Numerical Simulation of the Morphodynamics in Rills

The objective of this research project was to develop a 1-dimensional hydrodynamic/ sediment transport model to simulate flows and sediment transport in rills. The present paper focuses on only the hydrodynamic component of this research. There are many challenging issues that need to be addressed regarding flow in rills. The most important issue is that flow under certain conditions can become transcritical. In this case, step and pool sequences become ubiquitous features of the geomorphology of a rill. In order to address this issue an enhanced TVD-MacCormack scheme was employed. The sensitivity and validity of the code, named 3ST1D (steep stream sediment transport 1-D), was tested for two cases. Because the emphasis here was on the hydrodynamic component of the model, the bed was fixed for the two test case scenario considered here. The model results satisfied the continuity equation for the stream reaches considered and provided and adequate mapping of the water surface profile and the depth averaged velocities.