HomeMy WebLinkAboutAPA1935ALASKA DEPARTMENT OF FISH AND GAME
SUSITNA HYDRQ AQUATIC STUDIES REPORT SERIES
September 1984
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Document No.1935
Susitna File No.4.3.1.6
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ALASKA DEPARTMENT OF FISH AND GAME
SUSITNA HYDRO AQUATIC STUDIES
REPORT NO.3
AQUATIC HABITAT AND INSTREAM FLOW
INVESTIGAT10NS (MAY-OCTOBER 1983)
Chapter 8:An Evaluation of Passage Conditions for
Adult Salmol';in SJcUJghs 2inQ Side Channels
of the Middle Susitna River
Edited by;
Christopher C.Estes
and
Douglas S.Vincent-Lang
Prepared tor;
ALASKA POWER AUTHORITY
334 W.FIFTH AVE.ARLISANCHORAGE,ALASKA 99501
Alaska Resources
. . &InformatlOn ServlcesLIbrary..kAnchorage,Alas a
ABY QOES'fiOIfS OR COMMBRTS COHCERRI:HG
'!IlLS RBPORlJI SHOULD BE DmBCTBD '1'0
'mE ALASD POWER AtnBORI:fi
SUS:I'ftJA PROJ~ORICB
PREFACE
This report is one of a series of reports prepared for the Alaska Power
Authority (APA)by the Alaska Department of Fish and Game (ADF&G)to
provide information to be used in evaluating the feasibility of the
proposed Susitna Hydroelectric Project.The ADF&G Susitna Hydro Aquatic
Studies program was initiated in November 1980.The five year study
program was divided into three study sections:Adult Anadromous Fish
Studies (AA),Resident and Juvenile Anadromous Studies (RJ),and Aquatic
Habitat and Instream Flow Studies (AH).Reports prepared by the ADF&G
prior to 1983 on this subject are available from the APA.
The information in this report surnnarizes the findings of the 1983 open
water field season investigations.Beginning with the 1983 reports,all
reports were sequentially numbered as part of the Alaska Department of
Fish and Game Susitna Hydro Aquatic Studies Report Series.
TITLES IN THE 1983 SERIES
Report
Number
1
2
Publication
Title Date=-=-=----
Adult Anadromous Fish Investigations:April 1984
May -October 1983
Resident and Juvenile Anadromous Fish July 1984
Investigations:May -October 1983
3
4
Aquatic Habitat and Instream Flow
Investigations:May -October 1983
Access and Transmission Corridor Aquatic
Investigations:May -October 1983
1984
1984
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....
.....
This report,"Aquatic Habitat and Instream Flow Investigations"is
divided into two parts.Part I,the "Hydrologic and Water Quality
Investigations ll
,is a compilation of the physical and chemical data
collected by th ADF&G Su Hydro Aquatic Studies team during 1983.These
data are arranged by individual variables and geographic location for
ease of access to user agencies.The combined data set represents the
available physical habitat of the study area withln the Cook Inlet to
Oshetna River reach of the Susitna River.Part II,the "Adult Anadro-
mous Fish Habitat Investigations",describes the subset of available
habitat compil ed in Part 1 that is util i zed by adult anadromous fi sh
studied in the middle and lower Susitna River (Cook Inlet to Devil
Canyon)study area.Jhe studies primarily emphasize the utilization of
side slough and side channel habitats of the middle reach of the Susitna
River for spawning (Figure A).It represents the first stage of
development for an instream flow relationships analysis report which
will be prepared by E.W.Trihey and Associates.
ARLIS
Alaska Resources
.Library &InfonnatIOn ServICes
Anchorage,Alaska
]1 )'1 1 -J J ]1 1 -1 1 )
MID OLE REACH
ADF 8G FIELD CAMPS
OVERALL STUDY AREA
r.ITI]
•
MAP AREA
o 25
I I
miles
-'Ct .....;
Figure A.Susitna River drainage basin.
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CONTENTS OF REPORT NO.3
Part One
Chapter
1 Stage and Discharge Investigations.
2 Channel Geometry Investigations.
3 Continuous Water Temperature Investigations.
4 Water Quality Investigations.
Part Two
Chapter
5 Eulachon Spawning in the Lower Susitna River.
6 An Evaluation of Passage Conditions for Adult Salmon in
Sloughs and Side Channels of the Middle Susitna River.
7 An Evaluation of Chum and Sockeye Salmon Spawning Habitat in
Sloughs and Side Channels of the Middle Susitna River.
8 An Evaluation of Salmon Spawning Habitat in Selected Tributary
Mouth Habitats of the Middle Susitna River.
-
9 Habitat Suitability Criteria for Chinook.Coho.and Pink
Salmon Spawning.
10 The Effectiveness of Infrared Thermal Imagery Techniques·for
Detecting Upwelling Groundwater.
Questions concerning this and prior reports should be directed to:
Alaska Power Authority
334 W.5th Avenue
Anchorage.Alaska 99501
Telephone -(907)276-0001
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AN EVALUATION OF PASSAGE CONDITIONS FOR ADULT SALMON
IN SLOUGHS AND SIDE CHANNELS OF THE MIDDLE SUSITNA RIVER
1984 Report,Chapter 6
By:
Joseph S.Sautner
and
Leonard J.Vining
Alaska Department of Fish and Game
Susitna Hydro Aquatic Studies
2207 Spenard Road
Anchorage,Alaska 99503
and
Larry A.Rundquist
Woodward-Clyde Consultants
ABSTRACT
An interim evaluation of passage conditions for adult Pacific salmon
into and within twelve slough and side channel sites in the middle reach
of the Susitna River is presented to determine the effects of mainstem
discharge on passage conditions into these habitat types.These habi-
tats were selected for evaluation as they are affected by mainstem
Susitna River discharges.A final evaluation will be completed in FY85.
The sites account for the majority of chum,sockeye and pink salmon
which spawn in sloughs and side channels in this reach.The evaluation
of salmon passage conditions at each site included the effects of
mainstem breaching discharge and backwater staging,and slough flo\'/s
(local flows)derived from local water sources·(e.g.,upwelling,tribu-
taries,precipitation).Timing and distribution patterns of salmon were
also evaluated as they relate to passage conditions and flow patterns in
the Susitna River system.
-
....Daily salmon catch data at three fishwheel sites on the mainstem river
were compared to mean daily discharge levels.These discharge data and
survey counts of peak numbers of 1ive and dead salmon in sloughs and
side channels indicate that the period from 20 August to 20 September is
a critical period for providing passage into and within slough and side
channel sites from the mainstem Susitna River.All analyses of passage
were therefore restricted to this time period.
Reaches within study sites which were restrictive to salmon passage
(passage reaches)were identified at each site on the basis of water
depth requirements for passage by salmon.Depth requirements for
successful passage increase with and increase in the length of a pas-
sage.The analyses of breaching and backwater discharges and local flow
effects on passage reaches were conducted independently ard their
relative importance is reported on a site by site basis.In general,
breaching discharges affect all passage reaches within a site simulta-
neously;whereas,backwater staging usually affects only one or two
passage reaches in the lower portion of a site.Local flow requirements
may affect all passage reaches,but vary among sites and among passage
reaches.These variations in local flow requirements are due to spatial
variations in sources of local flow.
i;
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....'
TABLE OF CONTENTS
ABSTRACT.•. . •••••. . . . . •. ••••. ••. . . . . . •••••. •... . •. . . •. . ••. . •. . . . . . . i
TABLE OF CONTENTS..................................................iii
LIST OF FIGURES................................................................................vi
LIST OF APPENDIX FIGURES •••.•..••..•••.•••••..•••....•..••.•..••..•vi i i
LIST OF TABLES •••••••••••••••••••••••~•••••••••••••••••••••••••••••xiii
1.0 INTRODUCTION..................................................6-1
1.1 Background 6-1
1.2 Objective •••.••.•.•...•...••...•...••.•....•.•.••..•..••.6-5
2.0 METHODS....................................•.••••..•.......••..6-6
2.1 Site Selection •.•.••••.••••......••...••..•.•.•.......•..6-6
2.2 Timing and Distribution of Salmon •..•••..•.........•....6-6
2.2.1 Mainstem Sites .••.•.•...•••••••..•••......•..•....6-6
2.2.2 Slough and Side Channel Sites •.............••...•.6-7
2.3 Passage of Salmon........................................6-7
2.3.1 Field Methods.....................................6-8
2.3.1.1 Thalweg Surveys...........................6-8
2.3.1.2 Cross Secti ona 1 Profil es.. . •••. . •. . . . . . . . .6-8
2.3.1.3 Stage and Flow Measurements 6-10
2.3.2 Analytical Methods .............•......••...•......6-10
2.3.2.1 Definitions of Fish Passage Criteria ....•.6-10
2.3.2.2 Identification of Passage Reaches 6-16
2.3.2.3 Evaluation of Passage Reaches ..:6-17
2.3.2.3.1 Breaching ....••.................6-17
2.3.2.3.2 Backwater ......•...........•..•.6-17
2.3.2.3.3 Local Flow 6-21
iii
3.0 RESULTS
3.1 Timing and Distribution of Salmon ••..••••••••.•••...•.•.•6-27
3.1.1 Mainstem Sites ••••••••.••.•..••••...••..•..••.••..6-27
3.1.2 Slough and Side Channel Sites •.••.••••.•.••••••.••6-27
3.2 Passage of Salmon •..••••••.•••••••.•••..••••••••.•..•.•••6-27
~I
""'.
4.0
3.2.1 Breaching and Backwater Discharges ••••..•.••.••••..6-38
3.2.2 Local Flow •.••••••.•••..•.....•..•.•.••....••..•••.6-38
DISCUSSION ..••••..•••••••••••••..••••..•..•••..•.••.•.•.••.•..6-45
4.1 Assumptions and Limitations of Analyses ••••.•..•••••••.•.6-45
4.1.1 Passage Criteria Assumptions and Limitations 6-45
4.1.2 Analytical Assumptions and Limitations •••....•••••6-46
4.2 Timing 6-47
4.3 Passage Conditions at Study Sites •..••.•...•.....•....•••6-47
4.3.1 Slough Sites •.•••...•..•..••...••......•.•........6-47
4.3.1.1 Whiskers Creek Slough ....•...••••.•.•••...6-47
4.3.1.2 Slough 8A .••...•..•.•.....••..••....••.•..6-48
4.3.1.3 Slough g••••••.••...•.•••..•.•.......•....6-48
4.3.1.4 Slough 9A ••...•..•...•.•............•...•.6-49
4.3.1.5 Slough 11 .....•.••...•..••.•..............6-50
4.3.1.6 Slough 20 ..••..........•..•....••.........6-50
4.3.1.7 Slough 21 .•.•......••.....•••..•.•........6-51
4.3.1.8 Slough 22 .•.....•.••...•••............•...6-52
4.3.2 Side Channel Sites .....••....•...•.•..•...........6-53
4.3.2.1 Mainstem 2 Side Channel.6-53
4.3.2.2 Side Channel 10 ................•.•...•....6-53
4.3.2.3 Upper Side Channel 11.•.....••............6-54
4.3.2.4 Side Channel 21.6--54
4.4 Previous Studies~Comparison of Results .............•...6-55
5.0 SUN~1ARY AND CONCLUSIONS •••..•............•.•.....••.•..•......6-59
5.1 Summary .........•.....••......•..........................6-59
5.1.1 Mainstem Influence .••............•............•...6-59
5.1.2 Local Flow Influence .....:.....•..................6-59
5.2 Conclusions •.............................................6-60
5.2.1 Timing and Distribution of Salmon 6-60
5.2.2 Passage of Salmon .......•.........................6-60
iv
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6.0
..-7.0
8.0
9.0
Page
GLOSSARY..•..••••.••.•••.••.••••••.••...••.•••..•••.. .•.•••...6-6 2
CONTRIBUTORS.•••....•.•.••••.••...•.••...••.. ••..••.... . .••.••6-66
ACKNOWLEDGEMENTS..••.•••••..••.••.••..••••.••.•..•...•. .••...•6-68
LITERATURE CITED .•.•.•..•••.•.••.••.••••.•..••••••••....••••..6-69
10.a APPENDICES •..................•...•...•.....•.•...............6-71
Appendix A.Site Descriptions •••••.••..••••••••..•.•.••••.•.•6-A-1
Appendix B.Supplement to Methods of Local Flow Analysis .••.•6-B-1
Appendix C.Timing Plots •••.•••..•.•.•••.•.••...•.••..•••...•6-C-1
Appendix D.Salmon Spawning Distribution Maps ••.•••••...•••••6-D-1
Appendix E.Thalweg Profiles of Sloughs and Side Channels •.•.6-E-1
v
Slough and side channel study sites
selected for passage evaluation,1983.............6-2
General spawning habitat preference of the
five species of salmon utilizing the
Susitna River Basin...............................6-3
Flaw chart displaying the methods employed
to evaluate passage reach conditions..............6-9
Passage depth requirements for chum salman
as a function of passage reach length
within sloughs and side channels having
substrates less than 3.0 inches in diame-
ter,uniform morphology and water veloc-
ities less than 2.0 ft/sec........................6-14
....Figure 6-5 Passage depth requi rements for chum sa 1man
as a function of passage reach length
within sloughs and side channels having
substrates greater than 3.0 inches in
diameter,non-uniform,braided and ob-
structed channels and velocities less than
2.0 ft/sec........................................6-15
....
~,
"".
Figure 6-6 Flow duration curve depicting Susitna
River discharge at Gold Creek for the
salmon migrational period (20 August to 20
September).Data obtained for years
1950-1981 at gage number 15292000 of the
United States Geological Survey...................6-18
Figure 6-7 Supplement to methods for the backwater
analysis..........................................6-20
Figure 6-8 Flow diagram depicting the process for
·selecting methods employed in the local
flow analysis.....................................6-26
Figure 6-9 Timing plots showing peak occurrence of
chum,pink and sockeye salmon migration at
mainstem Susitna River fishwheel sites,
1981.(Note:first run sockeye salmon
not included).....................................6-28
Figure 6-10 Timing plots showing peak occurrence of
chum,pink and sockeye salmon migration at
mainstem Susitna River fishwheel sites,
1982.(Note:first run sockeye salmon
-not included)6-29
Vl
....
-
LIST OF FIGURES (Continued).
Peak periods of chum salmon presence in
relation to mainstem Susitna River dis-
charge in slough and side channel study
sites,1981, 1982,1983...........................6-31
-
Figure
Figure 6-11
Figure 6-12
Timi ng plots showi ng peak occurrence of
churn,pink and sockeye salmon migration at
mainstem Susitna River fishwheel sites,
1983.(Note:first run sockeye salmon
not included).6-30
_.
['
,....
Figure 6-13 Peak periods of sockeye salmon presence in
relation to mainstem Susitna River dis-
charge in slough and side channel study
sites,1981,1982,1983...........................6-32
vii
-LIST OF APPENDIX FIGURES
Figure
.-
-
-
6-8-1
6-8-2
Appendix 6-8
Relationship between mean depth and
passage depth.....................................6-8-3
Relationship between mean depth and unit
flow..............................................6-8-4
viii
F·
Figure
6-C-l
6-C-2
6-C-3
6-C-4
6-C-5
6-C-6
6-C-7
Appendix 6-C
Timing of salmon presence,Slough 8A,
1981,1982,1983..................................6-C-2
Timing of salmon presence,Slough 9,1981,
1982,1983 6-C-3
Timing of salmon presence,Slough 9A,
1981,1982,1983 •.....•......••...................6-C-4
Timing of salmon presence,Slough 11
Complex,1981, 1982,1983 ..........•..............6-C-5
Timing of salmon presence,Slough 20,
1981,1982,1983 •...............•........•........6-C-6
Timing of salmon presence,Slough 21
Complex,1981,1982,1983 •..........•.............6-C-7
Timing of salmon presence,Slough 22,
1981, 1982,1983 6-C-8
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.P!I!'
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-,
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~ll\lllU
Figure
6-0-1
6-0-2
6-0-3
6-0-4
6-0-5
6-0-6
6-0-7
6-0-8
6-0-9
6-0-10
6-0-11
6-0-12
6-0-13
6-0-14
6-0-15
6-0-16
6-0-17
Appendix 6-0
Pink salmon spawning areas,Whiskers Creek
Slough,1982......................................6-0-2
Chum salmon spawning areas,Mainstem 2
Side Channel,1982,1983 ..•........•..........•...6-0-3
Chum salmon spawning areas,Slough 8A,
1981,1982,1983 ............••....................6-0-4
Sockeye salmon spawning areas,Slough 8A,
1981,1982,1983 ...•...•.................•........6-0-5
Pink salmon spawning areas,Slough 8A,
1982..............................................6-0-6
Chum salmon spawning areas,Slough 9,
1982................•..........•...6-0-7
Sockeye salmon spawning areas,Slough 9,
1982,1983 III .. .... .... .... .. .. .. ..6-D-8·
Pink salmon spawning areas,Slough 9,
1982.. . . . . . . •. . . . . . . . . . . . . . •. ••. . . . . . . . . . . . . . . . . . .6-0-9
Chum salmon spawning areas,Slough 9A,
1981. 1982.1983 6-0-10
Sockeye salmon spawning areas.Slough 9A.
1981, 1982,1983..................................6-0-11
Site map of Side Channel 10 6-0-12
Chum salmon spawning areas,Slough and
Upper Side Channel 11,1981,1982,1983 6-0-13
Sockeye salmon spawning areas,Slough and
Upper Side Channel 11,1981,1982,1983 6-0-14
Pink salmon spawning areas,Slough and
Upper Side Channel 11,1982 6-0-15
Chum salmon spawning areas,Slough 20,
1982,1983 ....•....•.............•................6-0-16
Pink salmon spawning areas.Slough 20,
1982 .......................•....................•.6-0-17
Chum salmon spawning areas,Side Channel
21,1981,1982.1983 6-0-18
.,
"
--Figure (Continued).
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""'"
F""
j.
F'"
I
I
6-0-18
6-0-19
6-0-20
6-0-21
6-D-22
Sockeye salmon spawning areas,Side
Channel 21,1982,1983 .•.......................••.6-0-19
Chum salmon spawning areas,Slough 21,
1981, 1982,1983 .•..•...........•..•..............6-0-20
Sockeye salmon spawning areas,Slough 21,
1981, 1982,1983..................................6-0-21
Pink salmon spawning areas,Slough 21,
1982.Note however,that spawning areas
are below mouth of slough •........................6-0-22
Chum salmon spawning areas,Slough 22,
1983.. . . . . . .. . ••. .•.•. . . . . .. •. . .. .. . . . . . . .. . .•. ...6-D-23
xi
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.!/i!5IiIlI
-
-
Figure
6-E-1
6-E-2
6-E-3
6-E-4
6-E-5
6-E-6
6-E-7
6-E-8
6-E-9 .
6-E-10
6-E-11
6-E-12
Appendix 6-E
Thalweg profile of Whiskers Creek Slough ••.••••••.6-E-2
Thalweg profile of Mainstem 2 Side Channel ••.•....6-E-3
Thalweg profile of Slough 8A .•.•••.........•......6-E-4
Thalweg profile of Slough 9 ••..•••.•••••..........6-E-5
Thalweg profile of Slough 9A......................6-E-6
Thalweg profile of Side Channel 10 ..••••••.•.••...6-E-7
Thalweg profile of Slough 11 ...•........•.•.......6-E-8
Thalweg profile of Upper Side Channel 11 ....•...•.6-E-9
Thalweg profile of Slough 20 ..•.•.•.........•.....6-E-I0
Thalweg profile of Side Channel 21 6-E-ll
Thalweg profile of Slough 21 ••.•....••...•........6-E-12
Thalweg profile of Slough 22 6-E-13
xii
LIST OF TABLES
Table•.
.....
_.
Table 6-1
Table 6-2
Tab1e 6-3
Table 6-4
Table 6-5
Table 6-6
List of staff gage numbers and locations
used in evaluating passage reach conditions
at slough and side channel study sites in
the middle Susitna River,1983.....................6-11
A summary of data sources and methods used
in the analysis of local flow requirements
for salmon passage.................................6-22
Dates and counts of peak escapement of chum
and sockeye sa 1mon observed in selected
sloughs in the middle Susitna River during
1981,1982 and 1983.(Data derived from
ADF&G 1981b;1983c;Barrett et al.,1984)..........6-33
Percent of tota1 number of chum,sockeye
and pink salmon in se1ected sloughs in
1981-1983.Percents are based on peak
counts of live and dead fish.(Derived
from data presented in ADF&G 1981b;1983c;
Barrett et al.,1984)..............................6-34
Selected physical characteristics of
passage reaches at the time thalwegs were
surveyed at each site..............................6-35
Summary of mainstem discharges required to
provide successful and unsuccessful salmon
passage conditions at selected spawning
sites in the middle Susitna River,Alaska..........6-39
Table 6-7 Required local flows for successful and
unsuccessfu1 passage conditions at each
passage reach identified in se1ected slough
and side channel habitats in the midd1e
Susitna River,Alaska .........••...................6-42
Table 6-8 Compari son of resul ts of the present
passage study to resul ts of previ ous
reports invo1ving sloughs in the middle
Susitna River •...r ••••••••••••••••••••••••••••••••6-57
,<1 i i
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1.0 INTRODUCTION
This chapter presents an interim evaluation of selected channel geometry
and hydraulic characteristics which influence passage conditions for
adult chum (Oncorhynchus keta),sockeye (Q.nerka)and pink (Q.
gorbuscha)salmon from the middle reach of the Susitna River into and
within selected slough and side channel habitats located between
Ta 1keetna (RM 98.0)and Devi 1 Canyon (RM 152.0)(Fi gure 6-1).The
influence of discharge on the timing of upstream migration of salmon in
the mainstem Susitna River and the distribution of spawning salmon
within the selected slough and side channel sites is also examined.
Timing and distribution patterns of these salmon species are addressed
only to the extent that they relate to,or affect,passage at slough and
side channel habitats.Passage conditions into selected tributaries
within the Talkeetna to Devil Canyon reach of the Susitna River have
been evaluated in previous studies (Trihey 1983)and are not repeated
here.This analysis is an interim step towards a final analysis which
will be completed in FY85.
1.1 Background
Five species of Pacific Salmon [chum,sockeye,pink,coho (0.kisutch)
and chinook (Q.tshawytscha)]presently spawn in various habitats of the
Talkeetna to Devil Canyon reach of·the Susitna River.These habitats
include mainstem,side channel,slough,and tributary sites.Utiliza-
tion of these habitats by salmon varies among species (Figure 6-2).
Tributaries are used primarily by chinook,coho.chum,and pink salmon;
whereas sloughs are used primarily by chum and sockeye salmon and to a
lesser extent by pink salmon.Various mainstem and side channel sites
received limited use by chum,coho,and sockeye salmon.
The distribution of spawning salmon in the Susitna River system is
influenced by various physical and chemical conditions that affect
salmon timing and passage events.Proper timing of the upstream mi-
gration of salmon is critical to ensure that salmon will ar'rive at
spawning areas when environmental conditions (flows,water depths,etc.)
are suitable for passage into and within these areas.Alteration of
these environmental conditions may affect the timing,passage,and
resultant distribution of salmon in the Susitna River system.
