A long flume study of the dynamic factors affecting the resistance of a loamy soil to concentrated flow erosion

Experiments were carried out in a 20 m long flume to assess the variation of the runoff erosion resistance of a loamy soil as a function of initial moisture content and compaction. The results of seven experimental runs show that the runoff erosion resistance of a loamy material is extremely sensitive to variations in initial moisture content and, to a somewhat lesser extent, in bulk density. The very low resistance to runoff erosion of initially dry material is explained by structural changes which take place at the time of wetting: slaking and microfissuration cause a considerable decrease of the soil's shear strength and therefore of its resistance to runoff erosion. A first analysis shows that, during a given rainfall event, initially dry soils may well show significantly more erosion than initially wet soils, despite the increase of infiltration with decreasing initial moisture content.