The heaviest floods in decades shut down the Canadian oil capital of Calgary on Friday, closing roads and bringing down bridges across southern Alberta, and forcing tens of thousands of residents to leave their soggy homes.
There were no reports of deaths or injuries, even as people retreated rapidly from flooded areas by road, boat or helicopter.
"The fact that we have to the best of our knowledge not one single injury is nothing short of a miracle," Calgary Mayor Naheed Nenshi told a news conference. "Last night I saw the river run faster and higher than I have ever seen in my life."
Around 100,000 people of Calgary's 1.1 million residents, were ordered to leave their homes, while smaller communities were evacuated elsewhere in the Western Canadian province.
City authorities said the downtown core of Calgary would be evacuated completely on Friday.
More than 100 millimeters (3.9 inches) of rain has fallen in some parts of southern Alberta in just two days, and forecasters say the rainfall won't let up until Saturday.
"The flooding situation is very acute in the foothills and the mountains," said Chris Scott, director of meteorology at The Weather Network, noting that 220 millimeters, nearly half a year's worth of rain, had fallen in 36 hours near Canmore in the Canadian Rockies.
"Now all that water is rushing downstream and that's why the situation is so bad in Calgary. This is an unprecedented flooding event."
Alberta lies to the east of the Rockies, and many parts of the province are normally very dry.
But a stubborn area of high pressure in Alaska and northern Alberta has pulled a stream of moisture up into southern Alberta from the United States, causing the heavy rainfall.
Alberta's oilfields lie to the north of the flooded areas, and energy output has not been affected. Provincial Municipal Affairs Minister Doug Griffiths said there was no threat to Alberta's network of oil and natural gas pipelines.
Some agricultural areas were also flooded, and while crops will likely recover, they will be more vulnerable.
"Any organism that has got stress has lower immunity, so they're going to be vulnerable to fungal diseases and insect pests," said Neil Whatley, a crop specialist at the Alberta government.
Alberta produces the second-largest volumes of wheat and canola among Canadian provinces.
Social media pictures showed trees and debris being swept down the swollen Bow River, which flows through central Calgary and which crested at around 1,500 cubic meters per second overnight, more than five times the normal flow rate for this time of year.
The TransCanada Highway, the country's main east-west artery, was closed at Canmore after Cougar Creek burst its banks.
Flows on the Bow, and on the Elbow River which flows into it, were around three times as high as during the last serious Calgary floods in 2005, which caused an estimated C$400 million ($384 million) worth of damage.
No figures were available for damage from the latest floods.
In Calgary, Mayor Nenshi urged people to stay at home on Friday. Schools were closed, as well as many offices in the downtown core, where lights were off and few people on the streets.
Suncor Energy Inc and Imperial Oil Ltd said staff in their Calgary headquarters had been told to stay at home. Shorcan Energy Brokers, which provides live prices for many Canadian crude grades, was trading out of Toronto on Friday rather than at its usual Calgary base.
Army spokesman Fraser Logan said Canada was making some 1,200 troops available to help with evacuations.
Calgary Zoo has a contingency plan to move its lions and tigers into holding cells in a Calgary jail if the flood waters threaten the animals' quarters. Nenshi said that had not been needed yet.
- Previous Redvers & District Oil Showcase May 10 and 11
- Next Canada says to keep Keystone XL issue alive with U.S.