Relocating Government Creek - Lessons from the Successful Re-Creation of a Salmon Stream and Estuary on Gravina Island, AK

As part of a multidisciplinary consultant team for the Alaska Department of Transportation, we addressed fisheries and estuarine ecology issues associated with expansion of the Ketchikan Airport.  All build alternatives would result in impacts to anadromous streams and associated estuaries.  Impacts were focused toward the south end of the runway where Government Creek flowed through a largely bedrock confined channel.  We designed approximately 850 m of new channel for Government Creek and a tributary to avoid the need to place the streams in a long culvert.  The channel design was developed by characterizing the geomorphology of an upstream reference reach, selected to represent natural channel characteristics. 

First a new valley with a broad (approximately 30-m) flood plain was cut as deep as 25 m through native bedrock and glacial till to reach the desired grade.  The stream channel was then cut into this floodplain surface.  The design team worked closely with field crews in the installation of habitat features including 40 pieces of large woody debris, 100 large boulders, and multiple riparian vegetation islands.  Three side channels were cut into the flood plain bedrock to provide off channel rearing habitat for coho salmon.  We also designed a new 0.7-acre brackish marsh estuary at the stream mouth to provide a gradual and natural transition from the new stream into the marine environment of Tongass Narrows. 

Flow was diverted into the new channel in mid-August 2007 and pink salmon were spawning in the channel within 10 days.  Monitoring is ongoing to assess effectiveness and longevity of the newly designed habitat features and to provide pre- and post-construction data on eelgrass, clams, salt marsh vegetation, and fish spawning and rearing.  Now in its fourth year, the new stream and estuary supports abundant rearing by coho salmon and habitat quality and stream bed benthos appear to be good and improving.  The 2009 and 2010 runs of pink salmon in the constructed reaches (fish returning from 2007and 2008 spawning in the new stream reach) have exceeded 3,000 fish.

This project demonstrates the value of:

• Continual agency involvement in project permitting and design;
• Benefits of using in-stream reference reaches in project design;
• Essential nature of attention to detail in writing bids and specifications and in providing construction oversight;
• Benefits of adaptive management to project success.