Using Open-Source Sentinel-1A Images for Flood Susceptibility Mapping in North Bihar, India

Abstract

Natural calamities such as floods are a severe menace, causing huge socio-environmental threats. Remote sensing technologies have proven to be a boon in precisely mapping the spatiotemporal effects and spread of floods, allowing remedial measures to be implemented on time. This paper aims to demarcate the extent of flooded areas in the study area by the application of remote sensing techniques that involve combining temporal images acquired during the flood (crisis images) with images acquired before the flood (archive images). In disaster mapping applications, the image that is acquired before the event takes place is referred to as the archive image, while the image that is acquired at the time of the event is referred to as the crisis image. The research objectives were achieved through the analysis of freely available Sentinel-1A data to delineate the extent of flooded areas in the European Space Agency's-Sentinel Applications Platform (ESA-SNAP) environment. Multi-looking, radiometric calibration, and range doppler terrain correction (geometric) were applied to the temporal images for better visualization and distinction and for projecting the pixels onto the proper map system. Later, the archive and crisis images were overlaid to form a Red Green Blue (RGB) composite that showed the extent and spread of floods in north Bihar, where each color represented areas of different significance. Further, the flood map was overlaid onto the Google Earth optical layer for better visualization and comparison. The work demonstrated the applicability and use of remote sensing and GIS technology to quickly gain insight into the spatial and temporal distribution of floods in a given region and could be used as a precursor for efficient flood management and relief measures.