中文摘要：

三峡水库蓄水对长江河口水下地形演变的影响，近年已日趋成为研究热点．但已有研究多受到水下地形数据范围和精度的限制，在一定程度上制约了长江口区域地形演变对三峡水库蓄水响应的客观认识．利用始于三峡蓄水前的2002年，截至2013年的5个代表性年份的长江口全区实测水下地形数据，通过构建水深．累积面积曲线和冲淤通量计算及与三峡水库和大通站输沙量的对比，揭示了三峡蓄水后长江口全区水下地形演变规律及其对三峡水库蓄水的响应，为判别三峡水库对长江口的影响提供了更客观和直接的证据．研究结果显示，长江口在三峡蓄水影响下的总体演化格局为：以一6．4m水深线为界，近岸以淤积为主，远岸以侵蚀占主导，一19m水深线以深水域水下地形相对稳定，受水动力影响较小．这种趋势到2013年发生显著变化，海床侵蚀明显加剧．总体而言，研究区于2002—2007年间发生由淤积主导向侵蚀为主的转变，且2007年后侵蚀趋势加剧，相比三峡蓄水前的2002年，2013年长江口侵蚀泥沙超过10亿t．2007～2011年间长江口冲淤量变化趋势与三峡水库出库输沙量及大通站年输沙量呈极好的线性正相关性，判别系数在0．99以上，说明2007年后三峡蓄水对长江口区域演化具有控制性作用，而2013年研究区海床侵蚀的加剧。还与长江口外和苏北海岸带泥沙补给受到限制有关．

英文摘要：

The Three Gorges Dam （TGD） is the largest hydraulic engineering structure in the world. Its downstream impacts, especially on the Yangtze River Estuary, have attracted worldwide attention since its impoundment in 2003. A lack of high-accuracy bathymetric data that completely accounts for the Yangtze River Estuary makes it difficult to reliably document the influence of the TGD to any degree of detail. In this study, high quality bathymetric data, covering the Yangtze River Estuary from 2002 （pre-TGD） until 2013, were analyzed to delineate the bathymetric evolution of the Yangtze River Estuary during the post-TGD period and the effects of the TGD impoundment. After the completion of the TGD, deposition occurred in the Yangtze River Estuary in the inshore area from a depth of 6.4 m below the lowest tide, whereas there was significant erosion in the area below that water depth that intensified severely until 2013. In the area below the -19 m isobath, the bathymetry changed little, indicating a weak influence from the force of local water, so the -19 m water depth contour was proposed as a reference boundary for local bathymetric monitoring. The study area gradually changed from being deposition-dominated to being erosion-dominated between 2002 and 2007, and the erosion intensified with time after 2007. The amount of sediment eroded from 2002 to 2013 was more than 10xl08 t. The trend in the local sediment flux from 2007 to 2011 relative to that in 2002 was correlated closely with the suspended sediment discharge from the TGD and the Datong gauging station, located 600 km from the Yangtze River Estuary, with a correlation coefficient greater than 0.99. This indicates that the TGD impoundment was the main mechanism that controlled the evolution of the Yangtze River Estuary after 2007. The intensified erosion in 2013 also in part reflects the insufficient sediment supply from the outer Yangtze River Estuary and the North Jiangsu coastal ocean.