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Paleohydrology of the Bella Coola River basin : an assessment of environmental reconstruction Desloges, Joseph R. 1987

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PALEOHYDROLOGY OF THE  BELLA COOLA RIVER BASIN  AN ASSESSMENT OF ENVIRONMENTAL RECONSTRUCTION By JOSEPH ROBERT DESLOGES B . E . S . , U n i v e r s i t y of W a t e r l o o , 1980 M . S c , U n i v e r s i t y of W i s c o n s i n - M a d i s o n ,  A THESIS  SUBMITTED  IN  PARTIAL F U L F I L L M E N T OF  THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY  in THE  FACULTY OF GRADUATE  (Department  We a c c e p t to  this  the  of  thesis  as  conforming  standard  OF BRITISH COLUMBIA  OCTOBER w  STUDIES  Geography)  required  THE UNIVERSITY  Joseph Robert  1982  1987 Desloges,  1987  In presenting degree at the  this thesis  in partial fulfilment  of the  University of British Columbia, I agree  requirements  for an advanced  that the Library shall make it  freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes department  or  by  his  or  her  may be granted by the head of my  representatives.  It  is  understood  that  copying  or  publication of this thesis for financial gain shall not be allowed without my written permission.  Department of  Geography  The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date  DE-6f.Vft-n  October 10, 1987  i i ABSTRACT Recent geomorphic and alpine  basin  are  investigated  p a l e o h y d r o l o g y . The response of change; 2) records and  hydrologic  aims of  selected  under the  integrative  t h i s research are:  b i o l o g i c a l and  to determine the  in the  environments of a  3)  theme of  to c h a r a c t e r i z e  the  g e o p h y s i c a l elements to r e c e n t  resolution  study area; and  1)  mid-latitude  and  length  to a s c e r t a i n  i n f e r r e d environmental change over the  of  the  Little  climatic  paleoenvironmental  s i g n i f i c a n c e of Ice Age  observed  interval.  2 Bella central  5050 km  Coola R i v e r d r a i n s  c o a s t of B r i t i s h  wide s c a l e  included:  Columbia. B i o l o g i c a l elements examined on  tree-growth  environments, damage to t r e e s variations  of g l a c i e r i z e d mountains along  in a v a r i e t y of  in temperature and  in g l a c i a l  and  primarily  basin-  moisture-stressed  fluvial  sedimentary d e p o s i t s and  G e o p h y s i c a l elements i n c l u d e  a  the  settings, soil  pollen  development.  g l a c i o - l a c u s t r i n e and  floodplain  sediments, g l a c i e r d e p o s i t s and  r i v e r channel morphology. A  retrospective  strategy  initially  relationships  was  adopted by  between s y n o p t i c period  of  testing  climate,  basin  instrument r e c o r d  f o r the  hydrology and  (1900  AD  element response d u r i n g  to p r e s e n t ) .  instrument environments were then made u s i n g the Events of s e v e r a l record.  Variations  behavior. Glaciers departures  persistent  appear to respond by  glacio-lacustrine  s h i f t i n g of  and  e p i s o d i c a l l y extreme  advancing or  the  Bella  retreating  for several  events, p a r t i c u l a r l y high-magnitude autumn f l o o d s , linked  pre-  in a response  and  in winter p r e c i p i t a t i o n p e r s i s t e n t  the  proxy d a t a .  s u b a l p i n e f i r growth,  glacier fluctuations  a combination of  Inferences about  c h a r a c t e r i s t i c a l l y mixed  in Douglas and  sedimentation rates, River r e f l e c t  types are  nature of  are  not  Coola  after  y e a r s . Extreme exclusively  to a p a r t i c u l a r set of mean c l i m a t i c d e p a r t u r e s . T h i s makes  inferences  from proxy data such as  f l o o d p l a i n d e p o s i t s and  flood-damaged  i i i vegetation d i f f i c u l t .  P e r i o d s of i n c r e a s e d f l o o d  r e l a t e t o an i n c r e a s e i n f l o o d p l a i n Except  a r e supposed t o  sedimentation.  i n very f a v o r a b l e c i r c u m s t a n c e s ,  not have the r e s o l u t i o n promised.  frequency  Climatic  paleoenvironmental  methods do  i n f o r m a t i o n r e c o v e r a b l e from  t r e e - r i n g data and g l a c i o - l a c u s t r i n e sediments i s of c o n s i d e r a b l y lower than annual as  resolution. S t a t i s t i c a l l y  independent  data sources  i n the b a s i n were l a r g e l y  i n the b a s i n reached  of the 19th  century  i n response  t o the l a s t  Little  300  t o kOO  Ice Age maxima i n the  t o below average  I n f e r r e d below average  temperatures and and 1855  AD. T r e e -  i n d i c a t e that  25 t o 30% g r e a t e r than the 1951-1980 mean.  temperatures  the b e g i n n i n g of the L i t t l e  i n the e a r l y  l8th c e n t u r y probably  Ice Age along the c e n t r a l  however, t h e r e was not a major response p o s i t i v e departures  1800  l i n e a l t i t u d e s on g l a c i e r s  p r e c i p i t a t i o n was on average  Little  restricted  p r e c i p i t a t i o n between approximately  r i n g data and e q u i l i b r i u m  signaled  data  Ice Age i n t e r v a l .  Most g l a c i e r s  above average  c l i m a t e models u s i n g proxy  v a r i a b l e s produce low l e v e l s of e x p l a i n e d v a r i a n c e . Proxy  years or L i t t l e  middle  based  in g l a c i e r s u n t i l  coast;  persistent  i n p r e c i p i t a t i o n o c c u r r e d . Recession o f g l a c i e r s  Ice Age maxima was slowed  by c o o l e r and wetter  from  c o n d i t i o n s between  I885 and 1900 AD. The p e r s i s t e n c e of warmer and d r i e r c o n d i t i o n s i n the first  h a l f of the  20th century was e x c e p t i o n a l i n comparison with  c l i m a t e o f the l a s t correspond  inferred  330 y e a r s . Major f l o o d s i n 1805/06, 1826, 1885 and 1896  to i n t e r v a l s of increased p r e c i p i t a t i o n .  iv PALEOHYDROLOGY OF THE BELLA COOLA RIVER BASIN: ASSESSMENT OF ENVIRONMENTAL RECONSTRUCTION  Chapter I: INTRODUCTION  (1.1) (1.2)  (1.3) (1.4) (1.5)  Systems Framework Operational Approaches Process models Empirical models Inductive models Objectives and Research Strategy Data Sources Organization  1 4 4 5 7 9 10 13  Chapter I I: STUDY AREA  (2.0) (2.1) (2.2) (2.3) (2.it) (2.5) (2.6) (2.7) (2.8) (2.9)  Location Physiography Bedrock Geology Late Quaternary Geology Climate Setting Hydrology Average Regime Major Floods During the 20th Century Sources and Transfer of Clastic Sediment Upland Sediment Sources Pedologic Setting Flora Settlement and Logging History  15 18 19 23 28 32 32 36 38 itO 46 48 50  Chapter III: HYDROPHYSICAL RECORDS OF ENVIRONMENTAL CHANGE: TESTS WITHIN THE INSTRUMENT PERIOD  (3.0) (3.1)  Introduction . Post-1945 Synoptic Climatology of the N.E. Pacific Sector Secular Trends in Temperature and Precipitation Comparison With Other Coastal Regions Atmospheric Circulation Frequency and Seasonal Persistence of Synoptic Types (3.2) Response of Hydrologic Variables to Climate Change Regional Winter Snowpack Spr i ng Runoff Spring and Summer Runoff - Bella Coola River Autumn Floods Flood Frequency (3.3) Long-Term, High Resolution Climate Analysis Comparisons With Other Regions (3.4) Conclusions  52 52 55 57 60 62 69 69 73 77 82 87 90 98 99  V  Chapter  IV:  GEOMORPHOLOGICAL EVIDENCE OF RESPONSE OF GEOPHYSICAL SYSTEMS TO ENVIRONMENTAL CHANGE:  TEST WITHIN THE  HISTORICAL RECORD  (k.O) (4.1)  Introduction G l a c i e r F l u c t u a t i o n s and R e c e n t C l i m a t e Mass B a l a n c e F l u c t u a t i o n s o f G l a c i e r s Mass B a l a n c e and C l i m a t e G l a c i e r Snout F l u c t u a t i o n s  (4.2)  Recent  (4.3)  (4.4)  S e d i m e n t S o u r c e s and P r o c e s s e s o f F l o o d p l a i n Development P r o c e s s e s of F l o o d p l a i n Development A l l u v i a l Sediment Sources E q u i l i b r i u m C o n d i t i o n s and I n f e r e n c e s f r o m C h a n n e l  (4.5) (4.6)  Morphology V e r t i c a l and L a t e r a l S t a b i l i t y o f B e l l a River I n f e r e n c e s From C h a n n e l M o r p h o l o g y Recent F l o o d p l a i n Sedimentation Conclusions  Chapter  (5.0) (5.1)  (5-2) (5.3)  (5.4)  (5.5)  V:  Fluctuations  in  Upland  Sediment  Transfers  VI:  121 121 127 131  Coola '  SEDIMENT0L0GICAL EVIDENCE OF ENVIRONMENTAL TESTS USING LAKE SEDIMENTATION RATES  132 137 140 141  CHANGE:  148 149 149 15^ 156 164 166 169 170 172 176 178 l8l 182  BIOLOGICAL EVIDENCE OF ENVIRONMENTAL CHANGE: TESTS USING VARIATIONS IN TREE GROWTH  (6.0) (6.1)  Introduction T r e e - G r o w t h and Methods  (6.2) (6.3)  Response C h a r a c t e r i s t i c s G r o w t h V a r i a t i o n s and C l i m a t e I n t e r i o r Douglas f i r s Subalpine f i r Development of T r a n s f e r F u n c t i o n s I n f e r e n c e s a b o u t 20th C e n t u r y H y d r o l o g y  (6.5)  115  Introduction P a t t e r n s o f S e d i m e n t a t i o n i n Ape L a k e Physical Setting Sediment F a c i e s R e c e n t and L o n g - T e r m S e d i m e n t a t i o n P e r i o d i c i t y o f S e d i m e n t a t i o n i n Ape L a k e Results C h r o n o l o g y and C o n t r o l s o f S e d i m e n t a t i o n R a t e s Recent Sedimentation Chronology C o n t r o l s of G l a c i o - L a c u s t r i n e Sedimentation Rates Inferences from Long-Term V a r i a t i o n s in G l a c i o Lacustrine Deposition Key E v e n t s H y d r o c l imati c Inferences Summary and C o n c l u s i o n s  Chapter  (6.4)  101 102 103 107 110  Change  184 184 187  Climate  191 194 19** 197 200 From  Tree-  vi  (6.6)  Rings Summer Runoff Rainstorm and Snowmelt F l o o d i n g Summary and C o n c l u s i o n s  Chapter V I I : INFERENCES  (7.0) (7.1)  (7.2)  (7.3)  208 208 212 215  ABOUT PRE-INSTRUMENT ENVIRONMENTS IN THE BELLA C00LA RIVER BASIN  Introduction Inferences of Environmental Change From Former G l a c i a l Extent Snowline F l u c t u a t i o n s and C l i m a t e Change Estimates of the Contemporary C l i m a t i c Snowline Estimates of Former Snowline and Inferences of H y d r o l o g i c Change L i t t l e Ice Age G l a c i a l Chronology Long-Term, Low and High R e s o l u t i o n B i o g e o p h y s i c a l Evidence F l u c t u a t i o n s i n Average Temperature and Precipitation Inferences from Lake Sedimentation High-Frequency V a r i a t i o n s i n T r e e Growth, Lake Sedimentation Rates and R e l a t e d H y d r o c l i m a t i c I nf erences E f f e c t s on the B e l l a Coola V a l l e y F l o o d p l a i n Age Evidence f o r a Long-Term Flood H i s t o r y Long-Term F l o o d p l a i n Sedimentation  217 217 218 221 223 227 230 231 235  237 240 240 245 246  Chapter V I I I : SYNTHESIS, CONCLUSIONS AND FUTURE DIRECTIONS (8.1)  (8.2)  (8.3)  M e t h o d o l g i c a l I m p l i c a t i o n s and B i o g e o p h y s i c a l Response Records Recent H y d r o c l imat i c Record Tree-Ring Response Record Glac i o - L a c u s t r i ne Response Record G l a c i e r Response Record A l l u v i a l Response Record General C o n c l u s i o n Recent Environments of the B r i t i s h Columbia Mid-Coast L i t t l e Ice Age Environment Future D i r e c t i o n s  REFERENCES  Appendix  (A.1)  A: RADIOCARBON DATES OF SELECTED DEPOSITS FROM THE BELLA COOLA BASIN  Radiocarbon Dating  252 253 252 256 257 259 26l 262 263 265  268  289 290  vi i  Appendix B: TEXTURAL AND MINERALOGICAL VARIATIONS OF THE BELLA COOLA VALLEY-FILL SEDIMENTS (B.1) (B.2) (B.3)  293 293 29^ 296 297  Introduction Bulk Gravel Samples Results M i n e r a l o g y of the V a l l e y - f i l l Results  Appendix C: RECENT PATTERNS OF SEDIMENTATION IN THE BELLA COOLA VALLEY (Cl) (C.2)  (D.l) (D.2) (D.3)  (E.1) (E.2)  MEASUREMENT 317  Introduction F i e l d and Laboratory Procedures Compaction and D i s t o r t i o n of Sediments P e r i o d i c i t y of S e d i m e n t a t i o n a t Ape Lake Results  Appendix E: TREE-RING SITE CHRONOLOGIES BELLA COOLA BASIN  (F.4)  318 318 319 321 324  IN AND NEAR  Introduction T r e e - R i n g Data A c q u i s i t i o n Tree-Ring Data  Appendix F: APPLICATION OF PALE0HYDR0L0GICAL TECHNIQUES FOR RECONSTRUCTING FORMER CONFIGURATIONS OF GLACIERS IN THE BELLA COOLA RIVER BASIN (F.l) (F.2) (F.3)  304 305 305 310 310 312 313 315  Introduction Sampling Design and Methods Rambeau Slough East Hagensborg Slough Walker Island Slough S n o o t l i Slough M c l e l l a n Road Slough  Appendix D: APE LAKE SEDIMENTS: SAMPLING, AND SUMMARY OF RESULTS  292  Accumulation Area R a t i o s . . . . . R e c o n s t r u c t i n g Former C l i m a t i c Snowlines G l a c i e r C h r o n o l o g i e s f o r the B e l l a Coola B a s i n Methods D e s c r i p t i o n of G l a c i e r C h r o n o l o g i e s a t S e l e c t e d Sites East Nusatsum V a l l e y T s i n i T s i n i and B o r e a l i s G l a c i e r s Fyles Glacier Deer Lake and Jacobsen G l a c i e r s  330 331 331 334  3^5 3^+6 3^9 350 351 355 355 358 3&0 3&1  vi i i LIST OF TABLES  (2.1)  (2.2)  (3-1) (3-2)  (3.3)  Summary of f o r m a t i o n s and c o n s t i t u e n t m i n e r a l assemblages of rock types found in the B e l l a Coola b a s i n a f t e r Baer (1973) and T i p p e r (1979)  22  Hydrometric data f o r s t a t i o n s Coola b a s i n  33  Climate Stations  in and near  in the B e l l a  the B e l l a  C l a s s i f i c a t i o n of s y n o p t i c c i r c u l a t i o n  Yarnel  (1983) and Barry et al. (1982)  Winter  p r e c i p i t a t i o n and s y n o p t i c type  Coola b a s i n types  from  65  66  frequencies (3.4)  Summer temperature  (3>5)  Winter  and s y n o p t i c type f r e q u e n c i e s  snow courses  in southwestern  70  (3-6)  Winter  (3>7)  S i g n i f i c a n t v a r i a b l e s and  (3.8)  f o r c l i m a t e - r u n o f f models Recognized trends in 20th century c o n d i t i o n s in the N.E. P a c i f i c s e c t o r  (4.2)  (4.3)  (4.4)  (4.5)  snowpack and  67  British  Columbia  (4.1)  5**  74  s y n o p t i c type f r e q u e n c i e s regression  coefficients 80 95  E m p i r i c a l response models f o r g l a c i e r net mass balance and c l i m a t e in southwestern B r i t i s h Columbia  105  Winter mass balance on B.C. south c o a s t a l and s y n o p t i c type frequency  108  Summer mass balance on B.C. s y n o p t i c type frequency  glaciers  coastal glaciers  and 109  Estimates of f l o o d p l a i n sediment volumes f o r the B e l l a Coola R i v e r between Atnarko/Talchako c o n f l u e n c e and mouth  126  M o r p h o l o g i c a l data f o r s e l e c t e d Coola R i v e r  136  reaches of B e l l a  (5.1)  Ape lake morphology  152  (5.2)  Pearson's r f o r v a r v e t h i c k n e s s and h y d r o c l i m a t i c var i a b l e s  173  ix  (6.1)  (6.2)  (6.3)  Summary of t r e e r i n g - w i d t h c h r o n o l o g i e s used i n t h i s study  190  C o r r e l a t i o n matrix between PC s c o r e s and h y d r o c l imati c v a r i a b l e s  202  C o e f f i c i e n t s of t r a n s f e r f u n c t i o n s f o r winter (Oct.-Apr.) p r e c i p i t a t i o n  203  APPENDIX TABLES (A.l)  Summary of r a d i o c a r b o n d e r i v e d dates  291  (B.1)  C l a s s i f i c a t i o n of b a s i c l i t h o l o g i c a l and m i n e r a l c h a r a c t e r i s t i c s of bedrock and a l l u v i a l sediments of major t r i b u t a r i e s to the B e l l a Coola R i v e r  299  C o n s t i t u e n t m i n e r a l s of f l o o d p l a i n and channel sediments f o r the B e l l a Coola v a l l e y  300  (B.2)  zone  (D.l)  Cesium-137 r e s u l t s f o r core 84E2  (D.2)  Ekman core data and s t a n d a r d i z e d chronology f o r Ape Lake  327  Summer and winter lamina cores from Ape Lake  328  (D.3)  (D.4)  (F.l)  (F.2)  326  thickness f o r percussion  S t a n d a r d i z e d s e d i m e n t a t i o n chronology percussion core  f o r Ape Lake  Accumulation glaciers  Canadian  area r a t i o s f o r s e l e c t e d  329  Summary of c h a r a c t e r i s t i c s of and e s t i m a t e d f o r s e l e c t e d t e r m i n a l moraines i n the B e l l a basin  3^7 ages Coola 356  X  LIST OF FIGURES (1.1)  (1.2)  (2.1)  (2.2)  (2.3)  (2.4)  (2.5)  A c o n c e p t u a l systems-framework model f o r environmental r e c o n s t r u c t i o n showing f u n c t i o n a l r e l a t i o n s h i p s and i n f e r e n t i a l pathways Temporal r e s o l u t i o n , c o n t i n u i t y and sampling i n t e r v a l for b i o g e o p h y s i c a l and h i s t o r i c a l / i n s t r u m e n t a l data sources  11  General l o c a t i o n of study locations  16  B e l l a Coola b a s i n and stations  (2.7)  Generalized c l a s t i c  (3.2)  (3-3)  (3-4)  mineral 20  in the lower S n o o t l i Creek  25  f o r s e l e c t e d c l i m a t e s t a t i o n s in  B e l l a Coola R i v e r annual  (3-1)  hydroclimate  Coola b a s i n and  Observed and i n f e r r e d v a l l e y - f i l l reaches of B e l l a Coola R i v e r near Hydroclimographs  sampling  17  Bedrock geology of the B e l l a sampling l o c a t i o n s  (2.6)  (2.9)  area and  l o c a t i o n of l o c a l  the v i c i n i t y of the B e l l a  (2.8)  3  31  Coola b a s i n hydrograph  f o r 1980  sediment r o u t i n g and  35  primary  t r a n s p o r t p r o c e s s e s in B e l l a Coola b a s i n I l l u s t r a t i o n s of primary c l a s t i c sediment sources for the h i g h e r - o r d e r f l u v i a l network in the B e l l a Coola b a s i n  39  44  Major sediment t r a n s f e r r o u t e s and s t o r a g e s i t e s f o r c l a s t i c sediment i n the B e l l a Coola b a s i n  47  Seasonal temperature and p r e c i p i t a t i o n d e p a r t u r e s for c o a s t a l and i n t e r i o r r e g i o n s of west c e n t r a l B r i t i s h Columbia between 1945 and 1983  56  G e n e r a l i z e d d e p a r t u r e s of w i n t e r p r e c i p i t a t i o n f o r southern, c e n t r a l and n o r t h e r n c o a s t a l areas of B r i t i s h Columbia. General d e p a r t u r e s i n sea s u r f a c e temperatures f o r the n o r t h e a s t e r n P a c i f i c ocean  58  500 mb s y n o p t i c s c a l e c i r c u l a t i o n p a t t e r n s which produce s p e c i f i e d c l i m a t e d e p a r t u r e s f o r c o a s t a l B r i t i s h Columbia  61  Winter snowpack d e p a r t u r e s f o r c o a s t a l and r e g i o n s of southwestern B r i t i s h Columbia  72  interior  xi (3-5)  (3.6)  (3.7)  (3-8)  (3-9)  S p r i n g r u n o f f d e p a r t u r e s f o r three c o a s t a l southwestern B r i t i s h Columbia  r i v e r s of 76  Ten day p r e c i p i t a t i o n time s e r i e s and a s s o c i a t e d r e c u r r e n c e i n t e r v a l s f o r f l o o d g e n e r a t i n g storms at B e l l a Coola  83  Frequency of autumn storm r u n o f f i n the B e l l a Homathko and Squamish R i v e r s between 19^5 and 1985  86  P a r t i a l d u r a t i o n curves of flow frequency of the B e l l a Coola b a s i n  Coola,  for rivers 89  Contoured s u r f a c e s of i n t r a - and i n t e r a n n u a l  climate  at B e l l a Coola: 1904-1983  91  (3-10) Contoured s u r f a c e s of i n t r a and i n t e r a n n u a l c l i m a t e at Big Creek:1904-1983 (4.1)  (4.2)  (4.3)  (4.4)  (4.5)  (4.6)  (4.7)  (4.8)  (4.9)  (5-1)  R e l a t i v e r a t e s o f advance and r e c e s s i o n f o s e l e c t e d g l a c i e r s i n the B e l l a Coola b a s i n West Saugstad G l a c i e r advances p o s i t i o n  in l a t e July  of 1985  112  showing 114  I n d i r e c t evidence f o r s e c u l a r changes in sediment d e l i v e r y to t r i b u t a r y channels and a l l u v i a l fans of B e l l a Coola River Morphology and channel zone sediments i n l a t e r a l l y s t a b l e and u n s t a b l e reaches of B e l l a Coola R i v e r A l l u v i a l sediment sources River f l o o d p l a i n  92  f o r the B e l l a  118  124  Coola 130  Water and bed s u r f a c e l o n g i t u d i n a l p r o f i l e s of B e l l a Coola R i v e r between Burnt Bridge Creek and r i v e r mouth  134  Changes in r i v e r planform and channel widths f o r a t r a n s i t i o n a l reach o f the B e l l a Coola River between 1945 and 1984  138  Topographic s e t t i n g of the McCall F l a t s backwater area o f B e l l a Coola River above Burnt Bridge Creek  142  S t r a t i g r a p h y and p o l l e n c o n c e n t r a t i o n s o f backwater sediments e x t r a c t e d from the McCall F l a t s ponds  144  L o c a t i o n and bathymetry o f Ape Lake, B r i t i s h Columbia  150  xi i  (5.2)  (5-3)  P h o t o g r a p h s o f t h e Ape L a k e b a s i n O c t o b e r 2 0 , 1984 g l a c i e r o u t b u r s t Facies distribution, sources  (5.4)  (5.6)  (5.7)  (5-9)  (5*10)  (5-11)  (6.1)  (6.3)  (6.4)  a t Ape Lake  155  157  Laminae t h i c k n e s s v e r s u s depth i n t h e e a s t b a s i n o f Ape L a k e  f o r Ekman  cores 159  Laminae t h i c k n e s s v e r s u s depth f o r p e r c u s s i o n c o r e s e x t r a c t e d f r o m t h e e a s t b a s i n o f Ape L a k e Mean g r a i n  size  versus  f o r samples  standard  taken  from  deviations  core  in grain  84C2  163  167  Composite sedimentation chronology s e d i m e n t s o f e a s t e r n Ape L a k e  171  f o r Ekman  sampled  Standardized sedimentation chronology f o r percussion c o r e r s a m p l e d s e d i m e n t s o f e a s t e r n Ape L a k e S e d i m e n t a t i o n a n o m a l i e s and f r e q u e n c y o f m i c r o l a m i n a t i o n s i n Ape Lake s e d i m e n t s c o m p a r e t o r u n o f f anomalies in the B e l l a Coola River  L o c a t i o n of Douglas f o r development  and s u b a l p i n e  f i r sampling  of t r e e - r i n g  chronologies  180  189  Response c h a r a c t e r i s t i c s o f growth i n Douglas F i r and s u b a l p i n e f i r t o v a r i a t i o n s i n s e l e c t e d h y d r o c l imati c v a r i a b l e s . . .  193  H i g h a n d low f r e q u e n c y g r o w t h Douglas f i r c h r o n o l o g i e s from area  196  s i g n a l s i n grouped the B e l l a Coola  High and low f r e q u e n c y growth s i g n a l s i n grouped s u b a l p i n e f i r c h r o n o l o g i e s from t h e B e l l a Coola 198  Reconstructed variations eastern  (6.6)  177  sites  area (6.5)  160  137 Concentration of Cs i n g r o u p e d c o u p l e t s f r o m c o r e 84E2 c o m p a r e d w i t h a t m o s p h e r i c f l u x r a t e t o L a k e Mi c h i g a n .  