Canmore's $14M flood plan takes aim at debris, erosion

A year after massive flooding destroyed homes and washed out highways in Canmore, residents are bracing for the spring melt and hoping a $14 million project will protect the community from another disaster.

Homes and lives in the Alberta mountain town were threatened last June when flood water turned the usually docile Cougar Creek into a raging river. It was debris, felled trees and giant boulders, swept up in the flood that did most of the damage, carving out 130,000 square metres of the creek bed and banks.

Canmore's manager of engineering, Andy Esarte, says the flood was terrifying. "We were all standing out there in the middle of the night watching the banks erode, it was quite frightening." 

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That night, the scope of the destruction and the cleanup job ahead quickly became clear. 

"We knew we had a big challenge on our hands to repair all the damage," Esarte said, "but [also] looking ahead — how we would try to prepare for the next flood season, being that potentially it would only be 10 months away."   

Urgent action

The damage was estimated at more than $50 million. Canmore Mayor John Borrowman says there was simply no choice but to come up with a plan to prevent another flooding disaster, even if the town of 12,000 had no idea where it would get the money to execute it.

"We had to get going now," Borrowman said. "We approved the first $600,000 budget in July to start the consultation study of what is the best thing to do with the creek."   

Canmore fast-tracked a plan it determined would be the town's best chance of saving lives and property along Cougar Creek if 2014 turns out to be a bad year for floods. The Alberta government quickly agreed to pick up $12.7 million of the tab through various flood recovery programs.

The first line of defence is a ring net 40 metres wide by 6 metres tall. The net, which is manufactured by Swiss company Geobrugg, is made of hundreds of rings of tensile steel. It's the same net technology that was used to block enemy submarines and torpedoes from harbours during World War II. 

In Canmore's case, the net is strung by cables across the mouth of Cougar Creek, just up from the homes built on its banks. The ring net is designed to work like a gigantic tea strainer, catching large debris such as rocks, boulders and trees, while allowing water to flow through.

"That net will stop a portion of the rocks and trees and all of that other stuff that came tumbling down and did so much damage," Borrowman said. 

The theory is simple: the less debris swept down the creek by floodwater, the less damaging the flood. But the ring net is only capable of trapping about 20 per cent of the debris that scoured the banks and bottom of Cougar Creek last June. So the second line of defence is a massive group of articulated concrete mattresses.

"We are covering 45,000 square metres of [the creek's] banks with mats," Esarte said. 

Lining the creek bed will help keep it place, protecting the banks from erosion.

The concrete mats were manufactured during the winter months in a makeshift factory in the town of Canmore. There was a scramble to get more than 3,700 mats made and installed before spring flooding season. 

"I think it's incredible the work our crews have done,"  Esarte said, noting many of the workers were also first-responders during the flooding, "These same crews were on-site, responding, working 24-hour shifts, putting themselves in harm's way [during the 2013 flood]. They haven't gotten a break since."

Apprehension

Wildlife photographer John Marriott is one of the local residents hoping that Canmore's plan gets it right. In 2013 he watched from his backyard deck as the floodwaters threatened his home along Cougar Creek. It did tens of thousands of dollars damage to his foundations and backyard, and stopped just shy of sweeping his home away.

"It's a reminder that we are not as in control of the situation as we might have thought," he says referring to nature's power.

Marriott's damaged foundation has been fixed and his backyard has been rebuilt.  Eleven months later, he's watching Cougar Creek again from his kitchen window as the crews work on the millions of dollars worth of flood remediation being done to protect the homes. 

It is reassuring, Marriott says, but still, there is apprehension building in the community.

"I've actually booked off my entire June," he says. "I don't have a single thing planned for it, just in case."

He is also checking the forecast over and over again. "It's a brand new spring tradition for us people who live along Cougar Creek and throughout flood areas in Alberta."

There is a collective hope in Canmore that the spring rains will fall gently and all the emergency flood remediation won't be put to the test this year.