CALGARY, Alberta, June 24 (Reuters) - With water levels receding after devastating flooding in southern Alberta, the Canadian oil industry capital of Calgary labored on Monday to restore power and assess damage to its downtown core, while a state of emergency remained in effect.
Officials said about 65,000 residents returned to homes they left on Friday after the Bow and Elbow rivers spilled their banks after days of heavy rainfall. But central Calgary remained mostly shut down.
"There's five different grids (downtown) and they have to be re-energized one at a time. In order to re-energize the grid we have to have assessments of every single building. So it is painstaking work," Calgary Mayor Naheed Nenshi told CBC radio.
The flood displaced tens of thousands of Calgary's 1.1 million residents, as well as closing key transportation arteries. Three people were killed near the southern Alberta town of High River.
In other cities, thousands more were evacuated, including in Medicine Hat, where the South Saskatchewan River was beginning to recede after cresting overnight.
The floods took place just two weeks ahead of the annual Calgary Stampede, a rodeo and exhibition that is a huge tourist draw. The low-lying Stampede grounds, were many of the festival's events take place, were badly flooded.
Nenshi said over the weekend that the Stampede would start on time. But logistical questions remain, with transit still shut in the central core and rail lines to the Stampede grounds warped and twisted by the flood waters.
Officials have yet to provide an estimate of the damage caused by the floods, but the cost is sure to be far greater than the floods of 2005, which caused C$400 million ($380 million) in damage.
BMO Capital Markets said the flood could cut Canadian gross domestic product by 0.1 percentage points in June.
"That would equate to lost output of about $2 billion, but the property damage will likely be multiples of that," BMO senior economist Benjamin Reitzes said by email. "It's a very rough estimate and is subject to upside risk depending on how many days and how much of the city remains closed."
Although oil company headquarters in Calgary were closed, traders monitored the crude market remotely.
"We are all working remotely using iPhones and BlackBerrys," said one Calgary-based crude trader, who expected volumes to be very thin.
"Other than not being able to stand up and holler across the desk, it's fairly normal." (Writing by Cameron French; Editing by Janet Guttsman; and Peter Galloway)