used (6.2)  s a m p l i n g ^ l o c a t i o n s and  and sediment  Lake  sizes  (5.8)  sediment  153  P h o t o g r a p h s o f Ekman c o r e s a n d c r o s s - c o r r e l a t i o n of laminae i n sediments from t h e e a s t b a s i n o f Ape  (5-5)  f o r runoff  after the flood  portions  Reconstructed variations eastern  portions  in annual  of the B e l l a  Coola  i n summer  of the B e l l a  Coola  precipitation for River  basin  205  temperature f o r River  basin  207  xi i i  (6.7)  (6.8)  O b s e r v e d , e s t i m a t e d and r e c o n s t r u c t e d summer r u n o f f i n d i c e s f o r B e l l a C o o l a R i v e r above Burnt B r i d g e Creek A c o m p a r i s o n o f i n t e r - and i n t r a a n n u a l persistence o f wet w i n t e r s a n s warms summers w i t h t r e e g r o w t h variability  (7-1)  210  and f l o o d i n g  Relationship for selected  on t h e  Bella  Coola River  213  b e t w e e n r e l a t i v e ELA and c l i m a t e indices g l a c i e r s in southwestern, British  Columbia (7.2)  Estimates of snowline for Bella  (7.3)  (7.5)  (7.6)  (7-7)  c o n t e m p o r a r y and f o r m e r climatic e a s t e r n and w e s t e r n p o r t i o n s o f the  Coola basin  Glacier and  (7.4)  220  moraine  selected  22k  chronology  areas  in  the  for  the  Canadian  Bella  Coola  basin  Cordillera  229  L o n g - t e r m , low f r e q u e n c y v a r i a t i o n s in r e c o n s t r u c t e d a n n u a l p r e c i p i t a t i o n and t h e f i r s t PC s c o r e o f subalpine f i r  232  L o n g - t e r m , high f r e q u e n c y v a r i a t i o n s in the first PC s c o r e s o f D o u g l a s and s u b a l p i n e f i r in the v i c i n i t y of the B e l l a C o o l a b a s i n  238  Spatial distribution the B e l l a f l o o d p l a i n  of  surfaces  of  different  ages  on 243  Stratigraphy, grain s i z e v a r i a t i o n s , organic matter c o n t e n t and p o l l e n c o n c e n t r a t i o n s i n v e r t i c a l a c c r e t i o n s e d i m e n t s o f t h e B r e k k e s i t e on t h e B e l l a Coola f l o o d p l a i n  248  APPENDIX FIGURES  (B.1)  Downstream the  (B.2)  (B.3)  Bella  variations Coola River  in and  grain  size  tributary  for  sediments  alluvial  of  fans  295  V a r i a t i o n s i n q u a r t z and l i t h i c f r a g m e n t content w i t h g r a i n s i z e in a l l u v i a l sand samples of B e l l a Coola River  298  T e r n a r y diagram showing d i s c r i m i n a n t functions d e v e l o p e d to d i s t i n g u i s h between sediment s o u r c e s u s i n g m i n e r a l c h a r a c t e r i s t i c s of alluvial sediments  301  xiv (C.1)  (C.2)  (C.3)  (D.l)  (F.l)  (F.2) (F.3)  (F.4) (F.5)  Sampling l o c a t i o n s of backchannel and s l o u g h of the B e l l a Coola v a l l e y  deposits 309  S t r a t i g r a p h y and p o l l e n c o n c e n t r a t i o n s f o r r e c e n t l y a c t i v e sloughs of the lower B e l l a Coola R i v e r (Rambeau, East Hagensborg and Walker I s l a n d s i tes)  311  S t r a t i g r a p h y and p o l l e n c o n c e n t r a t i o n s f o r r e c e n t l y a c t i v e backchannels of the lower B e l l a Coola R i v e r ( S n o o t l i and M c l e l l a n Rd. s i t e s )  31^  E s t i m a t e s of d i f f e r e n t i a l sediment compaction i n Ape Lake sediments u s i n g bulk d e n s i t y and laminae thickness  I l l u s t r a t i o n of a t y p i c a l g l a c i e r i n the B e l l a b a s i n used to i n f e r p a l e o e q u i l i b r i u m l i n e altitudes L o c a t i o n of moraine sampling s i t e s basin  i n the  322  Coola ik8  study 352  (a) Photograph of r e c e s s i o n a l moraines i n East Nusatsum v a l l e y and (b) l e f t l a t e r a l moraine of Tsini Tsini Glacier  357  Photographs of r e c e s s i o n a l moraine f i e l d s (a) B o r e a l i s and (b) F y l e s G l a c i e r s  359  for  Photographs of t e r m i n a l and r e c e s s i o n a l moraine f i e l d s for (a) Deer Lake and (b) Jacobsen Glaciers  362  XV  ACKNOWLEDGEMENTS  I would l i k e to thank D r . M i c h a e l Church who as a d v i s o r has g i v e n me tremendous encouragement throughout the c o u r s e of t h i s r e s e a r c h . As teacher and s c i e n t i s t , h i s s a g a c i t y has both i n s p i r e d and m o t i v a t e d me to a g r e a t e r u n d e r s t a n d i n g of geomorphology and the e a r t h s c i e n c e s . T h i s p r o j e c t has b e n e f i t e d s u b s t a n t i a l l y from the e x p e r i e n c e of D r . Robert G i l b e r t who was i n s t r u m e n t a l i n a l l phases of f i e l d work at Ape Lake and D r . June Ryder who p r o v i d e d i n v a l u a b l e guidance i n the c o l l e c t i o n and assessment of e v i d e n c e f o r g l a c i e r f l u c t u a t i o n s i n the study a r e a . D r . Glenn Rouse k i n d l y made a v a i l a b l e h i s p o l l e n l a b and p r o v i d e d d i r e c t i o n and a d i v c e i n the p r e p a r a t i o n and a n a l y s i s of the p o l l e n d a t a . D r s . John Hay, W i l l i a m Mathews and Olav Slaymaker reviewed e a r l y d r a f t s of the t h e s i s and made many v a l u a b l e s u g g e s t i o n s d u r i n g the e x e c u t i o n of t h i s r e s e a r c h . A b l e f i e l d a s s i s t a n c e was p r o v i d e d by Mark C a n t w e l l , L o m e D a v i e s , Dan Hogan, Tom M i l l a r d and Jane Weninger. I would a l s o l i k e to thank Sandy Hart f o r h i s a s s i s t a n c e i n p r e l i m i n a r y r e c o n n a i s s a n c e of B e l l a Coola R i v e r . Accommodation and v a l u a b l e i n s i g h t to the B e l l a Coola r e g i o n was g r a c i o u s l y p r o v i d e d by Tony and L i s K a r u p . A p p r e c i a t i o n i s extended to my graduate c o l l e a g u e s at UBC who were always w i l l i n g to d i s c u s s the r e s e a r c h problem at hand. D r a f t i n g of s e v e r a l diagrams was k i n d l y p r o v i d e d by Mary A r t m o n t . My g r e a t e s t thanks and a p p r e c i a t i o n goes to Pamela Moss des Loges who not o n l y endured my o f t e n cantankerous n a t u r e but a l s o a s s i s t e d i n the f i e l d and i n p r e p a r a t i o n of t h i s d i s s e r t a t i o n . F u n d i n g , i n the form of a p o s t - g r a d u a t e s c h o l a r s h i p from the N a t u r a l S c i e n c e s and Research C o u n c i l of Canada and a p r e - d o c t o r a l f e l l o w s h i p from the K i l l a m Memorial Fund f o r Advanced S t u d i e s i s g r a t e f u l l y acknowledged.  1  Chapter I INTRODUCTION  It has long been r e c o g n i z e d t h a t c e r t a i n b i o l o g i c a l and g e o p h y s i c a l components of the environment respond  i n a p r e d i c t a b l e manner to e x t e r n a l  f o r c e s . Remaining e v i d e n c e of these components a l l o w s i n f e r e n c e s about the d i s t r i b u t i o n and magnitude of f o r c e s i d e n t i f i c a t i o n of past e n v i r o n m e n t a l s e t t i n g s the a t t e n d a n t p h y s i c a l p r o c e s s e s ,  to be made  i n the p a s t . C o n f i d e n t r e l i e s upon some knowledge of  the n a t u r e of system responses and how  the system might be a f f e c t e d when c e r t a i n boundary c o n d i t i o n s are An i n t e g r a t e d  altered.  approach towards u n d e r s t a n d i n g e n v i r o n m e n t a l change p r i o r  to  the p e r i o d of instrument r e c o r d s u t i l i z e s e v i d e n c e from s e v e r a l b i o g e o p h y s i c a l subsystems to e v a l u a t e e r r o r s  involved in interpretations  purpose of t h i s t h e s i s the a n a l y s i s ,  i n order to a s s e s s the c o n s i s t e n c y of r e s u l t s and r e l a t e d  inferences.  and The  i s to a s s e s s the u t i l i t y of s e v e r a l methodologies i n  interpretation  geomorphological processes.  and r e c o n s t r u c t i o n of r e c e n t The t e s t f i e l d area  g l a c i e r i z e d a l p i n e b a s i n of w e s t - c e n t r a l  British  h y d r o l o g i c a l and  is in a m i d - l a t i t u d e , Columbia.  (1.1) Systems Framework In t h i s work the  i n t e r a c t i o n s amongst a t m o s p h e r i c , h y d r o l o g i c a l ,  b i o l o g i c a l and e a r t h s u r f a c e  processes  are a n a l y z e d around the  theme of p a l e o h y d r o l o g y . Leopold and M i l l e r term to d e s c r i b e "the  (195*0 f i r s t  i n t e r a c t i o n of c l i m a t e , v e g e t a t i o n ,  and r u n o f f o b t a i n e d under c l i m a t e s d i f f e r e n t Schumm (1965) suggested  this  stream regimen present".  to t h a t p o r t i o n of  h y d r o l o g i c a l c y c l e t h a t i n v o l v e s the movement of water the s u r f a c e of the e a r t h  introduced  from t h a t of the  t h a t the term be " r e s t r i c t e d  integrative  [and sediment]  the  over  . . . " . Brown (1982) has proposed t h a t the term be  2 even more n a r r o w l y d e f i n e d as "the a p p l i c a t i o n s of c o n c e p t s , methods and models d e r i v e d from h y d r o g e o m o r p h o l o g i c a l s t u d i e s sediments and forms of the p a s t " . T h i s l a t t e r frequent  emphasis on f l u v i a l  p r o c e s s e s but  to f l u v i a l  processes,  d e f i n i t i o n stems from  the  i s c o n s i d e r e d here as  u n n e c e s s a r i l y r e s t r i c t i v e . The common theme i n p a l e o h y d r o l o g i c a l s t u d i e s  is  an attempt to p r o v i d e a more comprehensive u n d e r s t a n d i n g of e n v i r o n m e n t a l settings  over l o n g e r time s c a l e s and w i t h  i n c r e a s i n g temporal r e s o l u t i o n .  It i s c o n v e n i e n t to view the environment as a system comprised of s e v e r a l morphogenetic components  l i n k e d by a s e r i e s of f u n c t i o n a l  relations  and a f f e c t e d by a s e t of boundary c o n d i t i o n s . F i g u r e 1.1 i l l u s t r a t e s morphogenetic subsystems of i n t e r e s t glaciolacustrine,  fluvial  in t h i s study:  four  glacial,  and mass w a s t i n g . A s e t of f u n c t i o n a l  relations  between the a t m o s p h e r i c environment and the e a r t h s u r f a c e environment can be d e f i n e d . These r e l a t i o n s are f o r m u l a t e d on the b a s i s of exchanges of energy and mass and are  i n f l u e n c e d by boundary c o n d i t i o n s such as  t o p o g r a p h i c and g e o l o g i c c o n t r o l s , n e o t e c t o n i c s and former g l a c i a t i o n . Energy from the a t m o s p h e r i c and h y d r o l o g i c a l components of f i g u r e 1.1 d r i v e s the system r e s u l t i n g i n the r e d i s t r i b u t i o n of mass and the f o r m a t i o n of new sedimentary d e p o s i t s .  Inferences  about former h y d r o l o g i c a l s e t t i n g s ,  t h e n , are made i n the r e v e r s e d i r e c t i o n from t h a t of the f u n c t i o n a l r e l a t i ons. The t r a n s f e r  of i n f o r m a t i o n between the h y d r o c l i m a t i c environment and  any one of the four morphogenetic subsystems subject  i d e n t i f i e d i n f i g u r e 1.1 i s  to a v a r i e t y of temporal and s p a t i a l f i l t e r i n g  w i t h i n any of the subsystems hydroclimatic processes,  integrate  or e v e n t s ,  the e f f e c t  of  effects.  Deposits  short-term  hence have a c h a r a c t e r i s t i c low  r e s o l u t i o n of the t r u e a m p l i t u d e and frequency of c l i m a t i c and h y d r o l o g i c variations.  For example, maximum advances of i c e are f r e q u e n t l y marked by  3  CLIMATE :  energy b a l a n c e water b a l a n c e • c i r c u l a t i o n regime  *  I  LAND SURFACE weatheri ng vegetation/ soi 1 s  RUNOFF/ STREAMFLOW  LAND USE SEDIMENT TRANSPORT  human decisions  \  \ GLACIER ACTIVITY  GLAC10LACUSTRINE PROCESSES  ALLUVIAL ACTIVITY  COLLUVIAL ACTIVITY  mass balance  physical 1imnology bathymetry  sediments, channel geometry  basin morphometry  "X" I moraines. till, outwash  floodplain and terrace a l 1 u v i um  1aminated lake sediments  _L_  1andslides/ rockslides earthflows  •  FUNCTIONAL RELATIONSHIP  •  INFERENTIAL PATHWAY  SEDIMENTARY DEPOSITS  Figure 1.1 F u n c t i o n a l and i n f e r e n t i a l pathways c o n n e c t i n g four morphogenetic subsystems of i n t e r e s t i n t h i s p r o j e c t . Not shown a r e boundary c o n d i t i o n s w h i c h i n c l u d e g e o l o g i c a l and n e o t e c t o n i c factors as w e l l as p a s t g l a c i a l a c t i v i t y ( a f t e r S t a r k e l and T h o r n e s , 1 9 8 l ) . Other subsystems not c o n s i d e r e d i n c l u d e e o l i a n , m a r i n e and glaciomarine environments.  it t e r m i n a l m o r a i n e s . However, f l u c t u a t i o n s movement may be a response  t o a c o m b i n a t i o n o f h y d r o c l i m a t i c changes which  occur over time s c a l e s much s h o r t e r f o r m a t i o n of t h e d e p o s i t , subaqueous  i n t h e d i r e c t i o n or r a t e o f i c e  than t h e i n t e r v a l r e q u i r e d f o r  in contrast,  l a n d s l i d e s , f l o o d d e p o s i t s or  s l o p e f a i l u r e s may r e p r e s e n t ' k e y e v e n t s '  without reference  to a  p a r t i c u l a r s e t of d e p a r t u r e s i n l o n g - t e r m mean c o n d i t i o n s of h y d r o c l i m a t e . These two s i t u a t i o n s , which g e n e r a l l y l i m i t t h e i n f e r e n c e s  t h a t can be  made, a r e commonly a s s o c i a t e d w i t h p r i m a r y m o r p h o l o g i c a l sources o f i n f o r m a t i o n and t h e r e f o r e A precursor  complicate the e x e r c i s e .  t o s u c c e s s f u l a p p l i c a t i o n of the model i n f i g u r e 1.1 t o  past environments  i s t h e i n t e r p r e t a t i o n of v a r i o u s m o r p h o l o g i c a l components  such as v e g e t a t i o n ,  soils,  s u r f a c e forms and sedimentary  (Gregory, 1983a). E n v i r o n m e n t a l r e c o n s t r u c t i o n s after  sequences  t h e n , can o n l y be made  a b s o l u t e and r e l a t i v e d a t i n g t e c h n i q u e s a r e a c c u r a t e l y a p p l i e d t o  sequences of sediment and p r e s e r v e d d e p o s i t i o n a l environments.  landforms which have c l e a r l y d e f i n e d  In t h i s c o n t e x t ,  a t r u e p a l e o h y d r o l o g i c a l model  is r a r e l y a c h i e v e d .  (1.2) Operational Approaches Brown (1982) suggested modeling can be u n d e r t a k e n :  t h a t t h r e e types of p a l e o e n v i r o n m e n t a l process,  e m p i r i c a l and i n f e r e n t i a l model  development. A m o d i f i e d v e r s i o n of t h i s scheme d i s c u s s e d here i n c l u d e s three general c a t e g o r i e s :  (1) p r o c e s s or p h y s i c a l models,  (2) e m p i r i c a l  models and (3) i n d u c t i v e m o d e l s .  Process Models The most d i f f i c u l t  of a l l t h r e e c a t e g o r i e s  i s t h e process model where  the f u n c t i o n a l r e l a t i o n s h i p s between v a r i o u s components o f the system a r e  5 q u a n t i f i e d and grouped t o form a g e n e r a l p h y s i c a l model which o p e r a t e s a c c o r d i n g t o p h y s i c a l and geochemical l a w s . The model i s c o n s t r u c t e d and c a l i b r a t e d under modern c o n d i t i o n s and then a p p l i e d t o past e n v i r o n m e n t s . The approach i s p u r e l y d e d u c t i v e and r e q u i r e s q u a n t i t a t i v e e s t i m a t e s o f input p a r a m e t e r s .  G e n e r a l c i r c u l a t i o n models a r e o f t h i s  type.  C l a r k e e t al. (1984) u t i l i z e a p r o c e s s - m o d e l , v e r i f i e d  u s i n g modern  outburst  f l o o d s , t o e s t i m a t e former d i s c h a r g e s o f ice-dammed g l a c i a l  Missoula  i n Washington s t a t e .  as g o v e r n i n g e q u a t i o n s  I c e - f l o w and heat t r a n s f e r  Lake  r e l a t i o n s a r e used  t o p r e d i c t the s i z e o f t h e s u b g l a c i a l d i s c h a r g e  t u n n e l . V a r i o u s parameters  such as l a k e volume, water  temperature  and i c e -  t h i c k n e s s a r e r e q u i r e d i n p u t v a r i a b l e s . Model s i m i l i t u d e and assumptions r e g a r d i n g i c e t u n n e l geometry and flow r e s i s t a n c e and Young  (1979). among o t h e r s ,  predict future  and former r u n o f f  remain p r o b l e m a t i c . Power  have used an i n t e g r a t e d watershed model t o from g l a c i e r - c o v e r e d c a t c h m e n t s . T h i s  type  of model i s c a l i b r a t e d a g a i n s t observed f l o w v a r i a t i o n s and a d j u s t e d accord i n g l y . The major assumptions u n d e r l y i n g p r o c e s s - m o d e l s a r e : (1) a l l dominant processes  have been i d e n t i f i e d and c o n t r i b u t i n g f a c t o r s p a r a m e t e r i z e d , o r ,  i n the case o f s i m u l a t i o n s , unknown but important f a c t o r s a r e c o n t r o l l e d ; (2) g o v e r n i n g r e l a t i o n s h i p s a r e p r o p e r l y c a l i b r a t e d f o r t h e expected and v a r i a n c e o f i n p u t d a t a ; the  range  and (3) t h e temporal and s p a t i a l r e s o l u t i o n o f  i n p u t data c o r r e s p o n d w i t h t h e c a l i b r a t i o n d a t a . V i o l a t i o n o f t h e f i r s t  or second assumption r e s u l t s  i n an u n r e l i a b l e model whereas v i o l a t i o n o f  the t h i r d assumption y i e l d s u n r e l i a b l e  Empirical  results.  Models  Though t h e d e d u c t i v e approach used i n process modeling i s a l s o t h e b a s i s f o r t h i s second group o f models, t h e u n d e r l y i n g p h y s i c a l p r o c e s s e s  6 are not q u a n t i f i e d . A p a r t i c u l a r s e t o f p r o c e s s e s g l a c i e r flow) attributes  (rainfall,  stream  flow,  i s r e l a t e d t o responses i n b i o l o g i c a l o r g e o p h y s i c a l  of the environment and then r e l a t i o n s h i p s a r e d e v e l o p e d , u s u a l l y  u s i n g s t a t i s t i c a l t e c h n i q u e s . The r e l a t i o n s a r e then  i n v e r t e d t o make  p r e d i c t i o n s o f former process based on response c h r o n o l o g i e s p r e s e r v e d i n the environment. These i n c l u d e t h e q u a n t i t a t i v e a n a l y s i s of v e g e t a t i o n growth p a t t e r n s , v a r i a b i l i t y  i n g l a c i o l a c u s t r i n e sedimentation, v a l l e y or  r i v e r channel morphology, p a l e o c h a n n e l s and f o s s i l Nominal,  fluvial  sediments.  i n t e r v a l o r r a t i o s c a l e data can be u s e d .  Mathewes (1973) and Mathewes and Rouse (1975) have q u a l i t a t i v e r e c o n s t r u c t i o n of Holocene p a l e o c l i m a t e s  attempted  i n t h e lower F r a s e r  V a l l e y of B r i t i s h Columbia u s i n g p a l e o e c o l o g i c a l e v i d e n c e p r e s e r v e d cores. Q u a n t i t a t i v e estimates  of temperature and p r e c i p i t a t i o n f o r the same  area and p e r i o d were then made u s i n g c a l i b r a t i o n t e c h n i q u e s s p a t i a l d i s t r i b u t i o n o f modern v e g e t a t i o n contemporary c l i m a t e s  in lake  is calibrated  (Mathewes and Heusser,  then used t o f o r m u l a t e t r a n s f e r  functions  i n which the  against  1981). These r e l a t i o n s a r e  i n order t o e s t i m a t e  former  h y d r o c l i m a t i c c o n d i t i o n s based on t h e i n f e r r e d p a l e o e c o l o g y . Two problems c o m p l i c a t e the " t r a n s f e r " a s s o c i a t i o n s . The f i r s t  of these r e l a t i o n s d e r i v e d from s p a t i a l is related  to the f a c t t h a t s p a t i a l v a r i a t i o n s i n  c l i m a t e can be g r e a t e r than those e x p e r i e n c e d a t a p a r t i c u l a r s i t e t i m e . The second i s t h a t f a c t o r s other  through  than the assumed dependent v a r i a b l e  ( i n t h i s case c l i m a t e ) may e x p l a i n a s i g n i f i c a n t p r o p o r t i o n o f t h e temporal v a r i a n c e and a r e not i n c l u d e d i n the development o f the t r a n s f e r  function  (Imbrie and Webb, 1983) . The major u n d e r l y i n g assumption i n t h e r e t r o s p e c t i v e a p p l i c a t i o n o f e m p i r i c a l models i s t h a t an e q u i l i b r i u m has been a c h i e v e d between a specific attribute  and a dominant p r o c e s s f o r both the c a l i b r a t i o n and  7 application adjust  i n t e r v a l s . C e r t a i n b i o l o g i c a l or geophysical a t t r i b u t e s  v e r y s l o w l y t o imposed change and thus may not r e f l e c t  frequency p e r t u r b a t i o n s  i n the system.  In c o n t r a s t ,  are r e p r e s e n t a t i v e  higher-  adjustments  r a p i d b u t s e n s i t i v e o n l y t o f o r c e s beyond an exceedence  may  may be  t h r e s h o l d and thus  of short-term conditions o n l y .  L i n e a r l e a s t - s q u a r e s s t a t i s t i c a l t e c h n i q u e s a r e commonly used  i n the  f o r m u l a t i o n o f e m p i r i c a l models. The a p p l i c a t i o n o f these r e l a t i o n s h i p s f o r environmental r e c o n s t r u c t i o n  i s based on t h e assumption t h a t t h e e x p l a i n e d  p o r t i o n of t h e t o t a l v a r i a n c e r e f l e c t s  the p r i m a r y response  characteristic  of the system and t h a t the r e s i d u a l v a r i a n c e i s random " n o i s e " . T h i s constraint  can s e r i o u s l y a f f e c t  the s i g n i f i c a n c e o f i n t e r p r e t a t i o n s  from a  l i n e a r model i f the system i s a l s o known t o respond s i g n i f i c a n t l y t o extreme d e p a r t u r e s .  These l e s s f r e q u e n t ,  higher magnitude events become  ' k e y ' elements which a r e l o s t i n the assumption o f l i n e a r i t y .  I n d u c t i v e Models  This category  i s based p r i m a r i l y on the i n d u c t i v e approach  s i t e - s p e c i f i c e v i d e n c e f o r drawing i n f e r e n c e s Sedimentary sequences  (1ithofacies)  about former  utilizing  environments.  and the remains or b y - p r o d u c t s of  b i o l o g i c a l a c t i v i t y a r e used t o r e c o n s t r u c t  a s e r i e s of p o s s i b l e  e n v i r o n m e n t a l c o n d i t i o n s . O r d i n a l and nominal s c a l e data a r e used frequently relate  and m o s t l y q u a l i t a t i v e r e s u l t s a r e a c h i e v e d .  Inferences  usually  t o a s p e c i f i c s e t of e n v i r o n m e n t a l c o n d i t i o n s such as s p a t i a l and  temporal v a r i a t i o n s glacier  or the c h r o n o l o g y and d i s t r i b u t i o n of  i c e movements.  Starkel character  in runoff,  (1984) has used v a r i o u s a l l u v i a l  sequences t o i n f e r the  o f c l i m a t e t r a n s i t i o n s over the Holocene Epoch i n c e n t r a l  Europe.  Ryder and Thomson (1986) have used s e v e r a l s o u r c e s o f e v i d e n c e from g l a c i a l  8 d e p o s i t s throughout southwestern B r i t i s h Columbia to i n f e r the t i m i n g and magnitude of g l a c i a l a c t i v i t y several d a t i n g techniques  i n p o s t - P l e i s t o c e n e t i m e . The a p p l i c a t i o n of  is c r u c i a l  for e s t a b l i s h i n g c h r o n o s t r a t i g r a p h i c  c o n t r o l both l o c a l l y and r e g i o n a l l y . P r e s e r v a t i o n of d a t a b l e m a t e r i a l s and i n a c c u r a c i e s a s s o c i a t e d w i t h r a d i o c a r b o n d a t i n g become major l i m i t a t i o n s of the e x e r c i s e . Commonly, p a r t i c u l a r l y f o r a l l u v i a l  sediments,  r e c o r d r e p r e s e n t s extreme or ' k e y ' events o n l y  the  stratigraphic  (e.g. flood  E r o s i o n a l h i a t u s e s or o t h e r u n c o n f o r m i t i e s may c o m p l i c a t e if  a s u b s t a n t i a l p r o p o r t i o n of the  otherwise d i s t u r b e d .  deposits). interpretations  i n t e r v e n i n g sequence i s m i s s i n g or  In t h i s way a s u b s t a n t i a l l y d i f f e r e n t  r e c o r d of  e n v i r o n m e n t a l change may e v o l v e u s i n g these data s o u r c e s . R e c o g n i t i o n of these d i f f e r e n c e s  i s important f o r s u c c e s s f u l model development.  In summary, e m p i r i c a l and i n d u c t i v e approaches,  despite  their  problems, are commonly employed to draw i n f e r e n c e s r e g a r d i n g past h y d r o l o g i c a l and c l i m a t o l o g i c a l c o n d i t i o n s i n the r e v e r s e d i r e c t i o n from t h a t of the u s u a l f u n c t i o n a l r e l a t i o n s . The p r o c e s s - b a s e d approach y i e l d s e s t i m a t e s of these f u n c t i o n a l r e l a t i o n s and, then the boundary c o n d i t i o n s and i n i t i a l  s t a t e a r e changed to approximate former e n v i r o n m e n t s . W h i l e  i n i t i a l l y more a t t r a c t i v e , to d e v e l o p and s t i l l  this latter  frequently suffers  type of model i s the most  difficult  from l i n e a r p a r a m e t e r i z a t i o n s which  do not e a s i l y accommodate c o n d i t i o n s beyond the c a l i b r a t i o n i n t e r v a l . The t h r e e types of models y i e l d d i f f e r e n t c h a r a c t e r i s t i c s of the past environment, and t h e r e f o r e environmental  s h o u l d be viewed as complementary approaches  reconstructions.  to  9 (1.3)  O b j e c t i v e s and Research S t r a t e g y  The s p e c i f i c study o b j e c t i v e s a r e : (1) to i d e n t i f y and r e l a t e the response c h a r a c t e r i s t i c s of s e l e c t e d g e o p h y s i c a l and b i o l o g i c a l a t t r i b u t e s o f the study basin to recent f l u c t u a t i o n s (2) t o determine  in hydroclimate;  the r e s o l u t i o n and l e n g t h of r e c o r d a v a i l a b l e  i n these a t t r i b u t e s and e v a l u a t e i n f e r r i n g the c h a r a c t e r  s e v e r a l methodologies f o r  of past h y d r o c l i m a t e s ; and  (3) to a s s e s s the w i t h i n - b a s i n and r e g i o n a l  (southwestern  B r i t i s h Columbia) s i g n i f i c a n c e o f measured and i n f e r r e d e n v i r o n m e n t a l change The p r i m a r y emphasis  i n the study  area.  i s on problems a s s o c i a t e d w i t h methods used i n the  r e c o n s t r u c t i o n of past e n v i r o n m e n t s .  