Dune Profile Evolution due to Overwash

A numerical model based on a new sediment transport formula is presented to predict overwashed dune profile evolution. This model can also compute the cross-shore variation of the depth-averaged suspend sediment concentration. The computed sediment concentrations are high over the dune and low below the still water level. The computed profile evolution and sediment transport rate are compared with the representative data from small-scale dune overwash experiments. This model can reproduce the overall dune profile evolution and cross-shore sediment trasport rate at least qualitatively but tends to underestimate the erosion of the dune crest due to the error of an empirical formula for overtopping rates. To predict overtopping rates more accurately, a probablistic model is developed together with the time-averaged wave statistics predicted by the nonlinear time-averaged wave model CSHORE. The predicted overtopping rates are in fair agreement with the measured overtoping rates.