Randall Slide Stabilization Project
Olema Creek, Marin County

Photos ©2003 by Brannon Ketcham of Point Reyes National Seashore.
Click on any image for slide show in a larger view.

The Randall Slide Stabilization Project was initiated to prevent further delivery of sediment from a landslide into primary spawning habitat in Olema Creek, Marin County, California. Partners in the project were the National Park Service at Point Reyes National Seashore and Trout Unlimited. Project funding came from the Department of Fish and Game. Work on the site was conducted through arrangements between Trout Unlimited and Prunuske Chatham, Inc. The project started in November 2002 and was completed in April 2003.

Olema Creek, the largest undammed tributary to Lagunitas Creek, flows northwest through the Olema Valley towards Tomales Bay. The creek provides critical habitat to the federally threatened coho salmon and steelhead trout. Coho has also been added to California’s Endangered Species List.

What had started out as a minor gully in 1997 turned into a major landslide after heavy rains in 1998. Because of the very steep slope and poor soil quality, vegetation has not been able to establish on the slide thus preventing the slide from stabilizing naturally. It is estimated that 3000 cubic yards of fine silt and clay entered the creek between 1998 and 2000. The most acute impacts associated with the slide were related to the mobilization, transport and deposition of fine sediment to about 1600 feet of significant spawning and rearing habitat immediately downstream.

Work to restore the hillside and prevent further erosion consisted of major biotechnical treatments throughout the slide complex, excavation of 700 yards of sediment perched at the top of the slide and the recontour of the old road above the slide to direct away water. Biotechnical treatments including brush layering, willow revetments, willow brush mattresses and willow wattles were employed to stabilize the gully. The intent of these structures was to stabilize the slope plains by interrupting flow paths. Annual rye grass was also planted on the slide slopes.

Since planting most of the willows have rooted and have sent out significant growth. Grass and willow cover have arrested most of the sedimentation and runoff from the site. Site visits following completion in April 2003 showed dramatic reduction in fine sediment delivery to the stream from Randall Slide.