In p a r t i c u l a r ,  to sources o f e r r o r and the s t r e n g t h  of i n f e r e n c e s  proxy data which may e x i s t  in quantitative,  consideration  is given  drawn from i n d i r e c t and  s e m i - q u a n t i t a t i v e or  q u a l i t a t i v e form. E m p i r i c a l and i n d u c t i v e methods o n l y a r e c o n s i d e r e d because o f d i f f i c u l t i e s i n a p p l y i n g and l i n k i n g e x i s t i n g models. The study c o n s i d e r s  the u t i l i t y of the model presented  1.1 as a framework f o r drawing i n f e r e n c e s paleoenvironments In o r d e r  process-based  regarding  in figure  recent  in a mid-latitude alpine basin.  to a s s e s s c r i t i c a l l y the r e a l r e s o l u t i o n of responses i n the  system and t o p r o v i d e a b a s i s f o r c a l i b r a t i o n of p a l e o e n v i r o n m e n t a l d a t a , a retrospective  s t r a t e g y has been adopted. T h i s i s o p e r a t i o n a l i z e d by  considering f i r s t  the r e l a t i o n s h i p between h y d r o l o g i c v a r i a b i l i t y and  g e o p h y s i c a l responses over the p e r i o d o f r e c e n t and d e t a i l e d records  instrument  (post-19^5)• The r e l a t i o n s h i p s a r e then t e s t e d u s i n g l e s s  detailed  10 but l o n g - t e r m instrument r e c o r d s as c o n f i r m a t o r y data  (1900-19^5)• T h i s  s t r a t e g y was adopted as a means of a s s e s s i n g the s t r e n g t h of  inferences  from b i o g e o p h y s i c a l d a t a i n the p r e - i n s t r u m e n t p e r i o d . Inferences e n v i r o n m e n t a l c o n d i t i o n s p r i o r to 1900 biogeophysical attributes Initially,  about  are then made from the e v i d e n c e of  alone.  i t was a n t i c i p a t e d t h a t t h i s methodology would a l l o w f o r a  r e s o l u t i o n of at l e a s t a n n u a l , or perhaps even s e a s o n a l , b i o g e o p h y s i c a l responses over the t e s t i n g p e r i o d . However, i n view of p o s s i b l e p e r s i s t e n t trends  i n b i o l o g i c a l and g e o p h y s i c a l a t t r i b u t e s ,  i t was r e a s o n a b l e  to  expect a r e s o l u t i o n o n l y on the o r d e r of years to decades. The p e r i o d  I65O  AD d e f i n e s the study i n t e r v a l . T h i s was found to be consonant w i t h  p r e s e r v e d e v i d e n c e . D e t a i l s are g i v e n i n the f o l l o w i n g  (l.k)  after  sections.  Data Sources  Biological,  and g e o p h y s i c a l data can be grouped and c l a s s i f i e d on the  b a s i s of temporal c o n t i n u i t y , temporal r e s o l u t i o n and i n t e r v a l of application  ( B r a d l e y , 1985)• Some p r o v i d e o n l y a d i s c o n t i n u o u s r e c o r d of  changes and may r e p r e s e n t  o n l y extreme events  (e.g. flood deposits),  o t h e r s may appear to g i v e a c o n t i n u o u s r e c o r d ( s e a s o n - t o - s e a s o n , year) of changing c o n d i t i o n s ( e . g . t r e e - r i n g s ) . C e r t a i n s o u r c e s  year-toare  a p p l i c a b l e to time s c a l e s of m i l l e n n i a or longer and o t h e r s may y i e l d concerning only recent  (decennial, centennial)  i n t o four  b i o l o g i c a l , g e o p h y s i c a l , h i s t o r i c a l and  a r c h a e o l o g i c a l , which are based on the most u s e f u l  i n d i c a t o r s of  e n v i r o n m e n t a l change i n m i d - l a t i t u d e , g l a c i e r i z e d a l p i n e b a s i n s 1.2).  data  processes.  The p r i m a r y data sources f o r t h i s study can be d i v i d e d groups of a t t r i b u t e s :  while  B i o l o g i c a l sources  (figure  i n c l u d e t r e e s , f l o w e r i n g v e g e t a t i o n and l i c h e n .  Tree r i n g - w i d t h time s e r i e s possess a r e s o l u t i o n of s e a s o n a l  (late-  11  10"  10  3  TO  10  2  10°  1  10''  -2  10  Tree-rings »•—^Tree-damage  00  >x  I  a. o LU  U3  oo  Lichen  il ta o —i a  Pollen  1  I  Soil  1  I  I — — —  ^  1  Lake Sediment Glacial Deposits  ea  h  1  Valley-fill Instrumental  < hZ  < K  LU  a  3  OO  ae i—i  o d  °  Legends  S  —  H  I  *- = y z  Written Records  I—  Artifacts  <  10  10  3  10  2  10  1  10°  10'  1  10  -2  10"  Years  Figure 1.2 B i o l o g i c a l , g e o p h y s i c a l and h i s t o r i c a l / a r c h a e o l o g i c a l s o u r c e s used f o r e n v i r o n m e n t a l r e c o n s t r u c t i o n i n t h i s s t u d y . The minimum s a m p l i n g i n t e r v a l ( a t t r i b u t e r e s o l u t i o n ) i n y e a r s i s g i v e n by a s o l i d h o r i z o n t a l l i n e f o r c o n t i n u o u s v a r i a b l e s and a dashed l i n e for n o n - c o n t i n u o u s v a r i a b l e s . Some a t t r i b u t e s have more than one s a m p l i n g i n t e r v a l . S o l i d c i r c l e s i n d i c a t e the p e r i o d open f o r study in y e a r s . R e s o l u t i o n of p o l l e n depends on the c h a r a c t e r of the host sediments.  12 wood/early-wood)  to annual  ( t o t a l r i n g - w i d t h ) growth v a r i a t i o n s and are  c o n t i n u o u s through t i m e . Damage to t r e e s by d i s c r e t e e v e n t s , floods,  or more c o n t i n u o u s s t r e s s ,  such as  l i k e i n s e c t damage, p r o v i d e some  i n d i c a t i o n of l o w - f r e q u e n c y , high-magnitude events but g e n e r a l l y these r e c o r d s are d i s c o n t i n u o u s . The o l d e s t u s u a l l y l e s s than 10^  t r e e s a v a i l a b l e f o r s a m p l i n g are  years.  P o l l e n and spores are produced s e a s o n a l l y , sediments  and i f p r e s e r v e d  in  a l s o c h a r a c t e r i z e d by a h i g h temporal r e s o l u t i o n , may y i e l d a  r e c o r d of changing p o l l e n c o n t r i b u t i o n s and thus e c o l o g i c a l v a r i a b i l i t y . Mostly, p o l l e n is useful for (10  years)  i d e n t i f y i n g changes over l o n g - t e r m  w i t h a r e s o l u t i o n of 50 t o 500  years  ( f i g u r e 1.2).  s o i l development can be used to e s t a b l i s h r e l a t i v e ages f o r  intervals L i c h e n and  different  k surfaces  as o l d as 10  In some i n s t a n c e s w i t h an a b s o l u t e  years.  i t may be p o s s i b l e to produce c o n t i n u o u s f o r m / t i m e curves temporal r e f e r e n c e  p a r t i c u l a r l y with  but they are d i f f i c u l t  to a c h i e v e ,  soils.  Lake d e p o s i t s terrain  years u s u a l l y w i t h a r e s o l u t i o n of 10 to 500  form d u r i n g an i n f l u x of sediment from the  surrounding  i n t o a n e a r l y c l o s e d system and may r e p r e s e n t s e v e r a l time  scales  and degrees o f c o n t i n u i t y depending on s e d i m e n t a t i o n c o n t r o l s . Lowfrequency,  high-magnitude d e p o s i t s may be the r e s u l t of i s o l a t e d r u n o f f  events which occur over a p e r i o d of hours or d a y s . These sediments d i s t r i b u t e d d i s c o n t i n u o u s l y throughout autogenous  are  the sequence. A l t e r n a t i v e l y ,  events may o c c u r , such as d e n s i t y u n d e r f l o w s , produced by the  b u i l d u p of d e l t a i c d e p o s i t s which then exceed s t a b i l i t y l i m i t s . The event i s the consequence of c o n t i n u o u s s e d i m e n t a t i o n , e x t r i n s i c event.  but does not mark an  However, i n a long r e c o r d the changing frequency of  f a i l u r e s may be s i g n i f i c a n t .  If c e r t a i n r u n o f f regimes p r e v a i l , a  c o n t i n u o u s r e c o r d o f s e a s o n a l or annual s e d i m e n t a t i o n might be p r e s e r v e d  13  ( e . g . a n n u a l l y - l a m i n a t e d sediments or v a r v e s ) . p r i m a r y sediment s o u r c e s ,  s e d i m e n t a t i o n r a t e s may be low and r e p r e s e n t 2  periods of accumulation Glacial  sediments  (10 - 10  years).  are g e n e r a l l y d e p o s i t e d d i s c o n t i n u o u s l y over  a c c u m u l a t i o n and a b l a t i o n  (10 -10  i f sediments  time of the  years).  i c e t o changes  time  in  A r e c o r d as o l d as 10 -10  are w e l l - p r e s e r v e d . V a l l e y - f i l l  downstream from the headwater  years  sediments,  source areas, a l s o represent discontinuous  s e d i m e n t a t i o n over l o n g e r time s c a l e s but may i n c o r p o r a t e deposited during short-duration  sequences  floods.  In a d d i t i o n t o b i o g e o p h y s i c a l s o u r c e s ,  i n f o r m a t i o n r e l a t e d t o human  a c t i v i t y can p r o v i d e i n d i r e c t e v i d e n c e of e n v i r o n m e n t a l change  (figure  1 . 2 ) . Data r e g a r d i n g annual or s e m i - a n n u a l changes and extreme  short  d u r a t i o n events  are most common. For w e s t e r n Canada w r i t t e n r e c o r d s  to the m i d d l e and l a t e  1800s are r a r e .  (1.5)  prior  I n d i a n legends and a r c h a e o l o g i c a l  e v i d e n c e a r e a l s o u s e f u l , a l t h o u g h they are environmental  long  3  s c a l e s commensurate w i t h the response  may be p r e s e n t  In s h a l l o w water away from  less d i r e c t  i n d i c a t o r s of  setting.  Organization  This d i s s e r t a t i o n  i s composed of e i g h t c h a p t e r s .  based on a format f o r a s s e s s i n g  the q u a l i t y of  the h y d r o c l i m a t i c environment t o the e a r t h reflect  the main o b j e c t i v e s .  The o r g a n i z a t i o n  information transfer  s u r f a c e environment  is  from  in order  to  Chapter 2 i s a summary of the g e n e r a l p h y s i c a l  s e t t i n g o f the B e l l a Coola R i v e r b a s i n and c h a r a c t e r i z a t i o n of p r i m a r y sediment sources  i n the b a s i n . Chapter 3 i s a d i s c u s s i o n of v a r i a t i o n s  several hydrological attributes  of the r e c e n t  period  (1900-1983). Chapter h documents  recent  forcing factors  and l o n g - t e r m  in  instrument  the r e l a t i o n s h i p s between  these  and the response of s e l e c t e d g e o p h y s i c a l components  14 of the l a n d s c a p e . The d i s c u s s i o n i s r e s t r i c t e d  to the post-1945 i n t e r v a l  f o r which t h e r e are s e v e r a l types of d i r e c t r e c o r d s of e n v i r o n m e n t a l change. Chapter 5 i s devoted to the  interpretation  h i g h - r e s o l u t i o n r e c o r d of l a k e s e d i m e n t a t i o n of  i n f o r m a t i o n about e n v i r o n m e n t a l change.  of  the response of growth v a r i a t i o n s  and s i g n i f i c a n c e of a  r a t e s as an independent  Chapter 6 i s an i n v e s t i g a t i o n  i n t r e e s , and an assessment of  r i n g s as a source of h i g h - r e s o l u t i o n data  in environmental  of h y d r o c l i m a t i c v a r i a b i l i t y d u r i n g the l a t e N e o g l a c i a l  summary of r e s u l t s presented in the  interpretation  i n t e r v a l . The  is also considered. A  and c o n c l u s i o n s i s g i v e n i n Chapter 8.  i n the main t e x t ,  appendices.  records  tree-  reconstruction.  Chapter 7 i s a d i s c u s s i o n of l o w - r e s o l u t i o n data sources and  r e g i o n a l s i g n i f i c a n c e of the r e c o n s t r u c t e d  source  Data not  p l u s a d d i t i o n a l t o p i c s and a n a l y s e s ,  are g i v e n  15 Chapter  I I  STUDY AREA  (2.0) Location S t a r k e l and Thornes  (198l) suggest t h a t s e l e c t i o n of a d r a i n a g e  basin  f o r p a l e o h y d r o l o g i c a l a n a l y s i s s h o u l d be based on the a v a i l a b i l i t y of data r e g a r d i n g landscape morphology, p r o c e s s mechanics and e a r t h materials.  In a d d i t i o n , l o n g - t e r m instrument  change are e s s e n t i a l  for q u a n t i t a t i v e  surface  r e c o r d s of r e c e n t h y d r o l o g i c  reconstructions.  In B r i t i s h  Columbia  t h e r e i s no b a s i n which f i t s these c r i t e r i a w e l l . B e l l a Coola R i v e r b a s i n , a p a r t l y g l a c i e r - c o v e r e d catchment a p p r o x i m a t e l y 500  l o c a t e d on the c e n t r a l  coast,  km northwest of Vancouver ( f i g u r e 2 . 1 ) , was s e l e c t e d  because of the a v a i l a b i l i t y of r e c e n t  hydroclimatic data,  comparatively  e a r l y h i s t o r i c a l r e c o r d s of e n v i r o n m e n t a l c o n d i t i o n s and the p o t e n t i a l  for  p r e s e r v a t i o n of p a l e o e n v i r o n m e n t a l e v i d e n c e i n upland source areas and lowland f l o o d p l a i n s . A c c e s s i b i l i t y , b a s i n s i z e and the e x i s t e n c e of preliminary studies  c o n c e r n i n g p h y s i c a l processes  change i n the b a s i n  (Tempest,  Church,  1983)  were a d d i t i o n a l  197^;  and r e c e n t  Church and R u s s e l l ,  1977;  several  environmental Hart, 198la;  factors.  2 B e l l a Coola R i v e r d r a i n s 5050 km of the g l a c i e r i z e d Coast Mountains of southwestern River  B r i t i s h C o l u m b i a . Two t r i b u t a r i e s j o i n to form B e l l a  ( f i g u r e 2 . 2 ) : the l a r g e r A t n a r k o R i v e r  2 (2,430 km ) o r i g i n a t e s  g e n t l y s l o p i n g , u p l i f t e d t e r r a i n to the e a s t , and T a l c h a k o R i v e r  Coola in  drains  2 1300 km  of h e a v i l y g l a c i e r i z e d mountains to the s o u t h . S e v e r a l s m a l l e r  tributaries  enter the 80 km long B e l l a Coola R i v e r as i t flows west  to  enter North B e n t i n c k Arm ( f i g u r e 2 . 2 ) , an i n l a n d e x t e n s i o n of the Burke Channel and Dean Channel f i o r d s y s t e m . A p p r o x i m a t e l y 1% of the catchment covered by c i r q u e , n i c h e and v a l l e y g l a c i e r s c o n c e n t r a t e d mountainous t e r r a i n  i n the s o u t h w e s t .  i n rugged  Two major v a l l e y g l a c i e r s , T a l c h a k o  is  16  F i g u r e 2.1 G e n e r a l l o c a t i o n o f study a r e a and h y d r o c l i m a t e s t a t i o n s used i n the a n a l y s i s of c l i m a t e v a r i a t i o n s . A x i s of the Coast Mountains i s an a p p r o x i m a t e boundary f o r s t a t i o n s which are r e f e r r e d to i n the t e x t as " c o a s t a l " and " i n t e r i o r " . A l s o i n c l u d e d are l o c a t i o n s of g l a c i e r and t r e e - r i n g d a t a used i n the s t u d y .  F i g u r e 2.2 B e l l a Coola R i v e r b a s i n i n c l u d i n g major t r i b u t a r i e s and the d i s t r i b u t i o n of upland i c e . A l s o i n c l u d e d are the l o c a t i o n s of c l i m a t e and r i v e r gauging s t a t i o n s .  18 and  Jacobsen, along with  several smaller  north-flowing  i c e masses, emanate  2 from the Monarch  Icefield  southwest b a s i n perimeter  ( t o t a l area  350 km ) which s t r a d d l e s the  f o r a d i s t a n c e of kS km.  (2.1) Physiography Three d i f f e r e n t p h y s i o g r a p h i c and  more g e n e r a l l y by H o l l a n d  b a s i n . To the south  r e g i o n s as d e f i n e d by T i p p e r  (196*0  of B e l l a Coola  can be d e l i n e a t e d  in B e l l a  d i s s e c t e d P a c i f i c Ranges of the Coast Mountains,  from sea l e v e l  to a l t i t u d e s greater  ranging  Icefield,  than 3500 m ( f i g u r e 2 . 2 ) .  The h i g h e s t  is similar  throughout,  1400 to 1600 m. Drainage d i r e c t i o n s a r e dominantly eastward or  northward r e s u l t i n g  i n s l o p e aspects which e x h i b i t a s t r o n g bimodal  d i s t r i b u t i o n of north/south s l o p e angle  or east/west and a c o m p a r a t i v e l y  high mean  of 27 degrees.*  Mountains of the K i t i m a t Range t o the north of B e l l a Coola west of Noosgulch Creek  (figure 2.2),  2500 m. V a l l e y bottoms tend (1000  Ranges. Although r e s t r i c t e d  (22^)  i n c l u d i n g U-shaped v a l l e y s ,  smaller  than those  to headwater r e g i o n s ,  eroded landscape to the south  River and  r a r e l y exceed maximum e l e v a t i o n s of  to be wider, average r e l a t i v e r e l i e f  m) and the mean s l o p e angle  glacial  extending  some of which a r e v i s i b l e o n l y as nunataks,  from 2500 t o 3500 m. L o c a l r e l a t i v e r e l i e f  averaging  Coola  R i v e r and west of Talchako River a r e the  rugged, deeply  peaks b i s e c t Monarch  (1971a)  i s lower  i n the P a c i f i c  landforms t y p i c a l of the  a r e a l s o found  i n the K i t i m a t Range,  c i r q u e s , horns, a r e t e s , hanging t r i b u t a r y  v a l l e y s and s e v e r a l t a r n s . 1. Mean s l o p e angle was determined as the average of 300 g r i d - p o i n t s sampled s y s t e m a t i c a l l y from 1:50,000 topographic sheets f o r each p h y s i o g r a p h i c r e g i o n . A r e p r e s e n t a t i v e s l o p e d i s t a n c e was d e f i n e d as ± 3 100-foot contours measured p e r p e n d i c u l a r t o the s l o p e (except i n lowg r a d i e n t v a l l e y bottoms where ±2 was used). Two sub-samples o f 50 g r i d p o i n t s each demonstrated t h a t b i a s e s due t o g r i d - s p a c i n g and o r i e n t a t i o n were not s i g n i f i c a n t .  19 C o n t r a s t i n g w i t h these two r e g i o n s F r a s e r P l a t e a u which dominates  i s the u p l i f t e d and l e s s  t e r r a i n t o t h e e a s t of T a l c h a k o R i v e r and  Burnt B r i d g e C r e e k . G e n t l y u n d u l a t i n g and h i l l y angle = 7^) c h a r a c t e r i z e s  rugged  topography  (mean s l o p e  t h i s r e g i o n i n which the average e l e v a t i o n i s  higher  (1300 m) than v a l l e y bottom l o c a t i o n s t o t h e w e s t . Average r e l a t i v e  relief  i s lower  (400 m) than elsewhere  i n the b a s i n r e s u l t i n g i n the  f o r m a t i o n o f hundreds o f s m a l l l a k e s a l o n g p r i n c i p a l d r a i n a g e poorly-drained,  low-gradient t e r r a i n .  l i n e s and on  C h a r l o t t e Lake i s the l a r g e s t ,  2 c o v e r i n g a p p r o x i m a t e l y 65 km concentrated Cr.,  ( f i g u r e 2.2). Drainage from t h e p l a t e a u i s  i n o n l y a few major streams  (Atnarko R . , Hotnarko R . , Young  Burnt B r i d g e C r . and Hunlen C r . - see f i g u r e 2.2) which e i t h e r  have  cut d e e p l y i n t o the e a s i l y eroded v o l c a n i c r o c k s forming p r e c i p i t o u s canyons f o r tens o f k i l o m e t e r s o r , where rock types a r e more  resistant,  formed w a t e r f a l l s w i t h v e r t i c a l drops as l a r g e as 250 m.  (2.2) Bedrock Geology Physiography and d r a i n a g e p a t t e r n s o f t h e B e l l a Coola b a s i n a r e i n f l u e n c e d by a d i v e r s i t y o f rock types and g e o l o g i c  structures  c h a r a c t e r i s t i c o f the Coast P l u t o n i c Complex and Intermontane of  Volcanic  the w e s t e r n Canadian C o r d i l l e r a . The g e o l o g i c s e t t i n g o f the study  d e s c r i b e d below f i t s Mountains  the g e n e r a l p a t t e r n  Belt area  o f t h e e a s t s l o p e o f the Coast  ( c f . Roddick and H u t c h i n s o n , 1972).  The geology o f the B e l l a Coola area has been mapped i n d e t a i l by Baer (1973) and more g e n e r a l l y by T i p p e r  (1979)  ( f i g u r e 2.3)- The o l d e s t  are m i d d l e T r i a s s i c p l u t o n s o f q u a r t z - d i o r i t e and g r a n o d i o r i t e southeastern  rocks  i n the  p o r t i o n o f the catchment and on t h e n o r t h f l a n k o f B e l l a  Coola  R i v e r near S t u i e . Metamorphism o f v a r y i n g i n t e n s i t i e s has generated g n e i s s i c and s c h i s t o s e f o l i a t i o n  i n some o f t h e s e r o c k s , p a r t i c u l a r l y i n  F i g u r e 2.3 D i s t r i b u t i o n o f bedrock l i t h o l o g i e s i n the B e l l a C o o l a b a s i n ( a f t e r Baer (1973) and T i p p e r (1979)). T r i a n g l e s a r e sampling l o c a t i o n s used t o c h a r a c t e r i z e l i t h o l o g i c a l and m i n e r a l o g i c a l a t t r i b u t e s o f sediments d e r i v e d from t r i b u t a r y b a s i n s . O  21 the headwaters of A t n a r k o R i v e r . V o l c a n i c , m e t a v o l c a n i c and sedimentary rocks  ( T r i a s s i c t o lower Cretaceous)  c h a r a c t e r i z e the c e n t r a l and s o u t h e r n  p o r t i o n s o f the catchment c o m p r i s i n g c h l o r i t e - r i c h greenstone and a n d e s i t e . The v o l c a n i c s e x h i b i t w i d e l y s c a t t e r e d  shear zones o c c u p i e d by s l a t e and  argi11i t e . Eocene q u a r t z - m o n z o n i t e s and g r a n o d i o r i t e s have i n t r u d e d these o l d e r v o l c a n i c s and form competent,  steepened s l o p e s where p r e s e n t .  J o i n t spacing  i s wide and f r a c t u r e d e n s i t y i s low i n these younger p l u t o n i c r o c k s ; the q u a n t i t y o f weathered d e b r i s  i s low and the t e x t u r e  thus,  i s usually large  b l o c k s of angular d e b r i s . Miocene v e s i c u l a r b a s a l t s and r h y o l i t e s a r e found i n t h e extreme n o r t h e a s t marking the boundary between r e c e n t  plateau  b a s a l t s d e r i v e d from a s e t o f t h r e e s h i e l d v o l c a n o e s o f the i n t e r i o r r e g i o n to t h e e a s t , and t h e o l d e r v o l c a n i c and p l u t o n i c r o c k s which dominate the west  (Souther, 1986) . T a b l e 2.1 i s a summary of t h e p r i n c i p a l  formations,  rock types and c o n s t i t u e n t m i n e r a l assemblages found i n t h e B e l l a  Coola  bas i n . Topographic e x p r e s s i o n o f s t r u c t u r a l f e a t u r e s boundaries  and f o r m a t i o n  i s not w e l l d e f i n e d i n t h e r e g i o n . Baer (1973) a t t r i b u t e s  to t h e s i m i l a r i t y o f m e c h a n i c a l p r o p e r t i e s  ( e . g . hardness,  most rock t y p e s . O r i e n t a t i o n of i n d i v i d u a l ranges  this  jointing) for  i s not c o n s i s t e n t  throughout the area except f o r t h e r e g i o n a l northwest t r e n d of the Coast P l u t o n i c Complex. F a u l t i n g does not appear  t o be common a l t h o u g h r e l a t i v e  displacements i n v o l c a n i c rocks are d i f f i c u l t  t o o b s e r v e . Baer (1973)  mapped two dominant f a u l t d i r e c t i o n s , n o r t h e r l y and n o r t h e a s t e r l y ,  both of  which s e p a r a t e the o l d e r c h l o r i t i z e d greenstone and g r a n o d i o r i t e from t h e younger  andesites.  Uplift  has o c c u r r e d d u r i n g two o r o g e n i c e v e n t s : a l e s s s e v e r e Lower  J u r a s s i c event and a s t r o n g e r p e r i o d o f u p l i f t  i n the l a t e T e r t i a r y . Baer  T a b l e 2.1.  Summary o f f o r m a t i o n s and found  Era  c o n s t i t u e n t m i n e r a l assemblages of rock  i n t h e B e l l a C o o l a b a s i n a f t e r B a e r (1973) and T i p p e r  Period  Lithology  Lower/ Pliocene  types  (1979).  Minerals very f i n e - g r a i n e d mafic  rhyolitic  lava  Upper/  minerals  occasional obsidian fine-grained mafic  minerals  Miocene  vesicular basalt  s m a l l amygdaloids 20-30% q u a r t z and  35-45% p a g i o c l a s e  Eocene  q u a r t z monzonite  k-spar  35%  Cenozoic as h i g h as  b i o t i t e , hornblende Eocene/ Paleocene  25-30% q u a r t z and granodiorite  and  40-60% p l a g i o c l a s e  minor k-spar, b i o t i t e mafic  muscovite  i s the o n l y  mineral  f i n e - g r a i n e d p l a g i o c l a s e and Cretaceous/ Jurassic  Middle Jurassic  andesite flows and  agglomerates  black  slate/  argillite  minor  k-spar p l a g i o c l a s e phenocrysts,  1-5  m i n o r e p i d o t e and q u a r t z  infilling  mm  long  fine-grained phyllosilicates  with  o c c a s i o n a l microconglomerate  or  w i t h pebbles  grit  of quartz monzonite  Mesozoic subhedral to anhedral p l a g i o c l a s e Lower Jurassic  (<0.5 greenstone  mm)  f i n e grained matrix of hornblende,  chlorite,  epidote  up t o 35% a n h e d r a l q u a r t z s m a l l amounts o f  Middle Triassic  quartz  diorite  plagioclase, biotite, e p i d o t e and m i n o r  and  k-spar hornblende,  chlorite  23 (1973) and P a r r i s h structures  (1982) have a t t r i b u t e d most of t h e p r e s e n t g e o l o g i c  t o the l a t t e r  event.  