上海近岸海域近30年来的地形演变和机制探讨

Underwater Topography Evolution and its Driving Mechanisms Over the Past Nearly 30 Years in Shanghai Offshore Area

利用1983、1997、2002和2009年四个典型年份的岸线和水下地形数据,按阶段综合分析了上海近岸海域(含长江口和杭州湾北岸,东至-10m水深线附近)近30年来岸线和水下地形演变的特点,并尝试探讨了不同阶段的主导动力机制。结果表明:上海海岸带总体向海淤进,不同阶段的冲淤规律和主导机制不同。其中,1983～1997年冲淤相对稳定,主导动力机制为规律性自然条件;1997～2002年冲淤形式发生突变,主导动力机制为1998年长江流域大洪水事件;2002～2009年继承了上阶段模式区别于一阶段发展,以"北淤南冲"为特征,主导动力机制为流域和研究区的重大工程活动。近年重大工程活动的影响日益凸显,随着南水北调工程的通水,推测未来数年内研究区海岸侵蚀程度趋于增强,需密切关注其可能导致的不利影响。

In Shanghai offshore area,four years of coastline and underwater topography data in 1983,1997,2002 and 2009,respectively,are analyzed and compared synthetically for recovering the topography evolution history and exploring their driving mechanisms.The results show that the Shanghai coastal area was generally in a silting-up state since 1983,but the evolutional patterns and dominant mechanisms changed remarkably in different stages.In the first stage from 1983 to 1997,the local coastline and seabed were relatively stable,and controlled majorly by regular natural conditions;in the second stage from 1997 to 2002,abrupt change happened to the pattern of accretion and erosion under the leading control of 1998 big-flood event in the Yangtze River basin;whereas in the third stage from 2002 to 2009,the model of second stage was kept on and developed toward a new pattern different from the first stage,characterized by north accretion and south erosion,its dominant driving mechanism was transferred to big engineering projects in the Yangtze River basin and the research area.It’s also proposed in this paper that,with the operation of South-North Water Diversion project,the local coastal erosion tends to increase in the following years,and close attention should be paid to its possible adverse effects.