Projects>Clear Creek Fish Passage
Clear Creek, a tributary of Rock Creek within the Yellowstone River drainage, provides spawning habitat for salmonid species such as Yellowstone cutthroat trout, a species of special concern within its historic range. A large box culvert constructed during the 1930’s was perched 3.5 feet above the channel, preventing fish from accessing 10 miles of spawning and juvenile rearing habitat in Clear Creek. In addition, the channel downstream of the culvert was unstable, with a three foot deep plunge pool beneath the outlet of the culvert and an unstable, 90 degree turn 20 feet downstream of the culvert.
Montana Fish, Wildlife, and Parks and the U.S. Fish and Wildlife Service retained Confluence to conduct a thorough feasibility assessment, which was used to procure funding for final design and construction of a rock step-pool structure to allow fish passage through the culvert. Field work involved measuring bed substrate composition, surveying channel cross sections, and developing a longitudinal profile. The step pools were designed to reduce the drop below the culvert to less than one foot per step, thereby allowing fish passage into and upstream of the culvert. Unique problems that Confluence addressed included stabilizing the 90 degree bend in the channel and supporting the downstream invert of the perched box culvert. The project is successfully passing fish at all discharges.