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Major Categories of Erosion
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Wind erosion is common on agricultural lands and large construction sites. Soil that is piled and left unprotected is especially vulnerable to wind erosion. In some areas, more soil is lost from wind erosion than from water erosion. The Natural Resources Conservation Service, or NRCS, recently estimated that wind erosion is responsible for 42% of the erosion damage occurring in Michigan annually. The amount of soil lost from wind erosion may not be realized because the soil particles disperse over a large area where they are not visible. In urbanizing areas, the most damaging aspect of wind erosion is dust. It creates traffic hazards, adds to cleaning costs, is abrasive to plant tissue and blights the appearance of structures and surfaces.
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Raindrop erosion is a result of rain splash - the direct impact of falling drops of rain on soil particles. The raindrop dislodges soil particles, making them more susceptible to movement by overland water flow. The loosened particles that are not washed away can form a muddy slick that clogs pores in the ground surface. The sealed surface further reduces inflitration and increase runoff. The magnitude of soil loss resulting from rain splash can best be seen on a gravelly or stony soil.
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Sheet erosion is the removal of a uniform layer of soil from the land surface as a result of rainsplash or runoff. The water moves as broad sheets over the land and is not confined to small depressions in the soil.
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Rill erosion is the development of small grooves spaced fairly uniformly along the slope. It is caused when runoff is heavy and water concentrates in rivulets. Individual rills range in depth and width up to several inches and reflect a tremendous loss of soil. If rilling is not corrected immediately, it will develop into gullies.
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Channel erosion occurs in both intermittent and permanent waterways and streams. Three causes of channel erosion are: increased runoff, removal of natural vegetation along the waterway and channel alterations resulting from construction activities. It includes both stream bank and stream bed erosion.
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