Field observations of passage conditions at several sloughs and side
channels within the study area (ADF&G 1983a,b:Appendix B)inC:icate
that it is unlikely that hydraulic velocity barriers would exist at
these or other spawning locations under present or projected flow
regimes.Therefore,the ability for salmon to enter slough and side
channel habitats from the mainstem Susitna River and access spawning
areas within these habitats is primarily a function of water depth and
the length of a reach when the water is shallow (ADF&G 1983b:Appendix
S,Trihey 1982).When passage is prevented at a particular passage
reach,spawning habitat above the impasse becomes unavailable for use by
adult salmon.Under these conditions,the overall distribution of
spawning salmon is restricted and the density of spawning adults in the
available spawning areas may be excessive.If these conditions persist,
6-1
SLOUGH AND SlOE
CHANNEL STUDY
SITES
.....
-
-.
.....
.....
WHISKERS CREEK
SLOUGH
UPf>ER SIDE CHANNEL II
SLOUGH II
SLOUGH 9A
LOUGH 9
SLOUGH SA
o,
IoIIL..ES
10
.....
Figure 6-1.Slough and side channel study sites selected for passage
evaluation,1983 .
6-2
SPAWNING HABITAT PREFERENCE
MS SC SL T
MS -MAl NSTEM
SC -SIDE CHANNEL
SL -UPLAND and SIDE SLOUGHS
T -TRIBUTARIES
1r -PRIMARY SPAWNING HABITAT
t -SECONDARY SPAWNING HABITATt-INCIDENTAL SPAWNING HABITAT
\~
\
\
\\
\ \
\
\
\
SOCKEYE
~I
MS SC
~
\
\,
\
\
COHO
T MS SC SL T
PI N K
MS SC SL T
CHINOOK
MS SC S L T
CHUM
Figure 6-2.General spawning habitat preference of the five
species of salmon utilizing the Susitna River
Basin.
6-3
,...,
-
.....
-
it will result in a reduction in the number of salmon originating from
and returning to the affected habitats.
Mainstem discharge levels directly influence backwater and breaching
conditions in slough and side channel habitats and consequently affect
fish passage into and within these habitats (ADF&G 1983a t 1983b:Appen-
dix B).At low mainstem discharges (unbreached conditionsL the backwa-
ter area formed at the mouth of sloughs and side channels may not have
sufficient depths to allow successful passage of fish from the mainstem
into the site.As mainstem discharge increases t the backwater area
normally increases in depth and extends its influence upstream t thus
increasing depths within those critical passage reaches affected by the
backwater.This elimination of passage restrictions within a reach by
inundation continues in the 'upstream direction with increasing mainstem
discharge t until a controlling discharge levels is achieved at which
point depths become adequate for passage at all passage reaches in most
slough and side channel habitats.
During conditions when the mainstem river breaches the upstream head of
the site t local flow (e.g.t upwelling t tributaries t precipitation)
normally constitutes a negligible contribution to the overall flow in
the site.However t during unbreached conditions t changes in local flow
alone can result in significant changes in passage conditions within
critical passage reaches.
Naturally occurring mainstem discharge levels and local 'flows provide
suitable depths and velocities during most years and support successful
passage conditions for adult salmon into traditional slough and side
channel spawni ng sites.These naturally occurring di scharges in the
Susitna River (as recorded daily at the USGS gaging station at Gold
Creek)commonly range between 20 t OOO and 30 t OOO cfs during June,July
and August (Scully,et al.t 1978L when adult salmon are migrating
upstream in the mainstem and 15 t OOO-20,000 cfs during the peak spawning
period (20 August -20 September).
The proposed Susitna Hydroelectric Project would alter existing dis,..
charge levels of the mainstem Susitna River.Discharges would be
reduced during the summer and increased during the winter (Acres 1982).
Average monthly post-project di scharges a"t Gol d Creek are projected to
range between 7,000 and Il t OOO cfs during June t July and early August,
with a proposed cont ro 11 ed di scha rge of no 1ess than 12,000 cfs from
mid-August to mid-September (Acres 1982).These projected discharges
would alter the breaching and backwater influence of mainstem discharge
on many of the sloughs and side channels within the Talkeetna to Devil
Canyon reach of the Susitna River.This will likely alter passage
conditions for salmon into and within some of these habitats.lJater
levels within these habitats would be primarily dependent upon local
flow from small tributaries,surface runoff,and upwell ing groundwater
under these controlled mainstem discharge conditions (ADF&G 1981a t 198L
1983a,1983b:Appendix B).
Therefore,evaluations of timing of the adult salmon migration within
the mainstem and to slough and side channel spawning sites,and the
passage conditions available at various mainstem discharges are
6-4
-
.....
important in determining their role on the overall distribution of
spawning salmon in these Susitna River habitats.This information,when
combined with the evaluation of other life phases (e.g.,spawning,
incubation and rearing)is essential for evaluating the effects that
regu 1a ted di scha rges of the proposed hydroe 1ect ri c proj ect wi 11 have
upon these habitats.Additionally,these data are necessary to assist
in developing appropriate mitigative options.
1.2 Objective
The primary objective of this continuing study is to evaluate the
influence of mainstem discharge and/or local flows on passage conditions
for adult salmon into and within selected slough and side channel
habitats of the Susitna River.In support of this objective,timing and
distribution patterns of spawning adult salmon in selected slough and
side channel habitats are analyzed to the extent that they relate to
passage conditions.
Previous investigations have evaluated the influence of mainstem dis-
charge on salmon passage conditions in selected tributary (Trihey 1983)
and slough habitats (ADF&G 1983b:Appendix B;Trihey 1982)of the middle
Susitna River.However,these studies were not sufficient to provide a
complete analysis of passage conditions for all mainstem affected salmon
spawning habitats in this reach of river.This was due to the relative-
ly small number of sites investigated,the lack of an evaluation of
local flow conditions,and a need to refine previous methods.The
present study is the first stage in expanding the number of study sites
(including relevant side channel sites)and refining the methods previ-
ously employed to provide a more comprehensive and precise evaluation of
salmon passage conditions in the middle Susitna River.Also included is
a preliminary evaluation of local flow conditions at most of these
sites.The second and final stage of the analyses will be completed in
FY85.
The primary objective of this analysis focuses on chum salmon due to
their more restrictive passage requirements (Scott and Crossman 1973)
and their wide distribution among slough and side channel habitats in
comparison with other salmon species in the Susitna River.Since chum
salmon are more restricted in their ability to surmount obstacles it is
assumed that passage criteria set for this species can be applied to
other species.Available information on sockeye and pink salmon is also
included to present a more comprehensive overview of salmon utilization
and potential passage problems within the middle reach Susitna River
slough and side channel habitats .
6-5
.',,,,
2.0 METHODS
2.1 Site Selection
A total of 12 slough and side channel sites were selected for the
passage eval uation studies (Figure 6-1).These study sites represent
the major slough and side channel spawning areas for chum,sockeye,and
pink salmon in the middle reach of the Susitna River.Sloughs 8A,9,11
and 21 are primary spawning areas for chum salmon.Mainstem 2 Side
Channel,Upper Side Channel II,Side Channel 21 and Sloughs 9A,20 and
22 support lesser concentrations of spawning chum salmon.Whiskers
Creek Slough supports limited pink salmon spawning and is also used by
salmon as a migrational corridor to access Whiskers Creek.Side Channel
10 was selected for study because of its potential as a mitigation
evaluation site.It was not evaluated in the local flow analysis.
Detailed descriptions of study sites are presented in Appendix 6-A and
site maps are presented in Appendix 6-0.
2.2 Timing and Distribution of Salmon
Comprehensive timing and distribution data have been collected an adult
salmon in the middle Susitna River since 1981 [ADF&G 1981b,1982,1983b:
(Appendix B),1983;Barrett et al.1984].A compilation and comparison
of these data are discussed betow by habitat type.
2.2.1 Mainstem Sites
Timing of the upstream migration of adult salmon in the mainstem Susitna
River was compared to mai nstem di scharge for the 1981, 1982,and 1983
open water field seasons.For each year,catch per unit effort data
were combined with mainstem discharge by plotting both vari.ables over
time.Adult salmon were counted during each of these years at
fishwheels located at three mainstem sites on the Susitna River:
Sunshine Station (RM 80.0),Talkeetna Station (RM 103.0),and Curry
Station (RM 120.0).More specific methods for fishwheel operations and
related data analyses are presented in ADF&G (1983c)and Barrett,et
a1.,'(1984).
Discharge data used to construct the timing plots were obtained from ·two
United States Geological Survey (USGS)gaging stations.Discharge data
used in association with the Sunshine Station fishwheel site were
recorded at the USGS gaging station at Sunshine (USGS gage #15292780),
RM 89.3.Discharge data for the Talkeetna and Curry Station fishwheels
were recorded at the USGS gaging station at Gold Creek (USGS gage
#15292000),RM 136.7.
Catch per unit effort data each fishwheel site on a daily basis were
plotted with mean daily Susitna River discharge data for the years 1982
and 1983.Flood events prevented continuous fishwheel operations.
Therefore,fishwheel catch data are plotted as catch per unit effort
rather than numbers of salmon.The timing of salmon migration was
compared with discharge data for a1l three years to detect trends that
may not be evident by evaluating data from a single year.
6-6
r-'
-
2.2.2 Slough and Side Channel Sites
ADF&G adult salmon survey data reported for slough and side channel
habitats in 1981~1982 1 and 1983 (ADF&G 1981b;ADF&G 1983c;Barrett et
al'l 1984 1 respectively)were analyzed to determine timing and dis-
tribution patterns of salmon at these sites.Field personnel surveyed
selected slough and side channel habitats in their entirety for adult
salmon between RM 98.6 and RM 16l.0.The surveys were generally con-
ducted weekly from July through October during each of these years.
Beginning and endi ng dates .of surveys vari ed each year dependi ng on
factors such as weather and timing of fish migration patterns.All
survey data are based on visual counts with visibil ity conditions rated
as poar l fair l good,or excellent.Visibil ity conditions were affected
primarily by turbidity levels but were also affected at times by other
factors such as sun 91 are and wi nd.For those surveys with fa i r,good
or excellent visibility conditions,the total number of live salmon,by
species~were recorded.Surveys conducted during periods of poor
visibility conditions were not used for this analysis.A more detailed
discussion of survey methods is included in ADF&G (l981b,1983c,1983d)
and Barrett et al.,1984.
Timing plots were developed for slough and side channel sites by plot-
ting numbers of fish over time.The plots include only the time period
of August through September because this was the period of peak occur-
rence of salmon within these habitats.For periods of poor or fair
survey conditions,where no usable data \ttere available,the data points
were interpol ated.
Timing plots were constructed for all slough and side channel study
sites with the exceptions of Side Channel 10 and Mainstem 2 Side Channel
these two sites were excluded because there were insufficient data to
construct a complete plot.
Numbers of fish counted in Upper Side Channel 11 were not differentiated
from those in Slough 11 due to sampling limitations.Data were combined
for those sites and the resultant plot is referred to as the Slough 11
Complex.Likewise,data from Slough 21 and Side Channel 21 were pre-
sented in a single plot referred to as the Slough 21 Complex.
Maps illustrating the distribution of spawning chum,sockeye,and pink
salmon were developed for each site (see Appendix D).These maps were
primarily used to determine the areas traditionally used for spawning in
each site and how the distribution of salmon relates to the location of
passage reaches.
2.3 Passage of Salmon
The methods presented below focus on the 1983 field and 1984 analytical
methods used to evaluate the influence of mainstem discharge and/or
local flows on passage conditions from the mainstem into and within
selected slough and side channel habitats.Many of these methods are
refinements of methods used in previous years.For more detailed
information on methods previously used,the reader should refer to ADF&G
(1983a,b:Appendix B)and Trihey (1982).
6-7
Physical and hydraulic conditions influencing·passage of adult chum
salmon into and within slough and side channel habitats were evaluated
by first identifying potential passage reaches and comparing passage
reach characteristics (i.e.,channel morphology,substrate composition,
water depths and lengths)at various mainstem discharges to chum salmon
passage requirements.A flow chart of the methodology employed to
evaluate passage reach conditions is presented in Figure 6-3.
2.3.1 Field Methods
2.3.1.1 Thalweg Surveys
Thalwegs were surveyed along the entire length of each slough and side
channel study site at low water conditions during October of 1982 and
1983.Thalweg data were collected using a surveying level,standard
surveying rod,and rod level using standard surveying techniques of
differential leveling (Bovee and ~l;lhous 1978;Trihey and Wegner 1981,
ADF&G 1983c).At the beginning of each survey,a temporary bench mark
(TBM)was established that was later surveyed to a known elevation.
Surveying the thalweg in a slough involved two steps.First,points of
significant change of the slough bed elevation along a longitudinal
gradient were determined by visual assessment (i.e.,upper and lower
ends of riffles,lower ends of pools,etc.).Next,a transect perpen-
dicular to the channel was visually established at each point.The
point of greatest water depth was identified along this transect.These
points of greatest depth were defined as thalweg points.The line
connecting these points was defined as the thalweg.Distances between
thalweg points were measured to the nearest foot by:1)using
fiberglass surveying tape;2)reading stadia and computing distances or;
3)measuring angles and distances,and computing distances between
thalweg points utiliZing trigonometric functions (triangulation).When
survey data (i.e.,cross sections at study sites,staff gage sites or
the mouth or head of a slough)were available from previous work which
met the requirements for developing a thalweg profile,these data were
used in conjunction with or in addition to other thalweg survey work.
..
2.3.1.2 Cross Sectional Profiles
Cross sectional profiles were obtained by surveying selected passage
reaches of slough and side channel sites to provide more accurate rep-
resentations of water depth 1n the shallowest areas in the passage
reach.These cross sections were located on riffles that were above the
mainstem backwater (on the day sampled),but below the uppermost limit
of reported spawning in 1981, 1982,and 1983.
Cross sectional profiles were obtained by surveying points of signifi-
cant changes in gradient along a temporary transect establ ished across
the shallowest part in the passage reach perpendicular to the flow.At
each transect,the end points were defined by placing temporary headpins
on the left and right banks.Stationing along each passage reach cross
section was determined by either measuring the distance with a surveyors
tape or from stadia readings taken while surveying.All surveying was
6-8
1 I 1 )I )1 1 B )1 1
SURVEY
THALWEG PROFILES
DEFINE FISH PASSAGE
CRITERIA CURVES
0"1
I
\D
IDENTIFY RESTRICTIVE PASSAGE
REACHES ON THALWEG PROFILES
BY APPLYING THE APPROPRIATE
FISH PASSAGE CRITERIA CURVE
EVALUATE PASSAGE CONDITiONS
AT EACH PASSAGE REACH
.DETERMINE THE MAINSTEM
DISCHARGE REQUIRED FOR
BREACHING OF THE
HEAD OF EACH SITE
DETERMINE THE MAINSTEM DIS-
CHARGES REQUIRED TO PROVIDE
SUCCESSFUL AND UNSUCCESSFUL
BACKWATER PASSAGE CONDITiONS
DETERMINE THE LOCAL FLOWS
REQUIRED TO PROVIDE
SUCCESSFUL AND UNSUCCESSFUL
PASSAGE CONDITIONS
Figure 6-3.Flow chart displaying the methods employed to evaluate passage reach
conJitions.
conducted accordi ng to standard surveyi ng techni ques of differenti a1
leveling (Bovee and Milhous 1978;Trihey and Wegner 1981).
2.3.1.3 Stage and Flow Measurements
Stage data were generally collected over a range of 1oca 1 flows (low,
medium and high)or local flows plus mainstem breaching discharges.
However,at some sites,insufficient data were collected to evaluate the
enti re range of di scharges.Staff gages were install ed at the mouth,
within,and at the head of each study site.Generally,gage readings at
the mouth and the head (and some gages within sloughs)were correlated
to mainstem discharge to evaluate backwater and breaching effects,re-
spectively.Selected gages located within the slough were used to
evaluate local flow effects by correlating staff gage readings with
measured local flow.Flows were measured using techniques described in
ADF&G 1983d.All staff gages were surveyed to a known elevation using
basic survey techniques of differential leveling so that resultant stage
readings could be converted to true water surface elevations (WSEL).
Table 6-1 provides a list of all study sites and their corresponding
staff gage numbers and locations.All discharge values related to these
gages are referenced from the USGS gagi ng station at Gol d Creek [USGS
1983 (gage #15292000,RM 136.7)]unless otherwise indicated.
2.3.2 Analytical Methods
The conceptual approach for analyzing salmon passage reaches in s10ughs
and side channels was based on a procedure involving three steps.
1)Define the necessary water depth and reach length requirements
for successful and unsuccessful salmon passage (passage
criteri a).
2)Based upon the passage criteria established in step number
one,identify all reaches within the selected study sites that
do not meet the criteria for successful salmon passage (under
all flow conditions).
3)Evaluate each passage reach in terms of its hydraulic cnarac-
teristics,and determine the amount of local flow and/or
mainstem discharge reqUired to provide passage conditions that
satisfy the requirements identified in step number one.
2.3.2.1 Definitions of Fish Passage Criteria
Several environmental variables may affect fish passage.In general,at
a given passage reach the water conditions (depth and velocity)interact
with conditions of the channel (length and uniformity,substrate size)
to characterize the passage conditions that a particular fish encounters
when attempting to migrate upstream.The likelihood of a particular
fi sh successfully navi gati ng through a difficult passage reach wi 11
depend upon both the environmental conditions as well as the unique
capabilities of that individual fish.In turn,the capabilities of a
particular fish will depend upon the unique genetic characteristics of
the individual,and the amount of stresses previously encountered.
6-10
Table 6-1.List of staff gage numbers and locations used in evaluating
passage reach conditions at slo~gh and ~ide channel study
sites in the middle Susitna River,1983 •
.....
.....
Study Site
Whiskers Creek Slough
Mainstem II Side Channel
Slough 8A
Slough 9
Slough 9A
Slough 10
Side Channel 10
Sl o~gh 11
Upper Side Channel 11
Staff Gage #
101.2W1
101.2S3
114.4W6
114.4S9
114.4S7
12S.3W5
125.3S6
125.3S4
125.3S8
125.3H7
128.3W3
128.3S1
128.3H2
No staff gages
133.8WS
134.1S1 (R&M)
133.8S78
133.8S18
133.8S218
135.3W1
135.3S6
136.3H3
136.2W3
136.2S4
136.255
136.251
6-11
Staff Gage Location b
200 ft upstream of mouth
400 ft upstrea~of
confluences with
Whiskers Creek
at mouth
850 ft upstream of mouth
1200 ft upstream of
mouth
mouth of slough
1000 ft upstream of mouth
1200 ft upstream of mouth
7150 ft upstream of mouth
head of slo~gh
mouth of slough
2300 ft upstream of ~outh
(ADF&G Q site)
head of slough
No access
determination possible
mouth of slough
R&M Q site
25 ft upstream of mouth
750 ft upstream of mouth
1000 ft upstream of
mouth
mouth of slough
1000 ft upstream of mouth
(ADF&G Q site)
head of slough
at mouth
225 ft upstream of mouth
450 ft upstream of mouth
1050 ft upstream of
mouth
(Continued)
Table 6-1 (Continued)
Study Site Staff Gage #Staff Gage Location
Slough 20 140.1W4 275 ft upstream of mouth
140.1S5 1150 ft upstream of
f'-mouth (ADF&G 0 site)
Slough 21 Complex
(Side Channel 21)140.6Wl mouth of side channel
140.6S4 in modeling site
Q site
(Slough 21)140.652 1500 ft downstream of mouth
140.657 400 ft downstream of mouth
142.0W5 mouth of slough
142.056 ·900 ft upstream of mouth
(ADF&G Q site)
142.0H3 NW head
142.0Hl NE head
Slough 22 144.3\-J3 at mouth of slough
144.3S4 1100 ft upstream of
mouth
144.3S6 2100 ft upstream of
mouth
a Additional information on these staff gage sites is presented in
Quane,et al.,1984.
b Q site refers to a site where discharge measurements were obtained.
6-12
,....,
!
I
r
i
-,
Thus,the process of evaluating salmon passage must account for the
natural variability of the environment where fish encounter passage
problems as well as the variability present in the population of migrat-
ing fish.Fish passage criteria in this study deal only with the
environmental variables,mainly those which may be subject to change
under with project conditions.
Two environmental variables (depth of water and length of the passage
reach)were assumed to be the most significant influences affecting
migrating fish in slough and side channel habitats of the middle Susitna
River.This assumption was based upon field observations made in those
habitats during the migrational period,at which time those habitats
were often unbreached by mainstem water and were characterized by
relatively low water velocities (2.0 f/s)and shallow water depths at
many ri ffl e areas.Factors of secondary importance were assumed to be
substrate size,and channel uniformity.
Previous criteria used for passage elevation into slough habitats in the
middle Susitna River include a single set of depth and length criteria -
a depth of 0.3 feet for a length of 100 feet.Since a single set of
criteria provided little guidance for evaluating longer or shorter
passage reaches,a number of criteria sets were developed in the form of
curves showing depth in relation reach length.
Based upon thi s concept of passage depth versus 1ength of travel (i.e.
passage reach)two sets of fish passage curves were developed from the
results of previous work conducted by ADF&G (ADF&G 1983b:Appendix B),
work of other researchers (Thompson 1972)field observations,and the
professional judgement of members of Woodward-Clyde Consultants,E.
Woody Trihey and Associates,and the ADF&G Su Hydro Aquatic Studies
biologists.These curves were developed to reflect different Substl~ate
conditions and channel uniformity between habitats.One set of curves
was developed for habitat conditions with small substrate (~3 inches
diameter)and a uniform,unobstructed channel.These conditions are
typical of many of the sloughs.The second set of curves was developed
for sloughs and side channels with large substrates (>3 inches in
diameter)and a non-uniform,obstructed channel.Each set of curves
consisted of two lines.The upper line represented the threshold limit
between successful passage and difficult passage while the lower line
represents the threshold limit between difficult passage and unsuccess-
ful passage.
The resulting criteria curves for small substrate and uniform,unob-
structed channel are presented in Figure 6-4 and the curves for large
substrate and non-uni form obstructed channel are presented in Fi gure
6-5.
Common cross-sectional depth measurements observed in the field are mean
depth and thalweg depth,neither of which accurately represent fish
passage conditions.Use of maximum or thalweg depth is not always an
accurate indicator of passage since it often represents the depth at one
location on a transect and this location may not be contiguous with the
maximum depth on an adjacent upstream transect.Since neither mean
depth nor thahJeg depth present an accurate representation of fish
6-13
1 J 1 1
CURVE I
1.0-.Substrate :s.3 inches
Uniform.unobstructed channel A B
0.9 .....Coordinates CoordinatesWaterVelocity<2.0 ft/sec X y X Y
o.a .....0 0.30 0 0.1 B
10 0.30 10 0.1 B
~0.7~20 0.35 20 0.24
100 0.35 100 0.26
Q)200 0.41 200 0.32-.....
::I:0.6
~
0-
0)
~0.5
I ~O.4 JI-'Successful .A.j::>
«en~0.3~Successful with Difficulty and Exposure ..B
0-
0.2,Unsuccessful
0.1
0.0 .....
0 10 20 30 40 50 100 200
PASSAGE REACH LENGTH (feet)
Figure 6-4.Passage depth requirements for chum salmon as a fun~tion of passage reach
length within sloughs and side channels having substrates less than 3.0
inches in diameter.uniform morphology and water velocities less than
2.0 ft/sec.
1 j I J I 1 1 i -1 ~1 1 1
CURVE n
Unsuccessful
Successful "A
II .•
Successful with Difficulty and Exposure •B
~.
