Based on the 2-D flow and sediment numerical model of the Yangtze Estuary and the Hangzhou Bay, the characteristics of water and sediment exchange in their joint waters is studied through quantitative calculation and analysis of the characteristics of water flow and sediment transportation. The results show that there is periodical water and sediment exchange in this joint waters, that the net water exchange appears mainly between 0～6 m depth (theoretical datum plane, the same below) offshore and the maximum is near the depth of 2 m, and that the net sediment exchange mainly appears between 0～5 m depth and the maximum is near the depth of 3 m, indicating that the range of water flow passage is different from that of sediment transport from the Yangtze Estuary to the Hangzhou Bay. Combined with the results of numerical simulation, this paper also analyzes the hydrodynamical mechanism influencing water and sediment exchange between the Yangtze Estuary and the Hangzhou Bay, including tidal fluctuation, tidal current kinetic energy, tide-induced residual current and the trace of water particles. Finally, the sediment transportation passage on the Nanhui tidal flat is discussed, and the results show that sediment is transported into the Hangzhou Bay from the south side of Shipilei, while sediment is brought back to the South Channel of the Yangtze Estuary from the north side.
According to analysis on field data obtained by ADCP(Acoustic Doppler Current Profiler),the flow regime of the Yangtze River Estuary is studied by use of a 3-D numerical model.The flow field characteristics,under the influence of Coriolis force,saltwater intrusion and freshwater inflow and tidal current interaction,are depicted in details.The main driving forces and some important effective factors of lateral,longitudinal and horizontal circulation are also analyzed.
Research on quantitative models of suspended sediment concentration(SSC)using remote sensing technology is very important to understand the scouring and siltation variation in harbors and water channels.Based on laboratory study of the relationship between different suspended sediment concentrations and reflectance spectra measured synchronously,quantitative inversion models of SSC based on single factor,band ratio and sediment parameter were developed,which provides an effective method to retrieve the SSC from satellite images.Results show that the b1(430-500nm)and b3(670-735nm)are the optimal wavelengths for the estimation of lower SSC and the b4(780-835nm)is the optimal wavelength to estimate the higher SSC.Furthermore the band ratio B2/B3 can be used to simulate the variation of lower SSC better and the B4/B1 to estimate the higher SSC accurately.Also the inversion models developed by sediment parameters of higher and lower SSCs can get a relatively higher accuracy than the sin-gle factor and band ratio models.
