The Effect of Sediment Transport Models on Simulating River Dune Dynamics

River dunes, dynamic bedforms in the river bed, limit navigable depths during low flows and increase bed roughness. To predict the navigable depth or where maintenance dredging is needed, a numerical dune development model can be a powerful tool. To study the effect of sediment transport on dune shape and propagation, four different sediment transport models were applied in an existing dune development model. Each sediment transport model was able to simulate dune propagation, while only sediment transport models based on the shear stress reshaped the river dunes. The tested sediment transport models can simulate dune celerity similar to observations and realistic, though different, dune shapes for low and median discharges. Implementation of a gravitational bed slope effect combined with a critical shear stress results in low angle dunes, which are representative for river dunes during low river flows. Sediment transport models with spatial relaxation, also result in low angle dunes. However, the relaxation parameters need to be redefined for low flow situation to prevent transition to upper stage plane bed at too low flow velocities. Further analysis of the resulting dune shapes shows that the sediment transport model determines the dune shape in terms of slope angles, while the dune height is related to the total transport capacity. River dunes are wave shaped sandy bedforms in the river bed which move in the direction of the flow. These sandy waves decrease the water depth for ships. Therefore, in rivers with a lot of shipping, the peaks of these river dunes are dredged away. Models of these dunes can help to plan these dredging interventions better. In this study, we have simulated these river dunes with four different models of calculating the sand transport that is responsible for the formation and moving the dunes. We found that all models were able to reproduce the propagation of the dunes in the field during normal to low flow conditions but resulted in different shapes of the dunes. When the effect of gravity is included, such that the sand needs more force to move up slope than down slope, the back side of the dunes become less steep which is observed in many rivers. Taking suspension of the sand from the bed into account, also results in less steep dunes. However, the height then decreases instead of increases with increasing water depth. Higher dunes with larger water depths can be achieved by increasing the force needed to make the sand move