Research On The Temporal And Spatial Changes Of The South China Mainland Coastline In The South China Sea In The Past 30 Years

As a transitional zone between the land and the sea,the environment of coastal areas is vulnerable to the changes of natural and human activities.The spatio-temporal evolution of coastal areas,such as the shape of coastline,morphological structure,utilization mode,trend direction and etc.not only reflects various dynamical actions but also represents the environmental changes of coastal area.Therefore,the aim of the study of spatio-temporal changes of coastline is to better understand the evolution of the environmental processes and its changing mechanism,in order to provide more scientific and reasonable decision making references for the sustainable development and planning of coastal areas.Based on remote sensing images,the coastline data of four phases of south mainland China in 1988,1998,2008 and 2018 were extracted.Subsequently,with the aid of GIS spatial analysis tools,statistical and fractal analysis,the temporal and spatial variation characteristics of the coastlines were studied,in aspects of the spatial distribution of coastline type structure,the characteristics of coastline fractal dimension,the development and utilization mode of coastline,the rate of change of coastline end point based on profile,and the changing area of coastline.Then the multi-scale analysis was done for the basic characteristics of the south mainland China coastline change,the development degree of coastline utilization and the change of coastline position in the past 30 years.Finally,three representative typical areas were selected to conduct detailed analysis of coastline variation characteristics to explore the driving factors of coastline changes.The main conclusions of the research have been obtained as follows:1)Between 1988 and 2018,under the combined influence of human development and sea-land interactions in the south mainland China,the length of coastline continued to increase.The proportion of artificial coastlines continues to increase,reaching 51 percent by 2018.Both the coastline fractal dimension and the coastline development and utilization intensity index are characterized by a continuous increase.When the length of the coastline changes significantly,the variation of the coastline fractal dimension and the coastline development and utilization intensity change significant and vice versa.2)Changes in coastline fractal,coastline utilization structure and sea-land spatial structure show significant characteristics of spatial discrepancy and time phase.The spatial difference is mainly manifested as follows: in the past 30 years,the coastline utilization intensity of the Pearl River Delta shore area is significantly larger than that of other subunit shore areas.The highest fractal dimension of the coastline is the Pearl River Delta,and the lowest is Hainan Island.The time phase is mainly manifested as: the large-scale reclamation and land-building activities in the Pearl River Delta occurred between 1988 and 1998.In other regions during this period,the main coastline development activities were cofferdam farming,and the filling tide began to appear in 2008-2018.3)Between 1988 and 2018,the coastline of the south mainland china continued to increase,and was dominated by the trend of sea expansion.The main reason for the expansion of the coastline to the sea was the artificial development construction activities based on reclamation and land reclamation.The more obvious areas are the Pearl River Delta and Taishan-Yangjiang shore section.The main reason for the backward trend of the coastline of south China is the erosion of coastline caused by natural factors.4)The changes of the coastline of the south china are affected by the natural attributes of the coastline and the natural sediment conditions,and on the other hand by the location conditions of the coastline and the economic and social development of the city.The information of the coastline changes of the south mainland china that were revealed and identified in this research can provide basic data and information support in the process of functional zoning in coastal areas,optimization allocation of resources,preventing and repairing the degradation of coastal environment and ecological system,and they could promote and support the development of the coastal areas towards healthy growth.