一、南门通道的发展及其危害[南门通道的险情] 长江口自徐六泾至中央沙头的一段河道称为南支(图1)。南支河段中靠近崇明岛一侧有一大片暗沙,西起东风西沙头,南至中央北水道西侧,东西长达26公里,南北向-2米线以上的最大宽度达到6公里左右。西部较高,东风西沙的最高滩面已达到+4.0米;南部较低,最高滩面在0～1米之间。扁担沙将南支河 I. Development of the South Gate Passage and Its Harm [Danger of the South Passage] The section of the Yangtze River estuary from the Xu-Li-Jing to the Central Sha Tau is called Nanzhan (Figure 1). Nanchonghe near Chongming Island side of a large dark sand, west of Dongfeng Xisha head, south to the north of the central North Waterway, east-west up to 26 kilometers, north-south to -2 meters above the maximum width of 6 km. Higher in the west, the highest beach in the Xisha of Dongfeng has reached +4.0 meters; the south is lower, the highest beach in 0-1 meters. Pillar sand south branch river