Decadal mapping of flood inundation and damage assessment in the confluence region of Rivers Niger and Benue using multi-sensor data and Google Earth Engine

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Climate change has made weather patterns more extreme, causing floods in Nigeria. Flooding is the most frequent and serious natural hazard in the confluence region of Rivers Niger and Benue, impacting lives, agriculture, and socio-economic activities significantly. Advancements in satellite technology and computational capabilities have enhanced rapid information about flood extent for monitoring, mitigation, and planning. However, there is a dearth of information based on time series analysis of flood inundation and monitoring in the confluence region. In this study, Sentinel-1 Synthetic Aperture Radar, Sentinel-2, and Landsat-7 and Landsat-8 data were used to extract flood inundation for 10 years (2012–2022) in the confluence region of Rivers Niger and Benue. Flood extent/surface waterbodies were extracted using the Google Earth Engine platform, modified normalized difference water index, and normalized difference water index methods. The findings revealed that within 10 years, four significant flooding incidents occurred in 2012, 2018, 2020, and 2022, inundating 60.57, 48.24, 39.98, and 84.39 km² of the area, respectively. The study underscores the need for the establishment of a decision support system for monitoring flood inundation and providing decision-makers necessary information for flood disaster preparedness, mitigation, and adaptation.