Gabion Evaluation for Salmonid · Gabion Evaluation for Salmonid Enhancement in a Landslide Impacted Stream on the Queen Charlotte Islands, British Columbia by H.D. Klassen Fish Forestry

Gabion Evaluation for Salmonid Enhancement in a Landslide Impacted

Stream on the Queen Charlotte Islands, British Columbia

by H.D. Klassen

Fish Forestry Interaction Program 2153 West 46th Avenue Vancouver, B.C. V6M 2L2

March 1984

Ministry of Forests

Canadian Cataloguing in Publication Data Klassen. Herbert D.

Charlotte Islands, British Columbia in a landslide impacted stream on the Queen

Gabion evaluation for salmonid enhancement

(Land management report, ISSN 0702-9861 ; no. 30)

Bibliography: p. ISBN 0-771 8-8404-2

Columbia - Queen Charlotte Islands. 2. Fish habitat improvement - British Columbia - Queen Charlotte Islands. 3. Logging - Environmental aspects - British Columbia - Queen Charlotte Islands. I. British Columbia. Ministry of Forests.

1. Artificial substrates (Aquatic biology) - British

11. Title. 111. Series.

0 1984 Province of British Columbia

Published by the Information Services Branch Ministry of Forests Parliament Buildings Victoria, B.C. V8W 3E7

Copies of thls and other Ministry of Forests titles are available at a cost-recovery price from the Queen's Printer Publications, Parliament Buildings, Victoria, B.C. V8V 4R6.

I

ABSTRACT

Tandem V-shaped gabion weirs for improving spawning habitar; f o r p i n k

(Oncorhynchus gorbuscha) and chum salmon (0. " keta) i n landslide-damaged streams were ins ta l led and examined i n Sachs Creek, Queen Cnarlotte Islands. Spawner use and egg su rv iva l , a s we l l a s s t ab i l i t y and quality of gravels entrapped by the s t ructures were compared to tha t o f na tura l cont ro l s i tes . Two gabion sites a t 1% slope gradient at tracted moderate spawner usage w i t h i n

weeks of i n s t a l l a t ion ; a t h i r d gabion s i t e a t a 3% slope gradient was beyond the upstream limit of p i n k and chum salmon b u t was used by coho (0. kisutcn) spawners. P i n k salmon egg survival appeared h i g h i n the first autumn and winter seasons after installation (approximately 11% t o the fleyedff stage), and improvement is ant ic ipated as tne gabion s i t e s undergo natural s taPi l izat ion of streambed configurations. Gravel staPility a t a l l t h r e e gaDion s i tes was poor over the first winter, and excessive scour threatened the integrity of the upstream, steeper slope gabion s i t e w i t h i n 1 year. However, the two gabion sites a t 1% slope gradient successfully stabil ized gravel over their second season of stormflows through local reductions i n streambed slope gradients. The effects of gabions on gravel composition and intragravel permeability were variable. Demonstrated improvements i n intragravel dissolved oxygen probably resulted from channel Itroughnesslf added by the gabions. Intrayravel dissolved oxygen had a s ignif icant ( p < .05) posit ive correlation w i t h egg survival. High juvenile coho and steelhead (Salmo gairdneri) densi t ies a t t h e gabion s i tes (average 1.6/m compared t o 0.9/m a t con t ro l si tes) indicated h i g h qual i ty rear ing habi ta t as an additional benefit . Achievement of cost effectiveness (recovery of construction costs througn increases i n returning adult p i n k salmon) was at ta inable i n gabion s i t e s well-used by spawners. The s t a b i l i t y i n s t reamed configurations provided by gabions i n t h e i r second year would b e useful i n rehabilitating low-gradient reaches of streams damaged by landslides. Recommendations for gabion ins ta l la t ion inc lude the i r r e s t r i c t ion t o downstream reaches of less than 2% slope gradient, where moderate t o heavy spawner usage would occur.

2

2

iii

PREFACE

T h i s paper may be of in te res t to fores te rs , f i s h b i o l o g i s t s , and f i sher ies managers a l ike. The major purpose o f the paper was t o evaluate one method o f

rehabilitating a debris-torrented stream, w i t h respect to f i s h production. Guidelines for gabion in s t a l l a t ion were included, as was a Denefit-cost analysis. T h i s s t u d y was designed t o f u l f i l l , i n part, the requirements f o r the degree o f Master of Science i n the Department o f Forestry a t t h e University o f British Columbia.

i v

ACKNOWLEDGEMENTS

Many i n d i v i d u a l s and agencies have c o n t r i b u t e d t o t h i s p r o j e c t . The

major i t y o f the fund ing dur ing the cons t ruc t ion phase was provided by the

multi-agency sponsored Fish/Forestry Interaction Program (FFIP) . The agencies

inc luded B.C. M i n i s t r y of Forests, B.C. M i n i s t r y of Environment, and Canada

Department of F i she r ies and Oceans. Funding i n the second year was through a

Program of Research by U n i v e r s i t i e s i n Fores t ry (PRUF) grant, sponsored by the

Canadian Fo res t r y Se rv i ce . O the r s ign i f i can t con t r i bu t i ons a re g ra te fu l l y

acknowledged: D. Kendall, D. Kendal l and Sons, Queen Char lo t te C i ty ;

P. Slaney, B.C. F i s h and W i l d l i f e Branch, Vancouver; J. Conners, MacMillan

Bloedel , Jaskat la Div is ion; G. Brennenstuhl and R. Frank, Crown Forests,

Sandspit; F. Beban, Westrock Contracting, Sandspit; and G. Derksen, EPS,

Vancouver. Manpower assistance so c r i t i c a l t o t h i s p r o j e c t was provided by

the F i she r ies Employment Bridging Assistance Program. The i l l u s t r a t i o n s

enclosed were d ra f ted by FFIP o f f i ce s ta f f p rov ided by the Department of

F i she r ies and Oceans; L. White, D. Dimoff, A. Brattkus, D. Day, and S.

Parker. Technical assistance i n evaluat ing the gabions was provided by D.

Bou i l lon , J. E l l i s , and M. Morr is .

Helpfu l on-s i te suggest ions were received from D r . L. Beaven, L. Dutta,

B. Eccles, E. Harding, J. Lamb, K. Moore, and D. Tripp. Thanks t o FFIP's

Technical Advisory Committee (T. Baker, M. Brownlee, A. Cowan, T. Dyer,

J. Lamb, K. Moore, L. Powell, J. Schwab, 3. Walker, V. Wellburn, and D. Wilfora) f o r program direction and the editing of prev ious draf ts .

Apprec ia t i on f o r academic advice, the generous use of equipment, and e d i t i n g

p rev ious d ra f t s is extended t o my thesis committee: Dr . T.G. Northcote,

Supervisor; D r . M. F e l l e r ; D r . D. Golding; D r . G. Hartman; V. Poul in; and

P. Slaney. Special thanks to FFIP program manager V. Poul in , w i thout whom

t h i s p r o j e c t would not have been possible.

V

TABLE OF CONTENTS

ABSTHACT ................................................................ iii

PREFACE ................................................................. i v

ACKNOWLEDGEMENTS ........................................................ V

1 INTRODUCTION ........................................................ 1

2 THE STUDY AREA ...................................................... 3

3 METHODS ............................................................. 3.1 Gabion Descr ip t ion ............................................. 3.2 Study S i te Loca t ions ........................................... 3.3 Pre-Treatment S i te Ana lys i s .................................... 3.4 Gabion Construction and I n s t a l l a t i o n ...........................

3.4.1 Treatment S i t e I ........................................ 3.4.2 Treatment S i t e I1 ....................................... 3.4.3 Treatment S i t e I11 ...................................... 3.4.4 Si te revege ta t i on and bank s t a b i l i z a t i o n ................

3.5 Pos t - Ins ta l l a t i on S i te Ana lys i s ................................ 3.5.1 G r a v e l s t a b i l i t y ........................................ 3.5.2 Grave l qua l i t y .......................................... 3.5.3 Streambed con f igu ra t i on ................................. 3.5.4 Spawner use ............................................. 3.5.5 Egg s u r v i v a l ............................................ 3.5.6 Juveni le use ............................................

9

9

9

10 12 14 16

16 17

17 17

19 19

20

21 22

4 RESULTS ............................................................. 23

4.1 S i t e S t a b i l i t y ................................................. 23 4.1.1 Gravel scour ............................................ 23

4.1.2 Gabion s i t e c o n f i g u r a t i o n s .............................. 27

v i

4.2 Si te Revegetat ion and Bank S t a b i l i z a t i o n ....................... 33

4.3 Gravel Qual i ty ................................................. 33

4.3.1 In t ragrave l d isso lved oxygen ............................ 33

4.3.2 In t ragrave l permeab i l i t y ................................ 38 4.3.3 Gravel composition ...................................... 40

4.3.4 Sedimentation ........................................... 40

4.4 Spawner Use .................................................... 44

4.4.1 Observed spawning ....................................... 44

4.4.2 Probabi l i ty -of -use ...................................... 47

4.5 Egg Surv iva l ................................................... 47

4.6 Juveni le Use ................................................... 54

5 DISCUSSION .......................................................... 59

5.1 S i t e S t a b i l i t y ................................................. 59

5.2 Gravel Qual i ty ................................................. 62

5.2.1 Treatment S i t e I ........................................ 63

5.2.2 Treatment S i t e I1 ....................................... 64

5.2.3 Treatment S i t e I11 ...................................... 65

5.3 Spawner Use .................................................... 66

5.4 Egg Surv iva l ................................................... 68

5.5 Juveni le Use ................................................... 70

5.6 Summary o f P o s i t i v e and Negat ive Ef fects o f Gabions ............ 72

5.7 Prel iminary Benefi t /Cost Analysis .............................. 74

5.7.1 Benef i ts ................................................ 78

5.7.2 Costs ................................................... 79

6 CONCLUSIONS AND RECOMMENDATIONS ..................................... 82

7 LITERATURE CITED .................................................... 85

v i i

APPENDICES

3

1

4

5

6

7

P r o b a b i l i t y - o f - u s e c r i t e r i a o f Sachs Creek pink redds ............... 90

Calcu la t ions o f benef i t / cos t ana lys is fo r T rea tment S i te I11 a t

Sachs Creek ......................................................... 91

Photographic plates o f g a b i o n s i t e s a t Sachs Creek, 1.5 years

post - insta l la t ion, February 1984 ....................................

TABLES

Depth o f gravel scour on s t u d y s i t e s a t Sachs Creek over winter 1982-83 and 1983-84 ......................................................... 24

A t - t es t ana lys i s o f g rave l scou r on s tudy s i t es a t Sachs Creek ..... 25

Summary o f streambed gradient changes with g a b i o n i n s t a l l a t i o n on

Sachs Creek, i982-83 ................................................ 32

Streambank stocking success on s t u d y s i t e s a t Sachs Creek, October 1982

t o February 1984 .................................................... 34

Summary o f i n t r a g r a v e l d i s s o l v e d oxygen and permeab i l i t y on s tudy s i t es

a t Sachs Creek ...................................................... 35

A t - t es t ana lys i s o f i n t rag rave l d i sso l ved oxygen on s t u d y s i t e s a t

Sachs Creek ........................................................... 37

A t - t es t ana lys i s o f i n t rag rave l pe rmeab i l i t y on s t u d y s i t e s a t

Sachs Creek ......................................................... 39

viii

8

9

10

11

12

13

14

15

16

17

18

19

D i s t r i b u t i o n o f salmon spawning a c t i v i t y on s t u d y s i t e s a t Sachs Creek,

f a l l 1982 and 1983 ..................................................

Summary o f p robab i l i t y -o f -use by spawning p ink salmon on s tudy s i tes

a t Sachs Creek, 1-year post gabion instal lat ion . . . . . . . . . . . . . . . . . . . . . Summary o f egg s u r v i v a l on study s i t e s a t Sachs Creek, f a l l and

winter 1982-83 ......................................................

A t - t e s t a n a l y s i s o f egg s u r v i v a l i n Year 1 on Treatment S i t e I11

and i t s c o n t r o l s a t Sachs Creek .....................................

Redd superimposit ion on egg-sampling s t a t i o n s a t Sachs Creek, 1982 ..

V e r t i c a l d i s t r i b u t i o n o f p i n k salmon eggs a t Sachs Creek,

December 1982 ......................................................

Juvenile salmonid usage o f s tudy s i tes on Sachs Creek, pre- and

post-f lood, summer 1983 ............................................

Juvenile salmonid populat ion dynamics through the 2 August, 1983,

f l o o d a t Sachs Creek ...............................................

A t - t es t ana lys i s o f j u v e n i l e coho length frequencies on s tudy s i t es

a t Sachs Creek, summer 1983 ........................................

A summary o f t he e f fec ts o f gab ion i ns ta l l a t i on on major physical-

chemical condit ions and t h e i r r e l a t i o n t o salmonid production i n

Sachs Creek ........................................................

Gabion i n s t a l l a t i o n c o s t s a t Sachs Creek ...........................

46

48

49

52

53

54

55

56

57

73

75

Increases i n r e t u r n i n g p i n k s r e q u i r e d t o o f f s e t i n s t a l l a t i o n c o s t s f o r

Treatment S i t e I11 a t Sachs Creek .................................. 81

i x

FIGURES

9

10

11

13

Si te l oca t i ons on Sachs Creek ......................................

L o n g i t u d i n a l p r o f i l e o f Sachs Creek ................................

Estimated spawner escapements a t Sachs Creek .......................

Logg ing h is to ry o f Sachs Creek .....................................

Generalized view o f gabion conf igurat ion ...........................

Flow diagram o f g a b i o n i n s t a l l a t i o n ................................

Procedure f o r p lac ing scou r mon i to rs i n to t he smeambed ............

Isop le ths o f g rave l scou r dep th (cm) a s i n d i c a t e d b y v e r t i c a l e r o s i o n

m o n i t o r s a t g a b i o n s i t e s a t Sachs Creek i n Year 1 and Year 2 .......

Temporal changes i n bathymetr ic contours (cm) below an arb i t rary

benchmark a t Treatment S i t e I a t Sachs Creek .......................

Temporal changes i n bathymetr ic contours (cm) be low an a rb i t ra ry

benchmark a t Treatment S i t e I1 a t Sachs Creek ......................

Temporal changes i n bathymetr ic contours (em) below an a r b i t r a r y

benchmark a t Treatment S i t e I11 a t Sachs Creek .....................

Temporal changes i n average aggradation above gabions a t Treatment

S i t e I. Sachs Creek ................................................

Gravel composit ion c f s t u d y s i t e s a t Sachs Creek pre- and post-yabion

i n s t a l l a t i o n .......................................................

5

6

7

a

13

15

18

26

28

29

30

31

4 1

X

14 Mean percent o f p a r t i c l e s l e s s t h a n 1.2 mm and 0.30 mm on s tudy s i t es

a t Sachs Creek ..................................................... 42

15 Sedimentation accumulated i n sediment t raps on s t u d y s i t e s a t

Sachs Creek, December 1982 t o March 1983 ........................... 43

16 Long i tud ina l d i s t r i bu t i on o f adu l t salmon i n Sachs Creek,

September t o November 1982 ......................................... 45

17 Accumulated the rma l un i t s a t Sachs Creek over f a l l and

winter 1982-83 ..................................................... 50

18 Juveni le coho length frequencies on s t u d y s i t e s a t Sachs Creek,

pre-f lood, summer 1983 ............................................. 58

x i

1 INTRODUCTION

Coasta l fo res t harves t ing and salmonid f i s h e r i e s have c o n f l i c t i n g

resource uses that have been recent ly rece iv ing inc reased a t ten t ion f rom

resource managers and the pub l i c . Lack o f knowledge of harvest ing impacts on

the f i sher ies resource has s t imu la ted many inves t iga t ions , most notably the

i n tens i ve s tud ies on the Alsea watershed, Oregon (Moring 1975), and on the

Carnation Creek watershed, Vancouver I s l a n d (Hartman 1982). One proolem not

s a t i s f a c t o r i l y d e a l t with i n these studies i s t h e e f f e c t o f mass wasting on

t h e f i s h e r i e s resource. ’ Steepland logging has accelerated the rate of

lands l ides i n the coastal mainland (Mersereau and Dyrness 1972; O’Loughlin

1972; Swanston and Swanson 1976) and p a r t i c u l a r l y i n the Queen Char lo t te

I s l a n d s ( W i l f o r d and Schwab 19821.’ The negative impacts o f l ands l ides on

f ish-bearing streams have been quanti f ied i n Oregon (Everest and Meehan 1981)

and Washington (Cederholm and Salo 1979). The most d e s t r u c t i v e t y p e o f

lands l ide f rom a f i sher ies perspec t ive is the debr is to r ren t , wh ich

des tab i l i zes s t reams caus ing the o r ig ina l meandering channels t o g i v e way t o

more chute-l ike channels devoid o f the in tegra l logs wh ich p rov ide s t ream

d i v e r s i t y and s t a b i l i z e d p o c k e t s o f spawning gravels and rearing areas. The

i m p e t u s f o r t h i s s t u d y l i e s i n t h e need t o develop appl ied restorat ion

techniques for salmonid spawning streams damaged ~y landsl ides on the Queen

Char lo t te I s lands .

Many f a c t o r s c o n t r i b u t e t o l o w e a r l y s u r v i v a l o f p i n k (Oncorhynchus

gorbuscha) and chum (0. keta) salmon stocks. Egg-to-fry survival has of ten been as l o w as 5% f o r w i l d s a l m o n i d s ( D i l l 1969; McNeil 1969; Langer 19741,

owing t o drought, predators, over-populat ion of spawning areas, and

”

3 . Hal l . Quoted i n : G.F. Hartman ( e d i t o r ) . Carnation Creek Worksnop. Malaspina College, Nanaimo, B.C. A p r i l 1982. p. 401.

wasting on t h e Queen Char lo t te I s lands ; and K.M. Rood. [1984]. Logging landuse and mass wasting on t h e Queen Char lo t te I s lands . F ish /Fores t ry I n t e r a c t i o n Program, Vanccuver, B.C.

* I n preparat ion: P. Gimbarvesky. [1983 J. A reg iona l overv iew o f mass

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sedimentation (Wickett 1958; Shelton and Pol lack 1Y66; Bjornn 1968; Koski

1975; Slaney " e t a l . 1977; Cederholm and Salo 1979). Gravel scour has also

been shown t o a f f e c t s a l m o n i d egg surv iva l . Dur ing s tormf low events , ent i re

s tocks o f ch inook salmon (0. - tshawytscha) have ueen destroyed by scour

(Gangmark and Bakkala 1960). Simi lar ly, McNei l (1966) at t r ibuted a 90% loss o f p i n k and chum salmon eggs t o a s ingle stormflow event; he suggested that

m o r t a l i t y was caused by uoth mechanical abrasion and stream f lushing act ion,

which removed embryos f rom the p ro tec t ive g rave l .

Debr is to r ren ts and s t reambank logg ing p rac t ices in tens i fy g rave l scour

by reducing the frequency o f "organic steps" described by Heede ( lY72) ,

thereby increasing streambed gradients and stormflow veloci t ies. Reduct ions

i n stable large organic debris decreased both channel I l roughnessl l and

abundance o f g rave l assoc ia ted w i th t he deb r i s (Swanson " e t a l . 1976). Add i t i ona l s t reambed i ns tab i l i t y and degradation may have resul ted f rom

sediments released from damaged banks or depos i t i ona l zones o f l a n d s l i d e s .

Recent developments o f in-stream structures have successful ly produced

s t m i l i z e d spawning areas (Hall and Baker 1982). Gabion weirs (wire cages

tha t a re p laced in to the s t ream bo t tom and f i l l e d with smal l rocks) were one

o f seve ra l s t ream rehab i l i t a t i on t echn iques recommended f o r e v a l u a t i o n i n t h e

Queen Char lo t te I s l ands by t he F i sh /Fo res t r y I n te rac t i on Program (FFIP)

(Bustard 1983). Gabion weirs can stabi l ize gravel movement by impounding

gravels and reducing stormflow energy (Gerke 1974). Gabions have been found

t o reduce streambed gradient and t o impound g rave l beds w i t h a mean p a r t i c l e

s i z e t y p i c a l o f s a l m o n i d spawning areas (Moreau 1981). Furthermore, the depth

of gravel scour can be reduced by subsequent reduc t ions i n stormflow shear

s t r e s s a t t h e s u r f a c e o f t h e impGunded grave ls (L is le 1981) .

3

3 The FFIP i s a mult i -agency sponsored invest igat ion into the extent, causes, and a m e l i o r a t i o n o f l a n d s l i d e damage i n fo res ts and streams o f t h e Queen Char lo t te I s lands . The program was c o n t r a c t e d t o V.A. P o u l i n & Associates L td. o f Vancouver B.C. One aspect o f FFIP undertaken by the author was to evaluate gabions as a r e h a b i l i t a t i o n t e c h n i q u e f o r landslide-damaged streams.

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The specific objectives of t h i s s t u d y were t o 1) examine the effectiveness of gabions i n improving gravel quality (dissolved oxygen, permeability, gravel composition, and depth of scour), as well as the ear ly survival of p i n k and chum salmon under conditions typical o f the Queen Charlotte Islands; and 2 ) ident i fy spawning gravel character is t ics re la ted to early survival i n p i n k and chum salmon.

2 THE STUDY AREA

Sachs Creek on the northeast end of Moresoy Island was se lec ted as the s t u d y stream f o r t h i s project. I n nis review of stream rehabilitation techniques for FFIP, Bustard (1983) recommended Sachs Creek for gapion evaluation. I t was considered the most suitaDle stream f o r several reasons:

i .

ii.

iii.

i v .

V .

The stream l i e s i n close proximity to sources of manpower, equipment, and gravel supplies. The stream was the si te of previous salmoniul enhancement work by

MacMillan Bloedel. Hence, there was in t e re s t i n further restoration work there. The stream had a major debris torrent i n 1974, depositing tonnes of material just upstream o f salmon spawning habitat . Release of entrapped sediments a f t e r mechanical removal of the terminal log jam by the Federal Department o f Fisheries and Oceans i n 1978 has subsequent ly destabil ized t h e stream, a s evidenced b y ac t ive l a t e r a l channel migration for several hundred metres downstream. T n i s la teral erosion and excessive sediment transport i s s imi la r to many other landslide-damaged streams. Tne stream size i s acceptable for in-stream work and s tudies , having an average wetted wid th of 10 m and a summer discharge of about 0.07 m /sec (2-3 f t / sec) . 3 3

Tne stream supports significant runs of p i n k , cnum, and coho (0. - kisutch) salmon, and a small r u n of steelhead trout (Salmo qairdneri) .

