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

TUOLUMNE RIVER TECHNICAL ADVISORY COMMITTEEHABITAT RESTORATION PLAN FOR THE LOWER TUOLUMNE RIVER CORRIDORCHAPTER 4The total cost for this project, including projectmanagement, planning, and implementation, is$414,500. Costs for future coarse sediment managementwill depend on the magnitude, frequency, andduration of gravel transporting high flow events.Replacing the quantity of gravel transported out ofthe gravel-bedded reaches would cost more duringwet years than during dry years years when flowsdo not transport appreciable quantities of coarsesediment, and gravel augmentation is not required.This proposal contains revised designs for aGasburg Creek Sedimentation Basin.For additional details, the complete projectconceptual design is available upon request.4.5.7. Dredger Tailing Reach ChannelRestoration Project (Threephases)BackgroundThe Dredger Tailing Reach restoration project islocated in the heart of the gravel-bedded zonebetween river miles (RM) 42.5 and 46.8 (Reach 6of the Restoration Plan). This reach was severelydegraded by gold dredgers in the early- to mid-1900s, and combined with flow and sedimentregulation, has not significantly recovered in thefollowing decades. The Dredger Tailing Reachcontains chinook salmon spawning riffles whichare degraded, of poor quality, and receive significantlyless spawning use than spawning areasfurther upstream. Within its current physicalconstraints, this reach cannot recover to adesirable state on its own, but offers real opportunityfor restoring natural channel and floodplainfeatures, chinook spawning and rearing habitats,and reducing predator populations.Project ObjectivesThe overall goal of this project is to convert afossilized, highly degraded, remnant channel backinto a dynamic meandering channel. Primaryobjectives include:• Rebuild a natural channel geometry scaled tocurrent channel-forming flows.• Allow the channel to migrate within therestored floodway to improve and maintainriparian and salmonid habitats.• Restore and increase salmon spawning andrearing habitats by restoring an alternate bar(pool-riffle) morphology, restoring spawninghabitat within the meandering channel.• Eliminate salmon stranding problems associatedwith backwaters and sloughs, and floodplain“traps” accessed during moderate flows.• Acquire adjacent floodplain properties fromvoluntary land owners, either through purchaseor conservation easements. The Bobcat FlatLand Acquisition currently being negotiated isan excellent example of the type of opportunityavailable within the Dredger Tailing Reach.• Restore native riparian communities onappropriate geomorphic surfaces (i.e., activechannel, floodplains, terraces) within therestored floodway.• Restore riparian canopy habitats for otherendemic wildlife species (e.g., egrets, ospreys,herons).Project DescriptionThe large size of this reach requires that implementationoccur in three phases, similar to projectphasing in the Gravel Mining Reach. The reacheswere delineated by unique restoration objectivesand sections of channel that will require little orno restoration (natural delineation breaks).Phase I: Zanker Reach (RM 45.4 to 46.5)The upstream portion of this reach is long andstraight, confined by encroached riparian vegetation(RM 46.0 to 46.5). Immediately downstream,the riparian vegetation is less confining and thevalley confinement decreases (RM 45.4 to RM46.0). During high flow events, the bed surface inthe confined section incises, with scouredmaterial depositing and aggrading where confinementceases. The result is a long deep chute-likereach upstream with functionally no alluvialdeposits, and an aggraded bar downstream thatbacks water upstream into a “lake.” The riffle isover-steepened to the point where preferablespawning depths and velocities are in the tail-outarea and the margins of the steep riffles. Proposedactivities in the unconfined section includingexcavating a large portion of the bar to restorenatural riffle gradient, using excavated materialsto build bankfull confinement locally and fillportions of the channel in the upstream section.166