B
Coordinates
K Y
o 0.30
10 0.30
20 0.35
100 0.35
200 0.41
A
Coordingtes
X y
o 0.41
10 0.41
20 0.48
100 0.48
200 0.54
Substrate >3 inches
Non -unifor ffi,braided and obstructed channels
Velocities <2.0 ft/sec
1.0
0.9
0.8--:0.1--
:I:0.6
t-
O-wo 0.5
O'l W
I (!)0.4f-l
Ul «
(/)
(/)«0.3
Q..
0.2
0.1
200100
0.0 , ,i ,I I I 1 I I
o 10 20 30 40 50
PASSAGE REACH LENGTH (feet)
Figure 6-5.Passage depth requirements for chum salmon as a function of passage reach
length within sloughs and side channels having substrates greater than
3.0 inches in diameter,non-uniform,braided and obstructed channels and
velocities less than 2.0 ft/sec.
r~I:J
passage conditions within a particular reach of slough,a new parameter
was developed -passage depth -which integrates mean depth and thalweg
depth.Simply stated,passage depth is an average of the mean depth and
maximum depth of a transect.Passage Se§i5§(d )was related to thalweg
depth (d )by the relation d =.77 d • •~he curves were developed
by estim£ting the required t~alweg depth for fish passage for a selected
reach length (ranging to 500 ft).These thalweg depths were then
converted to passage depths by.use of the equation.
2.3.2.2 Identification of Passage Reaches
Thalweg and surveyed water surface elevation (WSEL)data were plotted
against streambed station to obtain a profile of the slough or side
channel.The location and length of passage reaches within each study
site were identified from the thalweg profiles.All passage reaches
were sequentially numbered in ascending order beginning at the down-
stream end of each site.Specific steps in the process of identifica-
tion are as follows:
1)Depth criteria for passage reach identification -the thresh-
old water depth for which salmon passage is considered suc-
cessful for a reach length of 200 feet:
Passage Criteria
Condition Depth Curves
Substrate .s 3.a inches .41 ft I
uniform,unobstructed
channel
Substrate >3.a inches .54 ft II
non-uniform,braided
channel
Figure
Number
6-4
6-5
.,.-.
~I,
-
2)Initial selection of passage reaches -passage reaches were
identified at base flow conditions (i.e.,1m-lest flow con-
ditions available during the field season)by locating all
portions of the thalweg having water depths less than the
appropriate criteria depth identified in step 1 above.The
.upstream limit of the analysis was the first passage reach
beyond the upstream limit of utilization by spawning salmon
during the years 1981,1982,and 1983;
3)The length of each passage reach was calculated as the dis-
tance along the thalweg from the poi nt where the depth of
water fi rst became 1ess than the criteri a depth (defi ned in
step 1)to the point where the depth exceeded the criteria
depth;
4)~lin;mum passage depth -the minimum passage depth was the
shallowest depth within each passage reach;and
6-16
r
.-
'i
r.,
~,
5)Passage reaches el iminated from analysis -those reaches for'
which passage reach lengths and minimum passage depths plot
above the successful curve at the lowest mainstem discharge
(for which data were available)were not considered as passage
problem areas and were eliminated from further consideration.
2.3.2.3 Evaluation of Passage Reaches
Three types of analyses were used to evaluate passage reaches:breach-
ing and backwater discharges,and local flows.Breaching and backwater
analyses were used to evaluate all passage reaches,whereas,the local
flow analysis was used to evaluate only a subset of passage reaches
which are most problematic for salmon passage.It is anticipated that
the local flow analysis will eventually be applied on the complete set
of passage reaches with the collection of additional information being
obtained in ongoing field studies.
In each of the three analyses,length and depth of passage reaches were
used as the primary criteria to evaluate salmon passage conditions.
Based on these criteria the three categories of passage conditions
established (successful,successful with difficulty and exposure,or
unsuccessful)were evaluated.In each analysis,the discharges and/or
flow requirements are defined for conditions that fulfill threshold
passage conditions for successful and unsuccessful passage (i.e.,for
points on the lines in Figures 6-4 and 6-5).By defining these upper
and lower boundaries the middle condition of IIsuccessful with difficulty
and exposure u is also defined.A flow duration curve was developed for
the period between 20 August and 20 September based on mainstem dis-
charge data at Gold Creek collected over a.32 year period (Figure 6-6).
This curve was used to evaluate the percentage of time that the dis-
charge requirements for passage reaches influenced by mainstem discharge
are equalled or exceeded.Although a flow duration curve of local flows
is also desired,the limited historical data base are insufficient to
develop such a curve.Specific methods employed in each of the three
types of analyses are presented separately in following sections.
2.3.2.3.1 Breaching'
The breaching.analysis was applied to an entire study site rather than
to individual passage reaches within each site.Two breaching con-
ditions were defined:initial breaching discharge and controlling
discharge.Initial breaching occurs when water first overtops the head
of the slough or side channel.The controlling discharge is a higher
discharge that directly.governs hydraulic characteristics within a
slough or side channel.Passage reach conditions within a site are
considered to be successful under controlling breaching discharge
conditions.Methods used in determining these discharges can be found
in ADF&G 1984:Chapter 1.
2.3.2.3.2 Backwater
The backwater analysis included an evaluation of all passage reaches
which were physically located in areas directly influenced by the rising
stage of the mainstem Susitna River the mouth of each site (backwater
6-17
r"
100,000
r·80,000
60,000r50,000
40,000
r 30,000II-fI)
~
CJ-
I.LJ 20,000
(,!)
a::«
~uen 10,000-0
8,000
~
IJJ 6,000~en 5,000z-<t 4,000~
3,000
2,000r
!
~
\
\.
"""...-...~~
~~'"........
"""'\
\
,....
1
,I 1,000
°20 40 60 80 100
'1'"'"
I
1 °k OF TIME DISCHARGE EQUALLED OR EXCEEDED
Figure 6-6.Flow duration curve depicting Susitna River discharge at
Gold Creek for the salmon migrational period (20 August
to 20 September).Data obtained for years 1950-1981 at
gage number 1529200 of the United States Geological
Survey.
6-18
Jl"""
!
I
"",,'
,_.
!
area)'before breaching occurs.This analysis disregarded the effects of
1oca 1 flow for two reasons:(1)1oca 1 base flow was presumed to be a
relatively insignificant factor relative to the effect of the mainstem
discharge at most sites'.and (2)local flow varies greatly in space
(i.e .•from site to site)and time (i.e ••dependent on temporal weather
patterns).The present data base is insufficient to define this varia-
tion or the frequency that one can expect various local flow conditions
to exist.
As the water surface elevation of the backwater increases.it shortens
the length of the passage reach by inundating its downstream end.
Intuitively.it can be deducted that passage will be successful at a
passage reach when the water surface elevation (i .e.,water depth)
submerges the highest thalweg elevation in the reach by a depth corre-
sponding to successful passage for a passage reach having a length of
zero feet on the appropriate,criteria curves (0.35 ft and 0.50 ft for
uniform and nonuniform channels.respectively).However,because of the
relatively minor break in thalweg gradient at the peak elevation of many
passage reaches and the relatively rapid rise in passage depth criteria
for a reach length of 20 ft.the successful passage criteria for 20 ft
reach lengths often requires water surface elevations greater than those
for a ft reach length.Thus,the analysis for successful and unsuccess-
ful passage involved computing required water surface elevations for
both 0 and 20 ft reach lengths and selecting the greater of the computed
values.
Six steps involved in the backwater analysis of each passage reach are
presented below.A diagram outlining each of these six steps is
presented in Figure 6-7.
1)Locate the'passage reach on the thalweg and identify the
streambed station that corresponds to the point of shallowest
depth within the passage reach (this point is referred to as
the index station in Figure 6-7A);
2)Identify the nearest surveyed point upstream (Station 3)and
downstream (Station 1)of the index station (Station 2)and
determine their streambed stations and true elevations on the
thalweg axes (Figure 6-7A).
3)Determine which criteria curve appl ies to the thalweg based OTi
substrate size and channel morphometry of the site.Assume
Criteria Curve II (Figure 6-5)applies for purposes of the
example depicted in Figure 6-7B.
4)Determine the depth required for successful passage for a zero
reach length (0.41 ft)from Criteria Curve II (Figure 6-5).
A.dd this depth to the index station elevation to obtain the
water surface elevation required for successful passage over
that point.
5)Calculate a common bed elevation (EL-5)for two points which
are 20 ft apart and which are positioned on both sides of the
index station.This calculation uses linear interpolation of
6-19
Figure 6-7.Supplement to methods for the backwater analysis.
6-20
r
!
r
I
I
fF"
:1
1F'
I
thalweg survey data points determined for Stations 1 and 3 to
define intermediate thalweg points with equal elevations.Add
the depth required for successful passage for a 20-foot
passage reach to this bed elevation to obtain a WSEL (EL-6 in
Figure 6-78).This new elevation is 2.28 ft (1.8 ft for EL-5
plus 0.48 ft).
6)Determi ne the resultant WSEL determi ned insteps 4 and 5 and
select the larger value;and
7)Use the WSEL derived in step 6 to obtain a corresponding
mainstem discharge.The mainstem discharge is calculated from
a rating curve equation representing the hydrau1 ic relation-
ship in the mouth of the study site (Figure 6-9C).The
mainstem discharge value represents the minimum discharge
required to meet the threshold condition of successful passage
defined in the criteria curve.
8)Repeat steps 2 through 7 for unsuccessful passage conditions.
2.3.2.3.3 Local Flow
The local flow analysis estimated the amount of local flow required at a
site to provide adequate depth of flow for passage reaches within a site
which are independent of backwater and breaching affects.Although the
data base varied for each slo\,Jgh,the general approach follows the four
steps outlined below:
1)Select required depths for successful and unsuccessful passage
for each passage reach from the appropri ate c riteri a cu rve
given the initial passage length,size of substrate,degree of
channel uniformity and water velocity in the passage reach;
2)Obtain a surveyed cross section for each passage reach that is
representative of the most difficult passage condition within
the reach.
3)Obtain a rating curve for each cross section;and
4)Calculate the water surface elevations (WSEL's)that corre-
spond to the required passage depths for successful and
unsuccessful passage from Step 1.Use the rati ng curve to
match the requ i red \~SELs to the 1oca 1 flows necessary for
successful and unsuccessful passage.
The two key items of information at each passage reach for the methods
described above are a surveyed cross section and a rating curve for the
cross section.Of the 74 passage reaches being evaluated in this
report,14 reaches had a surveyed cross secti on and a correspondi ng
rating curve which was representative of,or assumed to be representa-
tive of,the passage reach (Table 6-2).Three other passage reaches had
surveyed cross sections,but no rating curve.The remaining reaches had
neither.There were 36 passage reaches which were not analyzed for
6-21
·-1 _..~]~l
Table 6-2.A summary of data sources and methods used in the analysis of local flow requirements for salmon passage.
Data Base at Passage Reach Method Used
Local
Surveyed Aerial Flows
Passage Cross Rating General Photo-Mannings Field Not
Site Reach Section Curve Approach graphic Equation Observations Calculated
Whiskers Creek I x
II x
III x
Mainstem 2 I x
"x
I"L x
III R x
IV R x
V R x
(J)VI R x
I VII R x
N VIII R xN
Slough 8A I x x x
II x
III x x x
IV x
V x x x
VI x
VII x
VIII x x x
IX x x x
.Slough 9 I x x x
II x x x
III x x x
IV x
V x x x
(Continued)
---1 ~-~Cl ~~~~~·1 --,~
Table 6~2 (Continued).
Data Base at Passage Reach Method Used
Local
Surveyed Aerial Flows
Passage Cross Rating General Photo-Mannings Field Not
Site Reach Section Curve Approach graphic Equation Observations Calculated
Slough 9A I x x
II x x
III x x
IV x x
V x
VI x
VII x
VIII x
IX x x
X x x
Side Channel 10 I x
II x
O'l III x
I IV xN
W V x
VI x
VII x
Slough 11 I x
I J x
I'll x
IV x
V x
Upper
Side Channel 11 I )(x x
II x x x
III x
Slough 20 I x
II x
"'x
IV x
V x
VI x
(Continued)
C~CC-~1 1 ~--1 C'''"--'1 0_,-~~~~~~,
Table 6-2 (Continued).
Data Base at Passage Reach Method Used
Local
Surveyed Aerial Flows
Passage Cross Rating General Photo-Mannfngs Field Not
Site Reach Section Curve Approach graphic Equation Observations Calculated
Slough 21 I x
II L x
II R x
Side Channel 21 I x
II x
III x
IV x
V x x x
VI x
VII x
VIII x
IX x x x
'"X XI
N.po
Slough 22 I x x x
II x
'"x
IV x
r"
'I
'r'"
I
j
local flow (Table 6-2)as explained in Section 2.3.2.3 (Evaluation of
Passage Reaches).
In order to provide estimates of local flow required for passage while
the passage reach cross sections and rating curve data are collected and
analyzed,special analytical techniques were developed.For sites with
surveyed cross sections but no rating curve,a technique based on
Manning is equation was developed.For those sites with no cross
secti on,a techni que based on aeri a1 photographs was developed.De-
scriptions of these techniques are provided in Appendix B.
The process for selecting the appropriate analytical technique is
depicted schematically in Figure 6-8.At two sites (Mainstem 2 Side
Channel and Slough 11),the aerial photographic coverage was inadequate
for using the aerial photographic method;local flow estimates for
successful and unsuccessful passage through passage reaches at these
sites were provided by E.W.Trihey and Associates based on field obser-
vations.Table 6-2 indicates the method used for analysis for each
passage reach analyzed during this phase of the study.
6-25
GET REQUIRED
DEPTHS FROM
CRITERIA CURVE
NO
USE DATA
FROM SURVEYED
CROSS SECTION
AT SAME SITE
AND AERIAL
PHOTOS TO
ESTIMATE
RATING CURVE
AT PASSAGE
REACH
YES
CALCULATE REQUIRED
WATER SURFACE
ELEVATIONS AND
USE RATING CURVE
TO GET REQUIRED
LOCAL FLOW
NO
USE MANNING
EQUATION TO
DEVELOP RATING
CURVE
Figure 6-8.Flow diagram depicting the process for selecting
methods employed in the local flow analysis.
6-26
/....
3.0 RESULTS
3.1 Timing and Distribution of Salmon
3.1.1 Mainstem Sites
Timing and distribution information on the upstream migration of adult
salmon in relation to Susitna River discharge for the years 1981,1982,
and 1983 is presented in Fi gures 6-9 to 6-11.Ma i nstem di scha rges
during the salmon migration period for the years 1981,1982,and 1983
ranged from 27,000 to 150,000 cfs at the Sunshine fishwheel (USGS
Sunshine gaging station)and from 12,000 to 61,000 cfs at the Talkeetna
and Curryfishwheels (Gold Creek gaging station).The plots show that
peak migration periods for chum salmon occurred between late July and
the middle of August during all three years at each of the sampling
locations.Peak periods for pink and sockeye salmon also occurred
within this same general time period.However,migrations for both
these species slightly preceded those of chum salmon.
3.1.2 Slough and Side Channel Sites
Timing information on the seasonal occurrence of chum and sockeye salmon
in slough and side channel habitats for the years 1981,1982,and 1983
is presented in Figures 6-12 and 6-13.Sufficient data to evaluate
timing of pink salmon for all three years were not available.Tables
6-3 and 6-4 present more detailed information on the timing and peak
numbers of each species at each site.Timing plots for each site for
the months of August and September for chum,sockeye and pink salmon are
presented by site in Appendix C of this report.
These data show that peak occurrences of chum and sockeye salmon within
these habitats occur between mid August and late September'over the
three year period.Generally,chum salmon are more prevalent in late
July and early August while larger numbers of sockeye appear in late
August through September.Sloughs 8A,9,11 and 21 account for the
majority of chum and sockeye salmon which spawn in slough habitats
evaluated in this study.
Maps which display salmon spawning distribution for the years 1981,1982
and 1983 are presented in Appendix 0 of this report.
3.2 Passage of Salmon
Salmon passage conditions were evaluated at individual passage reaches
at each study site.Individual passage reaches were identified on the
appropriate thalweg profile (Appendix E)and selected physical charac-
teristics of each reach are summarized in Table 6-5.Based on physical
characteristics present at each passage reach,passage conditions were
evaluated according to one of two sets of fish passage criteria curves
(refer to Figures 6-4 and 6-5).
.6-27
1/30
I Medlon.,SO'CI'!PIt'Q1I I.~ilj.
~
5°/0 CU-Llot1....95 D/o C~mu.Qtlw.
Caten "..,E'ffart Coate"D."Effort
IIISIll!lI'I
DATE
T/ill1/1lI/lll
SUNSH INE FISHWHEEL
RN 80
1981
I~i~",""__~_"""",,,,,,,,__,,,,;;:;,_
6/1
16~
oo
2..
en
~Ol
-at.,..
"'N
j:
~!
Q<n
..III 6
aU):;:::1
a-4
iii
•.......
"U)
9/30"I~"11'1111'11/11lT/I
FISHWHEEL.
lI/ili
~i""'-"""--"""'---""'--""---..,.--....,----r--
6/1
DATE
0 60 CURRY FISHWHEEL2RN120..:28 S~
~o 411 Chum..N
...Ill
...;0..1
0",3~...-"..U)
.-<:I 2~QU)
"'::1-.:-y "
"'0 II
<:I 1I/1 lI/lll 1/1 7/1~1I/1 &/15 9/1 1/15 1/30--DATE,
Figure 6-9.Timing plots showing peak occurrence of chum,pink
and sockeye salmon migration at mainstem Susitna
River fishwheel sites,1981.(Note:first run
sockeye salmon not included).
6-28
Chum
Pin k
•.
1982
§105 SUNSHINE FISHWHEEL__RM 80
:~9ur-i:715
~C\I.....!;a
Cia:_~4',,-
::3O+----.....,.---~r__---.,....---...,....---.....,----,_-.;;::;;;..":"'T'"':_--__!
;5/30 61"6/30 7/1'7130 6/"6/30 9/1'9/30
CD
....,
DATE
'5 40 TALKEETNA FISHWHEEL0
Q RM 103-...3828_0 30
'"'N~m
"'lD 2':-Pink.-CD
Q<l)20.........~.-u "...
!""""0 '0
<l)5/30 6/t'8/30 7/18 7/30 lIlI 8 lI/30 9/15 9/30
DATE
9/309/15
Chum
8/308/15
•
7/307/"6/306/"
CURRY FISHWHEEL
RM 120
O-+-------r---.....,r__---.,....---...,....---.....,----,_----,...-----r
~/3O
DATE
Fi gu re 6-10 .Timing plots showing peak occurrence of chum,pink
and sockeye salmon migration at mainstem Susitna
River fishwheel sites,1982.(Note:first run
sockeye salmon not included).
-6-29
1983
I "".ciIO",sater.p.Q.I
i--:rL--:'1~
,%cu,.Ga'IV;.9~o/o C~",uIQlr...
CQ:1CIll ~.,Effa,t Calch ".r Effort
DAT£
10/19/159/18/158117//!I7/16/15
SUNSHIN£FISHWHEEL
RM 80
15+---....,----...,:-----T----....,----.,..----"""'l'----,...---,;;;"
6/1
10/19/159/18/158/17/1!I7/1
FISHWHEEL
6/15
61----"""'l'----"'T"---...,-----~---.,...----.,..---...,----.,
6/1
DATE
CURRY FISHWHEEL
RM 120
0
0 35
S2.
IIJ-30...008-N 25
-Ill~N
OlD 20,..-
~'"-I!lQ",15.-::1.--10c:;...6'0
I!l 6/1 6/15 7/1 7/15 8/1
•
8/15 9/1 9/15 10/1
DATE
Figure 6-11.Timing plots showing peak occurrence of chum,pink
and soc~eye salmon migration at mainstem Susitna
River fishwheel sites,1983.(Note:first run
sockeye salmon not included).
6-30
I 1 ]--1 )1 ]1 ]1 )1 1 1 )]1 )
CHUM
/,';HlLpllll')h.li,l'r /fl'ih Plesenctl 1I~----------,
~---'j ~:~---~l~"I/01...7!!1,Ih
P.runili.P..,t.,-.,iI.hre."tll,
U...dlan)
1981 I li/ltl -~~-i
t/V.lnold.,,"0'
.olmon "I .1,,,1
lolal "a.ot.1'.vl.'h.
I/V=70/209
I I I1----iii Iii i 0
.......
o
50 g
X
(J)
40 t;
w
(!)
30 0::<{
:I:o
(J)
20 0
~
W
W
0::10 0
o
..Jo
(!)
I/V:77/318
I/V=74/287
,,",',',,
'-'
I
I
........,,1
,.
'\1982,\,\,\
I \
I \
),\\
~,to"
I ,...
1981
1982
0'\II I l r'-..\J ,\1983w
I-'\I \'\' •,~I I I ,\",
\'-\",'I....\,,'..,I
'.,,I p',\"",'I ''V"\ ,...\-'\.-
'"",',I 'II..........\,'\.....,J ',,'\""\'
\.,'""....
'-~"/983 I-1-------------
6/30 7/15 7130 8/15 8/30 9/15 9/30 10/15
DATE
Figure 6-12.Peak periods of chum salmon presence in relation to mainstem Susitna River
discharge in slough and side channel study sites,1981,1982,1983.
1 I §J ]j i 1 ]1 J i I 1
SOCKEYE
1981
/'5'Jlllpll1l J h'll,-Il:'r ./f-l~t;'P;uuce 1r-----=r
~----/~C _..~l~"/0'.7~,.
PlI,until.P,runtile f'lrnntil.
(M.dlQll~
t-,--~~~j0*in0~\'i;!;;1ij;ii;~;!;f'i!i.1 ---I
I/v.lnoldenll of
lollnon al lilill
10101 1\0.of lill
"I.ill.
IIV=49/209
.....
aoa
50 x
en
l1..
U
40-
W
(!)
0::<t30::I:
Uen
a
20 ~
W
W
0::
U
10 a
..Ja
(!)
IIV =42/318
I/V =45/287
r .....\J """.I'I \'I ' '........1983 I \-1982
'J'I \I \I ' •\...,,'.....\ \',,,III....I I \/",\
)."I ~"~\I \\'J""\I'II', ,I',.\I \\\II '_~'\/\..:....'('"I \.....J \I -"\\ ,I \
\_1 ......,,-.......,\./..,'\'"/',I .\
1-------------'-...--",.........I ,,',.-'/\~.",-,,...
"I \",...I...',I
'__JI
1981
1983
1982
O'l
I
W
N
'J I i I Iii i '0
6/30 7/15 7/30 8/15 8/30 9/15 9/30 10/15
DATE
Figure 6-13.Peak periods of sockeye salmon presence in relation to mainstem Susitna River
discharge in slough and side channel study sites 1981.1982.1983.
I J 1 1 1 I 1 "'J r J J ~I
Table 6-3.Dates and counts of peak escapement of chum and sockeye salmon observed in selected sloughs in the middle Susitna River
during 1981,1982 and 1983 (Data derived from ADF&G 1981b;1983cj Barrett et al.,1984).
