (see Day and Anderson, 1976) . 3.3.2 I c e Wedges I c e wedges can a f f e c t b o t h t h e morphology and s t a b i l i t y o f a bank o r s l o p e . I n low i c e c o n t e n t e n v i r o n m e n t s , i c e wedges w h i c h a r e exposed a l o n g cutbanks can m e l t o u t f o r m i n g s m a l l , s t a b l e g u l l i e s . However i n some ca s e s subsequent t h e r m a l and f l u v i a l e r o s i o n can g i v e t h e s e f e a t u r e s . t h e s u p e r f i c i a l appearance o f a r o t a t i o n a l f a i l u r e as i l l u s t r a t e d i n P l a t e 8a. I f e x t e n s i v e t h e r m a l and f l u v i a l e r o s i o n o c c u r i n l a n d a l o n g a p a t t e r n o f i c e wedges, w e l l d e v e l o p e d i r r e g u l a r g u l l i e s o r beaded d r a i n a g e f e a t u r e s may r e s u l t . I n somewhat h i g h e r i c e c o n t e n t m a t e r i a l s , l o c a l i z e d r e t r o g r e s s i v e thaw f l o w s l i d e s are f r e q u e n t l y a s s o c i a t e d w i t h i c e wedge exposure and can l e a d t o complex g u l l y development as i l l u s t r a t e d on P l a t e 8b. I n c a s e s where t h e r m o - e r o s i o n has r e s u l t e d i n the u n d e r c u t t i n g o f a bank, i c e wedges can f r e q u e n t l y form the p l a n e o f weakness a l o n g w h i c h the o v e r h a n g i n g b l o c k may c o l l a p s e . As p r e v i o u s l y d i s c u s s e d i n S e c t i o n 3.2.3, i n i t i a l s u r f a c e d i s t u r b a n c e due t o t h e r m a l e r o s i o n o r t h e r m o k a r s t a l o n g i c e wedges may r e s u l t i n r e t r o g r e s s i v e thaw f l o w s l i d e f o r m a t i o n w i t h i n h i g h i c e c o n t e n t m a t e r i a l . The a d d i t i o n a l m e l t w a t e r d e r i v e d from th e m e l t i n g o f wedge i c e a l s o appears t o p l a y a s i g n i f i c a n t r o l e i n the maintenance o f r e t r o g r e s s i v e thaw f l o w s l i d e s o c c u r r i n g i n m a t e r i a l n e a r th e lower l i m i t o f i c e c o n t e n t s o b s e r v e d f o r t h e s e f e a t u r e s . F i n a l l y , i n o r g a n i c r i c h t e r r a i n , e r o s i o n a l o n g i c e wedges proceeds more r a p i d l y t h a n i n the s u r r o u n d i n g m a t e r i a l , and produces a c h a r a c t e r i s t i c a l l y i r r e g u l a r morphology as i n d i c a t e d on P l a t e 8c. 113 a) Typical g u l l i e s formed i n low ice content gravels as a res u l t of erosion along ice wedges. Bernard River (Western Lowlands) 73° 26' N, 122° 35' W b) Gullying and r e s u l t i n g bank collapse t y p i c a l of fine grained material of moderate ice content. Un-named River (Northern Cretaceous Complex) approximately 73° 18' N, 119° 25• W c) Typical bank morphology r e s u l t i n g from the presence of i c e wedges i n organic r i c h material. Thomsen River (Northern Cretaceous Complex) 74° 02' N, 119° 44' W Plate 8. The e f f e c t of ice wedges on bank morphology. 3 . 3 . 3 V e g e t a t i o n V e g e t a t i o n mats, p a r t i c u l a r l y when f r o z e n , can form an e f f e c t i v e p r o t e c t i o n a g a i n s t f l u v i a l a t t a c k , as i l l u s t r a t e d i n P l a t e 9 . S i m i l a r l y , the v e g e t a t i o n o c c u r r i n g a t t h e t o e o f s o l i f l u c t i o n s l o p e s ( P l a t e 3 a ) o r s k i n f l o w s ( P l a t e 2 b ) i n c r e a s e s the a b i l i t y o f t h e s e f i n e t e x t u r e d f e a t u r e s t o prograde i n t o the a c t i v e c h a n n e l zone. T h i c k v e g e t a t i o n c o v e r may a l s o a s s i s t i n the s t a b i l i z a t i o n o f s m a l l s c a l e r e t r o g r e s s i v e thaw f l o w s l i d e s , i f r e c e s s i o n o f the h e a d w a l l r e s u l t s i n t h e d e p o s i t i o n o f t h e o v e r l y i n g o r g a n i c m a t t e r onto the thaw f a c e . V e g e t a t i o n c o v e r may a l s o p l a y a r o l e i n the development o f s k i n f l o w s as t h e headward r e g i o n o f the s e f a i l u r e s was., f r e q u e n t l y o b s e r v e d t o have a denser v e g e t a t i o n c o v e r t h a n t h a t o c c u r r i n g on s i m i l a r n o n - s k i n f l o w s i t e s . T h i s o r g a n i c c o v e r ( p r i m a r i l y composed o f g r a s s e s , w i t h some sedges, mosses and f e r n s ) may p r o v i d e a s u f f i c i e n t l y i m p e r v i o u s upper boundary t h a t i t p l a y s a r o l e i n the g e n e r a t i o n o f h i g h pore water p r e s s u r e s . 3 3 3 3 4 4 . D e f l a t i o n Bankforms produced by e o l i a n p r o c e s s e s were obse r v e d t o have a l i m i t e d d i s t r i b u t i o n , b u t l o c a l l y produced d i s t i n c t i v e bank m o r p h o l o g i e s , as i l l u s t r a t e d i n P l a t e 1 0 . Wind e r o s i o n i n such s i t e s was g e n e r a l l y l o c a t e d w i t h i n o r a d j a c e n t t o f l u v i a l d e p o s i t s c o n t a i n i n g c o a r s e s i l t s and sands. D e f l a t i o n o f m a t e r i a l was obs e r v e d t o o c c u r i n o t h e r p o o r l y v e g e t a t e d u n l i t h i f i e d m a t e r i a l s b u t produced no d i s t i n c t i v e f e a t u r e s and i s t h o u g h t t o be o f r e l a t i v e l y minor i m p o r t a n c e . The vegetation cover on th i s riverbank was not s i g n i f i c a n t l y damaged during peak spring d i s -charges despite water levels reaching within a few centimeters of the terrace surface. Dissection Creek (Northern Cretaceous Complex) N, 73° 17 ' 119 32 ' W Plate 9. An example of vegetation protecting a r i v e r bank from l a t e r a l erosion. The rounded edge of the bank, i r r e g u l a r "blow-out" features and levee-like appearance are charac-t e r i s t i c of eolian features along the margin of f l u v i a l terraces. Thomsen River (Northern Cretaceous Complex) 73° 15 ' N, 119° 37 ' W Plate 10. An example of d e f l a t i o n modifying the appearance of an angle of repose bank. 116 3.4 RECOGNITION OF REPRESENTATIVE MORPHOLOGIES R e c o g n i t i o n o f the d e s c r i b e d bank o r s l o p e m o r p h o l o g i e s g e n e r a l l y p r o v i d e s l i t t l e d i f f i c u l t y d u r i n g low l e v e l h e l i c o p t e r s u r v e y s i n mid o r l a t e summer. However e a r l i e r i n the season, wind blown d e p o s i t s o f snow can f r e q u e n t l y obscure s m a l l s c a l e f e a t u r e s , and thus f i e l d o b s e r v a t i o n s o f c o a s t a l o r r i v e r b a n k morphology a r e b e s t u n d e r t a k e n a f t e r t h i s snow c o v e r has m e l t e d . I n some l o c a t i o n s s k i n f l o w s and r e t r o g r e s s i v e thaw f l o w s l i d e s can be c o n f u s e d as t h e headward p o r t i o n o f s k i n f l o w s i s f r e q u e n t l y s u b j e c t t o some t h e r m o k a r s t a c t i v i t y due t o the l o s s o f the i n s u l a t i n g v e g e t a t i o n c o v e r . D i a g n o s t i c a i d s t o the s e p a r a t i o n o f t h e s e two f e a t u r e s i n c l u d e : a) -the p r e f e r r e d l o c a t i o n o f s k i n f l o w s on s o l i f l u c t i o n s l o p e s ; b) the appearance o f the h e a d w a l l a r e a w h i c h p r o v i d e s an i n d i c a t i o n o f the t h i c k n e s s o f t h e exposed h i g h i c e c o n t e n t m a t e r i a l (which i s g e n e r a l l y s h a l l o w e r i n s k i n f l o w s ) ; and c) the form o f the s l o p e a t t h e base o f the f e a t u r e . I n s k i n f l o w s i t e s t h i s a r e a f r e q u e n t l y c o n t a i n s l a r g e mounds o f r e l a t i v e l y c o h e r e n t m a t e r i a l s r e s u l t i n g from s u r f a c e sloughing," w h i l e the sediments produced from r e t r o g r e s s i v e thaw f l o w s l i d e s a r e e s s e n t i a l l y s t r u c t u r e -l e s s and g e n e r a l l y t a k e the form o f mud f l o w s o r c o l l u v i a l f a n s . Repose banks and t h e r m o - e r o s i o n a l n i c h e s a re r e l a t i v e l y e a s i l y d i s t i n g u i s h e d i f b l o c k f a i l u r e has o c c u r r e d as a r e s u l t o f u n d e r c u t t i n g . However, i n s i t u a t i o n s which lack-.these d i a g n o s t i c 117 b l o c k f a l l s , d i s c r i m i n a t i o n may prove more d i f f i c u l t . D u r i n g p e r i o d s of h i g h d i s c h a r g e , t h e r m o - e r o s i o n a l n i c h e s may be under w a t e r , however the h i g h r a t e s o f sediment p r o d u c t i o n a s s o c i a t e d w i t h t h e s e f e a t u r e s was o b s e r v e d to produce a l o c a l i z e d i n c r e a s e i n suspended sediment c o n c e n t r a t i o n , w h i c h may be a r e l i a b l e i n d i c a t o r . L a t e r i n the season, f a c i a l s l o u g h i n g a t thermo-e r o s i o n a l n i c h e s i t e s may r e s u l t i n t h e s e f e a t u r e s h a v i n g an appearance s i m i l a r t o t h a t o f a repose bank. However the g e n e r a l l y much s t e e p e r p r o f i l e , as w e l l as the p r e s ence o f mud-f l o w s , d e b r i s p i l e s and remnants o f u n d e r c u t n i c h e s , p r o v i d e c l u e s f o r the a s t u t e o b s e r v e r . O r g a n i c banks and repose f e a t u r e s can a l s o have a s i m i l a r appearance, and thus may r e q u i r e ground c h e c k i n g t o ensure c o r r e c t c l a s s i f i c a t i o n . However when the o r g a n i c d e p o s i t s are a s s o c i a t e d w i t h i c e wedges, the r e s u l t i n g bank form i s c h a r a c t e r i s t i c and p r o v i d e s a r e l i a b l e i n d i c a t o r . R e c o g n i t i o n o f t h e d e s c r i b e d f e a t u r e s on a i r photographs ( P l a t e s 11a t o n) i s c o n s i d e r a b l y more d i f f i c u l t and r e q u i r e s a s u b s t a n t i a l amount o f e x p e r i e n c e . T h i s i s p a r t i c u l a r l y t r u e on s m a l l s c a l e (1:60,000 o r 1:100,000) photography w h i c h , a t the time o f w r i t i n g , i s a l l t h a t i s a v a i l a b l e f o r much o f the A r c t i c I s l a n d s . However under f o u r power enlargement most o f t h e r e p r e s e n t a t i v e bank o r s l o p e forms are r e c o g n i z e a b l e . Large s c a l e f e a t u r e s such as s o l i f l u c t i o n s l o p e s , n i v a t i o n h o l l o w s and most repose f e a t u r e s are e a s i l y d i s c r i m i n a t e d . W e l l d e v e l o p e d r e t r o g r e s s i v e thaw f l o w s l i d e s are g e n e r a l l y r e a d i l y d i s t i n g u i s h e d , b u t s m a l l e r f e a t u r e s a s s o c i a t e d w i t h i c e wedges, o r b l a n k e t e d by snow d e p o s i t s may p r o v i d e some d i f f i c u l t y . R e t r o g r e s s i v e thaw f l o w s l i d e s o c c u r r i n g a l o n g s t e e p , a c t i v e l y 118 Plate: Features Materials: Location: Coordinates 11a Scale: 1 cm = 510 m asymmetric v a l l e y , s o l i f l u c t i o n slope, skin flows, angle of repose banks with small longitudinal nivation hollows (see Plates 3a and 2b) colluvium derived from the poorly l i t h i f i e d s i l t s and clays of the Kanguk and Christopher formations Un-named tri b u t a r y to Able Creek 73° 35' N, 120° 20 1 W Physiographic region: Northern Cretaceous Complex O N - X " Plate: Features: Materials Location: Coordinates l i b Scale: 1cm = 470 m s o l i f l u c t i o n slopes, eroded skin flows associated with nivation hollows colluvium, p a r t i a l l y derived from lacustrine and t i l l deposits, overlying poorly l i t h i f i e d s i l t s and clays of the Christopher formation Thomsen River, opposite the mouth of the Musk-ox River 73° 49' N, 119° 50' W Physiographic region: Northern Cretaceous Complex Plate 11. The appearance of representative bank or slope morphologies on a i r photographs. 