A new waterfront area opening in Toronto this summer was built with a goal in mind: to help save the city from a flood.
The a new island called Ookwemin Minising — an Ojibway term meaning "place of black cherry trees" — will feature new parks, marshes, bridges and streams, as well as a new housing community.
Most of the park will open to the public in July and August, and all of it by fall 2025.
The creation of the island, carved out of the revitalized path of the Don River, stemmed from the need to undo damage caused over a century ago when the natural river mouth was cut off and the marshland area turned into an industrial site. With nowhere for water to go, a rise in water levels could cause flooding that would destroy the east end of the city.
Returning the area to a more natural state to mitigate flooding — with a new riverbed and river pathways — has been a complex feat of geographical and environmental engineering.
TorontoToday dug into the construction of the Port Lands area and the creation of this new phase of Toronto’s waterfront.
The site in October, 2024 / Waterfront Toronto
Preventing a flood
With climate change looming, environmentalists feared a future superstorm, one that would create a vast mass of water — and that the size and shape of the Don River's mouth would stop that water from flowing freely into the Lake Ontario harbour.
The water, backed up, would have to go somewhere, likely causing a large area of the southern part of the city's east end to flood.
In the late 19th century, the city straightened the Don River's meandering course, filled in the marsh that once blurred the edge between river and lake for industry, and carved a sharp right turn into the river as it enters the Keating Channel, a few hundred metres before it finally joins the inner harbour.
It's been a liability ever since.
"In a nutshell, floodwater comes down the Don River and it hits what is now the Keating Channel. Water does not like to make a 90-degree bend, so it overtops the banks of the Keating. It overtops all this land, instead of just running safely out into the lake."
That’s what happened in western Toronto when Hazel, a 1954 hurricane, killed 32 people living on Raymore Drive in Etobicoke's Humber Valley when their houses suddenly flooded.
As well as endangering existing east-end neighbourhoods, flooding concerns long made it impossible to build new housing on the eastern waterfront.
With this in mind, in 2017 the city, the Toronto Region Conservation Authority and Waterfront Toronto started an ambitious project aimed at reconstructing the mouth of the river to add green space and lots of room for floodwater to go.
Engineers planned to open the Keating Channel and create new pathways for the river to flow, as well as absorbent marshland and parkland.
Use the slider to contrast the plan for the park's final form with a recent Google Earth satellite shot of the new Don Valley riverbed under construction. (WATERFRONT TORONTO/GOOGLE)
A former marshland
The Ashbridge’s Bay marsh sprawled for thousands of years at the mouth of the Don River (or mouths: there may have been as many as five).
About five square kilometres, it was one of the largest marshes in what became eastern Canada. Until a violent storm in 1858 created the Toronto Islands, it was sheltered by a long sand peninsula that stretched from modern Woodbine Beach to the west entrance to the harbour.
Once a rich home for fish and waterfowl that fed generations of people, the marsh became increasingly foul as waste from the tanneries and slaughterhouses of Victorian Toronto washed sluggishly into it.
Before the First World War, the city filled in the marsh, and used the area for sprawling industrial waste. It was a grim, toxic place for decades, meaning the river mouth restoration involved cleaning contaminated soil on a large scale.
"This area was used for oil refining, as well as a tank farm for petroleum distribution," Forbes said.
"It was a coal hub. Coal would come in on the ships, it would be stored on site and then shipped off to homes and businesses and factories. So there was residual coal in the soil."
"They were making artillery shells down there at one point, which is why Munition Street is called Munition Street."
Is the project an attempt to restore the pre-industrial river mouth?
Not really, Forbes explained, though nature has certainly been invited back in.
“The primary goal of this is to bring land back into productive housing use. We have to pull that land out of the floodplain."
Forbes said letting the river go back to its natural state would be too unpredictable.
“We can't just let this river do its own thing naturally, because a purely natural river would sort of change over time.”
The site in October 2024 / Waterfront Toronto
So the efforts were focused on giving the river more space and a more natural pattern, but ideally in a permanent place: no easy feat.
