Nooksack River Side Channel Enhancement Pilot Project 

Nooksack Side Channel vicinity map

Summary

Vegetation and sediment will be removed from the Nooksack River channel to encourage more flow into an existing small side channel that runs parallel to the Twin View Levee along the left (west) bank of the river directly upstream of Everson. This project is a short-term action that can be permitted and implemented before the next winter season to increase river capacity in the Everson Flow Split area. Flow and habitat changes in the project area will be monitored and evaluated after a full wet season. Results will inform future mid- and long-term actions.

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Project Benefits

  • Potential to improve side channel connectivity, increase flow capacity, and reduce flood water levels upstream of the Everson Bridge
  • Potential to improve off-channel fish habitat 
  • Pilot project evaluation will measure effectiveness and inform future project planning

Background

This pilot project was identified by the Everson Flow Split Reach Team (link to new page) in the spring of 2022 as a short-term, multi-benefit action to reduce flood impacts in the Nooksack River and the flood overflow corridor from Everson to the Fraser River. The project is anticipated to be completed before the 2022-2023 winter season. The Whatcom County Flood Control Zone District (FCZD) is completing this project in consultation with the cities of Everson, Nooksack, and Sumas, the Nooksack Indian Tribe, and Lummi Nation. 

The Nooksack River overtops its east (right) bank at Everson in large flood events, and that flow moves north through the cities of Everson, Nooksack, and Sumas as well as adjacent agricultural areas, posing significant risks to people, infrastructure, and land uses. An interdisciplinary planning and design charette focused on this river “flow split” was held in April 2022 as an initial step to identify both short-term and long-term multi-benefit solutions for reducing flood impacts in the overflow corridor. 

This project is a short-term solution identified through this planning effort to encourage a greater amount of flow into a small side channel that runs parallel to the Twin View Levee along the left (west) bank of the Nooksack River immediately upstream of the Everson Road (State Route 544) Bridge. This side channel was active a decade ago, but now only has flow conveyance during high-flow events. Preliminary analysis suggests that increased flow down this side channel could lead to a modest increase in local river flow conveyance and an associated reduction in the volume and rate of flow that overtops the river’s right bank during large flood events.


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Project funding provided by:

  • Washington State Department of Ecology Floodplains by Design
  • Flood Control Zone District