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利用近２０年来长江河口所观测的地形、水文、悬沙和河床沉积物资料，着重对１９８８、１９８９、１９９６和１９９７年最新观测资料进行计算分析。结果表明，长江河口航道拦门沙河段来水来沙量大，潮流作用强，潮波变形明显，水流挟沙力强。该河段潮流速随时间和空间变化，又处在盐淡水交换地带，流域和海域来沙在此河床时淤时冲，悬沙与床沙交换频繁，表现在涨急、落急时将河床淤积层泥沙再次起动悬浮，憩流时又重新淤积河床，在一个潮周期中含沙量出现２高２低。近河床若存在一层浮泥时，在下击和上升流的作用下，在一个潮周期中河床泥沙被３次或４次再悬浮。在大潮期河床泥沙普遍扬起，小潮汛期间再次淤积，河床冲淤层变幅为０．２－０．４ｍ左右（南槽）。洪季来沙多，使河床普遍发生淤积；而枯季来沙少，河床发生自然冲刷，多年平均冲淤层变幅为０．６ｍ左右，部分河床可达１．４－２．４ｍ。
Based on the topography, hydrology, suspended sediment and riverbed sediment data from the Yangtze River Estuary in the past 20 years, the latest observation data of 1988, 1989, 1996 and 1997 are mainly analyzed and calculated. The results show that the incoming water and sediment from the Shahe reach of the estuary of the Yangtze River estuary is large, the tidal current is strong, the tidal wave is obviously deformed, and the sediment carrying capacity is strong. The trend of tide velocity changes with time and space, and in the salt water exchange zone, the basin and sea to the sand in this river bed when the silt flushing, suspended sediment and bed sand exchange frequently, the performance of rising, falling into the river bed Silt sediments start again suspended, re-siltation river bed, in a tidal cycle sediment concentration 2 high 2 low. If there is a layer of mud in the near river bed, the sediment in the river bed is resuspended three times or four times in a tidal cycle under the action of the downdraft and the ascending stream. During the tidal period, the silt in the riverbed is generally raised and is re-silted during the flood season. The riverbed silting layer fluctuates about 0.2-0.4m (south channel). Sediment in the flood season often causes siltation in the riverbed. In the dry seasons, the riverbed is washed off naturally. The average erosion and sediment change over many years is about 0.6m, and some of the riverbed can reach 1.4-2.4m.