Simulated sediment flux during 1998 big-flood of the Yangtze (Changjiang) River, China

The result also indicates a unique pattern of sediment transport downstream through the drainage basin during the high flow season (early July to mid-September). While the upper Yangtze tributaries delivered about 580 million-tonnes of sediment downstream, the 3-Gorges valley added additional 270 million-tonnes. This totals about 850 million-tonnes that supplied the middle and lower Yangtze catchments, of which about 450 million-tonnes were silted in the middle catchments, immediately downstream of the exit of 3-Gorges. This amount is almost 6.5 times the normal flood season averaged over the last 50 years. High sediment load was also recorded in the river mouth area during the flood season, where 460 million-tonnes were delivered to the estuary and East China Sea, about 3.8 times that in a normal flood season. Intensifying human activity in the upper catchment is responsible for the large amount sediment sources delivered downstream and to the coastal region.