Some of our West Creek residents

Site 9

Site 9 begins where West Creek emerges from a culvert on the northeast side of I-480 and extends approximately 550 feet to where gabions protect the north bank. At the end of the culvert the water drops approximately 6 feet over a concrete weir. Throughout this site, West Creek has been relocated and straightened to accommodate I-480 and commercial development on the southeast bank. The channel in this reach is generally incised with a gradual to steep forested bank on the northwest side, and a short, steep, generally grassy embankment leading to the commercial properties on the south bank. Throughout the reach, the channel has incised down to bedrock and is primarily a shallow glide/run habitat. Approximately 250 feet downstream from the weir, a headcut has formed in the more friable bedrock. This headcut may hinder fish passage during periods of low discharge. Approximately 350 feet downstream a tributary enters the channel from the west. The last 10 feet of this tributary cascades approximately 4 feet to the West Creek channel. Major problems through this site are the fish blockages associated with the weir, headcuts and severe bank erosion as the channel has downcut below the original elevation (presumably from the velocities and shear coming from the culvert). The preferred concept will create fish passage and stabilize the eroding banks.

The concept for this site will involve raising the channel invert through the upstream portion of the site to tie-in with the elevation of the weir at the culvert. A series of steps will be constructed beginning downstream of the bedrock headcut to gradually make up the elevation difference between the tributary and the culvert weir. The pool immediately downstream of the culvert will be constructed as a larger stilling basin to manage the high discharge velocities exiting the culvert. The drop at each step will be designed for passage of all fish by including additional cascade rocks below each step. The cascade rocks and pools between each step help dissipate energy and offer a refuge for fish to rest. Step pool sequences will allow sediment to move downstream, thus preventing the generation of mid channel bars and potential bank erosion. Bioengineering such as live branch layering will be installed along the toe of the bank between steps. Raising the invert to the elevation of the culvert will also facilitate grading the banks to a stable angle and establishing native riparian vegetation especially on the southeast bank. This sites receives ample sunlight making them ideal for bioengineering and riparian enhancement. In addition the growing trees of a forested buffer will eventually begin to shade the stream from the sunlight which warms the channel within this reach.

Benefits

• Remove fish barrier
• Enhanced riparian habitat and bank stability with bioengineering and native plants
• Added vegetation also will help shade the channel
• Steps, pools and cascades will offer a habitat for fish
• Stable bank angles can be graded with little or no impact to adjacent properties
• Reduce bank erosion and sediment yield

Risks and Constraints

• Existing slope instability along the south bank
• A significant elevation gain is necessary to reach the weir
• The cost of fill material and rock necessary build the structures
• Litter may collect in the newly established vegetation

Maintenance

• Remove debris jams
• Replace the dead or inadequately established vegetation within the first year

Project Plans, Maps & Photos

These maps are large, so download time may take a while - especially for dial-up connections. You will need to have the Adobe Acrobat Reader installed on your computer. If you do not already have it, you can download it for free at the Adobe Acrobat website.

West Creek Site Overview Project 9

West Creek site 9 concept plan

West Creek Site 9 photos

West Creek Site 9 FINAL Engineering Plans

Pre and Post Restoration Photos