Environmental and hydrological expertise for creek and habitat restoration

Dry Creek Habitat Enhancement

When the National Marine Fisheries Service issued a Biological Opinion requiring Sonoma County Water Agency (SCWA) to enhance habitat and promote the recovery of endangered and threatened fish species, we were commissioned by SCWA to design 1.25 miles of habitat enhancements for federally listed Coho and Chinook salmon, and Steelhead trout in Dry Creek. Seasonal high flow releases from Lake Sonoma to Dry Creek provide vital water supply to over 600,000 consumers in Sonoma and Marin counties, but adversely affect juvenile rearing habitat. Also, impacts from flood control activities by the U.S. Army Corps of Engineers (USACE), and historical land uses, have cumulatively altered the geomorphic and hydrologic regime of Dry Creek to the detriment of aquatic habitat.

Working with the USACE, SCWA, and resource agencies, our team prepared aquatic and riparian habitat enhancement plans, starting with initial concept plans through all phases of engineering design to a complete set of 99% design drawings, with 100% design plans to be completed prior to commencing construction. We’ll also provide construction management for implementation of the habitat enhancements.

Workshops were held with the resource agencies and land-owners at key milestones of the project. Habitat enhancements include developing side channels, low velocity alcoves, a more sinuous planform with meander bends holding deep pools, engineered wood jams, and grading to reconnect Dry Creek with former floodplain surfaces within an incised channel corridor. These enhancements provide juvenile salmonoid rearing and high-flow refuge habitat allowing SCWA to release water into Dry Creek for delivery to community water supplies and to improve conditions during prolonged high flow flood control releases by the USACE. Our expertise in natural resource management and aquatic habitat restoration is a key step towards the recovery of these fish species, while maintaining water supply and enhancing flood control.