Rock s h o u l d e r s on t h e e a s t e r n  l a r g e r m a s s i f s a l o n g T a l c h a k o R i v e r have been i n t e r p r e t e d  as remnants o f a  T e r t i a r y e r o s i o n s u r f a c e which extends eastward as t h e F r a s e r Uplift,  estimated  t o be as much as 1800 m (Souther,  f l a n k s of the  Plateau.  1977. 1986), warped t h e  e r o s i o n s u r f a c e and r e a l i g n e d the d r a i n a g e such t h a t the A t n a r k o and T a l c h a k o R i v e r s , which were thought  t o f l o w eastward from a d i v i d e c e n t e r e d  along t h e a x i s of t h e Coast Mountains ( T i p p e r , 1971a. 1971b), a r e supposed to have been captured by k n i c k p o i n t i n c i s i o n of a r a p i d l y g r o w i n g , orographically-fed,  B e l l a Coola R i v e r  (Baer, 1973)•  (2.3) Late Quaternary Geology The major v a l l e y / f i o r d  systems o f B r i t i s h Columbia have been  deepened  by m u l t i p l e g l a c i a t i o n s . The s e v e r i t y of W i s c o n s i n a n g l a c i a l a c t i v i t y near the end o f the P l e i s t o c e n e has p r e c l u d e d t h e p r e s e r v a t i o n of i c e - c o n t a c t m a t e r i a l s d a t i n g from events e a r l i e r B . C . coast probably experienced  i n t h e Q u a t e r n a r y . However, t h e e n t i r e  i c e - a d v a n c e s e s s e n t i a l l y synchronous w i t h  the c h r o n o l o g y i d e n t i f i e d f o r the southern coast  (Armstrong, 198l).  D e t e r i o r a t i n g c l i m a t e f o l l o w i n g the Olympia n o n - g l a c i a l p e r i o d resulted  i n the advance of i c e (28,000 - 15,000 y e a r s B . P . ; C l a g u e , 198l).  Ice f l o w was from major a c c u m u l a t i o n areas along t h e a x i s of the Coast M o u n t a i n s . From here i c e spread both e a s t and west, major v a l l e y s and f i o r d s u n t i l  i n i t i a l l y occupying  i c e t h i c k n e s s exceeded the l o c a l  relief,  resulting  i n flow d i r e c t i o n s l e s s dependent on t h e u n d e r l y i n g topography  (Clague,  1981). E r r a t i c s found on the s h o u l d e r s o f e x t i n c t a c t i v e s h i e l d  volcanoes  (Rainbow, Ilgachuz and Itcha Mountains) t o the e a s t of B e l l a  Coola, along with  i c e - b e v e l e d p l a t f o r m s on some o f t h e h i g h e s t peaks  i n the  Monarch I c e f i e l d , i n d i c a t e t h a t i c e t h i c k n e s s e s exceeded 2000 m ( T i p p e r ,  2k 1971a)«  Ice flow d i r e c t i o n s e s t i m a t e d by s t r i a e ,  fluted  t e r r a i n show n o r t h e a s t e r l y  d r u m l i n s , e s k e r s , and  flow away from Monarch I c e f i e l d  C h a r l o t t e Lake and w e s t e r l y down t h e B e l l a Coola V a l l e y Tipper,  1971b). D u r i n g the maximum advance,  towards  (Baer, 1973;  about 15,000 years B . P . , i c e  from t h e Coast Mountains p r o b a b l y extended as f a r west as t h e c o n t i n e n t a l shelf  (Clague, 198l) and as f a r e a s t as W i l l i a m s Lake, t h e r e merging w i t h  west-flowing  i c e from the C a r i b o o Mountains ( T i p p e r , 1971a).  Evidence from t h e P r i n c e R u p e r t - K i t i m a t and B e l l a B e l l a areas i n d i c a t e s that d e g l a c i a t i o n along the outer glaciers retreating  to their  coastal  r e s p e c t i v e f i o r d head p o s i t i o n s by 12,500  years B . P . (Clague, 1981; Andrews and R e t h e r f o r d , control  1978). A l t h o u g h no d a t i n g  i s a v a i l a b l e t o the e a s t of the d i v i d e , the g r e a t e r e l e v a t i o n and  ice t h i c k n e s s e s  t h e r e may have r e s u l t e d  and v a l l e y bottom d e p o s i t s related  lowlands was r a p i d w i t h  in a less rapid r e t r e a t .  l a i d down by t h e eastward  retreating  Coastal i c e were  t o t h e p o s i t i o n of s e a - l e v e l , c o n t r o l l e d by i s o s t a t i c and e u s t a t i c  responses of the l a n d and ocean t o m e l t i n g i c e . R e l a t i v e sea l e v e l s were 150 t o 200 m higher u n t i l a p p r o x i m a t e l y 9000 years B . P . (Andrews and Retherford,  1978; Clague e t al.,  terminating  i n the s e a , p r o d u c i n g c o n d i t i o n s s i m i l a r t o those found  in G l a c i e r Bay, A l a s k a  (Powell,  1982), which r e s u l t e d  in ice fronts today  1983). G l a c i g e n i c sediments d e p o s i t e d i n  p r o g l a c i a l f i o r d s comprise a v a r i e t y of m a t e r i a l s  i n d i c a t i v e of these  changing e n v i r o n m e n t a l c o n d i t i o n s . The c h a r a c t e r i s t i c s  of the B e l l a Coola  valley-fill  have been i d e n t i f i e d u s i n g l o c a l b o r e h o l e and r e g i o n a l data and  sedimentary  e v i d e n c e found i n o u t c r o p s  O v e r a l l the v a l l e y - f i l l  (figure  2.k).  r e p r e s e n t s f a c i e s produced by g l a c i a l ,  g l a c i o m a r i n e , marine and a l l u v i a l p r o c e s s e s .  Thick deposits of glaciomarine  s i l t y - c l a y were d e p o s i t e d d u r i n g the marine i n u n d a t i o n phase between 12,500 and 9»000 years B . P . At the same t i m e , t r i b u t a r y  streams were d e p o s i t i n g  25  c  > 0)  +40  E gravel-capping floodplain sequence: silty fine sand and fine gravel channel zone gravels: coarse, cobble-boulder gravel to fine sandy gravel cross-valley prograding alluvial fan: coarsening upward sequence f r o m fine gravelly sand to coarse sandy gravel overlain by coarse cobble-boulder gravel  downvalley prograding delta of Bella C o o l a River: coarsening upward f r o m fine sandy gravel to coarse cobble gravel  9 5 8 0 t 8 0 yr BP ( G S C 3 9 8 0 ) : w o o d laminated fine sandy silt and marine mud  marine m u d : massive silty clay continuation o fsequence inferred from regional observations (Howes, 1983; Powell, 1983; Clague, 1985)  glaciomarine m u d : massive silty clay, somewhat stony (drop stones?) outwash or subaqueous flows at ice margin: gravelly sand basal till  bedrock  F i g u r e 2.h Observed and i n f e r r e d v a l l e y - f i l l B e l l a Coola R i v e r near S n o o t l i C r e e k .  i n the  lower reaches of  26 material  i n d e l t a s a l o n g the margin of B e l l a Coola v a l l e y . Continued i c e  r e c e s s i o n and p r o g r a d a t i o n of the main v a l l e y d e l t a produced t h i c k  deposits  of sand and g r a v e l i n a c o a r s e n i n g upwards sequence. C o n c o m i t a n t l y , alluvial  fans a l o n g the v a l l e y margin prograded a c r o s s the  valley  d e p o s i t i n g sandy g r a v e l s and c o a r s e r c o b b l e m a t e r i a l . Till  of v a r y i n g t h i c k n e s s mantles most s l o p e s above the v a l l e y  Prominent l a t e - g l a c i a l f e a t u r e s are r a r e  such as t e r m i n a l or r e c e s s i o n a l moraines  i n t h i s catchment as i n many o t h e r  (198l) has a t t r i b u t e d p o s s i b l e mechanisms:  headwater  Coast Mountain v a l l e y s . Ryder  t h i s s c a r c i t y of d e g l a c i a t i o n d e p o s i t s to one of two (1) r a p i d but o r d e r l y r e t r e a t of i c e f r o n t s  f o r n o t h i n g more than b r i e f (2) in situ  floor.  allowing  s t a t i o n a r y p e r i o d s and minimal d e p o s i t i o n or  a b l a t i o n of main v a l l e y  i c e which has been cut o f f from  the  ice source.  A hummocky, k e t t l e d r i d g e e x t e n d i n g p a r t way a c r o s s the narrow B e l l a Coola v a l l e y above Nusatsum R i v e r may be a subdued t e r m i n a l or m e d i a l moraine t h a t was formed d u r i n g a b r i e f  pause i n l a t e g l a c i a l  Although morphology i n d i c a t e s t h a t the r i d g e i s i c e - c o n t a c t  ice r e t r e a t . in o r i g i n ,  exposures of s t r a t i g r a p h y a l o n g margins of the d e p o s i t are m o s t l y d e l t a i c , and d i p d i r e c t i o n s of f o r e s e t  beds and c o n s t i t u e n t  l i t h o l o g i e s suggest  that  sediment and water were d e r i v e d m o s t l y from the upper B e l l a Coola v a l l e y , rather  than from the adjacent  Nusatsum R i v e r .  In any e v e n t ,  the b e d r o c k -  c o n t r o l l e d r e s t r i c t i o n of the main v a l l e y and c o n f l u e n c e s of the S a l l o o m t and Nusatsum R i v e r s at t h i s p o s i t i o n , appear  to have formed a complex  d e p o s i t i o n a l environment c h a r a c t e r i z e d by g l a c i a l , marine and a l l u v i a l processes. With the e x c e p t i o n of d e l t a i c d e p o s i t s and a h i g h t e r r a c e of marine d e p o s i t e d c l a y e y - s i l t s , l a t e - g l a c i a l d e p o s i t i o n i s found m o s t l y i n the upper B e l l a Coola v a l l e y c o m p r i s i n g marine d e l t a s ,  v a l l e y bottom kames,  27 till  benches,  lacustrine s i l t s ,  e s k e r s and some e o l i a n t r a n s p o r t e d  d e p o s i t s . However, the number and s i z e of t h e s e d e p o s i t s a r e Clague e t al.  (1982) and Clague (1985) demonstrate  were w i t h i n 11 m of p r e s e n t by at area. near  A date of 3,550 ± 80 years  limited.  t h a t sea  levels  l e a s t 9720 years B . P . f o r the B e l l a  B e l l a Coola a r e a was s t i l l marine r e g r e s s i o n a t  (Armstrong, Glacier  t h a t time than a t p r e s e n t ,  the s i t e o c c u r r e d soon a f t e r .  and south c o a s t r e g i o n s adjustments,  i n d i c a t e s t h a t r e l a t i v e sea l e v e l  h i g h e r at  indicates that  alluvial  (elevation is 6l m . s . a . l . ) .  the o u t l e t of S a l l o o m t R i v e r  The e l e v a t i o n of t h i s c o n t a c t  Bella  (GSC 396**) was determined f o r wood sampled  the c o n t a c t of s u b a r e a l l y exposed marine c l a y and o v e r l y i n g  d e l t a i c sands near  sand  i n the although  E v i d e n c e from both n o r t h  isostatic uplift,  sea  level  and i c e r e t r e a t were a l l complete by 8,000 years B . P . 1 9 8 l ; C l a g u e , 1985). f l u c t u a t i o n s d u r i n g the Holocene Epoch have been documented  f o r a number of d i f f e r e n t Washington t o A l a s k a  l o c a t i o n s a l o n g the n o r t h e a s t  (Mathews, 1951; M i l l e r ,  1972; Denton and K a r l e n ,  Pacific  rim from  19&9; E a s t e r b r o o k and B u r k e ,  1977; Mann and U g o l i n i ,  1985; Ryder and Thomson,  1986). E a r l y Holocene advances are r e c o g n i z e d o n l y i n the A l e u t i a n s 1981; 1983), Copper R i v e r (Mann and U g o l i n i ,  I985)  ( S i r k i n et al.,1971)  and L i t u y a Bay d i s t r i c t s  of A l a s k a , and even then appear  s u g g e s t i n g t h a t they were l o c a l i z e d e v e n t s ,  (Black,  t o be asynchronous  g e n e r a l l y not r e p r e s e n t a t i v e  the warmer and d r i e r c o n d i t i o n s which dominated the n o r t h e a s t  of  Pacific  between 6,000 and 10,000 years B . P . (Clague, 1981). Miller  (1969) and Ryder and Thomson (1986) document e v i d e n c e f o r  an e a r l y N e o g l a c i a l advance  (Garibaldi  Stade)  a p p r o x i m a t e l y 5.000 y e a r s  b e f o r e p r e s e n t . S i m i l a r e v i d e n c e has not yet been found i n mountain t o the n o r t h of the G a r i b a l d i  Park r e g i o n i n southwestern  British  regions  Columbia.  28 Several  investigators  g l a c i e r s o c c u r r e d between  have i n d i c a t e d t h a t an advance of mountain 1800 and 3000 years B . P . , which v a r i e d i n  i n t e n s i t y , d u r a t i o n and t i m i n g between r e g i o n s , throughout  the c o a s t a l  but i s g e n e r a l l y  recognized  r e g i o n from A l a s k a t o Oregon. Tiedemann G l a c i e r t o  the south o f B e l l a Coola b a s i n reached t h i s p e r i o d , u n l i k e most other  i t s maximum N e o g l a c i a l e x t e n t d u r i n g  g l a c i e r s w i t h i n the region  (Ryder and  Thomson, 1986). In a c c o r d w i t h c h r o n o l o g i e s developed f o r Dome Peak and Mt. R a i n i e r in Washington  ( C r a n d e l l and M i l l e r ,  and s o u t h e a s t A l a s k a  1964), G a r i b a l d i  (Mann and U g o l i n i ,  Park  (Mathews, 1951)  1985). Ryder and Thomson (1986)  found e v i d e n c e w i t h i n the P a c i f i c Ranges f o r i c e advances  commencing around  1,000 years B . P . w i t h maximum p o s i t i o n s a c h i e v e d by 300 t o 400 y e a r s B . P . In most r e g i o n s t h i s was the most pronounced e x c u r s i o n o f a l p i n e throughout  the e n t i r e  Holocene Epoch. A r e g i o n a l l y synchronous  glaciers  response of  g l a c i e r s appears t o have o c c u r r e d d u r i n g r e c e s s i o n from t h e L i t t l e maximum, b e g i n n i n g 100 t o 350 y e a r s B . P . ( F i e l d , in Chapter 1 i n d i c a t e s  that a L i t t l e  1975)- Evidence p r e s e n t e d  Ice Age c h r o n o l o g y , s i m i l a r t o t h a t  developed by Ryder e t a J . (unpublished) study a r e a ,  Ice Age  f o r r e g i o n s t o t h e south of t h e  i s a l s o a p p l i c a b l e t o the B e l l a Coola b a s i n .  (2.4) Climate Setting B e l l a Coola R i v e r and the r e s t of t h e B r i t i s h Columbia c o a s t w i t h i n the P a c i f i c c o a s t m a r i t i m e c l i m a t e regime, c h a r a c t e r i z e d  fall  by t h e o n -  shore movement of c y c l o n e s and a n t i c y c l o n e s generated i n t h e m o i s t , and u s u a l l y warm, North P a c i f i c  r e g i o n . The i n t e n s i t y and frequency  v a r y w i t h l a t i t u d e and season, c o n t r o l l e d by the s e a s o n a l Kerr  of c y c l o n e s  and annual c l i m a t e along t h e c o a s t i s  pattern of fronts  and a i r masses. Kendrew and  (1955) r e c o g n i z e d the importance o f s e v e r a l a i r masses and t h e i r  29 associated front  fronts.  D u r i n g summer a northward s h i f t o f t h e m a r i t i m e  towards s o u t h e a s t A l a s k a i s accompanied by t h e i n c r e a s i n g  arctic  influence  of m i l d P a c i f i c a i r and the o c c a s i o n a l i n c u r s i o n of m a r i t i m e t r o p i c a l a i r a l o n g the c e n t r a l and southern B . C . c o a s t .  Warm and d r y c o n d i t i o n s p r e v a i l ,  a l t h o u g h t h e p a t t e r n i s not i n v a r i a b l e , p a r t i c u l a r l y i f h i g h p r e s s u r e ridging  i s p o o r l y d e v e l o p e d , and m o i s t u r e b e a r i n g c y c l o n e s m i g r a t e  southward. The t r a n s i t i o n a l seasons  (spring/autumn)  a r e marked by r a p i d  shifts  i n mean f r o n t a l p o s i t i o n s and changes i n z o n a l c i r c u l a t i o n i n t e n s i t y . As the w i n t e r season p r o g r e s s e s , north c o a s t b i s e c t s  convergence of major a i r streams a l o n g t h e  the r e g i o n i n t o a n o r t h e r n h a l f ,  i n f l u e n c e d by m a r i t i m e  a r c t i c a i r , and a southern h a l f , dominated by warmer and m o i s t e r P a c i f i c a i r (Wendland and B r y s o n ,  1981; Y a r n e l ,  season t h e c o n t i n e n t a l a r c t i c f r o n t  1985). Throughout  maritime this  tends t o occupy a p o s i t i o n a l o n g the  a x i s o f the Coast Mountains forming a s t r o n g r i d g e o f h i g h p r e s s u r e e x t e n d i n g v e r t i c a l l y t o m i d - t r o p o s p h e r i c l e v e l s and h o r i z o n t a l l y as f a r west as the outer  coast  (Hare and Hay, 1974). Hence, the eastward  of c y c l o n i c d i s t u r b a n c e s the warm s e c t o r  can be impeded. F r o n t s n e a r l y always o c c l u d e and  a l o f t y i e l d s h i g h p r e c i p i t a t i o n a l o n g the c o a s t .  of a r c t i c a i r a r e not uncommon e a r l y Wright,  movement  i n t h e w i n t e r season  Outbreaks  (Baudat and  1969). and i t i s the t i m i n g and d u r a t i o n of these anomalously c o l d  and d r y p e r i o d s which determine  snowpack s t a b i l i t y and the p o t e n t i a l f o r  w i n t e r f l o o d i n g and s p r i n g avalanche a c t i v i t y . A s u c c e s s i o n of c y c l o n e s i n t e r s e c t s season and t h e s e p a r a t i o n  the coast during the winter  and i n t e n s i t y of these systems a r e m o s t l y  dependent on o r i g i n . Kendrew and Kerr  (1955) suggest t h a t t h r e e  areas f o r c y c l o n e development a r e i m p o r t a n t : s t a r t as waves on the P o l a r f r o n t  source  (1) a s o u t h e r n group which  i n t h e west P a c i f i c ,  tracking  30 northeastward effects  towards the B . C . c o a s t ;  (2)  a n o r t h e r n group generated  by the  of P o l a r a i r u n d e r c u t t i n g M a r i t i m e A r c t i c a i r o f f Japan and then  t r a c k i n g east between f r o n t s  i n t o the Gulf of A l a s k a ; and  (3)  a t r a n s i t i o n a l group forming  i n the western and c e n t r a l P a c i f i c .  O c c l u s i o n and  i n s t a b i l i t y through a c o n s i d e r a b l e depth are common to a l l groups of c y c l o n e s as they approach the c o a s t . i s an i n c r e a s e  in cumulative r a i n f a l l  and water content spring  With d e c r e a s i n g storm s e p a r a t i o n  there  l e a d i n g to a higher snowpack volume  and thus g r e a t e r p o t e n t i a l f o r high-magnitude w i n t e r and  runoff.  Compounding the e f f e c t s  of s y n o p t i c - s c a l e c i r c u l a t i o n f e a t u r e s  are  l o c a l and r e g i o n a l t o p o g r a p h i c c o n t r o l s on temperature and p r e c i p i t a t i o n . V a r i a b i l i t y of mean temperature, precipitation,  temperature extremes and t o t a l  i n c l u d i n g the p r o p o r t i o n s of s n o w f a l l and r a i n f a l l ,  marked h o r i z o n t a l and v e r t i c a l g r a d i e n t s .  For a s e r i e s of t h r e e  forming a w e s t - t o - e a s t t r a n s e c t from the o u t e r c o a s t  to the  annual temperatures d e c l i n e from 8.1^C to 3-9^C, and t o t a l  a l l show  stations  i n t e r i o r , mean annual  p r e c i p i t a t i o n d e c r e a s e s by an order of magnitude from 4390 mm to 410 mm ( f i g u r e 2.5)-  This strong  i n l a n d g r a d i e n t from a mesothermal,  c l i m a t e to one of c o n t i n e n t a l c h a r a c t e r  perhumid  o c c u r s over a d i s t a n c e of l e s s  200 km. Superimposed on the h o r i z o n t a l p r e c i p i t a t i o n g r a d i e n t are orographically  induced v a r i a t i o n s  May 1 snowpack water e q u i v a l e n t s ,  large,  i n p r e c i p i t a t i o n w i t h e l e v a t i o n . Using recorded 1800  m above the B e l l a  c l i m a t e s t a t i o n , as a measure of t o t a l w i n t e r p r e c i p i t a t i o n at elevation,  than  i t appears t h a t , on a v e r a g e ,  Coola  this  p r e c i p i t a t i o n i n c r e a s e s by  a p p r o x i m a t e l y 100 mm per 100 m of e l e v a t i o n . A p p r o x i m a t e l y 60% of the B e l l a Coola b a s i n l i e s i n the l e e of Coast M o u n t a i n s , which i s r e f l e c t e d  the  i n the d i s t r i b u t i o n and a c c u m u l a t i o n of  s n o w f a l l d u r i n g the w i n t e r season. Snow c o u r s e d a t a ,  c o l l e c t e d for a  BELLA COOLA 52° 22' N 126° 41" W Elev. 18 m 600  I  300  200  3  TP 412 urn TS 142 mm TR 270 mn 30 g  600  20 f 1 o>  500  lOg O 3  i — 400 e o ™ 300  a.  £ 200  ,snowfal1 ralnfalI  o.  100  MONTH  S-1  -10 o  mean maximum mean temperature mean minimum  o. u  M A M J J A S O N D  |  20  0  — 400 c o  t a.  30  10 * c  600  5  TATLAYOKO LAKE 61° 40' N 124° 24' M Elev. 8S3 m  TP 1614 TS 191 TR 1424  100  J  F M A M J J ASO MONTH  ND  J F MA M J  J A S O N D  MONTH  F i g u r e 2 . 5 Climographs f o r a west t o e a s t t r a n s e c t through B e l l a C o o l a b a s i n . S t a t i o n s are l o c a t e d i n f i g u r e s 2 . 1 . and 2 . 2 . TP i s t o t a l p r e c i p i t a t i o n , TR i s t o t a l r a i n f a l l and TS t o t a l s n o w f a l l (Source: Atmospheric Environment S e r v i c e , 1981) .  32 l i m i t e d number of c o r r e s p o n d i n g years from an e a s t e r n s i m i l a r e l e v a t i o n s w i t h i n the catchment  show t h a t l a t e s p r i n g snowpack  water e q u i v a l e n t s a r e 8 t o 10 times g r e a t e r 1753 mm) than those i n the e a s t  and a w e s t e r n s i t e a t  i n the west  ( r e c o r d mean of  ( r e c o r d mean of 230 mm).  (2.5) Hydrology Average Regime  W i t h i n the b a s i n , n i n e r i v e r gauges have been o p e r a t i v e a t v a r i o u s times s i n c e 1930, years a f t e r  but o n l y f i v e p r o v i d e d a t a f o r p e r i o d s longer than  1948. The combined d a t a s e r i e s  from two s t a t i o n s  five  on the main  r i v e r cover the p e r i o d 1948-present, w h i l e t h r e e o f the t r i b u t a r y gauges ( A t n a r k o , Nusatsum, S a l l o o m t ) were e s t a b l i s h e d d u r i n g the summer of 19&5 and have been i n o p e r a t i o n c o n t i n u o u s l y s i n c e t h e n . The main r i v e r relocated  gauge,  i n 19&5. i s o n l y a few k i l o m e t e r s below the c o n f l u e n c e of  T a l c h a k o and A t n a r k o R i v e r s , confluence,  the l a t t e r  allowing for estimates  of which i s gauged j u s t above the  of flow i n the ungauged T a l c h a k o R i v e r  by s i m p l e s u b t r a c t i o n . Gauge l o c a t i o n s and a summary of h y d r o m e t r i c from each s i t e are g i v e n i n f i g u r e 2.2 and t a b l e 2.2 Variability  in basin-wide runoff  data  respectively.  i s s t r o n g l y a f f e c t e d by the  d i s t r i b u t i o n of snow. It a l s o i s a f f e c t e d by the l o c a t i o n o f s h o r t and l o n g - t e r m water s t o r a g e s i t e s runoff  such as l a k e s and g l a c i e r s . Mean annual  from the b a s i n above Burnt B r i d g e Creek i s 790 mm w i t h a maximum of  1023 mm r e c o r d e d situated  i n 1976.  For p a r t l y g l a c i e r - c o v e r e d t r i b u t a r y  i n the s o u t h e r n and w e s t e r n p o r t i o n s of the b a s i n  R i v e r ) mean annual r u n o f f  catchments  ( e . g . Nusatsum  i s s i g n i f i c a n t l y h i g h e r , a v e r a g i n g over 2000 mm  ( t a b l e 2.2).  Mean annual r u n o f f from the l a r g e r A t n a r k o R i v e r d r a i n i n g i c e -  free  i s one t h i r d of the d i s c h a r g e from T a l c h a k o R i v e r ,  terrain  d r a i n s a 25% g l a c i e r - c o v e r e d a r e a .  which  I n t e r - c o r r e l a t i o n of annual mean and  33  Table  2.2.  Hydrometric  data  W.S.C. Station  Coola  Coola  Burnt  of  in  R.  near  of  R.  above  Bella  Coola  basin.  Mean A n n u a l  Area 2 (km )  years)  1947-68  (08FB002)  the  Drainage  Operation (#  Hagensborg  Bella  stations  Interval  name  (number)  Bella  for  (Source:  Water  Mean A n n u a l  Discharge 3 - 1 (m s )  Runoff  (mm)  of  Canada,  Spring  Autumn  (date)  (date)  668  3,730  of  Spring  1  (01/24/68)  558  (21)  X Difference Autumn v s .  963  (06/11/64)  1965-present  1982)  Maximum D a i l y D i s c h a r g e 3-1 (m s )  4,040  (21)  Bridge C r .  Survey  703  (06/11/69)  (01/23/68)  (08FB007)  Bella  Coola  Bella  Bella  R.  Coola  Coola  R.  Hagensborg  Nusatsum  at  1929  (08FB001)  at  1930-32  (08FB008)  R.  R.  83  161  9.3  1,820  43.3  2,430  2.2  2,390  1980-present  481  1965-present  of 2.  