Tuolumne River Report - U.S. Fish and Wildlife Service

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TUOLUMNE RIVER TECHNICAL ADVISORY COMMITTEEHABITAT RESTORATION PLAN FOR THE LOWER TUOLUMNE RIVER CORRIDORSEDIMENT SIZE FINER STREAM SLOPE STEEPERCHAPTER 2SEDIMENTDEGRADATIONAGGRADATIONWATERFigure 2-13. Conceptual flow-sediment balance necessary for channel equilibrium, and channel response todisequilibrium (from Lane 1955).Lane (1955) provided a simple formula to illustratethe way in which rivers balance slope, sedimentparticle size, sediment transport, and streamflow tomaintain a dynamic equilibrium:Q w* S µ Q s* D 50(2-1)where Q w= stream discharge, S = slope, Q s=sediment discharge , and D 50= median grain size(Figure 2-13).A balance in the sediment transport capacityprovided by the high flow regime with sedimentsupplied from the watershed over time anddistance results in a “dynamic quasi-equilibrium,”in which sediment is mobilized, transported, anddeposited. The channel migrates (dynamic), butthe size and shape of the channel remain similar(equilibrium) (Schumm 1977). While thispresentation of the quasi-dynamic equilibriumconcept of sediment supply and transport isconsiderably simplified, its use as a quantifiableobjective to balance flow and sediment supply is apowerful tool for assessing fluvial processes. Italso helps predict channel responses to alteredflow and sediment regimes.Dams, aggregate extraction, agricultural andurban encroachment, and other land uses havecaused sediment imbalances in the TuolumneRiver channel. For example, reduced magnitude,duration, and frequency of high flows imposed byupstream dams has allowed fine sediment toaccumulate in the river. Elimination of coarsesediment supply below the dams and accumulationof fine sediment from reduced flood flowshave degraded chinook salmon spawning habitat.The impact of these imbalances is also a functionof distance along the Tuolumne River because the28
LINKING PHYSICAL PROCESSES AND SALMON LIFE HISTORYrelationships between slope, sediment particle size,sediment transport, and streamflow changelongitudinally as the Tuolumne River travels fromheadwaters to the San Joaquin River. Differencesin valley slope, valley confinement, particle size,channel forming discharge, and vegetation createlocal variation in channel morphology. Fluvialprocesses and the resultant channel morphologydepend on these longitudinal differences, andmust be incorporated into restoration planning.2.2.2. Geomorphic reach delineationDownstream of La Grange Dam, the TuolumneRiver can be divided into two distinct geomorphiczones broadly defined by the channel slope andbed material: the sand-bedded zone extends fromRM 0.0 to RM 24.0, and the gravel-bedded zoneextends from RM 24.0 to RM 52.0 (Figure 2-14).The transition from gravel-bedded to sand-beddedzones is a remnant of pre-NDPP processes: wherethe valley widens and slope decreases, the riverwas unable to transport gravel and cobble-sizedparticles. These larger particles deposited inupstream reaches, while sand continued to betransported downstream. During moderate andlarger flows the dominant clast in transport isthus different in each zone. The transition fromgravel-bedded to sand-bedded at approximatelyRM 24 caused a noticeable change in planformmorphology: in the sand-bedded zone sinuosityincreased, amplitude increased, meanders becamemore tortuous, and channel migration was morecontinuous than in the upstream gravel-beddedzone. Channel morphology is characteristically ameandering alternate bar morphology, rather thanthe less sinuous alternate bar morphologyprevalent upstream. These changes also influencedthe composition of woody riparian species.These two geomorphically-based zones weresubdivided into seven reaches based on presentand historical land uses, the extent and influenceof urbanization, valley confinement from naturaland anthropogenic causes, channel substrate andslope, and salmon habitat quality. Differencesbetween these reaches warrant unique restorationvisions and strategies. The major reaches are:REACH 1 (RM 0-10.5): “Lower Sand-beddedReach,” defined by agricultural land use andencroachment (row crops and vineyards), novalley confinement during high flows, low slope(
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CHAPTER 3100Elevation (ft)110105100
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CHAPTER 3104Elevation (ft)195190185
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CHAPTER 3108Table 3-8. Wy 1970-1997
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134Relative elevation (ft)140130120
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CHAPTER 3136Relative elevation (ft)
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ADAPTIVE MANAGEMENT5. ADAPTIVE MANA
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ADAPTIVE MANAGEMENTmonitoring progr
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ADAPTIVE MANAGEMENTWILDLIFE POPULAT
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ADAPTIVE MANAGEMENT• Distribution
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REFERENCESREFERENCESAlderdice, D. F
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REFERENCESKjelson, M. A., P. F. Raq
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REFERENCESTID (Turlock Irrigation D
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APPENDIX AAPPENDIX AANNUAL HYDROGRA
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APPENDIX BAPPENDIX BTUOLUMNE RIVER
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VEGETATION SERIESNATURAL DIVERSITY
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VEGETATION SERIESNATURAL DIVERSITY
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Nature Conservancy Heritage Program
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215Scientific Name Common Name Loca
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APPENDIX BAPPENDIX B217
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