FLOOD MAPPING IN VALLEY DISTRICTS OF MANIPUR USINGSATELLITE-BASED SYNTHETIC APERTURE RADAR (SAR)IMAGESAbujam Manglem Singh
Impacts from flood pose high risk to lives and properties of river plain inhabitants across the globe. Plainsof Northeast India, including central valley in Manipur, often experience floods of variable intensities indifferent seasons of the year. Current flood mitigation measures of the region scarcely consider thedissimilarity in inundation patterns produced by floods of different seasons. Considering this, the currentstudy examined the inundation pattern of pre-monsoon and monsoon floods in five valley districts ofManipur using Synthetic Aperture Radar (SAR) data of Sentinel-1 satellite. SAR images of April (premonsoon)and July (monsoon), and a pre-flood image (March) of the year 2017 were employed for theanalysis. The results indicate that the extent of inundation during monsoon flood (20222 ha) was about fourtimes larger than the pre-monsoon flood (4297 ha). Imphal West and Thoubal districts witnessed largestarea under inundation during pre-monsoon and monsoon flood respectively. And moving from premonsoonto monsoon, Kaching, Thoubal Imphal East, and Bisnupur experienced the largest percentageclimb in inundation area while it only changed slightly in Imphal West. This suggest that spatial pattern offlooding exhibited significant variations among the districts between the floods. Therefore, to be moreeffective in future, flood management strategies need inputs from flood mapping studies performed usingspace-based SAR data.