Canadian Forces personnel sandbag a house against the floodwaters Thursday in Laval. Ryan Remiorz / THE CANADIAN PRESS
During his Sunday tour of Île Bigras, a picturesque Laval community in the middle of Rivière des Prairies that’s been flooded twice in the last three years, Premier François Legault said Quebec was going to have to rethink its compensation strategies given the increasing frequency of flooding events caused by climate change.
Spring flooding in Canada: City of Ottawa declares state of emergency as Quebec calls for further evacuations
“We’re going to see more and more of these extreme weather events more regularly,” Justin Trudeau said.
As Quebecers grapple with another disastrous season that has flooded 1,900 homes so far, only two years after water levels rose to historic levels and flooded out more than 5,000 residences, there is a common perception that the frequency and severity of flooding events has increased significantly over the last decades.
Backing that perception up with hard figures is difficult, however, due to a lack of historical data and the extreme swings seen in natural variability.
For instance, explains Daniel Henstra, a University of Waterloo professor specializing in flood-management policies, and a fellow at the Centre for International Governance Innovation, a so-called “100-year flood” refers to a flood the magnitude of which has a statistical probability of occurring once every 100 years, or, in other words, has a 1 per cent chance of occurring in any given year. Since the probability is the same from year to year, it is possible for a community to experience such a flood in two consecutive years.
Among 84 closed roads across the province is a stretch of the Trans-Canada Highway between Oromocto and River Glade. Everyone from community volunteers to federal officials and Canadian Armed Forces are pitching in to help – even federal fisheries officers are aiding evacuation efforts in Fredericton, Quispamsis and St. George.
Quebec officials warn of possible dam failure on Rouge River
“Due to a lack of available (longitudinal) data, it is practically impossible to know whether the frequency of these ‘100-year floods’ has increased in Canada,” Henstra said. “Although it would seem that way, given the number of events we have been experiencing, we don’t have sufficient, convincing evidence that these events are actually becoming statistically more likely.”
Add to that the fact it’s difficult to separate climate change effects from natural variability. Quebec has experienced several devastating inundations in the past since all rivers flood at some point as part of the natural life cycle of a river, said Pascale Biron, an expert in river dynamics and professor in Concordia University’s department of geography, planning and environment. The Canadian Disaster Database run by Public Safety Canada records that Quebec has suffered several major flooding events over the last decades. They include one in the Saguenay region in 1996 that forced the evacuation of 15,825 residents, and another in 1998 in eastern Ontario and Quebec that evicted 3,757 from their homes. In 1974, major flooding ravaged the Maniwaki region.
But whether there are more frequent, severe storms now than in decades past is hard to tell, Biron notes, because there are not many gauging stations in Quebec that have long historical records, and the way flood levels are measured has evolved technologically, so it’s not always possible to compare discharge levels from the 1930s with those from the 2000s. At the same time, changing land use from forested zones into urban areas can also have a major effect.
“Unfortunately the science is just not good enough to attribute a particular local extreme weather phenomenon to climate change, particularly in a data-poor country like Canada,” Henstra said.
What scientists have concluded is that most climate change models predict more frequent extreme precipitation events in the future, Henstra noted, which could lead to more river flooding, as well as urban flooding and coastal flooding as sea levels rise.
“Overall (not just in Quebec), scientists believe that events that were on average occurring once in 20, 50 or 100 years, may occur more frequently in the future because warmer air is able to hold more moisture, so perhaps a 50-year flood will become a 40-year flood in the future,” Biron said.
All this precipitation will also add to the strain on local rivers and the City of Ottawa has declared a state of emergency, calling in the military to help just like it already is across the border in western Quebec.
“I think what is safe to assume is that the climate will become more unpredictable in the future, so we need to prepare for flood events that we have not seen yet, realizing that the natural variability will always remain, but the amplitude of the changes will likely increase,” Biron said.
Canadian capital Ottawa declares state of emergency as waters swell
The inability to present hard data can be frustrating for researchers who note it makes it more difficult to convince Canadians to pay now in order to prevent catastrophes in the future.
Environment Canada is advising that between 20 and 35 millimetres could fall in Ottawa-Gatineau and communities south and east of the capital today and tonight.
In its overview of climate change nationally, Natural Resources Canada wrote that national trends in precipitation are difficult to assess largely due to the fact it comes in different states (rain, snow, freezing rain) and differs largely by region.
“Nevertheless, Canada has, on average, become wetter during the past half century, with mean precipitation across the country increasing by about 12 per cent,” the overview finds.