Chum Salmon Sockeye Salmon
River 1981 1982 1983 1981 1982 '1983
Site Mile Date/No.Fi sh Date/No.fish Date/No.Fish Date/No.fish Date/No.Fi sh Date/No.Fish
Whiskers Creek Slough a 101.2
Mainstem 2 Side a
Channel 114.5
Slough 8A 125.3 9/4 (330)8/23 (307)8/30 (34 )9/4 (170)8/12 (68)9/11 (63)
Slough 9 128.3 9/4 (212)9/5 (242 )9/5 (121)9/4 (10)9/13 (3)9/7 (2)
0'\Slough 9A 133.2 9/20 (136 )9/6 (107 )9/11 (93)9/12 (2)9/19 (1)9/11 (1)I
Ww Side Channel lOa 133.8
Slough 11 Complex b 135.3 8/27 (403)8/30 (395)9/9 (214 )9/11 (710)8/30 (455)9/11 (237)
Slough 20 140.1 9/3 (12)9/4 (23)8/18 (57)8/26 (2)
Slough 21 Complex c 141.8 9/3 (270)9/4 (615)9/9 (149)9/11 (38)9/4 (43 )9/9 (180)
Slough 22 144.2 ----B/18 (109)
a Complete survey data are not available for determining peak counts of chum and sockeye salmon in these sites of these three sites
chum salmon have been observed only at Mainstem 2 Side Channel.
b Includes fish from Slough 11 and Upper Side Channel 11.
c Includes fish from Slough 21 and Side Channel 21.
)-]J J I --I J I J ]1 J 1 1 j
Table 6-4.Percent of total number of chum,sockeye and pink salmon in selected sloughs in 1981-1983.Percents were based on peak counts
of live and dead fish.(Derived from data presented in ADF&G 1981bi 1983ci Barrett ~!l.•1984).
Percent Distribution
River 1981 1982 1983 Average
Location Mile Chum Sockeye Pink Chum Sockeye Pink Chum Sockeye Pink Chum Sockeye Pink
Slough SA 125.9 23.9 14.3 0.0 15.0 11.2 5.5 2.5 11.9 14.2 15.1 13.0 5.2
Slough 9 128.3 10.0 0.8 0.0 13.4 0.8 2.4 11.5 0.3 0.0 11.1 0.7 2.1
Slough 9A 133.6 7.0 0.1 0.0 5.3 0.2 0.0 7.2 0.2 0.0 6.2 0.1 0.0
Slough 10 133.8 0.0 0.0 0.0 0.1 0.0 0.0 a 0.2 0.0 b 0.0 0.0
(J)
J
W
-Po Slough 11 135.3 15.8 72.0 0.0 20.5 75.2 25.8 16.2 44.7 33.3 16.9 66.3 24.1
Slough 20 140.1 0.6 0.1 0.0 1.3 0.0 12.6 4.3 0.0 33.3 1.7 0.1 12.6
Slough 21 141.8 10.6 3.1 0.0 32.8 8.7 12.6 21.8 35.5 4.8 20.2 12.0 11.5
Slough 22 144.2 b b 0.0 0.0 b b 7.8 0.0 0.0 5.2 0.0 0.0
a ~Less than 0.1%of total numbers of fish.
b ~Insufficient data.
J )1 I J I CC-1 ]I ]1 C I I
Table 6-5.Selected physical characteristics of passage reaches at the time thalwegs were surveyed at each sitea •
Conditions at Time of Thalweg Survey
Shallowest Depth Criteria
Location Passage Mainstem Thalweg Passage Length Passage Curve
(River Mile)Reach Discharge (cts)(ft)(ft)(ft)Evaluation Used.
Whiskers Creek Slough I 8440 0.10 0.10 270 unsuccessful II
(101.2)II -0.15 0.14 120 unsuccessful II
III -0.10 0.10 100 unsuccesliful II
Mainstem 2 I 9080 0.30 0.26 105 unsuccessful I
Sice Channel II -0.35 0.30 170 unsuccessful I
(114.4)III L -0.30 0.26 360 unsuccessful II
III R -0.30 0.26 165 unsuccessful II
IV R -0.25 0.22 25 unsuccessful I
V R -0.10 0.10 295 unsuccessful II
VI R -0.00 0.00 85 unsuccessful II
VII R -0.00 0.00 355 unsuccessful II
VIII R -0.10 0.10 390 unsuccessful IIm
I Slough 8A I 6750 0.20 0.18 170 unsuccessfulw
U1 (125.91 II -0.15 0.14 265 unsuccessful
III -0.20 0.18 510 unsuccessful
IV -0.30 0.26 260 unsuccessful
V -0.20 0.18 190 unsuccessful
VI -0.40 0.34 80 successful/difficult
VII -0.40 0.34 75 successful/difficult
VIII -0.20 0.18 435 unsuccessful
IX -0.10 0.10 475 unsuccesliful
Slough 9 I 10,700 0.30 0.26 200 unliucces5ful I
(128.31 II -0.20 0.18 520 unliuccessful I
III -0.20 0.18 275 unsuccelisful I
IV -0.40 0.34 30 ~uccessful/difficult I
V -0.00 0.00 3140 unsuccessful II
Slough 9A I 9,400 0.30 0.26 115 unsuccessful II
(133.6)II -0.30 0.26 1,,5 unsuccessful II
III -0.15 0.14 320 unsuccessful II
IV -0.20 0.18 30 unsuccessful II
V -0.45 0.37 20 successful/difficult II
VI -0.50 0.41 205 successful/difficult 1/
VI J -0.50 0.41 20 successful/difficUlt II
VIII -0.40 0.34 40 unsuccessful II
IX -0.20 0.18 310 unsuccessful II
X -0.00 0.00 255 unsuccessful II
(Continued)
1 J -1 -1 .--~-1 --1 I I J I J -1 1 ··-1 J i
Table 6-5 (Continued).
Conditions at Time of Thalweg Survey
Shallowest Depth Cr i teri a
Location Pa::,sage Mainstem Thalweg Passage Length Passage Curve
(River Mile)Reach Discharge (cfs)(ft)(ft) (ft)Evaluation Used
Side Channel 10 I 13,200 0.00 0.00 340 unsuccessful
(133.8)II -0.00 0.00 365 unsuccessful
III -0.00 0.00 40 unsuccessful
IV -0.00 0.00 40 unsuccessful
V -0.30 0.26 10 successful/difficult
VI -0.00 0.00 200 unsuccessful
VII -0.00 0.00 265 unsuccessful
Slough 11 I 6,600 0.30 0.26 250 unsuccessful I
(135.3)II -0.30 0.26 745 unsuccessful I
III -0.30 0.26 115 unsuccessful I
IV -0.15 0.14 480 unsuccess ful II
V -0.20 0.18 2,640 unsuccessful II
0'\Upper Side Channel 11 I -0.20 0.18 105 unsuccessful I
I (136.1)II -0.05 0.41 735 unsuccessful "to.>
0'\III -0.00 0.00 935 unsuccessful II
Slough 20 I 8,480 0.15 0.14 170 unsuccessful II
(140.1)II -0.15 0.14 300 unsuccessful II
III -0.25 0.22 170 unsuccessful II
IV -0.50 0.41 100 successful/difficult II
V -0.30 0.26 50 unsuccessful II
VI -0.05 0.41 660 unsuccessful II
Side Channel 21 I 7,800 0.20 0.18 45 unsuccessful II
(140.6)II -0.30 0.26 155 unsuccessful II
III -0.50 0.41 135 successful/difficult II
IV -0.20 0.18 35 unsuccessful II
V -0.40 0.34 505 unsuccessful II
VI -0.30 0.26 160 unsuccessful II
VII -0.40 0.34 360 unsuccessful II
VIII -0.25 0.22 105 unsuccessful II
IX -0.30 0.26 940 unsuccessful II
X -0.30 0.26 600 unsuccessful II
Slough 21 I 7,800 0.50 0.41 30 successful/difficult II
(141.8)II L -0.25 0.22 1,260 unsuccessful II
II R -0.00 0.00 2,030 unsuccessful II
(Continued)
I
Table 6-5 (Continued).
1 1 1 1 ]J J J )f ]J
m
I-w
'-J
Conditions at Time of Thalweg Survey
Shallowest bepth Criteria
Location Passage Mainstem Thalweg Passage Length Passage Curve
(River Mile)Reach Discharge (cfs)(ft)(ft)(ft)Evaluation Used
Slough 22 I 16,500 0.25 0.22 350 unsuccess fu I /I
(144.2)II -0.40 0.34 35 successful/difficult I
ill -0.40 0.34 30 successful/difficult I
IV -0.10 0.10 295 unsuccessful I
a Mainstem discharge values are from data collected.at the United States Geological Survey gaging station at Gold Creek.Mainstem dis-
charges correspond to date of survey and do not necessarily reflect base flow conditions at each site.
-.
3.2.1 Breaching and Backwater Discharges
Mainstem discharges and corresponding percent exceedence values that are
required to provide successful and unsuccessful salmon passage con-
ditions at selected spawning sites are summarized in Table 6-6.In this
table,all mainstem discharges are paired with a corresponding percent
exceedence that represents the percent of time that the indicated flow
was equalled or exceeded during the critical salmon·spawning period (20
August -20 September)based on a 32 year flow record (USGS gage
#15292000).All exceedence values were derived from the resultant flow
duration curve previously provided in Figure 6-6.
3.2.2 Local Flow
Local flow estimates corresponding to successful and unsuccessful
passage conditions at selected passage reaches are provided in Table
6-7.The estimates provide an indication of how much local flow is
required for passage in the absence of mainstern discharge effects.
6-38
]1 1 -1 1 1 1 -1 1 1 -J 1 -~I ]
~e 6-6.Summary of mainstem discharges required tg provide successful and unsuccessful salmon passage conditions at selected spawning sites
in the middle Susitna River,Alaska,1983 ••
BREAOII NG ANAL YS IS BACKWATER ANALYSIS 0
(CFS)(CFS)
Passageb Jnitl al Criteria Staff
Site Breaching Exceedance Controlling Exceed2nce Unsuccess·Exceegence Success·Exceegence Curve Gage
(River Mile)Reach Discharge ~Discharge ~ful 'I(,ful 'I(,Used Used
Whiskers Creek Slough I 22,000 16 23,000 14 22,500 15 d -II 101.2W1
(101.2)II 22,000 16 23,000 14 d -d -II
III 22,000 16 23,000 14 d -d -II
Mainstem 2 I 12,000 71 16,000 45 11,500 74 12.200 70 I 114.6W6
Side Channel II 12,000 71 16,000 4S d -d
(114.4)
III L 12,000 71 16.000 45 d -d -II 114.6W6
III R 23.000 14 25,000 10 _18,400 32 19,200 28 I 114.457
IV R 23,000 14 25,000 10 d ~d -II
V R 23,000 14 25,000 10 d -d -II
m VI R 23,000 14 25,000 10 d -d -IIIVIIR23,000 14 25,000 10 d .d -IIw
\.0 VIII R 23,000 14 25,000 10 d -d -II
Slough 8A e J 27,000 7 27,000 7 <10,600 79 <10,600 79 I 125.3W5
(125.9)II 27,000 7 27.000 7 14,600 54 15,600 48 I 125.356
III 27,000 7 27,000 7 d -d
IV 33,000 72 33,000 72 d -d
V 33,000 72 33,000 72 d -d
VI 33,000 72 33,000 72 d .d
VII 33,000 72 33.000 72 d -d
VIII 33,000 72 33,000 72 d -d
IX 33,000 72 33.000 72 d -d
Slough 9 I 16,000 45 19.000 29 <12,OOof 71 <12,200f 70 I 128.3W3
(128.3)II 16,000 45 19,000 29 d -d -II
III 16,000 45 19.000 29 d -d -II
IV 16,000 45 19,000 29 d -d -II
V 16.000 45 19,000 29 d -d -II
Slough 9A I-X No data No data No data No data
(133.6)
(Continued)
1 1 1 1 1 J 1 J ]J i J -)]J 1 i
Table 6-6 (Continued).
BREACHING ANALYSIS BACKWATER ANAL YS ISo
(CfS)(CFS)
Passageb Initial Criteri a Staff
Site Breaching Exceedsnce Controlling Exceedsnce Unsuccess-Exceegence Success-Exceegence Curve Gage
(River Mile)Reach Discharge ~Discharge %ful ~ful "Used Used
Side Channel 10 I 19,000 29 19,000 29 17,400 37 18,200 33 I 133.81'15
(133.8)"19,000 29 19,000 29 d -d
III 19,000 29 19,000 29 d -d
IV 19,000 29 19,000 29 d -d
V 19,000 29 19,000 29 d -d
VI 19,000 29 19,000 29 d -d
Slough 11 I 42,000 1 42,000 1 15,200 50 16,200 44 I 135.31'11
(135.3)"42,000 1 42,000 1 31,900 3 33,200 2 I
III 42,000 1 42,000 1 38,300 1 39,600 1 I
IV·42,000 1 42,000 1 d -d -II
V 42,000 1 42,000 1 d -d -"Upper Side I 13,000 65 16,000 45 11,400 75 12,400 68 I 136.21'13
Channel 11 II 13,000 65 16,000 45 d -d -II
(136.1).III 13,000 65 16,000 4S d -d -II
0'1
I
.f::>Slough 20 I 22,000 16 23,000 14 20,800 21 22,100 16 II 140.11'14
0 (140.1)"22,000 16 23,000 14 22,700 15 d .-"III 22,000 16 23,000 14 d -d -II
IV 22,000 16 23,000 14 d -d -"V 22,000 16 23,000 14 d -d -II
VI 22,000 16 23,000 14 d -d -"Side Channel 21 I 9,200 85 12,000 71 <12,OOOf 71 <12,000f 71 II No Gage
(140.6)"9,200 85 12,000 71 e -e -"III 9,200 85 12,000 71 e -e -II
IV 9,200 85 12,000 71 e -e -"V.9,200 85 12,000 71 e -e -"VI 9,200 85 12,000 71 d -d -II 140.654
VII 9,200 85 12,000 71 d -d -"VIII 9,200 85 12,000 71 d -d -II
IX 9,200.85 12,000 71 d -d -"X 18,000 34 24,000 12 d -d -"
(Continued)
1 J -~I 1 1 I J J 1 !,l i 1
m
I
~
I-'
Table 6-6 (Continued).
BREACHING ANALYSIS BACKWATER ANAlYSISo
(CFS)(CFS)
Paliliage b InitIal Criteria Staff
Site Breaching Exceedgnce Controlling Exceedgnce Unsuccess-Exceegence Success-Exceegence Curve Gage
(River Mile)Reach Discharge ~Discharge \fu!\;ful \~Used
Slough 21 I 23,000 14 25,000 10 d -d -II 142.0W5
(141.8)II l i3,000 14 25,000 10 d -d -II
II R 26,000 14 No Data -d -d -II
Slough 22 I 20,000 24 23,000 14 <23,ooof 14 <23,000f 14 II 144.3W3
(144.2)II 20,000 24 23,000 14 e -e -I
III 20,000 24 23,000 14 e -e -I
IV 20,000 24 23,000 14 e -e -I
a This analysis assumes that local flows are negligible.
bleft and right channels of sites (facing upstr'eam)are indicated as Ill"and uRII,respectively.
cpercentage of total time for a 32 year flow record,that the indicated flow is equalled or exceeded during
the period 20 Aug -20 Sept.(USGS gage at Gold Creek,gage #15292000).
dlnfluence of backwater was not evaluated since.breaching occurs at discharges lower than those required for
providing backwater influence.
elnfluence of backwater based on staff gage reading taken at mainstem discharge of 10,600 cfs;backwater
rating curve not adequately defined below 15,000 cfs.
fBackwater rating curve not defined below the indicated (or preceeding)table value.
J 1 J -1 J 1 J 1 I I i J J
Table 6-7.Required local flows for successful and unsuccessful passage conditions at each passage reach identified in selected
slough and side channel habitats in the middle Susitna River.Alaska.1983.
Passage Reach Successful Conditions Unsuccessful Conditions
River Passage Local Passage Local
Site Mile Number length (tt)Depth (ft)Flow (ets)Depth (ft)Flow (ets)
Whiskers Creek 101.2 I 270 .54 18 .41 5
II 120 .49 16 .37 8
III 120 a a a a
Mainstem 2b 114.4 I 105 a a a a
II 170 a a a a
III L 360 a a a a
III R 165 a a a a
IV R 25 .35 5 .24 3
V R 296 .54 5 .41 3
VI R 83 .48 5 .35 3
VII R 354 .54 5 .41 3
VIII R 388 .54 5 .41 3
O'l,
-Po
N Slough 8A 125.9 I 170 .40 2 .30
II 265 a a a a
III 510 .41 4 .32 2
IV 260 a a a a
V 190 .41 5 .31 3
VI 80 a a a a
VII 75 a a a a
VIII 435 .41 4 .32 2
IX 475 .41 4 .32 2
Slough 9 128.3 I 200 .41 2 .32 1
II 520 .41 1 .32 1
III 275 .41 6 .32 4
IV 30 a a a a
V 3140 a a a a
(Continued)
j ....J J 1 1 !1 I 1 1 )I --J -1 --I l ---1 B !
Table 6-7 (Continued).
Passage Reach Successful Conditions Unsuccessful Conditions
Site
River
Mile Number Length (ft)
Passage
Depth (ft)
Local
Flow (cfs)
Passage
Depth (ft)
Local
Flow (efs)
Slough 9A 133.6 I 115 .49 1 .36 1
"145 .51 3 .38 2
III 320 .54 3 .41 2
IV 30 .48 1 .35 0.5
V 20 a a a a
VI 205 a a a a
VII 20 a a a a
VIII 40 a a a a
IX 310 .54 2 .41 0.5
X 255 .54 3 .41 0.5
Side Channel 10 133.8 I 340 a a a a
O'l II 365 a a a aI
~III 40 a a a awIV35aaaa
V 10 a a a a
VI 200 a a a a
VII 265 a a a a
Slough l1 b 135.3 I 250 .41 4 .32 3
II 745 .41 4 .32 3
III 115 .36 4 .27 3
IV 480 .54 8 .41 5
V 2.639 .54 '4 .41 3
Upper I 105 .36 6 .26 1
Si de Channell-I 136.1 II 735 .54 12 .41 7
III 935 a a a a
Slough 20 140.1 I 170 .52 6 .39 3
II 300 .54 9 .41 4
III 170 .52 6 .39 3
tv 100 a a a a
V 50 a a a a
VI 660 a a a a
(Continued)
1 1 I ]J J l J I J I I I )1 )1
Table 6-7 (Continued).
Passage Reach Successful Conditions Unsuccessful Conditions
River Passage local Passage Local
Site Mile Number length (ft)Depth (ft)Flow (ds)Depth (ft)Flow (cts)
Side Channel 21 140.6 I 45 a a a a
II 155 .51 8 .39 4
III 135 a a a a
IV 37 .48 7 .35 2
V 505 .54 18 .41 10
VI 160 a a a a
VII 360 a a a a
VIII 105 a a a a
IX 940 .54 20 .41 10
X 600 a a a a
Slough 21 141.8 I 30 a a it a
II L 1260 a a a a
O'l " R
20BO a a a a
I+:>+:>Slough 22 144.2 I 350 .54 11 .41 6
II 35 a a a a
III 30 a a a a
IV 295 .41 2 .32 1
a Values not determined
b Discharge values obtained by observation (personal communication,E.W.Trihey).
1.
.-
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I
I
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lI'J'I'\
,
I···..
:
4.0 DISCUSSION
4.1 Assumptions and Limitations of Analyses
4.1.1 Passage Criteria Assumptions and Limitations
In order to develop criteria to evaluate successful and unsuccessful
fish passage several assumptions were made.These assumptions enable
the fish passage criteria to be generalized for application at all
sloughs and side channels.These assumptions are as'follows:
1.All passage reaches can be descri~ed as either uniform,
straight channels with small.substrate,or as non-uniform,
braided channels with large substrate;
2.Successful and unsuccessful passage conditions for a given
channel type for chum salmon are dependent only on passage
depth and passage reach length;
3.Existing temperature variation effects are negligible in the
development of criteria curves;
4.All velocities in the passage reaches are less than 2 fps and
do not limit fish access.This assumption is a simplifica-
tion.Velocities occasionally approach 4 fps in the middle of
some side channels during high mainstem discharges;and
5)Water depths at which passage becomes successful at a reach
length of 200 feet are adequate for passage at longer reach
lengths;
All assumptions appear justified by field observations by biologists.
Most passage reaches conform to one of the two categories described in
the first assumption.Those passage reaches which did not conform were
classified using repeated field observations.Passage depth and reach
length are judged to be the most important factors influencing fish
passage.Small ranges in temperature variability and water velocities
below 2 fps seem to have little effect on fish passage.Field obser-
vations also indicate that at reach lengths exceeding 200 feet,depths
required for passage do not increase.
Additional assumptions a're made for the evaluation of passage reaches.
Some apply to the general application while others relate to the method
of analysis.The general assumptions which apply to all analytical
methods are as follows:
The channel geometry at cross section locations does not
change with varying discharge.No erosion or deposition
occurs over the study period.
2.Reach lengths remain constant with variations in local flow.
6-45
·,...,
f""1
....
....
-
3.The relationship between passage depth and mean depth.and
passage depth and thalweg depth which are developed from
surveyed transects can be applied at all cross sections.
The first assumption appears justified on two levels:1)most cross-
sections studied typically did not experience significant variations
during the period of study;and 2)the analysis attempts to represent a
stable long-term,system.Erosion and deposition would be approximately
in equilibrium in such a system.
The second assumption can be supported through consideration of the
small range of depths of interest in the passage reach.Such a small
range would not cause a significant change in passage reach length.
The third assumption is based on regime theory in which channel shapes
are similar between river systems.Additional data collected during the
1984 field season will be used in an attempt to provide refinement and
verification of this assumption.
4.1.2 Analytical Assumptions and Limitations
The breaching analysis assumes that when breaching occurs,passage is
successful throughout the slough.This assumption appears justified
based on repeated field observations.When a slough is breached,
sufficient volumes of water are present to permit fish access throughout
the slough.
In the backwater analysis,it is assumed that local base flow is a
relatively insignificant factor in comparison to the effect of the
mainstem and thus,is considered negligible in backwater calculations.
The justification for this assumption depends on the small increase in
water depth due to the 1oca 1 flow.The passage reach depths wi 11 not
increase significantly until the backwater directly influences the water
depth.
Five assumptions are made specifically for the analysis of the local
flow.These are:
1.Slough flow is constant throughout the length of the slough
unless data exist for estimating the effects of tributaries or
groundwater upwelling on local flow;
2.Local unit flow is a function of mean depth and reach gradi-
ent;
3.The reach gradient from the thalweg survey corresponds to the
energy slope;
4.Uniform flow is assumed;that is Manning's equation is appli-
cable at passage reaches;and •
5.Manning's roughness coefficient as calculated at a gaging site
is applicable at a passage reach and is constant for varying
depths of flow.
6-46
"....
I
I
.....
.....
.....
The first assumption appears justified by field experience.Unless the
data indicate a change in slough flow,the effect of upwelling is
considered negligible.Additional data will be used in an attempt to
refine this assumption in the FY85 report on fish passage.
The second assumption is justified by empirical calculations using data
from surveyed cross sections.
The last three assumptions relate to the use of Manning1s equation and
will be refined when additional data become available.
Field observations form the primary justification of the assumptions
made in the analysis.The accuracy of these assumptions are thus
difficult to evaluate.However,for the present conditions,the analy-
sis correlates well with observed conditions.
4.2 Timing
Data on the migration of chum,sockeye,and pink salmon in the mainstem
Susitna River indicate that natural variations in mainstem discharge
from year to year during the salmon spawning migration period do not
affect the overall timing of salmon arrival at the mouth of slough and
side channel spawning sites.Fishwheel catch rates of salmon show that
peak periods of migrational activity in the mainstem occurred at approx-
imately the same time period (mid-August)for the years 1981,1982 and
1983.Since the overall timing of the salmon migration remained rela-
tively constant during all three years,despite higher than normal
discharges in 1981,it appears that present flow regimes of the Susitna
River provide adequate passage conditions to allow proper ti~ing of the
salmon migration in the mainstem Susitna River.
