Situated on the Columbia River near Washougal, Washington, nearly 1,000 acres of floodplain habitat were recently reconnected at the Steigerwald National Wildlife Refuge, representing the largest single floodplain restoration in the Pacific Northwest to date. W2r led the project's 10-firm consulting team through multiple design, permitting, and construction phases—each with expedited timelines.
Prior to the restoration, the historic floodplain of the refuge was cut off from the Columbia River by a five-mile long levee. Gibbons Creek, a large tributary into the refuge, was diverted into an elevated canal and fish ladder.
Refuge wetlands were dominated by invasive vegetation species, and adjacent uplands cleared for agricultural use. Meanwhile, the Port of Camas-Washougal incurred high annual pumping costs to manage creek overflows, and US Fish and Wildlife Service dredged sediment at the creek diversion to keep WSDOT’s State Route 14 Bridge from flooding.
With restoration efforts implemented, Gibbons Creek now has full access to both its historic alluvial fan and the river, native salmonids can access rearing and spawning habitat for the first time in 60 years, and a mosaic of floodplain wetlands is actively re-establishing on the site.
In addition to benefits for fish and wildlife, the Steigerwald project brings reduced flood risk for neighboring industrial development properties, the city of Washougal, and the state highway by approximately five fold.
Key design components of the Steigerwald Project:• Removal of over two miles of existing levee and construction of one mile of setback levee using 100% on-site levee borrow materials.• The reconnection of Gibbons Creek and its alluvial fan to the floodplain and the Columbia River essentially eliminates interior drainage pumping costs by the levee district (it is estimated to reduce the Port of Camas-Washougal’s annual flood risk and water management costs by $80,000).• Levee protection consisting of a vegetated earthen overbuild (“living shoreline”) planted with shrubs, trees, and grasses that serves habitat functions, saves $1M compared to riprap, and requires less maintenance.• WSDOT right-of-way improvements in Gibbons Creek and along SR 14 that significantly reduce flood and erosion risks to the highway bridge and embankment.• Reduced wildfire risks via maximal, year-round groundwater-floodplain connectivity along the Gibbons Creek alluvial fan.• Design and construction aspects were optimized to sequester 100% of project emissions (including those associated with burning more than 400,000 gallons of diesel fuel).
AWARDS
Society for Ecological Restoration Project of the Year, ACEC Oregon People’s Choice, NAFSMA Innovative Water Project
Client
Lower Columbia Estuary Partnership
Keywords
USACE levee modification and removal, creek realignment, floodplain enhancement, flood protection, trail enhancement, road raise, fish passage, sediment transport analysis, hydrologic and hydraulic modeling, CLOMR/LOMR
