Canmore's Cougar Creek flood aftermath visible 100 days later

CBC's Carolyn Dunn recently spent three days touring Canmore and Kananaskis in Alberta to see the aftermath of June's flood and she spoke on the Calgary Eyeopener this morning about what she learned.

• Listen to her full interview below:

Professor John Pomeroy, Canada Research Chair in Water Resources and Climate Change with the University of Calgary's Biogeoscience Institute, took the seasoned reporter up in a helicopter to survey the damage. He says the changes to the landscape are significant.

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"A lot of the mountain erosion proceeded very, very rapidly during the flood.... I think when people go in here and start hiking and really see the landscape and detail they'll notice that they don't recognize their old trails and certainly they won't recognize their stream crossings," he said.

The biggest reason why Cougar Creek flooded was the amount of precipitation that hit June 20. 

"Environment Canada had forecast about 150 millimetres of rain and that in itself is just a pretty big rain event to say the least. But think about this, it turns out well over 250 millimetres of rain actually fell. Then a metre of snow melted in a really short period of time, adding hundreds of millimetres more to the mix and that's where that sheer volume of water comes from," said Dunn.

Pomeroy says the video his university students shot of the flooding streams demonstrated the river's power. 

"What's evident from there is it's not just water moving down. These are boulders, these are full sized trees, lots of sediment with it and so all that's doing far more damage than the water can itself," he said.

Debris created a 'ticking bomb'

"It's now completely filled with rubble, with trees. The trees, we saw them in some places peeled, literally skinned going up 20, 30 feet above the ground from boulders passing them by and ripping them off."

Pomeroy says all this debris has made some areas of vulnerability. 

"Well there is lots of material that's been mobilized now and already moved down the mountain and it's sitting there waiting for the next rain to move it further down, so the mountains are in this sense a bit like a ticking bomb right now," he said.

Dunn says Canmore is planning to put in some mitigation measures before next spring.

"A couple of things they're looking at is maybe putting a super heavy industrial net up at the very top of Cougar Creek to catch the big debris like trees and boulders before they tumble down and cause a problem and also they're considering something called a gabion mattress, which is really a wire mesh liner that would go along the bottom of the creek bed to stabilize it," she said.

Paul and Marion Kutzer check on their Cougar Creek home almost every day after the flood ripped the foundation out from under the back half of their house. The floodwaters severely damaged 44 homes along the creek, and now they are not safe to live in.

"Well it's been hell, that's all I can say about it," said Paul.

Report outlined 'catastrophic flood potential'

What the Kutzers and others didn't know when they bought the property is that a 1980 engineering report concluded — among other things — that the area was not ideally suitable for development because of its "catastrophic flood potential."

"We felt that because it was approved with certain mitigating measures that they would be followed, but they weren't unfortunately," said Paul.

University of Calgary geoscientist Gerry Osborne says the problem is previous studies treated Cougar Creek as a regular river and not an alluvial fan — which carries debris and sediment, often migrating from side to side.

"It's another example of development pressures [trumping] hazard potential in [the] growing town of Canmore," he said.

Canmore Mayor John Borrowman says lessons have been learned. 

"We're gonna have to step back and look at how we plan land use and how we give development approval," he said.

An important step as development plans for several other Canmore creeks — also on alluvial fans — move ahead.