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HomeMy WebLinkAboutAPA2898VOLUME 1 MAIN TEXT FINAL REPORT AUGUST 198''S DOCUMENT No.2898 PREPARED BY [XJ~~l£~c=J~[ID~@©@ SUSITNA JOINT VEr~TURE UNOER CONTRACT TO • '1tihey& .'..',Associates :.·.·a.·••.•...•~'.AClUa!ic .Resource "SpedaJists SUSITNA HYDROELE:CTR~C PROJECT FEDERAL ENERGV·REGULATORY COMMISSION PROJECT No.7114 .~.......---Alaska Power Author;~y ---- co -M==N.... 'I:t_'I:t "'-0iii===O <0 1.0,:~I ~J HYDRAULIC RELATIONSHIPS AND MODEL CAL.eRATION PROCEDURES AT 1984 STUDY SITES IN THE TALKEETNA-TO- DEVIL CANYON SEGMENT OF THE SUSITNA RIVER,ALASKA HYDRAULIC RELATIONSHIPS AND MODEL CALIBRATION PROCEDURES AT 1984 STUDY SITES IN THE TALKEETNA-TO-DEVIL CANYON SEGMENT OF THE SUSITNA RIVER,ALASKA - \. ''0 SUSITNA HYDROELECTRIC PROJECT Prepared by N.Diane Hilliard Shelley Williams Eo Woody Trihey R.Curt Wilkinson Cleveland R.Steward,III Trihey and Associates Under Contract to Harza-Ebasco Susitna Joint Venture Prepared for Alaska Power Authority Document No.2898 Susitna File No.4.3.1.3 TY\ p-IdS <.,'R u....-'0 f L_r=t~ (\0.2-~~ A.Rl..JIS .Alaska Resources Librarv &[nforiTi<tUon ServIces Ancbora~e)Alaska Final Report August 1985 - - -- ACKNQWLEDGH1ENTS Preparation of this report was funded by the Alaska Power Authority as part of the licensing studies for the proposed Susitna Hydroelectric Project.The engi neeri ng and envi ronmenta 1 studi es bei ng conducted to support the Application for License are directed by Harza-Ebasco Susitna Joint Venture. Alaska Department of Fish and Game Susitna Hydro Aquatic Studies Team (ADF&G Su Hydro)provided essential support for the successful completion of the field studies,stage-discharge analysis and model calibration.In addition, - ADF&G Su Hydro had lead responsibility for data base management and preparation of the three appendices which accompany the main text.The ADF&G Su Hydro staff members who participated in the field studies,analyses,and -report preparation are listed below: Andy Hoffmann Karen Meier John McConnaughy Kathy Sheehan Dan Kingsley Mary Shiffer Sheryl Sal asky Kathy Johnson Jim Anderson Jeff Bigler Allen Bingham Donna Buckholtz Alice Freeman ARLIS - 00 M N...... ~ ooC) LO l!) r0- M (If) John McConnaughy developed and appl i ed numerous computer programs whi ch facilitated data reduction and model calibration.In addition he produced the preliminary site-specific W'UA and time series plots.Allen Bingham selected the statistical analyses and assembled the data base necessary to test the degree to which models were calibrated.Special recognition is given to Karen Meie~for completing the stage-discharge analysis and drafting Part II of this report as well as coordinating the ADF&G Su Hydro effort which supported the preparation of this work. Alaska Resources i Library &Information ServIces Anchorage,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 occurring fish populations and habitats is the preferred goal in agency mitigation policies. In 1982,follClwing two years of baseline studies,a multi-disciplinary approach to quantify effects of the proposed Sus i tna Hydroe 1ectri c Proj ect on existing fish habitats and to identify mitigation opportunities was initiated. The Instream Flow Relationships Studies focuses on the response of fish habitats in the middle Susitna River to incremental changes in mainstem discharge,temp1erature and water quality.As part of this multi-disciplinary effort,a technical report series was planned that would (1)describe the existing fish rl~sources 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 sl~asonal availability of fish habitat. The summary report for the IFRS,the Instream Flow Relationship~Report (IFRR),(1)identifies the biologic significance of the physical processes evaluated in the technical report series,(2)integrate the findings of the technical report series,and (3)provide quantitative relationships and discussions reglarding the influences of incremental changes in streamflow, ;i - - - ..... .- stream temperature,and water quality on fish habitats in the middle Susitna River on a seasonal basis. The IFRR consists of two volumes.Volume I uses project reports,data and professional judgement available before March 1985 to identify evaluation species,important life stages,and habitats.The report ranks a variety of physical habitat components with regard to their degree of influence on fish habitat at different times of the year.This ranking considers the biologic requirements of the evaluation species and life stage,as well as the physical characteristics of different habitat types,under both natural and anticipated with-project conditions.Volume II of the IFRR will address the third objective of the IFRR and provide quantitative relationships regarding the influences of incremental changes in streamflow,stream temperature and water quality on fish habitats in the middle Susitna River on a seasonal basis. The i nfl uence of incremental changes in streamflow on the ava il abil ity and quality of fish habitat is the central theme of the IFRR Volume II analysis. Project induced changes in stream temperature and water qual ity are used to condition or qualify the forecasted responses of fish habitat to instream hydraulics.The influence of streamflow on fish habitat will be evaluated at the microhabitat level and presented at the macrohabitat level in terms of a composite weighted usable area curve.This composite curve will describe the combined response of fish habitat at all sites within the same representative group to incremental changes in mainstem discharge . iii 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. - Quantify Wetted Surface Area Response Assess the Representa- tiveness of Modeled and Non-modeled Sites Determine Site- Specific Hydraulic Conditions - Quantify Streamfl ow Dependent Habitat Response Functions for Juvenile Chinook and Spawning Chum Salmon RESPONSE OF AQUATIC HABITAT SURFACE AREAS TO MAINSTEM OISCHARGE IN THE TALKEETNA-TO-DEVIL 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 discharge and presents the necessary photography and surface area measurements to quantify the change in wetted surface area associated with incrementall decreases in mainstem discharge between 23,000 and 5,100 cfs.The report also describes the influence 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 Characteri zati on Report.Surface area measurements presented in thi s report provi de a basi s for extrapolating results from intensively studied modeling sites to the remainder of the middle Susitna River. iv - - CHARACTERIZATIOIN OF AQUATIC HABITATS IN THE TALKEETNA-TO-DEVIL 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 type to another in response to incremental decreases in mainstem dis- charge 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 fjj e1d reconnaissance surveys.Representati ve groups and structural habitat indi~es 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. 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-speci fi c habitat responses to incremental changes in depth and velocity for both steady and spatially varied streamflow conditions.Summaries of site-specific stage-discharge 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. RESPONSE OF JUVENILE CHINOOK AND SPAWNING CHUM SALMON HABITAT TO MAINSTEM DISCHARGE IN THE TALKEETNA-TO-DEVIL CANYON SEGMENT OF THE SUSITNA 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 weighted usable area are the principal determinants of habitat ind.ices provided in Part A of the report for juvenile chinook at each specific area and the ten rE!presentative groups identified in the habitat character- i zati on report.Part B of thi s report provi des 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 middle Susitna River under a wide range of natural and with- project streamflows. v ..... I~ TABLE OF CONTENTS ACKNOWLEDGEMENTS .•. PREFACE .•.......••. LIST OF FIGURES. LIST OF TABLES .. LIST OF PLATES .... I.INTRODUCTION ...••..•.•..•.••••...........•....•••.•.•.•••••......• II.RELATIONSHIPS BETWEEN MAINSTEM DISCHARGE,SITE FLOW AND WATER SURFACE ELEVATION ....•.•.•...•..••.•................•.. FIELD PROCEDURES ...............•.•......... Staff gage location and installation •. Stage measurements ....•.•.•.•.•. Flow measurements. DATA ANALySIS .•...•...... Mainstem discharge ...•...........................•.•........ Relationship between stage and mainstem discharge (WSEL vs.Q)...••.•.•........••...•.......•.••••.....•. Relationship between site flow and mainstem discharge (q vs.Q)••••••••••••••••• Relationship between site flow and stage (q vs.WSEL)••••••••••••••••••••••••••••••••••••••••••• RESLfL TS ••••••••••••••••••••••••••••••••••••••••••••••••• i ii xi xxi xxii I-I II-I II-7 II-7 II-8 II-8 II-9 II-9 II-9 11-10 11-12 11-14 ,...., ..- - Site Site Site Site Site Site Site Site Site Site Site Site Site Site Site 101.2R .. 101.5L .. 101.7L.. 105.8L . 112.6L . 114.1R ...•.. 115.OR . 118.9L...•.•. 119.1L . 119.2R . 125.2R. 130.2R. 131.3L... 131.7L... 132.6L •. vi II-15 11-18 II-21 11-24 11-26 II-29 11-31 II-32 II-33 11-34 11-36 II-39 II-41 11-43 II-45 TABLE OF CONTENTS (Continued) - Site Site Site Site Site Site Site 133.8R. 136.0L. 137.5R ••. 138.7L.••.• 139.0L.. 139.4L •. 147.1L •. ................. 11-48 11-49 II-51 II-53 II-54 II-56 II-57 installation ••••••••••.•....•..•....•.•. - - - - III. DISCUSSION .. CALIBRATION AND APPLICATION OF IFG HYDRAULIC MODELS. FI EL D PROCEDURES •••...••.•••••••• Site Cross secti 011 and streambed profil e su rveys •.•••••• Depth and vel oc;ty III .. Substrate and cover . GENERAL TECHNIQUES FOR HYDRAULIC MODEL CALIBRATION. GENERAL TECHNIQUES FOR HYDRAULIC MODEL VERIFICATION •• GENERAL TECHNIQUES FOR HYDRAULIC MODEL APPLICATION. IFG MODEL RESULTS •••••••••••••• Site IOl.2R . Site Description •• Calibration ••.•••. Verification .• Application .•• Site lOl.5L .. Site Description •.•. Calibration •••••••.. Verification. Application •• Site 112.6L •..•.•• Site Description •• Calibration •••••..•. Verification .•. Application •.•••••.. vii II-59 II 1-1 111-3 III-lO I II-I0 III-ll II 1-12 III-12 I II-18 I II -30 II 1-32 II 1-32 II 1-32 II I -37 II 1-39 III-39 111-45 II 1-45 II 1-48 II I-51 III-51 I II-56 III-56 III-61 II 1-62 II 1-65 ..... ..... TABLE OF CONTENTS (Continued) Site JL19.2R . Site Description •••• Calibration ••••••••• Verification .••••••••. Application ••••.••.•.• Site :L 31.7L••••••••••••••••••••••••••••••••••••••••••••••••• Site Description •.•• Calibration •. Verification. Application •• Site 132.6L . Sit~Description •• Calibration ••••••• Verification •• Application. Site 136.0L . Site Description ••••••• Calibration .••.•••••• Verification •••••.••• Application ••••••••••.• Site :l47.1L . Site Description ••••••• Calibration •.••••••.••• Verification •• I\ppl ication. DISCUSSION,..•.......•.....•.•.•••••.•.•.•••.•.•...•.••.....•.•••• II 1-69 I II-69 I II-69 II 1-75 III-75 II 1-81 II 1-81 II 1-81 III-86 III-90 II 1-92 II 1-92 III-95 II 1-98 III-102 I II-106 II 1-106 I II-lOg III-113 II 1-113 III-115 II 1-115 III-118 III-121 III-121 III-125 FIELD PROCEDURES •• IV.CALIBRATION AND APPLICATION OF DIRECT INPUT HABITAT MOIJELS ••••••••••••••••••••••••••••••••••••••••••••••••••• ............................................... Depth and Ve 1ocity •••••.•• Substrate and Cover .••. Upwe 11 i ng •••••••••••••••• Fish Utilization •...•.•.. Streambed Profile Surveys .. viii IV-1 IV-5 IV-5 IV-6 IV-6 IV-9 IV-9 -TABLE OF CONTENTS (Continued) INPUT REQUIREMENTS OF DIHAB MODEL •• Mainstem Discharge . Stage . Depth and Velocity ....• Substrate and Cover .... Upwelling Information. Habitat Suitability Criteria. OUTPUT OF THE DIHAB MODEL •••.•.... Weighted Usable Area Curves •. Wetted Surface Area Curves •.. Time Series Curves •.•..••.•.• DIHAB MODEL RESULTS. Site lOl.7l .. Site Description .•.. Spawning Habitat ••.• Si te 105 .8l .. Site Description .•••.•.•.• Spawning Habitat .•...•.•.. Site 114.1R .. IV-9 IV-9 IV-9 IV-lO IV-lO IV-ll IV-ll IV-ll IV-IS IV-16 IV-16 IV-17 IV-17 IV-17 iV-20 IV-22 IV-22 IV-26 IV-28 -Site Description .•.•.•.• Spawning Habitat .•.•••.•......................IV-28 IV-32 -I Site lIS.0R.,.. Site Description •.. Spawning Habitat ••. Site lI8.9L . Site Description .. Spawning Habitat .. Site 119.1L . Site Description. Spawning Habitat. Site 125.2R .. Site Description .. Spawning Habitat .. ix IV-34 IV-34 IV-38 IV-40 IV-40 IV-44 IV-47 IV-47 IV-47 IV-50 IV-50 IV-54 - ,~ TABLE OF CONTENTS (Continued) Site 130.2'R II •••••• Site Description •• Spawning Habitat •••. Site 131.3L . Site Description •• Spawning Habitat •• Site 133.8R ". IV-57 IV-57 IV-57 IV-57 IV-57 IV-61 IV-64 Site Description. Spawning Habitat. Site 137.5R ••••••.•••.• Site Description •• Spawning Habitat •.•• .'...IV-64 IV-68 IV-70 IV-70 IV-70 DISCUSSION.- Site 138.7L . Site Description •. Spawning Habitat .. Site 139.0L . Site Description ...••••••. Spawning Habitat •.•.•.•.•. Site 139.4L . Site Description •.•.•.•.•. Spawning Habitat •••.••... ....................................................... REFERENCES .. APPENDICES IV-75 IV-75 IV-75 IV-80 IV-80 IV-83 IV-83 IV-83 IV-86 IV-86 V-I Appendix A Summary of site-specific data collected for rating curve analysis ••.•.•.•.••....A-I Appendix B Data supporting calibration and application of IFG hydraulic models .•...•.•.•....••..•..8-1 Appendix C -Data supporting calibration and application of DIHAB models . x C-l II-5 Page II-3FigureII-l. Figure II-2. Fi gure II-3. LIST OF FIGURES Middle Susitna River modeling sites ••................ Flow-duration curves for June and July based on mean daily Susitna River discharges at Gold Creek,1950-1984 and corresponding exceedence values for 1984 mean monthly discharges ........•..... Fl ow-durati on curves for August and September based on mean daily Susitna River discharges at Gold Creek,1950-1984 and corresponding exceedence values for 1984 mean monthly discharges............................11-6 .- .~. - ..... Figure II-4. Figure II-5. Fi gure II-6. Fig ure II -7. Figure II-8. Figure II-9. Figure II-10. Fi gure II-1l. Figure II-12. Figure II-13. Fig ure II -14 . Stage-discharge,flow-discharge,and flow-stage relationships for cross section 8 at site lOl.2R 0 oil Stage-discharge,flow-discharge,and flow-stage relationships for cross section 1 at site lOl.5L . Stage-discharge relationship for cross section 1 at site 101.7L . Stage-discharge relationships for cross sections 3 and 4 at site lOl.7L .....................•......... Stage-discharge relationships for cross sections 1 and 4 at site IOS.8l . Stage-discharge,flow-discharge,and flow-stage relationships for cross section 7 at site 112.6L . Stage-discharge relationship for cross section 2 at site 114.1R ...........•........................... Stage-discharge relationship for cross section 1 at site lI5.0R . Stage-discharge relationship for cross section 2 at site lIB.9L ·. Stage-discharge relationship for cross section 2 at s;te 119.1L . Stage-discharge,flow-discharge,and flow-stage relationships for cross section 3 at site 119.2L . xi 11-17 II-20 11-22 II-23 II-25 11-28 II-30 II-31 11-32 II-33 II-35 LIST OF FIGURES (Continued) - - .- Figure 11-15. Fi gure 11-16. Figure 11-17. Figure 11-18. Figure 11-19. Fi gure 11-20. Fi gure 11-21. Fi gure II -22. Figure 11-23. Fi gure 11-24. Figure 11-25. Fi gure 11-26. Fi gure II -27. Figure II 1-1. Fig ure II I-2• Stage-discharge relationship for cross section 1 . at site 125.2R.......................................11-37 Stage-discharge,flow-discharge,and flow-stage relationships for cross section 2 at site 125.2R...............................................11-38 Stage-discharge relationship for cross section 2 at 5 i te 130.2 R.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I 1-40 Stage-discharge relationships for cross sections 3 and 1 at site 131.3L...............................11-42 Stage-discharge,flow-discharge,and flow-stage relationships for cross section 3 at site 131.7L.....................11-44 Stage-discharge,flow-discharge,and flow-stage relationships for cross section 3 at site 132.6L...............................................11-47 Stage-discharge relationship for cross_section 3 at site 133.8R.......................................11-48 Stage-discharge,flow-discharge,and flow-stage relationships for cross section 3 at site 136.0L II-50 Stage-discharge relationships for cross sections 1 and 2 at site 137 .5R...............................II-52 Stage-discharge relationship for cross section 2 at site 138.7L.......................................II-53 Stage-discharge relationship for cross section 2 at site 139.0L.......................................II-55 Stage-discharge relationship for cross section 2 at site 139.4L.......................................II-56 Stage-discharge,flow-discharge,and flow-stage relationships for cross section 4 at site 147.1L II-58 Middle Susitna River IFG and DIHAB modeling sites 111-4 Juvenile chinook salmon suitability criteria for depth applicable to clear and turbid water habitats.Source:Suchanek et al.1984;EWT&A and wee 1985.........................................II 1-26 LIST OF FIGURES (Continued) """ ...... Fi gure I II-3. Figure III-4. Figure III-5. Figure III-6. Fi gure II 1-7 • Figure III-8. Fig ure II I-9• Juvenile chinook salmon suitability criteria for velocity appl icable to clear and turbid water habitats.Source:Suchanek et ale 1984;EWT&A and wee 1985 .•...•.•.•.•.••.••...•••.•••....•........111-27 Juvenile chinook salmon suitability criteria for cover applicable to clear and turbid water habitats.Source:Suchanek et ale 1984;EWT&A and wee 1985.........................................II 1-28 Cross sections for site lO1.2R depicting water surface elevations at calibration discharges of 25 and 279 cfs "II 1-34 Compari son between measured and adjusted cross sections 1~3 and 4 at site 101.2R •...•....•••••.•..•111-38 Comparison of observed and predicted water surface profiles from calibrated model at site lOl.2R 011 111-40 Comparison between water surface elevations forecast by the calibrated hydraulic models and the stage-flow relationship for 101.2R cross 5 e'c t;0 n 8 ••••••••••••••••••"•••••••".................II 1-41 Surface area and juvenile chinook habitat response curves for site 101.2R.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area {WUA).•.••••..•.•..•111-43 - Figure 111-10.Time series plots as a function of time for site 101.2R.A -Juvenil e chi nook WUA.B -Site flow 111-46 Figure III-H.Cross sections for site 101.5L depicting water surface elevations at calibration discharges of 1696 and 2213 cfs 111-49 Figure 111-12.Comparison of observed and predicted water surface profiles from calibrated model at site lOl.5L...............................................III-52 Figure III-13.Surface area and juvenile chinook habitat response curves for site 101.5L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA).••.•••.••••..•III-54 xiii - -- - - ..... LIST OF FIGURES (Continued) Figure 111-14.Time series plots as a function of time for site 101.5L.A -Juvenile chinook WUA.B -Site flow III-57 Figure 111-15.Cross sections for site 112.6L depicting water surface elevations at calibration discharges of 355,721,1430 and 2980 cfs..•••••••...•.....•••.••..III-59 Figure 111-16.Comparison between measured and adjusted cross sections 2,3 and 3A at site 112.6L ..•.•.•.••...•••••111-63 Figure 111-17.Comparison of observed and predicted water surface profiles from calibrated models at 5 ;te 112 ..6L.. ...... .. .. ...... .. .... .. .... ....... .. .. .. .. .. .. .... .. .. ............... .. .... ..II 1-64 Figure 111-18.Surface area and juvenile chinook habitat response curves for site 112.6L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA)•••••••••••••••111-66 Figure 111-19.Time series plots as a function of time for site 112.6L.A -Juvenile chinook WUA.B -Site flow 111-68 Figure 111-20.Cross sections for site 119.2R depicting water surface elevations at calibration discharge of 316 cfs..........................................................................................I 11-71 Figure II 1-21.Compari son between measured and adjusted cross sections 1,2 and 3 at site 119.2R.....•.••••••••••••111-74 Figure 111-22.Comparison of observed and predicted water surface profiles from calibrated model at site 119.2R a-a...................................................111-76 Figure 111-23.Surface area and juvenile chinook habitat response curves for site 119.2R.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA)•.•••.•..•••...111-78 r-Figure 111-24.Time series plots as a function of time for site 119.2R.A -Juvenile chinook WUA.B -Site flow...111-80 Figure 111-25.Cross sections for site 131.7L depicting water surface elevations at calibration discharges of 18,58,150 and 240 cfs .•.•••••.••••.••••.•.••••••.•.111-83 xiv LIST OF FIGURES (Continued) Figure III-26.Comparison between measured and adjusted cross sections 2,6 and 7 at si te 131.7L...................II 1-87 -Figure III-27.Comparison of observed and predicted water surface profiles from calibrated model at site 131.7L........111-88 - - .-.. Figure 111-28.Comparison between water surface elevations forecast by the calibrated hydraulic model and the stage-flow relationship for 131.7L cross section 3 .........•.•................................111-89 Fi gure II 1-29.Surface area and juveni le chinook habi tat response curves for site 131.7L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA)...............III-91 Figure III-3D.Time series plots as a function of time for site 131.7L.A -Juvenile chinook WUA.B -Site flow..111-93 Figure III-31.Cross sections for site 132.6L depicting water surface elevations at calibration discharges of 27 and 141 cfs.......................................111-96 Fi gure I II-32.Compari son between measured and adjusted cross section 9 at site 132.6L .•••..•............•....•..•.111-99 Figure 111-33.Comparison of observed and predicted water surface profiles from calibrated model at site 132.6L ......•.............................•........•.111--100 Figure 111-34.Comparison between water surface elevations forecast by the cal ibrated hydraul ic model and the stage-discharge relationship for 132.6L cross section 3 111-101 Figure III-35.Surface area and juvenile chinook habitat response curves for site 132.6L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA)........•......111-103 Figure 111-36.Time series plots as a function of time for site 132.6L.A -Juvenile chinook WUA.B -Site flow 111-105 Figure III-37.Cross sections for site 136.0L depicting water surface elevations at calibration discharges of 81,153 and 265 cfs III-108 xv .- LIST OF FIGURES (Continued) Figure 111-38.Comparison of observed and predicted water surface profiles from calibrated model at site 136.0L 111-111 Figure III-39.Comparison between water surface elevations forecast by the calibrated hydraulic model and the stage-flow relationship for 136.0L cross section 4 111-112 Figure III-40.Surface area and juvenile chinook habitat r-response curves for site 136.Ole A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA)..•...•.•......111-114 Figure 111-41.Time series plots as a function of time for site 136.0L.A -Juvenile chinook WUA.B -Site flow II 1-116 Figure III-42.Cross sections for site 147.1L depicting water surface elevations at calibration discharges of 1860 and 2236 cfs 111-119 .....Figure 111-43.Comparison of observed and predicted water surface profiles from calibrated model at site 147.1L 111-122 Figure I II-44.Surface area and juvenil e chi nook habitat response curves for site 147.1L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA).•.••..........111-124 Figure 111-45.Time series plots as a function of time for site 147.1L.A -Juvenile chinook WUA.B -Site flow 111-126 Spawning chum salmon suitability criteria for depth.Source:Estes and Vincent-Lang 1984.........IV-12 Spawning chum salmon suitabil ity criteria for velocity.Source:Estes and Vincent-Lang 1984......IV-13 Summary location of upwell ing areas at DIHAB modeling site 131.3L.................................IV-8 Spawning chum salmon suitability criteria for substrate.Estes and Vincent-Lang 1984..............IV-14 Cross sections for site 101.7L depicting water surface elevations at discharges of 11,400, 15,300 and 18,500 cfs................................IV-19 Figure IV-1. Figure IV-2. Figure IV-3. Figure IV-4. Figure IV-5. ,.... - - xvi LIST OF FIGURES (Continued) Figure IV-6.Surface area and spawning chum habitat response curves for site 101.7L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B- Weighted.Usable Area (WUA)................•.•.•..•...IV-21 Figure IV-7.Time series plots as a function of time for site 101.7L.A -Spawning chum WUA.B -Mainstem di scharge..................... .. .. .. ........ .......... .................... .. .. .......... ......IV-23 Surface area and spawning chum habitat response curves for site 114.1R.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B- Weighted Usable Area (WUA)...........................IV-33 - - - Fi gure IV-8. Figure IV-g. Fig ure IV-10 . Fi gure IV-l1. Figure IV-12. Cross sections for site 105.8L depicting water surface elevations at discharges of 7,320, 15,300 and 18,500 cfs e ••••••• Surface area and spawning chum habitat response curves for site 105.8L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B- Weighted Usable Area (WUA)•.••..•.•.••.......•.•.•..• Time series plots as a function of time for site 105.8L.A -Spawning chum WUA.B -Mainstem discharge II .. Cross sections for site 114.1L depi cti ng water surface elevations at discharges of 7,680, 15,100 and 17,900 cfs . IV-25 IV-27 IV-29 IV-31 Figure IV-13.Time series plots as a function of time for site 114.1R.A -Spawning chum WUA.B -Mainstem discharge.......................................................................................IV-35 - Figure IV-14. Figure IV-15. Figure IV-16. Figure IV-17. Cross sections for site 115.0R depicting water surface elevations at discharges of 7,680 and 14,500 cfs II"II .. Surface area and spawning chum habitat response curves for site 115.0R.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B- Weighted Usable Area (WUA)...•.•.•.•.•......•.•.•.•.. Time series plots as a function of time for site 115.0R.A -Spawning chum WUJ~.B -Mainstem discharge .. Cross sections for site 118.9L depicting water surface elevations at discharges of 7,680, 10,300,15,100 and 17,900 cfs ..••.~••.•.•..•......... xvi i IV-37 IV-39 IV-41 IV-43 LIST OF FIGURES (Continued) Figure IV-18.Surface area and spawning chum habitat response curves for site 118.9L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B- Weighted Usable Area (WUA)•................•••.......IV-45 ..- Figure IV-19. Figure IV.-20. Figure IV-21. Figure IV-22. Figure IV-23. Figure IV-24. Figure IV-25. Figure IV-26. Fi gure IV-27 . Time series plots as a function of time for site 118.9L.A -Spawning chum WUA.B -Mainstem di scharge..... . . . . . . . ... . . . . . . .... . . . . . . . . . . . . . . . . . . .IV-46 Cross sections for site 119.1L depict-ing water surface elevations at discharges of 7,680, 13,600 and 19,100 cfs................................IV-48 Surface area and spawning chum habitat response curves for site 119.1L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B- Weighted Usable Area (WUA)...........................IV-49 Time series plots as a function of time for site 119.1L.A -Spawning chum WUA.B -Mainstem dis cha rg e.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I V-51 Cross sections for site 125.2R depicting water surface elevations at discharges of 7,680, 13,600 and 19,100 cfs................................IV-53 Surface area and spawning chum habitat response curves for site 125.2R.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B- Weighted Usable Area (WUA)...........................IV-55 Time series plots as a function of time for site 125.2R.A -Spawning chum WUA.B -Mainstem discharge............................................IV-56 Cross sections for site 130.2R depicting water surface elevations at discharges of 7,680, 14,500,16,100 and 19,900 cfs..•.....IV-59 Cross sections for site 131.3L depicting water surface elevations at discharges of 7,680, 16,100 and 19,900 cfs................................IV-62 Figure IV-28.Surface area and spawning chum habitat response curves for site 131.3L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B- Weighted Usable Area (WUA).........................•. xviii IV-63 LIST OF FIGURES (Continued) - Fi gu re IV-29. Figure IV-30. Figure IV-31. Figure IV-32. Figure IV-33. Figure IV-34. Figure IV-35. Figure IV-36. Figure IV-37. Figure IV-38. Figure IV-39. Figure IV-40. Time series plots as a function of time for site 131.3L.A -Spawning chum WUA.B -Mainstem discharge............................................IV-65 Cross sections for site 133.8R depicting water surface elevations at discharges of 7,680, 16,100 and 19,900 cfs................................IV-67 Surface area and spawning chum habitat response curves for site 133.8R.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B- Weighted Usable Area (WUA)...........................IV-69 Time series plots as a function of time for site 133.8R.A -Spawning chum WUA.B -Mainstem di scharge............................................IV-71 Cross sections for site 137.5R depicting water surface elevations at discharges of 19,900 cfs IV-73 Surface area and spawning chum habitat response curves for site 137.5R.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B- Weighted Usable Area (WUA)...........................IV-74 Time series plots as a function of time for site 137.5R.A -Spawning chum WUA.B -~1ainstem di scharge...... . . . . . . . . . . . . . . . . . . . . . . . . . . .... . . . . . . . .IV-76 Cross sections for site 138.7L depicting water surface elevations at discharges of 10,400, 14,500,17,900,19,000 and 27,700 cfs................IV-78 Surface area and spawning chum habitat response curves for site 138.7L.A-Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B- Weighted Usable Area (WUA)...........................IV-79 Time seri~s plots as a function of time for site 138.7L.A -Spawning chum WUA.B -Mainstem discharge............................................IV-8! Cross sections for site 139.0L depicting water surface elevations at discharges of 10,400, 14,500,17,900,19,000 and 31,700 cfs................IV-82 Surface area and spawning chum habitat response curves for site 139.0L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B- Weighted Usable Area (WUA)...........................IV-84 xix LIST OF FIGURES (Continued) Fi gure IV-41. Figure IV-42. Time series plots as a function of time for site 139.0L.A -Spawning chum WUA.B -Mainstem discharge . Cross sections for site 139.4L depicting water surface elevations at discharges of 8,370, 14,500, 14,900,19,000 and 31,700 cfs •.•••.•••.•..•.. xx IV-85 IV-87 .... .... """ LIST OF TABLES Table II-I. Tab 1e I II-I. Table III-2. Table III-3. Table III-4 . Table III-5. Table III-6. Table 1II-7. Tab 1e II 1-8. Table 1II-9. Table lII-lO. Identification codes for staff gages ....••.•.•....... Types of hydraulic models applied at 1984 middle Susitna River modeling sites for rearing chinook ...•. Substrate code cl assifi cati on .••...•..•...........•.. Cover code classification •.•••.••..•.••........•..... Juvenile chinook salmon cover suitability criteria,applicable to clear and turbid water conditions.Sources:Suchanek et al.1984; EWT&A and wee 1985 •••••.•••.•.••'•••.••••••••••••••••• Hydraulic data available to calibrate IFG-4 model for site lOl.2R . Hydraulic data available to calibrate IFG-2 model for site lOl.5L . Hydraulic data available to calibrate the IFG-2 model for site 112.6L . Hydraulic data available to calibrate the IFG-4 model for site 119.2R . Hydraulic data available to calibrate the IFG-4 model for site 131.7L ........................•....... Hydraulic data available to calibrate the IFG-4 model for site 132.6L . 11-8 II 1-10 1II-13 1II-13 I II-29 I II -37 II I-50 I II-61 II 1-73 II 1-85 II 1-95 Tab 1e I II -11. Table III-12. Hydraulic data available to calibrate the IFG-4 model for site 136.0L................................111-110 Hydraulic data available to calibrate the IFG-2 model for site 147.1L................................111-118 Tab 1e IV-I. Table IV-2. Table IV-3. 43 candidate areas for side channel and mainstem chum spawning evaluation .•.•.•...•...•.•........•.•.. 1984 middle Susitna River DIHAB modeling areas ..•.... Criteria used to determine the strength of upwe 11 i ng ••••••••••••••••••••.••••.•••.•••••••••••••III xxi IV-3 IV-4 IV-7 Pl ate II I-I. Plate III-2. Plate III-3. Plate III-4. Plate 1II-5. Plate III-6. Pl ate II 1-7 . Plate III-8. Plate IV-I. Plate IV-2. Plate IV-3. Plate IV-4. Plate IV-5. Plate IV-6. - Plate IV-7. Plate IV-8. L1ST OF PLATES Modeling site 101.2R on June 1,1982 at mainstem discharge:23,000 cfs .•...••.........••..••••••.•.....111-33 Modeling site 101.5L on June 1,1982 at mainstem discharge:23,000 cfs •...•.•.•...••..•.••••••..•.....•111-47 Modeling site 112.6L on September 6,1983 at mainstem discharge:16,000 cfs .....•••••••••.•..••••••III-58 Modeling site 119.2R on June 1,1982 at mainstem. discharge:23,000 cfs •.•.•.•••.••••••••••..•....•.••..111-70 Modeling site 131.7L on June 1,1982 at mainstem discharge:23,000 cfs •••••••...•.•.•.•••.•.••••..••.•.111-82 Modeling site 132.6L on June 1,1982 at mainstem discharge:23,000 cfs •.•••.•..••.•••.••••.•••...•.•••.111-94 Modeling site 136.0L on June 1,1982 at mainstem discharge:23,000 cfs .•.••.....•.•~•.•....••••••...•.•111-107 Modeling site 147.1L on June 1,1982 at mainstem discharge:23,000 cfs .•......•......••..•••.•.•......•111-117 Modeling site 101.7L on June 1,1982 at mainstem discharge:23,000 cfs.................................IV-I8 Modeling site 105.8L on June 1,1982 at mainstem di scharge:23,000 cfs.................................IV-24 Modeling site 114.1R on June 1,1982 at mainstem discharge:23,000 cfs.................................IV-3D Modeling site 115.0R on June 1,1982 at mainstem discharge:23,000 cfs.................................IV-36 Modeling sites 118.9L and 119.1L on June 1,1982 at mainstem discharge:23,000 cfs.....................IV-42 Modeling site 125.2R on June 1,1982 at.mainstem discharge:23,000 cfs.................................IV-52 Modeling site 130.2R on September 6,1983 at mainstem discharge:16,000 cfs........................IV-58 Modeling site 131.3L on June 1,1982 at mainstem discharge:23,000 cfs.................................IV-60 xxii LIST OF PLATES (Continued) IV-77 -- Plate IV-9. Plate IV-10. Plate IV-l1. Modeling site 133.8R on June 1,1982 at mainstem discharge:23,000 cfs.................................IV-66 Modeling site 137.5R on June 1,1982 at mainstem discharge:23,000 cfs.................................IV-72 Modeling sites 138.7L,139.0L and 139.4L on June 1,1982 at mainstem discharge:23,000 cfs ••.•.