Modeling of Rainfall Characteristics for Monitoring of the Extreme Rainfall Event in Makassar City

Flooding is a common problem that occurs in some regions of Indonesia, including Makassar city. In the planning of flood control, rainfall variables are very necessary as the frequency, intensity and duration of rainfall. The relationship of these variables can be expressed in a curve Intensity-Duration-Frequency (IDF). The objectives of this study are to identify the best fitting distribution of rainfall data of Makassar city and also to model the relationship between rainfall intensity, rainfall duration and rainfall frequency that is described through IDF curves. The annual maximum daily rainfall data from Ujung Pandang rainfall station of Makassar is used in this study for the period 1986-2015. Data collection was performed at the Department of Water Resources Management in South Sulawesi province. Five distributions which are considered are Gumbel, Generalized Extreme Value (GEV), Generalized Pareto (GPA), Generalized Logistic (GLO) and Pearson type III (P3) distributions. The study result found that the probability distribution of rainfall data in Makassar city has a generalized extreme value distribution. Meantime, based on IDF curves shown that the longer the rainfall duration, the rainfall intensity decreases for various return periods. The results of this study are expected to be valuable information for designers of water management.