Dam break analysis and development of inundation map: a case study of asa dam, ilorin, kwara state, nigeria

Abstract

This paper presents the dam break analysis and development of inundation map for Asa dam in Ilorin, Kwara State. Empirical equations and hydrodynamic simulations with HEC-RAS software were employed to assess the potential flood impact resulting from a hypothetical dam break. The data collected on the dam’s structural and the hydrological characteristics were used to perform a detailed dam break analysis to evaluate flood risks and identify flood-prone areas downstream. MacDonald and Langridge-Monopolis and Froehlich models were used to estimate breach parameters, while HEC-RAS was applied to simulate the flood wave propagation and inundation extent. The empirical analysis produced a peak discharge of 14,152 m³/s, a breach width of 130.86 m, and a failure time of 1.48 hours. Simulation results revealed that the maximum velocity ranges from 6 - 8 m/s with flood depths exceeding 10 meters in low-lying downstream areas. Flood hazard maps identified critical locations at risk, including Coca-kola Road, Amilegbe, and Isale Koko as critical risk locations, with varying degrees of inundation severity. These maps, along with the hydrographs generated, provide valuable information for flood emergency preparedness and early warning systems. A break at Asa Dam could lead to devastating consequences for downstream communities. To prevent the ugly incidence, immediate structural reinforcement, routine maintenance, sedimentation control, and the implementation of community-based flood awareness programs are recommended as decision-making tool for engineers, policymakers, and disaster risk managers.