Climate Change Impact on Design Storm and Performance of Urban Storm-Water Management System - A Case Study on West Central Mountain Drainage Area in Canada

A number of future climate projections indicate a likelihood of increased magnitude and frequency of hydrological extremes for many regions around the world. The urban storm-water management infrastructures are designed to mitigate the effect of extreme hydrological events. Changes in extreme rainfall events will have a significant implication on the design of storm-water management infrastructures. This study assessed the potential impact of changed rainfall extreme on drainage systems in the West Central Mountain drainage area located in Southern Ontario, Canada. First, the design storms for the study area were calculated from observed rainfall data and the North American Regional Climate Change Assessment Program (NARCCAP) climate simulations based on SRES A2 Scenario. Frequency analysis was performed on the annual maximum time series data by using the best fitted distribution among twenty seven distributions. The Pearson chi-square test and Kolmogorov-Smirnov were used to test the goodness of fit of each distribution. The results show that L-moment Pareto distribution was selected the most often for data from six RCM+GCM pairs. Overall increase of storm depth in the future is highest when the distributions were identified by the Kolmogorov-Smirnov test. The design storm depths calculated from the observed and climate model simulated data were used as input into an existing PCSWMM model of the study area for flow simulation and hydraulic analysis for the storm-water management system, specifically storm sewer and detention pond. The results show an increase in design storm depths under projected climatic change scenarios that suggest an update of current standard for designing both the minor system and detention pond in the study area. The assessment results of storm water management infrastructures indicate that performance of the detention pond as well as the storm sewer network will deteriorate under future climate condition.