119 Plate: Features: Materials: Location: Coordinates 11c S c a l e : 1 cm = 860 m a n g l e o f repose banks, s h a l l o w t h e r m o k a r s t l a k e s s u r f a c e veneer o f f i n e t e x t u r e d f l u v i a l / e o l i a n m a t e r i a l o v e r l y i n g f l u v i a l sands and g r a v e l s Un-named t r i b u t a r y t o the B e r n a r d R i v e r 7 3 0 25 • N, 121° 10' W P h y s i o g r a p h i c r e g i o n : Western Lowlands P l a t e : F e a t u r e s M a t e r i a l s : L o c a t i o n : C o o r d i n a t e s l i d S c a l e : 1 cm = 866 m a n g l e o f repose banks w i t h l o c a l i z e d snow d e p o s i t s , s h a l l o w t h e r m o k a r s t l a k e s , g u l l i e s a s s o c i a t e d w i t h d r a i n a g e a l o n g i c e wedges s u r f a c e veneer o f f i n e t e x t u r e d f l u v i a l / e o l i a n m a t e r i a l o v e r l y i n g f l u v i a l sands and g r a v e l s Un-named t r i b u t a r y t o the B e r n a r d R i v e r 7 3 0 18• N, 120° 32• W P h y s i o g r a p h i c r e g i o n : Western Lowlands P l a t e 11. The appearance o f r e p r e s e n t a t i v e bank o r s l o p e (cont'd) m o r p h o l o g i e s on a i r p h o t o g r a p h s . P l a t e : F e a t u r e s : M a t e r i a l s : L o c a t i o n : C o o r d i n a t e s l i e S c a l e : 1 cm = 1240 m n i v a t i o n h o l l o w s , s o l i f l u c t i o n s l o p e i n the low e x p o sure environment b e h i n d the s p i t (see P l a t e s u r f a c e veneer o f marine and t i l l d e p o s i t s o v e r l y i n g B e a u f o r t sands and g r a v e l s B e r n a r d I s l a n d 7 3 0 3 5 1 N, 124° 20' W 6b) P h y s i o g r a p h i c r e g i o n : Western Lowlands P l a t e : F e a t u r e s : M a t e r i a l s L o c a t i o n : C o o r d i n a t e s l l f S c a l e : 1 cm = 490 m c i r c u l a r n i v a t i o n h o l l o w (see P l a t e 6a) s u r f a c e veneer o f t i l l and l a c u s t r i n e d e p o s i t s o v e r l y i n g the p o o r l y l i t h i f i e d s i l t s and c l a y s o f the C h r i s t o p h e r f o r m a t i o n s o u t h o f Mercy Bay 7 3 ° 55' N, 1190 2 5 1 W P h y s i o g r a p h i c r e g i o n : N o r t h e r n C r e t a c e o u s Complex P l a t e 11. The appearance of r e p r e s e n t a t i v e bank o r s l o p e (cont'd) m o r p h o l o g i e s on a i r p h o t o g r a p h s . Plate: Features Materials: Location: Coordinates l l g Scale: 1 cm = 340 m retrogressive thaw flow s l i d e s along exposed coast, s o l i f l u c t i o n slope below transverse nivation hollow on sheltered coast high ice content g l a c i a l and marine sediments overlying Beaufort sands and gravels Norway Island 73° 43 1 N, 124° 40 1 W Physiographic region: Western Lowlands Plate: Features: Materials: Location: Coordinates l l h Scale: 1 cm = 625 m shallow retrogressive thaw flow s l i d e s fine textured surface veneer of lacustrine and marine deposits overlying t i l l , which o v e r l i e s marine or f l u v i a l deposits of sand east coast south of Johnson Point 72° 42' N, 118° 55' W Physiographic region: Eastern Morainal B e l t Plate 11. The appearance of representative bank or slope (cont'd) morphologies on a i r photographs. 122 H i Scale: 1 cm = 470 m l o c a l i z e d retrogressive thaw flow s l i d e s associated with ice wedges t i l l overlying marine deposits (?) adjacent to the Thomsen River 72© 51 i N, 119° 40' W Plate: Features: Materials: Location: Coordinates: Physiographic region: Eastern Morainal B e l t Plate: Features: Materials: Location: Coordinates H j Scale: 1 cm = 750 m point bar opposite bank observed to have a 5 m deep thermo-erosional niche i n 1975. Repose banks i n lower exposure locations f l u v i a l deposits overlying Beaufort sands and gravels "Murchison River" 74° 05 1 N, 122° 43' W Physiographic region: Beaufort Plain Plate 11. The appearance of representative bank or slope (cont'd) morphologies on a i r photographs. Plate: Ilk Scale: 1 cm = 1360 m Features: steep "smooth" shoreline associated with thermo-erosional niche development, breached lakes and "bay-mouth" bars Materials: fine textured f l u v i a l , lacustrine and eolian veneers overlying f l u v i a l or marine sands Location: south coast, immediately east of Sachs Harbour Coordinates: 71° 51' N, 124° 52' W Physiographic region: South Western Coast P l a t e : Features: Materials: Location: Coordinates J 11 Scale: 1 cm = 640 m steep "smooth" shoreline associated with thermo-erosional niche development, s p i t s , breached lakes (see Plate 4d) Beaufort sands and gravels west coast adjacent to Blue Fox Harbour 72° 07 ' N, 125° 48' W Physiographic region: Western Lowlands Plate 11. The appearance of representative bank or slope (cont'd) morphologies on a i r photographs. P l a t e : F e a t u r e s : M a t e r i a l s : L o c a t i o n : C o o r d i n a t e s 11m S c a l e : 1 cm = 1080 m r e pose banks w i t h c h a r a c t e r i s t i c e o l i a n f e a t u r e s ; l a c k o f v e g e t a t i o n , p o o r l y d e f i n e d "blow-out" forms f l u v i a l and e o l i a n sands Thomsen R i v e r 7 3 ° 42 1 N, 119° 55' W P h y s i o g r a p h i c r e g i o n : N o r t h e r n C r e t a c e o u s Complex P l a t e : F e a t u r e s : M a t e r i a l s : L o c a t i o n : C o o r d i n a t e s l l n S c a l e : 1 cm = 480 m i r r e g u l a r bank form a s s o c i a t e d w i t h i c e wedges i n o r g a n i c r i c h t e r r a i n (see P l a t e 8c) f i n e t e x t u r e d f l u v i a l d e p o s i t s n e a r the mouth o f the Thomsen R i v e r 740 02' N, 119° 4 5 1 W P h y s i o g r a p h i c r e g i o n : N o r t h e r n C r e t a c e o u s Complex P l a t e 11. The appearance o f r e p r e s e n t a t i v e bank o r s l o p e (cont'd) m o r p h o l o g i e s on a i r p h otographs. 1 2 5 e r o d i n g b l u f f s can sometimes be c o n f u s e d w i t h n i v a t i o n h o l l o w s . However the presence o f r e l i c t ? s c a r s , a n d a more i r r e g u l a r p l a n form and s p a c i n g s e r v e t o d i s c r i m i n a t e those f e a t u r e s r e s u l t i n g from t h e r m o k a r s t a c t i v i t y . S k i n f l o w s a re a l s o g e n e r a l l y e a s i l y r e c o g n i z e d , b u t can be c o n f u s e d w i t h r e t r o g r e s s i v e thaw f l o w s l i d e s i n c i r c u m s t a n c e s where s i g n i f i c a n t t h e r m o k a r s t i s o c c u r r i n g , as p r e v i o u s l y d i s c u s s e d . W i t h o u t the p r e s e n c e o f b l o c k f a l l s , t h e r e c o g n i t i o n o f s i t e s u n d e r g o i n g t h e r m o - e r o s i o n a l n i c h i n g poses a s i g n i f i c a n t p roblem. I f t h e photography i s t a k e n d u r i n g h i g h f l o w , l o c a l i z e d sediment plumes may p r o v i d e an i n d i c a t i o n o f u n d e r c u t t i n g . How-e v e r , i n g e n e r a l , i n f e r e n c e must be made on the b a s i s o f s l o p e , exposure and o t h e r i n d i c a t o r s o f r a p i d r e c e s s i o n such as the presence o f breached l a k e s o r w e l l d e v e l o p e d p o i n t b a r s and s p i t s , h i s t o r i c p a t t e r n s o f meander and v e g e t a t i o n p r o g r e s s i o n , e t c . E o l i a n f e a t u r e s a r e g e n e r a l l y o f i n s u f f i c i e n t s i z e t o be o b s e r v e d on s m a l l s c a l e photography. However t h e presence o f e o l i a n t r a n s p o r t e d m a t e r i a l can f r e q u e n t l y be i n f e r r e d on the b a s i s o f v e g e t a t i o n p a t t e r n and t e r r a i n l o c a t i o n . S i m i l a r l y o r g a n i c f e a t u r e s a r e t o o s m a l l t o be e a s i l y r e c o g n i z e d , b u t can sometimes be i n f e r r e d by the presence o f an i r r e g u l a r s h o r e l i n e i n r e g i o n s o f l o w - l y i n g f l u v i a l d e p o s i t s . SECTION FOUR 126 STABILITY OF REPRESENTATIVE MORPHOLOGIES 4.1 TYPICAL RATES OF RECESSION 4.1.1 Me t h o d o l o g y The c o m p a r a t i v e s t a b i l i t y o f t h e v a r i o u s bank o r s l o p e f e a t u r e s was i n v e s t i g a t e d t h rough a v a r i e t y o f t e c h n i q u e s . Measurements o f n e t r e c e s s i o n o r downslope movement o v e r the summer p e r i o d were u n d e r t a k e n f o r a number o f r e p r e s e n t a t i v e f i e l d s i t e s . However the s h o r t p e r i o d o f r e c o r d d i d not a l l o w an assessment o f i n t e r - s e a s o n a l v a r i a b i l i t y . T h u s , i n a r e a s w i t h m u l t i - y e a r a i r photograph c o v e r a g e , a number o f c o m p a r a t i v e s t u d i e s were u n d e r t a k e n t o p r o v i d e e s t i m a t e s o f average r a t e s o f r e c e s s i o n o v e r a l o n g e r time frame. I n a d d i t i o n t o the problems r e l a t e d t o i n t e r - s e a s o n a l v a r i a b i l i t y , t h e measurements o f n e t r e c e s s i o n s u f f e r from a number o f o t h e r l i m i t a t i o n s . When the f i e l d season commenced i n l a t e May snow s t i l l c o v e r e d the f a c e s o r banks o f most f e a t u r e s and p r e c l u d e d the p o s s i b i l i t y o f u n d e r t a k i n g d e t a i l e d t o p o g r a p h i c s u r v e y s . Thus e r o s i o n had t o be e s t i m a t e d on the b a s i s o f head-ward r e c e s s i o n . T h i s i n t r o d u c e s a s e r i o u s c o m p l i c a t i o n as r e c e s s i o n can f r e q u e n t l y be e p i s o d i c i n n a t u r e , even though sediment removal may be r e l a t i v e l y c o n t i n u o u s . A good example o f t h i s t y pe o f p r o c e s s i s p r o v i d e d by the p e r i o d i c c o l l a p s e