中文摘要：

为分析长江口北支缩窄工程对长江口南北支水动力环境的影响，建立了长江口一杭州湾二维垂向平均潮流数学模型，对长江口北支缩窄工程前后的潮流场进行了数值模拟研究。研究表明：工程实施后新岸线的走向顺应了涨落潮流主流流向，南北支潮流特性基本不变；缩窄工程减小了北支入海口门的河宽，导致北支涨潮量明显减小，达到了减轻北支成潮倒灌南支的目的；工程后整个河道的高潮位均有不同程度的降低，对北支两岸的防潮将产生积极影响；低潮位有增有减，但是变化幅度相对不明显，仅对北支中上段的排涝有略微影响；从全河段来看，工程后涨潮流速除了三条港河段增大外，其余河段均有不同的减小；而落潮流速总体增大。

英文摘要：

To analyze the effect of channel - narrowing project of North Branch at Changjiang River estuary on hydrodynamic condition, a 2D vertical average tidal current numerical model for Changjiang Estuary- Hangzhou Bay was established and the current fields before and after the project construction were simulated. The results show that, after the narrowing - project, the new shoreline direction conforms with the main current direction of tide, the characteristics of flooding and ebbing tide basically remains unchanged ; the project narrows the estuary width of north branch, resulting in obvious reduction of tide volume and miti- gating saltwater invasion from the North Branch to the South Branch; the high tidal level lowers after the project construction, which has positive effect on tide control for the north branch; on the other hand, the low tidal levels change little and only has slight influence on waterlogging drainage in upper and middle reach of the North Branch; for the whole river after the project con- struction, except for the increase of current velocity in Santiaogang reach, the current velocities in other reaches decrease to a certain degrees, while the ebb velocities show an increase overall.