Coastal Sedimentary

Processes and Sediments, Southern Beaufort Sea

C.P. LEWIS and D.L. FORBES

Technical Report No. 24

COASTAL SED IMENTARY PROCESSES AND SED IMENTS,

SOUTHERN CANADIAN BEAUFORT SEA

C . P . Lewis and D . L . Forbes

Terrain Sciences D ivision Geological Survey of Canada

Department of Energy , Mines and Resources Ottawa, Ontario

Beaufort Sea Technical Report #24

Beaufort Sea Proj ect Dept . of the Environment

512 F ederal Bui lding 1230 Government St.

Victori a , B . C . V8W lY4

December, 1975

Reprinted October, 1976 Price $1.50

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CONTENTS

SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 . 1 Objectives of the study . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 . 2 Sc i ent i fi c Conclus ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . 3 Imp l icat i ons and Recommendat i ons . . . . . . . . . . . . . . . . . . . .

1 . 3 . 1 General Scientific . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 . 3 . 2 Matters Rel evant to Development . . . . . . . . . . . . . .

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 . 1 General Nature and Scope of Study . . . . . . . . . . . . . . . . . . .

2 . 2 Specific Objec t ives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 . 2 . 1 Kay Po int . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 . 2 . 2 Coastal Sus cept ib i l ity to Oi l Spi l l s " . . . . . . .

2 . 3 Rel evance to Development Prob l ems . . . . . . . . . . . . . . . . . . .

2 . 4 Acknow l edgments . . . . . . . . . . . . . . . . . . ; . . . . . . . . . . . . . . . . . .

CURRENT STATE OF KNOWLEDGE '" . . . . . . . . . . . . . . . . . . . . . . . . . . . .

STUDY AREA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SOURCES , METHODS AND RATIONALE OF DATA COLLECTI ON . . . . . . . .

5 . 1 Kay Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5 . 2 Coastal Suscept ib i l ity to Oi l Sp i l l s . . . . . . . . . . . . . . . .

RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " . . . . . . . . . . . . . . . . . .

6 . 1 Kay Point , 1 9 7 4 F i e l dwork . . . . . . . . . . . . . . . . . . . . . . . . . . .

6 . 1 . 1 Babbage Delta and Estuary . . . . . . . . . . . . . . . . . . . .

Morphol ogy and s ed iment s . . . . . . . . . . . . . . . . . . . . . . . . . .

Seas onal flow charact er i s t i c s . . . . . . . . . . . . . . . . . . . . . 6 . 1 . 2 Coastal C l i ffs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 . 1 . 3 Kay Po int Spit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6 . 2 Coastal Sus cept i b i l ity to Oi l Sp i l l s , 1974 F i e l dwork . 6 . 2 . 1 B l ow River Delta . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6 . 2 . 2 Shing l e Regi on Coastal C l i ffs . . . . . . . . . . . . . . . . 6 . 2 . 3 Coastal Sp i t s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

DISCUSS I ON

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8 . CONC LUSI ONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

9. IMPLICAT I ONS AND RECOMMENDATI ONS . . . . . . . . . . . . . . . . . . . . . . . . . 36 9 . 1 General Sc i entific . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 9 . 2 Matters Rel evant to Devel opment . . . . . . . . . . . '" . . . . . . . 36

1 0 . NEEDS FOR FURTHER STUDY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

11 . REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

1 2 . APPEND I X : Phys ical Aspects of the Beaufort Sea Coast . Prepared Test imony Present ed to the Macken zie Val l ey P ipel ine I nquiry , F ebruary 1 3 , 1 9 7 6 . . . . . . . . . . . . . . . . , 4 1

TABLES

I Yukon coastal p l ain rivers 9

II Yukon coast spit morphometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 0

F IGURES

1 Yukon B eaufort Sea coast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2 Genera l i zed process-response model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3 Vi ew east over the B abbage delta during spring break-up . . . . . . . . . . 14

4 Kay P oint region : g enera l i z ed surface facies 1 6

5 B l ow River delta : pre-break-up flooding over winter ice . . . . . . . . . 18

6 Babbage River estuary : pre-break-up flooding over winter ice . . . . 18

7 Unvegetated intertidal flat at the mouth o f the main distributary of the B abbage delta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

8 S ediment covered winter ice with thermo- eros ional bedforms which has risen to the surface in the Babbage estuary . . . . . . . . . . . . . . . . 1 9

9 Undercut cl iff at Kay P oint during August storm . . . . . . . . . . . . . . . . . . 2 2

1 0 C l i ffs southeast o f Kay Po int . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2

1 1 Genera l i zed sections and stratigraphy , c l i ffs s outheast o f Kay Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 3

12 Coastal ground ice s lump and associated mudflows , Spring River area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 4

13 Kay P o int spit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 6

1 4 Kay spit , distal is land : foreshore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 6

15 S elected cro s s - s ect ions with sediment types , Yukon coast spits . . . 2 7

1 6 B l ow River delta pl ain : organic coastal foreshore scarp 2 9

1 7 Shing le P oint spit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 9

18 Nunaluk spit , proximal end . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1

1 9 Nunaluk spi t , second distal i s l and . . . . . . . . . . . . . . . . . . . . . . '" . . . . . . 3 1

2 0 Shingl e spit : unvegetated backshore I sediments (washover l obes) advancing over b ackshore II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2

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1 . SUMMARY

1 . 1 Object ives of the Study

Th i s t echnical report is based primar i ly on fieldwork conducted during the summer of 1 9 74 int o the geometry , compos it ion , origin and stab i l ity of coastal l andforms bordering the Beaufort Sea from the Alaska-Yukon boundary east to the Macken zie Delta . The 1 9 7 4 study fol l owed general reconnai s s ance invest igat ions of the northwest coast of the Tuktoyaktuk P eninsula in 1 9 7 3 and of the Yukon coast in 1 9 7 2 (McDonald and Lewi s , 1 9 73) . The results of these ear l ier studies have b een incorporat ed here to extend coverag e as far east as Cape Dalhous i e at the east ern end of the Tuktoyaktuk Peninsul a . As wel l , prepared test imony by the senior author , presented to the Mackenzie Val l ey P ip e l ine Inquiry on February 1 3 , 1 9 7 6 , i s inc luded in thi s report a s an appendix . The reader i s referred to this app endix for a more general overvi ew of physical aspects of the Beaufort Sea coas t , di scus s ion of the impl ica�ions of offshore hydrocarbon resource development on the coastal zone , and for addit ional detai led informat ion on the modern Macken z i e de lta p l ain .

The purposes of the 1 9 7 4 fieldwork were twofo ld:

1 . The general reconnais sance studies in 1 9 7 2 and 1 9 7 3 rai s ed many quest ions about the detai led nature , magnitude and frequency of processes and responses in this arct ic coastal zone, quest ions whi ch could best be answered by a longer t erm instrumented study at a representat ive samp l e location . Kay Point , Y . T . ( F i gure 1 ) was cho s en as the samp l e site becaus e it offers a wide range of coastal features in a smal l ar ea . Concentrated fieldwork at th i s locat i on wi l l cont inue through the summer of 1 9 7 7 with occas ional v i s its thereafter . Scient ific studies inc lude (see F igure 1 , ins et , for locat ions) :

a . Erosion of and s ediment transport from the coastal c l iffs southeast of the po int ;

b . Growth , migrat ion and short period chang es in Kay spit ; c . Morphol ogy, sedimentology and hydrau l i c s of the Babbage River delta ,

an estuarine delta of the Mackenzie type ; and d . Sediment transport and depo sit ion in Phi l l ips Bay , a nearshore

sed iment s ink .

2 . The second objective of 1 9 7 4 fieldwork was t o examine the geological aspects of coastal sus cept ib i l ity to oil spi l l s , a part of the joint industry - gov ernment Beaufort Sea study of the pot ent ial environmental hazards of proposed exp l orat ory offshore dri l l ing . In this context , the intent ions of th i s study were to :

a . I dentify and determine the extent of those areas of the coastal zone most susceptib l e to inundat ion by sea water ;

b . Det ermine the present geometry , nature of sediments and vegetat i on of these areas ;

c . Examine patt erns of s ediment eros ion , transportat ion and deposition ; and

d . Ident ify and discuss cond itions pecu l i ar to an arct ic coast al environment relating to pot ent ial damage from an o i l sp i l l .

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During the summer of 1 9 74 , fieldwork was carri ed out on the maj or spits at Shing le and Kay Po int s , on Nuna luk spit in the F irth River region , on the B low and Babbage River deltas and , as examples of sed iment source areas , on c l iff segment s at Shingl e Po int and Kay Point (Figure 1 ) .

1 . 2 Scient ific Conc lus ions

The main s c i ent ific conc lus i ons result ing from this study are :

1 . The maj or geomorphologic features of the Yukon Beaufort Sea coast are: (a) steep coastal c l iffs , often containing s igni ficant amounts of ground i c e , and front ed by narrow beaches ; (b) spits and barri ers up to 1 0 or more kilometres in exposed l ength and several hundred metres wide ; and ( c ) deltas of coast al p l ain rivers with vegetated or part ially vegetated exposed delta pl ains up to 50 �m . 2 in area .

2. C l iff sediments range from gravel to icy c l ay . The fine material i s moved off shore and beaches , spits and barri ers are usua l ly composed of remnant gravels and s ands. Coastal p lain rivers have gravel beds but thi s gravel does not reach the l ower delta p lains where sediment s are primari ly organ ic-rich s i l t s and fine sands .

3 . C l i ff retreat of up to 9 0 m . in 1 6- 1 8 years has occurred , largely through undercutting and subs equent b l ock s lump ing , gul l eying , and mud flow assoc iated with ground ice s lumps . Sediment derived from thi s retreat i s moved al ong shore and has l ed to hundreds of metres of spit and b arrier extension over the same period .

4 . Significant sediment transport events are assoc iated with spring break-up and storm floods on the rivers and with meteoro logical tides and wave act ivity during these storms al ong the coast . B erm e l evat ions of over 1 . 5 m . on spits and dri ftwood l ines more than 2 m . above normal high tide on exposed delta p l ains attest to the rise in sea level and inundat ion of coastal deposit ional features during these storms , most commonly in the summer and fal l but occas iona l ly during winter .

5 . F irst flow in rivers , deltas and estuaries occurs wel l before sea ice break-up and i s commonly over bottomfast winter i c e . Thi s i c e inhibits bed s cour during ear ly fl ooding . F o l lowing spring break-up , river discharge decl ines except for brief r i s es during storm events .

6 . The direct effects of sea ice on the stab i l ity of coastal features appear to be smal l . Only minor examples of the movement of beach sediment by ice push and s cour of the nearshore seabed by i c e have been obs erved , thi s l atter phenomenon apparent ly ceas ing shoreward of the 1 0 m . i sobath . Indirect effects , part i cularly the influence of the amount and locat i on of ice on storm surges and associated wave activity , are much more import ant .

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7 . Offshore grad ients can be quite st eep off many port ions of the Yukon coast , most common ly where the shore l ine i s c l iffed . Profi les are general ly concave upward and few nearshore bars exist . Off river deltas , though , depths are very sha l l ow , s e l dom exc eed ing 2 m . a k i l ometre or more from shore . Sha l l ow depths in the Babbage estuary prevent the development of s ignificant vert ical variations in water temperature and sal inity .

8 . Rapid coastal retreat , sha l l ow wat er depths and low water temperatures have enab l ed the pres ervat ion or format ion of permanent ly fro zen ground beneath estuary and nearshore areas .

9 . Un l ike the Yukon coast , the northwest coast of the Tuktoyaktuk Peninsul a is deep l y embayed al ong its l ength , its shape reflect ing the breach ing of thermokarst l akes wh ich cover larg e port ions of the coastal pl ain . Maj or spits and long barrier bar s equenc es have formed because of the much lower offshore grad i ent than off the Yukon coast . Sediments in coastal deposit ional features are mixed grav e l s and sands west of the set t lement of Tuktoyaktuk and , most common ly, pure s and east of Tuktoyaktuk . Like the Yukon coast , the shorel ine of the Tuktoyaktuk Peninsula is retreat ing , with most of the derived s ediment being moved northeast toward Liverpool Bay .

1 . 3 Impl i cat ions and Recommendat ions

1 . 3 . 1 General S c i ent ific

In an average year , the southern Beaufort Sea coast , part i cularly east of Herschel I s land , has a relat ively l ong open wat er season and cannot be cons idered true arct i c in nature . Normal marine processes dominat e for about three months of the year . During thi s t ime period , the arct i c environment influences these processes only through the increased relative importance of extreme storm events , the occas ional movement of sea ic e near shore during thes e events and , as was so wel l demonstrat ed dur ing the summer of 1974 , through the maj or year to year variat i ons in c l imate and sea ice cond itions which may occur .

The response of coastal material s to summer marine processes , however , is conditioned by the arct ic environment . Fro zen ground p l ays an important ro le in the coastal zone , most important ly through its influence on rat es of coastal retreat and , along the Tuktoyaktuk P eninsul a , through the contro l by thermokarst lakes of coastal configurat ion .

1 . 3 . 2 Matters Re l evant to Development

Development is considered here primar i ly with respect to the potential effect s on the Beaufort Sea coastal zone of an o i l spi l l during expl oratory offshore dri l l ing . Consideration i s g iven as wel l , however , to the po s s ib l e use of the coast for stag ing areas or other shore inst a l l at ions associat ed with petrol eum expl oration and development .

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The detai l s of coastal process es and respons e s , part icularly for short-per iod event s , are not yet wel l understood in the Beaufort Sea area . The studies undertaken at Kay Po int wi l l go far toward remedying th is si tuat ion . The d i s cus s ion whi ch fo l lows , however , precedes the comp l et i on of these stud i es and its value must be cons idered in the cont ext of thi s lack of knowl edge .

1. The coastal zone i s a dynamic one , part icular l y so in thi s part of the Arctic where shore mat erials are unconsol idated and often contain s ignifi cant quant ities of ground ice . It s instab i l ity must be taken into account in cons iderat ions of both o i l sp i l l s and coastl ine development .

2. The largest areas subj ect to frequent inundat ion by sea wat er and thus , potent i a l l y , by o i l in that wat er are the river deltas , part icular l y the Macken z i e its e l f and , a l ong the Yukon coast , the B l ow and Babbage deltas . The s e deltas have a high s i l t c�ntent and their sed iments are froz en to cons iderab l e depths . Thermal d i sturbance through vegetation damage could l ead to compaction of thawed sediment s . Because the delta p l ains are maj or wi ldfow l nest ing areas , oil must be prevented from reaching them .

3. O i l is most l ike ly to reach the coast during summer and fal l but open water and wave act ivity are pos s ib l e even during winter . The sea ice was broken up off Kay P oint and the Babbage estuary flooded during a severe storm in early January 1 9 7 4 C R . Macken z i e , pers . cornrn.) .

