Nelson Creek is a tributary that feeds into the upper Yakima River near river mile 193. Here, a perched, undersized culvert (24″ plastic pipe) at the confluence with the Yakima River created a fish passage barrier. Because of the barrier, fish could not access the creek, which provided important rearing habitat.
To address this issue, KCT collaborated with Yakama Nation Fisheries and Yakima Tributary Access and Habitat Program (YTAHP) to reconnect the creek to the river. Young fish need shelter from the high flows released from the Yakima River reservoirs. These flows are released for irrigation and run contrary to the biological needs of salmon, steelhead, and bull trout.
For the project, KCT removed the old perched culvert and installed an 11-foot span horizontal ellipse-shaped culvert with an 8-foot rise to support a road. Then we filled in the new culvert bed with cobbles, gravel and sand to form a semi-natural stream channel connecting the Yakima River with upstream habitat in Nelson Creek. The larger drainage structure allows for flood flow, facilitates the passage of wood and debris, and enhances natural sediment transport. Additionally, upstream of this new culvert, we constructed a 20-foot long roughened channel to minimize head cut into the natural Nelson Creek streambed.
For detailed information on this project, including site maps, project designs, and additional photos, go to the Washington State Recreation and Conservation Offices website: https://secure.rco.wa.gov/prism/search/ProjectSnapshot.aspx?ProjectNumber=07-1634