The Study Of Suspended Sediment Transportation And Distribution In Xiangshan Harbour

Extensive field observations of sediment distributions have been carried out in the micro-tidal Xiangshan Harbour in South China since 1980s. However, the knowledge about dynamics of sediment in this region is still quite poor. The present work reports data on laboratory modeling experiments in combination with field observations in order to understand the net transportation of sediment across a section and the distribution of suspended sediment concentration. The Princeton Ocean Model (POM) with a sigma coordinate system has been used as the hydrodynamics module of the 3-D model with introducing the drying and flooding algorithm and the open boundary of salinity using the equation of Thatcher-Harleman and the open boundary of SSC using a function of sine. The sediment-induced buoyancy effects and the consequent turbulence damping effects have been taken into account in the sediment transportation model. Simultaneous currents and SSC (Suspended Sediment Concentration) time series data from a mooring site and from ship-born observations over a tidal cycle in Nov. 2003 enable the calibrations of the sediment transportation model.Sediment transport is a very complicate process. The knowledge about the Mechanism of sediment transportation is very poor, but BP ANN model is good at to solve this kind problem, so a Sediment BP ANN (Back Propagation Artificial Neural Network) model is built and verified by field observations for further understanding the sediment transportation and distribution in Xiangshan Harbour.Through the comparison of sediment transport model and sediment BP ANN model, we can understand the distribution and transportation of sediment in Xiangshan Harbour very well. The BP ANN model is introduced into the study of sediment distribution and transportation that provides a good idea for the study ofsediment.With the simulation of transportation of sediment, we know that thetransportation of sediment is dominated by tidal currents at the outer part of Xiangshan Harbour. The contour lines of sediment concentration are push into inner part of Xiangshan Harbour at the flooding time, and move outer part of Xiangshan Harbour at the ebbing time. The silty of suspended sediment travels with the water current in a long way. the concentration of sediment is influenced by spring tide or neap tide, the resuspension and deposition are the main factors of sediment concentration.The SSC of bottom layer is higher than the SSC of upper layer. The contour line of SSC O.lkg/m3 in bottom layer moves from the mouth of Tiegang and Huangdungang to the mouth of Xihugang during the time of through flooding to ebbing at the spring tide, and that moves from the mouth of Xihugang to the section of Xize during the time of through flooding to ebbing at the neap tide.A feasible method for analysis of net transportation of suspended sediment is applied to account for the effect of co variations of quantities (velocity, concentration) and water depth during the tidal cycle. The suspended sediment concentrations which are obtained from the Sediment ANN model and the Sediment Transportation model are applied to calculate the net transportation of suspended sediment . The results present that the net transportation of suspended sediment across the section of Xize direct to the inlet of the Xiangshan Harbour.