Analysis of Eastern Anatolia Region rainfall intensity-duration-recurrence interval (frequency) curves

Rainfall intensity-duration-recurrence interval (frequency) curves (IDF) express the relationship between the duration, intensity and frequency (recurrence) of rainfall obtained from a series of analyzes of observed rainfall data. These curves are used in safe and economical planning and design of water resources projects and urban rainwater systems. The aim of this study is to develop IDF curves using rainfall series of standard durations (5, 10, 15, 30-minute and 1, 2, 3,4, 5, 6, 8, 12, 18 and 24 hours) at the twelve gauge stations loacted in the Eastern Anatolia Region, Turkey. For this purpose, first of all, three (3) different homogeneity tests (Standard Normal Homogeneity test, Buishand test and Pettitt test) were used to determine possible anthropogenic effects in data series. Then, the statistical significance of the trends in the data was analyzed with the Mann-Kendall trend test. In the modeling phase, Gamma, Gumbel, Normal, Lognormal, Logistic, Log-Logistic and Weibull probability distribution functions, which are widely used in the literature, were used. Five different criteria (Akaike Information Criterion (AIC), Bayesian Information Criterion (BIC), Kolmogorov-Smirnov test (KS), Cramer-Von Mises test (CvM) and Anderson Darling test (AD) were used to determine the best distribution among potential candidates. According to the test results, Log-Logistic, Lognormal and Gamma were selected as the best three distributions for modelling the rainfall intensities. In the last stage of the study, rainfall intensities for different return periods (i.e. 10, 20, 50, 100 and 200 years) were computed using the best fitted distrbution functions and the IDF curves were then computed.