HomeMy WebLinkAboutAPA2909Document No.2909
Susitna File No.4.3.1.3
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SUSITNA HYDROELECTRIC PROJECT
RESPONSE OF JUVENILE CHINOOK HABITAT
TO.MAINSTEM DISCHARGE
IN THE TALKEETNA-TO-DEVIL CANYON SEGMENT
OF THE SUSITNA RIVER,ALASKA
Prepared by
Trihey and Associates
Cleveland R.Steward,III
Robert C.Wilkinson
Alexander M.Milner
Under Contract to
Harza-Ebasco Susitna Joint Venture
.Prepared for
Alaska Power Authority
j
Final Report
December 1985
ARLIS
L 'b Alaska Resourcc<s
.1 .rary &Infonnati"o S
An .n.enrlCes
chorage,Alaska
NOTICE
ANY QUESTIONS OR COMMENTS CONCERNING
THIS REPORT SHOULD BE DIRECTED TO
THE ALASKA POWER AUTHORITY
SUSITNA PROJECT OFFICE .
ARLIS
.Alaska Resources
LIbrary &Informatj"S.on ervlCes
AndlOrage,Alaska
PREFACE
The goal of the Alaska Power Authority in identifying environmentally
acceptable flow regimes for the proposed Susitna Hydroelectric Project is
the maintenance of existing fish resources and levels of production.This
goal is consistent with mitigation goals of the U.S.Fish and Wildlife
Service and the Alaska Department of Fish and Game.Maintenance of
naturally occur~ing fish populations and habitats is the preferred goal in
agency mitigation policies.
In 1982,following two years of baseline studies,a multi-disciplinary
approach to quantify effects of the proposed Susitna Hydroelectric Project
on existing fish habitats and to identify mitigation opportunities was
initia~ed.The Insteam Flow Relationships Studies (IFRS)focus on the
respon.se of fish habitats in the middle Susitna River to incremental
changes in mainstem discharge,temper~ture and water quality.As part
of this multi-disciplinary effort,a technical report series was
planned that would (1)describe the existing fish resources of the
Susitna River and identify the seasonal habitat requirements of selected
species,and (2)evaluate the effects of alternative project designs and
operating scenarios on physical processes which most influence the seasonal
availability of fish habitat •
the technical report series,and (3)provides quantitative relationships
The summary report for the IFRS,the Instream Flow Relationships Report
(IFRR),(1)identifies the biologic significance of the physical processes
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evaluated in the technical report series,(2)integrates the findings of
and discussions regarding the influences of incremental changes in stream-
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Susi tna River on a seasonal basi s.
the middle Susitna River.
requirements of the·eva1uation species and life stage,as well as the
flow,stream temperature,and water quality on fish habitats in the middle
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important 1i fe
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Volume II of the IFRR will
This ranking considers the biologic
judgment to identify evaluation species,
be evaluated at the microhabitat level and presented at the macrohabitat
level in terms of a composite weighted usable area curve.This composite
curve wi 11 ,.describe the .combined response offish habitat,at all 5i tes
within the ".same representative group (to incremental changes in main-
stem discharge).
physical characteristics of different habitat types,under both natural and
professional
qua 1i ty of fi sh habi tat is the central theme of the IFRR Vol ume II
ana 1ysi s.'Project-induced changes in stream tempera ture and water qual i ty
ships on a seasonal basis regarding the influences of incremental changes
in streamflow,stream temperature,and water quality on fish habitats in
The influence of incremental changes in streamflow on the availability and
di fferent times of the year.
stages,and habitats.The report ranks a variety of physical habitat
components with regard to their degree of influence on fish habitat at
anticipated with-project conditions.
address the third objective of the IFRR and provide quantitative re1ation-
The IFRR consists of two volumes.Volume I uses project reports,data and
are used to condition or qualify the forecasted responsesotJi~~b~~_hClbtt~Lt__
.-•._"--._.-_.._._,..•.._..--~~_.__.-..--_.._-_..__._,.-~-----._.-----_.__._"---_..•._.,.__.__."~_.__._----_..•.'..'•....•'.....'....-._.'.'._.__.-.'-_...__..,..".,.,_.,...._-,.....-_.----_.,.._-_...-_..•_••.•..............•_.".._._--_.__..__._-_.-._--_.-..--_.~-~"---~----_.",..•_--.'--.._-,_._---'-•......_--
~------~-_to--instraam--hyaraTn-i-c-s-:--Tfje-lnfTue nee-aT-stream f1 owonrTs hha blta t -Vi-ill
Four technical reports are being prepared by E.Woody Trihey and Associates
in support of the IFRR Volume II analysis.The function of each report is
depicted in a flow diagram and described below.
1)Quantify Wetted
Surface Area
Response
2)Assess the Representa-
tiveness of Modeled
and Non-modeled Sites
3)Determine Site-
Sp~cific Hydraulic
Conditions
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4)Quantify Streamflow-Dependent Habitat Response
Functions for Juvenile Chinook and
Spawning Chum Salmon
1)RESPONSE OF AQUATIC HABITAT SURFACE AREAS TO MAINSTEM DISCHARGE IN
THE TALKEETNA-TO-OEVIL CANYON SEGMENT OF THE SUSITNA RIVER,ALASKA
This report identifies five aquatic habitat types within the
middle Susitna River directly influenced by changes in mainstem
di scharge and presents the necessary photography and surface area
measurements to quantify the change in wetted surface area
associated with incremental decreases in mainstem discharge be-
tween 23,000 and 5,100 cfs.The report also describes the in-
fluence of mainstem discharge on habitat transformations and
tabulates the wetted surface area responses for 172 specific
areas using the ten representative groups presented in the
Habitat Characterization Report.Surface area measurements
presented in this report provide a basis for extrapolating
results from intensively studied modeling sites to the remainder
of the middle Susitna River.
2)CHARACTERIZATION OF 'AQUATIC HABITATS IN ,THE TALKEETNA-TO-OEVIL
CANYON SEGMENT OF THE SUSITNA RIVER,ALASKA
This report describes the characterization and classification of
172 specific areas into ten representative groups that are hydro-
logically,hydraulically and morphologically similar.Emphasis
is placed on the transformation of specific areas from one
habitat t¥pe to another in response to incremental decreases in
mainstem discharge from 23,000 cfs to 5,100 cfs.Both modeled
and non-modeled sites are classified and a structural habitat
index is presented for each specific area based upon subjective
evaluation of data obtained through field reconnaissance surveys.
iv
Representative groups and structural habitat indices presented in
this report provide a basis for extrapolating habitat response
functions developed at modeled sites to non-modeled areas within
the remainder of the river.
3)HYDRAULIC RELATIONSHIPS AND MODEL CALIBRATION PROCEDURES AT 1984
STUDY SITES IN THE TALKEETNA-TO-DEVIL CANYON SEGMENT OF THE SUSITNA
RIVER,ALASKA
This report describes the influence of site-specific hydraulic
conditions on the availability of habitat for juvenile chinook
and spawning chum salmon.Two aquatic habitat models are applied
to quantify site-specific habitat responses to incremental
changes in depth and velocity for both steady and spatially
varied streamflow conditions.Summaries of site-specific stage-
discryarge and flow-discharge relationships are presented as well
as a description of data reduction methods and model calibration
procedures.Weighted usable area forecasts are provided for
juvenile chinook at 8 side channel sites and for spawning chum
salmon at 14 side channel and mainstem sites.These habitat
response functions provide the basis for the instream flow
assessment of the middle Susitna River.
4)RESPONSE OF JUVENILE CHINOOK AND SPAWNING CHUM SALMON HABITAT TO
~=.__._--_.__._--~-~.~~
MAINSTEM DISCHARGE IN THE TALKEETNA-TO-DEVIL CANYON SEGMENT OF THE
SUSlTNA RIVER,ALASKA
This report integrates results from the surface area mapping,
habitat characterization,and hydraulic modeling reports
to provide streamflow dependent habitat response functions for
juvenile chinook and spawning chum salmon.Wetted surface area
--_..._~-'---------~"'---and~wei-g'hted -~us-aDle~ar-ea-a-re-'-tliepri-ncTpiif1-ae-ter~miiia nts'of--na:5i"=---~-"'"
..~-_..-·--·-----·-------~~ta-t-----i-n-d-i-ce-s----·p-rovi-de·d--·--;-n~-Part·---A--'-o·f~---the--·-·-re-p-o-r-t-·~for----~'fuverri-l·e·----clfi noo R----~---.---.-.
at each specific area and the ten representative groups identi-
fied in the habitat characterization report.'Part B of this
report provides habitat response functions for existing chum
salmon spawning sites.The habitat response functions contained
in this report will be used for an'incremental assessment of the
rearing and spawning potential of the entire middleSusitna River
under a wide range of natural and wi th-project streamfl ows.
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TABLE·OF CONTENTS
Page
No.
PREFACE ••••••••••••••••••••••••••••••••0 ••0 a 0 •(J G •••••0 0 D •••••••••••••ii
LIST OF FIGURES •..••..•••.•...•..••••••.••••.••ll o •••••••••oo •••••••••viii
LIST OF TABLES ••••••••••••••••••••.••••••••••••••••••••••oo ••••••••••xiv
LIST OF PLATES ••.0 ••0 ••••tl ••0 0 •••a 0 •••••••0 Cl.0 •••ID 0 ••00.00.11 ••0 ••••00 xv
1.0 INTRODUCTION •••0 ••0 0 •0 • 0 ••••G • 0 0 ••00.G •a 0 0 ••0 •G •e .,.0 •••0 • 0 ••••CI 0 1
2.0 METHODS 0 0 ••••••••••••••••••••••••••0 ••••••••0 0 CD 0 ••••••••••••••••13
2.1 Habitat Characterization of the
Middle Sus;tna River 0 0 •••0 ••••••••••••••••••••••13
I
2.1.1
2.1.2
Study Site Classifications....•••••••••••••••••••13
Representa tive Groups ••••••••••.•.•••••"..........15
2.2 Quantificat~on •••••·••.•••••••••••••••000 ••000 ••••••••••••.••21
Description of Wetted Surface Area Responses.....21
Forecasting WSA with Regression Equations........26
Habitat Modeling Studies..........................29
Overview of Modeling Techniques..................29
Hydraulic Data Requirements......................31
Habi tat Sui tabi 1 i ty Cri teria...•. •. •.•••••.••••.•35
.Aerial Photography...............................23
2.2.1
2.2.2 .
2.2.3
2.3 Physi ca 1
2.3.1
2.3.2
2.3.3
2.3.4 Habitat Model Response Variables.................41
2.4 Extrapola ti on of Model i ng Resul ts to
Non-modeled Specific Areas ••••••••••••••••~................46
2.5 Integration o •••••••••••••••••••••••••••••••52
vi
300 RESULTS.0 •••••••••••0 Cl ••0 0 ••••••••CI ••••••••••0 •••••••0 ••••0 ••0 0 0 54
3.1 Representative Group I ..~....0 ••CI ••1).0.0 CI GO ••••••••••G.0 •••
3.2 Representative Group 11 ••0 ••••••0 e ••••0 0.0 ••00 a 0 o.GO •••••••
3.3 Representative Group I I I ••••••••0 •GO.CI 0 0 «I •0 0 •'.0 •CI • 0 0 0 0 0 • 0 ••
3.4 Representative Group IV.e ••0 ••0 •00.0 ••0 • 0 G.o •••eo.0 eo ••••••
54
63
76
89
3.5 Representative Group V•••••••••••••••••••••••••••••••••••••102
3.6 Representative Group VI •••••••••••••••••••.••••••••••••••••108
3.7 Representative Group VII •••••••••••••••••••••••••••••••••••116 -
3.8 Representative Group VIII ••••••••••••••••••••••••••••••••••122
3.9 Representative Group IX ••••••••••••••••••••••••••••••••••••127
3.10 Representative Group X•••••••••••••••••••••••••••••••••••••135
4.0 SUMMARy •••••••••••••••••;•••••••••••••••••••••••••••••••••••••••141
LITERATURE CITED ••0 •••0 •«I ••0 ••••0 ••••••••0 • 0 00 0 Cl ••••0«1 0 0 0 «I CI "CI eo •••0 •"•146
APPENDICES:
Appendix A-Aerial Photography of Modeling Sites ••••••••••~....150
Appendix B-Habitat Availability Indices (HAl)
for Specific Areas •••••••••o.o ••o~.oo.ooooao.~.ooo.193
Appendix C -Wetted Surface Area (WSA)Values
for Specific Areas •••••••••••••••••••••••••••••••••211
_~~__~~Rend ix _D__....Wej_ghted_Usable-Ar-ea-{-WUA-)-Va-lues .-----------
--for Specific Areas ...•...•.••...••..............•..228
Appendix E -Weighted Surface Area (WSA)Regression Equations...245
Figure
No.
LIST OF FIGURES
Page
No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Natural and with-project mean weekly discharges for the
middle Susitna River.
Percentage distribution of juvenile chinook salmon
within different habitat types of the middle Susitna
River during the open water period
Density distribution of juvenile chinook salmon by
macrohabitat type on the Susitna River between Chulitna
River confluence and Devil Canyon,May through November
1983.
Flow chart indicating steps followed in the extrapola-
ti9n of site-specific juvenile chinook habitat indices
to the entire middle Susitna River.
Juvenile chinook habitat modeling sites in the middle
Susitna River.
Key to habitat transformation categories used to
classify specific areas to representative groups.
,Flow 'chart indicating the steps followed in the
quanti fi ca ti on of wetted surface area response to
mainstem discharge for specific areas used in the
extrapolation methodology.
RJHAB and PHABSIM modeling pathways followed in the
analysis of juvenile chinook salmon ,habitat.
Sampling design for RJHAB modeling sites.
Sampling design for PHABSIM modeling sites.
Cover suitability criteria used to model juvenile
chinook habitat (WUA)in the middle Susitna River.
Depth suitability criteria used to model juvenile
chinook habitat (WUA)under clear and turbid water
conditions in the middle Susitna River.
4
5
7
12
14
19
27
30
32
33
36
37
13.
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Velocity suitability criteria used to model juvenile 38
chi nook habi ta t (WUA)under cl ear and turbi d wa ter
conditions in the middle Susitna River
Derivation of a non-modeled specific area (sa)HAl 51
curve using a modeled specific area (ms)HAl curve.
viii
LIST OF FIGURES
(cont.)
Figure
No.
15.Flow chart indicating the steps followed in the inte-
gration of stratification,simulation,and quantifica-
tion for specific areas used in the extrapolation
methodology.
16.Surface area and chinook rearing habitat index response
curves for modeling site 107.6L.
17.Surface area and chinook rearing habitat index response
curves for modeling site 112.5L.
18.Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 107.6L of Representative Group I.
19.Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 112.5L of Representative Group I.
40.Aggregate response of A-wetted surface area (WSA)and
B -chinook rearing habitat potential (WUA)to mainstem
discharge in specific areas comprising Representative
,---~----·----Group Iof--the·mtddteSusi·tna-Riv~r·~-·~~··-···-··------.-
21.Surface area and chi nook reari ng habi ta t index response
curves for modeling site 101.4L.
22.Surface area and chinook rearing habitat index response
curves for modeling site 113.7R.
_......__..._23._.Surface·areaandchinookrearing-habi-ta·t·index--response----··
......._._..__.~_.__cur-v.es __formode-l-ing-s.i-te--12.6-.·QR-.----·....-..------.----
24.Surface area and chinook rearing habitat index response
curves for modeling site 144.4L.
25.Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
n1odelingsiteI01.4L of Representative GroupH ..
26.Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas-of
the middle Susitna River which are associated with
modeling site 113.7R of Representative Group II.
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Page
No.
53
55
57
59
60
62
65
66
68
70
71
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Figure
No.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
LIST OF FIGURES
(cont.)
Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated'with
modeling site 126.0R of Representative Group II.
Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 144.4L of Representative Group II.
Aggregate response of A-wetted surface area (WSA)and
B-chinook rearing habitat potential (WUA)to mainstem
discharge in specific areas comprising Representative
Group II of the middle Susitna River.A
Surface area and chinook rearing habitat index response
curves for modeling site 101.2R.
Surface area and chinook rearing habitat index response
curves for modeling site 128.8R.
Surface area and chinook rearing habitat index response
curves for modeling site 132.6L.
Surface area and chinook rearing habitat index response
curves for modeling site 141.4R.
Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 101.2R of Representative Group III.
Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 128.8R of Representative Group III.
Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 132.6L of Representative Group III.
Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 141.4R of Representative Group III.
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No.
72
73
74
77
78
79
80
83
84
85
86
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87
90
94
91
93
96
92
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100
104
Page
No.-
105
LIST OF FIGURES
(cont.)
Surface area and chinook rearing habitat index response
curves for modeling site 112.6L.
Surface area and chinook rearing habitat index response
curves for modeling site 131.7L.
Surf~ce area and chinook rearing habitat index response
curves for modeling site 134.9R.
Surface area and chinook rearing habitat index response
curves for modeling site 136.0L.
Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 112.6L of Representative Group IV.
Aggregate response of A-wetted surface area (WSA)and
B-chinook rearing habitat potential (WUA)to mainstem
discharge in specific areas comprising Representative
Group III of the middle Susitna River.
Figure
No.
39.
47.Aggregate response of A-wetted surface area (WSA)'and
B-chinook rearing habitat potential (WUA)to mainstem
discharge in specific areas comprising Representative
Group IV of the middle Susitna River.
49.Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 141.6R of Representative Group V.
48.Surface area and chinook rearing habitat index response
curves for modeling site 141.6R.
38.
44.
45.
42.
43.
41.
40.
Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with-----------------------mode 1i ng slte 131.7LOfReprese-n-ia five Group~------
Response of chinook reari~g habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 134.9R of Representative Group IV.
46.Response of chinook rearing habitat availability to
-------------------------matnstemdischarge wtthin-non-modeled----spe-cifi c-areas--of-------------------
--------------------the--mi-dd-le-Sus-i-tna----R-iver-whicha-re---a-ssoci-a-ted--with--
modeling site 136.0L of-Representative Group IV.
xi
Figure
No.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
LIST OF FIGURES
.(cont.)
Aggregate response of A-wetted surface area (WSA)and
B -chinook rearing habitat potential (WUA)to mainstem
discharge in specific areas comprising Representative
Group V of the middle Susitna River.
Surface area and chinook rearing habitat index response
curves for modeling site 133.8L.
Surface area and chinook rearing habitat index response
curVes for modeling site 136.3R.
Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 133.8L of Representative Group VI.
Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 136.3R of Representative Group VI~
Aggregate response of A-wetted surface area (WSA)and
B-chinook rearing habitat potential (WUA)to mainstem
discharge in specific areas comprising Representative
Group VI of the middle Susitna River.
Surface area and chinook rearing habitat index response
curves for modeling site 119.2R.
Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 119.2R of Representative Group VII.
Aggregate response of A-wetted surface area (WSA)and
B-chinook rearing habitat potential (WUA)to mainstem
discharge in specific areas comprising Representative
Group VII of the middle Susitna River.
Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 132.6L of Representative Group VIII.
Response of chinook rearing habitat availabili~to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 144.4L of Representative Group VIII.
xii
Page
No.
107
110
111
113
114
115
118
120
121
124
125
LIST OF FIGURES
(cont.)
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128
Page
No.
126
129
131
132
133
139
144
138
xiii
Compari son of the aggregate response of chi.nook reari ng
habitat [WUA]for Representative Groups I through IX.
Aggregate response of A-wetted surface area (WSA)and
B-chinook rearing habitat potential (WUA)to mainstem
discharge in specific areas comprising Representative
Group VIII of the middle Susitna River.
Surface area and chinook rearing habitat index response
curves for modeling site 147.1L.
Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 101.5L of Representative Group IX.
Response of chinook rearing habitat availability to
mainstem discharge within non-modeled specific areas of
the middle Susitna River which are associated with
modeling site 147.1L of Representative Group IX.
Aggregate response of A-wetted surface area (WSA)and
B-chinook rearing habitat potential (WUA)to mainstem
discharge in specific areas comprising Representative
Group IX of the middle Susitna River.
Surface area and chinook rearing habitat index response
curves for modeling site 101.5L.
Figure
No.
69.
62.
61.
67.
66.
64.
63.
65.
Response of chinook rearing habitat availability to
mainstem discharge for specific~reas of the middle
Susitna River within Representative Group X.
68.Aggregate response of A-wetted surface area (WSA)and
B -chinook rearing habitat potential (WUA)to mainstem
discharge in specific areas comprising Representative
----------------------Gro up-Xof--themidd-le -Susitna River •.......-.......---------........-..--
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Table
No.
1.
2.
3.
4.
LIST OF TABLES
Primary hydrologic,hydraulic and morphologic
characteristics of representative groups identified for
the middle Susitna River.
Cover suitability criteria used to model juvenile
chinook habitat (WUA)in the middle Susitna River.
Separa te cri teria are presented for cl ear and turbi d
water conditions (Steward 1985).
Wetted surface area (WSA),weighted usable area (WUA)
and related habitat indices used in the evaluation of
chinook rearing habitat potential within the middle
Susitna River.
Mainstem breaching discharges and structural habitat
indices (SHI)determined for specific areas within the
middle Susitna River.Specific areas are arranged in
representative groups by subgroup,where the modeled
specific area representing each subgroup is located at
top.
xiv
Page
No.
17
40
42
49
LIST OF PLATES
Plate
No.
A-1 Aerial.photography of modeling site 107.6L at mainstem
discharges of 23,000 cfs and 16,000 cfs.
A-2 Aerial photography of modeling site 112.5L a~mainstem
discharges of 23,000 cfs and 16,000 cfs.
A-3 Aerial photography of mode-ling site 101.4L at mainstem
discharges of 23,000 cfs and 16,000 cfs.
A-4 Aerial photography of modeling site 113.7R at mainstem
discharges of 23,000 cfs and 16,000 cfs.
A-5 Aerial photography of modeling site 126.0R at mainstem
discharges of 23,000 cfs and 16,000 cfs.
A-6 Aerial photography of modeling site 144.4L at mainstem
discharges of 23,000 cfs and 16,000 cfs.
A-7 Aerial photography of modeling site 101.2R at mainstem
discharges of 23,000 cfs and 16,000 cfs.
A-8 Aerial photography of modeling site 101.2R at mainstem
discharges of 12,500 cfs and 7,400 cfs.
A-9 Aerial photography of modeling site 128.8R at mainstem
discharges of 23,000 cfs and 16,000 cfs.
~~------------~---------_..-.----------------
A-10 Aerial photography of modeling site 128.8R at mainstem
discharges of 12,500 cfs and 7,400 cfs.
A-ll Aerial photography of modeling site 132.6L at mainstem
discharges of 23,000 cfs and 16,000 cfs.
A-12 Aerial photography of modeling site 132.6L at mainstem
-------------------d-ischarges-of12,-500--cfs·anq·7,400··cfs;;----~--------....--.-._----------
A-13
A-14
A-15
A-16
A-17
Aerial photography of modeling site 141.4R at mainstem
discharges of 23,000 cfs and 16,000 cfs.
Aerial photography of modeling site 141.4R at mainstem
discharges of 12,500 cfs and 7,400 cfs.
Aerial photography of modeling site 112.6Lat mainstem
discharges of 23,000 cfs and 16,000 cfs.
Aerial photography of modeling site 112.6L at mainstem
discharges of 12,500 cfs and 7,400 cfs.
Aerial photography of modeling site 131.7L at mainstem
discharges of 23,000 cfs and 16,000 cfs.
xv
162
163
164
165
166
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Plate
No.
A-18
A-19
A-20
A-21
A-22
A-23
A-24
A-25
A-26
A-27
A-28
A-29
A-30
A-31
A-32
A-33
LIST OF PLATES
(cont.)
Aerial photography of modeling site 131.7L at mainstem
discharges of 12,500 cfs and 7,400 cfs.
Aerial photography of modeling site 134.9R at mainstem
discharges of 23,000 cfs and 16,000 cfs.
Aerial photography of modeling site 134.9R at mainstem
discharges of 12,500 cfs and 7,400 cfs.
Aerial photography of modeling site 136.0L at mainstem
discharges of 23,000 cfs and 16,000 cfs.
Aerial photography of modeling site 136.0L at mainstem
discharges of 12,500 cfs and 7,400 cfs.
Aerial photography of modeling site 141.6R at mainstem
discharges of 23,000 cfs and 16,000 cfs.
Aerial photography of modeling site 133.8L at mainstem
discharges of 23,000 cfs and 16,000 cfs.
Aerial photography of modeling site 136.3R at mainstem
discharges of 23,000 cfs and 16,000 cfs.
Aerial photography of modeling site 136.3R at mainstem
discharges of 12,500 cfs and 7,400 cf~.
Aerial photography of modeling site 119.2R at mainstem
discharges of 23,000 cfs and 16,000 cfs.
Aerial photography of modeling site 119.2R at mainstem
discharges of 12,500 cfs and 7,400 cfs.
Aerial photography of modeling site 101.5L at mainstem
discharges of 23,000 cfs and 16,000 cfs.
Aerial photography of modeling site 101.5L at mainstem
discharges of 12,500 cfs and 7,400 cfs.
Aerial photography of modeling site 147.1L at mainstem
discharges of 23,000 cfs and 16,000 cfs.
Aerial photography of modeling site 147.1L at mainstem
discharges of 12,500 cfs and 7,400 cfs.
Aerial photography of modeling site 105.8L at mainstem
di scharges of 12,500 cfs and 7,400 cfs.
xvi
Page
No.
167
168
169
170
171
172
173
174
175
176
171
178
179
180
181
182
xvii
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Page
No.
183
188
186
185
184
189
187
190
LIST OF PLATES
(cont.)
Aerial photography of modeling site 105.8L at mainstem
discharges of 23,000 cfs and 16,000 cfs.
Aerial photography of modeling site 119.1L at mainstem
di scharges of 12,000 cfs and 7,400 cfs.
A-38
A-41
A-39
A-36
A-35
A-34
A-37
Plate
No.
_A"40
Aerial photography of modeling site 119.1L at mainstem
di scharges of 23~000 cfs and 16,000 cfs.
Aerial photography of modeling site 133.8R at mainstem
di scharges of 12,000 cfs and 7,400 cfs.
Aerial photography of modeling site 133.8R at mainstem
discharges of 23,000 cfs and 16,000 cfs.
Aerial photography of modeling site 138.7L at mainstem
discharges of 12,000 cfs and 7 ,400 cfs~
Aerial photography of model i ng si te 138.7L at l11afnstel11
discharges of 23,000 cfs and 16,000 cfs.
