Developing rainfall intensity-duration-frequency curves at the western flank of Mt. Merapi, Indonesia

The intensity and frequency of extreme events are continuously increasing due to climate change, leading to a rise in flood probability. Considering flood discharge by connecting the recent rainfall data is critical. This research aims to provide temporal characteristics of rainfall intensity in the western flank of Mt. Merapi. The 10-, 20-, 30-, 40-, 50-, 60-, 120-, 180-, 360-, and 720-minutes annual maximum rainfall data from five stations were used to develop the intensity-duration-frequency (IDF) curves by using logarithmic and power equations. Distribution frequency analysis was carried out using extreme value type-I, normal, lognormal, Pearson type-III, and log Pearson type-III methods. The results showed that the proposed model is satisfying for short-duration rainfall of less than 360-minutes with R-values of more than 90%. These alternative IDF curves based on short-duration rainfall data significantly improve the accuracy of lahar flood mitigation measures in Mt. Merapi.