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Spring flooding tops Environment Canada’s Top 10 weather stories

Historic flooding across Saskatchewan and Manitoba logged in as the No. 1 weather story in Canada in 2011, Environment Canada says.

“Everything about the flooding, including its size, magnitude and duration, was unprecedented. It was also one of Canada’s few billion-dollar disasters,” the department says in its annual Canada’s Top 10 Weather Stories for 2011 report.

But it was a pretty dramatic year all the way around.

“From the death and destruction following the Japanese earthquake/tsunami to extreme weather in the United States that killed more than 1,000 people through the course of the year, Mother Nature seemed to be on the warpath,” the report said.

2011 was the second-costliest year on record for weather catastrophes globally, with 2005 still holding the No. 1 slot.

For the third year in a row, the Canadian insurance industry faced billion-dollar losses due to weather-related catastrophes. As was the case globally, Canada also had the second-most expensive year for weather losses.

Spring into summer flooding

Epic melts occurred everywhere – from the Qu’Appelle Valley to eastern Manitoba and from The Pas south to the Canadian-American border – resulting in more acreage under water than ever recorded, the report says.

Flood talk was continuous and exhausting, lasting from October 2010 when a weather bomb soaked the southern Prairies through to late July when the military on flood patrol finally went home.

“Known as the flood that would never end and the spring flood that became the summer flood, it featured the highest water levels and flows in modern history across parts of Manitoba and Saskatchewan.” Statistically, the flooding on the Assiniboine River in 2011 was estimated to be at levels experienced once in 330 years. And on Lake Manitoba, engineers called the flood a one-in-2,000-year event. Governments at all levels spent close to $1 billion on flood fighting and victim compensation, some of which is still outstanding.

The disaster actually began unfolding in 2010 when what is know as a “weather bomb” dumped 50 to 100 mm of rain and big snows across the southern Prairies.

Southern Manitoba was within a millimetre of having its wettest year on record in 2010. At freeze-up, soil moisture levels were the second highest since 1948; only 2009 had more. Cold temperatures throughout the winter resulted in deep soil-frost penetration, meaning spring meltwater was likely to spread out instead of soaking in.

Lots of snow

At the season’s midpoint, the snowfall total was at a 15-year high. In January, hydrologists estimated an elevated spring run-off potential above 120 per cent across almost all of Manitoba south of the Nelson River. When spring did arrive, cold temperatures slowed the melt and the inevitable flooding. By mid-April, there was plenty of snow left to melt and nowhere for the water to go.

Then came heavy spring precipitation, with rains and snow that added to an already bad flooding situation.

On May 9, the Manitoba government declared a province-wide state of emergency, issuing evacuation notices for several municipalities along the Assiniboine River.

Brandon was at the epicentre of the months-long flood battle. There, the Assiniboine reached its highest level since 1923 and kept rising. The river was nearly seven metres higher than normal and 20 to 30 times wider in some places.

“Flooding on the Assiniboine near Brandon lasted 120 days and was the largest on record,” the report says.

In late May, the flood fight opened up a front on the Manitoba lakes, where lakes Manitoba and Winnipeg and at least four others reached record water levels. Hundreds of residents and cottage owners were ordered to leave due to high winds and waves.

Lake levels were higher than the flooding experienced there in 1955 and were enhanced due to water diverted from the Assiniboine River. A late-May storm with strong north winds sent water crashing against dozens of homes at Delta Beach on the south shore of Lake Manitoba. The inundation was so far inland that beachfront cottages were now located three km “out to sea.”

Displaced

In all, 7,100 Manitobans were displaced from their homes, with 2,700 still evacuated at the end of the year. Flooding swamped three million hectares of farmland, causing ranchers to move thousands of cattle. And local states of emergency were declared in 70 Manitoba communities. In addition, flood waters forced the closure of 850 roads, including parts of the Trans-Canada Highway.

In southern Saskatchewan, the historic flooding was the result of a number of events, including intense June rainfalls at the same time snowmelt waters were arriving from the Rockies and excessive precipitation during the previous summer, fall and winter.

Alberta owned two of the year’s top weather stories, including story No. 2: a wildfire that almost destroyed the entire town of Slave Lake – the second-most expensive insurance loss in Canadian history. Flooding along the Richelieu River in Quebec took the No. 3 spot when it spilled its banks for 69 days in spring. While not the worst natural disaster in the province, it was surely the longest.

Disappearing sea ice

At the top of the world, Arctic sea ice continued to disappear, reaching its second-lowest seasonal minimum and the least volume on record. While more climate related in nature, shrinking ice continued to have a profound impact on the environment at home and abroad.

The Atlantic Ocean had an active hurricane season in 2011 with 19 named storms. Although a disproportionately large number of the tropical storms were relatively weak, seven were categorized as hurricanes, and all three that were considered “major” were felt in Canada.

Everywhere, growers faced a very wet spring and a month-long delay to the start of the growing season. Yet their worst enemy turned out to be their best ally when summer weather extended well into the fall, saving what would have been a crop disaster.

As always, given the reality of long, often cold and snowy winters in Canada, we think nature owes us a nice summer. For those in the middle of the country, payback was sweet with a “summer of summers,” while on the coasts summer didn’t show up until vacations were all but over. Also on the list of this year’s top Canadian weather events were a Groundhog Day blizzard that hammered North America from New Mexico to Newfoundland, a strong tornado that pummelled parts of the picturesque town of Goderich on the shores of Lake Huron and powerful Chinook winds that ripped through downtown Calgary at hurricane-force speeds causing millions of dollars in property damages.

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