Conditions That Cause Erosion
Erosion is a problem endemic to semi-arid lands. In more humid climates, vegetation holds soil in place, limiting the amount of material that can be carried down hill slopes and into rivers and streams. In extreme arid climates there is insufficient flow to transport sediment. It is in semi-arid lands - where there is incomplete vegetation cover yet sufficient water to move surface materials, especially during and after intense rain storms - that maximum sediment is carried downstream. Working solely from the general relationship between precipitation and
sediment production, the simplest of potential erosion
maps can be made. This map of erosion potential is based on annual precipitation
data from Oregon State University
http://www.ocs.orst.edu/prism/prism_new.html, which has been combined with a
general relationship between annual precipitation and
basin sediment production. It ignores many important factors that control sediment production and
transport, such as soil characteristics, actual vegetation cover, slope, and rates of rainfall
(a few large precipitation events move more sediment than many small events having the same
annual total).
Next: A high-erosion location - the Rio Puerco basin of New Mexico
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