Enhanced flood hazard modelling using hydraulic, analytical hierarchical process and height above nearest drainage model
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ORIGINAL ARTICLE
Enhanced flood hazard modelling using hydraulic, analytical hierarchical process and height above nearest drainage models in Ogunpa river basin, Ibadan, Southwestern Nigeria Akinola Adesuji Komolafe1 · Idowu Ezekiel Olorunfemi2 · Francis Omowonuola Akinluyi1 · Michael Adetunji Adeyemi1 · Jesutofunmi Adeola Ajayi1 Received: 15 June 2020 / Accepted: 31 October 2020 © Springer Nature Switzerland AG 2020
Abstract Flood risk mapping and analysis have gained much attention globally due to the increasing rate of flood disasters in most coastal and riverine areas. As a key element of flood risk study, mapping and delineation of flood hazard areas are very important for risk management and disaster reduction. We analysed potential flood hazards zones in Ogunpa river basin using integrated hydraulic modelling, the height above nearest drainage (HAND) model and multi criteria decision analysis (MCDA). An event-based flood simulation using FLO-2D model was done for the 28 h of the flooding event, while HAND model was employed in modelling the terrain to delineate inundation extent in the basin. In addition, seven flood causative factors were integrated using the Analytical Hierarchical Process (AHP) to delineate potential hazard zones in the study area. Flood inundation model result from FLO-2D revealed inundation depths between 0 and 5.24 m, an indication of intense flood hazards capable of causing lots of damages. MCDA results were classified into least, low, moderate, high and extreme flood hazard zones, while the classified HAND model include none, very low, low, moderate and high flood hazard zones. The MCDA results revealed that the downstream portions of the basin are mostly susceptible to moderate flood hazard compared to low vulnerability observed majorly in the upriver parts of the catchment. The comparison between the estimated flood depths ranges of 0.3–5.2 m by the FLO-2D model and the HAND model value range of 0–5 m (high flood hazard zone) revealed a strong similarity. In all, areas closed to the river course are highly vulnerable to flooding. The output of this study can serve as policy and decision-making tools for future flood hazard analysis, prevention and reduction plans at the research location. Keywords Flood modeling · HAND index · FLO-2D · Multi-criteria analysis · Remote sensing and GIS
Introduction Flood is one of the major annual natural hazards of global concern due to its impacts on the socio-economic and environmental development of several affected countries (Karmokar and De 2020). Many regions of the world have witnessed increasing floods and damages in recent years (Chang and Guo 2006). According to UNISDR (2013a), * Akinola Adesuji Komolafe [email protected] 1
Department of Remote Sensing and GIS, Federal University of Technology, Akure, Nigeria
Department of Agricultural and Environmental Engineering, Federal University of Technology, Akure, Nigeria
2
floods cause more than 20,000 deaths annually and affect around 75 million individuals globally. With po
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