How building near Edmonton's river could mean more housing — and higher flood risk

A proposal to build several residential buildings up to 17 storeys, in the heart of Edmonton's river valley, stands out in more ways than one.

Beyond the height changing sight lines in the area, some Edmontonians also showed concern during community engagement because the structure lies within an identified flood plain.

It's a unique water-front proposal in a city that cherishes its river valley as a central green space that is largely undeveloped. It also raises questions about the risks of building so close to the water — and whether those are worthy trade-offs in exchange for more housing.

The project, submitted by Dub Architects on behalf of Five Oaks Inc., proposes three buildings that could reach 17 storeys and create up to 490 residential units. The land along 100th Street in the Rossdale neighbourhood includes the historic Rossdale Brewery, which the project plans to restore and integrate.

To build that tall, the land needs a rezoning, which will be discussed at a public hearing Monday. If approved, the rezoning would bring in extra environmental requirements, too.

A report submitted for the hearing outlines tension between the city's goals for housing and the potential flood risk.

"While this land already has zoning that would allow for urban development, increasing the intensity of this development in an ecologically important area where there are potential climate change flood risks is not necessarily aligned with the idea of climate resilience," the report says.

How do we assess flood risk?

Alberta flood-mapping tools are used to determine what areas are most at risk. In those maps, a flood hazard area is divided into two zones: the floodway and the flood fringe.

That tells you what to expect in the event of a one-in-100-year flood, according to Evan Davies, a professor of civil and environmental engineering at the University of Alberta who specializes in water resources.

The floodway will have fast-moving water that can be deep and destructive. The flood fringe will be shallower and less dangerous.

City administration worked with the applicant on their original proposal so the development falls outside the floodway. The three buildings are now "almost entirely outside the one-in-100-year flood line," the report says.

This means most of the project falls within the one-in-200 year flood zone, leaving a 0.5 per cent chance of flooding in any given year.

That's too close for comfort for organizations like the Edmonton River Valley Conservation Coalition, which would like to see the area protected.

"It's really risky to think that we understand what a flood could do in this area," said Kristine Kowalchuk, the organization's president.

She said other cities that live next to water around the world are, instead, "restoring and rewilding" their flood plains and removing infrastructure. 

"That's the way that we need to go," Kowalchuk said.

What are the rules?

The Alberta government has created flood maps to help municipalities determine risk, but it is up to them to set the rules, said Kevin Lee, a press secretary for the Ministry of Municipal Affairs, in an emailed statement to CBC News.

"Municipalities have the autonomy and accountability to approve development permits and analyze the risks associated with them within their municipal boundaries," Lee said.

Jason Thistlethwaite, an associate professor at the University of Waterloo in Ontario who studies climate risk, said this contrasts to Ontario, where it is prohibited to build in flood plains — which are determined by the historic Hurricane Hazel.

"It's more of a black-and-white approach, whereas Alberta has sort of adopted a couple shades of grey," Thistlethwaite said.

The lack of provincial regulation in Alberta is a problem, especially because local politicians often face pressure to allow development, said Ryan Ness, director of adaptation at the Canadian Climate Institute, a policy research organization.

"Without a provincial backstop, there's nothing to keep that pressure from resulting in decisions that allow development where it's really too risky to be safe," Ness said.

Thistlethwaite said there's a conflict of interest for municipal governments who want property tax revenue and more housing, but don't typically pay the bill when disaster strikes.

"Municipalities, historically, have been able to be bailed out by upper-tier governments for poor development decisions," he said.

But the rules around that are changing quickly, Thistlethwaite said, noting the federal government uses the one-in-200-year line to determine regulations around disaster assistance.

How do we plan for climate change?

But these models are based on current and historical circumstances. The City of Edmonton asked the applicant to make a model with additional risk due to climate change.

Dub Architects created a model that accounts for a 10 per cent water discharge increase. It shows two of the buildings almost entirely in the flood fringe.

Western Canada is likely to see more extreme weather, said Davies, of the U of A, citing the Intergovernmental Panel on Climate Change.

"It's reasonable to expect that we'll get both wetter conditions in some years, and drier conditions in others, than we've seen historically," Davies said.

Wetter years could lead to higher river flows, he added, but it's still uncertain what will happen.

"That's one of the concerns about climate change, is that there's a lot that's unknown," he said.

The city's report clarifies that a development permit will not be given for this project until additional geotechnical, hydrotechnical and environmental studies and mitigation measures are done.

CBC News contacted Dub Architects for comment, but did not hear back. 

Is there a way to build in flood-prone areas responsibly?

Thistlethwaite said, in Ontario, a common approach has been to elevate a building by turning the first few floors into above-ground parking. 

Davies mentioned raising the structure, or at least making sure that all electrical components, furnaces and water boilers are above the flood level.

Davies and Thistlethwaite agree that, with the right engineering and plenty of planning, developers can defend against risk and make a project like this pretty flood resilient.