A SIMPLIFIED HILLSLOPE EROSION MODEL WITH VEGETATION ELEMENTS FOR PRACTICAL APPLICATIONS

Abstract

Soil and water conservation practices are increasingly being considered for curbing non-point source pollution from agricultural land. Several studies have demonstrated that stream power is a simple and good predictor of soil detachment and transport and can be used to predict the effect of soil and water conservation practices on soil loss. Our objective was, therefore, to develop a simple water erosion simulation model that is physically based on stream power, handles vegetation in terms of contact cover, and considers the settling velocity characteristics of the eroding sediment. The model assumes that rill flow can occur on hillslope segments with net erosion, but on segments with net deposition sheet flow is assumed. Input parameters include the depositability of the soil, rill shape, rill density, net precipitation, and an empirical power function describing the decrease of sediment concentration with vegetative cover increase. The model was evaluated by comparison of predicted and observed relationships between sediment concentration, slope, and vegetative residue cover in two experimental studies using simulated rainfall: one that involved erosion plots with various uniform slopes and levels of vegetative cover, and another that involved the observation of soil movement on mechanically shaped concave, uniform, and convex slopes with negligible vegetation. Without calibration, the model appeared to represent soil erosion relationships observed in these studies and is simple enough to be included in grid-based variable source hydrology models.