Projects

Nason Creek Merritt Oxbow Reconnection Project

In the Wenatchee watershed, Nason Creek has been identified as the top priority stream for implementation of habitat restoration actions. Nason Creek is a major spawning area for spring Chinook salmon, steelhead, and bull trout, providing foraging, migration, and over-wintering habitat. Nason Creek has a high potential to increase Endangered Species Act (ESA)-listed salmonid abundance and productivity by addressing factors limiting productivity. The restoration of ecosystem function through the reconnection of off-channel habitats and floodplain is a high priority.

Cascade Fisheries selected Rio ASE to design a project that would reconnect Nason Creek to a historical oxbow, providing high flow and temperature refugia and year-round rearing habitat for juvenile spring Chinook and steelhead. The preferred alternative included installation of mainstem and side channel constructed riffles, a mainstem apex jam and engineered log jams, and wood habitat structures within the side channel and portions of an existing side channel to increase instream hydraulic diversity and habitat value. Under current conditions, Nason Creek only activated the oxbow and adjacent wetland at approximately the 2-year flow event. This project provides ESA-listed fish perennial access to the side channel and oxbow habitat, creating over 2 acres of juvenile off-channel rearing and refugia habitat near the town of Merritt, Washington.

2D hydraulic model results showing depth at the 1.25-year flow for existing and proposed conditions. The green dots mark historical Chinook redds.

Rio ASE provided geomorphic and engineering design (hydrology, hydraulics, restoration and revegetation design, and engineered log jam [ELJ] designs) from concept through final design. Major features included 600 feet of new side channel, 220 feet of mainstem constructed riffle, one apex and two mainstem ELJs, 17 wood habitat structures, and revegetation of native species within the riparian zone.

Timelapse video of contractor using large equipment to drive piles for apex jam.