4 . Shor e l ine mat erial s are constant ly in mot ion during the open wat er season and , with the continuous pos s ib i l ity of storm surges , o i l from a spi l l could cover deposit ional coastal features at any time , be buried by subs equent sediment accumulat i on , exposed again , transported along the shor e , re-bur i ed , and so on .

5 . In the event of an o i l spi l l approaching the coast l ine , it may be pos s ib l e to use l agoons behind spits and bars or , a l ong the Tuktoyaktuk Peninsu l a , breached thermokarst lakes to contain i t . The resultant pot ent ial for destruct ion of fish and w i l d l ife is criti cal to thi s suggestion but , i f other methods of containment are l e s s re l i ab l e or cause even greater destruct ion , use of natural features may become v iab l e .

6 . Shore instal lat ions must be careful ly l ocated so as to avoid areas where large amount s of ground ice are present . Disturbance of the ground thermal reg ime wi l l only s erve to further increas e already rapid rat es of coastal retreat . Construct ion off shore must take into account the l ikely pres ence of and , because of low sea water t emperatures , the pos s ib l e growth of sub -bottom fro zen ground .

7 . Beach material is primar i ly local in origin, its maximum travel defined by the d i stance to the outer boundary of the feeder area of the nearshore sed iment s ink toward wh ich it is moving . Removal of mat erial or b lockage of longshore dr ift for construction purpos es wi l l have effect s both up- and down-drift . Because many natural features are important nest ing areas and because di sturbance at one construct ion site may affect condit ions at another , final s e l ect ion of s ites should be made on ly aft er the detai led nature of sediment supply in the area is known .

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2 . INTRODUCTION

2 . 1 General Nature and Scope of Study

Th i s technical report is based primari ly on fieldwork conduc ted during the summer of 1974 into the geometry , compos it ion , origin and stab i l ity of coastal landforms bordering the Beaufort Sea from the Al aska- Yukon boundary east to the Mackenzie Delt a . The 1 9 74 study fol lowed the general reconnai s sance invest igations of the northwest coast of the Tuktoyaktuk P eninsula in 1 9 7 3 and of the Yukon coast in 197 2 (McDona ld and Lewi s , 1 9 7 3 ) . The results of these earl ier studies have been incorporat ed here to extend coverage as far east as Cape Dalhous i e at the eastern end of Tuktoyaktuk P eninsula . As we l l , prepared test imony by the senior author, presented to the Macken z i e Val l ey Pipel ine Inquiry on F ebruary 1 3 , 1 9 7 6 , i s inc luded i n this report as an app endix . The reader is referred to thi s appendix for a more general overvi ew of phys ical aspects of the Beaufort Sea coast , d i s cussion of the imp l i cations Df offshore hydrocarbon resource deve lopment on the coastal zone , and for additional detai l ed information on the modern Macken z i e delta p l ain .

The purposes of 1 9 7 4 fieldwork were twofo l d:

1 . The general reconna i s s ance studies in 1 9 7 2 and 1 9 7 3 rai s ed many questions about the detai led natur e , magnitude and frequency of processes and respons es in this arct i c coastal zone , quest ions which could best be answered by a l onger term instrumented study at a representative samp l e l ocat ion . Kay Point , Y . T . ( F i gure 1 ) was chosen as the samp l e site because it offers a wide rang e of coastal features in a smal l area . Conc entrated fieldwork at this locat i on was begun in 1 974, cont inued in 1 9 7 5 and wi l l be comp l eted in 1 9 7 7.

2 . The second obj ect ive of 1 9 7 4 fieldwork was to examine the geolog ical aspects of coastal suscept ib i l ity to o i l sp i l l s , a part of the jo int industry - government Beaufort Sea study of the potent ial env ironmenta l hazards of proposed exp loratory offshore dri l l ing . In thi s cont ext , the intent ion was to examine those coastal features most suscept ib le to inundat ion b y s ea water . Be cause of extremely poor weather and sea ice conditions during the summer of 1 9 7 4 , work was confined to the Yukon coast .

2 . 2 Specific Object ives

Specific obj ect ives can conven i ent ly be divided into two parts: those concerned with the Kay P oint process - respons e study and those concerned with coastal suscept ib i l ity to oil sp i l l s .

2 . 2 . 1 Kay Po int

Work at Kay Point is focussed on the natur e , magn itude and frequency of stresses exerted on a variety of coastal sed imentary environments and on the response of these envi ronments to the imposed stres ses . The emphas i s i s on system responses to storms o r fl oods but seasonal and longer t erm changes are be ing examined as wel l . In al l cases , greatest at tent ion is g iven to tho s e characteri s t i c s which differ from coasts in more temperate locat ions and wh ich might make an arct ic coast a special case from a development po int of view .

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Spec ific studies inc lude (see Figure 1, inset, for locat ions ) :

1 . Eros ion of and sed iment transport from the coastal c l i ffs southeast of the po int ;

2 . Growth, migration and short-period changes in Kay spit; 3 . Morphol ogy, sedimentology and hydrau l i c s of the Babbage River delta,

an estuar ine delta of the Mackenzie type ; and 4. Sediment transport and deposit ion in Phi l l ips Bay, a nearshore sed iment

s ink .

2 . 2 . 2 Coastal Sus cept ib i l ity to Oil Spi l l s

The degree and durat ion o f damage t o the coastal zone resulting from an offshore o i l sp i l l are dependent primari ly on : (a) whether or not the o i l reaches the coastl ine, (b) the frequency and durat ion of inundat ion of coastal features by sea water containing o i l, and ( c ) the react ion between the o i l , once present, and the sediments, vegetat ion and w i l d l ife exist ing within the coastal zone .

I n thi s context, the int ent ions of this study are to:

1 . Ident ify and determine the ext ent of tho s e areas of the coastal zone most suscept ib le to inundat ion by sea water ;

2 . Determine the present geometry, nature of sediments and vegetat ion of these areas ;

3 . Examine patt erns of sed iment eros ion, transportat ion and deposit ion ; and

4 . Ident ify and d i s cuss conditions pecul iar to an arctic coastal environment relat ing to potent ial damage from an o i l spi l l .

During the summer of 1 9 7 4 , fieldwork was carr ied out on the major spits at Shing le and Kay po ints, on Nunaluk spit in the Firth River reg ion, on the Blow and Babbage River del tas and, as examp l es of sediment source areas, on c l iff s egments at Shing l e Po int and Kay Po int (F igure 1 ) .

2.3 Re l evance t o Deve l opment Prob lems

The coastal zone is one of the most comp l ex and dynamic environments with which devel opment must cont end . Because of the importance of the Beaufort Sea for transportat ion, harbours, staging areas and perhap s pipel ines wi l l accompany the development and movement of resourc es on l and . This study i s intended to provide both reconna issance-l evel and detai l ed process-response informat ion rel evant to construct ion at the coast .

The development of resources at sea wi l l also affect the coastal zone, both through the need for support fac i l it i es on l and and because of the dangers of and need to prot ect the coast against pol lut ion as sociated with offshore devel opment . An o i l sp i l l during offshore dri l l ing could reach the coastl ine and hav e seri ous detrimental effects on vegetat ion, wi l d l i fe and man . It is the intent ion of this study to provide background information relevant to an evaluat ion of the nature, magnitude and durat ion of potent ial damage and of methods of minimi z ing this damag e .

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2 . 4 Acknowledgments

The authors are indebted to many peop l e for co- operat ion in the field during 1 9 7 4 . Ass i s tance at Kay Point was prov ided by B . Hawl ey, M . Kras tman, S . N i cho l s, and A . P insonnault . G . R . Bernyk l ed the sub­party invest igating coastal susceptib i l ity to o i l spi l l s and was as s i sted by B . Gamb le, D . Hunt er, R . Jurchuk and P . Sma l e . Dr . J . A . M . Hunter of the Geological Sl'rvey provided advice and support for sha l l ow wat er seismic studies at Kay Point carried out by J . Cars on and S . Carson . E l ectrical resi s t ivity sounding and profil ing on coastal spits done by L . E . St annard was he lped great ly by advice and support from Dr . W . J . Scott of the Geological Survey . Vegetat ion studies in a l l areas were carri ed out by J . M . Teversham of the University of Brit i sh Columbia . Dr . R . G i lbert of the Queen's Univers ity supervi s ed the March 1 9 7 4 dri l l ing program at Kay Point . Log ist ic support offered by the I nuvik Res earch Laboratory and by the Polar Cont inental She lf Proj ect i s also grateful ly acknowledged .

Thanks are due also to H . Kerfoot and L . Light stone for a s s i stance in preparat ions for the field s eason, to G . R . Bernyk for help in the reduction of field data and to D . J . Egan and the Geo l ogical Survey Cartography and photography sect ions for ass i stanc e in i l lustrat ing this report .

3 . CURRENT STATE OF KNOWLEDGE

Geomorphic and s edimentologic stud ies of the Yukon coast are few . Rampton ( 1974a) has mapped surficial materials at and landward of the coast. Hughes ( 19 7 0) d i s cussed the history and features of g l ac iation and Mackay, Rampton and Fyles ( 19 72) report ed on coastal exposures indicat ive of g lacial ly- deformed rel i c P l e istocene permafrost . Mackay ( 1 960, 1 963) comment ed on the nature of sma l l boat harbours and noted evidence of shorel ine retreat al ong the Yukon coast . Walker and McC loy ( 1 969) and McC loy ( 1 97 0 ) examined the morpho logy and hydrology o f the B low River d e l t a with emphas i s on the ro l e p l ayed b y the arctic environment i n morpho logic change . McDonald and Lewis ( 1973) discussed the distribut ion and variety of marine sediment types along the coast, inferred from coastal depos it i onal features the broad patt erns of nearshore sediment movement and storage, and produc ed several maps showing photogrammetri c measurements of coastal change and typical stratigraph ic sections of segments of coast .

The types of knowl edge of the Yukon coast which pre sent ly exist, therefore, are primarily strat igraphic, very local i z ed or reconnai s sance­l evel in nature . D etai l ed mapping of coastal depositional features has not been att empt ed and the charact eristics of shore and nearshore processes and respons es can only be inferred by extrapolation from the Alaskan port ion of the Beaufort Sea coast ( eg . Wiseman et aI, 1 973; Walker, 1 974) .

4 . STUDY AREA

The nature of the Yukon Beaufort Sea coastal zone has been condit ioned primarily by eros ion and redistr ibut ion of the unconso l idated Quaternary sediments of the Yukon coastal plain . The se d eposits are greater than 30 m . thick and cons ist mainly o f : lacustrine s i lty- c l ay ; al luv ial fan sands and gravel s ; p lus, east of the F irth River (Figure 1 ) , mar ine, estuar ine and fluvial s i lt, sand and gravel, commonly gl acial ly- contorted and capped by till ; and g laciofluvial gravel and sand (Rampton, 1 9 74b) .

- 9 -

Coastal p l ain rivers a l s o supply s ignificant amounts of sediment to the coastal zone . Of the s e, the largest are the F irth, the Babbag e and the B low (Tab l e 1 ) . No estimates of annual sed iment load are availab l e for these rivers but differences i n this together with contrast ing phys iographic s ettings, his tory and coastal current conditions must account for the great d i s s imi lar ity of their deltas .

I n addit ion to the deltas , two other maj or coastal types can be d i s tinguished : st eep c l iffs fronted by narrow beaches and large spits and barri ers . Erosion of the c l iffs has been rapid in recent years, part i cularly where the s ediments contain cons iderab l e pore, wedge or mas s ive ice . Material derived from thi s erosion and from the coastal p l ain rivers i s d i spersed b y we l l developed longshore current s t o four main sediment s inks : (a) Demarcation Bay, (b) between Herschel I s l and and the mainland, (c) Phi l l ips Bay and (d) Shoalwater Bay ( F igure 1 ) . Photogrammetric data i nd icate recent extens ion of the spits and barriers, evidence of this l ong shore movement of s ediment (McDonald and. Lewis, 1973) .

TABLE I

Yukon Coastal P lain Riversa

F irth Babbage B low

Basin area (km . 2 ) 3

6 2 0 0 5 0 0 0 3 7 0 0 Maximum probab l e flood area (m . /s ec . ) 1 00 0 1 1 30 7 1 0 Delta type

(km . 2 ) fan estuarine arcuate

Delta p l ain area 25 SO

aAfter McDonald and Lewis, 1 9 7 3 and Church, 197 1 .

- 1 0 -

5 . SOURCES, METHODS AND RATIONALE OF DATA COLLECT ION

The purpo se of this section of the report i s to detail the spec i fic types of information coll ected, the methods by wh ich th is informat ion was obtained, and the uses to which it has been put .

5 . 1 Kay Point

The evolut ion of a coastal landscape can be examined in the cont ext of any of severa l different t ime scal es . As has been ment ioned previous l y , the scal e o f most concern i n the various component s of the Kay Po int study is that of the storm event - changes over several hours to several days . The seasonal scale - changes over weeks and months - is also of great importance, however, because of its rel evance to the quest ion of the ro l e pl ayed b y the arct i c environment in coastal processes and responses . Of lesser interest to this study but s t i l l essent i al to it are changes which have oc curred over periods of years . These can only be det ermined indirectly but, if rel iab l e evidenc e is avai lab l e , attest to the sum effect of shorter period event s .

The framework for data col lection in each component of the Kay Point study i s detai l ed in the proces s -response model shown i n Figure 2 .

FIGURE 2

Generalized Process - Response Model

Initial Morphology

- geometry, both subaerial and submarine

- properties of sediments

- frozen ground and permafrost

- vegetation

Response Processes

- sediment erosion

- sediment transportation

- sediment deposition

- diagenesis

- freezing, thawing

+

Energy and Mass Sources

- astronomical tides

- meteorological tides

- waves

- currents

- river discharge

- ice

- wind (aeolian)

- gravity (mass movement)

- thermal gradients

Final Morphology

-geometry

- properties of sediments

- frozen ground and permafrost

- vegetation

- 1 1 -

In a pract i cal sens e , measurement to the necessary accuracy of a l l variables rel evant to a particular event at any of the t ime s cal es of int erest i s not pos s ib l e . The model i s idea l i zed and wi l l ind icate the weaknesses of specific studies as well as their strengths .

