Abstract

Prediction of flood frequency is vital for flood management and construction of hydraulic structures. It is on this basis that this study is set to analyse flood frequency of river Benue at Ibi using the Gumbel distribution method. The study applied a 40-year hydrological record of stage / discharge of river Benue at Ibi for the analysis to predict flood flows for return periods (T) 5, 10, 20, 30, 50, 60, 75 and 100 years. The modelled water level / flood flow magnitude obtained for the respective return period are as follows: 11.50m / 9, 864.10 cumecs, 14.20m / 11,481.00 cumecs, 16.80m / 13, 040.23 cumecs, 18.30m / 13,937.02 cumecs, 20.20m / 15,051.00 cumecs, 20.90m / 15,467 cumecs, 22.50m / 16,568.00 cumecs. The results revealed a gradual rise in both water level and flood flow magnitude with increase in return period. The result of goodness of fit test via non-parametric Chi square test returned insignificant, which indicates that the flood flow data fits Gumbel distribution and hence, can be used to predict the frequency of flood flow of river Benue at Ibi. The study recommends that Taraba State Emergency Management Agency (TSEMA) should note and be guided by both short and long term predictive floods of the return periods for appropriate flood response actions to safeguard communities, economic activities and infrastructure from flood dangers.