TOPOGRAPHIC INFORMATION SYSTEM FOR FLOOD RISK ASSESSMENT OF ATIBA LOCAL GOVERNMENT AREA, OYO, OYO STATE, NIGERIA

ABSTRACT Flooding remained one of the most frequent and destructive environmental hazards in Nigeria, particularly in rapidly developing regions where unregulated urban expansion intensified exposure to flood risks. This study developed a comprehensive Topographic Information System (TIS) for Atiba Local Government Area in Oyo State to support flood risk assessment and sustainable spatial planning. The project utilized secondary geospatial datasets including Shuttle Radar Topography Mission (SRTM) elevation data, Landsat 9 imagery, rainfall records from CHIRPS, and administrative boundary data from OpenStreetMap. All datasets were pre-processed and analyzed within a GIS environment using ArcGIS 10.8. Land Use/Land Cover (LULC) classification identified five major classes: vegetation 38%, bare land 24%, built-up areas 20%, farmland 17%, and water bodies 1%, with vegetation occupying the largest. Topographic parameters including elevation, slope, drainage density, and underground water network were derived from the SRTM data and reclassified into flood susceptibility levels. Rainfall data were also grouped into intensity classes and spatially analyzed to identify high-precipitation zones. Weighted overlay analysis was applied to integrate all influencing parameters, assigning weights according to their relative contributions to flood occurrence. The final flood risk assessment map categorized the study area into five susceptibility zones: very low, low, moderate, high, and very high risk. Results revealed that the central and southern portions of Atiba LGA were most vulnerable to flooding due to low elevation, gentle slopes, high rainfall intensity, and dense built-up surfaces, while the northern highlands exhibited significantly lower flood potential.