The National Soil Erosion Research Laboratory
Today's society often times focuses on sensational news and short term crises which surround us. By constantly dwelling in the present, many people ignore the long term problems that compound slowly until they reach a crisis level, and may then be very difficult or impossible to correct. Soil erosion is a continuing long term problem.
Natural processes such as the production of soil occur at an alarmingly slower rate than soil can be lost. It is estimated that over 3 billion metric tons of soil are eroded off of our fields and pastures each year by water erosion alone. The main variables affecting water erosion are precipitation and surface runoff. Raindrops, the most common form of precipitation, can be very destructive when they strike bare soil. With impacts of over 20 mph, raindrops splash grains of soil into the air and wash out seeds. Overland flow, or surface runoff, then carries away the detached soil, and may detach additional soils and then sediment which can be deposited elsewhere.
Sheet and interrill erosion are mainly caused by rainfall. However, some of the more severe erosion problems such as rill erosion, channel erosion, and gully erosion all result from concentrated overland flow. Other types of erosion by water include landslides.
When fertile soil is removed, along with it go the nutrients and organic matter which are significant to the growth of plants and crops. Without this soil, plants and crops will not survive. Thus, it's easy to see that a reduction in this protective cover will only expose more soil to the detrimental effects of wind and water erosion. In addition to the use of conservation tillage to control sheet and rill erosion, there are several other control practices which are available. In particular, vegetated waterways can be very important in small watersheds in which water flows from hillslopes concentrate in natural drainageways, and can cause significant gullying.
The Water Erosion Prediction Project (WEPP) is a computer program that predicts soil erosion by water at the field scale.
Soil erosion can also be caused by wind. For more information on wind erosion and the WEPS model see the USDA-ARS Wind Erosion Research Laboratory website.