Flood Frequency Analysis of Osse River Using Gumbel’s Distribution

Abstract

This paper shows the result of the study carried out on Osse River with flow measurements carried out at Iguoriakhi. Flood frequency analysis was carried out on the river (Osse river) using Gumbel’s distribution which is one of the probability distribution used to model stream flow. This was necessitated by the need to protect lives and property at the downstream of the catchment area. Gumbel’s distribution was used to model the annual maximum discharge of the river for a period of 20years (1989 to 2008). The measurement was carried out by Benin Owena River Basin Development Authority .From the trend line equation, R² gives a value of 0.954 which shows that Gumbel’s distribution is suitable for predicting expected flow in the river.   From the Gumbel’s distribution using return periods (T) of 2yrs, 5yrs,10yrs, 25yrs, 50yrs, 100yrs, 200yrs and 400yrs; the expected estimated discharges obtained are: 2156.61m³/s, 2436.24m³/s, 2621.38m³/s, 2855.31m³/s, 3028.85m³/s, 3201.11m³/s, 3372.74m³/s and 3544.05m³/s respectively. These values are useful for storm management in the area.

Keywords: flood frequency analysis, probability, Gumbel’s distribution, return period, flow measurement.