Charley Cr and N Fk Asotin Cr Channel Restoration

WA Dept of Fish and Wildlife (WDFW) restored LWD and channel heterogeneity to 4 km of N Fk Asotin Cr and 4 km of Charley Cr on the Asotin Wildlife Area in SE WA. The completed project work comprised the 2nd & 3rd habitat treatments within the Asotin Intensively Monitored Watershed (IMW), which began assessment and monitoring of fish habitat and populations in 2008 to understand the effect of restoration actions. The IMW assessment identified sedimentation; embeddedness; high temperature; decreased riparian function, floodplain connectivity, and habitat diversity; and low LWD and pool frequency/quality as limiting factors to salmonid production. The goals of the treatment were to restore pool abundance and gravel bar deposition, and increase channel length and floodplain connectivity through the placement of LWD. Populations intended to benefit include Snake River steelhead and Chinook Salmon, Bull Trout and Pacific Lamprey.
WDFW built 205 Post Assisted Log Structures (PALS) in Charley Creek in Summer 2013 and 130 PALS in North Fork Asotin Creek in Summer 2014. Fewer Structures were built in North Fork Asotin than in Charley Creek because the North Fork Asotin is a larger stream and the structures were therefore larger and spaced further apart. As of the end of 2014, WDFW documented a 100% increase in LWD (large woody debris) in the treatment sections of both streams compared to control sections. The basic design of the PALS is to drive 4-12 posts trimmed to bank full height, into the stream bottom in a zigzag pattern. Small pieces of LWD are woven into the posts but not tethered in place. The use of structures to reduce channel width by 50-75% will help build more heterogeneous channel shape, increase gravel bar deposition, diversify widths/depths, reduce incision and increase channel length. This method was successfully tested in 2012 spring high flows on S Fk Asotin Cr.

The goals of the treatment were to restore pool abundance and gravel bar deposition, and increase channel length and floodplain connectivity .