Vegetative Cover
"Vegetative cover maintained on the downstream faces of embankment dams provides some protection against normal weathering effects and rill development due to rainfall. During small overtopping flows of short duration, vegetation can also provide protection against the initiation of concentrated erosion that can otherwise lead to headcut development and dam breach, and may allow for the planned use of the embankment to convey a portion of a flood hydrograph. For larger flow rates and/or for longer overtopping durations, vegetation alone may not fully protect against failure, but vegetation may delay breaching sufficiently to permit evacuation of downstream areas. Vegetative cover is most viable as an overtopping protection method for small dams in humid climates that receive sufficient moisture to establish relatively dense, uniform turf grasses. Good maintenance of the grass cover is essential to achieve significant protective benefits. Grass needs to be cut relatively short on the downstream face of an embankment dam (between 2 and 6 inches) to facilitate visual inspections and to promote uniformity of growth. Vegetative cover is generally not suitable for very steep embankments because of the difficulty of mowing and other maintenance required to achieve a uniform cover. Installation costs for vegetation are often lower than for other forms of overtopping protection, but maintenance costs can be higher. An advantage of vegetative overtopping protection systems, where applicable for use, is the potential for unlimited sustainability via annual growth and renewal, if proper maintenance can be achieved." [1]
"Vegetation provides protection to an embankment in two ways:
- Protection of the soil surface by reduction of velocities and shear stresses at the embankment boundary as a result of the coverage provided by stems and leaves that lay down in the flow and blanket the surface.
- Reinforcement of the underlying soil due to the presence of plant roots." [1]
"The reinforcement aspect may be further improved by the use of turf reinforcement mats that can improve root mass continuity following full vegetation establishment." [1]
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