By Nia Williams
CALGARY, Alberta (Reuters) - Some residents began returning to damaged homes on Saturday after record-breaking floods in southern Alberta that killed at least three people, displaced more than 100,000 and will leave the core of Canada's oil capital, Calgary, without power for days.
Communities to the south and east of Calgary were on high alert as flood waters washed across the region. And even as Calgary lifted some evacuation orders, officials warned people not to become complacent.
"We have a situation across southern and particularly south-west Alberta of intense saturation, which means 20 millimeters (0.8 inch) of rain that would typically be absorbed could cause massive flooding and run-off," Alberta Municipal Affairs Minister Doug Griffiths told a news conference.
"Please do not assume because the clouds have cleared and the streets are not flooded with water it is perfectly safe to move back into your community."
The floods followed 36 hours of unusually heavy rainfall which pushed the volume of water in local rivers to record levels. Some communities received six months of their normal rainfall in under two days.
Evacuations started on Thursday, and utility Enmax switched off power to central Calgary on Friday afternoon to avoid water damage to its downtown facilities. The area was still without power and closed to vehicles on Saturday.
A few tourists and residents strolled in the carless streets of the city's core, but the area was eerily quiet.
Officials said it was too early to say how much it would cost to repair flooded homes and rebuild roads and bridges washed away by the murky brown floodwater.
But the floods already look significantly worse than those of 2005, which caused C$400 million ($383 million) in damage in the western Canadian province.
"We are not through the crisis yet," Alberta Premier Alison Redford told a news conference in Medicine Hat in south-east Alberta, where the South Saskatchewan River is expected to crest at 6,000 cubic meters (1.59 million U.S. gallons) per second on Monday morning.
The bulk of the evacuations were in Calgary, a city of 1.1 million that is home to Canada's biggest energy companies, although evacuations in other communities brought the total of displaced people to well above 100,000.
Calgary urged drivers to stay off the roads, and warned people not to get too close to still-raging rivers.
"If you want to help your city, the best thing you can do is stay home," Calgary Mayor Naheed Nenshi, visibly tired after two days of crisis management, told a news conference.
Canada's main oil-producing region in the north of the province, was not affected, although some farmland was flooded, which will likely weaken crops that include wheat and canola.
Police said three bodies had been found near High River, about 60 km (40 miles) south of Calgary.
In Calgary, authorities said water levels were expected to drop in the coming days. But the Bow River was still flowing at around five times its normal rate.
Nenshi said downtown could be off limits until the middle of next week "at the earliest."
A spokesman for Imperial Oil, Canada's second-largest producer and refiner, said the company was working on plans to maintain essential operations, including allowing employees to work from other locations.
Shell Canada said its downtown Calgary offices would be closed until Wednesday and employees would work from home.
It was not clear when trading in Canadian crude oil would resume after little if any trade took place on Friday.
Shorcan Energy Brokers, which provides live prices for many Canadian crude grades, operated out of Toronto on Friday rather than from Calgary, although there were no trades in Western Canada Select heavy blend or light synthetic crude.
Net Energy Inc, the other main Calgary crude broker, was closed on Friday and no trading took place.
Many roads and bridges remained closed, and the city banned the use of tap water for car-washing or other outside activities because treatment plants take more time to process the sludgy water. But Nenshi said Calgary water was still safe to drink.
And as flood waters receded, a few residents were allowed back home to flooded basements and thick layers of silt on streets and sidewalks.
"We had four feet of water," said Gordon Weir, 53, standing outside his home in the city's Elbow Park community as a pump spewed water from his basement onto the street.
"It was all from ground water, so coming up from the sewers and through the concrete. This is one of the higher houses on the block. Our neighbors had seven or eight feet."
Canada's ruling Conservative Party scrapped plans to hold its annual party convention in Calgary next weekend.
"Postponing the convention is the right thing to do for the people of Calgary," said Michelle Rempel, Chair of the convention's Host Committee.
Flood water covered the grounds of the Calgary Stampede, an annual extravaganza of cows, cowboys and horses scheduled to start on July 5. But Nenshi insisted the rodeo would go ahead.
"We're Calgarians. We'll make it work," he said. "It may look different, but the show will go on."
(Writing by Janet Guttsman; Editing by Eric Walsh)