中文摘要：

基于在长江口北港上段利用多波束测深系统获得的2014年7,10月（洪季）和2015年2月（枯季）河床微地貌资料,结合浅地层剖面仪获得的2010年1月和2014年10月的浅层沉积结构资料,分析了北港中上段河床微地貌和浅层沉积结构变化特征。研究结果表明：（1）洪、枯季微地貌形态变化明显,洪季沙波比枯季发育范围广。新桥通道内洪季为复合沙波,枯季变成单一沙波。横沙通道北口水域洪季发育有弯曲型和顺直型两种沙波;枯季弯曲型沙波发育区沙波消失且发育着许多椭圆形的麻坑,顺直型沙波波长变大。（2）2010年1月至2014年10月北港上段整体呈冲刷趋势;新桥通道内浅地层剖面表层形态及分层结构基本无明显变化,且均为单层分层、厚度约2 m;在北港上段横断面最窄处附近,2014年10月断面大幅度冲刷并向下游延续较长,最大刷深约为7 m;长江大桥以西浅层沉积结构变化显著,上游分层由双层变为单层,中间分层消失,下游部分分层变厚、部分分层由双层变为单层。

英文摘要：

Based on the bed micro -topography data in July and October, 2014 （flood season） and February, 2015 （dry sea- son） and the shallow sedimentary structure data in January 2010 and October 2014, the variation characteristics of micro - topog- raphy and shallow riverbed sedimentary structure in middle and upper part of Nangang Channel（ NC ） are analyzed. The results showed that： （ 1 ） from the flood season to dry season, the change of micro - geomorphology was evident, and the development of sand waves was larger during flood season than that during dry season ; the superimposed sand ripples of Xinqiao Channel in flood season became single sand ripples in dry season. In the north entrance of Hengsha Channel, the sand ripples developed into curved and straight - linear types during flood season ; while the curved ripples disappeared and many elliptic pockmarks devel- oped during dry season; the wavelength of straight - linear sand ripples became larger. （2） From January 2010 to October 2014, the upper NC was scoured and the surface morphology and layered structure in Xinqiao Channel changed little, which was a 2m - thick single layer. In the reach near the narrowest cross section, the substantial scouring distance of downstream section in Octo- ber 2014 was long, and the maximum scouring depth was about 7m. From January 2010 to October 2014, the layered structure changed significantly on the west of Yangtze River Bridge; the upstream stratification changed from double to single, the middle stratification disappeared and the downstream part stratification thickened with some changing from double layers into single layer.