Freshwater lake inundation monitoring using Sentinel-1 SAR imagery in Eastern Uganda

Abstract

In flood hazard assessment, little attention has been given to the seasonal observation of freshwater inundation using Sentinel-1 Synthetic-Aperture Radar (SAR) images in the tropics. To assess these spatial variations, this study examined the inundation magnitudes and reflectance of riparian flora in the raining seasons (February-April and September-November) and dry-periods (May-August and December-January). The inundation areas were determined using an object-oriented classification algorithm, whilst the merits concerning the lake, riparian vegetation and shoreline were well-defined using backscatter-coefficient values. Findings indicated that the SAR images are practical to monitor inundation coverages and discern lake basin specific features such as highland areas, shoreline, water and riparian-vegetation. Seasonally, inundated sizes were comparatively higher in February (902 sq. km) and October (700 sq.km). Backscatter values of inundated parts varied from −16 dB to −19 dB, whereas those of riparian vegetation were higher in the months of May and August. This study hence displays a clear-cut correlation between riparian-vegetation, hydrology and climate variables.