DESCRIPTION
Snohomish County continued outreach and planning for Thomas' Eddy restoration on the Snohomish River to improve the quality and quantity of channel edge and off-channel habitat and connectivity between the main channel, floodplain and associated floodplain waterbodies. The project is located in the Heirman Wildlife Preserve between river mile 16 and 18 of the Snohomish River. In the 1930s, levee construction in this area isolated more than 200 acres of Snohomish River floodplain including approximately 1.5 miles of off/side channel habitat and added nearly a mile of modified and rip-rapped edge to the river. Planned restoration actions include removal of portions of levee, side channel and edge habitat enhancements, jam construction, and riparian planting. The project funded preliminary design (60% design) and outreach and stakeholder engagement to achieve agreement on a preferred alternative. Floodplains by Design funded 30% design (attached in PRISM). Outreach and planning involved substantial engagement with County Parks Dept. and stakeholders including the Heirman family, fishing community, birders, and other park users.
The completed 60% design proposes to remove a total of 3,685 ft of levee in multiple breaches and return natural floodplain connection to more than 200 acres of floodplain, while fully connecting 1.5 miles of off-channel habitat. The lower 1,600 feet of the channel will be enhanced with 17 small wood structures. Along the outer riverbank of the site, up to 2,000 ft of bank armor will be removed, and 12 bank log jam structures will be added to provide edge complexity. An additional 10 Bar Apex Log Jams are proposed on mainstem locations along the reach. On the floodplain, 45 wood structures were designed to provide roughness and habitat complexity. Other planned work includes replacing a trail culvert to improve hydraulic connection and fish passage, improved trail drainage, and 50 acres of invasive plant removal and native riparian planting. This project is also proposed to have future phases that include additional recreational and agricultural elements to address additional stakeholder desires.