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大通水文站和泥沙观测断面位于长江河口的上边界。长江下游从大通(潮区界)至长江口门的距离长达680 km。20世纪80年代以来,长江流域日趋强烈的人类活动,显著改变了长江入海水文和泥沙数量和特性,从而对长江下游至河口动力地貌和动力沉积产生了显著影响。主要研究长江潮区界大通断面20世纪50年代以来床沙粒径的长期变化。1977～2004年床沙粒径(d_(50))有一稳定增大的趋势,这主要是对上游河道悬沙来量持续减少的响应。值得注意的是床沙粗化过程是发生在该河床长期加积的背景上的。研究表明:导致床沙粒径粗化的原因,主要是上游河段进入本河段床沙粒径的增加和本河段冲淤过程中悬沙与床沙颗粒的交换。随着三峡水库的正常运行和其它大型水库的建设,预计未来几十年长江上游悬沙来量将进一步大幅度下降,可以预计,长江潮区界河段的床沙粒径将继续呈现增大的趋势。
Datong Hydrometric Station and Sediment Observation Section are located at the upper boundary of the Yangtze River estuary. The distance from Chase (tidal zone boundary) to the mouth of the Yangtze River in the lower reaches of the Yangtze River is 680 km. Since the 1980s, the increasing human activities in the Yangtze River Basin have significantly changed the quantity and characteristics of hydrology and sediment entering the sea and have had a significant impact on the dynamic geomorphology and dynamic deposition of the Yangtze River from the estuary to the estuary. Mainly studies the long-term changes of bed sand diameter since the 1950s in the Datong section of Changjiang tidal region. The bed sediment diameter (d_ (50)) tends to increase steadily from 1977 to 2004, which is mainly the response to the continuous decline of suspended sediment in the upper reaches of the river. It is noteworthy that the bed sediment coarsening process takes place on the background of long-term accretion of the river bed. The results show that the reason of the coarsening of sediment particle size is mainly the increase of bed sand diameter of the upper reach and the exchange of suspended sediment and bed sand particles during the scouring and silting of this reach. With the normal operation of the Three Gorges Reservoir and the construction of other large reservoirs, the amount of suspended sediment in the upper reaches of the Yangtze River is expected to decline further in the next few decades. It is expected that the grain size of bed sediment will continue to increase in the boundary sections of the Yangtze River tidal section trend.