Bathymetry Mapping of Hikkaduwa Coral Reef Using Satellite Images

Abstract

Earlier Bathymetric methods measured water depth of a single point at once. Then with the development of technology it becomes more accurate but high in cost. Then shallow water areas which have depth up to 25m can be mapped with remote sensing technology by reflection intensity of the wavelengths which were captured by the satellite sensors. The ENVI Suite Relative Water Depth Tool can be used to determine relative depth values scaled from zero to one. They do not gives actual depth values and we can have just an idea of the underwater environment. To get actual depth values they must be calibrated with field data. Hikkaduwa coral reef is the most diverse and accessible coral reef in the Sri Lankan coastal line. But recently it was degraded heavily due to both human and natural causes. In this research it shows that coral reef was changed around 48.5% in past 25 years according to relative water depth values. By analyzing increment of average depth values of the study area, it emphasizes that reef was debased about 5% from 2002 to 2019. This empowers to create a new tool to use multispectral satellite images to make bathymetry maps of shallow water areas. But with the availability of data like high resolution satellite images, it limits the performances of these satellite derived bathymetry models.