North Wind's Weir Restoration Project

Location: Cecil B. Moses Park on the Duwamish River, King's County, Washington

Funding Source: City of Seattle/Metro Settlement

Design Objectives:

• Create a one acre intertidal basin for use by juvenile salmon.
• Shoreline protection improvements.
• Provide native intertidal and riparian vegetation.
• Improve habitat for out-migrating salmonid acclimation to salt water at a critical location in the Duwamish River.
• Provide refuge and food sources for trust resources.
• Protect the site in perpetuity for natural resources.

Site Summary

The North Wind’s Weir project is on a 3.1-acre parcel of King County’s Cecil B. Moses Park on the free-flowing Duwamish River about a mile upstream of Turning Basin No. 3. The Elliott Bay/Duwamish Restoration Program purchased 1.03 acres of the park to construct an intertidal basin. The site was originally developed in the 1930’s and 1940’s for single family residential housing. All dwellings have been removed. A steep bank along the river right-of-way sloped downward (almost vertical) approximately 20 feet to the riverbed where the shoreline was poorly protected by riprap and debris in the lower intertidal to subtidal areas.

Restoration Activities

A 1.03-acre intertidal basin was constructed by excavating from an elevation of +6 to +15 feet MLLW. A curvilinear edge creates a more natural appearance and maximizes habitat diversity at the zone edge. A connection to the Duwamish River was made at the northeast end of the property and will be achieved by using natural bank slopes stabilized with vegetation. The "softer” engineering approach will allow a more natural stabilization process to occur at the site. A riparian buffer was planted, incorporating as many mature trees and native shrubs present on the site as possible and to restrict human access from the surrounding park. See design map.

The intertidal project with 500 feet of intertidal river frontage and a one-acre intertidal off-channel lagoon, is complemented by upland park improvements undertaken by King County, including parking, restroom facilities, trails, shoreline stabilization, plantings, and interpretive features highlighting the cultural significance of the site to Native Americans.

Monitoring for intertidal habitat success will be conducted until 2015 under the Elliott Bay/Duwamish Restoration Program's restoration monitoring plan.

The Common Names of Plants Established at the North Wind's Weir Restoration Project Site

Salt Marsh Plants: Lyngby’s Sedge, Saltgrass, Pickleweed, American threesquare rush, Seaside arrowgrass.

Riparian plants: Red alder, Paper birch, Black cottonwood, Douglas fir, Red osier dogwood, Oregon grape, Pacific ninebark, Nootka rose, Hooker’s willow, Scouler’s willow, Snowberry