Southern Flow Corridor Project Reduces Chronic Flooding and Restores Critical Habitat for Fish and Wildlife

The Southern Flow Corridor project is at the head of Tillamook Bay, and at the confluence of the Wilson, Trask, and Tillamook Rivers in Tillamook County, Oregon. Tidal influence, extensive levee and slough systems, land subsidence, and high sediment loads create an environment with complex and chronic flooding patterns. The project, featured in the video linked here, will restore over 500 acres of tidal wetland habitat, while reducing flooding to 3000 acres of land in the community. Northwest Hydraulic Consultants (NHC) was selected by Tillamook Oregon Solutions, a locally driven, state supported stakeholder group, to develop alternatives to reduce flooding.

Following a series of stakeholder and public meetings with presentations by NHC, a preferred alternative was selected, which will reduce flood levels up to one and a half feet on Highway 101 through a wide range of floods, up to the 100-year event. The main element of the project the Southern Flow Corridor - consists of the removal of over 40,000 feet of existing levee, construction of 9,000 feet of new setback levee, new flood drainage structures, removal and containment of contaminated soils, and tidal habitat restoration of approximately 500 acres of land. As part of the funding package, NHC prepared a benefit-cost analysis that was used to successfully obtain $3.5 million from FEMA. NHC led a consultant team through final design, bidding, and now construction management services for the project, slated for completion in fall 2017.