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Sachs Creek d r a i n s i n t o S k i d e g a t e I n l e t on the nor thern end o f Moresby

I s l a n d and i s about 11 km l o n g w i t h i n a 19-km2 watershed ( f igure 1). I t s

bedrock type is mainly sedimentary. The streambed slope gradient averages

for the lowermost 1 km, 2% f o r t h e n e x t 1 km, 3% f o r t h e n e x t 0.5 km, then

r ises sharply upstream through a canyon (Figure 2 ) . The stream discharge

averages about 0.3 m /sec (12 f t / s e c ) d u r i n g t h e f a l l , with stormfiow

discharge up to about 65 m /sec (2300 f t /sec) based on unmetred

ca l cu la t i ons (Manning I s Equation) .

3 3

3 3

From l a t e August through November, Sachs Creek supports runs o f a d u l t

1%

chum, p ink , and coho salmon successively. Pinks and chum spawn i n the lower

1.5 km with maximum density from 0.6 km t o 0.8 km above the estuary

(Figure 1 6 ) . Coho d is t r ibu te themse lves more evenly through the lower 2.5 km

upstream t o t h e canyon ba r r i e r . P ink salmon e x h i b i t a two-year cycle, with

even years having dominant runs typical o f most Queen Char lo t te I s l ands

streams. "Even year" p ink salmon escapements have h i s to r i ca l l y ranged f rom

about 200 t o 30 000, with a mean o f about 4600 (Figure 3 ) . Recent escapements

have been about 3000 t o 4000. Adul t chum escapements h i s t o r i c a l l y have ranged

from about 25 t o 1500; however, they have seldom exceeded 200 i n t h e p a s t

decade. Estimated coho escapements have r a r e l y been i n excess o f 200 adu l t s .

Sachs Creek watershed l i e s m a i n l y within MacMil lan Bloedel 's TFL 39, with

about 5% i n Crown Fores t ' s TFL 2. About 40% o f tne watershed has been logged

s ince the ear ly 1960's (Figure 4) .

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Skidegate Inlet f Treatment Sites 0 Control Sites A

k- TERMINUS OF 19% DEBRIS TORRENT)

x \

Moresby Island : \

N c t

0 i 2km

FIGURE 1. Site locat ions on Sachs Creek.

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STREAM ELEVATION (m)

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Even Year

i ! IO OOO-

5000-

PINK

CHUM

Y E A R

FIGURE 3. Estimated spawner escapements a t Sachs Creek.a

a Federal Dept. Fisheries and Oceans records.

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Scale 1:5o,ooo - LEGEND

0 1 km

Rivers and Creeks ............. Symbols: Watershed Boundaries ........ - - 0 .... loggod aroas Logged Areas .................. H .... hlghload ,7"-""j

Unlogged Areas .................. pT.lw-h RE. . . rogeneratlon ostabllshod 8.:. :2::<;:.;.;.7 -.... *:LA P .... proposod logglng

""""

year loggod

type of logglng dopktlng loggod aroas, past and prosont

FIGURE 4. Logging history o f Sachs Creek.

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3 METHODS

Three s i t e s on Sachs Creek were selected f o r gabion in s t a l l a t ion . Gabions were ins ta l led i n p a i r s a t each of the three t reatment s i tes and were matched w i t h two control s i tes to enable s ta t is t ical evaluat ion o f tne resu l t s . The approach to evaluating gabions involved three main phases:

i. Pre-installation site analysis, including stream and s i t e s e l ec t ion , s i te surveying, intragravel dissolved oxygen, and permeability sampling.

ii. Gabion construction and instal la t ion, involving e ight men and heavy equipment.

iii. Post-installation site analysis, including monitoring of salmon spawner use, configurational changes i n gravel, measurements of subs t ra te s tab i l i ty , g rave l qua l i ty , and salmon egg survival.

The project was in i t i a t ed i n May 1982 w i t h reconnaissance surveys of po ten t i a l s i t e s on various Queen Charlotte Islands streams. Final site selection, pre-installation sampling, and surveying were completed i n J u l y 1982. The construction-installation phase was conducted d u r i n g the month of August 1982. Parameters noted above were remeasured a t 0.5-year, 1-year, and 1.5-year in te rva ls a f te r ins ta l la t ion .

3.1 Gabion Descr ipt ion

Gabions (0.91 m h i g h by 0.91 m wide) consisted of galvanized steel twisted mesh ( 3 mm diameter, 8 x 10 cm aperture) manufactured by

Maccaferri Gabions. Combinations o f gabions 1.82 m, 2.73 m , and 3.64 m l o n g were wired together t o span the stream (see 3.4.1 and 3 . 4 . 2 ) .

3.2 Study S i t e Locations S tudy s i t e s were selected largely based on t he c r i t e r i a developed i n

Northern California (Moreau 1981). I n b r ie f , these c r i te r ia inc luded: 1) adequate road access, 2 ) a straight section of stream channel, and 3 ) a wide floodplain w i t h shallow banks. Three t reatment s i tes were selected, each representing different habitat configurations. Treatment S i t e I was

- 10 -

loca ted 2300 m

deb r i s t o r ren t

Treatment S i t e

Treatment S i t e

upstream of t he es tua ry a t t he po in t o f eg ress o f t he 1974

(F igures 1 and 2 ) i n a r i f f l e a t t h e t a i l o f a pool.

I1 was s i t u a t e d i n a 60 m r i f f l e 950 m from the estuary.

111 was i n a deeper, slow moving (g l i de ) sec t i on o f the

stream 880 m above the estuary. All s i t e s met the recommended c r i t e r i a

and were considered marginal spawning habitat; i .e., the si tes lacked

s u i t a b l e spawning substrate, having mean par t ic le d iameters cons iderably

l a r g e r or smal ler than the 25 mm found i n the top layers o f Carnat ion

Creek chum salmon spawning areas (Scrivener and Brownlee 1982).

Two c o n t r o l s i t e s were se lec ted f o r each t r e a t m e n t s i t e i n o r d e r t o

a p p l y p a i r e d t - t e s t s f o r s t a t i s t i c a l a n a l y s i s . One c o n t r o l (llAll - poor

spawning hab i ta t ) was se lec ted to resemble the par t i cu la r t rea tment s i te

before the gabions were i n s t a l l e d . The second c o n t r o l (I1Bl1 - prime

spawning h a b i t a t ) was se lected - a p r i o r i t o resemble the treatment s i t e

a f te r the gab ions were ins ta l led . Th is was accomplished by select ing 20-m

l o n g r i f f l e s a t t h e t a i l s o f p o o l s h a v i n g e i t h e r 1) poor spawning

cond i t ions or 2) sui table water depth, veloci ty, and subst rate f o r spawning. C r i t e r i a f o r s u i t a b l e spawning condi t ions approximated high

probabi l i ty-of-use values (see 3.5.2, 3.5.3, and Appendix 1). Only

m in ima l i n f l uences o f gab ion i ns ta l l a t i on were an t i c ipa ted on these

c o n t r o l s i t e s . Two methods o f parameter comparison between the treatment

and the con t ro l s i t es (bo th t ypes 1 and 2 o f c o n t r o l where poss ib le ) were

used. F i r s t , mean values o f the var iab les were ca l cu la ted f o r each s i t e .

Second, i n d i v i d u a l sample p o i n t s within the t reatment s i tes, based on

distance downstream o f t h e i n i t i a l p o o l and distance f rom ei ther

streambank, were pa i red w i th representa t ive po in ts i n t h e c o n t r o l s i t e s .

A por tab le gr id system us ing benchmarks on e i t h e r bank f a c i l i t a t e d t h i s

comparison. S t a t i s t i c a l a n a l y s i s u s i n g t h e two types o f c o n t r o l s i t e s

provided a more r igorous comparison than using before-and-after

comparisons without controls.

3.3 Pre-Treatment S i t e Analys is

In t rag rave l pe rmeab i l i t y and d isso lved oxygen, gravel composit ion,

and streambed topography were measured p r i o r t o g a b i o n i n s t a l l a t i o n .

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Measurement o f t h e above var iab les was done on a s t r a t i f i e d g r i d system

rather than on a randomly selected basis. The s t ra t i f ied des ign enab led

values a t p o i n t s i n t rea tment s i tes to be pa i red with those i n c o n t r o l

s i t es f o r t - t es t ana lys i s . I n t rag rave l d i sso l ved oxygen was determined

from 18 t o 2 1 100-mL samples pe r s i t e o f i n t rag rave l wa te r ex t rac ted f rom

25 cm below the g rave l sur face w i th a s ta in less s tee l syr inge. Dissolved

oxygen i n these water samples was immediately measured with r e g u l a r l y

c a l i b r a t e d oxygen meters from the Yellow Springs Instrument Co.

Semi-micro Winkler t i t r a t i o n s (Rand " e t a l . ( e d i t o r s ) 1975) were used f o r

f u r t h e r c a l i b r a t i o n o f t h e oxygen meters.

I n t rag rave l pe rmeab i l i t y was measured us ing a Mark V I standpipe

(Terhune 1958). This technique operated on t h e p r i n c i p l e o f measured f low

i n t o a p ipe through per forat ions 25 cm below substrate surface. The

d r i v i n g f o r c e was a negative pressure head o f 2.5 cm, provided by a hand

suc t ion pump i n t h e p i p e . Between 15 and 21 measurements were made per

s i t e .

Stream bottom contours were determined to eva lua te t he an t i c ipa ted

changes i n t h e i r c o n f i g u r a t i o n due t o gabion placement. The treatment

s i t e e l e v a t i o n s were surveyed by theodoli te (Wild). Measurements were

made on approximately 60 s t a t i o n s within t h e g r i d systems, as w e l l as on

cross sect ions a t 10-m i n t e r v a l s . Stream grave l was sampled a t t h e gabion s i t e s with two t echniques t o

enable comparison with grave l compos i t ion a t the s i tes a f te r gab ion

placement. The s ta t i ons sampled were s t r a t i f i e d ( u s i n g t h e g r i d system)

across the width o f t h e stream, and 2 m upstream o f t h e f u t u r e l o c a t i o n s

o f lower gabions. For pre - ins ta l l a t i on ana lys i s , seven grave l samples

were taken i n Treatment S i t e I11 using a McNeil gravel sampler (Cederholm

and Sal0 1979). Gravels at Treatment Si te I1 were sampled by two

techniques: each sample taken wi th the McNei l gravel sampler was matched

w i t h a freeze-core sample (Scrivener and Brownlee 1982). Gravel

composition was analyzed using 18 s ieve s i zes t o accu ra te l y i nd i ca te

composition o f f ines. The la rge subs t ra te s ize a t T rea tment S i te I (p re- ins ta l la t ion) p rec luded sampl ing by e i ther method. Hence, four

- 12 -

randomly se lected s ta t ions a t Treatment S i te I were photographed f o r l a t e r

analysis. The ana lys is invo lved ca lcu la t ing sur face par t i c le d iameter

frequencies from 140 (random) measurements, us ing the pnotographic s l ides

p r o j e c t e d t o a c t u a l s i z e .

3.4 Gabion Construction and I n s t a l l a t i o n

Se lec t ion o f a gab ion con f igura t ion fo l lowed rev iew o f severa l tes ted

i n Washington, Oregon, and C a l i f o r n i a (Gerke 1974; Engels 1975; Anderson

and Cameron 1980; Anderson 1981; Moreau 1981; Ward 1982). Moreau (1981)

i n Ca l i f o rn ia f ound tha t a pa i red V-shaped con f igu ra t i on was the most

successful design i n t rapp ing bed load su i tab le fo r sa lmon id spawning and

for wi thstanding s tormf lows. Th is conf igurat ion was used a t a l l treatment

s i t e s i n th i s s tudy , with some minor modif icat ions (Figure 5) . Splash aprons were mod i f i ed t o maximize the dep th o f t he p lunge poo l c rea ted a t

t h e downstream edge of the gabions. The m o d i f i c a t i o n was made t o prevent

undercu t t i ng t he gab ion , wh i l e f ac i l i t a t i ng adu l tem ig ra t i on . Tne splash

aprons measured 0.30 m high by 0.91 m wide by 1.82 m long, and were

instal led underneath the gabion, out extending approximately 0.6 m beyond

the gab ion to fo rm a scour - res i s tan t p la t fo rm a t t he base o f t he gab ion

apex (F igure 5) .

Gabions were p o s i t i o n e d t o a l l o w a d u l t salmon migra t ion Dut prevent

l a t e r a l bank scour (Moreau 1981). The top o f the ups t ream gab ion was

pos i t ioned 50 cm above t h a t o f t h e o r i g i n a l streambed. To ach ieve t h i s

height, the streambed was excavated t o a dep th o f 50 cm, and t o 90 cm i n

the reg ion o f the sp lash aprons. The e l e v a t i o n o f t h e downstream gaDion

was ca lcu la ted f rom c r i te r ia g iven by Moreau (1981) and Reeves and Roelofs

(1982) ; i .e . , the top o f the downstream gabion was l e v e l w i t h t h e base o f

the upstream one. Although surveying techniques were used, t h e a c t u a l

placement varied up t o 10 cm from these guidelines. Gabion trenches were

excavated t o p r o v i d e an 8-15 cm drop a long the top o f the gabions f rom the

streambank t o t h e apex, thus ensur ing concentrated water f low for f ish

passage d u r i n g c r i t i c a l summer low f lows.

- 13 -

- 14 -

Simi lar ly , hor izonta l p lacement o f the gabions fo l lowed

recommendations by Moreau (1981). Recommended angles between the wings o f

the gabions varied from 90 t o 120° -- the sharper the angle, the less

res is tance to s tormf lows. Suf f ic ient d is tances between the gabions were

se lec ted to enab le p roper e leva t iona l pos i t ion ing a f te r account ing fo r

streambed gradients. The gabion ends were bu r ied up t o 4 m i n the

streambanks, and p r o t e c t e d b y r i p r a p . S p e c i f i c c h a r a c t e r i s t i c s o f t h e

hor izonta l p lacement are descr ibed for each s i t e i n 3.4.1, 3.4.2, and

3.4.3.

To p e r m i t s i t e usage by a l a rge run o f p ink salmon an t i c ipa ted i n

f a l l o f 1982, gab ion s i t es were surcharged (i.e., f i l l e d t o a h e i g h t l e v e l

with the top o f the gab ions) with g r a v e l s u i t a b l e f o r spawning.

Approximately 300 m p e r s i t e o f u n s o r t e d " r i v e r run" gravel was

del ivered f rom a nearby quarry.

3

Add i t i ona l manpower and heavy equipment were r e q u i r e d i n g a b i o n

cons t ruc t ion and i n s t a l l a t i o n . Seven men were ava i lab le th rough the

F i she r ies Employment Br idging Assistance Program; crew s ize var ied f rom

one t o f i v e d u r i n g th is phase. The heavy equipment used t o excavate

gab ion s i tes was suppl ied by a l oca l con t rac to r . The equipment supplied

inc luded a 12-yd dump t ruck ; a 2-yd f r o n t end loader; a 22-tonne, 1

1/4-yd bucket excavator; and a 3/4-yd bucket excavator. Gabion

cons t ruc t ion and i n s t a l l a t i o n was car r ied ou t i n 20 s teps to min imize

c o s t l y " i d l e equipment" t ime (Figure 6).

3 3

3 3

In-stream work was carr ied out under gu ide l ines and the pe rm iss ion o f

t h e l o c a l Department o f F i s h e r i e s and Oceans, and P r o v i n c i a l F i s h and

Wi ld l i f e o f f i ces . S tandard p rocedures ou t l i ned he re res t r i c ted work t o

low-f low periods and per iods when there were no spawning salmonids,

developing eggs, or l a r vae i n the system.

3.4.1 Treatment S i t e I The i n t e r - g a b i o n d i s t a n c e s e l e c t e d f o r t h i s s i t e was 6.5 m,

l a r g e l y based on s u i t a b i l i t y o f t h e streambank fo r keying i n t h e

gabions. An ap ica l ang le o f 90° was used (Moreau 1981). Three o f

- 15 -

Site preparation 1 Gabion b

Excavator gains ’ access to creek assembly a) tree removal I I 7 b) reference marking * Dig upstream trench

the stream laterally

t gravel

t I Back-fi l l downstream

trench ends I

Fill rock delivered > - +

Load and place splash aprons

1

-~

1

In situ final assembly

v Begin downstream

trenching

I

I Thread logging cables through gabions

l + Load upstream gabions

. I Spawning gravel

delivered I Manually sort f i l I rock and fasten gabion lids I

I Manually sort f i l l rock and fasten gabion lids

Load and place

In situ final assembly and thread logging cables through gabions

- * - Load downstream gabion

Back - fill upstream trench ends

FIGURE 6. Flow diagram of gabion installation.

- 16 -

the gabion ends were buried 2 m t o 4 m i n t o the streambank; the fourth was bu t t ed up and cabled t o a stable log 1 m i n to the bank. The gabion length required was 43 m. An abundant supply of r iprap was available on t h i s previously destabilized s i te ; hence a l l t h e

banks were le f t well armoured. Commercially sorted gabion fill rock was not required on t h i s site.

3.4.2 Treatment Site I1 The inter-gabion distance selected for t h i s s i t e was 10.5 m w i t h

an apical angle of 90°. All four gabion ends were buried 3 m t o 5 m i n t o the streambank. The t o t a l gabion length required was 50 m. Natural r iprap was ava i lab le to p ro tec t the ends of the upstream gabion only. Bank scour from t h e f a l l 1982 stormflows at t he

downstream gabion ends (not protected by r iprap) was l a t e r stopped by

handplacing large alder root wads and securing them wi th logging cables and r iprap . Commercially sorted gabion fill rock (15-30 cm diameter) was required a t t h i s s i te because of a lack of su i tab le natural material . In addition, 21 m of commercially sorted "drain rock" of 2-15 cm diameter was distributed over the spawning platforms t o d i l u t e the proportion of fines i n the river-run gravels used t o surcharge the sites. (The f ines less than 2.4 mm were d i l u t e d t o 9%

of gravel composition samples w i t h t h e addition of drain rock. The amount of f ines was greater where no drain rock was applied -- 11% and 19% for Treatment Sites I and 111, respectively; see Figure 13.)

3

3.4.3 Treatment S i te 111 An inter-gabion distance of 10.5 m was used. The apical angle

of 120° was selected to en la rge the area of the spawning platform created by t h e downstream gabion. Three of t h e gabion ends were buried 2-4 m i n t o the streambank. The fourth gabion end was butted up and cabled onto a s table log. The t o t a l gabion length required was 35 m. Natural riprap was lacking a t t h i s s i te , so the streambanks were i n i t i a l l y l e f t unprotected. Laterai bank scour during f a l l stormflows prompted handplacement of r i p r a p a t these

gabion ends.

- 17 -

i.

ii.

iii.

3.4.4 S i te revege ta t i on and bank s t a b i l i z a t i o n

Streambank mod i f i ca t ion was considerable during gabion

i n s t a l l a t i o n , e s p e c i a l l y where trenches extended deep i n t o t h e

banks. Although the trenches were b a c k f i l l e d and p i l e s o f excavated

m a t e r i a l smoothed, areas along the bank f o r t h e l e n g t h o f t h e s i t e s

were l e f t with bare minera l so i l . To f a c i l i t a t e streambank recovery,

several steps were taken fo l lowing construct ion:

Banks a t Treatment Sites I1 and I11 were hand seeded with a

grass-legume mix. Treatment S i t e I was l e f t as a cont ro l .

A t o t a l o f 90 j uven i l e a lde rs , hemlock, and forbs were

p lan ted with a 24-11 spacing on the banks o f Treatment S i t e s I1 and 111.

A l a y e r o f seaweed mulch was d i s t r i b u t e d on Treatment S i t e I1 t o se rve as b o t h f e r t i l i z e r and a c t as a s o i l b i n d e r upon

decomposition.

3.5 P o s t - I n s t a l l a t i o n S i t e A n a l y s i s

3.5.1 G r a v e l s t a b i l i t y

Depth of gravel scour was closely monitored as a measure o f

g r a v e l s t a b i l i t y i n the three t reatment and th ree o r f ou r con t ro l

s i t es ove r t he w in te r o f 1982 and t h e f a l l and w i n t e r o f 1983-84.

Approximately 20 ver t i ca l e ros ion mon i to rs (VEM'S) were i n s t a l l e d a t

each o f these s i tes i n December 1982, and again i n August and/or

October 1983. The VEM's employed c o n s i s t e d o f a column o f e i g h t

pe r fo ra ted p las t i c go l f ba l l s t h readed th rough with 100-lb (45-kg)

t e s t monofilament l i n e . The assembly was i n s e r t e d v e r t i c a l l y i n t o

the g rave l with the method i l l u s t r a t e d i n F igure 7. A p l a s t i c d i s c

a t t h e d i s t a l end o f the 1.5 m long monofilament prevented loss o f

ba l l s re leased by scouring. The number of bal ls scoured out o f t h e

g r a v e l a f t e r a stormflow event was used as a measure of the depth o f

scour a t tha t loca t ion . The depths o f scour a t i n d i v i d u a l s t a t i o n s

a t t rea tmen t s i t es were pa i red with t h a t a t c o n t r o l s i t e s f o r t - t e s t

analysis.

- 18 -

INNER PIPE SCOUR

Y E M O V E D

I - OUTER PIPE REMOVED

J

FIGURE 7. Procedure for p lac ing scour mon i to rs in to the streambed.

- 19 -

3.5.2 Grave l qua l i t y

The q u a l i t y o f spawning grave ls impounded by the gabions was

examined throughout the post - insta l la t ion per iod. In t ragravel

d isso lved oxygen measurements (see Sect ion 3.3) were taken dur ing

1982-83 salmon egg incubation. These were repeated along with

permeab i l i t y measurements (see Section 3.3) i n summer 1983. Sampling

o n t h e g r i d systems enabled pair ing o f s t a t i o n s i n treatment and

t h e i r c o n t r o l s i t e s f o r t - t e s t a n a l y s i s . Between 15 and 27

measurements were made a t each s i t e .