Aerial photography of modeling site 139.4L at mainstem
di scharges of 12,000 cfs and 7,400 cfs.
A-42 Aerial photography of modeling site 139.4L at mainstem 191
---------~----------------ai scnarge s -of~Z3--;OUO-cTs an(r--r6--;0-OUcfs:---------------~-------
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1.0 INTRODUCTION
Due to the economi c importance of the species,the ecol ogi ca 1 sensi tivi ty
of the life stage,and their extensive use of mainstem-associated habitats,
juvenile chinook have been designated as a primary evaluation species to be
used in analyses of existing and with-project conditions.Chum salmon
spawning and incubation life stages comprise the other two primary
species/life stages selected for evaluation (EWT&A and Entrix 1985).
This report addresses the effects of flow variation on the availability and
quality of juvenile chinook salmon habitat within the Talkeetna to Devil
Canyon reach of the Susitna River.The response of juvenile chinook habi-
tat to changes in streamflow within this middle reach of the Susitna River
has been the subject of several years of data collection and modeling
studies conducted by the Alaska Department of Fish and Game (ADF&G)and
Trihey and Associates (EWT&A).These investigations are part of an
extensive environmental assessment program conducted to ful fi 11 1i censi ng
requirements for the proposed Susitna Hydroelectric Project.
The Alaska Power Authority (APA),the state agency responsible for
developing the hydropower potential of the Susitna River,has indicated a
desire to maintain existing fish resources and levels of production within
affected reaches of the river (APA 1985).This goal may be attainable
through a variety of mitigative options (Moulton et al.1984).However,to
protect existing fisheries resources and,to ensure the success of selected
mitigation and enhancement efforts,it is necessary to identify and adopt
instream flows and reservoir operation schedules which will provide for the
needs of the fish species inhabiting the middle Susitna River.
1
The storage and release of water to meet the instream flow needs of fishes
downstream is not necessarily incompatible with hydropower interests.The
recharge and storage capabil i ties of the proposed Devil Canyon and Wa tana
reservoirs [refer to APA (1985)for a description of the design criteria
and construction schedule for these facilities]will permit water to be
stored during periods when natural runoff exceeds both the water demand for
power generation and the instr-eam flow needs of resident and anadromous
fishes.This will allow for the controlled release of water during periods
of greatest demand for power.
Under the 1 i cense appl i ca ti on presentl y before the Federa 1 Energy
Regulatory Commission the development of the Susitna hydroelectric project
is planned to occur in three stages'(APA 1985).
o Stage lis the constructi on a nd opera ti on of the Wa tana dam by 1999
which will provide 2.37 million acre feet of active storage.This is
approximately 40 percent of the mean annual flow at the damsite and
affords some seasonal regulation.
o Stage II is construction of a dam by 2005 in the narrow Devil Canyon.
The principal purpose is to develop head relying upon the Watana dam
---------------------------------_...__._--_._----_....-•.•.....•-.....,.__.__..._._._-_.__..~-_.""_.-----_._-_.""---_._.__.
~=~~=~===~---t~T~9 ~_~te_fJg_ws fg!"_po~e rJ)r()_<t~j:lon_"-_______
o Stage III involves raising the Watana dam 180 feet by 2012 to increase
active storage to 3.7 mill i on acre feet,approxima te ly 64 percent of
the mean annual flow.
The license application presents environmental flow cases E-1 through E-VI
which are aimed to provide different maintenance levels of habitats most
responsive to mainstem flows.Case E-VI is the selected flow case in the
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application and is designed to maintain 75 percent of the existing chinook
salmon side channel rearing habitat in all years except low flow years.
There are four projected flow scenarios for Case E-VI depending upon the
stage of development of the project.Figure 1 compares natural with
simulated with-project mean weekly discharges at Gold Creek for these four
scenarios.
The frequency and rate of change of daily flow fluctuations in the middle
Susitna River will be highest during Stage I and II.However,by Stage III
daily flow fluctuations are expected to be minimal.Over the long-term,
use of the combined storage volume of the two reservoirs will result in
lower summer a'nd higher winter flows than presently occur.
As the demand for electricity varies over time,so do the instream flow
needs of a fish species vary accord:ing to their life history stage.Adult
chinook spawn exclusively within tributaries of the middle reach of the
Susitna River,principally Indian River and Portage Creek.Consequently,
the reproductive and early post-emergent fry life stages of chinook (unlike
those of chum,pink and sockeye salmon which spawn'in both tributary and
non-tributary habitats of the middle Susitna River)are not likely to be
affected by project operation.The later freshwater life stages of chinook
salmon,including juvenile and migratory phases,will be subjected to
altered streamflow regimes since they utilize mainstem and mainstem-
influenced habitats (Figure 2).The summer growth season is an important
period for chinook juveniles since it is at this time that density-
dependent factors will typically have their greatest effect on the
popul a ti on.
3
30,000
LEGEND
NATURAL
--STAGE I
-----STAGE II
-.-.STAGE III EARLY
--.STAGE III LATE
18 1 -.
6 ~3 [20 27 4 II I~25 I 8 15 22 29 !5 12
JiNf JULY !AUGUST SEPTEMBER
I •
NatJrJl and with-project mean weekly discharges for the
mid1l~Susitna River.:Natural flows are based on 35 year
record [(1950-1984)froml USGS Station 15292000 at Gold Creek.
SimJlaited with-projectlflows are based on Case E-VI p demandlev~ls Stage I.Stagel II.early and late Stage III (datafro~f.i.PA 1985),:
:!!
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I :.1 .'L/-:"-~-".
'-C - -".".....•Ii;,."/~.'.
/I:,__•.-..:J#I""
;'·1 !,./!
/,.•!
:•~._._.I 1 ;'/............,..--~--.'-::-::~-._._.~.;;/I i-'-'.-
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Figure 10
~ooo
10,000
MONTHS
w
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II)....
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.~----...,......-.~'---i
~
COHO
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TRIBUTARIES
50
60
40
40
60
10
50
I-
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~30
ffi
Q.20
I-
Z
Woa:·wQ.
RELATIVE
ABUNDANCE
OF JUVENILE
SALMON
~
CHUM
2.5.,m;.";;"\";;;{"""~";".,,,,,JW;%'lil@iii;{:t··
UPLAND SIDE
SLOUGHS CHANNELS
10
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50
60
40
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Q.
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W 30oa:w
Q.20
Jl
CHINOOK SOCKEYE
Figure 2.Percentage distribution of juvenile salmon within different
habitat types of the middle Susitna River during the open
water period (Dugan,Sterrltt,and Stratton 1984'.
Following emergence in March and 'April juvenile chinook typically spend
several months rearing in their natal streams.However,the numbers and
biomass of juvenile fish may exceed the carrying capacity of the tribu-
taries by midsummer and a percentage of the chinook population respond by
emigrating to the Susitna River.During the remainder of their freshwater
residency,whic~usually lasts until the spring of the following year,
juvenile chinook typically occupy a range of habitats.Densities are
hi.ghest in tributaries,side channels and side sloughs,respectively,
during July to September of the open water season (Figure 3).Chinook
distribution during the winter months is not well documented other than a..
noted tendency for individuals in mainstem and side channel areas to seek
relatively warmer upwelling areas in side sloughs.During the fall a
signi fi cant number of young-of-the-year chi nook apparen tl y mi gra te down-
stream late in the summer,although it is uncertain whether they overwinter
in fresh or sal twa ter (Dugan et a 1.1984).
The biological and physical factors affecting juvenile chinook salmon in
their rearing environment and their interrelationships are complex.Milner
(1985)reviewed these environmental factors and their potential effects.
,._..,.£<?~~.~.~tla.~ilt!:Y~.I:>.r~.c1Cl~t()n,.Cl.I1.c1..c::()mPg1:ttjQI'Ljtr.~t.aIJLQI19_tb!=!_..m,o.r.e_imp.or..tan.t___-.:....._.
oi"orogfcal-factors:'A1Tareme--dla-tecitosomede'gree by the quan ti ty and
quality of physical habitat which constitute the fish's living space.
Physical habitat .includes the combination of hydraulic,structural and
chemical variables to which juvenile chinook tespondeitffer behaviorally or
physiologically.Stream temperature,turbidity,suspended sediment level,
water depth and velocity,.cover,and substrate texture are important
physical habitat variables w'hich are either directly or indirectly
influenced by the volume and pattern of streamflow.
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Malnatem II'
9.3°/.Oxbow One
Eioht Silu \/8.20/.
Combined 4.0%
SlouOh 22.
Whiskers Creek
SlouOh
Side Channel 10
Oxbow One
10.7%
~.Side Channel
10 "17.9%
Twelve Situ
Combined
SlouOh 9
SIDE
CHANNELS
6.7~UPLAND SLOUGHS
COMBINED MACROHABITAT
TYPES
SIDE SLOUGHS~
Five Tributaries
Combined 10.4 %
-..l
Figure 3.Density distribution of juvenile chinook salmon by
macrohabitat type on the Susitna River between Chulitna
River confluence and Devil Canyon,May through November
1983.Percentages are based on mean ca tch per cell (Dugan,
Sterri tt,and Stratton 1984).
The goal of minimizing potentially adverse effects of flow alterations
associated with hydropower generation is possible only if the magnitude of
the impacts is known,thereby presenting two major problems.The first
relates to the quantification of existing resources and the relationships
which sustain them.The second problem is methodolog.ical:how can predic-
tions of with-project conditions be superimposed on natural conditions to
enable accurate forecasts?
For e'xample,our knowledge of the population dynamics of chinook salmon
stocks of the middle Susitna River yields little insight into their likely
long-term response to wi th-project flow regi meso Popula ti on adjustments
are frequently deterrnined by com inations of environmental properties
occuring far in advance of the biological response.Thus,although fish
production and its component parameters (i.e.,density,mortality,growth,
.etc.)may eventua llYr~fJ~c:1;'t;hEtjl'lfll,Le-Rc-ep_fca.usative.envjJ··o-nmentaL..-------------_._..~~~_.._-_.._------_~__..___._-.---~_._•........-_-_..
factors,the complexity of these relationships is too great and there is
too much variability in our estimates to base our forecasts entirely on
population studies.We are not limited as much by our ability to
conceptualize the relationships linking juvenile.c:.hLnQOk__1;Otheir _
----_._._~._---_.~-_._..-_.._-_.._--------_.•._--_..,.-._--_._,.._._-_..•---_._--~_._----,,---_..-....-.--------_.-.-----.._-----.------_...'.._----------_....,..--_.•.-.....__.•.._._--_..•...•---------.-.-.-..--..._..-----..-._"._--------•....-.__...•.__.._-_•..,--_..__.'...
ships.
This problem i·s not a new one.Fisheries biologists faced with the tasK of
identi fying acceptable -instream flows often make their sel ecti On because it
appears to make biological sense,and not on the basis of mathematically
defined relationships between streamflow and biological response.In the
past decade,however,an instream flow assessment methodology has been
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developed which partially bridges this gap.The Instream Flow Incremental
Methodology (IFIM)descri bed by Bovee (1982)provi des a computer assi sted .
capability of simulating important components of fish·habitat based,on
site-specific field measurements.The suitability of fish habitat at a
given flow is eva!uated by reference to preference criteria.These are
frequency distributions which describe the probability that a fish will be
found in association with a particular level or interval of the habitat
component in question.Once the spatial distribution and levels of habitat
compone[lts are known or are reliably simulated for a range of flows,and
the relationships between these components and behavioral preferences have
been quantified,then a habitat response index may be calculated for each
flow of interest.Following standard IFIM terminology,this habitat
response index is termed Weighted Usable Area (WUA).From an assumption
that the amount of suitable habitat in a stream varies with flow,the
direction and magnitude of WUA may be considered reliable indicators of the
probable population response to discharge alterations.This assumption has
been verified for some salmonid streams but not for others (Nelson 1980,
Loar 1985).Factors other than the amount of usable habitat,such as
inadequate food supplies and catastrophic events (e.g.,floods),may ,have
been responsible for the conflicting results.
Nevertheless,the concept of habitat preference appears valid for this
study and the linkage between biological response and flow-related habitat
changes,as indexed by WUA should be strong enough to make inferences
concerning the present status and likely trends in juvenile chinook
)popul a ti ons .
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9
Included in this report are WUA functions and related habitat indices
defining the relationship between mainstem discharge and chinook rearing
habitat potential at 20 study (modeling)sites on the middle Susitna River.
Model ing resul ts are extrapola ted from individual study si tes to descri be
the response of juvenile chinook habitat within a number'of different sub-
environments of the middle Susitna River.Conventional methods of
extrapolating WUA in single channel rivers based on the concept of con-
tinuous homogeneous subsegments represented by individual modeling sites
are not applicable to large braided rivers like the the Susitna River due
to large spatial variations in hydraulic and morphologic character (see
Aaserude et al.1985).Consequently,investigators concentrated on
sampling smaller areas or portions of the middle Susitna River possessing
relatively uniform yet comparatively distinct hydrologic,hydraulic and
water clarity characteristics.This sampling design prompted the develop-
ment of an extrapolation methodology,first outlined by Steward and Trihey
........_._jJ_~.~_'!l ,.!!Dj~t:J \'J~i9t:J"t:~jIVA j 114.i c l:.~gl:.'Ll:.l QRl:.df Qrea.c 11._lIlod e 1jng __stte
according to the portions of the middle reach possessing similar hydro-
logic,hydraulic and water clarity attributes.Characterizing fish habitat
at this level acts to overcome problems associated with the large degree of
environmental variability resent in the s stem and im roves the
--------------ap·pl-i-ca-b-i-l-i-ty---'-'o'f'---t-he-s'e---r-e-s·ui··ts---to-·--the---en-t-lre--lfriaa-le-·---S us i-tna----R-iv e r.--------------..----~--.---..-.---.
Within the overall framework of the Susitna aquatic habitat assessment
program,habitat modeling results obtained for individual habitat types are
particularly appropriate since related studies of juveriilefiSh'diStribu....
tion were conducted at this level (Hoffman 1985).An evaluation of habitat
modeling results in combination with fish utilization data will permit an
accura te assessment of reari ng habi ta t response to na tura 1 and project-
10
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induced changes in streamflow for the entire middle Susitna river segment.
Figure 4 illustrates the primary steps in the extrapolation analysis.An
outl i ne of the da ta requirements and steps which compri se the methodology
follows in order that the reader gain an appreciation of the utility of the
rearing habitat response curves.The results of applying the full extrapo-
lation analysis to existing flow regimes will be detailed in Volume II of
the Instream Flow Relationships Report,scheduled for release by EWT&A in
December 1985.
11
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charge for the entire
middle Susitna Rivero
life stage:
Integra tion
For each evaluation species/
cation.stratjfication •.
and simulation components
Flow chart indicating steps followed in the extrapolation of
site-specific juvenile chinook habitat indices to the entire
middle Susitna River.
to determine the aquatic
.........----...-."'hab itat-response·····to····d i·s-·······-·····-........-........._.
Figure 4s
Quanti fi ca ti on Stra tifi ca tion Simulation
Quantify surface areas of Use available morpho-Simula te the response
individual channel branches logic.hydraulic.and of aqua ti c habi ta t
in the middle Susitna River hydrologic information qualit¥to discharge
for each flow for which to stratify individual wi th habi tat model i ng
aerial photography is aquatic habitats into techniques at selected
available to determine groupstha tare hydro-areas of the middle
the surface area response logically and morpho-Susitna Rivers
to mainstem discharges logically similaro
2.0 METHODS
2.1 Habitat Characterization of the Middle Susitna River
2.1.1 Study Site Classification
For,the middle reach of the Susitna River,Klinger and Trihey (1984)
describe six habitat types,on the basis of water source and morphology:
mainstem,side channel,side slough,upland slough,tributary,and tribu-
tary mouth.Rearing habitat modeling sites were initially selected to
conform with the concept of aquatic habitat types.The degree to which
these habitat types are utilized by juvenile salmon as well as their
susceptibility to project impacts determined the extent to which they were
represented in model ing studies.Of the large number of loca ti ons sampled
for juveniles in 1981 and 1982,significant numbers of chum,soc'keye,and
chinook salmon were found in tributary,side channel,side slough and
upland slough locations.Chinook salmon utilization of these habitat types
was summarized in Figure 3.Recognizing that rearing habitat in
tributaries will not be affected by project operation,investigators
excluded this habitat type from modeling studies.Utilization of mainstem
and tributary mouth areas by juvenile salmon was low and -not intensively
studied.The sites chosen for modeling studies of juvenile chinook habitat
are identified by river mile and bank orientation (L and R denote left and
right bank looking upstream)in Figure 5.
13
_-CM100l.E-SUSITHA-RIVER·)··--_··__··_-
JUVENILE CHINOOK
.__J:fA8J.TA.1.MOOELING ..SITES.
-1
10
!
MILES
o
I
Figure 5.Juvenile chinook habitat modeling sites in the middle
Susitna River.Sites are identified by river mile and bank
orientation,where Land R denote left and right bank
looking upstream.
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2.1.2 Representative Groups
While the habitat type·concept described by Klinger and Trihey (1984)is
useful in the identification of attributes characterizing'a particular
location within the middle Susitna River at a given time,the static
quality implicit in the concept makes it less practical as a means of
stratifying the river for extrapolation purposes.The results of the
11 habitat modeling analyses are WUA forecasts for sites which frequently
r I
transform from one of these habitat types to another over the range of
evaluation flows.The habitat quality and the distribution of the juvenile
chinook is dependent upon these transformations and the progressive
physical changes which attend them.
In order that the dynamic and site-specific nature of rearing habitat
response to a constantly changing aquatic environment be acknowledged by
the extrapolation methodology,an alternate means of stratifying the middle
Sus i tna River was developed.The concept of represen ta ti ve groups as a
further set of distinct portions of the middle Susitna River and the
criteria used by Aaserude et al.(1985)to define them ensures that the
modeling sites are truly representative of .the habitats of the river they
are intended to charac teri ze.Accura teo foreca s ts of the respon se of
juvenile chinook to natural or imposed changes in flow regime require that
this condition be satisfied.
Aaserude et al.(1985)delineated 172 specific areas of the middle Susitna
.J River from aerial photography interpretation and field verification
stud i es.Specific areas formerly divided among four habitat types (side.
15
channel,side slough,upland slough,and in some cases mainstem habitats)
were reassigned among ten representative groups,each characterized'by
unique and readily identifiable combinations of flow-related attributes.
Representative groups and the primary hydrologic,hydraulic and morphologic
forms and processes which distinguish them are summarized in Table 1.
Each modeling site is associated with a corresponding specific area;from
an analysis of aerial photography and reconnaissance level field data,a
modeled specific area may also be determined to be representative of
several non-modeled specific areas within the same representative group.
A
Within the framework of the extrapolation methodology,the collection of
modeled and non-modeled specific areas which comprise a particular repre-
sentative group may be thought of as a discontinuous (i.e.,spatially
discontin~ous)yet homogeneous subsegment of the river.
Figure 5 indicates the repres~n~~iY~gY'()lJP c1~~tgng1:.jol1 of ectchJ'earing.
--_._-"--~._~~-___._---_..__._--_.--------_._-_.•.._.....•._._-_-___...•........_-__.._.-
habitat modeling site.Because the delineation of representative groups
occurred subsequent to study site selection and data collection,some
representative groups do not possess specific areas in which modeling
studies were conducted.In particular,specific areas which dewater at
._--------.----..-----..
---~-·~-rela-t_i·ve-1-y·hi·ghma·instem--discharges (Grou p'YI-n }-rfha-nfalfrste m....a rea swlficlf
remain shoal-like at most evaluation flows (Group X)are not represented by
juvenile chinook habitat modeling sites.The remainder of the representa-
tive groups have at least one specific area with an associated modeling
study site.This fact is important since the dbjectiveiS to extrapolate
habitat indices from specific areas with modeled sites to non-modeled
specific areas,assuming that modeling sites generally reflect the habitat
character of non-modeled areas within the same representative group.As
16
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i~\PRESENTATIVE NUMBER OFIGROUPSPECIFICAREAS
,I
DESCRIPTION
HABITAT
mOELIHG
SITES
II
III
IV
v
VI
VII
VIII
IX
x
19
2B
18
21
9
13
7
24.
21
13
Predominantly upland sloughs.The specific areas comprising this group are
highly stable due to the persistence of non-breached conditions (i.e.,
possess high breaching flows).Specific area hydraulics are characterized
by pooled clear water with velocities frequently near 0.0 fps and depths
grea tel'than 1.0 ft.Pools are cOll1llOnly connected by short riffles where
velocities are less,than 1.0 fps and depths are less than 0.5 ft.
This group includes specific areas commonly referred to as side sloughs.
These sites are characterized by relatively high breaching flows
(>19,500 cfs),clear water caused by upwelling groundwater,and large
channel length to width ratios (:>15:1).
Intermediate breaching flows and relatively broad channel sections typify
the specific areas within this Representative Group.These sites are side
channels which transform into side sloughs at mainstem discharges ranging
from B,200 to 16,000 cfs.Lower breaching flows and smaller length to
width ratios distinguish these sites from those in Group 11.Upwelling
groundwa tel'is present.
Specifie areas in this group are side channels that are breached at low
discharges and possess intermediate mean reach velocities (2.0-5.0 fps)at
a mainstem discharge of approximately 10,000 cfs.
This group includes mainstem and side channel shoal areas which transform
to clear water side sloughs as mainstem flows recede.Transformations
generally occur at moderate to high breaching dhcharges.
This group is similar to the preceding one in that the habitat character of
the specific areas is dominated by channel morphology.These sites are
primarily overflow Channels that parallel the adjacent mainstem,usually
separated by a sparsely vegetated gravel bar.Upwelling groundwater mayor
lIIIly not be present..Habitat transformations within this
group are variable both in type and timing of occurrence.
These specific areas are typically side channels which breach at variable
yet fairly low lIIIlinstem discharges and exhibit a characteristic riffle/pool
sequence.Pool s are frequentl y large backwa tel'areas near the mouth of the
si teSt
The specific areas in this group tend to dewater at relatively high
mainstem discharges.The direction of flow at the head of these channels
tends to deviate sharply (>30 degrees)from the adjacent ma instem.
Modeling sites from Groups II and III possessing representative post-
breaching hydraulic characteristics are used to model these specific areas.
.This group consists of secondary mainstem Channels which are similar to
primary mainstem channels in habitat character,but distinguished as being
smaller,and conveying a lesser proportion of the total discharge.Speci-
fic areas in this group have low breaching discharges and are frequently
similar In size to large side channels,but have characteristic mainstem
features,such as relatively swift velocities (,.5 fps)and Visibly coarser
substrate.
Large mainstem shoals and the margins of mainstem channels which show signs
of upwelling are included In this representative group.
107.6L,112.SL
101.4L,113.7R,
I26.0R,I44.4L
101.2R,I2B.aR,
l32.6l,l4l.4R
112.6l,137.7L
134.9R,136.0L
141.6R
l33.al,l36.3R
119.2R
132.6L,l44.4L
101.Sl,147 .ll
10S.8ll,l19.lll,
l3B.7ll,l39.4ll,
l33.81R
t 1J Table 1..Primary hydrologic,hydraulic and morphologic character-
istics of representative groups identified for the middle
Sus i tna Ri ver.
17
will be discussed later in section 3.8,juvenile ~hinook habitat response
wi thin Group VIII was represented using model ing resul ts from study si tes
in Groups II and II 1.The response for Group X was eva 1 ua ted usi ng Di rect
Input Habitat (DIHAB)models for spawning chum habitat at five of the
sites,'as outlined in section 3.10.
Important criteria used to partition specific areas into representative
groups are the type and rate of change in hydrol ogi c character documented
for the specific areas.The hydrologic component of the method used by
Aaserude et al.(l985)to stratify the middle Susitna River focuses on the
systematic transformation in habitat type of specific areas within the
5,100 to 23,000 cfs flow range.For example,as flows recede mainstem
areas frequently becomeshallC5w water shoals,arid side channels may
transform into side sloughs;both habitat types may eventually dewater as
flows decrease further.The emphasis .on habitat transformation
acknowledges the transient nature of riverine habitat availabili
distribution.The dichotomous key in Figure 6 delineates the eleven habi-
tat transformation categories derived from an evaluation of the 172 speci-
fic areas and eight streamflows for the middle river.Note that the final
categories approximate the original "habitat type"designations used by
----~~--K-l-i-nger--and-~~r-i-hey-(-19 84-)~and~ADF&G -(-19 83-).----rwo+mpor-ta-n-t--mo d-i-f~;'ea-t-ions---to -
the habi tat type classi fi ca ti on system are the incl usi on of shoal habi tat
and the presence/absence of upwelling.Shoals are areas which at high
flows are visually inseparable from adjacent mainstem or side channel
areas.As flows recede the shoal or riffle character of these sites be-
comes obvious,even though the boundaries separating shoals and adjacent
18
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r~--
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1.0
WETTED AREA OF SITE
@ 23,000 CFS
I
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CLEAR WATER TURBID WATER
@ 23,000 CFS @ 23,000 CFS
I I I
Side Sloughs Distinct Channel Indlsllnct Channel (Shoals)
Tributary Mouths Upland Sloughs @ 23,000 CFS @ 23,000 CFS
'0 1
Dewatered
@ 9.000 CFS
9 I
Clear Water Turbid Waler Turbid Waler Clear Water
@ 9.000 CFS @ 9.000 CFS @ 9.000 CFS @ 9.000 CFS
I I I
I I I I I I
With Apparent Without Apparent Side Channel Mainstem Become Distinct Remain Indistinct With Apparent Wilhout Apparent
Upwelling Upwelling (less than 10%Side Channels @ 9.000 UPwelling Upwelling
01 Flow)@ 9,000
2 3 4 10 5 6 ...8I
Figure 6.Flow chart for classifying the transformation of aquatic
habitat types between two flows (Categories 0-10).It is
important to note that habitat transformations can be
·monitored between any two flows of interest.
habitat types are usually indistinct.Specific areas fitting this descrip-
tion are further distinguished on the basis of whether their bou,ndaries
remain indistinct or transform into well-defined channels at lower flows.
Upwelling groundwater,usually discernable in aerial photos by the presence
of clear water,is accentuated in the classification step of the extrapola-
tion methodology because of its pronounced effect on the distribution of
juvenile and adult salmon within the middle Susitna River.
