The Influence of Re-Establishing Upstream Large Wood Transport Processes in the Green River, King County, Washington

The Green River flows from the Cascade Mountains entering Puget Sound in Seattle’s Elliott Bay.  It sustains six anadromous salmonid species including ESA-listed Puget Sound Chinook salmon and steelhead. Army Corps of Engineers (USACE) construction of Howard Hanson Dam (HHD) at river mile 64 on the Green River in 1962 prevented upper Green River large wood (LW) from reaching the middle and lower river salmon populations.  Permitting documents for Tacoma Water’s Green River Habitat Conservation Plan (HCP) and the USACE HHD Additional Water Storage Project (AWSP) stipulated at least 50% of LW entering the HHD pool be transported to the middle Green River to re-establish channel and habitat forming processes afforded by delivery of LW from upstream sources. Delivery of loose wood to the middle Green River was an untested and experimental process.  Thus a research requirement was developed to monitor LW levels in the middle Green River over the first fifteen years, following AWSP implementation, to evaluate resulting distribution and architecture of transported LW.  Data collected from this project will be used to guide future HCP/AWSP wood management efforts.  A comparative analysis from the first five years of post project implementation monitoring, relative to baseline conditions, is presented.