Geoscience Reference
In-Depth Information
the entire RWB study area (Renard et al.
1997
). The RUSLE model is formulated as
an equation that includes six factors:
A
=
R
×
K
×
LS
×
C
×
P
(7.1)
Where
A
=
soil loss in tons per acre per year
R
=
rainfall factor
K
=
soil erodibility factor
L
=
slope length factor
S
=
slope gradient factor
C
=
cropping management factor
P
=
conservation practice factor
In the RWB, the RUSLE model was implemented in raster mode using a 30 m
cell.
7.4.1 Rainfall (R) Factor
The rainfall erosion factor provides a measure of the intensity of rainfall events. It is
calculated from the annual summation of rainfall energy in every storm (correlated
with raindrop size) times its maximum 30 min intensity. The
R
factors for Nebraska
were obtained from the USDA Natural Resources Conservation Service.
7.4.2 Soil Erodibility (K) Factor
The soil erodibility factor measures the soil's ability to resist being dislodged and
transported due to rainfall. The principal soil properties affecting the
K
factor are soil
texture (including the amount of fine sand in addition to the usual sand, silt, and clay
percentage used to describe soil texture), organic matter, structure and permeability
of the soil profile. Lower values of the
K
factor value indicate higher susceptibility
to erosion. The
K
factors were determined using SSURGO digital soils data.
7.4.3 Slope Length (LS) Factor
Slope length is defined as the horizontal distance from the origin of overland flow to
the point at which either the slope gradient decreases enough that deposition begins,
or runoff becomes concentrated in a defined channel (Wischmeier and Smith,
1965
).
The
LS
factor was derived from digital elevation data downloaded from the USGS
National Elevation Dataset.
LS
values were estimated using computed percent slope
