The Sunrise Side Channel, located on the Lower American River, is an existing, natural, seasonal side channel about 0.5-miles downstream of the Sunrise Boulevard Bridge and approximately 3.5-miles downstream of the Nimbus Dam. The side channel cuts across a large point bar of gravel and contains running water when river flows exceed about 4,000 cfs. At flows greater than 4,000 cfs, the channel has sufficient flow to attract spawning steelhead and salmon. Steelhead spawn in the lower American River from December through March, which coincides with flood control operations at Folsom and Nimbus Dams. It is common for flood control releases to exceed 4,000 cfs for several days or more, followed by a reduction below 3,500 cfs that results in dewatering and desiccation of redds (fish nests).

This project reduces the likelihood that that the redds of wild-spawning steelhead in the American River will be dewatered due to dam operations. The existing side channel will be deepened to allow water to move through it at lower flows (900 cfs and higher). Through a design charrette, geomorphic reconnaissance and hydrodynamic modeling, PWA, as part of an interdisciplinary team, worked to design and build modifications to the side channel to reduce the potential for redd desiccation. Construction included channel excavation and grading to a lower elevation and the removal of invasive, non-native vegetation in the immediate work area. This reduced juvenile fish stranding areas (existing holes and depressions in the adjacent gravel bar) by filling them with gravel removed from the side channel and replanting the reconfigured side channel banks with native vegetation.

The finished project ultimately provides conditions that will increase the frequency and duration of spawning habitat available to steelhead and salmon, while reducing the stranding of redds. Cumulatively, the project should enable the survival of a greater number of eggs to the aelvin stage.