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Floods are a natural environmental process, but they can be expensive, damaging, and deadly. They’re actually the costliest natural disaster for Canadians, causing more home insurance claims than any other event. They occur five times more often than wildfires, which is Canada’s next-most common natural disaster, and they can cost cities billions of dollars in damages.

Flood management structures, like dams and levees, have been used for centuries to reduce the impact of sudden shifts in water levels. But new technology has changed how cities and governments approach flood management. Innovative structures, more accurate measuring tools and new data collection methods have made early detection crucial for flood response plans.

Canadian floods sit in the cultural memory as scary but fascinating occurrences. Here are some that have left the biggest impact in Canadian history - as well as the technology that contained them.

Hurricane Hazel - 1954

In early October 1954, hurricane planes spotted Hazel just east off the island of Grenada. Days later the storm crossed Haiti, leaving a thousand people dead and the landscape devastated. It moved extremely fast for a hurricane, more than thirty miles per hour, and soon reached Washington after hitting and damaging large cities in North and South Carolina.    

Hazel eventually reached Toronto, just before midnight in mid-October.  The Humber River flooded and the city, unprepared for serious flooding, suffered serious infrastructure damage to highways, roads, and bridges - including the recently-constructed Highway 400. Hurricane Hazel caused over eighty Canadian deaths and left hundreds more stranded and homeless.

The disaster was a wake-up call for Canadians, who had felt that hurricanes were a “southern problem” until Hazel hit home. The Toronto and Region Conservation Authority was created in response, and their first order of business was creating a comprehensive Plan for Flood Control. The plan proposed developments of large dams, flood channels, and erosion control methods. Hazel, while devastating, lead to the creation of some of the first Canadian disaster management programs, some of which are still in place today.

Red River Flood - 1997

Manitoba has seen more floods than any other province in Canada, largely due to the Red River. The Red River has flooded more than a dozen times in the last two hundred years, (2013 being the most recent) and 1997 was one of the biggest.

Manitoba was hit with an unseasonably severe blizzard in April after a long and cold winter. A flood had been forecasted - similar conditions had led to the Red River floods of 1950 and 1979 - but the unexpected severity of the blizzard created the perfect storm for the “flood of the century”.

As the snow and ice melted, surrounding land was flooded as far as three miles inward of the waterway. Plains were completely submerged, and more than 28,000 people were evacuated from neighbouring cities and the United States.

Still, the flood avoided causing the catastrophic damage it should have due to Winnipeg's Red River Floodway. Constructed decades earlier, at high cost and against many citizen’s wishes, the floodway was able to divert most of the water away from the city. To combat the overflow, citizens armed with sandbags constructed emergency dikes and blockades just days before the flood reached critical volume.

In the aftermath, drainage was a problem - most homeowners couldn’t return until more than a month later. Ultimately the flood caused over three billion dollars in damages, and more than five hundred million for Manitoba - but the Floodway undoubtedly saved dozens, if not hundreds of lives. It paved the way for high-cost disaster management systems across Canada, and cities began planning their own flood measures.

Toronto Flood of 2013

Most Torontonians remember the summer flash flood in 2013, which turned out to be one of Ontario’s costliest natural disasters ever. Ninety millimeters of rain fell in less than an hour during a busy Monday evening commute, resulting in massive flooding across the GTA. Thousands were stranded on trains and buses as the city saw ninety-seven millimeters of rain, while Pearson International Airport recorded a single-day rainfall of 126 millimeters - higher than previous record-holder Hurricane Hazel.

All transportation halted as major arteries, train tracks and underground subway stations flooded. Fourteen hundred commuters were stranded for more than seven hours in a northbound Go Train, and abandoned cars littered the Don Valley Parkway. More than 300,000 Torontonians lost power at some time during the deluge, and Mississauga saw power outages for more than eighty percent of its residents. The Insurance Bureau of Canada says property damage exceeded $850 million.

The storm raised debate once again over the city’s flood preparedness infrastructure, which had been called aging at best and useless at worst. Many took it as a sign that the weather is changing on us - the flood was linked to a then-recently commissioned study by the city, which had predicted a sharp increase in extreme storms as a result of climate change.

But Toronto’s transportation manager, Stephen Buckley, resisted that connection. “On a probability curve, this event was way off the charts,” Buckley said during a press meeting. “We don’t design systems to handle something of this size and magnitude... This is sort of an anomaly.”

The Future

The debate continues - but new technology is allowing us to track weather patterns better than ever before. We can now see each drop of rain as it’s collected, allowing for real-time alarming and flood forecasting once rainfall hits critical thresholds. Automated alarms are triggered after certain volumes are reached, and operation staff and flood maintenance workers can be notified immediately of sharp water increases.

Heated tipping bucket rain gauges can also monitor frozen precipitation, by triggering read switches after snow or frozen rain melts and reaches a certain volume. Data collection improvements allow us to set up access points in more remote locations across Ontario, and we can now record precipitation in areas that were completely unaccessible before.

Toronto’s rain mapping is improving - and by combining these with Mississauga and Peel Region’s data, and data from across Canada, we can get a much more comprehensive picture of rainfall patterns on a larger scale. As time goes on we can consistently track and compare weather patterns to see how much, and to what scale, climate change is affecting flood rates.