Soil Creep and the Development of Hillside Slopes

A mathematical theory of erosion on soil-covered slopes is proposed. The model is based on the hypothesis that soil particles subject to the influence of forces normally operative within soil covers execute randomly directed movements of minute extent. The distribution and characteristics of the pore space of the soil aggregate exert a restrictive influence and determine the nature and magnitude of the particle displacements. Macroscopically, the motion of the soil particles induces a rate of flow on the hillside slope proportional to the surface gradient. The model is used to supply a series of illustrations of the humid cycle of erosion.