Similarly,surveys at slough and side channel sites show that peak
numbers of salmon occurred during the same general time period (August
20 to September 20)for all three years.However,survey counts (con-
ducted at these same sites)during the three year period show that there
are fluctuations in the numbers of salmon within these sites from year
to year.This suggests that although present mainstem discharges may
not affect the time period when salmon arrive at those sites,they may
affect the numbers of salmon that are able to successfully spawn in
portions of the slough due to passage restrictions.Fluctuations in the
numbers of salmon observed at study sites may also be attributed to year
to year variations in escapement.
4.3 Passage Conditions at Study Sites
4.3.1 Slough Sites
4.3.1.1 Whiskers Creek Slough
Hhiskers Creek Slough is not utilized as a spawning site for chum or
sockeye salmon.Pink salmon spawn in the slough below the confluence
with Whiskers Creek.The slough is primarily used by chum salmon as a
migrational corridor to gain access to Whiskers Creek where they spawn.
6-47
F"'"I
Therefore~any passage restrictions in Whiskers Creek Slough could
affect the spawning distribution of salmon in Whiskers Creek.
Three passage reaches have been identified in Whiskers Creek Slough.
Successful passage conditions exist at all three of these passage
reaches at a controlling discharge of 23,000 cfs.However,this dis-
charge only occurs 14 percent of the time during the critical spawning
peri ad.There are no backwater effects on these passage reaches at
mainstem discharges below the breaching discharge.Relatively high
local flow estimates of about 18 cfs are required for successful passage
at Passage Reaches I and II.These flows probably occur frequently due
to the input of .flow from \alhiskers Creek which is the primary water
source for providing successful passage conditions within the slough
under unbreached conditions.
4.3.1.2 Slough 8A
Slough 8A provides spawning habitat for relatively large proportions of
chum and sockeye salmon in slough habitats within the middle reach of
the Susitna River.In addition,it provides spawning habitat for a
relatively smaller proportion of pink salmon.The distribution of
spawning adults for each species is affected by a series of beaver dams
located approximately 2,000 feet upstream from the mouth.These dams
impede upstream movements of fish significantly at mainstem discharges
below those required for breaching.
Nine passage reaches ranging in lengths from 80 to 510 feet,were
identified in this slough.Successful passage conditions occur at all
passage reaches when the head of the northeast channel becomes breached
at a controlling discharge of 33,000 cfs.Successful passage conditions
occur at the three lowermost passage reaches at a controlling discharge
of 27,000 cfs when the northwest channel breaches.At discharges below
27~OOO cfs,passage conditions are determined by local slough flows
and/or backwater.
Backwater affects only the two lowermost passage reaches.Successful
passage conditions occur at Passage Reaches I and II at mainstem dis-
charges of 10,600 and 15,600 cfs,respectively (rating curve not defined
for mouth gage below discharge of 10,600 cfs).At these discharges the
length of the backwater affected zone is approximately 1,000 and 1,200
feet,respectively.
Estimated base slough flow is relatively high in this slough compared to
most other sloughs evaluated in this study (Quane,et al.,1984).This
flow is primarily maintained by surface runoff and groundwater sources.
Estimates of local flow requirements for passage reaches in this slough
range from 2 to 5 cfs and are well below the estimated base flow of 10
cfs for this slough.
4.3.1.3 Slough 9
Slough 9 provides spawning habitat for a relatively large proportion of
the spawning chum salmon within the middle reach of the Susitna River.
In addition,it provides spawning habitat for relatively smaller
6-48
""",
proportions of sockeye and pink salmon.Within this slough,the dis-
tribution of adult spawners of each species are restricted to the lower
half of the slough because the upper half is largely dewatered under
non-breached conditions.
ft,tota 1 of fi ve passage reaches,rang i ng in 1engths from 30 to 3,140
feet,were identified in this slough.Successful passage conditions
occur at all reaches at a controlling breaching discharge of 19,000 cfs.
At mainstem discharges below 19,000 cfs,passage conditions at individu-
a1 passage reaches may be affected by backwater and/or 1oca 1 slough
flows.Although both Passage Reaches I and II are affected by backwater
at mainstem discharges below the controlling discharge,successful
passage conditions do not occur at Passage Reach II until the head of
the slough breaches (l9,000 cfs).However,successful passage con-
ditions at Passage Reach I occur at a mainstem discharge less than
12,000 cfs.This discharge is presently unrefined because the rating
curve developed for the staff gage in the mouth of the slough is unde-
fined at mainstem discharges less than 12,000 cfs.
Base slough flow is primarily maintained by two small creeks and upwell-
ing groundwater.Collectively,these sources provide a base flow of
approximately 5 cfs.This base flow appears adequate to provide suc-
cessful passage conditions at Passage Reaches I and II whi ch requi re
estimated slough flows of 2 and 1 cfs,respectively.However,this flow
is not adequate to provide successful passage conditions at Passage
Reach III which requires 6 cfs.Although it is not certain,it is
likely that successful passage conditions would also occur at Passage
Reach IV at a similar slough flow.However,Passage Reach V is located
upstream from the uppermost tributary and is typically dewatered except
for a small trickle of water maintained by upwelling groundwater.This
passage reach restricts upstream passage to over 3,000 ft of slough.It
therefore represents a major restriction to the full utilization of this
slough by spawning salmon at mainstem discharges less than 19,000 cfs
due to the absence of sufficient local flow to provide passage depth.
4.3.1.4 Slough 9A
Chum salmon are the predominant salmon species utilizing Slough 9A for
spawning.They have been observed throughout the entire length of the
slough.A limited number of sockeye salmon have also been observed in
the slough,however,their distribution is limited to the 1cwer third
portion.
Ten passage reaches have been identified in this slough ranging from 20
to 320 feet in length.Stage data are not available for this site to
evaluate the effects of mainstem backwater and breaching on passage
conditions within the slough.An analysis of local flow conditions
indicates that a slough flow of approximately 3 cfs provides successful
passage throughout the slough.Salmon have been observed in the upper
reaches of the slough under base flow conditions,which are maintained
predominately by up\tlelling.Since chum salmon have had to the entire
slough during 1981,1982 and 1983,it appears that they are able to
surmount all passage reaches under natural flow condi tions to provi de
passage depth.
6-49
....
""'.
~,
,.....
4.3.1.5 Slough 11
Slough 11 supports a major proportion of the chum,sockeye,and pink
salmon which spawn in slough and side channel habitats within the middle
reach of the Susitna River.Distribution of salmon within this slough
is normally restricted to the lower half because under typical flow
conditions the habitat in the upper reaches of the slough is mostly
dewatered.
Five passage reaches have been identified within this slough.The first
three are affected by backwater at mainstem discharges below the con-
trolling discharge.Successful passage conditions due to backwater
effects,for these three passage reaches will occur at mainstem dis-
charges of 16,200,33,200,and 39,600 cfs,respectively.However,·it
appears that local flow from upwelling and/or other groundwater sources
provides successful passage conditions at mainstem discharges less than
those required for backwater effects.During the critical spawning
period Passage Reaches II and III,which are seldom affected by back-
water (less than two percent of the time),and Passage Reach IV,which
is not affected by backwater,have been.accessible to salmon in past
years without any influence from mainstem discharge.
During periods of higher than normal mainstem discharges (42,000 cfs or
above)the slough head is breached and there are no apparent passage
problems.Under these conditions salmon have access to habitats above
Passage Reach V and have been observed throughout most of the length of
the slough.However,this controlling discharge occurs less than one
percent of the time during the critical spawning period.These con-
ditions last occurred during 1981 due to higher than normal precipita-
tion.
4.3.1.6 Slough 20
Slough 20 supports a relatively small proportion of the spawning chum
salmon that use slough and side channel habitats in the middle reach of
the Susitna River.However,pink salmon in Slough 20 have accounted for
an average of 12.6 percent of the pink salmon population in this reach
of the Susitna River over the last three years (Barrett,et al.,1984).
Only a few,apparently incidental,sockeye salmon have been observed at
this site.Distribution of salmon is limited to the lower part of the
slough from the large pool above Waterfall Creek to the mouth.
Six passage reaches have been identified in Slough 20 ranging from 50 to
660 feet in 1ength.The fi rst fi ve passage reaches are located below
the confluence with Waterfall Creek.Only Passage Reach I is fully
affected by backwater with successful passage conditions occurring at a
mainstem discharge of 22,100 cfs.However,this discharge occurs only
16 percent of the time.It appears that local flow,primarily from
Waterfall Creek,is adequate to provide successful passage conditions
during most of the critical spawning period.Local flo\'/s needed for
successful passage conditions through Passage Reach V have been estimat-
ed to be approximately 9 cfs.
6-50
F'"
I
Both chum and pink salmon were observed approximately 2,000 feet up-
stream in the large pool above Passage Reach V during 1982.However,
chum salmon distribution during 1983 was limited to the first 900 feet
of the slough even though successful passage conditions appeared to have
been provided periodically during the critical spawning period.This
may have been due to the fact that the low densities of chum salmon in
1983 did not allow for full utilization of the habitat.
Passage Reach VI begins above the large pool above the mouth of Water-
fa 11 Creek and extends for 660 feet.Spawni ng salmon have not been
observed within or above this passage reach.The low percent exceedence
value (l4%)associated with the controlling discharge for this slough
results in passage conditions at Passage Reach VI being unsuccessful the
majority of the time.
4.3.1.7 Slough 21
Slough 21 provides spawning habitat for a major proportion of the chum,
sockeye,and pink salmon within the middle reach of the Susitna River.
Side Channel 21 serves as a migrational corridor through which fish must
pass in order to reach the mouth of Slough 21.Once fi sh reach the
mouth,they are able to mill and hold in a relatively large pool area
before continuing up the slough to spawn.In general,salmon of each
species are restricted in distribution to the lower half of the slough
during periods when the slough is not breached.If breaching occurs
fish are able t~continue upstream and spawn in pools that later become
shallow isolated pools when breaching flows subside.
Three passage reaches ranging in lengths from 30 to 2,080 feet were
identified in this slough.None of these reaches are affected by
backwater at mainstem discharges below those required for breaching.
Breaching of the left fork occurs at a mainstem discharge of 25,000 cfs,
at which time Passage Reaches I and II are inundated.At present the
controlling discharge for the right fork is unknown.However,based on
an initial breaching flow of 26,000 cfs,it is likely that the control-
ling discharge is in the range of 27,000 to 29,000 cfs.
Base flow in this slough is estimated to be approximately 5 cfs.This
flow is maintained by upwelling groundwater and a very small tributary.
Estimates of local flow requirements at passage reaches were not possi-
ble due to an insufficient data base.However,observations made by
ADF&G personnel during the spawning period for chum salmon in 1982 (a
relatively dry year)suggest that local flow is insufficient for provid-
ing successful passage conditions at any of the three passage reaches
identified.
During the spawning period in 1982,four observations were made.
1)The majori ty of the 1oca 1 flow was rna i nta i ned by upwell i ng
groundwater originating in the lower half of the slough (below
the confluence of the two forks);
2)Chum salmon were densely concentrated in the pool directly
below Passage Reach I;
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3)Attempts to pass through Passage Reach I were not successful
by adult chum salmon during unbreached conditions;and
4)During mid September,the slough was breached and several chum
salmon moved upstream and spawned in areas within the defined
limits of Passage Reaches IlL and IIR.
These observations suggest that during 1982,local flows were not ade-
quate to provide successful passage conditions at any of the three
defined passage reaches.However,since 1982 was an exceptionally dry
year,local flow contributions from the small tributary were also likely
to have been unusually low.But,even if local flows were significantly
higher than those observed during 1982,it is not 1ikely that passage
would be successful at Passage Reaches IlL and I1R since these passage
reaches are above the region where most of the upwelling groundwater
originates and have exceptionally steep gradients (refer to Appendix
Figure 6-E-11).
4.3.1.8 Slough 22
Chum salmon,the only salmon species recorded at Slough 22,were first
observed spawning there in 1983.Previous to this salmon had not been
observed at this site.Although this s·lough does not appear to be a
major spawning habitat for chum salmon,7.8 per cent of chum salmon
recorded at slough and side channel habitats in the middle reach of the
Susitna River used this site during 1983 (Barrett,et al.,1984).The
salmon were distributed in the lower 1,500 feet of the slough,primarily
in the second large pool located between Passage Reaches III and IV.
Four passage reaches have been identified in Slough 22 ranging from 30
to 350 feet in length.All passage reaches have successful passage
conditions at a controlling discharge of 23,000 cfs.Below this dis-
charge,passage conditions are dependent upon backwater and/or 1oca 1
flow.
Only the first passage reach is affected by backwater.However,since
backwater rating curves are not available for this site,·it is not
possible to determine specific ~ainstem discharges required for success-
ful and unsuccessful passage.Backwater affects this passage reach at
discharges somewhere below 23,000 cfs.
Data on required local slough flows for successful and unsuccessful
passage are only available for Passage Reaches I and IV.Slough flows
required for successful passage at these two passage reaches are 11 and
2 cfs,respectively.It is likely that a combination of slough flow and
backwater act to provide successful passage conditions in Passage Reach
I.Passage Reaches II and III are relatively short and may be passable
under local flow conditions.Since estimates of local flow are not
available for this slough it is difficult to determine why salmon do not
use habitat within or above Passage Reach IV.Since it is a relatively
long passage reach without backwater,local flol,l/s may not be adequate to
provide successful passage conditions.
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4.3.2 Side Channel Sites
4.3.2.1 Mainstem 2 Side Channel
Chum salmon were observed spawning in Mainstem 2 Side Channel during
1982 and 1983.Spawning occurs primarily in the right channel,although
spawning salmon have been observed in the lower 200 feet of the left
channel.Other salmon species have not been observed at this site .
Nine passage reaches were identi-fied within this side channel.The
fi rst two Passage Reaches (I and II)occur in the main channel,one
passage reach is located in the left channel,and six passage reaches
were identified in the right channel.
Passage Reaches I and II (located in the main channel)and Passage Reach
IIIl (located in the left channel)have successful passage conditions at
a controlling discharge of 16,000 cfs,which occurs 45 per cent of the
time during the critical spawning period.Passage Reach I becomes
successful due to backwater i nfl uence at a di scharge of 12,200 cfs.
These rel atively low di scharge requi rements for successful passage at
these sites indicates that passage is not a problem a large portion of
the time.
Passage Reaches IIIR and VIIIR in the right channel have successful
passage conditions at a controlling discharge of 25,000 cfs.This
discharge occurs only 10 per cent of the time during the critical
spawning period.Passage Reach IIIR is affected by backwater at a
discharge of 19,200 cfs (successful passage).Available data on local
flows indicates that a flow of 5 cfs is needed for successful passage at
Passage Reaches IVR to VIIIR.With the limited data available on local
flows,it is not possible to determine how often successful passage
conditions would exist at these sites at discharges below the control-
ling discharge.
4.3.2.2 Side Channel 10
Side Channel 10 is not known to be used by spawning salmon.However,
some portions of this channel contain what appears to be suitable
habitat for spawning.Thus,passage conditions within this site were
evaluated to determine if the absence of spawning salmon was attribut-
able to fish passage restrictions.
Six passage reaches were identified ranging in lengths from 10 to 365
feet.Successful'passage conditions occur at all reaches at a control-
ling discharge of 19,000 cfs in the mainstem Susitna River.
Passage Reaches I and II are affected by backwater at discharges below
the controlling discharge.Successful passage conditions due to backwa-
ter influence occur at Passage Reach I at a mainstem discharge of 18,200
cfs.However,the backwater i nfl uence on Passage Reach II is not
sufficient to provide successful passage conditions below the control-
ling breaching discharge.
A base flow of 5 cfs is rna i nta i ned in th is channel by groundwa ter
upwe 11 i ng and 1oca 1 runoff.Est i mates of 1oca 1 flow requ i rements fo r
successful passage at passage reaches were not possible due to an
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insufficient data base.It does not appear that passage restrictions
account for the total absence of spawning salmon in this channel because
passage conditions in this channel do not differ substantially from
those in some sloughs where spawning occurs.
4.3.2.3 Upper Side Channel 11
Upper Side Channel 11 provides spawning habitat for a significant number
of chum salmon.The majority of fish spawn in the lower one third of
the channel which is affected by backwater.Significant numbers of fish
will also spawn in the middle reaches of this channel if temporary
breaching flows permit passage into the area.Salmon have not been
observed spawning in the upper one third of this channel.
Three passage reaches were identified t ranging in lengths from 105 to
935 feet.All reaches are inundated with mainstem water at a control-
ling discharge of 16,000 cfs.At flows less than 16 t OOO cfs t passage
conditions are determined by backwater and local flows.
Successful passage conditions due to backwater occur at Passage Reach I
at a mainstem discharge of 12,400 cfs.At this discharge t the backwater
extends approximately 450 feet into the side channel to the beginning of
Passage Reach II.Successful passage conditions at Passage Reaches II
and III do not occur as a result of backwater,at mainstem discharges
below that required for breaching.
Base flow in this channel is primarily maintained by groundwater upwell-
ing originating within the area defined as Passage Reach II.Above this
reach,some upwelling occurs,but it accounts for a relatively small
proportion of the base flow.Collectively,these sources maintain an
estimated base flow of 5 cfs (Quane,et al.,1984)which is less than
the local base flow requirements for Passage Reaches I and II (6 and 12
cfs,respectively).Passage Reach III could not be evaluated for local
flow requirements due to an insufficient data base.Because this
passage reach exists above the primary source of groundwater,it is
probable that local slough flows are substantially less than 5 cfs and
are not adequate to provide passage into the uppermost reaches of this
channel.
4.3.2.4 Side Channel 21
Side Channel 21 provides spawning habitat for a significant proportion
of the chum salmon and a relatively small proportion of the sockeye
salmon spawning within slough and side channel habitats in the middle
reach of the Susitna River.However,a refined estimate of the total
number of spawning salmon is not possible because turbid water is often
present in the channel,reducing the potential to visually identify
spawning fish.However,it is known that chum spawn throughout the
entire length of the side channel and that sockeye salmon spawn in the
upper one third.
Ten passage reaches were identified t ranging in lengths from 40 to 940
feet.Passage conditions at these reaches are primarily affected by
breaching conditions at one or more of the numerous side channels which
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connect Side Channel 21 to the mainstem Susitna River.Successful
passage conditions occur at all but the uppermost passage reach at a
controlling discharge of 12,000 cfs in the mainstem Susitna River.The
uppermost passage reach requires a mainstem discharge of 24,000 cfs for
successful passage conditions due to breaching flows .
Only the lowermost passage reach is affected by backwater at di scharges
below breaching di scharges.Successful passage conditions are provi ded
at a mainstem discharge of somewhat less than 12,000 cfs (rating curve
not defined below 12,000 cfs).
Base flow in this channel is maintained by flow originating from Slough
21,upwelling groundwater and two small tributaries.Due to an incom-
plete data base,only four of the ten passage reaches were evaluated for
local flow requirements.However,for Passage Reaches II,IV,V,and
IX,estimated local flow requirements for successful passage ranged from
7 to 20 cfs.These flows are well within the base flow of 25 cfs
estimated for this channel (Quane,et al.,1984).
4.4 Previous Studies:Comparison of Results
Upstream passage of adult salmon into selected slough habitats in the
middle Susitna River has been previously evaluated in two reports
(Trihey 1982;ADF&G 1983b).These reports used a conceptually similar
approach as used in the present study but differed in scope,methods
employed and terminology used (Table 6-8).The earlier of the two
reports (Trihey 1982)only evaluated two passage reaches in the mouth of
Slough 9 where adult chum salmon were observed to have passage
difficulty.In that report,the consideration of passage included only
the question of access of adult salmon into the mouth of the slough and
viewed passage as a threshold phenomenon in which conditions were
evaluated as either a "pro blem ll to fish access or "no restriction"to
fish access.In spite of these limitations,the study was valuable for
two primary reasons:1)it provided emperically based depth criteria for
passage requirements of chum salmon (0.3 ft for reach lengths ~100
ft),and 2)it focused attention on the need to evaluate passage in
greater detail.
In the second report ADF&G evaluated passage conditions into 9 sloughs,
including a reevaluation of Slough 9 (ADF&G 1983b).In four of the nine
sloughs,the methods employed were similar to those presented in Trihey
(1982).For the other five sloughs a less labor-intensive method was
employed,using available cross sectional data obtained in the mouttl
reaches of each site (for methods refer to AOF&G 1983b).As in the
earlier report,mainstem Susitna River discharges were provided for two
threshold conditions at the restrictive passage reach at the mouth of
each slouqh.The threshold conditions evaluated were described as
Uacute ll and Itunrestrictivell for access and essentially described the
same condition reported in Trihey (1982).
The.results of the second report (ADF&G 1983b)significantly expanded
the data base regarding access conditions in the mouths of slough
habitats.However,there were conceptual and operational difficulties
during the evaluatiqn process used in determining threshold passage
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conditions.One such difficulty was that the "threshold"concept of
passage was insufficient to represent the passage conditions which
actually exists at study sites.Conceptually,the "threshold"concept
was deficient in that it failed to account for conditions that occurred
between acutely restri ctive and unrestri ctive conditi ons.Oper-
ationally,the concept was difficult to apply because the criteria were
defined for a single depth/reach length (i.e.0.3 ft depth and 100 ft
reach length).Additionally,the criteria were difficult to apply to
conditions in which the length of reach changed with increasing mainstem
stage.In light of the conceptual and operational difficulties of the
previous reports,the approach undertaken in the present report was
modified to account for the continuum of depth/length combinations
encountered at various passage reaches (refer to Figures 6-4 and 6-5).
In addition,the present report expands the analyses of passage within a
site beyond the consideration of backwater,to include the effects of
breaching mainstem discharges and local flows.Finally,the present
report was expanded in scope to include the side channel sites which
were not evaluated in previous studies.
In spite of the differences in scope,methods and terminology,the
results from the two previous passage reports are in general agreement
for most sites with the findings in this chapter.Table 6-8 provides a
compari son of the results of the three passage studies (Trihey 1982,
ADF&G 1983b,and the present study)for seven sloughs evaluated in the
middle Susitna River.In one of the seven sloughs for which data is
reported (t~hi skers Creek Slough),passage reaches were i dentifi ed and
evaluated at different locations on the thalweg;therefore results are
not directly comparable.Of the remaining six sloughs,only one (Slough
9)was evaluated in each of the three reports.
Generally,the differences between reports are smaller for estimates cf
mainstem di scharges whi ch provi de successful (or unrestri cted)passage
conditions.This general trend is likely to be a result of rating
curves being better defined for discharges in the higher ranges.
In general ~where discrepancies in the results occur,it should be
assumed that the results of the present study are more rel iabl ethan
that in previous reports.This assumption cannot be verified at the
present time,but is in part substanti ated by the combi ned results
reported for Slough 9.The same two passage reaches were evaluated at
510ugh 9 in each of the three reports.For both passage reaches ill
Slough 9,the discharg~estimates for successful and unsuccessful
passage conditions reported in the present study are bracketed by the
values reported in the previous two reports.We believe that this
suggests that the values presented in this chapter are refinements of
those reported previously.
