Deriving regional Intensity–Duration–Frequency relationship using l-Moment-based regional frequency analysis

Abstract

Regional intensity-duration-frequency (rIDF) relationships are vital for stormwater system design, flood estimation and many other hydrological applications. However, a poor density of measuring stations and short records of sub-daily rainfall measurements are a mong the most important problems when
estimating rIDF. Therefore, this study proposed the application of L-moment-based regional rainfall analysis as a robust and effective way of deriving rIDF for homogenous rainfall regions. The application was demonstrated to one homogenous rainfall region in the North Central Coast in Vietnam (called as - Region IX). Results showed that the region IX formed by 8 rainfall stations was homogenous according to both of the discordancy and heterogeneity criteria. Generalized Logistics provided the best distribution for the duration of 5, 10, 15, 90, 120, 180 min, while General Extreme Values, Log Normal and Pearson Type 3 provided better distributions for durations of 30, 60, 360, 720 và 1440 min. By using the corresponding regional best fit distributions for the different durations, the dimensionless rIDF curves of the region IX were constructed for the respective durations. Finally, a regression model relating the mean values of annual maximum rainfall intensity and their durations and their mean annual rainfall rates was proposed to derive the rainfall intensity of duration d, for the desired return period T at any location of interests in the region