Historic incision had simplified and diminished floodplain function along a critical 2-mile reach of Desolation Creek, a tributary to the North Fork John Day River. Hired to help maximize floodplain connectivity along the reach, W2r provided concept to final design and construction phase support services for the Desolation Creek project.
By pursuing a Stage 0 design approach for the project, restoration actions addressed key challenges related to sediment supply, wood supply, and active grazing practices. Specifically, the design promotes full engagement of the floodplain system by spreading out flows, increasing sediment retention, raising groundwater tables, and reestablishing a robust riparian zone. It is the first project of its type to go through BPA’s HIP process.
Specific design elements included channel-spanning wood jams that minimize disturbance to existing vegetation while maximizing floodplain connection; floodplain grading that promotes engagement and avoids disturbance to wetlands; and localized channel aggradation to increase floodplain and hyporheic exchange while promoting vegetation success through elevated groundwater tables. To address the bed material limitation, as revealed by W2r’s sediment transport analysis, the design pursued placement of excavated gravels in stream, rather than exporting them off site, while balancing cut and fill. Without addressing this, the site would require multiple centuries to refill passively.
Construction of this project was completed in 2023.
Client
Confederated Tribes of the Umatilla Indian Reservation
Keywords
Stage 0, side channel reconnection, engineered log jams, wood habitat structures, geomorphic assessment, sediment transport analysis, hydrologic and hydraulic modeling
