Model for Surface Erosion of Cohesive Soils

A model is proposed for the surface erosion of cohesive soils on the basis of the physical interaction of turbulent bursts with the sediment bed. More specifically, the model deals with floc-by-floc erosion, appropriate for conditions of relatively low shear stress. The role of turbulent burst structures on the entrainment of particles has been well-established. A number of models have been developed for soil erosion on the basis of the interaction of turbulent burst structures with sediment beds in open-channel flow. What has been lacking in this type of model and in other models for the surface erosion of cohesive soils in general is an understanding of the aggregate size distribution in cohesive sediment beds. In this study, a relationship is developed for the aggregate size distribution as a function of the bed bulk density and fractal dimension of aggregates in soils, and this relationship is incorporated in a turbulent burst erosion model. The model is applied to experimental data, and the resulting model parameters are found to compare closely to the physical values reported in the literature.