Evaluation of Stormwater Infrastructure Design Storms Developed Using Partial Duration and Annual Maximum Series Models

Abstract

This study assesses the advantages and limitations of developing design storms using the partial duration series exceedance-based (PDS-E) rainfall frequency model in comparison with the annual maximum series (AMS) model. Rainfall records were obtained from 21 rainfall gauges in Ontario. A procedure to develop the PDS-E was derived, addressing sensitivities to missing values, selection of thresholds, and quantile and confidence limit estimates. The reference values of 1-h duration and 2- and 5-year return period design rainfall intensities were 1% and 3% greater in PDS-E than in AMS data, on average, indicating the merits of using PDS-E data for exceedance-based modeling of frequent events. The PDS-E estimates of 1-h duration and 5-year return period events were 3.5% greater than AMS estimates. The use of the PDS-E method over the AMS method for developing design storms for stormwater infrastructure is recommended.