1996-02-06_REVISION - M1977493 (14)

Home Browse Search

VWhat Is It Stream bank stabilization is used to prevent stream bank erosion from high velocities and quantities of storm water runoff. Typical methods include the following: • Riprap-Large angular stones placed along the stream bank or lake • Gabion-Rock-filled wire cages that are used to create a new stream bank • Reinforced Concrete-Concrete bulkheads and retaining walls.that replace natural stream banks and create a nonerosive surface • Log Cribbing-Retaining walls built of logs to anchor the soils against erosive forces. Usually built on the outside of stream bends • Grid Pavers-Precast or poured-in-place concrete units that are placed along stream banks to stabilize the stream bank and create open spaces where vegetation can be established • Asphalt-Asphalt paving that is placed along the natural stream bank to create a nonerosive surface. • When and Where to Use It Stream bank stabilization is used where vegetative stabilization practices are not practical and where the stream banks are subject to heavy erosion from increased flows or disturbance during construction. Stabilization should occur before any land development in the watershed area. Stabilization can also be retrofitted when erosion of a stream bank occurs. What to Consider Stream bank stabilization structures should be planned and designed by a professional engineer licensed in the State where the site is located. Applicable Federal, State, and local requirements should be followed, including Clean Water Act Section 404 regulations. An important design feature of stream bank stabilization methods is the foundation of the structure; the potential for the stream to erode the sides and bottom of the channel should be considered to make sure the stabilization measure will be supported properly. Structures can be designed to protect and improve natural wildlife habitats; for example, log structures and grid pavers can be designed to keep vegetation. Only pressure-treated wood should be used in log structures. Permanent structures should be designed to handle expected flood conditions. A well-designed layer of stone pan be used in many ways and in many locations to control erosion and sedimentation. Riprap -rotects soil from erosion and is often used on steep slopes built with fill materials that are subject o harsh weather or seepage. Riprap can also be used for flow channel liners, inlet and outlet r0tection at culverts, stream bank protection, and protection of shore lines subject to wave action. is used where water is turbulent and fast flowing and where soil may erode under the design • ow conditions. It is used to expose the water to air as well as to reduce water energy. Riprap :.d gabion (wire mesh cages filled with rock) are usually placed over a filter blanket (i.e., a gravel layer or filter cloth). Riprap is either a uniform size or graded (different sizes) and is usually applied in an even layer throughout the stream. Reinforced. concrete structures may require positive 4-57