An appropriate formula of rainfall data is the Intensity Duration Frequency (IDF) relationship. The rainfall IDF relationship is one of the tools used considerably in water resources engineering, either in planning, designing and operating projects of water resources, or in flood control projects. The purpose of this paper is to update rainfall IDF curves of Baghdad city developed in previously. The frequency analysis of available rainfall data is perform by three statistical methods, namely, the Gumbel Distribution Theory, the Log Pearson Type III and Log Normal Distribution to attain rainfall intensities for various short durations (0.25, 0.5, 1, 2, 3, 6, 12 and 24) in hours and return periods (2, 5, 10, 25, 50 and 100) in years. IDF equation was derived based on Bernard equation and the results of three distributions were compared using Kolmogorov-Smirnov goodness of fit test with help of the Easy fit software 5.6. The results of three methods were close and accepted at 10% significant level. The maximum rainfall intensity of 118.052mm/hr was happened at the duration 0.25hr of the return period 100yr, whereas the minimum rainfall intensity of 1.257mm/hr was happened at the duration 24hr of the return period 2yr.
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