Comparative analysis of flood extent mapping using sentinel-1A and Landsat-8 data

Abstract

Applications of Synthetic Aperture Radar (SAR) data in the civic sector are rapidly growing. It is being used in flood monitoring, flood depth estimation, and flood extent mapping also. Seasonal independency makes SAR data more usable and effective in the monitoring of natural hazards and managing disasters. In this study, the potential of freely available moderate resolution sentinel-1A data were explored to map the flood extent by observing the strength of backscattering over the region of interest. Subsequently, Landsat-8 data were also used to accomplish the same task so that results could be compared. Chitral city, located in northern areas of Pakistan, was selected for this study, which had been experiencing frequent flooding. The flood of July 2015 was selected as the subject event. The Sentinel1-A and Landsat-8 images of pre, amid and post flood were downloaded. The hypothesis was tested that the SAR data would provide better results than the Optical data of Landsat-8, but the outcome of the study did not support the hypothesis and the results were totally inverse. The Independent Component Analysis (ICA) technique provided better and improved output with an area of 4.67 Sq. Kilometer under water from a total area of Chitral city (only) and its suburbs — which was estimated at around 26 Sq. Kilometer.