Changes of Siltation/Erosion in the Yangtze Estuary Subaqueous Delta

The sediment of the Yangtze estuary primarily comes from the Yangtze drainage area. After the operation of Three Gorges reservoir, the water flow and sediment transportation of the Yangtze drainage have greatly changed. To study quantificationally the influence on the estuary stability, this paper analyses the rate of siltation/erosion in the Yangtze Estuary Subaqueous Delta, and finds that the vertical accretion rate of the suaqueous delta front is 48.9mm/a during 1958 similar to 1985; the vertical accretion rate is -24.8 min/a during 1985 similar to 1989; the vertical accretion rate is -25.5mm/a during 1989 similar to 1997, and establishes the relation among the vertical accretion rate the annual sediment discharge and the runoff amount of dry season. Next, the paper separately adopts the material analysis and one dimensional mathematical model, which are used to forecast the runoff and sediment discharge at Datong station after the Three Gorges reservoir running 20 years. The result shows that the vertical accretion rate of the suaqueous delta front is -117.7mm/a before the Three Gorges reservoir running 20 years.