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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?6.4 m水深线为界,近岸以淤积为主,远岸以侵蚀占主导,?19 m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.
The impact of the Three Gorges Reservoir on the submarine terrain evolution in the Yangtze River estuary has become a research hot spot in recent years, but many studies have been limited by the scope and accuracy of underwater terrain data, which restricted the evolution of terrain in the Yangtze Estuary to a certain extent. Objective understanding of reservoir water storage response.Using the measured underwater topographic data of the Yangtze Estuary in 2002 before the Three Gorges impoundment and the five representative years up to 2013. By constructing the water depth-cumulated area curve and the scouring silt-pass Volume calculation and comparison with the sediment discharge of the Three Gorges Reservoir and Datong Station reveal the evolution of the underwater topography in the Yangtze River estuary and its response to the impoundment of the Three Gorges Reservoir after the Three Gorges Reservoir was impacted so as to determine the impact of the Three Gorges Reservoir on the Yangtze Estuary More objective and direct evidence.The research results show that the overall evolution pattern of the Yangtze Estuary under the influence of the Three Gorges water storage is as follows: the 6.4 m water depth line is bounded by siltation, while the far shore is dominated by erosion. In the deep water area, the underwater topography was relatively stable at 19 m depth and was less affected by the hydrodynamic force, which showed a significant change in 2013 with the seabed erosion significantly aggravated. Overall, the study area occurred between 2002 and 2007 Sediment-dominated erosion-dominated change, and the trend of post-2007 erosion is aggravating. Compared with the pre-impoundment of the Three Gorges, the sediment erosion in the Yangtze Estuary was over 1 billion tons in 2002 and 2002. It has a very good linear positive correlation with the sediment discharge of the Three Gorges Reservoir and the annual sediment transport of Datong Station with the discriminant coefficient above 0.99, indicating that the three gorges water storage has a controlling effect on the regional evolution of the Yangtze Estuary after 2007, while in 2013 The intensification of seabed erosion in the study area is also related to the limitation of sediment supply outside the Changjiang Estuary and the northern Jiangsu coast.