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Canada’s summer storms can fuel catastrophic flooding. Here’s how to prepare

Sponsored by First Onsite 1 - TWN

Monday, July 19th 2021, 12:00 am - Thunderstorms are a fact of life in Canada, and when they turn severe, they can deliver weeks of rain in just a few hours – bringing floodwaters onto properties and into businesses.

Getty Images: Lightning strike during thunderstorm over city at night (Getty Images)

Its wintry reputation notwithstanding, Canada’s summers can be sweltering, and feature frequent and sometimes damaging summer storms.

Often, those storms are beneficial, with their brief bursts of heavy rain welcomed by gardeners and farmers. But when certain conditions are met, a steady shower can turn into an absolute torrent, fuelling severe localized flooding – with a substantial cleanup cost for property and business owners.

“It can be really severe. Things can happen potentially in a matter of a couple of hours,” Jim Mandeville, a senior project manager with First Onsite Property Restoration told The Weather Network. “If you get a couple months’ worth of rainfall [in a short burst, producing] several inches of a commercial building, they’re just not designed for that, and the damage can be quite catastrophic.”

Flood risk may not be something a property owner would think about if they don’t live along the banks of rivers like the Red, the Ottawa, and the St. John, with their semi-regular ice jams and spring flood crises. But as Mandeville says, sometimes, the ingredients align for severe thunderstorms to deliver extreme rainfall in a very short period of time.

Getty Images: Flood damage (Getty Images)

In July of 2013, for example, Toronto found itself the target of two consecutive lines of relatively ordinary summer thunderstorms that slowed, then stalled, over the city. With abnormally high precipitable water in the atmosphere, and plenty of time for the snail’s-pace storms to discharge it, almost 100 mm of rain fell on the city’s downtown in only two hours – more than the entire July monthly average.

The city’s infrastructure, already strained from rains in recent days, couldn’t cope, and by the time the floods receded, some 3,000 basements had flooded, 500,000 households were without power, and the total insured damages exceeded a billion dollars – the single costliest natural disaster in Ontario, and the third costliest in all of Canada that decade.

In 2014, Burlington found itself beneath a rapid series of thunderstorms, following one another like a train. The resulting 191 mm of rain, about two months’ worth, flooded thousands of basements, and left such a mark that the city’s website has a memorial page.

There are, indeed, some things property and business owners can do to head off the biggest flood risk, Mandeville says. Care and attention should be paid to drainage and grading if building new, and backflow preventers should be installed in any case. For more built-up urban locations where property and business owners have a bit less control over the area, care should be taken to keep flat roofs and rain drains clear of any debris.

But when flooding from thunderstorms does occur, cleanup can be a substantial task, Mandeville says. Not only must all the water be removed but, depending on the severity of the damage, much of the interior finishes may have to be removed and replaced. In extreme cases, there may even be structural damage to the foundation.

Getty Images: Cleanup after flood damage (Getty Images)

Mandeville says one thing he sometimes sees in business and property-owners stricken by floods is a reluctance to recognize the severity of the impact – not denial but a kind of hopefulness that it’s a matter of simply mopping up the water and everything will be OK. Unfortunately, because of the complex way in which buildings are constructed, that hopefulness is misplaced.

“There’s going to be substantial damage to those interior finishes, to the walls, to the flooring, potentially to the mechanical systems,” he says. “In many cases, cleanup and repair is not a simple task.”

So, if the worst happens, and floodwaters begin pouring into your property’s basement or storefront, Mandeville says the first thing to do is contact your service provider or restoration specialist, then the municipality, since often flooding occurs due to a blockage in your community’s drainage system.

“You’re not going to be able to clean something like that yourself. If you’re in your store, in your business, and the water is up to your ankles, all you’re doing by staying in that business is endangering yourself,” he warns. “So really, the best thing to do is to secure it as best you can, lock the door, and call a qualified, trusted partner to get there and help you begin the process of cleaning it up.”

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