Detection of Groundwater Discharge Points in Coastal Regions around Mt. Chokaisan by Using Landsat ETM+ Data
Yoichi Kageyama, Chieko Shibata, Makoto Nishida, Hideyuki Kodama
The flow of freshwater into the sea, termed as submarine groundwater discharge, is a key factor for understanding the hydrological cycle in both the sea and land regions. The numerous positions from which freshwater gushes out or its quantity impedes the understanding of its properties. Only sea surface information is obtained by remote sensing; however, multispectral band properties acquired from the Landsat-7 are sufficient for determining the differences between seawater and freshwater. In particular, the features extracted from the multitemporal scenes of Landsat will help determine the conditions responsible for the differences in water qualities in coastal regions. Therefore, this paper detects groundwater discharge points arising due to the difference in freshwater and seawater by using the multispectral Landsat ETM+ (Enhanced Thematic Mapper, plus) signals. This study comprises three procedures: (1) computer simulation of the flow of submarine groundwater discharge in the study area, (2) performance of preliminary experiment on the band properties of the Landsat ETM+, (3) detection of the difference in water properties by using the Landsat multispectral bands. Our experimental results obtained by the Landsat ETM+ are in considerable agreement with the realities in the study area.