The speed and extent of the flooding in southern Alberta has taken people in the province by surprise.

"Yesterday, I was kind of being a little flip about it. I could see what was going on in the mountains and that didn't surprise me," says Arlene Dickenson, one of the judges on the CBC TV show Dragon’s Den, who has been watching the scene unfold from her condo in downtown Calgary.

"I woke up

[this morning] and I went, ‘Oh my god.’ Shocked. I'm shocked."

Several days of heavy rainfall have swelled the Bow and Elbow rivers, carrying fast-moving water through Calgary and towns such as Canmore, High River, Black Diamond and Turner Valley.

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Arlene Dickenson, a judge on CBC TV's Dragon's Den, has been watching the flooding unfold from her condo in downtown Calgary. (Arlene Dickenson/Instagram)

Dickenson has taken to Twitter and Instagram to document the damage in downtown Calgary. Many of the streets in this usually bustling metropolis are submerged in water and "eerily silent."

"I'm taking pictures of what I can see right now. 4th Street is almost completely shut down. We've been watching as the underpass started to fill with water," Dickenson says.

"You can see city crews, like police and fire trucks, at every intersection stopping cars from going down. We've seen cars floating down, we've seen cars stuck. I can see all of that. It all just shocks me. You just can't believe it."

75,000 people evacuated

A number of Calgary neighbourhoods have been evacuated, affecting an estimated 75,000 people.

Shawn Atleo, the national chief of the Assembly of First Nations, is in Calgary to attend the grand opening of an indigenous centre at Bow Valley College, part of activities for National Aboriginal Day.

The opening at the downtown Calgary facility was cancelled due to the flooding, and Atleo is currently at a city hotel. "Even in the place where I'm staying, the electricity is out. They've got backup generators. We don't have TV, but the officials in the hotel are providing us with updates."  

He described "high anxiety" in the city and "a lot of concern" among First Nations community members.  

A number of the Treaty 7 First Nations are located along the river. Some were evacuated as a precaution and there's a major concern about loss of property.  

"My focus and attention is working with my colleagues considering next steps, because where I'm staying has been a place where some evacuated residents have been brought to," he said.

'Devastating'

While the situation in Calgary is bad, Dickenson says she is even more astounded by the flood photos coming from Canmore, which is about 100 kilometres west of Calgary.

"It's devastating what's going on in Canmore — I just couldn't believe that the highway was blown away the way it was," she says.

Canmore resident Wade Graham says he watched as a nearby creek that usually runs three centimetres deep swelled to dangerous levels.

"At first it was just intense, pretty powerful, [an] amazing thing to watch. As daylight came, it just got bigger and bigger and wider and wider. And it's still getting bigger and bigger and wider and wider.

"All you can hear is, like, boulders and trees. I watched a refrigerator go by, I watched a shed go by, I watched couches go by. It's insane."

'Kind of scary'

Author and musician Dave Bidini, who is in Canmore working on a new book, said that the town has come to a halt.

"There’s no way in and there’s no way out [of town]. I know people at the hotel were worrying about looking a few days down the road, about supplies, and the town [is]

really kind of in a state of atrophy, which is where it appears to be headed right now," Bidini says.

"So it’s actually starting to get kind of scary."

John Pomeroy, who is director of the Centre for Hydrology at the University of Saskatchewan, has done extensive research on how river basins generate streamflow from rainfall and snowmelt.

He is also a resident of Canmore, and reports that his local research basin, Marmot Creek in Kananaskis, was destroyed yesterday by high flows.

He says he currently has 11 people in his house - a variety of friends and colleagues who have been stranded by the flooding.

"Canmore is a mess, but our house is up on a hill and so OK," he wrote CBC News in an email.

'It's just wild down there'

Citizens in High River, which lies about 37 kilometres south of Calgary, are under a mandatory evacuation order. The water trapped residents in their cars and forced others to flee to the rooftops of their homes.

Resident Randy Livie said he came to High River to help a friend and almost didn't get out. He said the water was over the hood of his car.

"There was a minivan that went in front of me. He stalled out. This other car, he came in and he started floating away — he bailed out. He had crutches. A truck pulled up and helped him out. It's just wild down there."

Tammy Beach, another High River resident, expressed her concern on CBC News’s Facebook page.

"This has been no laughing matter — people have lost their homes and livelihoods. I live in the farthest east end — and I have just found out that my house has flooded as well. I have a pit in my stomach that hasn't gone away since yesterday at noon - I'm a single mom who has a worry now as to where I'm going to live and how am I going to clean up.

"Yes, we can't control Mother Nature — and yes we can control how we treat the environment. But we can also control our human tolerance and empathy — and at this point this is all we ask for. I write this as I have tears streaming down my cheeks wondering what the days ahead will bring for my family."