Gravel composition was ana lyzed tw ice a f te r gab ion i ns ta l l a t i on

as fo l lows: 1) t h ree g rave l samples were taken from the surcharged

spawning g r a v e l s a t each o f t he t h ree t rea tmen t s i t es immed ia te l y

fo l l ow ing gaD ion i ns ta l l a t i on ; and 2 ) f i v e s t a t i o n s were sampled a t

a l l t rea tment and con t ro l s i tes 1 y e a r a f t e r i n s t a l l a t i o n (summer

1983) t o d e t e c t changes i n g rave l compos i t i on a t t r i bu ted t o w in te r

stormflows and spawner a c t i v i t y .

Sedimentation i s de f ined i n th i s study as t h e i n f i l t r a t i o n and

impaction o f streambed gravels with f i n e sediments less than 3 mm.

Between 10 and 16 sediment traps were d i s t r i b u t e d p e r s i t e a t t h e

t h r e e t r e a t m e n t s i t e s a n d a t f i v e o f t h e c o n t r o l s i t e s t o de tec t

d i f f e rences i n sedimentation rates between treatment and control

s i t e s on Sachs Creek. The t raps c o n s i s t e d o f wide-mouth 1.5-L

p l a s t i c j a r s f i l l e d with so r ted pea g rave l l a rge r t han 3 mm. The

t raps were b u r i e d f l u s h with the sur face, as described by Slaney - e t

- a l . (1977) . The traps col lected sediments f rom December 1982 t o

March 1983 and were l a t e r analyzed by dry sieving. About 60% o f t h e

t r a p s were destroyed by scour. Average f ine sediment accumulation a t

the t rea tment s i tes were g raph ica l l y compared t o t h a t o f c o n t r o l

s i t e s .

3.5.3 Streambed con f igu ra t i on

Stream bottom contours o f t he gab ion s i t es were surveyed with an

a u t o m a t i c l e v e l ( K e r n ) a t s e v e r a l t i m e s a f t e r i n s t a l l a t i o n :

- 20 -

1) immedia te ly fo l low ing ins ta l la t ion , 2 ) af te r w in te r s to rmf lows i n

February 1983, 3) 1 y e a r a f t e r i n s t a l l a t i o n i n Ju l y 1983, and

4) a f t e r a second cyc le o f w in te r s to rmf lows i n February 1984. An

add i t iona l survey o f T rea tment S i te I was made fo l lowing major

changes i n streambed con f igu ra t i on caused by the August 1983 f lood.

3.5.4 Spawner use

Two methods o f measur ing t he su i tab i l i t y o f t r ea tmen t s i t es as

salmon spawning h a b i t a t were examined: 1) t a b u l a t i o n o f salmon

spawner a c t i v i t y on a l l c o n t r o l and treatment s i tes; and

2) e v a l u a t i o n o f h a b i t a t s u i t a b i l i t y based on probabi l i ty -of -use

curves (Bovee and Cochnauer 1977) developed for Sachs Creek pink salmon.

A c t u a l f i s h usage o f t h e s i t e s was ob ta ined by p lo t t ing spawning

loca t ions o f spawning or redd-defending female salmon. F i s h

pos i t i ons usua l l y were mapped every other day throughout the spawning

season o f 1982 and every other week fo r t he sma l le r run i n f a l l

1983. A standard form was used i n conjunct ion with the on-s i te

r e f e r e n c e g r i d s y s t e m t o f a c i l i t a t e b o t h p l o t t i n g f i s h p o s i t i o n s and

la te r ana lys i s . I n add i t i on , t he po r t i on o f t he c reek used was

surveyed every 7-10 days from September t o December 1982.

Approximate t iming o f runs, abundance o f salmon, and l o n g i t u d i n a l

d i s t r i b u t i o n o f t h e p i n k , chum, and coho salmon were recorded.

Probabi l i ty-of-use curves (Bovee and Cochnauer 1977) were

es tab l i shed f o r p ink salmon i n October 1982 t o determine whether

cond i t i ons conduc ive t o t he i r spawning were found a t gabion s i tes.

These cond i t ions may or may n o t b e r e l a t e d t o an i n t r a g r a v e l

environment required for h igh egg and alevin survival . Parameters

measured on a t o t a l o f 230 redds included average water depth, water

v e l o c i t y a t spawner "nose height" (5 cm above the subst rate) , and

sur face subst rate composi t ion (a subject ive est imate o f percent

gravels ( 2 cm< x < 12 cm) and "D50" the d iameter at which 50% o f t h e

sur face par t i c les a re smal le r o r l a r g e r ) . The average

- 21 -

probab i l i t y -o f -use ca lcu la ted fo r the t rea tment s i tes was compared t o

t h a t o f r e s p e c t i v e c o n t r o l s i t e s .

3.5.5 Egg s u r v i v a l

Egg s u r v i v a l s t u d i e s complemented t h e above s tud ies i n two

ways: 1) they were designed t o d e t e c t d i f f e r e n c e s i n egg m o r t a l i t y

r a t e between c o n t r o l and t rea tment s i tes th rough pa i red t - tes t

ana lys is ; and 2 ) they enabled a c o r r e l a t i o n o f egg s u r v i v a l r a t e s t o

q u a l i t y o f g r a v e l a s measured by in t ragrave l d isso lved oxygen,

i n t rag rave l pe rmeab i l i t y , g rave l qua l i t y , and depth o f scour.

Egg and a l e v i n d e n s i t i e s were sampled with a hyd rau l i c egg

sampler (McNeil 1964a). - Sampl ing stat ions were se lec ted with

reference t o spawner mapping da ta ; on l y s ta t i ons exh ib i t i ng a minimum

f i s h usage (2 p ink salmon spawner-days) were sampled t o minimize

sampling areas with no eggs. Th is c r i te r ion p rec luded sampl ing s i tes

other than Treatment S i te 111 and i t s two c o n t r o l s i t e s (IIIA and

IIIB), owing t o l a c k o f s u f f i c i e n t spawner d e n s i t i e s a t t h e o t h e r

s i t e s . About 20 s t a t i o n s p e r s i t e were sampled f o r each sampling

per iod: 1) a t t h e Ileyedll stage i n December 1982, and 2 ) immediately

p r i o r t o p i n k f r y tlemergencetf f rom the gravel i n March 1983.

Sampling consisted o f 0.2 m per sample and four adjacent samples

pe r s ta t i on . The eggs and a lev ins were e x t r a c t e d t o a depth o f 40 cm.

Egg sampl ing for 29 o f t h e December samples was m o d i f i e d t o

determine the approximate depth that eggs were deposited. These were

sampled by i nse r t i ng t ne hyd rau l i c p robe i n the g rave l , i n increments

o f 10 cm deep t o a maximum o f 40 cm. The eggs c o l l e c t e d a f t e r each

increment were analyzed separately. Selection o f t h e 29 depth

samples was based on whether an adjacent sample had more than

approximately 20 eggs.

2

Two methods o f c a l c u l a t i n g egg surv iva l (McNei l 1964a) - were

a p p l i e d t o t h e egg sampling data. F i r s t , t h e r a t i o o f l i v e t o dead

eggs sampled was used zs a r e l a t i v e measure o f s u r v i v a l t o

date-of-sampling. A second method was developed t o e l i m i n a t e t h e

- 22 -

b i a s i n su rv i va l i n t roduced f rom na tu ra l egg loss. This method

r e q u i r e d c a l c u l a t i o n o f p o t e n t i a l egg depos i t ion f rom adu l t

fecund i t ies , egg retent ion, and spawner mapping data. An average

spawner l o n g e v i t y o f 10 days (McNeil 1964b) - was assumed t o be

necessary f o r an average deposition (1300 eggs; n=12 l1greenl1 Sachs

Creek p ink salmon females). A p a i r e d t - t e s t a n a l y s i s o f s u r v i v a l a t

i n d i v i d u a l s t a t i o n s was used t o i n d i c a t e d i f f e r e n c e s i n s u r v i v a l r a t e

between Treatment S i t e I11 and t h a t o f i t s t w o c o n t r o l s i t e s (IIIA and 1116). Stepwise mul t ip le regress ions (Rao 1973) were run with

egg surv iva l aga ins t phys ica l parameters to examine t h e r e l a t i o n s h i p s

between the physical environment and egg survival . Intragravel

dissolved oxygen and permeabil i ty, and depth o f g r a v e l s c o u r ,

measured e i t h e r d u r i n g summer 1982 o r win ter 1982-83, were run

a g a i n s t b o t h i n d i c e s o f egg s u r v i v a l a t i n d i v i d u a l s a m p l i n g s t a t i o n s .

3.5.6 Juveni le use

Juvenile salmonids were enumerated on the gabion and cont ro l

s i t e s on Sachs Creek i n summer 1983 t o i n d i c a t e t h e e f f e c t o f g a b i o n

i n s t a l l a t i o n on salmonid rear ing habi tat . Juveni le enumerat ion

involved two sampling sessions separated by a 2-3 hour period, which

enabled marked f i s h f r o m t h e f i r s t s a m p l i n g t o r e t u r n t o t h e i r

o r i g i n a l l o c a t i o n s p r i o r t o t h e second sampling. Each sampling

enta i led mul t ip le ( two- to- three) passes with Doth e lectroshocker

(Smith Root, Type VIII) and pole seine (3 m long, 4 rnrn mesh).

Juven i le coho and steelhead were marked P Y c a u d a l f i n - c l i p p i n g t o

enable enumeration by the Petersen single census mark-recapture

technique. Their fork lengths were measured t o d e t e c t p o s s i b l e

d i f f e rences i n s i z e between the gabion and control s i tes. Stop nets

del ineated the study areas dur ing sampl ing and the re-or ientat ion

period. A t - test analys is based on unpai red measurements o f

i n d i v i d u a l O+ coho lengths was made t o determine di f ferences i n

average length between t reatment and control s i tes.

- 23 -

4 RESULTS

4.1 S i t e S t a b i l i t y

4.1.1 Gravel scour

Gravel scour at two of the gabion si tes ( I and 11) over the

f i r s t w i n t e r (1982-83) was s ign i f i can t ly g rea ter (p < .05, t - t e s t

analys is) than a t the i r respect ive cont ro l s i tes (Tables 1 and 2).

The areas of concentrated gravel scour were genera l ly on the

downstream s ide o f t h e l a t e r a l wings of the gabions and i n the h igh

velocity channels establ ished by bank def lect ion (F igure 8) . The

ex ten t o f t he bank scour i n these corners prompted riprap placement

a t Treatment S i t e s I1 and I11 where there prev ious ly had been none

(see 3.4.2, 3.4.3, and 3.4.4). Gravel scour i n the second year

(1983-84) was no t as severe i n gabion and c o n t r o l s i t e s as i n the

f i r s t year (1982-83) (Table 1). However, gravel scour at the lower

two t reatment s i tes (I1 and 111) decreased more (from 13 cm i n the

f i r s t year t o 4.4 cm i n the second year) than that o f t h e i r c o n t r o l

s i t e s (IIB, IIIA, and IIIB; from 5.1 cm t o 4.5 cm). Scour was

the re fo re s im i l a r ( p < .05; Table 2) i n the lower two t reatment s i tes

(I1 and 111) and c o n t r o l s i t e s (116, IIIA, and IIIB) a f t e r t h e

i n i t i a l s t a b i l i z a t i o n p e r i o d o f one year. Gravel scour a t Treatment Site I , a t a 3% s lope grad ien t , a l so decreased i n t h e second year

f rom that i n the f i r s t yea r ( f rom an average o f 22 cm t o 12 em;

Table 1). Scour a t Treatment S i t e I was greater than a l l o t h e r s i t e s

i n the second year (Table l), and s i g n i f i c a n t l y g r e a t e r t h a n i t s

c o n t r o l IB (Table 2).

- 24 -

TABLE 1. Depth o f g rave l scou r on s t u d y s i t e s a t Sachs Creek over winter 1982-83 and 1983-84

Year l a Year 2

S i t e

No. of Avg . Std. No. o f Avg . Std. s t a t i o n s scour dev . s t a t i o n s scour dev . monitored (cmP (sx ) monitored (cm) (5x1

Treatment I 18 22 13 11 12 9.5 Treatment I1 17 11 12 19 1.1 2.4 Treatment I11 19 15 15 26 6.8 8.2

Tota ls I1 and IIIC 36 13 13 45 4.4 6 . 9 I, I1 and I11 54 16 14 56 5.9 8.0

C o n t r o l I 6 12 7.0 11 9 0.9 2.8 C o n t r o l I I B 16 1.1 2.9 9 0.5 1.4 Cont ro l IIIA 15 7.8 8.7 13 5.8 6.3 C o n t r o l I I I B N.A. - 11 9.2 9.5

Tota ls : IB , 116, IIIA and 1116 43 5.1 8.4 42 4.5 7.0

a Peak stormflow i n Year 1 (1982-83) was 1.32 m on s t a f f gauge. Peak stormflow i n Year 2 (1983-84) was 1.14 m on s t a f f gauge.

b As ind ica ted by Ver t i ca l Eros ion Mon i to rs .

C These s i t e s a r e a t 1% slope gradient .

- 25 -

TABLE 2. A t-test analysis of gravel scour on s t u d y sites a t Sachs Creek

Treatment Control Mean Std. Dev. S i t e ( X ) s i t e ( Y ) Yeara Diff.b of t df Signi f -

(X-Y) Diff. icancec

I I6 1 2.3 2.6 2.7 9 Sig . 2 3.8 1.1 9.9 7 Sig .

I1 116 1 2.4 2.0 4.3 12 Sig . 2 0.55 1.5 1.1 8 N.S.

111 IIIA 1 0.72 2.5 1.1 14 N. S. 2 0.23 2.6 0.31 11 N.S.

I11 IIIB 2 -0.24 2.7 -0.30 10 N.S.

a Monitoring Year 1 from early December 1982 through mid-March 1983; monitoring Year 2 from early September 1983 through l a t e January 1984.

b Values of gravel scour (cm) transformed by square root.

p <.05; one-tailed paired t-test; Ho: X GY; H1: X > Y .

- 26 -

YEAR I

FIGURE 8. Isopleths o f gravel scour depth (em) as indicated by ve r t i ca l erosion monitors a t gabion s i t e s a t Sachs Creek i n Year 1 and 2 .

- 27 -

4.1.2 Gabion s i t e c o n f i g u r a t i o n s

Con f igu ra t i on o f t ne gab ion s i t es changed during exposure t o

t h e i r f i r s t w i n t e r (1982-83) stormflows. Pools about 80 cm deep

formed i n the downstream la te ra l corners f rom g rave l scour (F igures

9, 10, and 11). Th is c rea ted two add i t i ona l poo l - r i f f l e sequences

pe r s i t e . Teardrop-shaped grave l bars formed downstream o f gabion

apices i n Treatment Sites I1 and 111. Although the gabions withstood

winter s tormf lows that ra ised the water sur face by 1.1 m, an

unseasonal f lood on 2 August, 1983, ( ra is ing the water sur face by

1.2 m) caused Treatment S i t e I t o l l f a i l l l ( i . e . , t o change enough t o

th rea ten s i t e i n teg r i t y ) ; app rox ima te l y 0.5 m o f s u b s t r a t e was

scoured away f o r a 30 m reach downstream of the lower gabion (F igure

9) . A wedge o f streambed sediments with boulders up t o 0.7 m d iameter inundated the s i te upst ream of the gabions dur ing th is f lood

(Figure 12); t h i s wedge averaged 13 cm th ick over a 20 m distance

upstream o f t h e gabions. Much o f t h i s wedge was scoured away du r ing

stormflows i n the second year (Figures 9 and 12). Streambed

conf igura t ions remained re la t i ve ly cons tan t a t the lower two

t rea tment s i tes (I1 and 111) over the second season o f w i n t e r

stormflows (Figures 10 and 11).

- 28 -

- 29 -

- 30 -

- 31 -

Flood I 6

Gabion Installation \\\ G"." -\ I \ \ .J " " I \

-U \

JULY SEPT 1982

JULY AUG. FEBRUARY 1983 1984

FIGURE 12. Temporal changes i n average aggradation above gabions a t Treatment S i t e I , Sachs Creek.

Changes i n local streambed slope gradients improved the gravel stabil izing a b i l i t y o f a l l t h r e e gabion sites: the pre-installation three-site average gradient o f -1.2% (facing downstream) decreased t o an average gradient of +3.1% 1 year after installation (Table 3 ) . (Slope is posit ive when the bottom o f plunge pools a re , on average, a t a lower elevation than gravels entrapped by gaoions further downstream.) The August 1983 flood increased the streambed gradient a t Treatment S i t e I t o -1.9%; however, t h i s was s t i l l a decrease from the pre-installation gradient of -2.8% (Table 3 ) .

- 32 -

TABLE 3. Summary o f streambed gradient changes with gab ion i ns ta l l a t i on on Sachs Creek, 1982-83

Average slope gradient (%) fac ing downstream

Locat ion Treat. r e l a t i v e Pre- 1-Year post- Post-f lood S i t e t o gabions i n s t a l l a t i o n a i n s t a l l a t i o n b Aug. 1983

I Upst ream Between Downstream

-3.0 -2.5 -3.0

Average

11 Upstream Between Downstream

Average

I11 Upstream Between Downstream

Average

Tota l : I, I1 and I11

-2.8

-0.2 -1.1 -1.1

-0.8

+l. 6 -1.2 0

+o. 1

-1.2

-1.4 +5.0 +4.0 - +2.5

+4.9 +3.1 +0.5

+2.8

+4.8 +4.2 +3.3

+4.1

+3.1

-3.2 +3.0 -5.6 - -1.9

a Surveyed Ju ly 1982. Surveyed Ju ly 1983.

- 33 -

4.2 Si te Revegetat ion and Bank S t a b i l i z a t i o n

Vegetative coverage o f m i n e r a l s o i l exposed dur ing gabion

cons t ruc t i on was more e x t e n s i v e a t s i t e s where bank s t a b i l i z a t i o n methods

were applied. The s i t e r e c e i v i n g no revegetat ive a t tent ion (Treatment

S i t e I) appeared t o have only minimal organic coverage 1.5 years after

gabion construct ion. The s i t e seeded with the grass-legume mix and

covered with a seaweed mulch (Treatment Site 11) had the highest

vegetat ive coverage at th is t ime . Po r t i ons o f t h i s s i t e i n a lower f lood

p l a i n remained bare, owing t o t h e seed and seaweed washed away p r i o r t o

seed germination. Most of t h e s i t e t h a t was seeded but n o t f e r t i l i z e d

with seaweed (Treatment S i t e 111) had sparse vegetative coverage. The

seaweed mulch also appeared to e f fec t i ve ly s tab i l i ze the s teeper mach inery

access route at Treatment Si te I1 when compared t o a s i m i l a r l y seeded but

u n f e r t i l i z e d access route at Treatment Site 111. Surv i va l o f j uven i l e a lde rs , hemlock, and forbs a t Treatment S i tes I1

and I11 after 1.5 years was approximately 60% (Table 4). Most o f these

were sub jec ted to f lood cond i t ions , suggest ing e f f i c ien t roo t systems were

already developed. Losses of approximately 40% of stock planted were

largely through streambank erosion 2nd beaver a c t i v i t y .

4.3 Gravel Qual i ty

4.3.1 In t rag rave l d i sso l ved oxygen

The e f fec t o f gab ion i ns ta l l a t i on on i n t rag rave l d i sso l ved

oxygen was va r iab le between t reatments but comparat ive to controls

within treatments (Table 5). Oxygen l e v e l s a t a combination of a l l

three t reatment s i tes were s i g n i f i c a n t l y "improvedvt when compared t o

t h a t o f the con t ro ls ; i .e . , the in t ragrave l d isso lved oxygen a t t h e

gabion s i tes was n o t s i g n i f i c a n t l y d i f f e r e n t (p < .05, p a i r e d t - t e s t )

from e i t h e r o f t h e i r c o n t r o l s i t e s p r i o r t o i n s t a l l a t i o n DUt was

s i g n i f i c a n t l y g r e a t e r a f t e r i n s t a l l a t i o n ( T a b l e 6). The oxygen

l e v e l s o f Treatment Sites 11 an I11 both were s ign i f i can t ly improved

- 34 -

TABLE 4. Streambank stocking success on s tudy s i t es a t Sachs Creek, October 1982 t o February 1984

Number of p l a n t s Treatment Date S i t e

Alders Hemlock Forbs, Total A l i v e Damageda e tc .

11 1982 34 3 2 39 1984 22 15 3 2b 27

111 1982 39 3 9 51 1984 20 4 1 4 25

11 and 111 1982 73 6 11 90 1984 42 19 4 6 52

a Trees damaged or destroyed by beaver i n w in te r 1983-84; add i t iona l losses

b Volunteers. r e s u l t e d from streambank erosion.

- 35 -

TABLE 5. Summary o f i n t rag rave l d i sso l ved oxygen and permeabil i ty on study s i t e s a t Sachs Creek

Dissolved oxygen Permeabi l i ty

S i t e Sampling N Average Std. N Average Std. per ioda (X o f sr fce) dev. (cm/hr ) dev .

Treat I

Contr I A

Contr I B

Treat I1

Contr I I A

Contr I I0

Treat I I1

Contr I IIA

Contr I I 1 6

Pre 0.5 Year 1 Year

Pre 0.5 Year 1 Year

Pre 0.5 Year 1 Year

Pr e 0.5 Year 1 Year

Pr e 0.5 1 Year


Pre 0.5 1 Year


Pre 0.5 Year 1 Year

18 20 18

18 18 15

20 18 20

19 23 23

18 23 21

20 23 23

19 25 18

21 26 19

18 27 19

88 86 92

61 85 96

24 64 43

30 80 65

54 58 45

43 49 33

13 72 74

60 46 44

58 55 47

12 9.6 8.5

32 15

4.7

26 31 32

27 22 28

28 25 28

33

25

17 22 18

31 31 26

29 25 28

28

N . A . ~ N.A. 14 2.3~103

N.A. N.A. N.A.

