Crooked River Valley Rehabilitation

The Crooked River Valley Rehabilitation project, in its entirety, is the reconstruction of 2.0 miles of the lower Crooked River Valley over a 6-year period. The purpose of the project is to restore natural processes and reduce the factors that limit the productivity and abundance of Snake River Basin steelhead and Snake River Spring/Summer Chinook salmon. The Crooked River valley, extensively dredged mined from the 1930s-50s, had large tailing piles, tailing ponds, and the river was in an unnatural meandered pattern. The large tailing piles along the river resulted in channel entrenchment and reduced floodplain interactions. The project removed the tailings, and constructed a new main and side channel, and floodplains. Large wood structures were installed within the new river channels to promote scour and increase instream habitat. The new side channel provides off-channel habitat and was routed through several existing ponds and depressions that exhibited groundwater interactions to provide off-channel cold-water refugia and habitat complexity. Constructed riffles consist of larger cobbles and buried small boulders to provide vertical stability in the channel. Pools were constructed along the meander bends of the new channels. Bank stability structures constructed with brush and small trees were installed along meander bends to provide stability in the short term, but allow for lateral movement of the channel over time. Floodplains were constructed at varying elevations that would flood frequently in order to deposit sediment and plant material to rebuild the soil profile, provide off channel habitat for juvenile fish during high flows, and improve riparian health through water storage. All constructed floodplain was treated with microtopography such as adding ridges and furrows, large and small wood, and depressions and swales. Over 22,000 potted plants have been installed and are currently at 80% survival; a native seed mix was successful at starting grasses in the project area, and forbs are coming naturally. Noxious weeds are on an annual treatment schedule.

Preliminary results show that juvenile fish are already using the off-channel habitat flows above bankfull, small channels and alcoves are forming on the floodplain that remain connected at flows less than the bankfull flow, and that juvenile fish have been observed using these newly created habitats into the summer months.

The variations in the proposed vs actual metrics implemented are from changes to the timing of each Phase/Option implemented rather than design changes. While the project in its entirety is a 6 year project, only four of these years included PCSRF funds. The contract was extended by one year to allow for OSC and NMFS to realize more of the habitat benefits from project implementation, since PCSRF funding was integral in completing the early phases. Work on this project will continue into 2022 using other funding sources. The proposed metrics did not include wetland metrics, however final metrics for wetland are reported.

This project will implement the following priority habitat actions, in a Priority 1 stream as directed by the 2016 NMFS proposed recovery plan. When implemented the actions are intended to improve productivity rates and increase the effective capacity for natural smolt production in the watershed for the South Fork Clearwater River population of the Clearwater River MPG and the Snake River steelhead DPS.

1. Improve riparian conditions
2. Restore stream channels and floodplain function in reaches impacted by historic dredge mining and other land uses. Projects may include restoring natural floodplain meander patterns by reconnecting historic meanders or reconstructing stream channels.
3. Restore mechanisms that facilitate exchange of surface and hyporheic flows. Remove unnecessary bank stabilization structures to allow natural channel migration, reconnect floodplains to recharge hyporheic flows, and increase channel roughness and complexity with natural wood recruitment or artificial structures to facilitate bar and pool formation.