The largest discrepancy in reported values occurred in Slough 11.This
difference is most likely related to the differential effects of dual
flow on the estimates in both the ADF&G 1983b report and this chapter.
In this report,attempts were made to eliminate the effects of local
flow in the backwater analysis.However,in the previous report (ADF&G
1983)local flows were included in the backwater analysis.Thus,one
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I 1 ~l I I -j I 1 J J
Table 6-8.Comparison of results of the present passage study to results of previous reports involving
sloughs in the middle Susitna River.
Passage Present Study ADF&G 1983b Trihey 1982
Location Reach Unsuccessful Successful Acute Unrestricted Acute Unrestricted
Whiskers Creek 1 22,500 23,OOOa b b b b
Slough 1 b b 8,000 10,000
Slough 8A 1 <10 ,600 e 10,600 d d b b
7,860 d 12,OOOd
2 14,600 15,600 12,000 16,000 b b
Slough 9 1 12,000 12,200 <12,500 12,500 d 10,000 12,000
2 16,000 19,OOOa 18,000 20,000 12,000 18,000
Slough 11 1 15,200 16,200 c·6,700 b b
Slough 20 1 20,800 22,100 20,000 21,500 b b
0'1
I 23,OOOa 25,OOOaU1Slough211 b b b b........23,OOOa 25,OOOa2 20,000 23,000 b b
Slough 22 1 <23,000 23,000 20,000 22,500 b b
a Breaching occurs at discharges lower than those required for providing backwater influence.Initial
breaching and controlling discharges are provided for unsuccessful and successful conditions,respectively.
b Site not evaluated.
C Insufficient data.
d Data derived from report text,not summary Table B-5.
e Backwater rating curve not defined below the indicated table value.
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would expect the estimated flows to be greater in the present study.
The amount of difference between the estimates should depend,in part,
on the relative amount of local flow contribution.In Slough 11,the
local flow is relatively large,and its affect may be compounded by the
restricted channel width of the slough.
The second 1argest di screpancy is reported for unsuccessful (Acute)
conditions in Slough 9.Trihey (1982)reports the lowest value (12,000
cfs)and ADF&G (I983b)the highest (18,000 cfs).Since the present
study is in reasonably close agreement with the value reported in ADF&G
(I983b)it is likely that the 12,000 cfs estimate reported in Trihey
(1982)is not reliable.
All other reported differences do not exceed 3,000 cfs.In the case of
Slough 8A,the estimate reported for acute passage conditions in ADF&G
(1983b)is probably more realistic than the one reported in the present
study.This discrepancy is due to the lack of definition of the rating
curve for the backwater gage used in thi s study in the mouth of Slough
8A.This same reasoning applies to the discrepancy for unsuccessful
passage conditions in Slough 22.
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5.0 SUMMARY AND CONCLUSIONS
5.1 Summary
~.5.1.1 Mainstem Influence
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The mainstem Susitna River influences salmon passage conditions in two
ways.The most obvious influence occurs when the head of a slough or
side channel becomes breached.When this occurs~all passage reaches
are inundated and depth related passage 'restrictions are alleviated.In
addition to breaching~mainstem discharges affect passage in the mouth
area of a site by creating backwater pools.In general,as mainstem
discharge levels rise,the stage rises in the mouth region creating a
relatively quiescent pool which progressively inundates the lower
portion of a site.The extent of inundation depends upon both the river
stage and the gradient of the streambed.If the gradient is steeply
incl ined~the length of the inundated reach will be less than if the
gradient is relatively flat.
In this study,breaching of most sites occurred at relatively high
mainstem discharges (19,000-42,000 cfs).At mainstem discharges less
than those required for breaching~the combined effects of backwater and
local flows detennine the conditions for salmon passage.Backwater
conditions influence only the initial few passage reaches (generally one
or two per site),yet regulate the movement of salmon into the entire
slough or side channel from the mainstem river.In contrast,local
flows can influence a greater number of passage reaches than backwater
within a site,but usually do not influence passage from the mainstem
site into the slough or side channel.At any particular site,the
relative importance of breaching backwater and local flows will vary
primarily with changes in mainstem stage and secondarily with local
hydrologic conditions at the site (e.g.,local rainshowers and upwelling
groundwater).These factors may vary concurrently,providing a shift in
the relative importance'of factors affecting passage conditions.
5.1.2 Local Flow Influence
Current information on the effects of local flow on passage conditions
within each site is incomplete (refer to Table 6-7).However,it is
clear that the effect of local flow is relatively greater in sloughs
than side channels.Local flow in sloughs appears to be adequate to
provi de successful passage conditi ons at many passage reaches if fi sh
are ~ble to access the slough from the mainstem.However,the effect of
local flow varies among sites as discussed previously:In side
channels~local flows are less important for providing successful,
passage conditions,whereas breaching becomes relatively more important.
Local flow is relatively less important in these habitats because they
generally have no adjoining-tributaries and have less upwelling
groundwater.
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5.2 Conclusions
5.2.1 Timing and Distribution of Salmon
1.Salmon use the mainstem Susitna River primarily as a migrational
corridor to reach their nata1 spawning grounds in slough and side
channel habitats in the midd1e reach of the Susitna River basin.
2.Overall timing of sa1mon migration to the mouth s10ugh and side
channel spawning sites appears to be independent of mainstem
discharge under present f10w regimes.
3.The critical spawning period for chum salmon in the middle Susitna
River occurs from 20 August to 20 September.
5.2.2 Passage of Salmon
1.Passage conditions at a particu1ar slough or side channel in the
middl e Sus itna River are i nf1 uenced by breachi ng and,backwater
effects of mainstem discharge and local flow conditions.
2.Breaching discharges are relatively more important in providing
successful passage conditions within side channels than in sloughs.
3.Local flows are relatively more important in providing successful
passage conditions within sloughs than in side channels.
4.Backwater may be the dominant factor in providing successful
passage conditions from the mainstem into some slough or side
channel sites.Backwater normally affects the lower most passage
reaches in each site.A total restriction of fish passage through
a backwater affected reach would deny fish access to spawning areas
above the restricted reach.
5.The effects of local flow vary widely but appear to pl'ovide suc-
cessful passage conditions at a majority of passage reaches within
slough habitats if fish are able to access the site from the
mainstem.More reliable estimates on local flow requirements at
each site are anticipated in a forthcoming ADF&G technical
memorandum which will supplement the data presented in this report.
6.Of the sloughs evaluated in this study,Sloughs 9 and 21 have the
most serious passage restrictions for mainstem discharges less than
the breaching discharge.
7.Insufficient data are available to project the influence of
mainstem discharge on sources of local flow such as upwelling
during unbreached conditions.This information is reqUired to
refine the analyses.
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8.Duration analyses of local flow conditions are also required
to refi ne these analyses.That is,the si gnifi cance of a
local flow condition is dependent on'the frequency that the
flow can be expected.Although insufficient data are
presently available for this type of analysis,attempts ~vill
be made to execute this or a similar analysis in FY85 .
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6.0 GLOSSARY
Acute passage condition:See unsuccessful passage.
Backwater Area:A segment of flowing water in which the depth of water
is greater than that which would otherwise exist for a given
discharge due to an obstruction downstream of the channel.
Berm:The controlling elevation of the alluvial material at the head of
--a side slough or side channel that separates the side slough or
side channel from the mainstem Susitna River or other side
channels.
Breaching:Anyone of three conditions of overtopping the head of a
side channel or side slough (see also initial,intermediate,and
controlling breaching discharges).
Controlling Breaching Discharge:The breaching condition in which
mainstem discharges at Gold Creek are equal to or greater than the
mainstem discharges required to directly govern the hydraulic
characteristics within a side slough or side channel.This condi-
tion can be denoted as equalling the flow rating curve beginning
with the point of inflection and beyond mainstem discharge at Gold
Creek.
Cross Section Profile:A streambed profile which describes the bank to
bank cross sectional shape of the channel.
Discharge:Water volume passing a fixed location at a specific point in
time.In this report,the term specifically refers to mainstem
habitat.
Flow:Water volume passing a fixed point per unit.In this report,the
term specifically refers to non-mainstem habitats.
Gaging Station:A location site which has been established for monitor-
ing water surface elevation,flow or discharge.
Gradient:Change in vertical elevation per unit horizontal distance.
Head:The upstream confluence or point of origin of a lotic environ-
ment .
Inflection Point:The point at which a rating curve changes slope.
Initial Breaching Discharge:The mainstem discharge at Gold Creek when
mainstem water initially begins to enter (overtops)the upstream
berm of a side slough or side channel.
Intermediate Breaching Discharge:The range of mainstem discharges at
Gold Creek representative of the conditions between the initial and
controlling breaching discharges.Intermediate breaching dis-
charges occur from immediately after mainstem surface water begins
to overtop the head (berm)of a side slough or side channel up to
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the point when the mainstem discharge begins to govern the hydrau-
lic characteristics of the site.
Mainstem Habitat:Consists of those portions of the Susitna River that
normally convey water throughout the year.Both single and multi-
ple channel reaches are included in this habitat category.
Groundwater and tributary inflow appear to be inconsequential
contributors to the overall characteristics of mainstem habitat.
Mainstem habitat is typically characterized by high water veloc-
ities and well armored streambeds.Substrates generally consist of
boulder and cobble size materials with interstitial spaces filled
with a grout-like mixture of small gravels and glacial sands.
Suspended sediment concentrations and turbidity are hi gh during
summer due to the influence of glacial melt-water.Discharges
recede in early fall and the mainstem clears appreciably in
October.
Mouth:The area of a lotic environment at its confluence with another.
--Used in this report in reference to sloughs and side channels.
Overtopping:See breaching.
Passage:Ability of adult salmon to migrate within'a slough,side
channel or tributary.(See successful passage,successful passage
with difficulty and exposure,and unsuccessful passage conditions).
Passage Depth:The depth of water through whi ch a fi sh must pass in
order to proceed upstream.As used in our report,passage depth is
the average of the mean depth and maximum depth at a transect.
Passage Reach:Segments of a channel between its mouth and head which
are potentially limiting to adult salmon migration to spawning
areas within it.
Peripheral Habitats:Aquatic habitats located adjacent to the mainstem
Susitna River habitat (e.g.,side channel,side slough,upland
slough,tributary mouth and/or tributary habitats).
Pool:A portion of a lotic environment that is relatively deep and
slow-moving in comparison to other areas.
Project Datum:An elevation to which all other elevations that are used
within the project area are referenced.
Rating Curve:A curve that describes the relationship between water
surface elevation and discharge at a site •
Riffle:A portion of a lotic environment that is relatively shallow and
fast-running in comparison to other areas.
Side Channel Habitat:Consists of those portions of the Susitna River
that normally convey water during the open water season but become
appreciably dewatered during periods of low mainstem discharge.
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Side channel habitat may exist either in well defined overflow
channels,or in poorly defined channels flowing through partially
submerged gravel bars and islands along the margins of the mainstem
river.Side channel streambed elevations are typically lower than
the mean monthly water surface elevations of the mainstem Susitna
River observed during June,July and August.Side channel habitats
are characterized by shallower depths,lower velocities and smaller
streambed materials than the adjacent habitat of the mainstem
river.
Side Slough Habitat~This habitat is located in overflow channels
between the edge of the floodplain and the mainstem and side
channels of the Susitna River.It is usually separated from the
mainstem and/or side channels by well vegetated bars.An exposed
alluvial berm often separates the head of the slough from mainstem
discharge or side channel flaws.The controll i ng streambed/bank
elevations at the upstream end of the side sloughs are slightly
less than the water surface elevations of the mean monthly dis-
charges of the mainstem Susitna River observed for June,July,and
August.At intermediate and low-discharge periods,the side
sloughs convey clear water from small tributaries and/or upwelling
groundwater.These clear water inflows are essential contributors
to the existence of this habitat type.The water surface elevation
of the Susitna River generally causes a backwater area to extend
well up into the slough from its lower end.Even though this
substantial backwater area exists,the sloughs function hydrau-
lically very much like small stream systems and several hundred
feet of the slaugh channel often conveys water independent of
mainstem backwater effects.At high discharges the water surface
elevations of the mainstem river is sufficient to overtop the upper
end of the slough~Surface water temperatures in the side sloughs
during summer months are principally a function of air temperature,.
solar radiation,and the temperature of the local runoff.
Staff Gage:A device used to visually monitor changes in water surface
elevation at a site.
Successful Passage (unrestricted):Fish passage into and/or within the
spawning area is uninhibited,and would not affect natural produc-
tion in the area.
Successful Passage With Difficulty &Exposure:Fish passage into and/or
within the spawning area is accomplished,but with stress and
exposure to predation with the potential of reducinq the level of
successful spawning in the area.-This condition over a long period
of time may result in a decline in natural production in -the area.
Thalwe f Profile:A longitudinal profile that describes the streambed
e evation of the deepest portion of the channel parallel to flow .
Tributary Habitat~Consists of the full complement of hydraul ic and
morphologic conditions that occur in the tributaries.Their
seasonal flpw,sediment,and thermal regimes reflect the
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f!illIWl'
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integration of the hydrology,geology,and climate of the tributary
drainage.The physical attributes of tributary habitat are not
dependent on mainstem conditions.
Tributary Mouth Habitat:Extends from the uppermost point in the
tributary influenced by mainstem Susitna River or slough backwater
effects to the downstream extent of the tributary plume which
extends into the mainstem Susitna River or slough.
Turbid:The condition of water quality at a site when water clarity is
decreased by inorganic and/or organic suspended materials.
Unsuccessful passa~e:Fish passage into and/or within the spawning area
may be accomp ished by a limited number of fish;however,exposure
to excessive stress and increased predation (which are associated
with these conditions)may eventually eliminate or greatly reduce
the natural production in the area.
Unrestricted Passage Condition:See successful passage.
Upland Slough Habitat:Differs from side slough habitat in that the
upstream end of the slough does not interconnect with the surface
waters of the mainstem Susitna River or its side channels even at
high mainstem discharges.These sloughs are characterized by the
presence of beaver dams and an accumu l.a t i on of silt coveri ng the
substrate resulting from the absence of mainstem scouring dis-
charges.
Water Surface Elevation (WSEL):-The elevation of the water surface at a
particular location.
6-65
.....
.-
,....
7.0 CONTRIBUTORS
Aquatic Habitat and Instream Flaw Studies
(AH)Project Leader and Principal Contact
AH Fish Habitat Utilization Subproject Leader
AH Instream Flow Subproject Leader
Hydraulic Engineer
Data Processing Project Leader
Graphics
Typing Staff
Editors
Data Collection
Data Analysis
6-66
Christopher Estes
Andrew Hoffmann
Tim Quane
E.Woody Trihey
Allen Bingham
Sally Donovan
Carol Hepler
Carol Kerkvl iet
Ann Reilly
Vicki Cunningham
Peggy Skeers
Mary Gressett
Christopher Estes
Doug Vincent-Lang
Jeff Blakely
Andrew Hoffmann
Chri s Kent
Jody !·1iller
Pat Morrow
Tim Quane
Issac Quera 1
Sheryl Sa 1asky
Gene Sandone
Don Seagren
Kathy Sheehan
Rick Sinnot
Klm Sylvester
Tommy Withrow
Jeff Blakely
Elizabeth Bradley
Janet Hearns .
Andrew Hoffmann
Tim Quane
Issac Queral
Craig Richards
Larry Rundquist
Gene Sandone
Joe Sautner
Don Seagren
Len Vining
-
CONTRIBUTORS (Continued).
Text
6-67
Larry Rundquist
Joe Sautner
Len Vining
......
,....
......
-
8.0 ACKNOWLEDGEMENTS
The authors express their appreclation to the following for their
assistance in preparing this report.
The other staff of ADF&G Su Hydro Aquati c Studi es Program
and Woodward-Clyde Consul tants who provi ded thei r support to
this report..
D.Hilliard,LW.Trihey and Associates,for her assistance
with data collection and analysis.
6-68
Phase 1.Fi na 1
Acres Ameri can,
and Game/Sus itna
9.0 LITERATURE CITED
Acres American,Inc.1982.Susitna Hydroelectric Project:FERC
license application.Exhibit E.Volume 1,Chapter 2 (Draft
Report).Prepared for Alaska Power Authority,Alaska Department of
Commerce and Economic Development,Anchorage,AK.
Alaska Department of Fish and Game (ADF&G).1981a.Aquatic habitat and
instream flow project.Phase I.Final Draft.Prepared for Acres
American Inc.,by the Alaska Department of Fish and Game/Susitna
Hydro Aquatic Studies Program.Anchorage,AK.
•1981b.Adult Anadromous Fisheries Project.
-----Draft Report.Subtask 7.10.Prepared for
Incorporated,by the Alaska Department of Fish
Hydro Aquatic Studies Program.Anchorage,AK.
•1982.Aquatic studies program.Phase I.Final Draft.
--""Subtask 7.10.Prepared for Acres American Inc.,by the Alaska
Department of Fish and Game/Susitna Hydro Aquatic Studies Program.
Anchorage,AK.
•1983a.Aquatic habitat and instream flow studies,1982.
--':'7Volume 4 of Phase II Basic Data Report.Alaska Department of Fish
and Game/Susitna Hydro Aquatic Studies Program.Anchorage,AK.
•1983b.Synopsis of the 1982 aquatic studies and analysis of
----.::'fish and habitat relationships,Appendices.Phase II.Prepared
for Acres Ameri can Inc.,by the Alaska Department of Fi sh and
Game/Susitna Hydro Aquatic Studies Program.Anchorage,AK.
1983c ..Adult anadromous fish studies,1982.Phase II.Final
Report:Volume 2.Alaska Department of Fish and Game/Susitna Hydro
Aquatic Studies Program.Anchorage,AK.
·1983d.Aquatic studies procedures manual.(Draft).Phase II.
--""Preparedfor Acres American Inc.,by the Alaska Department of Fish
and Game/Susitna Hydro Aquatic Studies Program.Anchorage,AK.
Barrett,B.M.,F.r,1.Thompson,and S.M.Hick.1984.Jl.dult anadromous
fish investigations,May-October 1983.Susitna Hydro Aquatic
Studi es Report Seri es.No.1.Alaska Department of Fi sh and Game.
Anchorage,AK.
Bovee,K and R.Milhous.1978.Hydraulic simulation in instream flow
studies:theory and techniques.Instream Flow Information Paper
No.5.U.S.Fish and Wildlife Service.Instream Flow Group.Ft.
Collins,CO.
Quane,T.,P.Morrow,and T.W.Withrow.1984.Chapter 1:Stage and
discharge investigations.In Report No.3:Aquatic Habitat and
Instream Flow Investigations (May -October 1983),by C.Estes and
D.Vincent-Lang,eds.Anchorage,Alaska.
6-69
.....
Scott,H.B.and E.J.Crossman.1973.Freshwater fishes of Canada.
Fisheries Research Board of Canada.&ulletin 184.Ottawa.
Scully,D.R.,L.S.Leveen,and R.S.George.1978.Surface water
records of Cook Inlet,Alaska,through September 1975.Open file
report 78-498.U.S.Geological Survey,Anchorage,AK.
Thompson,K.1972.Detennining streamflows for fish life.pp.31-45.
In:Proceedings of the Instrearn Flow Requirements Workshop.March
~-16,Portland,OR.1972.
Trihey,E.W.1982.Preliminary assessment of access by spawning salmen
into side slough habitat above Talkeetna.Prepared for Acres
American,Incorporated.Anchorage,AK.
1983.Preliminary assessment of access by spawning salmon into
Portage Creek and Indian River.Prepared for Alaska Power
Authority.Alaska Department of Commerce and Economic Development,
Anchorage,AK.
and D.L.Wegner.1981.Field data collection procedures for use
---with the physical habitat simulation system of the Instream Flow
Group.(Draft).U.S.Fish and Wildlife Service.Cooperative
Instream Flow Group.Ft.Collins,CO.
U.S.Geological Survey (USGS).1981.Water Resources Data,Alaska .
Water Year 1981.
1982.Water resources data.Alaska.Water year 1982.
.1983.Provisional summary of 1983 water resources data for
--....Alaska.
6-70
-I
-i
I
I
'e
-I
I~
-
10.Appendices
6-71
.....
-
....
.....
Appendix 6-A
Site Descriptions
6-A-l
.....
APPENDIX 6-A
This appendix presents a site by site description of the physical and
hydrological characteristics of slough and side channel study sites.
The sites are presented in order beginning with the most downstream
site,Whiskers Creek Slough (RM 101.2),and continuing upstream to
Slough 22 (RM 144.2).
Whiskers Creek Slough -RM 101.2
Whiskers Creek Slough is located on the west bank of the Susitna River,
3.3 miles above the confluence of the Chulitna and Susitna Rivers
(Appendix Figure 6-C-1).The slough is 2940 feet long and semi-circular
in shape.Whiskers Creek enters the slough approximately 1200 feet
upstream of the slough mouth.The lower third of the slough has a
gradient of 18.8 ft/mi while the upper two thirds is relatively flat
with a gradient of 4.9 ft/mi.The slough has both steep and gentle
sloping banks with sparse vegetative cover.Gravel/rubble substrate is
predominant in the lower half of the slough with mostly cobble/boulder
substrate in the upper half of the slough.Silt/sand deposits are found
in the pools in the backwater area at the mouth.
The primary water source of the tributary is surface runoff from bogs.
Tannins originating from the bog discolor the creek,along with sus-
pended silts at high discharges.The slough1s water clarity is affected
by the creek and mainstem backwater in the lower section,and by the
mainstem Susitna River when breached,causing the entire slough to flow
turbid.~ihen unbreached,the slough flows clear above its confluence
with Whiskers Creek.
The controlling discharge of the slough is 23,000 cfs.At this,or
higher discharges,the typical pool/riffle sequence changes to long runs
or pools.At mainstem discharges below the controlling level,slough
flow is maintained by ground seepage and flow from Whiskers Creek.A
backwater pool at the mouth extends 700 feet up the slough at mainstem
discharges of 21,600 cfs or higher,eliminating the first riffle
upstream of the mouth.
Mainstem 2 Side Channel-R~1114.5
Mainstem 2 is a broad V-shaped side channel located on the east bank of
the Susitna River (Appendix Figure 6-C-2).The left channel extends
4,400 feet upstream from the mouth in a northerly direction.The right
channel joins the left channel approximately 1600 feet upstream of the
mouth and·extends 4,400 feet upstream in a north-northeasterly di rec-
tion.Cobble/boulder is the predominate substrate throughout the side
channel,especially in the right channel.Gravel/rubble and silt/sand
deposits can be found in the pool and riffle areas.Silt/sand suhstrate
is especially predominant in the backwater area at the mouth.The side
channel has both steep and gentle sloping banks with sparse vegetative
cover.The Alaska Railroad parallels the slough on a high steep bank
from the mouth to the head of the right channel (RM 116).
6-A-2
.....
.....
The two channels of Mainstem 2 side channel have different controlling
discharges.The controlling discharge of the left (NW)channel is
16,000 cfs while the right (NE)channel is 25,000 cfs.When the left
channel breaches,it affects the backwater pool at the mouth and the
left channel itself.Except at the confluence of the two channels,it
has little if any effect on the right channel.Below controlling
discharges,base side channel flow is maintained by seepage from the
mainstem and runoff from the surrounding area.
A typical pool/rjffle sequence is evident in both channels below breach-
ing flows.The water in both channels remains clear until it enters the
area at the mouth where it mixes with the turbid water that enters from
the mainstem and forms the backwater area.
