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长江是世界著名大河之一,全长6380公里,其流域面积为180.85万平方公里.由于区内气候湿润、雨量充沛,平均年迳流量高达9240亿立方米.其迳流具季节变化特征,夏半年为洪水期,冬半年则为枯水期.随着近2000年来人类活动的频繁,以及长江中、上游自然生态破坏的加剧,长江向海输出泥沙也与日俱增.据长江大通水文站观测,年平均输沙量已高达4.86亿吨,其结果势必加速了长江口水下三角洲的演变和发展(图1).长江口门宽达87公里,长江远流入海后,由于水流展宽,迳流表面比降减小,迳流速度必然降低,加之咸淡水的混合,促进水中细粒物质的絮凝作用,使得长江口门外成为长
The Yangtze River is one of the most famous rivers in the world, with a total length of 6,380 km and a catchment area of 1,880,500 km2. Due to the humid climate and abundant rainfall in the area, the average annual flow reaches 942 billion cubic meters, with a seasonal variation and summer The flood season in half a year and the dry season in winter.With the frequent human activities in recent 2000 and the aggravation of natural ecological damage in the upper and middle reaches of the Yangtze River, the sediment output from the Yangtze River to the sea is also increasing day by day. According to the observation of Datong Hydrological Station, Sediment discharge has reached 486 million tons, the result is bound to accelerate the evolution and development of the Yangtze River Delta underwater delta (Figure 1). The Yangtze River Estuary wide door 87 km, the Yangtze River inflow into the sea, as the flow broadening, Reduce, 迳 flow rate will inevitably reduce, combined with a mixture of fresh and brackish water to promote the flocculation of fine particulate matter in water, making the Yangtze River Estuary become a long outside