Flood Mapping in Valley Districts of Manipur Using Satellite-based Synthetic Aperture Radar (SAR) Images

Abstract

Impacts from flood pose high risk to lives and properties of river plain inhabitants across the globe. Plains of Northeast India, including central valley in Manipur, often experience floods of variable intensities in different seasons of the year. Current flood mitigation measures of the region scarcely consider the dissimilarity in inundation patterns produced by floods of different seasons. Considering this, the current study examined the inundation pattern of pre-monsoon and monsoon floods in five valley districts of Manipur 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 the analysis. The results indicate that the extent of inundation during monsoon flood (20222 ha) was about four times larger than the pre-monsoon flood (4297 ha). Imphal West and Thoubal districts witnessed largest area under inundation during pre-monsoon and monsoon flood respectively. And moving from premonsoon to monsoon, Kaching, Thoubal Imphal East, and Bisnupur experienced the largest percentage climb in inundation area while it only changed slightly in Imphal West. This suggest that spatial pattern of flooding exhibited significant variations among the districts between the floods. Therefore, to be more effective in future, flood management strategies need inputs from flood mapping studies performed using space-based SAR data.