Experts watch mountain snowpack for flood warning signs

Experts are carefully monitoring just how much snow is stacking up in the mountains west of Calgary.

Heavy snowpack contributed to last June’s devastating flood in southern Alberta. After a winter of heavy snowfall and skiers enjoying a spring season, some people living along rivers are feeling anxious.

• Flood forecasting expanded after 2013 Alberta floods
• No flood fears as Calgary prepares for mountain snow melt
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Hydrologist John Pomeroy, of the University of Saskatchewan, says his team is monitoring the situation closely. There is more snow compared to this time last May. When it melts, the water will eventually feed the Bow, Elbow and Highwood rivers.

"We have one of the ingredients for rain-on-snow flood and that is a snowpack," he said. "We also have a long-range forecast that is not particularly accurate – but gives you something to work with – of very unsettled weather for May and June and that can mean some rains in there, so we need to be quite prepared."

Data from dozens of mountain monitoring stations show the same trend –​ snowpack above average. Snow in Marmot Creek’s middle elevations is at the highest point since studies began ten years ago.

The longer the snow packs linger, the greater risk a heavy rain will fall, creating a rapid melt. Last year’s heavy rain was exceptional because so much warm rain fell over a short period of time, he said.

"It was also very warm rain, and it appears it may have had some elements of a tropical rain fall formation in the clouds which is rare, basically unheard of in Alberta."

If the snowpack melts slowly, the flood risk is reduced, but a heavy warm rain in the spring could create a rapid melt and that could cause flooding.