Development of New Extreme Rainfall Maps for Urban Infrastructure Design in Canada Using the Scale-Invariance Generalized Extreme Value Distribution

Abstract

AbstractInformation on extreme rainfall events for a given duration and a given frequency of occurrence is commonly required for the design of various urban hydraulic structures. More specifically, this information is extracted from the rainfall “intensity–duration–frequency” (IDF) relations. In Canada, these IDF relations are provided by Environment Canada for approximately 650 stations across Canada with at least 10-year record by fitting the Gumbel distribution to the annual maximum (AM) rainfall data for nine different rainfall durations (from 5 min to one day) using the method of moments. However, it has been widely known that the Generalized Extreme Value (GEV) distribution using the L-moment estimation method can provide more accurate extreme rainfall estimates. In addition, rather than fitting the GEV distribution to AM rainfall series for each duration independently as commonly used in the traditional method, the scale-invariance GEV model has been shown to provide more robust estimates of extreme rainfalls since it can take into account the relationship between the statistical properties of the AM rainfall processes over different durations. Therefore, this study presents the development of more accurate and more robust site-specific IDF relations as well as regional extreme rainfall maps for different locations across Canada based on all available historical AM rainfall data and using the improved scale-invariance GEV model. It is expected that these newly developed IDF relations and regional extreme rainfall maps could produce more cost-effective design of urban infrastructure in Canada.