as  [Q^/Q^]  discharge  due  X 100  to  (24/10/47)  21.2  85.6  (05/21/82)  1,300  62.7  (08/09/82)  407  1,521  552  (06/11/67)  (21)  daily  36.5  (06/18/50)  (5)  1. C a l c u l a t e d  (01/24/68)  21.6  (4)  R.  289  (30/05/72)  1946-1950  Falls Cr.  141 (12/16/80)  258  (21)  (08FB009)  190 (09/27/73)  (16/05/70)  1965-present  (08FB003)  561 (09/17/30)  (16/05/70)  (21)  Tastsquan C r .  Talchako  269  1965-present  (08FB006)  Clayton  561  (21)  R.  430 (16/10/29)  (10/06/30)  1965-present  (08FB004)  Atnarko  4,800  (2)  (08FB005)  Salloomt  405 (07/09/29)  (1)  where  an autumn  Q,, i s  the  rainstorm  maximum for  the  daily period  discharge of  due  record.  to  spring  Not computed  (01/23/68)  snowmelt for  and  is  stations with  the  maximum  a limited  length  record.  Flows join  estimated the  by  subtracting  system between  these  Atnarko two  R.  gauging  data  from  sites.  Bella  Flows  Coola  may b e  R.  data  above  underestimated  Burnt  Bridge  b y 2-3Z.  Creek.  No m a j o r  tributaries  3** annual maximum d i s c h a r g e s  i n d i c a t e s t h a t Nusatsum/Talchako R i v e r s  are  h y d r o l o g i c a l l y d i s t i n c t from S a l l o o m t / A t n a r k o R i v e r s , p r i m a r i l y on the b a s i s of g l a c i e r m e l t c o n t r i b u t i o n s to r u n o f f  and h i g h e r mean e l e v a t i o n s .  However, the A t n a r k o R i v e r r e t a i n s a somewhat s i n g u l a r s i g n a l due to much lower annual p r e c i p i t a t i o n and frequency of l a k e s , which tend  the  to  reduce peak d i s c h a r g e s . S e v e r a l s e a s o n a l runoff  regimes can be i d e n t i f i e d  R i v e r , which are t y p i c a l of o t h e r Beginning in l a t e A p r i l  for B e l l a  Coola  r i v e r s a l o n g the B r i t i s h Columbia  through mid to l a t e June, r u n o f f  coast.  due to snowmelt i s  somewhat v a r i a b l e , but s t e a d i l y i n c r e a s i n g d i s c h a r g e s are e v i d e n t . Occasionally,  runoff  i s augmented by r a i n f a l l  on the r i p e n e d snowpack.  F o l l o w i n g the snowmelt peak i n e a r l y to m i d d l e June rivers),  runoff  declines until  (or l a t e May f o r some  l a t e J u l y , when d i s c h a r g e a g a i n i n c r e a s e s  as  g l a c i e r m e l t b e g i n s to c o n t r i b u t e s i g n i f i c a n t volumes of s t o r e d water ( f i g u r e 2.6).  Superimposed on s t e a d i l y d e c l i n i n g r i v e r d i s c h a r g e s from  August onwards are high-magnitude s y n o p t i c r u n o f f sources:  (1)  rainfall  m e l t i n g snow or freezing  d e r i v e d f l o o d s w i t h o n l y minor c o n t r i b u t i o n s from  r a i n - o n - s n o w events a s s o c i a t e d w i t h r a p i d l y  Finally,  rising  from January to A p r i l w i n t e r low flows dominate the  regime.  Maximum d a i l y and i n s t a n t a n e o u s the s h o r t - d u r a t i o n autumn f l o o d s runoff  events d e r i v e d from two  l e v e l s f o l l o w i n g the eastward movement of autumn c y c l o n i c  disturbances. runoff  (2)  late  d i s c h a r g e s almost always o c c u r d u r i n g  ( t a b l e 2.2),  but the h i g h e s t  average  i s d u r i n g the summer snow and g l a c i e r melt p e r i o d ( f i g u r e 2.6).  (198lb) has shown t h a t the r a t i o of maximum i n s t a n t a n e o u s  Hart  to mean d a i l y  d i s c h a r g e f o r autumn f l o o d s i n the K i t i m a t and P a c i f i c Ranges v a r i e s w i t h d r a i n a g e area but  i s g e n e r a l l y between 1.5  d i s c h a r g e s from r a i n s t o r m - g e n e r a t e d  and 1.9.  Maximum d a i l y  f l o o d s i n the gauged catchments are on  BELLA COOLA RIVER Annual Hydrograph of Mean D a i l y Flow,  1980  Water Survey of Canada Gauge 08FB007 Ad = 3,430 km 2  1 = R a i n s t o r m generated 2 = Rain-on-snow f l o o d  flood  W i n t e r Low Flow  "jAN  I  FEB  1  F i g u r e 2.6  MAR  Snowmelt  I  The 1980  APR  I  MA?  I  Glacier  JUN  annual hydrograph f o r  1  JOT  melt  1  AUG  Autumn R a i n s t o r m s  '  SEP  '  OCT  T  B e l l a Coola R i v e r above B u r n t B r i d g e  NOV  Creek.  "DEC  ^  36 average 25~40% g r e a t e r  than s p r i n g snowmelt f l o o d s . However, as g l a c i e r  cover and l o c a l  i n c r e a s e and b a s i n s i z e d e c r e a s e s ,  relief  can be as high as  this  difference  300%.  Major F l o o d s D u r i n g the 20th Century H i s t o r i c a l and instrument r e c o r d s show t h a t t h e r e were a p p r o x i m a t e l y t h i r t e e n major f l o o d events between 1896 and I98O. The pre-1948 r e c o r d of l e s s extreme f l o o d i n g  i s p r o b a b l y i n c o m p l e t e , however; a l l the  f l o w s were documented. With the e x c e p t i o n of a f l o o d all  h i g h - m a g n i t u d e , autumn and s p r i n g runoff  R i v e r were a s s o c i a t e d w i t h w i n t e r seasons  largest  i n the f a l l  of  events on the B e l l a  (October to A p r i l )  1950,  Coola  characterized  by p o s i t i v e p r e c i p i t a t i o n a n o m a l i e s . Only s i x o t h e r seasons i n the 88 year r e c o r d e x h i b i t e d s t r o n g l y p o s i t i v e p r e c i p i t a t i o n anomalies and no e v i d e n c e of responses not p r e v a l e n t temperatures  i n the form of s i g n i f i c a n t f l o o d i n g . in these years because  Large r u n o f f  i n a l l s i x cases s p r i n g and summer  were w e l l below normal promoting water  storage.  The most o u t s t a n d i n g f l o o d events o c c u r r e d i n the m i d d l e  1960's.  The four f l o o d s  events were  (1934, 1936, 1965, 1968)  1930's  are among the s i x  measured or e s t i m a t e d flows on the r i v e r . As such they r e p r e s e n t events'  i n the l o n g - t e r m h y d r o l o g y of the b a s i n because  i n each  and  largest  'key instance,  p a r t i c u l a r l y the r a i n - o n - s n o w e v e n t s , major channel r e a l i g n m e n t or s i g n i f i c a n t overbank s e d i m e n t a t i o n o c c u r r e d . For t h i s reason a b r i e f d e s c r i p t i o n of the h y d r o c l i m a t i c c i r c u m s t a n c e s a s s o c i a t e d w i t h these two sequences  i s g i v e n , and the i m p l i c a t i o n s for e f f e c t s  events are c o n s i d e r e d  from lower-magnitude  briefly.  The f l o o d of October 10,  193^  r e s u l t e d from the o c c l u s i o n of  a s s o c i a t e d w i t h an i n t e n s i f i e d low p r e s s u r e system (960 Vancouver  fronts  mb) to the west of  I s l a n d . A b l o c k i n g r i d g e of high p r e s s u r e over the western  United  37 S t a t e s l e d t o the low s t a l l i n g as i t approached  the coast.  High-water  appears t o have been more l o c a l i z e d because o f s i g n i f i c a n t l o g jams on t h e r i v e r . S t o r a g e of o r g a n i c d e b r i s  i n the channel was p r o b a b l y s i g n i f i c a n t  s i n c e the l a s t documented f l o o d was t e n years b e f o r e . 19.  F l o o d i n g on November  1936 was more severe than t h e 193** f l o o d f o r two r e a s o n s .  First, a  s e r i e s o f low p r e s s u r e systems moving southward from the G u l f of A l a s k a , preceded  the l a r g e r system y i e l d i n g s n o w f a l l a t m i d d l e and a t lower l e v e l s  i n the b a s i n . Second, a w e l l developed warm f r o n t  swept, through the area  r a i s i n g t h e f r e e z i n g l e v e l s u b s t a n t i a l l y . A m e l t i n g snowpack c o n t r i b u t e d g r e a t l y t o the r u n o f f . S y n o p t i c c o n d i t i o n s f o r t h e October 22, 1965 f l o o d were s i m i l a r t o those i n 193**: northward moving d i s t u r b a n c e s  produced seven-day  p r e c i p i t a t i o n of 190 mm p r i o r t o the peak d i s c h a r g e ; flood-related  rainfall  p e r i o d s . Ridge development  c h a r a c t e r i s t i c of t h e January 23, 1968 f l o o d . d i s c h a r g e s were much h i g h e r due t o s u b s t a n t i a l level  total  one of t h e l a r g e s t  i n A l b e r t a was  L i k e the 1936 f l o o d ,  peak  snowmelt as t h e f r e e z i n g  i n c r e a s e d d u r i n g a four day p e r i o d p r i o r t o t h e f l o o d . Maximum  instantaneous  flows from t h i s event were p r o b a b l y t h e l a r g e s t  t o occur  this  century. With the e x c e p t i o n o f moderately h i g h s p r i n g r u n o f f  i n l a t e May of  19**8, t h e r e were no f l o o d events of n o t a b l e between 1936 and 1950. The f l o o d of November h, 1950 was the f o u r t h l a r g e s t to have had minimal explain t h i s .  estimated  f l o w and appears  impact i n terms of channel changes. Two f a c t o r s  F i r s t , both the r i s i n g and f a l l i n g  limb o f the f l o o d  hydrograph were v e r y s t e e p so t h e peak d i s c h a r g e was of s h o r t Second, r u n o f f  duration.  i n two o f t h e p r e c e d i n g t h r e e s p r i n g s was s i g n i f i c a n t l y h i g h  (although not of major f l o o d p r o p o r t i o n s ) organic debris  might  so t h a t any a c c u m u l a t i o n o f  i n t h e channel may have been removed. The i m p l i c a t i o n i s  38 t h a t not a l l l a r g e r u n o f f  events may have an impact on the r i v e r . There i s  some e v i d e n c e f o r i n c i p i e n t i n s t a b i l i t y  i n c e r t a i n reaches o f the r i v e r  such t h a t moderate f l o o d s may produce s u b s t a n t i a l changes.  In most cases t h e i n s t a b i l i t y  l o c a l i z e d channel  i s r e l a t e d to the occurrence of l o g  jams w h i c h , when removed, modify t h e d i r e c t i o n o f channel  flow.  (2.6) Sources and Transfer of Clastic Sediment An important s t e p i n d e t e r m i n i n g the t r e n d s o f b a s i n sediment and  yield  p o s s i b l e a s s o c i a t i o n s w i t h changing h y d r o c l i m a t e i s c o n s i d e r a t i o n o f  sediment sources and p r o c e s s e s of sediment t r a n s f e r .  The purpose o f t h i s  s e c t i o n i s t o document t h e c h a r a c t e r i s t i c s o f the sediment cascade and a s s e s s the d i s t r i b u t i o n o f s e v e r a l p r i m a r y sediment sources and r e s i d e n c e times i n a s s o c i a t e d sediment s i n k s . A c o n c e p t u a l m o d e l , shown i n f i g u r e 2.7, has been adapted from g i v e n i n Simons e t al.  (1982) and R o b e r t s and Church  here t o i l l u s t r a t e the p r i m a r y s o u r c e s , sediment  transfer  those  (1986) , and i s used  and s t o r a g e o f c l a s t i c  i n t h e B e l l a Coola R i v e r b a s i n . Three p r i m a r y sediment s o u r c e s can  be i d e n t i f i e d :  (1) in situ weathered bedrock;  (2) g l a c i a l d e p o s i t s i n  p r o g l a c i a l and i c e - m a r g i n a l areas o f contemporary g l a c i e r s ; and (3) c l a s t i c materials,  i n c l u d i n g s o i l , which mantle h i l l s l o p e s o r i n f i l l e d g u l l i e s , t h e  bulk o f which was d e p o s i t e d d u r i n g t h e l a t e P l e i s t o c e n e and e a r l y Holocene epochs. These m a t e r i a l s a r e m o b i l i z e d by mass w a s t i n g avalanche, debris flow,  g u l l y wash, s o i l creep)  Storage o f r e c e n t l y produced sediment  (rockfall/  and f l u v i a l  rockslide,  processes.  i n the upland o r headwater  areas i s i n the form o f c o l l u v i a l d e p o s i t s or p a r t l y i n f i l l e d  proglacial  l a k e s which were formed d u r i n g i c e r e t r e a t . Residence times w i l l v a r y as a f u n c t i o n o f r e s e r v o i r c a p a c i t y , s l o p e s t a b i l i t y and sediment rates.  transfer  F l u v i a l e r o s i o n and mass w a s t i n g o f s l o p e d e p o s i t s may i n t r o d u c e  39  Fresh G l a c i a l Deposits t e r m i n a l , l a t e r a l and ground m o r a i n e s  Weathered Bedrock joint spacing, fracture density  rockfal1/ rockslide mixing  T i l l and In S i t u S o i l on Hi 11 slopes  fIuvial transport  I  debris slide debris flow avalanche  4  i  Colluvium, Talus Composite Debris Slopes  Proglacial Lakes: Lacustrine Deposits  I  footslope erosion Upland V a l l e y s : Channel Storage  f 1 uvial transport  —  .  J I  i  1 channel erosion  i  Tributary A l l u v i a l Fans  Long-Term Lake Storage  T fan u n d e r c u t t i n g , channel e r o s i o n Channel Zone and Floodplain Storage  1 channel migration bank e r o s i o n  ±_  Marine Delta  F i g u r e 2-7 G e n e r a l i z e d c l a s t i c sediment r o u t i n g transport processes in B e l l a Coola b a s i n .  and  primary  ko c l a s t i c d e b r i s d i r e c t l y to the channel zone of l o w - o r d e r t r i b u t a r i e s . s i z e s are u s u a l l y v e r y c o a r s e  (bouldery to b l o c k y )  and thus  transport-  l i m i t e d c o n d i t i o n s p r e v a i l . F l u v i a l t r a n s p o r t moves some of the i n t o downstream s t o r a g e s i t e s such as t r i b u t a r y a l l u v i a l valley trains,  h i g h and sediment t r a n s f e r conditions  fans,  sediment upland  l a k e s a l o n g p r i n c i p a l d r a i n a g e l i n e s or u l t i m a t e l y to  channel and f l o o d p l a i n s of h i g h e r order s t r e a m s .  the  If s t o r a g e c a p a c i t i e s  are  r a t e s low, a t r a n s i t i o n to s u p p l y - l i m i t e d  i s l i k e l y to occur downstream. F i n a l l y ,  the main stem of the system w i l l where sediments are d e p o s i t e d Interpretation  Grain  fluvial  processes  along  pass sediment through to the b a s i n o u t l e t  i n a growing marine d e l t a .  from a e r i a l photographs o f f e r s  the o n l y p r a c t i c a l  method of e v a l u a t i n g c l a s t i c sediment sources and d i f f e r e n t i a l movement r a t e s , even though the t e c h n i q u e y i e l d s l i m i t e d q u a n t i t a t i v e  i n f o r m a t i o n on  s t o r a g e volumes and d e p o s i t s t a b i l i t y . Two s c a l e s of mapping were undertaken to e v a l u a t e sediment s o u r c e s : f e a t u r e s from medium s c a l e photography and (2) subcatchments:  (1)  i n t e r p r e t a t i o n of b a s i n - w i d e  (1:21,000 to 1:40,000) b l a c k and w h i t e a i r  d e t a i l e d a i r photograph and f i e l d mapping of  Salloomt River  (169  2  km ) , Burnt B r i d g e Creek (215  three  2  km ) , and  2 Nusatsum R i v e r variations  (269  km ) , * w h i c h are r e p r e s e n t a t i v e  of the s p a t i a l  i n h y d r o l o g i c , p h y s i o g r a p h i c and g e o l o g i c c o n d i t i o n s w i t h i n  the  bas i n . Upland Sediment Sources  Seven types of sediment sources were i d e n t i f i e d : composite d e b r i s slopes, cones,  talus slopes  rockfal1/rockslide deposits,  felsenmeer, of  till  (gravity sorted),  in situ  l a t e r a l and p r o g l a c i a l t i l l  along forested  slopes.  alluvial  fan or t a l l u v i a l  mountain top d e t r i t u s  d e p o s i t s , and b l a n k e t s or  debris or veneers  kl  Composite d e b r i s s l o p e s a r e p o l y g e n e t i c landforms produced by any c o m b i n a t i o n of r o c k f a l l ,  avalanche and d e b r i s flow  C h a n d l e r , 1973; Church e t al.,  ( c f . Rapp,  1979)- H i g h l y f r a c t u r e d  greenstone rocks i n the b a s i n a r e an important  I960;  and j o i n t e d  source f o r these b l o c k y  d e p o s i t s which form below open rock s l o p e s d i s s e c t e d by numerous and r o c k f a l l c h u t e s .  avalanche  They a r e a l s o found on c o n f i n e d rock s l o p e s above t h e  f l a n k s of a c t i v e c i r q u e g l a c i e r s , where removal of i c e by m e l t i n g has promoted the f a i l u r e of rock s u r f a c e s . c o n s i d e r a b l e volume throughout o v e r a l l an important coarse-grained  A l t h o u g h w i d e l y d i s t r i b u t e d and o f  the v o l c a n i c t e r r a i n ,  these s l o p e s a r e not  source o f onward moving c l a s t i c sediment due t o the  n a t u r e of the d e b r i s and t r a n s p o r t l i m i t e d c o n d i t i o n s which  result. Talus slopes are g r a v i t y - s o r t e d , forming d i s c r e t e above t r e e l i n e , deposits  rockfall  dominated  landforms,  but s m a l l sheets or m u l t i p l e c o a l e s c i n g cones, p r i m a r i l y or below steep bedrock c l i f f s  occur f r e q u e n t l y  extension faults  along the edges of former  i n the plateau  are p o o r l y connected  a t lower e l e v a t i o n s .  These  l a v a f l o w s and below  areas of t h e n o r t h e a s t e r n catchment, but  to the f l u v i a l  network.  High magnitude r o c k f a l l s / r o c k s l i d e s a r e d e f i n e d on the b a s i s of c r i t e r i a suggested slope-base surface.  by Mudge (1965) . the most  important o f which a r e the  p o s i t i o n of coarse b l o c k y d e b r i s and a v i s i b l e u p s l o p e  The l a r g e s t  deposits  metamorphic rock t y p e s .  failure  occur on t e r r a i n u n d e r l a i n by p l u t o n i c or  For example, o f t h e twelve d e p o s i t s  identified in  the Nusatsum b a s i n , e i g h t a r e d e r i v e d from i n t r u s i v e rocks and four volcanic/sedimentary sources.  This i s s i g n i f i c a n t given that the  d i s t r i b u t i o n o f r o c k - t y p e i s about t h e r e v e r s e recognized deposits  from  ( f i g u r e 2.3). Most  a r e a t or above t r e e l i n e and i n some cases have  impounded s m a l l l a k e s . E s t i m a t e s of volume a r e d i f f i c u l t  t o make because of  unknown d e p t h s , but appears to range downward from 10^ m^. The r o c k s l i d e mapped o c c u r r e d  largest  i n a p p r o x i m a t e l y 1951 i n the headwaters of  A t n a r k o R i v e r as a r e s u l t of a f o l i a t i o n  plane f a i l u r e  in gneissic  the  rocks g  (J.J.  C l a g u e , p e r s o n a l communication, 1986). The volume i s e s t i m a t e d  a t 10  3  m . The d e p o s i t  resulted  i n minor r e a l i g n m e n t of the d r a i n a g e d i v i d e  between the A t n a r k o and N o r t h K l i n a k l i n i Alluvial  fans  and t a l l u v i a l d e b r i s cones are found below l o w - g r a d i e n t  and s t e e p b a s i n o u t l e t s , surface  Rivers.  r e s p e c t i v e l y , and u s u a l l y c o n t a i n a p e r e n n i a l  stream a l o n g one margin of the d e p o s i t .  avalanches  and r o c k f a l l s d e l i v e r sediment  P e r e n n i a l streamflow on the s u r f a c e  Fluvial  processes,  t o the s u r f a c e of these  B l o c k f i e l d s a r e found on e l e v a t e d  rock p l a t f o r m s ,  and c o l s . Sediments are d e r i v e d by in situ  contacts  order  sediment.  i c e eroded benches  m e c h a n i c a l and c h e m i c a l  p a r t i c u l a r l y along  non-conformable  of v a r i o u s v o l c a n i c rock t y p e s . They are perhaps the  important sediment  deposits.  and a c t i v e toe e r o s i o n by h i g h e r  streams i n d i c a t e t h a t these landforms are an important s o u r c e of  w e a t h e r i n g of w e l l j o i n t e d b e d r o c k ,  snow  least  s o u r c e s because of l i m i t e d volumes and s t a b l e  upland  pos i t i o n s . L a t e r a l and p r o g l a c i a l t i l l valley,  formed by the r e c e s s i o n of  hanging v a l l e y , c i r q u e and n i c h e g l a c i e r s are the most  s o u r c e s of sediment where the d e p o s i t s torrent  deposits  channels  i n g l a c i e r i z e d p o r t i o n s of the catchment,  (i.e.  debris  ( f i g u r e 2.8a and b ) . A l t h o u g h the volume of m a t e r i a l i s low i n r e l a t i o n to the amount a v a i l a b l e f o r  low sediment d e l i v e r y r a t i o ) ,  b r a i d i n g are o b v i o u s impacts on the f l u v i a l from t h e s e s o u r c e s . overall  particularly  are on s t e e p t e r r a i n d r a i n e d by a v a l a n c h e and  d e l i v e r e d to the stream transport  important  importance.  On a b a s i n - w i d e a v e r a g e ,  a g g r a d a t i o n and channel  network  immediately downstream  l a t e r a l deposits  a r e of  less  F i g u r e 2.8 I l l u s t r a t i o n s of p r i m a r y c l a s t i c s e d i m e n t s o u r c e s f o r the h i g h e r - o r d e r f l u v i a l network i n B e l l a C o o l a b a s i n . (A) N i c h e g l a c i e r on the w e s t e r n f l a n k o f the Nusatsum b a s i n s u p p l i e s a s i g n i f i c a n t amount of sediment to c h a n n e l s b e l o w the g l a c i e r . The d e b r i s t o r r e n t s a r e w e l l c o n n e c t e d t o the h i g h - o r d e r f l u v i a l network. (B) Rock g l a c i e r / a b l a t i o n d e b r i s i n the s o u t h f o r k o f G y l l e n s p e t z Creek i s d i s s e c t e d by numerous a v a l a n c h e c h u t e s on e a s i l y eroded v o l c a n i c r o c k s . T h i s s i t e i s a s i g n i f i c a n t s o u r c e o f sediment f o r Talchako R i v e r . (C) P r o g l a c i a l l a k e of J a c o b s e n G l a c i e r a c t s as an i m p o r t a n t s t o r a g e s i t e f o r a b l a t i o n sediments and d e b r i s t r a n s p o r t e d by i c e m a r g i n a l streams. (D) Upland p l a i n i n the e a s t Nusatsum v a l l e y i s one o f s e v e r a l storage s i t e s for g l a c i a l derived sediments.  44  MS  **5 The f i n a l  s o u r c e s of c l a s t i c m a t e r i a l s are s u r f a c e wash, s o i l  and bank e r o s i o n . R o b e r t s and Church s o i l c r e e p , on a v e r a g e ,  (1986) e s t i m a t e t h a t s u r f a c e wash and  c o n s t i t u t e l e s s than 10-20% of the t o t a l  volume d e l i v e r e d to s m a l l , p a r t l y logged watersheds  sediment  i n the Queen C h a r l o t t e  I s l a n d s . R e l a t i v e d e l i v e r y r a t e s i n l a r g e , unlogged t r i b u t a r i e s , most of those  of the v e g e t a t i o n and a h i g h e r frequency of  l o w e r - g r a d i e n t s l o p e segments.  yield  Streambanks are an important source f o r  e n t r a i n m e n t of sediment b u t ,  e s t i m a t e s of c o n t r i b u t i o n to sediment  i n t e g r a t e d over an e n t i r e watershed are d i f f i c u l t  to make.  Four major types of sediment s t o r a g e have been i d e n t i f i e d B e l l a Coola b a s i n . F i r s t , lines,  such as  i n the B e l l a Coola b a s i n , would be p r o p o r t i o n a l l y lower due  to the s t a b i l i z i n g e f f e c t s  fluvial  creep  i n the  r e l a t i v e l y deep l a k e s a l o n g p r i n c i p a l  p a r t i c u l a r l y i n the A t n a r k o w a t e r s h e d , e f f e c t i v e l y  drainage  trap a l l  c l a s t i c sediment d e r i v e d from above each l a k e s i t e . The l a r g e s t ,  the  Charlotte  2  Lake  (65 km ) ,  i s fed by c r e e k s which d r a i n an area of a p p r o x i m a t e l y 750  2  km , thereby e l i m i n a t i n g any s i g n i f i c a n t c o n t r i b u t i o n from t h i s area of e a s t e r n catchment  the  (see f i g u r e 2.2 for l o c a t i o n s ) . Residence times i n these  s i t e s are comparable i n l e n g t h to the i n t e r v a l of d e g l a c i a t i o n (10 Shallow, p r o g l a c i a l  l a k e s formed d u r i n g r e c e n t g l a c i a l  retreat  years).  (figure  2.8c) a r e l e s s e f f i c i e n t s i n k s but e q u a l l y important over a s h o r t e r  time  2  scale  (10  years) ( c f . Smith et al.,  1982).  Second, upland v a l l e y t r a i n s form on l o w - g r a d i e n t , b e d r o c k c o n t r o l l e d , v a l l e y f l a t s a t h i g h e r e l e v a t i o n s i n p r o g l a c i a l areas of s o u t h w e s t e r n catchment, or on p l a t e a u areas of the e a s t e r n  the  catchment. 2  G l a c i a l and f l u v i a l sediments d e r i v e d areas as l a r g e as 30 km are s t o r e d a t these s i t e s ( f i g u r e 2 . 8 d ) . Trap e f f i c i e n c y i s l e s s than t h a t of l a k e s 3 4 but r e s i d e n c e times are e q u a l l y long  (estimated at  10  - 10  years).  