近年长江口北支涌潮变化及其成因分析

长江口北支的围垦使北支上、中段形成了河宽沿程变率较小的弯曲河槽,沿北支北岸的深槽水深条件得到改善,减弱了涌潮发生的条件,导致青龙港涌潮自2003年以来大为减弱。通过引进局部地形指数,建立了局部地形指数与青龙港平均涨率之间的良好相关关系。研究表明,青龙港平均涨率的年际变化与人类活动(围垦)在北支的进程以及青龙港附近的局部地形变化相应,并认为对于复式断面,采用全断面水力指标并不能很好地反映局部地形对涌潮的影响。由于长江口北支涌潮的近年变化将对长江南、北支分流点水域的河床演变产生重大影响,因此本研究对北支的航道整治和岸线开发利用具有现实意义。

Analysis of the changes and formation causes of tidal bore at the north bayou of the Yangtze River estuary in recent years

The tidal bore is getting weak greatly at the Qinlonggang position of the Yangtze River estuary since 2003.The reason is that the reclamation projects make the up and middle river segment to form a bend channel with the small change rate of the river width along the channel.At the same time,the condition of the river depth is meliorated.The occurrence of tidal bore is bated.On the other hand,the reasonable relation between local terrain and the average tide fluctuation rate at Qinlonggang is set up by introducing local terrain index.The research shows that the annual variatiion in the average tide fluctuation rate at Qinlonggang correspond to the course of human activity(e.g.the reclamation projects) and the variation in the local terrain.It also indicates that using whole section index for the tidal bore can not reflect the effect from the local terrain very well.Owing to the variation in the tidal bore at the north bayou of the Yangtze River estuary in recent years affecting the river bed evolution at the bifurcation area of the north and south branches,this research has realistic meaning for the repairing of the water course and the utilization of the river banks.