Fluvial sedimentation of the permanent backwater zone in the Three Gorges Reservoir, China

The amount of fine sediment deposition in some river reaches in the permanent backwater zone of the Three Gorges Reservoir has exceeded predictions made during the design period of the reservoir. In this study, a series of laboratory experiments were conducted on field samples of fine sediment from the Zhongxian reach, a typical reach in the permanent backwater region of the Three Gorges Reservoir. Compared with the existing formulas, an improved incipient velocity function for fine-grained sediment deposits was developed that includes the influence of water pressure and molecular force. Here we present a 2-dimensional (2D), depth-averaged, hydrodynamic-morphological model for simulating channel evolution processes. The proposed velocity formula was considered in the calculation of sediment transport, and the improved 2D numerical model was applied to the sedimentation process of the Zhongxian reach. Comparisons between model simulation results and field measurements were in acceptable agreement, illustrating the ability of the 2D model to predict fine sediment behavior and assist navigation management decisions in the permanent backwater region of the Three Gorges Reservoir.