The Probability Distributions of Daily Rainfall for Kuantan River Basin in Malaysia

The extreme hydrological events such as flood and drought can have severe impacts on society. Malaysia has experienced extreme rainfall events during the monsoon seasons that last for several hours and lead to flash flood. The location of interest of this study is Kuantan river basin in Pahang State, Malaysia since flash floods occur in Kuantan every year. Rainfall data at four stations for Kuantan river basin are collected and used in this study. The objectives of this study are: (i) to perform the frequency analysis with some commonly used probability distributions, (ii) to identify the most appropriate probability distribution, and (iii) to estimate the maximum annual daily rainfall for selected return periods. In this study, Normal, 2P and 3P Lognormal, Gamma, Gumbel, Generalized Extreme Value, Pearson Type III and Log-Pearson Type III are identified to evaluate the best fit probability for rainfall distribution in Kuantan river. Based on the analysis of goodness of fit tests, Generalised Extreme Value distribution proves to be the most appropriate distribution for annual maximum daily rainfall at all stations under study for Kuantan river basin. The estimated extreme rainfall with various frequencies can be used as the basic inputs in hydrologic design such as in the design of storm sewers, culverts and many other structures as well as inputs to rainfall runoff models.