GIS-Based Analytical Hierarchy Process Modeling for Flood Vulnerability Assessment of Communities Along Otamiri River Basin Imo State, Nigeria

Abstract

In recent times, communities along the Otamiri River Basin in Imo State have been grappling with flooding issues, especially during the rainy season. This occurs despite the presence of underground drainage systems. The primary concern is heavy rainfall causing the river to overflow and lead to flooding. Hence the study aimed at identifying the flood-prone areas in the Otamiri River Basin in Owerri, Imo State. The objectives are to establish factors for evaluating flood vulnerability within the study area;  to classify and standardize the factors according to levels of vulnerability; to determine the reliability of the classified factors; and  to produce a flood vulnerability map showing vulnerable areas in the study area. The methodology involved collecting Shuttle Radar Topography Mission and Sentinel 2A imagery of July 2022, and processing the data with ArcGIS and QGIS software to determine the topography and vulnerability areas through geo-referencing and classification. The Analytical Hierarchy Process (AHP) model was employed to identify high flood risk areas, considering factors like drainage density, slope, soil type, precipitation, population density, Euclidean distance, and land use. The study's results categorized vulnerability into five levels: Very Low (0.09% of Owerri, minimal risk), Low (12.93% with lower risk), Moderate (68.83% facing substantial risk), High (18.18% with significant risk), and Very High (0.03% posing extreme risk). These findings are recommended as foundational data for future flood studies in the region.