Hazard Flood Mapping and Monitory in Parts of the Niger Delta Region Using Sentinel 1 Synthetic Aperture Radar

Abstract

In this study, the RGB band and threshold techniques were used to distinguish between the flooded area and permanent water bodies with the use of Sentinel 1 images to map and monitor flood hazards in Yenagoa, Bayelsa State. The acquired images were before the flood events in January 2019 and during the events in October and November 2019 with the aid of Snap 7.0 and ArcGIS software. The preprocessing of Sentinel-1 images and the mapping procedure have been described in detail, and the results have been evaluated. The results show that the Sentinel 1 sensor can rapidly provide quality data in mapping floods. The applied techniques, RGB and Threshold, show a clear disparity between permanent water bodies and floods by applying contact stretch to histograms. Zones with low backscatter signify flooded areas in red, with high radar response signifying land in the archive indicating surfaces. Areas with black indicate permanent waterbodies, while areas with white indicate built up areas. The estimated significant difference in mean water surface for January and October 2019 is -0.23 dB, while for January and November 2019 it is-0.36 decibels (dB). The difference between October and November 2019 is -0.12 decibels (dB) for the estimated mean water surface in the study area. Therefore, emphasizing remote sensing and GIS as essential tools for flood mapping, risk analysis, and better flood management is therefore essential.