In Quebec, government ministries base their strategies and actions on studies published by scientists and researchers in the domain, said Louise Quintin, a spokesperson for the province’s ministry of public security. After the 2017 floods, Quebec ordered the creation of costly flood maps for the whole province by the end of 2020, after decades of going without.
In Quebec, the combination of science and repeated, heavily publicized flooding events occurring in rapid succession appear to be shifting government attitudes.
Public Security Minister Geneviève Guilbault says the dam is expected to hold up, but the province isn't taking any chances and is asking residents to leave their homes.
Water levels at the hydroelectric dam at Bell Falls on the Rouge River in Quebec's western Laurentians reached heights never before seen Thursday, triggering a mandatory evacuation of houses downstream.
Provincial police were going door-to-door to ensure residents left the area, Quebec Public Security Minister Geneviève Guilbault said Thursday evening. Some people had to be evacuated by helicopter.
Flooding expected to exceed 2017 levels in Ottawas west end
The area around the dam is mainly forest dotted with small farms. It's sparsely populated, but there are around 23 principal residences and 38 cottages — many of which may not be occupied — so the exact number of people affected is unknown, Guilbault said.
The Public Security Ministry sent an evacuation alert Thursday afternoon after Hydro-Québec notified the ministry that the Rouge River had reached levels never before seen.
"A dam like Bell Falls is designed to withstand a flood that happens once in a thousand years," said Simon Racicot, head of production at Hydro-Québec. "Today at noon we reached that level, and at that point there's a protocol in which we notify civil security and residents of imminent danger."
A "once in a thousand years" scenario means there is a 0.1 per cent chance of a flood of this magnitude happening in any given year.
Ottawa declaring state of emergency in response to flooding; calling for military and provincial help
The average flow at Bell Falls is 103 cubic metres per second, Hydro-Québec data shows. On Thursday, it increased ninefold to reach 980 cubic metres per second.
Ottawa declares state of emergency due to threat of flooding
The utility is confident that the dam will not break, Racicot said, but for the safety of citizens, it could take no risks.
"We're entering an unknown zone, really," he said. "So we have to wait and see what happens over the next few days."
Ottawa declares state of emergency due to flooding
If the dam ruptures, it would take around 45 minutes for floodwaters to reach those buildings under the evacuation order, police said.
Police said they are using "all the means at their disposal to ensure people's safety."
Officials say the flood risk remains high because of a combination of precipitation in the forecast and melting snow to the north.
Canadian capital declares state of emergency as flood waters rise
"We are asking residents of areas affected by forced evacuations to co-operate with the authorities," the Sûreté du Québec said on Twitter.
Brenda Finn, who lives on Rivière Rouge Road, was among those evacuated from her property by helicopter Thursday.
She said her house is high and dry, well above the road that skirts the river, so when soldiers arrived at her door last Sunday to say she should think about leaving, she told them she wasn't worried.
"I said, 'I'm not going.' But it's a different story when you have a dam breaking," she told CBC News.
When a municipal official called Thursday to tell her to call her neighbours and let them know the dam may not hold, she said she "knew it was all over. I knew they were coming."
"It was really beautiful," she said of her helicopter ride. "The sun was out; you're looking at the River Rouge — the nice farmland and the trees."
However, rain in the forecast for the next few days means water levels at the dam could rise a further 70 centimetres, so Finn is well aware the worst might be yet to come.
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On Thursday evening Transports Québec reopened Highway 50 in both directions along the stretch that passes through Grenville-sur-la-Rouge, after closing it in the afternoon.
“You’re going to see more firefighters, you’re going to see more police officers and more municipal workers to help for floods that could come this weekend,” said Martin Guilbault, operations chief of the Montreal fire department.
That highway, which links Gatineau to Highway 15 at Mirabel, crosses the Rouge River about 16 kilometres downstream from the dam, where the Rouge empties into the Ottawa River.
“They told us that there was no time to pack our bags and that we had to leave because the dam was maybe going to break,” Denise Audet said. She said everything happened so quickly she “didn’t have time to be scared.”
The evacuation order for the area downstream from Bell Falls comes as large swaths of Quebec and neighbouring eastern Ontario are dealing with spring floods.
Ottawa declared a state of emergency on Thursday, while Montreal warned water levels could rise even higher this weekend.
Greg MacCallum, director of the New Brunswick Emergency Measures Organization, said flooding forecasts had dipped slightly and may not reach last year’s levels, but warned they were still well above the flood stage.
Bell Falls, or Chute-Bell, is about 23 kilometres northwest of Grenville-sur-la-Rouge, Que., which is on the north side of the Ottawa river, across from Hawkesbury, Ont.
John MacFarlane is a journalist at CBC Montreal. He has lived and worked in Australia and the U.S. He also works as a filmmaker and producer.
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