Stream Care Guide:

Management Tips for Streamside Property Owners

Addressing Streambank Problems

Streams are constantly reshaping their routes through a process of active scouring on outside curves and deposition of sediment bars on inside curves. The natural tendency for the stream course to change or meander may lead to problems on your streambank property.

Increased runoff volumes due to urbanization in the watershed may aggravate this natural process, creating erosion problems on banks that used to be stable. In addition, direct disturbance of the streambank through construction or stripping of the natural vegetation may have occurred, leaving the bank in an unstable condition.

In all of these cases, you may need to stabilize your bank (see illustration below) to protect your property and the stream. Unstable banks can lead to extensive bank failures that result in property loss and add large volumes of sediment to the stream system.

However, streambank stabilization is usually not a simple matter. Changes in stream flow due to stabilization work can occur and are difficult to predict. Actions taken to protect your bank may have unforeseen consequences downstream, with the result that you may simply pass your erosion problem on to your neighbor. For this reason, County ordinances require a permit for any work done to your streambank or stream bed, and you should consult a qualified professional in planning any streambank project.

Streambank stabilization usually involves one or a combination of the following activities:

• Regrading and revegetating the streambank to eliminate overhangs and attain a more stable slope
• Armoring the bank to control further erosion (see illustration below)
• Occasionally deflecting the water flow away from vulnerable sites. [Remember though, for every action, there's a reaction.]

Streambank Stabilization and Revegetation Strategies

(Click image for larger view)

Armoring the bank takes a variety of forms, some of them structural and most incorporating revegetation as a necessary component. Several of these are listed below:

• Stone riprap consists of large rocks that are dumped or hand-placed along an appropriately sloped bank and often interplanted with vegetation.
• Gabions are large wire baskets filled with rock and wired together to form a somewhat flexible, permeable barrier useful where banks are steep or space is at a premium.
• Retaining walls or revetments of redwood or other materials are engineered for locations where dwellings abut the stream or spacing along the bank is scarce.
• Log or concrete crib walls are constructed of a rectangular framework of logs or precast concrete members keyed into the bank and filled with soil or cobble in which vegetation can be planted.
• Post and wire revetments consist, essentially, of a wire fence constructed at the bank and back-filled with cobble, which can then be planted.
• Vegetation alone is sometimes used to armor streambanks. Live cuttings of willow driven into the bank to root or bundles of live cuttings secured to the bank are two among many possible vegetation schemes.

All of these armoring techniques require specialized knowledge to apply and should never be attempted without professional help. Again, the soundest advice is to seek advice.

If no streambank damage has yet occurred, but riparian vegetation has been depleted or removed, you may be able to reestablish or augment this vegetation on your own. Consult the local office of the Placer County Resource Conservation District or the Natural Resources Conservation Service for assistance in determining which plants to use on your particular site and how to care for them.

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