Alpowa Creek Instream PALS – Phase II

The Alpowa Instream Post Assisted Log Structures resulted in 1.5 miles of stream being restored. This project resulted in installation of 282 structures and 200 pools in Alpowa Creek, west fo Clarkston WA in Asotin County.

The pools were created through eddy or back water processes that ponded water to a depth between 1.5 to 2 feet, or deeper. With future high flows, we envision almost all of the 282 structures either creating better pools or making existing pools better with the sorting of spawning gravels in the tailout areas. Alpowa Creek is a spring-feed system and it may take more time for flows to create pools associated with all the structures. With the current added pools the project area went from 2.8 pools/100 m to 8.4 pools/100 m. With the added structures we went from 7.5 pieces of wood/100 m. to 34 pieces of wood/100 m.

Improved floodplain connection through the strategic placement of wood structures worked both on the main channel and also connecting some smaller springs that had little to no surface water connection during low flows was also achieved.

This project benefits Snake River steelhead and Chinook.

The goal of this project is to improve habitat complexity, provide coolr water later in the summer, and reconnect floodplain and hyporrheic flow in Alpowa Creek. This is achieved by installing over 200 post assisted log structures in the project area. This project will benefic Snake River steelehad and Chinook.