•....... xxiii PART I INTRODUCTION This report presents data reduction methods and results of the 1984 field studi es conducted by E.Woody Tri hey and Associ ates (EWT&A)wi th assi stance ,,,,",,from the Alaska Department of Fish and Game Su Hydro Aquatic Studies Team (ADF&G Su Hydro).These studies were undertaken in the Talkeetna-to-Devil Canyon segment of the Susitna River,hereafter referred to as the middle Susitna River,to describe anticipated changes in site-specific hydraulic con- ditions due to altered streamflows and to assess the response of fish habitat to incremental changes in depth and velocity. Although field studies and analyses described in this report were completed by a joint EWT&A and ADF&G Su Hydro study team,EWT&A is responsible for the field study design,hydraulic model calibration and analyses presented in this ,~,report.Thus,the information and technical interpretations contained in this report are those of EWT&A and do not necessarily represent the viewpoint of the Alaska Department of Fish and Game. The primary evaluation species for the middle Susitna River have been iden- tified as.juvenile chinook salmon (Oncorhynchus tshawytscha)and spawning chum sa 1mon (Q.keta)(EWT&A and WCC 1985).Therefore,the habitat model i ng ~results presented in this report are limited to these species and life stages. Due to the marked difference in hydraulic conditions typically associated with the habitats occupied by these species and life stages,two habitat modeling concepts were applied. I-I .... ...... Central to the middle Susitna River analysis is the U.S.Fish and Wildlife Service's Instream Flow Incremental Methodology (IFIM)and its associated hydraulic models (IFG-2 and IFG-4).These models are intended for use where streamflow is a primary determinant of fish habitat and instream hydraulics can be classified as being gradually varied and within a rigid channel (Trihey 1979;Trihey and Baldrige 1985).When evaluating rearing conditions for juvenile chinook in the middle Susitna River these requisites generally prevail.Thus,application of the IFIM models 'is well-suited for the habitat conditions being evaluated. In contrast,chum salmon spawning typically occurs in side channel backwater areas or along shore margins (Barrett,Thompson,and Wick 1984),where hydraulic conditions are often spatially varied or possess near zero velocity . Neither of these conditions is compatible with the theoretical assumptions of the IFG hydraulic models.Therefore,an alternative approach which did not require that gradually varied flow exist in a defined channel,was developed for calculating the response of chum spawning habitat to incremental changes in mainstem discharge.This model is referred to in this report as the Direct Input Habitat,or DIHAB,model. The IFIM and DIHAB models used in the analyses calculate.wetted surface area (WSA)and weighted usable area (WUA).The DIHAB model produces identical results as the IFIM HABTAT model using the same habitat suitability criteria within both models to calculate WUA.Habitat suitability criteria used in the models are based on data collected in middle Susitna River habitats by ADF&G Su Hydro (Suchanek et al.1984,Estes and Vincent-Lang,eds.1984c)and further described by EWT&A and WCC 1985 and Steward 1985. 1-2 .... This report is organized into a general introduction (Part I)and three technical sections (Parts II through IV).Each technical section is supported by an appendix which contains field data and intermediate analytic results. Part II of the report describes water surface elevation and site-flow analysis and presents various relationships between mainstem discharge,site-specific flow,and water surface elevations (stage).These relationships are extensively used in Parts III and IV of the report to calibrate and validate IFG hydraulic models,estimate water surface elevations at modeling sites corresponding to unobserved mainstem discharges,and convert the mainstem streamflow hydrograph into site-specific flow hydrographs.Part III of the report describes the calibration procedures for the IFG hydraulic models and presents WUA forecasts for juve!1i1e chinook in side channel and mainstem habitats based on evaluations of turbidity,structural cover,depth and velocity.Part IV describes application of the DIHAB model developed by EWT&A and presents site-specific WUA forecasts for spawning chum salmon in side channel and mainstem habitats based on evaluation of upwelling,substrate composition,depth and velocity • I-3 I.... ..... I - PART II RELATIONSHIPS BETWEEN MAINSTEM DISCHARGE, SITE FLOW AND WATER SURFACE ELEVATION The hydraulic parameters of depth,velocity,and wetted surface area influence aquatic habitat availability in the middle Susitna River.Their magnitudes are dependent on the discharge and the water surface elevation,or II s tage,11 of the river.'This section presents the relationships,and the methods used to determine them"of stage to mainstem discharge"the flow in side channels to mainstem discharge,and the flow in side channels to stage (hereinafter referred to as stage-discharge,flow-discharge,and flow-~tage,respectively). A notable transition is expected to occur in existing mainstem and side channel habitat as a result of project-induced changes in the natural flow regime of the middle Susitna River.Aerial photography and relevant project literature (ADF&G Su Hydro 1981;ADF&G Su Hydro 1983a;Barrett,Thompson,and Wick 1984)provided the basis for selecting candidate areas for evaluating project effects on juvenile chinook and spawning chum salmon habitats.As a result,130 juvenile chinook side channel and mainstem sites,and 43 spawning chum side channel and mainstem margin sites were identified.Potential juvenile chinook study sites were either known or suspected rearing habitat. Potential spawning chum study sites were of two types:areas where chum salmon spawning had been observed,and areas with apparent upwelling based on open thermal 1eads in the March 1983 aeri a1 photography where spawni ng chum salmon had not been preViously reported (upwelling is discussed in detail in -Part IV). II-I - - The candidate study sites,for both juvenile chinook and spawning chum,were classified into eleven "representative groups"according to the habitat transformation they underwent as the mainstem discharge decreased from 23,000 to 5,100 cfs (Aaserude,Theile,and Trudgen 1985).Included in each representative group are sites for which habitat models were developed.Eight juvenile chinook and 14 spawning chum salmon sites were selected for habitat modeling in 1984.Inherent to the habitat models are the hydraulic relationships of stage-discharge,flow-discharge,and flow-stage. To collect the data for the stage-discharge,flow-discharge,and flow-stage relationships,staff gages were installed during the 1984 field sea.son at cross sections within the 22 sites (Figure II-I).The stage at varying numbers of cross secti ons at each site was monitored throughout August, September,and October and site flows were measured periodically at side channel sites.The data collected were used to develop relationships between stage and mainstem discharge at each cross section where a staff gage was installed.In addition,one cross section at each of the nine side channel sites was chosen to develop a relationship between site flow and both stage and mainstem discharge. A mainstem discharge range of 5,000 to 35,000 cubic feet per second (cfs)was selected as the ideal range for evaluating hydraulic conditions and for assessing juvenile rearing habitat potential in the middle Susitna River. Thi s range is appropri ate because it encompassl~s nearly all mean daily di s- charges that have occurred during the rearing season,May 20 to September 15, as well as the mean daily discharges that are expected to occur during the open water season under with-project conditions,from about April to October. 11-2 10, IBM FG AND DlHA8 MOOEIMG 8ITE8 NILES o, _~__-.....J.' r./u_t ' - Fi gure II-I.Middle Susitna River modeling sites. II-3 Flow-duration analyses for both natural and with-project conditions for this period indicate this is an appropriate evaluation range (Williams 1985). Associated with the 90~50,and 10 percent exceedance values at that time were discharges of 13,600;21,900;and 33,200 cfs for the natural conditions and 8,100;9,400;and 12,600 cfs for with-project conditions. Included in the juvenile rearing evaluation period is the chum salmon spawning period (August 12 to September 15).A mainstem discharge range of 5,000 to 25,000 cfs was selected for assessing spawning habitat potential for this period.Separate flow-duration analysis were not undertaken for the spawning season as it is encompassed within the rearing season.Discharges occurring in June,July,August and September 1984 correspond to exceedance values of 49.9,29.3,51.8 and 73.1,respectively.This indicates for the first three months of the open water season the discharges were average or slightly higher than normal whereas in September,the dischclrges were lower than normal (Figures 11-2 and 11-3). Aerial photographs of the middle Susitna River have been obtained at the following discharges:5,100;7,400;10,600; 12,500;16,000;18,000;and 23,000 cfs.These photographs were used extensively in determining the breaching discharges at each study site.A breaching discharge is that mainstem discharge at which mainstem stage at the channel entrance is sufficient to overtop the head berm,thereby initiating the flow of turbid mainstem water through the site.The photographs were also used to determine the mainstem range over which the relationships that were developed could be applied. II-4 Figure 11-2.Flow-duration curves for June a,nd July based Susitna River discharges at Gold Creek, corresponding exceedence values for 1984 discharges. II-5 on mean daily 1950-1984 and mean monthly AUGUST tooooo -r------------------------ 90000 Boooo ~70000 t.l -60000 "'.. ~50000 .c.... ttl 40000J:: t.len 30000..... CJ 20000 toooo 0 0 10 20 30 40 I 50 I 60 70 Bo gO too Percent of Time Equalled or Exceeded SEPTEMBER T~100000 ..,-----------------------1 90000 BoooO ~70000 t.l -60000 100gOBo706050403D2010 :::::j ~10000 .-------------_ o f-----r--------r-----r------rl-.----r-~-----r-------l o ~50000 .c.... ~40000 t.len •.-4 CJ Percent of Time Equalled or Exceeded Figure II-3.Flow-duration dai ly Susitna corresponding discharges. curves for August and September based on mean Ri ver di scharges at Gal d Creek,1950-1984 and exceedence values for 1984 mean monthly II-6 In this report,the word IIflow ll is consistently used in association with ,~"'site-specific streamflow,while IIdischarge ll refers to Susitna Riv'er streamflow as gaged at Gold Creek. FIELD PROCEDURES ,"'''''The collection of site-specific data to develop the relationships described above entailed locating and installing staff gages,measuring stage over a wide range of mainstem discharges,and periodically measuring site flow at the side channel sites. Staff gage location and instaJlation:At each study site,a varying number of Leopold and Stevens staff gages were installed.Cross sections were estab- 1i shed withi n each study reach and represented uni que subreaches based on channel hydraulics and habitat characteristics.At cross sections where the ?~ standard gage height,3.33 feet,was inadequate to monitor the full range of ~~stages that occurred during August,September,and October,as many as three gages were installed in a tiered formation.Staff gages were identified by river mile (RM),location within the site,position relative to flow level, (low,medium,high)and the associated cross section number (Table II-I). .~~'F. Aquatic study teams conducted differential level surveys between the top of ~~each staff gage and a point of known elevation (project datum),established by R&M Consultants,Inc.between 1980 and 1982. Further information regarding staff gage installation may be found in the 1984 ~' ADF&G Su Hydro Procedures Manual (ADF&G Su Hydro 1984). II-7 Table II-I.Identification codes for staff gages. ~'"Location in Si te Code Flow Level Code Mainstem M High A Side Channel S Medium B Side Channel Mouth W Low C Side Channel Head H -!("~ Other X r-~.Spawning Sites P Stage measurements:Staff gages were typically read three to five times and covered a range of mainstem discharges.Stage was read to the nearest 0.01 ft.When a staff gage was dewatered,the water surface elevation was obtained ""...through differential level surveying.Water surface elevations were also obtained during cross section and streambed profile surveys.Whether the channel was breached (that is,receiving flow from the mainstem)or unbreached at the time of the stage measurement was also recorded. ?or,Flow measurements:Site flow was measured at each of the side channel model- ing sites at a minimum of three different mainstem discharges.One cross section at each site was selected as the flow measurement cross section.This section was ideally located in a portion of the site where channel shape and slope were stable and where flow was relatively uniform across the channel.A top-set wadi ng rod and either a Marsh-McBi rney or Pri ce AA flow meter were used to measure depth and velocity.Depth was measured to the nearest 0.05 ft and velocities were measured to 0.1 feet per second (fps).t-'leasurements II-8 were taken across each cross section at 20 to 25 verticals in accordance with standard methods of the U.S.Geo 1ogi ca 1 Su rvey (Buchanan and Somers 1969). The flow ang 1e was also recorded when the flow was not pe rpendi cu 1ar to the ~"cross section. DATA ANALYSIS Mainstem discharge:Mean daily streamflows for the Susitna River at Gold Creek were obtained from USGS for the years 1950 -1984 (USGS 1950 -1984). Relationship between stage and mainstem discharge (WSEL vs.Q):As mainstem discharge in the middle Susitna River increases,the stage at each of the cross secti ons within the 22 model i ng sites also increases.The extent to !"'"'whi ch stage increases depends on channel geometry and channel morphology, whether the site is breached,and whether the site is affected by mainstem backwater.The stage at cross sections within pool habitats remain relatively constant until site flow is sufficiently high enough to drown out the riffles and pools and occur as a run.In riffle or run habitats,stage typically p",increases steadily with increases in mainstem discharge.A site which is unbreached may be dewatered except at the mouth,where mainstem backwater may be present. Mathematical formulae were developed to relate stage to discharge at each l....cross section.A linear regression using a least squares method was used. Straight line functions were obtained by logarithmically transforming both variables,and equations were thus,of the form: - II-9 where: WSEL =true water surface elevation in ft Q =mean daily discharge at Gold Creek in cfs a,b =coefficients determined from regression analysis C =a reference elevation in ft,used in the analysis to allow one full log cycle to represent 1 to 10 ft of stage. More than one equation was often required to relate stage to discharge at a ~.single cross section.This was due to physical attributes of the site,such as geometry at the head berm and hydrologic and hydraulic characteristics of the other channels in the vicinity.Equations could not be developed for mainstem discharges less than the breaching discharge since site flow and stage is then controlled by local runoff or groundwater inflow rather than by ~~the mainstem. Aerial photography and field observations were used in determining the dis- charges at which changes in stage-discharge relationships might be expected. Stage-discharge plots are included in Figures 11-4 to 11-27 and Figures A-I.l ~~to A-l.30 for the 22 study sites.Also shown on the plots are the equations which were developed,the application range of each equation,the number of data points (n)used in the regression analysis,and the coefficient of determination (r2 ). .....Relationship between site flow and mainstem discharge (9 vs.Q):Like the stage~discharge relationship,the relationship between site flow and mainstem 11-10 discharge is a straight line function when both variables are logarithmically transformed.Equations were developed through.linear regression analyses for the side channel modeling sites and were of the form: where: q =site flow in cfs Q =mean daily discharge at Gold Creek in cfs a,b =coefficients determined by regression analysis / Site flow may be present when a side channel is ~nbreached,due to tributary inflow,upwelling,and local runoff.Once the channel is breached t however, site flow includes flow from the mainstem.Site flow is said to be II con - trolled ll by the mainstem when local sources are insignificant in comparison to inflow from the mainstem.These controlling discharges were identified ~~primarily by distinct breaks in the flow-discharge plots.For some sites,the breaching discharge and controlling discharge are the same.For others,the controlling discharge is as much as 2,000 cfs higher than the breaching discharge. Aaserude,Thiele,and Trudgen (1985)demonstrated that site flow in a channel with gently sloped sides at the head berm would increase rapidly with small increases in mainstem stage.At a site With the same breaching discharge and a narrow,incised channel entrance,site flow will increase at a much lower rate for the same increases in mainstem stage.The flow-discharge curve will be steep for the first channel type and flat to moderate for the second type. In addition,a major grade break in channel geometry at the entrance may II-ll - result in a transition from a flat flow-discharge curve to a steep one,or vice versa.More than one equation would thus be required to relate site flow to mainstem discharge. The need for multiple flow-discharge equations at a site could also be due to addi ti ona 1 channel s becomi ng acti ve.The channel s may contribute additi ona 1 flow to the site and thus effect a steeper curve.Conversely,the site flow could level off as other channels are breached and mainstem water is diverted before it reaches the site,thus resulting in a flatter curve. In the regression analyses,site flows were generally correlated to mean daily discharges at Gold Creek.When discharge was rising or falling rapidly, however,it was not appropriate to use the mean daily value.To estimate the ~~instantaneous mainstem discharge at the site in this case,a time-lag analysis was used which incorporated the distance of the site from Gold Creek,the average mainstem velocity,and the time of day that the site flow measurement was made. Flow-discharge plots for the side channel modeling sites are included in Figures 11-4,11-5, 11-9,11-14,11-16,11-19,II-20,11-22,and 11-27.Also shown on the plots are the equations that were developed,the application range of each equation,the number of data points (n)used in the regression analysis,and the coefficient of determination (r2 ). Relationship between site flow and stage (9 vs.WSEL):Equations to relate site flow to stage were developed for each of the flow measurement cross 11-12 sections at the side channel modeling sites.Both variables were logarithmi- cally transformed,and an equation developed through linear regression by the least squares method.Equations were of the form: where: q =site flow in cfs WSEL =true water surface elevation in ft atb =coefficients determined by regression analysis C =a reference elevation in ft used in the analysis to allow one full log cycle to represent 1 to 10 ft of stage Flow-stage plots for the side channel modeling sites are included in Figures 11-4,11-5,11-9,11-14 t 11-16,11-19,11-20,11-22,and 11-27.Also shown on the plots are the equations that were developed,the application range of each equation,the number of data points (n)used in the regression analysis,and the coefficient of determination (r2 ). The plots of each of the three relationships (stage-discharge,flow-discharge, flow-stage)developed at the flow measurement cross sections are presented on !"""the same page and are aligned in such a manner as to allow simultaneous inspection of the relationships developed from a common data base.The plots also show the application range of the equations in relation to the data from which they were developed. 11-13 ,.... RESULTS The following section provides site-specific descriptions at the 22 modeling sites of the flow conditions,relationships between stage,flow and discharge as well as the appropriate application ranges for each relationship.Data used in the plots and in the development of the regression equations are presented in Appendix A. II-14 I"''' Site 101.2R:This side channel becomes breached at 9,200 cfs.Below 9,200 cfs,ponded water is present throughout the site with only the backwater area near the mouth connected to the mainstem.The small overflow channel in the right side of the study site becomes breached at 14,000 cfs. Staff gages were installed and stage monitored at each of the nine cross sections that were established.A stage-discharge equation for breached conditions was developed for each cross section.The lower limit of the application range of the stage-discharge equations is 9,200 cfs for all cross sections except cross sections 2 and 5.These cross sections do not extend beyond the small overflow channel into the main channel;the lower application limit,therefore,is 14,000 cfs.The highest mainstem discharge for which stage was recorded at all nine cross sections was 23,000 cfs.The stages at cross sections 1 and 2 were also recorded at 27,700 cfs.This additional data point was in line with the other points on the log-log plot,and indicated no changes in the stage-discharge relationship between 23,000 and 27,700 cfs. Above 27,700 cfs,however,it appears from cross section plots and aerial photography that hydraulic conditions in the site may change significantly. The upper limits of the stage-discharge relationships therefore,were set at 27,700 cfs for all nine cross sections. Although the channel is breached at 9,200 cfs,flow is not controlled by the mainstem until 10,300 cfs.Flow was measured at cross section 8 when mainstem discharge was 11,200, 15,300,and 17,400 cfs and the resulting flow-discharge curve is very steep.When the equation is applied to 35,000 cfs,a site flow of 120,000 cfs is produced.The upper limit of the application range was thus,set at 17,400 cfs.The lower limit is the controlling discharge of II-15 lOt300 cfs.Additional data is required to determine the mainstem discharge ~~at which there is an inflection point in the flow-discharge curve. A flow-stage equation was also developed at cross section 8 and has the same application range as the flow-discharge relationship of lOt300 to 17 t 400 cfs. Plots and equations for the three relationships at cross section 8 are shown in Figure 11-4.The plots and equations for the stage-discharge relationships at the other eight cross sections in this study site are shown in Figures A-l.l through A-l.4.A staff gage was also installed at the head of the site in the mainstem.The plot and equation for this gage are shown in Figure A-I.5. 11-16 CROSS SECTION 8 GAGE 101.2S8 p:!lItilI: ~~ ~r t =1.00 ~ ..J n "3 .:... .J;lIll~8 I~ § ~It'l, CONTROLLED 10,300 4 0 ~17,I,00 c f s q "10-!g·7~0 7 .66 '0MIlINSTtItOJ5Cl'1'RGE AT GOllJ CREEK [10000"51 ~r------"'---'------------, CROSS SECTION 8 GAGE 101.2S8 ~....----------------, CROSS SECTION 8 GAGE 101.2S8 B r 2 "1.00 n "3 A:NOT CONTROLLED 5,000 ~0 ~10,300 cfs NO EOUA T1 ON DEVELOPED A B:CONTROLLED 10,300 4 0 ~17,400 cfs q =10-T.40 -(WSEL _360)6.96 ~5[L '·360 fEETI UNBREAOiED 5.000 ~0 L..9,2oo eh NO EQUATI ON DEVELOPED BREACHED 9,200 ~0 L 27.700 cis WSEL .-'0-3.~6 0°·95 •360 ! / rt "0.98 n ,,5 A "r'J1!NST01 DISCHRRGE fl.T GelD CR~r:i(~lODDerS]'''' Figure II-4.Stage-discharge,flow-discharage,and flow-stage relationships for cross section 8 at site IOI.2R. II-I? Site 101.5L:This large side channe~becomes breached at a mainstem discharge less than 5,100 cfs.Stage was monitored at two of the five cross sections, numbers 2 and 5,in 1982 and 1983,and stage-discharge relationships were developed (Estes and Vincent-Lang,eds.1984a).In 1984,an additional staff gage was installed at cross section 1.The data base for the equations at cross sections 2 and 5 were relatively large with both indicating a distinct- change in the relationship between stage and discharge.This change is identified by an inflection point at 7,980 cfs (cross section 2)and at 16,400 cfs (cross section 5).The slope of the lower portion of the curve at cross section 2 is quite flat and reflects mainstem backwater influence.The change in slope at the inflection point is less pronounced for cross section 5, however,with the break in the stage-discharge relationship due to cross sectional geometry.In developing a stage-discharge relationship at cross section 1,only six points,considerably less than the others,were available. Since cross section 1 is downstream from cross section 2,however,an inflection point in the stage-discharge relationship at about 8,000 cfs due to mainstem backwater effects was also expected to occur,and the relationship was broken at 7,830 cfs.The data base covered the mainstem range of 6,210 to 28,900 cfs at cross section 1 and 4,500 to 26,600 cfs at cross sections 2 and 5.The lower limit of the application range was standardized at 5,000 cfs at each of the three cross sections and the upper limits at 35,000 cfs since applying the formulas beyond the data range did not produce questionable results. Channel hydraulics in this side channel are controlled by the mainstem for the entire evaluation range of 5,000 to 35,000 cfs with site flow slightly influ- enced by tributary inflow and distributary outflow.In addition,Whiskers II-18 Creek flows into the site just below cross section 2 but does not contribute significantly to the total site flow.An overflow channel on the right bank of the study site between cross sections 3 and 4 redirects flow back into the mainstel1l at discharges greater than 12,000 cfs,but outflow amounts to less than ten percent of the total site flow. Flow measurements in this study site were made at cross sections 3,4,and 5. However,the two relationships involving site flow (q vs.Q and q vs.WSEL) were developed at cross section 1 as it was the only cross section for which stage had been monitored in conjunction with the site flow measurements. The flow-discharge relationship was broken at 7,830 cfs,the discharge at which mainstem backwater effects are diminished at cross section 1.The highest discharge at which flow was measured was 14,400 cfs with the relation- ship determined to be valid for up to 35,000 cfs ..An equation was also developed to relate stage and flow at cross section 1 and it is applicable to the entire evaluation range of 5,000 to 35,000 cfs. Plots and equations for the three relationships at cross section 1 for this site are shown in Figure 11-5.Stage-discharge relationships the cross sections 2 and 5 are shown in Figure A-1.6.No stage data was collected at cross sections 3 and 4. 11-19 ...... ,.." ~ c '".., + -CROSS SECTION 1 GAGE .101.2X1 8 r 2 =0.99 n =3 A r 2 =1.00 n •2 CONTROLLED 5,000 ~0 ~7,830 cfs q ~101.480°.19 B:CONTROLLEO 7,830 ~0:35,000 cfs q =10-1 ,41 01.19 _..,+--------~~'O:-----------:'!,," tlfllNSTEtl OISOfflGE AI SOUl =EK «OOOCl'S ( ~'r=:::=_::_:::__:====::=':7""':-------_____..,CROSS SECTION 1 GAGE 101.2X1 A:CONTROLLED 5,000 ..0 ..7,830 cfs WSEL =-10-0 •88 00.28 +360 B:CONTROLLED 7,830 L.0 ~35,000 cfs WSEL =-10-1 .25 00.a8 +360 8 r 2 =0.99 n =5 A r 2 =1.00 n =2 -CROSS SECTION 1 GAGE 101.2X1 r:=.99 n =4 COHTROLLED 5,000 ..0 L 35,000 cfs q =102 .97-(WSEL _360)1.35 wso..:"'360 rEEll -,r----------;:,,:----------.-J l'\RINSTO'I O1SCHARG(AT ca.n CREEl(r:OCCCF'Sl lOO Figure II-5.Stage-discharge,flow-discharge,and flow-stage relationships for cross section 1 at site lOl.5L. II-20 Site 101.7L:The gravel bar that constitutes the right bank of this side channel becomes overtopped near cross section 2 at 9,600 cfs.Below 9,600 cfs mainstem backwater extends from the mouth of the side channel (about 125 ft downstream of cross section 1)up to cross section 2.Once the side channel is breached (at 9,600 cfs),backwater extends up to cross sections 3 and 4. f1"fl'" At 23,000 cfs,the head of the site,which is about 100 ft upstream of cross F~section 4,is also breached. Staff gages were installed at cross sections 1,3,and 4.One stage-discharge relationship was developed for each cross section from data collected when the mainstem discharge was greater than 9,600 cfs.The upper limit of the appli- cation range was extended only slightly beyond the range of available data to 23,000 cfs (from 21,200 cfsf at cross section 1 and to 35,000 cfs (from 29,800 cfs)at cross sections 3 and 4. _. The plots and equations for the stage-discharge relationships at this site are shown in Figures 11-6 and 11-7. II-21 .... 5!r;::';;'~""':":"::=::"':":"'""'-----------"CROSS SECTION GAGE 101.8S1 A:BACKWATER 5,000 ~0 ~9,600 cfs NO EQUATION DEVELOPED B:BREACHED 9,600 <.0"23,000 cfs WSEL =-10-~·25 0°·67 +365 A B r Z =0.94 n =5 ."''' Figure 11-6. -l:'------------~------------J MRINSTEl1 OlSCHRRGE At D GOLD CREEK {lDOOCFSJ 100 Stage-discharge relationship for cross section 1 at site 101.7L. II-22 -'Il II 1 1_JI J )i ]11.- ..~ •',1 ~ 1•1 ~•1•11• !at 7 I I-l I-l \ N W ~ "-l<I '+' ~ ,~~. CROSS SECTION 3 GAGE 102.0P1 'r 2 =0.96 n =5 A A:NO OACKYIATER 5,000 ~0 ~9,600 cfs NO EOUATION DEVELOPED B:BACKWATER 9,600 ~0 <35,000 cfs WSEL =-'°.2 .28 0°·72 +367 ~ ..... l<I '+' ~ CROSS SECTION 4 GAqE 102.0P2 A A:NO BACKWATER 5,000 ~0 <.9,600 cfs· r~o EOUATI ON DEVELOPED B:BACKWATER 9,600 <0 <35,000 cfs WSEL =-,0·T.95 0°·65 +367 " B r 2 .,0.99 n ..3 -1 wNRINSTEMDISCHRRGEATGOLD CREEK (IOOOCrS)\00 -1 wMRINSTEMDISCHRRGERTGOLD CREEK (IOOOCrSJ 100 Figure 11-7.Stage-discharge relationships for cross sections 3 and 4 at site lOl.7L. ..... Site 105.8L:This site is located on the left bank of the mainstem.Staff gages were installed at,two of the four cross sections,numbers 1 and 4.The available data at cross section 1 is limited and covers the mainstem range of 7,320 to 9,330 cfs with the application range of the stage-discharge relation- ship was limited to the range of available data.The data for cross section 4 covers the range of 7,320 to 29,800 cfs with the plot indicating an inflection point at 24,000 cfs.The change in slope of the stage-discharge relationship at this cross section may be due to a cross-sectional grade break.Because of the high correlation coefficient calculated for the lower portion of the curve,the lower limit of the application range was extended to the stan- dardized 5,000 cfs.The application range for the upper portion of the curve at cross section 4 was limited to the range of available data since only two points were used to develop the equation. Figure II-8 shows the plots and equations for the stage-discharge relation- ships at this site • 11-24 1 I D JI i ..~ Jl 1I'I ]1•§ ~ t.1 !1 i r 2 "1.00 n "10 B r 2 =1.00 n =2 2.I CROSS SECTION 1 GAGE 105.6PO g I CROSS SECTION 4 i GAGE 105.8P1 .............. I N 01 § ..... '"D:l ';' ~ -I /r 2 "0.99 n ,,5 7,320 ~0 ~9,330 cfs WSEL "-'0-1 .09 0°·89 +395 wMAINSTEMDISCHAAGEATGOLD CREEK I!OOOCFSI 100 ~ ~ ';' ~ -I A: 5,000 £.0 (24,000 cfs WSEL =-10-0.Z4 0°·37 +395 B: 24,000 ~0 <29.800 cfs WSEL =~0-2~98 0°·89 +.395 wMAINSTEMDISCHARGEATGOLD CREEK rlDDOCFSI 100 Figure 11-8.Stage-discharge relationships for cross sections 1 and 4 at site l05.8L. ""'. Site 112.6L:This large side channel with nine cross sections,becomes breached at a mainstem discharge less than 5,100 cfs.Mid-channel gravel bars divide the flow at the head of the site at cross section 8 and at the lower end at cross sections 1,2,3,3A,and 4.Due to the gravel bars,the water surface elevation is not constant across the sections,and staff gages had to be installed on both banks.Stage-discharge relationships were developed for each gage and were generally defined for the range of available data.The appl ication range for gages that corresponded to the largest portion of channel conveyance at each cross section was extended to 5,000 cfs on the lower end and 35,000 cfs on the upper end.Insufficient data was available at cross secti ons 3A and 4.to descri be the stage-di scha rge response over the entire range of 5,000 to 35,000 cfs. Channel hydraulics for this site are controlled by the mainstem for the entire evaluation range of 5,000 to 35,000 cfs.Five flow measurements were made at cross section 7.When developing the flow-discharge relationship,a high correlation coefficient was calculated using the lowest four data points. When the fifth data point was incorporated,a much lower correlation coeffi- cient resulted and a flow of 40,000 cfs was predicted for a mainstem discharge of 35,000 cfs.The relationship was thus,broken at 10,800 cfs.When the upper portion of the curve was applied to a mainstem discharge of 35,000 cfs, a site flow of 17,000 cfs was produced.The physical explanation for the inflection is probably head berlll geometry;at 10,800 cfs the mainstem stage at the channel entrance may coincide with a cross-sectional grade break.The data base covers the mainstem range of 6,210 to 24,00Q cfs with the applica- tion range at 5,000 to 35,000 cfs. II-26 _. '''''" """ "'.. The flow-stage relationship at cross section 7 was developed from data corre- sponding to the mainstem range of 6,210 to 10,800 cfs.The application range was not extended beyond the ra~ge of available data. The plots and equations developed for the three relationships at cross section 7 are shown in Figure II-9.The plots and equations developed for the stage- discharge relationships at the other eight cross sections of this study site are shown in Figures A-l.7 through A-I.17. II-27 §1r==-:----------r----. CROSS SECTION 7 GAGE 112.3X7 B ~Ir=::-=:::-=-:~---------­ CROSS SECTION 7 GAGE 112.3X7 r''"1.00 n '"2 A r'~0.99 n =It A:tONTROLLED 5,000 =0 ...10,BOO c f s q =10-10 •85 0 3 .47 r'=0.99 /n =It WSE1.!«tSQ Fa:n -, 13:CONTROLLED 10,800 ...0 '-35 000 ct. q =10-S.35 -0 2 .;1 'lZl CONTROLLED 6,210 ~0 ...10,800 cf. q =10-Z•7S (WSEL _450)7.08 --::-,------------In ,,,.,2',.....,...------------.....,------ CROSS SECTION 7 GAGE 112.3X7 r'•1.00 n •1 CONTROLLED 5,000 ~0 ~35,000 ct. ~ISEL "'-10-n.96 0°.1'4 +450 ,., I'lIlIHSTO'lIJI3i:HRRG£RT Gail CRW(lllJOllCf"SI IlZl Fi gure II-g.Stage-discharge.flow-discharge.and flow-stage relationships for cross section 7 at site 112.6L. II-28 ..... Site 114.1R:Two channels direct flow into this study site.The larger channel becomes breached at a mainstem discharge of less than 5,100 cfs,and the smaller one at 10,000 cfs.One staff gage was installed in the study site and was located at cross section 2.The stage remains relatively constant for mainstem discharges below 8,800 cfs,suggesting no mainstem backwater influ- ences.Above 8,800 cfs,however,stage increases rapidly and a stage- discharge relationship was developed from data covering the mainstem discharge range 8,800 to 19,000 cfs.The application range of the equation was not extended beyond the range of available data as only four points were used to develop the relationship and these were not evenly distributed within the range of available data. Figure II-I0 shows the plot and equation developed from the stage-discharge data for this site. II-29 2:r:::==-':""":":::-::~------------CROSS SECTION 2 GAGE 114.0P1 B r 2 =1.00 n =4 A A:NOT CONTROLLED 5,000 ~Q ....8,800 cfs NO EOUATION DEVELOPED B:CONTROLLED 8,800 ( 0 ...1 9,000 cf s WSEL :-10-2 .14 00 .68 +495 -lr------~-------~MAINSTEn DISCHARGE AfoGOLD CREEK [IOODerS]100 Figure 11-10.Stage-discharge relationship for cross section 2 at site 114.1R. II-3D Site 1I5.0R:Two channels direct flow into this study site.One becomes breached at 12,000 cfs and the other at 23,000 cfs.One staff gage was installed and was located at cross section 1.Stage is relatively constant below 10,400 cfs and is influenced primarily by upwelling and local runoff in the upper reach of the study site.Above 10,400 cfs,stage ;s backwater- influenced.One stage-discharge equation was developed for the site from data covering the mainstem range of 10,400 to 31,700 cfs with an application range of the equation at 10,400 to 35,000 cfs. The plot and equation for the stage-discharge relationship at this site are shown in Figure II-II. .."" CROSS SECTION 1 GAGE 114.9P1 r Z •0.98 n •16 i9~ ~ lo.. 0....... ~-..t ~ ~- A A:NO BACKWATER 5,000 ~Q ~10,400 cfs NO EQUATION DEVELOPED B:BACKWATER 10,400 ~Q ~35,000 cfs WSEL •10·,:S5 0°·55 +'70 lDMAIHsttMOISCHRRG£AT GOLO CR££K tlOOOCrSJ lCD Figure II-II.Stage-discharge relationship for cross section 1 at site 1I5.0R. II-31 r~..'.00 n =12 Site 118.9L:This site is located on the l~ft bank of the mainstem.Stage was measured at cross section 2 for discharges between 7,380 and 19,000 cfs with one relationship developed from the data,applicable to the mainstem discharge range of 5,000 to 23,000 cfs.Figure II-12 shows the plot and equation of this stage-discharge relationship. 