Severe weather is increasing in frequency and intensity, and that spells trouble with storm drains, roads and hillside developments designed without giving due consideration to climate change, says a report cited in the Vancouver Sun today.
The report is based on research – dubbed “controversial” by the Sun – contained in a 2001 University of British Columbia master’s thesis published last summer in the Journal of the American Water Resources Association. The thesis says there are going to be even more massive mudslides and floods of the kind seen across southern B.C. “If we are experiencing climate change,” said Robert Millar, UBC civil engineering professor, “then engineers are using old data to design for future conditions that may not be valid.” The UBC study jolted skeptics at the Greater Vancouver Regional District into a mad scramble of damage control. Not surprisingly, the GVRD’s findings were “at odds” with those at UBC. With the back of its hand, the GVRD dismissed the UBC research as merely “short-term changes.” The records used for UBC’s analysis, moreover “are simply too short to be meaningful.” It also warned that “A long-term rise in the magnitude of high intensity rainfall events could … necessitate the replacement of the storm water and sewerage drainage, which would be associated with very high costs.”
But Millar said because municipalities replace pipe and drains regularly, it would be cheap and easy to increase capacity gradually. Also, the UBC projections have been re-run using several mathematical techniques and come out the same. “We stand by these results.” Miller said the severe weather trend is easy to miss using standard analysis, which assumes that past conditions are a good indicator of future conditions. Total annual rainfall figures from Vancouver International Airport show a 15- to 20-per-cent increase over the past 40 years. But five-minute bursts of rainfall have doubled in intensity to a rate of over 60 millimetres an hour in 2001, up from about 25 millimetres an hour in the mid-60s. “In North Vancouver, over the past 30 years, we observe an increase in intensity of 40 per cent in two-hour high intensity rain bursts,” he said.
“That’s a huge difference for someone designing infrastructure.” Storm sewers are designed to last about 50 years, “so we argue that it would be prudent to begin to accommodate these increases,” Millar said. (City of Surrey engineers estimate the cost of replacing one block of storm sewers at about $200,000.) Most municipal sewers installed over the past 30 years would be designed for flows that would overwhelm the system about once in 10 years and cause “nuisance flooding.
“Millar and his associates, Catherine Denault and Barbara Lence, believe those one-in-10-year events could soon be happening every year. Short periods of intense rain tend to destabilize hillsides and result in mudslides of the type that have plagued the area around Hope and that caused the death of a woman in North Vancouver last year.
On Monday, Highway 3 was buried by 50 metres of mud three metres deep. “We know that landslides tend to be triggered by high intensity short duration rainfall and if the frequency and intensity of rainfall is increasing, then we are likely to see more landslides,” Millar explained. The projections cited in the UBC article were first completed in 2001 for Denault’s master’s thesis, but the trio reworked the data last year to account for the most recent weather trends and their conclusions remain the same.
Elsewhere, insightful Sun columnist Stephen Hume muses at the way climate-change skeptics dismiss recent weather as “anomalies,” saying “There’s nothing you can do about it, so just get on with adapting to changing circumstances.” Scientists, on the other hand, see a predicted pattern in which normal extremes in the weather cycle will be exacerbated by rising temperatures accelerated by the greenhouse effect. “And extrapolating outward from what they see now, some are saying things can get much nastier.” Hume notes that even publications like The (ultra-conservative) Economist are now embracing the notion that human activities, particularly the burning of fossil fuels, are contributing to global warming and helping to accelerate the pace of change.
“And the global insurance business, which has a vested interest in getting this right if any industry does, is warning that human activities are altering global climate.” Hume wrote. “Weather-related disasters in 2005 caused the largest losses ever recorded and insurers now warn that homes and businesses located in areas at risk from weather extremes may be considered uninsurable. “Perhaps this helps explain why two-thirds of Canadians say they believe the scientists who say humans are accelerating global warming while only a third believe it is all just business as usual.”