Assessment of changes in precipitation intensities in Ontario

The intensities of short-duration rainfalls are fundamental inputs to design of stormwater management infrastructure for urban areas. Such infrastructure, are designed, in part, to control urban flooding and require specification of storms for specific recurrence intervals. However, implicit in design tasks of stormwater infrastructure is the need for the infrastructure to function for many decades. Given that there is widespread evidence that climate change is likely occurring, there is extensive interest in whether the frequencies of urban storms are changing and hence, whether urban infrastructure designs need to be changed in response to the global climate change reality.; To examine whether the recurrence intervals of severe storms are changing, historical records for thirteen locations distributed throughout Ontario are evaluated. The results of the analyses of the historical records for rainfall intensity/recurrence interval/duration are provided for each of these locations, and demonstrate there is evidence that rainfall intensities are, indeed, changing in Ontario.