Probable maximum precipitation for 24-h duration over an equatorial region: Part 2-Johor, Malaysia

Probable maximum precipitation (PMP) is a characteristic of rainfall at a particular location that can be used in designing water impounding structures. The PMP for rainfall stations in Malaysia by Hershfield statistical method in earlier studies was estimated using a frequency factor of 15 which is the highest value in the world. The value of 15 as frequency was found to be too high for a humid country like Malaysia. The objective of this study therefore was to provide a fresh and reliable estimates of PMP in Malaysia using historical rainfall data. In this updating study, annual maximum 1-day rainfall data from 39 rainfall stations with records longer than 15 years found in the state of Johor, Malaysia, were analysed to obtain estimates of 24-h point PMP using an appropriate frequency factor calculated. Results of the 24-h PMP are presented in the mapped form. It was found that 24-h PMP over Johor varied from about 400 mm to over 1000 mm and there is a tendency for PMP to be higher on the east coast while decreasing westwards. The average ratio of the 24-h PMP to the highest observed rainfall was found to be about 2.0.