Using habi tat types present at 23,000 cfs as a point of reference,si te-
specific habitat transformations have been defined for several discharges
of 18,000 cfs and less.The sequential changes in habitat type observed
within this flow.range offers a powerful tool with which to combine speci-
fic areas into representative groups.Other hydrologic parameters used
with varying degrees of confidence to cluster specific areas into
r_~Presel1ta tiv~_9rQMR~_ar'e.bre~~l1ing_flpw ,_J;ross-~~te_ctJgnaLpro_fjJJ;_s,oJ_t_bfiL
head berm and adjacent mainstem channel,and upwelling.
Of the hydraulic variables examined by Aaserude et ale (1985),mean reach
veloci under breached conditions was considered the most ate for
---------classi-f}/-i ng spe c i-f,c a rea s wi-tIfHr-tfie miCialeSu s i-tna 'RTver:---O nfor tuna 'te TY~
the relatively low flows (8,000 -11,000 cfs)at which field sampl ing was
conducted precl uded standardi za ti on of mean reach vel oci ti es on the basi s
of a common flow ortransforma ti ona 1 sta teo Mean reach ve loci ties were
Una va.i la.bTea.t sa.-m pling flow's for two'"thi rdsOfthe specific areas
delineated in the middle Susitna River;the majority of the sites were
unbreached during reconnaissance field studies.Nonetheless,the velocity
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da ta coll ected was used to further refi ne transforma ti on ca tegory
definitions.
Of more practical value in the development of representative groups were
channel morphology indices derived from aerial photo interpretation and on-
site visits in the field.Specific areas within the middle Susitna River
exhibit sufficient similarities in plan form to provide a theoretically
attractive means of grouping sites together.Use of channel geometry,
sinuosity;length-to-width ratios and related morphologic indices to
classify specific areas according to representative group is justified by
the repeti tiveness of simi lar channel features wi thi n the mi ddle Susi tna
River segment.
2.2 Quantification
2.2.1 Description of Wetted Surface Area Responses
Although each specific area is assigned to the same representative group
for all flows,the wetted perimeter and therefore its wetted surface area
(WSA)varies with discharge.Furthermore,the rate of change in WSA
relative to mainstem discharge varies between specific areas.Successful
appli ca ti on of the extrapola ti on methodology requires that the WSA response
to mainstem discharge be quantified,since the amount of rearing habitat
available within a specific area is dependent on its areal extent at
di fferent flows.
The concept of a specific area requires fixed upstream and downstream
boundaries.For example,a side slough specific area has a line across the
21
head berm and a line across the mouth which do not change with flow.The
WSA response for the side slough is due to flow-induced changes in length,
wid th and convo 1 uti on of the wetted peri meter wi thi n these bounda ri es.
Once the head berm is overtopped,all increases in WSA are related to
increases in channel width with increasing flow,as the channel.length
should remain constant.
The end product of the extrapolation methodology is the Representative
Groups'WUA responses to ma i nstem di scharge.Therefore,the WSA response
curves should not include WSA response due to any sources other than
mainstem discharge.If the WSA response of a site is not correlated with
mainstem discharge,i.e.,it varies widely or is constant,an average WSA
value should be used to show the absence of mainstem influence.If the
site WSA is correlated to mainstem discharge,then the WSA response should
approximate a loglinear function..
To illustrate these concepts,consider a specific area which transforms
from a side slough to a side channel at a mainstem flow of 15,000 cfs.
Although for all flows below the 15,000 cfs breaching flow the specific
area is a side slough,there are two ways mainstem flow can affect the WSA
----..-.----~re·spon·s·e~-of··the-·si--te-~-··P-i-r·s-t-l-y-,~a--ba·ckwa-ter-zo·ne-a-t-the-··mo·uth-wo·u-l-d-i-n-"
crease the WSA with increasing mainstem stage and,secondly,the mainstem
may be a.source of upwelling which in.creases the site flow with a concom-
mitant increase in WSA.If these effects are strong,they will approxi-
mate a loglinear function,otherwise the site will have a flat WSA response
to mainstem discharge.The WSA need not be constant,but may vary widely
due to other local variables.Above breaching,the mainstem flow is the
driving variable and again WSA should display a log linear relationship
22
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·.·-~-depending onthedegY'eeof-ir'Y'egular'~i-tyof the·channel geometry.Smooth
parabolic cross sections should fit the loglinear relationship better than
irregular cross sections.
2.2.2 Aerial Photography Database
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Klinger and Trihey (1984)describe a methodology for obtaining wetted
surface areas from aerial photographic plates,and are the source of the
database of WSA's used in the WUA extrapolation for juvenile chinook
salmon.There are two differences between the digitizing methods described
for habi tat types and those used for speci fi c areas.Del i nea ti on of habi-
ta t types was not 1imi ted by the upstream and downstream boundari es used
for specific areas,and,secondly,the control corridors used for habitat
types were not employed for specific areas.
The aerial photography database consists of WSA measurements for all
specific areas at seven mainstem discharges:5,100,7,400,10,600,12,500,
16,000,18,000,and 23,000 cfs.To forecast WUA above 23,000 cfs and below
5,100 cfs,a method of extrapola ti ng WSA beyond the range of the database
was required.Since WSA is expected to follow a loglinear function,an
extrapolation above 23,000 cfs'using a logarithmic regression was the
obvious choice.The use of logarithmic regression equations to approximate
WSA response below 23,000 cfs would have the added.benefit of minimizing
errors in the aerial photography da tabase.
,The accuracy of the database in forecasting WSA response to mainstem
discharge is dependent on two major forms of error:
23
1.Errors in es ti rna ti ng the true WSA of a speci fi c area.These errors
are caused by photographic distortion,shadows which obscure the sites,
delineation of the specific area,and digitizing errors.There are two
principal types of photographic error.Firstly,the aerial photography was
not ground survey controlled,so when mosaics of the photographs were made
into plates,there was a significant amount of topol~gical distortion which
varied from plate to plate.Second,due to differences in weather condi-
tions at the flight time,slight variations in scale occurred in the sets
of photography.These sources of error were not significant in the habitat
type analysis since WSA's for each habitat type were summed for each flow,
and'distortions tended to cancel out.However,the extrapolation
methodology.follows the WSA response of individual specific areas,and this
increased resolution over habitat type analysis is much more susceptible to
distortion errors.
The 23,000 cfs photography,taken on.Qljnfi!l.,l~J~4.,_W_(i~9btajoe_d~.ttb.e time
-------_.~~~_.,.__.•."_•..__._..,__..__._._---_.__.___-_._----_.___.-_-._-_.-..-----_......•-___-----_-__-_.___-_-..•
of year corresponding to high solar altitude and the deciduous vegetation
had not fully leafed-out.This resulted in few shadows,thereby enabling
excellent delineation of the wetted perimeter.However,the 5,100 and
7,400 cfs photography,obtained on October 4 and 14,1984,res
---------have--ex-te ns-i-ve--area-s-of---shadowsa-long-the-southand--e-a-stshOrtfl;-nEfs---dlre-to
the low autumn sol ar a 1 ti tude.These shadows obscured the water's edge of
some specific areas making WSA delineation difficult and sometimes specula-
tive.The remaining sets of photography have isolated shadow problems.
As mentioned previously,specific areas have upper and lower boundaries.
Proper delineation of the WSA necessitates consistent positioning of the
boundaries on each plate.The best method for accomplishing this is to
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.fi rstJieftn ~..tt1~J~9u nQ~J..j~.~.()l'!.~t1~.§.,!QQ ...c:f~J~Ji!"t.~.~\'J~~.Y'~C:.'>.rl."t r ()}2.'>.111.t s
which may be submerged at a higher flow are readily identifiable,and use
these bounds as a templa te for the higher flows.Unfortuna tely,r the 5,100
and 7,400 cfs plates were not available until early 1985 after the other
flows had already been digitized.This fact,and photographic distortion,
lead to less than optimal control of WSA delineation.For some specific
areas,determination of the wetted perimeter was exacerbated by the diffi-
cul ty in discriminating between gravel bars and highly turbid water,both
of which had approximately the same shade of grey on the black-and-white
photography.
The Numonics Digitizing Tablet,used to convert delineated areas to a
digital value,is accurate to a thousandth of an inch.However,since the
photographic plates are taken at a scale of 1"=1",000·,some specific
areas have a WSA value of only a few thousandths of an inch at certair
flo'ws and thus have a higher percent error.
2.Error induced by natural covariables.These are not true errors,but
simply variables we do not want to include in the WSA responses used in the
extrapolation methodology.These covariables fall into two types:
firstly,those which affect the water mass,and secondly those related to
channel geometry.In the first group,the effects are most noticeable in
the nonbreached state.Some sites have large amounts of subsurface intra-
gravel flow which acts as storage.If the hydrograph is falling at the
time the photography was taken,there is a time lag petween the stage of
the nonbreached si te and wha t we expect when the stage has s tabi 1 i zed.
This timelag effect was quite pronounced for some sites.Also,local water
sources such as small tributaries and runoff,may have greater influence on
25
The a im of thi s methodology was to produce WSA response curves whi ch w'hen
used in the extrapolation methodology will produce WUA response curves
Figure 7,which outlines the quantification process,·s.hows the analytical
steps and the direction of flow for particular representative groups.The
first step was to identify outliers in the digitized data set;if due to
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Forecasting WSA with Regression Equations
Extrapolate beyond the limits of the aerial photography
Minimize errors in estimating WSA for the photographic plates
Minimize variance of WSA due to "local"variables3.
Regression equations were used to predict WSA for specific areas in order
to:
L
2.
2.2.3
the stage of some specific areas,most notably in Representative Groups I
and II,tha.n the mainstem when the sites are nonbreached.Since WSA is
related to channel geometry as well as flow,any changes in the channel
structure between the ti me di fferent photo sets were taken will cause i~SA
errors.High-flow events following the 18,000 cfs photography caused sma 11
changes at some sites which,although negligible for habitat type
summations,made the 18,000 cfs photography inappropriate for several
speci fi c areas.
_~..._______~c h~!.[~(Jn l~.__tt_s ho.l,!l<tQ~lJIlde r~tood tha t _~t.be se
regression equations do not show observed WSA at a particular flow,but are
a good approximation of the rate of change for WSA due to mainstem
di scharge.
26
QUANTIFICATION
AERIAL
PHOTOGRAPH'i
5100 to 23,000
ch
DELINEATE
,DIGITIZE
SPECIFICE AREAS
DEBUG
DATABASE
WSA V BY
Q uATA
m:a
POINTS
TAKE AVERAGE
QF WS!'".
BELOW 0 b
DEVELOP
REGRESSION EO.
FOR WSA.e 5000 >0 ...<0 b
NO GENERATE WSA
CURVE FOR
5000 >0 <0
lIlI b
REP GRP I -.
AMPLITUDE ADJ.
1i~~A.~,YliSA
..clift
WSAe23,'fOO
cfs L.I liSA dlff -
WSA -liSA••m
WSAe23,6'80
cfs
BREACHING ADJ.liSA •.a,x
liSA +0 diU
..b
o b diU -
°baa_Obm
TAKE liSA ..
CORVE FROM
SllB!llDEL
REP GRP II ,VIII ~
NO
'iES
REP
GRPSIII
1/1VIVIIVIII
IX
N
-J
DEVELOP
REGRESSION
EO.FOR liSAeo>0b...
<35,000
o MAIN STEM DISCHARGE
mso BREACHING FLOW
bsa SPECIFIC AREA
m MODELED SITE FOR'SUBGROUP
x 0 COMPONENT OF ~ISA CURVE
Y AREA CCHPONENT OF WSA CURVE
Figure 7.Flow .chart indicating the steps followed in the
quantification of wetted surface area response to mainstem
discharge for specific areas used in the extrapolation
me thodo logy.
noncorrectable errors,they were not used in the analysis.If a specific
area had a nonbreached range,the data points below breaching were visually
inspected for an apparent increasing trend in WSA.If a trend was
observable,a loglinear regression was performed and used to predict WSA in
this range.If WSA was constant or highly variable below breaching,an
average WSA value was computed and subsequently used as a representa tive
WSA for the nonbreached state.Above breaching,if two or more rel iable
data points were available,a regression was taken and used to forecast WSA
for the speci fi c area from the breaching flow to 35,000 cfs.The predi c-
tions thus developed were "spliced"at the breaching flow by visual exami-
na tion.
Unfortunately,specific areas for Representative Group II and some specific
areas in V,VI,and VIII did not have enough data points above breaching to
develop regression equations.This required an alternative procedure to
specific areas were obtained by extrapolating the WSA response of the
modeled sites in the respective Representative Group to the nonmodeled
sites.This was done using the extrapolation methods,described in section
2.4,with minor revisions.Firstly,the WSAcurve from the ~1.!Q.9X·gl1P!JIQge.L
---~--_._---_.---------.-._.---_.~-.>-_....,_.,_._.----"-~~-~----"'--'----'-"._-----'--"----'--------~--------
·~----s-i-te~w·a-s~a-d-Jus-tE:d-fo-r-Drea-clfi ng,ttl usn 0 r rna lTzi n g-tne curve to·tfle
breaching flow.The amplitude of the curve was then adjusted by raising or
lowering the curve to coincide with the aerial photography WSA value for
23,000 cfs ..
The WSA responses for specific areas used in the extrapolation process are
1i sted in Appendi x C.
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--2.3Phys-ical HabitatModelingStudi es
2.3.1 Overview of Modeling Techniques
The quantitative assessment of juvenile chinook rearing habitat response to
streamflow in the middle Susitna River is based on investigations conducted
by ADF&G and EWT&A from 1982 through 1985.Sufficient data were collected"
to model chinook rearing habitat potential at 20 modeling sites typical of
9 of the 10 representative groups which characteri4:e the middle Susitna
River.These studies utilized two modeling tethniques:1)the Resident
Juvenile Habitat (RJHAB)model developed by ADF&G;and 2)the Physical
Habitat Simulation (PHABSIM)System developed by the Instream Flow and
Aquatic Systems Group of the U.S.Fish and Wildlife Service.Data require-
ments and sampling methods employed by the two models are similar,and
model parameters and standard output variables are identical (Figure 8).
The major differences between RJHAB and PHABSIM modeling approaches relate
to the resolution of input and output data and the ~echniques used to
proces?these data.The RJHAB model generates surface area and WUA output
only for those discharges for which hydraulic information was collected.
The PHABSIM modeling system incorporates hydraulic models which may be used
to forecast synthetic hydraulic data for any streamflow within an accept-
able calibration range.These data serve as input to a program (HABTAT)
which calculates wetted surface area and various habitat indices for the
mode 1 i ng si teo WUA forecas ts for unobserved flow s ba sed on the PHABS I M
models are more reliable than those obtained using the RJHAB modeling
techni que.
29
\
RJHAB! '
HYDRAULIC·HABITAT
MORPHOLOGIC ~SUITABILITY ESTIMATION BY EYE OF'~II--__....
DATA COLLECTION -MODEL AREA RESPONSE FOR i
(see Figure 9 )(RJHAB)UNOBSERVED FLOWS
\
l'0[TI]
S.'.I
0.0
cwo
SELECTION ,OF
STUDY ,SITES I
I
JUVENILE PHINOOK
HABITAT SUITABILITY
•CRITERIA
l'0l]1.0 [Z[]'"Sv Sd I
I
0.0 0.0',
v (J
I
WSA
ilFUA
DISCHARGE
AREA RESPONSE CURVES
AND RELATED INDICES
"
HYDRAULIC·
MORPHOLOGIC
DATA COLIlECTIO'N
(see Figure 10 )
!IIFG 'HfiYD,RAULlC _t1YDRAULlC MODEL HABITAT
!MpDEL "OUTPUT FOR,SUITABILiTY I I 'C~L1BRATION UNOBSERVED FLOWS MODEL
I i (HABTAT)
I !I
I
PHAB,SIM
!
Figure 8.RJH~Bland PHABSIM mode ing
of ~u~enile chinook sa man
!,
pathways followed in the analysis
habi tat.
-------'
-_:.'-'
..~",
oA-------
Source documents for information relating to RJHAB and PHABSIM model
1-1 development for middle Susitna River study sites include Estes and Vincent-
Lang (1984),Hale et al.(l984),r~arshall et ale (1984),and EWT&A and
Entri x (1985).Habi ta't sui tabi 1 i ty cri teria serving as model parameters
I]
for HABTAT are described in Steward (1985).
2.3.2 Hydraulic Data Requirements
[1
I J RJHAB and PHABSIM models applied in this study assess the influence of
11 three key physical habitat variables known to significantly influence
juvenile chinook salmon distribution,namely instream and overhead cover,
water velocity and water depth.The availability of areas characterized by
suitable combinations of these variables varies directly with changes in
streamflow.The primary objectives of both habitat models are to quantify
the distribution of various combinations of these habitat variables within
a representative segment of stream and to describe this distribution in
terms of its usability or potential as rearing habitat for juvenile
chinook.
I 1IJ
u
u
In order to describe rearing habitat potential based on the availability of
suitable cover,velocity and depth within a study site,field measurements
were obtained at discrete intervals along multiple transects.Figures 9
and 10 illustrate the basic differences between the RJHAB and PHABSIM
sampling methods,including transect placement,number of verticals where
hydraulic variables are sampled and the dimensions of the cells or mapping
elements represented by these point measurements.In the case of the RJHAB
modeling sites,cover and hydraulic data were collected at four to seven
31
n
Vi =LV.
j=1 J
n
where di =depth (ft)for ith cell
dj =depth (ft)at jth vertical
d n =depth (ft)at nth vertical
vi =velocity (ftIsec)for ith cell
Vj =velocity (ftIsec)at jth vertical
vn =velocity (ftIsec)at nth vertical
n =number of verticals
measurement verticals 1 - n
32
Figure 9.Sampling design for RJHAB modeling sites.The RJHAB model
assumes that average values obtained for habitat variables
within 6'x 50'bank and mid-channel cells are
representative of larger areas within the modeling site.
'I
J
)
].
r
54
~~~v RJHAB
Bank Cell
representing
shoreline area
Vi =velocity (ftlsec)for ith cell
di =depth (ft)for jth cell
wi =width (ft)for jth celf
Ii =length (ft)for ith cell
PHA8S'M
654
.~FlOW
u
I
J Figure 10.
Sampling design for PHABSIM modeling sites.
}
33
different discharges.Two bank cells and one mid-channel cell,each 6 ft
wide by 50 ft long,were sampled per transect.However,the areas
represented as bank cells in surface area and WUA calculations extended 6
ft out from the left or right banks and upstream to the next transect.The
mid-channel cells were considered representative of the area located
between the 6 foot wide bank cells.
Cover,velocity and depth data for PHABSIM models were collected at several
irregularly spaced verticals along the study site transects.The surface
area associated with each cell extended halfway to adjacent verticals and
transects (Figure 10).In contrast to the "RJHABmode1,the field data
obtained in the PHABSIM analysis are used to calibrate a hydraulic model
capa.ble of forecasting depth-velocity combinations for each cell at
unsamp1ed discharges.Two types of hydraulic models were used for this
purpose,depending primarily on hydraulic conditions at the study site.The
I FG-2 model is a ~.c3.~~r:~ur-faC:~J~...ofjJe J~YP~rnQd~lQa.sec1 Qf11:_hgMa.f1n ill~-_.....__._..---_.
equation and the principle of conservation of mass and energy (Milhous et
a1.1984).Data requirements for the IFG-2 model include a single set of
velocity data and several measurements of transect water surface eleva-
tions.Model calibration involves iterative adjustments of Manning's n
.--------va-l-ues-un-tH--agreement--be-twee n-observed-and--predi-c1:ed-wa-tersurfa-cee-leva-"
tions is obtained.Once reliably calibrated,the IFG-2 model may be used
to predict velocities within each cell across the transect at different
discharges.
The second type of model used to simulate hydraulic data in rearing habitat
investigations was the IFG-4,which employs linear regression analysis to
predict depth and velocity as a function of discharge for each cell.The
34
J
J
-)
I
I
I
'~l
)
.)
)
1
i J
J
)
1
)
)
]
r
,--,~-~-~-~--I-FG-""4mode~requ-iresam-i-n4mumoftwohydrauli c data sets but is better
suited than the IFG-2 model for simulating rapidly varied flow conditions
(Tri hey and·Ba 1dri ge 1985).
Estes and Vincent-Lang (1984),Hale et ale (1984),and Hilliard et ale
(1985)provide further information ·on hydraulic data collection and
analytical procedures.
2.3.3 Habitat Suitability Criteria
LJ
u
The next stage in the RJHAB and PHABSIM modeling process requires that
habitat suitability criteria be developed for the species/life stages of
interest•.Habitat suitability criteria (curves)indicate the preference of
a fish for different levels of a particular habitat variable;suitability
curves are needed for each physical habitat variable incorporated in the
habitat models.The cover,velocity and depth suitability criteria used in
this study to evaluate chinook rearing habitat potential in the middle
Susitna River are based primarily on field observations of juvenile chinook
densities in side channel and side slough areas of the middle Susitna River
(Suchanek et ale 1984).EWT&A and Entrix (1985)and Steward (1985)discuss
these data with regard to their applicability to mainstem,side channel and
side slough habitats.The juvenile chinook suitability criteria
recommended by Steward (1984)and summarized in Figures 11,12,and 13 were
applied in this study.
Of pa rti cul ar in teres t are the separa te vel oci ty and cover habi ta t
suitability criteria which apply under clear and turbid water conditions ..
35
0.50.1 0.50.1 0.50.1 0.50.1 0.50.1 0.5
;
4!5 6 7 8 9
Larq~Rubb\~Cobble or Debrl&a Overhon9 in 9 Undercut
Gravel 3-5 Boulder ••Deadfall Riparian Bank&
over 5
0.50.1
PERCENT COVER BY COVER TYPE
I o.~0.1
2 i f 3iiEmerqentIAquotic
Veqetatibn I Veqetation!!
I
0.50.1
No .Cover
o.
0.0 t···:·········,·,·,·······,·,···,·····,·····,············r·'·'·'·····
1.0
I I
CLEARl
0.8-1 I
TURSli
Percent covt
0.1 0-5
X O.6~'0.2 6 -2~
W 0.3 26 -50
0 0.4 51 .7~Z
76 -Ibo0.5
I.>-
~-
...J-0.4£D
w <!
0)~-:::>
(J)
0.2.
Figure 11.
i !,ICoversuitability criteria used to model ju.venile chinook
habitat (WUA)iO the middle Susitna River.Separate
c~iteria are pres~nted for clear and turbid water conditions
(~rom Steward 1985).
.f
I.---.:::-:..,.;.......1
DEPTH SUITABILITY CRITERIA FOR JUVENILE CHINOOK SALMON
1.0
.9
10.03.0
0.00 0.00
0.14 0.00
0.15 1.00
10.00 1.00
DEPTH SUITABILITY (Sd)
2.01.0
+-.......---..---....---......----..---.....--------1'---
.7
"i:i
(J).6->I-
::J .5
CD
~
:::).4
(J)
.3
.2
.1
0
0
DEPTH (ft)
Figure 12.Depth suitability criteria used to model juvenile chinook
habitat (WUA)under clear and turbid water conditions in the
middle Susitna River (from Stewar~1985).
37
)
J,.,
VELOCITY SUITABILITY CRITERIA FOR JUVENILE CHINOOK SALMON )
I
3.02.52.0
LEGEND
---Turbid
---Clear
1.5
Clear water less than 5 NTU
Turbid water 50 to 200 NTU
SUITABILITY (Sv)
Velocity Clear Turbid
0.00 0.42 0.42
0.05 1.00 1.00
0.20 1.00 1.00
0.35 1.00 1.00
0.50 1.00 0.80
0.65 1.00 0.60
0.80 0.68 0.38
1.10 0.44 0.25
1.40 0.25 0.15
1.70 0.18 0.07
2.00 0.12 0.02
2.30 0.06 0.01
2.60 0.00 0.00
1.00.5
0.8
0.6
0.2
1.0
0.4
0.0 +-----or--------,,..------,.-----.,.---==..,..-----,
o
VELOCITY (ftlsec)
I 1
1...,
Figure 13 ..VeloCity suitabllity criteria used to model juvenile chinook
habitat (WUA)under clear and turbid water conditions in.the
middle Susitna River (from Steward 1985).
38
j
I
1
1
I ]
U
Clear water habitats occur in side channel areas which are not breached by
the turbid waters of the mainstem river yet maintain a base flow via
groundwater upwelling or tributary inflow.The frequency and duration of
thi s cond i ti on depends on the eleva ti on of the thalweg at the head of the
site relative to the water surface elevation of the adjacent mainstem.,
Site flow versus mainstem discharge relationships were used to determine
when clear and turbid water veloci~and cover criteria were to be applied.
Rearing salmon use cover to avoid predation and unfavorable water
vel oci ties.Instream objects such as submerged macrophytes,large
substrates and organic debris,and overhanging vegetation in near shore
areas can provide cover for juvenile chinook salmon.Instream object cover
in most rearing areas of the middle Susitna River is provided by larger
streambed materials,primarily rubble (3-5 inch diameter)and boulder (>5
inches)size substrates.The cover suitability criteria presented in
Figure 11 and Table 2 suggest that juvenile chinook tend to associate wi th
some form of object cover in bo th cl ear and turbi d wa ter habi ta ts.
Preference generally increases in prop~rtion to the percentage of object
cover presen t,pa rti cul arl y under cl ear wa te'r condi tions.The di fferent
preferences for the same type and percent of object cover indicated by the
clear and turbi d water sui tabi 1i ty cri teria are due to the uti 1i za ti on of
turbidity as cover by rearing chinook.Dugan et ale (1984)documented
higher densities of chinook in breached,turbid water side channels than
were found at the same si tes under nonbreached,cl ear wa ter condi ti ons.
IJ This disparity was most pronounced at sampling sites possessing minimal
object cover.
39
Table 2.
