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A farm is surrounded by floodwaters in Abbotsford, B.C., on Nov. 23, 2021.JONATHAN HAYWARD/The Canadian Press

Chilliwack, home to 114,000 people, is a hundred kilometres east of Vancouver, on the banks of the Fraser River. Its relatively affordable housing in British Columbia’s Lower Mainland makes it one of Canada’s fastest-growing places.

According to a new analysis by The Globe and Mail, Chilliwack is also home to the country’s highest proportion of buildings in what is known as a 100-year floodplain. Almost half its buildings could be flooded. The Globe looked at data and flood models from the University of Western Ontario, and assessed 150 communities of 10,000 people and more.

The results showed a worrisome one in five communities with at least 10 per cent of buildings exposed to river floods. The threat is greatest in Chilliwack, but there is danger across the country, from High River and Canmore in Alberta to Yellowknife in the Northwest Territories to Peterborough in Ontario and Fredericton in New Brunswick.

Floods are, year after year, the most expensive disaster faced by Canada’s cities. One year it’s Calgary. Then it’s Montreal. Fredericton often sees flooding. Last fall in B.C., high water didn’t come from the Fraser but from south of the border. Sumas Prairie, southwest of Chilliwack, was submerged. About $4-billion in costs will be shouldered mostly by federal taxpayers.

The bills from flooding keep escalating. In 2016, the Parliamentary Budget Officer looked at the disaster financial assistance program, started in 1970 and mainly funded by Ottawa. In the quarter century from 1970 through 1994, the flood bill (all figures adjusted for inflation) was $1.1-billion. In the next decade, it jumped to $1.6-billion. Then things starting going parabolic. The cost was $3.8-billion in the decade from 2005 to 2014.

The bills are unlikely to ease, as a warming climate increases the frequency and severity of floods. And The Globe/Western analysis is based on one-in-100-year river floods. That means there’s a 1-per-cent annual chance of flooding. But that is a bare minimum standard, and generally inadequate for building flood defences. One in 200 years is safer, and Winnipeg’s Red River Floodway system is built to withstand a one-in-700-year event. It was built following the flood of 1950 and was bolstered after the 1997 flood. Completed in 2014, it cost $627-million.

And there it is, another big dollar sign. Floods cost a lot money, in three ways. The first is rebuilding after the water recedes. The second is building flood defences before a flood, whether dikes in Chilliwack or the floodway around Winnipeg. The third is bolstering defences after they fail, usually owing to underbuilding or years of neglect – both of which were partly to blame for last fall’s flooding of Sumas Prairie.

In theory, Chilliwack is protected from the Fraser River by dikes. But analyses have suggested that protection is inadequate, and provides a false sense of security. The height of dikes has been recently judged as fair to poor. The city has slowly improved them, but finishing the job could take another decade.

Ideally, cities should back away from rising water – but the reality is usually the opposite. And backing off is also costly. Look at Calgary and the 2013 flood. There was briefly consideration of ceding ground to nature, but a quick eyeballing of the $2-billion-plus cost to buy out homeowners most in danger led to the idea being dropped. Instead, $432-million is being spent on a flood reservoir west of the city on the Elbow River. Work started this year; it won’t be done until 2025 – a dozen years after the big flood.

Then there are Canada’s missing basics: detailed flood maps that are publicly accessible, easily discernible, and up-to-date. While such things should be the national standard, it is unlikely that you, the average Canadian, could pinpoint your home on such a resource. In 2019, after flooding near Montreal, one affected owner, who had been told the home was safe when he bought it, said: “I never thought it could happen here.”

As the PBO reported, flooding is getting more expensive by the year. It’s a trend almost certain to continue, and the ugliest scenarios are truly jarring. For example, a massive Fraser River flood could cost $30-billion, according to a 2016 report. The report notes the “chilling cost of inaction.”

Flooding is a countrywide issue. To prevent a lot of pain and loss in the decades to come, Canada would be wise to spend, today, on prevention.

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