N.A. N.A. 14 3 .8~103

15 3 . 1 ~ 1 0 ~ N.A. 17 1 .7~103

18 2 .8~102 N.A. 17 6 . 0 ~ 1 0 ~

21 6 .5~102 N.A. 20 6 . 0 ~ 1 0 ~

16 1 . 4 ~ 1 0 3 N.A. 18 3 .1~103

21 8 . 2 ~ 1 0 ~ N.A. 20 2 .5~103

19 1 .1~103 N.A. 17 2.4~103

2 .8~103

2 .7~103

3.0x102

2 .5~103

4 .0~102

1.1~103

7.0~102

6 .9~102

6. 1x102

2 .8~103

1 .1~103

2 .1~103

1 .7~103

2 .4~103

- 36 -

TABLE 5. Continued

Dissolved oxygen Permeabi l i ty

S i t e Sampling N Average Std. N Average Std. per ioda (% of s r f ce ) dev. ( cm/hr) dev.

Totals:

TreatC Pre

and I11 1 Year I, 11 0.5 Year

ContrC Pre I A , IIA 0.5 Year and IIIA 1 Year

ContrC Pre IB, I I B 0.5 Year and I I I B 1 Year

56 68 59

57 67 55

58 68 62

43 79 76

58 60 58

41 55 41

38 31 8.7~102 7. 3x102 20 N.A. 23 49 2.4~103 2. 7x103

30 39 5.7~102 8. 7x102 30 33

N.A. 37 1 . 6 ~ 1 0 ~ 2 . 0 ~ 1 0 3

32 40 8 . 6 ~ 1 0 ~ 1 . 3 ~ 1 0 3 29 29

N.A. 37 1.4~103 1.9~103

a Pre- insta l la t ion sampl ing i n Ju l y and August 1982; 0.5-year post - insta l la t ion sampl ing i n February and March 1983; 1-year post - insta l la t ion sampl ing i n Ju ly and August 1983. N.A. = Not Avai lable.

IIIA, I I B , and I I I B only. C Totals for permeabi l i ty included Treatments I1 and 111, and Controls IIA,

- 37 -

TABLE 6. A t - t es t ana lys i s of in t ragrave l d isso lved oxygen on s tudy s i tes a t Sachs Creek

Treat. Control Sample Mean Std. t d f S i g n i f - S i t e ( X ) s i t e ( Y ) da t e a d i f f .b dev. of icancec

( x-Y ) d i f f .

I

I

I1

11

I11

I11

IA (Marginal h a b i t a t )

I0 (Prime hab i ta t )

IIA (Marginal h a b i t a t )

IIB (Prime hab i ta t )

IIIA (Marginal hab i ta t )

1116 (Prime h a b i t a t )

Pre 0.5 Year 1 Year

Pre 0.5 Year 1 Year

Pxe 0.5 Year 1 Year

Pre 0.5 Year 1 Year

Pre 0.5 Year 1 Year

Pre 0.5 Year 1 Year

20 1.1

-1.6

61 22 49

-27 22 21

-14 31 32

-55 22 29

-45 15 24

26 16 6.1

27 30 35

41 30 46

45 36 43

28 38 30

27 27 31

2.8 0.3

-0.96

8.9 3.1 6.0

-2.6 3.5 2.1

-1.4 4.1 3.4

-8.3 2.9 4.1

-7.1 2.8 3.3

13 17 12

15 17 17

15 22 20

18 22 21

17 24 17

17 25 17

S ig . N.S. N.S.

S ig . S ig . S ig . N.S. S ig . Sig.

N.S. Sig . S ig . N.S. S ig . S i g . N.S. Sig. sig .

Totals: I, IA, IIA, IIIA Pre -24 44 -3.7 47 N.S. 11 , (Marginal 0.5 Year 17 31 4.3 64 Sig . and 111 h a b i t a t ) 1 Year 18 36 3.6 50 S ig . 1, IB, IIB, IIIB R e -2.3 55 -0.3 52 N.S. 11 , (Prime 0.5 Year 23 31 5.8 65 Sig . and I11 h a b i t a t ) 1 Year 35 38 7.0 57 S ig . a Pre- insta l la t ion sampl ing i n Ju l y and August 1982; 0.5-year post-

i n s t a l l a t i o n sampling i n February and March 1983; 1 -year pos t - ins ta l la t ion sampling i n August 1983.

b I n t r a g r a v e l oxygen values were expressed as percent of dissolved oxygen o f surf ace water . P < -05; one- ta i led pa i red t - test ; Ho: X GY; H1: X > Y . C

- 38 -

a f t e r g a b i o n i n s t a l l a t i o n . The oxygen l e v e l s o f Treatment S i t e I

decreased a f t e r g a b i o n i n s t a l l a t i o n when compared t o t h a t o f i t s

c o n t r o l s i t e s ; t h e average dissolved oxygen concentrat ion at th is

g a b i o n s i t e was s i g n i f i c a n t l y g r e a t e r t h a n C o n t r o l S i t e I A p r i o r t o

i n s t a l l a t i o n , b u t was n o t d i f f e r e n t a f t e r i n s t a l l a t i o n ( T a b l e 6).

The in t rag rave l d i sso l ved oxygen a t Treatment S i t e I remained

s i g n i f i c a n t l y g r e a t e r t h a n C o n t r o l S i t e I B b e f o r e and a f t e r

i n s t a l l a t i o n ( T a b l e 6).

4.3.2 In t rag rave l pe rmeab i l i t y

The e f f e c t o f g a b i o n i n s t a l l a t i o n on i n t rag rave l pe rmeab i l i t y

a lso var ied cons iderably between the s i tes (Table 5). Permeabi l i ty

o f g r a v e l s a t a combination o f Treatment S i t e s I1 and I11 were s i g n i f i c a n t l y ( p < .OS) improved r e l a t i v e t o C o n t r o l S i t e s IIt3 and

IIIB, and maintained a s i g n i f i c a n t l y g r e a t e r p e r m e a b i l i t y t h a n t h a t

a t C o n t r o l S i t e s IIA and IIIA (Table 7). The p e r m e a b i l i t y o f

Treatment S i t e I1 s ign i f i can t l y i nc reased fo l l ow ing gab ion

i ns ta l l a t i on (p< .05 ; Tab le 7). The permeab i l i t y o f T rea tment S i te

I11 a lso inc reased a f te r gab ion ins ta l la t ion (Tab le 5). However, t h e

p e r m e a b i l i t y a t t h e g a b i o n s i t e was s i g n i f i c a n t l y g r e a t e r t h a n t h a t

a t i t s t w o c o n t r o l s i t e s p r i o r t o g a b i o n i n s t a l l a t i o n , whereas i t was

n o t s i g n i f i c a n t l y g r e a t e r a f t e r i n s t a l l a t i o n ( T a b l e 7). Th is was

probably owing t o a th ree- fo ld inc rease i n t h e v a r i a b i l i t y o f

permeab i l i t y a t T rea tment S i te I11 (standara deviat ion; Table 5). A t

Treatment S i t e I, the stream substrate was too coarse fo r

permeab i l i t y measurements p r i o r t o g a b i o n i n s t a l l a t i o n ; and t h e

p o s t - i n s t a l l a t i o n measurements i n d i c a t e d t h a t i t s p e r m e a b i l i t y a l s o

was n o t s i g n i f i c a n t l y g r e a t e r t h a n C o n t r o l S i t e I B ( T a b l e 7). Stream

s u b s t r a t e o f C o n t r o l S i t e I A remained too coarse for permeabi l i ty

measurements at both sampl ing per iods.

- 39 -

TABLE 7. A t-test analysis of intragravel permeability on s t u d y s i t e s a t Sachs Creek

Treat. Control Sample Mean Std. t df Signif- S i t e (X) s i t e ( Y ) datea d i f f . b dev. o f icancec

(X-Y) d i f f .

I IB (Prime habi ta t )

I1 I IA (Marginal habi ta t )

I1 IIB (Prime habitat)

I11 IIIA (Marginal habi ta t )

111 IIIB (Prime habi ta t )

Pre

Pr e 1 Year

Pre 1 Year

Pre 1 Year

Pre 1 Year

-8.1

1.2 15

-4.5 15

5.2 -0.18

5.8 7.5

25 -1 .3 14 N.S.

3.2 1.4 13 N.S. 21 3.2 20 Sig .

9.3 -1.9 14 N.S. 21 3.3 20 Sig .

10 2.0 14 Sig . 20 -0.04 20 N.S.

11 2.1 15 Sig . 18 1.7 17 N.S.

To ta ls :

and I11 (Marginal 1 Year 7.3 22 2.2 41 Sig . 11 f IIA and IIIA Pre 3.3 7.7 2.3 28 Sig.

habitat)

11 , IIB and 1116 Pre 0.87 11 0.42 30 N.S. and I11 (Prime 1 Year 11 20 3.6 38 Sig .

habitat 1

a Pre-installation sampling i n J u l y and August 1982; 1-year post-installation sampling i n June and J u l y 1983. Intragravel permeability values expressed as mL/sec entering the standpipe, before conversion t o cm/hr (Terhune 1958). p <.05; one-tailed paired t-test; Ho: X <Y; H1: X > Y .

- 40 -

4.3.3 Gravel composition

The composition o f gravels on the Treatment Si tes i n Sachs

Creek changed with the add i t ion o f g rave ls f rom a quarry and again

with a c y c l e o f spawning and winter stormflows. A t Treatment S i t e I

(3% streambed slope gradient) the most notable changes were found

with grave ls between 10 mm and 70 mm d iameter , the su i tab le range for

p ink and chum salmon spawning. The p r o p o r t i o n o f t h e s e g r a v e l s i z e s

increased with the add i t i on o f qua r ry g rave ls , bu t were reduced t o

a lmost the low p ropor t ions found be fore ins ta l la t ion fo l low ing the

f lush ing e f fec t o f w in te r s to rmf lows (F igure 13) . Grave ls 20-60 mm

i n diameter a t Treatment S i t e s I1 and I11 ( a t a 1% streambed slope

grad ien t ) appeared more abundant 1 y e a r a f t e r i n s t a l l a t i o n t h a n t h o s e

b e f o r e i n s t a l l a t i o n ( F i g u r e 1 3 ) .

The amount o f f i n e sediments i n the gravel entrapped by

gabions and measured by gravel sample s i e v i n g v a r i e d between t h e

s i t e s . The I1fines1l i n Treatment S i t e I11 decreased more than 50%

between pre-gabion i n s t a l l a t i o n t o 1 -year pos t - ins ta l la t ion

(Figure 14) ; t h i s reduced the f ines to leve ls be low those i n both o f

i t s c o n t r o l s i t e s (IIIA and IIIB). Changes i n f i n e s a t Treatment

S i t e I1 were minor, with l e v e l s r e m a i n i n g s l i g h t l y b e l o w i t s c o n t r o l

s i t e s (IIA and IIB; Figure 14). Only a minor f lush ing o f f ines f rom

t h e added quarry gravels was ev ident a t Treatment S i te I (Figure 14);

t h e c o a r s e n a t u r e o f t h e s u b s t r a t e p r i o r t o i n s t a l l a t i o n p r e v e n t e d

pre- and p o s t - i n s t a l l a t i o n comparison o f t h e f i n e r component o f t h e

g r a v e l s a t t h i s s i t e .

4.3.4 Sedimentation

The loss o f most o f t h e sediment t raps through winter

stormflows ( a l l i n t h e case o f Treatment S i t e I ) precluded

s t a t i s t i c a l a n a l y s i s o f r e s u l t s . F i n e s e d i m e n t ( l e s s t h a n 3 mrn)

accumulation i n t r a p s a t Treatment S i t e I1 was 40-50% lower than that

of i t s two c o n t r o l s i t e s (IIA and IIB; Figure 15). Fine sediment

accumulation a t Treatment S i t e I11 ranged from 10-70% h igher than

t h a t o f i t s two c o n t r o l s i t e s (IIIA and 1116; Figure 151.

- 41 -

0 Pre-Installation (n=140)

A I Year Post-Installation (n=5)

Control IA 1983 (n=117)

0 Control IB (n=5)

D

20

10

m

Bo

SITE II

0 Pre-Installation (n=7) 0 Post-Installation (n=3) A I Year Post-Installation ( ~ 5 ) W

W Control I I A (n=5) Cl Control IIB (n=5)

YTEIU

Pre-Installation (n=7)

=O Post-Installation (n=3) A I Year

60-m ControlIUA (n=5) 0 Control IIIB (n=5)

40,

1

J

FIGURE 13. Gravel composition o f s t u d y s i t e s a t Sachs Creek pre- and post-gabion ins ta l la t ion .

- 42 -

Lo- .

,

0- I

'C

FIGURE 14. Mean percent o f p a r t i c l e s l e s s t h a n 1.2 and 0.30 rnm on study sites a t Sachs Creek.

- 43 -

8-

6-

4-

2-

0- 0.10 0.50 1 . 0 0

PARTICLE DIAMETER (mm)

FIGURE 15. Sedimentation accumulated i n sediment traps on s t u d y sites a t Sachs Creek, December 1982 t o March 1983.

- 44 -

D i f f e ren t s i zes o f I l f i nes l l may vary i n s e v e r i t y o f e f f e c t s on

egg surv iva l . I t was no t u n t i l t h e p a r t i c l e s i z e examined i n another

study was reduced t o l e s s t h a n 0.03 mm diameter that a s i g n i f i c a n t

nega t i ve co r re la t i on was found between amount o f f i n e s and egg-to-fry

surv iva l (S laney " e t a l . 1977). Fines less than 0.30 rnm diameter were

analyzed i n both s ieved gravel samples (Figure 14) and sediment

accumulation (Figure 15). The e f f e c t s o f gabions on the amount o f

f i nes l ess t han 0.30 mm diameter was s im i la r t o t ha t d i scussed above

f o r f i n e s l e s s t h a n 1.2 mm diameter (Figure 14) and f o r f i n e s l e s s

than 3.0 mm diameter (Figure 15).

4.4 Spawner Use

4.4.1 Observed spawning

L o n g i t u d i n a l d i s t r i b u t i o n o f p i n k and chum spawners i n 1982

(Figure 16) ind ica ted tha t the gab ion loca t ions were upstream o f t h e

main concentration o f spawners, with Treatment S i t e I beyond tile

upstream l i m i t s o f p i n k and chum spawning. Fewer salmon were

observed spawning i n 1983 than i n 1982, because 1983 was an " o f f

year " fo r p ink salmon runs and s i tes were monitored only

approximately 10% as o f t e n as i n 1982 (Table 8 ) . Spawner

observations i n 1983 were i n s u f f i c i e n t f o r s i t e comparison. The 1982

coho spawner usage o f Treatment S i t e I was grea ter than tha t i n i t s

con t ro l s (IA and IB; Table 8 ) . Treatment S i t e I1 had more spawning

a c t i v i t y t h a n d i d i t s ( m a r g i n a l h a b i t a t ) C o n t r o l S i t e IIA b u t l e s s

than i t s (p r ime hab i ta t ) Cont ro l S i te IIB. Treatment S i t e I11 had

l e s s spawning a c t i v i t y t h a n e i t h e r o f i t s two c o n t r o l s i t e s (IIIA and

IIIB; Table 8). The e f f e c t o f t h e l o n g i t u d i n a l d i s t r i b u t i o n o f

spawners on s i t e usage i s d iscussed fur ther i n 5.2.2.

The sequence o f spawning a t Sachs Creek was f i r s t chum, then

pink, and f i n a l l y coho salmon. However, t e m p o r a l d i s t r i b u t i o n o f t h e

m a j o r i t y o f t h e p i n k spawning overlapped with the chum and coho.

Chum spawning rarely over lapped with coho. Gradual spawner migra t ion

- 45 -

12

IO

0

6

x 4

a

0 2

W w u LL

v E

a w

a 0.6

v)

PINK

I I

I I

CHUM

r

1 I n

COHO

400 800 DISTANCE

1200 1600 2000 2400 ABOVE ESTUARY ( m 1

FIGURE 16. L o n g i t u d i n a l d i s t r i b u t i o n o f a d u l t s a l m o n i n Sachs Creek, September t o November 1982.

- 46 -

TABLE 8. D i s t r i b u t i o n o f salmon spawning a c t i v i t y on s tudy s i t es a t Sachs Creek, f a l l 1982 and 1983

Sum o f female salmon a c t i v i t y a Avg . Distance 1982

S i te hab i ta t es tuary p ink Spawning above 1982 1983 densi tyb

q u a l i t y (m) Pink Chum Coho c Pink Chum Coho c (No./m2)

Treatment I Contro l I A Marginal Cont ro l IB Prime

Treatment I1 Contro l I I A Marginal Cont ro l I I B Prime

Treatment I11 Cont ro l IIIA Marginal Contro l 1116 Prime

2285

2185

1820

935

1100

985

875

360

575

0

0

0

138

99

342

445

676

894

0

0

0

5

0

3

27

67

186

~~ ~

18 18 0 0 1 1 0

0 0 0 0 1 1 0

14 14 0 0 0 0 0

7 150 1 2 0 3 0.072

7 106 0 0 0 0 0.079

12 357 0 0 0 0 0.27

0 472 0 0 0 0 0.30

14 757 2 4 0 6 0.53

20 1,100 5 5 0 10 0.71

a 1982 values were t h e t o t a l numbers o f observa t ions o f female salmon spawning or redd-defending. Values were t h e t o t a l s o f 53 observation days with in terva ls averaging 1.5 days. I n d i v i d u a l spawners remaining on t h e s i t e were counted several t imes (ca. six) on d i f f e r e n t days. 1983 values were the sums over s ix observat ion days (1-2 week i n t e r v a l s ) ; a d d i t i o n a l f i s h spawned on the s i t es , as evidenced by t h e i r redds.

P ink salmon dens i t y ca l cu la t i ons were based on 42 observation days within a temporal range o f 62 days o f p i n k presence on the si tes. Therefore, each observation represented an average o f 1.5 spawner days. Since pink spawners remain on a s i t e an average o f 10 days (McNeil 1964b), each observation represents 0.15 spawners.

-

- 47 -

up the stream was evident as the lowest s i tes (Contro ls IIIA and

1115) exh ib i ted spawning about 10 days p r i o r t o Treatment S i tes I1

and I11 f u r t h e r upstream.

4.4.2 Probabi l i ty -of -use

Treatment S i t e I1 showed t h e g r e a t e s t s u i t a b i l i t y o f spawning

h a b i t a t i n comparison t o t h a t o f i t s m a r g i n a l h a b i t a t c o n t r o l

(IIA) -- a d i f f e r e n c e o f 440% (Table 9 ) . Treatment S i t e I11 showed

g r e a t e r s u i t a b i l i t y t h a n i t s p r i m e h a b i t a t c o n t r o l ( I I I B ) -- a

d i f f e rence o f 13% -- b u t l e s s t h a n i t s " m a r g i n a l h a b i t a t " c o n t r o l

(IIIA). Probabi l i ty -of -use measurements were made a f t e r Treatment

S i t e I had I t fa i led l1 dur ing the August 1983 f lood (see Section 5,

Discussion). Treatment Site I showed poorer p ink spawning h a b i t a t

t h a n e i t h e r o f i t s c o n t r o l s ( I A and 15).

4.5 Egg Surv iva l

Pink salmon egg su rv i va l s measured i n March were lower than in

December, p a r t i c u l a r l y i n the con t ro l s i tes (Tab le 10). The di f ference i n

s u r v i v a l was p robab ly t he resu l t o f some p i n k f r y emergence from the

gravels between the two sampling periods. Fry emergence p r i o r t o March

sampling was supported by Accumulated Thermal Unit (ATU) ca lcu la t ions .

Salmonid embryo development was propor t ional to water temperature; oetween

250 and 400 ATU's were r e q u i r e d f o r t h e development o f p i n k a l e v i n s from

h a t c h i n g t o emergence (G. Taccogna, personal communication) .5 It was

assumed tha t p ink ha tch ing began about December 1, as 3% o f t he p inK

embryos sampled between December 3 and 8 i n th i s s tudy were recent ly

hatched.

4

One ATU = one degree C day; e.g. an average temperature for 1 day o f 5OC y i e l d s an ATU value = 5. ATU's were approximated by the noon temperatures, as recorded i n Sachs Creek by a ca l i b ra ted Ryan/Peabody continuous recoraing thermograph.

F isher ies and Oceans, Queen Char lo t te C i ty , B.C. 5 G. Tacconga, Community Advisor, Salmonid Enhancement Program, Dept .

- 48 -

TABLE 9. Summary of probabil i ty-of-use by spawning pink salmon on s tudy s i t es a t Sachs Creek, 1-Year p o s t g a b i o n i n s t a l l a t i o n

S i t e Distance

Hab i ta t above Sta t ions Average qua l i t y es tua ry sampled p r o b a b i l i t y a

(m> (N)

Treatment I Cont ro l I A C o n t r o l I B

Treatment I1 Cont ro l IIA Control 116

Treatment I11 Cont ro l IIIA C o n t r o l I I I B

2285 Marginal 21 85 Prime 1820

935 Marginal 1100 Prime 985

875 Marg ina l 360 Prime 575

33 20 20

38 38

40

34 31 40

0.014 0.052 0.051

0.052 0.012 0.15

0.11 0.15 0.091

a Average probab i l i t y -o f -use was the average o f t h e p r o d u c t o f t h e p r o b a b i l i t i e s of four var iab les measured a t each s t a t i o n where t h e i r v a l u e s were determined from probabil i ty-of-use curves (Appendix 1). The probabi l i ty-of-use curves descr ibed by Bovee and Cochnauer (1Y77) and es tab l i shed f o r p ink salmon i n Sachs Creek (Appendix 1) are i nd i ces of " s u i t a b i l i t y t t r a t h e r t h a n a c t u a l " p r o b a b i l i t y " . T h i s i s o w i n g t o a value der ived f rom a curve i s n o t one o f a group o f weights whose c o l l e c t i v e sum equals a p r o b a b i l i t y o f one.

- 49 -

TABLE 10. Summary o f egg survival on s t u d y sites a t Sachs Creek, f a l l and winter 1982-83

Potential survivala Relative survivalb Sampling Average Std. Average Std.

