Deriving rainfall intensity–duration–frequency (IDF) curves and testing the best distribution using EasyFit software 5.5 for Kut city, Iraq

Abstract The intensity of rainfall can be considered as an essential factor in designing and operating hydraulic structures. intensity–duration–frequency (IDF) curve is used for projects such drainage networks, road culverts, bridges, many other In the field water resources engineering, IDF dependent widely on plan, designing, project. Additionally, it different flood engineering purpose this research to get frequency rain duration Al KUTcity, Iraq, find curves. Three techniques analysis (Gumbel distribution, lognormal, log Pearson Type III) were depended formulate relationship based data during period between 1992 2019. Distribution methods involving Gumbel, III applied by Indian Meteorological Department (IMD) short periods 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 12, 24 h with 10, 25, 50, 100 years return periods. results showed that reduced storm increased, if was large, any specific a higher intensity. Using EasyFit 5.5 software, all durations, lognormal probability distribution best fit group estimated intensities precipitation years. According obtained results, one notice increased increment periods, but decreased duration. resulting models could improve accuracy results.