Initial invest igat ions in the Kay Po int reg ion were ori ent ed primarily toward estab l i sh ing a grid network for data coll ect ion and obtaining the detai l ed background informat ion necessary for future studies - i e . the init ial morphol ogy . I n addit ion to qual itative ob servat ions of coastal morphology and proces s es, the fo l l owing data were co l l ected in 1 9 74 :

1 . Meteoro logical information, most important ly cont inuous recording of atmospheric pressure and wind speed and direct ion to rel ate to waves, currents and meteoro logical t ides ;

2 . Continuous t ide gauge data (through the co-op erat i on of the Marine Sciences Directorate, D epartment of the Environment) ;

3 . Continuous recordings of water l evels on the Babbage R iver and Deep Creek above their j unction to define water inputs t o the Babbage delta ;

4 . Spot measurement s of wat er transm i s s iv ity, sal inity, conduct ivity and temperature in the Babbage estuary and delta channel s ;

5 . Survey profile s both along and acros s Kay spit, the c l i ffs and the B abbage delta and acro s s the de lta channel s ;

6 . E stab l i shment of detai l ed study zones with permanent ly marked profiles at 500 m . interval s along Kay sp it to enab l e morphologic change during storm and seasonal t ime per i ods to be monitored ;

7 . E cho s ounding (Raytheon DE- 7 l 9 - B with 2 0 0 kHz . narrowbeam transducer) and s ide s can sonar profi l es up the l argest Babbage delta distributary and along 1 00 0 m . grid l ines in the Babbage estuary and in the nearshore zones ( out to a maximum of 1 0 m . wat er depth) off Kay spit and the coastal c l i ffs ;

8 . Se ismic refract ion profiles al ong the above grid l ines to locate the upper boundary of sub-bottom fro z en ground ;

9 . Surface sediment s amp l es of the Babbag e delta and estuary on a 1 00 0 x 5 0 0 m . grid, suppl emented by more detailed s ampl ing a t sel ected s i tes including channel cross- sections ;

1 0. Dri l l ing (up to 6 0 m . depth) on the cl iffs, the spit and the delta to define strat igraphy and sediment propert ies and to permit insta l l ation of ground t emperature cab l e s ; data from the s e and future cables together wit h surface temperature, dri l l log and s e i smic refraction information wi l l be used in the devel opment and testing of a mode l of the perturbat ion in the ground temperature field caused by the presence and migrat ion of the coastal c l i ff and spit ; and

1 1 . Vegetat ion mappi ng on the Babbage delta plain, the spit and the c l iffs.

Data co l l e ct ion was cont i nued during the summer of 1 97 5 and ful l analysis awaits comp l etion of the field program in 1 9 7 7 .

5. 2 Coastal Sus cept ib i l it y to O i l Spi l l s

F i e l dwork for this port ion o f the proj ect was des igned t o augment the 1 9 7 2 reconnaissanc e study (McDonald and Lewis, 1 9 7 3) in the part icular cont ext of the goals discussed previous ly. The res earch des ign used in the Kay Po int process- respons e study so that compar i sons and, perhaps, extrapo lations

- 1 2 -

could most eas i ly be made .

The approach taken was spat ial ly hierarchical in nature with progressively more detai l ed work be ing done with each step down in the hi erarchy . Th e highest l evel, the region, was defined as the s egment of coastl ine prov id ing sed iment to each of the nearshore sediment s inks discussed earl ier (F igure 1 ) . Within each region studi ed, areas - i e . coastal types such as c l i ff segment s, maj or spits and bars , deltas , et c . -were se l ected and examined in more detai l . Intens ive fieldwork was carri ed out in two to four 80 m . wide zones in an area, each zone ext ending, if pract ical, from the offshore- nearshore boundary ( 1 0 m. i sobath) we l l into the backshore (beyond the l imit of marine act ivity) .

The geomorphologic data col lected in a zone inc lude the fo l l owing :

1 . Sketch map and photographs - of general topography, maj or geomorphic features, abrupt changes in sed iment propert i es, etc . ;

2. Definition of subaeri a l stratum boundari es - between port ions of the zone whi ch appear homogeneous with respect to type or gradi ent o f processes, ego foreshore, backshore and subdivis ions o f each ;

3 . Subaerial profi l e surveys - three to five, oriented normal to the trend of the shorel ine ;

4 . Subaerial sediment s amp l es - five surface samp l e s in each stratum, positioned syst ematically within strata along the zonal centre-l ine ;

5 . Active layer thicknesses - mean of five probing s at each s ed iment sample si t e ;

6 . Bathymetric prof i l es - high frequency echo soundi ng and s ide scan sonar along the extens i on of the zoneal centre- l ine to the offshore­nearshore boundary ;

7 . Submarine stratum boundari es - as for subaerial, subdivis ions of the nearshor e ; and

8 . Submarine grab s amp les - as for subaerial .

Th i s dat a wi l l be us ed to produce a topographic map of each zone, to estimat e mean grain s i z e and grain s i ze gradi ent for the z one and for each stratum within it and , when data for all zones in an area are combined, to infer areal grad i ents and the type and nature of act ive processes .

In addition to the geomorpho logic studi es, botanical work was carr ied out in connect i on with surveyed profi l es in the Shing l e Point and Kay Point regions and on Nunaluk spit . Col lect ions of a l l vascular p l ant s and representative bryophytes were made for a l l areas stud i ed . The distribut ion of the vegetat ion was examined in relation to the var i ed g eomorph ic units within each study zone us ing a quadrat method for cont inuous vegetated areas and by a l ine transect method for discont inuous areas . The co l l ect ions are present ly being ident i f i ed and, when compl et ed, p l ant communities pres ent w i l l be des cribed and discussed in terms of the ir geomorphi c s i gnifi cance (J . M . Teversham, pers . comm . ) .

As we l l, el ectrical res i s t ivity sound ing and profi l ing were compl eted on Shing l e, Kay, Spring River ( F i gure 1 ) and Nuna luk spits . The aim of th i s experiment was to test the us efulness of this geophys ical method in distingui shing the top and bottom of permafrost and the thickness of gravel in coastal spit s .

- 1 3 -

F inal ly, general ob s ervations on river and sea ice break-up and on the morphology of port ions of each region not inc luded in the study areas were made, the surface area of coastal features subj ect to frequent inundation by sea water measured, and spot surveys taken of the elevat ion of high water driftwood l ines .

F igure 3 .

- 1 4 -

View east over the Babbag e delta during spring break-up; note the floating channel ice . ( 8 June 1 9 7 2; GSC 2 0 2 7 l 7-J)

6 . RESULTS

6 . 1 Kay Point , 1 9 74 F i e l dwork

6 . 1 . 1 Babbage Delta and Estuary

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The estuarine Babbage delta (F igure 3 ) receives discharge and sediment direc t ly from both the Babbag e River and from its tribut ary, Deep Creek . These streams drain a 5000 km . 2 catchment on the Barn and British mountains and the Yukon coastal pl ain . Data on total water and sediment discharge from the drainage bas in are l acking , but indirect estimates (Church , 1 9 7 1 ) suggest max imum probab l e floods of 9 1 0 m.3jsec . for the Babbag e ab ove Deep Creek and 2 2 0 m . 3jsec . for Deep Creek . Total annua l precip itation averages 20 0 mm . (Shing l e Po int , 1 962- 1 9 7 1 ) and four months (June through Sept ember) have mean temperatures over OOC . Most s ed iment movement probably occurs during spring break-up in late May and June and during summer and fal l

' storm floods . The delta plain may a l s o be flooded

by storm t ides , most commonly in the summer and fa ll but occas ionally during winter (R . Macken z i e , pers . comm . ) . As a result , some marine sediment , including a large amount of dri ftwood , i s also incorporated in the delta .

Morphology and sed iments

A genera l i z ed surface fac ies map of the Kay Point area i s given in F igure 4 . The subaerial Babbage delta compris es by far the largest land area below the h ighest dri ftwood l ine , the upper limit of the storm surge fl ooding ( 2-3 m . above mean high t ide) . On two s ides , the de lta and its estuary are bounded b y upland gl acial , marine and lacustrine sed iments of the Yukon coastal p lai n . Al luvial surfaces in the val ley above the highest storm l ine are associat ed with a variety of sediments : from channel gravels of the braided Crow River on the south to fine-grained overbank depos i t s of Deep Creek o n the north (Figure 1 ) . Polygonal ice-wedge structures are common on thi s fac ies and wint er or spring accumulation of aeo l i an sed iment , apparently der ived from channel bars , was noted along some banks .

The delta plain, as mapped her e , includes al l deltaic surfaces above normal h igh tide which are subj ect to storm surge fl ood ing . The lower floodp l ain , general ly l es s than 1 m . above mean high t ide, compr ises vegetated l evees and int er l evee flat s and part ially vegetated shal low flood bas ins , interspersed with numerous t i dal ponds and connect ing channels . Levees , except along minor channe ls have neg l ig ib l e rel ief : veg etat ion mapp ing (J. Teversham, pers . comm . ) revealed l it t l e cons istent contrast b etween levee and inter l evee fl ora and a comp l ex di stribut ion of the few species pres ent over the floodp l ain . I nc luded in the delta pl ain facies are s c attered higher surface s , inact ive l evees flanking abandoned channe ls and a maj or abandoned channel at the head of the delta, all subj ect to dri ftwood accumulation under occas ional storm flooding .

Litt l e is known of the strat igraphy of the delta p lain . Channel banks expos e strat ified s i l t and organi c detritus inc luding occas ional large dr iftwood logs . A boreho l e at the delta front (F igure 4 , dri l l ho le # 4) dri l l ed i n March , 1 9 7 4 was logged a s fo l lows :

� I I \ \

SURFACE FACIES BELOW HIGHEST STORM TIDE

D intertidO!

ocll ve beach

D deJ'op'Oln

§ surtocepeot

§ milted peal,dello plain

ABOVE HIGHEST STORM TIDE:

� alluvjOI

II upland surface - 91'OCIOI, L-.J mOrln8,Iocu strine

Figure 4 .

" I '--81 \ "

- ] 6 -

Kay Po int Region:

®

KAY POINT REGION

tonlou r > isobol h (me Ires)

dr til hole loco lion

03 channel cross-secllon

WET RES �oo 1000

General i zed Surface Facies .

I , I

J 15;

0 - 2 . 6 m . 2 . 6-6 . 1 m . 6 . 1 - 2 2 . 9 m . 2 2 . 9 m .

- 1 7 -

peat, med ium sand with 30-40% i ce by volume 90- 1 00% i ce by vo lume med ium gravel with less than 20% ice by vo lume abundant salt water encountered

The gravel may der ive from the Babbage River but is more probably fluv io-g l ac ial val ley fi l l assoc i ated with late-Wiscons in i ce at King Po int (Figure 1 . ) .

Sediments in the several maj or d i stributary channels wh ich cross the del ta are predominant ly sand . Gravel , present in both the Babbage and Deep Creek above the del t a , is absent from del ta channels. The main di stributary was sounded in August 1 9 7 4 and scour holes up to 7 . 5 m. deep were encountered . I t i s probable that fro zen ground under l ies the del ta channels. Hand prob ing at sect i on N3 ( F i gure 4) revealed fro zen substrate 0 . 5- 2 . 0 m . beneath the channel bott om at least out to 3 m . water depth and pos s ibl y continu ing beneath the thalweg at 5 . 5 m . McD onald and Lewis ( 1973) interpreted as fro zen ground a prominent reflector observed in July 1 9 7 2 echograms from Babbage del t a channels.

Surface peat ( F i gure 4 ) occurs extens ively at or near sea level around the estuary and as rel i c patches on the modern del t a p l ain . I t also occurs beneath s i l t s i n cut-bank exposures i n and above the del ta . In several p l aces ( F igure 4 ) peat and del ta pl ain facies are mixed . The age or ages of the peat exposures i s unknown at this t ime.

I ntert idal surfaces are essent ially unvegetated (Figure 7) . Sediments of this fac ies range from s i l t t o sand , with rare i ce- rafted gravel , l ittle dri ftwood, and occas i onal cl ast s of peat . Bedforms exposed at low water attest to up stream s and movement on channel bars under low - stage flood- t ide condi t ions . Initial impress ions suggest that the intert idal areas may be expanding in pl aces at the expense of the del ta plain .

The Babbage estuary between the delta and Kay spi t is both very sha l l ow and flat ; except near shore , water depths are cons i stent ly in the 1 - 2 m . range and only one bar , 5 0 0 m. behind the spit and paral lel to it, was found . Bot t om surface sediment s are largely wel l sorted fine sands and coarse s i l t s . Neither echo sounding nor s ide s can dat a showed any evi dence of ice or strude� s cour (Reimnit z et aI, 1 9 7 4 ) , although the estuary probab ly freezes to the bot tom in many pl aces in winter and a strudel vortex was observed near the d i s tal end of Kay sp it in June 1 9 7 2 (McDonald and Lewis , 1 9 7 3) . Seismic refract i on data indicate sub-bott om fro zen ground with in the es tuary (Carson et aI, 1 9 7 5) .

Seasonal flow character i s t i c s

A break-up and summer flow sequence s imilar t o that reported for Alaskan river s ( Barnes and Reimnit z , 1 9 7 2 ; Walker , 1974) was observed on rivers of the Yukon north s l ope in 1 9 7 4 . Three phases were dist ingui shed : (a) pre-break-up flooding over winter ice, (b) break-up accompanied and fo l l owed by snowmelt fl ooding with pronounced diurnal fluctuat ion, and (c) general summer flow reces s ion interrupted by brief storm flooJs .

* bottom marks left by water draining through holes in ice .

F igure S.

F igure 6 .

- 1 8 -

B low River delta : pre-break-up fl ooding over winter ice . ( 2 0 May 1974 ; GSC 2 0 2 7 1 7 - 0)

Babbage River estuary : pre-break-up flooding over winter ice ; Kay sp it at extreme l eft centre, Niako 1 ik Point at right centre . ( 2 0 May 1 9 7 4 ; GSC 2 0 2 7 1 7-D)

Figure 7 .

Figure 8 .

- 1 9 -

Unvegetat ed int ert idal flat at the mouth of the main distributary of the Babbage delta . ( 1 0 July 1 9 7 2; GSC 2 0 2 7 l 7-C)

Sediment covered winter ice with thermo- eros ional bedforms which has risen to the surface in the Babbage estuary . ( 1 2 June 1 9 7 2 ; GSC 2 0 2 7 l 7 - B)

- 2 0 -

Pre-break-up flooding began at the head of the Babbage delta on May 1 6 , 1 9 7 4 . Flow in the Firth River had already advanced over ice to Nuna luk sp i t (Figure 1 ) , but ot her rivers along the coast , includ ing the Mal colm, Spring , Running and Bl ow , showed no evidence of flow . Pre-break-up flood ing in the Blow Delta began by May 1 8 (Figure 5 ) and was we ll advanc ed by May 30 in the Ma lcolm and Spr ing rivers .

On the Babbag e , the flow front advanced through the del ta at a rat e of about 3 km . per day and , by May 2 0 , the southern part of the estuary and a zone of sea ice out s ide Kay sp it , to or beyond the 2 m . i s obat h , were water covered (Figure 6) . At the s ame t ime, winter ice in some delta distributar ies began to l i ft free of the bottom but remained in place unt il mid- June or lat er (Figure 3) . Repeated fros t s produced fresh ice cover behind and around the float ing winter ice throughout the early part of June .

At B 2 ( Figure 4 ) , j ust above the del t a , channel ice approximately I m. thic k began to l i ft on May 28 but remained in the reach unt i l June 1 . Soundings to bottomfast i ce suggested a lat e autumn wat er l evel 3 . 5 m . below the top of the cut bank . Water stage after May 28 fluctuated general ly b etween 2 . 8 and 2 . 2 m . below bank top but rose to a peak of 1. 9 m on June 8 and again on June 1 0 . Snow against cut banks indicat ed that no higher flooding had occurred before regul ar obs ervat i ons began . The June 8 peak produc ed the first ext ens ive flooding of the Babbage delta p l ain and fl ooded the ent ire estuary over the wint er ice . The estuary ice sub sequent ly float ed and c leared comp l et e ly by Ju ly 9 . I ce remained c l o s e against the seaward s ide of Kay sp i t unt i l the last week in Jul y , however . I t should be noted i n this cont ext , though , that sea ice break-up i n the Beaufort Sea was except ional ly late in 1974 .

