Meteorological Data Analysis for Drainage System Design

Abstract

The frequency analysis of point rainfall data is examined. Particular emphasis is placed on the distinction between meteorological events observed in nature and the definition of events for statistical analysis. A meteorological event may involve several periods of intermittent rain, all of which are associated with the same atmospheric disturbance. The return period of such an event is determined from analysis of synoptic data. In contrast, statistical events are based on the external characteristics (volume, duration, average intensity, and interevent time) of recorded rainfall, without reference to the return period of the synoptic conditions which caused that rainfall. Statistics of storm event characteristics are calculated, correlations between characteristics are explored, and probability density functions for individual storm event characteristics and for combinations of characteristics are developed. Intensity‐duration‐frequency, volume‐duration‐frequency, and intensity‐volume‐frequency analyses are performed. A frequency analysis on rainfall volumes demonstrates that event volumes derived from an intensity‐duration frequency (IDF) curve do not have the same frequency as that IDF curve. It is concluded that for a particular location, there is no single design storm that is suitable for all types of drainage designs.