Too early to predict southern Alberta flood risk despite above average snowpack

Click to play video: 'Too early to predict spring flood risk for rest of Alberta'
Too early to predict spring flood risk for rest of Alberta
Environment and Parks Minister Jason Nixon addressed the flood risk for the entire province of Alberta, saying we're not yet into the traditional flooding season when mountain melt runoff and rainfall causes rivers to rise across the province so it’s too early to predict what will happen. – Apr 30, 2020

Officials say it’s too early to tell whether a higher-than-average snowpack in the Rocky Mountains could mean parts of southern Alberta will have any flooding.

“There’s quite a lot of snow in the front ranges, the first set of mountains when you come in from the east, from Calgary,” Dr. John Pomeroy with the University of Saskatchewan said. “Quite a lot of snow at high elevation in there but also at some medium elevations.”

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Pomeroy said under normal circumstances, there would be about 400 millilitres of water at places like the headwaters of the Elbow River — equivalent to the snowpack — if the snow was melted instantly. This year, he said it’s closer to 530 millimetres, which is “quite a bit above normal.”

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“[There is] quite substantial snowpack in areas, so that all feeds into the Kananaskis River and the Bow River system and eventually to Calgary but also to communities like Banff, Canmore and others on the streams that drain the Rockies like High River,” Pomeroy said. “So all of these communities need to keep an eye on things.”

Pomeroy said the snowpack alone likely won’t cause flooding, instead the snow typically intensifies a flood that’s brought on by rain.

“If you look back to 2013, we had 250 to 350 mm of rain that came down but there were hundreds of millimetres of snow on the ground in high elevation, even in late June,” he said. “So we had over 100 mm of snow melt which contributed to stream flow in many areas.”

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Pomeroy also said that in 2013, the snowpack wasn’t actually higher than usual, but because of a cold May, the snow didn’t melt very much.

Right now, Pomeroy said double-digit temperatures are only being recorded at lower levels, for example just above Canmore, but temperatures are only in the single digits, and dipping below freezing at night, higher up in the mountains, which is slowing the melt.

“As the sun gets a bit higher, the days longer, when we look towards warm spells happening in mid to late May, we’ll see things picking up quickly as we move into June,” Pomeroy said.

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“There’s so much snow up there, you’ve got packs of three metres and excess of three metres in some places, it takes a long time to melt that stuff.”

Speaking about the flooding impacting communities in northern Alberta on Thursday, Environment Minister Jason Nixon said the province’s flood seasons usually happen later in spring.

“We can tell you that we do have significant in parts of the eastern slopes and parts of the province that we’re monitoring, but this far out we don’t know what precipitation and the rainfall will be, so we’ll be monitoring it closely,” Nixon said.

Click to play video: 'Flood mitigation in the works amid 100-year Fort McMurray flood'
Flood mitigation in the works amid 100-year Fort McMurray flood

He added that municipalities and the province have programs in place to deal with flooding if it happens.

Calgary Mayor Naheed Nenshi said Friday “right now, there is nothing to worry about,” when it comes to the city’s flood risk.

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The Glenmore Reservoir has been opened, as it is every spring, meaning water levels in the Elbow River are fluctuating and fast-flowing.

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Nenshi said that’s part of getting the reservoir ready in the event that flooding does happen.

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