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:: Home > Watersheds > Vegetation & Topsoil > Erosion

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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. 

No buffer along stream...

Note: Logging practices like this are counter
to the Oregon Forest Practices Act

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.