Flood Mapping and Analysis in Anambra State, Nigeria, Using Synthetic Aperture Radar

Flooding has become a recurring and destructive natural hazard in Anambra State, Nigeria, exacerbated by climatic variability, inadequate urban planning, and the lack of up-to-date flood mapping resources. This study investigates the spatial-temporal dynamics of flooding from September to November 2022 using Sentinel-1 Synthetic Aperture Radar (SAR) data. The objectives were to determine flood extent, analyze expansion trends, and identify highly affected local government areas (LGAs). Sentinel-1 datasets were collected, preprocessed, and analyzed using thresholding and change detection techniques in a GIS environment. The findings revealed a significant increase in flooded areas, from 425.07 km² in September to 1379.72 km² in October, before receding to 845.56 km² in November. Grasslands and water bodies were the most affected land cover classes, while Anambra West, Ogbaru, and Ayamelum LGAs emerged as the most severely impacted. The study concludes by advocating for flood early warning systems and improved land use planning based on reliable SAR-derived flood maps.