Site period N survival dev. survival dev. (56) (% 1

Treatment I11 Dec. 20 11 10 95 38

March 15 4 . 3 19 a9 37

Control IIIA Dec. 20 11 15 71 36

March 17 1.0 4.1 16 22

Control 1118 Dee. 20 7.9 14 68 27

March 19 1.6 3.7 39 34

a Survival to date of p i n k salmon eggs and alevins from potent ia l egg

b Relative survival of p i n k , chum and coho salmon = deposition.

c l ive eggs and alevins x 100% c l i v e + c dead

- 50 -

Between hatching and the embryo sampling period i n March, the ATU value exceeded 300 (Figure 171, suggesting p i n k emergence was underway p r i o r t o March sampling. The ATU value may have been considerably higher i n the intragravel water than tha t recorded i n the surface; studies i n Carnation Creek ind ica ted tha t a t some locations, subsurface temperatures may be 2.5OC higher than surface water dur ing much o f the winter period, w i t h

local measurements a s much a s 5 .9OC greater (Hartman and Leahy 1983).

W u 5 200-

v) k z 3 -I 150- a E I- 100-

W I

n W

1982 1983

FIGURE 17. Accumulated thermal u n i t s a t Sachs Creek over f a l l and winter 1982-1983.

- 51 -

Another factor that influenced the March survival values was the t i m i n g of egg deposition. P i n k salmon spawning began 10 days l a t e r on Treatment S i t e I11 than a t i ts cont ro l s i tes (IIIA and 1116) ; a corresponding l a t e r emergence may account for some of the higher survival values found there i n March (Table 10). The probable f r y emergence from the gravel prior to the March sampling precluded i ts further analysis; only the egg survival to December was included i n later discussion.

Average egg survival appeared t o be g rea t e r a t Treatment S i t e I11 than a t i t s two controls (Table lo), b u t paired t- test analysis indicated tha t t h i s difference was not significant ( p < .05) for e i ther the re la t ive or the potential survival index (Table 11). An "egg capacity" for p i n k

salmon spawning areas was established from an optimum spawner density of one female p i n k per square metre (McNeil 1964b). - Egg capacity was exceeded i n a l l t h r e e s i t e s sampled, w i t h a proportion of potential deposition i n excess of egg capacity i n the s ta t ions sampled ranging from 10% f o r Treatment Site I11 t o 30% for both of i ts controls (IIIA and IIIB; Table 12). Egg survival a t individual s ta t ions was examined i n a stepwise multiple regression analysis (Rao 1973) to detect correlations w i t h

intragravel dissolved oxygen, intragravel permeability, and depth of gravel scour. Although no s ignif icant ( p < .OS) multiple regressions were found, three simple correlations were indicated. Significant correlations ( p <.05) were found between the index o f r e l a t ive egg survival and three different groups o f intragravel dissolved oxygen measurements: 1) a t Treatment S i t e I11 i n February 1983 (correlation coefficient r=0.54; D.F.=18); 2 ) a t Control S i t e IIIA i n August 1982 (r=0.48; D.F.=18); and 3) a t a combination o f Treatment S i t e 111 and Control S i t e IIIB i n February 1983 (r=0.41; D.F.=37).

During sampling, eggs were frequently encountered w i t h i n 10 cm o f the gravel surface. On fur ther examination of 29 depth samples, approximately one-half of the p i n k eggs were deposited w i t h i n reach o f the hydraulic probe when inserted i n the surface 20 cm of gravel, and the other half when inserted betwen 20 cm and 40 em (Table 13).

- 52 -

TABLE 11. A t - t e s t a n a l y s i s o f egg su rv i va l i n Year 1 on Treatment S i t e I11 and i t s c o n t r o l s a t Sachs Creek

Treatment Control Type o f Mean Std. t d f S i g n i f - S i t e ( X ) s i t e ( Y ) s u r v i v a l a d i f f . dev. icanceb

(X-Y)

I11 IIIA P o t e n t i a l -3.6 18 -0.87 18 N. S. Re la t i ve 0.16 0.50 1.4 18 N.S.

I11 1116 P o t e n t i a l 1.0 12 0.37 18 N. S. Rela t ive 0.14 0.36 1.7 18 N.S.

a Survival from t ime o f depos i t i on t o t he I1eyed1l stage i n December 1982 was expressed by two indices:

i) Potent ia l surv iva l equa ls :

(Number o f l i v e pink eggs sampled) x 100% (Poten t ia l number o f p i n k eggs deposited)

ii) Relat ive surv iva l equals :

(1 l i v e pink, chum and coho sampled) (1 l i v e ) + (1 dead eggs sampled)

b p <.05; one- ta i led pa i red t - tes t ; Ho: X <Y; H1:

[t ( a t p <.05 f o r df=18) = 1.731

x 100%

x> Y.

- 53 -

TABLE 12. Redd superimposition on egg-sampling stations a t Sachs Creek, 1982

S i t e

S ta t ions with Percent o f redd super imposi t iona potent ia l p ink egg

depos i t ion i n By pinks By chum By a l l excess o f p i n k on1 yb and cohoc species egg capaci tyd

Treatment I11 4 0 4

Cont ro l IIIA 10 2 12

Con t ro l I I I B 13 8 16

10

30

30

a 19 s t a t i o n s were sampled f o r egg d e n s i t i e s a t each o f Treatment S i t e I11

b Where p ink dens i t i es exceeded one female per square metre, calculated from and i t s c o n t r o l s .

one redd=lO female spawner days observed. Where chum or coho spawned over previous pink salmon redds.

(McNeil 1964b). - Effect o f super imposi t ion by o ther spec ies was not inc luded d Assuming an optimum egg capaci ty of one female pink per square metre

TABLE 13. V e r t i c a l d i s t r i b u t i o n o f p i n k salmon eggs a t Sachs Creek, December 1982

Egg deptha L i v e p i n k eggsb

Number Percent

Dead eggs

Numoer Percent

0 - 10 10 - 20 20 - 30 30 - 40

38 7 31 3 13 25 279 22 2 80 22

164 38 159 37 37 9 67 1 6

T o t a l 0 - 40 1259 100 427 100

a This was the depth to which the hydraul ic probe was inser ted . It was assumed t h a t eggs from below t h i s d e p t h were n o t drawn t o t h e s u r f a c e by t he bubb l ing ac t ion o f the probe. Eggs below 40 cm were n o t sampled.

b N = 19 s ta t i ons .

- 54 -

4.6 Juvenile Use Coho salmon and rainbow t r o u t were the predominant juvenile salmonids

occurring throughout summer on the s t u d y s i t e s i n Sachs Creek. P i n k and chum salmon fry migrated to s ea soon a f t e r emergence from the gravel i n ear ly spr ing . Before the August 1983 flood, t h e densit ies of juvenile coho and rainbow t rout were 69-92% higher i n the gabion s i t e s than i n their respective control si tes (Table 14 ) . After t h i s flood, the densit ies of juveniles were 91-224% higher i n the gabion s i t e s than i n their respective control si tes (Table 14 ) . The August 1983 flood reduced these populations between 20 and 80% (Table 1 4 ) . Many o f the juveniles (16-77%) marked prior to the f lood were present at the same s i t e afterwards (Table 15). Gabions d i d not appear t o have any consistent e f f ec t on survival ra te of marked juveniles dur ing the flood event (Table 15). The coho lengths most frequently encountered were ident ica l f o r a l l gaDion and cont ro l s i tes i n the lower 2 km of Sachs Creek (Figure 18). Larger coho were more abundant than smaller ones ( s ign i f i can t a t p <.OS) i n the higher slope gradient si tes (Treatment Site I and Control IA; Table 16 and Figure 18).

- 55 -

TABLE 14. Juvenile salmonid usage o f s tudy s i t es on Sachs Creek, pre- and post-f lood, summer 1983

Pre-f lood (July) Post-f lood (August) S i te Loca t ion t Y Pe r e l a t i v e No. Avg. densi tya No. Avg. dens i ty

t o of of gabions s i t e s Coho Coho+Rbb s i t e s Coho Coho+Rb

Treatment: Upstream 3 Between 3 Downstream 2

Tota lC 3

Contro l A 's (marg ina l habi ta t ) 2

Cont ro l B ' S (p r ime hab i ta t ) 3

All Contro ls 5

1.7 1.0 1.3

1 2 2

1.2 1.6 2

3d

0.59 0.82 2

0.82 0.93 2

0.73 0.89 4

0.54 0.43 0.96

0.67 1.1

0.53 0.89

0.16 0.33

0.34 0.56

0.25 0.45

a Density i n f i s h p e r square metre. Rb = Rainbow Trout = Steelhead.

C Data from above categor ies were t o t a l l e d t o c a l c u l a t e o v e r a l l d e n s i t i e s a t t he s i tes .

d T h i s t o t a l i n c l u d e s t h e d e n s i t i e s o f Treatment S i t e I, heav i l y damaged by the 2 August, 1983, flood.

- 56 -

TABLE 15. Juveni le sa lmonid populat ion dynamics through the 2 August, 1983, f l o o d a t Sachs Creek

Locat ion Change i n Recurrence o f marked S i t e re la t i ve popu la t i on dens i t y p re - f l ood f i sha t Y Pe t o

gabions Coho Rbb T o t a l Coho Rainbow T o t a l

Treatments I1 and I11 Combined :

Upstream -53% Between -61% Downstream -26%

1 6% 55% 31 46

T o t a l - 51% +26% -36% 36% 77% 42%

Controls IIA & IIIA (marg ina l hab i ta t ) -84% ?C -70% 59%d ? 43%

Controls 116 & 1116 (p r ime hab i ta t 1 -21% ? -1 9% 27% ? 21%

Treatment I e -92% -34% -76% ? 46% 33%

a Values approximate the proport ion of f ish found on a s i t e b e f o r e t h e f l o o d tha t a re found on t h e same s i t e a f t e r t h e f l o o d , where recurrence =

( p r o p o r t i o n o f marks i n pop. pos t - f lood) x 100% ( p r o p o r t i o n o f pop. marked pre- f lood)

b N.B. r e c r u i t m e n t o f O+ rainbows hatched i n l a t e s p r i n g was inc luded i n post - but not pre- f lood populat ion est imates.

c Sample s i z e was i n s u f f i c i e n t t o ca lcu la te the popu la t ion . When t r o u t d a t a were added t o coho data, a t o t a l was possible.

d A recur rence o f 59% o f t h e coho a t t h e C o n t r o l S i t e s IIA and IIIA was i n c o n f l i c t with the est imated 84% reduc t ion i n coho popu la t ion a t these s i tes . Th is may be f rom e f fec ts o f sampl ing smal l popu la t ions a f te r the f lood (about 14 and 42 respec t i ve l y ) .

e Treatment S i t e I was separated, owing to ex tens i ve damage a t t h i s h i g h energy s i t e .

- 57 -

TABLE 16. A t - t e s t a n a l y s i s o f j u v e n i l e coho length frequencies on study s i t e s a t Sachs Creek, summer 1983

Mean Mean X N l eng th Y N l e n g t h t a d f S i g n i f-

(mm) (m> icanceb

Treat I

Treat I

Cont r IA

Treat I

Treat I

Treat I1

Treat I1

Treat 111

Treat I11

62

62

48

62

62

41

41

99

99

56

56

50

56

56

47

47

47

47

Cont r IA

Contr IB

Contr IB

Treat I1

Treat I11

Contr I IA

Contr I IB

Contr IIIA

Contr IIIB

48

66

66

41

99

40

49

26

26

50

44

44

47

47

43

46

46

47

4.6

11

4.8

7.3

8.1

2.0

0.88

0.31

-0.33

108 Sig .

126 S ig .

112 S ig .

101 Sig .

159 S ig .

79 Sig .

88 N.S.

123 N.S.

123 N.S.

a C a l c u l a t i o n s o f t based on unpaired observations o f i n d i v i d u a l O+ coho salmon lengths. p <.05; one- ta i led t - tes t ; Ho: X <Y; H1: X >Y.

- 58 -

40- n=62 - Treatment I

20- - July 12

0- 4

40. n = 4 9 - Control I A July 12

20-

0- r 1 1 . Control I B July II

40-

20-

0

- n.43 - Treatment I I July 14

r 1 -n A

$ 40-

- Control II A n=41 July 14

> 20-

2 v - !A 0- I $ 9 n= 49 b Control I I B p” 40-

20- la.-

July 13

0- - n=103 40-

20-

0-

Treatment Ill August I

r 1

n=2? Control 111 A 40- July X)

20-

0 - n.26 40-

20-

Control 1 1 1 B July 31

O- 30-35 L 4 ! 42-47 ‘,d “sj 66-71 72-77 78-83 84-89

LENGTH (mm)

FIGURE 18. Juvenile coho length frequencies on s t u d y s i t e s a t Sachs Creek, pre-flood, summer 1983.

- 59 -

5 DISCUSSION

To be successful for stream rehabil i tat ion, gabion weirs should:

i. create streambed conf igurat ions conducive to adul t salmonid spawning;

ii. trap g rave l tha t i s no t sub jec ted to excess ive scour and aggradation

act ion o f s tormf lows;

iii. t r a p g r a v e l t h a t has a qual i ty conducive to h igh egg- to- f ry surv iva l ;

i v . p rov ide a p o o l - r i f f l e c o n f i g u r a t i o n s u i t a b l e f o r r e a r i n g j u v e n i l e

salmonids (coho and steelhead);

v. e x h i b i t an acceptable benef i t /cost ef fect iveness.

The fol lowing discussion considers the ef fect iveness of gabion weirs i n

Sachs Creek i n meeting the above c r i t e r i a .

B e n e f i t s o f g a b i o n i n s t a l l a t i o n i n streams devastated by debris torrents

may be more pronounced than i n many streams with n a t u r a l l y s u i t a b l e spawning

hab i ta t . I n Sachs Creek, t he uppermost gabion s i t e (I) was i n a reg ion

severely af fected by the 1974 debr i s t o r ren t ; t he downstream gab ion s i tes (I1 and 111) d i d n o t appear g rea t l y a f fec ted by the debr is tor rent . A l though i t

was t h e i n t e n t i o n o f t h i s s t u d y t o p r o v i d e r e s u l t s t h a t c o u l d be extrapolated

to other landslide-damaged streams, such extrapolation should only be made

with caution.

5.1 S i t e S t a b i l i t y

Gabions a t 1% slope gradient reaches i n th i s s tudy were beginning t o

s t a b i l i z e entrapped gravels i n the second year af ter cons iderable changes i n s i t e morphology i n t h e f i r s t year. Gravel scour and aggradation was

h i g h a t a l l t h r e e g a b i o n s i t e s d u r i n g s t o r m f l o w s i n t h e f i r s t w i n t e r a f t e r

const ruct ion (Table 1). The changes i n stream morphology caused by gabion

ins ta l la t ion induced scour and fill as the stream approached a new

equ i l i b r i um (Reeves and Roelofs 1982). Reshaping o f gabion s i tes by

stormflows was expected t o decrease over time, owing to se l f -a rmour ing o f

scoured high-f low channels that developed after gabion instal lat ion.

Streambed conf igura t ions appeared t o have achieved an equi l ibr ium i n the

second year , espec ia l l y ev ident a t the s i tes a t 1% slope gradient

(Treatment Sites I1 and 111; Figures 10 and 11).

- 60 -

A s t a t e o f dynamic equilibrium was evident over some of the s t u d y s i t e s when gravels from further upstream replaced those being scoured downstream. Dynamic equilibrium resulted i n gravel scour being registered by vertical erosion monitors, although no net change i n streambed configuration occurred. A successful gabion would reduce the depth of gravel scour t o minimize the physical removal o f salmonid eggs (see 5.3).

Success i n reducing gravel scour was evident a t t h e two lower treatment s i t e s (I1 and 111) over the second season of winter stormflows; the average scour a t Treatment S i t e s I1 and I11 was about the same as the average of the control s i tes (4-5 cm; Table 1). T h i s depth of scour may have directly affected up t o 15% of the p i n k eggs (see 5.3). However, mortality through scour was o n l y one o f several factors that fur ther reduced p i n k egg survival t o approximately lo!% (Table 10). I t would appear that attempting t o s tabi l ize gravel more than the 4-5 cm of scour found i n control si tes (Table 1) may become detrimental t o overall salmonid egg survival, owing t o tradeoffs w i t h beneficial aspects of gravel scour. Engels (1975) concluded that :

Seeking t o t a l s t a b i l i t y of a gravel bar becomes self-defeating, since such permanence can o n l y be obtained by reducing stream velocities t o a p o i n t where the u t i l i t y of a gravel bar as a spawning area is negated due t o i ts being completely buried under f ine sand and si l t . The optimum goal -- t ha t of provid ing reasonable stabil i ty w i t h water veloci t ies still h i g h enough t o prevent burial under sand and s i l t -- requires approximating the natural equilibrium condition noted above [ a s t a t e of semi- or dynamic-equilibrium]. Under such conditions, gradual scour o f a gravel bed is considered b o t h necessary and normal, and Deriodic replenishment o f the gravel s u p p l y must be considered a s a normal maintenance expense.

Gravel scour a t t he upper 3% slope gradient Treatment S i t e I remained above average (12 cm) i n the second year. The substantial decrease i n local streambed gradients at, the gabion s i t e s (Table 3 ) probably was responsible f o r part of the s tab i l iza t ion e f fec t ev ident a t the lower two treatment s i t e s (I1 and 111). By reducing the local slope, gabions reduce the shear stress at the water/gravel interface, causing gravel deposition (Lis le 1981). Although the local streambed gradient of Treatment S i t e I

also decreased after gabion ins ta l la t ion , the h i g h stormflow energy a t

- 61 -

t h i s 3% s l o p e g r a d i e n t s i t e was probab ly su f f i c ien t to p roduce excess ive scour, even a t these reduced local gradients. Some o f t h i s scour i n the

second year may have been induced from an event i n August 1983, which

severely changed t h e c o n f i g u r a t i o n o f Treatment S i t e I. The apparent " fa i lu re" o f T rea tment S i te I was a consequence o f

natural stream dynamics i n t h i s p r e v i o u s l y d e s t a b i l i z e d system. Two new

channels 40 m downstream o f t h e gabions were formed, one dur ing the

1981-82 win ter f loods , the second du r ing t he 1982-83 win ter f loods . The

s teep s lope gradient a t the upst ream end o f these new channels was

main ta ined by o ld bur ied logs and boulders u n t i l t h e August 1983 f lood;

these gave way, r e s u l t i n g i n a more gent le s lope g rad ien t . The e f f e c t o f

t h i s was no t un l i ke "n i ck po in t m ig ra t i on t1 (L. Beaven, personal

communica t ion) ;6 the s teep s lope g rad ien t (n ick po in t ) por t ion o f the

stream channel moved progress ive ly upst ream as mater ia ls a t the base o f

t h i s n i c k p o i n t were washed downstream. T h i s n i c k p o i n t m i g r a t i o n was

tempora r i l y ha l ted a t t he l ower gab ion a t T rea tmen t S i te I. Lack of the

suppor t p rov ided p r i o r t o t he f l ood by streambed mate r ia l aga ins t t he

downstream edge o f t h i s g a b i o n e n a b l e d t h e g a b i o n t o s t a r t r o l l i n g i n t o

i t s now-enlarged plunge pool (Figure 9); the he igh t o f the water fa l l over

th is lower gabion increased f rom the previous 40 cm t o t h e new he igh t o f

90 crn. The gabion responded t o these changes by bowing approximately 1 m

downstream and ro l l i ng app rox ima te l y ZOO o f f t h e v e r t i c a l . Should t h i s

gabion and the upstream one f a i l p r o g r e s s i v e l y , t h i s n i c k p o i n t will

migrate upstream and endanger the foundat ion of a l o g b r i d g e 20 m sbove

the upper gabion.

One problem with t h e V-shaped gabion conf igurat ion was t h a t o f bank

scour. Water changed d i r e c t i o n when encountering gabions, f lowing

perpendicular ly across them. This in t roduced a l a t e r a l component,

d i rect ing streamflow towards the banks. Stormflows resul ted i n

6 L . Beaven, F l u v i a l Geomorphologist, Fish/Forestry Interaction Program, Queen Char lo t te C i ty , B.C.

- 62 -

considerable bank erosion a t t h e downstream corners of the gabion wings. Riprap placement a t s t ra teg ic po in ts a l lev ia ted t h i s problem a t t h e lower two t reatment s i tes (I1 and 111). The nick p o i n t migration a t t h e upper Treatment S i t e I removed r iprap, exposing the two la teral corners t o subsequent erosion (Figure 9 ) .

5.2 Gravel Qual i ty Gabions i n t h i s s t u d y were successful i n creating h i g h quali ty

salmonid embryo and alevin incubational properties i n their entrapped gravels. These h i g h quality incubational properties included suitable: 1) intragravel dissolved oxygen content, 2 ) subsurface water velocities for oxygen provision and metabolic waste removal, and 3 ) salmonid fry access to surface waters for emergence. These properties are not necessarily those that are conducive to adu l t spawning, as discussed i n 5.2.1. Gabions fac i l i t a ted the exchange o f surface/intragravel waters necessary t o meet t hese c r i t e r i a by increasing channel roughness. Vaux (1962, 1968) suggested the factors that controlled t h i s interchange included: 1) the stream surface profile, 2 ) gravel perrneabilities, 3 ) gravel bed depth, and 4 ) i r regular i ty of the streambed surface. His examination o f three cases of streambed profile indicated: 1) no interchange w i t h a s t ra ight surface, 2 ) water flowed out of the gravel at a concave surface, and 3 ) water flowed in to the g rave l a t a convex surface.

Results of intragravel oxygen measurements of t h i s s t u d y were i n agreement w i t h the above f i n d i n g s of Vaux (1962, 1968); intragravel dissolved oxygen was maintained a t a h i g h concentration a t t h e upper treatment s i t e (I) and s ignif icant ly improved w i t h gabion i n s t a l l a t i o n a t Treatment S i t e s I1 and I11 (Tables 5 and 6 ) . Where there was only one convex region of the stream profiles per gabion s i t e prior t o gabion i n s t a l l a t i o n a t t h e t a i l (downstream end) of the upstream pool, there were three convex regions per s i t e a f t e r i n s t a l l a t i o n : 1) a t t h e t a i l of the i n i t i a l pool above the upstream gabions, 2 ) a t t h e t a i l of the plunge pool between the gabions, and 3 ) a t t h e t a i l of the plunge pool downstream of t h e lower gabions (Figures 9 , 10, and 11). Streamflow turbulence was

- 63 -

another factor found t o f a c i l i t a t e t h i s surface/intragravel water interchange (Vaux 1962; Wickett 1962). Turbulence was provided a t t h e gabion s i t e s by the plunge over the gabions.