2~--------------------...., CROSS SECTION 2 GAGE 118.9P1 5,000 L 0 "-23,000 cfs WSEL =-'0-2 .37 0°·72 +505 Ie MRINSTEM DISCHRRGE:AT GOLD CRfD(llClOOCfSJ ICD r~Figure 11-12.Stage-discharge relationship for cross section 2 at site 118.9L. 11-32 r Z =1.00 n =10 !'''~ ..."" Site 119.1L:This site is located on the left bank of the mainstem.Stage F'~was measured at cross section 2 for discharges between 7,380 and 19,000 cfs with one relationship developed from the data,applicable to the mainstem discharge range of 5,000 to 23,000 cfs.Figure II-13 shows the plot and equation of this stage-discharge relationship. CROSS SECTION 2 GAGE 119.1P1 5,000 <.Q ~23,000 cfs WSEL =-10-1 .30 0 0 .50 +50S -l~----------~lO------------llOO MAINSTtM DISCHARGE AT GOLD CREEK (lOOOCrS) ......Figure 11-13.Stage-discharge relationship for cross section 2 at site 119.1L. 11-33 Site 119.2R:This side channel site becomes breached at 10,000 cfs.Below 10,000 cfs,mainstem backwater is present in the lower end of the study site, with the upper end dewatered.Mainstem backwater effects persist in the lower end at higher discharges.Stage was monitored at all six of the cross sections over the mainstem discharge range of 7,080 to 24,500 cfs and one curve was fit to the stage-discharge data for each cross section.The rela- tionships for the lower four cross sections (the mouth and numbers 1,2,and 3)are applicable to mainstem discharges of 5,000 to 24,500 cfs and for the upper two cross sections (numbers 4 and 5),10,000 to 24,500 cfs. Site flow was measured at cross section 3 when mainstem discharge was 13,600, 17,400 and 22,700 cfs.The lower limit of the application range for the flow-discharge relationship is the breaching discharge of 10,000 cfs with the upper 1 imit at 23,000 cfs.The appl i cati on range was not extended beyond 23,000 cfs because the banks become inundated,changing the channel hydraulics and suggesting an inflection point. The flow-stage relationship developed for cross section 3 is applicable to the mainstem range of 10,000 to 23,000 cfs. The plots and equations of the.three relationships developed for cross section 3 are shown in Figure 11-14.The plots and equations for the stage-discharge relationships at the other four cross sections at this site are shown in Figures A-1.18 through A-1.20. II-34 CROSS SECTION 3 GAGE 119.2S3 ~.-------------------. -CROSS SECTION 3 GAGE 119.283 ~!t"~~r'=1.00 ,.r'=1.00 n 2 3,. 0 n =3 0t:_...J '-- i 8 i "",,,, BACKWATER 10,0004.Q....23,000 cf~ q =10-!0.14 0 5.32 BACKWATER 10,000 ....0:23,000 cfs q =10-j·91 (WSEl -505)8.80 -r,------:::-------.....J rt=!lNS1El1 OISD-flRGE Ar GOLD C'RE1X {100CCf"S I 100 _',,+--------------------1'0 WSEL 1"'505 faT l CROSS SECTION 3 GAGE 119.283 ~,.oo /~':12 / ,~ BACKWATER 5,000 i.Q ~2..500 c:h WSEl K-10-T.66 'OO.S6 +50S .... -i'+--------::,..-----_---l I"!AIHSTE:M'OISCHARSf:Ria GOLD CR.E£.I(f lcoocrSl Figure II-14.Stage-discharge,flow-discharge,and flow-stage relationships for cross section 3 at site 119.2L. 11-35 ..... Site 125.2R:This side channel becomes breached at a mainstem discharge of less than 5,100 cfs.Even though it is breached at a low discharge,the amount of turbid mainstem water that enters the site is limited by head berm geometry.Flow at this site is also derived from upwelling and local runoff. At some mainstem discharge,stage at the head berm coincides with a cross- sectional grade break and side channel hydraulics become controlled by the mainstem.This is reflected in the stage-discharge plot at cross section 2. Stage at cross section 2 was observed for mainstem discharges ranging from 4,300 to 19,100 cfs,and the lowermost data point did not align with the other ten points.Two stage-discharge equations were thus,developed with the breakpoint at 6,120 cfs.The equation for the lower portion of the curve is applicable to the range of 4,300 to 6,210 cfs,and for the upper portion, 6,210 to 23,000 cfs. Stage was also monitored at cross section 1 over the mainstem discharge range 6,210 to 19,100 cfs,and one equation was developed from the data,applicable to the range of 6,210 to 23,000 cfs. Site flow was measured at cross section 2 at mainstem discharges of 4,300, 6,210,7,680,and 9,000 cfs.Since site flow becomes controlled by the mainstem between 4,300 and 6,210 cfs,the lowermost data point was not used in developing the flow-discharge equation.When the equation is applied to 23,000 cfs,it produces a site flow of 19,000 cfs,suggesting an inflection point in the relationship.The application range of the flow-discharge -- equation is thus,the range of available data from 6,210 to 9,000 cfs. II-36 Two equations were developed for the flow-stage relationship at cross section _.2.One is applicable to the mainstem range of 4,300 to 6,210 cfs when channel hydraulics are not controlled by the mainstem,and the other is applicable to the range of 6,210 to 9,000 cfs. The plot and equation of the stage-discharge relationship at cross section 1 are shown in Figure II-IS.The plots and equations of the three relationships developed at cross section 2 are shown in Figure 11-16. CROSS SECTION 1 GAGE 125.0P1 -.. a a 6,210 l..0 ...23,000 cfs WSEL =-,0-T.09 0°·44 +552 r 2 =0.98 n =8 10MRINSTEMDISCHRRGERT GOLD CREEK £lOOOCrSl 100 Figure 11-15.Stage-discharge relationship for cross section 1 at site 125.2R. 11-37 ~T:C::R::O::S:-::S=-=S=EC-T=-I-O-N-2---------""" GAGE 125.0P2 CROSS SECTION 2 GAGE 125.0P2 ....Il ~~A:NOT CONTROLLED !r'•0.99 \,300 ~0 ~6,210 cfs n ·3 q •10.3 •06 (WSEL -SS2)7.~7 B fr~~~ 8:CONTROLLED~r'-0.96 ..6,210 _Q 9,000 cfs n ·3 ~!~q •10-3 •63 (WSEL -552)8.27 I c_ J,'llf~I A A .-,oi r'•1.00 n • 2 2 'I:NOT CONTROLLED 4,300 ~0 ~6,210 cfs 2 pl\ll!t. NO EOUA TI ON DEVELOPED B:CONTROLLED 6,210 ~Q L..9,000 cfs q.10.11.3603.63 ~... -L IIl[NSro'!OISCH'lRGE Ri"SOLD CREI)(1I000Cl'S1 '00 -,wso..(+552 rEETI to /''-00!n =10 .~...1.00 n ..2 "1=::-:'":'-:-:-=-=--------------. CROSS SECTION 2 GAGE 125.0P2 A:NOT CONTROLLED 4,300~0 L 6,210 cfs WSEL "-10-1 .51 0,·11 +552 B:CON1ROLLED 6,210 L..0 '-23,000 cf. WSEL =-10-~·5B 0°·34 +552 Figure II-16.Stage-discharge,flow-discharge,and flow-stage relationships for cross section 2 at site 125.2R. II-38 Site 130.2R:This study site is located at the mouth of a large side channel. In aerial photography taken when mainstem discharge was 18,000 cfs and less, water is present in the study site bl.At is separated from the main conveyance area of the side channel by a gravel bar.The presence of water in the study site at these discharges is due to backwater influences with some flow also across the gravel bar.In aerial photography taken at 23,000 cfs,the gravel bar is submerged and side channel flow encompasses the study site. Three cross sections were established at this site.Stage was measured at cross section 2 at mainstem discharges ranging from 7,380 cfs to 31,700 cfs. The lower nine data points from 7,380 to 16,100 cfs were used to develop a stage-discharge equation for the unbreached condition,and the upper five data points from 19,900 to 31,700 cfs for the breached condition.Solving the equations simultaneously yielded a break point of 18,200 cfs.The equation for unbreached conditions is valid for mainstem discharges of 5,000 to 18,200 cfs and for breached conditions of 18,200 to 35,000 cfs. The plot and equations of the stage-discharge relationship for this site are shown in Figure 11-17. 11-39 - - - - 5!T'""-:-:-:------------------------.CROSS SECTION 2 GAGE 129.8P1 •0.99 • 5 r 2 •0.98 n •9 oo CD !. A:~8REACHED 5,000::0 (..18,200 ch WSEl •100.0-~~9.19 +600 8:BREACHED 16,100::0 :-35,000 ch WSEl •10-1 •58 0 0 •56 +600-1+-----.--------.....--------------1w~ MAIN~~DISCHARGE AT GOLD CREEK (IOOOCrsJ Figure 11-17.Stage-discharge relationship for cross section 2 at site 130.2R. 11-40 - - ",... Site 131.3L:Four cross sections were established at this side channel site. The lower reach,below cross section 3,becomes breached at 9,000 cfs and the upper reach becomes breached at 10,700 cfs.Water is present throughout the site in unbreached conditions due to groundwater upwelling.Stage was moni- tored at cross sections 1 and 3,and one equation was developed for each cross section.The stage-discharge equation for breached conditions at cross section 3 was developed from data covering the mainstem discharge range of 10,700 to 19,900 cfs with the upper limit of the application range extended to 23,000 cfs.The stage-di scharge equation for breached condftions at cross ,-section 1 was developed from limited data,covering the mainstem discharge range 9,000 to 11,800 cfs.The application range,therefore,was not extended beyond the data range. The plots and equations'of the stage-discharge relationships at cross sections ~1 and 3 for this study site are shown in Figure 11-18 . .- ..... I -11-41 ~I 1 1 ·1 1 J 1 1 1 l 1 l i }J ~l 9.i -I CROSS SECTION 1 1 GAGE 131.1P2 ~ ~ I.po N m o 'f ~ CROSS SECTION 3 GAGE 131.1Pl .... A A:NOT CONTROLLED 5,000 :0 <.10,700 cfs NO EQUATION DEVELOPED B:CONTROLLED 10,700 <.0 <.23,000 cfs WSEL ~10-0:39 00 .29 +610 /',0,"n =5 l-- W L..l L.. D <.fl. di,..... ::: /: d' A A:lHJREA01EO 5,000 ~0 <9,000 cfs NO EOUATION DEVELOPED B:BREACHED 9,000 <0 <11,800 cfs WSEL =-10·,·62 00 .57 +610 r Z '"1.00 n "3 -I wMAINSTEMOISCHARGEATGOLO CREEK [IOODe,S)100 MQINST£M SJ~[hARGC At::C·.r]LS ~~f\[[t\,~or:~/-'~-::J )::':: Figure 11-18.Stage-discharge relationships for cross sections 3 and 1 at site 131.3L. Site 131.7L:This study site is located in the lower reach of a side channel that becomes breached at 5,000 cfs.Two other channels that direct flow into the side channel become breached at 10,500 and 14,500 cfs.The entrances of the three channels are more than 3,000 ft upstream of the study site. -Seven cross sections were established at the study site.Only one staff gage was installed and was located at cross section 3.Stage was monitored over the mainstem discharge range 6,210 to 27,700 cfs.Although the channel ~becomes breached at 5,000 cfs,stage at cross section 3 is also influenced by upwelling and local inflow.Aerial photography shows that stage became !'- controlled by the mainstem at about 7,400 cfs.The lowermost stage-discharge point of 6,210 cfs was thus,not used in developing the stage-discharge equation,and the range for which the equation is valid is 7,470 to 27,700-cfs. ,~ Site flow was measured at cross section 3 when mainstem discharge was 6,210 to 21,000 cfs.For the same reasons discussed above,the lowermost data poi nt was not used in developing a flow-discharge equation and the mainstem discharge range for which the equation is valid is 7,470 to 21,000 cfs. - .- A flow-stage equation was developed for cross section 3 and is also applicable to the discharge range 7,470 to 21,000 cfs . The plots and equations of the three relationships at cross section 3 in this site are shown in Figure 11-19. 11-43 -CROSS SECTION 3 GAGE 131.5S3 ~r------------------. -CROSS SECTION 3 GAGE 131.5S3 ;~ ~;;; ~ li r 2 =0.96 '"r 2 '"0.99c:>c_.... n = 7 "--n '"7~I ,... CONTRCcl.L1'D 71,70 <0 '-21,000 cfs q'= ,0=11.'i4 03 .31. "IVIINSTEl'l CISCHMRSE Ai SOLD CREEl(1I0ocasJ -,---------_....:-_---------, CROSS SECTION 3 GAGE 131.5S3 A:NOT CONTROLLED 5,000 ~0.1.7,470 cfs NO EQUATION OEVE1.0PED B:CONTROLLED 7,470 L.Q£27,700 cfs WSEL =-1Q-~·33 0°·66 +615 B r 2 =0.96 n =9 A CONi ROLLED 7470"Q "'21,000 ch q'='O~"~(WSEL -615)5.~~ -,·---·------------------:"0· I<SEl.l-SIS fEl:Tl -', Figure II-19.Stage-discharge,flow-discharge,and flow-stage relationships for cross section 3 at site 131.7L . •-II-44 - - .- Site 132.6L:Two channels direct flow into this side channel.One becomes breached at 10,500 cfs with the other at 14,500 cfs.Below 10,500 cfs,ponded water is present throughout the study site but eventually dries up.Flow just downstream of the study site is augmented by the confluence of another side channel,which becomes breached at 5,000 cfs. Staff gages were installed at each of nine cross sections that were estab- lished in this channel.Stage was monitored over the mainstem discharge range of 10,700 to 27,700 cfs and additional stage data were available at 8,800 cfs at some of the cross sections.At discharges greater than 23,100 cfs,stage in the lower portion of the study site (cross sections 1 and 2)is influenced by backwater from the side channel downstream that becomes breached at 5,000 cfs.One stage-discharge equation was developed for each cross section.The equations for cross sections 1 and 2 are applicable to the mainstem discharge range 10,500 to 23,100 cfs and for cross sections 3 through 9,10,500 to 27,700 cfs.The upper limit of the application range was not extended beyond the range of data because an overflow channel begins to direct flow out of the site from the right bank between cross sections 4 and 5 at a mainstem dis- charge of 25,000 cfs,thereby altering the channel hydraulics • Site flow was measured when mainstem discharge was 10,700,12,700,and 21,500 cfs.A flow-discharge equation was developed from data collected at cross section 3 with the equation valid for the mainstem discharge range of 10,500 ,~ to 25,000 cfs. The flow-stage equation for cross section 3 is also applicable to the mainstem discharge range 10,500 to 25,000 cfs. 11-45 - .... I ,I$\@li, - .- .... ..... The plots and equations for the three relationships at cross section 3 in this site are shown in Figure II-20.The plots and equations for the stage- discharge relationships at the other eight cross sections are shown in Figures A-2.21 through A-2.24 . 11-46 ~r--__--------------' CROSS SECTION 3 GAGE 132.583 ai,----------------, -CROSS SECTION 3 GAGE 132.5S3 lC WS!l.I+620 FEET I CllNTROLLfD 10 500 L Q L 25,000 cf$ q :10-~.1I2-(WSEL _620)13.52 -, r%c 0.99 n ·3 CONTROLLED 10.500"-0 ....25,000 ch q ..10-TII.71:03 •93 -,.+------~----..1O--------~ !'flINSIDl OISCIiPRGE RT SOUl CRllX llOOOVSl ~~t; '"'"".:9-...-c~8.....i~r 3 •0.99 n ..3 A CROSS SECTION 3 GAGE 132..583 II-47 Stage-discharge,flow-discharge,and flow-stage relationships far cross section 3 at site 132.6L. CONTROLLED 11 900 L 0 L..23.,00 chWS~L ..10-0 •32 0°·27 +620 NOT CONTROLLED 5,000 ~Q '10,500 cf$ NO EQUATION DEVELOPED B: _,.1..---------------- ~~!r.r'it(."1 ~':;;Shffi";~:=:f"~-rll.!~:::::I\[~~:r ~:-::·:~~:;-':..I Figure II-20. Site 133.8R:This site is located on the right bank of the mainstem.One staff gage was installed at the site and was located at cross section 3.Two equations were developed from the stage-discharge data with the equation for the lower portion of the curve developed from data covering the mainstem di scharge range of 7,680 to 10,400 cfs and for the upper porti on,16,100 to 31,700 cfs.The mainstem discharge at which the "inflection occurred (15,600 ~cfs),was determined by simultaneously solving the equations for stage.The inflection is probably due to a cross-sectional grade break.The equation for the lower portion of this curve is applicable to the mainstem discharge range of 5,000 to 15,600 cfs and for the upper portion,15,600 to 35,000 cfs. The plot and equations for the stage-discharge relationship at this site are shown in Figure 11-21. '~:,.----------------------, CROSS SECTION 2 GAGE 133.7P 1 - ,.,... - A r 2 =0.97 n =8 A: 5,000 ~Q'15,600 cfs WSEL =10.0 •27 00 .23 +645 B: B r%.=0.97 n =10 .., 15.600 :0:35.000 cfs WSEL m 10.1•57 0°·54 +645 Figure 11-21.Stage-discharge relationship for cross section 3 at site 133.8R. 11-48 -- .~ Site-136.0L:This side channel becomes breached at a mainstem discharge of less than 5,100 cfs.Six cross sections were established at the site and a staff gage was installed at each.Stage was observed when mainstem-discharge was 7,680 to 27,700 cfs and one stage-discharge equation was developed for each cross section.The application range of all equations is 5,000 to 35,000 cfs. Site flow was measured at cross section 3 when mainstem discharge was 8,520, 10,600,12,700,15,600,and 21,000 cfs with the flow-discharge equation valid for the mai nstem di scharge range of 5,000 to 35,000 cfs.The flow-stage equation developed for cross section 3 is also applicable for the range of 5,000 to 35,000 cfs. The plots and equations of the three relationships at cross section 3 at this site are shown in Figure II-22.The plots and equations of the stage- discharge relationships at the other five cross sections are shown in Figures A-1.25 through A-l.27 • 11-49 - -CROSS SECTION 3 GAGE 136.0S3 -CROSS SECTION 3 GAGE 136.0S3 in SQ,.~r Z =0.99 0 C n ..4 ~- r 1 =0.98 I~n ..·S CONTROLLED 5,000 <.0 ~35,000 ch q ..'0~8.5T 02.59 ir--------~---~-----1 t7![r<S1E!'l OfSC>ftll;E trl"OOUl C'lE!J<[JOOOCfOt liD CROSS SECTION 3 GAGE 136.0S3 r',.0.99 -'n ..8 / CONTROLLED 5,000 ...0 <..35,000 ch WS£L =-'O·T.oo 0 0 •43 +670 CONTROLLED 5,000 ~O "-35,000 ch q ,.10-2 •31 (WSEL -670)5.85 _,:I--------------------!.,Q WSIl.f +£70 ra:n ""'" Figure II-22.Stage-discharge.flow-discharge.and flow-stage relationships for cross section 3 at site 136.0L. II-50 ...... Site 137.5R:This site is located along the right bank of the mainstem and is separated from the main conveyance area by a large gravel bar.The site becomes breached at 22,000 cfs.At very low mainstem discharges,site flow is maintained by upwelling.As discharge increases,backwater from the mainstem extends into the site.Three cross sections were established,and staff gages were installed at cross sections 1 and 2.From the stage-discharge plots, stage at both cross sections is influenced by the mainstem at about 11,800 cfs.A stage-discharge equation was developed for cross section 1 and the data used covered the rna i nstem di scharge rangle 11 ,800 to 31,700 cfs.The upper limit for the application range was extended to 35,000 cfs with the lower limit at 11,800 cfs.Stage measurements at cross section 2 when stage was governed by the mainstem were limited to two very similar discharges and thus,no equation was developed. The plot and equation of the stage-discharge relationship at cross section 1 and the plot of cross section 2 data at this site are shown in Figure 11-23 • II-51 1 1 )l 1 J J -I J 1 1 1 1 j 1 I 1 ]j ............ I (Jl N f-. U <..1 ~ "-c'U"' ...J ~ 0.:: IfJ'1 CROSS SECTION 1 GAGE 137.4P1 r~..0.98 n ..8 ... A A:NO BACKWATER 5,000 .!a<.11,800 cfs NO EQUATION OEVELOPEO B:BACKWATER 11,800 ~a ~35,000 cfs WSEL =10-3.11 00 .89 +687 iJ M9rN~T[~[;tSO-1f':Rr:[p.r L~r:-Jl.:'J C{;T:::~·:/lC:j~JC:FSl f-. U t..l L.. "-",a:-+ .J L.J;,:) :< u I CROSS SECTION 2 I GAGE 137.4P2 B 'II"'' A A:NO BACKWATER 5,000 ~0 {11,800 cfs NO EOUATION DEVELOPED B:BACKWA TER 11,800 ~0 ~35,000 cfs NO EQUATION DEVELOPED I I "I J:; M91NSTEM DlSU-IARG[fiT ['Gl!~CREEK 'I,~:;JF,,; Figure 11-23.Stage-discharge relationships for cross sections 1 and 2 at site 137.5R. .- Site 138.7L:This site is located on the left bank of the mainstem.Stage was monitored at cross section 2 over the mainstem discharge range of 9,890 to 19,900 cfs with the stage-discharge equation applicable to the range of 5,000 to 23,000 cfs. The plot and equation of the stage-discharge relationship at this site are shown in Figure 11-24. "r:-::-:--------------------,CROSS SECTION 2 GAGE 138.7P1 - 5,000 L 0 ~23,000 cf$ WSEL ~-'0-~·07 0'.54 +705 r 1 ..0.98 n ::9 lG "iLi:~iS rCM ~!'-:,,'J1AR(;[AT C';GU~(),EEK (1 CGSCPS 1 Figure 11-24.Stage-discharge relationship for cross section 2 at site 138.7L. II-53 - ..., Site 139.0L:This site is located on the left bank of the mainstem and is separated from the main conveyance area by a large gravel bar.At low mainstem discharges,cross sections 3 and 4 are dry and upwelling may be detected.The site gradually becomes breached over a wide range of mainstem discharges and turbid mainstem water begins to flow laterally over the lower end of the gravel bar at about 12,000 cfs.At 23,000 cfs the gravel bar is entirely submerged. Stage was monitored at cross section 2 over the mainstem range of 9,890 to 31,700 cfs.Above about 11,800 cfs,stage at cross section 2 is primari1y influenced by mainstem discharge rather than by upwelling,as indicated by the stage-discharge plot.The equation developed from the data is valid over the mainstem range of 11,800 to 35,000 cfs. The plot and equation for the stage-discharge relationship at this site is shown in Figure 11-25 • II-54 -- '.:.---------------------------.CROSS SECTION 2 GAGE 139.0P 1 B r 2 =0.97 n =7 ""'" ;:::. w W to. <f'<:., ~ .OJ bl "l: ... A A:NO BACKWATER 5,000 =0"-11,800 cfs NO EOUATION DEVELOPED B:BREACHED 11 800 <0 (,35,000 cfsWS~L ='10-27010°.64 +705 Figure 11-25.Stage-discharge relationship for cross section 2 at site 139.0L. II-55 r 2 =0,99 n =9 - - - Site 139.4L:This side channel becomes breached at a mainstem discharge of less than 5,100 cfs.Stage was monitored at cross section 2 over the mainstem discharge range of 7,410 to 19,900 cfs and one equation was developed.The application range for which the equation is valid was extended slightly beyond the range of available data to 5,000 cfs on the lower end and 23,000 cfs on the upper end. The plot and equation for the stage-discharge relationship are shown in Figure 11-26. --r-----------------------, CROSS SECTION 2 GAGE 139.4P1 5,000 (.o.c.23,000 cfs WSEL =-10·,·49 0°·49 +710 Figure 11-26.Stage-discharge relationship for cross section 2 at site 139.4L. II-56 .- - Site 147.1L:This large side channel becomes breached at a ma"instem discharge of less than 5,100 cfs.Six cross sections were established at the site,and a staff gage was installed at each of them.Stage observations covered the mainstem range of 8,130 to 20,000 cfs,and one stage-discharge equation was developed for each cross section.The side channel is not influenced by overflow channels or cross flow from the mains-tern and the application range for the stage-discharge curves is thus,5,000 to 35,000 cfs. Site flow was measured at cross section 4 when the mainstem discharge was 8,130,9,000,and 17,400 cfs with the application range for the flow-discharge equation set at 5,000 to 35,000 cfs. A flow-stage equation was developed for cross section 4 and is val id for ~ mainstem discharges of 5,000 to 35,000 cfs. The plots and equations for the three relationships at cross section 4 are shown in Figure II-27.The plots and equations for the stage-discharge relationships at the other five cross sections in this site are shown in Figures A-l.28 through A-l.30. -II-57 -CROSS SECTION 4 GAGE 147.0M4 r 2 ..1.00 n ..3 >ISU.{-eIG fEET) CONTROLLED 5 000 L 0'"35,000 cfs q'=10~·a4-(~SEL •610)3.44 -, a-------------r---,-CROSS SECTION 4 GAGE 147.0M4 IlIJ r 2 =1.00 n =3 I. '''fHNS!'01 DISomGE AT GOLD CR£:O(11 OOCCf'S I CONTROLLED 5,000::0 ...35,000 <:h q c 10-1.~n 01 •20 CROSS SECTION 4 GAGE 147.0M4 -, CONTROLLED 5,000 LOt.35,000 <:1:. ~SEL "-10·n.n 0°·38 +810 Figure II-27.Stage-discharge,flow-discharge,and flow-stage relationships for cross section 4 at site 147.1L. ~II-58 ,.... - - - DISCUSSION The equations developed in this section provide the basis for evaluating the response of juvenile chinook and spawning chum salmon habitat to mainstem discharge.Discharge directly affects stage,and stage influences the hydrau- lic parameters of aquatic habitats,such as depth velocity,and wetted surface area. For the 14 DIHAB study sites,the stage-discharge curve was used to estimate depths at unobserved streamflows,further refining the habitat response curve (Part IV).For the eight IFG study sites,the stage-discharge,flow-discharge and flow-stage equations were required to calibrate the hydraulic models.The flow-discharge equations were also used to relate simulated channel hydraulics to mainstem discharge (Part III).Further discussion as to how the results from Part II were used in subsequent analyses can be found in the following sections. II-59 - ,~ PART II I CALIBRATION AND APPLICATION OF IFG HYDRAULIC MODELS This section deals with calibration and application of the IFG hydraulic models at eight study sites and the WUA forecasts for juvenile chinook salmon at those sites.Two different hydraulic models were used in the analysis - the IFG-2 and IFG-4.The IFG-2 model is a water surface profile program (or step-backwater model)which is based on uniform flow theory.This model is most applicable to stream reaches with relatively mild gradients and uniform cross sections (or gradually varied flow conditions).The IFG-4 mode is an empirical model based on regime theory and regression analysis.This model provides greater latitude for application to stream reaches with non-uniform gradients and irregular cross sections (or rapidly varied flow conditions). One or two sets of data are recommended for calibration of the IFG-2 model, whereas a minimum of three data sets are recommended for cal ibration of the IFG-4 model (Bovee and Milhous 1978). Selection of one hydraulic model over the other depends on three consid- erations.These include:(1)the level of resolution of the aquatic habitat microhabitat desired,(2)the level of effort available for commitment to field data collection and,(3)site-specific considerations.Both IFG hydrau- lic models are based on the assumption that steady flow conditions exist within a rigid stream channel.Streamflow is defined as Il s teady ll if the depth of flow and velocity at a specific location remains constant throughout the III-1 - - time interval under consideration.This definition is commonly accepted to mean that the discharge remains constant through the study 'site during the time interval required to collect a set of calibration data.A stream channel is "rigid"if it (1)does not change shape during the time period required to collect all sets of calibration data,and (2)does not change shape while conveying natural streamflows of the magnitude to be simulated (Trihey 1980). The quantity of rearing habitat for juvenile chinook salmon at each study site is described by the relationship between WUA and mainstem discharge.The hydraulic models are calibrated to reproduce stage and horizontal velocity distributions observed at desired streamflow conditions.Both models use stream channel geometry and velocity data from several cross sections within a relatively short stream reach.Each cross section can be subdivided into as many as 100 cells (conveyance areas)to facilitate detailed analysis of the spacial distribution of depth and velocity combinations.Once it is properly calibrated,the computer program wi1l calculate stage and the respective horizontal velocity distribution at each cross section for all desired dis- charges.The simulated depth and velocities are then used in the HABTAT model (Main 1978). Within the HABTAT program,surface areas associated with the occurrence of various combinations of depth and velocity val.ues are,calculated by multi- plying the width of the cell by the reach length.The util ity of each cell is evaluated at a specified flow by calculating a joint preference factor defined in this study as the product of the individual suitability values associated .- with the velocity,depth and cover conditions.The WUA is calculated for each -III-2 cell by multiplying its surface area by its joint preference factor.The WUA for the study site is the sum of the WUAts for the individual cells. When the hydraulic models were calibrated,the flow-discharge functions were used to convert data collected on channel hydraulics to specific mainstem,- discharges.The channel hydraulics,in addition to the habitat parameters and -suitabil ity criteria from a previous study summarized by Estes and Vincent-Lang,eds.(1984d)are then combined with the HABTAT program to determine WUA and WSA for given site flows.Beyond the application range of the different functions,alternative methods were employed to determine WUA and WSA values. A total of eight study sites were selected for detailed analysis from 130 candidate sites (Part II).The locations of the study sites are idetified in Figure III-1 with the type of hydraulic model for each site listed in Table III-I.Plots describing the relationship between WUA and mainstem discharge are provided for each study site.In addition,time series WUA plot?based on the 1984 USGS record of average daily streamf"lows for the Susitna River at .- Gold Creek are also provided to indicate the temporal stability of rearing conditions at the study sites throughout the open water growing season (May 20 -September 15). FIELD PROCEDURES -Field procedures included site installation,cross section and streambed profile surveys,depth and velocity measurements,and collection of substrate and cover information. 111-3 ..... ..... - Whiskers Creek.__~"\I 8 Slough IOI~5L (I FG) STATION o 1 MILE (Approlt.Scale) E9 RIVER MILE Figure 111-1.Middle Susitna River IFG and DIHAB modeling sites. 111-4 .- - -~ - Figure 111-1 (Continued). 111-5 Creek o I MILE (Approll.Scale)e RIVER MILE - - 5fl1 of July Creek Figure 111-1 (Continued). (Curry)CriJek 1II-6 o I WIL.E (Appro...Seale) $RIVER WIL.E - - - -~ ..... I~ - 4th of July--- Cre.k RM .'..: Creek Figure 111-1 (Continued). ..........,.-131.3L (DIHAB) Crsek II 1-7 o I MILE (Approx.Scole) ffi RIVER MILE - ,~ - - Indian 136.0L (IFG) ft"'r.......",...~--139.4L (DIHAB) 139.0L (DIHAB) 138.7L (DIHAB) ~-137.5R (OIHAB) Gold Creek \---Railroad Bridge (DIHAB) o 1 MILE (Approx.Scale) €B RIVER MILE Figure 111-1 (Continued). 111-8 -- - - - ,- Figure 111-1 (Continued). II1-9 Portage Creek o ! MILE (Approx.Scale) e RIVER MILE - Table III-I.Types of hydraulic models applied at 1984 middle Susitna River modeling sites for rearing chinook. Site Type of Model 101.2R 7 cross section IFG-4 101.5L 5 cross section IFG-2 112.6L 9 cross section IFG-2....119.2R 5 cross section IFG-2 131.7L 7 cross section IFG-4 132.6L 9 cross section IFG-4 136.0L 6 cross section IFG-4 147.1L 6 cross section IFG-2 Site Installation:A varying number of cross sections were established and staff gages installed at each study site to describe pools,riffles,and runs. Cross sections were also located at the transitions between riffles and pools. Methods for installing staff gages are described in Part II of this report and the ADF&G Su Hydro Procedures Manual (1984). ..... - Cross Section and Streambed Profil e Surveys:Cross section profil es were determi ned for each cross secti on with a 1eve 1 and survey rod.Hori zonta 1 distances between headpins were measured to the nearest 1.0 ft by stadia surveyor measuring tapes.Streambed elevations were measured to the nearest 0.1 ft using differential leveling techniques.In conjunction with the cross secti on survey,the stage was determined at the 1eft and ri ght edges of the cross section,and depth was measured at a minimum of three points.Streambed profile surveys were completed using procedures described in Su Hydro Procedures Manual (1984).The results of the surveys are presented in Figures B-1.1 through 1.3 and Tables C-1.1 through 1.3. II 1-10 - - .... Calibration of the IFG-4 hydraulic model requires the stage at which no flow occurs for each cross section.Therefore,for these sites,the stage of zero flow was determined at each cross section.The-"s tage of zero flow" corresponds to the lowest streambed elevation for riffles and runs or the elevation of the hydraulic control immediately downstream of pools.A hydraulic control is identified by a change in the cross sectional dimensions in a relatively short distance such as sudden contractions and expansions vertical,horizontal or both (Chow 1959).The surveyed streambed profile was used to evaluate the stage of zero flow when the cross sections were not located on hydraulic controls. Depth and velocity:Information on depth and velocity necessary for model calibration were collected at each site using a Marsh-McBirney or Price AA velocity meter and a top-set wading rod.Water depth was measured to the nearest 0.05 ft _and velocities were measured to 0.1 fps.These measurements were classified as either I1calibration"or "s horeline"data.Calibration data were collected for use with the IFG-4 model at the smaller study sites and were obtained at verticals across an entire cross section.Shoreline data were collected at the larger study sites and II/ere obtained at verticals on that portion of the cross section extending from each bank out into the channel until either the depth or velocity were unsafe for field personnel (depth)4 ft or velocity)4.5 fps).Shoreline data were used to calibrate the IFG-2 model and to provide high resolution along the channel margins where fish habitat might exist.In mid-channel cells of the IFG-2 model sites, depths were estimated from cross secti on and water surface profi 1es.When cross section profiles were not available,the continuity equation was used. III-ll - .- The continuity equation assumes that the volume rate of flow at cross section 1 is equal to the volume rate of flow at cross section 2,written in the form where: v =velocity in fps A =area in ft 2 The equation was applied by assuming the same flow in adjacent cross sections. The mid-channel flow was calculated by subtracting the flow along the channel margins from the total site flow.The velocity for the mid-channel was determined by dividing the mean cell depth from the mid-channel flow. Substrate and Cover:Substrate composition and the cover value for juvenile chinook salmon were visually estimated across each cross section and recorded. Substrate composition was classified using the criteria presented in Table 111-2 and cover was described according to criteria presented in Table 111-3. GENERAL TECHNIQUES FOR HYDRAULIC MODEL CALIBRATION Input data requirements for an IFG-4 model include streambed elevations, stationing,reach lengths and stage of zero flow for each cross section,as well as individual cell velocities for each calibration flow.Input data requirements for the IFG-2 model include streambed elevations and stationing for each cross section,Manning's II nil values for each individual cell and a stage at the lowermost cross section for each flow.Data reduction and coding I II -12 Table 111-2.Substrate code classification. Substrate Visually Estimated Particle Size Classification Silt 1 2 Sand 3 4 Sma 11 Gravel 1/8-1 11 5 6 Large Gravel 1-3 11 7 8 Rubble 3-5"9 10 Cobble 5-10 11 11 12 Boulder )10 11 13 Table 111-3.Cover code classification. PERCENT COVER CODE COVER CODE- silt,sand 1 0-5 .1 emergent vegetation 2 6-25 .2 aquatic vegetation 3 26-50 .3 1-3 11 gravel 4 51-75 .4 3-5"rubble 5 76-100 .5 >5"cobble,boulder 6 debri s 7 f~overhanging riparian vegetation 8 undercut bank 9 ,,- II1-13 procedures suggested by Trihey (1980).Calibration of the IFG-4 model was P-undertaken following recommended IFG guidelines (Main 1978;Milhous,Wegner, and Waddle 1984)as supplemented by Trihey and Hilliard (I984).Guidelines I'ilIii:Iii, suggested by Trihey and Hilliard include: 1.Forecast depths and velocities for streamflows representing the anticipated extrapolation limits of the calibrated model during the initial calibration runs. 2.Visually examine water surface profile plots for each calibration discharge.as well as the streamflows represent"ing the upper and lower extrapolation limits of the model. If the observed and predicted water surface profiles do not agree, or the forecast water surface profi 1es for the upper and lower extrapolation flows appear unreasonable (i.e.,water flowing uphill or conflicting with the slope of the calibration profile),the following procedures were completed through an iterative process. a.The stage of zero flow was examined to see that it has been correctly defined. b.The cross section coordinates were checked that they were correctly calculated and transferred to the IFG-4 input deck. III-14 ,..", .... "".. _. c.The right and left bank stages were checked that they were properly used to provide a horizontal water surface across the cross section.If a large discrepancy existed between the right and left bank stages,the streambed elevations were adjusted to cause a horizontal stage across the cross section. To do thi s,the stage for the area with the majority of flow was extended across the cross section.The difference between thi s stage and the measured stage was added to the streambed elevations. d.The calculated stages were adjusted at each cross section within the following limits to provide more realistic forecasts of water surface profiles for the extrapolation flows: flat gradient ±0.02 ft steep gradient ±0.05 ft e.If steps II a"through lid II did not result in reliable water surface profiles for the extrapolation flows,it was quite possible that the stage-discharge relationship was non-linear and that more reliable hydraulic simulations would result from high and low flow models used in combination rather than from model to simulate the entire flow range of interest.If this was the case,separate the field data into two subsets and develop two hydraulic models following the guidelines and procedures described. II 1-15 3.The velocity adjustment factors (VAF's)were reviewed in"accordance with the IFG guide1ines (Milhous,Wegner,and Waddle 1984)after reasonable water surface profiles are forecast by model. While reviewing the VAF 's for thi s study,measured velocities were adjusted p. ±0.10 fps in low velocity areas or ±10 percent when in excess of 2 fps,and extremely small non-zero velocities (.01 to .05 fps)or abnorma 11y large Mann"i ng I s II nil values (.1 to .9)were assigned to pool and shoreline areas where zero velocity was reported in order to improve the predictive capability of the IFG-4 model over the range of extrapolation flows.Assigning a small non-zero velocity to a cell steepens the stage-discharge relationship more ~-than assigning a large II nil value:A steeper stage-discharge relationship predicts higher stage at the upper end of the relationship and lower stage at the lower end. Calibration of IFG-2 models also followed recommended IFG guidelines and was .....supplemented by procedures developed by EWT&A (Milhous,Wegner,and Waddle 1984).These procedures utilized the shoreline depth and velocity data collected over a wide range of flows,and the stage-discharge and flow-discharge curves established for several cross sections in the study site.Manning's II nll values were adjusted for each cell of the cross section .