Percent
Cover
ICoversuitabilityc~it~ria recommended Ifor use in modeling juvenile chinook habitat under clear and
turbtd water conditi1ons.Sources:Suchanek et al.1984;Steward 1985.I :,I
No Emergent I Aquatic Large \RUbble Cobble or Debris &Overhanging Undercut
Cover Veg.Veg.Gravel 3"-5"Boulders <5"Deadfall Riparian Banks
. I
Cl ear Water Ie Such&nek et al.1984))
I
I
.j::>
o
0-5%
6-25%
26-50%
51-75%
76-100%
0.01
0.01
0.01
0.01
0.01
0.01
0.04
0.07
0.09
0.12
0.07
0.22
0.39
0.53
0.68
0.07
0.21
0.35
OA9
0.63
0.09
0.27
0.45
0.63
0.81
0.09
0.29
0.49
0.69
0.89
0.11
0.33
0.56
0.78
1.00
0.06
0.20
0.34
0.47
0.61
0.10
0.32
0.54
0.75
0.97
Turbid water[(EWT&A and WCC 1985)1
0.31 0.31 I 0.39 0.39
0.37 0.58 0.35
0.67 0.41
0.77 0.46
0.85 0.52
0-5%
6-25%
26-50%
51-75%
76-100%
0.31
0.31
0.31
0.31
0.31
0.31
0.31
0.31
0.31
0.31
0.39
0.46 0.42
0.52 0.48
0.58 0.54 , I
0.47
0.54
0.62
0.69
0.51
0.59
0.68
0.76
0.48 0.26 0.44
0.56
0.65
0.74
0.82
1Multip11cation factors:
----...-0
I I
0-5%.r.38;6-25:t -1.1 5 ;26-50%-1.20;51-75%-0.98;76-100%-0.85
I \I.J
Water depth is not a significant factor limiting juvenile chinook habitat
potential,as indicated by the open ended depth suitability curve in
Figure 12.Provided that other microhabitat conditions are suitable,
juveniles tend'to prefer depths exceeding 0.15 feet to an equal degree.
This observation has been corroborated in other habitat utilization studies
of juveni le chi nook salmon (Steward 1985).
A distinct preference by juveniles for low velocities under turbid water
to detect drifting prey items (Milner 1985).
2.3.4 Habitat Model Response Variables
The RJHAB model was modified slightly in order that the methods of
calculating various indices of habitat potential,including WUA,and wetted
surface areas were consistent for all modeling sites.Wetted surface area
(WSA)estimates based on RJHAB and PHABS.IM model ing approaches were com-
pu ted by summi ng the surface area s of wa tered ce 11 s withi n the mode 1i ng
site (Table 3).Flow related increases in wetted surface area at RJHAB
sites were apportioned among mid-channel cells of the sites since the
dimensions of the area represented by bank cells remained essentially
unchanged for all flows.At study sites modeled with IFG-2 or IFG-4
41
Parameters/Units~quation
I
i i.I 1
I I !
I I iII,I
Wetteq syrface area (WSA).weighted usable area (WUA)and related habitat indices used in
the evaluation of chinook re~ring habitat potential within the middle Susitna River.I I I
I 1
I I
Statistic
Table J.
Calculations erformed for Each Cell (i)
Surface Area (Ai)
I
Composite Suitabil t~(Si)
Ai =1 will
,
I
Si =s(c 1)s(vi)s(di )
wi =cell width (ft)
li =cell length (ft)
(ft2 )..
s(c1)'s(v1)and s(d i )
(ft2)
(ft2)
are weighting factors for
includes all cells (ft2)
includes cells with WUA >0.0
cover.velocity and depth
(dimensionless)
(dimensionless)
(dimensionless)
(dimensionless)
n
WUA =~A·Sii =1 1
n
GHA =L Ai
1 =l'
HOI =GHA /WSA
HQI =WUA /·GHA
I
I
I 1WeightedUsableAr~a l0olUA1)WUAi Ai S1 (ft2 )
1 II.calcul~tilons Performed for a MOdeling Site Comprised of (n)Cells
!,
I I
!I n
Wetted Surface Are~(IWSA)WSA =L Ai
I !1 =1I I!I
IGrossHabitatAreal(GHA)
i
IIWeightedUsableAreaI(WUA)I I
I IHabitatAvailabili,ty Ilndex (HAI)HAl =WUA/WSA
I 'Habitat Distribution Ilndex (HOI)I !
Habitat Qual ity In~eJ (HQI)
+:-
N
~.'---or
~----.;
hydrau 1ic models,the si ze and 1oca ti on of cells generally rema i ned con-
stant but the total number of cells increased or decreased as wetted top
widths responsed to c~anges in flow.Hence,the cumulative surface area of
the IFG modeling sites increased through the addition of new cells along
the shore 1i nee
The composite suitability of each cell within the RJHAB and IFG modeling
sites was determined by multiplying the individual suitability values
associated with prevailing velocity,depth and cover conditions (Table 3).
This method of calculation implies that the physical habitat variables
evaluated by the models are assumed to be independent in their influence on
habitat selection by juvenile chinook.Weighted usable area is computed
for each cell by multiplying the cell's composite suitability by its sur-
face area.The sum of the cell WUAs obtained for a given discharge yields
the modeling site WUA;when plotted as a function of discharge~the
modeling site WUA curve indicates the response of usable rearing habitat to
changes in streamflow.
Habitat simulation results include WUA and WSA estimates for each study
si te for ma i nstem di scharges ranging from 5,000 to 35,000 cfs as measured
at the USGS Gold Creek gaging station.In order to facilitate comparisons
between modeling sites,WSA is expressed in units of square feet per linear
foot of stream.WSA is therefore proportional to the mean width of the
modeling site.These units are less satisfactory for comparisons of WUA
J since usable habitat at a site is a function of surface area weighted by
the suitability of its physical habitat attributes.An interpretation of
ha.bitat availability should not be made without reference to the total
wetted surface area of the si teo As an example,consider two study si tes
43
possessing relatively equal amounts of weighted usable area;the smaller
site,particularly where there is a large disparity in size,possesses a
greater amount of usable habitat relative to the prevailing wetted surface
area.Therefore,a more meaningful index of habitat availability is the
ratio of WUA to WSA,which is designated the Habitat Availability Index
(HAl ).
In the context of the extrapolation analysis,the Habitat Availability
Index has the added merit of being unitless.Assuming that the HAl of a
modeling site is representative of the associated specific area (i.e.,both
possess the same frequency distributions of cover,velocity and depth),the
WUA of the specific area is equal to the product of the HAl and the total
wetted surface area of.the specific area.Total surface areas are known,
as di scussed in Secti on 2.2,and therefore a fl ow-dependen t habi ta t
response curve may be derived for any specific area represented by a
The HABTAT program of the PHABSIM modeling system and the RJHAB model were
modified to compute the Gross Habitat Area (GHA)for each discharge of
-----'---'irrte're$t-~'--nfErGHA-is-t:neci.imura-tr'lerunw-elghtecrrSlirface ar,e a-,a f,c errs
-~.._------_..~---~-~----_.__._--_.,._-~-_.._._...__.-.---_..__.....__..---_._-
possessing non-zero WUA values within a site.Gross Habitat Area is impor-
tant because it represents the maximum area of rearing habitat available.
Two other habitat response indices,the Habitat Distribution Index (HOI)
and the Habitat Quality Index (HQI)are calculated by the following
formulas:
r
1
I
I
i
I
)
I
j
J
I
I
I
I
l
I
1
I
J-
HOI (%)=GHA/WSA x 100
HQI (%)=WUA/GHA x 100
and
most WUA-based interpretations of habitat potential,namely,that WUA is a
quantification of the an,ount of suboptimal habitat within a study site
expressed as an equivalent amount of optimal .habitat.In other words,a
II cell wi th a ~urface area of 100 sq.ft.and a joi nt preference factor of
1.0,that is,optimal cover,velocity and depth conditions,is assumed to
prov;'de as much usable habi ta t as an area ten ti mes its si ze whi ch
III,
(1I.
L \
I [
I
J
possesses a joint preference factor of 0.10.Although flow-related changes
in the composite suitability of individual cells (i.e.,at discr.ete loca-
tions within the modeling site)were not evaluated,we examined relation-
ships between a modeling site's weighted usable area,gross habitat area
and wetted surface area over a range of discharges to gain an understanding
of probable changes in habitat quality within cells containing usable
habi tat.
Surface areas and habitat indices were simulated for site flows
corresponding to mainstem flows ranging from 5,000 to 35,000 cfs at Gold
Creek.Of the 20 study sites investigated,six were modeled using the
RJHAB model and 15 were modeled using the PHABSIM model ing system.One
study site,132.6L (Representative Group III),was modeled using both RJHAB
and PHABS IM techni ques.In most ins tance s,WSA,WUA and HAl va 1 ues for
unobserved site flows (in the case of RJHAB models)or flows lying outside
the ·recommended extrapolation range of the hydraulic models (a frequently
encountered situation in PHABSIM applications)were estimated by interpola-
tion and trend analysis techniques (Hilliard et al.1985).In fitting
curves to data points forecast by the habitat models,reference was made to
45
aerial photographs and site-specific channel ge.ometry and breachi ng flow
i nforma ti on.
2.4 Extrapolation of Modeling Results to Non-modeled Specific Areas
Whereas the general habitat characteristics of a m.odeling site may be
assumed to be representative of the associated specific area,the same
combi na ti on and qua 1i ty of habi ta t a ttri butes may not be found in other
specific areas,even those classified in the same representative group.
Aaserude et a 1.(1985)concl uded that varia ti ons in structural characteri s-
ties,including several attributes known to affect the quality of juvenile
chi nook reari ng habi ta t,are common among speCi fi c areas of the samerepre-
sentative group.These differences are significant enough that direct
transfer of WUA functi ons from mode 1 ed to non-mode 1 ed speci fi c area sis
considered impracticable.For this reason,Structural Habitat Indices
s were developed from field data in order to rank specific areas
within the same representative group according to their relative structural
habitat quality.As indexed by SHI values,specific areas are evaluated on
the basis of six variables:1)dominant cover type,2)percent cover,3)
······-(romlnant·sU5!rtrate·size~····4)siibstrate·emoeddednesS,sycha nnel ·cro·ss··sec=
~--~----~~~._--------~-"-_•.._.__._.._..._.~--_.__._-------_._-_..._--~.__.-._---------..._-_._._..__._-~_.._-_.~-_...-------_..__._--_._--------_...._-------~-_.._._--_.._-------_..__._-_.~.__..•._--_._~----
tional geometry,and 6)riparian vegetation.These variables were weighted
according to their relative importance to juvenile chinook salmon.For
each variable,specific areas were placed in one of five descriptive cate-
gories,rangi ng from "non-exi s ten til to u exce llen til in qua 1i ty.Each
variable category received a corresponding numerical rating factor.A
single SHI value was calculated for each specific area,including those
containing modeling sites,by summing the products of variable weighting
[
I
]
j
I
J
1
J
1
1
i
1
1
I
1
I
J
,f
I.
[j
and rating factors.For further details concerning the collection and
synthesis of data into structural habitat indices,see Aaserude et ale
(1985 ).
In this,the integration step of the extrapolation methodology,Habitat
Availability Indices (HAls)derived for the modeling sites are used to
estimate juvenile chinook WUA for each specific area of the middle Susitna
River.As discussed above,the amount of usable rearing habitat at a
specific area'containing a modeling site may be calculated by multiplying
the modeling site's HAl value (i.e.,the WUA:WSA ratio obtained as model
output)by the wetted surface area of the speci fi c area.For each
discharge,this calculation can be represented as
WUA sa =HAlm,sa x WSA sa
where the sUbscripts m and sa refer to the modeling site and the specific
are a wit hi n whi chi tis f 0 und.Asp 0 i n te d 0 utear 1 i er , HAI val ues
determined for'the modeling site are assumed to be applicable to the entire
speci fi c a rea.
If it were reasonable to assume that the HAl response curves for all
specific areas within a representative group were identical,then WUA
values for non-modeled specific areas within the same group could be
calculated by the above equation using a single HAl function.The.
structural habitat data of Aaserude et ale (1985),as well as the modeling
results presented in this report do not support this assumption.Be tween-
site variations in rearing habitat availability appear to result from
I dissimilarities in channel morphology (which are reflected by differences_J
in breaching flows and the rate of change in WUA and WSA)and structural
47
habitat quality (as indexed by SHl values).Therefore,each specific area
of the middle Susitna River is assumed to possess a unique HAl curve which
may nonetheless be patterned after the modeling site within the same
representative group having the most similar hydrologic,hydraulic,and
morphologic attributes.Specific areas within a representative group with
more than one modeling site are divided between modeling sites by
morphological similitude based on aerial photography and habitat
recon na is sance survey s.Thus,each mode 1i ng site may be con si dered
representative of a subgroup of specific areas.
HAl curves are developed for non-modeled specific areas by modifying the
HAl functions of associated modeling sites using information obtained in
the classification and quantification steps of the extrapolation analysis,
including:1)breaching flows to normalize HAl functions on the discharge
axis;and 2)'structural habitat indices to adjust for differences in the
__.~quaJtty-()f.l!~able r~~ring habitat.TabJe4 summarizes-breaching-flowa.nd -.--------
SHl information used in the development of HAl curves for non-modeled
specific areas within R~presentative Groups I through X.
~-~----_.~..-_._.~~..__._.-_.~_.-----".
.--------domi'na-nt--hydro·logtc--va-r;-a:bTeaffec tfng theava flaoflTtyofc hlnook rearing
habitat.As will be demonstrated later,the vast majority of juvenile
chinook HAl functions obtained for the middle Susftna River modeling sites
exhibit a maxima just to the right of the breaching flow on the discharge
(hori zon tal)axi s.To develop an HAl respon se curve for a non-mode 1ed
specific area,the HAl curve obtained for the associated modeling site is
shifted left or right on the abscissa depending on whether the breaching
flow for the non-modeled specific area is lower or higher than that of the
.I
j
]
1
1
I
I
I
I
J
(
GROUP I GROUP II GllOOP III GROUP IV GROUP V
I \
I j
Spec1 tic
Arel
o 107.61.
105.211
108.3L
119.4L
120.OR
135.611
136.911
139.OL
o 112.Slo
102.21.
121.911
123.111
123.311
127.2M
129.411
133.9L
134.OL
135.511
139.911
BreaChing
Flaw
(ctsl
>35.000
>35,000
>35.000
>35,000
>35,000
>35.000
>35.000
>35.000
>35.000
>35.000
>35.000
>35.000
>35.000
>35.000
>35.000
>35.000
>35.000
>35.000
>35.000
SHI
0.44
0.69
0.70
0.45
0.50-
0.54
0.69
0.45
0.68
0.83.
0.72
0.45
0.67
0.58
0.44
0.67
0.1I9
0.32
0.74
SpeCifiC.......
o 101.41.
115.611
118.01.
121.811
125.111
131.511
137.8L
o 113.7a
113.111
Ul.8L
133.911
137.Slo
131.91.
140.211
142.211
143.41.
+126.0It
122.411
122.511
123.611
125.911
126.311
o 144.41.
100.611
101.8L
111.9L
135.31.
142.111
llreachlng
Flow
(cfsl
22.000
23.000
22,000
22.000
20.000
22.000
20,000
24.000
25.000
25,900
30.000
29,000
21.000
25.500
25,000
23.000
33.000
25.000
20.000
25.500
25,000
27 .000
21.000
33.000
22.000
22.000
23,000
23.000
SHI
0.54
0.54
0.39
0.27
0.48
0.44
0.54
0.51
0.31
0.45
0.50
0.44
0.50
0.50
0.52
0.55
0.51
0.29
0.51
0.43
0.56
0.59
0.60
0.60
0.65
0.62
0.30
0.60
SpecifiC
~
+101.ZIl
100.411
100.61.
115.011
117.BL
12B.511
12B.711
13O.ZR
130.21.
137.211
+1211,.
110.41.
133.711
+0 m.a.
101.61.
101.1L
119.31.
+141.41
Bre.ching
Flaw
(ctsl
9.200
12,500
9.200
12.000
B,ooo
12,500
15.000
B,2oo
12.000
10.400
lli.OOO
12.000
11.500
to.5OO
14,000
9,600
15.000
11.500
SHI
0.56
0.51
0.42
0.55
0.4B
0.48
0.49
0.64
0.60
0.49
0.45
0.61
0.44
0.49
0.56
0.45
0.56
0.56
Specific
ArIa
+112.61.
108.7L
110.8M
111.511
139.4L
139.6L
..131.1L
119.5L
119.6L
124.1L
127.41.
+ti4.'11
100.711
114.011
U6.SA
121.711'
125.211
129.511
140.411
145.311
+m.OL
127.OM
BreaChing
Flow
(ctsl
<5.100
<5.100
<5,100
<5.100
<5,100
<5,100
<5.100
<5,100
<5,100
<5.100
<5.100
<5.100
<5,100
<5.100
<5.100
<5.100
<5,100
<5.100
<5,100
<5.100
<5.100
<5.100
SHI
0.60
0.53
0.48
0.48
0.61
0.51
0.41
0.54
11.53
0.46
0.45
0.56
0.49
0.43
0.48
0.48
0.56
0.56
0.48
0.53
0.55
0.65
Speci flc
Area
+141.6it
101.7L
117.014
11B.9L
124.014
132.BII
139.01L
139.711
143.0L
Breaching
Flow
(ctsl
21.000
9,600
15.500
<5.000
23.000
19,500
<5,000
22.000
7,000
SHI
0.56
0.48
0.31
0.48
0.51
0.57
0.37
0.51
0.31
Breaching
Specific Flaw
Area (cHI SHI
GROUP VII
are.chlng.
Specific Flow
Are.(ctsl SHI
8r"Chlng
Speci flc F10111
Area (cfs)SHI
Breaching
SpecifIc Flow
Area (etsl SHI
0.57
0.41
0.47
0.51
0.41
0.~8
0.48
0.48
0.48
0.55
0.48
0.56
0.48
MSS
MSS
MSS
MSS
MSS
MSS
IlSS
MSS
11.500
10.500
7.000
"5S
MSS
GROUP X
BreachIng
SpecifIc Flow
Arel (cfsl SKI
,105.BIL
,119.11L
121.111
,13l1.71L
,139.41L
142.2A
,133.8111
109.3H
111.611
113.611
113.911
139.31.
148.211
0.45
0.4B
0.45
0.35
0.35
0.41
0.63
0.62
0.48
0.61
0.56
0.57
0.53
0.58
0.53
0.56
0.48
0.69
0.69
0.53
0.53
<5.100
<5,100
<5,100
<5,100
<5.100
<5.100
<5,100
<5,100
<5,100
<5.100
<5.100
<5.100
<5,100
<5,100
<5.100
<5.100
<5.100
<5,100
<5,100
<5.100
<5.100
GIIOUP IX
..101.51.
104.011
109.411
111.011
113.8R
117.7L
12B.311
129.31.
131.ZR
139.211
142.BII
..147.1L
105.711
108.9L
127.1"
129.811
135.OL
141.ZR
141.311
144.OR
144.ZR
0.49
0.27
0.32
0.32
0.35
0.51
0.32
0.32
0.60
0.26
0.46
0.51
0.44
0.44
0.31
.0.60
0.57
0.43
0.48
0.49
0.44
0.56
0.62
0.48
10.500
22.000
15.500
20.000
14,000
15.500
12.500
19,500
15,500
23.000
19,500
14,500
21,500
20,000
22,000
21,000
9.200
10.000
21.000
16,000
25.000
9,000
22.000
25.500
GROUP VIlI
..13Z.6L
112.4L
117.1"
117.ZK
11B.614
119.8L
120.OR
121.5A
121.611
123.211
124.811
132.5L
135.0A
135.111
144.OM
..144.41.
101.314
102.OL.
104.314
100.SM
125.611
12B.411
145.611
146.6L
0.41
0.31
0.43
0.39
0.52
0.31
0.31
10.000
<5,100
7.400
<5.000
<5.000
<5.000
9.000
+119.211
114.111
121.1L
123.01.
12$,61.
121.SM
131.31.
0.54
0.69
0.53
0.32
0.61
0.53
0.49
0.69
0.49
0.51
0.53
0.31
0.31
GROUP VI
.17.500
9.600
7.300
23.000
8.000
6.000
8.900
13.000
6.500
4.800
21,500
12.000
10.500
..133.8L
107.1L
111.911
l1g.1L
138.01.
138.811
139.511
+136.311
102.6L
106.311
135.111
140.611
142.011
11
1l£T:
I )I J,~J
o
+,.
MSS
Specific areas wi tft RJHAS lIlOdel
Specific areas wi tft IFG BOdel .
Specific area~wi th 0lHA8 lIlOdel
Modeled si tes frOlll other groups
132.6L froe Croup 111 .114 144.41.
ire.Group II
Mllnstelll shoal
Table 4.Mainstem breaching
(SHI)determined
Susitna River.
discharges and structural habitat indices
for specific areas within the middle
49
modeling site.The distance moved is equal to the difference in the
si tes'breachi ng di scharges.Thi s-la tera 1 shi ft,di agrammed in Figure 14,
identifies the horizontal coordinates of the HAl curve for the non-modeled
specific area.The lefthand curve in Figure 14 represents HAl values
forecast for a hypothetical modeling site.The curve on the right is an HAl
function obtained for a related non-modeled specific area (also
hypothetical)from the same representative group.
Structural habitat indices are used to determine the magnitude of the HAl
response to flow at a non-modeled specific area (i.e.,to "fix"the
location of the HAl curve with respect to the vertical axis)as illustrated
in Figure 14b.For each discharge,the following calculation is made:
HAI~a =HAl m x (SHlm/SHl sa )
In this case,the subscript.!!!.refers to the modeling site whose HAl
___fun.c_ti_o.n ..-ha.s ...·.be.en_adj-u-s-ted_·u-s-i-ng---the--br-ea-e-h-i-ng·-f-l-ow-o-f-the--no'n-m·ode~l·ed----·-··
specific area,identified by the subscript sae
The non-modeled specific area in Figure 14c HAl curve has been shifted to
___.._.theJ:tgtl~__~J'l(L~o wnw aLd_.to__.ac.c_o_un_t_.for-the __htgher ....breach ing.f-low-a.nd-..-the--
------_.~-
·-----1 ower ·structura1 habi tat qual i ty of the non-modeled si te re 1a ti ve to the
modeled site.An HAl response curve derived in this fashion may be
multiplied by wetted surface area estimates to calculate WUA values for
each flow of interest.Preliminary HAt functi ons have been developed for
all middle Susitna River specific areas and appear in Section 3.0 and
Appendix B of this report.
,I
,i
j
I I
(
i
1
J
.1
I
I
I-
I
I
I
I
J
!
T
BREACHING FLOW ADJUSTMENT
SA"
aSA
-
I
I
M
a ..
MAINSTEM DISCHARGE
STRUCTURAL HABITAT QUALITY ADJUSTMENT
....
--------~
--.--.----.......
,SA
".......
M
MAINSTEM DISCHARGE
MODELED SPECIFIC
AREA (M.)CURVE
\DERIVED NON·MODELED
/SPECIFIC AREA (SA)CURVE
MAINSTEM DISCHARGE
J Figure 14.Derivation of a non-modeled specific area (sa)HAl curve
using a modeled specific area (ms)HAl curve.
A.Lateral shift to account for differences in breaching
discharge (Q s Q$q)
B.VerticaT shltt proportional to (SHlsa/SHl ms )to account
for differences in structural habitat quality.
C.Final hypothetical modeled and non-modeled specific
area curves.
2.5 Integra ti on
The data obtained in the stratification,quantification,and simulation
steps in the extrapolation analysis are integrated by following the process
outlined in Figure 15.Inspection of the flow chart shows the integration
is comprised of three nested loops.The inner loop (3)is repeated for
each speci fi c area ina subgroup.Func ti ona 11 y,it com pu tes the WUA
re spon se curve for a speci fi c area gi ven the models i te HAl curve,SHI
ratio,and WSA curve for the specific area.The middle loop (2)drives the
inner loop through all members of a subgroup and provides the HAl curve for
the subgroup model site.The outer loop (1)drives the inner two loops
through each representa ti ve group.Thi s syn thes is provi des es ti rna tes of
juvenile chinook rearing habitat for the 172 specific areas and their
summati·on within each of the ten representative groups.
In regard to the rearing habitat potential of different representative
groups,the relative significance of aggregate WUA functions in future
decisions will likely be influenCed by data concerning present and prospec-
tive uti 1i za ti on by juveni le c~i 11~c:>~~§.<!lmgn~_YngeXJlatUl:aL~and."wjth~project-...._"._----------_..•.__.._--~,-------,._~.~-"_._.~"...•_..-...•_-_.,-,.._-_.,-•.._..-._-,...._-.._----_._-.-.---,..__._._.._--~_._--.-._-._-'.'--
--flow·~re-g;-m"e-s-.-An assessmentof-the rera:lrve fmportanc"eof-thedi fferen"t-·-~
representative groups in terms of their utilization by rearing chinook
salmon will appear in Volume II of the Instream Flow Relationships Report.
When coupled with information relating to food aVailability,water tempera-
ture,suspended sediment and other env ronmental factors,·the aggregate
physi ca 1 habi tat response functi ons will a 11 ow for concl usi ons and recom-
mendations at the management level.
'---
INTEGRATION SIMULATION
FOR EACH ~FOR EACH ~HABITAT ~HAl M•
~FOR EACH
START RJHAB WUA M
SA IN
SUBGROUP~REPRESENTATIVE SUBGROUP
--GROUP IN REP.GROUP
DlHAB
WSA H
STRATIFICATION
........................................................................................................................................................
i i
SHI SA _LITUP'AIlJ HBREACHI'G AIlJ.
STRATIfICATION l(SHl sA HAl SA,Y -HAl l-J HAIsA
REPORT -SA,x '"CURVE
SHIH SHI
HAl X~HAl H,X +Q diff
SHIH V M , Y SHI H b
01
W
QUANTIFICATION
Q HAINSTEM DISCHARGE
ms
Q BREACHING FLOW
bsa SPECIFIC AREA
m MODELED SITE FOR
x Q COMPONENT OF WSA
Y AREA COOPONENT OF WSA
STOP
SUM
WUA
FOR REP.GROUPHAlSAXWSASA
WUA SA •
Figure 15.Flow chart indicating the steps followed in the integration
of stratification,simulation,and quantification for
specific areas used in the extrapolation methodology.
300 RESULTS
3.1 Representative Group I
The 19 specific areas within this group include all upland sloughs occuring
in the middle Susitna River.Except during flood stage,these sloughs are
connected to the main channel only at their downstream end.In addition to
high breaching flows and low turbidity levels,typical features of specific
areas in Representative Group I include low velocity pools of greater~than
average depth separa ted by short,hi g her vel oci ty ri ffl es.Cl ear water
enters these sites via seepage or tributary inflow and maintains relatively
stable base flows under non-breached conditions.Substrates are frequently
homogeneous over large areas and are often characteri zed by fi ne 5i 1 t/Sand
sediments overlaying cobble materials.Cover is usually provided by over-
hanging and emergent vegetationo These sites are used .only to a small
extent by juvenile chinook salmon (Marshall et al.1984).
