Through the end of September, we will be working on a project to replace two culverts located in Cougar Gulch near Liberty, WA. This relatively small project will have huge impacts for fish by removing culverts that are too small for the stream at higher flows. The project will also ensure the longevity of the road. Modeling shows that a 100-year flood will cause water to rise over the road because the culverts are too small, destroying the road and likely washing the culvert downstream.
For Fish Present and Future
Currently, cutthroat trout, rainbow trout and sculpin live in the creek. Historically, steelhead and Coho salmon would have used the creek and the Williams Creek drainage is considered critical bull trout habitat. Cougar Gulch is a tributary of Williams Creek, which steelhead use for spawning, and the project will benefit them in the future. In addition, the creek can provide critical spawning and rearing habitat for migratory bull trout, since it has the cold, clean waters that bull trout require to survive.
The Negative Effects on Fish
The undersized culverts in Cougar Gulch are detrimental in multiple ways. They create high velocity flows that fish cannot travel through. In addition, the water, when moving at high flows, scours out pools when it exits the end of the culvert. When the flow lessens, the water level drops creating a waterfall – a passage barrier to fish trying to move upstream.
The culverts are being replaced in a way that expands connectivity to the flood plain and improves passage. Instead of being a typical circular culvert, the metal portion is a semi-circle with no bottom (shaped like an arch). The stream bed underneath is comprised of large rocks with smaller diameter material on top similar in size to what is in the stream currently. This allows the creek to remain connected to the floodplain, which is important for aquatic health. This design also ensures that a passage barrier won’t develop (pool and waterfall) and better passes materials like large logs and trees.
In preparation of the construction of the project, our executive director Mitch Long, worked with Washington Department of Fish and Wildlife (WDFW) staff to conduct a fish survey of the stream. During the survey, they captured 32 cutthroat trout in the pool below the upper culvert, which they moved to a neighboring stream. Prior to the start of the project, fish screens will be installed to keep fish from moving into the area during construction and all fish will be removed from the site.
Other Project Details
The project will take approximately two weeks. The roads will be impassible during replacement. A detour will be available for the culvert on the #9718 road using Williams Creek Road. There will be no detour for the project on the #9718-112 road since it is a spur road.
We are doing this project in partnership with the Forest Service, Washington State Department of Fish and Wildlife, the Yakama Nation, and Yakima Tributary Access and Habitat Program (YTAHP). Funding for this project came from State Salmon Recovery Funding Board through the Washington State Recreation and Conservation Office (RCO). Additional funding support is being provided by the Bonneville Power Administration through the 2018 Yakima Tributary Access and Habitat Program.