Comprehensive GIS-Based Flood Risk Assessment of Vulnerable Areas in Anambra State, Nigeria
Abstract
Flood risk assessment is critical for effective flood management and mitigation strategies. Understanding spatial variability in flood susceptibility helps in designing targeted interventions. This study aims to evaluate flood risk in a specified area by integrating multiple hydrological and topographical parameters. The assessment incorporates drainage density, slope, land use and land cover (LULC), rainfall, elevation, and proximity to rivers and roads. Data were analyzed to categorize regions into five flood risk levels: very low, low, moderate, high, and very high. The study reveals significant spatial variability in flood risk. High-risk areas, constituting 37.28% of the study area, are primarily near drainage networks and steep slopes. Regions with low to moderate drainage density, covering 40.25%, are prone to waterlogging, while areas with high drainage density, accounting for 59.75%, manage local runoff but may exacerbate downstream flooding. The LULC analysis shows that forested areas (43.62%) mitigate flood risk, whereas built-up areas (35.20%) increase it. Higher rainfall in the southern part of the study area and varied elevation also influence flood risk distribution. High-risk regions need robust flood defenses and efficient drainage systems. Sustainable land management practices and advanced flood control measures are essential for mitigating flood risk, particularly in high rainfall and steep slope areas. This study uniquely combines multiple parameters to provide a comprehensive flood risk assessment, offering valuable insights for targeted flood mitigation strategies and enhancing regional flood resilience.
Keywords
Drainage Density
Hydrological Studies
Slope Analysis
Spatial Variability
References
Adewumi, R., Agbasi, O., & Mayowa, A. (2023). Investigating groundwater potential in northeastern basement complexes: A Pulka case study using geospatial and geo-electrical techniques. HydroResearch, 6, 73–88. https://doi.org/10.1016/j.hydres.2023.02.003 Ahlmer, A. K., Cavalli, M., Hansson, K., Koutsouris, A. J., Crema, S., & Kalantari, Z. (2018). Soil moisture remote-sensing applications for identification of flood-prone areas along transport infrastructure. Environmental Earth Sciences, 77(14). https://doi.org/10.1007/s12665-018-7704-z Aja, D., Elias, E., & Obiahu, O. H. (2019). Flood risk zone mapping using rational model in a highly weathered Nitisols of Abakaliki Local Government Area, South-eastern Nigeria. Geology, Ecology and Landscapes, 4(2), 131–139. https://doi.org/10.1080/24749508.2019.1600912 Akaolisa, C. C., Agbasi, O. E., Etuk, S. E., Adewumi, R., & Okoli, E. A. (2023). Evaluating the Effects of Real Estate Development in Owerri, Imo State, Nigeria: Emphasizing Changes in Land Use/Land Cover (LULC). Journal of Landscape Ecology, 16(2), 98– https://doi.org/10.2478/jlecol-2023-0012 Azizian, A., & Brocca, L. (2019). Determining the best remotely sensed DEM for flood inundation mapping in data sparse regions. International Journal of Remote Sensing, 41(5), 1884–1906. https://doi.org/10.1080/01431161.2019.1677968 Buba, F. N., Ojinnaka, O. C., Ndukwu, R. I., Agbaje, G. I., & Orofin, Z. O. (2021). Assessment of flood vulnerability in some communities in Lokoja, Kogi State, Nigeria, using Participatory Geographic Information Systems. International Journal of Disaster Risk Reduction, 55, 102111. https://doi.org/10.1016/j.ijdrr.2021.102111 Chukwuma, E., Okonkwo, C., Ojediran, J., Anizoba, D., Ubah, J., & Nwachukwu, C. (2021). A GIS based flood vulnerability modelling of Anambra State using an integrated IVFRN-DEMATEL-ANP model. Heliyon, 7(9), e08048. https://doi.org/10.1016/j.heliyon.2021.e08048 Da Silva, L. B. L., Alencar, M. H., & De Almeida, A. T. (2020). Multidimensional flood risk management under climate changes: Bibliometric analysis, trends and strategic guidelines for decision-making in urban dynamics. International Journal of Disaster Risk Reduction, 50, 101865. https://doi.org/10.1016/j.ijdrr.2020.101865 Dike, V. N., Lin, Z. H., & Ibe, C. C. (2020). Intensification of Summer Rainfall Extremes over Nigeria during Recent Decades. Atmosphere, 11(10), https://doi.org/10.3390/atmos11101084 Dim, C. I. P., Onuoha, K. M., Okwara, I. C., Okonkwo, I. A., & Ibemesi, P. O. (2019). Facies analysis and depositional environment of the Campano – Maastrichtian coal-bearing Mamu Formation in the Anambra Basin, Nigeria. Journal of African Earth Sciences, 152, 69–83. https://doi.org/10.1016/j.jafrearsci.2019.01.011 Dottori, F., Szewczyk, W., Ciscar, J. C., Zhao, F., Alfieri, L., Hirabayashi, Y., Bianchi, A., Mongelli, I., Frieler, K., Betts, R. A., & Feyen, L. (2018). Increased human and economic losses from river flooding