o f u n d e r c u t banks r e s u l t i n g from t h e r m o - e r o s i o n a l n i c h i n g . Thus the o b s e r v e d r e c e s s i o n v a l u e s may r e f l e c t more th a n one season's e r o s i o n , o r no r e c e s s i o n may have been r e c o r d e d , d e s p i t e the f a c t t h a t sediment was eroded o v e r the o b s e r v a t i o n p e r i o d . A r e l a t e d problem p e r t a i n s t o the n a t u r e o f f a i l u r e as the head w a l l s o f 127 f e a t u r e s such as r e t r o g r e s s i v e thaw f l o w s l i d e s and n i v a t i o n h o l l o w s were f r e q u e n t l y o b s e r v e d t o s t r e t c h and c r a c k p r i o r t o c o l l a p s e , and t h i s o c c a s i o n a l l y r e s u l t e d i n an a p p a r e n t advance r a t h e r than a r e c e s s i o n . The s t a b i l i t y o f r e f e r e n c e markers a l s o posed some d i f f i c u l t i e s . The e f f e c t s o f thaw s e t t l i n g - a n d f r o s t heave are w e l l documented i n the l i t e r a t u r e . However f i e l d e x p e r i e n c e i n d i c a t e d t h a t w i l d l i f e a c t i v i t y may a l s o r e s u l t i n the d i s p l a c e -ment o f r e f e r e n c e p o i n t s . Wooden s t a k e s were f r e q u e n t l y used as " r u b b i n g p o s t s " by musk-oxen and thus e i t h e r damaged o r removed. S i m i l a r l y , b o t h musk-oxen and c a r i b o u appeared t o l i k e e a t i n g f l a g g i n g and c o n s e q u e n t l y u p r o o t e d a l a r g e number o f c o m m e r c i a l l y manufactured " p i n f l a g s " which were used as r e f e r e n c e s a t most s i t e s . I n o r d e r t o overcome many o f t h e s e problems, two e x p e r i -m e n t a l a t t e m p t s were made t o m o n i t o r r e c e s s i o n t h rough the use o f a p h o t o - t h e o d o l i t e t o t a k e ground based, s t e r e o photography. However the n e c e s s i t y o f e s t a b l i s h i n g a photo base l i n e on the same e l e v a t i o n as t h e s i t e o f i n t e r e s t r e q u i r e d t h a t the camera be l o c a t e d on t h e o p p o s i t e s i d e o f t h e v a l l e y . As the a v a i l a b l e equipment d i d n o t i n c l u d e a t e l e p h o t o l e n s , the r e s u l t i n g r e s o l u t i o n p r o v e d t o be i n s u f f i c i e n t f o r t h e d e s i r e d measurements. However,with a p p r o p r i a t e o p t i c s , t h i s t e c h n i q u e appears t o be p o t e n t i a l l y u s e f u l a t s i t e s u n d e r g o i n g r a p i d r e c e s s i o n as p e r i o d i c measurements are r e l a t i v e l y q u i c k l y o b t a i n e d once the i n i t i a l photo base l i n e i s e s t a b l i s h e d . A t t e m p t s t o measure n e t downslope movement o f near s u r f a c e m a t e r i a l due t o s o l i f l u c t i o n r e q u i r e d a somewhat d i f f e r e n t m o n i t o r i n g p r o c e d u r e . Three i n c h n a i l s and s m a l l p i e c e s o f 128 f l a g g i n g were used t o mark sur v e y e d l i n e s a c r o s s s l o p e s w i t h v a r y i n g a s p e c t , v e g e t a t i o n c o v e r and water s u p p l y . However, the d e s t r u c t i o n o f a l l r e f e r e n c e s t a k e s by " i t c h y " musk-oxen, the a p p a r e n t u p s l o p e r o t a t i o n o f some o f t h e c l o d s c o m p r i s i n g the s u r f a c e v e g e t a t i o n and the g e n e r a l l y s low r a t e s o f downslope movement.resulted i n t h e s e measurements b e i n g o f l i m i t e d s u c c e s s . P r o c e s s e s o f e o l i a n e r o s i o n and d e p o s i t i o n were a l s o m o n i t o r e d a t a number o f s i t e s , t h r o u g h the use o f s t e e l s t a k e s and washers, and i n d i c a t e d t h a t s i g n i f i c a n t amounts o f sediment t r a n s p o r t o c c u r r e d l o c a l l y on a s e a s o n a l b a s i s . As p r e v i o u s l y mentioned, c o m p a r a t i v e s t u d i e s o f r e p e t i t i v e a e r i a l photographs were used t o p r o v i d e e s t i m a t e s o f n e t e r o s i o n o v e r p e r i o d s l o n g e r than one f i e l d s e ason. However the a p p l i c a -b i l i t y o f a i r photo s t u d i e s was- s e v e r e l y r e s t r i c t e d due t o the s m a l l s c a l e o f most o f the a v a i l a b l e photography and the f a c t t h a t r e p e t i t i v e photo coverage i s o n l y a v a i l a b l e f o r the s o u t h - w e s t e r n p o r t i o n o f Banks I s l a n d . P h o t o g r a p h i c s c a l e and the number o f y e a r s between s u c c e s -s i v e photography d e t e r m i n e th e minimum amount o f r e c e s s i o n r e q u i r e d f o r r e s o l u t i o n by c o m p a r a t i v e a i r photo s t u d i e s . On the assumption o f l e v e l t e r r a i n , w e l l d e f i n e d r e f e r e n c e p o i n t s (such as the sharp break i n s l o p e g e n e r a l l y a s s o c i a t e d w i t h the h e a d w a l l o f a r e t r o -g r e s s i v e thaw f l o w s l i d e ) and good l i g h t i n g a t the time o f photography, n e t r e c e s s i o n s o f a p p r o x i m a t e l y 0.1 mm (±0.05 mm) can be r e s o l v e d t h r o u g h th e use o f r e l a t i v e l y s i m p l e equipment such as a " L e i t z . 8x m e asuring m a g n i f i e r " . *1 Poor q u a l i t y photography, * 1 Medley and L u t e r n a u e r (1976) r e p o r t measurements o f h o r i z o n t a l d i s p l a c e m e n t s o f ,± 5 m i c r o n s can be r e s o l v e d , u s i n g - t h e Jena I n t e r p r e t o s k o p . However i t i s "the ..author 's e x p e r i e n c e t h a t the d i s t i n c t n e s s o f r e f e r e n c e p o i n t s i s f r e q u e n t l y the l i m i t i n g f a c t o r , r a t h e r t h a n the p r e c i s i o n o f t h e measuring i n s t r u m e n t . heavy v e g e t a t i o n c o v e r o r i n d i s t i n c t r e f e r e n c e p o i n t s (such as f r e q u e n t l y rounded upper s u r f a c e o f a n i v a t i o n h o l l o w ) can e a s i l y i n c r e a s e t h i s v a l u e t o 0.2 o r 0.3 mm. On the assumption o f i d e a l c o n d i t i o n s ( i . e . 0.1 mm r e s o l u t i o n ) , T a b l e X i n d i c a t e s t h e minimum r e q u i r e d average ann u a l r e c e s s i o n n e c e s s a r y f o r d i s c r i m i n a t i o n o f n e t r e t r e a t a t v a r y i n g s c a l e s o f photography and p e r i o d s between s u c c e s s i v e c o v e r a g e . Most o f the a e r i a l photography o f Banks I s l a n d has a s c a l e o f 1:100,000. For the optimum c o n d i t i o n s shown on Ta b l e X i t can be seen t h a t n e t e r o s i o n on the o r d e r o f 10 meters i s t h e r e f o r e r e q u i r e d f o r between photograph d i s c r i m i n a t i o n . W i t h i n the s t u d y a r e a , the maximum time p e r i o d between s e q u e n t i a l p h o t o -graphy i s on t h e o r d e r o f 10 t o 15 y e a r s . Thus t h e 10 meters n e t r e c e s s i o n c o r r e s p o n d s t o an average a n n u a l r e c e s s i o n r a t e o f 0.7 t o 1.0 m/year. T h e r e f o r e w i t h i n the c o n t e x t o f t h i s s t u d y r e p e t i t i v e a i r photography a n a l y s i s i s o n l y u s e f u l f o r p r o v i d i n g e s t i m a t e s o f n e t r e c e s s i o n a t s i t e s which a re u n d e r g o i n g r a p i d r a t e s o f r e t r e a t . 4.1.2 R e s u l t s S o l i f l u c t i o n S l o p e s Rates o f s o l i f l u c t i o n movement were m o n i t o r e d on f o u r s l o p e s , w i t h t h e maximum obser v e d d i s p l a c e m e n t s o f t h e s u r f a c e m a t e r i a l b e i n g l e s s t h a n 1.5 t o 2 cm. However, due t o the p r e v i o u s l y mentioned problems, the e r r o r s i n h e r e n t i n these measurements may be e q u i v a l e n t t o the o b s e r v e d movements. N e v e r t h e l e s s these r e s u l t s do n o t appear u n r e a s o n a b l e as s i m i l a r o b s e r v a t i o n s on Banks I s l a n d by F r e n c h (1974) have a l s o i n d i c a t e d r a t e s o f A i r Photograph S c a l e S m a l l e s t average o b s e r v a b l e a n n u a l o v e r a r e c e s s i o n ( i n p e r i o d o f m) R e p r e s e n t a t i v e F r a c t i o n c h a i n s i n c h inert per meters per 0.1 mm 1 year l year.. 2-years 2-* y e a r s 5,..years j-'years 10 r tyears ~0J y e a r s 20,.years' 30 y e a r s 1:7,920 10 0.79 0 .79 0 .40 • 0 .016 0 .08 0 .04 0 .03 1:15,840 20 1.58 1.58 0 .79 0 .32 0 .16 0 .08 0 .05 1:31,680 40 3 .17 3 .317 1.59 0 .63 0 .32 0 .16 0 .11 1:47,520 60 4 .75 4 .75 2 .38 0 .95 0 .48 0 .24 0 .16 1:63 ,360 80 6 .34 6 .34 3 .17 1.2-7 0.63 0 .32 0 .21 1:79,200 100 7 .92 7 .92 3 .96 1.58 0 .79 0 .40 0 .26 1:95,040 120 9 .50 9 .50 4 .75 1.90 0 .95 0 .48 0 .32 1:110,880 140 11.06 11.06 5 .53 2 .21 1.11 0.55 0 .37 TABLE X: R e q u i r e d average annual r e c e s s i o n n e c e s s a r y f o r d i s c r i m i n a t i o n o f n e t r e t r e a t a t v a r y i n g s c a l e s o f photography and p e r i o d between s u c c e s s i v e a i r photo c o v e r a g e . H o 131 downslope movement i n the range o f 1.5 t o 2 cm/year, and E g g i n t o n (1976) has o b s e r v e d s i g n i f i c a n t l y l a r g e r movements o f 6 t o 15 cm o v er a one y e a r p e r i o d . Thus,on the b a s i s o f t h i s d a t a , commonly o c c u r r i n g r a t e s o f s o l i f l u c t i o n appear t o be as h i g h as 1 t o 10 cm per y e a r . A number o f l i n e s were su r v e y e d a c r o s s t h e d e b r i s p r e v i o u s l y d e p o s i t e d a t the base o f the s k i n f l o w shown on P l a t e 7 and i n d i c a t e d t h a t no f u r t h e r movement due t o s o l i f l u c t i o n o c c u r r e d o v er the summer p e r i o d . A s e r i e s o f s i m i l a r l i n e s was, p l a c e d a c r o s s the s u c c e s s i v e l y o l d e r d e p o s i t s o f m a t e r i a l o c c u r r i n g downslope o f one o f the r e t r o g r e s s i v e thaw f l o w s l i d e s shown on P l a t e 2c. Downslope movement was o n l y o b s e r v e d i n the most r e c e n t d e p o s i t , w i t h d i s p l a c e m e n t s o f up t o 3 cm b e i n g l i m i t e d t o a narrow bank i n the c e n t r e o f the r e d e p o s i t e d m a t e r i a l , and l o c a t e d d i r e c t l y downslope o f the a r e a o f m e l t w a t e r c o n c e n t r a t i o n . S k i n Flows O b s e r v a t i o n s by Mackay and Mathews (1973) and by F r e n c h (1976) i n d i c a t e t h a t s k i n f l o w f a i l u r e s o c c u r r a p i d l y , w i t h t h e c h a o t i c appearance o f t h e t e r m i n a l l o b e s s u g g e s t i n g t h a t the d i s p l a c e d m a t e r i a l r e a c h e d an a p p r e c i a b l e v e l o c i t y b e f o r e b e i n g d e p o s i t e d . S k