Study on Characteristics of River Evolution of Chengtong Reach in the Lower Reach of the Yangtze River Before and After Operation of the Three Gorges Project

Abstract

After the impounding and operation of the Three Gorges Project and other large water conservancy and hydropower project on the upper reach of the Yangtze River, the condition of incoming water and sediment in the main stream of the middle and lower reaches has changed to some extent, and the corresponding changes of deposition and erosion are appearing progressively from up to down. This paper has collected and analyzed years of measured flow and sediment and topography data, calculated and analyzed the amount of scouring and silting on a riverbed under different elevations, and mainly studied the flow and sediment condition and characteristics of channel change of Chengtong Reach before and after the operation of the Three Gorges Project. The results show that, under the situation of sharp decline of incoming sediment in the upper reaches, the sediment concentration in Chengtong reach obviously reduced in recent years, the channel is generally in scouring situation, which is benefit for the Yangtze River to draw off floodwater; The recession trend of the silting inlet majored in suspending sediment and d0eposition has been slow down, which is benefit for the maintenance and development of such kind of inlets; the low beach in the channel is generally turns from silting up into slight scour. Especially for the key low beach near the navigation project, after scouring, the quirk broadens and attenuates, which go against the maintenance and development of the navigation. The study results provide technical reference for the research on comprehensive treatment of Chengtong reach.