Couse Creek RM4 Floodplain and Aquatic Habitat Restoration Phase 2

Couse Creek is a tributary of the Walla Walla River located near Milton-Freewater in Umatilla County. The project area includes a half-mile reach beginning at River Mile 4. Couse Creek is a primary spawning and rearing area for ESA-listed summer steelhead. An OWEB-funded 2020 watershed assessment documented limited aquatic habitat complexity, seasonally dry reaches, and high summer water temperatures. The RM 4 project area has limited floodplain connection, dry stream terraces dominated by invasive species, and impaired hydrology and sediment routing. This project is the second phase of an effort to use a low-tech, process-based restoration approach to restore the natural hydraulic functions that facilitate healthy riparian vegetation and diverse instream habitat. Phase one produced the restoration design and treated 1/4 mile of the stream by installing instream wood structures. Phase two will treat the remaining 1/4 mile by installing Post-Assisted Log Structures (PALS) and Beaver Dam Analogs (BDA). In addition to instream treatment, the project includes invasive species removal and riparian planting on the floodplain terraces. Partners include WWBWC, OWEB, the landowner, and Bonneville Power Administration as a funding partner.

The project will restore physical and ecological processes that produce productive salmonid habitat. The placement of instream structures will facilitate floodplain expansion that will enhance the riparian community. Healthy riparian corridors will provide habitat cover, channel shade, and nutrient inputs.
By slowing and spreading water, the project will increase the wetted extent of the channel during low flow conditions, which will increase the quantity of habitat available to juvenile steelhead during summer low flow when stream flow in much of lower Couse Creek is intermittent.
The project will increase essential spawning and rearing habitat, which is currently limited in the Walla Walla Basin. It will improve channel complexity, creating refugia for juvenile steelhead and restore natural sediment routing, which will enhance spawning conditions for salmonids. The project will also increase longitudinal connectivity in Couse Creek by providing a suitable migration corridor for steelhead moving to the upper Couse Creek watershed.