[Code of Federal Regulations]
[Title 7, Volume 6]
[Revised as of January 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 7CFR610.12]

[Page 350-351]
 
                          TITLE 7--AGRICULTURE
 
   CHAPTER VI--NATURAL RESOURCES CONSERVATION SERVICE, DEPARTMENT OF 
                               AGRICULTURE
 
PART 610--TECHNICAL ASSISTANCE--Table of Contents
 
              Subpart B--Soil Erosion Prediction Equations
 
Sec. 610.12  Equations for predicting soil loss due to water erosion.

    (a) The equation for predicting soil loss due to erosion for both 
the USLE and the RUSLE is A = R x K x LS x C x P. (For further 
information about USLE see the U.S. Department of Agriculture Handbook 
537, ``Predicting Rainfall Erosion Losses--A Guide to Conservation 
Planning,'' dated 1978. Copies of this document are available from the 
Natural Resources Conservation Service, P.O. Box 2890, Washington, DC 
20013. For further information about RUSLE see the U.S. Department of 
Agriculture Handbook 703, ``Predicting Soil Erosion by Water: A Guide to 
Conservation Planning with the Revised Universal Soil Loss Equation 
(RUSLE).'' Copies may be purchased from the National Technical 
Information Service, 5285 Port Royal Road, Springfield, VA 22161.)
    (b) The factors in the USLE equation are:
    (1) A is the estimation of average annual soil loss in tons per acre 
caused by sheet and rill erosion.
    (2) R is the rainfall erosivity factor. Accounts for the energy and 
intensity of rainstorms.
    (3) K is the soil erodibility factor. Measures the susceptibility of 
a soil to erode under a standard condition.
    (4) LS is the slope length and steepness factor. Accounts for the 
effect of length and steepness of slope on erosion.
    (5) C is the cover and management factor. Estimates the soil loss 
ratio for each of 4 or 5 crop stage periods throughout the year, 
accounting for the combined effect of all the interrelated cover and 
management variables.
    (6) P is the support practice factor. Accounts for the effect of 
conservation support practices, such as contouring, contour 
stripcropping, and terraces on soil erosion.
    (c) The factors in the RUSLE equation are defined as follows:
    (1) A is the estimation of average annual soil loss in tons per acre 
caused by sheet and rill erosion.
    (2) R is the rainfall erosivity factor. Accounts for the energy and 
intensity of rainstorms.
    (3) K is the soil erodibility factor. Measures the susceptibility of 
a soil to erode under a standard condition and adjusts it bi-monthly for 
the effects of freezing and thawing, and soil moisture.
    (4) LS is the slope length and steepness factor. Accounts for the 
effect of

[[Page 351]]

length and steepness of slope on erosion based on 4 tables reflecting 
the relationship of rill to interrill erosion.
    (5) C is the cover and management factor. Estimates the soil loss 
ratio at one-half month intervals throughout the year, accounting for 
the individual effects of prior land use, crop canopy, surface cover, 
surface roughness, and soil moisture.
    (6) P is the support practice factor. Accounts for the effect of 
conservation support practices, such as cross-slope farming, 
stripcropping, buffer strips, and terraces on soil erosion.