受到第三驱动力的作用，长江河口发育模式由两侧岬角控制转变为中间依靠工程建筑向外突出的格局。这种格局的转变及利用航道疏浚土吹填，使得横沙东滩不断淤涨成陆。长江口南港南槽与北港之间的长兴岛、九段沙、横沙岛及横沙东滩组成串珠状岛链，形成长江口亚三角洲体系。横沙东滩新形成的约400 km2的土地和18 km深水岸线，加上远期建筑人工岛，可开发河口深水港区，与两侧河口湿地保护区相兼容，为上海提供城市发展的新空间。

The natural evolution pattern of the Yangtze estuary was changed by human activities. The estuary is not controlled by the sides' cape as it did in the past. In the middle of the estuary, a beaded island chain was formed by the Changxing Island, the Jiuduansha mudflat, the Hengsha Island and the Hengsha east shoal, and a new sub estuarine delta is coming into being. This sub delta keeps expanding outward relying on the engineering constructions. The Hengsha east shoal will become land due to mudflat enclosure and siltation with waterway dredging soil. The new reclaimed land area could reach 400 km2 and more than 18 km deep-water shoreline exists along the north coast of the mudflat edge. The plenty resources of the new sub estuarine delta and an artificial island outside the estuary could become a new space for Shanghai City development and a suitable location of deep-water harbor site.