Canada is pushing to build more homes. Many could end up in the path of floods, fire, report warns

With the push on to build more housing in Canada, new research is warning that tens of thousands of those homes could be built in flood- and fire-prone areas if governments don't step in.

The report from the Canadian Climate Institute uses data and modelling that some governments and insurance companies have access to — but the average homebuyer does not — to see where new homes are likely to face dangers made worse by climate change. 

The report's author says governments need to act on the data — or homeowners and insurers could be on the hook for billions of dollars in future damages.

"Many provinces and territories don't use their full authority," said Ryan Ness, an author of the report and research director on climate adaptation at the Canadian Climate Institute.

"They do not create regulations that stipulate or that limit the amount of construction that can occur in hazard-prone areas."

The report's analysis is focused on future housing rather than current buildings, with the goal to prevent risky development and the costs that will come with it. 

Available flood mapping outdated

For calculating flood risk, the report used cutting-edge analysis from Fathom, a U.K.-based firm that provides flood modelling to governments, researchers, insurance companies and other clients. The company used data collected by planes and satellites that use radar or shoot lasers down to the surface and build a picture of the terrain across Canada.

It's not the same as sending engineers out to collect much more detailed terrain information from the ground, but it allows for risk analysis over much larger areas, especially places that don't have or can't afford much more expensive flood mapping.

With that vast picture of Canada's surface — all its ridges, hills, mountains, plains, cliffs — Fathom's scientists can simulate the flow of water and model which areas are more prone to flooding from overflowing rivers or heavy rain. 

Just last year, Fathom announced a contract with the Canadian government to build a flood hazard map. Ness said this would eventually be turned into a public portal. The U.S. has a map showing flood hazard available online; Canada does not, and local flood maps in many provinces are outdated by decades.

How that new data should be used, however, remains a question. 

Huge risks loom over new homes

In its report, the Canadian Climate Institute focussed on the 5.8 million homes that the Canada Mortgage and Housing Corporation estimates need to be built by 2030 to address the housing crisis.

Based on current development policies, the institute projected where those new homes are likely to be built.

Then the institute commissioned modelling, from Fathom and others, to assess the flood and fire risk for those likely-to-develop areas, as well as Canada's existing 16 million addresses.

The report found that 150,000 homes could be built in areas of very high flood hazard and over 220,000 homes could be built in municipalities exposed to high wildfire hazards by 2030. 

Flood damages could be up to $2 billion annually in a worst-case scenario, and fire damages could be $1.1 billion — adding to potentially $3 billion in losses every year.

"Ultimately those costs will undermine the affordability goals of boosting housing supply," Ness said. 

"Not only for the households and communities who will be directly impacted by flooding and wildfire disasters, but ultimately for all Canadians in the form of things like increased insurance premiums and higher taxes to pay for emergency response and disaster relief."

What about where I live now? 

So, what does the report say about those 16 million current addresses? It doesn't. At least, not at a lot-by-lot scale.

The report only spoke of the areas in general terms — by province or region — because of the terms of their use of Fathom's and other companies' data. Ness says that provinces need to do their own analysis, which can estimate flood risk down to a much more granular level than the big-picture analysis they have done.

"It's important to note this doesn't replace more detailed flood mapping that really needs to be done locally in the longer term. It really is only useful maybe at the community or neighborhood scale," he said. 

"For people to understand sort of one property, one lot to the next, this requires the type of detailed flood mapping that provincial governments and regional authorities are usually responsible for."

Fathom's chief scientific officer Oliver Wing says it's important to find a way for people using the data understand the uncertainties that go into it.

"How do you explain to someone that, oh, actually we got it wrong for your house because the model is uncertain, and you can't sell it now because your house prices dropped because we've said it's too risky," said Wing.

Wing says presenting the data on a large scale, like in the Canadian Climate Institute report, can be useful. The report pointed out, for instance, that stronger rules in Ontario and Saskatchewan meant that new developments were generally at lower risk there.

But disclosing the data completely could have big impacts on individual homeowners, whose house values might drop if their plot is perceived to be in a high-risk zone, Wing said.

What to do about it

Also, putting the data out there does not necessarily mean that homebuyers will be able to do anything about it, says Sharmalene Mendis-Millard, director of Partners for Action, a research initiative at the University of Waterloo aimed at making communities and people more flood-resilient.

"It's one thing to make it available, it's another thing to walk people through what does this mean?" she said.

"Yes to flood maps, but we need to pair it with programming, action, incentives [and] regulations," that push municipalities to build in safer places and protect homebuyers from flood and fire risks.

That's echoed by Wing at Fathom, who says his company's analysis can only give a general view of risk over larger neighbourhoods and regions. 

"I'm really keen to emphasize that it doesn't mean that we can tell you, you know, how climate change is going to affect your individual property in 30 years time," he said, "No model can do that." 

Still, the Fathom's high level mapping provides a much easier way to map flood risk across the country. Wing said his team at Fathom is made up of about 25 scientists, compared to the hundreds or even thousands of engineers working in the field that would be required to build more traditional flood maps for all of Canada.

"We don't go and visit the site, get our waders on, measure the flows, survey the local floodplain," he said. 

"We're relying heavily on an automated way of building these tools to get the kind of large scale data that we need from satellites, from local governments… and just letting computers do all that work for us."