中文摘要：

依据1958-2006近50年海图资料，在GIS技术平台下，对海图进行数字化处理，建立不同时期水深数据库，对比计算不同时期河槽容积的变化，探讨近50年来流域来水来沙减少背景下长江口南、北港分汊型河槽容积变化及演变趋势。结果表明：（1）近50年来南、北港冲淤变化趋势一致，整体上略有淤积之势，局部性波动明显；复式河槽的出现与南支主泓摆动、涨落潮流路分异关系密切，是长江口多级分汊格局形成的缩影。（2）南、北槽河槽演变在20世纪80-90年代呈现此消彼长特征，经过南岸边滩淤积，南槽主泓偏移，水流深切边滩，巩固沙体4个过程形成江亚南沙，长江口二级分流节点处地貌演变复杂，总体可归纳为上游沙体下移，沙体合并，水道消亡。（3）近期河槽演变受人工设施影响显著，来水来沙减少使河槽延伸减缓，南北槽分水分沙条件逐渐改变。

英文摘要：

The Changjiang estuary is a typical branching estuary because of morphologic pattern characterized by three-order bifurcation and four distributary channels discharging into the sea. Based on the data of digitized charts from 1958 to 2006, database of depth is set up, and the channel volumesat different time are calculated to investigate the change and evolution in the South and North Channel. The result suggests that in the past 50 years there was a trend of gradual siltation in the South and North Channel with some fluctuating changes. The swing of main channel in the south branch and difference between ebb and spring flow path have an effect on the formation of compound channel which is a miniature of morphologic pattern about three-order bifurcation in the South and North Channel. The process about Jiangya＇nansha includes four periods：the siltation of the south bank, the swing of main channel in the south passage, the erosion on the top of the south bank by runoff, difference between ebb and spring flow path. The change of morphology in the secondary branching node is complicated including upstream sand bar moving down, combination of sand bars and disappearance of channel.