Worldwide large dams are being discouraged on environmental, social or political grounds. Small-to-medium-sized cascade reservoirs with the hydropower projects are being preferred. However, the flushing of sediments by drawing down the reservoir is of immense interest to increase the useful life of a reservoir. In our research, we applied a depth-averaged, Godunov type model to simulate the 2D flushing. The solution technique employed possesses shock-capturing property and is especially suitable to dam-break accompanied by intense sediment transport phenomenon. The retrogressive erosion and flushing out a large volume of sediment in a very small time interval with creation of transitory flow conditions was tackled by this technique. We applied the model to two experiments; the first was a physical model study, while the second case pertained to a laboratory flume. The model validation was made through the bed topography change and the computation of the flushing efficiency. The model was in good agreement with the bed changes demonstrating its suitability to reproduce the phenomenon of retrogressive channel as well as lateral erosion. The accompanying sensitivity analysis focused on evaluating the influence of a number of parameters critical to a successful flushing simulation exercise.