Estimating the Intensity Equations for Rain Intensity Frequency Curves (Mosul /Iraq)

The relationship between the rainfall intensity, duration, and frequency (IDF) is widely used in water resources engineering in designing hydraulic structures, such as culverts and sewage systems, and for reducing and controlling floods. In this study, the curves of (IDF) were found for five rain stations registered in different regions in northern Iraq, i.e., Mosul, Tal-Afar, Sinjar, Rabia, and Tal-Abta, and for different periods extending from 1990 to 2019. The Indian Meteorological Department (IMD) empirical equation was utilized to obtain data during short periods, i.e., 10, 20, 30, 60, 120, 180, 360, 720, and 1440 minutes. Also, three probability distributions were used: the Gumble Distribution, the Log Pearson Type III Distribution, and the Log-Normal Distribution, for various return periods (2, 5, 10, 25, 50, and 100) years. Easy fit 5.6 software includes the tests (Kolmogorov-Smirnov, Anderson -Darling (AD), Chi-Squared (χ2)) was used to determine the most suitable distribution for the observed data among the three used distributions. The results demonstrated an insignificant difference between the three applied distributions and the statistics values that fell within the significance level, with priority to the Log Pearson-III distribution.