Specific areas assigned to Representative Group I are represented by two
RJHAB modeling sites:107.6L and 112.5L.Photographs of these sltes when
mainstem discharges were 23,000 and 16,000 cfs are presented in Plates A-I
_....---a-nd-A-2{AppendixA}-;-~Formuch--ofits-le-n9th;---STteT07.6I-Tsa--low----~-
gradient,narrow meandering stream.At mainstem discharges above
20,000 cfs,the turbid backwater area at the slough mouth advances upstream
and inundates lower sections of the site;this phenomenon accounts for the'
marked relative increase in wetted surface area indicated in Figure 16.
Usable chinook rearing habitat at Site 107.6L does not respond dramatically
to increases in wetted surface area,as evidenced by the WUA and HAl curves
I 1
j
j
\
I 1
I
-j
j
j
1
I
]
1
]
I
.-J
1
1
1
SITE 107.el
A150
135 -/'ICSA
/'
120 -,/'-·...105 -I--"-I·90-...--I·75-0"
~60 -/
ltl -45-/Q)c............./.<30 -
f1 -'--'is-_.-.~.
llUA
0 I I I I {{I I I
0 .coOO BOOO 12000 16000 20000 2.cDOO 28000 32000 36000 40000
Mainstem Discharge (cfs)
lJ
IJ
B
100
90
so
70...60c:
Q)50uc..
Q)
~a-
30
20
,
10 HAl
0
0 4000 BOOO 12000 16000 20000 2.cDOO 28000 32000 36000 40000
Mainstem Discharge (cfs)
Figure 16.Surface area and chinook rearing habitat index response curves
for modeling site 107.6L..
A-Wetted surface area (WSA)and weighted usable area (WUA).
B-Habitat availabil i ty index (HAl)
55
shown in Figure 16.WUA at this site gradually increases at higher flows
due to the reduction in water velocity and water clarity caused by rising
backwater.Water velocities ranging up to 0.8 fps are common at transects
up'stream of the backwater pool.Therefore,under clear water condi ti ons
nearly ideal velocities exist for juvenile chinook.A silt substrate is
dominant,which affords little cover value for juvenile chinook,resulting
in a low composite suitability for most cells within the site regardless of
the suitability of their depths and velocities.As the extent of the
backwater increases,velocities in these cells decrease to O~O fps,
slightly reducing suitability with respect to this habitat variable,but
turbidity levels i~crease,yielding a higher overall suitability (the
weighting factor associated with the "no cover"class of cover using turbid
water suitability criteria is 0.31,compared to 0.01 for clear water
criteria).When coupled with an increase in surface ar:ea,this leads to
the sl igh't ri se in WUA observed at higher flows.However,because the ra te
_...__oJ._change_in .WSA-.is ...so-gr-ea-trelati-ve-to··the change ...·in-WUA,···the-proporMon-··
of the site containing usable rearing habitat declines as flows increase.
HAIs decrease from 11.9 percent at 5,000 cfs to 5.4 percent at 26,000 cfs.
________IFl_~.lJ~~r~..!.'L~Q_~t!~_~Q7.!'§J".,_YJ~.rY_Jjll]j;Lr~S.P.o.o-s.e io_W.SA,_W ..U.A,.and_H.A I to -...
changes fnrna-instem discharge were observed at Site 112.5L (Figure 17).
The latter si te is an upland slough wi th steep banks whi ch prevents large
changes in surface area as site water surface elevations change (Plate A-
2).As a consequence,physical habitat conditions within this site remain
relatively cOrlstant and little variation in WUA and HAl results from main-
stem flow fluctuations below 35,000 cfs.Slight inconsistencies in ADF&G
field data required that an average HAl value (4.2 percent)be used to back
56
I
I I
I I
i
i I
A
120
loa -
96--·..u 64--"-·72-..u-·60-cr
.E2 .ca-
('CJ 3&-CL1c..-<24 -
12-
0
0
SITE 112.5l
__·--lfSA---_.-.-'-------
J I I J J J I J I
<4000 aooo 12000·16000 20000 2.cocJO 28000 32000 36000 40000
Mainstem Discharge (cfs)
B
100
90
I 1 so
I ,
70
..u 60c:
CL1 50c.:lc..
CL1 -40c..
30
20
10
0
0 4000 aooo 12000 16000 20000 2-iOOO 28000 32000 36000 .coooo
Mainstem Discharge (cfs)
I
J Figure 17.Surface area and chinook rearing habitat index response curves
for modeling site 112.5L.
A -Wetted surface area (WSA)and weighted usable area (WUA).
B -Habitat availability index (HAl)
57
ca 1 cul a te WUA va 1 ues for Si te 112.5L.Va 1 ues deri ved for these habi ta t
indi ces were comparable to those recorded for Si te 107.6L.
Specific areas assigned to Representative Group I are former side channels
and side sloughs that have become increasingly isolated over time from the
mainstem owing to long-term channel activity.Due to the infrequency of
breaching events,the primary response in habitat character at these sites
results from backwater effects at the upland slough/mainstem interface.
Di fferences between speci fie areas are re la ted primarily to the extent of
backwater areas,and secondarily to the presence or absence of riparian and
.ins t rea m ve ge ta t ion.Va ria t ion sin 1 0 cal run 0 f f res u 1 tin g fro m
preci pi ta ti on may also affect short--terrn habi tat ava i labil i ty and qual i ty.
Of the two modeling sites in th'i's'Repre~'~'~tat:ive'Group,''Site 107~6L
represen ts a sUbgroup of 8 speci f1 c areas whose hahi ta t eti~~acterfs
strongl yin fl uenced by tri ~u~a ryi ~f'l ~~'~Si 1:ellg:'5L~reJ~r~ie_Ris_the__.
~~•'.--.<"-~_...._..._--_...~_._.._._._-_._•.~._.._--~._."-"--~._.~.._-_.._--_•...,._..•._._-_._---~~~•.._---"'-'.--•
remaining 11 upland slough,s"in,Representative Group I whose hab;'tat...
character appea ~s ~~restronglYi nfl uenced"byground~aterfnffow.'HAl
func ti ons were deri ved for modeled and non-modeled speci fic areas
associated with each of the modeling sites and are presented in Figures 18
.______..aXLd __19__J_see aJ_so_.Append-i-x-BL .T-hese--HAI-·"'c-urves'were--no-t---a-d-j-us-ted--,------.
laterally on the discharge axis since the specific areas within Representa-
tive Group I are breached at extremely high mainstem discharges.Dif-
ferences in habitat availability between specific areas are assumed to be
due todi ssi mi larities instrlJcturalhaoi tat-quali ty ..
For each specific area included in Representative Group I,HAl ratios
representing the amount of usable rearing habitat per unit surface area at
58
I
I I
I
I I
I
J
y
I
i~__L __
REPRESENTATIVE GROUP I
32000
20.00
lB.50
17.00
'0
0
..-t
X 14.00
<r
U)
:J:12.50........
<r:::>I U1 ~11.00\0
I-i 9.50<r:c
B.OO
6.50
5.00
I
0 4000 BOOO 12000 16000 20000 24000 28000
SITE 107.6L
n =8
36000 40000
Figure 18 •.
~AINSTEM DISCHARGE (CFS)
Response of chinook rearing habitat availability to mainstem
discharge within non-modeled specific areas of the middle
Susitna River which are associated with modeling site 107.6L
of Representative Group 1.
.---
SITE 112.5L
n =11
RE1RESENTATIVE GROUP I
I
I
400
I
8000
I I I I I I
12000 116000 20000 24000 28000
iMAI~STEM DISCHARGE (CFS)
I
I
I
32000
I
36000 40000
'---
Figure 19.
I
~esponse of chinoak rearing habitat availability to mainstem
~ischarge within non-modeled specific areas of the middle
S:usitna River whi~h are associated with modeling site 112.5L
olf RepresentativeiGroup I.
i
I
------..J
fl'
11
I)
(]
[1
u
flow increments of 500 cfs were multiplied by corresponding wetted surface
area estimates interpolated from areas digitized from scaled aerial
photography.The product of flow-specific HAl and WSA values are estimates
of the total amount of WUA (in square feet)present at a particular site
for mainstem flows ranging from 5,000 to 35,000 cfs.Aggregate WSA.and WUA
values were obtained for Representative Group I by summing individual
specific area WSA and WUA forecasts.The results of these calculations are
presented in Figure 20.
The overall response of juvenile chinook habitat for Group I sites is
influenced by changes in backwater-related surface area and by the relative
constancy of HAl values,particularly at lower flows.WUA tends to
increase slightly as flows increase from 5,000 to 16,000 cfs;rearing
habitat is maximal at the latter flow.Rearing-habitat potential remains
'fairly constant between 16,000 and 35,000 cfs.It should.be noted that the'
total amount of rearing habitat provided by Group I is small in comparison
to other Representative Groups due to their comparatively low surface area
and HAl values recorded for its individual specific areas.
61
)
)
I
I
I
I
)
)
J
]
j
)
,]
]
1
)
)
]
/1
liSA
I
4000 8000 12000 16000,20000 24000 28000 32000 360Q0 40000
62
MAINSTEM DISCHARGE (CFS)
Aggregate response of A -wetted surface area (WSA)and B -
chinook rearing habitat potential (WUA)·to mainstem dis-
charge in specific areas comprising Representative
Group I of the middle Susitna River.
o
4-~__r-==;==:;:::=:;::===::;==:;::=:;:=.!IIU~A-_l0.00
.
~1.60.g 1.40
....1.200
enc:
0.-.80................60e
.40
<C
~.20
Figure 20.
B
200 -r------------------------,
_~~__~~~~~,.180-~~~--~~~.,---,~..-..-.~-..-~.~.-.--~--,,'..-~~-~~----~-~-,---,--~-~-~--~---~
O-!----.-----,.--T"""""-..,.---,---.,.--r----r---.--!
o 4000 8000 12000 16000 20000 24000 28000 32000 36000 40000
.
go 1:.0
.
~160
MAINSTEM DISCHARGE (CFS)
REPRESENTATIVE GROUP I
-1.80
2.00 ....,.------------------------,
A
"-o 120
en
"C 100c:
~eo
=:J..-~-..-~....~-..----..~-..-.~--~~--jg~..-60 ~-..~-~-~"-.-----:--.....,..~..--""~.
~--_..~-----_._~--~-----
lJ
II
3.2 Representative Group II
Associated with this group are modeling sites 101.4L,113.7R,126.0R and
144.4L.These sites include side sloughs having moderately high breaching
flows (>20,000 cfs)and enough upwelllng groundwater to keep portions of
the sites ice-free during the winter months.Side sloughs classified in
Representative Group II were found to contain significant numbers of
juvenile chinook during the growth season,particularly in their breached
state (Dugan et al.1984).
The 28 specific areas included in this group are typically separated from
the mainstem by large,vegetated islands or gravel bars.When breached,
these channels convey only a small percentage of the total mainstem flow.
Cross-sections vary from relatively broad,uniform and rectangular in shape
·to narrow,irregular and v-shaped in profile.Head berms generally fall in
the former category.Backwater areas occur at the mouths of most specific
areas within Group II but their effects on hydraulic conditions and there-
fore juvenile chinook habitat are not as extensive as those observed for
upland sloughs.Substrates range from silt and sand in backwater areas to
rubble/cobble/boulder throughout the rest of the site.
Aerial photography indicating the general features of modeling sites
101.4L,113.7R,126.0R,and 144.4L and their associ a ted speci fi c areas at
23,000 and 16,000 cfs are presented in Plates A-3, A-4,A-S,andA-6
(Appendix A).The appearance of these sites does not change appreciably at
mainstem flows below 16,000 cfs.
63
Response curves for wetted surface area (WSA)and habitat indices (WUA,
HAl)developed for the four modeling sites within Group II exhibit strong
similarities in appearance due to the dominant influence of shared hydro-
logic,hydraulic and morpho10gfc properties (cf Figures 21-24).In the
non-breached state,wetted surface areas remain relatively constant,
responding primarily to local runoff and upwelling conditions.Following
breaching,rapid increases in WSA occur in response to further changes in
mainstem flow.Increases in WSA are attenuated as flows approach bank full
levels.
Juvenile chinook WUA values simulated for Group II modeling sites are
generally constant until the si tes are breached,whereupon 1arge increases
occur in response to incremental changes in site flow.The amount of
usable rearin~habitat tends to.peak shortly after the head berms are
overtopped.This relatively sudden and rapid increase in juvenile chinook
habitat results from a combination of factors:1)the rapid accrual of
wetted surface area,2)the enhanced cover value provided by higher
turbidities,and 3)the preponderance of velocities falling within the
optimal preference range for juvenile chinook.In general,the magnitude
·,--~-,-,------...---"-".-.•.-"-."---~--'".~--'"-..------~~..~.=~=-~_of_~he_~_UA il1c:!"_~~~~_t!J~.r_Q.por~i ona l_to~I}~.increase j n_.wetted SJwface are.a __..
possessing suitable velocities.Site velocities,however,soon become
limiting in mid-channel areas following breaching,leading to a reduction
in rearing WUA at higher flows.
On the basis of limited gross habitat (GHA)and habitat quality (HQI)data
obtained for Site 126.0R (Figure 23),usable rearing habitat appears to be
more uniformly distributed and of better quality at flows associated with
64
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I
.1
1
1
1
1
1
l'
1
1
j
]
1
L
11
I I,
A
7S
67
60-·52..u...............s·..u-37·C"
~30
ro 22
C1.1c:...15<:
7
0
0
SITE 101.4l
__
_--lISA---r_________J
JJ
-4000 8000 12000 16000 20000 24000 28000 32000 36000 40000
Mainstem Discharge (efs)
4000 8000 12000 16000 20000 24000 28000 32000 36000 40000
Mainstem Discharge (cfs)
HAl
B
100
90
80
70
..u 60c
C1.1 50.c.J
c:...
C1.1a..40
30
(
i 20
I 10,_---..J
0
[I a
1.~....1
11
L.)
Figure 21.Surface area and chinook rearing habitat index response curves
for modeling site loi.4L.
A -Wetted s~rface area (WSA)and weighted usable area (WUA).
B-Habitat availability index (HAl)
65
,!
I
)
:1
j
j
)
)
]
]
}
r
.j
1
1I
!
J
]
I
HAl
Mainstem Di~charge ~fs)
SITE 113.7R
4000 8000 12000 16000 20000 24000 28000 32000 36000 40000
o 4000 8000 12000 16000 20000 24000 2S000 32000 36000 40000
Mainstem Discharge (efs)
Surface area and chinook rearing habitat index response curves
for modeling site 113.7R.
A-Wetted surface area (WSA)and weighted usable area (WUA).
B-Habitat availability index (HAI).
A
50
45
40-..
35..u............30.
..u.....25
C"
~20
ltl 15QJ
c..
<C
10
5
0
0
B
100
90
SO
70
..u 60c:
QJ
50uc..
QJc..40
Figure 22.
..._--~----_._...'-"'20-
10
O+-----,---,...---r----r----,r-----..,.---,----,r-----..,.---;
66
[I
A
100
90
80--·.u 70~........·60.u-·50c:r
.!!l 40
"'30Q)
Co.<:20
10
0
a
8
:~
80
70
.u 60c::
Q)
50c.:l
Co.
Q)c....40
30
20
10
0
0
SITE 126.0R
r~:
----------------.-11__________._--1
_____________---11 KUA
.4000 8000 12000 16000 20000 2.4000 28000 32000 36000 .40000
Mainstem Discharge (cfs)
r-0 'ttl(!_________._.-J"
-.---------------....;--:~
.4000 8000 12000 16000 20000 24000 28000 32000 36000 40000
II
LJ Figure 23.
Mainstem Discharge (cfs)
Surface area and chinook rearing habitat index response curves
for modeling site 126.0R.
A -Wetted surface area (WSA),gross habitat area (GHA)and
weighted usable area (WUA).
B -Habitat.availability index (HAl),habitat distribution
index (HOI)and habitat quality index (HQI)response
functions.
67
,i)
]
j
I
I
I
}
)
1
1
I
I
I
l
I
,1
J
I
, J
40000
-4000 8000 12000 16000 20000 24000 28000 32000 36000 <40000
Mainstem Discharge (cfs)
68
Surface area and chinook rearing habitat index response curves
for modeling site 144.4L.
A-Wetted surface area (WSA)and weighted usable area (WUA).
B-Habitat availability index (HAl)
Mainstem Discharge (cfs)
SITE 144.4l
B
100 -r--.:..--------------------
90
.u 60c::
lU
U 50c..
lU
Q..-40
A\
120
108
-96·.u 84............·72.u-·:j0-
J!!
l't:I !
Q,)36
c..
oct:24
12
a
0
Figure 24.
_._"._....-..---~..-"_._-_.__._-----1-.
----------..---------20-------~~--==
1:I~I =r==;:::::::;:=::::;::::'-'--.-~HAI I~I.1 I I I
-II 4000 8000 12000 16tl00 20000 24000 28000 32000 36000
:'
iJ
I
the ascending left hand limb of the WUA curve than at non-breached or high
mainstem discharges.Under non-breached conditions,unsuitably shallow
depths often occur in riffle areas of the site,resulting in slightly lower
HQI values.Although surface area and habitat indices for Site 126.0R were
not extrapolated to flows exceeding 35,000 cfs,it is likely that juvenile
chinook habitat becomes more restricted to peripheral areas as mid-channel
ve loci ties increase.
Specific areas in Representative Group II are listed in four subgroups
according to similarities among their morphologic and hydraulic
characteri sti cs.Si te 101.4L represents 7 specific areas wi thin Group II
that have relatively large broad channels.Site 113.7R is associated with
9 smaller specific areas with narrower channels.The 6 specific areas
associated with Site 126.0R are all from two similar side slough complexes
within several miles of each other.The last subgroup is comprised of 6
specific areas that are similar in size and channel gradient to modeled
si te 144.4L.HAl functions are plotted for speci fi c areas associated wi th
each of these modeling sites in Figures 25 through 28.HAl values used to
plot these curves are tabula ted in Appendix B.
Figure 29 depicts the aggregate WUA curve obtained by multiplying Group II
specific area HAl values by their wetted surface areas and summing the
results for each flow of interest.Because of their high breaching flows,
most specific areas exhibit peak HAl values in the range of 20,000 to
30,000 cfs.When adjusted by their wetted surface areas these sites yield
cumulative WUA values which increase slowly at low to intermediate flows,
69
----_..,.----
4000036000320002800024000
I'r'"2000'MAINSTEM DISCHARGE (CFS)
I
t2000BOOO
I
REPRESENTATIVE G~OUP III'
f i~
I
SITE 101.4L
n =7
I
I I .IReslpo~se of chinook r~aring habitat !availability to mainstem
disch~rge within non-~odeled specific areas of the middle
SUS\itpa River ~hich a~e associated with modeling site 101.4L
of rerresentatlve Gro~p II.
I f II'
I
I
.cooo I
Figure 25.
40.00
36.00
32.00
0;.o 28.00
..-t
><24.00«
CJ')
3:20.00"«
;::)
~t6.00
H 12.00«.......:r:
0 B.OO
.c.00
0.00
I
0
L_~)i.
~l ~--~.
REPRESENTATIVE-GROUP II
.--~I
_----J
I
I",
.-.
I
50
45
40
(3
350
~
X 30
<Cf)
3:25.........<::;)
20~
t-I 15<:x:
10
5
0
I
0 4000 BOOO 12000 16000 20000 24000 28000 32000 36000 40000
Figure 26.
MAINSTEM DISCHARGE (CFS)
Response of chinook rearing habitat availability to mainstem
discharge within non-modeled specific areas of the middle
Susitna River which are associated with modeling site 113.7R
of Representative Group II.
SITE 126.0A
n ~6
REPRESENTATIVE:GROUP III
t r-----------
I
II 16000 20000 2-4000 28000
IM~INSTEM OISCHARGE rCFS)
I
32000 36000 -40000
Figure 27.
:
I !
~eslponse of chinook I rearing habitat availability tomainstemdis~harge within no~-modeled specific areas of the middleII•
Suslitna River whichlare associated with modeling site 126.0R
df ~epresentative G~oup II.
i iI',.
~'--~~'~'------'
~-'---'
REPRESENTATIVE GROUP II
32000
40.00
36.00
32.00
(3
0 28.00
~
><24.00«en
:J:20.00---...«
-....J ::::::l
w ~16.00
H 12.00«
:I:
B.OO
4.00
0.00
I
0 ~OOO BODO 12000 16000 20000 24000 28000
SITE 144.4L
n =6
36000 .cOO 00
Figure 28.
MAINSTEM DISCHARGE (CFS)
Response of chinook rearing habitat availability to mainstem
discharge within non-modeled specific areas of the middle
Susitna River which are associated with modeling site 144.4L
of Representative Group II.
REPRESENTATIVE GROUP II
,I
I
I
!
f
i
..
IiISA
~-----IiIUA
-------
4000 8000 12000 16000 20000 2.(()OO 2BOOO 32000 36000 40000
A
6.00
5•.cO.
.L.J 4.80......
g 4.20
....3.600
en 3.00c
0......2•.c0.-I..........1.80e
1.20
«en .603:
0.00 "I
0
MAINSTEM DISCHARGE (CFS)
o .(()QO BOOO..12000 16000 20000 24000 28000 32000 36000 .cOOOO
MAINSTEM DISCHARGE (CFS)
j
]
1
!
j
I
:1
i
!
174
Aggregate response of A -wetted surface area (WSA)and B -
chinook rearing habitat potential (WUA)to mainstem dis-
charge in specific areas comprising Representative
Group II of the middle Susitna River.
B
<C
~.20
0.00 +---,.---,.--,.----r---,.---,.--r---...---,---i
Figure 29.
~U
~1.00
o
;:::.80
-..._-~~~_..._--~--~-_.._-_._--....~~._-~.._-~.-~~~~~~.~~~~-------~~.~--~---~~_._...--~-
2.00...,------------------------,
-~~~~~~~~~---~----~----t;80--I~~-~-~··~--·
11I )
'j
j l
.\1
increase more rapidly after this point and peak at 29,000 cfs.
Approximately 1.2 million square feet of juvenile chinook WUA is provided
by Group II specific areas at this discharge.The large differences in WUA
over the range of evaluation flows indicate that rearing habitat potential
in Representative Group II as a whole may be considered highly sensitive to
fluctuations in mainstem flow.Figure 29 also illustrates aggregate WSA
response for Representative Group II •
75
3.3 Representative Group III
Sites lO1.2R,128.8R,132.6L and 141.4R are all side channel s which become
nonbreached at intermediate (8,000 to 16,000 cfs)mainstem discharge
levels,and transform into side sloughs at lower discharges.These
modeling sites and the Group III specific areas they represent,shown in
Plates A-7 through A-14 (Appendix A),are larger and convey greater volumes
of wa ter when breached than the si de s 1 oug hs discussed in the preced i ng .
section.Site geometry tends toward broad cross-sections.Reach gradients
are sufficient to promote mid-channel velocities of 2 to 5 fps following
breaching.Upwelling occurs sporadically within these specific areas and
in a few cases may be insufficient to provide for passage between
clearwater pools formed at low mainstem flows.
The 18 specific areas comprising Group III represent some of the most
.._..__..~~a.Yil y_.!l!iJi :zegr~~rilJ.g _Q,re!.qs jrL t.be.._rnJddle segment-ot-the .Susftna River..···_·····
Juvenile chinook are found in these areas primarily under turbid water
conditions (Dugan et ale 1984).
Surface area and juveni le chi nook habi ta t respg_rl.~~.C:~tY~sQ,r§!..-p.Qr.1;rg,Yed.tr:L.-
----F-i·g-ure·s-3()-;----3-1-a:n·d-J3-f·or mooer;ng s i-'fes-rOT:-2-R,128.8 Ran d 141.4R,
respectively.These sites were modeled using IFG hydraulic simulation
models coupled with the HABTAT model of the PHABSIM system.A fourth site,
132.6L wa.s modeled using both PHABSIM and RJHAB model i ng techniqUes a.ppli ed
to separate sets of da ta~Resul ts for thi s si te are found in Figure 32.
An inspection of the aerial photography (Plates A-7 through A-14,Appendix
A)WSA curves developed for the modeling sites suggests a rapid response of
I
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]
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1
J
1
1
1
·~l
]
I
1
A
220
19B
I i 176-I ·..I..J i54"-........
132 J·
f1
..I..J
"-I I ·110C'"
~BBIIn::J 66I)QJc:..
<C .014
II 22
A
0
0
SITE 101.2R
4000 BOOO 12000 16000 20000 2.01000 28000 32000 36000 .40000
Mainstem Discharge ~fs)
U
1.1
8
100
90 j"·---....v\fill
BO
70
..,60c:::
QJ 50uc:..
QJa...40 -30
20
10
0
0 4000 8000 12000 16000 20000 2.4000 2BOOO 32000 36{]00 40000
Mainstem Discharge (cfs)
Figure 30.Surface area and chinook rearing habitat index response curves
for modeling site 101.2R.
A -Wetted surface area (WSA),gross habitat area (GHA)and
weighted usable area (WUA).
B -Habitat availability index (HAl),habitat distribution
index (HOI)and habitat quality index (HQI)response
functions.
77
8
SITE 12808R
l
I
i
!
I
!
I
j
.~
I
j
I
I
j
I
·1
j
1
I
40000800012000150002000024000 28000 32000 36000
",-0-WSA
./.../"
..?.
./7 \
.//\.//_._0_0_0_0--'/\
-....-SHA
4000 BOOO 12000 16000 20000 24000 2BOOO 32000 36000 ~OOOO
78
Mainstem Discharge (efs)
Surface area and chinook rearing habitat index response curves
for modeling site 128.8R.
A -Wetted surface area (WSA),gross habitat area (GHA)and
weighted usable area (WUA).
B -Habitat availability index (HAn,habitat distribution
index (HOI)and habitat quality index (HQI)response
functions.
A
160
1<14
I
128 I-
112 ~·....,
~....,I·96 .,....,
~i·ao l0-
.2!I64.,
ra
<181lUc..-<
32 ]
16
0
0
Figure 31.
Mainstem Discharge ~fs)
70 1
.u 60 I~50 ~
&:<10 l ........_....._..~_.......·..········..··3ifj==.~........
::-l~--.,....::=::::;:::=::::;::===;:::::.----r----r---.,---..--r-----la I
o 4000
100 ...,.-----------------------,
.(OY·::-:=\.,_..~.__..~_..~90..../.
80 \
\
\
\.
-.....·-HDI
f1.I SITE 132.6L
A
140
126
__.~lISA
/.