with anthropogenic warming. Nature Climate Change, 8(9), 781–786. https://doi.org/10.1038/s41558-018-0257-z Dwarakish, G. S., Pai, B. J., & Rajeesh, R. (2024). Urban Flood Hazard Zonation in Bengaluru Urban District, India. Journal of Landscape Ecology, 17(1), 89–106. https://doi.org/10.2478/jlecol-2024-0006 Egbinola, C., Olaniran, H., & Amanambu, A. (2015). Flood management in cities of developing countries: the example of Ibadan, Nigeria. Journal of Flood Risk Management, 10(4), 546–554. https://doi.org/10.1111/jfr3.12157 Ekeu-Wei, I. T., Blackburn, G. A., & Giovannettone, J. (2020). Accounting for the Effects of Climate Variability in Regional Flood Frequency Estimates in Western Nigeria. Journal of Water Resource and Protection, 12(08), 690–713. https://doi.org/10.4236/jwarp.2020.128042 Ezeokoli, F. O., Okoye, P. U., & Ugochukwu, S. C. (2015). The Upshot of the 2012 Flooding on Structural Components and Fabrics of Buildings at Ogbaru, Anambra State Nigeria. 3(4), 129–136. https://doi.org/10.12691/ajcea-3-4-3 George, N. J., Agbasi, O. E., Umoh, J. A., Ekanem, A. M., Ejepu, J. S., Thomas, J. E., & Udoinyang, I. E. (2022). Contribution of electrical prospecting and spatiotemporal variations to groundwater potential in coastal hydro-sand beds: a case study of Akwa Ibom State, Southern Nigeria. Acta Geophysica, 71(5), 2339–2357. https://doi.org/10.1007/s11600-022-00994-2 Huang, Y., Chen, X., Li, F., Zhang, J., Lei, T., Li, J., Chen, P., & Wang, X. (2018). Velocity of water flow along saturated loess slopes under erosion effects. Journal of Hydrology, 561, 304–311. https://doi.org/10.1016/j.jhydrol.2018.03.070 Idowu, D., & Zhou, W. (2019). Performance Evaluation of a Potential Component of an Early Flood Warning System—A Case Study of the 2012 Flood, Lower Niger River Basin, Nigeria. Remote Sensing, 11(17), 1970. https://doi.org/10.3390/rs11171970 Ifeanyichukwu, K. A., Okeyeh, E., Agbasi, O. E., Moses, O. I., & Ben-Owope, O. (2021). Using Geo-electric Techniques for Vulnerability and Groundwater Potential Analysis of Aquifers in Nnewi, South Eastern Nigeria. Journal of Geology, Geography and Geoecology, 30(1), 43–52. https://doi.org/10.15421/112105 Jimme, M. A., Bashir, A., & Adebayo, A. A. (2016). Spatial Distribution Pattern and Terrain Analysis of Urban Flash Floods and Inundated Areas in Maiduguri Metropolis, Borno State, Northeast, Nigeria. Journal of Geographic Information System, 08(01), 108–120. https://doi.org/10.4236/jgis.2016.81011 Kandissounon, G. A., Kalra, A., & Ahmad, S. (2018). Integrating System Dynamics and Remote Sensing to Estimate Future Water Usage and Average Surface Runoff in Lagos, Nigeria. Civil Engineering Journal, 4(2), 378. https://doi.org/10.28991/cej-030998 Komolafe, A. A., Awe, B. S., Olorunfemi, I. E., & Oguntunde, P. G. (2020). Modelling flood- prone area and vulnerability using integration of multi-criteria analysis and HAND model in the Ogun River Basin, Nigeria. Hydrological Sciences Journal, 65(10), 1766– https://doi.org/10.1080/02626667.2020.1764960 Liu, J., & Niyogi, D. (2019). Meta-analysis of urbanization impact on rainfall modification. Scientific Reports, 9(1). https://doi.org/10.1038/s41598-019-42494-2 Mahmoud, M. I., Duker, A., Conrad, C., Thiel, M., & Ahmad, H. S. (2016). Analysis of Settlement Expansion and Urban Growth Modelling Using Geoinformation for Assessing Potential Impacts of Urbanization on Climate in Abuja City, Nigeria. Remote Sensing, 8(3), 220. https://doi.org/10.3390/rs8030220 Malgwi, M. B., Schlögl, M., & Keiler, M. (2021). Expert-based versus data-driven flood damage models: A comparative evaluation for data-scarce regions. International Journal of Disaster Risk Reduction, 57, https://doi.org/10.1016/j.ijdrr.2021.102148 Ogunrinde, A. T., Oguntunde, P. G., Akinwumiju, A. S., & Fasinmirin, J. T. (2019). Analysis of recent changes in rainfall and drought indices in Nigeria, 1981–2015. Hydrological Sciences Journal, 64(14), 1755–1768. https://doi.org/10.1080/02626667.2019.1673396 Okoli, E., Akaolisa, C. C. Z., Ubechu, B. O., Agbasi, O. E., & Szafarczyk, A. (2024). Using VES and GIS-Based DRASTIC Analysis to Evaluate Groundwater Aquifer Contamination Vulnerability in Owerri, Southeastern Nigeria. Ecological Questions, 35(3), 1–27. https://doi.org/10.12775/eq.2024.031 Olorunfemi, I. E., Komolafe, A. A., Fasinmirin, J. T., Olufayo, A. A., & Akande, S. O. (2020). A GIS-based assessment of the potential soil erosion and flood hazard zones in Ekiti State, Southwestern Nigeria using integrated RUSLE and HAND models. Catena, 194, https://doi.org/10.1016/j.catena.2020.104725 Owokotomo, A. I., Ajayi, O. O., Alabi, O. O., & Chukwuka, A. V. (2020). Watershed land use, surface water vulnerability and public health risks of two urban rivers, Ado-Ekiti, South-West Nigeria. SN Applied Sc
