CPESC Questions and Answers Verified by
Experts
R factors Erodability of rainfall
Base on Isoerodant Maps
Units; Hundreds f*tonF*in/(ac*H*yr)
K: soil erodibility factor Rate of soil loss per rainfall erosion index unit
[Tons x acres x h/(hundreds of acres Rt-tons x in)
Conceptually, it is the ease at which soil is detached by a rain drop impact for an area.
K-Factors and soil horizons K factors are determined for A, B and C horizons in a given
area. The A horizon number is used for normal conditions, the B horizon number is used for
construction.
Determining K for a given location The K can be given by a mapped unit or estimated
from a monogram based on a textural analysis of a soil which includes, texture, soil structure,
permeability and percent organic material.
, Slope Length - L Length of slope= horizontal distance from the initiation of the slope
until either flow is reduced enough to begin deposition or channelization of flow begins.
Slope Lengths typically used in the RUSLE Equation 400' to 1000' is typical
Average erosion for slope lengths equation L=(gama x 72.6)^m
Where 72.6 is the RUSLE unit plot length in feet
^m = a variable slope-length exponent.
Gama = slope length
^m Slope length component ^m=beta/(1+beta)
Where:
Beta= rill erosion to inter-rill erosion factor
Rill - inter-rill erosion equation or Beta equation Beta = (sin theta/0896/(3.0 sin
theta^.08+0.56))
Angle is the slope angle
Experts
R factors Erodability of rainfall
Base on Isoerodant Maps
Units; Hundreds f*tonF*in/(ac*H*yr)
K: soil erodibility factor Rate of soil loss per rainfall erosion index unit
[Tons x acres x h/(hundreds of acres Rt-tons x in)
Conceptually, it is the ease at which soil is detached by a rain drop impact for an area.
K-Factors and soil horizons K factors are determined for A, B and C horizons in a given
area. The A horizon number is used for normal conditions, the B horizon number is used for
construction.
Determining K for a given location The K can be given by a mapped unit or estimated
from a monogram based on a textural analysis of a soil which includes, texture, soil structure,
permeability and percent organic material.
, Slope Length - L Length of slope= horizontal distance from the initiation of the slope
until either flow is reduced enough to begin deposition or channelization of flow begins.
Slope Lengths typically used in the RUSLE Equation 400' to 1000' is typical
Average erosion for slope lengths equation L=(gama x 72.6)^m
Where 72.6 is the RUSLE unit plot length in feet
^m = a variable slope-length exponent.
Gama = slope length
^m Slope length component ^m=beta/(1+beta)
Where:
Beta= rill erosion to inter-rill erosion factor
Rill - inter-rill erosion equation or Beta equation Beta = (sin theta/0896/(3.0 sin
theta^.08+0.56))
Angle is the slope angle