Gravel composition and intragravel permeabili ty are interrelated factors which affected the s u p p l y of intragravel dissolved oxygen t o incubating salmonid eggs and alevins. The proportion of fine sediments I n stream gravels has been inversely correlated w i t h intragravel dissolved oxygen (McNeil 1969; P h i l l i p s 1971; Langer 1974; Skaugset 1980). T h i s

relationship was a result of a reduced intragravel permeability (and thereby reduced intragravel water velocity) observed when increased fine sediments fi l led intragravel pore spaces (Wickett 1962; Cooper 1974). The negative effects of fine sediments on salmonid egg survival have been extensively documented (Merrell 1962; Shelton and Pollack 1966; djornn 1968; Cooper 1974; Koski 1975; Tagart 1376; Slaney " e t a l . 1977) , and summarized by Cederholm and Salo (1979). I n addition to fine sediments reducing the permeability of the gravels (Wickett 1962), they also may obstruct access to the surface waters for emerging fry (Slaney " e t a l . 1977). The effect of gabion ins ta l la t ion on the composition and

permeability of entrapped streambed gravels was not ciearly demonstrated i n t h i s study; improvement o f gravel quali ty was inconsistent both Detween parameters measured and between gabion sites, as discussed separately below.

5.2.1 Treatment S i t e I Changes i n gravel quality a t Treatment S i t e I could not be

determined, owing to the coarse nature of StreamDed materials prior t o gabion installation; coarse suostrate precluded sampling o f

intragravel permeability and gravel composition before gabion ins ta l la t ion . Sediment t rap analysis was also unavai lable , s ince a l l t r a p s a t Treatment S i t e I were scoured out d u r i n g winter stormflows.

- 64 -

The qual i ty of gravel a t Treatment S i t e I one year af ter gabion ins ta l la t ion can be compared t o t h a t a t o t h e r sites. The proportion of fines i n samples a t Treatment S i t e I was lower than a t f ive other s t u d y s i tes (Figure 14) . On the other hand, Treatment S i t e I had more coarse material than a l l o f the other s t u d y s i t e s sampled except i ts "marginal habitat" Control IA (Figure 13). Permeability 1 year af ter instal la t ion here was above the average of the six s i t e s sampled before instal la t ion b u t below the average of the e ight s i tes sampled 1 year af ter instal la t ion (Table 5). These results suggest that both low f ines and low permeability existed here a f t e r i n s t a l l a t i o n , i n contrast to the observations of Cooper (1974)

and Wickett (1962) tha t a low proportion of fines result i n h i g h

permeability. Because of the h i g h spa t ia l var iab i l i ty i n gravel composition found i n streambeds (Scrivener and Brownlee 19821, the gravel sample size here ( n = 5 ) may have been in su f f i c i en t t o represent the whole s i t e . The problem o f seasonal variabil i ty i n intragravel permeability and gravel composition (Scrivener and Brownlee 1982) was minimized i n the present s t u d y w i t h the sampling of both these parameters d u r i n g the summers.

5.2.2 Treatment S i t e I1

Three gravel quality parameters indicated that gabions improved the quali ty of salmonid egg incubat ion habi ta t a t Treatment S i t e 11. Intragravel permeability and dissolved oxygen b o t h increased after gabion ins ta l la t ion ( see 4.1.2). Sediment t rap analysis suggested there was less sedimentation here than at i ts cont ro l s i tes (IIA and 116; Figure 15). These improvements were not reflected i n the amount of fine sediments i n gravel samples a t t h i s s i t e . No change was detected w i t h gabion in s t a l l a t ion , perhaps a resu l t o f the in i t ia l ly lower proportion of f i n e s a t Treatment S i t e I1 before gabion ins ta l la t ion than a t most other s i tes (Figure 14).

Where the propor t ion of f ines was i n i t i a l l y h i g h , such a s a t

- 65 -

Treatment S i t e 111, t h e amount of f lushing by spawning f i sh and

gravel scour reduced f ines to the low proport ions found at Treatment

S i t e I1 (Figure 14).

5.2.3 Treatment S i t e I11

Three o f t he g rave l qua l i t y pa ramete rs measured ind i ca ted t he

gabions a t Treatment S i t e I11 r e s u l t e d i n i n c r e a s e d q u a l i t y o f

i ncuba t iona l hab i ta t . The f i n e sediments found i n g rave l samples

decreased with gab ion i ns ta l l a t i on (F igu re 14 ) . However, t h e

reduct ions i n f i n e s i n g rave l samples was n o t i n agreement with sediment t rap resul ts. Greater f ine sediment accumulat ion was found

i n sediment traps a t Treatment S i t e I11 when compared t o t h a t o f

Con t ro l S i tes IIIA and I I I B ( F i g u r e 15). Th is con t rad ic t ion may be

an a r t i f a c t o f t h e sediment t rap resu l ts . S ince many o f t h e t r a p s

were l o s t from scouring, those recovered and analyzed were

necessar i l y i n deposi t ional areas and low-scour areas ( < 5 cm). The

higher sediment accumulations a t Treatment S i t e I11 may have r e s u l t e d

f rom a h igher propor t ion o f t raps recovered f rom deposi t ional areas

t h a n t h a t o f i t s c o n t r o l s i t e s (IIIA and I I I B ) . B o t h i n t r a g r a v e l

permeab i l i t y and d isso lved oxygen inc reased a f te r gab ion i ns ta l l a t i on

(Tables 5, 6 and 7 ) . Di f fe ren t p rocesses tha t a f fec t g rave l qua l i t y p robab ly were

i n t e r a c t i n g on the s tudy s i tes. Natura l scour and fill processes

dur ing stormflows sort gravels behind '!roughness elements" such as

gabions (Lis le 1981). Dur ing the receding l imb of the hydrograph,

upwel l ing behind stream obstruct ions keep f i n e sediments i n suspension while coarser gravels deposit i n the prev ious ly scoured

areas. The redd-digging process o f spawning salmon also can reduce

the p ropor t i on o f f i ne sed imen ts i n spawning gravels (McNei l and

Ahnel l 1964; Shapely and Bishop 1965). Although scour during

f reshets may b e s i g n i f i c a n t i n f l u s h i n g f i n e s i n the upper 5-6 cm

(Year 2 average; Table l ) , spawning a c t i v i t y may f l u s h g r a v e l s deeper

than the 25 cm inse r t i on dep th o f the permeabi l i ty standpipe. The

- 66 -

flushing action of u p t o about 150 p i n k s per s i t e (Table 8 ) may be responsible for the apparent increases i n permeaDility observed i n Control S i tes IIIA and IIIB from summer 1982 t o summer 1983. The dominance of the even year p i n k r u n allowed 20 months of f ines accumulation prior t o the 1982 sampling b u t on ly 8 months accumulation prior t o 1983 sampling. A similar seasonal increase i n permeability w i t h spawning ac t iv i ty was found i n Carnation Creek for the pre-logging period (Scrivener and Brownlee 1982). T h i s coincided w i t h a seasonal trend of decreased fines d u r i n g spawning and winter stormflows and an accumulation of f ines over summer.

5.3 Spawner Use The gabions succeeded i n producing gravel beds sui table for salmon

spawning, as indicated by b o t h spawner observations and calculated probability-of-use (see 4.3.3, 4.4, and 4.4.1) . The observed spawning activity indicated gabions had variable effects on s i t e usage compared t o controls. Treatment S i t e I was upstream of p i n k ana chum d i s t r i b u t i o n , b u t had greater coho usage than i ts cont ro l s i tes (IA and I B ; TaDle 8) .

P i n k usage a t Treatment S i t e I1 was greater than i t s marginal control (IIA) , b u t l e s s than its prime control (IIB; Table 8 ) . The greater abundance of p i n k and chum spawners i n lower reaches of Sachs Creek (Figure 16) was probably the cause o f lower observed use of Treatment S i t e I11 than i ts cont ro l s i tes (IIIA and 1116; Table 8 ) . The higher use of Treatment S i t e I11 than Treatment S i t e I1 may be a resu l t of the "drain rock'! on t h e l a t t e r s i t e n o t being of a s i ze a t t r ac t ive t o p i n k spawners.

Probability-of-use calculations for Treatment S i tes I and I1 and their controls were i n agreement w i t h the observed spawning ac t iv i ty (Tables 8 and 9 ) . However, the calculated probability-of-use for Treatment Si te I11 compared t o tha t of i ts controls was n o t i n agreement w i t h the relationship of oDserved spawner usage of Treatment S i t e I11 compared t o t ha t o f i ts controls. Where observed pinK spawner usage of Treatment S i t e I11 was 0.5 t ha t of its control IIIB (Table 8 ) , i t s calculated probaDility-of-use was s l i g h t l y greater than t h i s same control

- 67 -

(Table 9 ) . The e x p l a n a t i o n f o r t h i s c o n t r a d i c t i o n p r o b a b l y l i e s i n t h e

spawner d i s t r i b u t i o n w i t h i n t h e stream. Less than 0.5 as many p ink

spawners were a v a i l a D l e t o spawn on Treatment S i t e I11 as were ava i l ab le

a t C o n t r o l S i t e IIIB (about 4.8 and 11 f ish per metre respect ive ly ;

F igure 16). Adjust ing the observed use o f Treatment S i te I11 by the

i n v e r s e o f t h e r e l a t i o n s h i p o f spawner a v a i l a b i l i t y (2.3) would b r i n g

observed use i n agreement w i th p robab i l i t y -o f -use . S im i la r re la t i onsh ips

were found between Treatment S i t e I11 and Con t ro l S i tes IIB and IIIA, as

explained below:

i.

ii.

iii.

i v .

The r a t i o s o f observed spawning a c t i v i t y o f C o n t r o l S i t e s IIB and

IIIA compared t o t h a t o f Treatment S i t e I11 were 0.90 and 1.8

respec t ive ly (Tab le 8).

The r a t i o s o f spawner a v a i l a b i l i t y on Contro l S i tes IIB and IIIA compared t o Treatment S i t e I11 were approximately 0.64 and 1.3

respec t ive ly (F igure 16).

To account for d i f ferences i n spawner a v a i l a b i l i t y , t h e r a t i o s o f

observed spawning a c t i v i t y i n (i) should be mu l t ip l ied by the

i n v e r s e o f t h e r a t i o s o f spawner a v a i l a b i l i t y I n (ii).

The r a t i o s o f observed spawner a c t i v i t y , when adjusted as i n

( i i i ) , approx imate the ra t ios o f t h e p r o b a b i l i t y - o f - u s e o f C o n t r o l

S i tes IIB and IIIA compared t o t h a t o f Treatment S i t e I11 ( b o t h a t

1.4; Table 9 ) . This suggests that d istance upstream of the estuary af fects spawner

d is t r ibu t ion independent ly o f o ther p robab i l i t y -o f -use fea tures .

Probabi l i ty -of -use ca lcu lat ions should therefore incorporate d is tance

upstream o f the estuary as a usage c r i t e r i a .

Treatment Site I may n o t have had spawning h a b i t a t s u i t a o l e for p ink

salmon (Table 9 ) , owing t o i t s 3% steep s lope gradient and resul tant h igh

energy o f stormflows, even i f p ink and chum spawners could have reached i t

(F igure 7). The l i k e l i h o o d o f e v e r c r e a t i n g a r t i f i c i a l spawning h a b i t a t

i n steep gradient, upper reaches o f llflashyll Queen Char lo t te I s l anos

streams i s poor. However, i n reaches having lower slope gradients (1-2%), gab ions can c rea te hab i ta t su i tab le fo r p ink and chum spawning.

- 68 -

5.4 Egg Surv i va l

Gabions i n th i s s tudy d id no t improve ea r l y su rv i va l o f p ink and chum

salmon i n t h e f i r s t y e a r a f t e r t h e i r i n s t a l l a t i o n . I n contrast , a study

i n Washington suggested that gabions there improved chum egg s u r v i v a l

d u r i n g t h e i r f i r s t y e a r o f o p e r a t i o n (Gerke 1974). The average p ink

salmon egg s u r v i v a l t o December a t Treatment S i t e I11 and i t s two Cont ro l

S i t e s IIIA and I I I B (11, 11, and 7.9% respect ively; Table 10) l i e within

the range o f o ther coas ta l streams. Frequently, 95% o f eggs deposited by

p ink and chum salmon d i e b e f o r e t h e f r y emerge from spawning gravels

( M e r r e l l 1962; McNeil 1966, 1969; Dill 1969; Langer 1974).

The subs tan t i a l d i f f e rence i n p ink salmon egg su rv i va l ca l cu la ted by

the two ind i ces used i n t h i s s t u d y ( r e l a t i v e egg s u r v i v a l was on average

68% higher than the egg su rv i va l f r om po ten t i a l egg deposit ion; December

values, Table 10) i nd i ca ted a h igh degree o f egg loss from the gravels.

The re la t ive surv iva l index d id not account for these egg losses. Both

b i o l o g i c a l and phys ica l fac to rs a f fec t sa lmon id egg s u r v i v a l . B i o l o g i c a l

fac to rs inc lude p redat ion by b i rds , f i sh , and i n s e c t s , n o n - f e r t i l i z a t i o n

o f egg, and redd superimposition. Redd superimposit ion egg losses resu l t

f r o m l a t e a r r i v a l spawners d igg ing new redds on top o f p rev ious ly

constructed redds. Physical-chemical factors that af fect salmonid egg

su rv i va l i nc lude g rave l scou r and gravel qual i ty. Extreme winter low

f lows and f reez ing were not considered a problem i n Sachs Creek i n

1982-83. A l l o f these factors have substant ia l ly reduced egg s u r v i v a l i n

events described elsewhere (McNeil 1969). Redd superimposit ion occurred

a t about 70% o f t h e s t a t i o n s sampled i n the two c o n t r o l s i t e s (IIIA and

1116) and a t about 20% o f t h e s t a t i o n s sampled a t Treatment S i t e I11

(Table 12) . This suggested t h a t even f o r an average size pink run,

spawning h a b i t a t was l i m i t i n g a t Sachs Creek. Less redd superimposition

occurred at Treatment Si te 111, probably due t o i t being fur ther upstream

beyond t h e peak density area for p ink spawners (F igure 16). I n a d d i t i o n

to t he phys i ca l remova l o f p rev ious l y spawned eggs, redd superimposit ion

a l so may have: 1) shocked the very sens i t ive eggs t h a t had not developed

t o t h e eyed stsge, o r 2) i f the eggs were eyed, r e d i s t r i b u t e d them

v e r t i c a l l y , making them more vu lnerab le to subsequent loss through gravel

scour.

- 69 -

Egg loss through gravel scour would be re la ted to the depth a t which

t h e eggs were deposi ted and the depth to which the gravels were scoured.

L i v e eggs were d i s t r i b u t e d f a i r l y e v e n l y down t o a dep th o f 40 cm, b u t

dead eggs were more common near the sur face (70% i n t h e t o p 20 cm;

Table 13). Observations from the Kodiak archipelago suggest that pinks

t h e r e i n i t i a l l y d e p o s i t e d eggs between 10 cm and 25 cm (K. Manthey,

personal communication) ; a l t e r a t i o n o f s i m i l a r d i s t r i b u t i o n s by g rave l

scour, aggradation, or redd superimposition probably produced the

d i s t r i b u t i o n found i n t h i s s t u d y . The predominance o f dead eggs near the

surface suggested redd superimposition was a t l e a s t p a r t i a l l y r e s p o n s i b l e ,

with m o r t a l i t y a consequence o f t h e j a r r i n g i n v o l v e d .

The depth o f g rave l scou r i n severa l " f lashy t1 Queen Char lo t te I s l ands

streams tend t o be high. Prel iminary egg depth measurements by FFIP

suggested t h a t o f t h e 65 s t a t i o n s measured, 15-20% o f t h e coho eggs and

3G% o f t h e chum eggs may have been d i r e c t l y a f f e c t e d b y g r a v e l s c o u r

( D . Tripp, personal communication) .8 Gravel scour i n t h e c o n t r o l s i t e s

a t Sachs Creek averaged 5.1 cm over winter i n t h e f i r s t year and 4.5 cm i n

the second year (Table 1). Gravel scour may therefore have accounted for

up t o 15% o f t h e p i n k egg m o r t a l i t y i n t h e c o n t r o l s i t e s a t Sachs Creek

for these years (Table 13). Although i t appeared t h a t a f t e r 2 years the

gabions here d id not reduce egg loss as a r e s u l t o f reduced gravel scour

(Table 11, t h e q u a l i t y o f t he g rave l f o r i ncuba t ion o f the remaining eggs

( > 85%) and a lev ins was improved by gabion i n s t a l l a t i o n ( T a b l e 17). I n th i s s tudy , i n t rag rave l d i sso l ved oxygen was found t o be

s i g n i f i c a n t l y c o r r e l a t e d with t h e i n d e x o f r e l a t i v e egg s u r v i v a l

(Table 13). Th is re la t i onsh ip was not detected with t h e i n d e x o f s u r v i v a l

f rom potent ia l deposi t ion, probably owing to the overwhelming in f luence o f

7 K. Manthey, Area Management Biologist, Kodiak Area, Alaska Dept . F ish and Game.

8 D. T r ipp , B io log i s t , F i sh /Fo res t r y I n te rac t i on Program, Vancouver, B.C.

- 70 -

egg loss ( >80%) on th is index; i .e . , oxygen depr i va t i on appeared a

s ign i f i can t source o f mor ta l i t y to those eggs t h a t had no t been phys i ca l l y

removed from the gravels (<20%). Other var iables such as intragravel

permeabi l i ty and depth of gravel scour may indeed have a f fec ted egg

s u r v i v a l i n Sachs Creek, bu t t he complex nature (with poss ib le syne rg i s t i c

e f f e c t s ) i n which a l l t hese f ac to rs i n te r re la te cou ld no t be modeled with

the mu l t ip le regress ion ana lys is app l ied .

5.5 Juveni le Use

Two main areas o f b e n e f i t s were offered by gabions i n th i s s tudy :

1) an improvement i n p ink and chum salmon spawning/incubation habitat, and

2) an improvement i n j u v e n i l e coho salmon and rainbow t r o u t (or steelhead)

rear ing hab i ta t . S ince juven i le sa lmon id dens i t ies were no t measured p r i o r t o gabion insta l la t ion, ev idence for improvement i n rea r ing hab i ta t

was indicated through deduct ion.

S u b s t a n t i a l l y h i g h e r j u v e n i l e d e n s i t i e s were found a t gabion s i t e s

than a t con t ro l s i t es (Tab le 14). H igh juven i le dens i t ies a t the gab ion

s i t e s i n th is study were i n agreement with increased coho d e n s i t i e s a t

gabion s i tes (here used as current def lectors) p laced on o ther coas ta l

streams (Ward and Slaney 1981). The a b i l i t y o f g a b i o n s i t e s t o

accommodate h ighe r j uven i l e dens i t i es was ind i ca ted by the l eng th

frequencies o f t h e O+ coho. I n other studies, coho s i z e was inve rse l y

c o r r e l a t e d t o t h e i r d e n s i t y ( F r a s e r 1969). One could therefore expect

t h a t coho lengths a t gab ion s i tes (h igher juven i le dens i t ies ) would be

l e s s t h a n a t t h e c o n t r o l s i t e s ( l o w e r d e n s i t i e s ) . However, coho lengths

a t the gab ion s i tes tended to be g rea ter than a t con t ro l s i tes

( s ign i f i can t l y g rea te r t han t h ree o f t he s i x con t ro l s i t es ; p <.05; Table

16 and F igure 18). The a b i l i t y o f gab ion s i t es t o accommodate more and

la rge r j uven i l es sugges t t ha t phys i ca l d i f f e rences a t t he s i t es a re

r e s p o n s i b l e f o r t h i s g r e a t e r use. I f i t can be shown that gabions

produced these physical d i f ferences, one can conclude that gabions

improved rear ing habi tat .

- 71 -

Salmonid rearing habitat requirements varied between species and

changed with season. I n i n t e r - s p e c i e s t e r r i t o r i a l c o n f r o n t a t i o n s , Hartman

(1965) found that coho were more successful i n l ower ve loc i t y llpoolsll and

steelhead were more successful i n h ighe r ve loc i t y " r i f f l es t1 . Bus ta rd and

Narver (1975a) - found that as stream temperatures decreased i n winter ,

these feeding posi t ions descr ibed by Hartman (1965) were exchanged f o r

hab i ta t c lose r t o cove r . I n winter , O+ coho were associated more with

organic cover, and O+ steelhead with rubble (Bustard and Narver 1975b- -7

Ward and Slaney 1981). The present study suggested that gabions increased

r e a r i n g h a b i t a t d i v e r s i t y because two a d d i t i o n a l p o o l - r i f f l e sequences

were c r e a t e d a t each s i t e (see 4.1.1). T h i s d i v e r s i t y f a c i l i t a t e d

in ter -species resource par t i t ion ing by prov id ing separate areas

bes t - su i ted f o r each species. A t the gab ion s i tes bo th r ip rap and bou lder

rubble below the plunge pools provided some win ter hab i ta t fo r s tee lhead.

Placement o f boulders i n coastal streams has been found t o improve

s tee lhead w in te r hab i ta t (Ward and Slaney 1979). The nooks and crannies

within the gabion s t ructures themselves s imi lar ly prov ided cover . For coho winter habi ta t , gabion s i tes prov ided some organic deDris cover.

However, t h e a d d i t i o n o f rootwads anchored i n t h e plunge pools would

g r e a t l y augment j u v e n i l e coho w in te r and summer h a b i t a t (G. Hartman,

personal communication). 9

The f l o o d on 2 August, 1983, i n Sachs Creek provided an unexpected o p p o r t u n i t y t o examine f l ood re la ted j uven i l e sa lmon id popu la t i on

dynamics. As ant ic ipated, the largest decrease i n coho popu la t ion (-9246)

occur red a t t he uppermost Treatment S i t e I (Table 15) where energy o f t h e

stormflow was grea ter than a t o ther s i tes . Th is was suggested Py t h e 3%

steep s lope gradient and s u b s t a n t i a l changes i n s i t e c o n f i g u r a t i o n ( s e e

Sect ion 5). Tne 51% decrease i n j u v e n i l e coho p o p u l a t i o n a t t h e o t h e r two

t rea tment s i tes (I1 and 111) was less t han t he 84% decrease a t t h e

marg ina l con t ro l s i t es (IIA and IIIA) but g rea ter than the 21% decrease a t

G. Hartman, Co-ordinator, Carnation Creek Watershed Stud ies , Pac i f i c B i o l o g i c a l S t a t i o n , Nanaimo, B.C.

