DEVELOPMENT OF INTENSITY - DURATION FREQUENCY RELA,T,IONSHIPS FOR BURUNDI COUNTRY

Abstract

The rainfall-Intensity-Duration-frequency (IDF) relationships is one of the most commonly used tools in water resources engineering , either for planning , designing and operating of water resource projects. The IDF allows for the estimation of the return period of an observed rainfall events for different time durations conversely, it may be used to estimate rainfall amount corresponding to a given return period for different aggregation times. The objective of the research is therefore, to develop operational IDF relationships for the Burundi whole country based on nineteen first class stations. The annual maximum rainfall magnitudes of varying durations were collected from rainfall charts and fitted to the probability distributions after which quantiles estimated for different return periods based on the best fitted distributions. Then, the rainfall intensities are computed and the parameters of the general mathematical form of IDF were generated for each station. Three different methods expressing rainfall intensities were established for the study area: the general mathematical form, curves relating Intensity-Duration-Frequency of rainfall and IDF maps. Burundi area has been regionalized and four different regions were established based pooled quantiles of the 24-hour durations. The regional IDF parameters, IDF curves and regression equations were developed for each region. This helps to extract the intensity of rainfall of any durations and frequency at areas farthest from the principal stations. The result of this research can be used to all water professionals and designers on the activities of water resources and other related disciplines with in the region by supplying important information's on rainfall Intensity, Duration and Frequency relationships.