Sediment Transport Research In Yangtze Estuary And Hangzhou Bay

Researches about numerical model of sediment transport, especially in the Yangtze Estuary and Hangzhou Bay, are reviewed in this thesis. And three questions such as Siltation in YEDWC (Yangtze Estuary Deep Water Channel),excessive siltation in the upside of YEDWC after the second phases of the deep water channel regulation project have been completed and the numerical simulation of three-dimensional cohesive sediment transport in Hangzhou Bay and Yangtze Estuary, China are pointed here according to the need of engineer and science research. The main fruits are as following:1,First based on the Numerical Model for Siltation Prediction in Yangtze Estuary Deep Water Channel, some ameliorations are carried through. And a Grant- Madsen Model is introduced into the new model to calculate the shear stress of wave and current. To realistically simulate the effects of sequential deposition and erosion, a vertically segmented model of the cohesive sediment bed is constructed. In order to be available in the use of models, These sub-models such wind model, wave model, sediment transport model,salinity model,Grant-Madsen model and sediment-bed model are integrated as a whole system. Siltations of North passage channel in Yangtze Estuary induced by storm are simulated since 2000, and coefficients of numerical model are betterment in reason. According to the results of numerical simulation, the following conclusions are determined: Channel siltation is caused certainly by the storm; The channel natural silations (not including storm and engineering)shows pronounced time-scale variations, i.e. the neap-spring cycle. The total volumes of silitation are affected by such as Typhoon process, tidal range, beach sand supply, water depth topography, rectification works and dredging throw mud, and other factors.2,A preliminary analysis included tidal flow, sediment and topography changes is done by use of Prediction Model of Erosion and Deposition in The Yangtze Estuary. The measured data analysis and numerical simulation results show that under the guide of the fairway embankment of the second phase project, the flow between the front and middle of channel is weakened. Because the engineering blocked sediment source of the tidal flat from Hengsha Shoal, suspended sediment concentration decreases; But after the second phase project of sediment relatively high value zone appears in the middle of the channel that is paragraph W23. After the second phase of project The width of channel is gradually widened, but the pitchs ofthe isobath among 7, 8 and 9 m in the upside of channel are smaller since project began; underwater topography of the channel is more steep, so sediment is more easily deposition into the channel.3,Sediment transport in the Hangzhou Bay and Yangtze Estuary is extremely complicated due to its bathymetry and hydrodynamic conditions. The ECOMSED model is employed to simulate three-dimensional (3-D) cohesive sediment transport in Hangzhou Bay. Dynamical factors such as Coriolis force, tides, salinity, river discharges, and waves are considered in the model. The wave parameters, including the significant wave height, period, and direction, are calculated with the SWAN model. The Grant-Madsen model is introduced for the bed shear stress due to the combined effect of waves and currents. The formulation of bed shear stress used to calculate the sink/source terms is modified based on previous research that sufficiently validated the formulation with measurement data. The integrated model of the above-mentioned models is applied to simulate sediment transport in Hangzhou Bay. The results of the simulation agree well with field observations concerning the distribution of suspended sediment, indicating that the sediments are remarkably suspended in Hangzhou Bay under the action of waves and currents.