RAINFALL INTENSITY CHARACTERIZATION IN SEMI-ARID REGIONS: DERIVATION OF IDF CURVES USING MULTI-MODEL APPROACHES FOR HILLA CITY, IRAQ

This study aims to develop a formula to estimate rainfall intensity depending on Intensity Duration Frequency (IDF) curves. The rainfall IDF relationship is one of the tools used in water resources engineering to classify rainfall intensity for a given return period. Daily rainfall data for 20 years from (2003 to 2022) from the Iraqi Metrological Organization and Seismology was used to generate IDF curves for Hilla City. Three methods, namely, Gumbel, Log Normal, and Log Pearson III, were used to derive IDF curves using MATLAB software for six durations (1, 2, 3, 4, 5, and 6 hr) and six return periods (2, 5, 10, 25, 50, and 100 years). Then, empirical equations were developed to estimate rainfall intensity for the various rainfall durations and frequency periods. The results showed an excellent correlation coefficient (R2) for these empirical equations with an average (94.4 %) the maximum rainfall intensity was 48.6 mm/hr during a 1 hr return period and a 100-year return period. However, the 2.7 mm/hr was the minimum rainfall intensity that occurred during the 6-hour duration period and 2-year return period