r o c k s l i d e dams of v a r i o u s magnitudes a l s o form e f f e c t i v e b a r r i e r s to  Third, the  46 throughput of c l a s t i c m a t e r i a l s . T h e i r frequency of o c c u r r e n c e  3 l o w e r , but r e s i d e n c e times are a l s o long c o l l u v i u m and t i l l ,  (10  i s much  4 - 10  s t o r e d on many of the f o r e s t e d  years).  Finally,  h i l l s l o p e s , are p r o b a b l y  the l a r g e s t sediment s i n k s i n the b a s i n . U l t i m a t e t u r n o v e r r a t e s are most  4 likely  in excess of 10  years.  A e r i a l photographs and f i e l d sediment  e v i d e n c e i n d i c a t e t h a t much of  i n the upland t r i b u t a r i e s  the  i s d e r i v e d from w e l l - d e f i n e d , u n s t a b l e  s l o p e s and bank e r o s i o n of m a t e r i a l a l r e a d y s t o r e d w i t h i n the v a l l e y The d i s t r i b u t i o n and volume of the major sediment s o u r c e s , l o c a t i o n s of major s t o r a g e s i t e s , tributaries  are p l o t t e d  p r o g l a c i a l deposits debris slopes  along w i t h  i n f i g u r e 2.9-  t h e r e are one or two p r i m a r y s o u r c e s ,  such as  flat. the  In s e v e r a l  unstable  ( e . g . Nusatsum, Nordschow, Thorsen Creeks) or composite  ( e . g . Burnt B r i d g e , Nordschow, Noosgulch  C r e e k s ) . The  combined area of the sediment sources i n f i g u r e 2.9 c o n s t i t u t e s l e s s than 16% of the e n t i r e w a t e r s h e d . These r e s u l t s suggest t h a t the t r a n s f e r of  2 sediment to the B e l l a Coola R i v e r over a time s c a l e of 10  3 - 10  a s s o c i a t e d w i t h a r e l a t i v e l y s m a l l number of upland sources and a c t i v i t y within several tributary  years  is  fluvial  channels.  (2.7) P e d o l o g i c S e t t i n g S o i l development variability  i n the B e l l a Coola b a s i n r e f l e c t s  i n topography,  frequent  the  strong  sediment a d d i t i o n s from r i v e r  flooding  i n the v a l l e y and, at h i g h e r e l e v a t i o n s , slow d e c o m p o s i t i o n of o r g a n i c m a t e r i a l . W i t h i n the c o n f i n e s of v a l l e y bottoms most s o i l s v a r y between p o o r l y developed o r t h i c r e g o s o l s and e u t r i c b r u n i s o l s M i n i s t r y of A g r i c u l t u r e ,  1973)* T h i n Ah h o r i z o n s  are common on many a l l u v i a l  (British  Columbia  (3 to 5 cm) over f i n e sand  s u r f a c e s where, a d d i t i o n s of m i n e r a l matter may  exceed o r g a n i c matter a c c u m u l a t i o n s i g n i f i c a n t l y .  Under t h i c k c o n i f e r o u s  F i g u r e 2 . 9 Major c l a s t i c sediment sources f o r the h i g h e r - o r d e r f l u v i a l network and e s t i m a t e s of r e s i d e n c e time in important s t o r a g e s i t e s . Arrows r e p r e s e n t the l o c a t i o n of both the sediment sources and p r i m a r y r o u t e s through which sediment i s t r a n s f e r r e d (see t e x t f o r d i s c u s s i o n ) .  ^  48 forest if  c o v e r , d y s t r i c b r u n i s o l s may develop i n t o o r t h i c h u m o - f e r r i c  the s i t e has remained s t a b l e  podzols  f o r some t i m e . Organic s o i l s a r e r e s t r i c t e d  to p o o r l y d r a i n e d l o c a t i o n s surrounded by both c o n i f e r o u s and deciduous vegetation.  T y p i c m e s i s o l s and h y d r i c f i b r i s o l s occupy many o f the w a t e r -  s a t u r a t e d a l p i n e meadows.  (2.8)  Flora The f l o r i s t i c  component o f the landscape  p r o v i d e s an e s s e n t i a l  geomorphic a c t i v i t y and h y d r o l o g i c change w i t h i n c e r t a i n boundaries.  The c a p a c i t y of many s p e c i e s  extremes y e t p r e s e r v e  to withstand  e v i d e n c e of s t r e s s f u l  with geomorphic/hydrologic events, r e l a t i v e d a t i n g . For t h i s purpose  periods,  key t o  growth-time  environmental provides  correlations  as w e l l as a b a s i s f o r a b s o l u t e and some of the dominant  vegetation  communities a r e n o t e d . S i x b i o g e o c l i m a t i c zones and s e v e r a l subzones  have been  identified in  the B e l l a Coola b a s i n , each based on the dominance or co-dominance of climax tree species  (Robinson and P o j a r ,  1981; Leaney and M o r r i s ,  Along the l o w e r - e l e v a t i o n w e s t e r n p e r i p h e r y where m i l d , m o i s t , c o n d i t i o n s p r e v a i l , a t h i c k cover of w e s t e r n red cedar and w e s t e r n hemlock and t a l l e s t  (Tsuga heterophylla  (Raf.)  Sarg.)  198l).  maritime  (Thuja plicata  Donn)  i s found. The o l d e s t  timber grows on c o m p a r a t i v e l y o r g a n i c - r i c h s o i l s of the  f l o o d p l a i n and steep c o l l u v i a l  slopes.  At e l e v a t i o n s below 500 m between  B e l l a C o o l a and F i r v a l e a m i x t u r e of Douglas f i r (Pseudotsuga menziesii (Mirb.)  Franco)  d e v i l ' s club  and w e s t e r n hemlock o v e r l i e an u n d e r s t o r y  (Oplopanax horridus).  Douglas f i r / r e d cedar/moss  of mosses and  T h i s a s s o c i a t i o n grades q u i c k l y  into a  ecosystem e a s t o f F i r v a l e .  The B e l l a Coola R i v e r f l o o d p l a i n i s dominated by a f o r e s t  cover  i n d i c a t i v e of e a r l y s u c c e s s i o n a l phases on r e c e n t l y f l o o d e d s u r f a c e s o r  ^9 areas w i t h h i g h water t a b l e s , more s t a b l e s u r f a c e s . red  alder  and l a t e s u c c e s s i o n a l s p e c i e s on h i g h e r and  Black cottonwood (Populus  (Alnus Rubra Bong.)  and w h i t e b i r c h  trichocarpa (Betula  T o r r . £ Gray),  papyrifera  Marsh.)  are most e v i d e n t on r e c e n t l y c o l o n i z e d p o r t i o n s of the f l o o d p l a i n  while  Western red c e d a r ,  Douglas  fir  S i t k a spruce  (P/cea sitchensis  and w e s t e r n hemlock dominate o l d e r s t a b l e  (Bong.) C a r r . ) ,  areas.  At m i d d l e e l e v a t i o n s throughout most of the b a s i n  (150  to 1000 m)  t h e r e e x i s t s a c l i m a x ecosystem comprised of hemlock, a m a b i l i s f i r amabilis  (Dougl.) Forbes)  and o c c a s i o n a l l y s u b a l p i n e f i r  (Hook.) N u t t . ) . Above 1000  lasiocarpa  m t h e r e i s a c o n t i n u o u s cover of mountain  hemlock, a m a b i l i s f i r and y e l l o w cedar Spach) a l t h o u g h the l a t t e r ,  (Abies  (Abies  (Chamaecyparis  nootkatensis  which o c c u p i e s a mesic h a b i t a t ,  the e a s t o n l y . A zone of Engelmann spruce  (Picea  (D. Don)  is present  in  engelmanni i P a r r y ) and  s u b a l p i n e f i r o c c u r s between the a l p i n e tundra and mountain hemlock z o n e . Lodgepole p i n e  (Pinus contorta  occur f r e q u e n t l y ,  D o u g l . ) i s a co-dominant s p e c i e s where  such as the d r i e r  I n t e r i o r P l a t e a u , p r o h i b i t i n g the  development of a c l i m a x s p r u c e - f i r f o r e s t  .  The e l e v a t i o n of the contemporary t r e e l i n e averages above sea l e v e l , but f l u c t u a t e s  s p a t i a l l y w i t h changes  1600  to 1650 m  in aspect,  slope  s t a b i l i t y and m i c r o c l i m a t e . W i t h i n the tundra are a v a r i e t y of a l p i n e meadow s p e c i e s such as mosses,  fires  l i c h e n and h e a t h e r .  50 (2.9) S e t t l e m e n t and Logging H i s t o r y  H i s t o r i c a l observations  and f a c t o r s  influencing settlement  patterns  p r o v i d e a p o t e n t i a l l y v a l u a b l e source of both d i r e c t and i n d i r e c t e v i d e n c e of e n v i r o n m e n t a l change.  P r i o r to European c o n t a c t  i n the l a t e  l8th century  the B e l l a Coola v a l l e y was p o p u l a t e d by Indians of the S a l i s h n a t i o n , a s p l i n t e r group from t r i b e s of the  1970). E s t i m a t e s by M c l l w r a i t h  (Kopas,  (I985) show t h a t at sites,  i n t e r i o r and s o u t h e r n c o a s t  least  regions  (19^8) and more r e c e n t l y by Lepofsky  2,700 p e o p l e , c o n c e n t r a t e d  i n 27 known v i l l a g e  o c c u p i e d the v a l l e y between S t u i e and B e l l a C o o l a . S i n c e f i s h i n g was  the p r i m a r y economic r e s o u r c e , a c c e s s i b i l i t y to r i v e r h a b i t a t s shifting  v i l l a g e l o c a t i o n s were m o s t l y determined by f a v o r a b l e f o r s a l m o n . F l o o d i n g and c h a n n e l  are known to have i n f l u e n c e d s e t t l e m e n t  structures  l o c a t i o n s and the type of  constructed.  F i r s t w h i t e c o n t a c t was made i n 1793  by a s h i p from the f l e e t of  C a p t a i n Vancouver making e x p l o r a t i o n s of Burke Channel and N o r t h and South B e n t i n c k Arms. One month a f t e r  the f i r s t d i r e c t c o n t a c t ,  Alexander  MacKenzie, t r a v e l l i n g by land from F o r t Chipewyan on Lake A t h a b a s c a , descended first  i n t o the v a l l e y along the e a s t f l a n k of Burnt B r i d g e Creek,  Caucasian  to reach the North American west c o a s t  (north of Mexico) by  l a n d . No permanent w h i t e s e t t l e m e n t s were e s t a b l i s h e d u n t i l years a f t e r  the  1867.  four  L i e u t e n a n t Henry S. Palmer made the f i r s t survey of the  route  between B e l l a Coola and F o r t A l e x a n d r i a on the F r a s e r R i v e r . S e v e r a l of v i l l a g e s i t e s were s t i l l  s e a s o n a l l y o c c u p i e d when the l a r g e s t  Europeans, m o s t l y Norwegians, s e t t l e d  1863*  I889-I893 and g e o l o g i c a l mapping by G . M . Dawson systematic notes,  1896.  the l e g a l survey of  (I878)  r e c o r d s of the B e l l a Coola e n v i r o n m e n t .  journals,  i n f l u x of  i n the v a l l e y i n the autumn of  The p r e l i m i n a r y land survey by Palmer i n  the  are the  first  E x p l o r a t i o n and survey  l e t t e r s and d i a r i e s from these sources a l o n g w i t h  limited  51 a r c h a e o l o g i c a l e v i d e n c e from the p r e - c o n t a c t  p e r i o d p r o v i d e some d a t a  r e g a r d i n g e n v i r o n m e n t a l c o n d i t i o n s over the l a s t s e v e r a l Interpretation  of a e r i a l photographs  e a r l y 1950s timber removal was r e s t r i c t e d bottom and was m o s t l y r e l a t e d  centuries.  demonstrates t h a t p r i o r to  the  to s m a l l p l o t s on the v a l l e y  to land c l e a r a n c e .  Between 1946  and 195^  only  2 about 3 km  had been c o m m e r c i a l l y l o g g e d , a l l of i t below the Nusatsum  R i v e r c o n f l u e n c e . Up u n t i l  1968  an a d d i t i o n a l 13 km had been logged m o s t l y z  a l o n g the s t e e p e r s l o p e s above B e l l a Coola R i v e r and i n the S a l l o o m t , Nusatsum, Noosgulch and C a c o o h t i n t r i b u t a r i e s .  From 1968  to 197** another  8  2 km  was l o g g e d , much of i t on the f l o o d p l a i n above Burnt B r i d g e Creek and  p a r t l y on v a l l e y s l o p e s of the lower T a l c h a k o R i v e r . D e c l i n i n g prices  i n the l a s t 5 years have r e s u l t e d  timber  i n renewed a c t i v i t y i n the more  2 a c c e s s i b l e t r i b u t a r i e s i n the B e l l a Coola b a s i n . Thus over 18 km has been logged s i n c e 1974, much of i t c o n c e n t r a t e d i n the Nusatsum and Noomst  2 Creeks and upper B e l l a Coola R i v e r . The t o t a l of 43 km  represents  less  than 1% of the b a s i n area but the c o n c e n t r a t i o n of commercial timber removal on lower s l o p e s and at t r i b u t a r y j u n c t i o n s catchment would suggest a g r e a t e r p o t e n t i a l f o r  i n the  southwestern  impact on sediment  yield.  52 CHAPTER I I I H y d r o p h y s i c a l Records o f Environmental Change: T e s t s W i t h i n t h e Instrument P e r i o d (3-0)  Introduction  Variations  i n r e g i o n a l c l i m a t e are u l t i m a t e l y r e l a t e d to  i n a t m o s p h e r i c c i r c u l a t i o n . These can occur as p e r s i s t e n t circulation features,  intensity,  shifts  i n the mean p o s i t i o n of  or l a r g e - s c a l e changes  inferences  change u s i n g p r e d o m i n a n t l y b i o g e o p h y s i c a l e v i d e n c e , r e l a t i o n s h i p s between v a r i o u s itself  departures in  atmospheric  in c i r c u l a t i o n p a t t e r n .  about the n a t u r e of atmospheric p r o c e s s e s  fluctuations  When making  and e n v i r o n m e n t a l the  functional  i n d i c a t o r s of c l i m a t e change and c l i m a t e  need to be examined f o r a p e r i o d i n which both the c l i m a t i c  perturbations t h i s chapter  and e n v i r o n m e n t a l responses are known. It to a s s e s s the s t r e n g t h  i s the purpose of  and form of these cause and  effect  r e l a t i onsh i p s .  (3.1) Post-1945 S y n o p t i c C l i m a t o l o g y o f the N.E. P a c i f i c  Sector  P r e c i p i t a t i o n and temperature are commonly a v a i l a b l e measures of c l i m a t e , and p r o v i d e a means f o r a s s e s s i n g  the e f f e c t s  of changing  a t m o s p h e r i c c i r c u l a t i o n . E s t a b l i s h i n g the n a t u r e of s e c u l a r v a r i a t i o n s temperature and p r e c i p i t a t i o n f o r a g i v e n r e g i o n can be d i f f i c u l t reasons:  (1)  for  three  i n s u f f i c i e n t s a m p l i n g d e n s i t y f o r an area which e x h i b i t s  large  s p a t i a l v a r i a t i o n s - t h i s may be due to r e a l d i f f e r e n c e s or  alternatively,  devices; changes  (2)  in  to apparent d i f f e r e n c e s  in l o c a l  climate,  produced by v a r i o u s s a m p l i n g  l a c k of temporal homogeneity at a s t a t i o n due to r e l o c a t i o n or  i n d a t a c o l l e c t i o n procedures  and equipment;  methods of a n a l y z i n g and p r e s e n t i n g d a t a . sources of e r r o r ,  (3)  inadequate  Keeping i n mind these p o t e n t i a l  d a t a from s e v e r a l c l i m a t e s t a t i o n s  Coola were examined i n order  and  to i d e n t i f y the r e g i o n a l  i n and around response.  Bella  53 E i g h t c l i m a t e s t a t i o n s , e x t e n d i n g as f a r west as the o u t e r  coastal  p l a i n and as f a r e a s t as the c e n t r a l C h i l c o t i n R i v e r b a s i n , were used t o c o m p i l e s e a s o n a l averages of monthly mean p r e c i p i t a t i o n and (see f i g u r e 2.1 f o r s t a t i o n l o c a t i o n s and t a b l e 3 - l ) » Winter  temperature i s d e f i n e d as  the i n t e r v a l October to A p r i l and summer as May to A u g u s t . September was not i n c l u d e d  i n e i t h e r s e a s o n a l average because of the s i g n i f i c a n t  c o r r e l a t i o n between summer temperature and September temperature  negative (i.e.  tends t o dampen the s i g n a l ) and r e l a t i v e l y low t o t a l p r e c i p i t a t i o n d u r i n g t h i s month. A l l s e a s o n a l d a t a s e r i e s were e n t e r e d  into a factor analysis  which y i e l d e d two d i s t i n c t groups based p r i m a r i l y on v a r i a t i o n s i n precipitation interior  ( t a b l e 3-1)• They are r e f e r r e d to here as c o a s t a l and  r e g i o n s and are s p l i t between the lower e l e v a t i o n s i t e s  west and h i g h e r e l e v a t i o n s t a t i o n s Secular trends  to  the  i n the l e e of the Coast M o u n t a i n s .  i n temperatures were s i m i l a r enough to a l l o w c o n s i d e r a t i o n  of a l l s t a t i o n s as one group, b u t ,  f o r c o n s i s t e n c y , temperature  trends  are  a l s o examined in the two r e g i o n s . To maximize the r e g i o n a l s i g n a l s e a s o n a l v a r i a b l e s f o r a g i v e n r e g i o n are s t a n d a r d i z e d , averaged and then p l o t t e d as a d j u s t e d p a r t i a l sums u s i n g the f o l l o w i n g  scheme:  n P  P  t  t  n  ,T  tn  X . X"!  tn' tn= T  x  tj -  X  J  /n  E  j= l  t=l  = c u m u l a t i v e sum of s t a n d a r d i z e d s e a s o n a l p r e c i p i t a t i o n (P J 4. IT \ c nt or temperature U ) f o r n s t4.a t4.i-o n s and tj _ years = observed s e a s o n a l v a l u e f o r year t and s t a t i o n j = 1951-1980 s e a s o n a l mean f o r s t a t i o n j .  A d j u s t e d p a r t i a l sums have advantages over s i m p l e moving average t e c h n i q u e s . These i n c l u d e g i v i n g equal w e i g h t t o g e n e r a l l y w e t t e r and  54  Table 3.1:  Climate Stations i n and near the B e l l a Coola River Basin.  Latitude  Longitude  Elevation  Years of Record  Variables  (ra)  number of  Rotated  station moves  Components  (year)  B e l l a Coola  52 20'  125 38'  1895-Present  B.C. Hydro  52 22'  126 49'  1961-Prasent  Ocean F a l l s  52°21'  127°41'  1924-Present  Bella Bella  52°10'  128°09'  Kleena Kleene  51 59'  124"56'  Tatlayoko Lake  51°40'  T a t l a Lake Big Creek  T,P  1  2  1 C1959)  0.712  0.431  0  0.599  0.395  0  0.812  0.298  1 (1966)  0.839  0.169  T,P  0  0.313  0.746  1928-Present  T,P  1 (1979)  0.453  0.865  51°54'  1973-Present  T,P  0  0.239  0.731  51°10'  1904-Present  T,P  1 (1978)  0.121  0.649  B e l l a Coola  T,P P only  INTERIOR  847  percent t o t a l variance OTHER STATIONS  Anahim Lake  52 20'  126 15'  52 21'  125 20'  1097  1954-1967  T,P  52°28'  125°18'  1054  1975-1980  T,P  T,P  1. See figure 2.1 f o r locations. 2. T i s temperature.  P i s precipitation.  3. Rotated component loadings f o r p r e c i p i t a t i o n stations. Stations are grouped according to the strength of t h e i r c o r r e l a t i o n with each factor. See text f o r discussion.  54.9Z  25.IX  55 g e n e r a l l y d r i e r s t a t i o n s w i t h i n a r e g i o n as w e l l as d i s p l a y i n g both h i g h frequency  (year t o year)  and low frequency  stations.  Secular v a r i a t i o n s  (decennial)  t r e n d s common t o a l l  i n s e a s o n a l p r e c i p i t a t i o n and temperature  between 19^5 and 1984 a r e shown i n f i g u r e 3 » 1 - P o s i t i v e s l o p e segments i n d i c a t e p e r s i s t e n t l y above average c o n d i t i o n s whereas n e g a t i v e s l o p e s a r e i n d i c a t i v e of below average c o n d i t i o n s . The i n t e r v a l 1945 t o 1984 was s e l e c t e d t o f a c i l i t a t e comparisons w i t h other c o l l e c t e d f o r t h i s p e r i o d o n l y . The 3 to be a r e p r e s e n t a t i v e  n  h y d r o c l i m a t i c data which were  year mean (1951-1980) i s c o n s i d e r e d  of the p e r i o d average and i s a l s o t h e adopted  s t a n d a r d by v a r i o u s atmospheric  agencies.  S e c u l a r Trends i n Seasonal Temperature and P r e c i p i t a t i o n  Winter temperatures show the g r e a t e s t y e a r - t o - y e a r  v a r i a n c e over the  common p e r i o d , and l o n g - t e r m t r e n d s show a h i g h s p a t i a l coherence the c o a s t a l and i n t e r i o r r e g i o n s  (figure 3 - l a ) .  between  Between 1948 and 1957.  c o n s i s t e n t l y below normal temperatures p r e v a i l e d i n both r e g i o n s , from 1958-1965 t h i s t r e n d r e v e r s e d  whereas  i t s e l f w i t h above normal w i n t e r  temperatures d o m i n a t i n g . F l u c t u a t i o n s which f o l l o w e d were o f lower magnitude, m a i n t a i n i n g near average c o n d i t i o n s u n t i l  1975 when w i n t e r  temperatures were once a g a i n m o s t l y above n o r m a l . Summer temperature departures Interior  ( f i g u r e 3 - l c ) a r e l e s s pronounced and more p e r s i s t e n t  w i t h i n the  region.  T o t a l October t o A p r i l p r e c i p i t a t i o n t r e n d s a f t e r  i960 show a s t r o n g  i n t e r - r e g i o n a l coherence w i t h above normal p r e c i p i t a t i o n from 196l t o 1968, average c o n d i t i o n s between I969 and 1976, and below normal a f t e r 1977 ( f i g u r e 3 - l b ) . P r i o r t o i960 t h e t r e n d s between r e g i o n s a r e i n v e r s e l y r e l a t e d , w i t h the e x c e p t i o n of a few years c h a r a c t e r i z e d by average p r e c i p i t a t i o n everywhere. Summer p r e c i p i t a t i o n ( f i g u r e 3 - l d ) has lower  56  1940  1950  1960  1970  1950  1960  1970  1980  1990  +—*—• c o a s t a l  1940  1980  1990  Years (AO)  F i g u r e 3 - 1 A d j u s t e d p a r t i a l sums of s e a s o n a l t e m p e r a t u r e and p r e c i p i t a t i o n f o r c o a s t a l and i n t e r i o r r e g i o n s of w e s t - c e n t r a l B r i t i s h C o l u m b i a . D e p a r t u r e s a r e from the 1 9 5 1 - 1 9 8 0 s t a t i o n normals and a r e summed from 1 9 ^ 5 to 1 9 8 3 - P o s i t i v e s l o p e segments i n d i c a t e p e r s i s t e n t above average d e p a r t u r e s and n e g a t i v e s l o p e s below average departures.  57  year-to-year  v a r i a n c e and the g r e a t e s t  most l i k e l y  related  d u r i n g the summer. Interior  to d i f f e r e n c e s  inter-regional differences,  in p r e c i p i t a t i o n generating  C o n v e c t i v e thunderstorms occur f r e q u e n t l y  r e g i o n whereas summer r a i n f a l l  from c y c l o n i c d i s t u r b a n c e s .  a l o n g the c o a s t  which  mechanisms  in  the  is mostly derived  S i n c e 1965» summer p r e c i p i t a t i o n a l o n g  the  c o a s t g e n e r a l l y has been above normal and normal to below normal f o r Interior.  Near average c o n d i t i o n s are e v i d e n t  except f o r  increases  Overall, coastal  i n the  trends  the  i n both r e g i o n s p r i o r to 1965  l a t e 1950s.  i n w i n t e r c l i m a t e are towards w e l l below normal  p r e c i p i t a t i o n and r e g i o n a l temperatures to 1957. above normal  p r e c i p i t a t i o n and temperatures to 1964/65, average c o n d i t i o n s until  is  everywhere  1976 and then below normal p r e c i p i t a t i o n and above average  temperatures to 1983- S e c u l a r v a r i a t i o n s v a r i a b l e because of the  increasing  i n summer c l i m a t e a r e  importance of l o c a l i z e d  more  atmospheric  i nstabi1i ty.  Comparison With  Other  Temperature  Coastal  Regions o f B r i t i s h  and p r e c i p i t a t i o n t r e n d s f o r most of the p r o v i n c e  been examined by Crowe (1963). P o w e l l al.  (1984).  climate shifts  unweighted moving  (Mitchell,  1966) . More r e c e n t l y ,  temperature and p r e c i p i t a t i o n f l u c t u a t i o n s  on the Queen C h a r l o t t e the B r i t i s h  Islands  have been  undertaken  (Karanka, 1986) and v a r i o u s s t a t i o n s a l o n g  Columbia and U n i t e d S t a t e s west c o a s t  and s o u t h e r n  of  investigations  (McGuirk,  1982; Y a r n e l ,  1985). A g e n e r a l i z e d summary of w i n t e r p r e c i p i t a t i o n t r e n d s f o r central  analysis  i n c l i m a t e when more p r e c i s e d e t e r m i n a t i o n s  are r e q u i r e d  have  (1975) and Thomson et  a method which i s p o o r l y s u i t e d for d e t a i l e d  secular v a r i a t i o n s  of w i n t e r  (1965). Thomas  In each a n a l y s i s , v a r i a b l y - l e n g t h e n e d ,  averages were used, of  Columbia  coasts is presented  in figure  3'2.  the  north,  58  A  North Coast  ' B  1 '  i  •  i  i  i  ^  i  i  i  i  i  r  i  1  Central Coast 1  i  i  i  i  i  i  - ~\  i  1  • o  1  I  1  SST anomalies N.E. Pacific i  1 i  r  r  1  i  T-  1  + o  i  1  1 ' South Coast • j  i  + o  + r—  F i g u r e 3 ' 2 G e n e r a l i z e d d e p a r t u r e s o f w i n t e r p r e c i p i t a t i o n from p o s t 1945 n o r m a l s . Bottom f i g u r e i s g e n e r a l i z e d t r e n d s i n s e a s u r f a c e t e m p e r a t u r e s . Areas above and below t h e z e r o l i n e d e f i n e p e r i o d s o f above and below normal p r e c i p i t a t i o n , r e s p e c t i v e l y . The magnitudes o f d e p a r t u r e a r e n o t i n d i c a t e d . A) n o r t h c o a s t t r e n d s from Karanka (1986) (normal p e r i o d 1900-1983) and Y a r n e l (I985) (normal p e r i o d 1948-1980); B) c e n t r a l c o a s t ( t h i s s t u d y ) ; C) south c o a s t from P o w e l l (1965) (normal p e r i o d 1900-1960) and Y a r n e l (1985); D) sea s u r f a c e t e m p e r a t u r e anomalies f o r t h e n o r t h e a s t P a c i f i c ( C h e l t o n , 1984) (normal p e r i o d 1947-1984) .  