Analysis on changes in coastline and reclamation area and its causes based on 30-year satellite data in China

Abstract: Since the reform and open-door policy in 1978, China coastal zone has experienced huge changes under a large number of coastal projects. However, there are few studies on the whole China coastline change and reclamation evolution during the period. For this reason, China's coastline and coastal reclamation change information were extracted from 1980 to 2010 period, from which four remote sensing images and the Chinese coastal survey data were used. In addition, Google Earth / Google Maps online remote sensing information was used as an auxiliary. Based on these, in-depth research on specific processes and driving forces of coastline change and reclamation evolution in the past 30 years were conducted. First, Chinese coastal zone was divided into nine regions combining with policy, economic, and natural factors as well as the administrative division. Then, we analyzed coastline change from five aspects which contained coastline length change, coastline change extent, coastline change area, coastline change direction and reasons of coastline change in combination with using two indicators: coastline change degree and coastline forward degree. Correspondingly, we also analyzed reclamation evolution from three aspects: reclamation added area, land use types of reclamation and reasons of reclamation evolution. The results demonstrated that China's coastline length showed an increasing trend and a drastic change degree in the past 30 years. The change direction of China's coastline has been promoting to the ocean and the trend became more and more obvious. Situations of coastline change varied with time and region. China's coastline length increment and trend to ocean were most remarkable from year 2000 to 2010. It had the largest change area in the 1980s, while the smallest change area was found in the 1990s. Shanghai - Jiangsu and Jing - Jin - Tang had significant coastline changes while the changes of Guangxi province and Hainan province were rather mild. The minimum increase of China's coastal reclamation area was found during the period of year 1990 to 2000, while the maximum area increase was found during the period of year 2000 to 2010 and much larger than the amount of area increase in other periods. The coastal reclamation for land use type had been changed from mainly agricultural land to the pond and then to unused water surface in the past 30 years. The unused water surface was the largest increased reclamation land use type. The proportion of port was increasing, while the proportion of agricultural land gradually decreased. China's coastline change was mainly induced by human factors for construction of ports, coastal aquaculture and etc. Natural and social factors such as economic development, population increase, coast type, distribution of tidal flat et al., together determined the evaluation of coastal reclamation. This paper can serve as the scientific foundation for management and sustainable development in the coastal areas of China.