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为了研究河口前缘沙洲演变过程与流域入海泥沙要素关系,建立了长江口前缘沙洲面积冲淤速率和流域入海泥沙要素关系曲线,并预测沙洲发展趋势。结果表明:长江河口前缘沙洲1958~1989年-5m以浅面积表现为淤涨,1989~2000年为淤涨和侵蚀交替变化,但幅度较小,自2000年起为冲刷趋势发展,这一过程伴随流域入海泥沙量和含沙量的减少而产生。同时沙洲面积的锐减过程中存在临界泥沙要素条件,并建立了相应的经验曲线,当沙洲面积冲刷和淤涨达到平衡时,临界入海沙量和含沙量临界值分别为2.83×108 t/a,0.318kg/m3。依据以往三峡水库蓄水后入海沙量预测数据,三峡水库蓄水后60a左右前缘沙洲-5m以浅面积将侵蚀到1958年水平,其后沙洲面积增加趋势,面积逐渐恢复。2003~2011年长江流域入海泥沙量小于三峡水库蓄水前的预测数值,沙洲面积的冲刷趋势将加剧,应引起有关机构和部门重视。
In order to study the relationship between sediment evolution and sediment transport in estuarine estuarine watershed, the relationship curve between sedimentation rate and the sediment input into the sea at the front of the estuary of the Yangtze River Estuary was established, and the trend of sand bar development was predicted. The results show that the shallow sand area of the front reaches of the Yangtze River estuary from 1958 to 1989 showed siltation, and the change of siltation and erosion alternated between 1989 and 2000, but the amplitude was relatively small. Since 2000, this process has been followed by the erosion trend Accompanied by a decrease of sediment and sediment into the sea basin. At the same time, there are critical sediment conditions in the process of sharp decrease of sandbank area, and the corresponding empirical curves are established. When the erosion and siltation of sandbanks reach a balance, the critical values of critical sediment load and sediment concentration are 2.83 × 108 t /a, 0.318 kg / m3. According to the prediction of the amount of sediment into the sea after the impoundment of the Three Gorges Reservoir, the shallow sand areas at the front sand bar of about 60 years after the Three Gorges Reservoir was impounded will erode to the level of 1958, and the area of sand bar will then increase and the area will gradually recover. From 2003 to 2011, the amount of sediment entering the sea in the Yangtze River Basin is less than the predicted value before the Three Gorges Reservoir was impounded. The scouring trend of sandbar area will be aggravated, which should arouse the attention of relevant agencies and departments.