Developing an empirical formulae to estimate rainfall intensity in Riyadh region

Abstract

The purpose of this paper is to develop an empirical formula to estimate design rainfall intensity based on intensity–duration–frequency (IDF) curves. These curves have been generated from a 32-year recorded rainfall data for Riyadh region. Rainfall intensity–duration–frequency curves describe rainfall intensity as a function of duration for a given return period which are important for the design of storm water drainage systems and hydraulic structures. The formula is derived using the analysis of results of three different frequency methods, namely: Gumbel, Log Pearson III, and Log normal. These methods are used to obtain the IDF curves for six different durations (10, 20, 30 min, and 1, 2, 24 h) and six frequency periods (2, 5, 10, 25, 50, 100 years) where the best method of IDF estimation is recommended for future analysis. The equation can predict rainfall intensity in Riyadh region for any return period with a given storm duration and calibrated parameters obtained from IDF curves. Good match was achieved between its results and other analytical methods results such as Gumbel method. Moreover, it allows incorporating data from non-recording stations, thus remedying the problem of establishing IDF curves in places with a sparse network of rain-recording stations.