Abstract:

The Wuhu-Yuxi reach, one of the vital links between cities in the Yangtze River Delta urban area, is located in the lower reaches of Yangtze River. Understanding the evolution of the Wuhu-Yuxi reach under new hydro-sedimentary conditions provides theoretical support for future flood control and river regulation. Observed field data for the Wuhu-Yuxi reach was analyzed to understand the altered flow-sediment regime and erosion-deposition features after the operation of the Three Gorges Reservoir (TGR). Results reveal that the Wuhu-Yuxi reach has remained generally stable. The riverbed is mainly subject to scouring, with the heads of sandbars eroded and retreating. Erosion on convex banks and deposition on concave banks have emerged in the sharp-bend section and the multi-braided section due to the development of the right sub-branch of upstream Qianzhou bar upstream which leads to an increased diversion ratio, and the mainstream chute cutoff resulted from the prolonged duration of medium-low water levels. Short sub-branches have also developed in the multi-braided section because the diversion ratio of the left sub-branch in the multi-braided section of Chenjiazhou bar has increased, which in turn intensifies the scouring of the Chenjie and Caojie waterways.

Key words: bed evolution, erosion on convex bank and deposition on concave bank, development of sub-branches, factor analysis, operation of TGR, diversion ratio, river channel of lower Yangtze River, Wuhu-Yuxi reach