Draining the rain

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If you pave it all, they will come — floods, that is. At least, that’s the logic some of Canada’s major cities are starting to consider.

For years, cities have been keen to replace the complexity of natural surfaces with non-porous asphalt — for streets, parking lots, driveways, you name it. But while vast expanses of asphalt are easier to clear and maintain, they have a downside. In big rainfalls, they shed a lot of water. And they shed it fast, often overwhelming infrastructure meant to provide safe drainage.

It’s a problem you can see in St. John’s and Mount Pearl. With even a marginally heavy rainfall, city tributaries like the Waterford River and Rennie’s River rise and flood quickly. With rainfalls as light as last week’s, morning in St. John’s can bring a harbour stained brown with soil and silt flushed either through the Waterford or carved from the river’s banks. Walk the river and you can see plenty of signs that flooding can be extreme. There’s significant bank erosion on both the Waterford and Rennie’s rivers, and there are plenty of rainy days when you can see signs that the city’s underground storm sewer system has reached its maximum capacity. Raise your hand if, in the past year, you haven’t driven in heavy rain in St. John’s and seen water coming up through city manhole covers.

Now, a national insurer, Intact Financial Group, is funding a series of pilot projects called “Depave Paradise” in Calgary, Mississauga, Peterborough, Kingston and Ottawa; 20 different projects will share $700,000. Some will replace pavement with more porous surfaces, while others will look at building swales that can catch and hold rainwater until it can safely disperse into the soil.

The idea is to come up with measures that can slow or stop the effects of flooding from high-intensity rainfall — the kind of rainfall that insurers admit is becoming more and more frequent with global warming.

You might argue that we’re not at the point in this province where we have to start ripping up pavement. Well, if we’re not, we certainly are at the point where we should start looking at the industrial floodplain that we’re intent on developing.

The watershed for the Waterford is more stressed every single year — and with major developers still using the cheaper “strip-off-every-piece-of-natural-groundcover” method of subdivision and industrial park construction, we can look forward to even more flood loading on our rivers and wastewater infrastructure.

The argument that Intact is making is that the time to start dealing with potential floods is before they happen. The costs for weather damage are well into the billion-dollar range now every year, and if we can mitigate effects before they happen, all the better.

Of course, that’s not always in the interests of builders’ bottom lines. The flooding generally comes after they’ve moved on to the next project. But we have to live here, and we have to live for a long time with the results of today’s decisions.

We can’t conquer nature, but perhaps we should spend a little more time thinking about how to work with it.

Organizations: Intact Financial Group

Geographic location: Mount Pearl, Waterford River, Calgary Mississauga Peterborough Kingston Ottawa

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Recent comments

  • Angus
    June 05, 2014 - 19:51

    Maybe it is time we revisited NL Housing Corporation?

  • McLovin
    June 05, 2014 - 11:15

    I believe Mount Pearl requires underground storm water detention systems for new developments along Topsail Road.

  • W Bagg
    June 05, 2014 - 08:04

    Another related issue is other municipalities have requirements for developers to maintain some green space in every development. I lived in Calgary and the developer was required to have one tree on every front lawn. This aids in drainage and the tree consuming water from the soil. In addition to the nice look of a tree. It seems here we can barely get developers to ha ve light poles at decent distances