Spatial-temporal Changes And Analysis Of The Coastline Of Hainan Island In The Past 30 Years

The coastal zone is an important eco-environment transition zone under the interaction of land and sea.Studying the law of change from the coastline information extracted from different periods is of great significance to coastal environmental protection and comprehensive utilization management of coastal zone resources.Hainan Island is surrounded by the sea on all sides and has many harbors.Since the establishment of Hainan Province in 1988,along with the gradual increase in the speed of Hainan 's economic construction,the development of the coastal zone has become more and more frequent,and the coastline has undergone violent effects under the dual effects of natural and human factors.Changes,the ecological environment of the coastal zone and the production and living of the coastal residents have been seriously affected.This article uses GIS and RS technology comprehensively,taking multi-temporal Landsat TM,ETM +,OLI series remote sensing images as data sources,and combining Canny edge detection and Modified Normalized Differences Water Index(MNDWI)to conduct preliminary coastline extraction.According to the coastline characteristics of the study area,the classification and interpretation marks were established,and finally the five coastlines of 1990,1995,2002,2009 and 2018 were obtained.On this basis,the spatial and temporal changes of the coastline of Hainan Island are analyzed in detail from four aspects of length,fractal dimension,type composition,and end point change rate,and the main driving factors that cause the coastline change are discussed.Finally,the typical shore section from Dongfang City to Changjiang County was selected to use Kalman filter to predict the future position of the coastline and put forward opinions on the management of coastal development.The main results are as follows:(1)The length of the coastline of Hainan Island has maintained a continuous upward trend,and the total length has increased by 246.82 km.There is a large difference in spatial distribution.Among them,the coastline of Sanya,Danzhou,and Haikou has the largest increase.The change trend of fractal dimension has a good consistency with the change of length.In addition to the slight fluctuations in Dongfang City and Chengmai County,the overall trend is a continuous growth,and the coastline is becoming more and more complex.(2)The coastline types change frequently,the artificial coastline increases sharply while the natural coastline decreases sharply,and the cumulative length decreases by 181.40 km.In 2018,the proportion of coastline has dropped to 67.04%.Areas that recede toward the land and advance violently to the sea are mostly concentrated in western cities.The speed of advancing toward the sea is significantly faster than that in the eastern cities.The main driving factors are natural factors such as waves,currents,and sea level rise.Transformation of human factors and location policy factors.(3)The erosion of Dongfang City to Changjiang County in coastal projects such as port docks,breakwaters,and the coasts protruding to the sea will continue.According to the 2028 prediction,the farthest retreat distance of the shoreline is 75 m.As the shoreline continues to erode,the retreat may endanger the surrounding woodland.