Flow related topographic parameters needed for hillslope erosion modeling are computed by flow tracing program r.flow, the combined grid-vector flowtracing algorithm used in this program is described in Mitasova and Hofierka 1993 and Mitasova, Mitas et al. 1995). Upslope flowlines shows terrain with flowlines generated uphill and flow path length draped as color.
Important terrain characteristics for soil erosion are slope gradient, length, aspect and shape. For example, land with a high hill slope will perpetuate the process of rainwater or runoff saturation in the area, particularly due to the faster movement of the water down a slope.