长江口拦门沙冲淤演变及其机理研究综述

Review of the study on morphological evolution and mechanism of mouth sandbars in the Yangtze River Estuary

长江口是长江入海和远洋航运的口门,然而长江口拦门沙的存在,对河口的泄洪、排沙以及通航都产生不利的影响。充分认识长江口拦门沙的冲淤演变,才能够因地制宜、合理开发。通过分析总结前人对长江口冲淤演变研究的成果,发现北支河段全面淤浅,在口内形成巨型沙坎。北港上游冲刷的泥沙在其下游的拦门沙河段淤积,且拦门沙滩顶呈下移趋势,如今长江口来沙量锐减,这种下移趋势可能进一步加强。北槽在深水航道工程建设后打通了航道拦门沙,使拦门沙滩顶的水深大幅度加深,但在中部淤积较为严重。南槽拦门沙形态由"双峰"转变为"单峰",拦门沙浅段缩短,滩顶水深变化不大。影响长江口拦门沙冲淤演变的原因有很多,主要分为自然条件变化和人类活动影响两个方面,而人类活动影响已成为长江口拦门沙冲淤演变的主控因素。

The Yangtze River Estuary is the gateway of the Yangtze River to the sea and ocean shipping. However,the sandbars of the Yangtze River Estuary have a negative impact on the flood discharge,sediment transport and navigation of the Yangtze River Estuary. Therefore,it is necessary to understand the processes of the Yangtze River Estuary sandbar,so as to adapt local conditions. Some conclusions are found based on the analysis and summary of the previous research results on the evolution of erosion and deposition in the Yangtze River Estuary. It is found that the North Branch reaches are deposited completely,and formed a huge sandbar in the mouth. The sediment scoured in the upper reaches of the North Channel is deposited in the lower reaches,and the top of the mouth sandbar is moving downward. With the rapid decrease of sediment inflow into the Yangtze River Estuary,the downward movement trend of the top of the mouth sandbar may be further strengthened.After the construction of the deep water channel project,the mouth sandbar was cleared in the North Passage,and the water depth at the top of the mouth sandbar has been further deepened. However,the deposition is serious at the middle reach of the North Passage. The shape of the mouth sandbar in the South Passage changes from "double peak" to "single peak",and the shallow section of the mouth sandbar is shortened,but the water depth at the top of the mouth sandbar changes seriously. The morphological evolution in the Yangtze River Estuary is mainly due to natural factors and the influence of human activities. Nowadays,the influence of human activities has become the main controlling factor for the morphological evolution and sediment deposition in the Yangtze Estuary.