Suspended sediment concentrat ions dur ing break-up flooding at B2 ranged from 50 mg . /l . on June 2 to l e s s than 5 mg . /l . on June 6 to a maximum of 300 mg . /1 . twelve hours after the flood peak on June 8 . Much of this sediment i s depo s i t ed on t op of bottomfast wint er ice in the es tuary (Figure 8) . In the r iver and delta channels some bedload movement prior to break -up also occurred over bottomfast ice . This movement was very l imited , however . Soundings encount ered hard ice surfaces with only occas ional pat ches of sediment exc ept above late autumn wat er levels where the bot tom was soft . Emergent bottom i c e in the channe l s was cl ean exc ept for rare pat ches of sand and some gravel . I n a few instances , wel l formed , asymmetrical ripp l es were observed in the upper surface of bottomfast i ce; the lee faces of some of these ripples carri ed thin s l ip- face accumulations of sand but the r ipp l e surface i t s e l f i s apparent ly thermo- erosional in orlgln . Thermo- eros ional bedforms were also obs erved in float ing bottom ice in the Babbage estuary (Figure 8 ) by McDonald and Lewis ( 1 9 73) . Bottomfast ice in channel s c l early inh ib i t s b ed s cour during pre-break-up flooding. Peak spring discharge may occur after break-up , however , and the ext ent to whi ch scour may then be inhib i t ed by a fro zen channel perimet er is not known .

Cont inuous wat er stage records were obta ined for Deep Creek from Ju ly 4 to August 2 2 and for the Babbage River over the same period with s ome breaks . The data indi cate an init ially s trong d iurnal fluctuat ion on both streams , d iminishing with t ime , but pers i s t ing into August . These

- 2 1 -

fluctuations were al so noted by McDonald and Lewi s ( 1 973) on the Babbage in June and early July 19 7 2 . The general reduct i on in discharge throughout the 1974 record was interrupted by brief floods on five occas ions: the l argest, August 1 3 - 1 5, produced a rise in stage on the Babbag e of 1 . 25 m. in 48 hours, of wh i ch 1 . 00 m. occurred in 14 hours . Babbage d i s charge exceeded 60 m . 3/sec . during l e ss than 10 per cent of the 5 0 day record and 2 0 m . 3/sec . during 75 per cent of the record . Deep Creek showed the s ame patt ern as the Babbage, but with lower more attenuat ed peaks .

I n late June, suspended sed iment conc entrat ions were higher in Deep Creek than in the Babbage : typ ical values on June 1 9 at 0 3 and B4 ( F igure 4) were 1 0 0 and 1 0 mg . /l . respect ive ly . This d ifference was a l so noted during storm floods l at er in the summer . Except for these floods, suspended sediment di s charge decreas ed with water d i scharg e through the summer, concentrations in August being general ly l e s s than 1 mg . /l . Surface wat er and sediment di scharg e to the delta probab l y c eases in l at e autumn or early wint er, a lthough ext ensive i c ings on the Crow and upper Babbage in August 1 974 attest to winter discharge at some po int s in the bas i n .

Pre l iminary measurement s of sal inity, conduc t ivity and temperature were made in the Babbage estuary in mid-July . The maximum sal inity, 2 . 5 % 0, was recorded in the estuary behind Kay spit and the minimum, 0 . 2% °' in river water of Niako l i k Po int ( F igure 4 ) . Wat er t emperatures var i ed from 7 . 00C in river wat er to 2 . 50C in water of intermediate sal inity off the distal end of Kay spit . No s igni fi cant vert ical variations in sal inity, conduct ivity or temperature were encount ered .

6 . 1 . 2 Coastal c liffs

To both the east and west of the Babbage estuary the shorel ine is fronted by rapidly retreat ing coas t a l c l i ffs . Sed iment i s fed from both direct ions into the Ph i l l ips Bay sediment s ink . The coast al c l i ff southeast of Kay Po int ( F igure 4 ) , probab ly the most rapidly retreat ing al ong the ent ire Yukon coast (McDonald and Lewis, 1 9 7 3 ) has been chosen for detai l ed study.

Thi s porti on of c l iff may be d iv ided into two segments (F igure 4) . In segment 1, th e c l i ff is 5- 1 0 m . high, vert ical, oft en undercut and has no v i si b le beach at normal wat er l eve l s (Figure 9 ) . A general i z ed sect ion is given in Figure l la . Retreat has ranged from 2 5 - 9 0 m . in 16- 1 8 year s (McDona ld and Lewis, 1 9 7 3) and is contro l led by melt ing and gul l eying al ong ice wedge l ines, undercutt ing, and subs equent b l ock s lumping .

In segment 2 , the c l i ff (Figur e 1 0 ) rises to 90- 1 00 m . , becomes l e s s steep, changes in strat igraphy and is fronted by pocket beaches . A 6 0 m . dri l l log sect ion near the edge of the cliff (Figure 4 ) taken in March 1974 is shown in F igure lIb . Sediment s are finer and ice cont ent higher than in segment 1 . Ground ice s lump s and. assoc iated mudflows p l ay an important ro l e in retreat wh i ch has been in the order of 25- 5 0 m . over the last 1 6- 1 8 years (McDona ld and Lewis, 1 9 7 3 ) . S imi l ar s lumps are encountered west of the Babbage es tuary (Figure 1 2 ) .

F igure 9 .

F igure 1 0.

- 2 2 -

Undercut cl iff at Kay Point during August storm ; view northeast from Kay spit . ( 2 0 August 1 9 74 ; GSC 2 0 2 7 l 7-A)

C l i ffs southeast of Kay Po int ; view southwest al ong March 1 97 4 dri l l ing l ine . ( 1 6 May 1 9 7 4 ; GSC 2 0 2 7 1 7 -M)

'10

60

50

: 40

'" E

30

20

1 0

0

-10

23 -

0, SEGMENT I 8

6

" E

2

o

-2 -2

b. SEGMENT 2

mecn sea ievel

r\

-20 0 20

0,

o

so n d.

o · o '0 o· 0 0 ,

o 8cin.dy�ora��1 :� 0': o _ 0 0, ' 0 ,0 '0.,

2 4 6 8

met res

relict slumps

cloY,silllo60m.

40 60 80 100 120 met r e s

,

160.0 m.

140 160

Figure 1 1 . Genera l i z ed Sect ions and Strat ig�aphy, Cliffs southeast of Kay Po int .

F igure 1 2 .

- 24 -

Coastal ground ice s lump and associ ated mudflows , Spring River area . ( 8 August 1 974 ; GSC 2027 1 7- G )

- 25 -

Bathymetric profi les off both c l i ff segment s are concave upward with the 5 m . isobath 1 50- 200 m . from the shorel ine . Anal ysis of seismic refraction data indicates the presence of sub-bottom fro zen ground in nearshore ar ea s (Carson et aI , 1 9 7 5 ) .

6 . 1 . 3 Kay Po int spit

Much of the coarser s ed iment eroded from the c l iff segments is carried northwest around Kay Po int and depos ited on Kay spit (Figure 1 ) . Thi s l inear feature (F igure 1 3 ) i s approximately 4 . 9 km . l ong , averages 61 m . in subaerial width and consi s t s l arg ely of gravel ly sand (Figure 14) depos ited over t h e estuarine sandy s i l t s . A March 1 9 74 dri l l ho l e (Figure 4) showed sand and medium gravel to a depth of 5 . 2 m . , gravel decreas ing to zero at 1 0 . 7 m . and s i l t content increasing with depth . A typ ical spit cros s- section near the dri l l ho l e i s given in F igur e 1 5 . Permanent ly fro zen ground exist s along the l ength of the spit but the dri l l ho l e penetrat ed a thin tali k (unfro z en z one) beg inning a t 1 1 . 0 m .

The sp it protects much of the Babbage estuary from marine wave act ivity and appears to be quite act ive , hav i ng ext ended about 4 0 0 m . and retreated on l ine with Kay Po int between 1 9 5 2 and 1 9 7 0 (McDonald and Lewis , 1973) . Mo st sediment movement occurs during storm surges . A surge which reached the high dri ftwood l ine on the Babbage delta, s everal metres above the astronomical t ide of about 0.7 m . , would comp l etely inundat e the spit . The transport of sediment i s a l s o great ly influenced by sea ice , both directly, through the movement of sediment by ice push - obs erved in 1 9 72 but not in 1 974 - and indirect l y , through the effect of the ice on storm surges and assoc iated wave act ivity . As has been menti oned , ice conditions during the summer of 1 9 74 were among the worst on record . The s ea ice remained so l id off Kay spit unt i l late July and , although broken , pers i s ted near shore for the rest of the summer . A storm in late August , with winds exceeding 64 km/hr . , c aused on ly a s l ight surge and only sma l l waves (Figure 9) because of the very short ice- free fetch . Because of the ice protect i on , the upper foreshore of the spit beach maintained its wint er profi l e throughout the open wat er season .

As off the coastal c l iffs , bathymetric profi l es off the spit are concave upward but the 5 m . isobath i s 400- 600 m . from the shore l ine , two to three t imes its distance from the c l iffs . One or two nearshore bars , 0 . 5- 1 . 0 m . in he ight , para l l e l the spit for mo st of its l ength and occas ional sand wave fields with l ee fac es toward shore l i e s eaward of the bars . S ide s can sonar showed l it t l e evidence of i ce scour out to the 1 0 m . isobath , the maximum depth scanned . Again, s e i smic refract ion data indi cat e sub-bottom fro zen ground , in this case extending offshore to a dis tance of at l east 400 m . , its upper surface 20- 30 m . b e l ow the bottom 200 m . from shore (Carson et aI, 1 9 7 5 ) .

6 . 2 Coastal Sus cept ib i l ity to Oil Spi l l s , 1974 F i e l dwork

This portion of the proj ect represent s , bas ica l l y , an extens ion, in considerab ly l e s s detai l , of the Kay Point study to other areas of the Yukon coast subj ect to frequent inundat ion by sea water .

F igure 1 3 .

Figure 14.

- 26 -

Kay Point spit ; view southwest . ( 26 June 1974 ; GSC 2027 1 7-H)

Kay spit , distal i s land ; view southwest along foreshore . ( 1 2 June 1 9 7 2; GSC 2027 1 7 - K)

-I

1 I

:1 -1. .•

S"

P venee r oier G,S

!lco

Sea

p,e

FSI l 1 1 1 :

FO

IS, ClC C a � I (> n 0 I ...

2 7

851

�c 0 I t e r ad C, P over �, G, S

.... a � h 0 lit r de p 0 �, ,

SHINGLE SPIT, PROXIMAL END

.SI SSII

P veneer ovef G,S

""oshover deposit

KAY SPIT, DISTAL END

NUNALUK SPIT, PROXIMAL END

FSIT

berm

• S II

S, '"lGCO �")nc: P,G

P,G, S Lagoon

.S

SAMPLING STRATA

85 bock.hore

LS IOQoon 'hore

SEDIIIIENT TYPE

C cobble

P .,ebble

Lo';loo"

Seo ...!.��e ____________________________________________ _________ _

NUNALUK SPIT, DISTAL ISLAND

-1O 10 me t, e �

Fi gure 1 5 . Se lected Cross- sect ions with Sediment Types , Yukon Coast Spit s .

- 2 8 -

0 . 2 . 1 Blow River Delta

The Blow River is somewhat smal l er than the Babbage but its delta has approximately twice the subaerial extent of the Babbage delta (Tab l e I ) . Unl ike the estuarine Babbage delta , the Blow de lta is arcuat e in form , protrud ing out from the coastal c l iffs rather than being prot ect ed by them .

Except in out l ine and exposure , the two delta p l ains are quite s imi lar . Both contain s everal maj or distributary channe l s , extens ive vegetated inter- l evee flats and numerous l akes , some with connect ing channels to the di stribut aries . Like the Babbag e , l evees in the lower B l ow delta are almost indist ingui shab l e , their rel i ef seldom exceed ing 0 . 5 m . Because o f its proximity t o the Macken z i e , much more driftwood has �een stranded on the surface of the Blow delta than on the Babbage . The highe st driftwood l ine on the Blow was formed dur ing a storm surge which reached more than 2 m . above normal high t ide and . covered considerab ly more than 50 per cent of the subaerial surface in front of the coastal c l iffs .

Textural l y , the two deltas are a l s o al ike . F ine gravel in the upper Blow delta chang es abruptly to s i l t in the l ower (Walker and McC l oy , 1 969) . Organic detritus appears t o b e more prominent i n the Blow than in the Babb ag e , however . Al l lower delta p l ain s amp l es show a high percentag e of organics , with l ow scarps (up to 0 . 8 m . in height) cut into the vegetated delta- front al luvial i s l ands being composed almo st entirely of organic material (F igure 1 6 ) .

These scarps , t og ether with the absence of s ignificant inter-t idal flats except near the mouths of active di stribut aries , suggest retreat of the subaerial front of the Blow delta , perhaps even more rapidly than the Babbage . Water depths off the front of the Blow are very shal low, though , so the retreat may depend upon the temporary l ocat i on of d i str ibutary mouths and thus be more apparent than rea l . At one site near the maj or western distr ibutary mouth , wat er depth was l e s s than 1 . 0 m . out to 1 . 2 km . off- shore , increas ed in a series of steps to 2 . 5 m

'. at 1 . 3 km . and was

constant at 2 . 5 m . depth to at l east 2 . 1 km . from shore .

6 . 2 . 2 Shing l e Region Coastal C l iffs

C l i ffed shorel ines offer onl y sma l l areas which are regularly covered by sea wat er . They are , however , the prime sources of sediment for the maj or spit s to be d i s cussed in the next section of this report . Between Shing l e spit and the Blow River delta the coast l ine i s c l i ffed except at the delta of the Running River . Two areas of this c l iff were examined in 1 9 7 4 , primar i ly for compar i s on with the Kay Po int c l iff study .

East of the Running River a l arg ely unvegetated gravel scarp , gul l eyed at interval s along its l ength, r i s es at an ang l e of 3 2 - 350 to an el evat ion of 1 5 - 2 0 m . Sediment eroded from thi s scarp i s moved eastward al ong the narrow b each whi ch front s it and is the sourc e of gravel found in a sequence of beach ridges on the west ern Blow River delta . West of the Runn ing River the s carp reaches e l evat ions of more than 30 m . but i s

- 29 -

F igure 1 6 . Blow River delta p lain , east side ; view southeast of organic coastal foreshore scarp . ( 7 July 1 9 7 4 ; GSC 2027 1 7 - 1 )

F igure 1 7 . Shing le Po int spit ; view Kest ; �ote shore l ine pressure ridge at upper right and prominent driftwood l ine . ( 2 1 June 1 9 7 4 ; GSC 2027 1 7 -N)

- 30 -

less steep , mostly vegetated and composed predominant ly of s i lt s . reaches sea l evel primarily by mudflows and by eros ion in gul l eys . c l iff segment i s simi lar in many ways to segment 2 at Kay Point .

