Regional rainfall distribution for Canada

Abstract Current point rainfall frequency analysis techniques used in engineering design are outdated. In this study, data distribution and analytical techniques are reviewed, and a new method for regional analysis of rainfall is presented. The regional analysis is performed using data across Canada, and takes advantage of recently developed linear order statistics of L-moments. Numerical analysis of 320 stations showed that Canada may be considered as one homogeneous region with respect to L-skewness and L-kurtosis. However, the L-coefficient of variation shows regional variability that is related to the mean annual precipitation (MAP). A regional parent distribution is identified as the general extreme value (GEV), with parameters depending on MAP and storm duration. These findings differ from present methodology, whereby the Gumbel I distribution is used irrespective of storm duration.