Cottonwood Island Slough Restoration Design

In December 2009, Skagit Conservation District’s engineering program received a grant from the Washington Salmon Recovery Funding Board (SRFB Grant No. 09-1443N) to complete a preliminary engineering design for restoring river flow from the Skagit River into Cottonwood Island Slough.  Cottonwood Island, which is located just upstream of the Skagit Forks, is part of WDFW’s Skagit Wildlife Area.  A century ago, a large side channel meandered around the island and reportedly provided high quality rearing habitat for out-migrating juvenile Chinook and other salmon.  Today, the channel only fills with water during floods. 

 SCD completed the preliminary engineering study in May 2011.  The study built upon two previous hydrologic and habitat assessments that were commissioned by the Skagit Watershed Council to design modifications to the existing channel for optimizing rearing conditions for Chinook smolts.  The project design parameters focus on ensuring a specific range of water velocity and depth conditions in the channel during the crucial March through June period when juveniles are migrating into the delta, while preserving other existing land uses, such as public fishing access and flood protection. Selected project documents can be accessed from the list below.

SCD and our partner organizations, the Washington Department of Fish and Wildlife and Skagit County Dike District No. 1, are excited about the prospects of this project for making a significant contribution to achieving the Skagit River Watershed’s numeric production goal for wild Chinook smolts, which is mandated under the U.S. Endangered Species Act for recovering threatened Puget Sound Chinook Salmon.  We currently are working through the process to finalize the design and to obtain construction funding.  For more information about this project, contact Tom Slocum at email tom@skagitcd.org .

Selected project documents

Project Design Report (SCD, 2011)

NHC 2011 Cottonwood Slough Preliminary Design Report

Preliminary Design Drawings - Inlet Area (SCD, 2011)