Risk of Exceeding Extreme Design Storm Events under Possible Impact of Climate Change

English Abstract:

In order to evaluate how the risk of intensive storms, which is the probability of exceeding certain storm intensity one or more times within a given number of years, is expected to change in central Alberta in the future. We proposed a new Risk Chart which represents the nonlinear relationship between storm intensity, design project life, and the risk of intensive storms being exceeded within the project life. First, a comparison between estimated Risk Charts of the past (1914–1995) and the present (1984–2010) for central Alberta shows that the risk of intensive storms occurring has increased for all storm durations in recent years, and the risk had been higher for storms of large return periods (≥ 50-yr). Given a design project life of 50-yr, the average increase in risk is 9 percentage points (pp). Second, the uncertainty associated with projecting the risk of intensive storms occurring in 2011–2100 was assessed by considering three Special Report on Emissions Scenarios (SRES) of four Global Climate Models (GCMs) of IPCC (2007) dynamically downscaled by a Regional Climate Model, MM5. Based on storms simulated by MM5 for central Alberta forced by SRES climate scenarios of IPCC for 2011–2100, the median risk for short-duration storms (≤ 1-h) of a design project life of 25-yr and 50-yr is projected to increase up to 37 pp and 38 pp, respectively. In other words, climate change impact could increase the vulnerability of central Alberta to the hazards of flooding by intensive storms in future. The proposed Risk Chart present the risk in a straightforward and meaningful way which will be useful for the long-term planning and engineering design of municipal infrastructure.