Advanced uncertainty quantification in rainfall-intensity duration frequency curve modeling: A case study of Hilla City and surrounding regions, Iraq

The rainfall-intensity duration frequency (IDF) relationship is mostly used in water resource engineering to plan, design, and operate water source projects and projects to manage flood dangers.Engineers must accurately calculate rainfall to design structures that effectively manage runoff collection, conveyance, and storage, as the hydrologic cycle relies on precipitation.An analysis is conducted on the annual rainfall measurements (mm) from five atmospheric observatories in Iraq (Najaf, Hilla, Kerbala, Diwaniya, and Baghdad) spanning 1989 to 2023.The objective is to determine the characteristics of the observed frequency distributions.The Gamma, Log Normal, and Normal distributions compare the data.Kolmogorov-Smirnov, Anderson-Darling, and Chi-Square are study tests.The IDF depict extreme rainfall values over 15, 30, and 60 minutes, with 5, 10, 15, and 50-year return periods.The results indicate that the Chi-Square test has the most optimal distribution among all the stations.The normal distribution was found to be the best for the years (5, 10, 15, and 50) through the IDF curves drawing of stations where the distributions were compared.Equations of Hilla station were found through an IDF equations curve to Hilla from its surrounding stations; and get the error.The result was good agreement, with a ratio Coefficient of Determination ranging from 83.2 to 94.7.