Estimating Soil Loss

Equations have been developed to estimate the amount of soil loss to water and wind erosion. These are called the Universal Soil Loss Equation (USLE) for water and the wind erosion equation (WEQ) for wind. The USLE for water has been updated and the new version is called the Revised Universal Soil Loss Equation

(RUSLE). Another version, RUSLE2, is a computer program. The WEQ is a computer program that can be utilized through a NRCS office. The USLE for water is:

where A = Predicted average annual soil loss (T/ac/yr); R = Rainfall factor; K = Soil erodibility factor; L = Slope length factor; S = Slope gradient factor; C = Cropping management factor; P = Erosion control practice factor.

For this discussion, several of these factors will be combined to give the following equation:

The USLE assigns numerical values to the factors that influence water erosion. Therefore, the accuracy of the calculated soil loss is only as good as the numerical values representing these factors. The tables and graph included here are generalized to show the influence of the different factors and to aide in the understanding of the equation. These values should not be used for the design of soil conservation structures or for estimating soil loss for government programs. More accurate values for specific areas can be obtained from the NRCS or similar agency.

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