Mapping of Flood Risk Zones Using Multi-Criteria Approach and Radar - A Case Study of Ala and Akure-Ofosu Communities, Ondo State Nigeria.

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Abstract Floods are among the world's most catastrophic natural disasters, claiming countless lives and destroying homes, businesses, public buildings, farms, and crops. Studies reveal that it's not the flood itself that's dangerous, but how vulnerable people are to its effects. This research examines flood-prone areas in Ala and Akure-Ofosu. Identify factors that produce flooding in the research region; categorize each criterion according to their influence on causing floods; construct a flood risk map; estimate flood damage using Sentinel-1A SAR data; compare AHP results. The research used a literature review and geo-data collecting with a GIS-computer database to georeference fieldwork data. Built-up, Cropland, Rock, Waterbody, and Forest were categorized using 2020 Sentinel 2A images. Thematic maps were employed for Land use and Land cover, slope, rainfall, soil, Euclidean River Distance, and Flow accumulation. Multi-criteria analysis was done by assessing flood risk and GIS elements. A flood risk map was created by weighting the overlay. Five flood zones were created (Very High, High, Moderate, Low, and Very Low). 5% of the study area, or 35km2, is at high risk, 21% is low, and 74% is mild. Copernicus SAR data pre- and post-flood were processed on Google Earth Engine to map flood extent and determine if the MCA map accurately represents flood-prone locations in the research area. The research suggests periodic review, real-time flood susceptibility monitoring, early warning, and swift damage assessment to prevent flood hazards and other environmental threats.

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