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 CORRIDORCHAPTER 3from being delivered directly to the TuolumneRiver. Tributaries that deliver fine sediment directlyto the Tuolumne River are few (Table 3-5).To estimate particle size delivered by tributariesand gullies, bulk samples were collected ofdeposited material at a road cut gully at RM 35.3and at the Gasburg Creek delta at RM 50.3 (Table3-5). Sandy loam soils along the Tuolumne Rivercorridor, typical of the road cut gully sample, had100 percent of particles finer than 2 mm but only18 percent finer than 0.125 mm. Therefore, soilerosion from hillslopes is predominately sandsizedrather than silt-sized, indicating thathillslope and orchard erosion on uplands candeliver a large proportion of sand to the river. TheGasburg Creek delta sample was coarser, but alsohad a low percentage of the sample finer than0.125 mm. The D 50(median grain size) was 14mm, 35% of the sample was finer than 4 mm, andonly 1% of the sample was finer than 0.25 mm.The 1997 flood accessed the New Don PedroDam spillway for the first time in its history.Approximately 45,000 cfs flowed down TwinGulch, causing 25 to 50 feet of incision down tothe underlying bedrock, generating a tremendousvolume of coarse and fine sediment. Most coarsesediment was deposited in La Grange Reservoir;however, much of the sand was transportedthrough La Grange Reservoir and deposited in theTuolumne River channel downstream. Threetransects were surveyed through Twin Gulch toestimate the volume of topsoil washed downstream,mapping soil/bedrock contact lines andextrapolating this contact across the gulch. Weestimate over 200,000 yd 3 of topsoil alone wasexcavated and delivered to La Grange Reservoir,with much of these finer sediments transportedover the dam into the lower Tuolumne River. Thisfine sediment was primarily sand, which depositedonto floodplain surfaces downstream. Sanddeposition on the "floodplains" between LaGrange Dam and Basso Bridge (RM 47.5) was upto three feet deep (estimated average depth wasapproximately 0.5 feet).The Lower Dominici Creek delta and GasburgCreek delta were measured to estimate theportion of fine sediment delivered to theTuolumne River during the January 1997 floods.The existing tributary deltas were assumed to havedeposited on the receding limb of the flood.Recent deposition, approximating recedinghydrograph limb deposition, was approximately100 yd 3 for both Lower Dominici Creek andGasburg Creek. The Gasburg Creek tributary deltawas difficult to discern because the tributarysediment deposits were intermixed with sanddeposits from prior depositional events. Therefore,these values represented a minimum volumeof fine sediment delivery; the actual value isprobably much larger. For a rough yardstick, 100yd 3 is enough fine sediment to cover 325 linearfeet of the Tuolumne River low water channelsurface to a depth of 1 inch. Actual fine sedimentdelivery to the Tuolumne River was most likelymuch larger because the tributary floods precededthe large (60,000 cfs) spill into the TuolumneRiver, which most likely eroded much of any deltamaterial deposited in the preceding days.Rivers naturally sort much of their fine sedimentby deposition onto floodplains during high flows.However, in regulated rivers such as theTuolumne River, sand is often delivered to themainstem channel by tributaries when the mainstemis not flooding the floodplains. This sandaccumulates in the low water channel rather thanbeing deposited on the floodplain. Therefore,chinook salmon habitat is quickly degraded by inchannelsand deposition.Non-point sourcesNon-point sand sources are those that supply sandover an extended area, rather than from a singlepoint. The two primary non-point sand sourcesare bank erosion and sheet/surface erosion. Thenumber of these non-point sources along theTuolumne River upstream of Waterford (RM 32)are few. The natural banks along the TuolumneRiver are composed of a variety of sedimentclasses, ranging from clay hardpan to cobbles tosandy loam. Bank erosion is nearly non-existentin the study reach based on sequences of aerialphotographs and observations during our riverreconnaissance. Channel migration has notoccurred since New Don Pedro Dam was built,except near the 7/11 Materials plant site (RM37.8) and from eroding topsoil dikes throughoutthe gravel mining reach (RM 35.7 to 39.0). Theriver was migrating into a cultivated field at the 7/11 Materials plant site, and was rip-rapped in1997. This rip-rap eliminated this source of finesediment, but it also eliminated an importantsource of gravel, which supported extensivelyused spawning riffles immediately downstream.Bioengineering approaches should be used in thefuture in place of rip-rap if bank erosion must be90
