Modelling morphodynamic evolution of river dunes

River dunes influence the hydraulic roughness and water levels in rivers. Especially during floods the interplay between dunes and the flow field could become significant. Therefore, it is desired to forecast the dimensions of dunes during such extreme and unsteady flood events. At present it is not yet feasible to predict the dimensions of dunes by computing the flow and sediment transport in full detail for operational spatial and temporal scales. In this paper, we present a morphodynamic model that simulates dune development, without computing all details in the flow field. The flow model is based on the 2D-vertical hydrostatic equations, with a constant eddy viscosity over depth. Flow separation and the sediment transport behaviour in the flow separation zone are included in a parameterized way. Results of the morphodynamic model using steady flow conditions, are in general agreement with flume experiments. A next step in the research will be to use forecasted dune dimensions for hydraulic roughness predictions.

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