Bad, confusing flood maps leave homeowners blindsided when water rises: expert

Flood risk maps could be an essential tool for helping Canadians avoid buying houses in flood-prone areas – or building them there in the first place.

But too often they are of poor quality, and what information is presented is hard to interpret, an expert charges.

Jason Thistlethwaite, who teaches climate change risk management at the University of Waterloo, studied flood maps across Canada and was disturbed by what he found.

“We looked at over 300 that exist in high-risk areas,” he explains. “We asked a simple question: Would an average property owner be able to look at this map and understand the risk to their property, or to a property they were considering purchasing?

“We found that Canada’s flood maps are low-quality, and they will not help with the decision-making that a property owner will have to make to protect their property from flooding. They’re designed for land use planners, they’re designed for engineers. They’re not designed to help an individual understand the flood risk.”

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Local governments are caught in a difficult bind, he explains. Part of their job is stopping homes from being built in flood plains — but the more development happens, the more money comes in.

“For municipalities, it’s actually very difficult to limit development in these areas, given the benefits associated with increased property tax revenue.”

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Properties near water are seen as more desirable — and bring in more tax revenue — until the day the water rises, he says.

Some flood-prone areas were developed generations ago, often when a community grew up around a water-powered mill. But some were built on much more recently.

In Quebec, over 3,000 homes are flooded and another 2,300 cut off by floods. Parts of New Brunswick downstream from Fredericton on the St. John River are also afflicted, as are the Muskoka and Ottawa areas in Ontario.

Nationally, over 1,500 troops are deployed to flooded areas in the three provinces.

Federal Public Safety Minister Ralph Goodale and Ontario Premier Doug Ford both blamed the floods’ destructiveness on climate change.

But Thistlethwaite says this mostly misses the point.

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“Climate change is a factor, but it’s nowhere near as big a factor as the neglect of governments to enforce effective land use, restricting development, giving information to the public so that they know, when they’re buying a property, whether or not it’s in a flood plain and aging infrastructure.”

Goodale said Friday that federal money is available to help local governments do better flood mapping, and he’s “surprised” it hasn’t been applied for more often.

Better maps would “help prepare province and municipalities to know what happens if you get five inches of precipitation, if you get 10 inches of precipitation, if you get 15 inches of precipitation, what happens to the rivers, the creeks, the drains,” he said.

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Flood maps in Britain and the United States are easily accessible and easy to understand, Thistlethwaite says.

“For the most part, Canadians are in the dark when it comes to the exposure of their big investment in their property to flood risk.”

In the long run, he argues, governments that allowed development need to offer to help people leave houses that never should have been built in the first place.

“Governments need to take responsibility for this. The property owner did not know they were buying in a high-risk area, so how is it contingent on them to take the liability, and the cost of the devaluation of their property? That’s where you need governments to come in and say, ‘We’d be willing to buy out your property.”

However, a controversy in Quebec illustrates some of the practical problems. The province has offered to buy out some flood-prone homeowners for up to $200,000, but affected residents say that’s far too little money.

— With files from The Canadian Press