ABSTRACT
The equilibrium bed load formulation of our dune evolution model has previously been replaced with separate models for the sediment pick-up and deposition processes. Using this approach enabled the modelling of the transition from dunes to the upper-stage plane bed. By increasing the step length (the average distance travelled by sediment particles) manually this lag increases and the dunes become smoother and lower, until they are so smooth that flow separation no longer occurs and finally the dunes wash out.
In the current version of the model the step length changes automatically. This lets the step length increase with increasing flow strength, in line with previous experimental results. This is tested with a synthetic data set where plane bed conditions were reached. With increasing discharge the flow strength increases, which leads to higher step length and which leads to the washing out of dunes.