Slough 8A -RM 125.3
Slough 8A is located on the east bank of the Susitna River (Appendix
Figures 6-C-3 to 6-C-5).The slough is approximately two mnes in
length and is separated from the mainstem Susitna River by a large
vegetated gravel bar.The slough mouth is adjacent to a side channel.
Two principal channels connect the slough with the mainstem Susitna
River.The slough channel is relatively straight ~/ith a gentle bend
near the head of the slough.Approximately 2,000 feet upstream of the
mouth,a series of beaver dams are located across the braided channel
which inhibit upstream migration of salmon.Some dams are completely
filled inwith cobble resulting in a semi-permanent barrier while others
are frequently modified by stage changes.During the 1983 season,
another beaver dam was constructed approximately 3,200 feet upstream of
the mouth.The banks range from low,gently sloping banks to five-foot
high steep cut banks.The Alaska Railroad parallels the south bank of
the slough.The overall slough gradient is 10.5 ft/mi.Cobble/boulder
substrate predominates in the upper half of the slough.Gravel/rubble
is the predominant substrate in the lower half of the slough.Silt/sand
deposits are found in the backwater area at the mouth and in the pools
formed by the beaver dams.
A backwater area extends approximately 1,000 feet upstream of the mouth
during periods ·of moderate to high mainstem discharge.Above the
backwater area is a 100-300 foot riffle followed by a large beaver dam.
The northwest overflow channel flows into a large pool behind the beaver
darn.Another dam 1,200 feet further upstream impounds the water from
the northeast channel.The controlling discharge of the northwest
channel is 27,000 cfs,while that of the northeast chanAel is
approximately 33,000 cfs.Base slough flow is maintained by surface
runoff,groundwater seepage and upwelling.
Slough 9 -RM 128.3
Slough 9 is a 1.2 mile long unobstructed "S~-shaped channel on the south
bank of the Susitna River (Appendix Figures 6-C-6 to 6-C-8).Both the
head and mouth of the slough open into side channels of the rna ins tern
Susitna River.The lower half of the slough has a relatively shallow
gradient which steepens past a point roughly 3,000 feet upstream of the
mouth where the slough makes a sharp bend.The overall slough gradient
6-A-3
.....
....
is 13.7 ft/mi.Gravel/rubble substrate is predominant in the lower half
of the slough,while cobble/boulder predominates in the upper half.
Silt/sand deposits are found in the pool areas and the backwater area at
the mouth.The area at the mouth consists of sand bars that are in a
constant state of change.The banks generally have a moderate to steep
slope and are 3-4 feet high.A small slough (9B)branches off in a
northeasterly direction near the head of Slough 9.The Alaska Railroad
parallels the southeast bank of the lower half of the slough.
The head of the slough has an initial breaching discharge of 16,000 cfs.
Below this discharge the upper half of the slough is primarily dry,with
an intragravel flow of water.There is little,if any,intragravel flow
in the lower half of the slough.At controlling discharge conditions of
19,000 cfs or above,water flows freely through the slough,changing it
to a completely turbid environment •
At mainstem discharges less than 12,000 cfs the backwater area at the
mouth extends 500 feet upstream to the base of the fi rst ri ffl e.At
higher mainstem discharges,the riffles are inundated and the lower half
of the slough becomes one long pool.The lower half of the slough is a
series of pools and riffles ending with the backwater area at the mouth.
Base slough flow is maintained by two small creeks and contributions
from groundwater percolation (upwelling).Contributions to base slough
flow by Slough 9B are negligible.A beaver dam was constructed across
the mouth of.Slough 98 in earl~1983 .
Slough 9A -RM 133.2
Slough 9A 5s located on the south bank of the Su-sitna River (Appendix
Figures 6-C-9 and 6-C-I0).It is a winding slough about 3,200 feet long
with an overall slough gradient of 16.1 ft/mi.The slough is separated
from the mainstem by a vegetated gravel bar with steep cut banks.The
south bank is generally lower in elevation than the north bank.A
vegetated flood plain is formed along the south bank before it rises
sharply.The Alaska Railroad parallels the slough on the south.
The slough habitat consists of a series of long pools separated by
riffles.A gravel bar at the mouth extending from the north bank is
exposed to varying degrees,depending upon mainstem discharge.This can
result in displacement of the mouth several hundred feet further down-
stream at low mainstem discharge levels.Cobble/boulder is the predomi-
nant substrate type in the slough.Silt/sand deposits are found in the
pools and the backwater area at the mouth.Base slough flow appears to
be maintained by ground \>Jater seepage (upwelling)and surface water
runoff.
Side Channel 10 -RM 133.8
Side Channel 10 is approximately 2,300 feet long and is located on the
west side of the Susitna River (Appendix Figure 6-C-ll).It joins with
Slough 10,379 feet upstream of the mouth of the slough.It ;s separated
from the mainstem Susitna River on the south bank by a low,sparsely
vegetated gravel bar with gently sloping banks.The north bank is a
6-A-4
-
....
high steep cut bank that is thickly vegetated with shrubs and trees.
Pool/riffle sequence predominates throughout the side channel except for
a backwater area at the mouth.The lower half of the side channel
consists mostly of a gravel/rubble substrate,while the upper half is
cobble/boulder.Silt/sand deposits are found in the pool areas and in
the backwater area at the mouth.The overall side channel gradient is
20.5 ft/mi.
Side Channel 10 is initially breached at a mainstem discharge of approx-
imately 19,000 cfs.The initial breaching and controlling discharges
are the same at this site.Once the channel is breached,the water
becomes turbid.The first 900 feet of the side channel is a long pool,
influenced by mainstem backwater.It generally remains turbid while the
rest of the slough is clear.There are several intermittent channels
intersecting the gravel bar forming the south bank,which contributes
additional flow to the side channel.The exact discharge at which they
become watered has not been determined.Below the breaching discharge,
base channel flow is maintained by runoff and groundwater seepage.
Slough 11 -RM 135.3
Slough 11 is approximately one mile long and is located on the east bank
of the Susitna River (Appendix Figures 6-C-12 to 6-C-14).Both the head
and the mouth of the slough join side channels of the mainstem Susitna
River.The slough has a winding channel that is a series of pools and
riffles with an overall gradient of 19.8 ft/mi.Substrate i~the upper
half of the slough is composed mostly of cobble/boulder with the lower
half composed of gravel/rubble.Silt/sand deposits are confined mostly
to the backwater pool at the mouth~This pool is formed by a relatively
stable sand/gravel bar at the mouth.The slough channel is broad in
general,being enlarged by dramatic break-ups which occurred in previous
years.The steep banks are approximately six feet high and sparsely
vegetated.
Slough 11 has an identical initial brea<;:hing and controlling discharge
of apgroximately 42,000 cfs.The slough was 1ast observed breached in
1981.In an unbreached state,intragravel flow can be observed enter-
ing the slough through the berm at the head.However,this flow is·
minimal and below breaching discharges most of the upper third of the
slough is dewatered with isolated shallow pools.Surface runoff and
upwe 11 i ng rna i nta in flow in the lower two thi rds of the slough.The
backwater pool at the mouth exhibits considerable fluctuation in direct
response to changes in rnainstem discharge.The backwater area is quite
broad,encompassing the entire slough width,in contrast to the narrow
channel in the rest of the slough.
Upper Side Channel 11 -RM 136.0
Upper Side Channel 11 is located on the east bank of the Susitna River
and flows in an approximate east-west direction (Appendix Figures 6-C-12
to 6-C-14).The head of the approximately 2,300 foot side char,nel is
a Although it was not observed during this study period,mainstem
discharge records indicate that this slough was breached in the
spring of 1984.
6-A-5
_.
located immedi,ately downstream of the Alaska Railroad bridge at Gold
Creek.The north bank of the channel is a low lying,gently sloping,
sparsely vegetated gravel bar.The south bank is characterized by a
steep high bank that is thickly vegetated.The predominant substrate is
cobble/boulder interspersed with silt/sand deposits in pool areas and at
the backwater area at the mouth.The relatively gentle gradient (11.0
ft/mi)for the fi rst 500 feet of the side channel changes to a steep
(21.9 ft/mi)gradient for the remainder of the side channel.A
pool/riffle sequence is predominant except for the first 500 feet of the
channel which is usually a backwater area.
The head of Upper Side Channel 11 has a controlling discharge of 16,000
cfs.Below this breaching level,the slough flow is maintained by
upwelling,seepage and runoff.The side channel is a series of riffles
and pools that become a long run once the head is breached.The
backwater area at the mouth is generally turbid.As mainstem discharge
increases to 19,000 cfs or above,the backwater area extends further up
the side channel inundating the first riffle.
Slough 20 -RM 140.1
Slough 20 is located on the south bank of the Susitna River (Appendix
-Figures 6-C-15 and 6-C-16).The winding 3,100 foot channel has tv/a
tributaries associated with it,Waterfall Creek (thalweg station 15+00)
and a smaller tributary near the head (thalweg station 27+00).The
slough habitat consists of alternating pools and riffles with an overall
gradient of 13.5 ft/mi.Gravel/rubble substrate predominates throughout
the slough,especially in the lower half.The upper half is inter-
spersed with cobble/boulder deposits.The mouth area and a deep pool
immediately upstream of Waterfall Creek are silt covered.The banks are
thickly vegetated.
Below the controlling discharge of 23,000 cfs,the primal'y source of
base slough flow is Waterfall Creek.The tributary near the head
contributes flow to a lesser degree along with runoff and seepage.Due
to the contributi on of Waterfall Creek,below cantrall i ng breaching
discharge,there is no direct correlation between water surface ele"'-
vation in the slough and mainstem discharge.A deep 500 foot long pool
is formed immediately upstream of the mouth of Waterfall Creek due to a
gravel delta at the mouth of the creek.The slough mouth area and pool
above Waterfall Creek are generally turbid,with the rest of the slough
remaining clear below controlling breaching discharges.
Side Channel 21 -RM 140.6
Side Channel 21 is located along the south bank of the Susitna River and
is approximately 0.9 miles long (Appendix Figures 6-C-17 and 6-C-18).
The head of the side channel flows directly into the mouth of Slough 2l.
The channel is relatively straight with a uniform shape and average
width of 200 feet.The north bank is a vegetated low lying gravel bar
with gentle sloping banks and several intermittent channels connecting
the side channel with the mainstem.The south bank is high,steep and
vegetated.There is a small creek with intermittent flows entering the
6-A-6
....
....
....
side channel along this bank,approximately 1,500 feet upstream of the
mouth.The middle of the side channel,with a gradient of 18.7 ft/mi,
is mostly a riffle/run area,while the mouth and head,which have lower
gradients (9.4 and 3.2 ft/mi,respectively)'are pool areas.
Cobble/boulder substrates,are predominant throughout the side channel
with silt/sand deposits in the pools,especially in the backwater area
at the mouth.
Base channei flow is primarily maintained by flow from Slough 21.
Groundwater seepage,runoff and flow from the small creek and channel s
are other contributing sources to the base flow.Except for the back-
water area at the mouth and the pool at the head,the side channel
remains clear at base flow levels.The backwater at the mouth extends
approximately 1,300 feet into the side channel.Controlling flows are
difficult to assess because of the numerous intermittent channels
connecti ng the side channel wi th the rna i nstem and the two heads to
Slough 21.One or more of the channels wi 11 be breached in the range of
mainstem discharge between 12,000 to 26,000 cfs.All channels are
breached at a discharge of 26,000 cfs.Once breaching occurs,the side
channel increases in velocity,turbidity and depth.
Slough 21 -RM 141.8
Slough 21 is approximately 3,000 feet long and ;s located on the south
bank of the Susitna River (Appendi x Figures 6-C-19 and 6-C-20).The
main channel,with a relatively uniform width of 100 feet,divides into
two channels for the upstream half of the slough.The gradient of the
slough is 22.9 ft/mi.The slough ;s separated from the mainstem on the
north bank by a thickly vegetated gravel bar ..The steep cut banks are
approximately five feet high and are thickly vegetated.Cobble/boulder
is the predominant substrate with silt/sand deposits at the mouth.The
mouth of Slough 11 flows directly into the head of Side Channel 2l.
The heads of the NE and NW channel of the slough are initially breached
at approximately 23,000 cfs and 26,000 cfs,respectively.At this
discharge range slough flow,depth and turbidity increase rapidly.
Controlling discharge occurs at 25~000 cfs in the NE channel and 28,000
cfs'in the NW channel.Additional water enters through channel A-6 at
mainstem discharges over 17,000 cfs.This additional discharge
increases the downstream flow of water into Side Channel 21 and creates
a backwater pool at the mouth of Slough 21.A small tributary,surface
water runoff and groundwater (upwelling)maintain the base slough flow
below initial breaching conditions.Below initial breaching conditions,
the upper half of the slough is dewatered with isolated pools.The
lower half is a shallow narrow channel with a pool at the mouth.
Slough 22 -RM 144.2
Slough 22 is semi-circular in shape and is located on the north bank of
the Susitna River (Appendix Figure 6-C-21).The overall gradient of the
slough is 15.2 ft/mi.Both banks are thickly vegetated with shrubs and
trees with a moderate to steep slope.The approximately 3,000 foot
6-A-7
-
....
....
""..
channel can be roughly divided into two parts.The lower half of the
slough consists of two long,deep (3-4 feet)pools separated by riffles.
The gradient of this lower section is 6.3 ft/mi.The upper half,with a
steeper gradient of 20.7 ft/mi,is a short shallow pool followed by a
long riffle.A small tributary and spring fed channel enter the slough
from the north bank near the head of this last pool (approximately
thalweg station 21+00).Cobble/boulder is the predominant substrate
throughout the slough.Gravel/rubble is the predominant substrate in
the riffle area in the middle section of the slough (streambed station
15+00).The two pools in the lower half of the slough have thick
deposits of silt/sand substrate..
The head of the slough is initially breached at a mainstem discharge of
approximately 20,000 cfs with a controlling discharge of 23,000 cfs.
Below the initial breaching discharge,the upper quarter of the slough
becomes dewatered.Base slough flow is maintained pr-imarily by the
small tributary and spring fed fork.Surface runoff and groundwater
seepage (upwelling)add to the base slough flow.Below breaching
discharges the slough is clear,including the two pools in the lower
half of the slough.Except at high Illainstem discharges (23,000 cfs and
above),these pools have 1ittl e or no backwater effect.They are cut
off from the mainstem by a 300 foot riffle .
6-A-8
"".
-.
Appendix 6-8
Supplement to Methods
of Local Flow Analysis
6-B-1
,.....
The general method used to estimate local flows as explained in Section
2.3.2.3.3 could not be applied to all passage reaches.For passage
reaches 1acking a surveyed cross-secti on,the 'Aeri a1 Photographi c Method
may be used;for passage reaches lacking a rating curve,the Manning
Equation Method may be used.The use of these methods,however,
requires additional assumptions and may result in less accurate local
flow estimations.Therefore,these methods should only be used if the
data necessary for the general method are not available.
Manning Equation Method
The Manning Equation Method is used to develop a rating curve for a
surveyed cross-section.From the rating curve,the required local flows
for successful and unsuccessful passage may be calculated.The Manning
equation Method is described as follows:
1)Establish a value for the Manning roughness coefficient by
calibrating to a nearby riffle reach having a developed rating
curve.
2)Calculate the overall reach gradient that includes the passage
reach and set this equal to the energy slope in the Manning
equation.
3).Use the Manning equation to calculate local flows for a range
of water surface elevations to define the rating curve for the
passage reach cross-section.
Aerial Photographic Method
The Aerial Photographic Method is used to evaluate the required local
flow at a passage reach when a surveyed cross-sect;on does not ex;st.
Several sets of aerial photographs at different mainstem flows are
required as is at least one surveyed cross-section in each slough.The
method proceeds as follows:
1)Use the Manning Equation Method for each surveyed
cross-section to calculate,for a range of water surface
elevations,the top width and local flow;plot top width
versus local flow for each surveyed cross-section.
2)Cal cul ate the mean depths for each passage reach that corre-
spond to the passage depths for successful ana unsuccessful
passage using Appendix Figure B-1.
3)Calculate the overall reach gradient applicable to each
passage reach from the thalweg survey data.
4)Evaluate the unit flows for successful and unsuccessful
passage using the mean depths,reach gradient,and A.ppendix
Fi gure B-2.
5)Measure the top width of 1Dca 1 flow at the surveyed
transect(s)and at each passage reach on each set of aerial
photographs.
6-8-2
,....
1.0
.9
-.8
.7
.6
,....5---...4~1Il .ca
Q.I
0
(I)
CIc 3Inen
C
Q.-
0 do =1.27 dO.91
"'0
d=.77d o1.10
..-.2 r 2 =O.96
.1 !----------=------J...-----J----!!:--+_-:!:-_~......,~..,J ..\.2
d (Mean Depth,ft)
Figure 6-B-1.Relationship between mean depth and passage depth.
6-B-3
J ~------]~--'-------"i'l
!)]1 J ]I 1 j -J 1
10
.9
.B
7
.6
.5
-"t-:4~
::I:
l-n.
W .30.-:0
Z
(J)<I
I W
OJ ~
I
+:00 .2
.1
.01 .02 .03 .04 .05 .06 .OB .10
UNIT FLOW (cfs/ft)
(q)
.2 .3 .4 .5 .6 .7 .B .9 1.0
Figure 6-8-2.Relationship between mean depth and unit flow.
.....
6)Use the measured top widths at the surveyed transect(s)and
the top wi dth versus 1Dca 1 flow plot developed inStep 1 to
get the 1oca 1 flow represented in each set of aeri a1 photo-
graphs.
7)Adjust the local flow estimates for upwell ing or tributary
inflow between the applicable surveyed transect and each
passage reach.(Note:Data were available only at Whiskers
Creek Slough and Slough 9A for making this adjustment).
8)Plot the adjusted 10cal flow estimates against the correspond-
i ng measured top wi dths from the aeri a1 photographs to defi ne
several points on a curve of top width versus local flow for
each passage reach.
9)Plot lines of constant unit flow (evaluated in Step 4)on the
top width versus local flow curves (developed in Step 8)for
each passage reach;the intersection of these lines with the
top width versus local flow curves gives the local flows
corresponding to successful and unsuccessful passage .
6-8-5
•
.....
.-.
Appendix 6-C
Timi ng Plots
6-C-1
..".
i
SLOUGH 400
I 1983SAen
i:i:300
W>....::i 200
IJ...
0 100 SOCKEYE
0 /
1"""Z
0
I 10 20 30 10 20 30
,....I.AUGUST .1 SEPTEMBER--I
.....
30 10 20 30
...1-SEPTEMBER.....-j
10 20·
AUGUST
1982
I •
O-f-...,.,alt::;..,-...,.;:::.:;.=-.....-_-.......;;;;.....-.....;.;;;;.;:~=a.
I
400
Zen
LL:300
W>:J 200
u.
o 100
o
Z
-
30 10 20 30-t-SEPTEMBER-i
1981
O,-+-.........,-_-.,.-.,....'-.....,..-_._--r-.....-;:::.-,p:::=._
1 10 20
I--AUGUST
400
Z
(f)u:300
W>::i 200
IJ...
o 100o
Z
....
Figure 6-C-1.Timing of salmon presence,Slough 8A,1981,
1982,1983 .
....
6-C-2
1983SLOUGH
9
400
:I:en
I.L 300
W
~200
-I
I.L ........_CHUMo100-...../....-.....d ,--SOCKEYE ',_
Z 0 -+---....-.....-...:.'.,......,.-...--..........\"'I'---"'I'---...-,.;-:::=.,
I-
10 20 30 10 20 30
AUGUST---~.-I~·~SEPTEMBER~
1982
10 20 30 10 20 30
AUGUST--~.~l~---SEPTEMBER~
400
:I:
(f)
~300
W
~200
-I
I.Lo 100
o SOCKEYE
Z O-l-........;~::::p.;.;;;.;:::...:;;=.I0¥--.,..'..,..--r-..,....~---,
I
30 10 20 30
..I-SEPTEMBER--f
10 20
AUGUSTI.
400
~1981
i:i:300
W>200 I'
:J I \CHUM
I \ /
I.I \o 100 / \
O·IISOCKEYE \
/I ...z O+-__...,...---,r--.,....'-r-....==:;:=::=p.-;..:::...,...........---,,
Figure 6-C-2.Timing of salmon presence,Slough 9,
1981, 1982,1983.
6-C-3
""'..
SLOUGH 160
::J:19839Aenu:120
W _ _CHUM
>80 I ,,/"
~...J I "
I.L.I ..........0 40 I ....
.....0 SOCKEYE IZ/0
I 10 20 30 10 20 30
t..AUGUST -,-SEPTEMBER~
160
30 10 20 30
-I'"SEPTEMBER--!
10 20
AUGUST
1982-xenii:120
W ?,
>80 /'CHUM
...J /'/
I.L./'
o 40 /"o I \
Z O,+-r'--,....-..,...~-or---r--r---r----T-\-..looor-or--...,
I
.-
160
::J:1981 /'enu:120 / \CHUM
W
/\/
>I \
80
/\!""'"...J ,\
I.L.,,/
\0 40 ,./
'...../\
r-0 SOCKEYE
Z /0
I 10 20 30 10 20 30
I-AUGUST -I-SEPTEMBER--I
Figure 6-C-3.Timing of salmon presence,Slough 9A,
1981,1982,1983 .
....
6-C-4
~1Il
SLOUGH 600
....II :::I:500 1983
COMPLEX rn
u..,400
LLI>300-...J SOCKEYE
IJ..200 /
0
d 100Z
0~~
I 10 20 30 10 20 30
~AUGUST -I-SEPTEMBER --t
600
:::I:1982-rn-u..
LLI>
...J
IJ..
0
0
Z
0
I 10 20 30 10 20 30
I--AUGUST -,-SEPTEMBER --t
~
600
:::I:1981
rn-u..40
I.Ll "CHUM
>"/"...J "IJ.."0 20 "!""'1 "0 10 "Z ""-0-,I 10 20 30 10 20 30
I---AUGUST -t-SEPTEMBER---I
Figure 6-C-4.Timing of salmon presence,Slough 11 Complex,
1981, 1982,1983.
6-·C-5
1983 ~''''-,..,
I I ...........CHUM....../I .....I ,
/\
I \
I \
I \
I \
./~INK \«'/~~........o"1--,...--r;)o"...,.....-,...--r-.,....--r-.,...._.....'t--r---ro---,
1 10 -20 30 10 20 30
~I.~-AUGUST---.~I·.-SEPTEMBER~
60 1
:1:40en
li:
lLl 30>
.-I
lL.20o
~10
SLOUGH
20
""",
I""",
I
I
I
I
/'.
1982 / \-c·.\='::.
'.PINK./\
\l-
I \CHUM
\
I \ /
I \
• I \
\,\---\\o -4--I---.-....-.:..;;.........,-.,......;....::lIop.-.,.....--,...-,;,.-;;;.-=...,........,
60
:I:50]en '%
G:
lLl 30>
.-I
u...20o
oz 10
10 20
I·AUGUST
30 10 20 30-1·SEPTEMBER----t
50
~40
u..
~30
~
~20
~10
1981
CHUM
I--,-,
SOC~YE "
10 20
1--AUGUST
30 10 20 30
II i"SEPTEMBER--i
Figure 6-C-5.Timing of salmo~presence,Slough 20,1981,
1982,1983.
