Topographic controls of soil moisture distributions

Abstract

SUMMARY Soil moisture distributions on an instrumented hillslope at Slapton, South Devon, are compared to two topographic indices. The index a/s has been used in a computer runoff model to predict the location of zones of surface saturation on a hillslope (Beven & Kirkby, 1979), whilst the index plan curvature is derived from techniques of terrain analysis using gridded altitude data (Evans, 1980). Neither index is entirely satisfactory for predicting the changing pattern of soil moisture on the hillslope; a combined index proved most appropriate, but only at times of high soil wetness. The potential value of topographic indices as a basis for the prediction of soil moisture distributions and hillslope runoff is briefly discussed.