As record-breaking rain and snowfall become regular events due to climate change, cities must work quickly to address the increased risk of urban flooding – a destructive new reality for many Canadian homeowners and a multi-billion-dollar challenge for governments.
Urban flooding happens when a city’s hard concrete surfaces and sewers struggle to sop up and redirect large, sudden amounts of precipitation or meltwater.
With nowhere to go, the excess water can cause significant and expensive damage to homes and businesses.
To keep neighbourhoods safe and dry, two Carleton University researchers, Jennifer Drake and Ruth McKay, are working on innovative solutions to the complex problem of urban flooding.
Drake, an Associate Professor in the Department of Civil and Environmental Engineering, is improving Canada’s stormwater infrastructure through Low Impact Development (LID) – a technique that mimics the natural environment and allows rainwater to be absorbed where it falls.
McKay, a management professor in the Sprott School of Business, is part of an international team studying how the private and public sectors can more effectively work together on building houses during climate change.
While their approaches differ, McKay and Drake both believe that a mix of thoughtful public policy and improved urban design are key to flood mitigation.
“Urban flooding is a challenge that’s not just about finding technical solutions. What often undoes our infrastructure isn’t a flaw in the original design – it’s poor operation and maintenance due to planning and financial decisions,” says Drake.
Finding Solutions Through Blue, Green and Grey Infrastructure
As the Canada Research Chair in Stormwater and Low Impact Development, Drake is one of several Carleton researchers focused on engineering solutions to urban flooding.
“Urbanization is a dramatic transformation of our land,” explains Drake. “You need surfaces that are hard and impervious in order to build roads, buildings and parking lots.”
However, the result of that transformation is that water can’t slowly absorb into the ground or be carried away by river systems, leading to large quantities of fast-moving run-off with nowhere to go.
While Canadian cities have manufactured infrastructure to help convey that water – typically a combined sewer which handles both sewage and stormwater – Drake warns that there will always be storms that overwhelm the system.
“Our cities have urbanized for one environment, but that environment is changing. We now have more intense, frequent rainfalls and a significantly changing winter environment,” says Drake.
Because overflow tanks cost billions and rebuilding legacy sewer systems from scratch isn’t viable, Drake advocates for LID projects that re-introduce natural water processes to the urban environment.
These projects – things like rain gardens, green roofs and purposefully “leaky” pipes – are designed to encourage infiltration, evaporation and a more leisurely flow of water across the city.
Drake says the best way to make cities flood resilient is through a combination of green, blue and gray infrastructure.
“Green infrastructure involves vegetation or living components and blue infrastructure is designed to hold, reuse and evaporate water. But gray infrastructure, our traditional urban infrastructure, also has a role to play. We need to make sure all these systems are working together efficiently.”
Reimagining and Regulating Flood-Resilient Housing
McKay is part of a team that includes Carleton researchers Gary Martin and Magda Goemans, the Insurance Bureau of Canada, the Canadian Home Builders’ Association and two engineering firms in the Netherlands. Together, they are conducting a bi-national study on urban development and flood risk.
“We chose the Netherlands because they have a much higher level of climate resilient housing than Canada,” says McKay, noting how Dutch policymakers have a thousand years-worth of water management expertise to draw on because a large percentage of their country is flat and below sea level.
According to McKay, creating climate resilient housing is a two-part adaptation process: retrofit existing homes and ensure new housing is designed with flood resilience in mind. McKay’s research focuses on this second aspect of climate change adaptation, where the first rule is to not build in areas that are known flood plains.
“Housing pressures are new in Canada because there’s always been a lot of land. Ironically, some of our most expensive, sought-after land – waterfront property – is also the most at risk for flooding,” says McKay.
This is where the need for new housing policies becomes apparent, explains McKay. Updated federal flood maps that reflect recent environmental changes and identify trouble areas are in the works, as are changes to how insurers cover flood risk.
“We need a cohesive mindset and plan for Canadian housing across municipal, provincial and federal lines, “says McKay, “as well as a common understanding of climate change’s impact on housing.”
“A simple, obvious solution that we don’t consider enough in Canada is to stop building basements.”
Another solution is to design more houses that sit on top of, rather than beside, their garages.
Until policy catches up to our new climate reality, McKay says, Canadians will be “getting an education” in adaptation each time we face flooding.
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