ABSTRACT
A “design storm” is a rainfall temporal pattern that is commonly used in the design of urban drainage systems. The design storm of a specified exceedance probability is obtained from the intensity-durationfrequency (IDF) relationship based on the specified probability and duration. For a site for which sufficient rainfall data are available, a frequency analysis of annual maximum rainfalls can be performed. Results of this analysis are often summarised by “intensityduration-frequency” (IDF) relationships for a given site, or are usually presented in the form of a “precipitation frequency atlas”, which provides rainfall accumulation depths for various durations and return periods over the region of interest (Hershfield, 1961; Hogg and Carr, 1985; Institute of Hydrology, 1999). Peyron et al. (2005) have provided a critical assessment of the performance several different design storm models in the estimation of peak flows and volumes for urban watersheds of different sizes, shapes, and imperviousness levels.
