三峡蓄水后清水下泄对长江口河床演变产生何种效应是泥沙研究者普遍关注的问题。在阐述长江口近期来水来沙和边界条件变化的基础上,分析了长江口基本河槽河床冲淤特点、形态演变及其趋势。分析表明,长江口基本河槽发生了全面的强冲刷,河床形态朝宽深比减小的方向发展。各分段基本河槽上、中、下3层河床的冲刷分布,体现了长江口愈向上游段受径流作用相对较大,而愈向下游口门受潮汐动力作用相对较大对河床冲刷影响的特性。在保滩护岸和近期圈围工程与岸线整治工程作用下长江口总体河势仍将继续保持相对稳定;在三峡蓄水后来沙大幅减小的大环境下,基本河槽将连续受到冲刷,河床形态仍将朝窄深方向发展。

The effect of clear water discharge on the river bed evolution of the Yangtze River estuary after the Three Gorges water storage is a common concern of sediment researchers. On the basis of recent changes of sediment and boundary conditions, we analyze the characteristics, morphological evolution and trend of erosion and siltation of the basic channel riverbed in the Yangtze River Estuary. Our findings reveal a comprehensive strong scour of the basic channel of the Yangtze River Estuary. The river bed shape develops toward a smaller width-depth ratio. The erosion distribution of the upper, middle and lower riverbeds in each section reflects that the upstream section of the Yangtze River Estuary is largely affected by runoff, while the downstream is largely affected by tidal energy. The overall river regime of the Yangtze River Estuary will remain relatively stable steadily under the actions of bank protection and recent encirclement projects and shoreline renovation projects. In the presence of a sharp decline of sediment after water storage in the Three Gorges, the basic channel will be continuously scoured, and river bed shape will still develop to be narrower and deeper.