Whychus Creek Fish Passage
Fish Passage and Screening
Client / Agency
Upper Deschutes Watershed Council
US Forest Service-Sisters Ranger District, Three Sisters Irrigation District
2008 to 2010
RDG worked with the Upper Deschutes Watershed Council, the U.S. Forest Service, and the Three Sisters Irrigation District to improve fish passage at the Three Sisters Irrigation District diversion near Sisters, Oregon.
RDG oversaw construction of a rock ramp designed to provide fish passage at the diversion dam. The rock ramp degraded during the January 2011 flood event, which was a 10-year event on Whychus Creek. RDG prepared a post-runoff appraisal of the rock ramp to determine probable failure mechanisms. RDG completed a maintenance design that was implemented during the 2011 in-stream work window. The maintenance design addressed the four likely failure mechanisms that were identified. The maintenance design included installing a series of rock ribs comprised of 2-3+ ft diameter boulders. The infill matrix included angular rock measuring 1-3 ft in diameter. Perturbation boulders were placed to create pocket water and low velocity channel margin areas to facilitate fish passage through the reach. Engineered soil lifts were planted with willow cuttings to facilitate site revegetation. A post-project planting effort included installing native riparian and upland plants.