Creek Bank Restoration & Repair Guidance

Repairing Creekbank Erosion - A downloadable guide on who to call for permits, how to outline the project before you begin, the steps to take, and how to follow up on your repair.

Groundwork: A Handbook for Small-Scale Erosion Control in Coastal California - New 2nd Edition from the Marin Resource Conservation District and MCSTOPPP.

Attention Property Owners Adjacent to Novato Creek - follow this link to learn more about making your bank stabilization design approach decision. For additional information on Proposed Bank Stabilization Guidelines for Novato Creek, read the report produced by the Marin County Department of Public Works: Proposed Bank Stabilization Guidelines for Novato Creek

Erosion
Erosion is usually the cause of most creek bank failures. Finding the cause of the erosion is essential to developing an effective solution. Erosion is caused by water from the following three possible sources or a combination thereof:

· Surface Flow - Often the easiest to address. Water flowing over the top of the ground usually causes steep, vertical bank erosion. Common sources include culverts, driveways, ditches or drainage from roofs.
· Ground Water - Water flowing a few inches to a few feet below the ground frequently surfaces on a streambank before reaching the creek channel. Planting these areas with native plants is a good method for controlling erosion caused by groundwater. Check to make sure you are not indirectly contributing excess subsurface flow through yard or garden irrigation.
· Stream Dynamics - Natural changes - such as big storm events or human activities - can cause the stream channel to adjust. Removing vegetation along a creek can reduce streambank stability. This can lead to streambank failure, particularly during large storm events.

Modifications to creek flow may increase erosion both upstream and downstream - An increase in sediment from erosion in the watershed will cause alternate banks to erode in a classic "S" pattern as growing gravel bars direct streamflow into the opposite bank. A fallen tree or other obstruction can cause site specific erosion.

Not all erosion is bad - Streams need to be able to adjust to events in the watershed by changing their shape. Undercut banks and fallen trees provide important habitat for salmonid fish (salmon and steelhead) and other stream dwellers. Answering the following questions may help you to determine whether to intervene, or let nature take its course.

1. Is the erosion threatening a structure, road, utility pole, or other important property?
2. Is the erosion threatening riparian habitat or a significant tree?
3. Is the erosion extremely active? Does it erode rapidly during most rainstorms?
4. Does the erosion appear to be caused by a person-made change, such as a road, culvert or yard drainage?

Planning A Repair or Restoration Project
Documenting your site is an important first step for any creek repair project. If you are planning on repairing the site yourself, you will need the following information in order to obtain any necessary permits. If an engineer or agency is helping you repair the site, this information will save them time and therefore save you money.

1. Photograph the site. It is a good idea to include some sort of reference object (such as a shovel, a basketball, a person in the photo, etc.) to help indicate the size of the actively eroding area..
2. Make a sketch of the site. Include length, width and height of the eroding area. Show structures and how far away they are. Include vegetation and any biological information you know, (what kind of fish use the creek there, etc.)
3. Walk up and down the stream if you can. Indicate on your sketch what is happening near your site. Usually something happening upstream is causing the erosion to occur, such as rock rip rap, a fallen tree, or anything that might redirect the flow of water. Are your neighbors experiencing similar erosion problems as well?
4. Observe the water flow. Does water flow year round? Does water only flow when it rains? Does the creek dry up in the summer?

Cooperative Projects - If some of your neighbors have similar stream bank erosion problems, you might want to consider working together. Benefits include sharing the permit and planning costs, and building repairs that complement and even enhance each other. Cooperative projects, done in conjunction with a local agency or group, can also be eligible for private or government grant programs.

Design Considerations
· Remember the needs of fish and wildlife - Does your design include native plants that will provide habitat and refuge for wildlife in the creek? Is your setback from the top of the creek bank adequate to allow appropriate riparian vegetation to grow along the creek? The extensive root systems of some native plants can help with streambank stability. Even rock rip rap, when interplanted with willows or other trees can enhance habitat.
· Be sure not to constrict the channel - By placing your retaining wall or rock work too close to the center of the stream you may be inadvertently reducing the space the water has to fit through the creek and you may be causing yourself more problems down the road, or causing erosion to occur on your neighbor's properties.
· Biotechnical Restoration - Biotechnical restoration is the term used primarily for using native vegetation to secure an eroding bank. The term biotechnical is synonymous with the term "bioengineering". Generally speaking this type of work is mostly planting, and usually does not require any permits. If your erosion problem is in an early stage that might be appropriate for some biotechnical restoration, this option will be much less expensive than an engineered design that may require permits. If you have enough time and room as a first step, try a restoration approach using biotechnical techniques initially. If for some reason they fail, and you have documented your efforts, this is a good basis for supporting your need for a hard surface design (rock rip rap, retaining wall, etc.). For more information on biotechnical restoration, see Stream Corridor Restoration: Principles, Processes and Practices, or Ann Riley's primer on Stream and River Protection for the Regulator and Program Manager. These documents can be viewed on line at www.mcstoppp.org
· Engineered Solutions - Sometimes bank restorations and repairs require an engineered solution. All engineered projects should integrate river science into the design, this method is sometimes referred to as the 'Geomorphic Approach'. Projects that incorporate geomorphic principles are designed to help the stream attain an equilibrium condition so that the channel will erode and transport sediment, and incorporate features that create and sustain in-stream habitat. Your project should never impair, and where possible, should enhance the natural creek functions. Some examples of bio-engineered or biotechnical designs include restoration of a stable creek channel and floodplain, willow wall structures, installation of brush matting, and vegetated rock rip rap. These and other approaches are addressed in the manuals referenced above.
· Permitting - Most creek bank repair projects require permits from the U.S. Army Corps of Engineers, the Regional Water Quality Control Board, CA Department of Fish and Game, and your local municipality. Go to our Creek Permits page at www.mcstoppp for application forms and instructions.

Other Considerations
· Preserve Water Quality - Be careful to protect water quality and existing habitat during construction. Proper measures should be taken to avoid muddying water in the creek. Protect existing native plants along the bank if possible, or salvage native plants prior to construction and incorporate them in the re-vegetation stage of the project. Generally, all work should be scheduled for the low flow period, usually between June and October.
· Watering - Projects that involve planting new plants often require watering for the first few summers in order for the plants to take successfully. Many large failures are caused by small problems that could have been avoided if caught early on. Check your repair before the winter rainy season and after each storm. Take photographs after a year or two from the same point where you shot the "before" photo. It's fun to watch the sites vegetation mature and settle in, and it may also help others design effective repairs.
· Be a Model - Share your successes with MCSTOPPP! We'd like to have a list of sites that have been repaired (especially those incorporating biotechnical designs), that we can use to recommend this approach to other property owners with similar problems. If you have photos or success stories, please send them to us at mcstoppp@co.marin.ca.us.
Good luck with your restoration projects!

MCSTOPPP would like to thank the California Regional Water Quality Control Board staff who provided input to this document and our web site: Marla Lafer and Anne Riley.

Marin County Stormwater Pollution Prevention Program: P. O. Box 4186 San Rafael, CA 94913-4186 Phone (415) 499-6528, Fax (415) 499-7221, e-mail: mcstoppp@co.marin.ca.us