-until predicted shoreline velocities and water surface prof"iles conformed to field data. Required "input data for an IFG-2 model includes the stage at the downstream cross section for each streamflow to be simulated.These elevations were .-I II-16 - .... ...., obtained from the stage-discharge relationship developed for each cross section (Part II).Stage-discharge curves developed at the other cross sections in the study site provided target stages with which to compare predicted water surface profiles.If the stage predicted by the model was lower than the measured stage~the II nil values were increased.If the pre- dicted stage was too high~"n"values were decreased. Once the desired water surface profile was attained for the cal ibration flow(s)~the distribution of velocities across each cross section was compared with the available field observations.Plots of observed-predicted velocities were used to identify cells where an adjustment in the II n"value was required. Changes in individual II nil values for large conveyance areas (mid-channel cells)significantly altered the stage at the cross section,whereas chang~s in individual "n"values for small conveyance areas~or shoreline cells resulted in little or no changes in the stage. Roughness or n-modifiers are utilized in the IFG-2 model to account for decreases in II nil values with increases in discharge (Milhous~Wegner,and Waddle 1984).N-modifiers are necessary to maintain the characteristic shape of the velocity distribution across the cross section.All the "nil values at each cross section were multiplied by a constant factor for every flow. Typical n-modifier values ranged from 1.02 for low flows to 0.60 for extremely high flows.The apparent skewness between n-modifiers for low and high flows exists because most calibration and shoreline data were co11ected during low flow conditions.Minimal adjustment was necessary to simulate 10w flow conditions compared to high f10w conditions. II 1-17 .,'" .... A single IFG-2 model was not always adequate to reliably predict both low and high flow hydraulic conditions.This inadequacy was primarily due to the interaction between channel geometry and flow that altered the stage-discharge relationship,such as the overtopping of gravel bars or transformation of a riffle pool sequence to a run.Unrealistic velocity distributions between low and high flow predictions,especially along the shorelines,indicated a need to utilize two models for a particular cross section • GENERAL TECHNIQUES FOR HYDRAULIC MODEL VERIFICATION The quality of each calibrated IFG-4 or IFG-2 hydraulic model was evaluated at two levels.Level one is a qualitative assessment of the model's overall performance with regard to four evaluation criteria.Level two evaluations are analytical procedures and are applied when the calibrated IFG-2 or IFG-4 model was not assigned an excellent rating by the level one evaluation.In the level one evaluations,each model was given a numeric rating depending upon its degree of compliance with each criteria.Numeric ratings were based on a comparison of model performance with criteria and professional judgment. Professional judgment was based on:an understanding of open channel hydrau- lics,familiarity with the study site,experience with the model,and knowl- edge of how the model would be used in the habitat analysis. Numeric ratings of 0,1 or 2 for each of the four criteria were added and used to indicate the overall quality of the calibrated models according to the following scale: Excellent Good Acceptable Unacceptable 8 (maximum possible score) 7 5-6 <5;or zero for any evaluation category TTT ..1R IFG MODEL EVALUATION:LEVEL ONE The evaluation criteria and appropriate ratings for the level one evaluation for IFG models are described below. Criteria 1:How well does the model conform to the IFG and EWT&A calibration guidelines?: Plot water surface profiles,stage of zero flow,and streambed profile. Are they reasonable?To be reasonable,water must flow downhill;an increase in discharge should cause the pool/riffle sequence to drown out and cause the water surface profile to become more uniform in gradient;a decrease in discharge should cause the water surface profile to more distinctly reflect changes in stream bed gradient and pool/riffle pro- files. After examining the stage forecast by the calibrated model,the predicted stages were checked over a broad range of discharges to see if they are coincident with the stage-discharge curves for each site. After comparing predicted depths and velocities at the calibration flows to field data,the predicted flows were checked for agreement with the flows measured in the field for each cross section (IFG-4 model only). Also,were the predicted velocities realistic?Were there more than a few outliers for the extrapolated flows? III-19 - .... - 1""" Ratings: 2 =A model that can forecast both stages and velocities accurately . 1 =A model that can define stages and velocities accurately at the calibration flows but may not be able to reliably define both stage and velocities near the limits of the extrapolation range. o ~A model that cannot accurately reproduce stages or velocities at the calibration flow. Criteria 2:How well does the extrapolation range of the calibrated model conform to the desired range? Subreaches of the overall extrapolation range of the calibrated model were rated excellent,good,acceptable or not acceptable depending upon the degree to whi ch predicted stages coi ncide with the stage-di scharge curve and the degree to which VAF1s coincide with IFG guidelines.The first assumption made in this evaluation is that accurate stage-discharge curves are available for several cross sections in the study site.The ability to evaluate the forecasting capabilities of the model improve with an increase in the number of well-defined stage-discharge curves. Were there sufficient changes in local channel geometry,or flow patterns (such as additional flow contributions from other channels become breached at higher mainstem discharges)to invalidate the stage-discharge relationship beyond the range of available data.These changes were also noted by reviewing aerial photography and incorporating field experience. 1II-20 ..""' .... Ratings: 2 =A model that can forecast stages coincident with the stage-discharge curve while retaining VAF1s between 0.9 and 1.1 throughout the entire extrapolation range. 1 =A model that can forecast either VAF's or stages within the extrapo- lation range. o =A model that cannot forecast acceptable VAF1s or stages within the defined extrapolation range. Criteria 3:Are the hydraulic models appropriately calibrated for the species and life stage being considered? Study sites established to evaluate a particular species or life stage may not accurately represent microhabitat conditions important to another species and/or life stage.For example,a good rearing site may not be an acceptable spawning site due to substrate composition or absence of upwelling.The microhabitat characteristics of the study site were reviewed in reference to life history requirements of the species or life stage being evaluated.Were the cross sections properly located to accurately define the channel morphology important to the species and/or life stage of interest.Verticals should divide each cross section into cells that provide an accurate description of the depth and velocity distribution. 1II-21 ."., ,.."" ,,,... ..... Ratings: 2 =A model that provides sufficient precision in its hydraulic-fore- casts to be applied to both adult and juvenile life stages with an equally high level of confidence. 1 =A model that can provide a high level of precision for evaluating the life stage for which the study site was primarily established, but hydraulic forecasts are only considered "acceptable"for other species and/or life stages.If cross sections and verticals within the study site had been laid out differently,additional data collected,or a separate hydraulic model calibrated,a "2"rating would have been possible. o =Insufficient data were collected to calibrate the hydraulic model in the flow range of interest for the species or 1ife stages to be evaluated. Criteria 4:How well does the range of forecast depths and velocities compare with the depth and velocity suitability criteria? The occurrence of predicted depths and velocities were checked within a range of values for which suitability indices are not sensitive even though the model may not accurately reproduce depths or velocities. These ranges are unique to the particular set of habitat suitability criteria being applied.In general,hydraulic models for juvenile salmon II 1-22 ..... ,... ,."" should be accurate at low velocities (0.8 fps),but need not be as accurate when velocities exceed 2 fps.Hydraulic models for spawning salmon should be able to accurately predict velocities up to 2 fps,and depths up to 1.0 ft.Water depths greater than 0.15 ft need only be approximate and are of little consequence in steep-sided channels where an error in the stage will not cause a significant change in top width. Rat"j ngs: 2 =The hydraulic model provides accurat~forecasts of depths and velocities present in the study site throughout the full ranges of depths and velocities for which suitability criteria are defined. 1 =Hydraulic forecasts are sufficiently accurate to describe the order of magnitude of the suitability index and therefore will result in a reliable habitat model even though the precision of the hydraulic forecasts are questionable. o =The hydraulic model is incapable of accurately identifying the order of magnitude of the habitat suitability index. II 1-23 IFG MODEL EVALUATION =LEVEL TWO... Level two evaluation criteria were applied when the calibrated IFG-2 or IFG-4 model was not assigned an excellent rating by the level one evaluation.These f"""analytical techniques can also be incorporated as additional steps in recom- mended model calibration procedures for other studies using the IFG hydraulic models.Separate procedures were required for the IFG-2 and IFG-4 models due to their inherent differences. IFG-4 Model: A visual comparison was made between scatterplots of the observed and pre- dicted depths and velocities at all cross sections for each calibration flow. An accurate model should reproduce the observed data and plot as a straight ..~line on the scatterplots.A quantitative assessment of observed and predicted data can be made by computing several statistics which describe the differences between a set of values (Willmott 1981).0 Pearson's Product-Moment Correlation Coefficient (r),Coefficient of Determination (r2 ),the slope (b) and intercept (a)of a least squares regression between observed and predicted values are measures·of a model IS predictive capabilities.The predictive capability of the model may also be evaluated through the use of the system- atic and unsystematic components of the root mean square error n RMSE S =[N-1 L ((a +bO i ) i=1 ..... and as well as the total root mean square error I II -24 RMSE .... ...... where: i =1,2,••••••••••n (sample size of the number of predicted cell s) o =observed or field measured data P =model predicted data. If RMSE U was equal to or similar in value to the RMSE,the model was expected to be well-calibrated (Willmott 1981).An index of agreement,"d",was also calculated to determine the degree to which a model's predictions are error- free.The index of agreement was computed by The value of d varies between 0.0 and 1.0 where a computed value of 1.0 indicates perfect agreement between the observed and predicted observations, and 0.0 denotes complete disagreement • IFG-2 Model: A visual comparison was made of the observed and predicted velocity dis- tribution plots for the IFG-2 models,where most of the observed data was obtained near the shoreline.In general,cells in the IFG-2 model do not coincide with verticals where field measurements were made,but rather with distinct changes in channel geometry,roughness,or habitat suitability.A representative velocity distribution 11 shape II using calibration flow data, therefore,was developed for each cross section. II 1-25 DEPTH SUITABILITY CRITERIA FOR JUVENILE CHINOOK SALMON 0.00 0.00 1.00 1.00 3.0 0.00 0.14 0.15 10.00 2.0 DEPTH SUITABILITY (Sd) 1.0 J-....L.-----........---~--""T""--__,.---r_--,.I..--- 1.0 .9 .8 .7 'i3 ~.6 >~ ::i .5m ~ 5 .4 UJ .3 .2 .1 0 0 DEPTH (tt) "'... "',.. Figure III-2.Juvenile chinook salmon suitability criteria for depth applicable to clear and turbid water habitats.Source: Suchanek et al.1984;EWT&A and wee 1985. I II-26 ,.... ...... VELOCITY SUITABILITY CRITERIA FOR JUVENILE CHINOOK SALMON 3.02.52.01.51.00.5 0.2 0.0 +-----,-----r----,...----.---....;;=-r~---.., o SUITABILITY (Sv) ,l':'itJ1llIl VelocIty Clear Turbid 1.0 0.00 0.42 0.42 0.05 1.00 1.00 0.20 1.00 1.00F-0.35 1.00 1.00 0.50 1.00 0.80 0.65 1.00 0.60 0.8 0.80 0.68 0.38 1.10 0.44 0.25 JI'lIIl~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 ft1Il~-..0.6!e >-~ :::i ;i'W!RlL iii ~LEGEND :5 TurbidIn---0.4 Clear <~ Clear water less than 5 NTU Turbid water 50 to 200 NTU VELOCITY (ftfsec) ,/"'''' Figure II 1-3.Juvenile chinook salmon suitability criteria for applicable to clear and turbid water habitats. Suchanek et al.1984,EWT&A and wee 1985. velocity Source: I II-27 .~ j 1 i 11,]I 1 J ·1 8 I ''\1,'11 8 )I 1.0 I .- ::~:tffii:CLEA R TURBIO 0.8-1 I Percent Cover 0.1 0-5 X O.6~0.2 6 -25 w 0.3 26 -50 Cl 0.4 51 -75Z-0.5 76 -100 >-t- -oJ......-0.4......lD......~I t-N co ::> (J) 0.2 0.50.50.10.50.10.50.10.50.10.50.10.50.10.5 0.10.50.10.1 0.0 "·······,,···,,·"·'·"te·······(·Yti"·,·,····..·····,, Emergtnt Aquatic Vegetation Vegttation No Cover 2 3 4 Largt Gravt' 5 RUbb~, 3-5 6 Cobblt or BouldtrJ, Ovtr 5 1 Debris a Oeadfall e Overhanging Riparian 9 Undercut Banks PERCENT COVER BY COVER TYPE Figure 111-4.Juvenile chinook salmon suitability criteria for cover applicable to clear and turbid water habitats.Source:Suchanek et al.1984,EWT&A and wee 1985. 1 '~ ~11II 1 1 '1\ II ,1 '~ II II J 1 II•--I 1 1 J 'lII Table 1II-4.Juvenile chinook salmon cover suitability criteria,applicable to clear and turbid water conditions.Sources:Suchanek et ale 1984;EWT&A and WCC 1985. Cobble or Over- Percent No Emergent Aquatic Large Rubble Boulders Debris &hanging Undercut Cover Cover Veg.Veg.Gravel 311 _5 11 511 Deadfall Riparian Banks Clear Water (Suchanek et al.) 0-5%0.01 0.01 0.07 0.07 0.09 0.09 0.11 0.06 0.10 6-25%0.01 0.04 0.22 0.21 0.27 0.29 0.33 0.20 0.32 26-50%0.01 0.07 0.39 0.35 0.45 0.49 0.56 0.34 0.54 51-75%0.01 0.09 0.53 0.49 0.63 0.69 0.78 0.47 0.75 ......76-100%0.01 0.12 0.68 0.63 0.81 0.89 1.00 0.61 0.97............ I Turbid Water (EWT&A and WCC)lN l.O 0-5%0.31 0.31 0.31 0.31 0.39 0.39 0.48 0.26 0.44 6-25%0.31 0.31 0.39 0.37 0.47 0.51 0.58 0.35 0.56 26-50%0.31 0.31 0.46 0.42 0.54 0.59 0.67 0.41 0.65 51-75%0.31 0.31 0.52 0.48 0.62 0.68 0.77 0.46 0.74 76-100%0.31 0.31 0.58 0.54 0.69 0.76 0.85 0.52 0.82 1 Multiplication factors:0-5%-4.38%;6-25%-1.75;26-50%-1.20;51-75%-0.98;76-100%-0.85 Where only shoreline data was available,the horizontal velocity distribution ""'"was modeled either by using measured values obtained at a similarly shaped cross section where a complete data set was available,or by simply estimating a mid-channel velocity distribution based on the channel geometry and the continuity equation.The highest velocities should correspond to the deepest portion of the channel. Applying the IFG-2 model at discharges other than the calibration flow pro- duces velocity distributions similar to the calibration flow velocity dis- tribution.When inconsistencies between field data and predicted velocities occurred at high flows,a second model was developed similar to the first model.At high flows,the velocity increas·es more rapidly,along the shoreline than at lower flows.The second or high flow model can thus more "'M accurately,predict the velocities in this area. GENERAL TECHNIQUES FOR HYDRAULIC MODEL APPLICATION "..... The calibrated hydraulic models and habitat suitability criteria from previous studies were linked with the HABTAT model to forecast WUA for juvenile chinook salmon as a function of streamflow.The habitat suitability criteria as demonstrated in curves for each physical habitat variable were derived from field observations of juvenile chinook in side channel and side slough areas (Suchanek et al.1984)as described by EWT&A and WCC 1985.These suitability criteria are summarized in Figures 1II-2,III-3,III-4 and Table III-4.Two of the criteria,velocity and cover,are different under clear and turbid water conditions.Clear water habitats are those which occur in unbreached side channel areas conveying base flows derived from groundwater or tributary inflow. II I-3D "'.. .... ...'" Total WSA and WUA curves for juvenile chinook were obtained at the eight hydraulic modeling sites corresponding to a range of mainstem discharge from 5,000 to 35,000 cfs at Gold Creek.WUA was calculated and expressed in units of square feet per 1,000 linear feet of stream.When plotted as a function of discharge,the study site WUA indicates the site-specific response of fish habitat to changes in flow.WSA and WUA values for site flows outside the recommended extrapolation range of the hydraulic models were estimated using trend analysis and professional judgment.Instances where this was necessary are documented in Tables B-6.1 through B-6.8.Both the WUA and WSA response to mainstem discharge as predicted by the HABTAT model were reviewed for all the sites for their application ranges.The expected responses beyond the application range was estimated using professional judgment based on comparison with other sites having similar morphologic characteristics and aerial photography.A decreasing exponential rate of increase function was determined for each of those sites with application ranges less than 5000 to 35,000 cfs. A time series plot of available juvenile chinook habitat was also developed If'i'!III!I for each site,and hydrographs of site flows were generated using the regression equations developed in Part II and the mean daily mainstem ,..11\10, discharges for the 1984 rearing season (May 20 to September 15).The result- ,...ing figures enable evaluation of habitat conditions on a site-by-site basis over the summer period. 111-31 IFG MODEL RESULTS The following section provides a description of important physical habitat components found in each of the IFG model sites and anticipated changes in these components with respect to different mainstem discharge.WSA,WUA curves and time series plots of WUA are presented at the eight study sites corresponding to a range of mainstem discharges from 5,000 to 35,000 cfs. Site 101.2R ..... Site Description:This site is located 2.2 miles above the confluence of the Chulitna River with the Susitna River on its east bank (Plate 111-1).The study reach is 1,500 ft in length and varies in width from 350 ft in the lower half of the site to 250 ft in the upper half.Substrate is mainly cobble and large gravel throughout the site with a layer of silt in the left channel. Cover is available predominately from the rubble and cobble substrate, although some debris is present.Cross sections 1,3,4 and 9 are located in the shallow,high velocity areas while cross sections 7 and 8 are sited in a deep,slow velocity area (Figure 1II-5)•.Cross section 6 separates the two areas.Cross sections 2 and 5,within the small right channel,did not extend across the main channel,as the hydraulic conditions at adjacent cross sections were similar.Cross sections 3 and 4 extend across a small backwater channel along the left bank. This study site was selected to represent side channels that become dewatered.... at low discharges.Upwelling was suspected to maintain low baseline flow ..... II 1-32 ."'" ,- .,.... - ,... ...'.,. 101.2 A .....CIO..Section -Suallna A,,,-. Ji'~J75 C~O••SECTION 1 CROSS SECTION 3,."Ion 0"00 a,.rlon 3 +74 ..... J70 370 ;1\""S"'1fJ:'~~~J ; ~z0 F~J85 ;;J85~~...w c."if0:"'-25 ct•........ 380 J80 j#1PIl'&1, J55 355 '00 ZOO 300 400 0 100 ZOO JOO 400..... OISTANCE F"RO-"L.EF'T BANI(HEADPIN (FT)DiSTANCE ,ROM LEIT BANK HEADPIN (IT) J75 J75.....C~O"IECTION I CROSS SECTION' !Itallon Q.81 8teUoft '+0" 370 370 f,llIIJIllill ~g Iz~0 !i 305 385~~_278 ct.......__25t:hl I'"''"~~ Jeo JeD ,- J55 J55 0 '00 200 JOO 400 0 '00 ZOO JDD 400 OISTANCI;....0 ..LEfT BANK ......KEft (F'T)DISTANCE fflQ"LUT IIo'HK HEADPIN (F'T) Figure III-5.Cross sections for site lOl.2R depicting water surface elevations at calibration discharges of 25 and 279 cfs. II 1-34 37~CRO"aECTIOH • at.n~"1'"It 370 g ~3e~\~... ~ ::leo 200100o ::I~"+-__,.-_--,..-_----.__....,.__--r-__,-----,--....,.--.., 300 ....00 ::leo ,,~ CROSS SECTION 6 St.non e to 37 ::170 g: Z~::Itl5~~ '"78.,7"J ::0 25 d,I! 310 375 T.:"CR;;;O:;';.::.:":.::E::::Cr;:IQ:::..::-:-.-----------------.., at.UOft 12'"1. ::170 ::IlI5 \""'<--,,.,:::.278 c" '"/25.,.~ 3~"3"" 0 100 200 300 "DO 0 100 200 300 "DO OIST.....CE mow \.EFT BANK HEADPIN (1'0)015T.....C[FRO"~[FT BANK HEAD PIN (FT) 37~37~ CRO ..IECTIOH 1 CAO"al(;ltON .. It.flo..10";>3 ! 118t60n ,.....'12 Ho 370 S S ~~ 3e"i 3'~\~_218 cr...._27Q cr •...'"_2&ell '"_26.:..•'"-......~~ :0 ::0 ~I: 360 3eO 3~~355 0 100 200 300 +DO 0 100 200 300 ..00 OIST.....C[!"ROW LUT BANK HEADPIN (FT)O'STAHCE F'RO ....u:ftT BANK HEAD P1N (FT) "...Figure 11-5 (Continued). II 1-35 conditions and the site appeared to have potentially good rearing habitat, although no previous utilization has been documented.An IFG-4 model was selected because of the non-uniform flow conditions present and the channel size.Chum salmon adults have been observed to use the site but no redds were detected.Some juvenile chinook salmon have been observed in the site (Hoffman 1985). Calibration:Table 1II-5 lists the data IJsed to calibrate the hydraulic model for this site.Depth and velocity measurements were made across each cross section at every calibration flow.Because the hydraulic model was estab- lished to describe the depths and velocities in the main channel,cross sections 2 and 5 were not included,as they do not extend across the main channel. Table 111-5.Hydraulic data available to calibrate the IFG-4 model for site 101.2R. Site Mainstem ~Flow*Di scharge Date (cfs)(cfs) 840830 279 15,300 840903 25 11 ,200 ~ *Mean site flow At discharges greater than 14,000 cfs,flow entered the right channel.The stages in the main and right channels differed across cross sections 1,3 ;w..., and 4.The streambed elevations were raised in the right channel to maintain a horizontal stage across a cross section (Figure 1II-6).The backwater area -III-36 r{E,l~SUREn ADJUSTED 375,,&-~,_'MQ~t ._0000.,....G"'oo.... 310 370 g g ~~385~'85 ~..w !! 380 380-0'" 355'55 0 ,oa 200 300 400 0 '00 200 300 400.... lllSTANC~""""u:n ......"HEADPIN (FT)DISTANCE """"u:n ......"Hu.D9.N (FT) '75 375 ClIO"UCTlOlf a _lIl!C'R*'ItIItIOft '-.74 .....1+1oC '70 310 ~g !~I 385 ~385...-~~......-0 ...0'"--380 380 ..- 355 3" 0 '00 200 JOO 400 0 '00 200 300 400 DtSTAHCE _LEn ......"HEAD"'N (n)DISTANCE""""LEl"T""""HEAD_(n) 375 P'l_1l!CTlOlI4 I ...................... ,70 370 -~. g g ~j ~'85~!,u ~-0",-I 3110 3110 .- 355'55 0 '00 200 300 400 0 '00 200 300 400.....DISTANCE ".,,,."-EFT ....."HEAD"'N (FT)DIST....CE __l.UT ......1(HEADPIN (FT) Fi gure II 1-60 Comparison between measured and adjusted cross sections 1,3and4atsitelO1.2R. 1II-37 ..- .... ..... at the mouth of the left channel also had different stages than the main chan- nel.The streambed elevations in the left channel were raised to maintain horizontal stages at cross sections 3 and 4. Observed and predicted water surface profiles from the calibrated model are shown in Figure 111-7.The extrapolation limits are also plotted.The IFG-4 model was calibrated with respect to depth by making comparisons between the stage-flow curves and the model predicted stages.The comparison made at the discharge cross section is illustrated in Figure III-8;similar comparisons were made at each cross section. Verification:To compare the predictive capabilities of the model,an analyt- ical analysis was made.Scatterplots comparing the observed and predicted depths and velocities (Figure B-2.1)indicate the model is capable of accu- rately predicting hydraulic data.Statistical tests were also made and the results summarized in Table B-5. Application:An excellent rating was assigned for the range of 9,200 to 17,600 cfs mainstem discharge.As discussed in Part II of this report,the flow-stage relationship changes as the gravel bar which separates the main and right channels becomes overtopped.Because there is no data available to describe exactly how this change affects the flow-stage relationship,the upper limit of the excellent rating was set at 17,600 cfs,the upper limit of the discharge measurements.Above 17,600 cfs the predictive capabilities are no longer reliable. IU-38 1 1 IJ i I J ]1 I 1 )1 I I 1 J 366 .------------- Observed WSEL Predi cted water surface profile at calibration flow Predicted water surface profile for modeled flow ranQe Staoe of zero flow Streambed 4 6 7 8 9 I I I 5+64 8t37 10+23 12+79 14+62 _,-------_----600 cfs------------~-~-~ ••---"279 ,"..... ~O.~9\~ t""""t·...o. • ..------ 3+74 "2./.____------of •..-::::-/;--------.-----//" ---./ 10 cfs - ------' ...-.....-- OtOO ".,....-"'" ./ / ,/ ".,....-,/.'-..:--, ""'POINT OF ..~.:p':' 141(ZERO FLO .C;ci:,'CO:.·· AT -1+45 ...Ob ...;:r -i::i·<?:····c:j :.:~:.".;".?§?/,,:r ,.358 362 356 I 3II 364 360 ---"-' z 0-t- <:{ >H WH...JHWI W \0 W :J ll: +- STREAMBED STATION (ft) Figure 111-7.Comparison of observed and predicted water surface profiles from calibrated model at site lOl.2R. I J 1 ~1 J J J 1 a I ]I 1 1000400600200100 ... -Site·specific WSEL vs flow relationship for staff gage 136.0S3 at cross section 8. ,.Predicted WSEL from calibrated hydraulic model. 40 6020 I Extrapolation rang,of mod,1 ! 104 "'IIIiI- I I Ir- SITE FLOW AT 101.2 R (cfs) 6 8 1042 365 w (,)« lL. a::: ~ CJ) a:::w ~~36 0 1---T"-r"""!""'~""-r~--"lr-...,r-:""'YnT'1~!:,"--'"T'-..,.-r-.........--i ,,i I I I , , , ,, , I I Iii ,,I I , , , , , z o 370 I-<t> W .J W --.:=315 H H H I ~o Figure 111-8.Comparison between water surface elevations forecast by the calibrated hydraulic models and the stage-flow relationship for lOl.2R cross section 8.. The application ranges and ratings are summarized in the bar chart below. __-l _ I I I I I 6000 I I I I 14000 I I I I I 22000 , I I I I I 30000 MAINSTEM DISCHARG E (eft)II Excellent o Unacceptable WSA and WUA curves for study site 101.2R are provided in Figure III-9.The curves are plotted to the vertical scale of sq ftll,OOO ft of stream reach and a comparison of them indicates the relative proportion of WSA which contain rearing habitat for juvenile chinook. Rearing habitat for juvenile chinook in the side channel is maximized at r-mainstem discharges in the vicinity of 11,000 cfs.The sharp rise in WUA which occurs near 9,000 cfs is caused by the site becoming breached and the associated increase in turbidity which provides additional cover value for juvenile chinook. The WUA curve is also plotted in Figure III-9b at an expanded vertical scale / to accent the response of rearing habitat to incremental changes in discharge. The presence of turbid water and the distribution of water velocity are the primary determinants of the WUA response curve at this site.Although much of the site exists as riffle-run habitat,the channel gradient is low enough that 1"""water velocities do not become 1imiting to juvenile chinook until mainstem discharges exceed 16,000 cfs.The large vegetated gravel bar which separates the side channel from the mainstem and another large gravel bar in the lower -III-41 A 220000 .,------------------------~ 198000 - ~176000 1.L 0154000 a ~132000 .......... ~110000 1.L c::J B8000 en 66000 WSA 'MJA22000 <C ~44000 <C O-j----r-~,_-_r_-_,_-_,--r__-_.___-.........-____,.-~ o 4000 BOOO 12000 16000 20000 24000 28000 32000 36000 40000 MAINSTEM DISCHARGE [CFS) .- 8 35000 31500 ~28000 1.L a 24500 a ~21000 .......... ~11500 1.L ci 14000 en 10500 <Cw 70000: <C 3500 0 0 4000 8000 12000 16000 20000 24000 28000 32000 36000 40000 MAINSTEM DISCHARGE (CFS) Figure III-g.Surface area and juvenile chinook habitat response curves for site lO1.2R.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). III-42 _. .... porti on of the study site whi ch is exposed at low flows do not provi de any appreciable increase in rearing habitat at higher flows due to the low cover value of their sand and gravel substrates.Nevertheless,this study site possesses fairly good habitat for juvenile chinook in the lower flow ranges (Fig ure II I-9a)• Because of this limited extrapolation range of the IFG-4 model at 101.2R,the WUA and WSA curves were estimated for mainstem discharges less than 9,200 cfs and greater than 16,000 cfs . The WSA of the channel was estimated at 31,600 and 46,500 sq ft/1,000 ft for -discharges of 5,100 and 7,400 cfs,respectively,using digitized measurements obtained from aerial photography,as described in Klinger-Kingsley (1985). Low turbidity habitat suitabil ity criteria were used to forecast juvenile chinook WUA at 9,200 cfs (breaching discharge for this side channel)and the amount of rearing habitat available under unbreached conditions was assumed to decline to zero at a constant rate between this discharge and 6,500 cfs.This assumption is supported by numerous field observations of clear standing water which is cut off from the mainstem ..Although still contributing to total WSA,clear ponded water provides progressively less suitable habitat for- juvenile chinook as mainstem flows recede. At mainstem discharges exceeding 16,000 cfs (the upper extrapolation limit of the IFG-4 model),estimates of the WSA at 23,000 and 27,000 cfs were also obtained from aerial photography.Surface areas associated with discharges .I between 16,000 and 27,000 cfs were interpolated.Surface area estimates for III-43 discharges greater than 27,000 cfs were obtained by extending the surface area curve to a maximum of 210,000 sq ft/1,000 ft at 35,000 cfs. Above 16,000 cfs,the WUA curve for juveni 1e chi nook was assumed to decay exponentially.This trend is evident at other middle Susitna River side channels for which high flow hydraulic models are available.Extension of the ,,-WUA curve beyond 16,000 cfs using this exponential decay does not appear inconsistent with the rate of decline forecast by the calibrated model for-discharges less than 16,000 cfs.Additional information is provided in Table B-6.1. ,....Time series WUA and site flow plots for this study site are presented in Figure III-lOa and b.Low site flows during late May and early September corresponding to mainstem discharges of 9,000 to 13,000 cfs resulted in comparatively high rearing habitat forecasts for these periods.High site flows during the intervening months produced low rearing habitat forecasts. Site 101.5L- Site Description:This site is located 2.2 miles above the confluence of the Chulitna River with the Susitna River on its west bank (Plate III-2).The -study reach is 3,100 ft long and 430 ft wide.A large backwater area is present throughout the lower half of the site for the entire discharge range· of 5,000 to 35,000 cfs.Cobble and rubble substrate predominate throughout the site and a thick layer of sand exists along the right bank of the mouth. Large substrate,with less than 25 percent considered acceptable,provides the available cover.One cross section is located in the backwater area with a -III-44 1 I ]J 1 I ,I I I I I 1 I 1 I I l J A30000 27000 24000 21000 18000 <t: :=l 15000 3: 12000 9000 6000 3000 0 I I MAY JUN JUL AUG SEP H 8 H 6000 H I 5400.po \J1 4800 3:4200 0 3600-l l.L.3000 W I-2400 Hen 1800 1200 600 0 I I I I I MAY JUN JUL AUG SEP Figure 111-10.Time series plots as a function of time for site 101.2R.A -Juvenile chinook WUA. B -Site flow. - .... - .... --second at the transition between the low and high velocity areas.In addi- tion,three cross sections are located in the deep,fast area in the upper half of the study reach (Figure 111-11). This study site was selected to represent large side channels which remain side channels from 5,000 to 35,000 cfs.An IFG-2 model was selected because -of the large size of the channel and its uniform shape.In addition,field reconnaissance indicated that rearing habitat was limited to the stream bank margins,therefore,a small amount of data would be adequate to simulate channel hydraulics. - Three channels were identified and labeled A,Band C.Channel B conveys mainstem flow at all discharges and Channel C at 10,000 cfs (Plate III-2). Channel A breaches at 12,000 cfs and redirects less than ten percent of the flow from the side channel to the mainstem.It was therefore considered negl i gi b1e.Spawni ng salmon have not been observed in the si de channel at this site.Juvenile chinook,coho and sockeye salmon have been identified in the site,however (Hoffman 1985). Calibration:The data available to model the site included level surveys for cross sections 1,2,and 5;stage-discharge curves developed by ADF&G Su Hydro at cross sections 2 and 5 (Estes and Vincent-Lang,eds.1984);and the hydraulic data summarized in Table III-6.Cross sections 3 and 4 were developed from the discharge measurement notes and were not surveyed. 1II-47 101.SL ......Cross SecUon J"T::c=ao=-s;;cs~S.;:C;;-;T;;:,O;;;N:;-;-3------------------~ St.lion 1'a +UI 100 ZOO ~OO 400 DISr....CE FROM "En BANK HEADPIN (n) 500 600 cl. 16'i8 el, J10 £ zg ~\, \~JeS ~.., ,;;, :;~\.i!'i JEO j J5Sj ........... .:::.......::...','.:~. .:...:.,'.:':.::.' .;".' -- .- ',--:;:::;_---_16tliJ c:,. J15 CROSS SECTiON 04- St.UQft U +041 J10 g ~J6'~..~ JeO j JE.]\~.;\~ J_,I-,---------------,r--.6OO~' "".,..----.'lell8 l:f,~7- ,-,"T"c-a-Os,..,.s-SE""O.".TIO.".N-'------------- ..,S1ahQn 0 +00 100 200 300 400 DISr....CE FROM "EFT BANK HEADPIN (n) o J55 +---,---,,---.,-----,-----,--,.---,-----,--,..