Enhanced flood hazard modelling using hydraulic, analytical hierarchical process and height above nearest drainage models in Ogunpa river basin, Ibadan, Southwestern Nigeria

• Published in: Modeling earth systems and environment 2021-06, Vol.7 (2), p.967-981
• Main Authors: Komolafe, Akinola Adesuji, Olorunfemi, Idowu Ezekiel, Akinluyi, Francis Omowonuola, Adeyemi, Michael Adetunji, Ajayi, Jesutofunmi Adeola
• Format: Article
• Language: English
• Subjects: Analytic hierarchy process; Catchment area; Chemistry and Earth Sciences; Computer Science; Decision analysis; Decision making; Disasters; Downstream effects; Drainage; Drainage basins; Earth and Environmental Science; Earth Sciences; Earth System Sciences; Ecosystems; Environment; Environmental risk; Flood control; Flood hazards; Flood management; Flood mapping; Flooding; Floods; Hazard assessment; Hazards; Height; Mapping; Math. Appl. in Environmental Science; Mathematical Applications in the Physical Sciences; Modelling; Original Article; Physics; Risk analysis; Risk management; River basins; Rivers; Statistics for Engineering; Two dimensional models; Vulnerability
• ISSN: 2363-6203; 2363-6211
• DOI: 10.1007/s40808-020-01037-9

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.