Illabot Creek Feasibility Study
Illabot Creek is a highly productive tributary of the upper Skagit River that supports relatively large populations of Chinook, chum, coho, and pink salmon, native char, and steelhead trout. Due to its importance in providing spawning and rearing habitat, much of the watershed has already been protected or restored. However, there is an approximately half-mile reach of Illabot Creek that is heavily degraded.
SRSC completed a feasibility study with a Salmon Recovery Funding Board grant (Smith and Ramsden 2006) that evaluated habitat conditions and restoration alternatives in the lower portion of Illabot Creek. This study determined that the straightening and diking of Illabot Creek in the vicinity of the Rockport-Cascade Road has had a significant negative effect on habitat conditions by creating a steeper gradient, reducing channel area and habitat complexity, increasing bed scour, and degrading riparian conditions. The preferred alternative identified in the study was to remove the dikes, relocate Illabot Creek to its historic channel, and construct a new large bridge span over that channel. The existing bridge would be left in place and Illabot Creek would be allowed to alternate between the two bridge crossings as the channel migrates over time.
Map of habitat conditions at Illabot Creek pre- and post-channelization.
View of straightened channel downstream of bridge at Illabot Creek.
Project Status/Timeline
The Illabot Creek Restoration Feasibility Study was completed in 2006. Hydraulic modeling will begin winter/spring of 2008 and should take approximately 8 months to complete. If the alternative is approved, the dike removal and bridge construction could start June 2009 and be completed by October 2009.
Primary Project Contact
Devin Smith, Senior Restoration Ecologist
Funding Sources
Washington State Salmon Recovery Funding Board
Seattle City Light Non-Flow Coordinating Committee
Project Partners
Pauline Ryan
Skagit County
Seattle City Light
Supporting Documents
Smith, D. and K. Ramsden. 2006. Illabot Creek Habitat Restoration Feasibility Study