A diffusive model for evaluating thickness of bedload layer

The thickness of the bedload layer is a crucial parameter for evaluating sediment transport rates in open channel flow, but it is often determined empirically. Based on the concept of the hydrodynamic diffusion related to particle–particle interactions, an analytical model is proposed in this study for computing the thickness of the bedload layer. The coefficient of diffusion is assumed to be associated with the momentum transfer induced by the random particle motion and thus can be derived from the shear-induced particle stress. The analytical result shows that the ratio of the bedload thickness to the particle diameter depends on the dimensionless particle diameter and dimensionless bed shear stress. Differences are also examined between the present study and a few empirical formulas that are derived from experimental results for limited bed conditions.