Last week’s rainstorm and resulting flood watch for Canmore put officials on high alert and caused significant damage along Cougar Creek.
Manager of engineering Andy Esarte briefed council Tuesday (June 12) regarding the flood event in the steep mountain watercourse that drains a 42.3 square kilometre watershed between Mount Lady MacDonald and Grotto Mountain.
Esarte said the rain event and warm overnight temperatures resulted in peak flows in the creak around 3 a.m. on June 6 resulting in high energy and high water volumes.
Because high water flows in the creek meander, he said the result is the banks can become significantly eroded where there is inadequate protection.
“In general our structures along Cougar Creek are generally protected,” Esarte said. “We had a close call at the pedestrian bridge but at the end of the event we had suffered no damage to structures.”
He said armoring at the abutments of the bridge on both banks suffered significant erosion along with parts of the pathways on each side along the creek.
“Several sections of the pathway were undermined completely,” he said.
Since the rainstorm crews have been working to move the material eroded by the water back upstream to restore the bank. He estimated the cost of the short term work for damage to the banks is between $250,000 and $500,000.
But it is the future of the creek and the possibility of more high water events that are a concern for the municipality.
Esarte said in 2016 there are plans to complete a $6.4 million project to better armour the creek banks and control the slope of the channel to protect downstream infrastructure like the CP Rail tracks, 1A and Trans-Canada Highways.
“This is a really challenging water course and it does not get your typical events,” he said.
However how that will be paid for is still a question council indicated should involve the province and CP Rail.
“There are potential disasterous consequence if we do not do something,” Esarte said. “It is probably timely for us to have some more substantive discussions with the province before there is major loss of property or other serious dangers to the community.”
Cougar Creek was created by the provincial government in the 1960s to allow for the residential development in the area.
In the ‘90s it handed over responsibility for the managing the stormwater aspects of the creek to the municipality.
It wasn’t just Cougar Creek, however, that experienced high flows. The Bow River and the ground water levels in Canmore were significant.
Manager of public works Andreas Comeau said the Town was actively monitoring the Wastewater Treatment Plant and the sewer system throughout the flood event.
Lift station one in South Canmore was of concern as it experienced problems in 2007’s flood event. Comeau said since then it had capacity added to it and a back up pump installed.
He said the lift station handled the flows and back up pipe to divert flows overland were not needed.
Part of the issue that high groundwater levels will infiltrate the sewer system and if it cannot handle the volumes it will backup.
The Wastewater Treatment Plant saw $7.2 million in upgrades since 2007 for increased capacity and it was able to handle the volumes it saw last week which were over 24,000 cubic metres.