[Code of Federal Regulations]
[Title 7, Volume 6]
[Revised as of January 1, 2008]
From the U.S. Government Printing Office via GPO Access
[CITE: 7CFR610.13]

[Page 407]
 
                          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. 610.13  Equations for predicting soil loss due to wind erosion.

    (a) The equation for predicting soil loss due to wind in the Wind 
Erosion Equation (WEQ) is E = f(IKCLV). (For further information on WEQ 
see the paper by N.P. Woodruff and F.H. Siddaway, 1965. ``A Wind Erosion 
Equation,'' Soil Science Society of America Proceedings, Vol. 29, No. 5, 
pages 602-608, which is available from the American Society of Agronomy, 
Madison, Wisconsin. In addition, the use of the WEQ in NRCS is explained 
in the Natural Resources Conservation Service (NRCS) National Agronomy 
Manual, 190-V-NAM, second ed., Part 502, March, 1988, which is available 
from the NRCS, P.O. Box 2890, Washington, DC 20013.)
    (b) [Reserved]
    (c) The factors in the WEQ equation are defined as follows:
    (1) E is the estimation of the average annual soil loss in tons per 
acre.
    (2) f indicates the equation includes functional relationships that 
are not straight-line mathematical calculations.
    (3) I is the soil erodibility index. It is the potential for soil 
loss from a wide, level, unsheltered, isolated field with a bare, 
smooth, loose and uncrusted surface. Soil erodibility is based on soil 
surface texture, calcium carbonate content, and percent day.
    (4) K is the ridge roughness factor. It is a measure of the effect 
of ridges formed by tillage and planting implements on wind erosion. The 
ridge roughness is based on ridge spacing, height, and erosive wind 
directions in relation to the ridge direction
    (5) C is the climatic factor. It is a measure of the erosive 
potential of the wind speed and surface moisture at a given location 
compared with the same factors at Garden City, Kansas. The annual 
climatic factor at Garden City is arbitrarily set at 100. All climatic 
factor values are expressed as a percentage of that at Garden City.
    (6) L is the unsheltered distance. It is the unsheltered distance 
across an erodible field, measured along the prevailing wind erosion 
direction. This distance is measured beginning at a stable border on the 
upwind side and continuing downward to the nonerodible or stable area, 
or to the downwind edge of the area being evaluated.
    (7) V is the vegetative cover factor. It accounts for the kind, 
amount, and orientation of growing plants or plant residue on the soil 
surface.