Articles | Volume 21, issue 5
Research article
09 May 2017
Research article |  | 09 May 2017

A two-parameter design storm for Mediterranean convective rainfall

Rafael García-Bartual and Ignacio Andrés-Doménech

Abstract. The following research explores the feasibility of building effective design storms for extreme hydrological regimes, such as the one which characterizes the rainfall regime of the east and south-east of the Iberian Peninsula, without employing intensity–duration–frequency (IDF) curves as a starting point. Nowadays, after decades of functioning hydrological automatic networks, there is an abundance of high-resolution rainfall data with a reasonable statistic representation, which enable the direct research of temporal patterns and inner structures of rainfall events at a given geographic location, with the aim of establishing a statistical synthesis directly based on those observed patterns. The authors propose a temporal design storm defined in analytical terms, through a two-parameter gamma-type function. The two parameters are directly estimated from 73 independent storms identified from rainfall records of high temporal resolution in Valencia (Spain). All the relevant analytical properties derived from that function are developed in order to use this storm in real applications. In particular, in order to assign a probability to the design storm (return period), an auxiliary variable combining maximum intensity and total cumulated rainfall is introduced. As a result, for a given return period, a set of three storms with different duration, depth and peak intensity are defined. The consistency of the results is verified by means of comparison with the classic method of alternating blocks based on an IDF curve, for the above mentioned study case.

Short summary
A new methodology to obtain design storms for Mediterranean convective episodes is presented, which not only reproduces observed rainfall intensities but also other variables such as temporal pattern, total rainfall volume or the storm duration. The formulation, without using IDF curves, introduces a 2-parameter analytical function and presents an original method to assign the storm return period. Three design storms with similar magnitude but different shapes are derived for each return period.