GIS based soil loss assessment using RUSLE model
A=R ∗ K ∗ LS ∗ C ∗ P
Where,
A = annual soil loss (metric tons ha1yr1),
R = rainfall erosivity factor (MJ mm h1 ha1 yr1),
#K = soil erodibility factor (metric tons ha1 MJ–1 mm1),
LS = slope length and steepness factor (dimensionless)
C = land cover and management factor (dimensionless) and
factor (P = conservation practice dimensionless).
Estimation the soil erodibility K factor is depended on the soil properties such as
the distribution of the particles size,
the content of organic matter,
the structure of soil and
the soil permeability
The soil erodibility K factor is calculated at the range from 0.02 to 0.69.
The high clay soil has low K values ranging from 0.05 to 0.15
while the coarse texture sand soil also low factor K ranging from 0.05 to 0.2, this deferent values due to the resistance to detachment.
the main important factor of soil erodibility is the silt percentage content from whole topsoil content because the silt is easily detached and tend to crust and produce high rates of runoff.
So the soil has been high silt content are the most erodible of all soil.
Organic carbon content has a computable effect on soil erosion.
It decreases erodibility factor, reduces susceptibility to soil erosion, while increases infiltration rates of water through soil layers.
Due to high infiltration rater of water decreasing the runoff and erosion
BELOW FORMULA FOR CALCULATING K_FACTOR USING Arc GIS
#Fraction of Organic carbon= (1((0.0256* [OC___topso])/( [OC___topso] +Exp ( 3.72(2.95 * [OC___topso]) ))))
Fraction of silt= (1((0.7*(1 [sand___top]/100))/((1 [sand___top]/100) +Exp ( 5.51 +22.9 *(1 [sand___top]/100) ))))
Fraction of Clay= ( [silt___top] /( [clay___top]+ ([silt___top])))^0.3
Fraction of Sand = (0.2+(0.3*Exp ((0.256 * [sand___top] *(1 [silt___top]/100 )) )))
K_RUSEL= [F_orgC] * [F_sand] * [F_silt] * [F_clay] *0.1317