Research On Spatial-temporal Changes Of Coastline In Countries Around The South China Sea In Recent Three Decades

Coastline refers to the division between ocean and land at annual average high tides, carrying a wealth of geographic and environmental information. Therefore, the research and analysis on the changes of coastline length, types, spatial distribution and temporal variation characteristics, is important to the research of the coastal beach and the marine ecological environment. In this paper, the author focused on the relevant coastal segments in nine countries around the South China Sea, obtained the coastlines in 1980, 1990, 2000 and 2010 by using the remote sensing and geographic information system technology, and systematically analyzed the spatial and temporal changes of the coastline in recent 30 years. The research conclusions include:1) Under the influences of human development and integrated land-sea interaction, the length of coastline changed significantly in recent 30 years: Under the 1:10 million map scale, the length of coastline in the countries around the South China Sea in 1980, 1990, 2000 and 2010 was 28835 km, 28445 km, 29355 km and 29247 km, totally increased 412 km, showing an overall increasing trend;2) The sandy coastline played a major role in the spatial distribution, accounting for about 30% of the whole coastline. The proportion of artificial coastline rose from 6.36% in 1980 to 22.90% in 2010, having a average increase of 1618 km in every 10 years. The natural coastline all showed a decreasing trend, biological coastline reduced 537 km, bedrock coastline reduced 437 km, silt coastline decreased 342 km, sandy coastline reduced 168 km in every 10 years.3) Most coastlines of study area are affected by human development factors significantly, and the spatial locations are mainly advancing seaward. The significant changed coastal section are mainly concentrated in the Pearl River Estuary of China, the Red River Estuary of Vietnam, Singapore and the Manila Bay of Philippines, and the average advancing speed is 11.69m/a; But in the North Central Vietnam and Mekong River Estuary, Thailand Bay and northwest Indonesia area, due to the erosion of sea water, the trend of landward retreat is clear, and the average retreat speed is 4.60m/a.4) In recent 30 years, countries around the South China Sea developed rapidly, and the regional characteristics of coastal change are significant. Among them, the development intensity of Singapore coastal is highest, mainly for port and dock construction; Coastal development around the South China Sea in China is mainly concentrated in the earlier period, mainly for reclaimed farmland and farming, while development intensity in the middle and later period is slowed, the propotions of port-dock construction and urban construction rise, coastal development present diversified development pattern; In other countries, besides some typical developed coast, the whole has yet entered the stage of large-scale border dike development which is convex to the sea.5) The Pearl River Estuary of China, Red River Estuary of Vietnam, Bangkok Bay of Thailand, Singapore and Manila Bay of Philippines, have the most significant change of the coastline space position in countries around the South China Sea in recent 30 years.(1) In the above coastal area, the land area increased 1157.4km2 due to coastline change, and the main reason is different degree of reclamation engineering in every coastal part; while coast erosion caused a loss of about 92.1km2 land area.(2)The spatial and temporal heterogeneity of coastal development of the above typical coast is significant in the three ten years. Among them, coastal development in China’s Pearl River Estuary is mainly in the way of reclamation farmland and farming, port and urban construction proportion rise in middle and latter period; coastal development in Vietnam’s Red River Estuary is mainly in the way of reclamation farmland in earlier period, and reclamation farming mainly in middle and latter period; Reclamation farming has been the main coastal development mode of Thailand Bangkok Bay, the proportion of urban construction has been strengthened in middle and latter period; the main mode of coastal development in Singapore is port and dock construction, supplemented by urban-construction; Reclamation farming and port construction is the main coastal development way in the Philippines Gulf of Manila.The South China Sea is one of China’ most important seas, also it is a vital sea lane to contact China with world. For the study of the temporal and spatial variation characteristics of coastline in countries around the South China Sea, it benefit to promote the application and development of coastal remote sensing. It also helps to understand the coastal type, geological structure and landform characteristics. Meanwhile, it can provide reference for seeking scientific, reasonable coastal resource management and development strategy.