Rock Creek Design

Existing and proposed flooding depths during a 100-year discharge event on Rock Creek.

Rio ASE in collaboration with the Confederated Tribes of the Umatilla Indian Reservation (CTUIR) completed the enhancement design of over 1 mile of lower Rock Creek, a tributary to the upper Grande Ronde. Rock Creek is a cold water tributary downstream of Hilgard that contains critical habitat for steelhead and Chinook salmon.

Through historical land use practices, the stream had become straightened and disconnected from its historical floodplain. This increased stream energy and removal of adjacent riparian vegetation produced an incised channel with little habitat variability. Project goals were focused around reconnecting the floodplain and increasing habitat complexity through channel realignment, alcove and side channel development, placement of large woody habitat structures, and ultimately developing a robust riparian plant community. The CTUIR had obtained an easement through the riparian corridor prior to this work, and continued collaboration with the landowner allowed for the design to reclaim the entire valley width.

Rio ASE participated in this project as the lead design engineer working directly with the CTUIR through design iterations where the CTUIR was taking the electronic data developed by Rio ASE and turning that into the production drawing set. The goal of the channel design and floodplain grading by Rio ASE included improving in-stream and off-channel habitat by restoring appropriate channel form/geometry and improving natural channel processes. Rio ASE’s lead engineer ultimately performed stability calculations for wood structures and reviewed and stamped the final construction design plans. This project created 36 large pools, 4,300 feet of new channel, 462 feet of new side channel, installed over 1,500 large wood pieces, and removed over 1,800 feet of roads and levees for steelhead and Chinook salmon utilization.