----{ 500500,00 ::zoo 300 ....00 DISTANCE FRO,,",I.EFT El.A.I\IK HEADPIN (FT) --CROSS S£C1IQN 2 J15 CROSS secTION S ,StilliOn.12 +23 Slation 31 .08 ~ '"~J10 ~g _..~OO ct. I L.r.z ~_lev,ct. Je5 ~i Je5 J \7 1"8I:f,...~.: :;"C /7 ... ~::>!!!! Jeo ~Jeo ..... J55 4'_--.__.--_.--_,....-_..-_...--_-.--_...,...._-.-_-1 o 100 200 JOO ....00 D'ST....CE FRO,""EFT BANK H£AOPIN (FT) 5C J'5 +---rr--,.,.o-o--r--,O.,.O--,...--J-Oro--,r---•...,o-o----,----jsoo OISTANCE FRO....I..EfT BANK HEADPIN (fT) Fig ure I II -11.Cross sections for site 101.5L depicting water surface elevations at calibration discharges of 1696 and 2213 cfs. III-48 f"'"*0 = S = **=.- Table III-6.Hydraul ic data available to calibrate the IFG-2 model for site 101.5L . ....- Site Mainstem Flow Di scharge Cal ibration ~Date (cfs)(cfs)Cross Section(s)Type* .....841012 1622 6210 4 0 841001 1696 7830 5 0 1,2 S 840911 2213 9330 3 0 840921 2250 11 ,400 1,2,5 S 940831 3530 14,300**3 0 .~ 840820 4500 18,500 1,2,5 S Discharge measurements (includes mid channel and shoreline measurements) Shoreline measurements (does not include mid channel measurements) Adjusted to instantaneous discharge Two models were required to accurately describe the site for mainstem dis- charges of 5,000 to 35,000 cfs.Velocity profiles for site flows of 1,696 and 2,250 cfs at cross sections 1,2,and 5 were similar.However,simulation of the velocity distribution across the channel at a site flow of 4,500 cfs required a different set of II n"values.Velocities increased gradually with distance from the water's edge at low flows,but rose quickly and approached maximum channel velocity much closer to shore at high flows. The velocity profiles for the two measured flows at cross section 3 were very similar and represented low and medium flows through the site.Only low flow data were available for cross section 4. III-49 ..... - - ,~ ~, In calibrating the two models with respect to depth,predicted stages at cross sections 2 and 5 were compared to the corresponding elevations calculated from the rating curves.Stages for cross sections 3 and 4 were checked by compar- ing the predicted top widths with the top widths determined from the discharge measurements.Figure III-12 shows water surface profiles based on IFG-2 output for the calibration flows of 1,696,2,250,and 4,500 cfs,water sur- faces corresponding to discharges of 5,000 and 35,000 cfs and the observed and rating curve stages • Verification:Figures 8-2.2 and 8-2.3 show velocity profiles produced by the two IFG-2 models at cross section 5 for calibration flows of 1,696 and 4,500 cfs.The observed shoreline velocities for those flows are also plotted.The figures demonstrate that the set of II nil values that produces the proper velocity profile at the low flow does not accurately produce that of the high flow,and vice versa. Application:The low flow IFG-2 model represents site conditions for mainstem discharges up to 10,600 cfs,while the high flow model is applicable to main- stem di scharges greater than 10,600 cfs.Thi s breakpoint corresponds to a site flow of 2,500 cfs.The limits for which the models can be considered excellent extend beyond the range of available data as evaluated by utilizing all available site information,including aerial photography,channel geo- metry,and field experience.The models were extrapolated beyond the data range to 5,000 cfs on the lower end of the low flow model and 23,000 cfs for the upper end of the high flow model.At 23,000 cfs,the channel geometry suggests that the total flow loss through channel A is less than ten percent III-50 1 -1 ]J ]]1 1 ]J ,I ... _---"i-- ~----- ./' .-/ ./' ---"------------...\0,600 cis-- •Observed WSEL ...WSEL from Itaoe-dilChoroe curve -_Predicted water IUrface profile at calibration f10wl Predicted water lurfoce profilll6 for modeled flow ronoe !2";/i Streambed 364 370 368 366 ....----- 360 ~ ~ z Q ~~362 ..J l.IJ l.IJ ~ I- I-l I-l H I \Jl I-' 358 ·v>-... 356 I I I I I I 2 3 4 5 CROSS SECTION NUMBER 01'00 12t28 19t16 24t47 31 tOO STREAMBED STATION 1ft) Figure 111-12.Comparison of observed and predicted water surface profiles from calibrated model at site 101.5L. and is therefore considered negligible.Because this outflow is minor,the upper model limit was extrapolated from 23,000 to 35,000 cfs with the overall rating for the high flow model for the mainstem range of 23,000 to 35,000 cfs considered good. The application ranges and ratings are summarized in the bar chart below. I I I I I 6000 I I I I 14000 I I I 22000 I I I I I 30000 MAINSTEM DISCHARGE (eh) -•Excell...t •Good l~' The WSA and juvenile chinook WUA curves for the study site are presented in Figure 111-13.In this figure,the WUA and WSA curves are plotted to the same scale and expressed in identical units;i.e.,sq ft/l,OOO ft of stream.A comparison of the two curves gives an indication of the proportion of the study site which contains rearing habitat. This site is distinguished by a comparatively narrow range of juvenile chinook WUA for mainstem discharges between 5,000 and 35,000 cfs,suggesting that areas suitable for chinook rearing are generally gained and lost at comparable _rates.Most of the rearing habitat is located in a narrow band along the right shoreline where velocities are not limiting (Williams 1985). i~ The response of the WUA curve to variations in mainstem discharge is plotted on an expanded vertical scale in Figure 1II-13b.The WUA forecasts are higher III-52 - .- -- 450000 A 405000 r-:360000 I.L 0 315 (100 0 ~270000 ...........r-:225000 I.L ci 180000 U1 135000 « L.l.J 90000cr« 45000 0 BOOO WUA 12000 16000 20000 24000 28000 32000 36000 40000 MAINSTEM DISCHARGE (eFS) - B 25000 22500 .....=20000 I.L a 17500 a ~15000 ...........r-:12500 u.... ci 10000 en 7500 « L.l.J 5000cc« 2500 0 0 4000 aooo 12000 16000 20000 24000 28000 32000 36000 40000 - Figure III-l3. MAINSTEM DISCHARGE (CFS) Surface area and juvenile chinook habitat response curves for site 101.5L.A -Wetted Surface Area (WSA)and Wei ghted Usable Area (WUA).B -Weighted Usable Area (WUA). III-53 ~, ,- ..... at low mainstem discharges in comparison to high discharges.This can primar- ily be accounted for by the hi gh vel ociti es at hi gh di scharges that are unsuitable for juvenile chinook salmon.The WUA forecasts at lower flows at this site reflect the combined effect of overtopping discharges (in both overflow and secondary feeder channels)and the channel geometry on nearshore velocities.At higher flows the small increases observed in juvenile chinook habitat are due to the progressive development of a low-velocity backwater area at the lower end of the study site.The significance of these changes in habitat potential in response to streamflow,however,becomes relatively insignificant when viewed in relation to the total WSA of the side channel. The WUA was forecast using low-and high-flow 1FG-2 models to account for flow-dependent variations in shoreline velocity distribution when using the HABTAT model.The WUA for juvenile chinook was forecast using only turbid water conditions because the side channel conveys turbid water at a mainstem discharge of less than 5,000 cfs.Application of low-and high-flow WUA models resulted in separate WUA functions which were joined together to form the single habitat response curve presented in Figure 111-13.This was accom- plished by overlapping the WUA forecasts from the low-and high-flow models and choosing a discharge value resulting in the smoothest transition from one habitat response curve to the other.The discharge value selected in this transition was 8,500 cfs (Table B-6.2). The time series plot of WUA for juvenile chinook bears a strong resemblance to the daily streamflow record at the site for the May 20 to September 15,1984 III-54 .- period (Figure 111-14).Site flows during this period typically vary between 4,000 and 8,000 cfs,accompanied by changes in habitat potential ranging from 12,000 to 22,000 sq ft/l,OOO ft.The seasonal variability of WUA is small, with the exception of a few high flow periods,site flows and juvenile chinook habitat at site 101.5L show a remarkable degree of temporal stabil ity during the rearing season. Site 112.6L Site Description:This site is located approximately 2 miles downstream of Lane Creek on the west bank of the Susitna River (Pl ate II 1-3).The study reach is 4,100 ft long and varies between 500 and 700 ft wide.Substrate composition is cobble and rubble with layers of silt and sand found in pool areas and in the backwater area located at the mouth.The 1a rge substrate provides cover.Eight cross sections were initially established during high mainstem discharges occurring in early August:cross sections 1,2,5,6 and 7 are located in low velocity areas and 3,4 and 8 in high velocity areas.As flows receded during the fall,cross section 4 was relocated and an additional cross section,3A,was added in the shallow,high velocity area midway through the site (Figure III-IS). The side channel breaches at mainstem discharges less than 5,000 cfs while the overflow channel along the right bank conveys side channel flow at discharges above 20,000 cfs.Below 10 ,000 cfs,pool and ri ffl e sequences domi nate the site and a gravel bar below the confluence of Slough 6A is exposed at cross sections 3,3A,and 4.At discharges above 10,000 cfs,the channel becomes a 1arge run. III-55 I -]I !1 ]J )I )1 )I J ) A. 25000 23300 21600 19900 18200 <t 16500:::l 3: 1<1800 13100 11.400 9700 8000 I I r i -----,- MAY JUN JUL AUG SEP H B H 13000 H I 11700V1 0\10.400 9100 3:78000 .-l 6500u..-.JlJ.J 5200 I- t-I 3900VI 2600 1300 0 I I MAY JUN JUL AUG SEP Figure 111-14.Time series plots as a function of time for site 101.5L.A -Juvenile chinook WUA. B -Site flow. z,...0 ~r::u UJ 0~£'>.~~0 00 ~ (l'J l , 0 1i-.....~(.).,... U ~g ~ ~.~..... ~ t:' m~ F J::: U ~..-"0 t- C·'g. ~j ~5 ~,... ~~.~ ~ ~ ~ ~ ~-'T""- ~ ~. ~.-~. ~e: ~t-~ ~~ Cij 1::' Yi .....J; @: ~~~-~; ~. ~.-. f€1' """.-y, ~5 f¥ ~ ~-~: ~ """"'""' ,1IIiW 9-{~ "'~- <!,;: ..... - l1Z.6L....erog SectIon surface 1430 and water 721, 112.6L depicting di scharges of 355, sections for site at calibration Cross elevations 2980 cfs. Figure III-IS. III-58 470 T:at=0""""-.=~=C':"'"4:-------------------­ .....11+" S 400Z~~... ! 480 444 0 200 400 000 O.ST....CE FRO"LEfT _I<KUJ)PIN (fT) 000 470 ..C::R::O"'S"'S..,S::e"'C"'T::,O"'N"S;----------------------, Sl..,.IS.<41 470 "C::R;;;O:;;S=S-=S"'EC;;:T"'IO;;:N::-;"'------------------, S1.Uon 30 +3<4 ~-S S Z 460 Z 460 °~!i '430 cf.~_-"'v ~":::::721 ct. ::N"30 ct.~56C1"......~----~r cf,...16 ct.. :::J $6 ct.:::J ~1$cfw !'" 450 480 ~' 444 444 0 200 400 600 SOO 0 200 400 600 800 O'ST.....CE FRO ..LEfT BANI<HEADPIN (FT)OISTANCE f"'RO'"LEf"T BANK HEADPIN (FT) ~~ <70 470CROSSSECltONe CliO..nCTION' 8'.lIon Ie ..8e I'.don 40 ..•• S s:\i 460 1\ 480 ~~~J:"~~1...../"-.....,-'",m:: :::";<430 cts ~;oj 121 ct. '"""..--/~"<f.... :::J 1111 cf,!~ ~f<.480 480 444 444 0 200 400 000 0 200 400 .00.oa DISTANCE FRO..LEfT BANI<HEADPIN (n)lIISTANCE "'OW LEfT ...,.1<HE.ADP'N (fT) -Figure 1II-15 (Continued). III-59 This large study site was selected to represent large side channels which reduce to small side channels at low discharges.An 1FG-2 model was selected due to the large size of the channel.Field reconnaissance indicated that rearing habitat was limited to streambank margins at high discharges,there-· fore a small amount of data would be adequate to simulate channel hydraulics with the 1FG-2 model.Salmon have not been observed spawning in the site but chinook fry have been observed using the channel,particularly below the confluence of Slough 6A (Hoffman 1985). Calibration:The data available to model the site consisted of level surveys for all nine cross sections and the hydraulic data summarized in Table 111-7. Table 111-7.Hydraulic data available to calibrate the 1FG-2 model for site 112.6L. Site Mainstem i~Flow Discharge Calibration Date (cfs)(cfs)Cross Section(s)Type* 841012 215 6210 7 D 840930 355 7500 6,8 D ~1,2,3,3A,4,5,7 S 840913 721 9000 7 D W~'"9 840904-05 1430 10,800 8 D 1,2,3,3A,4,5,6,7 S 840830 2980 15,300 6 D 840822 4820 19,100 1,2,3,4,5,6,7,8 S * D =Discharge measurements (includes mid channel and shoreline measurements). S =Shoreline measurements (does not include mid channel measurements). III-60 - -- .- Adjustments were made to cross section survey data to create a horizontal stage at some cross sections.Observed depths for the calibration site flow of 355 cfs were plotted with the cross section survey data.Cross sections 2, 3,3A,and 4 did not have horizontal stages and were modified as described.A comparison of the measured and adjusted cross sections is shown in Figure III-16. Stage-discharge curves were not available at cross sections 3A and 4,there- fore these cross sections were calibrated by comparing the predicted velocity profile with the measured profiles.Overtopping of the gravel bar in the lower reach affecti ng cross secti ons 2 through 4 duri ng hi gh flow events caused a transformation in the velocity distribution across the site,and two hydraulic models were required to accurately describe the different dis- tribution in this area. In calibrating the models with respect to depth,predicted stages at all cross sections except 3A and 4 were compared to the corresponding elevations cal- cul ated from the stage-di scha rge curves.Fi gure II 1-17 shows water surface profiles based on IFG-2 output for the calibration flows,the flows correspondi ng to 5,000 and 35,000 cfs,observed stages,and stage-d i scha rge curve stages for the model limit flows. Verification:Figures 8-2.4 and 8-2.5 show the velocity profiles produced by the two IFG-2 models at cross section 3 for calibration flows of 355 and 4,820 cfs.The observed velocities for these flows are also plotted.The figures demonstrate that the set of "n"values that produces the proper velocity III-61 r~EASURED ADJUSTED 470 CIIOII ,loTlON a 470 CIIOII .loTION I.....,.,."a..1IofI I.'" ;: 460 ;: ~460 §~i ~.........~!,_do~--1ao-dI.~~'-J4~0 4~0 444 +---,.----,.--.......--,.----,.--.......--.___---1 444 ~--.___---,.--.......--,.----r---.---..--~o zoe 4QQ &00 DISfAHCI:f"'II'OW LEn-BAHt<HEADPIN (I"T) aoo o 200 400 600 OISTAHC[""OW t.1:"SANK HODP'H (F'T) aoo 470 T:CII'::"O:::.:-:.-:..:-::O:::TION::~.:------------------. •tallOfl 40 ...470 _--------------------,aoou aEOTlOOl • et.ttoft 40." ..... - 200 400 '00 DlST""':E FlOC ..LEFT .....K HLADP'N (l'T] ;:4ao~~ I '4:10 aoo 44" 0 200 400 SOD DIST....CE P'ftOU LEFT .....K ..EADP'N (") '00 Fi gure II 1-16.Comparison between measured and adjusted cross sections 2,3 and 3A at site 112.6L. III-62 i J 1 \i l t l i 1 't r J i I • 4 -----------.---- 1~\Oc\~--- \,-------"'-------.....,----- ,-4 / 41 ,/ Observed WSEL WSEL from Itooe-dilchoroe Curve Predicted water lurfoce prof i Ie ot calibration fiowl Predicted water lurface profiles for modeled flow ranoe Streambed 4 ·c··tr -Y ./:<p'SJ .../-V .....:d<).o.6·f:~r·.~··o··r..:.<;.'0.., ,..01>'2""?;~p~c",.v,,"....".~-(l<~:'.'.C ..,.,,:o,Q .....<:\.-.0'0,·..IY .:O;'~';:~'j;tf"",.N·;',,,,·:sP.id~, ('~'o"r:\7'o'~'" :./pro ..·o:·'?' ·ZJ·/D~:o-r' ·:·~~r .... ......-----/ 464 I • 462t ... - -- y':-, 460 .~C;r1 458 448 452 450 456 454 446 ~..... z 0 H ~H H ::>I WC1' ....JW W W::::> 0:: I- CROSS SECTION NUMBER 765433A2 444 I I t I I I I I 8II 40 +983Ot343+970+00 8+36 1008 12-+92 15+41 19+86 STREAMBED STATION <tn Figure 111-17.Comparison of observed and predicted water surface profiles from calibrated models at site 112.6L. ,- profile at the low flow does not accurately produce that of the high flow,and vice versa. Application:Both models were given an excellent rating from 5,000 cfs to 35,000 cfs.The low-flow model describes depths and velocities present in the channel for mainstem discharges up to 10,000 cfs with the high-flow model applicable to site flows corresponding to mainstem discharges greater than 10,000 cfs.The transition from low-to high-flow model occurs at a site flow of 1,070 cfs.Because of the limited data available to calibrate cross sections 3A and 4 at high flows,the high velocities are projected throughout the entire extrapolation range.However,these cross sections represent only about 10 percent of the total area of the site and actual velocities at the high flow are probably beyond the usable range on the suitability curve, therefore the overall model rating was not reduced from excellent. The application ranges and ratings are summarized below in the bar chart. I I I I I 6000 I I I I I 14000 I I I I 22000 I I I I I 30000 MAINSTEM DISCHARG E (eft) •EaceU...t In Figure III-18a,WSA and juvenile chinook WUA are presented at the same sca 1e per 1,000 ft of stream.Fi gure II I-18b is plotted at an expanded vertical scale. At discharges below 8,000 cfs the side channel conveys less than 10 percent of the total mainstelll discharge and conta"ins an extensive amount of low velocity ~turbid water habitat.Hence the WUA values for juvenile chinook are quite III-64 A ~600000 540000 WSA-~480000 l.L 0420000 0 ~360000,................. ~300000 l.L c:i 240000 c.n 180000 4: ~120000 4: ~'*r 60000 ~WUA 0 0 4000 8000 12000 16000 20000 24000 28000 32000 36000 40000 MAINSTEM DISCHARGE reFS) "~l!!J!l; BI""""100000 90000 - I-BOOOO l.L 70000 WUA00060000........,~........... I-50000 l.L.40000Clc.n 30000 4: l.U 20000a: 4:.....10000 a a 4000 BOOO 12000 16000 20000 24000 28000 32000 36000 40000 MAINSTEM DISCHARGE (CFS) ..... Fi gure II 1-18.Surface area and juvenile chinook habitat response curves for site 112.6L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable ARea (WUA). III-65 large.Williams (1985)demonstrated that the shoreline area within Side Channel 6A,possessing suitable chinook rearing velocities,is five times greater at 13,500 cfs than at 33,000 cfs.The WSA possessing suitable velocities more than doubles as discharge decreases from 13,500 to 8,000 cfs. Figure 1II-19 shows time series plots of the 1984 site flow and WUA indices which reflect considerable variation in habitat potential. 1II-66 1 )I 1,l 1 l 1-}l .~I J.1 ~ A50000_._--_...~ .(5000 .40000 35000 30000«25000::J 3: 20000 15000 10000 5000 0 I I I I I MAY JUN JUL AUG SEP H 25000 8 H H I 22500 0' -...J 20000 3=17500 0 15000---1 l..L 12500 W I-10000 I--l U1 7500 5000 2500 0 I I-~----l-------·----I-~I MAY JUN JUL AUG SEP Figure 111-19.Time series plots as a function of time for site 112.6L.A -Juvenile chinook WUA. B -Site flow. ...... Site 119.2R Site Description:This site is approximately 1.5 miles below Curry Station on the east bank of the Susitna River (Plate 111-4).The study reach encompasses the entire side channel which is 1,800 ft long and 180 ft wide.Substrate varies from cobble and rubble at the upper two cross sections to silt in the backwater area.Riprap from the railroad is present along the right side of the channel and provi des 5 to 25 percent acceptable cover.Three cross sections were established in the deep,low velocity area at the mouth and two cross sections in the shallower,faster velocity area near the head of the channel (Figure 111-20).A large backwater area is present at all flows and extends from the mouth up to cross section 3.Upwelling and groundwater seepage occur near cross sections 3 and 4 along the right bank,and a small tributary enters from the right bank upstream cross section 3. This small side channel was selected to represent channels with high veloc- ities at the head and low velocities at the mouth.An IFG-2 model was select- ed to describe the channel hydraulics because of the small amount of data available.Spawning salmon have not been observed in the side channel but small numbers of juvenile chinook and sockeye salmon were identified (Hoffman 1985). Calibration:The data available to model the site consisted of cross section surveys for all cross sections and the hydraulic data summarized in Table II 1-8. 111-68 ..... 1""'" "'~-~_.-~-, -;:Sli - - _Su.ltna RI..., 4::;,".-.:.":... :-:··~:r.:-:.,'::;",::::-:::",..'::.'::"",:'::':'',;:".:.....::..'::::':'.'.;.::.:::.:..... 520 -r----~---------~-----------CROSS SECTION , 81.lIon 0'"00 ... ~5tO 505 +--,-,-....-..--.--,--r-,-.,.----,-,-....-..--.--,---1 119.2 R -ero ••SecUon o eo 120 1 so 2.00 2 .....0 260 DIST....CE FRO"LE"BIoNK HEADPIN ("l 320 320eo120160200240280 DISTANCe:FRO"LE"BIoNK HEADPIN ("l 40o32028080120180200240 DISTANCE "'0"LE"BIoNK ("l 40o 505 +--,-,--r-,--r-;r-.,.----,--r--r-r--r-,-.,.----,----l 520 520efto••liEC110N •WOUTH CAOSS SECTION :z .,•.."·3 ..11 8t.not!:5 ..80 g:515 g 515 ~~~~...t'-..._31.c;t.... ~:l 510510~~~- - - Fi gure II 1-20.Cross sections for site 119.2R depicting water elevations at calibration discharge of 316 cfs. surface III-70 "'0 '-;C:;R;;:O:;S~'-;.:;EC:::";-:IO;;;N:;-;-'-------------------, SlaUon 6"." s ~" ~~......_3'15 d.::l I!'5'0 o 40 80 '20 1150 200 240 015T""C~....0 ..LEn BANK H£AOPIN (f"T) 280 320 520 520 CROSS 8£CTIQN 4 atOll 8ECTION 5 Bgt'on 1·63 ...tIon 14·., g 515 g 515 Z ~~318 ct. ~~...... ::l 5'0 ~510P!- 505 +-,,---.--,,--...,--.--...,--,-...,--,-...,--.--...,--,-.,--,---1 - o 80 120 ,80 200 240 DlSTANC~FltO..~~n BANK H£ADP'N (FT) 280 320 o 80 '20 '80 200 240 OISTANCE ....0 ..~~f"T BANK Ht:AOP'N (f"T) 280 320 Figure 111-20 (Continued). 1II-71 - ~,Table III-8.Hydraul ic data available to the calibrate IFG-2 model for site 119.2R. ~1Il Site Mainstem Flow Discharge Calibration Date (cfs)(cfs)Cross Section(s)Type* .),'WM..840831 71 13,600 3 0 840819 316 17,400 1,2,3,4,5 0 ~840824 1090 22,700 3 0 ~~* D =Discharge measurements (includes mid channel and shoreline measurements S =Shoreline measurements (does not include mid channel measurements) ,-From August 24 to 29,the streambed elevations were lowered due to the scouring from high flows in the mainstem.Because most of the data was taken before the high flow event,the cross section elevations were determined by -sUbtracting the depth of flow from the water surface elevations as recorded during a discharge measurement rather than by using the elevations determined from the cross section survey (Figure 111-21). A velocity profile was developed for each cross section,based on the site ~flow of 316 cfs.Velocities associated with the other two flows were avail- able only at cross section 3.Velocities predicted by the model were judged to be reasonable at all cross sections throughout the application range of 10,000 to 23,000 cfs (mainstem)based on channel geometry.Unreasonable velocities (large differences from cell-to-cell)were forecast by the model at discharges greater than 23,000 cfs. 1II-72 110 120 1ao 200 240 280 ~_~LEn _..H~(n)110 1 ~o ,80 200 2 ....0 280 DISTANCE:~..LEfT I!!ANI<I-lEAOP'N (fT) 320 Fi gure II I -21.Comparison between measured and adjusted cross sections 1,2 and 3 at site 119.2R. III-73 To calibrate the model with respect to depth,comparisons were made between observed and mode l-predi cted stages.Water surface profi 1es based on I FG-2 output for the three calibration flows and for the flows corresponding to di scharges of 10,000 and 23,000 cfs are shown in Fi gure I II-22.Observed stages for the calibration flows and stages determined from the stage-discharge relationship for the model limit flows are also shown. Verification:One model adequately reproduces the velocities over the range ~~of available data (Figure 8-2.6). Application:The IFG-2 model was assigned an excellent rating for site flows of 15 to 1,240 cfs,corresponding to mainstem discharges of 10,000 to 23,000 cfs.At very high mainstem discharges,the flow regime at the site changes i'"''such that the large volume of water flowing through the site drowns out the backwater area,and the silty,vegetated left bank becomes inundated.The distribution of predicted velocities at the upper cross sections become unrealistic at flows above 23,000 cfs.Therefore,an unacceptable rating was assigned to the mainstem range of 23,000 to 35,000 cfs. The application range and ratings are summarized below in the bar chart. ""'-----1-_ I I I I I 6000 I I I I 14000 I 22000 I I I 30000 MAINSTEM DISCHARGE (eft) •Excell"t o Unacceptable 1II-74 I 1 1 )I 1 I 1 l I I \-I 1 1 1 l 1 • ------1240 cfs 1090 cts •Observed WSEL •WSEL from staoe dilcharoe curve Predicted water lurface profile at calibration fiowl Predicted water surface profiles for modeled flow range ~":;9-n'"S tr e am bed_0. •316 cts •...71 ,f,..------/'..../.----/, ......_---.!5Cfs_.-----------/'./---',./~--.._./--~------_....- ,..~,,~yi~ .0":Q.a.·.•:O.;~· .6...:Cl:,;.06.0 :~. A ..··9 .66.O >.:': .?",\~C'i.:a·:·..c ." ...:o.o-:~:'o.¥:.t·r:-­ .rO:-0_0'9';- •-c:>U:O~·":"'·-.~:.o':-!~':o:;'"r _..•.:•.~...o:.~::O··::~,:.'.,q:..,Y''':'.'.... .._..':.:..".,:p':~j)~~.9'''' " .~,'\),~,r-,S)..0 .. 00 ,o ..o..~•.•_...~.c,o·oQ··r._~."'~n'..,...c:;",.",..o·""'·.·\,)···C-.o:.'i?,,~........n;,_""A ~;.:.;;;;f<"f],Nb<:5c";-: 516 514 50 512--::!:: Z 0 ~ H ~510H..JHWI "WV1::l 0:: I- 50 - - ,~ .."" The WSA and juvenile chinook WUA curves are presented in Figure III-23a.Both curves are plotted to the same scale and expressed in identical units;i.e., sq ft/1,000 ft of stream.The largest amount of rearing habitat for juvenile chinook is available at mainstem discharges between 10,000 and 12,000 cfs. The WUA curve plotted in Figure III-23b at an expanded vertical scale accents the rapid increase in rearing habitat associated when this site breaches near 10,000 cfs.This marked increase is attributed to turbid mainstem water entering the site and significantly increasing the cover value afforded juvenile chinook.As mainstem discharge increases beyond 13,000 cfs veloc- ities begin to reduce the rearing potential at this site.Above 24,000 cfs available rearing habitat is restricted to shoreline margins where sufficient object cover is available to retard velocity. It was necessary to estimate WSA and juvenile chinook WUA beyond the extrapolation limits of the hydraulic model.The WSA was evaluated by digi- tizing enlarged air photographs obtained at mainstem discharges of 5,100, 7,400 and 10,600 cfs.The surface area measurements at 5,100 and 7,400 cfs were equal.The ratio of the digitized surface area at 10,600 cfs to that forecast by the hydraulic model at the same flow was 0.47.This ratio was used to adjust the digitized surface areas from aerial photography at 5,100 cfs and 7,400 cfs before using these surface areas to extend the WSA curve from 10,000 cfs to 5,000 cfs. 1II-76 - A 250000 225000 ~200000 I.L 0175000 a ~150000 ......... ~125000 I.L ci 100000 ~ 75000 « UJ 50000a:« 25000 0 0 4000 8000 12000 16000 20000 2~000 28000 32000 35000 ~OOOO MAINSTEM DISCHARGE (CFS) B 50000 -r--------------------------. ~5000 5000 O-t---,----y--r---,---,-----,,-----.,..---,----.--~ « ~10000« ~40000 I.L a 35000 a ~30000 ......... ~25000 I.L ci 20000 en 15000 - - o 4000 8000 12000 16000 20000 24000 28000 32000 36000 ~OOOO MAINSTEM DISCHARGE !CFS) Fi gure II I -23.Surface area and juvenile chinook habitat response curves for site 119.2R.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). III-77 l~ Juvenile chinook WUA estimates for unbreached conditions are based on the assumpti on that reari ng habi tat potenti a1 decl i nes at a constant rate as mainstem discharge declines from 10,000 to 7,400 cfs.The percentage of the WSA providing potential rearing habitat at 7,400 cfs was assumed to be approximately 0.5,the proportion of clear water habitat present immediately preceding breaching.The WUA values for mainstem discharges between 7,400 and 10,000 cfs were linearly interpolated.Since WSA remained constant as mainstem discharge declined from 7,400 to 5~100 cfs,WUA for juvenile chinook was assumed to remain constant. An exponential decay function was used to extend the WUA curve beyond the upper extrapolation range of the calibrated hydraulic model.The decay function selected reproduced a habitat response trend similar to other middle Susitna River side channel sites.The habitat area curve was extended from 22,000 to 35,000 cfs using a positive exponential function.Similar trends in the WSA curves are present at other model ing sites.Both the WSA and WUA curves should be applied with discretion in the 23,000 to 35,000 cfs range. Table B-6.4 contains further details regarding the synthesis of surface area i~and WUA response curves for this site. Time series plots of WUA and average daily site flow (Figure 111-24)indicate that fairly low habitat potential for juvenile chinook exist at this siter- duri ng mi d-summer,but comparatively hi gh WUA i ndi ces are associ ated with r-early summer and fall site flows.Rearing habitat is maximized at this site when the mainstem discharges range between 10,000 and 14,000 cfs (Figure 111-23b),the WUA values within this range are over five times greater than - III-78 J }i 1 ··11 R }1 I 1 -,1 1 1 A 45000 40500 36000 31500 27000 <t:::::>22500 :3= 18000 13500 9000 4500 0 I I I MAY JUN JUL AUG SEP 3000 B H H H 2700I -....J 2400\0 ~2100 a 1800-l ~lLL1500 W I-1200 ~ UJ 900 600 300 0 I I I I MAY JUN JUL AUG SEP Figure 111-24.Time series plots as a function of time for site 119.2R.A -Juvenile chinook WUA. B -Site flow. "'.... - vJUA values associated with typical mid-summer discharges (20,000 to 25,000 cfs).Hence,the time series plot reflects greater fluctuations in juvenile chinook habitat at this site compared to other side channel study sites. Site 131.7L Site Description:This site is located directly above the confluence of Fourth of July Creek along the west bank of the Susitna River (Plate 111-5). The study reach is 1,900 ft long and ranges from 250 ft wide in the lower half of the site to 400 ft in the upper half.Cobble and rubble are the principle substrates found in the lower half of the site while gravel and rubble sub- strate dominate the upper half.Silt and sand deposits exist in pool areas and backwater zones and cover is provi ded by the 1a rger substrate and two debris zones found in the site.Three cross sections are located in the deep, low velocity area and two cross sections are located in the shallow,high velocity areas.In addition,two cross sections were established in the transition areas below low and high velocity areas (Figure 111-25). This stiJdy site was selected to represent side channels that remain side channels for a broad range of discharges.Upwelling was suspected to maintain baseline flows and the site appeared to have good rearing habitat.An IFG-4 model was selected because of the non-uniform flow conditions and channel size.Chum salmon and juvenile chinook have been observed to utilize the channel (Hoffman 1985). Calibration:To calibrate the IFG-4 model for the site,four data sets were collected at each cross section (Table 111-9). III-80 ..... - - ...... -- ...... - zo i=uw tJ) - .::+':•....-SusJtn.Rivet ..:::.:.::...•:,:~::..::.:.:.:;":"..'.;:.::'.:''':.::':':..,::;.:.:. 131.1L ,100-04 era••Se<:tlon CROSS SECTtON 1 St.UOfl 0"00 CAO"1I0TlOOf r It.ltIon ,....... 82. g ~/~820 !1\_... leo ... 'C7 .~"':::." 81J ~0--.,....--,,..OO--,..--2-,OrO--,--JO.,....o--r--.0.....0---...j DIST....cE nto..LUT lIAHK Hv.oP'N (rr) CillO'"se:C::TION :).1 .........fl. I~ 82.125 g g ~~~820 ~820 1M 1M ~:>~ _... :!l60dI -"66cN-.....1.d. 815 815 813 113 0 100 200 300 <OlI 0 CMST.ANCI:""0...\.1:"BANI<M~("1 .00 200 :sou 400 OtST.AHC1:I'1tOW ,-(I"T .......IK H€AOPtH (n") Figure 1II-25.Cross sections for site 131.7L depicting water elevations at calibration discharges of 18,58,150 cfs. III-82 surface and 240 CROSS SECTION ... :S~.11ofI 1 .....5 C.-Oil l(eltON..1 ..t~,."so 025 825 g g Z ~~ ~020 a 820....... ::l ,...,do ~~-"'lI60dI ~cf.---.....1 •.c.. ~ 0"0'5 013 0'3 0 '00 200 300 <O()Q 0 DISTANCI:FRO"t..E"8AI'rIl)l(H-EAOPIN (fT) '00 200 300 400 OISTAHCE noow LEPT ......"I-l€ADP'",(FT) 1 00 200 .300 ....00 DISTANCE'ntOW lE"BANK H-EAOPIN (IT) CRO••SECTIOtf T It.11oft 11 ~o" CROI.I(CTION • Ite._"•eo 125 025 ~ g g ~~ ~820 ~.20 ...~~do-~OO'"~U ...tam .'5 .'5 .,3 .'3 0 100 200 300 400 0 OOSfAHCE "'OW LEn ......">1EADP1N (FT) Figure 111-25 (Continued). III-B3 1""" ..... Table 111-9.Hydraulic data available to calibrate the IFG-4 model for site 131.7L. Site Mainstem Flow*Discharge Date (cfs)(cfs) 840927 18 7470 840919 55 9390 840902 150 11800 840817 240 14800 *Mean site flow The input data required that a stage of zero flow value be assigned to each cross section.Because a streambed profile was not surveyed for the site,the stage of zero flow at cross section 1 was estimated during the iterative calibration process.A large riffle area below the study site controlled the stage of zero flow at cross section one. Horizontal stages were not maintained across three cross sections in the site. At cross section 2,the backwater area along the left bank had a lower water surface than the main channel and was raised as much as 0.4 ft to maintain a horizontal water surface.Along the right bank at cross sections 6 and 7,a shoal area raised the water surface to higher elevations than the main channel.The streambed was lowered in this area nearly 0.3 ft at both cross sections to maintain horizontal water surfaces.Also,along the left bank at cross section 7 there was a backwater area whi ch had a lower water surface 1II-84 _. than the main channel.The streambed elevations for these cross sections were also raised (Figure 111-26). A plot depicting the observed and predicted water surface profiles for the calibration flows as well as profiles for the extrapolation limits is shown in Figure III-27.Above 600 cfs,the reliability of the stage and velocity predictions decrease. To calibrate the IFG-4 model with respect to stage,comparisons were made between the flow-stage curve and the model-predicted stages (Figure 111-28). Flows were forecast in the model including several beyond the IFG recommended extrapolation range (7 to 600 cfs).Although similar comparisons were made at each cross section only the discharge cross section is shown in the figure. The performance of the calibrated model can be evaluated by comparing the observed and predi cted stages,di scharges and velocity adjustment factors (Table 8-4.2).The difference between observed and predicted stages is generally less than 0.03 ft.The largest difference in observed and predicted discharges is 5 percent.The velocity adjustment factors ranging from 0.92 to 1.04 indicate that the models are suitably calibrated. Verification:Figure B-2.7 illustrates the scatterplots of observed and predicted depths and velocities.The one-to-one relationship between observed and predicted velocities demonstrates that the model predicts accurately.The results of the statistical tests are shown in Table 8-5.For both depth and velocity comparison,the RMSE U is nearly equal to the RMSE,an indication that the model is calibrated.The index of agreement is 0.99 for both depth and velocity. III-8S - ~~EASURED ADJUSTED CI\08&SECTION 2 CROSS 8l!CTlOII IIt.,bn 2'~St.tbt I ••us n..2. ~ g g z ~/0 1=~.20 ~.20~~...... ::l ~e: -1••,....-.,..,. •'3 .'3 0 100 200 300 400 0 '00 200 3·00 400 DISTANCE FfltOW LEFT I!SAHK HE:AQPIN CrT)DlSTA.NCE F"RO-.al L£FT SANK HE:AQP1N (rT)-- CROSS STATION •CROSS 8ECTlON $e••non 11.30 alattoft l'~.)0 $2..2. ~~ z ~~01= §.20 ~.20......-11_... ::l ~e: ....,. .'3 .'3 0 100 200 300 400 0 '00 200 JOO '00 DtSTANCE flItOM L£"IIMn(HlEAOPtN (")DfST'AHC[~LEF'T SANK HEADPIN CrT) CItOsa SECTION 7 CAO••aEOT1OfO 1au_1.~01 .'attoft I'+01 n..2. ~~I /' ~I§no .20 ,$<fa......... ::>~e: ....,. ..... .'3 .13 0 'DO 200 30Cl 400 Q 100 200 300 +00 OlSTAHCE ~cUT _.."'~N (,.,.)DISTANCE ~U""""'1(H£.AOP,N (FT) Figure III-26.Comparison between measured and adjusted cross sections 2,6 and 7 at site 131.7L. 1II-86 J ]J I J 1 I ))I )1 1 I J 61 5--'I I I Iii i I I I I I I I Iii I I I Iii iii I ...... 400200100 -Site-specific WSEL vs flow relationship for stoff gage 131.553 at cross section 3. ..Predicted WSEL from calibrated hydraulic model. 