FIELD-DEMONSTRATED EVIDENCE OF CHANGING RAINFALL INTENSITIES IN ONTARIO FOR SHORT DURATION STORMS

1. B. Vasiljevic, E. McBean, and R. Rudra University of Guelph Guelph, Ontario, Canada FIELD-DEMONSTRATED EVIDENCE OF CHANGING RAINFALL INTENSITIES IN ONTARIO FOR SHORT DURATION STORMS

2. Designs for sewers, culverts, and stormwater management ponds rely upon the intensity-duration-frequency (IDF) curves • Stormwater facilities intended to last for decades • Implications also for water supplies

3. Implication of rainfall intensity is clear and profound Wells become submerged

16. Interpretation of Trends in Precipitation • Increases in precipitation intensity are occurring throughout Ontario • The changes of rainfall intensities in southern Ontario are more profound, but substantial regardless • For example, there is evidence of the five-year storm increasing at 2% per year in Waterloo so in thirty years, this translates to a sixty percent increase in precipitation intensity in thirty years in Waterloo if these trends continue • Design features for water infrastructure must be modified, to reflect the changes in intensity that are being observed.

18. Conclusions • There is evidence that rainfall intensities are changing, since the five year storm of four decades ago is now the two year recurrence interval storm, and hence translates to implications for design of urban infrastructure. • Implications to water supply systems are highly relevant

19. Questions?