Sonoma Creek Bank Restoration

Glen Ellen, CA

Private Homeowner
Summer 2009

Sonoma Creek runs 31 miles from its headwaters in Sugarloaf Ridge State Park to the San Pablo Bay.  Development in the watershed has increased peak flows on the creek, resulting in substantial bank erosion in many locations.  During the 2004 New Year’s Day storm, this property suffered major erosion causing failure of an existing retaining wall. 

In July, 2009 Hanford ARC contracted to re-grade portions of the bank and armor the slope with rock and several soil bioengineering techniques.    Prunuske Chatham Inc. completed the design.  We carefully planned implementation, including a gravity stream bypass to address several special status species, including California freshwater shrimp, found within the reach.

The stream bypass included 200 feet of 24” HDPE pipe and 400 sandbags.  This system isolated the work area from the active channel.  The scope of construction included removal of the deteriorated retaining wall, excavation and removal of rock and debris from behind the wall and removal of several large trees.  We imported approximately 450 tons of rock, 2-3 ton size for in-stream structures and ¼ ton for armoring a brush mattress.  Approximately 90 tons of cobble was placed directly in the channel bottom and used to fill gaps in the larger rock.

We installed three log structures including rootwads incorporated at the toe of the rock to provide roughness and habitat for the endangered freshwater shrimp.  We removed approximately 350 CY of soil as part of the bank layback.

The newly graded banks were further stabilized with a brush mattress utilizing 600 willow cuttings and 30 dogwood stakes, 3000 SY of erosion control blanket covering native seeding and 115 native plants. Our crew installed a temporary irrigation system which will be in place until the revegation is established.