7-20世纪崇明沙洲变迁新探

Study on the Evolution of Chongming Sand Islands during the 7^(th)-20^(th) Century

崇明沙洲自7世纪初渐次出露,此后数量、方位、形态变动不居。通过提取古旧地图等史料信息,可以有效重建历史时期崇明沙洲的演化过程。重建结果表明:11世纪中叶长江口缩窄,沙洲加速发育;13、14世纪之交形成第一代主岛,后渐坍;16世纪后期在南侧形成第二代主岛;17世纪后期,近代崇明主岛规模奠定。北外沙自明初出露,陆续连接长江口北岸。南外沙迟至晚清出露。沙洲演化受多种外力影响,包括涨、落潮流交互作用等自然因素,以及垦殖、筑堤等人为因素。研究结论可为今日崇明生态岛及长三角区域建设提供参考。

From the early period in the 7^(th)century,Chongming sand islands (崇明沙洲) gradually formed and had changed in quantity,location,and shape.On the basis of previous studies,this research made use of ancient maps and other documents to reconstruct more specific processes of the sand islands during the historical period,which could provide a reference for the current construction of Chongming EcoIsland and the Yangtze River Delta region.The results show as follows.The Yangtze River Estuary narrowed in the mid-term in 11^(th)century accelerated the expansion of Chongming sand islands.The original island formed when humanity was about to enter the 14^(th)century,and subsequently collapsed.In the late 16^(th)century,the main island formed again in the southern side of the Yangtze River Estuary.The scale of the Chongming main island in modern times came into being in the late 17^(th)century.From the early period in the Ming Dynasty,the northern outer sands(北外沙)continuously formed and successively connected to the land on the northern shore of the Yangtze estuary.The southern outer sand(南外沙)did not emerge until the late period of Qing Dynasty.The evolution of Chongming sand islands was influenced by a variety of external forces.For example,the natural factors included the interaction among rising and falling of tides at the estuary and the human factors included the reclamation and dam construction.