Christopher Hume: Why Downsview Park's new bioswale is money in the bank
At a time when once-a-century storms occur every few years, keeping the city from sinking city isn’t as easy as it once was. Subways and basements flood regularly now, sewers overflow and roads disappear beneath the deluge. During the most recent such event, two weeks ago, a month’s worth of rain fell in two hours. And who can forget the storm in July, 2013, that left Toronto submerged.
For the most part, the city’s response has been all wet. Mayor John Tory proved himself unequal to the task of keeping up with climate and civic change when he led the charge to reject a plan to modernize the city’s stormwater management system. The problem was that it included fees. That’s a scary prospect for a mayor as timid as Tory, who doesn’t believe that Torontonians should have to pay the costs of living in a big city.
In truth the cost of these downpours is far greater than the price of readiness. The 2013 storm alone resulted in more than $1 billion in insurance claims.
Fortunately, not all branches of government are as inept as the political; the proof is a large bioswale commissioned by the Canada Lands Corp. at Downsview Park. If you haven’t heard that word, bioswale, don’t worry, you will. Essentially a landform feature that drains storm run-off before it can do damage, it goes a step further than the stormwater ponds with which we are now familiar.
“It combines the art of landscape architecture and the performance of engineering,” explains Ian Gray, senior landscape architect at WSO Global. “It’s designed to take the load off storm sewers, which don’t have the capacity to deal with the sort of storms that now occur more often.”
And, Gray makes clear, that’s money in the bank.
But the bioswale represents more than a simple mechanical response to infrastructural need. It’s based on the assumption that the city is a system as much as a place, a human construction as well as a natural phenomenon. Walking past the still unfinished feature, you see what appears to be a linear garden running along Downsview Park Blvd. across the road from a new townhouse subdivision. Filled with native plants — Joe Pye weed, cone flowers, echinacea — along with indigenous grasses and a row of sweet gum trees, it looks more decorative than utilitarian.
Because the dirty work happens underground, the process remains invisible. A series of street-level channels directs water from the road, which means the usual sewer grates are conspicuously absent. The bioswale occupies a trench divided by weirs into sections and filled with a bottom layer of gravel and soil chosen for extra porosity. The soil absorbs and filters run-off as it sinks into the ground and eventually ends up in the water table. In the case of a truly biblical flood, a pipe has been added to convey excess water to the sewer.
Mimicking natural processes gives the city a fighting chance to cope with the realities of climate change. If extreme weather weren’t enough, Toronto has also become a place of hard surfaces. Paved in concrete and asphalt, the ground no longer functions as an absorbent. Water has nowhere to go but subways, sewers, basements and similar low points.
One of the most notorious is the underpass on Lower Simcoe St. south of Front. Though completed in 2009, long after climate change was acknowledged as the greatest issue of our time, it floods with every storm. The most famous image of the 2013 deluge showed a Ferrari abandoned to the water in the underpass. It is emblematic of Toronto’s failure to understand that 21st-century infrastructure must transcend the sort of traditional engineering that creates as many problems as it solves.
The holistic thinking implicit in the Downsview bioswale anticipates the future. Its starting point is the totality of the context not the application of narrow professional perspectives. Because infrastructure must address unprecedented levels of complexity, only a multidisciplinary approach is up to the challenge.
In addition to stormwater, the bioswale deals with social, economic, environmental and even esthetic issues while enhancing biodiversity. It doesn’t exist in physical and intellectual isolation but is fully engaged in the urban landscape.
The implications are significant. Every element of the city must take on critical new duties, especially streets, which form the largest part of the public realm. “We have to start thinking of them as parks,” says Gray.
Christopher Hume is a former Star reporter who is a current freelance columnist based in Toronto. Follow him on Twitter: @HumeChristopher