Frequency Analysis of Extreme Events and Developing Intensity Duration Frequency Curves: The Case of Jimma Town, Ethiopia

Abstract

Frequency analysis of rainfall data enables to determine the future extreme events and developing IDF curves. The object of this study was to analysis the frequency of extreme events in precipitation, and develop Intensity, duration and frequency (IDF) curves. In this study 30 years daily rainfall data (1986-2015) from the National Meteorological Agency (NMA) was used. To develop IDF curves graphical and statistical methods were used. The result obtained indicates, the General Extreme Value (GEV) was the best fitted distribution function to the maximum annual daily observed data, at 95% of confidence interval. As the result of the computed sub daily rainfall data, the highest rainfall value for the duration of 24 hrs. and 100-year return period was 83.86 mm, whereas the lowest rainfall value was obtained for the duration of 10min and 2 year of return period was 13.34 mm. The correlation coefficient between the IDF curves developed from observed data and the Computed IDF curves was (R 2 =0.99).