3.3 Soil loss assessment
Soil loss assessment for the UNW was based on the USLE established by (Wischmeier et al.,1987) and the integration of the USLE factors was digitally performed using GIS. (Fig 3.) The USLE is presented in the form: A = R x K x LS x C x Where A is soil loss
R is the rainfall erosivity index
K is the soil erodibility factor
LS is the slope length and slope factor
C is the crop management factor
P is the conservation practice factor
This equation is widely accepted worldwide for erosion prediction that based on empirical research and field experiments. These factors are varied from place to place depending on the numerical values for each of the factors or variables. Determination of the various variables is described here below. Each variable is considered as a thematic layer in the GIS database to be used in the modeling process.