6040.20106 !.ItExtrapolationrangeofmodelI •-I !j I. I• I 421 625 620 -::630 z 0-..... <{ > W H -lHWH I 00 W00u«u.a:: ::> (f) a:: w ~ 3= SITE FLOW AT 131.7 L (cfs) Figure 111-28.Comparison between water surface elevations forecast by the calibrated hydraulic model and the stage-flow relationship for 131.7L cross section 3. Application:The IFG-4 model is calibrated for baseline flow conditions of 5, ~10 and 15 cfs occurring at 5,000,6,000,and 7,000 cfs mainstem,respectively. For site flows of 15 to 600 cfs (7,400 to 19,300 cfs mainstem),an excellent rating was assigned.An overall rating of unacceptable was assigned to the model between 19,300 and 35,000 cfs due to the breakdown in the depth and velocity predictions from the model. The application range and ratings are summarized below in the bar chart. L...-._ I I I J I 6000 I I I I 1 14000 I I I I I 22000 I I I I I 30000 MAINSTEM DISCHARGE (eft) •Excell...t o Unacceptable - Figure III-29a depicts the WSA and WUA response curves for this site.Because this side channel conveys mainstem water at 5,000 cfs,turbid water suitability criteria were used for juvenile chinook.The pronounced increase in WUA as mainstem discharge increases from 5,000 to 8,000 cfs (Figure III-29b)is associated with a rapid increase in WSA with suitable rearing velocities,rather than with a change from clear to turbid water habitat as is the case at other study sites. An extensive gravel bar located on the inside of the bend near the head of this site (Plate 111-5)exerts the greatest influence on the shape of the WUA curve at this site.As mainstem discharge increases above 5,000 cfs,a large shallow riffle develops which provides significant amounts of juvenile chinook rearing habitat.At higher flows this shoal area is characterized by ---------------- .... A 300000 1-------------- _210000 ~_____________ WSAr-.:240000 LL g 210000.~ ~IBOOOO ........ ~:::~ 90000 <C ~60000 <C 30000 O-t----r--.------.-----r--....----.,..----.---.,..--~---I o B ~OOO BODO 12000 16000 20000 24000 28000 32000 36000 40000 MAINSTEM DISCHARGE (CFS) ~OO BODO 12000 16000 20000 24000 28000 32000 36000 40000 """ - BOOOO l 72000 ..j r-.:6~OOO 1..L o 56000 o ~48000 ........r-.:40000 LLg 32000 I :2~00 1 ~16000 ~-l 8000 o r--,------r--__,---.----r---..-----.-- o MAINSTEM DISCHARGE (CFS) Figure 111-29.Surface area and juvenile chinook habitat response curves for site 131.7L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). IlI-90 - i~ .- - - unsuitably high water velocities and the habitat potential of the site dimin- ishes accordingly. The WUA and WSA response curves for this site were forecast using the HABTAT model linked to an IFG-4 hydraulic model calibrated for a range of mainstem discharge from 5,000 to 23,000 cfs.A constant rate of change was assumed for both curves as mainstem discharges increased to 35,000 cfs (Table B-6.5). Time series plots (Figure III-30)indicate relatively constant juvenile chinook habitat within the side channel during the mid-summer months,however, fairly large variations in habitat exist between mid-summer and late spring or early autumn habitat forecasts.A notable feature of this site is the large amounts of rearing habitat provided during the rearing period relative to other study sites. Site 132.6L Site Description:This site is located in the channel immediately upstream of site 131.7L on the west bank of the Susitna River (Plate III-6).The study reach is 1,140 ft long and ranges in width from 140 ft at the mouth to 180 ft at the upper end.Silt and sand substrate is present throughout the deep area while cobble and rubble substrate is generally found in the shallow areas. Vegetation,including horsetails,lines the left bank of the channel and provides some cover.Cross sections 1,3 and 9 are located in the fast, shallow areas.Cross sections 2 and 4-8 are site in the deep,slow velocity III-91 1 ]I )I i 1 l i -]1 1 ]j I SEP SEP AUG AUG JUL JUL JUN JUN -,-,i ~:=;--------j P-- 55000 51500 .48000 .4.4500 .41000 <37500:::J 3: 3.4000 30500 27000 23500 20000 I -~ MAY B H 7500 j~H H 6750 I 1.0 6000N 3:5250 a .4500--l I.L 3750w I-3000 Hc.n 2250 1500 =1-.750 0 ~iAY Figure III-3D.Time series plots as a function of time for site 131.7L.A -Juvenile chinook WUA. B -Site flow. - ..... ,~ ,~ - - areas.A small backwater area is present on the left bank of cross section 9 (Figure 1II-31). Three channels were identified and labeled A,B &C.Channels Band C breach at mainstem discharges of 10,000 ~nd 14,500 cfs,respectively.Below 10,000 cfs,the water in the study area is ponded and eventually dries up.An overflow channel along the right bank conveys a small amount of site flow at 25,000 cfs into Channel A.In addition,a backwater area is present from the mouth through cross section 2 at mainstem discharges greater than 23,100 cfs. This site was selected to represent small side channels that remain small throughout a large range of discharges.An IFG-4 model was selected because of the small channel size and the non-uniform channel conditions.No adult sa 1man have been obse rved in the site.Howeve r,a 1a rge numbe r of chi noo k juvenile rear in the site (Hoffman 1985). Calibration:To calibrate the IFG-4 model for this site,two data sets were collected at each cross section.These are summarized in the following table. Table III-10.Hydraulic data available to calibrate the IFG-4 model for site 132.6L. Site Mainstem Flow*Discharge Date (cfs)(cfs) ~ 940901 27 12,700 ~ 840708 141 21,500 .-"*Mean site flow -~tII-94 132.6L Hera••SecUon - _IECTIOII 1 .....0·00 CROSS .seCTION 3 S~.rIorl 2 l"46 g g ~no ~a30 ~~.....~! 52~..,L 524 a:Z4 a 40 eo 120 180 200 a 40 ao 120 lao 200 DISTANCE FRo...I..En'SANK HEADPIN (FT)DISTANCE F'RO"LEFT BANK HEADPIN (FT) CROS6 S[CTION 2 CROSS SECTION .. 81.1_1.2"SI.~lon 3 t GO g g ~a30 ~a30 ~~ '"'"104'c:l.::l !"--...21c;:1,.. .l4'~. ___27ctl 52~a2~ 524 824 a 40 110 120 lao 200 0 40 eo 1:Zo lao :zoo DISTANCE F'RO"LEFT BANK HEADPIN (rr)OISTANCE "RO"LEI'T .....K HEADPIN (FT) - ~I r-" Fi gure II 1-31.Cross s~ctions for site 132.6L depicting water surface elevations at calibration discharges of 27 and 141 cfs. 1II-95 CROSS SECTiON 6 Stallon 6"11 g ~530 ~...::r~ 52~ 524 f-0 "'"-(..1 ..1 cr• 40 50 120 '50 200 DiSTANCE nro..LEn BANK H£,o.OPIN (fT) - I~ - g z 530 ~~...::r~ n~ 524 0 CROSS SECTION' 6t.t~on S ~~" ',--,.-<:_'4'ct. 27.;:1. ~eo '20 H50 OIST.....CE FRO"LEfT BANK HEAOPIN (fT) CROSS SECTION 7 S1.lm a+-52 200 g ~530 ~...::> ~ n~ 524 0 CR08S SECTION S $'.lIon 1IiI"711i1 I_I.....,..,ct. \-..,-/__27 c:1. 40 ao 120 11150 OISTANCE FRO..LEfT BANK HEADPIN (fT) 200 - g g B 830 ~no ~_1.,d.~..._27cl.I! 52~02~ 824 024 0 40 1IO '20 '00 200 [) OIST.....CE noo..LEI'T BANK HEADPIN (FT) Figure 111-31 (Continued). III-96 40 eo '20 leo OlSTAHCE .-LEn _HEAl)PIN (l"T) 200 Due to the small backwater area on the left side of the channel a horizontal stage did not occur at cross section 9.The streambed elevations in this area were raised so that the left and main channel water surfaces had the same elevation (Figure 111-32). A plot depicting the observed and predicted walter surface profiles for the calibration flows as well as profiles for the extrapolation limits is shown in Figure 111-33.Because only two data sets are used in the model,the pre- dicted stages are equal to the observed elevations.The discrepancy between expected and predicted depths and velocities above a site flow of 300 cfs are unacceptable,therefore,300 cfs was set as the upper limit of the model. The IFG-4 model was calibrated using the guidelines previously described. ~Figure 111-34 shows a comparison between the flow-stage curve and the model- predicted stages for the discharge cross section in the site.Similar compar- isons were made for each cross section.After model calibration,the observed and predicted stages are identical.The pred"icted discharges vary greatly from the mean at cross sections 1 and 8,as did the actual field measurements. The velocity adjustment factors ranged from 0.87 to 1.02. -Verification:The IFG-4 model is based on regression analysis and two data sets.For this two-point model,scatterplots (Figure B-2.8)and statistical tests (Table B-5)were made to compare the observed and predicted depths and velocities.False precision is implied with a nearly perfect one-to-one relationship in the scatterplots and with the index of agreement (0.99). ~- III-97 - r-MEASURED ADJUSTED r-'~COIOMIECTlON.lltallcft11.JI --~ "'0 i~~~\?L~I ~830 ~~j -'D.'.I~~...... i i "'L 825 823 823 0 4<)aD 120 180 200 0 4<)110 120 180 200 DlSTAHCI:P'IlOW I.UT .....OC HEAllI'IN (rT)OOSTANCI:"'0"l.I:n .....OC Hu.<:lP,N (rT) - - .... ..,.. - Figure III-32.Comparison between measured and adjusted cross section 9 at site 132.6L. 1II-98 1 J 1 I 1 1 ]1 I 1 l I 1 1 l 1 ...::..--- :::----- __33~cfs _ _ ___ 141 cfs.•-------------. •27 cfs---..-----....~~- /'_-IOcts ----------------- ~...------- Observed WSEL Predicted water lurface profile at calibration flow Predicted water lurface profile for modeled flow ranoe Staoe of zero flow Streambed • ~:::-9~~~,--,'..•. -----------/ /' ---_/~ 628 626 629 627 625 624 --.... ~ H Z H 0 o-t ~I \C:~-.c IJJ ....J W IJJ :::Ja::.... 11+319-+-798...52 6543 2+46+24 2 0+00 623 :3 +90 5+II 6 +94 STREAMBED STATION (ft) Figure 111-33.Comparison of observed and predicted water surface profiles from calibrated model at site 132.6L. J )J I j 1 I ,1 1 1 1 J J ..~'1 400200 I I I I •• 10060 Site specific WSEL vs flow relationship for staff gage 13206S3 at cross section 3. •Predicted WSEL from calibrated hydraulic model. 4020 I Extrapolation range of model jI· I I I I 1 • 106..1 830' I 835 826 820 ,Iii iii Ii'Iii i','i i i --.... z 0-.... <I> WH-.JH H W0_°1 ...... C Wc0 <I lL.a: :::> en a::w.... <I ~ SITE FLOW AT 132.6L (cfs) Figure 111-34.Comparison between water surface elevations forecast by the calibrated hydraulic model and the stage-discharge relationship for 132.6L cross section 3. - Application:Baseline flow at this site is estimated as 10 cfs for discharges below 10,000 cfs.For site flows of 10 to 17 cfs (lO,OOO to 11,900 cfs ma'instem),the model is not able to forecast velocities accurately,thereby reducing the rating for this flow range from excellent to good.The site was assigned an excellent rating,however,for the 17 to 300 cfs range (11,900 to 25,000 cfs mainstem).Above 25,000 cfs the model was assigned an unacceptable rating. The application range and ratings are summarized below in the bar chart. ----------_--1 I I 1 I I 6000 I I I I I 14000 I I I I 22000 I I I I I I 30000 MAINSTEM OISCHARG E (ch) The WSA and juvenile chinook WUA curves for site 132.6L are plotted at the same vertical scale in Figure III-35a,and the WUA curve is replotted at an enlarged scale in Figure 111-35.In both figures,WSA and WUA are expressed as sq ft/1,000 ft of side channel.A comparison of the two curves indicates that the ratio between WUA and WSA is approximately 0.3 at 12,000 cfs and declines to 0.1 at 25,000 cfs. - •Excel1...t •Good 0 UnClcceptobte ,.... This study site is breached at a mainstem discharge of 10,000 cfs and dewaters as mainstem flows continue to decline.The associated rapid decline in both WSA and WUA is evident in Figure 111-35.In addition,the juvenile chinook WUA curve drops sUddenly when the side channel transforms from the breached to the unbreached condition at 10,000 cfs.This drop is attributable to the site III-lOI I~ WUA WSA t- O 4000 8000 12000 16000 20000 24000 28000 32000 36000 40000 A 150000 135000 J ~120000 . l.L I g "5000 j890000 .......... ~75000 l.Lo 60000 !!2 45000 «w 30000CC« 15000 0 - MAINSTEM DISCHARGE (CFS) Figure III-35.Surface area and juvenile chinook habitat response curves for site 132.6L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). III-I02 - 1""".. - - flow becoming non-turbid,thereby eliminating the high cover value associated with turbid water.As mainstem discharge declines toward 5,000 cfs,both the WSA and WUA approach zero. The WSA and habitat response curves were forecast with the HABTAT model and the IFG-4 hydraulic model calibrated for mainstem discharges between 10,000 and 25,000 cfs.For rna instem di scharges betll/een 25,000 and 35,000,both curves were extended using exponential functions as indicated in Table B-6.6. For mainstem discharges less than breaching (10,000 cfs),WSA and WUA estimates were obtained by using clear water cr'iteria for juvenile chinook at 9,000 and 10,000 cfs to determine the magnitude of change in WUA attributable to the site flow clearing and enlargement were then reviewed.At 7,400 cfs, clear ponded water exists while the 5,100 cfs photography indicates that the site is nearly dry.Digitized surface area measurements of ponded water connected to the mainstem at 7,400 and 5,100 cfs were used as a basis for interpolating surface areas between discharges of 10,000 and 5,000 cfs.The WUA was assumed to decrease to zero at a constant rate through this range. Time series analysis of 1984 site flow and juvenile chinook WUA are presented ~ as Figure III-36.Rearing habitat was fairly stable throughout mid-summer 1984 with notable increases being apparent in late spring and early fall when mainstem discharges were approximately half their mid-summer level. -III-I03 1 1 1 I 1 i J 1 1 ]1 I I j I j J SEPAUG -1 , JUL 1---------I MAY JUN 20000 18300 16600 14900 13200 11500 9800 8100 6400 .fl00 3000 <t :::l 3:: H H H I t-'o.po 3::o ~ wr- 1--1 Cf) 2000 1800 1600 1400 1200 1000 800 600 400 200 o B MAY JUN JUL AUG SEP Figure 111-36.Time series plots as a function of time for site 132.6L.A -Juvenile chinook WUA. B -Site flow. 1~' !~ - Site 136.0L Site Description:This site is located approximately 1 mile downstream of Gold Creek along the west bank of the Susitna River (Plate 111-7).The study reach is 580 ft long and 80 ft wide with steep banks.The substrate is composed of cobble,rubble,and gravel throughout the site.Debris and log jams are present along the right bank and provide cover.Slough 14 enters the channel 20 ft above the study site.Cross sections 1-4 and 6 are located in shallow high verocity areas while cross section 5 is located in a deep,slow velocity area (Figure 1II-37).The channel has been observed breached at mainstem discharges as low as 5,000 cfs.At moderate to high discharges,the channel appears to be a run. This small study site was selected to represent small side channels that remain side channels.An IFG-4 model was selected because of the small size of the channel.Relatively few spawning coho and chum have been observed in the site with juvenile chinook were caught in the side channel (Hoffman 1985). Calibration:In order to calibrate the IFG-4 model for this site,three data sets were collected at each cross section (Table III-II). III-lOS - - - - tt?ii'o 0:o II !.......:::... - 136.oL H Croa SectIon ee5 ...."CR="0'""'sa.,....",se=-=C=TIO=HC'"2-----------------, S.elkln O.aa e70 4---.--....,.-----.--,-----r---,---,---,.--r-..-, ..- o 20 40 eo ao DISTANCE f'RO'"LEFT BANI<H£.O,OPIN (FT) '00 8e5 CROSS KCTION ,ee5 St.ltotl 0 ...00 CAoee HCT'OH a 81_uGfl-1 +-196 ~ g eeo g eao z ~~ f-=~~......286 cf•...•216 c,•..._Ul3cfll :>I!875 _163 eta ~e75 _81 cf. _81ct.. e70 +---.--..,....-.,...-...,..--,---,---,----.----r---1 •100~40 eo eo DlSTAHCE !'ROW l.UT _I(H£.O,OPIN (fT) 870 +--.-.--....,.--......--,-----r---r---,r----,....--r-~ o1002040eoeo I)IS'TAHCE _l.UT _I<H£ADf'lN (1'Tl o Fi gure II 1-37.Cross sections for site 136.0L depicting water surface elevations at calibration discharges of 81,153 and 265 cfs. III-I07 .... ellS .,-;:CR=O::::SS::-.=C"'TlON=-;.:-------------------, 11.1_2." e70 +-""T--,--.....--.--.,---,---....------,.--,---j o 20 040 eo eo OISTANCE FRO..LEFT _K H£AOPIN (I"T) 100 e,,"CROSS SECTION :5 St.'ion "+23 g ello ~~...... ~'7S 1170 +-....,..-.....,--,--.......----,.--,---"'T'"-.,.---,.----l ells T':C;;:AO"'."'.-;.:::."'Cr"""'IQ"'Nc.-'-=---------------------, a,.non-a +12 1170 +--,----,.--...--.--.....,--...---r----,--.---I """ o 20 040 eo 110 DISTANCE _U7T .""U(HEADPIN (I"T) 100 o ~040 eo 110 DISTANCE ""OW LEFT _K HUoDPIN (I"T) 1QQ Figure 111-37 (Continued). III-lOB - Table III-II.Hydraulic data available to calibrate the IFG-4 model for site 136.0L. *Mean site flow No unique problems were encountered at this site in following the calibration guidelines.Figure III-38 shows the observed and predicted water surface profiles for the calibration flows as well as profiles for the extrapolation limits.To calibrate the IFG-4 model with respect to stage,comparisons were made between the flow-stage curve and the mode l-predi cted stages for the discharge cross section (Figure 1II-39).Similar comparisons were made for each cross section. The performance of the calibrated model is evaluated by comparing the observed and predicted stages,discharges and velocity adjustment factors (Table B-4.4).The difference in observed and predicted water surface elevations is 0.02 ft at each flow and each cross section with cross sections 4 and 6 having as much as 0.7 ft difference.The largest difference in observed and pre- di cted di scharge is 3 percent.The velocity adjustment factors range from .-0•99 to 1.01. - -III-109 1 -,1 J ))_C]]I l ]-, f ]j J \1 50Y·fo---------------------_.-------'----. -------------------- 679 ----• _._---------- .;;o~C:;:~:ri·D~·~·~:~\.-.' •Observed WSEL --Predicted water surface profile at calibration flow Predicted water surface profile for modeled flow range Staoe of zero flow ~;19~~~Streambed,-..;...•. ----- ,oclo ---------.---------_.-----.-----------. 675 678 673 676 674 677 ~-~ z 0 ~>H WH ..JH WCI..,.. t-' W0 ::la::... 54 672'I I I I I 6I 0 ...00 0+88 I ~95 2 ~91 4 +23 5 -I-82 STREAMBED STATION (ft) Figure 111-38.Comparison of observed and predicted water surface profiles from calibrated model at site 136.0L. 1 1 ,J ~])1 1 1 1 1 1 I J j , 670 iii iii iii iii iii iii i I -Site-specific WSEL vs flow relationship for staff «:loge 136.0S3 at cross section 3. ..Predicted WSE L from calibrated hydraulic model. L Exlra.ol.tlon rango 01 model ~ I I I I I I --!---..675 685 680 --....- z 0- I- et> l.LJ -J W W H U H etH I LL to-'a:: to-' to-':J (J) a::w l- e:{ 3= 10 20 40 80 100 200 400 600 1000 2000 SiTE FLOW AT 136.0L (cfs) Figure 111-39.Comparison between water surface elevations forecast by the calibrated hydraulic model and the stage-flow relationship for 136.0L cross section 4. Verification:The scatterplots of observed and predicted depths and veloc- ities are shown in Figure 8-2.9.There appears to be more scatter in the depths than velocities but a one-to-one relationship can be observed from the plot.The results of the statistical tests are shown in Table 8-5.Both depth and velocity comparisons of the RMSE U are nearly equal to the RMSE (.167 compared to .170 and .157 compared to .165).The index of agreement for both variables is 0.99. Application:An excellent rating was assigned for site flows of 10 to 1,750 cfs corresponding to 5,000 to 35,000 cfs mainstem,as shown below in the bar cha rt. 1 I I I I 6000 I I I I I 14000 I I I I I I 22000 I I I I I I I I I 30000 --I - MAINSTEM DISCHARGE (eft) •Eacellei1t WSA and WUA forecasts are provided for a mainstem discharge between 5,000 and 35,000 cfs (Figure III-40a and b).In the first figure both curves are plotted using a common vertical scale and are expressed in the same units.An eightfold increase in the vertical scale is used with Figure III-40b.Both the WSA and WUA curves for this site were forecast using an IFG-4 hydraulic model calibrated for mainstem discharges ranging from 5,000 to 35,000 cfs. Five of the six cross sections established at this small,high gradient side channel were located in riffle zones.The channel cross section lacks the gently sloped stream banks and gravel bars associated with other side chan- nels.Consequently,velocities throughout this site tend to exceed those 1II-112 A 80000 72000 ~64000 lJ.... o 56000 0 "....~48000 .......... ~40000 lJ.... ci 32000 U1 24000 « ~16000 « BOO a -WUA 0 4000 7200 10400 13600 16800 20000 23200 26400 29600 32800 36000 MAINSTEM DISCHARGE (CFS) '.~ .... 8 10000 .. 9000 .BOOOl- lL. 0 7000 0 0 6000.- .......... I-5000 lL. c:J 4000 ~3000 « LU 2000II« 1000 a 4000 WUA 1200 10400 13600 16800 20000 23200 26400 29600 32BOO 36000 MAINSTEM DISCHARGE (CFS) Figure III-40.Surface area and juvenile chinook habitat response curves for site 136.0L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). r III-1l3 preferred by juvenile chinook salmon.Hence,the rearing habitat potential f"'''"steadily decreases between 5 ,000 and 18,000 cfs,but remains at nearly the same level through 35,000 cfs.This is primarily attributed to the large ~amount of shoreline debris and undercut banks which exist at this site.When this habitat response curve is compared to WUA curves for other sites,it is t~ apparent that this site provides less rearing habitat on a per 1,000 ft basis than most other side channels.However,because the WSA of this side channel is also small,the proportion of the study site possessing suitable chinook habitat is actually greater than the proportion at some of the larger side channels. ~Shoreline debris and undercut banks influence the temporal stability of chinook rearing habitat at this site as shown in the time series plots pre- sented in Figure 1II-41.Despite the rather erratic pattern of daily site flows,corresponding WUA values are notably stable.Although low early summer F"'" and fall streamflows result in an increase in available habitat,this increase -is not as pronounced as that which occurs at other side channel sites. Site 147.1L Site Description:This site is located on the left of Fat Canoe Island on the west bank of the Susitna River (Plate III-8).The study reach extends the entire length of the site (1,780 ft)and ranges from 350 ft wide at the mouth to 250 ft wide at the head.The substrate is large cobble and boulder with a thick layer of sand along the right bank of the lower three cross sections. ~ The available cover is created by the large substrate.Six cross sections 111-114 ]i t 1 1 J I l 1 }I I 1 1 A 6200 57BO 5360 -49-40 -4520 <t: ~-4100 3: 36BO 3260 2B-40 2420 2000 MAY JUN JUL AUG SEP H BH2-400H I t-'2160 t-' VI 1920 3:16BO 0 1-4-40..-l I.L.1200 W ~960 t-I Ul 720 -480 2-40 0 ----.-I -----T I MAY JUN JUL AUG SEP Figure 111-41.Time series plots as a function of time for site 136.0L.A -Juvenile chinook WUA. B -Site flow. .- - - zo-tiw UJ flJ f/)oc:u ,... were established in areas with deep,fast velocities in the channel (Figure ,....II 1-42). This large study site was selected to represent large side channels that remain side channels at low mainstem discharges.An 1FG-2 model was selected because of the large size of the channel and its uniform shape.Previous reconnaissance to the site indicated that rearing habitat was limited to the right streambank margin and a limited amount of data would be required to model this site with an 1FG-2 model.Shoreline velocities were collected along both streambank margins. Calibration:The data available to model the site included level surveys for all six cross sections and the hydraulic data which is summarized in Table 1II-12. Table 111-12.Hydraulic data available to calibrate the IFG-2 model for site 147.1L. 828 CA088 SECTION 2 atatlon a ••2 820 g ~SilSOO c1. ~81' 1807 ct•... ~ ~ 810 147.11.. ....Cro ..Secllon o 100 200 300 OISTANCE FRO...U:FT BANI<H[,Ol)PIN (FT) 400 S2'828 CROSS SECTION I CROaS SECTION 3 SI.Uon o •00 ataUOll 7 +17 820 820 g g ~~_&eOO eta 81'81'_I&07c:1.~~ I __'801cn I 810 810 80'+---r---,--,.--...,....--r---,r---,..---r--j 808 +---r-.....,--,.--...,....-........--,.---...,....--r-~ o 100 200 300 400 DIST,ONCE ""OW UI'T _HEIlDPlN en) o tOO 200 ~OO OISTNlc:1!:FRO...UI'T SANK HEADPIN eFT) 400 ..... Figure II 1-42.Cross sections for site 147.1L depicting water surface elevations at calibration discharges of 1860 and 2236 cfs. III-US .- 62S Tr'cCAOiiOissos;u;i'£cCirn;ION;N;.;------------------. St.11On 10 +00 620 \-----1_0-ci, \--------1_'801 ci. 6'0 60S ~0~---r---,OO,..---r---2.,OO----r--~-r--.....--4-,00r--....j DISTANCE I"ftOM LEFT _I<HI:.4C.....(IT) Ull CIllO••aec flON t 62S CROSS SECTION e...-lJ"36 ataUon 17 ..Tfl -620 620 g g _~600 ctl _6"'00 ch ~~1liKJT c1. _1'807cl. 61S ~6'S ...I~ 6'0 6'0 80S +--..---,----,---..---,r---r---,---,---l 60S -l-----r--.----.--.-----.--.----.-----.-- - o '00 200 ~ OISTAHC£I'ItOtd .LDT _I<HEAllPIN (IT) o '00 200 .300 DISTANCE '""OM LEFT _I<HI:AOPtN (FT) 400 Figure 111-42 (Continued). III-1l9 Two models were required to simulate side channel hydraulics over the mainstem range of 5,000 to 35,000 cfs.This was mainly due to the increasing propor- tion of side channel conveyance in the shelf area along the right bank at high flows.Velocity profiles were developed at each cross section based on the site flows of 1,907 and 5,600 cfs for the low and high flows hydraulic models, respectively.In calibrating the two models with respect to depth,predicted ~stages at cross sections 2 through 6 were compared to stages calculated from the stage-discharge curves over a wide range of flows.Figure 1II-43 shows water surface profiles based on IFG-2 output for the calibration flows of 1,907,2,154,2,650,4,742,and 5,300 cfs,and the flows corresponding to mainstem discharges of 5,000 and 35,000 cfs. Verification:Figures 8-2.9 and 8-2.10 show velocity profiles produced by the-two IFG-2 models at cross section 2 for calibra.tion flows of 1,907 and 5,600 cfs.The observed velocities for those flows are also plotted.The figures-demonstrate that the set of II nil val ues that produces the proper velocity -.profile at the low flow does not accurately produce that of the high flow,and vice versa. - - Application:The low-flow model represents site conditions for mainstem discharges up to 13,500 cfs,while the high-flow model is applicable for mainstem discharges greater than 13,500 cfs with the breakpoint corresponding to a site flow of 3,500 cfs.Limits for which the models can be considered excellent exceed the range of available stage information,as the models were extrapolated beyond the data range down to 5,000 cfs in the low flow model and up to 35,000 cfs in the high flow model.The overall rating for both models is exce 11 ent. -I 1 1 ]1 J I J J \1 1 1 j 1 s 6 ...-------- 5 CROSS ~SECTION NUMBER _..---------A 43 ------------.---...-------- .,cb,l:i,J.D';f':<"()•....~. ...-'._.~.•.o.~··-·,,··~.~"".~.".0-'.•o~.-'_"_'?.,.""'0"0·.-.·0'''''-'o'.<;>.•.rvc-.·n'().~"~ ..~...,,;,..:.o:o...o ..C""0 ..>,·.;/""'•••...•..- .J6.-__-_-4---- ..------ 2 .- •Observed WSEL ...WSEL from stooe-dilchoroe curve --Predicted water lurfoce profile at calibration fiowl Predicted water lurface profilu for modeled flow ranoe if~i1 Streambed ...~ I \0 gOO cts,-------r------... .....- 810 820 812 818 814 816zo ~ W ...J W W ::> 0::t- ~..-.....- H H H I I-' N I-' 808'I I I I I I 0+00 3+62 7+17 STREAMBED 10tOO STATION (tt) 13+35 17+76 Figure 111-43.Comparison of observed and predicted water surface profiles from calibrated model at site 147.L. - The application range and ratings are summarized below in the bar chart. I I I I I 6000 ,I I I 14000 I I 22000 I I I 30000 -MAINSTEM DISCHARGE (c:1I) •EZCIII...t The WSA and juvenile chinook WUA response functions for this study site,shown in Figure III-44a and b may be considered fairly representative of mainstem areas.The ratio of juvenile chinook WUA to \I~SA at this site is very low. Williams (1985)demonstrated that suitable rearing areas in large side ~channels of the middle Susitna River are primarily confined to nearshore zones,due to high (non-suitable)velocities existing elsewhere in the channels.Figure 1II-44b indicates a slight increase in juvenile chinook WUA with increasing discharge.However,when viewed in perspective with WSA, juvenile chinook WUA may be considered relatively constant between 5,000 and --35,000 cfs. The WSA and WUA response functions were forecast using the high-and low-flow IFG-2 models previously described and the HABTAT model.Because this large side channel conveys mainstem water at discharges well below 5,000 cfs,the turbid water suitability criteria were used.The separate WUA curves forecast -- ..... by the high and low flow models were similar within the range of overlap and intersected between 20,000 and 21,000 cfs.Therefore,WUA predicted by the low-flow model was used for discharges of up to 20,500 cfs;above this discharge the high-flow model was used . III-I22 WSA___________ A300000.,--------------- 270000 ~240000 LL 0210000 ~1BOOOO l ~150000 ...j LL ci 120000 U1 90000 WUA MAINSTEM DISCHARGE [CFS) 30000 o +--r====r===;====::;==::=:'===:::::;':I-=-=:::;==:::=;::==--.----J o 4000 BOOO 12000 16000 20000 24000 2BOOO 32000 36000 40000 4: ~60000 4: - ~B 12000 10BOO....~ I-9600 LL 0 B400 WUA i~ 00 7200~--..... t-6000 LL Cl 4BOO ~ 3600 4: lJ.J 2400 jJ-~a: 4: 1200 0 0 4000 BODO 12000 16000 20000 24000 2BOOO 32000 36000 40000 MAINSTEM DISCHARGE (CFS) !"""" Fi gure II I -44.Surface area and juvenile chinook habitat response curves for site 147.IL.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). 1II-123 Because of its large size and low breaching discharge,the site flow hydro- graph strongly resembles that for the mainstem throughout the open water season (Figure III-45).The time series plot for juvenile chinook WUA has /"'''''- little response to streamflow fluctuation because of the relatively constant amount of shore 1i ne habitat that exi st.A simi 1ar time seri es response is evident for the 136.0L site where rearing habitat is also restricted to shoreline margins because of unsuitable mid-channel velocities. DISCUSSION The results of this section show that side channel study areas appeared to have both increasing and decreasing trends in the WUA as a function of mainstem discharge with these areas limited by depths at lower discharges.As discharges increased,the depths became usable.Also,as the velocities exceeded 0.65 fps,the WUA values decreased.The amplitude of the WUA curve was determi ned by both the amount and qua 1ity of cover present with in the site. - 111-124 I 1 J I I 1 i J )i l J i 12000 11100 10200 9300 8..j00«=>7500 3= 6600 5700 ..j800 3900 3000 A -~ MAY JUN JUL AUG SEP SEP l(\ AUG f\ JULJUNMAY eo ~ ~\ ~ r--'1---I T-' ,-I H 13000 H I 11700I'-' II-'10..j00lTI 3:9100 0 7BOO--.1 LL 6500 W I-5200 H [f)3900 2600 1300 0 Figure 111-45.Time series plots as a function of time for site 147.1L.A -Juvenile chinook WUA. B -Site flow. PART IV APPLICATION OF DIRECT INPUT HABITAT MODELS This section describes the application of the Direct Input Habitat (DIHAB) model at fourteen side channel and mainstem study sites in the middle Susitna River.Chum salmon often spawn in backwater areas or the shoreline margins of side channel and mainstem habitats (Barrett,Thompson,and Wick 1984). Applications of the IFIM hydraulic models,as described in Part III,was not appropri ate at the majority of these spawnli ng areas because streamflow conditions were not consistent with the hydraulic theory upon which the IFIM hydraulic models are based. The IFIM hydraulic models simulate depths and velocities for unobserved streamflows based on the assumption that steady,gradually varied streamflow exists in a rigid channel (Trihey 1979).The DIHAB model was developed by EWT&A as an alternative for calculating the response of chum spawning habitat to incremental changes in mainstem discharge at those sites where steady, gradually varied flow did not exist. The DIHAB model uses substrate composition and upwelling data from one or more cross sections as well as measured depths and velocities for several streamflows to calculate WUA at each observed streamflow.WUA indices for unobserved streamflows within the range of observed values are determined by linear interpolation between calculated WUA indices.Outside the range of observed values,WUA indices were estimated on the basis of trend analysis and field experience. IV-1 - - The influence streamflow variations may have on spawning habitat is generally evaluated using three microhabitat variables:depth,velocity and substrate. However,upwell i ng groundwater is also considered important for successful chum salmon spawning in the middle Susitna River habitats (ADF&G 1984b).Of the four microhabitat variables used in the modeling processes,upwelling appears to be the most important variable influencing the selection of redd sites by spawning chum salmon (Trihey et al.1985).Because of this strong preference,a binary criterion was used in the DIHAB model for this microhabitat variable.The habitat suitability criterion for upwelling assumes optimal suitability for areas with upwE!lling and non-suitability for areas without upwelling.Habitat suitability criteria for the other microhabitat variables are based on field observations and data obtained in the middle Susitna River habitats by ADF&G Su Hydro (Estes and Vincent-Lang, eds.1984)as described by Steward 1985. Fourteen sites were chosen for detailed study from among the 50 candidate study ares to represent three types of habitat:1)side channel areas influenced by backwater,2)side channel areas not influenced by backwater, and 3)mainstem margin areas (Table IV-I,Figure 111-1).Spawning chum salmon were reported at six of these areas,by ADF&G SU Hydro (ADF&G Su Hydro 1981;ADF&G Su Hydro 1983a;Barrett,Thompson,and Wick 1984)with the other eight sites suspected of upwelling;however spawning chum salmon had not been reported at these sites prior to 1984 (Table IV-2). IV-2 -"'~<.-,,~,,',.'••''. )j 1 1 J J I }1 J J »]J 1 Table IV-1.Forty-three candidate areas for side channel and mainstem chum spawning evaluation. Specific Spawning Specific Spawning Area Reported Model Area Reported Model 100.6 R 1981,1983 128.7 R 1982 100.7 R 129.4 R 1981,1982 101.2 R IFG-4 130.2 R 1981 DIHAB 101.7 L DIHAB 131.3 L 1981 DIHAB 105.2 R 131.7L 1982,1983 IFG-4 105.81L DIHAB 133.8 L IFG-4 110.4 L 133.8 R DIHAB 112.6 L IFG-2 134.9 R IFG-2 113.8 R IFG-2 136.3 R 1981,1982,1983 IFG-4 114.1 R DIHAB 136.8 RMS 1983 115.0 R 1982,1983 DIHAB 137.5 R 1982 DIHAB 115.6 R 138.0 L 115.9 LNR 138.71L DIHAB 117.8 L 139.01L 1982,1983 DIHAB 118.91LMS 1983 DIHAB 13~.41L DIHAB 119.11LMS DIAHB 139.7 R I-l 119.3 L 140.2 R 1981,1982,1983 <:119.5 L 141.2 R1I124.0 L 141.4 R 1981,1982,1983 IFC-4w125.2 R 1981,1983 142.0 R 125.1 R 148.2 M 1982 No open lead 127.1 M - 1 Side Channel 21 identified as side slough spawning escapement in ADF&G reports. .- - Table IV-2 .1984 middle river spawning study areas. IV-4 - - .- ..... FIELD PROCEDURES Field data included water depth and velocity measurements,substrate and cover descriptions,observations of upwelling,fish utilization and streambed profile surveys. Depth and Velocity:Procedures followed for measuring depth and velocity were similar to those used in measuring discharges at the IFG model sites (Part III).Depth and velocity data were collected along cross sections established perpendicular to flow over one to five mainstem discharges (usually 3)from 4,300 to 31,700 cfs.A minimum of 10 verticals (cells)were measured for each data set.Verticals were referenced by horizontal distance from left bank streambed marker.Depth of water,mean column velocity (6/10ths of the depth beneath the water surface)and nose velocity (0.4 ft above the streambed when the depth was greater than 1 ft)measurements were collected until depths or velocities were unsafe for the field personnel.In addition,upstream and downstream distances of the representative habitat were estimated for each cross section.Extrapolation for depths and velocities were also made beyond the last measured vertical based on habitat conditions. IV-5 - ,.,... Substrate and Cover:Substrate type was vi sua lly assessed to determi ne mean particle size and was coded using criteria in Table III-2.Cover type and percent of site were coded using criteria in Table 111-3.Water clarity (turbid or clear)was also noted. Upwelling:Presence of upwelling was determined at the DIHAB study sites using the combination of the following data sources:1)field observations during the 1984 open-water season,2)two winter field reconnaissance trips in 1985,3)winter temperature data for site-specific intragravel water compared to mainstem surface water,and 4)location of chum salmon redds.The relative extent and strength of upwelling areas within a study site were determined during the winter reconnaissance field trip with suspected upwelling areas confirmed if site intragravel temperature were significantly warmer than surface waters of the mainstem.Since chum salmon selectively utilize areas of upwelling for spawning,for the purpose of this study,areas of observed active spawning and redd locations were assigned a llslight"strength of upwelling. Upwelling areas were sketched on aerial photographs and field notes and referenced to cross section or identifiable land marks.The extent of the upwelling was measured and the strength recorded as slight,moderate or strong,based on visual observations.Table IV-3 gives the criteria used to determine the strength of upwelling.Figure IV·-1 is an example of a map that summarizes the upwelling data for study site 131.3L. IV-6 Table IV-3.Criteria used to determine the strength of upwelling. STRENGTH OF UPWELLING SLIGHT MODERATE STRONG CRITERIA Areas within open thermal leads where less than 20 percent of the area was affected by upwell i I1g or detectab 1e ban k seepage. Areas where upwelling was observed during the open water season or indicated by intragravel temperature data but produced no open thermal leads during the winter observations. Areas where chum salmon were actively spawning or redds were identified during the open water season. Areas in open thermal leads where 20 to 79 percent of the area was affected by upwelling or obvious bank seepage. Areas in open thermal leads during winter observations where 80 percent or more of the area was affected by upwelling or bank seepage or flowing water. IV-7 ••-••-..