Santa Cruz, CA
831.421.9291
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  Portland, OR
503.227.5979
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Seestrom Tidal Floodplain Restoration

Picture1Client: U.S. Fish and Wildlife Service

This “Working Lands” project balances habitat improvement with improving or maintaining existing agricultural uses in a 300-acre sheep and cattle ranch on the tidal floodplain along the Coquille River in coastal Oregon. Conversion to pastureland at the site began in the early 1900s with the clearing of native forest, construction of levees and linear drainage ditches, and installation of tidegates, which were in disrepair and prevented active tidal flows and fish access to critical vegetated floodplain habitat. Waterways was contracted by the US Fish and Wildlife Service and the Coquille Watershed Association to support USFWS, ODFW, and the Coquille Watershed Association to design, permit, and implement the project. The project area is privately owned by a local family and will continue to function as a ranching operation following project completion. The project involves excavating new tidal channels, filling drainage ditches, installing large wood, re-establishing fish access to the floodplain, and building two large concrete box culverts with muted tidal regulator (MTR) controlled tide gates to allow managed tidal flows.

Waterways conducted technical analyses and design, including geomorphic and hydraulic analyses, geotechnical investigation, alternatives analyses, engineering design, permitting, bid support services, construction staking, and construction oversight for the project. Waterways’ used a 2-D hydraulic model to ensure that the design met geomorphic, hydraulic, and fish passage objectives, and minimized the hydraulic risk to the MTR culverts. When complete, the project will include about four miles of new tidal floodplain channels and partially restored tidal flows in the lower reach of the Coquille River. Phase 1 of the project was constructed in 2019 with grant funding from Oregon Watershed Enhancement Board and others. Waterways is currently assisting the project with data collection for a performance evaluation of the muted tidal regulator, which will support potential changes to the engineering design for Phase 2 which is anticipated to be implemented in 2022, pending the receipt of an additional $1.3 million in grant funding.

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