6-C-6
SLOUGH
21 J:500 1983
COMPLEX en
L£:.400
ILl>300~CHUM
lL.200 "'-0
0 100Z
0
t 10 20 30 10 20 30
I-AUGUST~SEPTEMBER~
600 -'\
r"\---:-CHUM
1982 /\
J:500 /\en
/"G:400 I \
/\
ILl 1 \>300 I.\
~I \
lL.1 \
0 200 I \
PINK I SOCKEYE \
0 I \.-Z 100 \.,..~{...\\
\
0
•••",#1'............
I 10 20 30 10 20 30
1-AUGUST -I-SEPTEMBER~
600
J:500 1981
en
G:400
W
~300~CHUM
IJ-",
'"//
0 200 /..
0 /,,
Z 100 ...SOCKEYE ........
"-........"'"
0
F""I 10 20 30 10 20 30
I-AUGUST -1-..SEPTEM BER--I
I"'""
Figure 6-C-6.Timing of salmon presence,Slough 21 Complex,
1981,1982,1983.
6 ··C-7
SLOUGH 22
(1983 SURVEY DATA ONLY)
""'"
120--
:I:\
(f)roo \-\u..
W \
>80 \
......J \..-\CHUM
U.\/0 \a::\w 40 \(l)
~\
::::>\.
z 20 ""...............
0 ......
1 10 20 30 10 20 30
I-AUG UST-----t--SEPTEM BER--i-
Figure 6-C-7.Timing of salmon presence,Slough 22,1981,
1982,1983.
6-C-8
.....
_.
Appendix 6-0
Salmon Spawning Distribution Maps
6-0-1
]1 1 I )1 )J J 1 I ~)1 "J
m 1982
..
o SOO
1 J
fEET
(ApprOi.lui.)
-PR Passage Reach
Pink Spawning Area.l
WHISKERS CR.SLOUGH
RIVER·-SUSlrNA
.•.,1,..•-,.,.;,.V"'~"'.....,'(.....:",,~..,,::.•'\,.\,.;.:'."',:,;.:',.~,n:')~",>:;:,..:.,...,.<:.;j'
ED 101.4
())
Io
I
N
Figure 6-D-l.Pink salmon spawning areas,Whiskers Creek Slough,1982.
·."J I 1 "1 ")~~-1 1 J I J
MAINSTEM 2
SIDE CHANNEL
-PR Pa55Qge Reach
Chum Spawning Areas
[)1983
IZI 1982
o 500
I I
FEET
IAppln.Scale'
~···Pi.••.
t9 /V .'.:..:....~~•...~..
"'"
io ~-a -.---.,-,.,;;.~~~
:-.,.......S lJ ".:.•.S ..
Irlll4
O"l
I
Cl
I
W
Fi~ure 6-0-2.Chum salmon spawning areas,Mainstem 2 Side Channel,1982,1983.
I "1 I j -I --1 J -I 1 I 1 1 I 1 1
m
I
CJ
I
~
••··.-·1'.
SLOUGH SA
-PR Passage R~ach
Chum SpawninQ Areas
rA 1983o1982
[)19B 1
o 500
I
FEET
(A ppro ••So DIal
"---126(9 SUSlrAl4~
........,..~\....
RIVER
Flgure 6-D-3.Chum salmon spawning areas~Slough 8A~1981 1982~1983.
!!J »-,]1 1 1 1 1 1 1
..-.
()')
I
Cl
I
11l
SLOUGH 8A
-PR Passage R~och
Sockeye Spawning Areas
eJ 198:3
[j 1982
13 1981
a ~oo
I I
fEn
(Appro •.Saoltl
~
126ED s liS I rAt4~
,.:t-:·":.:\·i'
RIVER
··f/:
Figure 6-0-4.Sockeye salmon spawning areas,Slough 8A,1981,1982,1983.
1 J -;'-'---')-~~I 1 J
RIVER
0'\
I
o
I
0'\Beaver
SLOUGH SA
-PR Passage Reach
P ink Spawning Areas
o 1982
o 000
I ,
fElT
IApproa.lea I,t
..._",.I",••jJ.:»I~··rC=i\i."·";'"
126ED ------S lJ SIr#4...-.-.
Figure 6-0-5.Pink salmon spawning areas.Slough BA.1982.
]CJ -1 -1 I 1 ]-1 J 1
B
fEU
(A pprOK.Sa Q II)
"""--PR Passage Reach
~hum Spawning Areos
rJ 1983
1m 1982
o 400.,
SLOUGH 9--K /V £R ill 129
:~.~~-~~.~::~~..''::'..~..
....~~.~
SUS/rNA
--r .....1.••!••':.:-:.i t"":~.~.~~
1 ~1.~~?~\PRII ~"""""'''~/-','~.:"'.~.i.:?::':..~~'"4 :.,••_~t:',::.•••-~.•=.'A
O'l
I
o
I
-....J
Figure 6-D-6.Chum salmon spawning areas,Slough 9,1982.
1 J '1 J ]~--~--1 )1 ))1
,...;.:.
SLOUGH 9
,,;.>••':;7t'~'~",:':':~"'!:'...,:...._-:';.;:;_.:.~
. -...--Slough 98'
o 400
I I
fEET
CApp,..loo'e)
-PR Passage Reach
Sockeye Spawning Areas
D 1983
Ell 1982
,:"'PRV
Tributary B
CD 129--,",'""./£fl~NA RIV
SUS~~'~..}~.•:...~!.:...~::..!.........:~.-..'..~-.""':-~:..~'...----
·:(I:~..·
O'l
I
Cl
eb
Figure 6-0-7,Sockeye salmon spawning areas~Slough 9,1982,1983.
j 1 1 .I .-)I )i J I 1 D
nIT
fApp,...IDa I.t
£]1982
SLOUGH 9
";"'••:;~':~:..":"';:':'::"".!:~.•,:.:..;':,;.;'.:'.:~~
..-Slougll 90'
o 400
•I
-PR Passage Reach
P ink Spawning Areas
B
~.,
..'
":
.~;.
'..'.
,;
.~
6)129---FelVER
~·':'4;··:~·..;;··"''::.~
CJJ-"!'"
...:~A"':~/fNc
5 U -'__....i ...")"""'.~.-:::"~~
_,"J""",'.,.'.,...,',0.,••,••,,."',,'.,,,,•
19:,,:..:r:~~..!;?.,;!.,:'.~~~.\"",~•...
O'l
Io
I
\,()
Figure 6-0-8.Pink salmon spawning areas,Slough 9,1982.
)]1 1 J )1
"':':{!{~;l~!)Ji;f~'!::
.~.:~:"~'~Cj ~~::,r;.~:~;~.~
'.;.....(J~:....~
E&133.5
~;::"""'".,"..,':;,;'".:-':<:':
RIVER
5 I rNA
"..,";"~7-~~:....~~.~::'.'::1'~'.':....~
....,~.......:.t·:,;.··:·:;:·:~·,;¢..·.;:·
S LJ
,/
SLOUGH 9A
-PR Passage Reach
Chum Spawnl ng Areas
~1983o1982
fJ 1981
o 21&,,
FEET
IApprn.SaDI.)
;/
/
...:',..;:....;',-:.-:
~{1:"PR r
0'1
Io
I
I-'o
Figure 6-0-9.Chum salmon spawning areas,Slou~h 9A,1981,1982,1983.
1 1 j 1 1 1 1 J J J -J 1 1 ]I
···~:·:~f(:,\E~~)~·~:}?,:~/::~:·:
D:::~~:,::.~:.:L~·':~':.:·...·
• '••e "~'••••"
.~.:~:"\\".';;~.::'.
".
~.';:'.'"~
()
~
EB 133.5
~.~:=.
_,,,JP'~.•:';"?~F"I::V:-';"'\PR'IX~¥ill
-++-+-t-.
ce:C,:'y
RIVER
'..";..~.:"[..•,:....-.~-:,,;::~---.....~.•.:t::.'":':".
......:~;~.....:;:.:..·i:!d~·I~~·
5 IT N A/slJ
//
SLOUGH 9A
-PR Passage Reach
Sockeye Spawni no Areas
YA 1983o1982
.:;.-~.;,:.'.;!...~:,~£.-':.",,)..PR I
m
I
Cl
I
I-',-
o 2711
I I
fEET
(Approl.Sao,.'
Figure 6-0-10.Sockeye salmon spawning areas~Slough 9A~1981~1982~1983.
I -1 J 1 -.-I J -J 1
.-:..:.;,';..;.;h:r:··,:'so ·.··..r,.r.;~:;';
PR PassaoeReach
o 500
,I
fEET
I Appro••Seal.1
SIDE CHANNEL 10
-:.4.:_:..
..........J•••'"S:....~.;~,;.....
--RIVER
,.,."=,-.,;.....,""',;;,,.....-...;,.".".
/
-.:S USI TNA
0'\
I
Cl
I
I-'
N
€a 134
Figure 6-0-11.Site map of Side Channel 10.
!j ,-I -I J 1 ~11 J )!
----PR Passage Reach
Chum Spawning Areal
r.a 1983
[J 1982n1981
o ~oo,,
FEET
(Appre ••llea h'
SLOUGH a UPPER
SIDE CHANNEL II
@ 136/
.IfF<
R I v
5
........','
~
0)
I
Cl
I
I-'
W
Flgure 6-0-12.Chum salmon spawning areas Slough and Upper Side Channel 11,1981 1982,1983.
-J -J -----I j -I J I 1
SLOUGH a UPPER
SIDE CHANNEL II
----PR Passage Reach
Sockeye Spawning Areas
D 1983m1982
[J 1981
o 300
I I
nn
(Approa.So.h,
@136
/,,~f<
R I v'~"'''''··'·····r·
·p·R"Y····"
..----5
-,,;.•~":.~.;'..
O'l
I
CJ
I
I-'
+:-
Figure 6-D-13.Sockeye salmon spawning areas,Slough and Upper Side Channel 11,1981, 1982,1983.
j -1 1 J -J ~1 J i 1 I 1
~:;....'.-,r,
lEJ 1982
o 300
I I
FEET
fA pprD •.SeD h.
-PR Passage Reach
Pink Spawnino Areas
SLOUGH a UPPER
SIDE CHANNEL II .
@ 136
/
.Iff<
R I v
5
PRY;:
~
m
Io
I
I-'
Ul
Figure 6-0-14.Pink salmon spawning areas,Slough and Upper Side Channel 11,1982.
1 J 1 t 1 )J 1 1 1 I -1 1
.".:";;":'.:~.i'i::·:...··~·:i \....~.~::··r:,::'~::'1 ,.{,....r"~:-..:.,:~:,:,~.....:.~.l.!....;,\•.;,~:',....(,:'=l,.~.::~.'..:-,.:~:I:.;::.::J~:::::'-:~:'::.~~'''.;'r:'!'":'~."'.'h ...;~I ...~.'t~....:....•".:.,:__I'd :.~.'_..~...::.
ffi 140.1 ..SUSlrNA RIVER -
0"'1
I
Cl
I.....
0"'1
SLOUGH 20
-PR Passage Reach
Chum Spawning Areal
l)1983
o 1982
o 2~OI,
fEET
IApprOlL.lea',)
•.•;::-:';<.:~;!i:~""~-':"~7,;.~:~::~:,'.=7.:::
Figure 6-0-15.Chum salmon spawning areas,Slough 20,1982,1983.
I ---I -1 1 1 1 I 1 1 J 1
¥.i"i:__...._~!r:,.~:.:-;.:i \··~~i !:".(";.
EB 140.1
SUSlrNA RIVER -
en
Io
I
I-'
'-J
SLOUGH 20
-PR Passage Reach
Pink Spawning Areas
o 1982
o 21i0
,I
FEn
!App,ol.Scale)
;'.
~
'"V
.':-.:~'\'::"'.~==:.:-;•.r~~~::~
'l"~:.••·"·•.w::·,·,,·';'~i:'
Figure 6-0-16.Pink salmon spawning areas~Slough 20~1982.
J ]1 1 1 j ,········1 I I 1 ]I
'..":'.
.1::~..;;..
'...1::-.,
~.~.
/
~
~
ED 141
fEET
(Appro •.Scale)
SIDE CHANNEL 21
-PR Passage Reach
Chum Spawnino Areas
I2l 1983o1982
E:l 198 I
o 400,,
,-,,,.,"'1,',";;.,••'.;;'.';"'.''!"""'''''''''''''"••"••..,."'""'.".;"":.','.'.;!',"'"";.,;.",.""'".',""•.•..,;"..
•..·..;..oi"'.
S :'~'r".../~''''.U'S/'o::!:"r /V4 ....!.•.~vV
c~
m
Io
I.....
CO
Figure 6-D-17.Chum salmon spawning areas~Side Channel 21~1981~1982~1983.
J ]I -]1 ·1 -)J 1 1 1 1 I I
::,.":~.............
."'.~..
...::.
/
~
.~':"~:'~/':~~'~"'".•.
••'~'.f~~-'.
~/v
.~~
SU S /r
4"4PRll
SIDE CHANNEL 21
-PR Passage Reach
Sockeye Spawning Areas
~1983
o 1982
o 400
,I
FEET
(Appro •.Scoll)
,,",.,·.··f'';"o';(';"n"';"....,,.,.,~"";;';"".c-.'.",'"""'0"'o';.,....,'""'",.,.•;.,,;•.,.;."",".
(j)141 '-"""';"";"~","';"""
;··:·,·······.":1 ';"':'.-,1;.f.;.,..~
m
I
Cl
I.....
l..O
Figure 6-0-18.Sockeye salmon spawning areas,Side Channel 21,1982,1983.
1 1 1 1 J 1 -]1 )J 1 I
({)142
PRnR III L
RIV ER ---
....·,·;.···i·..::.~~:...~/'.:.::..:..:........•.:.::.!:.•;:'.•
.','_~.l ~~.~:::",-;.;00
'~":...iI-·
sus/rNA
;0 ~~~.~••
;_~:.•.:.';"X:·~:·;·'i···
~;'.''-.,t.;.•...•:.:i:~~:.,,:.~.::..;:..
~.~;......
"':&"';"('::;j ';.;-,.'''':'·'i·;'':·:,;...•..":;;1":oj:'.")';;r.'...·~
,.rrrnlJ7 -Slough.2/LtL~:}.~.:..~.W4.:.11:.t(Z~....1;1;:"".""'0'.'...'t ••••.\•••:~.••;,••'::~:"•.;:"::'.-.,
~
SLOUGH 21
-PR Passage Reach
Chum SpowninCj Areos
f'A 1983o1982
f]1981
o lIOO,,
fEET
(A"roa.ll~.l.)
".;.-:,,;..:~-.
/Ii
'./
-:'.'"
0'\
I
CJ
I
No
Figure 6-0-19.Chum salmon spawning areas,Slough 21.1981.1982.1983.
J ]1 1 ]I J J J 1 1 ]1 J
'i""~7',,"';";",..~
6:)142
RIVER ---
sus/rNA'
~
Ie
PUT
IAppru.loolo'
SLOUGH 21
.::".•..,-~.
-PR Passage Reach
Sockeye Spawning Areas
fA 1983
[]1982
rJ 1981
o ~oo,p
Q')
I
Cl
I
N
t--'
Figure 6-D-20.Sockeye salmon spawning areas,Slough 21,1981,1982,1983.
--]J i --I --OJ )-J J j 1 1
/
.:.iq;:,,:,;,,~~:·:;.;J.,,;:,·,···r.·::~:··:·:·
ED 142
RIVER ;.----
•.,a:_.,:.~....:~.-,....._,
..#..••;!.:'~I!..,:•.,:~.....I •.~
:-...
SUS/INA
~
ill 1982
SLOUGH 21
o 300
I J
fEET
(ApprOl.SeQlel
-PR Passage Reach
Pink Spawnino Areas
"";'::
0'1
I
CJ
I
N
N
Figure 6-0-21.Pink saln~n spawning areas,Slough 21.1982.Note that spawning areas are located
downstream of the designated mout~of the slough.
)1 )-1 i 1 1 -J ]1 j --1 ]'11
B
Q)
Io
I
N
W
~"";i"'~-..l~""'
~~'i'~""')~"':~'~'".
:'.:..~.·.:,~';'~I;·.:.·k\·,··~~··~~......)·;·::;·~:.;·;:~~!"~~..~,',
SLOUGH 22
-PR Passage Reach
Chum Spawning Areas
f1 1983
o 2::10
,I
fEET
('pprol,SeD '.1
.._------~-~-~------.-
Slough 22
~~=::'i,,·.f'IIt'..!J..............~l:::..:!.;A~~. "•.•••••:••:,•.:.1 ••'.'.•••'"'.• •..···:··J..,W:f:~.··."':~:,\-;;,~;l'."
··~:.,:...,:.,.'.'.';.'-';.,~.'j.i{.i·.~'.-..·.;...•~;\:.;~..:.:,;£1:fr.!:."~'i.;···<::_~·-i;;!"·;:,w··,:·
sus/rNA R/VER
@ 144.5
Figure 6-0-22.Chum salmon spawning areas,Slou1h 22,1983.
-
.....
Appendix 6-E
Thalweg Profiles of Sloughs and Side Channels
6-E-J
1 J 1 1 J i f I ,·1 'j f 1 1
WHISKERS CREEK SLOUGH
THALWEG PROFILE
no
WHISKERS CREEK SLOUGH
D '.0''''.1 ""ay .Ian ",.~
4 IT....IIND n"~I••..".ff ......,,~,.t.','
~'.
RI
SUIIVfY DATI:110821
MAIN.TlY Q C..Go4t1 Ct.....1 ',080 "It
Inl Q:<Z~',
IUIITNA 'U"II .UCH GRADIIM'1 4 .•11/.1
.tTl .....DI£.."•.a tt/.i
PRm
--.Anl IUR,Af;i 011I PAll W ....."IY
EO..."VIL I IU"',IE CO••LI'lOULDlR
...--ulErT..EatlMAUD
-WATE.SuRfACI f ••IT".I DAY"
,..tL,"USAGE:RlAe ..
0'\
Irn
I
N '6'....o
t-..>..
..J 360....
"a:
t-
:~~o:::::----L~~~:::::==~=,---~..,---:======-----=="".<"~..A!I~~=.=.....:;~:>!.~:)flt~f:-,~.;.r:•~.......___,~..~.:~~.:~;~,~Ii
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Figure 6-E-1.Thalweg profile of Whiskers Creek Slough.
1"1 )J j I -J -1 I i J B )
MAINSTEM 2 SIDE CHANNEL
THALWEG PROFILE
UAINSTEM 2 SIDE CHANNEL
a ,ItOfIU:"up.,.,uu
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-....u.ISURfACE ON GAil Of IUfII'IIIY
r1SIUlUIIDm.....VliL 'RU'.U
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STfI£AMSEO STATIO"U"••
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Figure 6-E-2.Thalweg profile of Mainstem 2 Side Channel.
CJ 1 I 1 J J I -1 I J -~-J i
SLOUGH SA THALWEG PROFILE
SJ..OUGH Ito
••PROflLl lTun AAlAA•ITHUllln ltAToON
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sua't'n DATI:e210lS/S21016
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Figure 6-E-3.Thalweg profile of Slough 8A.
--1 1 1 1 1 J 1 I 1 1 I 1 1
SLOUGH 9 THALWEG PROFILE
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SlOUG",o PROfiLE STUD..AREA
.0.!Hfl(AM8ED SY,Q.T10N
SURVEY DATE,820824/820812/821012
MAINSTEM "'0'Gold Crookld2.S00/14,40011.'1IQ •••
SITE"'o.tI,8 ...
SUSITNA RIVER RUC"GRADIENT,8.1 111m;
SITE GRADIENT,13.8 II/ml
--WATER SURFACE ON DATE Of SURVEY
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STREAMBED STATION (,••11
Figure 6-E-4.Thalweg profile of Slough 9.
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SLOUGH II THALWEG PROFILE
-WATER SURfACE ON DATE I)f SURVEY
DSILT/IAND
C··,;,:':"I GRAVEll RUBBLE
ffilj COBBLE I BOULDIUl
--WATER SURfACE fROM STASE DATA
,..eo..,PASSAGE REACH
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SURVEY DATE:&21017
MAINSTEM Q 101 Gold Cnlkh &,&&0 GIl
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Figure 6-E-7.Thalweg profile of Slough 11.
-1 1 1 1 --I -C-l )J J J.-1 J
UPPER SIDE CHANNEL II
THALWEG PROFILE
2 ,
STUDY TRANSECT LOCATIONS lADf II G MODELING STUDY,19831
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686
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IIAINSTEII Q tal Gald erooU,18,600 ct.
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SITE GRADIENT,23.6 film.
PRR
-WATER SURFACE 011 DATE Of SURVEY
lid SILT I5AIID
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HEAD Of
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136.2H2
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STREAMBED STATION t1utl
Figure 6-E-8.Thalweg profile of Upper Side Channel 11.
-]1 1 I "I 1 ]1 1 1 I 1 J )I
SLOUGH 20 THALWEG PROFILE
SLOUGH 20
---sus;,.~~
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SURVEl OAlI,83011S
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IITI GRADIINT:1'.0 IIlmi
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Figure 6-E-9.Thalweg profile of Slough 20.
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SIDE CHANNEL 21
C).PROfiLE nl)or Alilt_
6 -5IRlAMBED nATION
/,
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SiDE CHANNEL 2/
THALWEG PROFILE
IU"""Y DATE:,210'4 --WAU"SUII'ACE OH DAn r:iI 1""'lIIY
MAIMUEM Q Ie'1,141 Gr••);J.liloo c:h L:lIILlIlAtiP
Jill Q:D "~I (5g coilLI ,IOULDII
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n.
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Figure 6-E-1O.Thalweg profile of Side Channel 21.
t ]j -1 1 ~-~-l 1 ]-1 -1 'j i
SLOUGH 21
THALWEG PROfiLE
SLOUGH 21
D·PROF ILl:STUD'V AREA
6.-5TR£-'MBED nATION
//SURVEY PAn,821014
MAINITEM g Cal Gold tr..~I,1.800 ...
.Ill g,5 <h
SUSlTN'"RIVU RE"'CH GA ...PIENT,12.1 11/..1
.ITE GAADlfNT,22.9 11/011
--....llA S\lAF...CE ON DATE 01 .URVEY
_.ILT/....NP
1m tOllLE I BOULDEA
__WATEA SURfACE fAOM ST...GE O"'T'"
,..!!-,PASS"'GE AEACH
750
755..,SLOuGH 21 NORTHWEST
(LEFT CHANNEL I
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'AOf&G GAGE'
1406S2
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SLOUGH 21 NOAltIEAST
IAIGHT CHANNELl
72!)"i I Iii iii iii Iii ,iii iii Iii •iii iii iii iii i i •iii iii Iii
-1~fOO -10'00 --5tOO 0+00 ~iOO IOtOO l~tOO
STREAMBED STATION «'0011
20+00 25.00 30tOO
Figure 6-E-l1.Thalweg profile of Slough 21.
1 I 1
SLOUGH 22 THALWEG PROFILE
()),
IT1
185
I
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180..,
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Figure 6-E-12.
IURvn D4n,850116
M41NITIM Q lot Gold Crookh '6,400 ~,.
IITI Q:'I:II
IUIITNA RIVIR 1I14CH G114D1INT'11.5 III...
IITI GUOIINT,15.0 III..,
STREAMBED STATION 110011
Thalweg profile of Slough 22.
--.4nll IUIIFACI ON DATI Of _vn
I:l:IIILT/l4NO
001l4VIL I RUIILI
1m CoIBLEI 10ULOIll
--W4T1R IURF4CE FROM 1'4GE 04'"
,..tIL,P41S4GE RE4CH
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