Nursery Bridge Reach Phase II Fish Passage and In-stream Habitat Enhancement III

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Limiting factors for Middle Columbia River summer steelhead in the Nursery Bridge Reach include: blocked and impaired passage, degraded floodplain connectivity and function, degraded water temperature, altered sediment routing, and hydrologic alterations (NMFS 2009). Due to the infrastructure constraints in the reach, it may not be feasible to address all of the identified limiting factors; however, this project intends to address fish passage and floodplain connectivity and function in the reach.



The proposed GCS notch and low flow channel in the immediate vicinity of the GCS will create a more stable channel adjacent to the entrance to the Eastside Fishway. Providing reliable fish passage at the Nursery Bridge GCS allows access to over 70 miles of some of the highest quality spawning and rearing habitat in the Walla Walla Subbasin, located within the North and South Forks of the Walla Walla River and Couse Creek. This project would increase the efficacy of the Eastside Fishway at the GCS and allow volitional passage for all life stages of ESA-listed salmonids to meet ODFW and NMFS fish passage requirements.



Degraded floodplain connectivity and function will also be addressed as a result of this project. Floodplain connectivity will be enhanced by reinitiating 3,258 feet of side channel which will increase floodplain activation at lower flows to provide off channel summer rearing habitat and low velocity refugia for winter rearing salmonids on the floodplain. Large wood additions will also increase complexity and functionality of the floodplain for juvenile salmonid rearing.



Due to the constrained nature of the flood control project in the Nursery Bridge reach, this project will likely not address the remaining limiting factors of degraded water temperature, altered sediment routing, and hydrologic alteration. These factors will be addressed in future phases of the Nursery Bridge reach project.