杭州湾北岸岸滩冲淤演变浅析

A brief analysis of scour and silting of the tidal flats at the north bank of the Hangzhouwan Bay

收集了1976 -2004年杭州湾北岸的多幅地形图,使用ARCGIS软件进行数字化处理,以这些资料为主要依据对杭州湾北岸岸滩冲淤的历史演变和近期演变特征及其影响因素进行了分析。结果表明：（1）历史上杭州湾北冲南淤,其北岸经历了先侵蚀后淤涨的过程。（2）由于圈淤围垦,近30年杭州湾北岸岸线全线外移。（3）近30多年杭州湾北岸的冲淤演变：1997年前芦潮港至南奉边界岸滩基本处于淤积状态,1997年后基本处于冲刷状态;金山岸滩基本处于稳定状态;金山嘴—金山卫滩涂一直比较稳定;漕泾—金山嘴滩涂经历了一个冲刷—淤积—再冲刷的过程,但冲淤幅度不大;奉贤部分岸滩处于侵蚀状态,1997 -2004年0 m等深线以上岸滩进入侵蚀状态,侵蚀带由东向西推进,同时也向岸北侵,使-5 m等深线以下滩坡侵蚀变成-5 m等深线以上滩坡侵蚀。杭州湾北岸岸滩冲淤受多种动力因子的影响,除受潮流和风浪等动力因子的作用外,南汇边滩和杭州湾北岸围垦工程的影响及长江来沙量的减少是造成杭州湾北岸岸滩冲刷的两个重要因素。

The estuarine bank is located at the transitional area between the river and sea,where the interaction of 4 spheres takes place and various interfaces meet.The coastal bank at the forefront of the estuary is the most sensitive zone of land-sea interaction and also the important land resource for the big cities in delta area.Beach scouring and silting is a kind of natural phenomena in estuary,the study of which is of great theoretical and practical significance.The north bank of the Hangzhouwan Bay is at the south edge of the Changjiang River delta.With the increasing need of the land resources,this area has got more and more attentions.Many scholars have studied this area and got a lot of valuable results.However,in the past tens of years this area has experienced significant changes and many issues need to be studied in depth.Based on the digitalized process of 4 maritime charts（1976,1993,1997,2004） with ARCGIS software,scouring and silting of the tidal flats at the north bank of the Hangzhouwan Bay is studied.The results show that：（1） the Hangzhouwan Bay was scoured at the northern bank and silted at the south bank in the history,while the north bank has experienced scouring first and then silting;（2） because of inning at the northern bank,the shoreline has moved outward in the past 30 years;（3） in the past 30 the Nanhui section was mostly in siltation state before 1997 and in erosion state after 1997;the Jinshan section was mostly in steady state;the section from Jinshanzui to Jinshanwei was mostly in steady state;the section from Caojin to Jinshanzui experienced a process from erosion to siltation and then to erosion again;and the Fengxian section was in erosion state,but the erosion zone moved from the east to the west and also to the north in 1997~2004,the erosion moved from the tidal flat below-5 m to the tidal flat above-5 m.The erosion and siltation at the northern bank of the Hangzhouwan Bay is affected by many factors.Besides tide and storm,inning and the decrease of sand from the Changjiang River is two important factors resulting in the scouring of the bank.