i n f l o w t r a c k s were o b s e r v e d t o r e a c h 700 m i n l e n g t h and thus t h i s t y p e o f f a i l u r e can be a s s o c i a t e d w i t h the movement o f a s i g n i f i c a n t q u a n t i t y o f m a t e r i a l . The subsequent r a t e o f h e a d w a l l r e c e s s i o n , due t o a com-b i n a t i o n o f t h e r m o k a r s t , t h e r m a l e r o s i o n and s o l i f l u c t i o n was measured a t t h e s k i n f l o w s i t e shown on P l a t e 7 and was found t o exceed 3.3 meters o v e r the summer p e r i o d . T h i s o b s e r v a t i o n i n d i c a t e s t h a t headward r e c e s s i o n subsequent t o the i n i t i a l 132 f a i l u r e may i n f a c t form an a p p r e c i a b l e p o r t i o n o f the t o t a l l e n g t h o f r e l i c t .skin f l o w s c a r s . Repose F e a t u r e s Rates o f r e c e s s i o n a s s o c i a t e d w i t h repose f e a t u r e s were m o n i t o r e d on f o u r r i v e r banks and headward r e c e s s i o n was n o t ob s e r v e d a t any o f the l o c a t i o n s . However t h e f r e q u e n t l y o b s e r v e d remnants o f s u r f a c e v e g e t a t i o n , as i l l u s t r a t e d i n P l a t e 5c, and p a t t e r n s o f meander p r o g r e s s i o n , as shown on P l a t e H j , i n d i c a t e t h a t f l u v i a l p r o c e s s e s a re c a p a b l e o f c a u s i n g s i g n i f i c a n t e r o s i o n and a re more than a " c a t h a r t i c " , as suggested by Cook (1967) . N o t w i t h s t a n d i n g , as the p e r i o d o f peak d i s c h a r g e s i s l i m i t e d t o a few weeks i n the e a r l y summer ( F i g . 12) and as t h e o b s e r v e d d i s c h a r g e s t o da t e are r e l a t i v e l y s m a l l compared w i t h t h o s e a t many more s o u t h e r l y l o c a t i o n s ( S e c t i o n 1.6), t h e r a t e s o f e r o s i o n w hich can be e x p e c t e d i n low i c e c o n t e n t m a t e r i a l a r e a t most s i m i l a r , and are more l i k e l y s m a l l e r , than those t h a t would be e x p e c t e d i n a s i m i l a r t o p o g r a p h i c s e t t i n g i n s o u t h e r n Canada. The e f f e c t o f l o c a l i z e d d e p o s i t s o f snow i n p r o t e c t i n g r i v e r banks from e r o s i o n , and the c o a r s e t e x t u r e o f t h e m a t e r i a l u n d e r l y i n g the t e r r a c e s . w h i c h c o n f i n e many o f the l a r g e r r i v e r s s i m i l a r l y t e n d t o reduce the p o t e n t i a l f o r l a t e r a l movement. Rates o f e r o s i o n a s s o c i a t e d w i t h s i x a n g l e o f repose banks l o c a t e d i n v a r i o u s c o a s t a l l o c a t i o n s were a l s o m o n i t o r e d , w i t h no headward r e c e s s i o n b e i n g o b s e r v e d o v e r t h e summer p e r i o d . How-e v e r , as f r e e z e u p o f the c o a s t a l a r e a had not o c c u r r e d when the f i e l d s t u d i e s were t e r m i n a t e d , t h e s e r e s u l t s a r e i n c o n c l u s i v e . O b s e r v a t i o n s o f remnant v e g e t a t i o n s i m i l a r t o t h a t d e s c r i b e d on r i v e r i n e l o c a t i o n s , and the presence o f a w e l l d e f i n e d break i n 133 s l o p e a t the base of most repose f e a t u r e , i n d i c a t e t h a t c o a s t a l e r o s i o n i n low i c e c o n t e n t m a t e r i a l i s an a c t i v e p r o c e s s . The p r e s e nce o f w e l l d e v e l o p e d s p i t s , b a r r i e r b a r s , and b r e a c h e d l a k e s i n d i c a t e t h a t the l o w - l y i n g a r e a s on the w e s t e r n and s o u t h - w e s t e r n c o a s t s are u n d e r g o i n g more r a p i d r a t e s o f e r o s i o n i n comparison w i t h most o t h e r a r e a s o f Banks I s l a n d . C o n s i d e r i n g the a p p r e c i a b l e a r e a o f open water which commonly o c c u r s i n t h i s r e g i o n ( S e c t i o n 1.6), and the o b s e r v e d f r e q u e n c y o f onshore winds ( S e c t i o n 1.5), t h i s r e l a t i v e l y r a p i d r a t e o f r e c e s s i o n i s n o t s u r p r i s i n g . A good example o f t h e l i m i t a t i o n s o f u s i n g h i s t o r i c a e r i a l photography t o q u a n t i f y the i n f e r r e d r a t e s o f e r o s i o n on t h e s o u t h e r n and w e s t e r n c o a s t s i s i l l u s t r a t e d by the s e q u e n t i a l p h o t o g r a p h i c coverage o f the a r e a i n the v i c i n i t y o f the 1913 t o 1918 Canadian A r c t i c E x p e d i t i o n ' s base camp a t "Mary Sachs". T h i s s i t e i s l o c a t e d on t h e s o u t h c o a s t o f t h e i s l a n d , a p p r o x i -m a t e l y 8 km e a s t o f Cape K e l l e t . S t e f a n s s o n (1921b) i n d i c a t e d t h a t the n o r t h e r n p a r t y o f t h i s e x p e d i t i o n e r e c t e d two sod h u t s a t t h i s s i t e , one i n 1914 and a n o t h e r i n 1915. F i e l d o b s e r v a t i o n s a s s o c i a t e d w i t h the p r e s e n t s t u d y i n d i c a t e t h a t t h e s e b u i l d i n g s were s i t u a t e d on top o f a 2 t o 3 meter h i g h f l u v i a l t e r r a c e composed o f low i c e c o n t e n t sands and g r a v e l s . P o r t i o n s o f t h e 1950 a i r photographs o f t h i s a r e a ( a t an o r i g i n a l s c a l e o f 1:44,000) are shown on P l a t e 12a. Remnants o f the t u r f w a l l s f o r m i n g the two houses can s t i l l be d i s c r i m i n a t e d , however c o a s t a l r e c e s s i o n has r e s u l t e d i n t h e e r o s i o n o f the seaward w a l l and major p o r t i o n s o f t h e s i d e w a l l s o f one o f the houses. An e x t e n s i v e s e a r c h o f the o f f i c i a l r e p o r t s and the p o p u l a r a c c o u n t s o f the e x p e d i t i o n ( i n c l u d i n g D e s b a r a t s , 1916, 134 1950 scale: 1cm = 335 m (1.3 times enlarge-ment) Remnants of rear and side walls extend approximately 3.5 to 4.5 meters from edge of bank. ^^^^^ Plate 12. Sequential a i r photographs of the 1913-1918 Canadian A r c t i c Expedition's base camp located 8 km east of Cape K e l l e t . 135 1917, 1918; Anderson, 1917; W i l k i n s , 1917; and S t e f a n s s o n , ] 1918a, 1918b, 1921a, 1921b), f a i l e d t o l o c a t e a good d e s c r i p t i o n o r photograph o f t h i s s i t e a t the time o f c o n s t r u c t i o n , and thus a b s o l u t e r a t e s o f r e c e s s i o n s i n c e 1915 cannot be c a l c u l a t e d . Subsequent photographs t a k e n i n 1961 are shown on P l a t e 12b. The s c a l e o f t h i s photography ( o r i g i n a l l y 1:103,000) i s s u f -f i c i e n t l y s m a l l and the r a t e s o f r e t r e a t a r e s u f f i c i e n t l y s l o w t h a t c o a s t a l r e c e s s i o n o v e r the p e r i o d o f 1950 t o 1961 i s u n d e t e c t a b l e by c o m p a r a t i v e a i r photograph a n a l y s i s . When the "Mary Sachs" s i t e was v i s i t e d i n 1975, c o n t i n u i n g c o a s t a l r e c e s s i o n had r e s u l t e d i n t h e complete e r o s i o n o f t h e s i d e w a l l s o f t h e f o r w a r d h u t , w i t h o n l y a p o r t i o n o f the r e a r w a l l s t i l l b e i n g i n t a c t , as i l l u s t r a t e d on P l a t e 12c. D e t a i l e d measurements from t h e 1:44,00 0 photography i n d i c a t e t h a t the s i d e w a l l s o f the hut were 3.5 t o 4.5 m l o n g i n 1950. Thus the a p p a r e n t c o a s t a l r e t r e a t i n the p e r i o d between 1950 and 1975 i s a p p r o x i m a t e l y 3 t o 4 m , which c o r r e s p o n d s t o an average ann u a l r a t e o f r e c e s s i o n on the o r d e r o f 0.10 t o 0.15 m. F i e l d o b s e r v a t i o n i n 1975 i n d i c a t e d t h a t l i t t l e o r no e r o s i o n o f m a t e r i a l o c c u r r e d a t t h i s s i t e o v e r the summer p e r i o d and, t h e r e f o r e , t h e c a l c u l a t e d r e t r e a t l i k e l y r e p r e s e n t s t h e e f f e c t o f a number o f e p i s o d i c e v e n t s r a t h e r t h a n b e i n g the r e s u l t o f a n n u a l l y c o n s i s t e n t p r o c e s s e s o f e r o s i o n . As p r e v i o u s l y d i s c u s s e d , the so u t h - w e s t e r n p o r t i o n s o f Banks I s l a n d has one o f the l o n g e s t open water seasons and l a r g e s t f e t c h p o t e n t i a l o f any a r e a o f Banks I s l a n d ( E n v i r o n m e n t a l P r o t e c t i o n S e r v i c e , 1978). Thus the ob s e r v e d r e c e s s i o n a t "Mary Sachs" may be a r e a s o n a b l y r e p r e s e n t a t i v e e s t i m a t e o f the maximum average a n n u a l r a t e o f e r o s i o n w h i c h c o u l d be e x p e c t e d a t any 136 c o a s t a l s i t e composed o f c o a r s e t e x t u r e d , low i c e c o n t e n t , repose banks o f a s i m i l a r h e i g h t . D e s p i t e the l i m i t a t i o n s o f t h e d a t a from t h e "Mary Sachs" s i t e i t i s i n t e r e s t i n g t o compare the i n f e r r e d r a t e s o f r e t r e a t w i t h t h o s e c a l c u l a t e d f o r s i t e s w i t h s i m i l a r m o r p h o l o g i e s , but l o c a t e d i n more s o u t h e r l y l o c a t i o n s . Harper (1978a, 1978b) has conducted s t u d i e s o f e r o s i o n r a t e s a l o n g t h e Ch u k c h i Sea c o a s t n ear Barrow, A l a s k a . The c o a s t i n t h i s a r e a i s comprised o f 10 meter h i g h c l i f f s composed o f low i c e c o n t e n t , u n c o n s o l i d a t e d c l a y s , s i l t s and sands. The p r i m a r y p r o c e s s e s r e s p o n s i b l e f o r c o a s t a l r e t r e a t a re thought t o be surface~wash~and d e b r i s , a v a l a n c h i n g due t o o v e r s t e e p e n i n g of the c l i f f by l i t t o r a l p r o c e s s e s . The r e s u l t s o f c o m p a r a t i v e a i r photograph a n a l y s e s i n d i c a t e t h a t o v e r a 75 km s e c t i o n o f c o a s t , the average a n n u a l r e c e s s i o n amounts t o 0.31 m/year, based on a 27 y e a r p e r i o d o f r e c o r d . Harper i n d i c a t e s t h a t the open water season a l o n g the Chuk c h i Sea i s u s u a l l y l e s s t h a n t h r e e months i n d u r a t i o n , and the p e r i o d o f open w a t e r i s t h e r e f o r e r e l a t i v e l y s i m i l a r t o t h a t o c c u r r i n g a t "Mary Sachs". The 0.31 m/year average r e t r e a t on the Chu k c h i Sea c o a s t i s on the same o r d e r o f magnitude, though somewhat h i g h e r than the 0.10 t o 0.15 m/year c a l c u l a t e d a t "Mary Sachs". The a v a i l a b l e i n f o r m a t i o n does n o t a l l o w a d e t a i l e d r e c o n c i l i a t i o n o f th e s e two f i g u r e s , p a r t i c u l a r l y c o n s i d e r i n g t h a t the "Mary Sachs" d a t a i s based on measurements a