Engineers kept the existing Keating Channel where the Don River enters the lake — but widened the curve allowing more water to flow. They also added a second branch to the river mouth, a little distance to the south, giving the new river a pleasing wiggle, and further south from that, a spillway facing the Shipping Channel that would effectively become a third mouth in a serious flood.
This required extensive excavation of existing lands.
In order to keep the industrial contaminants where they belong, engineers created a three-layer environmental barrier system on the bottom of the river, made up of a geosynthetic clay liner and a geomembrane.
How do you fill a new river valley? Cautiously
Building a riverbed was one thing, but filling it with water required a complex process involving giant "plugs" and underwater divers.
Though it would have been satisfying to let the Don into its new home with a roar, engineers had to be careful to protect the new river bed, a dry trench covered with the specialty liner that could balloon out of place if it was hit with water too quickly.
They used a pair of temporary concrete barriers, or plugs, to stop river water from entering at the north and lake water from entering from the harbour to the west.
Once the barriers were in place, water was slowly pumped in over the course of several weeks. After the patient process, the plugs were removed and the river could once again run its course.
"The west plug we removed using a wire saw, just a big wire cable on pulleys, and it would just sort of cut sections of the wall out, and then an excavator on a barge was holding on to each section, and then just moved it to shore," Forbes said.
"For the wall at the north end, we used a carbide grinder on the end of an excavator sitting in the river to grind all the concrete out. And then we had underwater divers cut out the reinforcing steel."
The new river remains buoyed off to keep boaters out of what is still an active construction site, but Forbes says the buoys will be taken away by summer, and people can explore the new river mouth in canoes and kayaks.
Buoys block the entrance to the Don's new channel, for now / Patrick Cain/Village Media
Bridges shipped up the St. Lawrence
The project also includes four new bridges, another feat of engineering.
Two bridges are located side by side across the Keating Channel, with a span for the future Waterfront East LRT and another for other traffic. The other two cross the new river at either end. Brightly coloured, they can be glimpsed from the Gardiner Expressway.
The bridges were manufactured in Halifax, shipped to Toronto by water and welded together on site.
Because the steel was so thick, the welding had to happen at unusually high temperatures.
Large, insulated thermal tents on the welding site helped to keep the temperatures high while workers were inside. Even protected by insulating suits, the workers could only endure it for a few minutes at a time before needing to cool down.
Living reminders of the marsh endure
Despite all the abuse from industrial use, plant life from the former marsh was still alive below layers of soil, more than a century after being buried.
When construction crews excavated a wet area down to the water table and left it alone for a time, they saw plants begin to grow.
"Plants started growing, and someone noticed that they didn't look like all the weeds that were growing on the rest of the site," said Forbes. "They were very similar to existing native plants, but they were a little bit different."
Researchers from the University of Toronto determined they were hard stem bulrush and cattails that had grown from seeds buried in the Ashbridge's Bay marsh — fauna that is genetically distinct from its modern cousins. A number have now been planted near the north end of the river.
After the river was filled in, nature continued to make the area home.
"It really was amazing when we first started putting in plants, how quickly nature came back," Forbes said.
"Within weeks we had species in there using that habitat. Almost immediately we had birds and amphibians coming back into the river. It's really amazing how quickly the local fish species and bird species, and mammals, even, have found this habitat in the middle of a construction site."
A space to interact with water
The new park will bring a waterfront experience different from the rest of the central city's waterfront.
Along most of the shoreline in Toronto’s downtown and west end, people are kept from connecting with the water by design features like docks — water is water and shore is shore.
At the park the Don Mouth Naturalization Project is creating, however, edges will blur by design.
"We really wanted to create a space where people could interact with the water," Forbes said. "You could come down and go fishing. You could come down here and put your canoe, your kayak in."
The park, south of the new residential area, will be an open area crossed by paths and footbridges, with space with small areas of wetland and a launch point for canoes and kayaks. Bridges will connect it to the city to the north, and to Cherry Beach and the Martin Goodman Trail to the south.
"You could come down here and sit on a rock beside the water and dangle your feet in. You could come down here and see the different species that use the wetland habitat now."
The bridges that will connect the area with the city are seen in February, 2025. The one at right is reserved for the future Waterfront East LRT. Patrick Cain/Village Media
