Swadabs Park,  along the waterfront of the Swinomish Village, two years after fill removal and marsh restoration.
Swadabs Park, along the waterfront of the Swinomish Village, two years after fill removal and marsh restoration.

 

The Swinomish Channel is a salt-water channel which connects Skagit Bay, to the south, and Padilla Bay, to the north, separating Fidalgo Island from mainland Skagit County. The Swinomish Channel Fill Removal and Restoration Project sites are strategically located along a salmonid migratory corridor (the Swinomish Channel) connecting the natal Skagit River with extensive juvenile salmon rearing habitat of Padilla Bay eelgrass, providing refuges along a straightened former distributary.

Rearing and refuge habitat along the Swinomish Channel, which would facilitate juvenile Chinook and other salmon migration between Skagit and Padilla Bays, is severely reduced compared to historical conditions, primarily because of dredging and straightening of the channel for navigation purposes that began in the early 1900’s. The type of habitat restored has been identified as a critical limiting factor in the Skagit Chinook Recovery Plan (SRSC and WDFW 2005).

This project removed Swinomish Channel dredge spoils from 10 acres of historical tidal marshes at five sites along the Swinomish Channel, on Swinomish Indian Tribal Community property. Additionally, one tidal channel was excavated on each site to create a total of 0.5 miles of channel, each channel being approximately 3-6 ft wide and 3-4 ft deep.

Fill removal at Rainbow Marsh, just north of the Rainbow Bridge in La Conner. 2008 Photo by Kari Neumeyer, NWIFC.
Fill removal at Rainbow Marsh, just north of the Rainbow Bridge in La Conner. 2008 Photo by Kari Neumeyer, NWIFC.
The Rainbow Marsh fill removal and restoration site, four years post construction.
The Rainbow Marsh fill removal and restoration site, four years post construction.

Channel design was based on a channel geometry model that uses marsh size as the predicting variable, developed with data from Skagit Delta tidal marshes (Hood 2007). A baseline study of the elevation distributions of native marsh vegetation along the Swinomish Channel was used to determine restoration site design elevations. Restored marsh vegetation will consist of Distichlis spicata, Salicornia virginica, and Triglochin maritimum. These native species dominate small marsh remnants fringing the Swinomish Channel.

Five sites were selected for fill removal and marsh restoration. The Rainbow Marsh, North Fornsby, and South Fornsby were constructed in 2008. Rainbow Marsh is just north of the Rainbow Bridge in La Conner. The Fornsby sites are south of the Highway 20 Twin Bridges at the northern end of the Swinomish Channel. In 2010 and 2011 the McGlinn and Swadabs sites were constructed. The McGlinn site is south of LaConner and across the Channel from Shelter Bay. The Swadabs site is at the waterfront of the Swinomish Village and is a central feature of the Swadabs Park and Canoe Landing. Archeological monitoring and oversight were important project components.

Excavated dredge spoils were hauled to upland locations for storage and disposal. Upland species were planted on the upper terrace above the fill removal sites. The marsh surfaces were allowed to passively revegetate, which happened relatively quickly (within 1-2 years post-construction).

Project Status/Timeline
This project resulted in the restoration of 10.3 acres of intertidal salt marsh, and the reconstruction of 1325 linear feet of tidal channel habitat between 2008 and 2011. Site monitoring and maintenance are ongoing.

Primary Project Contact
Nora Kammer – Restoration Ecologist

Funding Sources
SRFB – Salmon Recovery Funding Board
ESRP – Estuary and Salmon Restoration Program
Swinomish Indian Tribal Community
NOAA – Puget Sound Critical Stocks Program

Project Partners
Swinomish Indian Tribal Community

References
Hood, WG. 2007. Scaling tidal channel geometry with marsh island area: A tool for habitat restoration, linked to channel formation process.