Flood frequency Analysis of River Bako, Niger State, Nigeria

Abstract

Estimation of design flood for River Bako Kpakungu, Minna, Niger State, Nigeria is an important components needed for the construction of hydraulic structures across the River. The unit hydrograph method was used to calculate the peak flow. Three distributions: Normal, Extreme value type (I) and Gamma distributions were applied to 25 (Twenty Five) years annual rainfall data to find the distribution that best fit the rainfall data employed. Among the three distributions used, the Extreme Value Type I (EVTI) was found to have the line of best fit with the regression coefficient of 0.96. Also, the annual maximum rainfall data for 25 years were employed to estimate design flood. For the design flood in the selected -River Bako four different types of land cover were considered and corresponding design flood estimated. The probable maximum precipitation obtained formed the basis for the estimation of Probable Maximum Flood for the return periods of 25, 50 and 100 years. The Probable Maximum Flood (PMF) obtained for the return period of 25, 50 and 100 years were 132.8, 144.2and 154.9 respectively.