112 .,.....-./.-·./.--....9B~.........~~- ---'-",-:..-6HA·8-4...
~/..';'-.·70 /.'/"cr
.!!56
,,-:;:;./
.::""'/
n:J •42 /euc..<28 /14
0
0 4000 8000 12000 16000 20000 2...000 28000 32000 36000 -40000
Mainstem Discharge lcfs)
- -001HAl
IJ Figure 32.
4000 SOOO 12000 16000 20000 2-4000 28000 32000 36000 <40000
Mainstem Discharge lcfs)
Surface area and chinook rearing habitat index response curves
for mOdeling site 132.6L.
A -Wetted surface area (WSA),gross habitat area (GHA)and
weighted usabl e area (WUA).
B -Habitat availability index (HAl),habitat distribution
index (HOI)a·nd habitat quality index (HQI)response
functi cns.
79
J
]
1
1
j
!
]
1
'-l
1
1
1
j
J
1
1
1
J
r
....----fflI
~--_./-;..........;;;;;..;::::=-.::;-:::...:=----HAl
--------...:.------lWA
.c000 BOOO 12000 16000 20000 24000 28000 32000 36000 .coooo
MainstemDiseharge (efs)
SITE'141.4R
80
Mainstem Discharge (efs)
B
o .c000 BOOO 12000 16000 20000 24000 28000 32000 36000 40000
Surface area and chinook rearing habitat index response curves
for modeling site 141.4R.
A -Wetted surface area (WSA),gross habitat area (GHA)and
wei ghted usabl e area (WUA).
B -Habitat ayailability index (HAl),habitat distribution
index (HDI)and habitat quality index (HQI)response
functions.
O+----r--,--,----...,.---,-----,---r----.-----r---I
100 .,.------------------------.
A.
280
252
224-·~196-.........·168~-·140c::r
.!!!112
"'84euc..<:56
2S
a
a
Figure 33.
,)
I I
I
wetted surface area to changes in mainstem di scharge following breaching.
This response is paralleled by changes in gross habitat area until
moderately high flows are attained,when the proportion of wetted surface
area possessing usable rearing habitat falls off.Peak HDI values for the
modeling sites typically range from 95 to 97 percent.These maxima usually
occur at much higher flows than those associated with peak WUA values.
Therefore,the quality of usable rearing habitat,as measured by the HQI
index,tends to decline at higher flows;i.e.,a greater proportion of the
total WUA is concentrated in a smaller area within the modeling sites.
This decline is caused by shifts in velocities in the majority of cells
toward the sUboptimal end of the velocity suitability curve.
Of the 18 specific areas classified within Group III,17 are represented by
sites 101.2R,128.8R,and 132.6L.Site 141.4R is considered atypical due
to its larger size and discharge under non-breached conditions.Therefore,
this model site only represents that specific area.Site 101.2R was used
to develop specific area HAl functions for 10 specific areas with
relatively broad shallow channels with mild gradients.Top widths
generally exceeded 100 feet and streambeds consisted of large gravels and
cobbles.Site 128.8R represents three specific areas possessing long
si nuous channe 1s 1ess than 100 feet wi de.Si te 132.6L was used to
represent four specific areas with relatively low velocities and sandy to
large gravel substrates.
81
Figures 34 to 37 illustrate HAl functions derived from modeling site
habitat data and underscore the singularity of the habitat response to flow
at Si te 141.4R.HAl curves developed for the rema i nder of the other
model ing si tes in this representative group exhibi t a strong unimodal peak
in HAl following breaching,whereas the HAl response to increasing dis-
charge at Site 141.4R is to progressively decrease for reasons stated
above.
A comparison of the magnitudes and shapes of the WSA,WUA and HAl curves
deriv.ed for Site 132.6L (Figure 32)suggests that the RJHAB and PHABSIM
modeling approaches yield similar results.The RJHAB method appears well-
suited to smaller channels where cross-sectional profiles (i.e.,velocity
and depth distributions)and cover characteristics are relatively homo-
geneous.We recommend limiting the use of RJHAB modeling techniques
primarily to baseline evaluations of fish habitat in lotic subenvironments
The aggregate WUA function derived from individual rearing habitat response
curves for specific areas in Representative Group III exhibits a pronounced
_····_·_···-·pea·k-i·n-th-e--vi·c·,-n·i-ty···(:ff-lS-;··SOO-cf~·-(·Figure--38T:--TneamoTin-t-of·ju\le·I'-fre-----·_-_.
chinook habitat provided by this flow (1.3 million square feet)represents
an increase of 3S0 percent over WUA values forecast for 9,000 cfs
(0.3 million square feet).This marked increase in usable habitat is
di rectl Ya.'t'.'t'.ri butil.I>J~..1:().1:he J:~cryi.1:rn~l:rI:Qf ..si d.e ..c.hanneJhabl::ta twtthin .the
9,000 to 12,SOO cfs flow range;12 of the 18 specific areas which comprise
Group III breach in this range (refer to Table 4 for site-specific
breaching flows).After peaking at IS,OOO cfs,juvenile chinook habitat
82
I I
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I
I
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I I
J
I 1
I
I I
I
I
,I
\
J
I
I J
L-L __
REPRESENTATIVE GROUP III
SITE 101.2R
n :::10
45.00
"'0.50
36.00
(3
0 31.50
...-i
X 27.00«
Cf)
3:22.50........«
::l
CO ~1B.00w
H 13.50
<!
:J:
9.00
....50
0.00
I
0 ...000 BOOO 12000 16000 20000 2...000 2BOOO 32000 36000 ...0000
Figure 34.
MAINSTEM DISCHARGE (cFsl
Response of chinook rearing habitat availability to mainstem
discharge within non-modeled specific areas of the middle
Susitna River which are associated with modeling site lOl.2R
of Representative Group Ill.
I I
,
II
\
I
II
REPRESENTATIVE GROUP III
I,
I,
SITE 128.8A
n '"3
i,I :
:400~
r I
I I,!
0000 12000 l6000 20000
M~INSTEM DISCHARGE
I
24000
(CFS)
20000 32000 36000 40000
. i
Figure 35.~e*ponse of chinooki rearing habitat availability to mainstem
~ischarge within n~n-modeled specific areas of the middle
Su~itna River Whic~are associated with modeling site 128.8R
bflRepresentative Group III.
iii, I
!
i I,
:L-
I L _---,
_.----J
REPRESENTATIVE GROUP III
SITE t32.6L
n =4
35.00
31.50
28.00-a 24.50a......
><21.00
<tenx 17.50-....<t
::l
~14.00
co H 10.50U1<t:r:
7.00
3.50
0.00
I
0 4000 BOOO 12000 16000 20000 24000 28000 32000 36000 40000
Figure 36.
MAINSTEM DISCHARGE (CFS)
Response of chinook rearing habitat availability to mainstem
discharge within non-modeled specific areas of the middle
Susitna River which are associated with modeling site 132.6L
of Representative Group III.
I
R~PRESENTATIVE GROUP III
I
30.00
27.00
24.00-0
0 21.00
...-i
><lB.OO«en
3:15.00 -..........«::::::l
00 ~12.00
(J)
H 9.00«:c',
6.00
3.00
0.00
I
0
Ii
40 90 BOOO 12000 i 16000 20000 UOOO 28000 32000
SITE 141.4R
n ::0 1
36000 40000
Figure 37.
f
MAINSTEM DISCHARGE (CFS)
I
I
!
Response of chinook rearing habitat availability to mainstem
d,scharge within npn-modeled specific areas of the middleS4sitnaRiverwhicnareassociatedwithmodelingsite141.4R
Of;Representative ~roup III.
----
REPRESENTATIVE GROUP III
A
15.00 liSA
-13.50
::12.00
·g 10.50
.......9.000
en 7.50c:
0
.1
.-6.00.......
I,.......
'i .-.4.50E
3.00
<:c.n 1.503::
0.00
0 .4000 BOOO 12000 16000 20000 2.4000 2BOOO 32000 36000 40000
MAINSTEM DISCHARGE (CFS)
B
2.00
LBO
·.....1.60.......·0"1..40en
.......1.200
en 1.00c:
0.-.BO..............
.-.60E
..40
<:
=:J .203::
0.00
0 .4000 BOOO 12000 16000 20000 2.4000 2BOOO 32000 36000 40000
MAINSTEM DISCHARGE (CFS)
Figure 38.Aggregate response of A -wetted surface area (WSA)and B -
chinook rearing habitat potential (WUA)to mainstem dis-
charge in specific areas comprising Representative
Group III of the middle Susitna River.
87
gradually declines to 0.9 million square feet at 26,000 cfs and remains at
this level through 35,000 cfs.Decreases in HAf values which occur within
this range are offset by gains in total wetted surface area,resulting in
relatively stable rearing habitat potential at higher flows.
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3.4 Representative Group IV
Aaserude et ale (1985)delineates the 22 specific areas within this group
on the basis of their low breaching discharges.and intermediate to high
mean reach velocities.The side channels which comprise these specific
areas possess lower mean reach velocities than adjacent mainstem channels.
Substrates range primarily fro in cobble to boulder.
Four mode 1i ng sites repre se nt Group IV:112.6L,131.7L,134.9 Rand 136.0L.
Of these,Site 112.6L is the largest and Site 136.0L the smallest of the
I)'sites investigated.In spite of their disparity in size,the modeling
tV
sites are characterized by similar surface area and habitat index re?ponse
curves.Compare the aerial photographs of the modeling sites presented in
Plates A-15 through A-22 (Appendix A)with the wetted surface cu~ves in
Figures 39 through 42.As is typical of most side channels of the middle
river,wetted surface area responds to changes in streamflow more rapi d1 y
at lower than at higher flows;the rate of change in WSA per 1000 cfs
increment in mainstem discharge declines perceptibly at flows exceeding
16,000 cfs.This response pattern is accentuated at sites with wide,
sha 11 ow channel cross secti ons such as Si te 131.7L (Plates A-17 and A-18,
Figure 40).
In terms of juveni 1e chinook habi tat potential,the most remarkable fea ture
of Group IV modeling sites is the comparatively large amounts of WUA they
provide at low to moderate mainstem flows.A comparison of the WUA values
and,more appropriately,HAl functions (Figures 43 through 46 )with esti-
mates obtained for modeling sites from other Representative Groups suggests
89
A
550
495 -
440 --·385 -..,
~
"-330 -·..,
~·275 -c:r
.!!?220 -
to 165 -Q)c..<'
110 -
55-
0
0
SITE'112.6l
I I I I I I I I T
~ooo BOOO 12000 16000 20000 24000 28000 32000 36000 .coooo
Mainstem Discharge (cfs)
I.I
B
o 4000 8000 12000 16000 20000,24000 25000 32000 36000 40000
Mainstem Discharge (cts)
Figure 39.Surface area and chinook rearing habitat index response curves
for modeling site 112.6l.
A -Wetted surface area (WSA),gross habitat area (GHA)and
weighted usable area (WUA).
B -Habitat availability index (HAl),habitat distribution
index (HOI)and habitat quality index (HQI)response
functi ons.
90
B
100
90
80
70
..,60ccu50uc..cuc..
--HOI
HAl
'1.1
Figure 40.
o 4000 8000 12000 16000 20000 24000 28000 32000 36000 40000
Mainstem Discharge ~fs)
Surface area and chinook rearing habitat index response curves
for modeling site 131.7L.
A -Wetted surface area (WSA),gross habitat area (GHA)and
weighted usable area (WUA).
B -Habitat availability index (HAI),habitat distribution
index (HOI)and habitat qual i ty index (HQI)response
functions.
91
A
350
315 -
-280 -·~245 -......
"-·210 -~......·175 -c::r
.!!!140 -
tt:I 105 -QJc..<70 -
35-
0
0
I I I I 1
~OOO 8000 12000 16000 20000
·1 I I I
2~000 2BQ00 32000 36000 40000
\
I,J
l r,.,.
\
l
i I
"
'1~''.
100
.8
90
~~~-'-ao---._._.•._-
70
~60c:
QJ
50t.:Ic..
QJc..40
30
o
Mainstem Discharge rcfs)
4000 BOOO 12000 16000 20000 24000 28000 32000 36000 40000
Mainstem Discharge rcfs)
Figure 41.Surface area and chinook rearing habitat index response curves
for modeling site 134.9R.
A -Wetted surface area (WSA),gross habitat area (GHA)and
wei ghted usable area (W UA).
B -Habitat availability index (HAl),habitat distribution
index (HOI)and habitat quality index (HQI)response
functi ons ~
I 1
)
\
'j
SITE'136.0L
A
75
67
60-·oI-J 52............·45-l-J.....·37c:r
~:iltl
aJ
Co.<15
7
a
I i a(l
------------------WUA
..c000 8000 12000 16000 20000 2..coOO 28000 32000 36000 ..coooa
Mainstem Discharge (cfs)
\1 8
100
90 ~'--'\
(['y.
80 \..,)
70
\.'"oI-J 60c:\aJ 50u
Co."'.aJc....co --...."""'-.
30 --------IilI
20 /_--__oHQI....--.......;.-
10
HAI
0.\lJ a ..cOOO 8000 12000 16000 20000 2..coOO 28000 32000 36000 40000
Mainstem Discharge (cfs)
,I
LJ Figure 42.Surface area and chinook rearing habitat index response curves
for modeling site 136.0L.
A -Wetted surface area (WSA),gross habitat area (GHA)and
weighted usable area (WUA).
B -Habitat availability index (HAl),habitat distribution
index (HOI)and habitat quality index (HQI)response
functions.
93
1
R~PRESENTATIVE GROUP IV
SITE 112.6L
n =6
MAINSTEM DISCHARGE (CFS)
I
I
~ooq
1
I
"
8000 12000 I 16000 20000 24000 28000 ,32000 36000 ~oooo
Figure 43.
:I :
i I I! ,'Re~ponse of chinookl rearing habitat availability to mainstem
hi~charge within n~n-modeled specific areas of the middle
~u~itna River which!are associated with modeling site 112.6L
pflRepresentative ~roup IV.
II I
I '
i
'---,''------..------L,-
"
-''~---
,---
'_1_-"-----:
REPRESENTATIVE GROUP IV
4000036000
SITE 131.7L
n =5
32000280002400020000160001200080004000
40.00
36.00
32.00-0 28.000
..-I
><24.00«
U)
3=20.00........«
:;::)
~16.00
'.0 H 12.00en~
8;00
4.00
0.00
I
0
MAINSTEM DISCHARGE (CFS)
Figure 44.Response of chinook rearing habitat availability to mainstem
discharge within non-modeled specific areas of the middle.
Susitna River which are associated with modeling site 131.7L
of Representative Group IV.
REPRESENTATIVE GROUP IV
SITE i34.9R
n =9
Re$ponse of chinookirearing habitat availability to mainstem
~i$charge within no~-modeled specific areas of the middle
Susitna River whichi are associated with modeling site 134.9R
?flRepresentative G~oup IV.
i I I
i I I
I
'.0en
Figure 45.
4qOO
I
BOOO i2000 i i6000 20000 24000 2BOOO
MA~NSTEM DISCHARGE (CFS)
!
!
32000 36000 40000
~-....::..-----.....
1.....--"..-------.....~'~.~.
~'--
REPRESENTATIVE GROUP IV
SITE 136.0L
n =2
35.00
31.50
28.00 •
(3
24.500
..-t
><21.00
<t:en
3:17.50.........<t:
'.0 ::::l
-....I ~14.00
H 10.50<t:
:I:
7.00
3.50
,0.00 .
0 .cooo 8000 12000 16000 20000 24000 28000 32000 36000 .40000
Figure 46.
MAINSTEM DISCHARGE (CFS)
Response of chinook rearing habitat availability to mainstem
discharge within non-modeled specific areas of the middle
Susitna River which are associated with modeling site 136.0L
of Representative Group IV.
that Group IV specific areas provide a significant amount of rearing habi-
tat within the middle river.This conclusion is supported by ADF&G
sampling data indicating high utilization of these sites by juvenile
chinook during the summer months (Dugan et ale 1984).
At all modeling sites except Site 131.7L,usable rearing habitat is
greatest at the lowest evaluated flow (5,000 cfs),and after a gradual
decline either continues to taper off or remains constant for flows above
16,000 cfs.Turbidity levels are high at all discharges and most areas of
the sites possess suitable depths for rearing fish.Changes in WUA and HAl
are therefore directly proportional to the increase or decrease in the
availability of suitable velocities.As an example,Williams (1985)
demonstrated that the total area within Site 112.6L possessing suitable
rearing velocities is five times greater at 13,500 cfs than at 33,000 cfs.
GHA and HOI curves reveal that the amount of gross habitat at the modeling
si tes is ne~_~l~eq~~_~~__~~e~.':__~ota 1 wetted_surface_aJ:ea_fQr Jl ows rangj n9-"__
---
from 8,500 (Si tes 112.6L and 134.9R)to 17,000 cfs (Si te 131.7L).However,
mean reach velocities measured at specific areas within this group averaged
3.3 fps at 10,000 cfs (Aaserude et a 1.1985),we 11 above the range of
velocities tolerated by juvenile chinook salmon,suggesting that for the
"grouR a saw ho 1e ,_tb~La_m_oun_t_a.nd-p~opo~ti-on-of--g-~o-s-s--r-ea-r-i-ng--ha-b-i-ta-t-i-s
probably greatest when flows are less than 10,000 cfs.Regardless of
discharge levels,the quality and quantity of usable rearing habitat is
greatest along the margin~ofth~mog~ltngsjtesdue to the reduction of
vel oei ties in th~seareas.
The specific areas assigned to Representative Group IV have been divided
among the four study sites on the basis of breaching flow,channel
98
I
"I
I I
I
I I
morphology,size and hydraulic characteristics.Five of the specific areas
are grouped with Site 131.7L.All of these sites breach just below
5,000 cfs,and possess large amounts of shallow riffle habitat in
comparison to their total wetted surface area.The 9 largest specific
areas are grouped wi th Si te 134.9R whi ch are all characteri zed by deep,
swift flows.These sites possess very little pool or riffle habitat.
Site 112.6L represents six intermediate sized specific areas which,in
general,contain a larger amount of submerged gravel bars and are not as
deep or swift as those represented by 134.9R.Site 136.0L represents two
small crescent-shaped specific areas with distinct riffle/pool patterns at
low flows·and high velocity runs at high flows.
The aggrega te WSA response for the group is shown in Figure 47.As
discussed above,the proportion of the wetted surface area providing usable
chinook habitat in Group IV sites,particularly in the lower flow range,is
high in comparison to specific areas from other representative groups.
This characteristic,when coupled with the fairly large surface areas
associated with Group IV specific areas,results in exceptionally large
rearing WUA forecasts for Representative Group IV as a whole (Figure 47).
The significance of this fact will be discussed in Section 4.0 following
presentation of aggregate WUA curves for all representative groups.
Juvenile chinook potential in Group IV sites is highest at mainstem
discharges of 10,000 cfs and less.Peak rearing WUA values (approximately
4.1 million square feet)are attained at 8 -8,500 cfs.This trend is
related to the low breaching flows characteristic of specific areas within
99
REPRESENTATIVE GROUP IV
4000 8000 12000 16000 20000 24000 2BOOO 32000 36000 40000
A
30.00
-27.00
;::24.00.
g 21.00
~16.00
~15.00
0
;:::12.00...........9.00E
6.00
«
U')3.003::
0.00
0
--------------------
WUA
I I
I
I
I
I
, I
MAINSTEM DISCHARGE (CFS)
B
5.00 -r-----------------------....,
4.50
;::4.00
I 1
J
I I
I
, I
I
WUA1.00
~3.00
~2.50
o
;:::2.00 -......I -------------..::~~--..-------------------------------------------------1---------------------------------------------·s -1~50--l-
----------~-
«
~.50
0.00 -+----,---,---..,..----,---,---..,..----.---,.---..,....---.1
o 4000 BOOO 12000 16000 20000 24000 2BOOO 32000 36000 40000
MAINSTEM DISCHARGE (CFS)
Figure 47.Aggregate response of A -wetted surface area (WSA)and B -
chinook rearing habitat potential (WUA)to mainstem dis-
charge in specific areas comprising Representative
Group IV of the middle Susitna River.
, I
I
!I
I
100 I
I J
this group.The composite suitability of velocity and depth within these
sites decreases rapidly as flows increase;WUA declines concomitantly,
reaching a low of 1.6 million square feet at 35,000 cfs.
101
3.5 Representative Group V
This group,comprised of nine specific areas,includes sh.oal areas which
transform into clear water si de 510ughs at lower rna i nstem di scharges.A
shoal is simiJar to a riffle in that both are topographic high points in
the longitudinal bed profile of the river and are therefore zones of
accretion.Shoals,however,are easily'distinguished from riffles by their
morphological features and the hydraulic processes responsible for their
existence.As a general rule,shoals form immediately downstream of point
gravel bars located at bends of the river or at the lower end of
established islands.Due to reduced velocity in these areas,shoals are
characterized by sand and gravels deposited on the falling stages of floods
and at low flow.Larger substrates are possible if the shoal has
stabil ized and beg~n to take on gravel bar characteristics.
ow across shoal areas may be transverse to mainstem flow and velocities
tend to be slower-than-average due to the drag effect exerted by the
streambed.As water levels drop,flow is concentrated in a few small
channels which feed a larger single channel on the inside of the shoal.
--"--"..'--~"---'-----'""~"_._-----".._--".""-----_._.~_._---------····-·--··-·Wni~fn··feeder···cfiann·ers-cre~iate-r·afTowerdrscharges···the re i s ll~ua 11)'suf fi ':'......_..
---__---'~-----_...•._---_._-----------_._-_._------_._------_.._._---_.•._.._---~--_._._---_._..__---_.._----_._.-,---------_._.__.._---_._.._----_._-~_.•.__~--__.._---_•.._--___._-_.._.._-'__--_._-----
cient mainstem seepage through the head and sides of the channel berm to
maintain a small amount of clear water ~lough habitat at the site.
The general morphologic features described above may be observed in aerial
photographs (Plate A-23)of Site 141.6R--the only modeling site found in
Representative Group V"Site 141.6R begins to convey mainstem water at
18,000 cfs but is not controlled by mainstem discharge until 22,000 cfs.
'I
I
:1
,f
!
f
.,(
r
-l
I
1
I
}
[
I)
I ].
I
I
'J
Si te flow sunder non-breached condi ti ons average 5 cf s.Wetted surface
area and juvenile chinook weighted usable area at Site 141.6R are assumed
to remain constant in the non-breached state;the ratio of WUA to WSA,
expressed as a percentage,is 13.4 percent (Figure 48).Gross habitat area
r III is esti rna ted to compri se 83 percent of the total surface area when clear
water conditions prevail.
As is common with most specific areas of the middle Susitna River,the
introduction of turbid mainstem water has an immediate effect on the
usabil i ty of Si te 141.6R by j uven il e chi nook.Other than turbi di ty,the
most significant factor contributing to the sharp rise in usable habitat is
the large increase in wetted surface area.Mos t of the recrui ted habi tat
is ~hallow and slow velocity areas that may be used to some extent by young
chinook.Figure 48 indicates that over 90 percent of the total surface
area has at least some reari ng habi tat val ue at di scharges between 23,000
and 32,000 cfs.Maximum WUA,HAl,and HQl values occur at the lower end
I (
11
I \
I I
1-._1
tJ
of this flow range;each of these habitat indices peak in the range of
24,000 and 25,500 cfs.Habitat index curves are drawn out at their upper
ends by the gradual loss of suitable velocity areas.Eventually,flow over
the shoals is fast enough to significantly reduce the availability and
qua 1i ty of chi nook reari ng habi ta tat the si teo
There are ni ne speci fi c area s wi thi n Representa ti ve Group V.The area s
breach over a wide range of mainstem discharges «5,000 to 23,000 cfs)and
exhibit large variations in structural habitat quality.The HAl function
ob ta i ned for Site 141.6 R,whi ch b rea c he sat 22,000 cf san d has a
comparatively high SHl value,was used as a template for deriving HAl
curves for all specific areas within the group (Figure 49 and Appendix B).
103
1
l
f
i
l
!
1
1
.{
j
l
[
]
i
'I
1
1
!
1
IfUA
/
/"
!~
.~"\
/)\
/~\GHA
----'----_...//______J
I I
<4000 BODO .12000 16000 20000 24000 28000 32000 36000 40000
Mainstem Discharge (cfs)
104
o <4000 8000 12000 16000 20000'24tl00 28000 32000 36000 .40000
Mainstem Discharge ~fs)
SITE 141 ..6R
Surface area and chinook rearing habitat index response curves
for modeling site 141.6R.
A -Wetted surface area (WSA),gross habitat area (GHA)and
weighted usable area (WUA).
B -Habitat availability index (HAn,habitat distribution
index (HOI)and habitat quality index (HQI)response
flJncti on$.
A
100
90
BO-·~70"4-
"·60~
0.&-·500"
.!!!
.40
10 30C1J
C--<:20
10
0
0
Fi gure 48.
........-_..···..__·..·_··__.._··30..._..........~..=.~~.~~==:l~.~~~=.~--_··..·1-..····..~..
.........-~___'2iJ"'.....fi
10
O-+----r--~--r--_,__--,--__,.--,..----_r_-___,_----i
\.----..-..,,--,L _
REPRESENTATIVE GROUP V
4000036000
~--~=-::---=-..:t~~::,........~~_
-r--r--I I
20000 24000 28000 32000
I
16000
SITE 141.6R
n =9
1--~~~.--r~~~~-I
4000 BOOO 12000
35.00
31.50
2B.00-0
0 24.50-x 21.00
4:en
3:17.50--.
4:
:::l
~14.00
I-'
.:::J
10.50U1I-i
4::r:
7.00
3.50
0.00
I
0
MAINSTEM DISCHARGE (CFS)
Figure 49.Response of chinook rearing habitat availability to mainstem
discharge within non-modeled ~pecific areas of the middle
Susitna River which are associated with modeling site 141.6R
of Representative Group v.
There does not appear to be any correlation between the magnitude of
breaching flow and structural habitat quality of peak habitat availability
for these speci fi c areas.
Collectively,the specific areas which make up Representative Group V do
not provi de si gn i fi cant a moun ts of j uvenil e chi nook hab ita t,even under
ideal flow conditions.The low aggregate WUA values portrayed in Figure 50
result from 1)the small number of specific areas assigned to Group V,and
2)the sma 11 amoun t of total wetted surface area associ a ted with these
sites.Overall,less than 0.4 million square feet of rearing WUA is pro-
vided by Representative Group V by streamflows within the range of 5,000 to
35,000 cfs.WUA values peak at approximately 26,000 cfs when joint surface
area arid HAl values are maximized (Figure 50).
