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长江河口被崇明岛分为南北二支.崇明岛在宋初(十世纪末)为海口小沙岛,但沙洲很不稳定,变迁较大,到宋建中靖国起(1101—— ),又出露一个名为‘三沙’的沙岛,并逐渐扩大,终于宋嘉定15年(1222)在该沙建天赐场.元至元14年(1277)建崇明州,至此长江口基本形成南、北二支. 北支的演变,与上端河段主流线的摆动关系相当密切,一般可分四个阶段,现将它的演变过程和今后发展趋势分述如下.
Chongming Island is divided into north and south 2. Chongming Island in the early Song Dynasty (late 10th century) for the small sand island of Haikou, but the sandbar is very unstable, changes are larger, to Song Jianzhong Yasukuni (1101 -), but also a Sand Island named ’Sansha’, and gradually expanded, and finally Song Jiading 15 years (1222) in the sand built Tianzhu Chang Yuan Yuan Yuan 14 years (1277) Chongming state, thus the Yangtze River estuary basically formed South and North II North Branch of the evolution, and the upper reaches of the mainstream line swing quite closely, generally divided into four stages, now its evolution and future development trends are described below.