Topography is a factor that directly affects soil erosion.
The LS factor reflects the effect of slope length and slope gradient on erosion.
A DEMbased procedure developed in the USA (Hickey, 2000; Van Remortel et al., 2001) was employed to resolve the difficulties for the estimation of the LS factor on a regional scale.
The algorithms of this procedure use the raster grid accumulation and maximum downhill slope
methods. However, the LS factor algorithms were limited to slopes ≤18% because the data used to develop RUSLE only included slopes up to 18% (McCool et al., 1989).
Liu et al. (1994) fixed the formula using soil loss data from natural runoff plots ranging from 9% to 55% slopes and reported that soil loss was linearly related to the sine of the slope angle.
Liu et al. (2000) reported that for an increase in slope steepness from 20 to 40 and 60%, the slope length exponent did not change.
Therefore, this study used the formula for L defined and developed by McCool et al. (1997), and the equations for slope gradient N18% formulated by Liu et al. (1994) were incorporated: