Submerged cars sits in the flood waters in High River, Alta. on June 20, 2013 after the Highwood River overflowed its banks. THE CANADIAN PRESS/Jordan Verlage

Downtown Calgary could look like a bit of a ghost town today, with entire neighbourhoods shut down and office workers told to stay home due to massive flooding.

As rain-swollen rivers burst their banks across southern Alberta on Thursday, more than a dozen towns declared states of emergency, with entire communities including High River and Bragg Creek under mandatory evacuation orders.

The impact was felt as far afield as British Columbia, where roads in the mountains were being closed, and Saskatchewan, where outflows were increased at the Gardiner Dam in anticipation of the coming crest.

In Calgary, officials started a series of rolling evacuations they estimated would result in 100,000 people being forced from their homes.

But as neighbourhood after neighbourhood emptied out, some people were steadfastly determined to stay.

Deputy police Chief Trevor Daroux said all officers could do was stress the dangers of staying, but admitted police aren't in a position to remove anyone physically.

"These are hazardous areas," he said. "There will not be power once the areas are evacuated and gas as well. So we're asking people to please comply and leave on their own."

Police were also concerned about the possibility of looters taking advantage of the thousands of empty homes.

"That's why we have a plan in place and as we evacuate the area we will be backfilling with security forces."

The RCMP called in the military, which sent two helicopters and a Hercules aircraft to help rescue those stranded on rooftops and in areas where roads had been washed out.

The traditional Edmonton-Calgary rivalry went by the wayside, with the capital city promising to send 100 of its police officers today to help out where needed.

Bruce Burrell, director of the Calgary Emergency Management Agency, said water levels on the Bow River aren't expected to subside until Saturday afternoon.

"Depending on the extent of flooding we experience overnight, there may be areas of the city where people are not going to be able to get into until the weekend," he told a news conference.

All schools — both Catholic and public — were to be closed today, while Catholic schools in Chestermere, Airdrie and Cochrane were also to be shuttered.

The Calgary Zoo, located on St. George's Island, closed its gates and started taking steps "to secure and move animals to safe locations."

It had been a rainy week throughout much of Alberta, but on Thursday the Bow River Basin was battered with up to 100 mm of rain.

There were flashpoints of chaos from Banff and Canmore and Crowsnest Pass in the Rockies, to Calgary and beyond in the north and south to Lethbridge.

"I woke up at about three o'clock in morning to the sound of this kind of rumbling and it was the creek," said Wade Graham of Canmore.

"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."

The flooding was particularly destructive in communities just south of Calgary such as High River, Turner Valley and Black Diamond, where the Highwood River swept away two people.

One was found, but the second — a woman — is still missing.

Environment Canada's forecast calls for more rain today in the area, but in much smaller amounts.

Premier Alison Redford was returning home to Alberta from a conference in New York and plans to visit the affected areas today.

News from © The Canadian Press, 2013