BACK-SILTING CAUSES UNDER NORMAL ENVIRONMENTS OF THE UPPER SECTION OF DEEP-WATER CHANNEL IN YANGTZE ESTUARY, CHINA

In this paper, the deep-water channel back-silting causes in the South Channel-Yuanyuansha section will be discussed by analyzing field data and physical and numerical simulation results. According to the field data, the causes were sought from the points of channel-silting characteristics, changes of flow, sediment and salinity environments and variation of riverbed. Sediment-character basic test and sediment-transport physical test were carried out for sediment-transport rules in the South Channel-Yuanyuansha section. The causes are also studied from the aspect of waterway deepening by numerical simulation. The following are the main causes: 1) sediment supply for South Channel-Yuanyuansha section from the upstream increases; 2) water with high sediment concentration flowing over the south training jetty to Yuanyuansha section offers a suspended sediment source; 3) waterway deepens in South Channel-Yuanyuansha section; 4) silting duration in Yuanyuansha section increases after the three-phase silting reduction engineering.