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Torontoist

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Flooding Across the GTA Will Only Get Worse With Climate Change

Severe flooding on Ward's Island has led to a plunge in business at the Rectory Cafe. It will close for good in October.

After one of the rainiest springs on record, Toronto is grappling with prolonged flooding. Here’s what the TRCA is doing to keep the damage at bay.

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Photo by Sean Tamblyn via Toronto Island Park.

The Rectory Cafe on Toronto’s Ward Island overlooks a large, marshy pond—a new addition this year to the tourist site. The wetland is the result of a particularly rainy spring that saw double the rainfall compared to the same period last year and by May 31, water levels of Lake Ontario reached the highest they’ve been on record. About 40 per cent of Ward Island has receded into the encroaching lake. During the calm after one of the season’s many rainfalls, the flooded island, with its Toronto skyline backdrop, makes for an eerily beautiful image. But the impact on the environment, and the people who rely on it, can be devastating.

Zorah Freeman-McIntyre, the chef and owner of the Rectory Cafe, will be closing shop in October on account of a huge plunge in business—down about 90 per cent from this time last year—because of the flood. “Islanders have been supporting us a lot, which is great, and city workers have been coming by… but the bulk of our traffic is tourists, and people can’t come across,” she told the CBC last month.

Indeed, damages from flooding create a significant financial burden on small businesses, homeowners and the economy in general. The 2013 summer storm in Alberta cost $1.7 billion in insured damages, making it the priciest natural disaster in Canadian history. Property damage from Toronto’s rainstorm that same year cost $850, and another Toronto storm in August 2005, cost $671 million. Damages from the record rainfall this April and May have yet to be tallied.

The waterlogged Toronto islands and waterfront this spring is due to lake-related flooding—the result of prolonged periods of rain, often in spring on top of a snow melt. High lake levels, and the flooding that comes with it, can persist for months.

The other type of flooding common in the GTA is riverine flooding. When all is running smoothly, Toronto’s extensive ravine network acts as a natural drainage system to protect against these floods. When heavy rain falls in a short period of time, the ground becomes saturated with water which can’t be absorbed into the earth fast enough. The runoff that results funnels into the ravines’ many capillaries which carry the water down to Lake Ontario.

But urbanization has left swaths of impermeable concrete in place of rain-absorbing green space. The result is huge amounts of runoff that stress our urban rivers. When that system becomes overwhelmed by rain—which it frequently does—surrounding properties and low-lying areas near rivers and streams pay the price. “Urbanization has to occur in a way that allows the ravines to fulfill their natural function,” says Rehana Rajabali, an engineer with Toronto and Region Conservation Authority (TRCA) who specializes in flood-risk management. But historically, that hasn’t always happened.

It doesn’t help that most of the city’s sewers aren’t equipped to deal with the onslaught of extreme weather brought on by climate change. Developments built before the 1980s (and before the region had effective stormwater management programs) have sewer systems designed for two– or five-year storms—weather events that have a 50 per cent and 20 per cent chance of happening respectively each year.

“The problem is that we’re getting a lot more intense storms than we were when these systems were built,” says Glenn MacMillan, senior manager of water and energy with TRCA. “The science is showing we’re getting 10 per cent more rain per year—not a huge amount more, but it’s how we’re getting the rain that matters.” Rather than getting small, 5-10 mm rainfall events, it’s more common now to see droughts and then a pummeling of rain in a short period of time.

“During big storms, there’s nowhere for the water to go,” MacMillan adds. “You’re going to have surcharging from the sewers, and then the water will pond and go wherever it can find a way out. A lot of it goes into the storm sewer system which can flood people’s basements.”

Unfortunately, it took a disaster to wake the region up to the importance of our river systems, and of our vulnerability to flooding. In 1954, after nearly a century of urban development near rivers and strain on the ravines, the calamitous Hurricane Hazel rocked the city. Homes near the Humber River, Holland Marsh and Etobicoke Creek were swept off their foundations and into the rivers and flooded streets, dozens of bridges were washed out by the rising water, and 81 people died. “With so many lives lost, and homes destroyed, Hurricane Hazel was truly the watershed moment for our region,” says Rajabali. “It was a reminder of the power of Mother Nature, and reminded us of the importance of city-building in a way that was mindful of natural hazards.”

Although Conservation Authorities existed prior to Hurricane Hazel, their mandate was expanded after the storm to include responsibilities like flood risk management. In response to the tragedy, the Toronto and Region Conservation Authority was formed with the amalgamation of four of the smaller watershed-based conservation authorities. Over the years, the organization has gained jurisdiction over 40,000 acres of land, including most of Toronto’s river valley areas in order to mitigate flooding and undertake myriad other conservation initiatives. “Many of the practices that we implement have benefits beyond flood protection,” says Rajabali. “They can also serve to improve water quality, reduce urban heat-island effect, and preserve access to green space for future generations”

Since the TRCA’s inception, the region’s municipalities have restricted building on floodplains. All new developments, meanwhile, no matter where they’re located, are required to account for stormwater on their lands. “When you have a development, you’re creating new impervious areas which alter the water balance,” says Sameer Dhalla, associate director of engineering services at TRCA, focusing on restoration and infrastructure. “You have less water infiltrating [the earth], less water evaporating and more water that runs off the landscape. This increase in runoff can cause flooding, erosion, and can create water pollution problems.” Adding green roofs, permeable pavement and infiltration trenches to properties can help avoid these problems.

Still, there are 43 sites in and around Toronto deemed “flood vulnerable area clusters,” most of which are located in historic urban areas that predate floodplain management plans and stormwater management practices. “For these existing flood vulnerable areas, we need to look at larger remediation solutions,” says Dhalla.

Those solutions involve ambitious, long-term projects aimed at protecting entire neighbourhoods from riverine flooding and to avoid another Hurricane Hazel-like calamity. The Corktown Common is one example of large-scale flood remediation. There, a 8.5 metre-high landform, cloaked with grassy hills and saplings, protects the West Don Lands in case of flooding from the Don River. The landform is one phase of a larger effort—the Don Mouth Naturalization and Port Lands Flood Protection project—to keep widespread flooding at the mouth of the Don River at bay. Another piece of the massive project is modifying the mouth of the Don River. The stretch was artificially straightened in 1886 to make space for boats to pass through and to divert sewage and waste water into Ashbridge’s Bay Marsh. But the plan, dubbed “Don Improvement,” made flooding worse. Now, Waterfront Toronto, in partnership with the TRCA, plans to restore the mouth of the Don to its more natural state, complete with recreation space, habitat creation for species and, most critically, flood control measures.

Indeed, building a number of benefits into one project is a core principle of the TRCA’s “Living City” mandate. Corktown Common, for instance, shows how well-designed greenspace can offer recreation space and conservation while, as well as rigorous flood protection to vulnerable parts of the city. It’s something earlier flood control measures failed to strive for. Dam building, for example, proved useful for stymying torrents, but they can harm species populations and habitats.

“Moving into the future we’re looking for new solutions to provide flood remediation on a larger scale that not only offers flood protection, but multiple benefits: that it provides habitats, it provides city-building with amenities like parks, and of course, it provides protection to people and properties from flooding,”  says Dhalla. “All these things work part and parcel with each other.”   

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