GEOMORPHIC AND RIPARIAN INVESTIGATIONSeliminated at a certain location. The topsoil dikesthrough the rest of the reach continue to fail andcontribute fine sediment to the channel, butrestoration of a wider floodway throughout thisreach will eventually replace these dikes withfloodplains. The other significant source of finesediment is infrequent failure of dikes that isolatefine sediment settling ponds at gravel extractionsites. Failure of dikes separating these settlingponds from the bankfull channel results in largevolumes of fine sediment input into the river.Additional fine sediment is introduced by the dikefailure itself. This occurred at several locationsduring the 1997 flood and at least one location in1998. While much of this sediment is probablywashload, there is probably a significant volumeof sand-sized fine sediment delivered to theTuolumne River. The floodway restoration projectthrough the gravel mining reach will greatlyreduce future fine sediment inputs from thesesites.3.1.4.2. SummaryOf all the gullies and tributaries investigated,Gasburg Creek, Lower Dominici Creek, andPeaslee Creek are the primary sand contributors.Much of the sand originating from Gasburg Creekhas historically resulted from sheet runoff fromthe sand extraction operation immediately northof the Old La Grange Bridge. Gasburg Creek hasthe highest potential to negatively impact salmonhabitat because it delivers sand at the upstreamend of the most important reach for salmonproduction. Remediation for Gasburg Creek issimple; a sedimentation pond near its mouthwould prevent nearly all harmful fine sediments(between 0.1 mm and 8 mm) from entering theTuolumne River (see Sediment Management Plansummary in Chapter 4). Lower Dominici Creekand Peaslee Creek enter the Tuolumne Riverthrough incised channels; there is little spaceavailable near their mouths to construct a sedimentationpond. There may be some opportunityto construct a head control structure on LowerDominici Creek immediately upstream of theMID canal, but no site reconnaissance has beenconducted. Improved land use practices, particularlyalong tributary watercourses, could alsoreduce fine sediment inputs. We recommend spotHelley-Smith bedload measurements with a 3-inch sampler during storm runoff events to betterevaluate sand contribution from Lower DominiciCreek before proceeding with remediation.Constructing floodplains and increasing themagnitude and variability of high flow releaseswill help mitigate the negative impact of finesediment delivery from the watershed by encouragingnatural deposition on floodplain surfaces.During high flow releases, sediment finer than 1mm is typically transported in suspension in themainstem Tuolumne River; fluvial access tofloodplain surfaces will cause these sediments todeposit on the floodplains, reducing the proportiondepositing in the mainstem channel.3.1.5. M.J. Ruddy 4-Pumps restorationproject evaluationBetween 1992 and 1993, a restoration andmitigation project immediately upstream of theSanta Fe Aggregates (formerly M.J. Ruddy) plantsite (RM 36.7 to 37.6) was implemented toreconstruct nearly one mile of channel. Theunique feature of this project was that it attemptedto reconstruct an alluvial channel sized to thepost-dam flow regime, with bankfull channel,floodplains, and terraces. Past restoration activitiesprimarily focused on modifying the activechannel (mostly riffle rehabilitation) and plantingriparian vegetation. In the summer of 1991, theM.J. Ruddy Mitigation Project reconstructedsouth bank dikes to increase floodway capacity to11,000 cfs from RM 36.7 to 37.0, and to providefloodplain and terrace surfaces through this reach.In the summer of 1993, the San Joaquin Districtof the California Department of Water Resources(DWR) implemented the M.J. Ruddy 4-PumpsChannel Restoration Project. This project constructeda new bankfull channel geometry andplanform from RM 36.7 to 37.6, and constructedfloodplain and terrace surfaces from RM 37.0 to37.6. The most significant component of theproject was moving the bankfull channel approximately200 feet north from RM 37.3 to RM 37.6to reduce erosion into an orchard, and redistributingsteep drops in channel elevation back into lowgradient pool-riffle sequences to improve chinooksalmon habitat.From the end of construction in 1993 to thebeginning of 1997, several high flow eventsoccurred, ranging from 5,000 cfs to 9,000 cfs,which were large enough to cause the channel toadjust its bed and bank morphology. These highflows provided a unique opportunity to evaluatehow a reconstructed, appropriately-scaled channelwould respond to high flow events. Would theCHAPTER 391
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Habitat Restoration Plan for theLow
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TUOLUMNE RIVER TECHNICAL ADVISORY C
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CHAPTER 226Table 2-5. Revised minim
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CHAPTER 2TUOLUMNE RIVER TECHNICAL A
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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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Tuolumne River Report - U.S. Fish and Wildlife Service

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