Monitoring And Analysis Of Spatial And Temporal Coastline Changes

Since the 20th century,under the pressure of global warming,sea level rising and frequent marine disasters,70%of the global beaches have been eroded for a long time[1].The typical geomorphological,climate and marine conditions in Southeast Asia have created various land-sea patterns and abundant coastline resources.However,with the protection of wetlands such as mangroves and coral reefs that along the coastal zone,sedimentation and erosion of estuarine beach,artificial island construction,and other exploitation and utilization activities,as well as natural disasters such as floods,tsunamis and earthquakes,the impacts of disturbance and destruction on the coastline are obvious and significant,the ecological and environmental problems need to be discovered and discussed urgently.Taking Thailand and Malacca Strait coastlines as the research objects.Six types of coastline interpretation feature and location definition rules were constructed.Four stages of coastlines information in 1990a,2000a,2010a and 201 5a were extracted.Then the temporal and spatial distribution of coastline information and its variation trends in the past 30 years were analyzed from the aspects of coastline length,type and proportion,fractal dimension,change rates,land-sea pattern changes and driving factors.The main conclusions are as follows:(1)To solve the coastline automatic extraction problems of false patch noise caused by coastal aquaculture pond,and using high-resolution image semantic information efficientiy.A coastline extraction algorithm based on image segmentation and mathematical morphology operator,and a coastline extraction algorithm based on object-oriented and membership rules are established.The first method could effectively remove the patch noise after image segmentation,and the second method can obtain the semantic features and membership rules to distinguish ground objects.Both methods can realize automatic coastline extraction.Compared with visual interpretation,the coastline positions are consistent in 95%and 85%areas,respectively.(2)Spatial and temporal coastline changes in Thailand:In the last 30 years(1990-2015),the length of Thailand's coastline has shown an increasing trend,with the annual average change rate of 7.24km/a which increased by 180.987 km,mainly due to the human actives factors,such as the policy of " Fishing and Mangrove development",ports and pond aquaculture constructions,and natural factors,such as tide movement,coastal sedimentary environment,and the growth and development of mangrove.The northern Bangkok Bay,the east KRA isthmus and the south Thailand(Changwat Pattani and Narathiwat)are the main coastline change areas.The Thailand coastline utilization is concentrated on the eastern coast of Thailand,which utilization types are main performed by aquaculture ponds,ports,land reclamation,with 180.036km total increaseing in 1990-2015a.Biological coastline increased by 123.4 1 km,mainly distributed in the west coast of Thailand(such as Phang Nga Bay).According to the coastline fractal dimension,the west coastlines has a high degree of tortuosity,while the east coastline has a good extension.According to the coastline characters of diversity index,the coastline in the east coast of Thailand are abundant and the coastline types is well-proportioned(No coastline of any kind has an has absolute advantage or disadvantage),while the west coast are single(the estuary coastlines and biological coastlines occupy the main part).(3)Spatial and temporal coastline changes in Malacca strait:In the last 30 years(1990-2015a),the length of Malacca Strait's coastline has shown an increasing trend,with an average annual change rate of 4.51 km/a which increased by 112.708km.The main types of coastline in Malacca Strait are biological coastline and estuary coastline,followed by artificial coastline.The artificial coastline has changed significantly,increased 264.853km from 1990a to 2015a.The intensity of development activities between the east and the west Malacca Strait coast is limited by the geological conditions of both sides.The utilization degree on the east coast of Malacca Strait is remarkable,which is performed in the growth of artificial coastline under the factors of the enclosed reclamation,port construction,and the development of aquaculture ponds,thus there has high urbanization along the coast.While the west coastline of Malacca Strait is also affected by mangrove expand and the natural disasters.The higher End Point Change rates on the eastern coast of Malacca Strait is concentrated in the port build areas,and higher End Point Change rates on the western coast of Malacca Strait is mainly distributed in estuary coastal and biological coastal areas that mainly drived by natural factors.There is little difference in fractal dimension and diversity index between the two sides of Malacca Straits,but the intensity and speed of change in the east coast are greater than that the west coast.Taking Thailand and Malacca Straits coastlines as examples,this paper discusses the temporal and spatial variation features,driving factors and utilization status,which could provide theoretical and data support for understanding the regulations of coastline changes,protecting marine ecological diversity,coastal scientific and economic development.