Material Th is

6 . 2 . 3 Coastal Spits

The three spit areas studied - Shing l e , Kay and Nunaluk (Figure 1) -

are among the most prominent depos it ional features found al ong the Yukon coast . Of thes e , Kay has already been discussed . Shing l e (Figure 1 7) and Nunaluk are longer , wider and higher (Tab l e I I ) but are s im i l ar in form

Spit

Shing l e

Kay

Nunaluk

Length (km . )

5 . 4

4 . 9

1 2 . 2

TABLE I I

Yukon Coast Sp it Morphometry

Mean Subaerial Width (m . )

1 4 1

6 1

1 63

Mean Berm Height (m . )

1 . 53

0 . 96

1 . 49

Foreshorea

S lope

0 . 08 5

0 . 066

0 . 04 1

aBerm crest to shorel ine

bShorel ine to 5 m . isobath

Nearshoreb

Slope

0 . 006

0 . 0 1 0

0 . 0 1 7

and , with loca l i z ed except ions , i n the presence of both s and and gravel s ediment types . The l ower berm el evation of Kay spit may b e due to the protection against the dominant southeast erl y moving storm waves offered by Herschel I s land and the b ar between it and Kay Po int (F igure 1 ) . I t does not appear t o be related to nearshore s l ope (Tab l e I I ) .

Typical subaerial profi les and s ediment types for each spit are shown in F igure 1 5 . Four morphologic components ( s amp l ing strata) are common to most of the spit z ones examined : foreshore , backshore I , back shore I I , and l agoon shore . The s ignificance of the surveyed foreshore geometry is difficult to evaluate because the upper port ion is rel ic , undi sturbed during the 1 97 4 open water season . Berm e l evat ion over the l ength of al l sp its is rel at ively constant except for a sudden drop from the end of the main Nunaluk spit to the distal i s l ands (Figures 1 5 , 1 8 and 1 9 ) . Behind the berm crest , the backshore I stratum cons i s t s of washover depos its which over l i e older backshore I I sediment s . The boundary between the two is commonl y an abrupt scarp . In the proximal zones of Shing l e (Figure 20 ) and Nunaluk spit s , the washover deposits appear t o b e transgres s ing , po s s ib l e evidence of shorel ine retreat . The l agoon shore stratum in al l cases i s l ower and d i sp l ays fewer and sma l l er ridges than the foreshore because of shal l ow depths , seldom exceed ing 2 m . , and short fetch in the lagoons .

Figure 18 .

F igure 1 9 .

- 3 1 -

Nunaluk spit , proximal end ; view west a long foreshore storm ridg e , berm at far l eft. ( 22 August 1974 ; GSC 2027 l 7 - E )

Nunaluk spit , second d i s t a l i s l and ; view west along for eshore . ( 1 6 August 1 9 74 ; GSC 2027 l 7 - L)

F i gure 2 0 .

- 3 2 -

Shing le spit : unvegetated backshore I s ediments Cwashover l obes) advancing over backshore I I . C 7 Jul y 1 9 74 ; GSC 2 0 2 7 1 7 )

- 33 -

No cons i st ent patt ern of l engthwise var iation in mean s ed iment s i z e is apparent among the spit s . Prel iminary observat ions show Shing l e to be relat ively constant along its l ength ; Kay coarsest a t i t s proximal end and const ant thereafter ; and Nunaluk (Figures 1 8 and 1 9 ) with a gradual increas e toward its distal end and a sharp decreas e to almost pure sand on the s econd and third d i stal i s lands . Lateral ly , the foreshore stratum is both coarsest and most var iab l e . Backshore I I is much finer than backshore I with s i l t commonly present in addit ion to the usual sand and some gravel . Mean s i z e increases , but not to foreshore l evel s , on the lagoon shore . These lat eral changes are normal for spi t s at any latitude .

Nearshore bars exi st off Shing l e as we l l as off Kay , but are neither numerous nor prominent . No bars were found off the attached s egment of Nunaluk spit in 1 9 7 2 but a comp lex system of bars and channe l s exi s ted s eaward and between the di stal i s l ands , probab ly due , at l east in part , to F irth River discharge (McDonald and Lewis , 1 9 7 3 ) . As at Kay , l it t l e evidence of ice scour was found in the nearshore areas of Sh ing l e and Nunaluk spits , this phenomenon apparent ly ceas ing at about the 1 0 m . is obath where wint er shorefast i c e begins (J . M . Shearer , p ers . comm . ) . Nor were s ignificant ice-related s edimento logical features observed on the beaches of the s e two spi t s in 1 974 but Al askan observat ions (Hume and Schalk, 1 964 and 1 9 7 3 ; etc . ) and 1 97 2 observations on Kay spit (McDonald and Lewis , 1 9 73) suggest that 1974 was an unusual year in thi s regard . A maj or shorel ine pressure ridge l ay off the proxima l half of Shingl e spit for most o f the summer of 1 974 (Figure 1 7 ) but , whi l e it undoubted l y moved cons iderab l e quant it ies of s ed iment i n the nearshore , it had no d irect effect on the subaerial b each .

- 34 -

7 . D I SCUSSION

Because the areal ext ent of 1 9 74 fieldwork represents only part of that covered by Geological Survey coastal investigat i ons in the B eaufort Sea, it seems appropriat e in this sect ion to briefly d i s cuss previous work to the east of the Yukon-Northwest Territories border in the context of the Yukon coast results .

The estuarine Babbage delta appeared to be of part icul ar int erest because , in a morphologic sens e , it i s s imilar to the modern Macken z i e delta . Hydro logically, however , the two are not nearly as s imilar . Unl ike the Babbag e , the Macken z i e flows all wint er along i t s ful l l ength and is exoti c , its break-up and flow being influenced to s ome ext ent by non- arctic conditions to the south . But l ike the Babbag e , s ignificant sediment transport events are confined to the break-up and summer flow periods and storm t ides on the Beaufort Sea p l ay an import ant ro le in deltaic s ediment at ion .

East of the Mackenzie delta , the northwest coast of the Tuktoyaktuk Peninsula , unl ike the Yukon coast , i s deep ly embayed al ong much of i t s l ength , i t s shape reflect ing t h e breaching o f thermokarst lakes which cover l arge port ions of the coastal p lain . Large sp i t s and long barri er bar s equences have formed becaus e of the low offshore gradi ent , much lower than off most of the Yukon coas t . Thes e features protect much of the coast from d irect wave attack .

The mat erials in the spi t s and bars ref l ect l argely the nature of nearby and underlying deposits . To the south and west of the set t l ement of Tuktoyaktuk , beach mat erials are s imi l ar to those of the Yukon coast : pebb le gravel in medium sand matrix, derived from gravel l enses in fluvial outwash and from a pebb ly c l ay t i l l . To the north and east of Tuktoyaktuk , the gravel d i s appears and beaches are composed of medium to fine sand eroded from the more distal portions of fluvial and deltaic outwash depos its . Because of the predominance of sand , it can be di

"fficu l t

to distinguish strat igraph ical ly between t h e depos itional features and the underlying outwash (McDona l d , Edwards and Rampton , 1 973) . Stab i l i z ed and part i a l ly stab i l i z ed dune zone s are common along this segment of coast .

Like the Yukon coast , the northwest coast of the Tuktoyaktuk Peninsula is retreat ing , with both rates of retreat and resulting coastal configurat ion affected great ly by the nature and distribut ion of fro z en ground . Thi s effect is both direct , in that local rat es of retreat are greatest where coastal c l iff sed iment s contain cons iderab l e ground i ce , and indirect , in that the shape of a large part of the coastl ine is contro l l ed by apparent retreat due to the breaching of thermokarst lakes . Rel i c submarine fro z en ground exists in many nearshore areas (Mackay , 1 9 7 2 ; McDonal d , Edwards and Rampton , 1 9 73) b ecause o f thi s coastal retreat .

Although st eep , c l i ffed shorel ines occupy a much smal l er proport ion of the total l ength of the Tuktoyaktuk Peninsula than of the Yukon coast and no maj or rivers enter the s ea along i t , the s i ze and numb er of

- 35 -

depos it ional features suggest , even with the l ow offshore gradient , a ready avai l ab i l ity of s ediment . Much of this mat er i a l i s moved northeast , under the contro l of offshore currents and of d i s charge from the East Channel of the Macken z i e River . In Kugmal l it Bay , the effect of thi s regional drift on deposit ional shore features i s very weak and these depo s its primari ly refl ect l ocal factors such as wind d irection , nearshore bathymetry and coastal ori entat ion . To the east , however , the regional transport direct ion has more influence and large spits and barrier bars suggest coastal s ed iment transport northeast to Liverpoo l Bay .

8 . CONCLUSI ONS

The main s c ient ific conc lus ions result ing from this study are :

1 . The maj or geomorpho logic features o f the Yukon Beaufort Sea coast are : (a) steep coastal c l iffs , often containing s ignificant amounts o f ground i c e , and front ed b y narrow beaches ; (b) spits and barriers up to 1 0 or mor e k i l ometres in subaerial l ength and s everal hundred metres wide; and (c) del tas of coastal p l ain r ivers with vegetated or part ial ly vegetated subaerial delta pl ains up to 5 0 km . 2 in area .

2 . C l i ff sediment s range from gravel to icy c l ay . The fine mat eria l i s moved off shore and beaches , spits and barri ers are usual ly composed of remnant gravel s and sands . Coastal p l ain rivers have gravel beds but thi s gravel does not reach the l ower delta p l ains where sediments are pr imar i ly organic-rich s i l t s and fine s ands .

3 . C l iff retreat of up to 9 0 m . in 1 6 - 1 8 years has occurred , iargely through undercutting and subsequent b lock s lumping , gul l eying , and mud flow associat ed with ground ice s lumps . Sediment derived from this retreat i s moved al ong shore and has l ed to hundreds of metres of spit and barrier extension over the same t ime period .

4 . S igni ficant sediment transport event s are associated with spr ing break-up and storm floods on the rivers and with meteorol og ical tides and wave activity dur ing these storms along the coast . Berm e l evat ions o f over 1 . 5 m . on sp its and dri ftwood l ines more than 2 m . above normal h igh tide on subaer ial delta p l ains at test to the r i s e in sea l evel and inundat ion of coastal depositional features during the se storms , most commonly in the summer and fal l but occas iona l ly during the wint er .

5 . First flow in rivers , del tas and estuar ies occurs wel l before sea ice break- up and is commonl y over bottomfast wint er ice . Thi s ice inhibits bed s cour during ear l y fl ooding . Fo l l owing spring break-up , river dis charge decl ines exc ept for brief rises during storm event s .

6 . The direct effects of s ea ice on the stab i l ity of coastal features appear to be smal l . On ly minor examp les of the movement of beach s ediment by ice push and scour of the nearshore s ea bed by ice have been observed , this l atter phenomenon apparent ly ceas ing shoreward of the 1 0 m . i s obath . I ndirect effects , particu l arly the influenc e of the amount and l oc at i on of ice on st orm surges and assoc iated wave activity, are much more important .

- 3 6 -

7 . Offshore gradients can be quite st eep off many port ions of the Yukon coast , most commonly where the shore l ine i s cl iffed . Pro fi l es are genera l ly concave upward and few nearshore bars exist . Off river deltas , though , depths are very shal low , seldom exceed ing 2 m . a ki lometre or more from shor e . Sha l l ow depths in the Babbage estuary prevent the devel opment of s igni fi cant vert ical variat ions in water t emperature and sal inity .

8 . Rap id coastal retreat , shal low wat er depths and l ow wat er temperatures have enab l ed the pres ervat ion or format ion of permanent ly froz en ground beneath es tuary and nearshore areas .

9 . Un l ike the Yukon coast , the northwest coast of the Tuktoyaktuk Peninsu l a is deeply embayed al ong its l ength , its shap e refl ect ing the breach ing of thermokarst l akes which cover l arge port ions of the coastal p l ain . Maj or spits and long barri er bar s equenc es have formed b ecaus e of the much lower offshore grad ient than off the Yukon coast . Sediment s in coastal depos it ional features are mixed grav e l s and sands west of the s ett l ement of Tuktoyaktuk and , most common ly, pure s and east of Tuktoyaktuk . Like the Yukon coast , the shorel ine of the Tuktoyaktuk Peninsula is retreat ing , with most of the derived s ediment being moved northeast toward Liverpoo l Bay .

9 . IMPLICATIONS AND RECOMMENDATI ONS

9 . 1 General Sc ient i fic

In an average year , the southern Beaufort Sea coast , part icularly east of Hersche l I s land , has a relat ively long open wat er s eason and cannot be cons idered true arc tic in nature . Norma l mar ine processes dominate for about three months of the year . During this time peri od , the arcti c env ironment influenc es thes e processes on ly through the increased relat ive importance of extreme st orm events , the occas iona l movement of sea ice near shore during the s e event s and , as was so we l l demonstrated during the summer of 1 9 74, through the maj or year to year variat ions in c l imate and sea ice condit ions whi ch may occur .

The response of coastal mat eri a l s to summer mar ine proces ses , however , is cond it ioned by the arctic env ironment . Fro zen ground p l ays an important ro l e in the coastal zone , mo st important ly through its influence on rat es of coastal retreat and , al ong the Tuktoyaktuk Peninsul a , through the cont rol of th ermokarst l akes of coastal configurat ion .

9 . 2 Matt ers Rel evant to D evelopment

Deve lopment is cons idered here primar i ly with respect to the potent ial effects on the Beaufort Sea coastal zone of an o i l spi l l during exp loratory offshore dri l l ing . Cons iderat ion is given as we l l , however , to the possib l e use of the coast for stag ing areas or other shore instal lat i ons assoc iat ed with petro l eum exp l orat ion and devel opment .

The detai l s of coastal processes and respons es , part icularly for shortTper iod events , are not yet we l l understood in the Beaufort Sea ar ea .

- 37 -

The studies undertaken at Kay Po int wi l l go far toward remedying this s i tuat i on . The di scuss ion whi ch fo l l ows , however , precedes the comp l et i on of the s e studies and i t s value must be considered in the cont ext of this know l edge .

1 . The coastal zone i s a dynamic one , part icular ly so in this part of the Arctic where shore mat er i a l s are unconso l i dat ed and oft en contain s ignificant quant i t i e s of ground ice . I t s instab i l ity must be taken into account in cons iderat i ons of both o i l spi l l s and coast l ine deve lopment .

