Influence of major water conservation projects on river channels and shorelines in the middle and lower reaches of the Yangtze River

To understand the influence of major water conservation projects on river channels and shorelines in the middle and lower reaches of the Yangtze River, current study comprehensively analyzed the historical underwater topography and water level data, field measurements of main channel, and laboratory testing. Some new progresses have been made. Firstly, a multi-mode sensor system is innovatively constructed to integrate the measurements of land and underwater hydrodynamic, sedimentary, and geomorphic characteristics and data acquisition. Secondly, it is found that the main channel of the Yangtze River experienced strong erosion, arc collapse, and strip collapse. Thirdly, the suspended sand and bed sand were coarsened. The resistance of the river bed declined, forming the erosional-type “chain bead”-shaped sand wave. The piers of the Yangtze River Bridges in Nanjing, Dashengguan, and Tongling were subjected to serious erosion. Finally, the tidal limit obviously moved up, and the geomorphology of the river changed significantly. From these findings, we put forward relevant suggestions and countermeasures. These outcomes are of great significance to the protection and restoration of the bank and beach of the Yangtze River, the waterway regulation, the coastal flood control, and the maintenance of the piers of the Yangtze River Bridge.