t ; o n l y one l o c a t i o n . However d i s c u s s i o n s w i t h Dr. Harper i n d i c a t e t h a t w i t h i n h i s s t u d y a r e a the m a t e r i a l s a r e much f i n e r i n , t e x t u r e (50% f i n e s v e r s u s the sandy g r a v e l s a t "Mary S a c h s " ) , the water t e m p e r a t u r e s can be s u b s t a n t i a l l y h i g h e r (maximum o f up t o 6°C v e r s u s 1 t o 2°C) and t h e r e i s a g r e a t e r l i k e l i h o o d o f f a l l storms w i t h f e t c h s o f o v e r 200 km. Thus i t does n o t seem u n r e a s o n a b l e t o e x p e c t the u n c o n s o l i d a t e d , low i c e c o n t e n t c l i f f s on the C h u k c h i Sea c o a s t t o have h i g h e r r a t e s o f e r o s i o n than those a t the "Mary Sachs" s i t e on Banks: Island:. Rates of r e c e s s i o n o c c u r r i n g i n s i m i l a r m o r p h o l o g i c s e t t i n g s i n s o u t h e r n Canada a l s o appear t o be p o t e n t i a l l y h i g h e r than those o b s e r v e d a t "Mary Sachs". F o r example, P r e s t (1973, in_ Owens, 1979) d e t e r m i n e d t h a t the r a t e o f c o a s t a l r e c e s s i o n o c c u r r i n g o ver p o r t i o n s o f the e a s t c o a s t o f P r i n c e Edward I s l a n d (composed o f 2 t o 3 m h i g h d e p o s i t s o f u n c o n s o l i d a t e d sand and g r a v e l ) ranged from 0 m/year i n s h e l t e r e d l o c a t i o n s t o 2.75 m/year on exposed h e a d l a n d s ; w i t h an average a n n u a l r e c e s s i o n o f 0.67 m/year o v e r a 23 y e a r p e r i o d . Thus,on the b a s i s o f the a v a i l a b l e d a t a , the r a t e s o f r e t r e a t a s s o c i a t e d w i t h low i c e c o n t e n t m a t e r i a l s i n a r e l a t i v e l y exposed l o c a t i o n on Banks I s l a n d appear c o m p a r a t i v e l y s m a l l e r than the o b s e r v e d r a t e s o f c o a s t a l r e c e s s i o n o c c u r r i n g i n s i m i l a r t e x t u r e d m a t e r i a l s i n s o u t h e r n Canada. W h i l e t h i s c o n -c l u s i o n must be c o n s i d e r e d t e n t a t i v e u n t i l more d a t a becomes a v a i l a b l e , the l ower r a t e s o f r e t r e a t a l o n g t h e c o a s t s o f Banks I s l a n d are n o t unexpected c o n s i d e r i n g t h e r e l a t i v e l y s h o r t e r p e r i o d s o f open water and s m a l l e r f e t c h e s o c c u r r i n g i n the s t u d y a r e a , t h e s t a b i l i z i n g a f f e c t o f pore i c e o c c u r r i n g w i t h i n sand and g r a v e l d e p o s i t s and the p r o t e c t i o n from e r o s i o n r e s u l t i n g from t h e l o c a l i z e d d e p o s i t s o f snow which f r e q u e n t l y b l a n k e t the c o a s t w e l l i n t o mid-summer. N i v a t i o n H o l l o w s Headward r e c e s s i o n was m o n i t o r e d a t f o u r s i t e s w i t h w e l l de-v e l o p e d • l o n g i t u d i n a l n i v a t i o n .hollows.. D e s p i t e the l a r g e volumes o f 138 sediment w h i c h were produced from t h e s e f e a t u r e s , no n e t r e t r e a t was o b s e r v e d a t any o f t h e l o c a t i o n s when the s t u d y ended i n mid-August. Thus s l o p e r e a d j u s t m e n t t o the i n f e r r e d o v e r s t e e p e n i n g may n o t o c c u r on an a n n u a l b a s i s . A v i s u a l e s t i m a t e o f the amount of'headward r e c e s s i o n n e c e s s a r y t o r e s u l t i n a s t a b l e p r o f i l e a t one o f t h e l a r g e h o l l o w s i l l u s t r a t e d on P l a t e 6b was i n the o r d e r of' c e n t i m e t e r s . " However- t h i s l i k e l y r e f l e c t s more than one summer's sediment y i e l d . .The o t h e r t h r e e s i t e s were s u b s t a n t i a l l y more s t a b l e >and would'not be e x p e c t e d . t o show a n e t r e c e s s i o n e v e r y y e a r . R e t r o g r e s s i v e Thaw Flow S l i d e s E r o s i o n r a t e s a t s i x r e t r o g r e s s i v e thaw f l o w s l i d e s were m o n i t o r e d , as summarized on T a b l e X I , and showed a v a r i e t y o f r e c e s s i o n r a t e s depending upon t h e i r l o c a t i o n and i c e c o n t e n t . S i t e s on the west and n o r t h c o a s t s appeared r e l a t i v e l y i n a c t i v e , p o s s i b l y r e f l e c t i n g t h e i r lower i c e c o n t e n t s , the e f f e c t o f w e s t e r l y winds b r i n g i n g c o l d a i r from o v e r the sea i c e , o r s m a l l e r r a d i a n t energy r e c e i p t s due t o i n c r e a s e d f o g o r c l o u d c o v e r a d j a c e n t t o the s e a . S i t e s i n the c e n t r e o f t h e i s l a n d and on the e a s t c o a s t had h i g h e r e r o s i o n r a t e s w i t h headward r e t r e a t o f g r e a t e r t h a n 4.0 meters b e i n g r e c o r d e d o v e r the summer. These h i g h e r r a t e s o f e r o s i o n appear t o be a r e s u l t o f b o t h the g e n e r a l l y g r e a t e r i c e c o n t e n t a s s o c i a t e d w i t h r e t r o g r e s s i v e thaw f l o w s l i d e s o c c u r r i n g w i t h i n the E a s t e r n M o r a i n a l B e l t and the N o r t h e r n C r e t a c e o u s Complex, and w i t h the importance o f a d v e c t i o n o f s e n s i b l e h e a t as an energy s o u r c e . O b s e r v a t i o n s on the e a s t e r n s i d e o f Banks I s l a n d by F r e n c h and E g g i n t o n (19 73) suggest t h a t the maximum r a t e o f h e a d w a l l r e t r e a t may be as h i g h as 6 t o 8 m/year, which i s comparable w i t h LOCATION COORDINATES PHYSIOGRAPHIC REGION OBSERVED ICE CONTENT OBSERVED RECESSION MAXIMUM AVERAGE (m) (m) D i s s e c t i o n Creek near the Mouth (see P l a t e 15.) D i s s e c t i o n Creek headwaters " I v i t a r u k R i v e r " (see P l a t e 2d.) Meek P o i n t (see P l a t e 2c.) Norway I s l a n d (see P l a t e l l g . ) 73° 17 119° 31 73° 36 118° 15 73° 23 120 18 n o r t h c o a s t , e a s t o f 74 B a l l a s t Brook R i v e r 27 122° 17 72° 54 125 05 73° 43 124° 40 N W N W N W N W N N o r t h e r n C r e t a c e o u s Complex Devonian P l a t e a u N N o r t h e r n C r e t a c e o u s W Complex NortheWestern C o a s t Western Lowlands Western Lowlands 98 73 42 h e a d w a l l 1975-1977 h e a d w a l l h e a d w a l l s i d e s 37 47 > 2.3 2 .4 0 .5 4.0 1.8 massive h e a d w a l l 1.1 i c e s i d e s 0.0 h e a d w a l l 3.7 h e a d w a l l 0.2 0.8 1.6 0.3 3.1 1.0 0.7 0.0 2 .6 s t a b l e n o t e : - " i c e c o n t e n t " i s e x p r e s s e d as a perc e n t a g e o f t h e sample d r y w e i g h t -"maximum r e c e s s i o n " r e f e r s t o t h e . l a r g e s t o b s e r v e d r e t r e a t a d j a c e n t t o one r e f e r e n c e p o i n t -"average r e c e s s i o n " r e f e r s t o the average, o b s e r v e d r e t r e a t a t s i t e s which were a c t i v e l y e r o d i n g - 1977 d a t a was s u p p l i e d by Dr. T. Day. The d a t a r e f l e c t the n e t r e c e s s i o n over a p e r i o d o f two y e a r s . TABLE X I : Observed r e t r e a t a t r e t r o g r e s s i v e thaw f l o w s l i d e s i t e s 140 t h e 3.5 t o 7 m/year o b s e r v e d i n the Mackenzie D e l t a a r e a by K e r f o o t and Mackay (1972), the 7 t o 10 m/year r e p o r t e d t o o c c u r i n the I s a c h s e n A r e a by Lamothe and S t . Onge (1961) and the 10 m/year o b s e r v e d near t h e Babbage R i v e r i n the n o r t h e r n Yukon by McDonald and Lewis (19 7 3 ) . Thus the c o m b i n a t i o n o f f i e l d d a t a and l i t e r a t u r e e v i d e n c e i n d i c a t e s t h a t r e c e s s i o n r a t e s f o r r e t r o -g r e s s i v e thaw f l o w s l i d e s can r e a c h 10 meters per season, w i t h v a r i a t i o n s r e f l e c t i n g m a t e r i a l s and l o c a l c l i m a t e . Comparative a i r photograph s t u d i e s i n d i c a t e the r a p i d i t y w i t h which r e t r o g r e s s i v e thaw f l o w s l i d e s can form and s t a b i l i z e , as w e l l as i l l u s t r a t i n g t h e u s e f u l n e s s o f even s h o r t time base s m a l l s c a l e photography i n s i t u a t i o n s o f v e r y r a p i d r e c e s s i o n . A good example o c c u r s on t h e south-west c o a s t where a l a r g e r e t r o g r e s s i v e thaw f l o w s l i d e i s e v i d e n t on the 1958 (1:60,000) photography, p o r t i o n s o f which are shown i n P l a t e 13a. Three y e a r s l a t e r t h e 1961 photography, a t an o r i g i n a l s c a l e o f 1:103,000 (shown i n P l a t e 13b), i n d i c a t e s t h a t the h e a d w a l l had r e t r e a t e d a p p r o x i m a t e l y 33 meters and t h a t the w i d t h o f the a c t i v e f a c e had d e c r e a s e d from 90 meters t o 30 m e t e r s . P h o t o -graphy t a k e n i n the f o l l o w i n g y e a r (1962, a l s o a t a s c a l e o f 1:103,000) shows t h a t the r e t r o g r e s s i v e thaw f l o w s l i d e had r e t r e a t e d a f u r t h e r 15 m e t e r s , s u b s t a n t i a l l y d e c r e a s e d i n w i d t h and a p p a r e n t l y s t a b i l i z e d , as shown on P l a t e 13c. The average r e c e s s i o n o v e r the 4 y e a r p e r i o d c o v e r e d by t h e photography i s t h u s 12 m/year. I f t h i s r a t e i s assumed t o be r e p r e s e n t a t i v e o f t h a t which o c c u r r e d o v e r t h e 400 m l o n g p a t h from t h e c o a s t t o the s t a b i l i z e d h e a d w a l l ; t h e n t h e t o t a l time r e q u i r e d f o r s t a b i l i z a t i o n i s a p p r o x i m a t e l y 30 y e a r s ; which i s s i m i l a r t o t h a t proposed by F r e n c h and E g g i n t o n (1973) . 141 1958 scale: 1cm = 280 m (2.1 times enlarge-ment) Note large active retrogressive thaw flow s l i d e . 1961 scale: 1cm = 600 m (1.7 times enlarge-ment) Fai l u r e has retreated approx. 33 meters. 1962 scale: 1cm = 550 m (1.9 times enlarge-ment) /F a i l u r e has retreated a further 15 meters and apparently s t a b i l i z e d . Plate 13. Sequential a i r photographs of a retrogressive thaw flow s l i d e located on the south-west coast, 20 km north-west of Masik River. 