Floods in Canada: On the Rise

It’s springtime in Canada. For many, spring brings a sense of relief that the cold, short days are behind us and gratitude for the warm sun on our skin and the sweet fragrance of blossoming trees.

However, this contentment may also be marred with ambivalence: worry that the wet days of spring may precipitate flooding.

And flooding it is. It’s only early May and already there’s flooding in the east and flooding in the west.

Canadians are starting to get used to news stories about springtime flooding. Although flooding has and will always happen—t is a natural part of the water cycle, and it’s how the physical characteristics of rivers and streams are themselves formed—“disaster floods” are becoming more prolific in Canada, according to the Canadian Disaster Database (CDD).

The CDD tracks events that meet one or more of the following criteria:  

  • 10 or more people killed;
  • 100 or more people affected/injured/infected/evacuated or homeless;
  • an appeal for national/international assistance;
  • historical significance; and
  • significant damage/interruption of normal processes such that the community affected cannot recover on its own.

According to the Canadian Disaster Database, the number of floods that meet these criteria in Canada have been increasing every decade for the past century.

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Although the database has only logged information up until 2016, this decade (2010-2020) seems on track to yet again be the worst decade for disaster flooding.

What’s more, disaster floods have been particularly destructive in recent years. The five most destructive floods in Canadian history have all occurred since 2010. In order of severity, these are:

  1. The 2013 flood in Southern Alberta, when a rain-on-snow event caused the Bow, Elbow, Red Deer, Sheep, Little Bow and South Saskatchewan rivers to swell well over their banks, forcing 100,000 people to evacuate from their homes. Damages totalled an estimated $2.72 billion.
  2. The 2014 flood in Southern Manitoba, when the Assiniboine, Qu’Appelle and Souris Rivers reached record flows after heavy rains. Damages totalled an estimated $1.16 billion.
  3. The 2010 flood in Southern Alberta and Saskatchewan, when record rainfall made the South Saskatchewan River and surrounding tributaries swell, causing evacuations on the Blood Tribe reserve and in Medicine Hat, AB. Damages totalled an estimated $1.03 billion.
  4. The 2013 flood in Toronto, ON when an intense storm dropped 126mm of rain in just three hours, causing flash flooding in the Don River Valley and other areas of the city. Damages totalled an estimated $940 million.
  5. The 2011 flooding in Manitoba, which affected 15 communities along the Assiniboine, Roseau, and Red Rivers after wet spring weather caused these rivers to breach their banks. 2500 people were forced to evacuate. Damages were estimated at just under $600 million.

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Understanding what is driving this apparent increase in disaster floods is complex—and one that we’ll explore further in a future piece. An important confounding factor is the growing population in Canada. Much of the country’s population lives in known floodplain areas. A flood risk model completed in 2016 estimated that 20% of households in Canada are at “high risk” of floods, and 10% are at “very high risk”. So, it makes sense that floods are having greater impact on society and property because there are more people and things that can be damaged in close proximity to flooding water bodies compared to the past when there were fewer people, less infrastructure, and smaller rebuilding costs.

When it comes to the role climate change is playing, the evidence is less clear. Although many scientists are suggesting that extreme flooding could well be our “new normal” in an era of climate change, there are a lot of confounding factors (like land-use change, quality of hydrologic data, etc.) that make it hard to conclude with certainty that climate change is driving more frequent and severe flooding. We’ll explore this more in a follow-up piece.

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Reasons aside, it’s early in the year, but across the country there’s  already been a fair share of incidents: an ice jam on the Grand River caused severe flooding in southern Ontario in February. Melting of unusually large snowpacks in B.C.’s southern interior have resulted in evacuation notices in some communities while others are on flood watch wondering if they will be next. In Southern New Brunswick, the floodwaters of the St. John’s River have already damaged thousands of properties.

As I write this, I occasionally glance out my window to the stream across the street. I live in Kelowna, B.C. right across from Mill Creek—a highly urbanized stream that flows through the city from east to west. The stream is rushing wildly by. Although it hasn’t yet reached the top of the channel walls in my neighbourhood, a bit upstream it has flooded out parts of the fields surrounding our community recreation center. In anticipation for the worst, the City has issued a state of emergency.

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Last year, there was extensive flooding along the creek that caught our local and provincial governments off guard. An intense thunderstorm brought significant rainfall, generating lots of runoff from the rain itself and from the snowmelt that the storm precipitated. Within 24 hours, whole swathes of land around the creek were inundated. Water levels continued to rise over the next couple days.

After the streams were done flooding, it was the lake that flooded. By early June, it was about one meter higher than full pool. Flooded beaches and impaired water quality kept me and many others away from our beloved lakes--a great reprieve from the 30°C+ weather and powerful sun of the Okanagan summer.

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Last year, when I was helping neighbours with sandbags, many shared incredulous observations. “I’ve been living here for 40 years and have never seen anything like this,” one man said.

I know that flooding has happened in the Okanagan for as long as the Okanagan has been a valley (i.e. not a glacial lake--it was definitely flooded then). However, years ago we built flood infrastructure to stop floods from happening (and then proceeded, foolishly, to build in floodplains). That infrastructure itself brought many ecological issues—but it did hold back water.

But after two years in a row of extreme flooding, it certainly seems as though we’ve entered a new era—one that is challenging the infrastructure built decades ago. Is this the “new normal” that we are increasingly hearing so much about, a bout of bad luck, or something else?


Our next piece in the series will examine the evidence around causes of extreme flooding, with a focus on climate change and land-use change.

 

This article was originally written in spring 2018. It was edited in spring 2019 on the advice of a preeminent flooding expert.