Smith, D., 2005. Off-Channel Habitat Inventory and Assessment for the Upper Skagit River Basin. Skagit River System Cooperative, La Conner, WA. pp. 32.

Off-channel habitat includes overflow channels, sloughs, wetlands, and small streams
found within the floodplains of larger river channels. These habitat features are created
and maintained by channel migration and avulsion of larger river channels during peak
flow events. Off-channel habitat has been a focus of habitat protection and restoration
efforts because it provides important spawning and winter rearing habitat for a variety of
salmon species (Beechie et al. 1994).
The operation of the Skagit Hydroelectric Project has significantly altered the flow
regime in the Skagit River and has reduced the frequency and magnitude of peak flows
during large flood events (Beamer et al. 1999). Off-channel habitat is often formed
during large flood events, so it is widely believed that over time flow regulation has
reduced the amount of off-channel habitat in the upper reach of the Skagit River. For this
reason, mitigation efforts have focused on protecting existing off-channel habitat and
replacing lost habitat by constructing artificial groundwater channels (Seattle City Light
1991).
The purpose of this study was to compile existing data on off-channel habitat for the
upper Skagit basin, which includes the Sauk, Whitechuck, Suiattle, and Cascade rivers
and the Skagit River upstream of Rockport. The intent was to document the location and
characteristics of off-channel habitat in the study area and to compare natural and
constructed habitat in the upper reach of the Skagit River with other river reaches that are
not affected by flow regulation. This information will be useful for evaluating the
effectiveness of off-channel habitat restoration efforts to date and in planning future
habitat protection and restoration actions.