Soil
Erosion and Sedimentation
Soil erosion is one form of soil degradation along with soil compaction, low organic matter, poor internal drainage, and soil acidity problems. Soil erosion is a naturally occurring process on all land. The agents of soil erosion are water and wind, each contributing a significant amount of soil loss each year. Soil erosion may be a slow process that continues relatively unnoticed, or it may occur at an alarming rate causing serious loss of topsoil.
The rate and magnitude of soil erosion by water are controlled by a number of factors, including rainfall intensity and runoff. The impact of raindrops on the soil surface can break down soil aggregates and disperse the aggregate material (Figure 50). Raindrop splash and runoff water can easily remove lighter aggregate materials such as very fine sand, silt, clay, and organic matter. Soil movement by rainfall (raindrop splash) is usually greatest and most noticeable during short-duration, high-intensity thunderstorms.
Figure 50: Impact of a single raindrop (NRCS)
Another form of erosion is sheet and rill erosion - the removal of layers of soil from the land surface by the actions of rainfall and runoff, the first step in water erosion. Sheet and rill erosion leads to the formation of gullies (Figure 51). Bank erosion is another type of erosion (Figure 52).