!
\
1
I
!
J
,1
I
I
1
t
1
J
1
,\
1
J
!
r. I
REPRESENTATIVE GROUP V
A
4.00
3.60
(1 ~3.20 liSAIJ
......g 2.80
.....2.400
en 2.00c::
0.....1.60.--..--......1.20E
.80.
<en .403:
0.00
0 4000 8000 12000 16000 20000 24000 28000 32000 36000 40000
MAINSTEM DISCHARGE (CFS)
IIUA
4000 8000 12000 16000 20000 24000 28000 32000 36000 40000
MAINSTEM DISCHARGE (CFS)
Aggregate response of A ~wetted surface area (WSA)and B -
chinook rearing habitat potential (WUA)to mainstem dis-
charge in specific areas comprising Representative
Group V of the middle Susitna River.
107
3.6 Representative Group VI
The 13 specific areas within this group are products of the channel
braiding processes active in the high gradient middl~segment of the
Susitna River.Included are overflow channels which parallel the adjacent
mainstem.Typically separated from the mainstem by a sparsely vegetated
bar,these channels mayor may not possess upwelling.These ~pecific areas
may represent more advanced stages of shoal development in which their
gravel bars have stabilized due to the growth of vegetation and further
high-stage sedimentation,and mainstem overflow is usually delivered by a
_single dominant feeder channel.Incision of the lateral channels has
gradually occurred over time,leading to lower head berm elevations and
coarser substrates.Side channel gradients are usually greater than
.
adjacent mainstem channels as a result of hydraulic processes which adjust
channe 1 morp ho logy to rna i nta in transpor t can ti nu i'ty.The spec trum of
______~sho_aJ_~to~_sjd.e ..channeLde velopm en ta 1.stag eS-l"epr-es entedby--the-sp ec-i-f-ic-----~-.--
areas of Group VI is i ndi ca ted by the wi de range of breachi ng di scharges
and structural habitat indices recorded by Aaserude et ala (1985).
----~_._--_._-_._--_.-------"--_._--~..__._._._-_._-_.~-_..•.._.__._._._._-_._~--~-_.__._-_..__._-_._---_.--~--
·_----~-~wlficlf--Dreachatlr;-5()lrand 13,OOOcfs~respectively,but remain watered at
non-breached mainstem discharges.Plates A-24 through A-26 (Appendix A)
give some idea of the morphologic features and wetted surface area response
to flow of Group VImodelihgsites.A large backwater occurs at their con-
fluence with the mainstem channel.The gravel bar at Site 136.3R appears
to be more stable than the bar at Site 133.8L,judging from differences in
the type and amount of vegetation cover.Both modeling sites are rela-
tively flat in cross section except for deep narrow channels running along
1 i
11
1 i
-!
!
,)
.(
1
1
r
r
I
1 ]
(
1 1
I
!
1
I
banks opposite the gravel bars.These banks are steep-walled whereas banks
formed by the gravel bars are gently sloping.These features are largely
responsible for the type of response of juvenile chinook habitat to changes
in mainstem discharge observed at the two Group VI modeling sites.
Habitat index and surface area response functions derived for Site 133.8L
and 136.3R are conspicuously similar,particularly if allowance is made for
differences in mean channel width (Figures 51 and 52).In both cases,the
anticipated increase in WUA following breaching occurs,but after attaining
moderate levels the amount of rearing habitat remains fairly constant at
higher mainstem discharges.This pattern,which is uncharacteristic of
more developed side channels (compare,for example,the WUA response curves
for sites from Representative Group VI with results for Group III and IV
modeling sites),is also apparent in the relationship between gross habitat
area and river discharge.The constancy of WUA and GHA values at moderate-
to-high mainstem flows results in generally stable habitat quality at the
sites,implying that areas suitable for chinook rearing are recruited and
lost at comparable rates.Regardless of flow levels,most juvenile chinook
habitat at Sites 133.8L and 136.3R is associated with the gravel bar
shoreline and backwater area of both sites.
HAl func ti ons developed for the two model i ng sites exhi bit the expec ted
rise and fall in juvenile chinook habitat availability which attends
breaching and further increases in discharge.However,because WUA values
remain constant at higher flows,the slope of the descending limb of the
HAl curves is not as grea t as observed for other represen ta ti ve groups.
Based on similaries in channel morphology and habitat reconnaissance data
109
I.1
I
SITE 133.8L I
A I J
150
135
....."...-WSA
t'
120 /-·.,105 ./'('\............/..J \.-6HA·90.,....-r/"·75 /cr ~.J~60 /1-.,.....-f""to 45 _._._._~~cuc..<30 /-----15
a ,I
a 4000 BODO 12000 16000
I
20000 24000 28000 32000 36000 40000
Mainstem Discharge (cfs)I
--j
B
100
90
BO-"_._._.._..~
_..
10
.,60c:o
cu 50t.Jc..cu ..cO0..
.~\r/'-.J--y.._I···........-------y--\--------..-
f \--HOI
-_._..--:1
30
---·-·····-·----------···-----·-·-·····-·--·--20··
10
o-+--....,...----...---.....--.....---....----.....--......--.....----.-----l
o 4000 BOOO 12000 16000 20000 2.4000 2BOOO 32000 36000 40000
Mainstem Discharge (cfs)
Figure 51.Surface area and chinook rearing habitat index response curves
for modeling site 133.8L.
Ao-Wetted surface area (WSA),gross habitat area (GHA)and
weighted usable area (WUA).
B -Habitat availability index (HAI),habitat distribution
index (HOI)and habitat quality index (HQI)response
functions.
110
!
.1
I
I
I I
I
A160
144
128-·~112-.........·96~-·eoc:ren-604
"'-18l13
C-<J2
16
0
0
B
100
90
BO
70
~60c:eu 50""C-eu .cO0-
30
20
10
0
0
SITE 136.3R
_----IflJA___-J/------r
.cooO 8000 1~000 16000 20000 2.c000 2BOOO 32000 36000 040000
Mainstem Discharge (efs)
__-HOI....-
:::::------/r----HAl
.coOO BOOO 12000 16000 20000 2-4000 28000 32000 36000 ,(0000
Mainstem Discharge (efs)
Figure 52.Surface area and chinook rearing habitat index response curves
for modeling site 136.3R.
A -Wetted surface area (WSA),gross habitat area (GHA)and
weighted usable area (WUA).
B -Habitat availability index (HAI),habitat distribution
index (HOI)and habitat qual i ty index (HQI)response
functions.
III
obtained at modeled and non-modeled specific areas in Group VI,7 of the 13
specific areas are grouped with site 133.8L and 6 with site 136.3R.HAl
functions derived from the modeling sites are presented for each subgroup
in Figures 53 and 54 and Appendix B.
Due to their relatively high breaching flows and rapid wetted surface area
response following breaching (Figure 55),specific areas within
Representative Group VI provide considerably more juvenile chinook WUA at
high as compared to low mainstem discharges.Figure 55 indicates the
aggrega te reari ng WUA functi on deri ved as the sum of i ndi vi dua 1 specifi c
area habi ta t va 1 ues for flows rangi ng from 5,000 to 35,000 cfs.Reari ng
habitat potential increas~~ste(lgiJYa:La,funct.ionof flow throughout this
range.The amount of juvenile chinook WUA forecast for 35,000 cfs (1.3
mi 11 ion square feet)represents over 30 ti mes the amount of WUA forecast
for 5,000 cfs (0.04 million square feet).The correlation between wetted
--_.._.,--_..,--'-_._---
surface are-a:'an-daggrega te rearil1-g'WUA va 1 ues is more pronounced in
Group VI than in other representative groups due to the relative constancy
of HAl values across all flows.
1
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I
-1
I
\
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-I
I
-I
I
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I I
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I
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112
-1
I I
L--L--..-,
~-~
REPRESENTATIVE GROUP VI
25.00
22.50 "
20.00
0
0 17.50
....-i
x 15.00
<t:
U)
3:12.50..........
<t:
t--':::>
t--'~10.00
eN
H 7.50
<t::r:
5.00
2.50
0.00
I
0 .4000 BOOO 12000 16000 20000 2.4000 28000 32000
133.BL
n =7
36000 .40000
Figure 53.
MAINSTEM DISCHARGE (CFS)
Response of chinook rearing habitat availability to mainstem
discharge within non-modeled specific areas of the middle
Susitna River"which are associated with modeling site 133.8L
of Representative Group VI.
SITE 136.3R
n =6
40.00
36.50
33.00-0
0 29.50
..-1
X 26.00«
U')
3:22.50-.......:
«'
:::::l
~19.00
H 15.50oCt
:t:
12.00
8.50
5.00
I I
0 ~OOO 8000
I
II-
~EPRESENTATIVE GROUP VI
I
i
12000 I 16000 20000 24000 28000
IMAINSTEM DISCHARGE (eFS)i .
32000 36000 ~oooo
Figure 54.Response of chino~k rearing habitat availability to mainstem
discharge within ~on-modeled specific areas of the middle
~usitna River whi~h are associated with modeling site 136.3R
qf RepresentativelGroup VI.
i
.,..-~---~Hi!,
REPRESENTATIVE GROUP VI
A
10.00
9.00
.....8.00"-HSA·0-7.00en
"-6.000
en 5.00c::
0.....4.00...............3.00e
1\
2.00
<:en 1.00 HUAr,3
0.00
0 .j000 8000 12000 16000 20000 24000 28000 32000 36000 40000
MAINSTEM DISCHARGE (CFS)
B
2.00
1.80
·.....1.60"-·g 1.40
"-1.200
en 1.00c::
0......80................60e
.40
<::::>.20'3:
0.00
a
Figure 55.
---HUA
.jOOO 8000 12000 16000 20000 24000 28000 32000 36000 40000
MAINSTEM DISCHARGE (CFS)
Aggregate response of A -wetted surface area (WSA)and B -
chinook rearing habitat potential (WUA)to mainstem dis-
charge in specific areas comprising Representative
Group VI of the middle Susitna River.
115
3.7 Representative Group VII
This group of seven specific areas is dominated by side channels possesing
low breaching discharges and organized into distinctive riffle/pool flow
patterns.In most cases,the specific areas are comparatively short with
small length:width ratios and are composed of a single riffle extending
from the head of the si te down 'to a large backwa ter area at the mouth.The
transition from riffle to backwater pool is defined by an abrupt step in
bed and water surface profile.Head berms are generally broad-crested and
the riffles of greater-than-average slope.The steep riffle gradients tend
to increase in streamflow tends to mimimize the staging effect of rising
mainstem flows at the mouth of the site.Consequently,the rate of change
in backwater area is less than is observed at lower gradient sloughs and
side channels over a comparable range of discharges.Backwater area varies
at Group VII sites primarily by expanding or contracting laterally as flows
change.Flow characteristics within backwater pools include near zero
velocities and a calm surface,as compared to the broken and rapidly moving
water of riffles.
ns rae 0 ngi tu ~i naJ_'L~ri a t i_0 tl_i n _s tr~_a_mb_e_d__te)ctu~e__o-c-cu.l"s--ir:t---------
-~.~-~-~~------~-_._~-----_..~-~~----
Group VI!specific areas.Riffles are composed of rubble and "boulder size
substrates,whereas backwater areas tend to have sandy beds.Periodic high
flows may temporari ly expose coarse sediment i n backwa~~r pool s whi ch is
subsequen tl y coveredbysa,nct anc1 __lijltdllri Og peri ods of low fl ow.High
turbidities also prevail at these sites since upwelling is not present.
116
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Modeling Site 119.2R is the sole representative of the 7 specific areas
classified within Group VII.This site possesses the typical riffle/pool
sequence characteristics just described (Plates A-27 and A-28 in
Appendix A).As indicted in Figure 56,a basal level of wetted surface
area and juvenile chinook WUA is maintained under non-breached conditions
by backwater effects.Peak rearing habi tat potential occurs shortly after
the berm at the head of the site is overtopped and the riffle area is
inundated.The relatively broad width and uniform elevation of the head
berm strongly influences the distribution and amount of juvenile chinook
habitat at Site 119.2R.Areas of usable habitat within the riffle rapidly
'expand until local velocities begin to exceed tolerable limits which in
turn prompts a decline in rearing habitat.Maximum WUA values are forecast
for discharges of 12,500 to 13,000 cfs,when juvenile chinook WUA is nearly
four times greater than WUA present under non-breached conditions (39.3
versus 10.5 sq.ft./ft.).
Gross habitat is widely distributed throughout Site 119.2R at flows ranging
up to 17,000 cfs,as demonstrated by the GHA response to discharge in
Figure 56.However,habitat availability and quality,as indexed by HAl
and HQl values,begins to diminish appreciably around 12,000 cfs.Peak HAl
and HQl estimates were similar at 40 percent,a fairly high value in
comparison to other modeling sites.The minimum HAl value was 3 percent at
35,000 cfs.This HAl value was estimated by extending the WSA and WUA
curves by eye for discharges exceedi ng 20,000 cfs (Hi 11 ia rd et a 1.1985).
The HQI curve was not extrapolated past 20,000 cfs,but HQI val ues may be
expected to be higher than HAl values to a degree which is proportional to
·t
the difference between gross habitat area and .wetted surface areas at high
discharges.
117
o 4000 8000 12000 16000 20000 2~000 28000 32000 36000 ~ooo
J
1
'1
1
1
.!
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1
·1
1
1
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Mainstem Discharge (efs)
118
SITE 119..2R
Mainstem Discharge (efs)
--"\'--'--"V "-
,...•._.~
•!{II
~ooo 8000 12000 16000 20000 2~000 28000 32000 36000 ~OOO
Surface area and chinook rearing habitat index response curves
for mOdeling site 119.2R.
A -Wetted surface ~rea (WSA),gross habitat area (GHA)and
weighted usable area (WUA).
B -Habitat availability index (HAn,habitat distribution
index (HOI)and habitat quality index (HQI)response
functi ons.
10
O-l---r---r---......----.---_-......----.---_--.-----l
8
100
90
---~---_•..._--~
so
70
....60c:eu 50c.Jc:..eu .coc..
A180
162
.144-·....126-"'-·108....-·90C"
..!!!72
n:J 54euc:..<36
18
0
0
Fi gure 56.
HAl functions derived from modeling results for Site 119.2R display the low
breaching flows and comparatively large habitat potential at low discharges
associated with specific areas of Representative Group VII (Figure 57 and
Appendix B)..Within a narrow range of low mainstem discharges (10,000 to
13,000 cfs),HAl values compare favorably with peak HAl values recorded for
speci fi c areas from other groups.The marked decl i ne in habi ta t ava il-
ability at higher flows and the overall poor structural habitat quality
(i.e.,low SHI val ues)of Group VII si tes suggests that hydraul i c geometry
plays a more important role than does object cover in determining the
collective rearing habitat potential of this group.
As was the case for side channels comprising Representative Group IV,which
are characterized by similarly low breaching discharges,the seven specific
areas of Group VII provide notably greater amounts of usable rearing
!]habitat at low than at high mainstem flows,as evidenced by the aggregate
WUA functi on in Figure 58.Thi s resul ts from the com para tively high HAl
values which occur immediately subsequent to breaching and their rapid
decline at higher flows.Juvenile chinook WUA peaks at 0.3 million square
feet at 8,000 cfs,remains·at this level through 13,000 cfs and declines to
0.08 million square feet at 35,000 cfs.
u
U
IJ
119
I
REPRESENTATIVE GROUP VII
I
SITE 119.2R
n =7
,.-··-···-1·--1-,--,I
4000 BOOO 12000 i 16000 20000 24000 2BOOO 32000 36000 40000
i
MAINSTEM DISCHARGE rCFS)
i
i
Figure 57.
i i
Response of chinook rearing habitat availability to mainstem
d,is~harge within no~-modeled specific areas of the middle
Sllus~tna River W.hiCh I,are associated with mOdeling site 119.2R
of representative G10Up VII.
I [.
~'-------'~~------..'
Figure 58.Aggregate response of A -wetted surface area (WSA)and B -
chinook rearing habitat potential (WUA)to mainstem dis-
charge in specific areas comprising Representative
Group VII of the middle Susitna River.
121
3.8 Representative Group VIII
This group is comprised of 22 specific areas which tend to dewater at
intermediate to high mainstem discharges.,The absence of an upwelling
groundwater supply may be due to the local structural geology and the
location of the channels relative to sources of subsurface flow.Aaserude
et ale (1985)noted that the heads of channels included in Group VIII were
frequently oriented at a 30 0 +angle to the adjacent mainstem channel.
Apparen tl y ground wa ter flow is ei ther di verted away from these si tes or
occurs at a lower elevation than the bed elevation of the exposed channels.
IJ
In spite of their tendency to dewater,specific areas in Group VIII are
similar to specific areas assigned to Groups II and III in their
hydrologic,hydraulic,and morphologic properties.Therefore,because
Group VIII does not possess a specific area with a rearing habitat modeling
~~~~sjte,_HJU_functions based on modeling~-s~i·tesfY'om Represen·ta~t~iveGroups ll~-
and III were used to represent Group VIII in the habitat extrapolation
process.An obvi OUS requi rement was tha t the habi ta t functi ons for
modeling sites selected to represent this group be modified to reflect the
_..,~,~._~,_.~_~o~LJ.C>.~§,.()LL~~rtlJ.g hg.bttat.as.~_ma instem.stagedeclines.below..-headberm·..···....-
~~~'-'eleva tlon s-:-"'Cand i da-te mode'll"g sites i ncl"L1desii 144:'41..fr o~Gro~p-ii 'a ~d ....~.._,
Site 132.6L from Group III.The first modeling site is recommended by its
high breaching discharge,its morphological similitude with several
Group VIII specific areas,and by the genera 1 shape of its habitat response
curves.Figure 24 illustrates the WSA,WUA and HAl curves which have been
derived from Site 144.4L to represent a subclass of Group VIII specific
areas.Note tha t the 1efthand 1i mb of the curves have been trunca ted at a
breaching flow of 21,000 cfs.
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Si te 132.6L has been selected to represent the subclass of specifi c areas
from Group VIII which dewater at intermediate discharges.Based on an
examination of aerial photography obtained at several mainstem flows,these
specific areas and Site 132.6L possess similar longitudinal and cross
sectional profiles.Site 132.6L,which breaches at 10,500 cfs,eventually
dewaters at 6,000 cfs as the water surface elevation drops below the eleva-
tion of the groundwater table (Figure 32).However,the revised modeling
site habitat response curves have been truncated at 10,500 cfs to
accurately reflect the rapid dewatering which occurs at Group VIII specific
areas.
HAl curves are presented in Figures 59 and 60 with aggregate WSA as
Figure 61.All specific areas in this Representative Group dewater at
intermediate discharge levels.Specific areas were grouped on the basis of
exposed streambed composi tion.The 15 speci fi c areas represented by si te
132.6L all possess streambeds lined with sand indicating low velocity or
backwater i~fluenced hydraulic conditions exist when these sites are
breached.The 9 specific areas associated with site '144.4L have channel
beds.consisting of large gravels and cobbles indicating that these specific
areas possess much higher veloci ties when breached.I
Since all of the specific areas associated with Group VIII are dewatered by
8,000 cfs,juvenile chinook habitat does not exist at flows below this
value.This is reflected in the aggregate rearing WUA curve developed for
Group VIII (Figure 61).WUA accumulates rapidly as the specific areas
become breached and peak values (0.7 million square feet)are attained at
29,500 cfs.Rearing habitat potential declines slightly at higher flows.
123
~EPRESENTATIVE GROUP VIII
MAINSTEM OISCmARGE
SITE 132.6L
n =14
40000360003200028000
(CFS)
240002000016000
I
1200~
I
!
8000
i~ooo
[
40.00
36.00
32.00 -
"0 28.00Cl.....
X 2UO
c:t'
CJ)
X 20.00.............<tN:::::l~~16.00
H 12.00
<t:c
8.00
4.00
0.00
I
0
Figure 59.
,i
I I
!Response ofchin~ok rearing habitat availability to mainstem
Idischarge withinl non-modeled specific areas of the middle
ISusitna River wh'ch are associated with modeling site 132.6l
lof Representativ~Group VIII.
i I
....:4~--
REPRESENTATIVE GROUP VIII
SITE 144.4L
n =8
40.00
36.00
32.00
(3
28.000
..-f
X 24.00«en
3:20.00.........I-'«N ~Ul ~16.00
H 12.00«::I:
B.OO
4.00
0.00 ..
0 ,(000 BOOO 12000 16000 20000 24000 28000 32000 36000 40000
Figure 60.
MAINSTEM DISCHARGE (CFS)
Response of chinook rearing habitat availability to mainstem
discharge within non-modeled specific areas of the middle
Susitna River which are associated with modeling site 144.4L
of Representative Group VIII.
WSA
1
1
1
1
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1
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1
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1
1
MAINSTEM DISCHARGE (CFS)
126
Aggregate response of'A -wetted surface area (WSA)and B -
chinook rearing habitat potential (WUA)to mainstem dis-
charge in specific areas comprising Representative
Group VIII of the middle $usitna River.
4000 8000 12000 16000 20000 24000 28000 32000 36000 40000a
.20
e
.
C"
(I)
4000 8000 12000 16Q00 20000 24000 28000 32000 36000 40000
REPRESENTATIVE GROUP VIII
B
MAINSTEM DISCHARGE OCFS)
<%:
~.10
0.00 -1---,----r-=-,...--..,.---,----r--r--..,.---,---l
....
e
(I)ce...............
.
.&J....
Figure 61.
1.00 ..,....-----------------------,
_~~_________~_---=----=---.90-=1-~--------------------
1
I J
3.9 Representative Group IX
This group contains 21 specific areas categorized as mainstem and mainstem
shoal habitat with mean reach velocities greater than 5 fps at 10,000 cfs.
These sites usually convey a significant percentage of the total discharge,
and possess small length to width ratios.
Modeling sites 101.5L and 147.1L are large channels classified as
mainstem habitat over the entire 5,100 to 23,000 cfs flow range (Plates A-
29 through A-32 in Appendix A).Site 101.5L represents those specific
areas which are generally shallower and possess lower velocities than those
represented by Si.te 147.1L.As many areas possess vel oci ties greater than
2.5 fps the modeling sites provide little juvenile chinook habitat in
relation to the total volume of water they convey.This conclusion is
strengthened by the large differences observed between WSA and GHA esti-
mates and the low rearing WUA values forecast for all mainstem discharges
(Figures 62 and 63).Wetted surface areas change at comparatively slow
rates as discharge varies at both sites due to their large size and a
tendency to compensate for varying flow more through adjustments in water
depth and velocity than in top width.
Both GHA and WUA increase slightly at higher mainstem discharges;thus,the
availability of usable rearing habitat and its distribution within the
.modeling sites tends to remain constant throughout the range of evaluation
flows.In a detailed analysis of cross section velocity profiles at
Si tes 101.5L and 147.1L,Williams (1985)noted that sui table reari ng areas
are confined to nearshore zones in the channels,primarily along the gently
sloped island banks,due to high mid-channel velocities.The ratio of
127
\ I
II
SITE'10 1.5l
A
450
~5j
-360·.u 3~~............·270.u....·2250"
.El I
180 I
n::J 135 ~euc..
90-1-<
45
0
0
__,_,_,oIlS4--.--'--'--'--'--.--'r'--'
-\---"'_-----SliA.......--.-.....-...-
4000 8000 12000 16000 20000 2400028000 32000 36000 40000
I I
"
I J
I 1
J
I 1
J
Mainstem Discharge (cfs)I 1
I J
B
I I
I J
I )
I
I I
j
I I
I J
I
I I
I I
r
:::/._~.-=..~_.__--L ....~..~~........-=-.-HIlI-··-
'-\
",-.-_.--_......--._""",--,_~'--'-'HIlI
10
O-l----..--,.--..,...-....,.----,.--..,...--.....----.--.....--~
100 ...,.-.---------.,..--------:..------.....,
90
80
70
~60 l
~50-1l:-euc..-40
30
..----.----_._..--'"20·'
o 4000 8000 12000 16000 20000 24000 28000 32000 36000 40000
Ma instem D~s~~~rge.lcfs)
I I
.I
I I
Figure 62.Surface area and chinook rearing habitat index response curves
for modeling site lOl.5L.
A -Wetted surface area (WSA),gross habitat area (GHA)and
weighted usable area (WUA).
B -Habitat availability index (HAI),habitat distribution
index (HOI)and habitat quality index (HQI)response
functions.
I 1
1
I I
I J
128
I
!J
\-----__'"'--_-_---GHA
\..-----
_·-WSA_._.
...-'--.--.--'---.--.--'.,....-.
--'
A
300
270 -
240 --·-4-J 210 -......-....·180 --4-J.......·150 -c::r
.:!!
120 -
C'C 90 -OJc..
0<:60 -
30 -
0
0
I
4000
I
8000
I
12000
I
16000
I
20000
j I
24000 ·28000
!lUATT
32000 36000 40000
8
100
90 -
i I ao -
cJ
70 -
-4-J 60 -c
OJu 50 -c..
OJc...40 -
30 -
20 -
10 -
a
il
Mainstem Discharge (efs)
\
\..
'\.....-.-'-""-'-:J--.-";"I_.--e::::r-.:::x:::='-IllJ
_____\.000-'--'-HGI------HAl
I I J J I I 1
4000 BOOO 12000 16000 20000 24000 28000 32000 36000 40000
Mainstem Discharge (efs)
j I
C,J
Fi gure 63.Surface area and chinook rearing habitat index response curves
for modeling site 147.1L.
A -Wetted surface area (WSA),gross habitat area (GHA)and
weighted usabl e area (WUA).
B -Habitat availability index (HAl),habitat distribution
index (HOI)and habitat quality index (HQI)response
functi ons.
129
juvenile chinook WUA to wetted surface area at these sites is very low,on
the order of 5 percent or less.These values are considerably lower than
HAl estimates obtained for modeling sites from other representative groups.
The ratio of WUA to GHA is predictably higher,ranging up to 22 percent,
but also slightly lower than HQI ratios calculated for other sites.Taking
these indi ces into account,the juveni le chi nook habi tat potential wi thin
Group IX specific areas is judged to be inferior in quality.
