Anti-flood projects include ripping up city asphalt to allow water run off

Concrete pavement. Photo from PavementSE

OTTAWA — They paved paradise, and put up a flood zone.

Five cities across Canada will see some of their asphalt torn up and replaced with porous brick and gravel this summer to help mitigate the flash flooding that frequently follows extreme rainfall.

Modern cities are ever more sheathed in concrete and pavement, sealing off the absorbent ground and leaving heavy rain with nowhere to go _ except basements, subway tunnels and underground corridors.

Last year, Calgary and Toronto homeowners and businesses were hit with severe flooding that was aggravated by sealed topsoil that could not absorb the sudden influx of water, costing billions in damages.

The University of Waterloo, Ont., and insurer Intact Financial Corp. announced a 20-project initiative today aimed at helping communities better survive the extreme weather that is the inevitable result of climate change.

The so-called “Depave Paradise” pilot projects are set for Calgary and the Ontario communities of Mississauga, Peterborough, Kingston and Ottawa.

The projects in five provinces range from construction of so-called bio-swales — which work as temporary holding tanks for excessive rainfall — to restoring urban wetlands, to carrying out home audits in Calgary so owners can flood-proof their properties.

“Cities used to be fields and forests, and now increasingly, we’re making them impervious to high-intensity rain,” said Blair Feltmate, a University of Waterloo professor helping to implement the initiative.

The 20 projects are receiving about $700,000 in direct funding from Intact, including about $75,000 for the depaving projects, which will remove at least 250 square meters of pavement.

Feltmate says all of the work is intended to help measure the effectiveness of each project to determine whether they should be adopted more generally.

“It’s amazing that nobody has done this en masse across the country,” said Feltmate, an associate professor in the environment department.

Intact, the largest property and casualty insurer in Canada with about 18 per cent of the market, has donated some $1.5 million to the University of Waterloo’s climate change adaptation project.

Feltmate says weather-hardening communities is in everyone’s interests, including insurers who are seeing an explosion in payouts for water damage from sewer backups and other weather-related problems.

Feltmate’s group last fall published a survey of insurance company executives who said that homeowners will never have access to comprehensive flood insurance in Canada unless there are new maps of flood-prone areas that take climate change into account.

Sewage back-up insurance is available in Canada, but not insurance for so-called overland flooding by which water enters basements through windows.

Feltmate says communities are becoming more vulnerable as aging storm-sewer infrastructure is less and less able to handle torrential downpours linked to climate change.

“These projects ultimately aim at calculating the return on investment for various forms of adaptation initiatives that should be deployed … across Canada to de-risk cities relative to flooding,” he said.

The Insurance Bureau of Canada says claims related to catastrophic weather events have surpassed $1 billion in every year since 2009. Flooding and storms in Toronto and Calgary last year cost about $3.2 billion in claims by property owners.