2 . The l argest areas sub j ect to frequent inundat ion by s ea wat er and thus , potent i al l y , by o i l in that wat er are the river deltas , part i cular l y the Macken z i e i t s e l f and , along the Yukon coast , the B l ow and Babbage del t as . The se deltas have a h igh s i lt cont ent and the ir sediment s are fro z en to cons iderab l e depths . Thermal di sturbance through vegetat ion damage could l ead to cons iderab l e consol ldat i on . Because the delta p la ins are maj or wi ldfow l nest ing areas , o i l must be prevent ed from reaching them .

3 . Oi l i s mo st l ikely to reach the coast during summer and fal l but op en water and wave act ivity are pos s ib l e even during wint er . The sea i c e was broken up off Kay Po int and the Babbage estuary fl ooded during a severe s torm in early January 1 9 74 CR . Macken z i e , p ers . comm . ) .

4 . Shore l ine mat er i a l s are constant ly in mot ion during the open wat er s eason and , with the cont inuous pos s ib i l ity of storm surges , o i l from a sp i l l could cover depo s i t ional coastal features at any t ime , be buri ed by subs equent s ediment accumu l at i on , exposed again , transport ed a l ong the shor e , re-buried, and so on .

5 . In the event of an o i l spi l l approaching the coast l in e , it may be pos s ib l e to us e l agoons behind spits and bars or , a l ong the Tuktoyaktuk Peninsula , breached thermokarst l akes to contain it . The resul tant potent i al for destruct i on of fish and w i l d l ife is cr it ical to this suggest ion but , i f other methods of containment are l e s s rel i ab l e or cause even greater destruction , us e of natural features may become viab l e .

6 . Shore instal'l at i ons mus t b e carefu l ly l ocated so as to avoid areas where l arge amounts of ground ice ar e pres ent . D i sturbance of the ground thermal reg ime wi l l only s erve to further increase already rapid rates of coasta l retreat . Construct ion off shore must take into account the l ikely present of and, because of l ow s ea wat er t emperatures , the pos s ib l e growth of sub-bot tom fro z en ground .

7 . B each mater i al i s primar i l y l ocal in ori g in , its maximum travel defined by the di stance to the outer boundary of the feeder area of the near­shore s ediment s ink toward whi ch it is moving . Removal of mat er ial or b l o ckag e of l ongshore dr i ft for cons truc t i on purposes wi l l have effects both up- and down- drift . Becaus e disturb ance at one cons truct ion s i te may

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affect cond i t i ons at anoth er , final s e l ect i on of s ites should b e made on ly aft er the detai l ed nature of s ediment supp ly i n the area is known .

1 0 . NEEDS FOR FURTHER STUDY

Work which has b een comp l eted to dat e has larg e l y been descriptive in nature . Both the Yukon and Tukotyaktuk P eninsula coasts have been covered in some detai l . There remains possibly the most crit i cal area of al l : the modern Macken z i e delta b e l ow the highest storm surge driftwood l ine and the rapidly retreat ing P l e i stocene i s l ands wh ich border it . F i e ld operat ions wi l l be more difficult to carry out in this area but should be comp l eted before any j udg ement s on the sus c ept ib i l ity of the Beaufort Sea coast to o i l sp i l l s are made .

The second important gap in pre�ent know l edge has been ment ioned several t imes in this report : the l ack of informat ion on the detai l s of sediment movement during short-period storm events . Data on this quest ion wi l l b e avai l ab l e fo l low ing the comp l et ion of the Kay Po int process- response study in 1 9 7 7 .

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1 1 . REFERENCES

Barnes , P . W . and Reimnit z , E . 1 9 7 2 : River overfl ow onto the sea ice off the northern coast of

Al aska , Spring ( 19 7 2 ) ; Abstract , Am . Geophys . Uni on, Trans . , 5 3 , p . 1 020 .

Church , M . A . 1 9 7 1 : Reconnaissance of hydro logy and fluvial characteristics of

rivers in northern Alaska and northern Yukon Territ ory ; Report prepared for Mackenzie Val l ey P ipel ine Research Lt d . , 1 9 7 p .

Carson , J . M . , Hunter , J . A . and Lewis , C . P . 1 9 75 : Marine se ismic refraction profi l ing Kay Po int , Yukon Territory ;

in Report of Act ivi ties , Part A , Geo 1 . Surv . Can . , Paper 75- 1 , Pt . A , p . 9- 1 2 .

Hughes , O . L . 1 9 70 : Surficial g eo logy of northern Yukon Territory and northwest ern

D istrict of Macken z i e , Northwest Territories ; Geo l . Surv . Can . , Paper 69- 36 , 1 1 p .

Hume , J . D . and Schalk , M . 1 9 6 4 : The effects of ice-push on arct i c b eaches ; Am . J . Sci . , 262 ,

p . 267 - 2 7 3 .

Hume , J . D . and Scha l k , M . 1 9 7 3 : The effects of i c e on the beach and nearshore, Point Barrow ,

arct ic Alaska; Part ial final report , U . S . Office of Naval Res earch Sub -c ontract ONR- 4 l 3 , 3 l 2a2 , Arctic Inst . North Am . , 29 p .

Mackay , J . R . 1960 : Notes on sma l l boat harbours of the Yukon coast ; G eogr . Bul l . ,

no . 1 5 , p . 1 9 - 3 0 .

Mackay , J . R . 1 9 6 3 : Notes on the shor e l ine recession along the coast of the Yukon

Territ ory ; Arct ic , 1 6 , p . 1 9 5 - 1 9 7 .

Mackay , J . R . 1 9 72 : Offshore permafrost and ground ice , southern Beaufort S ea , Canada ;

Can . J . Earth Sci . , 9 , p . 1 5 50- 1 5 6 1 .

Mackay , J . R . , Rampton , V . N . and Fyles , J . G . 1 9 7 2 : Relic P l eistocene permafrost , Western Arct i c , Canada ; Scienc e ,

1 76 , p . 1 3 2 1 - 1 32 3 .

McC loy, J . M . 1 9 70 : Hydrometeoro logical relat ionships and their effect s on the l evees

of a sma l l arctic del t a ; G eografiska Annal er , 52A , p . 2 2 3- 24 1 .

McDonal d , B . C . and Lewis , C . P . 1 9 7 3 : G eomorphic and sed imento l og i c processes of rivers and coast ,

Yukon coastal p lain ; Environmental- Social Commit t e e , Northern Pipel ines , Task Force on Northern Oil Development , Government of Canada, Report no . 73- 39 , 245 p .

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McDonal d , B . C . , Edwards , R . E . and Rampton , V . N . 1 9 73 : Position of fro st tab l e in the nearshore zone , Tuktoyaktuk

Peninsu l a ; in Report of Act ivi ties , Part B , Geol . Surv . Can . , Paper 7 3- 1 , Pt . B , p . 1 65- 1 68 .

Rampton , V . N . 1 9 74a : Surficial geol ogy and landforms for parts of Aklavik ( 1 0 7B) ;

B l ow River ( 1 1 7A) ; Demarcat i on Po int ( 1 1 7C ) ; Herschel I s l and ( 1 1 70) ; G eo l . Surv . Can . , Open F i l e 1 9 1 .

Rampton , V . N . 1 9 74b : Terrain evaluat ion with respect to pipel ine construct ion,

Macken z i e transportat i on corridor , northern part , lat . 680N to coast ; Env ironmental -Social Committ e e , Northern P ipel ines , Task F orce on Northern O i l Development , Government of Canada , Report no . 73- 4 7 , 44 p .

Reimnit z , E . , Rode ick , C . A . , and Wo l t S . C . 1 9 74 : Strudel scour : a unique marine geo l og i c phenomenon ; J . Sed .

P etro l . , 4 4 , p . 4 0 9 - 42 0 .

Walker , H . J . 1 9 74 : The Colvi l l e River and the Beaufort Sea : some interact ions ;

Unedited preprint , Sympos ium on Beaufort Sea Coastal and She l f Res earch , San Franc i sco , Jan . 7- 9 , 1 9 74 , Arct ic . Inst . North Am . , 4 1 p .

Walker , H . J . and McC loy, J . M . 1969 : Morpho logic chang e in two arctic deltas ; Arct i c Inst . North Am . ,

Res . Paper no . 4 9 , 9 1 p .

Wiseman , W . J . , Jr . , et al . 1 9 7 3 : Al askan arct i c coastal processes and morpho logy ; Louisiana State

Univ . , Coast al Studies Inst . , Tech . Report no . 1 4 9 , 1 7 1 p .

1 2 . APPENDI X : Phys ical Aspects o f the Beaufort Sea Coas t . Prepared Tes timony Presented t o the

Macken z i e Val l ey Pip e l ine Inquiry , February 1 3 , 1 9 7 6 .

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Introduction

1 . My int ent ion i s t o d i s cuss those phys i cal aspects of the Beaufort Sea coast wh i ch might be important in any p l an to develop hydrocarbon resources offshore .

2 . In this development I include both construction and operat ional requirements : for examp l e , pipel ines coming ashore , harbour develop­ment , staging faci l i t i es , and the coars e aggregat e mining necessary for their construct ion .

3 . Because any p ipel ine from offshore wi l l probably need to move crude o i l as wel l as gas , the consequences of an o i l spi l l are also rel evant .

The Coastal Zone

4 . For the purposes of this discuss i on I have defined the coastal zone as the area between the highest storm t ide l ine on l and ( about 3 m . above mean s ea l evel ) and the 1 0 m . wat er depth ( common ly assumed to be the s eaward l imit of bottom material movement by waves ) .

5 . The e ffects o f deve lopment in thj s zone are o f parti cular importance becaus e it contains l arge b ird and fish populat ions and is the part of the Beaufort Sea mos t us ed by man at the present t ime .

Sl ide 1 *

(Map of Southern Canadian Beaufort Sea Coas t )

6 . The length of coast with whi ch I am personal ly fami l iar and whi ch I wi l l cons ider today extends from the Alaskan border to the east ern end of the Tuktoyaktuk Peninsula at Cape Dalhous ie .

7 . The top i cs I intend to cover include : the effects of an Arct ic environment , nearshore water ci rculat ion , storm surges , coastal landforms and mat eri al s , and coastal stab i l ity - a l l set in the context of the influence they should have on the typ e , ext ent and locat ion o f faci l it i e s assoc i ated with hydrocarbon resource development .

E ffects of an Arct ic Environment

8 . It i s , I think , important to real i z e that the area under discus s ion i s , in s ome s ens es , not "true Arct i c" in nature . The open wat er season , part i cularly where the influence of the Macken z i e River i s fel t , is long by arct i c standards . For 3 to 4 months a year there can be t ens or even hundreds of mi l es of open wat er on \<Jhich wind can generate waves to cut back the coast .

*Bl ack and white prints of co lour s l ides used during presentation o f thi s test imony are included at the end of the text .

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9 . The response of coastal materials to wave attack i s , however, "true Arctic" in nature . Fro z en ground p l ays an important ro l e in the coastal zone . Unl ike areas such as the Canadian west coas t , coastal materials along the Beaufort Sea are unconso l idated . No bedrock i s present . But becaus e this unconsol idated material i s permanently froz en and contains cons iderab l e ground ice in many locat ions , both the nature and rates of coastal change differ con s iderab ly from what they might be in a more t emperate c l imati c set t ing .

1 0 . The net effect of thes e factors i s comp l ex . Because o f the long open water s eason and the unconsol idated nature of the coastal material s , the entire coas t line is retreat ing . The rate of retreat , however, i s contro l l ed to a large extent by the nature , amount and locat ion of ground i ce in the s ediment s . Where the coast i s compo s ed of coars e sands and grave l s , the froz en nature o f the materials may s l ow down wave ero s i on . But where l arge amounts o f ground i ce are present , retreat w i l l be even more rap id .t han i f the mat erial s were unfroz en .

1 1 . From the devel opment point of view , these factors are crit ical . Faci lit ie s mus t cont end with both an act ive summer marine environment and the presence o f fro zen ground - a s ituat ion for whi ch there i s n o paral l e l i n past hydrocarbon development .

Nearshore Water Movement

1 2 . The patterns o f water movement in the coastal z one are quite di fferent from the offshore c irculat ion . As you w i l l see , they are very rel evant to the e ffect an o i l sp i l l might have on the coast .

S l i de 2

(Topkak spi t )

1 3 . Because the nature o f the Beaufort Sea coast has been conditioned by the relat ively rapid erosion and redi stribut ion o f the materials of which it i s compo sed , the pos it ion and ori entat ion of resultant depos i t i onal feature s , l ike this spit j ust north of Tuktoyaktuk , can be used to infer the dominant direction o f sediment movement and thus the dominant longshore current direction at any locat ion where they are pres ent .

1 4 . Pl ease not e that I use the term dominant direction . I don ' t mean to imp ly that this i s the only direction in which nearshore current s can flow . I t i s probab l e , though , that the dominant direct ions are those in whi ch o i l would move during maj or s ediment transport events , that i s to say during summer and fal l storms when low lying areas could be flooded by the s ea l evel rises as sociated with s trong onshore winds , and thus would be open to inundat ion by oil .

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S l i de 3

(Map o f Southern Canadian Beaufort Sea Coas t )

1 5 . I have p l otted dominant current direct ions for the Beaufort Coast on this map as b lack arrows and, on the bas i s of these direct ions , I ' ve divided the coast into s egments . Each s egment cons i sts of a sediment s ink toward whi ch s ediment i s being moved and the cont ribut­ing source area . The s egment boundaries are indicated by the l i ght l ines on the map and each segment (there are 1 1 in a l l ) is label l ed by the b lack l etters on l i ght backgrounds .

1 6 . The import ance o f thi s s egmented circulation pattern i s that , part i cular ly during storm events , oi l reaching the nearshore z one wil l tend to remain w ithin the coastal s egments I have i dent i fi ed and to move t oward the s ediment s ink o f each s egment .

1 7 . It might appear attractive, as wel l , to locate shore instal lat ions having a high potential for spil l age in the s ink areas . Unfortunately, however , because these areas are s ediment as well as potential o i l s inks , they t end to b e very shal l ow and t o contain spits and lagoons that make them favorite l ocati ons for fish and shore bird populat ions .

Storm Surges

1 8 . I have already menti oned sea l evel rises associat ed with strong onshore winds during summer and fal l storms ; thes e rises are somet imes cal l ed storm surges .

1 9 . Based on an examinat ion of t i de gauge records at Tuktoyaktuk , Dr . R . F . Henry of Ocean and Aquati c Affairs , DOE identi fi ed 2 2 surges which caused water level rises o f more than 1 m . b etween 1 962 and 1 9 7 3 , inc luding 2 whi ch caused rises of more than 2 m . A September 1 9 7 0 storm , for whi ch no t ide gauge data are avai lab l e , may have caused a ris e of as much as 3 m . at Tuktoyaktuk .

2 0 . These surges are o f importance for s everal reasons : first , waves as sociated with them cause much of the erosion and longshore sediment movement whi ch occurs along the Beaufort Sea coast , Q top i c I wi l l di s cuss lat er ; and , s econd , they l ead to the inundation of l ow- lying coastal areas by s ea wat er , water whi ch mi ght contain oil in the event of a spi l l .

