Bonanza City Stream and Floodplain Project, P3

Project Narrative

Phase III of the Bonanza City Stream & Floodplain Project completed the final phase of planned construction for rehabilitation of a 0.83 mile section of river and associated floodplain that was impacted by a dredge-mine operation in the 1950s. The work required diverting the Yankee Fork Salmon River into a combination of newly constructed river channel segments (constructed in Phase II (PCSRF project 003 18 SA) and temporary bypass channels. Concurrently, 0.32 miles of existing river channel received installations of fish habitat improvements, 0.29 miles of stream channel were reconfigured, and 0.14 miles of stream channel were created. Four new large pools were constructed, and 10 new large pools have already formed or are expected to form in response to wood structure placement. Large-wood structures were installed instream and portions of existing streambank were stabilized through brush bank and roughened edge treatments. Simulated landslide jams and relic beaver dam analogues were constructed (captured under other engineered structures in metrics). Potted plants, pole-cuttings, and seed were installed across riparian, floodplain, and upland areas, in addition to noxious weed treatment. Dredge tailings were removed from the project site. The project has restored sinuosity, habitat complexity, and floodplain connectivity to this section of river, which is needed for salmonid habitat recovery in the Yankee Fork watershed. This project received two amendments to extend, including one that decreased the award amount. The project finished underbudget, and was multi-year funded with grant funds from FY17 and FY19. FY17 funds were spent out within that grant award period. The overall goal of the three-phase Bonanza City Stream & Floodplain Project is to reconstruct this 0.83 mile section of river to repair the damage caused by the historic dredge-mining. Reconstructing the river includes removal of more than 100,000 cubic yards of dredge tailings that currently confine the river to a flume-like channel. The removal of these tailings was accomplished during Phase I. Phase II included building new sections of river channel in the dry. Phase III of the project rehabilitates existing sections of river. The final goals and objectives for the finished project are for the river to have a level of sinuosity and complexity that more closely resembles the historic conditions that the Yankee Fork chinook salmon and steelhead populations evolved to thrive in. The rehabilitated sections of channel will have pools for rearing juvenile salmonids, glides for spawning adults, slower water velocities that are more suitable for all age-classes, and complexes of large and small wood to restore levels of cover. These critical fish habitat elements are almost completely lacking in the existing river channel. The final objective of Phase III is to initiate revegetation of the of the project areas riparian areas, uplands, and floodplains.