142 T h e r m o - e r o s i o n a l N i c h e s F i v e t h e r m o - e r o s i o n a l n i c h e s i t e s were v i s i t e d . The depth o f the u n d e r - c u t v a r i e d from 2 t o 4 meters a t 2 c o a s t a l s i t e s , t o up t o a t l e a s t 5 meters a t two o f the t h r e e r i v e r i n e l o c a t i o n s . T h i s r e l a t i v e l y deep u n d e r c u t t i n g may r e s u l t i n t h e c o l l a p s e o f s i g n i f i -c a n t amounts o f o v e r h a n g i n g m a t e r i a l , as i l l u s t r a t e d i n P l a t e 3b. However, as p r e v i o u s l y d i s c u s s e d , t h e r m o - e r o s i o n a l n i c h e s may t a k e more than one y e a r t o form and, s i m i l a r l y , i t may ta k e a number o f y e a r s f o r t h e m a t e r i a l i n the c o l l a p s e d b l o c k t o be removed from t h e base o f t h e s l o p e . O b s e r v a t i o n s i m m e d i a t e l y f o l l o w i n g a severe summer storm on the n o r t h c o a s t o f t h e m a i n l a n d i n the v i c i n i t y o f B a i l l i e I s l a n d ( p e r s . obs. 1971) i n d i c a t e t h a t t h e r m o - e r o s i o n a l n i c h i n g i n c o a s t a l l o c a t i o n s can cause e x t e n s i v e u n d e r c u t s and r e s u l t i n c o l l a p s e d b l o c k s much l a r g e r t h a n any o f thos e o b s e r v e d on Banks I s l a n d . A good example o f t h e p o t e n t i a l s i z e o f t h e r m o - e r o s i o n a l n i c h e s a t c o a s t a l s i t e s i s p r o v i d e d by G r i g o r y e v (1966 iin F r e n c h , 1976), who r e p o r t e d t h e o c c u r r e n c e o f 3 m h i g h and 20 m deep u n d e r c u t s i n n o r t h e r n S i b e r i a . S i m i l a r l y , o b s e r v a t i o n s by Yefimov and S o l o v ' e v (1951 in_ Yefimov, 1964) , Walker and Morgan (1964) , Czudek and Demek (1970) , and McDonald and Lewis (1973) , i n d i c a t e t h a t t h e r m o - e r o s i o n a l n i c h e s a l o n g r i v e r s can commonly r e a c h depths r a n g i n g from 2 t o 10 m. Thus t h e r m a l - e r o s i o n a l n i c h e f o r m a t i o n i n even moderate i c e c o n t e n t m a t e r i a l s can r e s u l t i n s i g n i f i c a n t " a m o u n t s o f l a t e r a l e r o s i o n . E o l i a n F e a t u r e s Rates o f d e f l a t i o n and d e p o s i t i o n were measured a t t h r e e 143 s i t e s s i m i l a r t o t h a t shown on P l a t e 10. Net e r o s i o n o f 4 t o 8 cm d u r i n g t h e s p r i n g was r e c o r d e d a t two o f the s i t e s , w i t h sub-sequent d e p o s i t i o n o f 2.5 t o 4 cm o c c u r r i n g d u r i n g t h e co u r s e o f the summer. Q u a n t i t i e s o f e o l i a n t r a n s p o r t e d o r g a n i c and m i n e r a l i n c l u -s i o n s were f r e q u e n t l y o b s e r v e d i n l o c a l i z e d d e p o s i t s o f snow. An e x c e p t i o n a l case i s i l l u s t r a t e d on P l a t e 14 where e o l i a n t r a n s p o r -t e d sand made up a s i g n i f i c a n t p o r t i o n o f the "snow" d e p o s i t e d i n th e c h a n n e l o f a s m a l l stream l o c a t e d a d j a c e n t t o an u n v e g e t a t e d sandy f l u v i a l t e r r a c e . Thus t h e o b s e r v a t i o n s i n d i c a t e t h a t e o l i a n p r o c e s s e s a r e l o c a l l y i m p o r t a n t and can r e s u l t i n s i g n i f i c a n t amounts o f sediment p r o d u c t i o n . O r g a n i c F e a t u r e s C o a s t a l r e c e s s i o n over the summer p e r i o d was m o n i t o r e d a t an o r g a n i c r i c h s i t e l o c a t e d on t h e west c o a s t o f Banks I s l a n d , j u s t s o u t h o f B e r n a r d R i v e r . Measurements o v e r an a p p r o x i m a t e l y 100 meter l o n g s t r e t c h o f c o a s t i n d i c a t e d t h a t the s e a s o n a l r e t r e a t was l o c a l l y v a r i a b l e , r a n g i n g from 0 t o 0.5 me t e r s . T h i s s i t e i s t y p i c a l o f t h e low l y i n g o r g a n i c r i c h t e r r a i n o c c u r r i n g a d j a c e n t t o the mouths o f many o f the major west c o a s t r i v e r s . S a t e l l i t e imagery i n d i c a t e s t h a t t h e r e g i o n s " adjaceh't-to t h e s e r i v e r s have a l o n g e r t h a n average p e r i o d o f open w a t e r . Thus t h e range i n magnitude o f o b s e r v e d r e c e s s i o n i s l i k e l y n o t u n u s u a l f o r such a r e a s . A nother o r g a n i c r i c h s i t e l o c a t e d on t h e o u t s i d e o f a meander bend (shown i n P l a t e 9) underwent no e r o s i o n o v e r the summer and i n d i c a t e s t h e p o t e n t i a l l y s t a b i l i z i n g e f f e c t o f a c o h e r e n t v e g e t a t i o n c o v e r . 1 4 4 Note: The mixture of sand and snow at the base of the tundra probe has been deposited by wind. The surface layers of sand resulted from f l u v i a l transport and deposition. Plate 14. An exceptional concentration of wind blown sand associated with l o c a l i z e d deposits of snow. 145 Summary Ta b l e X I I l i s t s t h e r e l a t i v e o r d e r s o f magnitude f o r a n n u a l r a t e s o f r e c e s s i o n o r downslope movement a s s o c i a t e d w i t h banks o r s l o p e s o f v a r y i n g morphology. E r o s i o n r a t e s have been g e n e r a l i z e d from t h e p r e v i o u s l y d i s c u s s e d f i e l d o b s e r v a t i o n s , a i r photograph s t u d i e s and l i t e r a t u r e r e v i e w s ; w i t h the t a b u l a t e d v a l u e s b e i n g r e p r e s e n t a t i v e o f t h e l a r g e s t r e c e s s i o n s o r movements which have been o b s e r v e d i n y e a r s o f a c t i v e r e t r e a t . The number o f o b s e r v a t i o n s and p e r i o d s o f r e c o r d are q u i t e l i m i t e d f o r most m o r p h o l o g i c c l a s s e s and thus subsequent i n v e s t i -g a t i o n s may r e s u l t i n t h e r e v i s i o n o f some o f t h e s e f i g u r e s . However w i t h i n the c o n t e x t o f t h e p r e s e n t s t u d y t h e t a b u l a t e d v a l u e s a r e s u f f i c i e n t t o i n d i c a t e the r e l a t i v e d i f f e r e n c e s i n o b s e r v e d e r o s i o n r a t e s f o r d i f f e r e n t m o r p h o l o g i c c l a s s e s . I t s h o u l d be n o t e d t h a t the r a t e o f l a t e r a l . , d i s p l a c e m e n t o f a r i v e r o r c o a s t c a n n o t'always be d i r e c t l y c o r r e l a t e d w i t h the l i s t e d r e s u l t s , as i t i s g e n e r a l l y o n l y a t s i t e s formed by repose banks, o r g a n i c d e p o s i t s , t h e r m o - e r o s i o n a l n i c h e s and some r e t r o g r e s s i v e thaw f l o w s l i d e s t h a t the o b s e r v e d r e c e s s i o n c o r r e s p o n d s t o an a c t u a l s h i f t i n t h e p o s i t i o n o f a r i v e r b a n k o r c o a s t l i n e . I n a l l o t h e r c a s e s the r a t e s o f r e c e s s i o n o r move-ment r e f e r t o t h e removal o f v a r y i n g t h i c k n e s s e s o f s u r f a c e o r near s u r f a c e m a t e r i a l . Thus the a c t u a l d i s p l a c e m e n t r a t e o f a c o a s t a l o r r i v e r b a n k formed by one o f t h e r e m a i n i n g m o r p h o l o g i c ty p e s i s c o n s i d e r a b l y s m a l l e r t h a n t h a t i n d i c a t e d by the t a b u l a t e d f i g u r e s . The a s s o c i a t e d r a t e s o f n e t d i s p l a c e m e n t would t h e r e f o r e be g e n e r a l l y q u i t e s m a l l and thus t h e i r measurement would r e q u i r e r e p e a t e d o b s e r v a t i o n s o v e r c o n s i d e r a b l e p e r i o d s o f t i m e . 146 r a t e s o f r e c e s s i o n Morphology o r downslope movement (m/year) s o l i f l u c t i o n s l o p e s 0 .01-0.1 downslope movement e o l i a n f e a t u r e s 0 .01-0.1 s u r f a c e e r o s i o n n i v a t i o n h o l l o w s 0 .01-0 .1 h e a d w a l l r e t r e a t repose f e a t u r e s •o .1 -1.0 l a t e r a l r e c e s s i o n o r g a n i c f e a t u r e s 0 I .1 -1.0 -10 l a t e r a l r e c e s s i o n r e t r o g r e s s i v e thaw f l o w s l i d e s 1 nl,-10 ,,0-lu h e a d w a l l r e t r e a t neaawai.'. - • -t h e r m o - e r o s i O n a l n i c h e s 1 ? U l i i o T a +• s ' " a r - ' - •- . . l a t e r a l r e c e s s i o n s k i n f l o w s 10-1000 (?) downslope movement d u r i n g i n i t i a l f a i l u r e n o t e : The d a t a on which t h i s t a b l e i s based a r e d i s c u s s e d i n the t e x t . The t a b l u a t e d v a l u e r e p r e s e n t s t h e average annu a l r a t e o f r e t r e a t o r downslope movement which might be e x p e c t e d t o o c c u r o v e r a r e l a t i v e l y l o n g t i m e p e r i o d a t an a c t i v e s i t e . However f a i l u r e i s f r e q u e n t l y e p i s o d i c and t h u s no r e c e s s i o n o r r e t r e a t may be ob s e r v e d i n some y e a r s . TABLE X I I : R e l a t i v e o r d e r s o f magnitude f o r a n n u a l r a t e s o f r e c e s s i o n o r downslope movement a s s o c i a t e d . w i t h banks o r s l o p e s o f v a r y i n g morphology. 147 4.2 TIMING OF SEDIMENT PRODUCTION The d a t a p r e s e n t e d i n S e c t i o n 4.1 i l l u s t r a t e t he v a r i a t i o n i n r a t e s o f e r o s i o n a s s o c i a t e d w i t h banks o r s l o p e s o f v a r y i n g morphology. S i m i l a r l y t he s e a s o n a l t i m i n g o f sediment p r o d u c t i o n appears s u b j e c t t o between morphology v a r i a t i o n . The o b s e r v a t i o n s u n d e r t a k e n f o r t h i s p r o j e c t were i n t e n d e d t o i n d i c a t e t h e n e t s e a s o n a l r e c e s s i o n and are t h e r e f o r e g e n e r a l l y u n s u i t a b l e f o r a d e t a i l e d d i s c u s s i o n o f t i m i n g . N e v e r t h e l e s s , the d a t a w h i c h a r e a v a i l a b l e i n d i c a t e t h a t t h e s e a s o n a l v a r i a t i o n i n f l u v i a l sediment l o a d f r e q u e n t l y does n o t d i r e c t l y c o r r e s p o n d w i t h the t i m i n g o f t h e r m o k a r s t a c t i v i t y and the subsequent i n t r o -d u c t i o n o f sediment i n t o the r i v e r c h a n n e l . The s e a s o n a l v a r i a t i o n s i n d i s c h a r g e , suspended sediment c o n c e n t r a t i o n and suspended sediment t r a n s p o r t o b s e r v e d on D i s s e c t i o n Creek- by Anderson (1978) are shown on F i g u r e 29. The maximum suspended sediment c o n c e n t r a t i o n s and t r a n s p o r t can be seen t o o c c u r d u r i n g t h e p e r i o d o f peak d i s c h a r g e i n mid-June, w i t h a subsequent ( p o o r l y d e f i n e d ) minor peak i n l a t e June. Water t e m p e r a t u r e s , c o l l e c t e d by Anderson, and a c a l c u l a t i o n o f p o t e n t i a l h e a t f l u x (on the b a s i s o f wa t e r temperature and d i s c h a r g e data) a r e a l s o shown on F i g u r e 29. The maximum w a t e r t e m p e r a t u r e s can be seen t o o c c u r i n l a t e June and c o r r e s p o n d w i t h t h e minor peak i n sediment l o a d . The p l o t o f s e a s o n a l v a r i a t i o n i n p o t e n t i a l h e a t f l u x appears t o i n d i c a t e t h a t two p e r i o d s o f maximum v a l u e s o c c u r a n n u a l l y ; one c o r r e s p o n d i n g t o the t i m i n g o f maximum d i s c h a r g e , and t h e o t h e r t o the p e r i o d o f maximum water t e m p e r a t u r e . However, as