59 The most o b v i o u s f e a t u r e o f c l i m a t e change a l o n g the n o r t h e a s t Pacific  sector  i s t h e synchronous s h i f t  i n 1976 t o above average  p r e c i p i t a t i o n a l o n g t h e n o r t h c o a s t and s o u t h e a s t precipitation  A l a s k a , and below average  i n the c e n t r a l and south c o a s t r e g i o n s . As i n d i c a t e d i n  f i g u r e 3-2, these changes were a s s o c i a t e d w i t h a s h i f t t o above normal sea s u r f a c e temperatures  (SST) i n t h e n o r t h e a s t  Pacific.  P r i o r t o 1976  p r e c i p i t a t i o n t r e n d s a l o n g the c e n t r a l c o a s t appear t o r e p r e s e n t a t r a n s i t i o n a l phase between the almost i n v e r s e l y r e l a t e d t r e n d s of t h e n o r t h e r n and s o u t h e r n c o a s t s . For example, above average p r e c i p i t a t i o n a l o n g t h e n o r t h c o a s t between 1958 and 1964 p e r s i s t e d u n t i l c e n t r a l c o a s t and u n t i l  1976 a l o n g the south c o a s t ,  1969 a l o n g the  s u g g e s t i n g a southward  shift  i n m o i s t u r e b e a r i n g d i s t u r b a n c e s through t h i s p e r i o d  1983;  Karanka,  ( c . f . Namias,  1986) . Between 19^5 and 1957 when w i n t e r p r e c i p i t a t i o n was  average t o below average f o r much o f c o a s t a l B r i t i s h Columbia, SSTs were average t o above a v e r a g e . U n l i k e p r e c i p i t a t i o n , w i n t e r temperature s p a t i a l and temporal coherence s i m i l a r average  t r e n d s show a much g r e a t e r  t o those  i n f i g u r e 3 - l a . Above  (1958-1964, 1976-1983) and below average temperatures  (1948-1957,  1965-1975) f o r a l l c o a s t a l areas c o r r e s p o n d c l o s e l y t o p o s i t i v e and n e g a t i v e SST a n o m a l i e s , r e s p e c t i v e l y . S e c u l a r v a r i a t i o n s i n summer temperature and p r e c i p i t a t i o n have not been examined c l o s e l y except f o r t h e earlier  i n v e s t i g a t i o n s of Crowe (1963) and P o w e l l  (1965)• There i s some  i n d i c a t i o n of r e g i o n a l l y c o n s i s t e n t t r e n d s w i t h above average p r i o r t o 1952 and average t o below average temperatures  I960.  temperatures  between 1953 and  60 Atmospheric  Circulation  Usually, adequately  no one f e a t u r e of the a t m o s p h e r i c c i r c u l a t i o n can e x p l a i n  variations  in surface  c l i m a t e s . Sea l e v e l p r e s s u r e p a t t e r n s ,  p o s i t i o n i n g of h e m i s p h e r i c semi-permanent d i r e c t i o n of f l o w a l o f t ,  p r e s s u r e systems,  mean p o s i t i o n of s e a s o n a l  fronts,  storms and o r i e n t a t i o n of storm t r a c k s a r e a l l important However, t h e r e i s i n c r e a s i n g e v i d e n c e of  interactive  a t m o s p h e r i c c i r c u l a t i o n and SST a n o m a l i e s .  i n t e n s i t y and frequency of  components.  linkages  It appears from f i g u r e 3-2 t h a t  much of the r e c e n t c l i m a t i c v a r i a b i l i t y a l o n g the B . C . c o a s t w i t h t h e s e a n o m a l i e s . H o r e l and W a l l a c e (1981) normal SSTs i n the e a s t e r n n o r t h P a c i f i c  result  demonstrated  R i d g i n g a l o n g the c o a s t  is  associated  that  above  i n the development of a  h i g h p r e s s u r e r i d g e over w e s t e r n North America and a trough Pacific.  between  i n the  central  i s o f t e n a s s o c i a t e d w i t h a westward  shift  i n the A l e u t i a n Low ( A n g e l l and K o r s h o v e r , 1982). If  r i d g i n g extends out  outcomes:  i n t o the P a c i f i c  c o o l / d r y c o n d i t i o n s as n o r t h w e s t e r l y  southward down the t r a i l i n g limb of the r i d g e conditions (Yarnel,  then t h e r e are two p o s s i b l e  i f the r i d g e a x i s  is centreed  1985)- Wet c o n d i t i o n s w i l l  i.e. z o n a l f l o w o c c u r s  airflow aloft  is  advected  ( f i g u r e 3'3a) or warm/dry  over the c o a s t  ( f i g u r e 3-3b)  p r e v a i l i f r i d g i n g is poorly developed,  ( f i g u r e 3 ' 3 c ) , or  i f the r i d g e i s d i s p l a c e d  by an i n t e n s i f i e d A l e u t i a n Low, i n which case the c o a s t upsweeping, s o u t h e a s t e r n quadrant of the  i s under  eastward  the  broad,  low ( f i g u r e 3 - 3 d ) . A n a l y s e s of  post-1945 s y n o p t i c - s c a l e c i r c u l a t i o n f e a t u r e s by B a l l i n g and Lawson (1982) and McGuirk  (1982)  i n d i c a t e t h a t f l o w p a t t e r n s have been d o m i n a n t l y  meridional,  c h a r a c t e r i z e d by a low Rossby wave number l e a d i n g to  and sometimes extreme c l i m a t i c d e p a r t u r e s and abrupt character  of the c l i m a t e .  shifts  in  persistent  the  F i g u r e 3-3 S y n o p t i c - s c a l e p r e s s u r e p a t t e r n s (500 mb) l e a d i n g to d i s t i n c t d e p a r t u r e s of t e m p e r a t u r e and p r e c i p i t a t i o n i n s o u t h w e s t e r n B r i t i s h Columbia (from Y a r n e l , 1985)- (A) High p r e s s u r e r i d g i n g e x t e n d s beyond the c o a s t to produce c o o l / d r y c o n d i t i o n s . (B) R i d g i n g i s c e n t r e d over the c o a s t r e s u l t i n g i n warm/dry w e a t h e r . (C) C o o l e r and w e t t e r c o n d i t i o n s o c c u r when r i d g i n g i s not dominant p r o d u c i n g zones of i n t e n s e 500 mb f l o w . (D) R i d g i n g o c c u r s to the e a s t of the c o a s t r e s u l t i n g i n warm/wet c o n d i t i o n s .  62 Based on the t r e n d s  i n f i g u r e s 3-1 and 3-2 and the r e s u l t s  reviewed  above, p o s i t i v e SST anomalies between I958 and 1968, a s s o c i a t e d w i t h r i d g i n g over the west c o a s t , c e n t r a l and n o r t h c o a s t s .  promoted above average p r e c i p i t a t i o n a l o n g the  Although s t a t i s t i c a l c o n f i r m a t i o n s cannot be made  w i t h the a v a i l a b l e storm t r a c k d a t a ,  t h i s would correspond to a northward  d i s p l a c e m e n t of c y c l o n i c t r a j e c t o r i e s .  Below average p r e c i p i t a t i o n  after  1976 f o r the c e n t r a l and s o u t h e r n c o a s t s o c c u r r e d when the A l e u t i a n Low s h i f t e d westward s i g n i f i c a n t l y f u r t h e r  enhancing the northward d i s p l a c e m e n t  of storm t r a c k s .  Frequency and Seasonal P e r s i s t e n c e o f S y n o p t i c Types  P e r i o d s of p e r s i s t e n t  departures  i n s e a s o n a l temperature  or  p r e c i p i t a t i o n are thought to be c h a r a c t e r i z e d by a s e t of unique s y n o p t i c c o n d i t i o n s which produce the observed trends Each season  (I.e. wet, d r y , c o o l , warm).  i s comprised of a l a r g e number of s y n o p t i c t y p e s . However, i t  i s l i k e l y the frequency or w i t h i n - s e a s o n p e r s i s t e n c e of o n l y c e r t a i n s y n o p t i c types d r i v e s the mean d e p a r t u r e .  This hypothesis  is tested  here  u s i n g an o b j e c t i v e l y d e f i n e d s e t of s y n o p t i c types which are known to certain climatic  yield  characteristics.  S y n o p t i c c i r c u l a t i o n types f o r a p a r t i c u l a r season and sequence of years were i d e n t i f i e d u s i n g a c a t a l o g u e of d a i l y 500 mb and d a i l y p r e s s u r e p a t t e r n s developed by Y a r n e l the n o r t h e a s t e r n  Pacific.  (1983) and B a r r y et al.  (1982) f o r  Both c a t a l o g u e s were c o n s t r u c t e d u s i n g the  o b j e c t i v e c l a s s i f i c a t i o n scheme of K i r c h h o f e r  (1973)  i n which e s t i m a t e s of  d a i l y atmospheric p r e s s u r e at p r e d e f i n e d h e m i s p h e r i c g r i d p o i n t s subjected of  surface  to a sequence of s e l e c t i o n and g r o u p i n g p r o c e d u r e s .  the c a t a l o g u e s and g r o u p i n g schemes are g i v e n i n K i r c h h o f e r  are  Full  details  (1973) and  63 Yarnel  (1984).  Only p o t e n t i a l problems w i t h the t e c h n i q u e are c o n s i d e r e d  here.  (>10,000  Because of the l e n g t h of the study p e r i o d studies)  a p o r t i o n of the p r e s s u r e / e l e v a t i o n data s e t  'key days' representative  days i n both  i s used to d e f i n e  of s p e c i f i c s y n o p t i c g r o u p s . The major  here i s t h a t the s m a l l e r data s e t  is representative  of the range of  s y n o p t i c c o n d i t i o n s over the longer study p e r i o d . Problems w i t h K i r c h h o f e r method i n c l u d e :  (1)  assumption  s e l e c t i o n of a c u t o f f  the  threshold for grouping  types - a low t h r e s h o l d produces a l a r g e r s e t of s y n o p t i c types and  leaves  few days u n c l a s s i f i e d , whereas a h i g h t h r e s h o l d produces fewer types l e a v e s many u n c l a s s i f i e d days selection - size w i l l  1986); (2)  (Key and Crane,  grid  but  size  i n f l u e n c e the s p a t i a l r e s o l u t i o n of s y n o p t i c p a t t e r n s  w i t h l a r g e g r i d s y i e l d i n g poor d e f i n i t i o n of mesoscale c i r c u l a t i o n phenomena;  (3)  w i t h i n - g r o u p v a r i a b i l i t y - even s m a l l changes  i n f l e c t i o n p o i n t of a trough or r i d g e can a l t e r or p r e c i p i t a t i o n over an area w i t h no apparent of c i r c u l a t i o n ; and  (4)  i n the  the p a t t e r n of differences  temperature  i n the z o n a l i t y  s e v e r a l key s y n o p t i c types may not be c l a s s i f i e d by  the d a i l y a n a l y s i s d u r i n g a p e r i o d when c i r c u l a t i o n p a t t e r n s are changing r a p i d l y and when t h e r e i s a h i g h frequency of m i s s i n g d a t a . stringent  g r o u p i n g of s y n o p t i c types r e s u l t s  from the use of ' k e y d a y s ' and  s p e c i f i c a t i o n of a s u b j e c t i v e l y d e f i n e d g r o u p i n g t h r e s h o l d  1986),  Although a l e s s  (Key and Crane,  the same methods were employed i n both s t u d i e s , which enhances  c o m p a t i b i l i t y of i n t e r p r e t a t i o n s The Y a r n e l eighteen,  500 mb  (1983)  catalogue,  d e r i v e d from the f o r the p e r i o d  catalogues.  19^6-1978,  p r e s s u r e - e l e v a t i o n patterns for a  2.5°  X  i s based on  2.5°»  30-point  g r i d c o v e r i n g the c o a s t a l r e g i o n s o f B r i t i s h Columbia and the f a r Pacific.  The B a r r y e t  al. (1982)  catalogue  the  i s based on  31 s u r f a c e  eastern pressure  p a t t e r n s f o r a 35 point, 5° X 5° diamond-shaped g r i d over western North -  America and i s f o r t h e p e r i o d 1899 t o 1980. Only 6 g r i d - p o i n t s i n t h e l a t t e r catalogue f a l l The  w i t h i n the c o a s t a l B . C . and Gulf o f A l a s k a r e g i o n .  l a r g e r number o f s y n o p t i c types i n the s u r f a c e p r e s s u r e c a t a l o g u e i s  due t o t h e g r e a t e r v a r i a b i l i t y  i n surface pressure patterns  and t h e l a r g e r  s p a t i a l coverage of the g r i d . C h a r a c t e r i s t i c s of s y n o p t i c types i n each c a t a l o g u e a r e summarized i n t a b l e 3 - 2 . D i f f e r e n c e o f means t e s t s were c a r r i e d o u t t o determine i f t h e r e a r e s i g n i f i c a n t changes  i n the frequency o f s u r f a c e and 500 mb s y n o p t i c types  a s s o c i a t e d w i t h w i n t e r p r e c i p i t a t i o n f o r : (1) p e r i o d s of above average and below average p r e c i p i t a t i o n i n d i c e s a l o n g the c e n t r a l c o a s t and (2) groups of y e a r s comprised of t h e most extreme d e p a r t u r e s  i n winter p r e c i p i t a t i o n  i r r e s p e c t i v e of o r d e r i n g i n t i m e . * The r e s u l t s p r e s e n t e d  i n t a b l e 3-3a show  t h a t t h e frequency of "wet" s u r f a c e and 500 mb s y n o p t i c types a r e not s i g n i f i c a n t l y d i f f e r e n t between the d r y p e r i o d period  (1948A9 t o 1957/58) and wet  (1959/60 t o 1968/69). In c o n t r a s t , when groups of y e a r s  c h a r a c t e r i z e d by t h e most extreme d e p a r t u r e s a r e t e s t e d  ( t a b l e 3-3b),  there  i s a s i g n i f i c a n t d i f f e r e n c e between wet and d r y i n t e r v a l s w i t h an average of  t e n more days per w i n t e r season dominated by "wet" 500 mb types and  fifteen  more days per season dominated by m o i s t u r e b e a r i n g , s u r f a c e  lows.  The same sequence of t e s t s was conducted f o r c o o l and warm summer p e r i o d s , but due t o the c o m p a r a t i v e l y weak c i r c u l a t i o n the summer, t h e r e  i s greater d i f f i c u l t y  pressure patterns  a s s o c i a t e d w i t h extremes  o n l y t h e 500 mb p a t t e r n s  in i d e n t i f y i n g d i s t i n c t surface i n summer t e m p e r a t u r e . Thus,  a r e c o n s i d e r e d ( t a b l e 3-*0 • S i m i l a r c o n c l u s i o n s  can be made f o r summer temperature that there  i n t e n s i t i e s during  regimes as f o r w i n t e r p r e c i p i t a t i o n i n  i s no s i g n i f i c a n t d i f f e r e n c e i n the dominance o f a p a r t i c u l a r  1. Extreme years were d e f i n e d as those y e a r s w i t h c l i m a t i c d e p a r t u r e s i n excess of one s t a n d a r d d e v i a t i o n o f the mean. Sample s i z e s were determined by t h e group w i t h t h e fewest years f i t t i n g t h i s c r i t e r i o n .  65  Table 3.2.  Synoptic Types from Yarnel (1983), Barry et a l . (1982).  Climate E f f e c t  Synoptic C i r c u l a t i o n  Group or Type (Yarnel - 500 mb) (Barry - surface)  - southwesterly cyclonic component and advection of moist a i r due to p o s i t i v e 500mb pressure Wet Y-(l,3,4,8,10) B=<3,4,7,11,12, 15,23,31)  anomalies  above average p r e c i p i t a t i o n and  over the western USA and c e n t r a l  temperature  Canada and an i n t e n s i f i e d A l e u t i a n  (upper a i r types 1,4) and the c e n t r a l  Low  and southern coast (upper a i r types  - surface lows are mostly from the  f o r the entire B.C. coast  3,8,10)  west and northwest but also migrate from the south  Dry Winter Y=(5,9,14,15,17) B=(8,14,18,26,30J  north or northwest flow a l o f t  below average temperatures and  and strong ridging centered on  p r e c i p i t a t i o n f o r the entire coast  the coast  (upper a i r types 5,9) and the southern  surface lows diverted into Gulf  coast (upper a i r types 14,15,17)  of Alaska or southern US west coast  strong zonal flow or ridging  dry and warm for most of the c e n t r a l  Y-C2.6,11,13,18)  centered west of Vancouver  and southern coasts (upper a i r types  B=(5,6,9,13,21)  Island  2,6) occasional cold lows (11,13,18)  Dry Summer  ridging centered over the coast  w e l l above average temperatures f o r  Y=(l,4,6,7,15,18)  or inland with advection of warm  the entire coast (upper a i r types 1,4)  B*»<3,4,6,11,23,25)  a i r a l o f t from the southwest  Warm Summer  and above average for the c e n t r a l and southern coasts (6,7,15,18)  1. Type numbers r e f e r t o the 18 o b j e c t i v e l y c l a s s i f i e d d a i l y synoptic-scale patterns (500 mb) of Yarnel (1983) (Y=) and 31 surface pressure types of Barry et a l . (1982) (B=).  Table 3.3.  Winter P r e c i p i t a t i o n  and Synoptic Type Frequencies.  A. S i g n i f i c a n c e t e s t between a dry p e r i o d and a wet p e r i o d along the c e n t r a l B.C. coast Mean winter precipitation (mean departure)  Wet synoptic type frequency^  Wet synoptic 3 type frequency"  dry:  1948/49 to 1957/58  -0.04 ± 0.03  82.2 ± 8.3  42.5 ± 10.5  wet:  1959/60 to 1968/69  0.07 ± 0.05  86.6 ± 8.8  44.4 ± 7.8  One-tailed  t-test  t = 2.73  (a = 0.10, d f = 18)'  significant  t = 1.11 not  t = 0.46  significant  not  significant  B. S i g n i f i c a n c e t e s t between wet years and dry years dry years: 1978,71,70, 56,49  -0.19 ± 0.08  78.8 ± 7.0  33.4 ± 7.23  0.27 ± 0.08  89.4 ± 5.8  48.0 ± 8.9  wet years: 1976,74,68, 64,54 One-tailed t - t e s t (<z = 0.10, d f = 8)  t - 8.48  t = 3.38  significant  significant  1. C a l c u l a t e d as the average departure o f winter p r e c i p i t a t i o n coast p r e c i p i t a t i o n  t = 2.80 significant  (Oct-Apr) f o r the c e n t r a l  index from the 1951-1980 normal.  2. Mean number o f days dominated by "wet", 500 mb,  synoptic types from October to A p r i l  a f t e r Y a r n e l (1983). 3. Mean number o f days dominated by "wet" surface synoptic types from October to A p r i l from Barry et a l . (1982). 4. A low s i g n i f i c a n c e the  analysis.  l e v e l was s e l e c t e d because of the exploratory nature o f  Table 3.4.  Summer Temperature and Synoptic Type Frequency.  A. S i g n i f i c a n c e t e s t between a c o o l p e r i o d and a warm p e r i o d i n B e l l a Coola b a s i n Mean Summer temperature (mean departure) cool:  Warm Synoptic type  frequency^  1948/49 to 1957/58  -1.7 ± 0.8  20.5 ± 7.0  warm: 1959/60 to 1971/72  1.9 ± 0.4  22.4 ± 8.0  One-tailed  t-test  (a = 0.10, d f - 21)  t = 4.62 significant  t = 0.56 not  significant  B. S i g n i f i c a n c e t e s t between c o o l years and warm years c o o l years: 1975,57,56, 54,49  -2.3 ± 1.0  14.5 ± 6.1  1.9 ± 0.7  26.5 ± 3.9  warm years: 1972,70,69, 67,61 One-tailed  t-test  (a = 0.10, df - 8)  1. Warm synoptic  t = 5.31  t - 3.00  significant  significant  types from Y a r n e l (1983).  68  (1959/60 to 1971/72)  group of s y n o p t i c t y p e s between a warm i n t e r v a l cool period  (1948/49 to 1957/58)  (table 3 . 4 a ) ,  but f o r groups of  c h a r a c t e r i z e d by extreme d e p a r t u r e s a s i g n i f i c a n t d i f f e r e n c e  is  and  years evident  ( t a b l e 3.*tb) . U n l i k e w i n t e r p r e c i p i t a t i o n , extreme d e p a r t u r e s tend to f a l l  w i t h i n p e r i o d s of the same t e n d e n c y .  an i n t e r v a l of p e r s i s t e n t  departures  p r o b a b i l i t y of extreme o c c u r r e n c e s  i n summer  T h i s would suggest  t o be r e s t r i c t e d  that  i n summer temperature has a h i g h e r  and i t  i s these extreme, w i t h i n - p e r i o d ,  y e a r s which are c h a r a c t e r i z e d by s i g n i f i c a n t l y d i f f e r e n t synoptic types.  temperature  frequencies  of  C o n v e r s e l y , anomalous w i n t e r p r e c i p i t a t i o n does not appear to these longer more p e r s i s t e n t  i n t e r v a l s of above or  below average d e p a r t u r e s . One or two e x c e p t i o n a l y e a r s may occur d u r i n g an i n t e r v a l of o t h e r w i s e average c o n d i t i o n s  (e.g.  197*+.  1976).  in a d d i t i o n t o s i g n i f i c a n t changes i n s y n o p t i c type p o s i t i v e anomalies  frequency  i n w i n t e r p r e c i p i t a t i o n can be d i s t i n g u i s h e d by  within-season persistence  of s y n o p t i c t y p e s .  wet w i n t e r season of 1 9 6 3 / 6 4 ,  the  For example, d u r i n g the v e r y  36 days between mid-October and mid-November  (with the e x c e p t i o n of one day) were c l a s s i f i e d as "wet" 5 0 0 mb s y n o p t i c types - c l e a r l y the most e x c e p t i o n a l s i g n a l  i n the e n t i r e  D u r i n g t h a t same w i n t e r season and for o t h e r s between i n t e r v a l s of between  33 year  record.  i 9 6 0 and 1969  10 and 12 days were not uncommon whereas d u r i n g  w i n t e r s w i t h i n dry periods  t h e s e w i t h i n - s e a s o n runs were m o s t l y l e s s  wetter than 5  to 8 days. The c o n c l u s i o n drawn here i s t h a t the s y n o p t i c s i g n a t u r e d r i e r and w e t t e r  intervals  is related  between  to the w i t h i n - s e a s o n p e r s i s t e n c e  "wet" s y n o p t i c types whereas anomalously wet years are c h a r a c t e r i z e d by both a h i g h e r  frequency  Extreme d e p a r t u r e s  and g r e a t e r p e r s i s t e n c e  of t h e s e same t y p e s .  i n p r e c i p i t a t i o n do not appear to be r e s t r i c t e d  to a  of  69 p e r i o d of g i v e n tendency. if  T h i s d i s t i n c t i o n i s an important one p a r t i c u l a r l y  t h e r e a r e w e l l - d e f i n e d response  thresholds  i n the b i o g e o p h y s i c a l  environment below which the impact o f changing weather  (3.2)  i s not s i g n i f i c a n t .  Responses o f H y d r o l o g i c V a r i a b l e s t o C l i m a t e F l u c t u a t i o n s  Large s c a l e motions of the atmosphere  are manifested  not o n l y i n  r e g i o n a l p r e c i p i t a t i o n and temperature i n d i c e s , but a l s o i n h y d r o l o g i c a l phenomena such as w i n t e r snowpack, r i v e r r u n o f f and g l a c i e r Linkages between these components of the t e r r e s t r i a l  fluctuations.  phase o f the  h y d r o l o g i c a l c y c l e and atmospheric c i r c u l a t i o n can be s p a t i a l l y n o n homogeneous and lagged i n time atmosphere,  the t e r r e s t r i a l  groundwater), response  t h i s reason  (Bradley,  environment  T h i s o c c u r s because the  1985)-  t o understand  lakes,  t o c l i m a t i c change. For  how feedback mechanisms might be  i n the s y s t e m . The s p a t i a l and temporal t r e n d s i n water  and r u n o f f a l o n g the southwestern  rapidly  i n a c t u a l s t o r a g e and the e x i s t e n c e of  a l l tend t o dampen the response  i t i s necessary  adjusts  The h i g h water s t o r a g e c a p a c i t y  ( e . g . snowcover, g l a c i e r s ,  spatial variability  thresholds  important  198l).  a system w i t h low heat and m o i s t u r e c a p a c i t i e s ,  to changing energy l e v e l s of  (Barry,  storage  B r i t i s h Columbia c o a s t a r e examined  here.  R e g i o n a l Winter Snowpack  Snowpack data have been c o l l e c t e d f o r a number of s i t e s B r i t i s h Columbia but few have r e c o r d s  i n southern  longer than kO y e a r s . The m a j o r i t y o f  s o l i d p r e c i p i t a t i o n f a l l s between e a r l y November and l a t e March. Thus A p r i l 1 snow water e q u i v a l e n t s were c o m p i l e d from a number o f s t a t i o n s f i g u r e 2.1 analysis  for locations) ( t a b l e 3-5)•  and grouped  i n t o homogeneous  (see  regions using  factor  Two s t a t i s t i c a l l y d i s t i n c t groups e x h i b i t i n g s i m i l a r  long term t r e n d s but minor i n t e r a n n u a l d i f f e r e n c e s were i d e n t i f i e d : a  Table 3.5.  Winter Snow Courses i n southwestern B r i t i s h Columbia.  Station  Latitude  Longitude  Elevation  Years o f Record  (m)  Rotated Components 1  2  COASTAL B e l l a Coola  52 31*  126°38'  1380  1953-1954  Newcastle Rdg.  50 24'  126°03'  1170  1961-Present  0.746  0.290  Powell (upper)  50 16'  1040  1938-Present  0.753  0.541  Dog Mountain  49 23'  1080  1945-Present  0.823  0.525  1220  1972-1973  INTERIOR Precipice  52 26'  125 38'  1970-1971 Tatlayoko Lake  T e n q u i l l e Lake  51°36'  50 32'  124°20'  122 56'  1710  1952-Present  0.280  0.848  1300  1952-Present  0.319  0.872  1680  1953-Present  0.332  0.895  1. See f i g u r e 2.1 f o r l o c a t i o n s . 2. Rotated component loadings f o r snow course s t a t i o n s . S t a t i o n s are grouped according to f a c t o r scores.  71 coastal of  zone to the west of the Coast Mountain c r e s t and a zone i n the  the Coast Mountains towards  the d r i e r  snowpack are p l o t t e d as a d j u s t e d  interior.  