OBSERVATION OF CURRENTS AND SUSPENDED SEDIMENT CONCENTRATION OFF NORTHERN JIANGSU COAST, CHINA

Abstract

The abandoned Yellow River delta off Jiangsu coast is an important sediment source area,where erosion occurs and large amounts of suspended materials are carried seaward. In order to understand the hydrodynamic process here,a 3-vessel simultaneous measurement was conducted with ADP (acoustic Doppler profiler) and water samplers in autumn of 2006. The analyses of survey data show suspended sediment fluxes,the changes of currents and suspended sediment concentrations. The net suspended sediment fluxes of a tidal cycle range from 103 kg m-1 to 104 kg m-1,mainly to the south. First order estimation of yearly fluxes through the area is similar to a long-term average estimation. The investigation shows the currents are controlled by tides. The suspended sediment concentrations change within a tidal cycle. There are peaks of suspended sediments concentrations corresponding approximately to the time just after the maximum current velocity. Data show that velocity gradients become larger when velocity is bigger. High velocity gradients mean high bed shear stress. The high bed shear stress in turn causes the erosion and resuspension of seabed sediments,resulting in a high suspended sediment concentration in the water column.