Probability distribution models for flood prediction in Upper Benue River Basin – Part II

The annual maximum series of discharge or flow data for 32 years (1955 to 1986) at three flow gauging stations namely; River Katsina Ala at Serav, River Taraba at Garsol and River Mayokam at Mayokam located within Upper Benue river basin of Nigeria were each fitted with three probability distribution models viz ;Log normal, Extreme value Type 1 and Log Pearson Type III and subjected to four specific measures of errors in prediction i.e., RMSE, RRMSE, CC and MAE in order to select the best probability distribution model that fits the observed flow data at the stations. The best fit distribution model at each station was then utilized to predict return period floods for each station for return periods of 2, 5, 10, 25, 50, 100, 200, and 500 years. The best fit probability distribution models obtained for the different stations are Log Normal, Log Normal and Log Pearson Type III for the stations at River Katsina Ala at Serav, River Taraba at Garsol and River Mayokam at Mayokam respectively. The corresponding return period flood prediction equations useful in the estimation of extreme flood discharge for the stations were also obtained .This type of information is used for urban development planning, flood plain management, establishment of insurance premiums and for efficient design and location of hydraulic structures. Key words: Discharge, probability distribution models, return period, gauging station goodness of fit tests