Using the HAl functions developed for Sites 101.5L and 147.1L as templates,
HAl curves were deri ved for speci fi c areas wi thin Group IX.Adjustments
were made to account for differences in breaching flow and structural
habitat quality.In regard to structural habitat,the mean SHI value for
specific areas in this group is high compared to other representative
groups.This results from the large substrate sizes which predominate in
the high 'velocity channels and the high cover value assigned to them in the
..__~lil.~~L~~lit1;jOJ1S.__El~veJ]J)j:the 21 specific areas wi thin-Gr-oup·-IX ha-ve ....
been grouped with Si te 101.5L;the rema in i ng 10 sites are repre sen ted by
si te 147 .1L.HAl functi ons deri ved for mode 1ed and non-mode 1ed spec i fi c
a reas are presen ted in Fi gures 64 and 65 and the aggrega te WSA re spon se
curve for IX in Fi ure 66.
The collective rearing habitat potential of the 20 specific areas in
Group IX increases from 0.3 mi 11 i on square feet at 5,000 cfs toa peak of
0 ..6 million square feet at 27,500 cfs (Fjgure 66).Aggregate WUA val ues
increase steadily over this flow range although the rate of change is very
low in com pa ri son to other represen ta ti ve groups,with the excep ti on of
Group I (upland sloughs),being only slightly greater than the rate of
change in wetted surface area.Juvenile chinook WUA remains constant at
REPRESENTATIVE GROUP IX
32000
10.00
9.00
8.00
'0
0 7.00......
><6.00«
U)
3:5.00'-.......«
w :;:)
.......~UO
H 3.00«:c
2.00
1.00
0.00 •
0 ~ooo 8000 12000 16000 20000 2.4000 28000
SITE 101.5L
n :::11
36000 .coooo
Figure 64.
MAINSTEM DISCHARGE (CFS)
Response of chinook rearing habitat availability to mainstem
discharge within non-modeled specific areas of the middle
Susitna River which are ~ssociated with modeling site 101.5l
of Representative Group IX.
RBPRESENTATIVE GROUP IX
4000036000
SITE 147.1l
n =10
320002800024000200001600012000BOOOI
4,000\
5.00
4.50
4.00
'0 3.500
...-f
X 3.00
<t
(J)::c 2.50'-.......<tW:::l
2.00N~
H 1.50<t:r:
LOO
.50
0.00
I
0
(CFS)MiINSTEM DISCHARGE
i
I
I I !,!!
IRe~ponse of chinookl rearing habitat availability to mainstem
I di~Charge within nqn-modeled specific areas of the middle.
Su~itna River ~hic~are -associated with modeling site 147.1L
pfl Representatlve Group IX.
I'
Figure 65.
'-----~----......:~-:-1£',---
REPRESENTATIVE GROUP IX
A
18.00
liSA
-16.20
11 ~'14.40
·g 12.60
~10.80
en 9.00c
0.....7.20.................5.40e
3.60
«en 1.803:
0.00
0 4000 BOOO 12000 16000 20000 24000 2BOOO 32000 36000 40000
MAINSTEM DISCHARGE (CFS)
B
1.00
.90·~.BO......·CT .70 WUA°en
.......600
en .50c
0......40......
.-4......30e
.20
«
::::J .10:3:
0.00
0 4000 BOOO 12000 16000 20000 24000 2BOOO 32000 36000 40000
MAINSTEM DISCHARGE (eFS)
Figure 66.Aggregate response of A -wetted surface area (WSA)and B -
chinook rearing habitat potential (WUA)to mainstem dis-
charge in specific areas comprising Representative
Group IX of the middle Susitna River.
133
higher flows as increases in wetted surface area are offset by gradual
reductions in rearing habitat availability.
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3.10 Representative Group X
Representative Group X is made up of "mainstem shoals and mainstem margins
11
which displayed signs of upwelling in the winter aerial photography.
As discussed in the methods section,Representative Group X did not possess
RJHAB or PHABSIM models.Unlike Group VIII,which was in a similar
position,none of the other models available were representative of the
specific areas in this group.Therefore a WUA response curve was developed
using Direct Input Ha~itat (DIHAB)models for spawning chum habitat which
\were available for five of the sites.These sites are illustrated in
Plates A33 through A42.
I~J The DIHAB model uses substrate composition.and upwelling data from one or
more cross sections as well as measured depths and velocities for several
I \i..)
i IlJ
\IL....;
I ]U
(.J
mainstem discharges to calculate WUA and WSA at each observed streamflow.
WUA and WSA indices for unobserved streamflows within the range of observed
values are determined by linear interpolation between calculated WUA and
WSA indices.Outside the range of observed values,WUA and WSA indices may
be estimated on the basis of trend analysis and field experience (Hilliard
et al.1985).
The chum spawning DIHAB model s were converted to juvenile chinook DIHAB
models as follows.Depth and velocity suitability curves for spawning chum
were replaced by depth and velocity suitability curves for juvenile
chinook.The substrate suitability curve for spawning chum was replaced by
135
the cover suitability criteria for juvenile chinook under turbid water
conditions.The upwelling criteria was eliminated.
WUA and WSA response curves were developed for each of the five modeled
sites.They were extended beyond the range of available data by regression
analyses to encompass the mainstem discharge range 5,000 to 35,000 cfs.
Trends,apparent from the plotted points,indicated where more than one
relationship was required to describe the response of WSA or WUA to
mainstem discharge.
In all cases WSA increased with mainstem discharge.The maximum WSA for
each site was determined by summing the product of cross section width and
representative reach length for all cross sections within the site.Cross
section plots,with water surface elevations at various mainstem discharges
superimposed,w,ere used to identify those discharges at which the
relationship between WSA and mainstem discharge might be expected to
change.For Representative Group X sites such changes were coincident with
discharges at which shoals become inundated.
WUA generally decreased wi th rna instem discharge.Some fl uctua ti ons were
--_.__.._.__._------
__~_'=-n6-tea.--"nley'we-re--due~'-to-{~e 0 pti mal ha bi'tat-a t thecr~ssie~ciL~~~s_Jif~a-- ,..
site peaking at different mainstem discharges.Velocity data and cross
sectional geometry were used to verify WUA forecasts beyond the range of
data •
HAl values were calculated (as WUA/WSA x 100)for each discharge associated
with a data set,for each dischar'ge where a change in the relationship
between WSA or WUA and mainstem discharge had been noted,and for 5,000 cfs
136
(
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and 35,000 cfs.Through linear interpolation,HAl values for 5,000 to
35,000 cfs in 500 cfs increments were obtained.The HAl curves for the
five modeled sites were very similar.In all cases the HAl was maximum at
5,000 cfs,and the rate of decline decreased with mainstem discharge.
Values of WSA for the eight nonmode1ed sites of Representative Group X were
obtained through the use of aerial photography.The areas were digitized
from 1"=250'scaled leria1 photos taken when mainstem discharge was
5,100,10,600,16,000,and 23,000 cfs.Regression analyses provided WSAs
for 5,000 to 35,000 cfs in 500 cfs increments.
To calculate WUA for the eight nonmode1ed sites,a composite HAl curve was
first developed.Extrapolation of the HAl response curves"for the modeled
sites to the nonmode1ed sites consisted of averaging the curves after first
norma 1i zi ng them to an SHI of 0.50.
HAI O•50 =HAISHI x (0.50/SHI)
The composite curve was similarly adjusted for the SHI of each nonmode1ed
site before applying it to the corresponding WSA curve,or:
HAISHI =HAI O.50 x (SHI/0.50)
HAl curves are given in Figure 67 and the summation of the WUA and WSA
values for the thirteen sites in Figure 68.
This representative group contains a small subpopu1ation of shoal areas and
ma ins te m mar gin s whie h con ta in up well ing and re ta ina sma 11 am0 un t 0 f
wetted surface area at low mainstem discharge levels.A much larger popu-
1ation of shoal areas become dewatered as mainstem flow decreases.Surface
137
REPRESENTATIVE GROUP X
!
I
iMA]NSTEM DISCHARGE (CFS)
=13
40000
~
Figure 67.
!;
R~sponse of chinoQk rearing habitat availability to mainstem
d~scharge for specific areas of the middle Susitna River
w~thin Representative Group x.
~.....----J
REPRESENTATIVE GROUP X
A
"'SA
500 -r-----------------------,
450
~400.
g 350....e 300
~250c:
~200
:::::Jo.c:150..u
11
100
<t~5:l--~=~=::::::::;:::::=::;==::;:==::;::=:::::::;:::=~A--~
o 4000 BOOO 12000 16000 20000 24000 28000 32000 36000 40000
MAINSTEM DISCHARGE (CFS)
B
lfUAB.OO
-<;::)4.00
3:
40.00 ..,.----:...--------------------,
-36.00
~32.00.
g 28.00.....
e 24.00
~20.00c:coen 16.00
:::::J
"g 12.00..u
\'1\
l(
0.00 -I----r----,-----,.--r---,.---r---,----,----r---;
o 4000 BODO 12000 16000 20000 24000 28000 32000 36000 40000
MAINSTEM DISCHARGE (CFS)
IIIJ Fi~ure 68.Aggregate response of A -wetted surface area (WSA)and B -
chinook rearing habitat potential (WUA)to mainstem
discharge in specific areas comprising Representative
Group X of the middle Susitna River.
139
area measurements of exposed gravel bars (Klinger Kingsley 1985)indicated
that dewatered surface area increases by approximately 1,037 acres as
ma i nstem di scharge decreases from 23,000 cfs to 10,600 cfs.
Because of the difficulty locating upwelling areas during moderate to high
flow periods,the entire subpopulation of shoal areas with upwelling are
not contained in Represen~ative Group X.From examination of air photo
mosaics it is apparent that at ,low mainstem discharges a large amount of
shoal surface area is present that was not included in Representative Group
X.Therefore,the surface area and WUA curves for this group are not
directly compatible with the curve sets for other representative groups as
they contain entire populations of specific areas belonging to a particular
habitat type.In addition,the 13 specific areas which are included in
Representative Group X all possess similar HAl curves (Figure 67)and
result in a composite WUA curve (Figure 68)which is relatively insensitive
·~------~"-"to"~c"han"g"e.·s--i-n-~m"ai-ns"'te-m-dlscnarg-e-:··"Tn er"efore~~WUJCf 0 r e 'cis t s'-for
Representative Group X will be excluded from further consideration in the
extrapola ti on process.
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4.0 SUMMARY·
The physical habitat modeling presented in this report provides a
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quantitative evaluation of the response of juvenile chinook weighted usable
area to incremental changes in streamflow for the middle Susitna River.
Underpinning the extrapolation methodology are several assumptions related
to physical habitat modeling and river stratification procedures.
The primary assumption of the habitat modeling studies is that weighted
usable area (WUA)is an index of physical habitat conditions and changes in
11 WUA are attended by adjustments in the distribution and relative abundance
I j
of juvenile chinook populations.Although other physical and non-physical
components of fish habitat not included in the calculation of ~UA may
influence the survival and growth of juvenile chinook salmon,the physical
environment affects to a substantial degree bioti~processes of the aquatic
community.Moreover,considerable data exist which indicate the importance
of individual microhabitat variables for influencing the distribution of
juvenile chinook within different subenvironments of the middle Susitna
II,j
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River.Hence,physical habitat modeling is an appropriate method for
assessing the influence of project-induced changes in streamflow on
juvenile chi nook habi tat.
Nume'rous environmental variables influence the availability of chinook
rearing habitat and these variables are typically not independent of one
another.Under some circumstances,however,the availability or quality of
juvenile chinook habitat may be governed primarily by one or two variables
whose infl uence is more pronounced than the combined effect of all other
141
142
influence of turbidity on juvenile chinook distribution,not the cause,
drifting invertebrate prey associated with turbid mainstem and side channel
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Nevertheless,if it isoftherelationshipofturbiditytofoodsupply.
applied.
The results of the rearing habitat modeling studies conducted at individual
modeling sites indicate surface area and rearing habitat response curves
are generally more similar within representative groups (where two or more
Water clarity was treated as a cover variable in the physical habitat
modeling studies since our present understanding of turbidity,food avail-
ability,and juvenile chinook distribution does not warrant an evaluation
flow whi ch juveni le chi nook are respondi ng to rather than the cover value
of turbidity,the physical habitat model r'emains valid.It is the
The influence of water clarity was incorporated into the modeling process
environmental variables.An example is the positive correlation during the
summer growing period between juvenile chinook distribution and turbid
water.This may reflect the value of turbidity as cover for juvenile
chi nook as re pOl'te d by 0uga net a 1.(19 84)0 r i t may ref1e eta grea te r
abundance of drifting inverteb'rate prey in the turbid mainstem and side
channel habitats than in clear water sloughs.
through the application of separate clear a'nd turbid water habitat suit-
, ,ability criteria for j uveni 1ec~j I1QQk.~...CJ!=!j:!r.w.a:t.er.velocJtyandcover ..-,
_."'-'-_.'-'""-~--'"~~~----"--"-"-"'---""""-'..•__._.._,-----.-----.---_._._._-,-.~-""_..__._---..•....•....•._--_.._-__._-.--_..--,,-____..-.__-__-_,.....•-,_..___--_...•••...._--.--'.".,--_.....-...
------------_..__.------,----_.,
'---"'--slIrtaofrrtycri-terfa-were used to'cal cul a tere'aring-WUA'i nct ices for
model ing si tes under non-breached conditions.Following breaching high
turbidities prevailed at the modeling sites and turbid water criteria were
mode 1i ng si tes occur)than between groups.The amount of reari ng habi ta t
available at a particular site is strongly affected by the mainstemdis-
charge at which its upstream berm is overtopped.Under non-breached condi-
tions,juvenile chinook habitat is typically relatively small.The combi-
nation of the influ,x of turbid water to the channel and the increase in its
wetted surface area which accompany breaching typically increases the
availability of rearing habitat significantly.Positive gains of WUA
I'IJ continue,but at a gradually declining rate,as mainstem discharge
increases and water velocities at the site remain favorable.Juvenile
chinook habitat tends to decrease more rapidly in smaller channels as
mainstem discharge increases than in larger channels due to a more gradual
response of near shore velocities to changes in flow in large channels.
Thus,relatively small changes in the availability of rearing habitat occur
as flows increase or decrease in the large side c;han'nels and mainstem.It
should be emphasized,however,that these large side channels and the
mainstem contribute a disproportionately small amount of habitat in
relation to their wetted surface area.
Based on the delineation of specific areas and their classification into
the representative groups described by Aaserude et a1.1985,we have
developed aggregate rearing habitat response functions for the majority of
the subenvironments which directly respond to changes in mainstem dis-
charge.These are summarized in Figure 69.We have not combined WUA
iJ va 1ues for the represen ta ti ve groups to obta in an aggrega te WUA value for
the entire middle Susitna River.Evidence of variability in juvenile
chinook abundance and distribution between repres~ntative groups is
provided by Hoffman (1985),suggesting that WUA indices for different
143
REPRESENTATIVE GROUPS I-IX
6
. 1
20000
____-2 8--..-------..L:.--:::._--==_-=.....5 7-;:::..;:::::--------------<-=----._----
16000
--~--------..-..-
./
./
/"
/'/__.__.-.-9----/_._._.-...---.-./.
30.00
27.00
2~.00
21.00....-r::ren 18.00-Q
en 15.00c:
Q..............12.00-e
<9.00~
6.00
3.00
0.00
0
MAINSTEM'OISCHARGE (efs)
REPRESENTATIVE GROUPS I-IX
5.00 -.----.....:---------------..,.------------......,
4.00
400003600032000280002~0002000016000120008000
--\
\
o
.50
1.00
:3 1.50
::J:
-Q
~2.50
Q-~~==·==···=_~=-2.00--1-..-~-.--.--.----.--".-.."..-_------.-----..~----~-.----~--·-·-""···---·"·-I~-"~-·.----.-.
MAINSTEM OISCHARGE (efs)
1
Figure 69.Comparison of the aggregate response of chinook rearing
habitat [WUA]for Representative Groups I through IX.
144 'J
representative groups may require adjusting for utilization prior to being
aggrega ted.
Other considerations which should be addressed prior to drawing final
11 concl usi ons from the habi ta t response functi ons provi ded in thi s report are
the influences of food availability and water temperature on the quality of
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rearing habitats.In addition such seasonal aspects as availability of
chi nook overwi nteri ng habi tat shoul d be consi dered.The habi tat model i ng
results presented in this report are not directly applicable to evaluations
of winter habitat since hydraulic characteristics and fishbehavior are..
different at this time of year.In regard to the open water period,
however,time series and habitat duration analyses at the representative
group level are recommended for comparisons between groups and flow
regimes.Whereas the primary utility of the WUA response functions is
"-
the.ir application to existing habitat conditions,the general shape of the
WUA response functions are also well-suited to assessing with-project
effects on juvenile chinook habitat.
145
LITERATURE CITED
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IJ
IJ
\1
LITERATURE CITED
Aaserude,R.G.,J.Thiele,and D.Trudgen.1985.Chara:cterization of
aquatic habitats in the Talkeetna-to-Devil Canyon segment of'the
Susitna River,Alaska.Preliminary draft report.E.Woody Trihey and
Associates and Arctic Environmental Information and Data Center,
University of Alaska,Fairbanks.Alaska Power ALithority.Susitna
Hydroelectric Project.1 vol.
Alaska Dept.of Fish and Game.1983.Phase II basic data report.Vol.4:
Aquatic habitat and instream flow studies,1982.Parts I and II.
367 pp.'
Alaska Power Authority.1985.Amendment to the application for license
for major project,Susi tna Hydroe 1ectri c Project,before the Federal
Energy Regulatory Commission.Draft.Exhibit E,Chaps.2 and 3.
Alaska Power Authority.Susitna Hydroelectric Project.Vols.6,7,8
and 9.
Bovee,K.D.1982.Aguide to stream habitatanalysis using the instream
flow incremental methodology.U.S.Fish ,and Wildlife Service.
Insteam Flow Information Paper 12.1 vol.
Dugan,L.J.,D.A.Sterritt,and M.E.Stratton.1984.The distribution and
relative abundance of juvenile salmon in the Susitna River drainage
above the Chulitna River confluence.51 pp.Part 2 in Schmidt,D.C.,
et al.Report No.2.Resident and juvenile anadromous fish investi-
gations (May -October 1983).Susitna Hydro Aquatic Studies,Alaska
Dept.of Fish and Game.Report for Alaska Power Authority,Anchorage,
AK.Document 1784.1 vol.
Estes,C.C.,and D.S.Vincent-Lang,e'ds.1Q84.Report No.3.Aquatic
habitat and instream flow investigations (May -October 1983).Chapter
7:An evaluation of chum and sockeye salmon spawning habitat in
sloughs and side channels of the middle Susitna River.Susitna Hydro
Aquatic Studies,Alaska Dept.of Fish and Game.Report for Alaska
Power Authority,Anchorage,AK.Document 1936.1 vol.
Hale,S.S.,P.M.Suchanek,and D.C.Schmidt.1984.Modeling of juvenile
salmon and resident fish habitat.48 pp.Part 7 in Schmidt,D.C.,et
al.Report No.2.Resident and juvenile anadromous fish investigations
(May -October 1983).Susitna Hydro Aquatic Studies,Alaska Dept.of
Fi s h 'and Ga me.Report for Ala ska Power Au thori ty,Anchorage,AK.
Document 1784.1 vol.
Harza-Ebasco Susitna Joint Venture.1985.Susitna hydroelectric project
case E-VI a1 terna tive flow regime:Vol ume 1,rna in report.Report for
Alaska Power Authori ty,Anchorage,AK.
Hilliard,N.D.,et al.1985.Hydraulic relationships and model
calibration procedures at 1984 stUdy sites in the Talkeetna-to-Devil
Canyon segment of the Susitna River,Alaska.E.Woody Trihey and
Associates.Report for Alaska Power Authority,Anchorage,AK.1 vol.
146
Hoffman,A.G.1985.Report No.9.Summary of sa 1 mon fi shery da ta for
selected middle Susitna River sites.Susitna Hydro Aquatic Studies,
Alaska Dept.of Fish and Game.Report for Alaska Power Authority,
Anchorage,AK.1 vol.
Klinger,S.,and E.W.Trihey.1984.Response of aquatic habitat surface
areas to mainstem discharge in the Talkeetna-to-Devil Canyon reach of
the Susitna River.E.Woody Trihey and Associates.Report for Alaska
Power Authori ty.Susi tna Hydroel ectri c Project.Document 1693.
1 vol.
Loar,J.f4.,ed.1985.Application of habitat evaluation models in
southern Appalachian trout streams.Oak Ridge National Laboratory.
Environmental Sources Division pUblication no.2383.310 p•.
Marshall,R.P.,P.M.Suchanek,and D.C.Schmidt.1984.Juvenile salmon
rearing habitat models.51 pp.Part 4 in Report No.2.Resident and
juvenile anadromous fish investigations (May -October 1983).Susitna
Hydro Aquatic Studies,Alaska Dept.of Fish and Game.Report for.
Alaska Power Authority,Anchorage,AK.Document 1784.1 vol.
Milhous,R.T.,D.L.Weyner,and T.Waddle.1984.Users guide to the
Physi cal Habi tat Simulation System.In stream F1 ow Informa tion Paper
11.U.S.Fish and Wildlife Service.FWS/OBS -81-43 revised.475 p.
Milner,A.M.1985.A framework for the assessment of chinook salmon
rearing in the middle Susitna River under al.tered flow,temperature
and sedi ment regi me.E.'Woody Tri hey and Associ a tes.Report for
Alaska Power Authority,Anchorage,AK.69 p.
Moulton,L.L.,et al.1984.Fish mitigation plan.Woodward-Clyde
Consultants.Report for Alaska Power Authority.1 vol.
Nelson,F.A.1980.Evaluation of four instream flow methods applied to
four trout rivers in southwest Montana.Montana Department of Fish,
Wildlife and Parks,Bozeman,Montana.105 p.
Suchanek,P.M.,R.P•Marshall,S•S•Hale a nd _D LC..S_c..hmJ..d_t....._1.9.84...........
·-·----·-·--.-.-Juvenlresa,1mo·n"reari ng"suitabil--:rtY-crfteria.~49J?IL__Part 3 in D.C •
..·,,--·--...."·Scnmnrt-----era-r:;-eci's:---Report No;-"2-.-Resi dent and j uveni 1e anadromous
fish investigations (May -October 1983).Susitna Hydro Aquatic
Studies,Alaska Dept.of Fish and Game.Report for Alaska Power
Authority,Anchorage,AK.Document 1784.1 vol.
Steward,C.R.1985.Suitability criteria recommended for use in IFR
habitat modeling studies of the middle Sl.Isitna River.Technical
Memorandum..E.Woody Trihey and Associates,Anchor~ge,AK•.Upp.
Steward,C.R.and E.W.Trihey.1984.Fish habitat and instream flow
relationships in the middle reach of the Susitna River:An
extrapolation methodology.Unpublished manuscript.
147
1
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J
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]
J
1
]
]
I
]
]
j
]
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U
IJ
L Woody Trihey and Associates and Entrix.1985.Instream flow
relationships report.Volume 1.Working draft.Alaska Power
Authority.Susitna Hydroelectric Project.1 vol.
Trihey,E.W.,and J.E.Baldrige.1985.An empirical approach for
evaluating microhabitat response to streamflow in steep-gradient,
large bed-element streams.Paper presented at symposium on Small
Hydropower and Fisheries,Aurora,CO.American Fisheries Society.
8 pp.
Williams,S.1985.The influence of middle Susitna River discharge and
suspended sediment on mainstem and side channel rearing habitats.
Technical memorandum.E.Woody Trihey and Associates,Anchorage,AK.
45 pp.
148
APPENDICES
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APPENDIX A
AERIAL PHOTOGRAPHY OF MODELING SITES
.(PLATES A-I THROUGH A-42)
149
Plate A-1 Aerial photography of modeling site 107.6L at mainstem discharges of 23,000
cfs and 16,000 cfs.Site breaches at>35,000 cfs and is included in Represen-
tative Group I.--
150
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Plate A-2 Aerial photography of modeling site 112.5L at mainstem discharges of 23,000
cfs and 16,000 cfs.Site breaches at >35,000 cfs and is included in Represen'::
tative Group I.._-
151
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tJ'
Plate A-3 Aerial photography of modeling site 101.4L at mainstem discharges of 23,000
cfs and 16,000 cfs.Site breaches at 22,000 cfs and is included in Represen-
tative Group II.
152
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[J.
Plate A·4 Aerial photography of modeling site 113.7R at mainstem discharges of 23,000
cfs and 16,000 cfs.Site breaches at 24,000 cfs and is included in Represen-
tative Group II.
153
I )
II
I )
I II \
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Plate A-5 Aerial photography of modeling site 126.0R at mainstem discharges of 23,000
cfs and 16,000 cfs.Site breaches at 33,000 cfs and is included in Represen-
tative Group II.
154
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Plate A-26 Aerial photography of modeling site 136.3R at mainstem discharges of 12,500
cfs and 7,400 cfs.Site breaches at 13,000 cfs and is included in Representative
Group VI.
155
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Plate A·7 Aerial photography of modeling site 101.2R at mainstem discharges of 23,000
cfs and 16,000 cfs.Site breaches at 9,200 cfs and is included in Representative
Group III.
156
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Plate A-a Aerial photography of modeling site 101.2R at mainstem discharges of 12,500
cfs and 7,400 cfs.Site breaches at 9,200 cfs and is included in Representative
Group III.
157
IJ
Plate A·10 Aerial photography of modeling site 128.8R at mainstem discharges of 12,500
cfs and 7,400 cfs.Site breaches at 16,000 cfs and is included in Representative
Group III.
159
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Plate A-11 Aerial photography of modeling site 132.6L at mainstem discharges of 23,000
cfs and 16,000 cfs.Site breaches at 10,500 cfs and is included in Represen-
tative Group III.
160
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Plate A-12 Aerial photography of modeling site 132.6L at mainstem discharges of 12~500
cfs and 7,400 cfs.Site breaches at 10,500 cfs and is included in Representative
Group III.
161
u
Plate A-13 Aerial photography of modeling site 141.4R at mainstem discharges of 23,000
cfs and 16,000 cfs.Site breaches at 11,500 cfs and is included in Represen-
tative Group III.
162
Plate A-14 Aerial photography of modeling site 141.1R at mainstem discharges of 12,500
cfs and 7,400 cfs.Site breaches at 11,500 cfs and is included in Representative
Group III.
163
r 1
Plate A-15 Aerial photography of modeling site 112.6L at mainstem discharges of 23,000
cfs and 16,000 cfs.Site breaches at <5,100 cfs and is included in Represen-
tative Group IV...-
164