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Erosion is a natural
process of weathering in which soil and sediments are
moved by wind or water. Water, in particular,
has the power to move vast amounts of soil and sediments,
potentially causing loss of important topsoil and damage
to streams and aquatic habitats.
All ecosystems have natural ways of decreasing the
effect of erosion. The roots of trees and other
vegetation in the watershed help to hold the soil
in place during rainfall or flooding. Vegetation
around streams in particular helps to strain out sediments
and pollution before they get into streams where they
can damage stream structure and destroy or damage
fish habitats.
Boulders, fallen tree trunks, and other woody debris
help to filter sediments that do make it into the
stream.
Damage to large areas of vegetation in the watershed
and particularly damage to areas around streams, or
riparian
areas, decreases the efficiency of the system
to regulate and control erosion. Once these barriers
to erosion are removed, the effects of erosion can
become more and more severe, even hindering the regrowth
of trees and other vegetation as topsoils are removed
and the ground becomes more unstable.
Note:
Logging practices like this are counter
to the Oregon Forest Practices Act
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The
major causes of erosion appear to be runoff from roads
and skid trails, and landslides.
Cutting which occurs too close to streams can deposit
large amounts of silt and sediment into the watershed
system. Timber harvesting in Oregon today leaves
a wide buffers around streams, keeping a protective
layer of vegetation to filter out sediments,
shade the stream from warming rays of sunlight, and
preserve habitat for wildlife. Not only does this make
good sense, but the
Oregon Forest Practices Act mandates this practice.
Click here to see a
diagram of water pathways in a managed forest.
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©2005 Oregon Forest Resources Institute. All Rights Reserved.