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

Abstract

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,