Dam break modelling and flood inundation mapping using GIS and HEC-RAS: a case study of the Tiga Earth dam, Kano State, Nigeria

A dam is constructed across a river, which stores and supplies water for various purposes. Though the dams have many benefits, there is always a threat of a break. The research is aimed at developing a dam break simulation model for the Tiga dam and producing an inundation map of affected areas. The study conducted a dam break analysis for the Tiga dam in Kano State, Nigeria, using HEC-RAS and HEC-HMS. The analysis simulated dam failure scenarios to predict breach parameters and flood hydrograph downstream. The results showed that 213 communities would be affected, with 122 in Jigawa State and 91 in Kano, covering an area of 4,397.06 km². Breach peak flow was estimated as 117,000 m³/s, arriving in 31.3 min. Validation of the hydrodynamic breach model performance was done using the observed annual outflow and simulated results, employing the Nash -Sutcliffe efficiency (NSE) statistical analysis. The NSE score of 0.71 indicates a decent fit of the HEC-RAS model to the data. The study recommends that the Hadejia Jama'are River Basin Development Authority implement the findings to develop emergency response plans and flood mitigation strategies to safeguard lives and property downstream. Future studies should conduct socio-economic impacts on affected areas.