SPATIAL AND TEMPORAL VARIATIONS AND HYDRODYNAMICS EXPLANATION TO SUSPENDED SEDIMENT CONCENTRATION IN THE CHANGJIANG (YANGTZE) ESTUARY, CHINA

Large-scale hydrological observations in the Yangtze Estuary in China have been carried out in February and July, 2003. Based on these data, temporal and spatial variations of suspended sediment concentration in the Yangtze Estuary are studied from the upriver sites to the mouth sites with the mutli-methods of hydrology and statistics. The results show that (1) the reach of upriver, in whose suspended sediment concentration is stable oppositely, is controlled mainly by the runoff current; (2) suspended sediment concentration of downstream to the mouth bar is effected by some factors, for example runoff, tide, landform etc, and its variation is complicated; (3) during a tidal cycle, suspended sediment concentration is related to the current velocity, but lags to the current velocity about one or two hours. The sediment transport flux exists space-time change complexly due to the runoff and tidal current. Also the process of sediment re-suspension is more complicated in the South Passage and North Passage than other passages in respect to the salinity, and the re-suspension process is an important source of suspended sediment for maximum turbid zone. Suspended sediment re-suspension is related to the critical velocity and the eddy diffusion coefficient.