----.·---..-....-•••••••••••..-•:. ••,,, ".,..,, ••,..',..."., czw fa ..I ..., II •..,••."........ I.••• '...,- ",, •.. 0 ' • t •'., "..,.,••,.>.., '. "'.•,,,,, ••"..-."", .,,'..'.'.I I •• •••-.-"•-."'-•••.-.~ ••••• .... Figure IV-I.Summary location of upwelling areas at DIHAB modeling site 131.3L. IV-8 Fish Utilization:Fish utilization data was recorded in the field byobser- vation of presence,location,life stage,number of fish and species informa- tion. Streambed Profile Surveys:Streambed profile surveys were completed for six of the study sites in the side channel and backwater areas using procedures described in the ADF&G Su Hydro Procedures Manual (1984).The results of the surveys are presented in Figures C-1.1 through 1.6 and Tables C-1.1 through 1.7. INPUT REQUIREMENTS OF DIHAB MODEL Input data required by DIHAB are mainstem discharge,stage,water depth, velocity,substrate type,and upwelling information at each x-coordinate. Suitability criteria for spawning chum salmon developed for the middle Susitna River were used to assign habitat value to each cell.Reach lengths associ- ated with the representativeness of the hydraLil ic conditions at each cross section were determined based on field estimates and aerial photography interpretation.These lengths were used to extend the cross section up and downstream an appropriate distance. Mainstem Discharge:For each data set,average daily streamflows for the Susitna River were obtained from the USGS Gold Creek gaging station.Mainstem discharges were correlated from these to changes in physical habitat. Stage:Stages for each cross section were determined from stage-discharge curves developed at each study site (Part II).Normally,one stage-discharge IV-9 ,~ "'""' -- curve per study site was sufficient to determine stage.Stages at cross sections within study areas were approximately the same for any given mainstem discharge due to gentle gradients and relatively short reaches between cross sections.At five study areas,as many as three stage-discharge curves were developed to account for differences in stage between cross sections. Depth and Velocity:Depth and velocity values were "assigned to each cell by direct measurement or estimation.To expedite field data collection,it was necessary to interpolate (skip unnecessary measurements)and extrapolate (use field observation)some depth and velocity values in each data set.In addition,direct field measurements of depth and velocity were not always measured at each cell because of the uniformity of the hydraulics along a cross section.All depths were used to calculate streambed profiles by subtracting depth from stage at each cross section for each discharge.An average elevation was determined for each cell in the cross section (Tables C-2.l through C-2.l4.At mainstem margin sites,the last velocity measurement was extended further into the mainstem to the end of the cross section. Although the velocities were greater further into the mainstem,the effect on WUA was negligible since little or no upwelling was recorded in these areas and the 0.05 suitability index was assigned to these typically high velocities (2.5 -3.0 fps).Interpolated and extrapolated depth and velocity values are listed in Tables C-3.l through C-3.l4. Substrate and cover:Substrate and cover codes for each cell are presented in Tables C-3.l through C-3.l4. IV-lO ,....Upwelling Information:A suitability index value of 0.0 was entered for cells where there was no upwelling.Slight,moderate and strong upwelling were coded as 1,2 and 3 to assist in future analysis.For purposes of this report all three strengths are assigned a suitability value of 1.0 to be consistent with bi na ry criteria used in previ ous studi es (Estes and Vi ncent-Lang,eds. 1984c)• The x-coordinates bounding upwelling areas were estimated by reviewing aerial photography,cross section profiles and lengths of effective areas associated with each cell were estimated from field observations.For example,at cross section 3 slight upwelling was estimated to occur from x-coordinates 48 to 54 ft with an effective length of 20 ft.At the same cross section,moderate upwell ing was estimated to occur from x-coordinates 54 to 60 ft with an effective length of 175 ft.Table C-4 summarizes upwelling surface areas and strengths for the DIHAB modeling sites.Table C-5 is an example input data check for the DIHAB model at site 131.3L. Habitat Suitability Criteria:Habitat suitability criteria curves for spawn- ing chum salmon have been identified for the middle Susitna River and are presented in Figures IV-2 through IV-4. OUTPUT OF THE DIHAB MODEL (Weighted Usable and Wetted Surface Area Curves) Output of the DIHAB model includes WSA and WUA values with corresponding mainstem discharge.Summaries of DIHAB output for each study area are presented in Table C-6.Procedures to develop WUA and WSA curves are presented below. IV-ll I i 1 1 1 -I 1 ]f J ]l'j ]1 CHUM SALMON SUITABILITY CRITERIA CURVE DEPTH SUITABILITY CRITERIA 1.0 .9 .8 Xw .70z-.6 >-t-.5--.J..... m .4 <: <i I t- ..... N -.3:J CJ) .2 .1 O. 0 1.0 2.0 3.0 4.0 5.0 DEPTH (FT) DEPTH 0.0 0.2 0.5 0.8 8.0 6.0 SUITABILITY INDEX 00 0.0 0.2 1.0 1.0 7.0 .i 8.0 Figure IV-2.Spawning chum salmon suitability criteria for depth.Source:Estes and Vincent-Lang 1984. I ]J 1 i -1 I 1 J -1 .J 1 l I -j -] CHUM SALMON SUITABILITY CRITERIA CURVE SUBSTRATE 1.0 .9 .8 xw .70z-.6 >- I-.5-...J......-<:m .4I<!.......I-(.oj ~.3 (J) .2 .1 0 I 2 3 4 5 ·6 7 SI SA SG LG SUBSTRATE 8 9 RU CODE .,--- 1011 12 13 CO BO SUITABILITY CRITERIA SUBSTRATE PARTICLE SUITABILITY CODE SIZE INDEX I SI SILT 0.00 2 0.00 3 SA SAND 0.025 4 0.05 5 SG 1/8 -I"0.20 6 0.60 7 LG 1-3"1.00 8 1.00 9 RU 3-9"100 10 0.85 II co 5-10"0.70 12 0.25 13 BO >10"000 Figure IV-3.Spawning chum salmon suitability criteria for velocity.Source:Estes and Vincent-Lang 1984. J J J J 1 1 J I I I I 1 )I I 1 CHUM SALMON SUITABILITY CRITERIA CURVE VELOCITY 1.0 1.0 0.2 0.0 VELOCITY 0.0 1.3 2.8 4.5 SUITABILITY CRITERIA SUITABILITY INDEX 1.0 2.0 3.0 4.0 5.0 VELOCITY (FT/SEC) 1.0 .9 .8 Xw .70z .6 >- I-.5--1-..... m .4 <:: <t I...... t-~ -.3::J (J) .2 .1 O. 0 Figure IV-4.Spawning chum salmon suitability criteria for substrate.Estes and Vincent-Lang 1984. .... - - Weighted Usable Area Curves:Plots of WUA values as a function of mainstem discharge were made for the period of the study using DIHAB output for each study area.Curves were developed assuming linearity between plotted values. The WUA values were generally available for mainstem discharges ranging from 7,600 to 18,000 cfs. The chum salmon spawning season has been identified as August 12 to September 15 (EWT&A and WCC 1985).During this period,mainstem discharge generally ranges from 5,000 to 25,000 cfs.To extend the curves to describe this flow range,it was necessary to develop additional WUA values.These were cal- culated using stage-discharge curves,cross sections and measured velocity data. Where data gaps occurred,estimated stages were determined for additional mainstem discharges (QA)using the stage-discharge curves developed for each study area (Part II).Water depths corresponding to QA were determi ned by subtracting streambed elevations at each cross section from extrapolated stages.In this manner,simulated depths were determined for each cell. To obtain velocities for each cell at additional mainstem discharges,the following linear relationship was used: IV-15 v =A Q =A QM= ..... ..... where: cell velocity,in fps of additional discharge mainstem discharge in cfs of an additional data set mainstem discharge in cfs of a measured data set with similar hydraulic condition similar to QA VM =measured cell velocity in fps Estimated cell depths and velocities were combined with substrate and upwell- ing codes and cell areas to calculate WUA using the standard calculation procedure identified by Milhous,Wenger,and Waddle (1984).Habitat response curves were plotted for discharges ranging from 5,000 to 25,000 using WUA values based on measured and simulated values • Wetted Surface Area Curves:Plots of WSA values as a function of mainstem discharge were made for each study area.These curves were developed similarly to the habitat response curves and are based on the same measured and simulated data sets.Insufficient cross section information was available to calculate WSA for QA greater than the highest QM.For each cross section, wetted top width was determined by projecting the stage for each cross section.Surface areas were calculated for each cross section as the product of wetted top width and reach length.By summing the surface areas associated with each cross section,the WSA was determined for each QA. Time Series Curves:Plots of WUA and mainstem discharge as a function of time were made for the period from August 12 to September 15,1984 using mean daily mainstem discharges for each study site.These curves are valuable to evaluate changes in habitat during the spawning period. IV-16 - DIHAB MODEL RESULTS The following section provides a description of important physical habitat components found in each of the DIHAB model sites and anticipated with-project changes in these components with respect to different mainstem discharges. WSA,WUA curves and time series plots of WUA are presented at 12 of the 14 study sites corresponding to a range of mainstem discharges from 5,000 to 25,000 cfs.Two of the study sites had no confirmed upwelling and therefore no WUA values are presented.Umited fish utilization observations are also included. Site 101.7L Site Description:This site is located about 0.5 miles upstream of the mouth of Whiskers Slough on the west bank of the Susitna River (Plate IV-I).The study reach is 2,450 ft long and 150 ft wide.The substrate is predominately cobble and rubble with a thick over layer of silt and sand in the upper half of the site.Three cross sections were established to describe the shallow, low velocity backwater area in the upper two-thirds of the study site with a fourth cross section placed to describe the deeper,fast flowing channel at the lower end of the study site (Figure IV-5). The sparsely vegetated gravel bar located at the upper end of this site (Plate IV-I)is overtopped at mainstem discharges greater than 23,000 cfs.At discharges greater than 9,600 cfs,the gravel bar which separates the channel from the mainstem is overtopped and directs flow into the channel. IV-17 ~.... Q:l ~1i'ihey& Assocjates Aflllatic Re:",.l\lfe SI)elBt:il Ll STAFF GAGE --CROSS SECTION 1'/=500' P1ilte IV-1.Mo~eling site 101.7L on June 1,1982 at mainstem discharge:23,000 cfs. ·..:..::.:":i \:.:.:...~:......:~:...~ .:::. •:=-.....:. ~~"-":~:'.:,~::;:::'::.::,...,."....,..'.,....::..::,,,'.','..::. 37~37~CROS1l SECTION 1 CllOsa SECTION 3 St.tloft 0'"00 Station 13 +32 18500 c1.c:::7 t5:100 e1.g g '\(1UOO el, ~370 ~~~~370 1asoa cIs ......15300 eft ... if I iI-11400 cf,... r-~J3.~-.............- 3.5-0 ~o 150 120 '.0 200 2~0 ~50 '20 lEO 200 240 OISTANCE FROM ~EFT BANK w.RKEII (FT)DISTANCe:!'ROM ~e:F'T BANK MARKER (FT) 375 375 CROSS SECTION 2 CROSS SECTION' Station a +85 StaUon HI ........... C /V_185OO era C?~_."1!l300 ch_ _'S300c:.la =-::::;:::::' -g _11400cte g Z Z 0 0 ~370 ~370~~.... :>~I!: 3.5 -!--r---r-...,...-,-,--..---.-...,...-.....-.,---.r---r-...,..---! o ~SO 120 150 200 DISTANCE ""0101 L.UT _IC ......,,£..(FT) 240 3.5 -+0--r--y~0-...,...--y50-...,...-,..,2-0-.,--'.r-0-..,......-2-0r-O--.--2~..-0-..j DISTANCE ntOw LEFT BANI<M....RK~R (FT) Figure IV-5.Cross sections for site 101.7L depicting water surface elevations at discharges of 11,400,15,300 and 18,500 cfs. IV-19 .... This backwater site was selected for study because of a substantial amount of upwelling was suspected,but no utilization by spawning chum salmon was recorded (Hoffman 1985).Upwelling was observed in varying strengths upstream r-of cross section one throughout the study site."During winter,warm ground water influences created an open lead downstream of cross section 1. Spawning Habitat:The WSA and WUA curves are provided in Figure IV-6a for this site.Figure IV-6b is plotted at an expanded vertical scale to emphasize the response of WUA discharge. The range of depth and velocity measurements extended from 11,400 to 18,500 cfs and a backwater area is present from cross section 1 to 2 at mainstem discharges below 9,600 cfs.Upwelling was observed at the upper two cross sections but,is too shallow to be utilized by spawning chum salmon.Above 9,600 cfs,the gravel bar along the right side of the channel is overtopped. The areas that were previously too shallow to support spawning are no longer limiting.As the mainstem discharge increases,the velocities ;n the upweliing areas increase,which in turn decreases the usable habitat. ..... Because the ran~e of mainstem discharges (11,400 to 18,500 cfs)for which site-specific depth and velocities were measured was so small,additional simulated data sets were developed for discharges of 5,100 and 24,000 cfs using aerial photography and data obtained from streambed surveys.To deter- mine the WSA at 5,100 cfs,the wetted area digitized from enlarged aerial photographs at mainstem discharges of 5,100 and 7,400 cfs were determined to be the same.This was an indication that the total WSA throughout the study IV-20 - WUA/--------- A 400000 -,i-------------"---------~ 360000 -i ////I 320000 ~,/WSA Ii . --:280000 ....~~ ~I ' 'l-240000 -i II g-200000 ~1/~l"OOO ~~I ~120000 -t<C , BOOOO -1 i 40000 ~ ia-r-.-,...--...,...-.L/'-,..---.----.---,.----.----,---~-~ 5000 7000 9000 11000 13000 15000 17000 19000 21000 23000 25000 Ma instem Discharge lcfs) 21000 23000 2500019000moo15000 40000 -,,8=----. 36000~~I I I 32000 J'I "WUA II -28000 I ".~I~24000 ~I "--\ :;f2DDOOl I ---~I 16000 1 I I ~12000 J I BOOO J I I 4000 ~I t o -je-'-....,..-.---,--'ll-..-.,---rj-----.---...----...----.--..-r-i 5000 7000 9000 11000 13000 Mainstem Discharge (cfs] Figure IV-6.Surface area and spawning chum habitat response curves for site 101.7L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). IV-21 - -~ - - reach remains constant in unbreached conditions (mainstem discharges less than 9,600 cfs).Stages measured in the streambed profile survey,completed in unbreached conditions were used in conjunction with the cross section elevations to determine the depth of flow in the upwelling areas.These depths did not exceed 0.2 ft,therefore the WUA at unbreached conditions was assigned a zero value. The stage-discharge curves for the site (Part II)were used to develop a data set at 24,000 cfs which corresponded with an August 10 site visit when the upstream berm (Channel A,Plate IV-I)was overtopped and the backwater area was a flowing channel.Due to the influence of this high velocity,the WUA index decreased at higher discharges.This agrees with the habitat response curves for other side channel sites in the middle Susitna River.The WUA curve was therefore,extended to 25,000 cfs to encompass the desired range of discharges.Actual WUA values used to plot this curve are presented in Table C-6.Time series plots of WUA and average daily mainstem discharge are presented in Figure IV-7. Site 105.8L Site Description:This study site is located approximately 2 miles upstream of Talkeetna Camp on the west bank of the Susitna River (Plate IV-2).The study area is 1,000 ft long and located along the mainstem margin.Large boulders are predominate throughout the site.Four cross sections were established to describe the mainstem margin (Figure IV-8). IV-22 ]I 1 )1 1 i I 1 1 I J 1 1 ]I ~1 Figure IV-7.Time series plots as a function of time for site lOl.7L.A -Spawning chum WUA. B -Mainstem discharge. - - -- ,~ .---Susitna Rivet <:~.:.~~J "'.'.,"".:,•.•.,,',,',..'w.,,"'",,.,..,•.'",.""..,,,".. 105.8 L ....Cross SecliQn +0:5 CROSS SECTION 1 $1_Ik)n 0 ...cO ~g 400 Z 0~~......... ~39:5... 18500 cIs IS3QOCf''''/~ ·7320c'0.~ 405 .,-;:C:;;RO;;;S;;;s,-;s;;"ec;::;T1;;::O~":-::3:--------------..:,--~ Station "..&4 .-::::::;;:::========18500 cisc:15300 cf..~73:20cts~ 190 +--.-----,----r--...-,---.,.----.---r--...--..,390 -l----,--.,-----r--.,..---....,..--,.....--.....--..-----J o 20 40 SO D1ST,l;NCE !'RO'"LEFT S"NK .....I'!KEI'!(FT) 80 o 20 ...0 60 DISTANCE F'ROM LEn'BANK MARKER (F"T) 80 +05 ..,...,C""RO-=-S"'S,.,S'"'Ec:C::T'-=-0"::-:-2-----------------~ St8Uon 2'...1'& 40:5 .,-;:C:;;R:;:;o=:ss=se;';c:::T:::'O::;"-:.c------------------- St.Uon 7 ~-49 ]lIO +---.---...,...--,.--....,..--.,.----.---r---,,--~ 11'500 cr_ 15300 cis so20-40 BO DIST....CE F'RO'"!.EFT BANK w.RKER (P-n 190 +--,.--......--.....---.---.---,.----,----,--- so =~.....,.~7320c" 20 .00 eo ~»l<:E rno ...LEJ'T !!ANK _EI'!(m o 400 Figure IV-8.Cross sections for site 105.8L depicting water surface elevations at discharges of 7,320,15,300 and 18,500 cfs. IV-25 This mainstem margin study site was selected because of the assumed presence of upwelling,although chum salmon spawning had not been reported prior to 1984.Open thermal leads in the ice were recorded in the 1983 winter photog- raphy and during our winter reconnaissance visits.Upwelling and bank seepage was identified throughout the study area with the upwelling strength decreas- ing to moderate above cross section 3.No spawning or juvenile salmon were ,-observed at the site in 1984 (Hoffman 1985). Spawning Habitat:The WUA response curves shown in Figure IV-9a are plotted with WSA and WUA at the same scale.Figure IV-9b provides a plot of the habitat response curve at an expanded vertical scale. Data sets were collected at 7,320,15,300 and 18,500 cfs.The stage-discharge curve presented in Part II of this report indicates that the stage response to mainstem discharge throughout this range of discharges remains constant up to a 24,000 cfs.Bank seepage was observed along the channel margins.The substrate throughout the site is generally too large to be used by spawning chum,explaining the small amplitude of the habitat response curve.The depths over the upwelling areas,however,are sufficient for spawning at. discharges above 7,000 cfs.An increase in mainstem discharge causes the velocities at the upwelling areas to increase above the range for spawning thereby decreasing WUA with increasing discharge. Additional data sets were developed for mainstem discharges of 5,100 and 24,000 cfs.The latter discharge corresponds to conditions observed during a trip to the study site on August 10.Stage-discharge curves for cross IV-26 ..... A::::1 /----~-I 40000 1 WSA I - I I~35000 l ~30000 l I~25000 ~ I ~20000 1-......../I ~:::j WUA I o ~-'--=;==::;=I===;::::::=::::::==::;==~I-=-~~=--i 5000 7000 9000 11000 1300D 15000 17000 19000 21000 23000 25000 Mainstem Discharge (cfs) .... B 3000 l 2700 2400 -2100...... ~iBOO. ~1500 1200 <2: :::::l 900:3: ~600 300 0 5000 WUA - 7000 9000 11000 13000 15000 17000 19000 21000 23000 25000 Mainstem Discharge lcfs) Figure IV-g.Surface area and spawni ng chum habi tat response curves for site lOS.al.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). IV-27 sections 1 and 4 were used to determine the stages at both discharges.Nearly all the upwelling area had estimated depths of less than 0.2 ft at the 5,100 cfs flow level.Thus,the WUA rapidly decreases from 7,320 cfs to 5,100 cfs. Velocities at this site are generally marginal for spawning chum at all dis- charges and become nearly unacceptable for spawning at high discharges.Time series plots of WUA and average daily mainstem discharges are plotted in ~Figure IV-10. "... Si te 114.1R Site Description:This site is located 0.4 miles upstream of Lane Creek in mid-channel on a vegetated gravel bar (Plate IV-3).The study reach is 675 ft long and 60 ft wide.Large gravel and rubble are predominate in the upper half of the study reach,and sand is present in the lower half.Cross section 1 is located in a backwater area at the mouth of the channel.Cross sections 2 and 3 define the shallower,high velocity area (Figure IV-II). Thi s study site was selected because of the open thermal 1eads in the ice which were visible in the March 1983 photography.No previous spawning had been reported at this location (Hoffman 1985)but spawning chum salmon were observed in moderate numbers during the 1984 field season.During winter 1984,upwelling was identified in slight to moderate amounts concentrated along the left bank.The upwelling begins below cross section 1 and extends ~ upstream of cross section 3. IV-28 J J 1 I )1 j i 1 1 i 1 A1000 900 800-700. .f-I....600. 0-500~ 400 -<300:::J::;c 200 100 0 I I AUGUST SEPTENBER 8-35000-CD 31500'+-<:oSI 28000N 1.0 Ql 24500 Cl '-21000ltJ.c 17500u CD •..-f 1.4000Cl E 10500 Ql .f-I 7000CDc:3500•..-f ltJ :E 0 I AUGUST SEPlEMIlER Figure IV-IO.Time series plots as a function of time for site I05.8L.A -Spawning chum WUA. B -Mainstem discharge. - - - ..... - j~ djJ I - ,7lIOOollo _ ::\..."""'==-----7;AJ-==:::::::::::7 20o 4a5 +--.,----,-.,---,---r-,..--r-.,----,--r----r----r-,-......---,--r----r-i -40 SO ao '00 t20 '40 16Q ~ac DISTANCE FRCt.!LEFT BANK t.lARKER CFT) 470 475 ..,..,C"'R"'OS""S=-se=C=TIOOl="'.-----------------, Sf.11oft 3"21 ~Susitna River <;~:::::..':"":~':':;::::..:.-.;-.::'.;.:.::.:.:,:':'; .~:: ••:••:::......_:.....:;"'l".:.,,",''''''::,.,....":'::.,-!~.:.•:.:. .:."~ ...:{....':<.:::::::,..:.;.:-:.;..::..~ ......:~{~.::::::::.:..:":..:....:..::::.::.:::.:."..... ~ 114.1R ~Cross Section _. ,... 475 .,...,C:=R""O::cSS:-:::SE:':C:=TJ:'::O"''''.s,••.•-----------------., Slacion 0 +00 475 ..,..,c:~R"'OS""S=-S""E"'c:=TI"'C".N..,,3-----------------, Station 1 +04-5 470 470 '1"680 c.1s '80~ro 50 100 120 140 DISTANCE:F"RCiM LEFT BANK MARKER (FT) 2Co2Do 4.'+--,,---,-,,---,-·--,--r.---.-,..-......---,----,,-..---.---.-.--,.-,-- ~~~'00 IW ,~1~,~ DISTANCE FROM LEFT BANK MARKER (FT) Fi gure IV-ll.Cross sections for site 114..1R depicting water surface elevations at discharges of 7,680,15,100 and 17,900 cfs. IV-31 .- ,~ Spawning Habitat:WSA and WUA curves for this study site are provided in Figure IV-12a and b with the values provided in Table C-6.A comparison of the two curves in Figure IV-12a indicates that a very small proportion of the WSA provides usable habitat over a broad range of mainstem discharges. However,Figure IV-12b,plotted at an expanded vertical scale,indicates that WUA indices are highest for mainstem discharges in the range of 11,000 to 15,100 cfs. Three data sets were collected at discharges ranging from 7,680 to 17,900 cfs (Table C-3.3).Below 8,800 cfs,the stage remains constant,suggesting that the WSA of the channel is stable during unbreached conditions.At 7,680 cfs, the depths in the upper portion of the study site are shallow,and unsuitably small substrate is present in the upwelling areas.As the channel conveys additional flow,these upwelling areas are no longer limited by shallow depth, and WUA indices for spawning chum peak near 11,000 cfs.Above this discharge, velocities exceed the maximum velocities preferred by chum salmon (3 fps), thereby causing a decrease in WUA.This agrees with field observations made from September to October. Additional simulated data sets were determined for mainstem discharges of 5,100 and 23,000 cfs.Field personnel were·at the site when the discharge was 23,000 cfs.Si nce the stage for unbreached conditi ons rema in unchanged,the WUA response curve was assumed constant,thereby extendi ng the curve to 5,100 cfs.Comparisons between the cross section and stage-discharge data reveal that depths are too shallow in the upper half of the stUdy site for spawning. A backwater at the lower end of the study site provides the majority of the IV-32 ,-A 90000 I -----_..-II 81000 ~----....j 72000 , WSAI ~63000 l "-54000 ....j g 45000 36000 / co l1.l l:.21000« 18000-9000 a -I WUA I .~-5000 7000 9000 11000 13000 15000 17000 19000 21000 23000 25000 Mainstem Discharge (c f s) WUA- 8::1 1600 "1 --:1400 j ~1200 g-1000 J BOO J « _~600 ~100 200 - - -----------------l I--- 5000 - Figure IV-12. o -+----.-----,c----.---~--I-11---1 7000 9000 11000 13000 15000 17000 19000 21000 23000 25000 Ma instem Discharge (c fsJ Surface area and spawning chum habitat response curves for site 114.1R.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). IV-33 usable spawning habitat at low discharges.Time series plots of WUA and mainstem discharges from August 12 to September 15,1984,are shown in Figure IV-13. Site 115.OR ...., - - - Site Description:This site is located in the lower portion of Mainstem II Side Channel on the east bank of the Susitna River (Plate IV-4).The study reach is 1,525 ft long and varies from 40 to 80 ft wide.Rubble is present throughout the study area with an overlay of sand in the pool area.Two channels (A and B,Plate IV-4)direct mainstem flow into the study site. Cross section 1 was established to define the large backwater area present in the lower half of the site (Figure IV-14).Cross section 2 described a riffle area just upstream of the backwater.Above this cross section,the channels divide but the study site is confined to Channel B.Cross section 3 defines a deep pool;cross section 4,a shallow low velocity run. Channels A and B breach at 12,000 and 23,000 cfs,respectively.When the channel s are unbreached,a large backwa tera rea extends from the mouth of the, side channel upstream nearly to the confluence of channels A and B. This study site was selected as a known upwelling area where chum spawning had been observed in previous years (Hoffman 1985).Upwelling varies between slight and moderate at the cross sections.Bank seepage was noted along both banks at cross section 1.Adult chum,coho,and sockeye salmon have been observed in the side channel.Juveniles of the same species have also been ....,observed in the site. -IV-34 }J I 1 1 J -1 I I 1 I A 1000 900 800-700. .f..J ~600. C'"soo3 <l00 <I:300==='% 200 100 0 I AUGUST SEPTEMBER B35000 "iii 31500........... <:~I 28000w 01 24500Q) C'Ic..21000lU..r::::.17500u III ·rl 1<lOOO0 e 10500 Q) .f..J 7000III C 3500.rl lU ::::E:0 I AUIilJST SEPTElflER Figure IV-13.Time series plots as a function of time for site 114.1R.A -Spawning chum WUA. B -Mainstem discharge. -- ,~ - - - - I V...36 - - ..- ItS.OR ....Cross SectIon ':':.:.:::.•.•::::::~:.::.'::::::::::.:.:.:::::.:::.:.'::':':':'.::i::':"::'(:i::"':::":.:.'.•.•. .At--susuna Riwer ••••::: ..eo ..eoCROSSSECTION,CROSS sEcnOH 2 81111k1ft 0 ..00 Station 2""13 g g z z ---_......,...2 _'4500 c/o 2:c !;(..75..75 j~____7eeoc/o ...7~'"......... ""IE::.. ..70 +-,.-....,.-,........,-...,...-,-....,.-,....-,,.----.--or--r--,--r-'""i 410 +-....,-.,....-,-.,....--,,............,...-,....-....,.--,....---r--,-....,...-..----r- o 40 eo ,2.0 180 2.00 2.4Q OISTANCE FRO""~EFT BANK ......RKER (rT) 2eo o .0 AO 120 If;(l 200 1/'\0 - 480...-::C"'ROSS=-=SECnON==-=S-----------------., Sf.lm $"'112 .so I CROSS S.eCTION .4 Stalt60n t.Zf!I~ 2S040eo120,ao 200 240 CHST.......CE:""0"I..E:F"T BANK MARkER (FT) "'""-----.,r.-7YO cIa \---------7-145OQ ct. !,g:;., !4 ~"'j~~i j mL 2eD Q8012C11802002-40 QtS"r""':E ,,_~UT ......"_1:10 err) 'r-------=,.,.:;-'4S00 c/o Q "75- Figure IV-14.Cross sections for site 1I5.0R depicting water elevations at discharges of 7,680 and 14,500 cfs.surface IV-37 "'"' - - .- Spawning Habitat:Figure IV-15a is a plot of the total wetted surface area and WUA curves.Fi gure IV-15b is the same WUA curve plotted on an expanded vertical scale. Depths and velocities were measured at all cross sections for two mainstem discharges,7,680 and 14,500 cfs.The northwest channel head berm was breached at the time field data were obtained at 14,500 cfs.Neither head berm was breached when depth and velocity data were collected at 7,680 cfs. The WUA remains relatively constant at discharges below 10,400 cfs.Above this discharge,the influence from the mainstem increases the stage of the backwater and depth of flow in the upwelling areas at cross sections 1 and 2, creating slightly more usable spawning habitat.The WUA continues to increase with increasing discharge up to 14,500 cfs,where it remains nearly constant until the northeast channel is breached at 23,000 cfs.No information has been obtained regarding the influence of higher stream flows on velocities at the upwelling areas. Additional simulated data sets were developed for discharges of 5,100,12,000 and 23,000 cfs.The stage-discharge curve developed for cross section 1 indicates that the stage is constant for mainstem discharges below 10,400 cfs. Therefore,the WUA and WSA measured at 7,680 cfs was assumed to be applicable to 5,100 cfs.At 12,000 cfs,the stage-discharge curve was used to determine the stage at cross section 1 and 2.The upstream portion of the study site, at cross sections 3 and 4,provide the same WUA and WSA at all discharges until the northeast channel (B)is breached at 23,000 cfs.An additional simulated data set was developed for a mainstem discharge of 23,000 cfs by IV-38 Mainstem Discharge (efs) ..... - - - A 5000 7000 9000 11000 13000 17000 19000 21000 23000 25000 """ B SOOO 4500 4000 -3500. -4-J "-3000 g 2500 1 2000 <t :::J 15003: lCiOO - - 500 0 /' /'WUA---/' I -l -Figure IV-15. 5000 7000 9000 11000 13000 15000 17000 19000 21000 23000 25000 Mainstem Discharge (cfs) Surface area and spawning chum habitat response curves for site U5.0R.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). IV-39 - - assuming that the linear trend in velocities occurring at cross sections 3 and 4 between mainstem discharges of 7,680 and 14,500 cfs would continue to 23,000 cfs.Above 23,000 cfs,the habitat response curve is expected to decrease,as the velocities in the upwelling areas are.expected to increase above the preferred range.This response is similar to the responses forecast for other study sites in the middle Susitna River where data are available.Time series plots of WUA and mainstem discharge for the 1984 chum spawning season (August 12 to September 15)are shown in Figure IV-16. Site 118.9L Site Description:This site is located along the mainstem margin approxi- mately 1.7 mil es downstream of Curry Station on the west bank of the Susitna River (Plate IV-5).Rubble and cobble predominate throughout the site with a layer of silt and sand deposited along the bank at the upper end.Three cross sections were established in the study area which is 475 ft long (Figure IV-17).A small tributary enters the mainstem just above the site.At mainstem discharges less than 23,000 cfs,a small channel is evident immedi- ately downstream of the tributary and extends downstream of cross section 3. This mainstem margin study site was selected because spawning chum salmon were previously recorded at this location (Hoffman 1985).In addition,chum salmon were observed spawning at the site during the 1984 field season.During April 1985 open thermal leads were observed throughout the study area.Small amounts of bank seepage kept the area from freezing for part of the winter. IV-40 1 1 j I 1 I t J 1 i }1 i }1 -~---------------,--------.--- -T SEPTEMBER SEPTENBER Figure IV-16.Time series plots as a function of time for site 11S.OR.A -Spawning chum WUA. B -Mainstem discharge. .,... -I - ..... ! l::o.....-OJ-?"" \--------------7680 eta. 20 40 60 eo 100 120 140 OI$"ANCt FRO'"L£"BANI<MAAt<£R (n) \----------------103:)0 cr. iI CROSS SECTtON 2 .Sta1klf'l 1 ~36 ",0 "'--================"""''''''';;;;;e:;';''~ r---------------U100ct• 118.9 l '-Cross Section ;:~::::G":::'..... '.::~......',:..~.:'::' '.':.~":".":'::">'....:...,.. .... - 505 +--r---r-..--..,-""T'"-r---r-"'T""-r--r-....--,r-""T'"~ ~~~~,~'M OISTANCE rRO'"\.£"BANK ~A"'KE"(FT) "020~60 80 100 120 OISTANCE ,....0"'1 LEFT SANte:WJlU<E:R crT') 7680 cIs 15100 r:b 10300 cia CROSS SECTION S SI.lio'~2"54 o 510 1 -================:::::::;'';;7900='0:'..:1 '''0 CROSS SECTlON , Slltlon 0 +00 o ~ ",0 \ 17900 cis 1 1$100 ct. S l000Q deI i5 ~7lS8O c:t.r-;:: .... "~ depicting water surface 10,300,15,100,and 17,900 for site 118.9L at discharges of 7,680, Cross sections elevations cfs. Fi gure IV-17. IV-43 Spawning Habita~:The WSA and WUA curves for spawning chum are presented in Figure IV-18a,with the WUA curve replotted to an enlarged scale in Figure IV-18b. Four data sets were collected from mainstem discharges of 7,680 to 17,900 cfs. From Part II of this report,the stage-discharge curve indicates that the ~relationship between stage and mainstem discharge remains constant from 5,000 to 23,000 cfs.The lower end of the gravel bar which extends from above the .-study area to midway between cross sections 2 and 3 provides shallow depths in upwelling areas.As discharge increases up to 15,100 cfs,the depth of flow increases in the upwelling areas until the entire area is optimal for spawning habitat.The WUA function begins to decrease as high velocities limit spawning in the upwelling areas. To expand the discharge range covered by the WUA curve,additional simulated,- data sets were developed at 5,100 and 23,000 cfs.The stage-discharge curve for cross section 2 was used to determine the stage at both discharges.A gravel bar influences the stage at the upper end of the study area,particu- larly in the upwelling areas.At low discharges,the upwelling area appears as bank seepage and is too shallow for spawning.The mainstem begins to flood,- the upwelling above 7,680 cfs and continues until the entire area is flooded F"'"at 15,100 cfs.Above 15,100 cfs,velocities begin to exceed 1.3 fps,the highest optimum usable velocity for spawning chum salmon.This decreasing WUA trend is similar to the habitat response at other side channel sites in the middle Susitna River.Time series plots of WUA and mainstem discharge are shown in Figure IV-19 for site 118.9L. IV-44 WSA 16000 10 ~i2000 <l:- 40000 lr.A:......------------------..-----------. 36000 l 32000 -1 -----::28000 -1 '~24000 j./// g20000 ~ I ! BOOO I 4000 WUA! o ~--==;.-===;::::===:;:::::::::::===::=====-..==-=:-==-.-.