lee  Secular v a r i a t i o n s  in  p a r t i a l sums i n f i g u r e J>.k. A g a i n ,  p o s i t i v e s l o p e segments r e p r e s e n t above average d e p a r t u r e s and  negative  s l o p e s below average d e p a r t u r e s . A greater snowpack  interannual  variability  index r e p r e s e n t a t i v e of the  is evident  f o r the  regional  i n t e r i o r but both s e r i e s e x h i b i t  p e r i o d s of p e r s i s t e n t d e p a r t u r e s : normal t o below normal snowpack 1957  and 1963f w e l l above normal snowpack between  finally  strongly negative departures after  normal s p r i n g snowpacks a f t e r  1976  w i t h normal to above normal w i n t e r mid-1960s and 1975 same c o a s t a l  1976.  corresponds  w i n t e r p r e c i p i t a t i o n along the c e n t r a l  1964  and 1976,  The o c c u r r e n c e  between and  of below  w e l l w i t h below normal  and s o u t h e r n  temperatures  c o a s t of B . C . c o u p l e d  ( f i g u r e 3-2).  Between  normal to above normal w i n t e r p r e c i p i t a t i o n a l o n g  zone i s r e f l e c t e d  snowpack f o r both c o a s t a l  three  the this  as p e r s i s t e n t p o s i t i v e d e p a r t u r e s of w i n t e r  and i n t e r i o r  r e g i o n s . Winter temperatures were on  average below normal d u r i n g t h i s same i n t e r v a l . Below normal w i n t e r p r e c i p i t a t i o n and above normal w i n t e r  temperatures dominated  c o a s t between  i n below normal  1957  and 1964  The a s s o c i a t i o n between  resulting  southern  snowpacks.  r e g i o n a l snowpack volume and frequency  "wet" w i n t e r c i r c u l a t i o n p a t t e r n s f o r p e r i o d s characterized  the  of  and groups of y e a r s  by anomalous d e p a r t u r e s i s t e s t e d u s i n g d i f f e r e n c e  of means.  U n l i k e the s t r o n g a s s o c i a t i o n between p o s i t i v e snowpack d e p a r t u r e s and above normal p r e c i p i t a t i o n ,  four of the s i x extreme low snowpack y e a r s were  not the same years w i t h low w i n t e r p r e c i p i t a t i o n . years winter  For t h r e e of t h e s e four  temperatures were above average which p r o b a b l y l e d to g r e a t e r  m e l t i n g near the b e g i n n i n g and end of each s e a s o n . Hence, p r e c i p i t a t i o n and above normal temperatures r e s u l t e d  average  i n low snowpack  72  —I 1950  1  1  1  1960  1970  1980  r 1990  Year (AD) F i g u r e 3-*» A d j u s t e d p a r t i a l sums f o r A p r i l 1st snowpack (water e q u i v a l e n t ) . Normal p e r i o d i s 1951-1980. C o a s t a l w i n t e r p r e c i p i t a t i o n taken from f i g u r e 3-1 i s i n c l u d e d f o r c o m p a r i s o n . P o s i t i v e s l o p e segments r e p r e s e n t p e r s i s t e n t above average snowpack y e a r s whereas n e g a t i v e s l o p e s r e p r e s e n t below average snowpack.  73 volumes. Even w i t h t h e s e c o m p l i c a t i o n s the r e s u l t s variations  i n t a b l e 3-6 show t h a t  i n s p r i n g snowpack a r e p o s i t i v e l y l i n k e d t o the mean number of  days dominated by "wet" s y n o p t i c types f o r groups of anomalous years and a l s o f o r the two p e r i o d s c h a r a c t e r i z e d by above average  (1966-1976) and  below average  is p a r t l y related  (1977~1980) d e p a r t u r e s . The l a t t e r  result  t o the l i m i t e d number of data d u r i n g 1977~1980 and the above  temperatures  which o c c u r r e d t h e n , but does i n d i c a t e t h a t s e a s o n a l l y i n t e g r a t e d h y d r o l o g i c parameters  such as snowpack are s e n s i t i v e to changes i n the  frequency of s p e c i f i c c i r c u l a t i o n p a t t e r n s not o n l y f o r extreme years but a l s o f o r sequences of y e a r s i n which a tendency f o r p e r s i s t e n t  departures  occur.  S p r i n g Runoff  S p r i n g runoff  i s l i k e l y to be g r e a t e r  following winters characterized  by anomalously high p r e c i p i t a t i o n and snowpack a c c u m u l a t i o n but s p r i n g and summer temperature c o n d i t i o n s may enhance or depress a c t u a l water Furthermore, s p r i n g runoff  yield.  s h o u l d be l e s s s p a t i a l l y homogeneous than  snowpack d i s t r i b u t i o n s because of the l a r g e s p a t i a l v a r i a b i l i t y  i n runoff  g e n e r a t i n g mechanisms and s t o r a g e c o n d i t i o n s w i t h i n and between b a s i n s . However, as b a s i n s i z e i n c r e a s e s , water y i e l d becomes l e s s r e s p o n s i v e t o i s o l a t e d storms or to snowmelt p e r i o d s of s h o r t d u r a t i o n . Thus, l a r g e s c a l e s y n o p t i c t r e n d s may be r e f l e c t e d more d i r e c t l y v a r i a b i l i t y w i t h i n larger basins  i n temporal runoff  (Bruce, 197*+).  Most h y d r o m e t r i c r e c o r d s f o r streams d r a i n i n g the west s l o p e of s o u t h e r n Coast Mountains are s h o r t e r  the  than kO years and the number of medium  2 sized basins  (3,000 - 6,000 km ) f o r which d i s c h a r g e d a t a e x i s t i s s m a l l .  Time s e r i e s of s p r i n g snowmelt r u n o f f Squamish R i v e r s ,  f o r the B e l l a C o o l a , Homathko and  t h r e e moderate s i z e catchments d r a i n i n g p a r t l y g l a c i e r i z e d  74  Table 3.6.  Winter Snowpack and Synoptic Type Frequency.  A. S i g n i f i c a n c e between a high snowpack p e r i o d and a low snowpack p e r i o d Mean A p r i l 1st  high: low:  water equivalent  Wet synoptic  (mean departure)  type frequency  1966-1976 1977-1980  2  0.69 ± 1.26  Wet synoptic type  frequency  3  40.3 ± 8.9  -1.01 ± 1.22  32.3 ± 12.1 catalogues only  One-tailed  t-test  (a = 0.10, df = 13)  t = 2.94  to  1978  significant  t = 1.61 significant  B. S i g n i f i c a n c e t e s t between high snowpack years and low snowpack years high snowpack years:  1.32 ± 0.93  91.5 ± 4.13  46.5+8.8  79.2 ± 6.3  29.8 ± 15.2  (1976,74,68,67,64,54) low snowpack years:  -1.28 ± 0.75  (1978,77,75,70,62,60) One-tailed  t-test  (a = 0.10, df = 10)  t = 5.22  t = 4.01  t = 2.32  significant  significant  significant  1. C a l c u l a t e d as the average departure f o r the three l e e s i d e snow courses: Tatlayoko and T e n q u i l l e . 2. Frequencies of 500 mb patterns a f t e r Y a r n e l (1983). 3. Frequencies of surface pressure patterns a f t e r Barry et a l . (1982).  Tashta,  75 mountains secular  of  southwestern  runoff  locations). interval  hydrographs  differences evident.  between  1947  average  spring  and  more v a r i a b l e  through  this  between  the  during  this  the  remainder  During  spring runoff  divergence  c a n be e x p l a i n e d  and  temperatures  runoff between  and  particularly Spring  (1982)  and in  the  runoff  has m o d e l e d  southeast  of  the  1972  when  decade. with  3-1.  three  discharges  this  when wet  b a s i n s was b e l o w well  during  all  four  years  from  secular  Similarly,  the  below  wet  Coola  some  near  average. and  important conditions  below  This  average  resulting cool  spring  the  sharply  average.  but  average  Bella  most of  are  winter  o c c u r r e n c e of  storage.  secular  equivalents  reveals  these  minor  above  in  was  flows  snowpack w a t e r  of  are  to  d i s c h a r g e s were  trend  Post-1980  1973-1976,  there  discharges for  and 3-5)  3-**  related  Following well  the  Squamish  runoff  1966,  The  discharges occurred  by  temperature,  catchment  After  3«5>  figure  long-term  Homathko R i v e r  1966.  trends  may e x p l a i n  data  average  average  winter  in  lower  conditions runoff,  River. the  north  trends  A l a s k a . The e s t i m a t e s  precipitation, various  1966  similar  for  p e r i o d because  While  2.6).  below  until  in  of  2.1  d i s c h a r g e peaks  1958,  in a l l  i n c r e a s e d water  1963  that  River.  interval  prevailed,  runoff  Coola  until  figure  spring  figure  near  (see  sums  each catchment, but  some e v i d e n c e  partial  Bella  (figures the  the  (see  period.  runoff  as  indicate  time  above average  precipitation  summer  as a d j u s t e d  rivers  prevailed  A comparison of  differences.  in  1958  runoff  c o a s t were w e l l for  post-19*t5 p e r i o d  Fluctuating,  and S q u a m i s h R i v e r s  reversed  plotted  three  occurred during  trends, are  the  Columbia, provide  t o m i d - J u l y was d e f i n e d from a l l  interannual  winter  during  Results are  May  snowmelt  trends  British  in annual  are  not  examined but  freshwater  discharges  b a s e d on s e a s o n a l t r e n d s  and w a t e r  data.  c o a s t were  storage  The annual  and a r e  trends  to  fit  in  in  calibrated  appear  Royer  against  quite  well  76  T  1940  1  1  1950  1  1  1  1960  r 1970  1  1 —  1980  Years (AD) F i g u r e 3-5 A d j u s t e d p a r t i a l sums o f s p r i n g r u n o f f (May - mid J u l y ) f o r t h r e e c o a s t a l r i v e r s . Normal p e r i o d s f o r each s t a t i o n c o r r e s p o n d to the l e n g t h of r e c o r d . P o s i t i v e s l o p e segments r e p r e s e n t p e r s i s t e n t above normal r u n o f f . Note the the r e g i o n a l response o f below average runoff after 1 9 7 2 .  77 the v a r i a t i o n s suggesting  i n w i n t e r p r e c i p i t a t i o n along the n o r t h c o a s t  t h a t p r e c i p i t a t i o n i s the dominant f a c t o r  temporal v a r i a t i o n of r u n o f f . interval  ( f i g u r e 3.2a),  in determining  Above average r u n o f f o c c u r r e d d u r i n g  1958 to 19&3 and a f t e r  the the  1976. and below average r u n o f f between 1964  and 1976. Below average r u n o f f and w i n t e r p r e c i p i t a t i o n p r i o r to 1958 have been documented f o r P r i n c e of Wales and Revi1 l a g i g e d o I s l a n d s Panhandle runoff  (Karanka, 1986) which c o n t r a s t  Alaska  w i t h the above average annual  i d e n t i f i e d by Royer (1982). These d i f f e r e n c e s  may be due to v a r i a t i o n s  i n the  f o r the e a r l i e r  i n the d e f i n i t i o n of the water y e a r ,  period  the much more  l i m i t e d area of the l a t t e r  study and the s e n s i t i v i t y of the r u n o f f model  used by R o y e r . In g e n e r a l ,  the s p a t i a l coherence of w i n t e r  and s p r i n g r u n o f f  precipitation  i s s t r o n g l y e v i d e n t but s p r i n g and e a r l y summer  temperatures a l s o c o n t r i b u t e  to r u n o f f v a r i a b i l i t y .  S p r i n g and Summer Runoff - B e l l a Coola R i v e r  F a c t o r s other  than w i n t e r p r e c i p i t a t i o n have been  incorporated  into a  number of e m p i r i c a l and p h y s i c a l l y based models f o r e s t i m a t i n g s p r i n g  flood  discharges  and high summer water y i e l d s  (Ostrem et aj.,1967; Tangborn and  Rasmussen,  1976; Power and Young, 1979; C o l l i n s and Young, 198l; Tangborn,  Young 1985)- The most important are the d i s t r i b u t i o n and magnitude of  1984;  temperature d e p a r t u r e s and the c o n t r i b u t i o n s of g l a c i e r melt to runoff.  G l a c i e r melt generated r u n o f f can be as h i g h as 50% of the  water y i e l d even when g l a c i a l cover  is r e l a t i v e l y l i m i t e d  E s t i m a t e s o f g l a c i e r melt c o n t r i b u t i o n s River  total  (21% g l a c i a l covered)  total  (Young, 1985).  to summer d i s c h a r g e  i n the Homathko  range as h i g h as 21% ( B r i t i s h Columbia Hydro,  1984). W h i l e a c c u m u l a t i o n season p r e c i p i t a t i o n and a b l a t i o n temperatures are  important model components,  these s t u d i e s  season of  ice-covered  78 basins  have shown the  importance of more s p a t i a l l y v a r i a b l e parameters such  as r e l a t i v e h u m i d i t y , summer r u n o f f  incident solar  r a d i a t i o n and wind i n  estimating  from i n d i v i d u a l g l a c i e r s . D i r e c t measurement, or even  i n d i r e c t e s t i m a t e s , of these a d d i t i o n a l parameters are g e n e r a l l y  not  p o s s i b l e f o r p a l e o h y d r o l o g i c a l m o d e l i n g . Models based on primary h y d r o m e t e o r o l o g i c a l v a r i a b l e s such as temperature and p r e c i p i t a t i o n l i k e l y to e x p l a i n l e s s of the y e a r - t o - y e a r  variance  i n r u n o f f . An  assessment of s i m p l e r u n o f f models f o r the B e l l a Coola R i v e r in order  to document  the  meteorological variables  only.  the B e l l a Coola R i v e r r e v e a l s  i n a l l four gauged  some i n t e r e s t i n g  v a r i a b i l i t y of e a r l y season r u n o f f  tributaries  differences.  Interannual  d i u r n a l runoff Rivers)  and  (2)  and n o r t h e r n  regimes become a p p a r e n t :  regime f o r the southern  catchment  (e.g.  During high snowpack y e a r s , which s p r i n g temperatures  a strongly  Talchako/Nusatsum i n the  eastern  (e.g. Atnarko/Salloomt Rivers) .  and normal to below-normal snowpack years i n ( A p r i l - May) are d e p r e s s e d , high s e a s o n a l  i s common to a l l t r i b u t a r i e s .  It  runoff  i s low snowpack y e a r s c o u p l e d w i t h h i g h  summer temperatures which a c c e n t u a t e the d i f f e r e n c e s Since t h i s  (1)  contributions  more u n i f o r m , but s t e a d i l y d e c l i n i n g f l o w s ,  segments of the catchment  the  from a b a s i n - w i d e  m e l t i n g snowpack. As the melt season p r o g r e s s e s and i c e m e l t runoff  of  (May-mid-July) i s s i m i l a r throughout  catchment, presumably due to the c o n t r i b u t i o n of water  two d i s t i n c t  i s made here  l e v e l of e x p l a i n e d v a r i a n c e u s i n g p r i m a r y  A n a l y s i s of a b l a t i o n season r u n o f f  increase,  are  in runoff  l a t t e r s i t u a t i o n occurs r e l a t i v e l y i n f r e q u e n t l y ,  regimes.  a summer  runoff  index was computed f o r the B e l l a Coola R i v e r below Burnt B r i d g e C r . , which integrates discharges  from both g l a c i e r i z e d and u n g l a c i e r i z e d  Although t h i s may reduce the c l i m a t e - r u n o f f populations,  the  index i n c o r p o r a t e s  sources.  r e l a t i o n s h i p by m i x i n g  a b a s i n - w i d e response to  changing  79 h y d r o c l i m a t e s and more p r o p e r l y e s t i m a t e s t o t a l summer d i s c h a r g e  through  the lower B e l l a Coola R i v e r . S e v e r a l e m p i r i c a l l y - b a s e d l i n e a r s t a t i s t i c a l models,  incorporating  s e a s o n a l l y and r e g i o n a l l y averaged c l i m a t e d a t a , were e v a l u a t e d u s i n g an i n t e r a c t i v e v e r s i o n of a l l - p o s s i b l e - s u b s e t s and monthly temperature,  regression.  I n d i c e s of s e a s o n a l  p r e c i p i t a t i o n and s p r i n g snowpack f o r both  coastal  and i n t e r i o r r e g i o n s comprise a group of independent v a r i a b l e s used t o estimate  spring runoff.  data s e t  (1952-1984),  E a r l y season  u s i n g a 33 year  l i m i t e d by the l e n g t h of s p r i n g snowpack  (May t o m i d - J u l y ) , l a t e season  (May t o August) r u n o f f presented  P r e l i m i n a r y models were c o n s t r u c t e d  i n t a b l e 3-7'  ( m i d - J u l y t o August) and summer  i n d i c e s were c o n s i d e r e d s e p a r a t e l y . Scatter  records.  p l o t s of b i v a r i a t e  Results are  relationships,  p r o b a b i l i t y p l o t s o f r e s i d u a l s and a t e s t f o r s e r i a l c o r r e l a t i o n f o r each model i n d i c a t e t h a t assumptions of the r e g r e s s i o n t e c h n i q u e have not been vi olated. All  t h r e e p r e l i m i n a r y models r e l a t i n g B e l l a Coola R i v e r r u n o f f t o 2  c l i m a t e a r e s i g n i f i c a n t but the s t r o n g e s t which w i n t e r p r e c i p i t a t i o n a l o n g the c o a s t , measured  i s summer r u n o f f  (Ra = O.58)  in  s p r i n g snowpack volumes  i n the l e e o f the Coast Mountains and summer temperature i n d i c e s  d e r i v e d f o r the i n t e r i o r , enter the e q u a t i o n . T h i s c o m b i n a t i o n o f v a r i a b l e s suggests t h a t summer r u n o f f energy  i s c o n t r o l l e d by snowpack c o n d i t i o n s and melt  i n the headwaters of the s o u t h e r n and e a s t e r n  catchment.  The t h r e e p r e l i m i n a r y models were t e s t e d by u s i n g independent  data  from the Nusatsum and S a l l o o m t R i v e r s . Runoff d a t a from these two downstream t r i b u t a r i e s were combined and compared w i t h p r e d i c t e d r u n o f f i n B e l l a Coola R i v e r . The use of Nusatsum/Salloomt data was p o s s i b l e because of the h i g h c o r r e l a t i o n between these data and observed d i s c h a r g e B e l l a Coola R i v e r  (r >  0.79)-  V e r i f i c a t i o n procedures  i n the  f o r r e g r e s s i o n models  80  Table 3.7.  S i g n i f i c a n t v a r i a b l e s and r e g r e s s i o n c o e f f i c i e n t s  f o r c l i m a t e - r u n o f f models.  Runoff Period Preliminary Models Climate  May  Indices  mid-Jul  to  F i n a l Model  mid-July to  Aug  Summer  Summer  Coefficients WP(I) WP(C)  0.62  SS(I)  0.23  0.49  0.56  0.68  0.18  SS(C) AT(I)  -0.09  AT(C) ST(I)  1.21  0.49  0.78  0.78  0.11  0.01  0.01  0.01  ST(C) Intercept  Summary S t a t i s t i c s : „2  Confirmatory  WP  =  0.52  0.29  =  0.62  =  =  0.45  0.24  =  0.58  =  0.52  =  1.50  2.22  =  1.51  =  1.94  F  =  7.15*  5.8*  SE  =  0.45  0.12  =  0.09  0.10  Statistics: r  0.74  0.41  0.89  0.84  RE  0.19  0.05  0.41  0.36  = winter p r e c i p i t a t i o n  R  (Oct-Ap)  SS = A p r i l 1st snowpack (water  R  equivalent)  D  AT = A p r i l temperature  2 a  ST = summer temperature (May-Aug) (I) = I n t e r i o r  F  c o e f f i c i e n t of determination  (R ) i s adjusted  f o r the number of p r e d i c t o r v a r i a b l e s i n each  = c o e f f i c i e n t of 2 = adjusted R  = F ratio  o  - no  autocorrelation)  (* s i g n i f i c a n t ; a = 0.025)  SE  = standard  RE  = reduction of e r r o r s t a t i s t i c  r  = correlation  ( y i e l d i n g Ra  equation.  determination  = Durbin-Watson d ( r e j e c t H significant  Region  (C) = C o a s t a l Region  The  17.16*  14.8* =  0.55  error coefficient  ) to account  81 e v a l u a t e how w e l l a model p r e d i c t s Two s t a t i s t i c s  reported  a new v a l u e of the  i n t a b l e 3-7  (confirmatory  t e s t the s i g n i f i c a n c e of the p r e d i c t e d coefficient  (r)  coefficients actual 1976)  and RE s t a t i s t i c .  has t h e o r e t i c a l  runoff.  statistics)  runoff values:  are used  the  correlation  In a l l t h r e e models the  correlation  are s i g n i f i c a n t s u g g e s t i n g  and p r e d i c t e d  independent v a r i a b l e .  a r e a s o n a b l e correspondence  The r e d u c t i o n of e r r o r  l i m i t s of -<» and 1.0  statistic  to  between  (RE)  (Fritts,  where a p o s i t i v e v a l u e  indicates  t h a t the p r e d i c t i o n s made by the model are b e t t e r than a p r e d i c t i o n  based  on the mean of the observed d a t a . Again a l l t h r e e models have p o s i t i v e and s i g n i f i c a n t RE v a l u e s s u g g e s t i n g  r e a s o n a b l e p r e d i c t i v e a b i l i t y of  the  models. The model which i n c o r p o r a t e s  s p r i n g snowpack,  lowest p a r t i a l c o r r e l a t i o n c o e f f i c i e n t ,  a variable with  was removed from  the  further  c o n s i d e r a t i o n because snowpack data p r i o r to 1952  are not a v a i l a b l e . The  c a l i b r a t i o n p e r i o d was extended  a v a i l a b l e runoff)  to 19^8  (earliest  o u t l i e r s which might have had a s i g n i f i c a n t coefficients  were t e s t e d u s i n g C o o k ' s D s t a t i s t i c  None were f o u n d . The f i n a l to 1948  i n f l u e n c e on the  A n a l y s i s of s p r i n g r u n o f f  i n chapter  hydrographs  events i n May or June are r e l a t e d  For t h i s  approximate  reason,  the p o t e n t i a l  to y e a r s w i t h p e r s i s t e n t  positive  spring  temperature  the f i n a l model p r e s e n t e d i n t a b l e 3-7  f o r high-magnitude  spring runoff but,  p r o v i d e a good e s t i m a t e of peak s p r i n g d i s c h a r g e . model i s h i g h e s t  prior  shows t h a t extreme r u n o f f  t h e r e i s no s p r i n g temperature index i n the f i n a l model,  in the f i n a l  spring runoff  6.  d e p a r t u r e s i n monthly w i n t e r p r e c i p i t a t i o n and n e g a t i v e anomalies.  regression  (Draper and S m i t h , 1981) .  model i s used to r e c o n s t r u c t  and these r e s u l t s are d i s c u s s e d  and a l l  because  i s apt not  Hence, r e s i d u a l  d u r i n g years c h a r a c t e r i z e d  c l i m a t i c anomalies which s i g n i f i c a n t l y i n f l u e n c e r u n o f f  may  to  variance  by monthly (e.g.  depressed  82  April  temperatures)  but are not i n c o r p o r a t e d i n t o any of the  seasonal  climate indices.  Autumn F l o o d s  As noted i n c h a p t e r dissimilar  2 the autumn r u n o f f  period is h y d r o l o g i c a l l y  to the summer d i s c h a r g e regime. S t e a d i l y d e c l i n i n g f r e e z i n g  l e v e l s promote reduced c o n t r i b u t i o n s of g l a c i e r meltwater as the progresses.  season  Superimposed on t h e s e d e c l i n i n g flows are s h o r t - d u r a t i o n ,  magnitude f l o o d s which have two d i s t i n c t s o u r c e s : p r e c i p i t a t i o n o n l y and  (2) r u n o f f  (1) r u n o f f  high-  due to heavy  due to high p r e c i p i t a t i o n combined w i t h  r a p i d l y r i s i n g f r e e z i n g l e v e l s and s i g n i f i c a n t snowmelt a t m i d d l e elevations. Typically,  the former events o c c u r e a r l y i n the autumn (August  to October) w h i l e the l a t t e r may occur as l a t e as January  following  a c c u m u l a t i o n of snow throughout much of the b a s i n . A n a l y s i s of d a i l y p r e c i p i t a t i o n r e c o r d s p r i o r to autumn f l o o d i n the B e l l a Coola R i v e r suggests t h a t f o r most high-magnitude  flows,  antecedent p r e c i p i t a t i o n i s i m p o r t a n t . Flood g e n e r a t i n g storms are preceded by a sequence of one or two day r a i n f a l l snowpack or s o i l so t h a t subsequent demonstrates  runoff  events  often  events which s a t u r a t e  the  i s m a x i m i z e d . F i g u r e 3*6  a mean s e p a r a t i o n of k to 5 days between s t o r m s , beyond which  the p o t e n t i a l f o r heavy storm r u n o f f  i s g r e a t l y r e d u c e d . T h i s s e p a r a t i o n of  storm peaks appears to be v a l i d f o r peak 2h hour p r e c i p i t a t i o n events w i t h recurrence  i n t e r v a l s of k years or l e s s ; t h a t  w i t h one-day r e c u r r e n c e  i n t e r v a l s greater  i s , flood generating  than k y e a r s g e n e r a l l y produce  enough p r e c i p i t a t i o n to y i e l d s i g n i f i c a n t r u n o f f preceded by h y d r o l o g i c a l l y f l o o d s of 1950, 1973) .  storms  (climatologically)  and are not n e c e s s a r i l y  d i s t i n c t events  ( e . g . autumn  83  F i g u r e 3-6 Antecedent autumn p r e c i p i t a t i o n f o r the s i x l a r g e s t p e r i o d - o f - r e c o r d f l o o d s on B e l l a C o o l a R i v e r . 24 hour p r e c i p i t a t i o n r e c u r r e n c e i n t e r v a l s a r e c a l c u l a t e d u s i n g 80 y e a r s of r e c o r d at the B e l l a C o o l a c l i m a t e s t a t i o n . Mean s e p a r a t i o n of storm p r e c i p i t a t i o n peaks i s 4 to 4 . 5 d a y s .  84 A n a l y s i s of s y n o p t i c c h a r t s  f o r ten-day  sequences p r i o r to each major  f l o o d on the B e l l a Coola R i v e r s u g g e s t s a number of s y n o p t i c c o n d i t i o n s must be met i n o r d e r to produce s i g n i f i c a n t r u n o f f . The most important the r a p i d r e d u c t i o n i n the v e l o c i t y of eastward moving low p r e s s u r e and i n s e v e r a l cases a s w i t c h to a more n o r t h e r l y t r a j e c t o r y  of  heavy r a i n f a l l  interior  become f u l l y o