Increasing Flood Protection While Improving Habitat for Fish and Wildlife

The Lower Russell Road Levee Setback is an important piece of an overall flood management strategy for the Lower Green River Valley, located in the City of Kent along the east bank of the Green River. Built to protect agricultural land, the original levee no longer met current design standards and became costly to maintain.

This chosen levee improvement was one of the few places on the Green River without major development along its bank. It provided a unique opportunity for substantial habitat restoration and enhancement of recreational opportunities, in addition to improved flood risk reduction. Setting the levee back from the river will provide greater flood storage and conveyance capacity, increase shallow water habitat for Endangered Species Act listed species, enhance recreational opportunities and reduce long-term maintenance costs.

Our team worked closely with King County, King County Flood District, the City of Kent, the Muckleshoot Indian Tribe and other partners. Our services included alternative analysis, preliminary design, final design and engineering during construction. This multiobjective project was designed to current engineering standards.

To balance the complex needs of the project including flood protection, habitat and recreational use, HDR assembled a team of experts in geotechnical, hydraulics, civil, structural, environmental and cultural resources. To support the analysis and design, the team completed robust investigations including existing habitat and critical areas, cultural resources, topographic survey, geotechnical and hydrogeology, geomorphology, hydraulic and scour assessment, as well as existing utilities.

We designed a cantilever floodwall for the new roadway embankment for Russell Road. Scour protection measures included barbs, rock riprap revetment and wood-based overbank protection of a bank roughening jam. The design included modifications to the channel by creating off channel habitat for spring rearing and a high-flow refuge for salmonids.

The new levee will provide better protection for the residential and commercial development behind it, while also improving riparian and aquatic habitats for fish and wildlife.