Model for Calculating Bed Load Transport of Sediment

Abstract

A bed load transport model based on the mechanics of sediment moving by saltation yields predicted values of bed load flux as a function of boundary shear stress, grain diameter and density. The parameters required to calculate bed load transport (particle velocity, bed load sediment concentration, and the height of the bed load layer) can all be determined from our model, which computes sequences of trajectories of individual saltating grains as well as the concentration of moving grains that the flow can support. The latter is related to the momentum the accelerating grains extract from the flow. Predicted curves of bed load transport vs. boundary shear stress agree well with transport data collected by Gilbert, Meyer‐Peter et al., and the Waterways Experimental Station; measured shear stress was corrected for pressure drag when bed forms were present. Comparison of predicted bed load transport with common bed load equations reveals considerable similarity among the relationships. The best agreement with the data is produced by relationships in which the transport rate vanishes as the shear stress approaches the critical Shields' number, as in our model and Yalin's equation.