U.S. Fish & Wildlife Service Low Hazard Dams - Association of State ...

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U.S. Fish & Wildlife Service Low Hazard Dams - Association of State ...

STANDING OPERATING PROCEDURESbe spread out in thin layers (sheet flow) on the grassy cover. When embankment sod is inpoor condition or flows are concentrated at any location, the resulting erosion will leaverills and gullies in the embankment slope. Look for such areas and be aware of theproblems that may develop. Eroded areas must be promptly repaired to prevent moreserious damage to the embankment. Rills and gullies should be filled with suitable soil(the upper four inches should be topsoil, if possible), compacted, and then seeded. Thelocal Natural Resources Conservation Service office can help select the types of grass touse for protecting dam surfaces. Erosion in large gullies can be slowed by stacking balesof hay or straw across the gully until permanent repairs can be made.Figure 5-15: Sparse Vegetation and Erosion of Downstream Embankment SlopeNot only should eroded areas be repaired, but the cause of the erosion should be found toprevent a continuing maintenance problem. Erosion might be caused or aggravated byimproper drainage, settlement, pedestrian traffic, animal burrows, or other factors. Thecause of the erosion will have a direct bearing on the type of repair needed.Paths due to pedestrian, livestock, or vehicular traffic (two- and four-wheeled) are aproblem on many embankments. If a path has become established, vegetation will notprovide adequate protection and more durable cover will be required unless traffic iseliminated. Small stones, asphalt, or concrete may be used effectively to cover footpaths.All vehicular traffic, except for maintenance, should be prohibited from the dam.Erosion is also common at the point where an embankment and the concrete walls of aspillway or other structure meet. Poor compaction adjacent to such a wall during5-26Revision No. 0October 2008

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