Soil erosion - Soil Essentials: Managing Your Farm's Primary Asset - page 99

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Soil erosion
Soil erosion is a natural process, and much of the earth's landscape is formed from
the action of wind and water eroding mountains and depositing the residue in
valleys, creating more or less level plains. This oversimplified statement, however,
does espouse the principle involved in erosion, which is that by the application of
energy provided by wind and f lowing water and the effect of gravity, material is
moved to a lower state of kinetic energy and deposited at rest, at least for the time
being. This process is never really completed, and with the effect of tectonic plate
movements constantly adjusting slopes, wind and water will always try to move
material from a higher to a lower level. The intervention of people into this natural
system can, and does, lead to usually localised soil erosion that may be quite
severe, causing high economic cost to the community and much inconvenience.
Erosion by water, or fluvial erosion
Water is very effective at eroding soil if the conditions are right, and names have
been given to the different effects resulting from the erosion.
(a) Sheet erosion (Figure 27 on p. 109)
This occurs when significant areas of the soil surface have been removed and
washed down slope. This is very damaging because the most fertile part of the soil
has been removed, leaving an area without plant cover that will shed nearly all of
any future rain events leading to more erosion down slope. It is also difficult and
expensive to revegetate as part of the rehabilitation process.