Computing RUSLE3D using GIS

The method is described here, we recall only the basic equations:
E = R K LS C P
where E  is the average soil loss, R is the rainfall intensity, K is the soil, C is the cover, P is the prevention practices and LS is the topographic factor:
LS(r)  =  (m+1)  [ A(r) / a0 ]m  [ sin b(r) / b0 ]n
where A is upslope contributing area per unit contour width, b is the slope, a0  = 22.1m,  b0 = 0.09, m is 0.4-0.6 and n=1-1.3 or use more complex equations (LINK). The techniques used to compute the necessary parameters in GIS are in the following sections: DEM (upslope area, slope), Soils (K-factor), Rainfall (R-factor), Landcover (C and P factors).

The model is simple enough to be run as a sequence of commands provided here for

See also:
Example Avenue script for running the model.

We use the analysis at 10m resolution as an example in this section of the tutorial (click on the highlighted text to see the related images).

GRASS GIS

Given data: 
raster: elevation, 
K, C, (P)
constants: R=220, grid resolution=10m
Computation 
1. r.flow elevation dsout=flowacc
2. r.slope.aspect  elevation slope=slope
3. r.mapcalc
      lsfac=1.6*exp(flowacc*resolution/22.1,0.6)*exp(sin(slope)/0.09,1.3)
      soilloss=R*K*C*P*lsfac
4. r.colors soilloss co=rules (click here to see suggested rules, you can also copy the colortable...)
5. r.reclass soilloss ....
6. nviz -q (create 3D map)
7. d.dm (view 2d map)
8. p.ps (create printable map)
9. r.report soilloss.class (print summaries)
10. r.sum (total soil loss)
 



Notes and Trouble shooting (what to do if the results looks weird)
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Helena Mitasova, Lubos Mitas, University of Illinois at Urbana-Champaign and North Carolina State University