Sediment Retention Structure
http://www.nwp.usace.army.mil/op/srs/home.asp
Built by the US Army Corps of Engineers to help reduce sediment loading of the Toutle and Cowlitz Rivers by erosion of tephra and debris from Mt St Helens.
Turnoff is 21.1 miles from the Castle Rock interchange along WA 504
Sediment retention structure on the north fork of the Toutle River, looking west towards the mountain. Note delta forming at east end of lake. Photo by US Army Corps of Engineers
Enhanced levee protecting the town of Castle Rock WA from flooding and lahars from Mt St Helens. Photo by James Maynard © 2010- free use with attribution
Flooding along Cowlitz River induced by heavy sediment load from Mt St Helens. Photo by US Army Corps of Engineers
Flooding along Toutle River at confluence with Cowlitz River after 1980 eruption. I-5 bridge in background. Note floating logs. Photo by US Army Corps of Engineers