In May 2017, record-breaking levels in Lake Ontario left much of the Toronto islands underwater throughout the summer.

The following year, a powerful storm hit the city in August, dropping more than 64 millimetres of rain in just a two-hour span.

The rising water washed out roadways, backed up sewage, submerged vehicles, flooded basements, and trapped two men in a north-end elevator filled with six feet of water — leaving them only a foot of air to breathe when they were finally rescued by police.

Before many residents had finished clearing liquid muck from their homes, another round of torrential rain flooded buildings and basements all over again a week later.

Is this the new normal for residents in Canada's largest city?

"We know that storms are getting stronger. They're becoming more frequent," said David Kusturin, chief project officer for Waterfront Toronto, the organization tasked with revitalizing the city's waterfront area.

'We know that storms are getting stronger. They're becoming more frequent,' says David Kusturin, chief project officer for Waterfront Toronto. For Kusturin, bracing for the next crisis is top of mind as he leads a $1.25-billion flood-protection project in Toronto's Port Lands area. (Lauren Pelley/CBC News)

For Kusturin, bracing for the next crisis is top of mind as he leads a $1.25-billion flood-protection project in Toronto's Port Lands district, a man-made, 100-hectare contaminated chunk of waterfront property.

The massive, years-long effort will create a new river system capable of preventing catastrophic flooding in the surrounding area. And the project becomes increasingly important as the city keeps experiencing record-breaking lake levels and powerful storm systems, which city officials warn could get worse thanks to climate change.

For Toronto, preventing the next potentially disastrous flood is increasingly urgent. And it's a reality facing many Canadian communities as they try to brace for the impacts of a changing climate in the years ahead.

A city on alert

Three months after last year's double whammy of storms, flooding was on city officials' minds yet again as representatives from all three levels of government attended the groundbreaking for the Port Lands flood-protection project in November.

The nearly 300-hectare area in Toronto's Port Lands and eastern waterfront area that's currently at risk of flooding from the powerful Don River. (Supplied by Waterfront Toronto)

The project aims to prevent flooding throughout a nearly 300-hectare chunk of land surrounding the mouth of the Don River — a flood plain that's around the same size as the downtown core — while allowing for new development.

Dubbed "one of the most ambitious construction programs in Toronto's history" by Waterfront Toronto, the effort was more than a decade in the making.

"It was being developed for the 100-year storm," explained Coun. Paula Fletcher, whose riding includes the Port Lands. "But we are certainly having storms that are very big, more often."

There's growing concern among municipal officials that one-in-a-century rainfall events, such as Hurricane Hazel in 1954, could happen more often.

(CBC) The two graphs above are based on what the Climate Atlas of Canada calls a high-carbon scenario, which assumes that world greenhouse gas emissions will continue to increase at current rates through the end of the century. (CBC)

Research, including a 2011 city report, suggests mid-latitude cities such as Toronto could experience fewer storms in the future overall, but those that hit could be more extreme.

"This may result in more severe weather occurrences, including extreme rain and snowfall events, as well as damaging winds," the report said.

This expanse, currently filled with heavy machinery, will one day be the site of a one-kilometre river valley in the Port Lands. The new river will connect with the Don River. (Lauren Pelley/CBC News)

Data from the city's resilience strategy, released earlier this year, also suggests the annual precipitation is expected to jump from around 790 millimetres to more than 850 millimetres by the year 2051.

And when it comes to heavy precipitation days — where more than 20 millimetres falls in one go — the number each year could jump from just over 6½ days to close to eight in the same period.

That's a particularly concerning trend for the Port Lands. The area is a huge expanse of concrete, built overtop wetlands once forming the natural mouth of the powerful, 38-kilometre-long Don River, which weaves through the city from the north.

During a major storm, water rushes down the river, and when it hits the Port Lands, an industrial area now mostly known for crumbling roads and dilapidated buildings, the water has nowhere to go, forcing it to surge into homes and businesses to the north and east.

"As soon as the first few drops of rain fall on the Don River watershed, it's like turning a tap on — the river starts flowing right away," said river science specialist Joe Desloges, a professor of geography and earth sciences at the University of Toronto.

"It's not just the fact you have an urban river that's very responsive to any weather event," he said. "Now you've added the extreme event of climate change on top of that."

Preventing disaster

To prevent a future disaster, hundreds of workers are spending roughly six years creating a new river valley.

"We are extending the Don River and creating new areas for the flood waters," Kusturin said.

Decked out in a hard hat and reflective vest, he's standing on ground that didn't exist this time last year.

The rocky area on the northwestern edge of the Port Lands was created by shipping in around 240,000 cubic metres of shale bedrock from other construction sites.

Along one stretch of the rebuilt shoreline, water flows from Lake Ontario through a grate — designed to keep out invasive fish species — and into a manufactured pond filled with dead trees, which will slowly decompose and create a new aquatic environment.

This area of the development will provide five hectares of land and shoreline, which will one day feature park spaces and wetlands — returning the area to its natural state while creating an elevated, protected area for new homes and businesses.

The project's goal is to protect a huge chunk of land from flooding by transforming the Port Lands from a concrete jungle to a river valley. On the northwestern edge, new land is being created by shipping in around 240,000 cubic metres of shale bedrock from other construction sites. Workers are also building a river to stretch across the area and collect surging storm water from the mouth of the Don River to the north.

Further east, an expanse currently filled with heavy machinery will be the site of the one-kilometre river valley.

The winding route will start at the mouth of the Don River at the north end of the Port Lands and stretch west, creating a new island ecosystem to the south.

What that means is river water will gain another entry point to Lake Ontario alongside the man-made Keating Channel, which requires water to make an unnatural, hard right turn before it reaches the lake.

Set to open in 2024, the river valley will allow flood waters to take a meandering course through a natural environment — and the banks will be reinforced to withstand fast-flowing waters if there's a big storm.

Workers using massive drill rigs are building the concrete supports for the river.

"We've been under construction on this part of the project for about 12 months ... the work that's happening all around us is constructing cut-off walls to act as structure when we excavate the river," Kusturin said.

The 38-kilometre-long Don River, seen here alongside a stretch of Toronto's Don Valley Parkway, winds from the Oak Ridges Moraine all the way south to Lake Ontario. (Lauren Pelley/CBC News)

That excavation will involve moving more than a million cubic metres of soil to build up the valley walls, elevate the land, and create wide swaths of parkland, he said.

When the project is finished, those involved hope the Port Lands will be transformed from a concrete wasteland to a new community, balancing natural and urban environments, providing a new space for living and leisure — and, most crucially, keeping the water at bay.

While there are years of work ahead, one climate change expert says Toronto's billion-dollar effort could inspire other cities.

Canada is warming at two to three times the rate of the rest of the world, said international climate change specialist Elliott Cappell, Toronto's former chief resilience officer, which means regions across the country need to be bracing for the impact of rising temperatures.

But the specific approach depends on the area, he said.

Most of the country's population lives in major cities, which could face issues like basement flooding and dangerously high summer heat in older apartment towers. In the coastal regions, rising sea levels pose a threat. In the North, the big concern is permafrost melting.

Concept art shows what the Port Lands could look like in the years to come, including this eastward view from a future bridge overlooking the new river and parkland. (Supplied by Waterfront Toronto)

For Toronto, Cappell said, a single waterfront project won't change the grim reality — in the decades ahead, the city is going to get "hotter, wetter and wilder."

"We need to make climate change part of everything we do," he said. "It has to be part of how we maintain our roads, how we plan our city blocks and buildings, how we maintain parks."