| Chongming Island and its vicinity are very important coastal areas in China.Due to the impact of silt of the Yangtze River,human activities,tidal movement and other factors,the sea and land boundaries are constantly changing,with the water area decreasing and the land area increasing every year.The reduction of water area not only causes environmental problems,but also damages biodiversity and its ecosystem.As an important economic development region in China,it is of great significance to study the changes of land and sea in this region and understand its dynamic change trend for decision-making of water resource protection,coastal resource management and ecological environment protection.Based on the deep learning method,this paper extracts the water bodies of Chongming Island and its nearby areas,analyzes their dynamic change trends,and studies the change areas and causes of water bodies.This paper mainly carries out the following research work:(1)In view of the traditional UNet network’s spatial information loss due to multiple convolution pooling,and the extraction effect of muddy water and turbid water is not ideal,this paper improved the traditional UNet by enhancing the skip connection operation,and proposed the ISUNet network.Compared with other baseline network models,the results show that ISUNet performs well in coastal water identification,especially in the water environment containing more detailed information and higher sediment content,such as silty coast and artificial coast,and can better extract the spatial detailed features of images.In addition,this paper analyzes the extraction effect of ISUNet in Chongming Island and its vicinity,and the results show that the model can be effectively applied to the task of coastal water identification and extraction.(2)ISUNet model was used to extract water bodies in Chongming Island and its surrounding areas from 2013 to 2022,and detailed spatio-temporal changes of water bodies over the years were analyzed,including area change analysis,variation area analysis,change reason analysis,etc.The results show that the water body area in the study area has decreased by 497.8 km~2 in the past 10years,showing a trend of gradual decline,with an average annual decrease of nearly 50 km~2.(3)This paper analyzes the variation of water body in Chongming Island and its vicinity.The research shows that the reduced water body area mainly comes from the silt deposition near the river channel port,the sand bar formed by the impact of the center of the river channel and the coast of the artificial port.The influencing factors are human activities and the impact of the Yangtze River estuary sediment.Among them,human activities such as artificial reclamation,port construction and sea aquaculture are the main reasons for the area change.In this paper,it is found that the water area of Chongming Island and its nearby areas decreases at a relatively fast rate.The reduction of water area will bring some environmental problems,such as the reduction of wetland area,the destruction of ecosystem,the weakening of species diversity and other hazards.Therefore,the government and relevant departments need to attach importance to the construction of ecological civilization and formulate effective policies to protect the coastal environment.Therefore,the following suggestions are put forward in this paper:Establish ecological protection areas and strictly examine and approve reclamation projects;Scientific industrial layout,development of tourism and other industries;Construction of water conservancy projects to guide and control sediment impact in the Yangtze River. |
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