Logjams are important salmon habitat.
Historically, downed trees washed into rivers where they would accumulate into logjams. These jams slowed the river, creating space for both juvenile and adult salmon to rest and feed.
Habitat degradation in the Green River has diminished the amount of large wood to only 5 percent of what salmon need.
According to the treaty tribes’ recently released State of Our Watersheds Report:
Estimates of LWD in the Green and Cedar rivers meeting NMFS size and frequency criteria are 89% to 95% below the levels necessary for “properly functioning conditions” for salmon habitat. Comparing the wood loads in these rivers to estimated historic conditions and expected natural wood loads to which salmon have adapted, these rivers have a mere fraction of the wood they once contained.
A study by King County of the presence and distribution of large wood in the Cedar River estimated 11,500 pieces of large wood on the Cedar River in 2010, and the vast majority of these were categorized as small logs and branches. Only 145 key pieces (wood pieces large enough to aid in the formation of a logjam) were counted for at an average of 6.5 per river mile. Watershed Analysis data on large woody debris (LWD) in the upper White River (above Mud Mountain Dam) suggests the LWD and key piece quantities is in a poor condition as it relates to necessary functions for salmon habitat.