wa t e r t e m p e r a t u r e s were n o t measured d u r i n g the P-c M CD t o D P-CO cn CD o rt P- 3 0 3 r t O O t i (D CD £ P> r t CD P. r t CD 3 1 3 (D t i 0) r t 3 i-i CD CD cn o 3 CD < PJ P-CD f t P-o 3 P-3 0J P-cn o 3* JD t i iQ CD CD 3 D . fD 3 O ft CD 3 tn 3 cn c+TJ 3" CD PJ f t (D 3 CL CD D i cn CD D -t-h P-3 X o tr cn CD P. < CD 3 c t f t t i PJ 3 cn CD V D - O t i r t p -3 3 O rt CD CD O rt rt CD CD t i f t CD 3 T J CD t i 3" CD PJ P> f t f t 3 t i CD PJ 3 D i Mi P 1 3 X 3* PJ D i cn p -cn o 3" PJ t i iQ CD Cu PJ r t P) CD ft) 3 CD cn f t p -3 JD rt CD D< O 3 f t cr CD tr PJ cn p -cn O Ml l €. PJ c t CD t i r t CD 3 T i CD t i PJ r t 3 M CD D i P-cn o 3" PJ t i iQ CD PJ 3 D i cn CD D i P-3 CD 3 f t D i PJ f t PJ PJ M CD t i O 3 P o t e n t i a l h e a t f l u x ( j o u l e s / s e c ) x 10~ 8 o CH 3 3 CD c_i C P" > 3 0 • 1 I I L _ J i m H ' ' ' ' r o c\ o ' i i i i r o o _ i Water t e m p e r a t u r e (°C) P 1 H 1 O W CTi v D r O U l ' ' I I L _ cn gal CD t> C - l 3 -P 1 > D i s c h a r g e (m /sec) and suspended s e d i m e n t c o n c e n t r a t i o n (mg/l) t o J i m o Suspended sediment t r a n s p o r t (kg/sec) o 149 p e r i o d o f maximum d i s c h a r g e , the c o m p a r a t i v e s i z e o f t h e s e two e v e n t s i s unknown. I n any c a s e , on t h e b a s i s o f t h e a v a i l a b l e d a t a , two p e r i o d s o f peak t h e r m a l e r o s i o n s u s c e p t i b i l i t y appear t o o c c u r w i t h i n the r i v e r c h a n n e l , and t h e s e c o r r e s p o n d t o the ob s e r v e d peaks i n sediment t r a n s p o r t . P l a t e s 15a t o e i l l u s t r a t e t he s e a s o n a l v a r i a t i o n s i n mor-pho l o g y o c c u r r i n g a t t h e o u t s i d e o f a meander bend l o c a t e d 1 km upstream o f t h e gauge on D i s s e c t i o n Creek. The m a t e r i a l s a t t h i s s i t e a r e composed o f c o l l u v i a t e d h i g h i c e c o n t e n t t i l l o v e r l y i n g l o wer i c e c o n t e n t f l u v i a l d e p o s i t s ; w i t h the t i l l u n i t b e i n g s u b j e c t t o b o t h t h e r m a l e r o s i o n and t h e r m o k a r s t . D u r i n g the p e r i o d o f i n i t i a l f l o w , i l l u s t r a t e d by P l a t e 15a (June 10, 1975), the bed and banks o f the c r e e k were w e l l p r o -t e c t e d by snow and i c e ; w i t h sediment s o u r c e s b e i n g l i m i t e d t o s u r f a c e r u n o f f ( i n c l u d i n g t h e l o c a l i z e d o c c u r r e n c e s o f mud f l o w s ) and e x p o s u r e s o f wind blown m a t e r i a l . The June 16 photograph ( P l a t e 15b) was t a k e n one day f o l l o w i n g the maximum r e c o r d e d d i s c h a r g e and suspended sediment t r a n s p o r t v a l u e s . T h i s p e r i o d c o r r e s p o n d s t o t h e i n i t i a l peak i n p o t e n t i a l h e a t f l u x and the r i v e r can be seen t o have eroded t h r o u g h the snow d e p o s i t s and be a c t i v e l y a t t a c k i n g the u n d e r l y i n g s e d i m e n t s . The mudflows have i n c r e a s e d i n s i z e and f r e q u e n c y , b u t s t i l l o n l y o c c u r l o c a l l y . The J u l y 1 s t photograph ( P l a t e 1 5 c ) , w h i l e c o r r e s p o n d i n g t o the p e r i o d o f maximum w a t e r t e m p e r a t u r e , was t a k e n f o u r days a f t e r t h e c a l c u l a t e d second maximum i n p o t e n t i a l h e a t f l u x . A l l remnants o f snow and i c e have d i s a p p e a r e d and t h e r m o k a r s t i s a c t i v e l y o c c u r r i n g , w i t h the m e l t w a t e r r e s u l t i n g from b o t h p r o c e s s e s h a v i n g caused t h e f o r m a t i o n o f numerous,small a l l u v i a l f a n s . However, due t o the s m a l l e r d i s c h a r g e and a) June 10, 1975 _ d i s c h a r g e : 10-20 m / s e c sediment c o n c e n t r a t i o n : 50-55 mg/l sediment t r a n s p o r t : 0.8-0.9 kg/sec water temperature: near 0°C not e : - e x t e n s i v e d e p o s i t s of snow and i c e - e o l i a n t r a n s p o r t e d sediments - l o c a l i z e d mud flow b) June 16, 1975 d i s c h a r g e : sediment c o n c e n t r a t i o n sediment t r a n s p o r t : water temperature: 110 m / s e c cn June 15 2,600 mg/l on June 15 2 60 kg/sec on June 15 between 1 and 4°C not e : - u n d e r c u t t i n g o f snow d e p o s i t s -more e x t e n s i v e mud flows - l o c a t i o n o f camera i n a l l other photographs c) J u l y 01, 1975 d i s c h a r g e : sediment c o n c e n t r a t i o n : sediment t r a n s p o r t : water temperature: 3.8 m / s e c 44 mg/l 0.17 kg/sec 4.7°C no t e : -disappearance of snow d e p o s i t s -mud f l o w s , a l l u v i a l / c o l l u v i a l fans e x t e n d i n g i n t o the r i v e r d) J u l y 18, 1975 d i s c h a r g e : approx. 0.5 m /sec sediment c o n c e n t r a t i o n : approx. 36 mg/l sediment t r a n s p o r t : water temperature: approx. 0.012 kg/sec approx. 6°C n o t e : - a c t i v e thermokarst - e x t e n s i v e sediment d e p o s i t i o n -low water v e l o c i t y e) J u l y 26, 1975 d i s c h a r g e : sediment c o n c e n t r a t i o n sediment t r a n s p o r t : water temperature: 0.3 m /sec 36 mg/l 0.012 kg/sec 6°C n o t e : -sediment s t o r a g e c o r r e s p o n d i n g t o are a under a t t a c k on P l a t e 15b P l a t e 15a to e. Seasonal v a r i a t i o n i n r i v e r bank morphology, D i s s e c t i o n Creek o 151 a s s o c i a t e d w a t e r v e l o c i t y , t h i s m a t e r i a l i s no l o n g e r b e i n g removed from the s i t e . R e connaissance f l i g h t s a l o n g t h e r i v e r s i n n o r t h e r n and w e s t e r n Banks I s l a n d , u n d e r t a k e n between June 16 and J u l y 1, i n d i c a t e d t h a t p r o c e s s e s o f l a t e r a l e r o s i o n were a c t i v e l y o c c u r r i n g d u r i n g t h i s p e r i o d . T h e r m o - e r o s i o n a l n i c h e s were w e l l d e v e l o p e d by June 26 and e x t e n s i v e sediment plumes extended downstream from t h e s e f e a t u r e s . These o b s e r v a t i o n s i n d i c a t e the w i d e s p r e a d importance o f t h e r m a l e r o s i o n as a sediment s o u r c e d u r i n g the time p e r i o d c o r r e s p o n d i n g t o the second maximum i n sediment t r a n s p o r t and a v a i l a b l e h e a t f l u x o b s e r v e d on D i s s e c t i o n Creek. Photographs t a k e n on J u l y 18 ( P l a t e 15e) i l l u s t r a t e t h e h i g h r a t e s o f t h e r m o k a r s t a c t i v i t y w hich o c c u r i n J u l y and c o n t i n u e i n t o e a r l y August. A s i m i l a r p a t t e r n was ob s e r v e d a t o t h e r r e t r o -g r e s s i v e thaw f l o w s l i d e s and has been w e l l documented by E g g i n t o n (19 76) . The r e s u l t i n g sediment can be seen t o be d e p o s i t e d w i t h i n the c h a n n e l a t a p o s i t i o n w h i c h c o r r e s p o n d s t o the a r e a o f f l u v i a l a t t a c k shown on the June 16 photograph ( P l a t e 15b). Thus, t h i s sediment w h i c h i s d e l i v e r e d t o the c h a n n e l i n m id- t o late:.summer i s n o t removed u n t i l the p e r i o d o f peak f l o w i n the f o l l o w i n g y e a r . A s i m i l a r p a t t e r n o f sediment s t o r a g e and p r o d u c t i o n was o b s e r v e d t o o c c u r a t o t h e r r e t r o g r e s s i v e thaw f l o w s l i d e s , and t o a s m a l l e r e x t e n t , w i t h i n n i v a t i o n h o l l o w s where l o c a l s u p p l i e s o f m e l t w a t e r w h i c h p e r s i s t e d i n t o mid-summer were o n l y s u f f i c i e n t t o move sediment as f a r as the s m a l l t r i b u t a r y c h a n n e l s l o c a t e d a d j a c e n t t o these f e a t u r e s . Thus the maximum r a t e s o f suspended sediment t r a n s p o r t o c c u r d u r i n g the p e r i o d o f peak d i s c h a r g e i n mid-June. As d i s c h a r g e s d e c r e a s e i n l a t e June and e a r l y J u l y the r e l a t i v e i m p o r t a n c e o f 152 f l u v i a l and thermal erosion decrease correspondingly. However sediment production due to thermokarst and nivation processes continues during the periods of low discharge i n late July and August and consequently results i n s i g n i f i c a n t amounts of sediment being stored u n t i l the following spring freshet. Thus the seasonal pattern of erosion and suspended sediment production does not d i r e c t l y correspond to the observed timing of sediment transport. 153 4.3 PREDICTING TERRAIN STABILITY ON THE BASIS OF BANK OR SLOPE MORPHOLOGY  The r e s u l t s o f the f i e l d and l a b o r a t o r y s t u d i e s d i s c u s s e d i n S e c t i o n Three have i n d i c a t e d t h a t t h e r e i s a r e l a t i o n s h i p between bank o r s l o p e morphology and t h e f a c t o r s o f i c e c o n t e n t , g r a i n s i z e and e x p o s u r e . The summary o f o b s e r v e d and r e p o r t e d n a t u r a l l y o c c u r r i n g r a t e s o f e r o s i o n p r e s e n t e d i n S e c t i o n Four f u r t h e r i l l u s t r a t e s t h a t morphology p r o v i d e s an i n d i c a t i o n o f t e r r a i n s t a b i l i t y . V e r t i c a l s t r a t i g r a p h y can a l s o be i n f e r r e d from morphology i n s i t u a t i o n s where one bank form i s superimposed on t o p o f a n o t h e r . By way o f example, photograph 16a i s from a s i t e where h i g h i c e c o n t e n t m a t e r i a l o v e r l i e s r e l a t i v e l y l o w e r i c e c o n t e n t d e p o s i t s . Photograph 16b i l l u s t r a t e s the c o n t r a s t i n g morphology r e s u l t i n g when the p o s i t i o n o f t h e h i g h and low i c e c o n t e n t m a t e r i a l s a r e i n t e r c h a n g e d . On t h e b a s i s o f t h e f i e l d , o f f i c e and l a b o r a t o r y s t u d i e s , a summary t a b l e o f r e p r e s e n t a t i v e bank o r s l o p e forms and t h e i r i m p l i c a t i o n s f o r t e r r a i n s t a b i l i t y i s p r e s e n t e d as T a b l e X I I I . I t s h o u l d a g a i n be n o t e d t h a t t h e p r e c i s i o n w i t h which morphology r e f l e c t s t h e a s s o c i a t e d m a t e r i a l p r o p e r t i e s i n c r e a s e s w i t h expo-s u r e , w i t h d e f i n i t i v e bank m o r p h o l o g i e s b e i n g more f u l l y e x p r e s s e d i n h i g h exposure e n v i r o n m e n t s . G e n e t i c o r i g i n has n o t been i n c l u d e d i n t h e t a b l e due t o the range o f m a t e r i a l s f o r m i n g banks o r - s l o p e s o f v a r y i n g morphology. 