S l ide 4

( Kay Point Sp it ; June 2 1 , 1 9 7 5 )

2 1 . Thi s view i s of Kay Point spit o n the Yukon coast . The spit i s about 5 km . l ong and its crest i s about 1 m . above normal mean sea l evel .

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S l ide 5

(Kay Point Spit ; Aug . 1 0 , 1 9 7 5 )

2 2 . Thi s view i s i dent i cal to the l ast one , but taken during a relatively minor storm surge whi ch occurred in August 1 97 5 .

S l ide 6

(Map o f Southern Canadian Beaufort Sea Coas t )

2 3 . Of even greater ext ent than the spits , bars and beaches are the low lying delta areas of the Beaufort Sea coast , al l maj or w i l dfowl nesting and staging areas , which coul d be inundated by a storm surge and by o i l or other p o l l utants contained in the wat e r .

2 4 . Dri ftwood l ines on the Macken z i e delta indic at e that the outer del t a could be inundat ed b y an extreme surge a s far s outh a s the l ower b l ack l ine ( 3 ) on thi s s l ide , a l ine whi ch represent s the location downstream from whi ch channel banks , the highest parts o f the delta p l ai n , are l ower than 3 m .

2 5 . Thi s i s an area o f almost 3900 s q . km . , which , i f it were square, would have s ides over 6 0 km . l ong . About 2 0% o f the area i s covered by sha l l ow l akes in which pol lutants could be dropped and , of thi s area , almost 30% o r 2 2 3 s q . km . i s connected b y channel s whi ch eventua l ly reach the sea . Pol lutant s could be carri ed into this type o f lake even by surges which were not h igh enough to flood the delta surface .

2 6 . Exact ly how far up de lta s ea water might penetrate during a surge is dependent upon the influence of river flow as we l l as upon surge flooding . To my knowl edge no res earch has been undertaken into water circulation patterns over flooded areas of the delta but Dr . Henry ' s storm surge stud i es suggest the pos s ib i l ity that s ea water and as sociat ed p o l l utants mi ght be drawn in on the Sha l l ow Bay side and river water divert ed out East Channel (Technical Report No . 19 for the Beaufort Sea Proj ect ) .

Coastal Landforms and Coastal Mat erials

2 7 . Let us move now to a dis cus s ion of the maj or l andform �ypes found along the Beaufort Sea coast and o f the importance of their nature to development .

2 8 . Within each of the coastal segment s I have defined , one or more of the fo l l owing types of l andform dominat e the coas t l ine :

a . Steep c l i ffs , o ften containing s i gnificant amounts o f ground i ce , and fronted by narrow beaches ;

b . Thermokarst lakes breached by coastal eros ion ; c . Spit s and barriers up to 12 km . in l ength and s everal hundred

metres wide ; and lastly d . River deltas , part i cularly that of the Mackenzie , one of the

largest deltas in the wor l d .

A . Coastal c l i ffs

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2 9 . Of thes e landforms types , coas tal c l i ffs occupy the l argest portion of shorel ine in a l l coastal segments except for the modern Mackenzie delta and the eastern end of the Tuktoyaktuk Peninsul a .

3 0 . High and steep c l i ffs are more common along the Yukon coast than along the lower- lying Tuktoyaktuk Peninsula where a rel atively smal l offshore gradient decreas es the effectivenes s of wave eros ion .

3 1 . The c l i ff form i s l arge ly a funct ion o f the material s o f whi ch it is composed . Gravel and sand dominate along the Yukon shorel ine but layers of s i l t and c l ay are common . Gravel i s al so common along the Tuktoyaktuk Peninsula west of Tuktoyaktuk , but sands and s i lt s prevai l to the eas t .

Sl ide 7

(Sand bluffs at the mouth of East Channe l )

32 . Where the mat erial is coars e , c l i ffs t end to be steep but not vertical , l ike this s and b luff near Kittigazuit at the mouth of East Channel ,

S l i de 8

(Cliff at Tuktoyaktuk)

or the s andy gravel c l i ff at Tuktoyaktuk itsel f .

S l i de 9

(Cli ff at Running River mouth)

They may even be vegetated l ike thi s one near Shingl e Point on the Yukon coast .

Sl ide 1 0

(Verti cal b luffs at Kay Po int )

3 3 . Where the mat erial is fine- grained , on the other hand , the c l i ffs wil l be verti cal l ike this one near Kay Po int ,

Sl ide 1 1

(Mult i - cycl i c ground ice s lump area near Tuktoyaktuk)

and i f the fine- grained mat erial contains l arge thicknesses of mas s ive ground ice , ground ice slumps l ike this one j ust west of Tuktoyaktuk ,

Slide 1 2

(Exposed mass ive ice in ground ice slump o f Kay Point )

or thi s one at Kay Point , wi l l develop . The banded material in the centre of this s l ide i s almost pure ice .

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34 . These c l i ffed areas may s eem des irab l e as locations for harbours , staging areas , etc . b ecaus e their tops are we l l above storm surge l eve ls , water depths offshore from them are usual ly relat ively deep , and , i f the c l i ff material i s coarse , a suitab l e s ource of construct ion material i s c lose at hand .

35 . But the nature of the cl i ff material i s crit i cal . The most ideal l o cation for a deep water port al ong the s outhern Beaufort Sea coast might s eem to be in the area of Babbage Bight j ust east of Kay Point because water depths close to shore are deep � The c l i ffs in thi s area , however, are fine- grained and contain con s i derab l e mass ive i ce . Verti cal b luffs and ground ice s lumps predominate . Hardly an ideal locat ion for land fac i l ities associ ated with a harbour .

36 . The pres ence o f froz en ground and mass ive i ce i s also relevant to any p ipe l ines whi ch might come ashore in c l i ffed areas .

Sl ide 1 3

(Undercut b luffs at Kay Po int )

In areas l ike thi s one near Kay Point mas s ive i ce bodies extend below s ea l evel and out under the s hal low water near shore . Wave eros ion during the August 1 9 7 5 s torm I TIlentioned previous ly cut a ni che at the base of the c l i ff and expos ed the ice behind . TI1is , incidentally , i s exact ly the situation whi ch exists along the c l i ffs whi ch front Tuktoyaktuk and i s the maj or reason why it wi l l be so di fficul t to stab i l i z e the c l i ffs ther e . A hot o i l pipe l ine would be subj ect to fai lure under these conditions .

B . Thermokarst Lakes

37 . In addition to the coastal c l i ff areas , there is a s econd type of coast - l ine in the southern Beaufort Sea whi ch is basi cal ly eros ional in nature .

S l ide 1 4

(Ph i l l ips I s l and Photomosaic)

Thi s photomosaic is typ ical of l arge parts of the coast along the Tuktoyaktuk P eninsul a , part i cularly east of Mc Kinley Bay .

38 . At first g l ance the coas t l ine appears drowned , but in fact , its out l ine reflects the breaching by coastal ero s i on of the l akes which cover much of the Peninsul a . These l akes are commonly thermokarst i n ori g in , result ing from ponding and resultant di fferential melting of excess ice in the sands and s i l t s which form their boundaries .

39 . Breaching l eads to at l east parti al draining o f the l akes and , if thi s drop i n water l evel i s suffic i ent to enab l e the l ake to freez e to the bottom in wint er , to the formation of pingos . The "two -pingo lake" on this s l i de i s about 1 m . deep .

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4 0 . As erosion cont inues , the former l ake area is deep ened , p artly b ecause of wave act ion and part ly because of continued me lting of excess ice in the s ediment s . The area b etween the barrier bar and the "two p ingo lake" on this s l ide is flat-bottomed and about 2 m . deep but low frequency e cho s ounding shows an irregular sub­bottom, generally l ess than 3 m. beneath the present bottom . This sub -bottom may represent the boundary between recent wave-deposited s ediments and the o lder and perhap s sti l l frozen coastal p l ain deposit s beneath .

4 1. In any case , a newly breached l ake provides an exce l l ent trap for an o i l spi l l . Oil could b e carried into a l ake during normal flood tides or storm surges .

Sl ide 1 5

(Two- P ingo Lake)

Granted the o i l might be pul l ed out again by ebb currents . Unfortunat e l y , the eastern end of the Tuktoyaktuk Peninsula , where breached l akes are most numerous , is also the only coastal segment , except for r iver del tas , which contains extensive t idal flat s . This s li de s hows exposed t idal flat s in and near the "two-pingo l ake" of the l ast photograph .

C . Spi t s and barriers

4 2 . Let us turn now to the depo s i ti onal features found along the Beaufort Sea coas t .

S lide 1 6

(Warren Point barrier)

Spit s , l ike the ones I have al ready shown you at Topkak and Kay Points , and barriers , like this one at Warren Po int on the Tuktoyaktuk Peninsul a , front s igni ficant portions of most o f the coastal segments I have ident i fied .

4 3 . They are particul arly extens ive near Herschel I s l and on the Yukon coast , around the old is lands (Pe l l y , Hooper , etc . ) whi ch front the eastern Macken z i e delta, and from Warren Po int east on the Tuktoyaktuk Peninsula . In these areas they reach l engths of more than 1 2 km . and widths in excess o f 2 0 0 m .

4 4 . As I have already menti oned , they l i e , i n their ent irety , below the highest storm t i de l ine and thus are susceptib l e , at any t ime , to inundation by o i l . As wel l , the shal low l agoons b ehind them could funct ion in much the s ame way as thermokarst l akes and act as trap s for o i l .

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4 5 . The s i z e of spits and barriers is a function o f both offshore gradient and s ediment supp ly . They are largest where offshore wat er depths are smal l as they are o ff the Macken z i e de lta and the Tuktoyaktuk P eninsul a , or where the supply of s ediment i s l arge a s it i s in the Herschel I s l and area where material from the F irth and Mal colm rivers i s added to that supp l ied by c l i ff ero s ion .

46 . Their height and cro s s - s ect i onal form , on the other hand , are at l east part i al ly dependent on s ediment s i z e .

Sl i de 1 7

(Nunaluk spi t , proximal end)

The sandy- gravel spits and barriers of the Yukon coast and west of Tuktoyaktuk on the Tuktoyaktuk Pe�insula tend to be higher and narrower than pure s and features east of Tuktoyaktuk . Thi s port ion o f Nunaluk spit near Hersche l I s l and rises over 2 m . above sea l eve l ,

Sl ide 1 8

(Atkinson Spit , proximal end)

whereas this sand spit at Atkinson Point reaches a maximum el evation of less than 1 m .

4 7 . The gravel in coastal beaches , spits and bars and their easy acce s s ib i l ity from the sea makes them attractive sources for borrow mat eri al s . They are not thi ck , however . Both dri l l ing and low- frequency sub-bottom echo s ounding suggest that s i gnifi cant gravel depos it s s e l dom extend more than 4 . 5- 6 . 0 m. below the surface , either on l and or near shore .

D . River deltas

48 . Deltas represent the cont inuing abi l ity of a river to supp ly and deposit sediment more rapidly that it can be removed by sea waves and currents . In the case o f the Mackenz i e de lta, the ab i l ity of the Mackenz ie River to dominat e the Beaufort Sea has l ed to the development of a gent l y s l oping delta p l ain of almost 1 3 , 000 sq . km . in surface area .

49 . Of this surface area, as I have already ment ioned, about 3900 s q . km . may be subj ect to inundati on by storm surges and thus i s properly part of the coastal zone . But even this outer de l t a i s river dominated . The clays , s i lt s and fine s ands o f which it i s composed are almost enti rely riverine in origin . The manner in whi ch these s ediments are deposited , however , i s great ly influenced by coastal processes .

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S l i de 1 9

(Outer Mackenz ie delta)

5 0 . The mos t important features of the outer de lta p lain are the s hal low , wide distributary channe l s ; the low , flat vegetated plains whi ch separate the channe l s ; and the lakes whi ch dot the plains . Thi s s l ide , looking s outh from the shore l ine , inc l udes examp l e s o f each . Except for the l ake s , the pattern you s ee i s common on most fine­grained de ltas in the world .

5 1 . The myriad of lakes on the Macken z ie delta pl ain are testimony to the effects of an arcti c environment : speci fi ca l ly to the re lat ively low p l ant product ivity of arct i c areas and to the pres ence of froz en ground .

S l ide 2 0

(Organic sc arp , Macken z i e delta front )

52 . Out er delta sediments are organic r i ch . Thi s scarp at the front o f the delta i s largely organic in nature . But this ri chness i s only re lative . On deltas in more temperate c l imates , lakes are a very short - l ived feature of delta plains . They are very qui ckly infil led by p l ant debris . Thi s rap i d infi l l ing does not occur in the Arct i c .

5 3 . Fro z en ground also plays an important ro l e in lake formation and evolution . The mos t s igni fi cant aspect of this ro l e may be in the effect of freez ing on the material conso l idat ion or set t l ement of delta s ediments under their own weight .

54 . The argument I am about to make i s pure speculation . It i s not based on hard data but I w i l l present it becaus e of the imp l i cat ions it might have for development on the delta surface and for a pip e l ine across Shal low Bay .

55 . A delta is not only a product o f the balance between the river and the sea but also o f the balance between river depos it ion and sub s idence . On the Mi s s i s s ip i delta , buri ed deposits which were above sea l evel l es s than 5 00 years ago are now as much as 2 0 m . below sea l evel , sol ely because of s ed iment consol idat ion under its own weight .

56 . On the Macken z i e delta, however, the ground beg ins to freeze as areas are bui l t up to near s ea l evel . Natural cons o l i dation w i l l be stopped at the po int in t ime at which the s ediment freezes . I f permafrost aggradation i s rap i d , the fro z en s ediments at depth wi l l be under­conso lidated w ith respect to the weight of the material over them . Added to this is the cont inuing addit ion o f new weight in the form of deposit ion on t op o f the de lta p l ain .

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5 7 . I f this fro z en ground i s thawed for any reason , natural or otherwi s e , conso l idat ion can begin again . On the outer de lta p lain, numerous l akes appear to have formed in areas o f low-centred i ce-wedge po lygons , possibly becaus e of water ponding , subsequent p ermafrost degradation and con so l i dati on .

5 8 . The bottoms of most l akes on the outer de lta are above sea level at the present t ime . But in the Ak lavik area , a much ol der and higher p art of the del t a , l akes whose bottoms are be low present s ea l evel h ave been reported . That this could occur in spite of infi l l ing during river floods and deposition of organic debris may indicate continuing conso l idat ion of the unfroz en s ediments beneath the l akes .

59 . Even in the abs ence o f excess ice , then - and there i s a l it t l e in the s ediments of the outer delta p l ain - thaw cons o l i dat ion remains an important prob l em . I am curious , as wel l , a s to what effect natural conso li dati on might have on a pipel ine across Shal low Bay -an area whi ch , because o f the presence o f frozen ground at depth b eneath it , may be a sub s i ding o l der part of the Mackenzie delta p lain . If the rates are in the rang e of those found in the Mi s s i ssip i , and I wou l d guess they wi l l be much l ower , conso l i dat ion o f anywhere from 0 . 5 to 1 . 2 m . coul d occur over a 30-year period .

