1622 / 2019-08-23 11:25:45

Coral reef geomorphology of the Spratly Islands: A simple method based on time-series of Landsat-8 multi-band inundation maps

7、地理与地理信息科学 > 专题6：海洋、湖泊与河流先进监测技术

Coral reefs are crucial for the maintenance of the marine ecological environment and for the sustainability of local societies and economies. The use of remote sensing methods with the support of field data has been proposed for mapping coral reef habitats and bathymetry. However, the geomorphology of coral reefs over substantial areas is poorly documented, because of the absence of field data, especially in disputed areas where in situ investigation is difficult. In this study, we developed a simple method for mapping the inundation frequency (within the penetration range of optical remote sensing) of coral reefs using time-series Landsat-8 OLI images. The method uses the reef-water reflectance contrast (which varies with bathymetry, bands, and water level) in time-series optical multi-band images in order to derive the inundation frequency and geomorphic zonation of coral reefs. The method was applied to the Spratly Islands—the largest coral reef system in the South China Sea (SCS) using more than 1,100 Landsat-8 OLI images. We established an inventory which comprises 137 reefs/sandbanks/islands, including their spatial extent, inundation frequency, and geomorphic zonation. We also interestingly found that the inundation frequency of reef flats around reclaimed areas has decreased since island construction, which probably reflects the influence of anthropogenic activity on the coral reef ecosystem. Our approach was validated by a study of the Great Barrier Reef in Australia, which demonstrated that the inundation frequency of coral reefs can serve as an indirect representation of their bathymetry.