Open this photo in gallery A flooded street in Calgary's Mission neighbourhood June 21, 2013. (John Lehmann/The Globe and Mail) John Lehmann

An ancient river channel that cuts through downtown Calgary is now plugged with concrete. Edmonton’s city-owned utility is ranking drainage basins by risk. Key roads in Fredericton have been elevated to guard against the next deluge.

Cities and utility providers across Canada are girding for a wetter future as rising global temperatures supercharge storms and lead to more frequent and severe flooding.

The preparation, while not entirely new, has gained urgency amid a push by major insurers, bond-rating agencies and governments to reduce the mounting financial and social costs tied to extreme weather. It aligns with an emerging consensus that worldwide efforts to curb emissions of planet-warming greenhouse gases are likely to fall short of targets, necessitating costly retrofits of infrastructure to cope with the worsening effects of climate change.

Story continues below advertisement

“We have a growing adaptation deficit in Canada, and we’ve got to reverse that trend,” said Blair Feltmate, head of the Intact Centre on Climate Adaptation at the University of Waterloo.

A new report from the think tank pegs flooding in major urban centres as Canada’s costliest and fastest-growing extreme-weather challenge, with implications for everything from residential insurance premiums to municipal credit ratings.

It cites data from the Insurance Bureau of Canada that show payouts for catastrophic losses jumped from an average $405-million a year between 1983 and 2008 to a yearly average of $1.8-billion since 2009, with flooding accounting for more than half of the increase.

The report is the latest in a series sponsored by major insurer Intact Financial Corp. and is also backed by the National Research Council of Canada and the Standards Council of Canada.

It makes the case for a national framework to limit flood risks in communities by taking into account factors such as local design standards, aging infrastructure and whether a region has a history of extensive flooding.

Some jurisdictions face threats from ice-jamming in rivers, while others are exposed to increased rainfall or coastal flooding. Communities built prior to 1970 are especially vulnerable.

Catastrophic Insured Losses in Canada In billions of dollars, 1983–2017 Loss + loss adjustment expenses Estimated trend Fort McMurray fire $5.5 5.0 4.5 Alberta and Toronto floods 4.0 3.5 Eastern ice storm 3.0 2.5 Ontario wind/rain 2.0 Quebec floods 1.5 1.0 0.5 0.0 1983 1990 1995 2000 2005 2010 2015 *Values in $2017; total natural catastrophe losses normalized by inflation and per-capita wealth accumulation JOHN SOPINSKI/THE GLOBE AND MAIL, SOURCE: Source: university of waterloo (IBC Facts Book, PCS, CatIQ, Swiss Re, Munich Re & Deloitte) Catastrophic Insured Losses in Canada In billions of dollars, 1983–2017 Fort McMurray fire $5.5 Loss + loss adjustment expenses 5.0 4.5 Estimated trend Alberta and Toronto floods 4.0 3.5 Eastern ice storm 3.0 Slave Lake fire 2.5 2.0 Ontario wind/rain Quebec floods 1.5 1.0 0.5 0.0 1983 1990 1995 2000 2005 2010 2015 *Values in $2017; total natural catastrophe losses normalized by inflation and per-capita wealth accumulation JOHN SOPINSKI/THE GLOBE AND MAIL, SOURCE: Source: university of waterloo (IBC Facts Book, PCS, CatIQ, Swiss Re, Munich Re & Deloitte) Catastrophic Insured Losses in Canada In billions of dollars, 1983–2017 Fort McMurray fire $5.5 5.0 Loss + loss adjustment expenses 4.5 Estimated trend 4.0 Alberta and Toronto floods 3.5 Eastern ice storm 3.0 Slave Lake fire 2.5 2.0 Ontario wind/rain 1.5 Quebec floods 1.0 0.5 0.0 1983 1985 1990 1995 2000 2005 2010 2015 *Values in $2017; total natural catastrophe losses normalized by inflation and per-capita wealth accumulation JOHN SOPINSKI/THE GLOBE AND MAIL, SOURCE: Source: university of waterloo (IBC Facts Book, PCS, CatIQ, Swiss Re, Munich Re & Deloitte)

Many were developed on floodplains without positive overland flow routes, for example. That means water can easily pool and flood homes as storms grow more intense and frequent.

Story continues below advertisement

“We’re seeing, particularly in these existing areas, the fact that some of the older systems were not designed to be resilient to these types of storms,” said Ron Scheckenberger, a principal at engineering firm Wood PLC.

Downtown Calgary was inundated in 2005 and 2013. The second deluge was the city’s largest since 1932. Fast-rising waters from the Bow River killed five people, forced the evacuation of 80,000 residents and led to as much as $6-billion in financial losses and property damage.

Frank Frigo, a river engineer with that city’s water resources department, said the disaster prompted a collaboration with energy company TransAlta Corp. to boost storage levels in large hydro reservoirs upstream of Calgary’s core.

About $30-million was also budgeted for berms and concrete flood walls, portions of which are designed to stop water flowing along an ancient channel that slices through modern-day downtown. Together the measures are meant to withstand more powerful storms and floods.

“And that’s in part because we learned our lesson very clearly in 2013,” Mr. Frigo said.

Similarly, Edmonton’s EPCOR Utilities Inc. is accelerating plans to deal with risks, with an emphasis on pockets of the city seen as vulnerable to overland flooding. “Those are events that as a utility or a community, you already see," said Susan Ancel, EPCOR’s director of storm-water strategies. “What is changing with climate change is they’re happening more frequently."

Story continues below advertisement

In Fredericton, critical sections of road were elevated and storm-water systems reinforced after flooding last year along the Saint John River smashed previous records. The measures are a stopgap for homeowners, acknowledged Jody Boone of the city’s operations division. "But it might gain them an extra couple of days to get things out of the basement.”