___j 5000 7000 9000 11000 13000 i5000 i7000 i9000 21000 23000 25000 Mainstem Discharge (cfs) - - B 2500 2250 2000 -1750 .J-l-1500 ~1250 iOOO <l: :::J 7503: ~r 5000 Figure IV-18.Surface area and spawning chum habitat response curves for site l18.9L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA.B -Weighted Usable Area (WUA). IV-45 1 )i 1 1 1 )1 1 )~1 1 A1000 !iOO 800-7DO. +J 800....... c:r SOC$ -400 <300:::l:z: 200 100 0 I I AU6UST SEPlBIIER B 35000 CD 3i500........... <::~I 28000~m lU 2..fiOOenc...21000I'D.r:.17500uen.....l.coooCl E 10500 lU +J 7000(tJc.3!iOO.... I'D ~0 I I N.I6UST SEPTBII:'R Figure IV-19.Time series plots as a function of time for site 118.9l.A -Spawning chum WUA. B -Mainstem discharge. Site 119.1L Site Description:This site is located approximately 1.5 miles downstream of Curry Station on the west bank of the Susitna River (Plate IV-5).A large side channel enters the mainstern at the upstream end of the study area.The study area,located along the mainstem margin,is 425 ft long.Cobble and large gravel are present throughout the site with some silty sand deposits along the bank and larger substrate in the mainstem.Three cross sections ~~ were established to describe the mainstem margin with a fourth cross section established at a clear backwater area (Figure IV-20).Below discharges of 18,000 cfs,the backwater area is dewatered. This mainstem study site was selected as a suspected upwelling area,however, chum salmon had not been observed at the site prior to 1984 but both adul t chum and juvenile chinook salmon were observed in the study site during 1984. No obvious upwelling areas were observed in this study site,however,redd locations were coded assuming the upwelling strength was slight. Spawning Habitat:WSA and WUA curves are presented in Figure IV-21 with the WUA replotted on an expanded sale in Figure IV-21b.Data sets were collected at 7,680,10,300 and 15,100 cfs.Figure IV-21a shows that WSA remains relatively constant however WUA shows a sharp increase at 10,300 cfs.The upwelling areas are covered sufficiently for spawning at 15,100 while the area in which cross section 4 describes first becomes usable at 18,000 cfs. Data sets were developed for 5,100 and 23,000 cfs. dewatered at 5,100 cfs causing a WUA value of zero. lV-47 The upwelling areas are At 23,000 cfs,the '19.'L t---ot Crass Section ~"CROSS Sl!CJ!ON 2 Slit.1 +Ie S 15'00 c11~"'"70300 ds i:;~10 \ d 1'880 cfs Wi.. ~05 -l---~--_._---,.----,---r-----r-----4 r~ o 20 40 SO OISTANCE FRO",LEFT BANI(w.RI(ER (FT) ~"-r:CR"'O~SS::-':U=CTlOH=::-:-:l----------------"'" s.t11k1n D"00 ~1~..,...,c..,."O~S"'S-:S=ECT=IO".,N..,3-----------------, St.lion :2'....c2 ~O'+--...,...--...,.----,.----,----,.....----,..----[~o~-1---~--_._---r----r------,r-----.-----4 ~10 o ...-15100 el. ,.....I0300cfs '\,-7680 el. 20 40 60 OISl"AHCE F1'tOIl LEFT BANI<~I<ER (m ~10 o 15100 Cfs_~------------l 10300 cf.--~--.::>'.".._-----------4 7680 e'.~.....:::'...,,-___! ~"- 20 40 60 OISTANCE FROM LEFT BANK :MARKER (ri') Figure IV-20.Cross sections for site 119.1L depicting water surface elevations at discharges of 7,680,13,600 and 19,100 cfs. IV-48 A20000......-----------------------~ 18000 16000 --:14000 -/.-J...... 12000. g 10000 BODOro Q) c...6000« ----- WUA 4000 2000 O-+--:::,---.-----,-----.--..,..---.--~--_,__-___._-___1 - 5000 7000 9000 11000 13000 15000 17000 19000 21000 23000 25000 Mainstem Discharge (e fs) 3500 B .-3150 2BOO -2450. -/.-J WUA......2100. CT 1750~ ~1400 « ::::J 1050 /~ 700 350 ,/ a 5000 7000 9000 11000 13000 15000 17000 19000 21000 23000 25000 Mainstem Discharge lcfsl - FigurE:!IV-21..Surface area and spawning chum habitat response curves for site 119.1L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). IV-49 velociities are at the peak of the optimum spawning range providing a large amount of WUA.A decreasi ng trend in the habitat response curve can be expected at higher discharges.Figure IV-22 includes time series plots of WUA-and mainstem discharge. Site 125.2 Site Description:Skull Creek is located downstream of this study site on the east bank of the Susitna River (Plate IV-6).The study reach is I t 475 ft long and 250 ft wide with sharpt flat gravel and rubble substrate is present throu!~hout the site t unlike the typical t smooth round substrate generally present throughout the river.Two cross sections were established to describe the high velocities present throughout the mid-channel (Figure IV-23).A deept low velocity area is present along the left bank of cross section 1.A large shoal area is present along the left bank of cross section 2.At low mainstem discharges t a gravel bar varies the stage across cross section 2. - This :side channel study site was selected because of suspected upwelling t and chum salmon adults were previously recorded.Adult chum and pink salmon and chinook fry were also observed using the site in 1984 (Hoffman 1985).Open thermi:il leads were recorded during winter 1984 in the entire channel.Strong upwerJing was observed along the left bank of cross section 1 with slight amounts of upwelling recorded along the mid-channel and right bank.At cross section 2 t moderate amounts of upwelling were present along the mid-channel and right bank. IV-50 1 )]J ]1 J .~)i i J 1 1 ]1 1100 990 B80-no +J 660...... CT 550oS 440 <C 330:::l % 220 110 0 A I l SEPTatBER SEPTEMBERAUGUST B 35000 'U) 31500o-t '+-<S 28000I (J1 24500 ...... cu C'l 21000'-10.c 17500u U) 14000•..-1 Cl e 10500cu 7000+J U)c:3500-..-1 10 0 AUGUST :::It: I Figure IV-22.Time series plots as a function of time for site 119.1L.A -Spawning chum WUA. B -Mainstem discharge. ..... ..... - IV-52 2 ",:,;':,~••'..... '.:~:.;.;;;~:i ':;~;',::,:.'....':,,:::.:..;.;.;,..::::,;.,. 125.2R ~CtOSS Sections ~6:1 ""'OR:-:O""S~S~S:::EO:::T:::'O""N"':"'----------------"" Station 0'"00 ~61J .....r_'gl00do \-----1__'3600 ... ~ss .,.-;;0:;;:RO;;';SS;:;";S:;;:EO:::T:::;IO:::N-=2----------------" Slf,lm 71'a7 . sso oso -4--_r--,---.,..-----,,---...,...---r--~-_r-___l ~so +---,---,---,---,---.,..----,,----,----,-----i r- i I I P"" I a '00 200 :lOO OISTANCE ~RO"L£n EWlK MARKER (~) 400 a 100 200 JOO OIST""'OE FRo..L£~ElANK MARKeR (~) 400 .- Cross sections for site 125.2R depicting water surface elevations at discharges of 7,680,13,600,and 19,100 cfs . IV-53 .... - Spawning Habitat:The WSA and chum salmon WUA response curves for this site are rl~presentative of medium to large side channel areas (Figure IV-24a and b).WSA and WUA response curves are presented in Figure IV-24a for site 125.2H.A relatively narrow range of WUA is predicted at mainstem discharges betwee!n 5,100 and 23,000 cfs indicating usable habitat remains constant.This is probably caused by comparable rates of availability of habitat at the site. The upwelling areas located along both banks range in strength from slight to stronu.Most of the suitable spawning habitat occurs along the left bank at cross section 1 in the large backwater area where velocities are not limiting through the range of measured mainstem discharges. The r1esponse of WUA as a function of mainstem discharge is shown in Figure IV-24b plotted on an expanded scale.The increase in WUA is due to the shallow upwell ing areas becoming usable.As the discharge increases,the upwelling areas along the left bank reach usable depths,while the velocities along the right shore begin decreasing in suitability.The substrate in the study reach is not of optimal quality,thus explaining the small amplitude in the 'rt~sponse curve. Data sets were estimated for discharge of 5,100 and 23,000 cfs.The 23,000 cfs data set was estimated based on stage-discharge curves,cross sections and aeria']photography.At 23,000 cfs,the high velocities in the spawning areas limited the upwelling.A field reconnaissance trip was made to the study site when the mainstem discharge was 4,300 cfs.At that discharge,much of the upwelling areas along both banks,with the exception of the backwater area at cross section 1,were too shallow for use.Time series plots of WUA and mainstem discharge are presented in Figure IV-25. IV-54 .... ----------------~SA ! / / / ,I /I /i 100000 I I 5000:+~:::;..-=::::;===:;:W=U=A==;~=:::;=:::==;::::====r=-_-=;---_-.--_~ 500000 """I A-- 450000 -j 400000 I ~350000 1 300000 -1i250000~ 200000ro l1.l~150000 - 5000 7000 9000 11000 13000 15000 17000 19000 21000 23000 25000 Mainstem Discharge (cfs) B 20000 ~ I18000 WUA 16000 I --:14000 I -&-l --12000 I g 10000 I ~8000 <X:I:::::l 60003:/4000 "'- 2000 ~I "'- a II "'-l-i, I 5000 7000 9000 11000 13000 15000 17000 19000 21000 23000 25000 Mainstem Discharge (c fs) Figurl~IV-24.Surface area and spawning chum habitat response curves for site 125.2R.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). ""'"IV-55 1 l -1 1 1 1 .~I I ~I I A....,I------(~----------­~/I I 100 !iii BO 70 +oJ 60.... 0 0-503 .40 -<30~ ;E 20 10 0 AUGUST B 35000 Ui 31500....1-1 U 28000 <:-I lJ1 24500O'l Q) C'I 21000c... to.c 17500t:l U) 1.4000.r-t Cl e 10500 Q) 70004J U) c:3500.r-t (D 0 AUGUST X I SEPTBIJER SEPTEMBER Figure IV-25.Time series plots a$a function of time for site 125.2R.A -Spawning chum WUA. B -Mainstem discharge. - - Site 130.2R Site Description:Sherman Creek is located just upstream of this large side channE~l along the east bank of the Susitna River (Plate IV-n.At discharges below 15,000 cfs,a small backwater area can be observed separate from the side channel.Cobble and rubble is present throughout the upper half of the site while the lower half is covered with a layer of silt and sand.The study reach is 700 ft long and varies between 100 ft at the downstream end,to 30 ft wide at the upper end.Three cross sections were installed in the shallow, low velocity area (Figure IV-26). This backwater study site was selected as a suspected upwelling area with no preViously observed spawning activity.Chinook juvenile salmon were observed to ut-ilize the site (Hoffman 1985).No upwelling was noted throughout the site. Spawn'ing Habitat:Because upwell i ng areas were not observed throughout the 1984-85 field seasons,habitat response curves were not developed for this site. Site 131.3L Site Description:This study site is located between vegetated gravel bars immedi ately upstream from·the confl uence of Fourth of July Creek and the Susitna River on its west bank (Plate IV-8).The substrate is predominately grave 1 and rubble throughout the site with a 1ayer of si1ty sand in the IV-57 .... .... r iV~58 800 +-,--,--,-...,...-,.--,.-.---..-.------.--.--,.--,--,.--1 8,0 .,.....C..RO;;."'CTlOH=..2-----------------, a'.tion 2.27 1402040GOSO100120 OISTANCE !"ROM LEFT BANK w.RKER (FT) o 130.2R 10-01 Cross Section ~:..:..:....:::;:~..:~...:.:.~ - 8'0 TCMR;;:O..SS"'-O;SEo;C:;:T1O;;:;wN"':'-----------------.., \"••0+00 ,~~""-----------------==- 18,00 c:ls:"~S~======:;::;;:::==-----~-g14500ets"",----=7~c~z~Q=~;;; iOl...::> ~ 610 T"rC:O:RO"'S-.S.-.S;oE:;:CTTo'O"'N..3-----------------..., S••tIQll ..+21 19900 c1s 16100 e't~14SOOC-1' 7600 c:ls 60~ 800 +.-,-..,......,--r--,--,--,.-....,..-r--r-.,.....-r-.,.........,-J .00 +----.-..,..-r--,-~,.--,.-..--,.-.---..-.------.-....---,r-_i o 20 40 .0 60 '00 '20 OISTANCE !"ROU L.1!:fT BANK W.RKER (I"T) '40 o 20 40 50 eo 1 00 1 20 DISTANCE FROM LEFT SANK MARKER (FT) depicting water surface 14,500,16,100 and 19,900 site 130.2R of 7,680, for discharges Cross sections elevations at cfs. Figurle IV-26. IV-59 ,1f"l"l'G. - - Z f"'\-fa- 0 W 0f.,?~; Cot)~~ CtJ !!n "CE --0 ..... pmqJ. - backwclter area at the mouth of the channel.The study reach is 1,075 ft long and 130 ft wide.Four cross sections define the habitat in the study area: cross section 1 is located in a deep low velocity area;cross sections 2 throu~Jh 4 are in faster,shallower areas (Figure IV-27).Two channel heads (A and B)direct flow into the site at 9,000 and 10,700 cfs respectively.Below breaching discharges,groundwater maintains flow through the study reach. This side channel study site was selected because it was known to have upwel~ling and to be a chum salmon spawning area.Chum salmon were observed spawning in the area,in 1984 particularly along the right bank.Chinook fry were also collected during sampling efforts (Hoffman 1985).Moderate to stron!)upwelling was noted along the right bank in the lower half of the study site and moderate upwelling was observed along the left bank in the upper half ,~ of thE~site. Spawn"j ng Habitat:The WSA and WUA curves for 131.3L are plotted in Fi gure IV-28a using the same vertical scale.The WUA curve is replotted with an enlarged vertical scale in Figure IV-28b. - I, The range of depth and velocity measurements extend from 7,680 to 19,900. Below 9,000 cfs,flow is maintained through the site by groundwater inflow. Above 9,000 cfs,the gravel bar on the left side of the channel is overtopped, directing flow into the lower portion of the study site allowing upwelling areas that were previously too shallow for utilization to become available. The hiibitat response curve rises as the channel head berm breaches near 10,700 cfs.At medium and high discharges the stage in the lower half of the channel IV-61 - -Susitna River .,..:..... -'"'"::.,. ..:"','..'....".:.~'",.:,".~.:'.::.;::,':.:,:............::. t31.3L _Craa.SeC:Uon- uo "T":CAO=SS=lIECTIOH==::-:'"'-------------------, ala"'"0.00 IlllIOO do 1ttlCX1 de.'"""__-=...."..~_=_=:-;;.,II'---=.-~~:..----,&aD do'.-..-/ &20 TtC;;;R;:;OSll~S;;E;;::C;;TlOll;;;;-.3-------------=-,-- "•.Itlan fI to 31 __________..,_,lllIOOdo r---~-"'OlI·f: zo ~filS ..i .,0 +--r--,--T"""-r._...,....-r-..,...-.....--r-..,...-,...........-"T"""---.-~ o SO 120 160 200 2.....0 DlSTANC£~RO"L.E~SANK ""'-RK£R (~) 2"0 &20 "CROSS==SE;=CT1Oll=::-2:-----------------..., alii .....:I +13 no .,,_:;;;:;~1eCTlON;;;;::=;;-4.-----------------, Station f +18 ---o::::::::::--,-:.-_-_-..,-~---------_-"'_;.-.------------------------_-_-_-_-:;-lllllClldoV-=____r'~::..........-= "'~ &'0 +--,-T""....,.-...-.....-r-...,..--,,..-..,.......,-.,........,.-..-.....~ o IlO 120 lao 200 240 !OIST....C£noo..LUT _I<_£R eP'T) 2110 '''0 Figure IV-27.Cross sections for site 131.3L elevations at discharges of 7,680, depicting water surface 16,100 and 19,900 cfs. \IV-62 I WUA jIII I r I==="l gOOD 11000 13000 15000 17000 19000 21000 23000 25000 Mainstem Discharge lefs) 70005000 A220000...,!~----------------..----- 198000 1 // 176000..J L -:154000 J~I /WSA ---132000 ~ g-110000 ~// :88000 ~I __--~/ Q)--~ ..5c 56000 1 44000 1 J 22000 -joh -~ - B 2000 1800 1600 -1400 ~ ---1200 ~1000 <C :::::J ~ --r-I 5000 7000 9000 11000 13000 15000 17000 19000 21000 23000 25000 Ma instem Discharge (efs] .- Figurl~IV-28.Surface area and spawning chum habitat response curves for site 131.3L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). -IV-G3 creates a backwater area,which deposits a layer of silt.Substrate such as silt and sand are too small to be used by spawning chum which decreases the magnitude of the habitat response curve.Velocities become limiting to the spawning chum salmon above 19,900 cfs,also decreasing the trend in the habitclt curve. Data sets were estimated at mainstem discharges of 5,100 and 23,000 cfs.The stage throughout the study reach is constant below 9,000 cfs,with indicating the WLJA in this range also is constant.The same WUA value determined for the 7,680 cfs data sets was assigned to 5,100 cfs.At 23,000 cfs,the velocities in thl~upwell i ng areas become too fast for spawni ng whi ch decreases the WUA curve..Time series plots of WUA and mainstem discharge are plotted in Figure IV-29 .. Site 133.8R.... ~Site Description:This study site is located at the head of Slough 9A on the east bank of the Susitna River (Pl ate IV-9).The substrate throughout thi s area varies from silt along the shore to cobble in the main channel.Three cross sections were established beginning on the right bank and converging at a common poi nt on a gravel bar.These cross secti ons descri be the fast velocity area along the mainstem margin (Figure IV-30).Below 15,600 cfs,the shoal area along the mainstem margin begins to have a pronounced eff-ect on depths and velocities. This mainstem margin study site was selected because upwelling was suspected, although no spawning chum salmon have been previously recorded.No adult or IV-64 \ A -1 1 I 1 1 1 )1 -1 1 1 J 1 2000 lBOO 1600-1-i00...... 'l-1200. c::r 10003 BOO <600:::J :E -iOO 200 0 I I AU&UST !iEP1'BlBER e 35000en31500......'l-<:u I -28000O'l <.n 2-4500Q.) C'l '-21000(tI L:17500u U) ·M 1-i0000 E 10500 Q.) +J 7000U) c:3500.M 10 ::E 0 1 ._--I ------- AUGUST SEPTEMBER Figure IV-29.Time series plots as a function of time for site 131.3L.A -Spawning chum WUA. B -Mainstem discharge. - - 64~+--""--"--.,--.,--...,---,--.,---,---,---,---i a~~..,-;:C;;,RO"S;OS.S"O'EC=nvOwN.2------------------ Stilian 0'1'"''' ·.::Ii"'::..;:~.::::':':':':O:'::":::::::::..:;:.:••;••''':':': .:~t 133.8R ..••;:••:::::::.;..H Cro..Section 6~0 a \19900 cl.\-.16100 eI.\:?'C='-~ 40 ao 120 160 200 QLSTANCE F"RCM RIGHT 'BANK MARKER {FT) CROSS SECTION 1 Sf_non a ...00 655 .,.-,;CRQ=..::-::."'O=T1ON=-=3-------------------, St••1on 1 +..e 71S8Q ds S~(] .---19000<:f5 \,,,a,oo cl. '\'<----~ 6~0 '\'.;..9900 cls \-.~1!)1aocls C\'<-":::>""-...-....!.:'7680clS ~\ 64'S +---,--.,--.,--.,--.,....--.,....--.,....--,...--.,....--.,....---1 645 +--...,--...,--.,---,--...,--.,---,---,---,--...,---i O'STANCE:F"ROM RIGHT SANK MARKER eFT) o 40 ao 120 160 OISTANOE I"ROM RIGHT BANK ""'-AKER (I"T) 200 o 80 120 ,60 Figur1e IV-30.Cross sections for site 133.8R depicting water surface elevations at discharges of 7,680,16,100 and 19,900 cfs. IV-67 .... ..... juvenile salmon activity was observed in 1984 (Hoffman 1985).Small upwelling and open thermal leads in the ice were observed along cross section 1 and 2. The upwelling is assumed to be slight to moderate in strength,as the area was frozen over during part.of the winter season. Spawn'jng Habitat:WSA and WUA curves for spawning chum salmon are presented in Figure IV-31a.The WUA curve was replotted to an enlarged scale in Figure IV-31b.Figure IV-31 shows that WUA remains relatively constant from 5,000 to 35,000 cfs • Data sets were collected at discharges of 7,680,16,100 and 19,900 cfs. Throu~~hout this range,the depths in the upwelling areas are sufficient for spawning and substrate is also good.However,there are only three small upwel'l i ng areas present within the site,thus the small ampl itude of the habitat response curve.An increase in mainstem discharge above 10,000 cfs causes the velocities at the upwelling areas to increase beyond the range of suitable velocities for spawning. Additional simulated data sets were developed for discharges of 5,100,10,400 and 2:2,700 cfs.The latter two discharges corresponded to conditions observed during trips to the study site on September 22 and August 24,1985.The stage-discharge curve for cross section 3 was used to determine the stage at the three discharges.Most of the upwelling areas have depths greater than 0.2 ft at the two lower discharges with becoming the entire area optimal at 22,700 cfs.Velocities at this site are usually unsuitable for spawning chum salmon at all discharges explaining the decreasing trend in the WUA curve. IV-68 WUA 30000 -i~-'---------­ ! 270001 / "'''0 l WSA --:21000 -1 _ ~li---- .18000 1 g 15000 l 12000 ..., rc I ~9000 1 6000 ~ 300 0 a ~­~I--~I==r--"""'l==r=l=""'"i"'''''"'''''''"'''l''........'''''''"'f'--,-l---.----,r-----.j 5000 7000 9000 11000 13000 15000 17000 19000 21000 23000 25000 Mainstem Discharge {c f s) ---, i I I i -- 17000-19000 21000 23000 25000 i i. I ------r-I-..,---,-----j-------T--------l 13000 15000 35h- o ~~- 5000 7000 9000 11000 -« ~105 70 140 B 350 ...,1------------------ ! 315 1 280 ~ j -245-i~210 I ./ cr 175 J./..!!2 I Mainstem Discharge (cfs) - Figurl~IV-31.Surface area and spawn;ng chum habitat response curves for site 133.8R.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). IV-69 ---------_.._----------- - - Time series plots of WUA as a function of mainstem discharge are presented in FigurE!IV-32~ Site 137.5R . Site Description:This study site is located one mile upstream of Gold Creek on the east bank of the Susitna River (Plate IV-I0).The study reach is 550 feet long and varies from 100 to 30 feet wide.The substrate is predominately bouldE!r and cobble covered with a layer of silt and sand.Two cross sections were 'established to describe the shallow,low velocity area throughout the entire site.Cross section 3 describes the riffle area at the head of the study reach (Fi gu re IV -33)• Thi s backwater study si te was sel ected because upwell i ng was suspected with chum salmon'spawning observations made in 1982 and adult chum and juvenile chinook salmon were observed in 1984 (Hoffman 1985).Upwelling was observed throu~lhout the study reach duri ng the streambed profi 1e survey.Ouri ng part of the 1984-85 winter season,nearly 50 percent of the site was open.This is an indication that the upwelling is slight to moderate in strength. Spawn'ing Habitat:The WSA and WUA curves are provided in Figure IV-34a for study site 137.5R.Figure IV-34b is plotted at an expanded scale to emphasize the response·of WUA to discharge. One data set was collected at 19,000 cfs.The entire study area is influenced by backwater at mainstem discharges greater than 11,800 cfs.Data sets at 5,100,16,000 and 21,000 cfs were simulated for the site.Nearly all of the IV-70 !I 1 1 1 1 1 J 1 J 1 i -i00 360 320-280 4.J 2.40-C'"200~ 160 «120::::3 X 80 .cO 0 A I 1 B AUGUST SEP1l:lIIER rn 35000 ...... <:-31500 I u -...J 28000 ...... lU 2.4500 Clc...21000ro.cu moo tn .r-t l4000CJ E 10500 lU 4.J 7000tnc:.•r-t 3500ro ::E 0 T-- AU6UST SEPTEMBER Figure IV-32.Time series plots as a function of time for site 133.8R.A -Spawning chum WUA. B -Mainstem discharge. -! - - ..... I,.~,.::""'7:"'::':':::' .:~/ '.',.. ••,::.:;.,.;.:,::.,J:.:..:.~~..:.;.;.-.:.:::., ~.:.;:-I ----''''''''"''~~ ••ST:::_==-==SECTlON==-=Zr------------------, Ita.....I." ••0 137.5R ......Cross :Sec1ion o 20 40 60 80 100 O'STANCE rIOt ow L,[f'T BANk """'kEIOt (f'T) '20 us CROSI.~1 us CROSS SECTION 3a.aIICIflI 0+00 Station .....1. '8000'" ~1ilI S V ~S 18000'"""V=7 Z Q z ~••0 I 690......... :::>...-~:> ~ ••S +---,....-....,..--.--.----.--,---r---,....-.....-......-......--1 120w~~eo tOO DISTANCE FRO'"LEn SANti(IrUlRK(R (FT) o 66S -t-..-,,-.-r-..,....-.--.....--.--....--....--...-..,..----I ,202040ao80'DO DISTANCE 'IOtO..L.En'.......WolOt1CClOt (n) o Fi gurle IV-33.Cross sections for site 137.5R depicting water surface elevations at discharges of 19~900 cfs. IV-73 A40000...,.---------------------------- 36000 -j 32000 ! -:28000 -:4J - 'l-24000 -1 21000 23000 25000 l __W_U_A"r-I--~ 1900017000 -r 1500013000110009000 --~-- 7000 .; cr I~200001 16000 -1 ....... l'O I OJ I c-12000 -l <.! 8000 1 .au:~--...----r------,----r--­ 5000,.... I Mainstem Discharge (cfs] I / ,WUA / ./ 21000 23000 2500013000 15000 17000 19000 ---------------------------------1 I I ! ! 1 8 100 T----- I 90 ~ 80 j! ~70 60 ~ ~50-j :j 20 I I 10 ..J o ~~-r-;~-'-I---rl--r--i--i-,----r--- 5000 7000 9000 11000 liJl!!DI, Mainstem Discharge (cfsl Figure IV-34.Surface area and spawn"j ng chum habitat response curves for site 137.SR.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). IV-74 ..... upwelling areas are too shallow to be utilized by spawning chum salmon at 5,100 cfs,but as discharge increases and the backwater area extends into the study area,the depths were no longer limiting.The habitat response curve climbs upward,which then begins to decrease just prior to the overtopping of the gr-avel bar separates the site from the mainstem.The upwell ing area at cross section 2 provides most of the WUA for the site with substrate limiting at the remaining cross sections.Time series plots are shown in Figure IV-35. Site l38.7L Site Description:This mainstem margin study site is located immediately upstream of the confluence of Indian River with the Susitna River on its west bank (Plate IV-II).The study area is 675 ft long and has substrate varying from small and large gravel along the bank to rubble and boulder in the main channel.The lower two cross sections describe mainstem habitat along a gentlE~slope into the main channel,while cross section 3 describes steeper slopes with some debris (Figure IV-36). This study site was selected as a suspected upwelling area where no adult chum salmon have been previously recorded (Hoffman 1985).Adult chum,however,were observed in the site in 1984 along with juvenile chinook.Large amounts of bank seepage were observed from the mouth of Indian River upstream to an area above cross section 2;the amount of upwelling decreased near cross section 3. Spawning Habitat:Figure IV-37a has WSA and WUA plotted on the same scale, and Figure IV-37b is a plot of WUA at an expanded vertical scale.Five data IV-75 I -I 1 -1 i I 1 I J j I 1 A100 90 80 I \ -70 +.!:J4-. 0" .E2 OIV <10 -<30:;:) :IE: 20 I SEPlENBER 10 0 I AU6UST B35000-31500en Of-..... u 28000 <:-I -..J 2.4500 0'1 Q.I C'I 21000"-I'D 17500.c.u U) 1<1000.,-i Cl 10500E Q.I 7000 --,- SEPTEMBER +.! U) 35D0c...... co 0 I AUGUST ~ Figure IV-35.Time series plots as a function of time for site 137.5R. B -Mainstem discharge. A -Spawning chum WUA. ~ :::J ~Trlhey& -Associates .....A.qUdhC FlcsoLnce S1JerJcl!i~;V) ,. STAFF GAGE --CROSS SECTION 1"=500' late IV-H.Modeling sites 138.7L,139.0L and 139.4L on June 1,1982 at malnstem alscnarge:2J,OUO CTS. ..... \::':';':~';' ..:.\~. 0::::;: -:: f\.::::W,':\::',,'::::::::::.::H.:::.::::.:.:.:.:..:.:.:-.~::~~i::':':':::":;: ~ Susitna Rlva. 7tS ..,.....,.CIlO=....,..-SI"'CTIOH","'"...,..Z----------------....., .....•·13 2'7100 ell 710 70S 138.7l. -Cro!SS S(!cUon 700 +--....--....,...--,.-_.---.,.--...,....-....,...--,.--.--~ °20 40 50 80 OISTANCE ,RO,",~EFT BANI(MMI(ER (F"T) 100 - 7'~CROSS SECTION'715 CAOaa8l!CTlON3 Section 0 to 00 8t...'''01 _2nOOd._27700 cts;:710 [71O '\Zg ,llOOQ cl1I z ..".'9000 cIs :::'11900 d.0 ~~<17900 ds ...J _145DOcts ~ .............. _14500 ct•..._10400 cia _10400 cis......~::J 70~ ... It:::J 70~I-It:I- 1002040SOeo O'ST.....CE F'ROW ~EFT e....."....RKER eFT) a 700 +-_......._....,..._--,__,--_-.-_...,...._----r_--r__.--~ 10020~50 80 O'ST.....CE FROM LEFT SANI<....RI(ER (n) 700 L.-.--r--.,.....-.......-....---.----,,.--r---r-- Cl - FigurE~IV-36.Cross sections for site 138.7L depicting water surface elevations at discharges of 10,400,14,500,17,900,19,000 and 27,700 cfs. IV-78 l I I i I I I .-A 50000 I 45000 j 0 /------ 40000 i o~------- i 35"0 j ~WSA ~:::::=///'/ 20000 // ~/// ~:::::1/0 I ~~A I o l==--~-==--..:;:r-==:::.,.[---'I--===r~==::;:==:::::::;::==;::-I=====r---~ 5000 7500 10000 12500 15000 17500 20000 22500 25000 27500 30000 Mainstem Discharge {cfs} -r--r 7500 10000 12500 15000 17500 20000 22500 25000 27500 30000 B 4000 13600 3200 - -2BOO ..j.j 'l-2400. g 2000- 1600 <t:=>12003: BOO 400 ./' o ~ l 5000 ./' ./' ./' Mainstem Discharge (cfs) Figurl~IV-37.Surface area and spawning chum habi tat response curves for site 138.7L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). IV-79 sets were collected at discharges from 10,400 to 27,700 cfs.Up to 14,500 cfs,depths are less than optimum for spawning chum salmon.Above 14,500 cfs, higher velocities present in the upwelling areas reduce WUA.A small percentage of the total study a rea is i nfl uenced by upwe 11 i ng and su itab 1e spawning substrate. An additional simulated data set at 5,100 cfs was developed to determine the habitillt response at low discharges.The stage-discharge curve for the site (Part II)and the cross section elevations were used to develop the depths at 5,100 cfs.A multiplier of 0.49 was used to adjust the velocities measured at 10,400 cfs to provide estimates of the velocities associated with the 5,100 cfs.The suitability values of the depths and velocities,as well as the substf'ate and upwelling were then combined to determine WUA at 5,100 cfs. Time series plots of WUA and mainstem discharge are presented in Figure IV-38. Site Jl39.0L Site Description:Slough 17 is located directly downstream of this site on the WI~St bank of the Susitna River (Plate IV-H).The study area lies along the mainstem margin and is 750 ft long.Gravel and rubble are predominant-- substrate throughout the site.Four cross sections describe a small channel along the shoreline margin (Figure IV-39).A gravel bar extends into the mainstem separating the study area from the main channel at discharges below 12,500 cfs. This mainstem margin study site was selected as a suspected upwelling area known to be used by spawning chum salmon.Spawning chum and sockeye salmon IV-80 !i 1 I I i i ")1 1 1 I -!1 1 700 830 560-..90 +I ..20...... C'"350~ 280 <C 210:::J :;I: 140 70 0 A l A I ·1 ...... <: I ex> ':""""' en...... ~ Q)enc... 10.c:u Ul .r!o E Q) +I Ul C..... lC :::E: 35000 31500 28000 2..500 21000 17500 1"000 10500 7000 3500 o B AUGUST 1- AUGUST SEPlBIIER SEPTEMBER Figure IV-38.Time series plots as a function of time for site 138.7L.A -Spawning chum WUA. B -Mainstem discharge. -- 139.0 L ....Cmu Section --~..:..::;.-'-s ...~//$It".F//~.• :..::.:::.:.:;;.:• •~I'••••~::. 71~CROSS SECTION 1 1l~ St.ttQn 0 ..00 CROSS SECTION 3 S'.11oft 2 -t 29 ..... 31700 \\ 31700 ds g:g: z2 z0 19<X'1Octs ~710 ~710 J 17900 c1s d ~"-'''"500 ets...'"~:::I '"10400 c:ts '"~~~~ 70~70~ 0 20 40 SO eo '00 120 '40 ,0 20 40 SO SO 100 120 140 O'ST....C£I'RO'"LUT B....K "'ARKm (I'T)OfSTANCE FROM lEF"T BANK MARKER U"'T) 71S CROSS SECTION Z 71~ Station t •05 CROSS SECTION 4 St.,1M 3-t 58 31700 .Ia 31100 ets g:g Z 0 Z ~01.0 71CI .Ia !i 710 ~=-~~~.,.~='\...1~500 C1'5 ....'""-:::I ...10400.ds r-~:::I ~l!: 70:,70~ ~20 40 SO lIlI '00 120 140 0 2CI 40 SO 80 100 120 140 D1ST....CI:.....-.uT __U (I'T)DISTANCE F'WOM LEFT BANI<MARKER (FT)-Figur,e IV-39.Cross sections for site 139.0L depicting water surface elevations at discharges of 10,400,14,500,17,900,19,000 and 31,700 cfs. IV-82 -- .- ~ , - have been observed in this area as well as chinook and coho juven"ile salmon (Hoffman 1985).Upwelling was observed to begin just upstream of cross section 2 and in the clear water areas below cross section 1. Spawning Habitat:WSA and WUA curves are plotted in Figure IV-40a.Both curves are plotted to the same scale.The largest proportion of wetted surface area provides WUA at discharges between 14,500 and 19,000 cfs. The WUA curve,plotted in Figure IV-40b at an expanded vertical scale, increases up to 14,500 cfs to when the depths are no longer limiting spawning. Upwelling and groundwater inflow maintain approximately the same stage at dischCllrges below 10,400 cfs.A large backwater area forms above 10,400 cfs and extends upstream with increasing discharge.The gravel bar which sepa- rates the study area from the mainstem is overtopped above 12,500 cfs and velocities increase in the upwelling areas.Near 20,000 cfs,the velocities exceed the optimum usability range,decreasing the habitat response curve. An additional simulated data set at 5,100 cfs was developed using stage and cross section data.The constant stage below 10,400 cfs impl ies that WUA at 10,400 is the same as that at 5,100 cfs.Time series plots of WUA and mainstem discharge are shown in Figure IV-41. Site 139.4L Site Description:This mainstem margin study site is located about 0.7 miles upstream of Indian River on the west bank of the Susitna river (Plate IV-II). IV-83 -----------------A100000~-------- 90000 I BOOOO ~ -70000 -"""l +-' ""-60000 ~ ~1~50000 -i I I 40000 -1 __-- ~~--~30000 1 20000 .., i 10000 I °T-I 5000 7700 ------.-----------------, _----.--------II ------~-----_.-,;r---WSA ! ../- ---"....,- -/'" .- ,/ i WUA I·...,....--,..---...---,..---'r---.I-T 1 10400 13100 15800 18500 21200 23900 26600 29300 32000 Mainstem Discharge (cfs) "-,"1 ----~--,._..._--_._-----_._-~ g 250 +---- 200 ~ ~150 ~ 100 ~I 50 -t, o t--r----i---i-r-j----,-l----l--r-·---~ 5000 7700 10400 13100 15800 18500 21200 23900 26600 29300 32000 500 -fr'------------------------ .450 JI 400 .J ! -350 .... +.l I "'-300-!...... - Ma instem Discharge (efs) FigurE!IV-40.Surface area and spawning chum habitat response curves for site 139.0L.A -Wetted Surface Area (WSA)and Weighted Usable Area (WUA).B -Weighted Usable Area (WUA). IV-84 1 J I 1 j 1 1 J J I 1 1 J 500 450 .400-350. ~ 300-. 0-250~ 200 <C i50:=I X 100 50 0 -35000-en.....31500<:~I 00 28000 In Q.l 2.4500 OJc...21000ra.r::u 11500en ·rl 14000Cl e 10500 Q.l ~7000tnc::::: ·rl 3500ra ::::£0 A I I AUGUST SEP1BIJER BI . I AU6UST SEPTBIlER Figure IV-41.Time series plots as a functionof time for site 139.0L.A -Spawning chum WUA. B -Mainstem discharge. .- ,- ..... - .... The study area is 575 ft long.Three cross sections were established to model the mainstem margin (Figure IV-42).Cobbles and boulders are present in the upper study reach near cross sections 2 and 3,with gravel and rubble present at cross section 1. This study site was selected as a suspected upwelling area though spawning chum salmon have not been observed.No adult salmon but juvenile chinook were observed in the study area during 1984 (Hoffman 1985).A small open thermal area in the ice was recorded near cross section 2 for a short period of time before freezing over. Spawning Habitat:No upwelling areas were observed throughout the 1984 and 85 field season.Therefore,no habitat response curves were developed for the site . DISCUSSION The results of this section show that side channel areas influenced by back- water had increasing trends in the WUA as ma"instem discharge increased,with WUA leveling off when depth are no longer limiting.In addition,high veloc- ities were not present in these areas at the range of modeled mainstem dis- charge (5,000 to 25,000 cfs). Mainstem margin areas had downward trends in WUA as mainstem discharge increased,with depths usually not limiting in these areas.The amount of available habitat was influenced instead by high velocities.As velocities IV-86 .-. 7'0 CROSS SECTlO~2 Station f +SS 31100 efa "'<-8370 ets 20 ~ DISTANCE F'ROM LEFT BANK MARKER (FT) o 7094-------.----.----r-----,----.----I 00 ..- Susltnl RIver 139.4 ~ .....Cross 5·ec:Uon CAOes SECTIO~1 Slatlon 0"00 CROSS SECTIOH ~ Stl.c&or\2 +12 7'5 ~1100 cts,,,...-_ ;715 Za ~~ '"'":le: 7'0 602040 DISTANCE FROM LEFT BANK "'ARKER (FT) o 709 .L--_.-----..----r-----,---__,_------l 902040 DIST....CE ",OM L.£FT BANK """'KER (FT) 709 .+---....,...---.-----r-----.---~--_l o Figure IV-42.Cross sections for site 139.4L elevations at discharges of 8,370, 31,700 cfs. depicting water surface 14,500, 14,900,19,000 and Iv-a7 - increaised with an increase in mainstem discharge,the amount of suitable habit,lt for spawning chum salmon decreased. Side channel study areas that were not located in backwater areas appeared to have both increasing and decreasing trends in WUA as a function of mainstem discharge,with these areas limited by depths at lower discharges.As dis- chargl~s increased,the depths in the upwelling areas became usable (greater than 0.8 ft).Also,the velocities in the upwelling areas exceeded 1.3 fps, ..... the WUA values decreased. The amplitude of the WUA curve was determined by both the amount of upwelling and quality substrate present within the site.Quality substrate in upwelling areas yielded higher WUA values than sites where either the upwelling was associ ated with poor spawni ng substrate or where quality substrate exi sted with no upwelling. ,~ - IV-88 ... ,.... ,- .- -I 'r- REFERENCES Adult Hydro Power PART 5 REFERENCES Aaserude,R.G.,J.Thiele,and D.Trudgen.1985.Characterization of aquatic habi tats in the Tal keetna-to-Devi 1 Canyon segment of the Susitna River, Alaska.Prel iminary draft report.E.Woody Trihey and Associates and Arctic Env'ironmental Information and Data Center,University of Alaska, Fairbanks.Alaska Power Authority.Susitna Hydroelectric Project.1 vol. Alaska Department of Fish and Game,Susitna Hydro Aquatic Studies.1981. Phase I final draft report.Adult anadromous fisheries project.Report for Acres American Inc.Alaska Power Authority. 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V-2 ..- ,..... Trihey,E.W.,and J.E.Baldrige.1985.An empirical approach for evaluating mi crohabitalt response to streamflow in steep-gradi ent,1a rge bed-element streams.Paper presented at symposium on Small Hydropower and Fisheries, Aurora,CO ..American Fisheries Society.8pp. Trihey,E.W.,and N.D.Hilliard.1984.Supplemental guidelines for ca1ibratin~1 the IFG-4 hydraulic model.In Bredthauer,S.R.,chairman. Alaska's water:A"critica1 resource.Proceedings of the Alaska Section, Ameri can ~Iater Resources Associ ation.Insti tute of Water Resources, University of Alaska.Fairbanks,AK.Report 1WR 106.1 vol. U.S.Geological Survey.Annual.Water resources data for Alaska:Water years 1950··1984.U.S.Geological Survey Water Data Report. Wi 11 i ams , S. suspended Technical 45 pp. 1985.The influence of middle Susitna River discharge and sediment on mainstem and side channel rearing habitats. memorandum.E.Woody Tri hey and Associ ates,Anchorage,AK. 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