154 a) A p o l y g e n e t i c c o a s t a l morphology r e s u l t i n g f r om a r e t r o g r e s s i v e thaw f l o w s l i d e o v e r l y i n g an a n g l e o f r e p o s e bank. The upper f i n e t e x t u r e d f l u v i a l o r l a c u s t r i n e s e d i m e n t s a r e i c e r i c h , w h i l e t h e u n d e r -l y i n g f l u v i a l o r marine sands have a low t o moderate i c e c o n t e n t ( S o u t h - w e s t e r n c o a s t ) . b) A p o l y g e n e t i c r i v e r b a n k morphology r e s u l t i n g from an a n g l e of r e p o s e bank o v e r l y i n g a r e t r o g r e s s i v e thaw f l o w s l i d e . The upper f i n e t e x t u r e d d e p o s i t s a r e composed o f low i c e c o n t e n t t i l l . The u n d e r -l y i n g i c e r i c h m a t e r i a l i s t h o u g h t t o be l a c u s t r i n e i n o r i g i n ( P a r k e r R i v e r d e l t a ) . P l a t e 16. An example o f t h e use o f bank morphology an an i n d i c a t o r o f s u r f i c i a l s t r a t i g r a p h y . MORPHOLOGY C 0 NTENT TEXTURE angle of low f i n e s to cobbly repose gravels features e o l i a n low predominantly features sand or coarse textured s i l t n i v a t i o n low fines to sandy hollows gravels s o l i f l u c t i o n low to s i g n i f i c a n t slopes high percentage of fi n e textured sediments s o l i f l u c t i o n low to s i g n i f i c a n t slopes with medium percentage of skin flows f i n e textured sediments organic medium f i n e grained deposits to high containing organic i n c l u s i o n s thermo- medium sand or f i n e e r o s i o n a l to high texture with niches possible coarser i n c l u s i o n s r e t r o g r e s - high f i n e grained sive thaw sometimes con-flow s l i d e s t a i n i n g coarser i n c l u s i o n s TABLE XIII: Summary table showing the ASSOCIATED TERRAIN STABILITY l i k e l y slow rate of erosion. Associated t e r r a i n generally stable unless blanketed with high i c e con-tent m a t e r i a l . Texture and q u a l i t a t i v e erosion rates can frequently be estimated from a i r photos. •low rates of erosion and generally stable t e r r a i n . •associated with high rates of sediment production. A r e l i a b l e i n d i c a t o r of low i c e content m a t e r i a l . •currently undergoing a slow rate of downslope movement. W i l l p e r i o d i c a l l y have a high water content within the active layer and can be subject to skin flows i f melt-water i s l o c a l i z e d . Possible high i c e contents, at e i t h e r the base of the f r o s t table or i n the underlying permafrost. as above except that high pore water pressures may occur within the ac t i v e l a y e r . Prone to episodic rapid s u r f i c i a l downslope movement and to r e t r o -gressive thaw flow s l i d e formation i f high i c e content material i s subsequently exposed. -generally low to medium rates of erosion i n high expo-sure environments. May be r e l a t i v e l y stable u n t i l a threshold i s reached a f t e r which rapid rates of erosion could occur. -high rates of erosion can be expected to occur p e r i o d i c a l l y . The surrounding t e r r a i n w i l l be subject to thermokarst i f disturbed. -high rates of erosion can be expected. The surrounding t e r r a i n w i l l be subject to thermokarst and thermal erosion i f disturbed. The r e l a t i v e thickness and i c e content of unstable material can frequently be e s t i -mated from a i r photographs. l a t i o n s h i p between morphology and t e r r a i n s t a b i l i t y . SECTION FIVE 156 SUMMARY, CONCLUSIONS AND FUTURE STUDIES 5.1 SUMMARY AND CONCLUSIONS D u r i n g the summer o f 1975, f i e l d s t u d i e s were u n d e r t a k e n on Banks I s l a n d , N.W.T., t o i n v e s t i g a t e t he f e a s i b i l i t y o f u s i n g bank o r s l o p e morphology as an i n d i c a t o r o f t h e l a t e r a l s t a b i l i t y o f c o a s t a l and r i v e r i n e a r e a s l o c a t e d i n a r e g i o n o f c o n t i n u o u s p e r m a f r o s t . F i e l d o b s e r v a t i o n s and a s s o c i a t e d a i r p h o t o g r a p h i n t e r p r e -t a t i o n i n d i c a t e t h a t a wide range o f c o n d i t i o n s and p r o c e s s e s o c c u r w i t h i n the s t u d y a r e a . Repose f e a t u r e s , s o l i f l u c t i o n s l o p e s , s k i n f l o w s , r e t r o g r e s s i v e thaw f l o w s l i d e s , t h e r m o - e r o s i o n a l n i c h e s , o r g a n i c d e p o s i t s and d e f l a t i o n f e a t u r e s were a l l o b s e r v e d w i t h i n a v a r i e t y o f g e o t e c h n i c a l and p h y s i o g r a p h i c e n v i r o n m e n t s . Sampling c o n d u c t e d a t s i t e s r e p r e s e n t a t i v e o f each o f t h e s e f e a t u r e s i n d i c a t e s t h a t t h e morphology o f a bank o r s l o p e composed o f u n l i t h i f i e d sediments i s r e l a t e d t o the t e x t u r e and i c e c o n t e n t o f t h e a s s o c i a t e d m a t e r i a l s , and t o the r e l a t i v e e xposure o f t h e s i t e t o f l u v i a l o r l i t t o r a l p r o c e s s e s o f sediment r e m o v a l . M a t e r i a l g e n e s i s i s a l s o an i m p o r t a n t parameter t h r o u g h i t s a s s o c i a t e d e f f e c t on g r a i n s i z e and the p o t e n t i a l f o r s e g r e g a t e d i c e growth. N i v a t i o n , i c e wedges, v e g e t a t i o n c o v e r and e o l i a n p r o c e s s e s a l s o a f f e c t morphology i n v a r y i n g d e gree. V a r i o u s c o m b i n a t i o n s o f i c e c o n t e n t , g r a i n s i z e and exposure t o p r o c e s s e s o f sediment removal were found t o r e s u l t i n t h e f o r m a t i o n o f d i s t i n c t i v e bank o r s l o p e m o r p h o l o g i e s . I n low exposure e n v i r o n m e n t s , a l l c o m b i n a t i o n s o f i c e c o n t e n t and g r a i n s i z e tend t o r e s u l t i n angl e o f repose banks o r s o l i f l u c t i o n 157 s l o p e s o f r e l a t i v e l y s i m i l a r appearance. However i n l o c a t i o n s s u b j e c t t o more a c t i v e p r o c e s s e s o f sediment r e m o v a l , the d i s t i n c -t i v e c h a r a c t e r i s t i c s o f the u n d e r l y i n g m a t e r i a l a r e more f u l l y e x p r e s s e d . Thus, w i t h i n t h e s e c o n s t r a i n t s , bank o r s l o p e mor-phology p r o v i d e s an i n d i c a t i o n o f the m a t e r i a l t e x t u r e and i c e c o n t e n t w i t h i n t h e a d j a c e n t t e r r a i n . Rates o f e r o s i o n as d e t e r m i n e d from f i e l d s t u d i e s and the i n t e r p r e t a t i o n o f a e r i a l photographs were a l s o found t o have a s t r o n g r e l a t i o n s h i p w i t h bank o r s l o p e morphology. On the b a s i s o f the a v a i l a b l e d a t a e r o s i o n r a t e s i n low i c e c o n t e n t m a t e r i a l s appear comparable w i t h o r l o w e r t h a n t h o s e i n s o u t h e r n Canada. However t h e r m a l e r o s i o n and t h e r m o k a r s t a s s o c i a t e d w i t h i c e r i c h sediments was o b s e r v e d t o r e s u l t i n s u b s t a n t i a l l y h i g h e r e r o s i o n r a t e s , r a n g i n g up t o 10 m per y e a r . O b s e r v a t i o n s on the t i m i n g o f sediment movement i n d i c a t e t h a t the maximum r a t e o f sediment t r a n s p o r t c o i n c i d e s w i t h the p e r i o d o f peak snowmelt r u n o f f i n the s p r i n g . However sediment p r o d u c -t i o n due t o m e l t w a t e r a s s o c i a t e d w i t h l o c a l a c c u m u l a t i o n s o f wind blown snow and t h e r m o k a r s t p r o c e s s e s c o n t i n u e s w e l l i n t o the summer. As the p o s t s p r i n g peak d i s c h a r g e s a r e g e n e r a l l y incom-p e t e n t t o t r a n s p o r t t h i s m a t e r i a l , s i g n i f i c a n t amounts o f i n -c h a n n e l sediment s t o r a g e o c c u r on an a n n u a l b a s i s . The d i s t i n c t i v e bank o r s l o p e forms i d e n t i f i e d i n t h i s s t u d y are g e n e r a l l y o f s u f f i c i e n t s i z e t o be d i s t i n g u i s h e d on a e r i a l p hotography. Thus, a knowledge o f t h e r e l a t i o n s h i p between morphology and the c o r r e s p o n d i n g e n v i r o n m e n t a l and g e o t e c h n i c a l c h a r a c t e r i s t i c s has p r a c t i c a l a p p l i c a t i o n i n t h e a n a l y s i s o f t e r r a i n s t a b i l i t y . I n a d d i t i o n , r i v e r i n e and c o a s t a l a r e a s which a r e u n d e r g o i n g a p p r e c i a b l e r a t e s o f e r o s i o n f r e q u e n t l y have 158 composite morphologies r e f l e c t i n g the geotechnical c h a r a c t e r i s t i c s of the underlying sediments. In these circumstances, morphology can therefore provide an inexpensive indicator of subsurface stratigraphy i n the adjacent t e r r a i n . 159 5.2 FUTURE STUDIES The f i e l d work and l i t e r a t u r e r e v i e w u n d e r t a k e n i n c o n j u n c t i o n w i t h t h i s s t u d y i n d i c a t e t h a t many o f t h e p r o c e s s e s w h i c h have r e s u l t e d i n t h e bank and s l o p e m o r p h o l o g i e s d e s c r i b e d i n t h i s r e p o r t are r e l a t i v e l y p o o r l y u n d e r s t o o d . Thus d e t a i l e d s t u d i e s o f the f o l l o w i n g t o p i c s a re thought t o be p a r t i c u l a r l y w o r t h w h i l e , n o t o n l y due t o t h e i r s c i e n t i f i c m e r i t , b u t a l s o as they would e x t e n d the a v a i l a b l e knowledge upon wh i c h t o base r e c o n n a i s s a n c e g e o t e c h n i c a l i n t e r p r e t a t i o n s : 1) the d e t e r m i n a t i o n o f t h e s o u r c e s , s e a s o n a l regime and magnitude o f pore w a t e r p r e s s u r e s (or t e n s i o n s ) a s s o c i a t e d w i t h s o l i f l u c t i o n s l o p e s and s k i n f l o w s ; 2) the d e t e r m i n a t i o n o f the energy b a l a n c e a s s o c i a t e d w i t h t h e r m o - e r o s i o n a l n i c h e s and r e t r o g r e s s i v e thaw f l o w s l i d e s ; 3) the i n v e s t i g a t i o n o f the f a c t o r s c o n t r o l l i n g t h e p l a n i m e t r i c form o f n i v a t i o n h o l l o w s ; 4) the l a b o r a t o r y d e t e r m i n a t i o n o f the optimum g r a i n s i z e d i s t r i b u t i o n f o r s e g r e g a t e d i c e growth, under v a r y i n g c o n d i t i o n s o f overburden and pore w a t e r p r e s s u r e ; 5) the d e t e r m i n a t i o n o f A t t e r b e r g l i m i t s f o r m a t e r i a l s r e p r e -s e n t a t i v e o f t h e v a r y i n g m o r p h o l o g i e s d i s c u s s e d i n t h i s r e p o r t ; 6) the i n v e s t i g a t i o n o f a l t e r n a t i v e t e c h n i q u e s f o r the q u a n t i -f i c a t i o n o f e r o s i o n r a t e s . 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