THE LAND CONSERVANCY OF SAN LUIS OBISPO COUNTY

Restoration Project: Natural Stream Bank Repair

Middle San Luis Obispo Creek

Overview/History

The Land Conservancy has been working with the Hayashi family for over a decade to improve stream conditions on their property along San Luis Obispo Creek. Since 1997 we have removed invasive weeds and replanted native plants along almost a mile of the creek's banks owned by the Hayashi's. The photos below show one part of our work on this site and illustrate the use of a more natural way to stabilize a stream bank.

The Problem

The washout on this streambank was causing soil to drop into the stream. This soil covers the bottom of the stream and can inhibit steelhead spawning. The lack of vegetation on this bank also let high velocity floodwaters scour vital agricultural soils adjacent to the stream.

Project Goals

The goals of the project were to prevent further bank erosion and help buffer the agricultural area from the higher velocity floodwaters. On this site, the extent of the erosion was isolated and there were stable banks both upstream and downstream. We felt the site was a good opportunity to build a biologically based stabilization project.

Project Approach

Re-sloping the bank was out first step. We were able to do this from the top of the bank with a backhoe. A silt fence and hay bales were used to keep any material from falling into the live stream. We chose not to divert the stream because our stabilization method did not call for any excavation of the bank toe. Once the bank was re-sloped, the toe was armored with Coir biologs. These flexible wattles are made from shredded coconut fibers and are very strong and durable. The coconut material is all-natural and will biodegrade in about 5 years. Live willows were planted along with the logs, and will become the main support for the bank when the logs degrade. They reach full strength in about 3 years. The final step was re-planting the bank with native plants.

Results

The plants grew quickly and covered the entire slope in under 12 months. Today it is difficult to even find the site where the work occurred due to the thickness of the vegetation. The bank is now stable and promoting the growth of native plants. It will still be a few years before the larger trees emerge as the dominant form of vegetation. The newly restored bank now provides important shading for the creek that will help prevent the sun from heating the water.

Using a bio-technical approach to repairing this bank worked well in stabilizing the bank while creating important habitat elements for fish.

Project Partners

This project was funded by the Avila Beach Trustee Council, which is made up of representatives of the California Department of Fish and Game's Office of Spill Prevention and Response and the U.S. Fish and Wildlife Service. The project is intended to improve habitats that were damaged by an oil spill in Avila Beach. The project was also made possible by the Hayashi Family, who own and farm the adjacent lands. Their participation in our stream repair program has facilitated the replanting of almost 1 mile of local streams.