River-bed Down-cutting Equilibrium of a Reach on Yangtze River

The Three Gorges Project (TGP) introduces significant flow and sediment variations after its impoundment, due to which remarkable geomorphic adjustments prevail in the Jingjiang reach of the middle Yangtze River. The present study deals with the hydro-morphological equilibrium, considering both the dam operation and large-scale bank protection works along the reach. Based on available data, the equilibrium is, by means of a regime-based approach of maximum flow efficiency, analysed for the reach. The study shows that the flow discharge of the reach has not changed considerably after the TGP impoundment in 2003. After the impoundment, the suspended load into the reach descends drastically and but comes to a relatively stable level after 2006. The reach had not come at a hydro-morphological equilibrium before 2012; there is seemingly a tendency to reach a new equilibrium with time. The maximum flow efficiency method is useful to explore equilibrium conditions of a large river if flow and sediment conditions are modified.

Keywords: Yangtze River, Jingjiang reach, geomorphic adjustments, river morphology, extremal hypothesis