Modelling the impact of upstream reservoirs on the fluvial processes in the Aojiang River estuary

The reduction of runoff due to upstream reservoir impoundment can substantially change the fluvial processes in estuaries influenced by strong tidal currents. This paper presents a numerical simulation of such impacts using a coupled 1D‐2D model, which takes into account the combined effects of water flow and tidal currents on sediment transport. Simulation results for the Aojiang River estuary on the coast of East China Sea indicate that, in contrast to what usually happens in inland rivers, siltation will dominate the fluvial processes after the reservoir impoundment, and the rise of bed elevation will start upstream from the dam site before it develops rapidly downstream during the first few years of reservoir operation. The deposition will slow down gradually until a balanced state is reached. The re‐distribution of sediment deposits in the estuary is found to be non‐uniform in both longitudinal and lateral directions. Most sedimentation occurs between two river bends, rather than limited in the bend itself, and a non‐uniform distribution is also found over the cross‐section of the channel. Reduction of water depth at the port and in the navigation channel will be caused by sediment deposition there, which may affect the navigation conditions.