60 . E l s ewhere along the Beaufort Sea coas t , deltas occupy only a sma l l proportion o f the coas tal zone . There are none at a l l on the Tuktoyaktuk Peninsu l a , al though the Peninsul a , i t s e l f , is composed l argely o f material depos ited in an old Macken z i e del t a .

Sl i de 2 1

( Blow River delta P l ain)

6 1 . Along the Yukon coast the deltas of the Blow and Babbage rivers are s imi l ar in form and sediment composition to the Macken z ie but are much smal l er : the Blow delta p l ain covers only 5 0 sq . km . and the Babbage 2 5 sq . km . Thi s s l ide looks north over the Blow de lta p l ain toward the Beaufort Sea .

Sl ide 2 2

( Babbage de lta during flood)

6 2 . Unl ike the Mackenz i e , however , both delta pl ains can be covered in their entirety by s torm surges . Thi s view of the Babbage delta during spring r iver flooding coul d be repeat ed at any t ime during the summer by a maj or storm surge .

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S l i de 2 3

(Firth River fan delta)

6 3 . The relatively steep , gravel ly fan deltas o f the F i rth and Malcolm rivers , on the other hand , do not flood s i gnficant ly during storm surges and thus are not as vulnerab l e to the effects o f an o i l spi l l . They al s o do not contain the low , fine-grained , fro z en al luvial flats I ment ioned ear l i er and would not be subj ect to s igni fi cant thaw conso l idat ion . Thi s view of the F irth de lta shows the aufei s deposits a l ready much discus sed i n thes e hearings . Possibl e borrow pit operations on these deltas have also been covered in ear l i er t est imony .

Coastal Change

64 . I have l e ft unti l the end any detai l ed discus s ion o f the nature and rates o f change o f the l andforms o f the B eaufort Sea coast b ecaus e I consider coast al stabi l ity to be the s ingle most import ant factor in relation to poss ib l e development acti vi t i es .

65 . Under the influence o f wave action , parti cularly during storm surges , the coastal c l i ffs within each coastal segment I have ident i fied are b eing cut back and the material moved along shore and depo s i ted , either in the form of spits and bars in the case of coarse sediment or o ffshore in the case of finer s ediment . The coas t l ine i s thus a very dynamic environment and , i f the desi gn o f onshore instal lat i ons or p ip e l ines from o ffshore does not t ake this into account , they wi l l eventual ly fai l .

6 6 . C l i ff retreat i s mos t rapid where o ffshore gradi ents are steep and where c l i ff s ediment s contain consi derab l e por e , wedge or mas sive i c e .

S l i de 2 4

( Kay Point , undercut c l i ff)

Photograrnrnetric measurements show that thi s undercut bluff at Kay Point retreated a lmost 9 0 m . between 1 9 5 2 and 1 97 0 . Retreat of 10-50 m . over t h e s ame period occurred along most of Babbage Bight , east of Kay Point . Other zones o f rap i d cl i ff retreat include the Herschel I s l and are a, the o l d i s l ands (Pe l ly , Hooper , et c . ) which front the Mackenz ie delt a , and the Tuktoyaktuk settl ement area .

6 7 . The way in whi ch retreat o ccurs i s unique to an Arc t i c environment and i s largely a funct ion o f features related to fro z en ground . The headwal l s of the ground ice slumps I showed you ear l ier are very rapidlY receding : we have measured over 1 0 m . o f retreat in a s ingl e year on one .

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Sl ide 2 5

( B l o ck s lumping near Kay Point)

68 . E l s ewhere , undercutt ing by waves and melting along ice wedge cracks can caus e entire polygon b locks to col l apse into the sea . Thi s view was taken near Kay Point this past summer ,

S l ide 2 6

(Slumped pOlygon block , ice-wedge fracture)

and this i s a c l o se-up of the fracture zone at the back of the s lumped b l o cks show ing the exposed wedge i ce .

69 . The imp l i c ations for development o f thes e rates o f retreat and o f the way in whi ch it occurs must be obvious . I shou l d add only that the rates of retreat are not constant either s easona l ly or annual ly . Most retreat occurs during storm surges ; 13 m . of l and was l ost near the RCMP s tati on of Tuktoyaktuk during the maj or 1 9 7 0 storm , almost one­quarter of the t otal retreat between 1 9 50 and 1 97 2 .

70 . I t wi l l be t empt ing to obt ain s and and gravel for construction purposes from the coas tal b eaches , bars and spits where continued coars e s ediment movement from cl i ff retreat promi s es rapidly rep l enished supplie s of high qual ity aggregat e . Spits have extended as much as 7 0 0 m . in l ength b etween 1 9 5 2 and 1 9 7 0 (Nunaluk spit ) .

7 1 . In addition to the biolog i c consequences that may make extraction o f thi s grave l unsuitab l e , there are a number o f things whi ch should be known before permits to mine gravel are granted .

7 2 . Material supp l i ed to the beaches , bars and sp its i s in cont inuous movement al ong the shore . Extracting gravel w i l l tend to accel erate nearby shore eros ion , part i cul arly in the downdri ft direct ion , and the effects of thi s must be determined . For examp l e , if s and were taken from the beaches north of Tuktoyaktuk the supp ly to the beach whi ch fronts the townsite would be interrupted and the coastal c l i ff there would retreat even more rapidly than it already i s . A permanentl y dredged deep channel into Tuktoyaktuk Harbour would have the same effect unl ess the dredged mat erial was pumped out downdri ft from the channel .

7 3 . The sources o f mat erial in the beaches i s primari ly local in nature . Litt l e coarse se diment wi l l move b etween the coastal s egment s I have ident i fied . In some s egment s , the spits and bars may be rel i c in nature and mat erial , once removed , wi l l not be rep l aced . For example , Avadl ek spit on Hers chel I s l and was formed from s ands and gravel s suppl ied by deposits on the north and west s i des o f the i s l and , depos i t s whi ch n o longer exist becaus e o f c l iff retreat .

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74 . The dynamic nature o f be aches , spits and bars i s a l s o rel evant to the effect o i l from a spi l l mi ght have on them. During the sma l l August 1 9 7 5 storm surg e , the b each surface along the spi t a t Kay Point was cut down by as much as a 0 . 3 m. and later reburi ed by a lmos t the s ame amount of sand and gravel . Thus o i l on the s e features could be buried at any t ime .

75 . In di rect contrast to the coastal c l i ffs and to the beaches , spits and bars , the delta p l ains of the Beaufort Sea coas t , including that of the Mackenzi e , are remarkab ly stab l e in nature .

7 6 . Examination o f aerial photograph sites spaced over a 2 2 year p eriod reveal ed l i t t l e shore l ine advance along the front of the Mackenzie del ta and no evidence of maj or channel shi fts on the out er delta p lain .

S l i de 2 7

(Macken z i e delta shore l ine)

In fac t , as thi s s l ide of the delta shorel ine s hows , many areas have undergone minor retreat .

7 7 . The rat e o f advance o f a delta p l ain i s dependent t o a great extent on the balance between river and wave forces . Wave power at the shorel ine , in turn, i s dependent upon deep water wave condit ions and the offshore gradient . Becaus e the Beaufort Sea i s froz en for much o f the year and becaus e the o ffshore gradient o f the Mackenzie de lta i s one of the flattest o f any maj or river delta in the wor l d , we might expect that the total annua l wave power exerted in the deltai c coastal zone would be very l ow in comparison with other maj or river del tas .

78 . Under thes e conditions the Macken z i e delta should b e advancing rapidly -but it i s not . The only exp l anat ion must be that river power i s also low and , now that the r iver has fi l l ed the protect ed trough between the Caribou Hi l ls and the Richardson Mountains , it i s not powerful enought to overcome the eros ive wave energy of the open Beaufort Sea .

79 . The lack of maj or channel shift ing on the outer delta p l ain may al s o be relat e d to low river power . Thi s effect i s accentuated b y the number of channe l s whi ch discharge into the Beaufort Sea - almost 6 0 with a total width o f over 3 0 km . Thi s divis ion o f a given amount o f river power leaves n o s ing l e channel with enough to actively erode its banks , part i cularly s ince they are froz en and therefore resi st ant t o ero s i on .

8 0 . Thi s horiz ontal stabi l ity i s , in i t s e l f , a s imp l i fying factor for poss ib l e faci l ities ass ociated with hydro carbon development . From this point of view , only , construct ion whi ch would b e unfeas ib l e on most other deltas in the world may be pos s ib l e on the Mackenz i e . There are , o f course , other p oints o f view , some of which I have di s cus s ed , whi ch make the de lta les s attractive than hor i z ontal stab i l ity considerations alone might suggest .

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8 1 . The l ast aspect o f coastal change I wish to d i s cuss i s the direct effect of s ea ice on the coastal zone and on the resultant need for careful s e lection of lo cat i ons for the construction of nearshore fac i l ities such as wharves and j etties . I think this can best b e done with a s l ide and a question .

Sl ide 28

(Shore l ine pressure ridge , Shing l e Point spit)

Would you want to be a wharf or a j etty in the path o f thi s 1 0 m . h igh shorel ine pressure ridg e ?

Conclus ions

8 2 . To brie fly summari z e and conclud e , then :

a . The coastal z one i s , in most areas , a dynamic area , part i cularly so in thi s p art of the arct i c , and its instab i l ity must be t aken into account i f it is to be us ed for pipel ines , staging areas or other shore instal l at ions .

b . Shore instal l ations must be careful ly located s o as to avoid areas where l arg e amount s of ground i c e are present . Disturbance of the existing thermal reg ime w i l l s erve only to acce l erate already rapi d rat es o f coas tal retreat .

c . Beach mat erial i s primari ly l ocal in origin and its removal w i l l l ead to increased coastal ero s ion . A s a general princip l e , therefore, I would recommend that beaches not be considered as sources of cons tructi on mat eri al .

d . There are very few good harbour locat i ons al ong the Beaufort Sea coast becaus e of general ly low offshore gradients , coastal instabi l ity and resultant longshore s ediment movement .

e . The haz ards of l iquid pol lut ant spi l l s from shore operat ions could be minimiz ed if these act ivi t i e s take p l ace in bays or l agoons behind spits or barri er bars .

f . Deltas are among the most complex active environments in the wor ld becaus e of the interact ion between river and sea forces . The effect s of an Arct i c environment must be added to normal deltaic processes on the Mackenz i e delta and these effects are not we l l underst ood . Because o f thi s great comp l exity and because the Macken z ie delta i s a unique North Ameri can environment , I would recommend that develop ­ment o n i t b e kept t o a minimum .

g . Oi l from a spi l l reaching the nearshore in a given coastal segment wi l l tend to remain in the s egment and to move toward its sediment s ink .

h . The l argest areas subj ect to frequent inundat ion by sea water and thus , potent i a l l y , by o i l contained in that water are the river deltas , part icu l arly the Mackenzie . Thermal disturbance through vegetation damage could l ead to cons iderab l e thaw cons ol idation, even in the abs ence of exces s i ce . Other susceptibl e coastal features are beaches , spits and barriers and breached thermokarst l akes .

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DOCUMENTS AND REPORTS USED

Canada , Department of Pub l i c Works 1 9 7 1 : Beaufort Sea storm , S ept ember 1 3- 1 6 , 1 9 70 .

of effects in the Mackenz i e Delta region . internal report , 2 3 p .

Canada , Department o f Pub l i c Works

Investigat i on Unpub l i shed

1 9 7 1 : Herschel I s l and - feasib i l ity of a marine terminal . Unpub l i sh ed internal report , 1 4 1 p .

Carson , 1 97 5 :

J . M . , Hunter , J . A . and Lewis , C . P . Marine s e i smic refraction profi l ing Kay Point , Yukon Territory ; G eo l . Surv . Can . , P aper 7 5 - 1 , Pt . B , 9- 1 2 .

Henry , R . F . 1 9 7 6 : Storm Surges . Beaufort Sea Proj ect ·technical report No . 1 9 .

Department o f the Environment , Victoria, B . C .

Lewis , C . P . and F orbes , D . L . 1 9 74 : Sediments and s ed imentary proc e ss e s , Yukon Beaufort Sea coast .

Environmental - Social Committee , Northern P ip e l ines , Task Force on North ern O i l Development , Government of Canada , Report no . 74 - 29 , 40 p .

Mackay, J . R . 1 9 6 3 : The Mackenz i e Delta area , Northwest Territories ; Dept . Mines

Tech . Surv . , Geographical Branch Mem . 8, 2 0 2 p .

McDonald, 1 9 7 3 :

B . C . and Lewis , C . P . Geomorphic and sed imentologic processes of r ivers and coast , Yukon coastal plain . Environmental - Social Committ e e , Northern P ip e l ine s , Task Force on Northern O i l Development , Government of Canada , Report no . 7 3 - 39 , 2 4 5 p .

Morgan , J . P . 1 9 6 7 : Ephemeral es tuaries of the deltaic environment ; in Lauff , G . H .

(Editor) , Estuaries . American Associ at ion for the Advancement of Scienc e , Pub . no . 83 , Washington , 1 1 5 - 1 2 0 .

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B E A U F O R T S EA

t�"''''� h.,'g)\t ltrh"ljf0'!.j

'-10'''''" I�oboth �m'7lr�t:

S l ides 1 , 3 and 6 . GSC 2 0 2 7 7 3 - R

S l ide 2 . GSC 2 0 2 9 2 5 - X

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S l ide 4 . GSC 2 0 2 9 5 8 - S

S l i de 5 . GSC 2 02958-0

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Sl ide 7 . GSC 2 0 2 7 7 3-0

Sl ide 8 . GSC 2 0 2 9 2 S - T

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S l ide 9 . GSC 2 0 2 7 73-M

S l ide 1 0 . GSC 2 0 2 960-M

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S l i de 1 1 . GSC 2 0 2 773-N

S l i de 1 2 . GSC 2 0 2 959-Y

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S l ide 1 3 . GSC 2 0 2 9 59-N

S l ide 1 4 . GSC 2 0 2 7 7 3-S

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S l ide 1 5 . GSC 2 0 2 9 2 5-W

S l ide 1 6 . GSC 2 0 2 7 7 3-P

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S l ide 1 7 . GSC 2 0 2 7 l 7-E

S l ide 1 8 . GSC 2 0 2 9 2 S - Y

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S l ide 19 . GSC 2 0 2 9 2 S - U

S l ide 2 0 . GSC 2 0 2 9 2 S -V

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S lide 2 1 . GSC 2 0 2 7 1 7-P

S l ide 2 2 . GSC 2 0 2 7 1 7- J

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S l ide 2 3 . GSC 2 02 7 1 7-Y

S l ide 24 . GSC 2 0 2 7 l 7-A

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S l ide 2 5 . GSC 2 0 2 9 5 8-U

S l ide 26 . GSC 20 2959- K

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S l ide 2 7 . GSC 2 0 2 9 2 5 - Z

Sl ide 2 8 . GSC 2 0 2 9 2 5 - S