Before the flood: Here’s how Port Coquitlam is getting ready for rising waters

Besides bumping up infrastructure upgrades, Port Coquitlam is also considering changes meant to keep basement suites out of flood plains

In an effort to get above the waters before they rise, Port Coquitlam council examined a range of initiatives Tuesday ranging from fast-tracking infrastructure upgrades to keeping future basement suites out of the flood plain.

Basements on the plain

Out of 12,200 properties zoned for single-family homes or duplexes, more than 18 percent are in the flood plain, according to a city staff report. For the city, the primary concern is when a homeowner turns a basement built below the flood construction level into a secondary suite.

While he acknowledged that changing the rules around construction may be contentious, Mayor Brad West supported moving the issue to a public hearing.


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“I do think we have a responsibility and an obligation as a city to be ensuring people – quite often out of desperation, seeking whatever type of housing they can – don’t end up in a place where they and their family are at risk,” he said.

photo supplied Port Coquitlam

City staff recommended drafting new rules – possibly banning windows in crawlspaces and limiting homeowners to one set of laundry machines – in order to avoid exacerbating the existing problem.

While considered “non-habitable,” basements are easily converted because “they are built with full height ceilings, bathrooms, windows and doors,” according to a city staff report. Those spaces are also exempt from the city’s floor area ratio rules, leading some homeowners to consider them “bonus” or “free,” according to the report.

“However, they are often valued and sold at the same price as habitable space; this increases the price of the home and the pressure to convert the space into un-permitted uses,” the report added.

Defending against the next big storm

image supplied Port Coquitlam

Between the Fraser, Pitt and Coquitlam rivers, a significant portion of Port Coquitlam is considered flood plain, noted a city staff report. Given the increasing frequency of atmospheric rivers and other extreme weather events, the city is analyzing possible weaknesses in its flood defenses.

The city has dikes in all three rivers. The dikes were originally designed to designed to withstand a once-in-200-years flood.

However, a study carried out by BC Hydro between 2000 and 2010 found that dikes on the Coquitlam River no longer met that standard.

City dikes could handle a water flow of 400 cubic metres per second – substantially below the rate of 573 cubic metres per second in the original design.

In addition, the accumulation of sediment substantially narrowed the clearance between the high-water mark and the top of the dike. The original clearance of 0.6 metres dropped to “little or no freeboard,” according to B.C. Hydro.

The city has nine drainage pump stations. In high river conditions, the stations pump water over the dikes into the river.

To lessen the city’s reliance on the dikes, Port Coquitlam signed a deal with B.C. Hydro in 2009 which involves BC Hydro storing more water in the reservoir. B.C. Hydro also diverts flows during winter to avoid swelling the Coquitlam River during storm season.

However, more protection may be needed to protect Port Coquitlam.

According to a study conducted by the City of Coquitlam, a once-in-200-years-flood could overwhelm infrastructure and result in the evacuation of Coquitlam and Port Coquitlam residents, according to a city staff report.

Staff from both cities have recently requested a meeting with B.C. Hydro to help identify vulnerable areas and discuss next steps.

Discussing the issue Tuesday, city staff said Port Coquitlam may be prepared for a once-in-200-years flood but not for the once-in-500-years flood. Possible solutions could include raising dikes, dredging rivers or using reservoirs to provide a broader flood buffer.

image supplied Port Coquitlam

Bumping up the upgrades

Following two collapses, council elected to replace the 37-metre failed drainage main on Fremont Street in 2022, rather than following the previous plan of waiting until 2025. The project is expected to cost $85,000.

The city previously installed a steel plate over the collapse to allow the street to stay open.

Given its limited capacity to handle heavy rain, council supported moving the upgrade of the Wellington/Patricia Sanitary Main from 2024 to 2022. The project is expected to cost $1,145,000.

The city is also fast-tracking $150,000 worth of design work for the Cedar drainage storm pump station. Built in 1980, the station is operating under capacity and is also not passable for fish. Between design, environmental permitting and construction, the upgrade is now set to be complete by 2024 – one year ahead of the previous schedule.

Help from Ottawa?

Mayor Brad West said he’s “very optimistic” Port Coquitlam will get financial support from senior levels of government to help shore up the city’s flood defenses.

“I think there’s a recognition that for too long the province and the federal governments have been absent from some of this work,” he said. “These types of projects very much line up with exactly what the federal and provincial government say they want to put money towards.”

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