- 72 -

the pr ime spawning habi tat control s i tes (116 and 116; Table 15). Despite

these major changes i n coho populations, many j u v e n i l e s resumed t h e i r

feeding s ta t ions on the same s i tes a f te r t he f l ood . The p r o p o r t i o n o f

j uven i l es marked i n the pre- f lood sampl ing that were accounted f o r d u r i n g

the post-flood sampling ranged from about 30 t o 60% between t h e s i t e s

(Table 15) ; that o f the two gabion s i tes again was between t h a t o f t h e i r

con t ro l s i t es (Tab le 15).

5.6 Summary o f P o s i t i v e and Nega t i ve E f fec ts o f Gabions

The e f f e c t s o f g a b i o n i n s t a l l a t i o n on the physical-chemical and

b io log ica l parameters measured on s tudy s i tes i n Sachs Creek were b r i e f l y

summarized i n Table 17. I n re la t ion to sa lmon id p roduc t ion , the

bene f i c ia l e f fec ts o f gab ions on gravel scour and streambed slope

gradients outweighed the negat ive three to one. S i m i l a r l y , g r a v e l q u a l i t y

parameters showing benef ic ia l e f fects o f gabions outweighed those with

negat ive by e igh t to two.

I n summar iz ing the e f fects o f gabions on spawner use (Table 171, the

observed spawning uses were ad jus ted f o r l ong i tud ina l spawner d i s t r i b u t i o n

(see 5.2.3). The ca lcu la ted p robab i l i t y -o f -use was entered unadjusted.

The e f fec ts o f gab ions on s u i t a b i l i t y o f spawning h a b i t a t was va r iab le

with one p o s i t i v e i n d i c a t o r , t h r e e n e u t r a l , and two negative.

Both o f the egg s u r v i v a l i n d i c e s showed b e n e f i c i a l e f f e c t s o f g a b i o n s

(Table 17). The i n d i c a t i o n o f 11 pos i t i ve t o t h ree nega t i ve

physical-chemical effects of gabions (Table 17) suggest that future egg

s u r v i v a l a t g a b i o n s i t e s may be expected t o be greater than that observed

i n t h i s study i n t h e f i r s t year o f operat ion. S imi lar ly , on ly benef ic ia l

e f fec ts o f gab ions on juveni le salmonid product ion were found by t h i s

study.

I n summing t h e p o s i t i v e and negat ive a t t r ibutes per s i te , Treatment

S i t e I ranked lowest with f i v e p o s i t i v e t o t h r e e n e g a t i v e i n d i c a t o r s ,

probably owing t o t h e e f f e c t s o f a steep (3%) slope gradient. Treatment

S i t e s I1 (seven pos i t i ve t o one negative) and I11 ( e i g h t t o one) i nd i ca ted

there were s u b s t a n t i a l s i t e improvements with g a b i o n i n s t a l l a t i o n a t t h e s e

s i t es . The o v e r a l l r a t i o o f 20 p o s i t i v e t o f i ve negat ive suggest tha t

- 73 -

TABLE 17. A summary o f t h e e f f e c t s of gab ion i ns ta l l a t i on on major physical-chemical condi t ions and t h e i r r e l a t i o n t o salmonid product ion i n Sachs Creek

Parameter Treatment I Treatment I1 Treatment I11

Site stability: Scour (Year 2 ) >control

( - )

reduced ( + )

=control ( = )

reduced ( + I

=controls ( = )

reduced ( + I

Slope gradient

Gravel quality: Dissolved oxygen decreased

( - 1 increased

( + )

increased ( + I

increased ( + )

increased ( + I

( = I =controls Permeability -""

Sites for spawning increased ( + I

increased ( + I

Fines low ( = )

large decrease ( + I

>controls ( - 1

Sediments in traps ""_ Spawner use: Observed >cntrls:coho

( + I

<controls ( - 1

<controls ( - 1

betw'n cntrls ( = )

between cntrls ( = )

between cntrls ( = )

Probability-of-use

Egg survival: Relative index >controls

( + I _""

Potential index >controls ( + I

""_ Juvenile use: Density >controls

( + I >controls

( + ) > controls

( + I

Pools riffles > controls ( + I

> controls ( + I

> controls ( + I

Totals: Positive 5 Neutral 1 Negative 3

7 3 1

8 4 1

Grand total: Positive = 20 Negative = 5

- 74 -

gabions may be an e f f e c t i v e way t o r e h a b i l i t a t e streams. However,

recommendations f o r f u r t h e r a p p l i c a t i o n may be determined by t h e i r c o s t

e f fect iveness.

5.7 Prel iminary Benef i t Cost Analysis

The c o s t s o f t h e p r o j e c t were d i v i d e d i n t o s i x c a t e g o r i e s , as l i s t e d

i n Table 18. There was an obv ious t rend o f decreas ing ins ta l la t ion cos ts

with exper ience o f ins ta l la t ion ( f rom $5200 t o $3800 t o $3000; f i r s t t o

l as t ) f o r t he t h ree t rea tmen t s i t es . The cost per metre o f gabion

i n s t a l l e d s i m i l a r l y decreased with experience (from $105/m t o $89/m t o

$85/m).

The costs were no t rep resen ta t i ve o f what should be expected i n an

opera t iona l sense. The cont rac tor employed t o excavate the s i tes discounted his equipment t ime 30%. The p r o j e c t was b i l l e d a r a t e o f

$50/hour rather than the normal $70/hour f o r the excavator. Considerable

cos t was a lso saved by us ing s lack t ime on the excavator; the excavator

operator loaded and hauled gravel dur ing the per iods he could not do

instream work. Many cont rac tors would have charged fo r bo th machines.

Resul tant cont ractor costs , therefore, were est imated at about 50% of

actua l costs . The projected non-discounted costs were inc luded i n

Table 18.

Manpower fo r gab ion cons t ruc t ion was suppl ied through F isher ies

Employment Br idging Assistance Program (Pro jec t No. 566). While t h i s

assistance made th is p ro jec t poss ib le , cons iderab le reduc t ion i n man-days

probably would have occurred i f a non-"job creation" labour force had been

used. Some loss o f p r o d u c t i v i t y was also evident through short work days,

owing to ex tens i ve t rave l t ime . I t was es t imated tha t t ra ined manpower

would have completed t h e j o b i n t w o - t h i r d s of the t ime expended. A

r e a l i s t i c c o s t f o r h i r e d manpower on the Queen Charlotte Islands would be

$80 per day (1982). Using these f igures, the projected manpower c o s t s f o r

gab ion i ns ta l l a t i on a re g i ven i n Table 18.

- 75 -

TABLE 18. Gabion i n s t a l l a t i o n c o s t s a t Sachs Creek

Treatment S i t e #: I I1 I11 T o t a l

Dates worked August 1982: 7-23 24-29 9-17

1) Gabions: l eng th ( m ) : Cost del ivered:

43 $ 954

50 $1086

35 $ 882

128 $ 2 922

2 ) Excavation: hours: 8 $50/hour: costs:

15.5 $ 775

20 $1000

12 $ 600

47.5 $ 2 375

3 ) Spawning gravel: Hauling: hours: 8 $50/hour: cost: Dis t r ibut ing: hours: 8 $50/hour: cost:

11.5

5 $ 250

$ 575 10

$ 500 6

$ 300

5.5 $ 275

4 $ 200

27 $ 1 350

15 $ 750

4 ) Equipment t ranspor t : $ 58 $ 58 $ 174

5 ) Sorted rock-del ivered: $ 0 950 $ 400 $ 1 350

6 ) Labour: man-days: 8 $45/rnan-day : cos t :

27 $1215

30 $1350

14 630

71 $ 3 195

$382 7 $5244 $2985 $12 057 Tota l cos t :

Tota l cost per gabion Length (per m) : $ 89 $ 105 $ 85 $ 94

Pro jec ted costs: Contractor 's d iscount : Labour: man-days: Cost @ $80/day:

$1658 18

$1439

$1858 20

$1600

$1133 10

$ 800

$ 4 649 48

$ 3 840

$5709 $7352 $4288 Tota l p ro jec ted cos ts : $17 349

- 76 -

Several hundred cubic metres o f g r a v e l and rock were used on t h e

gabion s i tes. The m a j o r i t y o f t h i s g rave l was donated from a nearby

MacMi l lan B loede l g rave l p i t . Th is mater ia l was u n s o r t e d r i v e r run

g rave l . I n i t i a l l y , conce rn was expressed that the f ines component o f t h e

p i t g r a v e l was h i g h and cou ld i n f l uence egg su rv i va l . To prevent th is , 21

m o f so r ted "d ra in rock1 ' (between 2 cm and 15 cm diameter) was

purchased and d i s t r i bu ted ove r a par t ia l ly surcharged Treatment S i te 11.

The h igh cos t o f t he d ra in rock (app rox ima te l y $600 de l i vered) de ter red

f u r t h e r u s e o f t h i s m a t e r i a l on Treatment S i t e s I and 111. The d r a i n r o c k

may have been respons ib le f o r t he l ower p ropor t i on (d i l u t i on ) o f f i nes i n

the surcharged mater ia ls o f T rea tment S i te I1 compared with Treatment

S i t e s I and espec ia l l y I11 (September 1982; F igu re 14). The a b i l i t y o f

t he s t ream to remove these f ines by the June 1983 sampling would suggest

t h a t t h e o v e r a l l d i l u t i o n e f f e c t o f t h i s dra in rock on egg s u r v i v a l was

n e g l i g i b l e .

3

I n f i l l i n g t h e gabions, l o c a l r o c k l a r g e r t h a n 10 cm diameter was

used before commercial ly sorted rock was purchased. Although there was

s u f f i c i e n t l o c a l m a t e r i a l a t Treatment S i t e I, $350 and $400 worth o f

so r ted rock was needed a t Treatment S i t e s I1 and I11 respec t i ve l y

(Table 18).

The c o s t e f f e c t i v e n e s s o f g a b i o n i n s t a l l a t i o n i n Sachs Creek remains

pre l iminary to date. A l though the costs are known, the inc rease i n f i s h

product ion and the longevi ty of the gabions are not . Gabion longevi ty i s

dependent on b o t h t h e i n t e g r i t y o f t h e s t r u c t u r e and t he res i s tance o f t he

w i re mesh to abras ion and rust. S imi lar s t ructures have wi thstood f loods

o f 100-year r e t u r n p e r i o d s i n Oregon (Anderson 1981). Longevity o f t h e

gabions i n t h i s s t u d y may be dependent on t h e l o c a l s l o p e g r a d i e n t o f t h e

stream. The dynamic na ture o f s t ream morphology i n h igher g rad ien t

reaches ( >2%), especial ly those rendered unstable from poor streamside

logg ing or debr is to r ren ts as a t T rea tment S i te I (see Section 5), reduced

t h e l i k e l i h o o d o f adequate s t ructure longevi ty . However, t h e a b i l i t y o f

s t ruc tu res i n t h e 1% slope g rad ien t reaches to w i ths tand the August 1983

f lood w i thout sh i f t ing suggested tha t gab ions a t low s lope g rad ien t s i tes

- 77 -

may have a l o n g e v i t y o f a few decades. A b r a s i o n a l s o was more p reva len t a t the h i g h e r g r a d i e n t g a b i o n s i t e i n this s tudy (Trea tment S i te I ) t h a n a t t h e lower gabions (Trea tment Sites I1 and 111). Abrasion was found only on the g a l v a n i z e d c o a t i n g o n the ups t r eam exposed po r t ions o f the gab ion mesh. R u s t i n g o f t h e mesh was n o t e v i d e n t b u t may limit the u s e f u l l i f e o f the s t r u c t u r e s .

The economic values of some o f the b e n e f i t s a n d c o s t s o f g a b i o n s were n o t c a l c u l a t e d b e c a u s e o f t h e u n c e r t a i n n a t u r e o f these f a c t o r s . One such c o s t was f i n e s e d i m e n t i n p u t d u r i n g g a b i o n c o n s t r u c t i o n . The suspended sed imen t s were estimated t o have exceeded 400 ppm ( 3 . Lamb, p e r s o n a l communication)" during streambed e x c a v a t i o n . S e t t l e m e n t o f the s e d i m e n t s was r a p i d , w i t h a c c u m u l a t i o n s u p t o 2 cm d e e p i n backwater areas immediately downstream of the s i tes . These were f lushed f rom the system d u r i n g the first minor stormflow. The effects here were similar t o t h o s e described f o r e x c a v a t i o n i n o t h e r c o a s t a l streams by Ward and Slaney ( 1979) .

B e n e f i t s o f g a b i o n s described i n p r e v i o u s s e c t i o n s a b o v e i n c l u d e d a n t i c i p a t e d i n c r e a s e s i n s a l m o n i d e g g - t o - f r y s u r v i v a l a n d i n c r e a s e s i n j u v e n i l e s a l m o n i d summer d e n s i t i e s a n d r e a r i n g h a b i t a t . I n a d d i t i o n , many a d u l t salmon were observed l lholdingl l o r r e s t i n g i n water ponded upstream o f the g a b i o n s i n a u t u m n 1982 and 1983. A n o t h e r b e n e f i t may be a n increase i n stream benthos p r o d u c t i v i t y e x p e c t e d w i t h r i p a r i a n v e g e t a t i o n r e m o v a l d u r i n g g a b i o n i n s t a l l a t i o n ; the l o c a l i z e d i n c r e a s e d s u n l i g h t i n p u t t o t h i s no r the rn co ld -wa te r stream may improve a lga l and ben thos p r o d u c t i o n , p r o v i d i n g more f o o d f o r r e a r i n g j u v e n i l e s a l m o n i d s ( D u b o w i t s 1979). Although gabions may make s i g n i f i c a n t c o n t r i b u t i o n s t o f i s h

p r o d u c t i o n t h r o u g h the b e n e f i t s described above, i t is on ly t h rough a n t i c i p a t e d i n c r e a s e s i n p i n k s a l m o n e g g s u r v i v a l t h a t the fo l lowing b e n e f i t / c o s t a n a l y s i s was made. The a c t u a l c o s t e f f i c i e n c y o f g a b i o n s would probably be g r e a t e r t h a n the f o l l o w i n g a n a l y s i s s u g g e s t s i f the o t h e r b e n e f i t s o f g a b i o n s were i n c l u d e d .

lo J . Lamb, Habitat P ro tec t ion , Dep t . Fisheries and Oceans, Nanaimo, B.C.

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A bene f i t / cos t ana lys i s was made t o determine what product ion goals

were requ i red t o o f f se t gab ion cons t ruc t i on cos ts , with s e n s i t i v i t y

expressed over t h e i r expected ranges. Treatment S i t e I11 was used f o r

t h i s a n a l y s i s because: 1) i t was t h e l a s t and hence least expensive

gabion s i t e , h a v i n g t h e b e n e f i t o f p r e v i o u s i n s t a l l a t i o n e x p e r i e n c e ; and

2 ) i t had s u f f i c i e n t spawner usage t o enable egg sampling. C r i t e r i a

considered i n the analys is are out l ined be low.

5.7.1 Bene f i t s

i. Pink spawner use of Treatment S i t e I11 was 60 females

(120 adul ts) i n 1982. After adjustment for e f f e c t s o f

l o n g i t u d i n a l spawner d i s t r i b u t i o n , a c t u a l usage o f

Treatment S i t e I11 was i n t e r m e d i a t e b e t w e e n t h a t o f i t s controls (see 5 .2 .3 ) . Hence, benef i ts f rom increased

spawner usage were no t i nc luded i n the bene f i t / cos t

analys is .

ii. Egg s u r v i v a l within Treatment S i t e I11 appeared higher t h a n t h a t o f bo th Con t ro l S i tes IIIA and I I IB . Inc reases

i n average egg s u r v i v a l were assumed t o have an equal

e f f e c t on increases o f r e t u r n i n g a d u l t s (e.g., a 100%

increase i n egg su rv i va l wou ld y ie ld an add i t i ona l 100%

o f t h e o r i g i n a l number o f f i sh spawning on t h e s i t e [120 adu l t s ] and re tu rn ing as adu l t s ) . An e x p l o i t a t i o n r a t e

f o r a d u l t p i n k salmon r e t u r n i n g t o t h e e a s t c o a s t o f t h e

Queen Charlot te Is lands averaged 56% over the past 10 years (S. Wright, personal communication). 11

iii. Current who lesa le p r ices o f p ink salmon were assumed t o

be $8.87 per p iece for net caught, and $6.00 per p iece

f o r t r o l l caught i n 1982 dollars.'' These f i gu res were

based on t h e 1976 p r o v i n c i a l c a t c h and ad jus ted fo r

11 S. Wright, Evaluation Economist, Dept. Fisheries and Oceans, Vancouver, B.C.

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i n f l a t i o n t o 1982 values. O f the p ink salmon caught i n

the Queen Char lo t te Is lands area, 96% were net caught and

4% were t r o l l caught. The adjusted wholesale price

averaged $8.76 per piece.

i v . Over the l i f espan of the gabions, an equal increase i n

p ink adu l t s was assumed forthcoming every other year.

Ana lys i s sens i t i v i t y was shown f o r l ongev i t i es o f 6, 12,

and 18 years.

5.7.2 Costs

i. The i n i t i a l c o n s t r u c t i o n c o s t o f Treatment S i t e I11

p r o j e c t e d t o r e f l e c t r e a l c o s t s was used ($4288;

Table 18). However, const ruct ion costs may cont inue to

decrease with experience.

ii. Once ins ta l l ed , gab ion s i t es were expected t o r e q u i r e no

a d d i t i o n a l work and maintenance cos ts were assumed zero.

iii. Subsequent costs included harvest ing and process ing o f

the increase i n return ing adul ts . Harvest ing costs i n

1982 do l la rs12 were $0.61 p e r p i e c e f o r t r o l l caught

and $0.19 per p iece for net caught, averaging $0.21 per

piece (adjusted f o r propor t ion net and t r o l l caught; see

5.7). Processing costs were $2.38 p e r p i e c e f o r t r o l l caught and $2.75 per piece for net caught, averaging

$2.75 per piece. Processing costs included acquisit ion,

in-plant processing, and marketing costs. The combined

harves t ing and processing costs averaged $2.95 per piece.

A d iscount ing ra te o f lo%, w i t h s e n s i t i v i t y a t 5 and 15%, was

used f o r both costs and benef i ts accrued over the gabion l i fespans

shown. This procedure brought future values to present value. If i n t e r e s t r a t e s were mainta ined a t leve ls lower than lo%, t h e f u t u r e

l2 I b i d .

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net benefits indicated i n t h i s s t u d y would be conservative to what may be expected (Table 1 9 ) . Similarly, i f the net values rose as a resu l t o f pr ice increases a f te r a l l cap t ia l cos t s were incurred d u r i n g construction, future benefits would be greater than expected.

Increases i n returning adult p i n k salmon required to offset gabion construction costs are summarized i n Table 19. A t a 10%

discount rate w i t h a gabion longevity of 1 2 seasons, 375 f i sh additional t o the 120 i n i t i a l l y spawning on the s i te are required bienially (major p i n k r u n s a re on even years only). A production of t h i s magnitude (about four times natural survival) may be at ta inable for gabion s i t e s , a resul t of improvements of gravel quality, w i t h

anticipated increases i n egg-to-fry survival as discussed above. Achievement o f cost effectiveness becomes more probable a t lower in t e re s t r a t e s and greater longevities (Table 19) and when benefits of gabions other than increases i n p i n k salmon egg-to-fry survival are.also considered. Lack of higher spawner usage of the gabion s i t e s (Table 17 ) suggested tha t no benefits would oe derived througn e f f ec t s of gabions on spawning habitat . However, gabion s i t e s w i t h

fewer spawners would require s t i l l greater improvements i n egg-to-fry survival to offset construction costs. The assumption tha t egg-to-fry survival was the l i m i t i n g factor i n smolt production appeared reasonaole, because o f the tlimmediatell seaward migration o f

fry emerging from the spawning gravels. However, mortality i n the ocean may yield a disproportionately lower return i n adul ts for increase i n smolt production (Peterman 1982).

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TABLE 19. Increases i n r e t u r n i n g p i n k s r e q u i r e d t o o f f s e t i n s t a l l a t i o n c o s t s for Treatment S i t e I11 a t Sachs Creek

Add i t i ona l number o f r e t u r n i n g a d u l t s r e q u i r e d b ienn ia l l y to recover cons t ruc t ion cos tsa

Number o f f i s h R e l a t i v e i n c r e a s e b

Discount rate: 5% 10% 15% 5% 10% 15%

GaPion longev i t y

6 years 4 18 5 20 6 32 348% 4 33% 527%

12 years 273 375 495 228% 312% 413%

18 years 2 17 325 4 52 180% 271% 377%

a Ca lcu la t ions o f requ i red re tu rns a re d iscussed i n Appendix B. b Increase i n production expressed as percent o f t h e i n i t i a l 120 spawners on

t h e s i t e i n 1982.

