Research on Jiepai riverbed evolution law and its evolution trend forecast in middle Yangtze river

摘要

After Three Gorges reservoir impoundment, sediment transport and bed evolution characteristic had changed in the lower Yangtze River. Based on the observational data, sediment transport and bed evolution characteristic of Jiepai reach had been analyzed. The results showed that Jiepai reach evolution had a close relationship with income flow and sediment conditions. In recent years, the income flow and sediment conditions were propitious to the development of left slot of heart beach. It also had accelerated the low beach erosion in transition section and siltation in Xindijia. A 2-D mathematic model and river physical model had been used to forecast the river evolution trend. The results showed that the staggered beach would still not stay steady with the reservoir impoundment. The periodic time of evolution could become longer. Xiru bank beach in right bank of upper Jiepai reach would deposit and move downwards. The main stream discharge would centralize and increase. The left channel of heart reach would be eroded and the right one would dwindle gradually by the squeezing of the heart reach. The right branch channel, as the main navigation channel, would deposit and become shallow. The transition reach would move downwards at outlet of left channel. The riffle would present a staggered shape and left branch channel would dwindle gradually. The waterway transportation condition would get worse.