Abstract

The aim of this study was to perform an assessment of flood vulnerability in Onitsha using Remote Sensing approach. Its objectives are; to delineate different vulnerability levels of flooding in the study area, to determine the effect or impact of flooding on different land cover types and to produce flood vulnerability map of the study area. The methodology involves the acquisition of sentinel-2 and SRTM covering the study area, image classification and accuracy assessment, SRTM processing and reclassification and flood modelling. The classification achieved an overall Classification Accuracy of 92.49% and kappa statistics of 0.9348. The image classification results indicate that built up area accounted for the largest land cover/use of about 57.97% with an area of 159.76sqkm while vegetation had the second largest with 23.09% and an area of 63.63sqkm, water body had 12.40% with an area of 34.17sqkm and bare ground had 6.53% with an area of 18sqkm. The flood hazard mapping results indicated that high-vulnerability zone occupied 40.85% of the entire study area, covering an area of 112.59sqkm, while moderate vulnerability zone occupied 24.52%, covered an area of 67.58sqkm low vulnerability zone occupied 20.28% covering 55.89sqkm while no vulnerability zone occupied 14.33% covering an area of 39.5sqkm. The flood hazard zone maps produced in this research are beneficial and are recommended that they be used in encouraging hazard zone residents to prepare for the occurrence of flooding. In order to achieve this however, local authorities must ensure that emergency procedures are established, and that information about what to do in the event of a flood is made available to the general public.