- a2 -

6 . CONCLUSIONS AND RECOMMENDATIONS

Gabion weirs met the f ive cri teria required of a successful stream rehabilitation technique as outlined early i n Section 5 :

i. Gabion weirs surcharged w i t h gravel created streambed configurations yielding moderate quali ty spawning habi ta t for p i n k and chum salmon i n s i t e s a t 1% slope gradient reaches. T h i s was demonstrated th rough b o t h observed spawner usage and calculated probability-of-use. Although another s i t e a t 3% slope gradient was used by coho spawners, i t was not suitable for p i n k spawners.

ii. Longitudinal p i n k salmon d i s t r i b u t i o n was independent of other probability-of-use features. Future site evaluations should include distance upstream of the estuary as a probability-of-use criterion.

iii. S tab i l i t y o f gravels entrapped by the gabions a t t h e two 1% slope gradient s i tes was demonstrated i n the second year after considerable s i t e reshaping by stormflows i n t he f i r s t yea r . However, the short duration of t h i s s t u d y precluded conclusions on g r a v e l s t a b i l i t y a t gabion s i t e s d u r i n g major stormflow events. The gabion s i t e a t 3%

slope gradient fa i led to s tabi l ize gravels , because of tne h i g h

energy of stormflows there. i v . Qual i ty of the surcharged and natural gravels entrapped oy the gabion

s i t e s was conducive t o h i g h egg-to-fry survival. Intragravel dissolved oxygen and gravel composition measurements indicated either improved or good incubational habitat. However, intragravel permeability and sedimentation measurements were inconsistent i n evaluating t h i s habi ta t . The apparent I1stability1l a t t h e gabion s i t e s a t 1% slope gradient i n the second year suggested that the h i g h

egg survival demonstrated here d u r i n g an l lunstablel l f i rs t year would yield substantial increases i n the future.

v . Juvenile salmonid rearing habitat was created w i t h the development of two additional pool/riffle sequences per gabion site. The good quality of t h i s habi ta t was demonstrated by h i g h juveni le densi t ies a t t he gabion s i t e s (average 1.6 per square metre) compared to t he control si tes (average 0.9 per square metre).

- 83 -

v i . Pre l im inary benef i t l cos t ana lys is p ro jec ted the requ i red inc reases i n

p ink salmon product ion for var ious gabion longevi t ies (e.g.,

approximately a 300% increase over a l o n g e v i t y o f 12 years). Cost

e f fect iveness may be a t ta inab le , espec ia l l y a t l ower i n te res t ra tes

and grea ter gab ion longev i t ies , ow ing to the e f fec ts o f h igh qua l i t y

and s t a b i l i t y o f gravels entrapped at the gabion s i tes i n increas ing

egg su rv i va l ; no b e n e f i t s were derived from spawner usage.

Recommendations for fu ture appl icat ion o f gabion wei rs adapted f rom the

e i g h t c r i t e r i a r e v i e w e d by Moreau (1981) are as fol lows:

i. Select a straight stream sect ion.

ii. Selec t a section wider than average channel width.

iii. The stream reach should have gradual ly s lop ing banks, p re fe rab ly with

an over f low ( f lood) p la in .

iv . Local channel s lope should be s l ight .

v. S i te subs t ra te shou ld be s l i gh t l y l a rge r t han des i red .

v i . The t a i l o f a poo l i s s u i t a b l e if t h e c r i t e r i a above are met.

v i i . The s i t e must have good access.

v i i i . Where we i rs a re to be p laced i n ser ies, p lace the downstream we i r

such t h a t t h e t o p o f t h e downstream weir i s l e v e l w i t h t h e base o f

the upstream weir.

Additional recommendations suggested by th is study include:

i x . Select downstream reaches within peak d i s t r i b u t i o n s o f spawning p i n k

salmon.

x. L i m i t streambed slope gradients t o < 2% (as i n [ i v ] above) i n

" f lashy" coastal streams.

x i . Generously r i p r a p t h e banks a t and below t h e p o i n t s t o which the

gabions are keyed, t o p r e v e n t l a t e r a l bank scour around the ends o f

the gabions.

x i i . The in te rgab ion d is tance shou ld equa l a t leas t 1.5 times the wetted

w id th o f t he s t ream to a l l ow su f f i c i en t l eng th o f p lunge poo l

upstream o f t h e entrapment area o f the downstream gabion.

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x i i i . Splash aprons are more u s e f u l i n the la te ra l w ing reg ions than near

t h e apex o f t h e gabions.

x iv. Further research may be bes t d i rec ted i n " f ine-tuningtt gabion

conf igurat ions to maximize areas o f pr ime spawning habi ta t .

xv. Low-cost procedures fo r m in im iz ing suspendea sediment re lease dur ing

instream excavation should be developed.

xv i . S i te cons t ruc t i on shou ld be du r ing an t t o f f t t p ink yea r t o a l l ow

reshaping from 1 year o f stormflows and so s t a b i l i z e t h e s i t e p r i o r

t o heavy spawner usage.

- 85 -

7 LITERATURE CITED

Anderson, J.W. 1981. Anadromous f i s h p r o j e c t s 1981. U.S. Dep. Agric., Bureau Land Manage., Coos Bay D i s t r i c t , Oregon.

Anderson, J.W. and 3.5. Cameron. 1980. The use o f gabions t o improve aquatic hab i ta t . U.S. Dep. Agric., Bureau Land Manage. Tech. Note No. 342.

Bjornn, T.C. 1968. Surv iva l and emergence o f t r o u t and salmon f r y i n var ious gravel-sand mixtures. In: Logging and salmon forum, Alaska Dep. F i s h and Game, Juneau, A l a s k z

Bovee, K.D. and T. Cochnauer. 1977. Development and evaluation of weighted c r i t e r i a - p r o b a b i l i t y o f use curves for instream flow assessments: f i sher ies . U.S. Dep. Agr ic . F ish and W i l d l i f e Serv., Coop. Instream Flow Serv. Group No. 77/63.

Bustard, D.R. 1983. Queen Char lo t te Is lands s t ream rehabi l i ta t ion s tud ies: a review of techniques and a proposed program f o r 1982. Fish/Forestry I n t e r a c t i o n Program. Res. Rep. 9 , Vancouver, B.C.

Bustard, D.R. and D.W. Narver. 1975a. Aspects o f the w in te r eco logy o f j uven i l e coho salmon (OncorhyncEus k isutch) and s tee lhead t rout (Salmo ga i rdne r i ) . 3. Fish. Res. Board. Can. 32:667-680.

. 1975b. Preferences o f i u v e n i l e coho salmon (Oncorhvnchus k isu tch) snd c u t t h r o a t t r o u t ( S a l i o c l a r k i ) r e l a t i v e t o s i m u l s t e d a l t e r a t i o n o f w i n t e r h a b i t a t . J. Fish. Res. Board Can. 32:681-687.

Cederholm, C.J. and E.O. Salo. 1979. The e f fec ts o f l ogg ing road l ands l i de s i l t a t i o n on the salmon and t r o u t spawning gravels of Stequaleho Creek and the Clearwater River basin, Jef ferson County, Washington, 1972-1978. Final Report-Part 111. Univ. Washington, College Fish., FRI-UW-7915.

Cooper, A.C. 1974. Physica l aspects o f sediment i n r e l a t i o n t o s u r v i v a l o f salmon eggs. In: Symposium on Stream Ecology. Centre f o r Cont. Ed., Univ. B r i t i s h Columbia, Vancouver, B.C.

Dill, L.M. 1969. The sub-gravel behaviour o f P a c i f i c salmon larvae. In: Symposium o f Salmon and Trout i n Streams. T.G. Northcote (editor). H.R. MacMil lan Lect. Series. Univ. Bri t ish Columbia, Vancouver, B.C.

Dubowits, 0. 1979. Logging e f fects : cont rary to popular be l ie f , not every logging aftermath harms f i sh habi ta t . B.C. Lumberman (Nov) 1979:12-13, 68.

Engels, J.D. 1975. Use o f gabions i n stream habitat improvement. U.S. Dep. Agric. Bureau Land Manage., Eugene, Oregon.

- 86 -

Everest, F.H. and W.R. Meehan. 1981. Forest management and anadromous f i s h hab i ta t p roduc t iv i t y . In: Trans. 46 Nor th Amer. Wildlf. Nat. Resour. Conf. 1981, Washington, D.C.

-

Fraser, F.J. 1969. Populat ion densi ty ef fects on s u r v i v a l and growth of j uven i l e coho salmon and s tee lhead t rout i n experimental stream channels. - In: Symposium on Salmon and Trout i n Streams. T.G. Nor thco te (ed i to r ) . H.R. MacMil lan Lect. Ser ies. , Univ. Br i t ish Columbia, Vancouver, B.C.

Gangmark, H.A. and R.B. Bakkala. 1960. A comparative study o f uns tab le and s t a b l e ( a r t i f i c i a l channel) spawning streams fo r incubat ing k ing salmon a t Mill Creek. C a l i f . F i s h and Game 46(2) :151-164

Gerke, R.J. 1974. Salmonid spawning hab i ta t improvement study. S t a t e o f Washington, Dep. F isher ies, Olympia, Wash.

Hal l , J.D. and C.O. Baker. 1982. Rehab i l i t a t i ng and enhancing stream habi ta t : rev iew and evaluat ion. In: Inf luence of forest and rangeland management on anadromous f i s h h a b i z t i n Western Nor th America. W.R. Meehan (ed i to r ) . U.S. Dep. Agric. For. Serv., Gen. Tech. Rep. FWW-138.

Hartman, G.F. 1965. The r o l e of behaviour i n the ecoloav and i n t e r a c t i o n of underyearl ing coho salmon (Oncorhynchus kisutch) and-steelhead trout (Salmo ga i rdner i ) . 3. Fish. Res. Board. Can. 22:1035-1081.

Hartman, G.F. ( e d i t o r ) . 1982. Proceedings of the Carnat ion Creek workshop: a ten year review. Feb. 24-26. Malaspina College, Nanaimo, B.C.

Hartman, G.F. and R.M. Leahy. 1983. Some temperature character ist ics of stream and in t ra-gravel water i n Carnation Creek, B r i t i s h Columbia. Canadian Rep. Fisher ies Aquat ic Sci . No. 1731.

Heede, B.H. 1972. Flow and channel character is t ics of two high mountain streams. U.S. Dep. Agric. For. Serv., Res. Pap. RM-96.

Koski, K.V. 1975. The s u r v i v a l and f i t ness of two stocks of chum salmon (Oncorhynchus keta) from egg d e p o s i t i o n t o emergence i n a con t ro l l ed stream environment a t B i g Beef Creek. Ph.D. thesis. Univ. Washilngton, Seat t le , Wash.

Langer, O.E. 1974. E f fec ts o f sed imenta t ion on salmonid stream l i f e . In: Symposium on Stream Ecology, Centre fo r Cont inu ing Ed., Univ. B r i t i 3 Columbia, Vancouver, B.C.

L i s l e , T.E. 1981. Roughness elements; a key resource t o improve anadromous f i s h h a b i t a t . In: Propagation, enhancement, and r e h a b i l i t a t i o n o f anadromous sa lmE id popu la t i on hab i ta t i n t h e P a c i f i c Northwest. T. J. Hassler (ed i tor ) . Symp. Proc. Am. Fish. Soc., Oct. 15-17, Humboldt S ta te Univ., Arcata, Calif.

- 87 -

McNeil, W.J. 1964a. A method f o r measuring m o r t a l i t y o f p i n k salmon eggs and larvae. U.S. F i s h W i l d l i f e Serv., F ish . Bu l l . 63(3):575-588.

. 1964b. - Redd superimposit ion and egg ca r ry ing capac i t y o f p ink spawning beds. J. Fish. Res. Board Can. 21:1385-1396.

. 1966. E f f e c t o f t h e spawning bed environment on reproduction o f p i n k and chum salmon. U.S. F i s h W i l d l i f e Serv., Fish. Bul l . 65:495-523.

. 1968. Migra t ion and d i s t r i b u t i o n o f pink salmon spawners i n Sashin Creek i n 1965, and s u r v i v a l o f t h e i r progeny. U.S. F i s h W i l d l i f e Serv., Fish. Bull. 66:575-586.

. 1969. S u r v i v a l o f p i n k and chum salmon eggs and alevins. In: Symposium on Salmon and Trout i n Streams. T.G. Nor thco te (ed i to r ) . HX. MacMil lan Lect. Series, Univ. Bri t ish Columbia, Vancouver, B.C.

McNeil, W.J. and W.H. Ahnell. 1964. Success o f pink spawning r e l a t i v e t o s i z e o f spawning bed mater ia ls. U.S. F i s h W i l d l i f e Serv., Spec. Rep. Fish. 469:l-15.

Mer re l l , T.R. Jr. 1962. Freshwater surv iva l o f pink salmon a t Sashin Creek, Alaska. In: Symposium on Pink Salmon. N. J. Wilimovsky (editor). H.R. MacMi l lanTect . Ser ies, Univ . Br i t ish Columbia, Vancouver, 6. C.

Mersereau, R.C. and C.T. Dyrness. 1972. Accelerated mass wast ing a f te r logging and slash burning i n Western Oregon. J . S o i l and Water Conserv. 27(3):112.

Moreau, J.K. 1981. Gravel entrapment and s t r u c t u r a l s t a b i l i t y o f a VI-shaped gabion weir design i n Nor thern Ca l i fo rn ia streams. M.Sc. thesis . Humboldt Sta te Univ., Arcata, Cal i f .

Moring, J.R. 1975. The Alsea watershed study: effects o f logging on the aquat ic resources o f 3 headwater streams o f t h e Alsea River, Oregon. Oregon Dep. F i sh W i ld l i f e , Co rva l l i s , Oreg. Fishery Research Rep. No. 9.

OILoughlin, C.L. 1972. A p re l im ina ry s tudy o f l ands l i des i n the coast mountains o f southwestern B r i t i s h Columbia. In: Mountain geomorphology. H. 0. Slaymaker and H. 3. McPherson (ed i to rs ) . 6 .C. Geographical Series

- 14:101-111.

Peterman, R. 1982. Nonl inear re la t ion between smolts and adu l ts i n 8abine Lake sockeye salmon (Oncorhynchus nerka) and imp l ica t ions fo r o ther salmon populat ions. Can. J. Fish. Aquat. Sci. 39:904-913.

- 88 -

P h i l l i p s , R.W. 1970. E f f e c t s of sediment on the growel environment and f i s h product ion i n f o r e s t l a n d uses and stream env. Symposium Proc. O.S.U.

Rand, M.C., A.E. Greenberg and M. J. Taras (edi tors) . 1975. Standard methods for the examinat ion of water and wastewater. Am. Pub. Health Assn. Washington, D.C., 14th Edi t ion.

Rao, C.R. 1973. L i n e a r s t a t i s t i c a l i n f e r e n c e and i t s appl icat ions. Wiley, New York, 2nd Ed i t i on .

Reeves, G.H. and T.D. Roelofs. 1982. Rehab i l i t a t i ng and enhancing stream h a b i t a t : f i e l d a p p l i c a t i o n s . In: Inf luence of forest and rangeland management on anadromous f i s h h x i t a t i n Western North America. W.R. Meehan ( e d i t o r ) . U.S. Dep. Agric. For. Serv., Gen. Tech. Rep. PNW-140.

Scrivener, J.C. and M.J. Brownlee. 1982. Analysis of Carnation Creek gravel-qual i ty data, 1973-1981. In: Proceedings of the Carnat ion Creek workshop; a ten year reveiw. G.FTHartman ( e d i t o r ) . Feb. 24-26, Malaspina College, Nanaimo, B.C.

Shapely, P.S. and D.M. Bishop. 1965. Sedimentation i n a salmon stream. J. Fish. Res. Board Can. 22(4) :919-928.

Shelton, J.M. and R.D. Pol lock. 1966. S i l t a t i o n and egg s u r v i v a l i n incubation channels. Trans. Amer. Fish. SOC. 95(2) :183-187.

Skaugset, A.E. 1980. Fine organic debr is and dissolved oxygen i n streambed gravels i n the Oregon Coast range. Masters thesis, O.S.U. 96 p.

Slaney, P.A., T.G. Halsey and A.F. Tautz. 1977. E f f e c t s o f fo res t harves t ing p rac t i ces on spawning h a b i t a t of stream salmonids i n Centennial Creek watershed, B r i t i s h Columbia. B.C. F i s h W i l d l i f e Br., Fish. Manage. Rep. No. 73.

Swanson, F.J., G.W. Lienkaemper and J.R. Sedell . 1976. His tory , phys ica l e f fec ts and management i m p l i c a t i o n s of large organic debr is i n western Oregon streams. U.S. Dep. Agric. For. Serv., Gen. Tech. Rep. PNW-56.

Swanston, D.N. and F.J. Swanson. 1976. Timber harvesting, mass erosion and steepland forest geomorphology i n the Paci f ic Northwest. In: Geomorphology and engineering. D.R. Coates ( e d i t o r ) . All?% and Unwin Inc., Winchester, Mass.

Tagart, J.V. 1976. The surv iva l f rom egg depos i t i on t o emergence of coho salmon i n the Clearwater River, Jefferson County, Washington. M.Sc. thesis. Univ. Washington, Seatt le, Wash.

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Terhune, L.D.B. 1958. The Mark V I groundwater standpipe for measuring seepage through salmon spawning gravel. J. Fish. Res. Board Can. 15 ( 5 ) : 1027-1063.

Vaux, W.G. 1962. Interchange o f stream and intergravel water i n a salmon spawning r i f f l e . U.S. F i s h W i l d l i f e Serv., Spec. Rep. Fish. No. 405.

. 1968. In t ragrave l f low and interchange i n a streambed. U.S. F i s h W i l d l i f e Serv., F ish . Bu l l . 66:479-489.

Ward, W.H. 1982. Pat r i ck Creek f i s h h a b i t a t improvement. Del Norte Country, Ca l i fo rn ia . U.S. Dep. Agric. For. Serv. Six Rivers National Forest, 1982.

Ward, B.R. and P.A. Slaney. 1979. Evaluation of in-stream enhancement s t ruc tu res fo r the p roduc t ion o f juven i le s tee lhead t rou t and coho salmon i n the Keough River: progress 1977 and 1978. 6.C. Min. Environ., Fish. Tech. Circ. No. 45.

. 1981. Further evaluat ions o f s t ructures for the improvement o f salmonid rear ing habi tat i n coastal streams o f B r i t i s h Columbia. In: Propagation, enhancement, and r e h a b i l i t a t i o n o f anadromous sa lmon iF populat ions and h a b i t a t i n t h e P a c i f i c Northwest. T.J. Hassler (ed i tor ) . Symp. Proc. Am. Fish. SOC., Oct. 15-17, Humboldt State Univ., Arcata, C a l i f .

Wickett, W.P. 1958. The rev iew o f ce r ta in env i ronmen ta l f ac to rs a f fec t i ng the p roduc t i on o f p ink and chum salmon. J. F i sh Res. Board Can. 15:1103-1126.

. 1952. Env i ronmenta l var iab i l i t y and reproduct ion potent ia ls o f p ink salmon i n B r i t i s h Columbia. In: Symposium on Pink Salmon. N.J. W i l i m o v s k y ( e d i t o r ) . H.R. MacMillG Lect. Series, Univ . Br i t i sh Columbia . Vancouver, B.C.

Wi l ford, D.J. and J.W. Schwab. 1982. S o i l mass movements i n the Rennell Sound area, Queen Char lo t te I s l ands , B r i t i sh Columbia. In : Proc. Canadian Hydrology Symp. on Hydrological Processes on FoGsted Areas. June 1982. Freder icton, N.B.

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0

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APPENDIX 2. Calculations of benefit/cost analysis for S i t e I11 a t Sachs Creek.

' Treatment

The increase i n p i n k salmon production required t o o f f s e t i n i t i a l gabion construction costs was derived below. The average wholesale price of $8.76 per piece less the average harvesting and processing costs of $2.95 per piece yields a net benefit of $5.81 per piece (discussion and assumptions i n 5.7). Discount r a t e s of 5, 10, and 15% were applied t o a l l values incurred after year zero t o br ing future values to present worth. All values were i n 1982 dollars.

Additional f i s h required per Net benefits per f i s h spawning year t o recover costsa

Harvestedb Returningc

Discount Rate: S% 10% 15% 5% 10% 15% 5% 10% 15%

0 2 4 6 8

10 12 14

16 18 20

$ 0 5.27 4.78 4.34 3.93

$18.32

$ 3.57 3.24 2.93

$28.06

$ 2.66 2.41 2.19

$35.32

"""

"""

"""

$ 0 4.80 3.97 3.28 2.71

$14.76

$ 2.24

1.53

$20.38

$ 1.26 1.05

.86

$23.55

"""

1. a5

"""

"""

$ 0 4.39 3.32 2.51 1.90

$12.12 234

$ 1.44 1.09

.82

"""

"""

$15.47 153

$ .62 .47 .36

"""

$16.92 121

291

210

182

354

277

253

418

273

21 7

520

375

325

632

495

452

a P ink salmon adults returning i n year x are the progeny o f spawners i n year x-2. Major p i n k r u n s are on even years only. The i n i t i a l gabion costs ($4288) were divided by the sum of net benefits per f i s h for the desired number o f years t o calculate how many adults addi t iona l to the in i t ia l 120 would be required to be harvested per spawning year t o recover construction costs; e.g., after discounting at 10% for 14 years the net benefits o f one f i s h every spawning year ($20.38) yield a requirement o f ($4288/$20.38 =) 210 f i s h every other year.

C The number o f additional f i s h required for harvest are adjusted t o account f o r an exploi ta t ion ra te of 56%, e.g., 210/.56=375.

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APPENDIX 3. Photographic plates o f gab ion s i t es a t Sachs Creek, 1.5 years pos t - ins ta l la t ion , February 1984

Treatment S i t e I: Note the en larged water fa l l over the downstream gabion ( a r e s u l t o f "n ickpoint migrat ion") . Large s ize o f subst rate was a consequence of t he h igh energy a t t h i s 3% s lope g rad ien t s i te .

Treatment S i t e I: The downstream l e f t gabion wing that responded t o t h e above changes by bowing approximately 1 m downstream and ro l l i ng app rox ima te l y 20° in to the p lunge pool .

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Treatment S i t e 11: Note vigorous growth where streambank was seeded and f e r t i l i z e d .

Treatment S i t e 11: Looking upstream. Note tile gravel bar formed downstream o f the gabions.

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Treatment S i t e 111: Note scoured bank on f a r s i d e and r i p r a p placement where gabions were keyed i n t o t h e bank. The water l e v e l a t t h i s s i t e was ra i sed by spruce blowdowns on r i g h t o f photograph and subsequent upstream gravel bar formation.

Treatment S i t e 111: Looking upstream, the old l o g jam a t the bo t tom o f photograph i s d e f l e c t i n g t h e stream, r e s u l t i n g i n a deep scour pool i n f r o n t .

Queen's Printer for Bmsh Columbia 'C Victoria, 1986

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Gabion Evaluation for Salmonid · Gabion Evaluation for Salmonid Enhancement in a Landslide Impacted Stream on the Queen Charlotte Islands, British Columbia by H.D. Klassen Fish Forestry