Little Cascade Dam made big difference in Canmore flooding

The alpine town of Canmore was hit with $30 million in damage when the usually placid Cougar Creek flooded last year, but the Cascade Dam — a few kilometres upstream — prevented even worse damage.

Town might not have survived the onslaught, Trans-Alta employee says

CBC's Erin Collins looks at how flooding in Canmore may have been a lot worse. 6:43

The damage done to the flooding that devastated Canmore last year was appalling, but it could have been much worse if not for the Cascade Dam. 

The dam, which is primarily part of Trans-Alta's power-generating system, was also one of the the town's last lines of defence during the emergency. And it was manned by one of the town's own, Trans-Alta worker Glen Isaac.

Asked whether his home would have survived if the dam hadn't held the water back, Isaac replied, "No probably not. I can pretty much say no.

"There is an extra incentive there to do the job properly. There is family and friends downstream, but I mean there is a bigger picture."

The town of Canmore, Alta., was inundated in the disastrous flooding last June. (Jonathan Hayward/Canadian Press)

Nearly 50 per cent more water would have rushed into Canmore if it hadn't been held back at the dam, though eventually the water had to be released to prevent it from going over top of the dam.

Breaching the dam would have been "a catastrophic event," Isaac said. "Flooding downstream, a lot of flooding downstream. We can't imagine — we understand what it might look like, but we know it would be very bad."

Releasing the water meant using the dam's antique spillway for the first time in its seven decades of operation, and Isaac had a first-hand look the power of the rushing water.

"Well if you look at this bank over here it probably eroded about 20 feet of that bank," Isaac told CBC News. "We were watching and you would see these large chunks of slate fly up into the air as the water would hit it and basically peel it back."

The torrent slammed into Trans-Alta's power station downriver, knocking it out for months, but the dam was left unscathed.

"Structurally sound it did what it was supposed to do," Isaac said. "Even the spillway, which saw water flowing through it for weeks on end, is intact … so if something happened again we could use the same facility."


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