The recent three-day rainstorm broke records across the province and resulted in more than 100 property owners in the Tri-Cities reporting flooding damage.
Coquitlam engineering staff described the atmospheric river as a once-in-200-year event which pushed the city’s infrastructure beyond its limits.
An elementary school teacher is dead after her home was destroyed in a mudslide on Saturday, Oct. 19; another man is missing, suspected to have fallen in the Coquitlam River on Sunday.
During an update from staff on Monday, Coun. Craig Hodge noted the city received 254 millimetres of rain in a 24-hour period, two and half times more than the 2021 atmospheric river.
“Coquitlam saw record breaking rainfall,” Hodge said. “We appreciate everyone’s ongoing patience and understanding as we work through the impacts of this extraordinary event – public resources across the region were stretched.”
Coquitlam appears to have suffered the most damage in the Tri-Cities, though official estimates are not yet available.
On Monday, city crews were working to restore access to 15 properties cut off from blocked roadways, clean out culverts, re-inspect ravines to look for erosion, and repair three washed-out roads, said Jonathan Helmus, acting general manager of engineering.
Helmus said nearly 80 calls were made to the city related to road flooding, manhole surcharging, culverts, trees and other issues, adding crews were working around the clock to remove debris blockages and keep its pump stations operating. Significant flooding led to portions of Cedar Drive, Woolridge Street, Pipeline Road, Quarry Road and Lougheed Highway being closed.
The city also received close to 60 calls related to private property flooding, though Helmus said the extent of the damage and exact causes are still unclear.
Double call volume
Coquitlam Fire Chief Scott Young said his crews responded to 84 calls over the weekend – double the average.
He said three crews initially attended to the mudslide on Saturday afternoon, but vehicle access was blocked by debris and downed hydro lines, firefighters had to continue on foot, and eventually had to call in assistance from Canada Task Force One.
“The home was not intact at all and had moved quite a distance from its original footings,” Young said, noting the body of the deceased resident was discovered 250 to 300 metres away.
Helmus said the volume of rain was “more than the system could handle,” noting Coquitlam has nearly 300 kilometres of creeks.
Municipal pipe systems can typically only handle a one-in-five-year storm. He said Coquitlam’s residential pipe network is designed to handle a once-in-10-year storm, and its commercial and high-density areas are designed for a one-in-25-year storm. The major drainage system for creeks and culverts, and its diversion sewers which take pressure off other systems, are both capable of weathering a one-in-100-year storm.
While there were widespread issues, Helmus said proactive work by staff alleviated some stress on the network.
The biggest infrastructure damage was related to the three washed-out roadways, which crews are working to re-establish to the drainage system before contractors are hired to complete a full restoration.
While the province’s River Forecast Centre issued a flood warning for the Coquitlam River, Helmus said its dikes were not close to breaching. They are designed to handle a once-in-200-year flood, and the spring freshet flooding is the larger concern, he said.
Coquitlam’s pump stations, however, were under pressure from the storm.
Drainage pump stations were nearing capacity, and its sanitary pump stations were beyond capacity and sounding “high-level alerts,” Helmus said, adding staff had to run multiple backup pumps.
Coun. Matt Djonlic said the frequency of atmospheric rivers are going to increase with climate change, and inquired about what the city could do to prevent future damage.
‘New reality’
“This seems to be increasingly the new reality that we are being faced with,” Djonlic said. “This level of rainfall, it’s going to happen again.”
Coquitlam is currently updating its emergency management portfolio, a hazard risk and vulnerability analysis, and identifying the city’s critical risks from natural disasters, according to Jim Ogloff, general manager of community safety.
“We’re also bringing forward specific disaster risk-reduction programming through our emergency management team,” Ogloff said. “Certainly, floods and wildfire interface are going to be near the top of that program.”
Port Coquitlam, meanwhile, recorded nearly 185 millimetres of rainfall, leading to portions of Coast Meridian Road and Langan Avenue being closed.
The city received 44 calls related to private property flooding, with five families registering with the city’s emergency support system for assistance, said Joshua Frederick, director of public works and engineering.
In a post to social media, Mayor Brad West said the city took 76 calls related to road flooding; 30 calls related to rising creeks, park flooding and other drainage issues; and 27 calls to its fire department.
West said the “unprecedented rainfall” in the Burke Mountain watershed combined with a high tide were significant factors which led to flooding in the city.
“Although culverts were clear and all city pumps fully operational, there was simply nowhere for the water to go until the tide receded,” he said.
While Port Coquitlam has recently upgraded culverts and storm mains, West said the city will be investing $24 million in two pump stations over the next two years.
“This all drives home the reality of Port Coquitlam being surrounded by multiple rivers, and much of the city being located in the floodplain,” he said. “While all of this infrastructure is critically important, it is not a silver bullet when faced with extreme weather situations that can overwhelm even the very best system.”
Frederick said most of the infrastructure damage relates to its culverts and drainage channels, and staff are still assessing the impacts.
West thanked Port Coquitlam’s work crew, stating the damage to the community would have been more severe if not for their efforts.
Only a small number of sewer backups occurred in Port Moody, and some residential basements flooded, according to Jeff Moi, general manager of engineering and operations.
He said there was a moderate-sized slope failure on Noons Creek near David Avenue which caused damage to a few locations, but they are being inspected and repaired.
Feature image: Multiple homes are seen surrounded by debris left by flooding from torrential rain from an atmospheric river weather system at Deep Cove in North Vancouver, on Tuesday, October 22, 2024. THE CANADIAN PRESS/Ethan Cairns
