Enhanced flushing of sediment deposits in the backwater reach of reservoirs

摘要

In hydropower and water-supply reservoirs sedimentation processes do not only occur in the storage area, but can extend far upstream along the backwater reach. This leads to undesired impacts such as a rise of flood levels. Using the erosive force of floods part of these deposits can be flushed downstream to the reservoir. Efficiency of flushing operations can be increased by mechanically pushing the deposits from bars and banks into the flushing channel. During flushing these displaced sediments propagate downstream as free bars in a combined one-dimensional (1D) and two-dimensional (2D) way. Analytical analysis shows that the ID celerity exceeds that of 2D propagation significantly. Simulations with a 2D computational model, including sediment sorting effects and unsteadiness of flow, are required for more profound analysis. Application of a 2D computational model to flushing operations in Sakuma Reservoir in Japan shows that these effects contribute significantly to the efficacy of flushing.