Urban flooding likely to worsen, say experts
‘Soft engineering’ more urban parks, porous pavement might help, but costly sewers will still need to be replaced
By Lucas Powers, CBC News
Posted: Jul 11, 2013 5:11 AM ET
Last Updated: Jul 12, 2013 10:10 AM ET
The Toronto floods on July 8 were caused by an unsually severe storm that dropped nearly twice the monthly average in just a few hours, but climate experts say these events will become more frequent in the coming years.
Southern Alberta’s June floods and those in Toronto this week may be freak occurrences that were caused by unusually severe storms.
But they have highlighted a desperate need for upgraded urban storm systems that account for increases in severe weather, engineers and municipal planners say.
In municipalities across Canada, outdated storm and waste water infrastructure has resulted in increased flood damage to homes and these types of situations will likely get worse in the near future, says Paul Kovacs, executive director at the insurance industry’s Institute for Catastrophic Loss Reduction.
“Today there is simply more people living in areas at risk of flooding, the infrastructure that we count on to prevent floods is not enough to do the job,” says Kovacs. “And on top of that we are getting more large storms than we have in the past.”
Kovacs points out that, according to his research, basement flooding has emerged as one of the fastest growing causes of losses and extreme damage in Canada, costing $2 billion just in direct insurance payments annually.
In March, the federal government announced that $53 billion would be put towards upgrading and replacing infrastructure throughout Canada over the next 10 years. But it remains unclear what portion of those funds will be spent specifically on water-related infrastructure like sewers and waste water management plants.
Claude Dauphin, president of the Federation of Canadian Municipalities, says that the new money is “a step in the right direction,” but he estimates that there is currently about a $200-billion infrastructure deficit in Canada.
In a 2007 report titled “The Coming Collapse of Canada’s Municipal Infrastructure,” the FCM estimated that up to $90 billion would be needed over 10 years just to maintain and update the existing water infrastructure in Canada.
It said there is a need to “rehabilitate water and sewage infrastructure” especially in older cities like Montreal where many sewer pipes in the downtown were built in the 1880s.
Soft engineering?
A significant problem with allocating money for water system upgrades is that many municipalities don’t really know how much work needs to be done.
“At the most basic level is a lack of a national inventory on infrastructure,” says Kovacs.
“What pipes do we have in place? What state of repair are they in? What is their capability to deal with heavy rain? Some very basic information is lacking.”
Jane Wolff, an associate professor of landscape architecture and design at the University of Toronto, says that outdated engineering approaches are a big cause of cities’ inability to deal with higher than average rainfall.
“The logic of 19th- and 20th-century engineering was to get water away from buildings and structures as quickly as possible,” says Wolff. “So roofs and streets are made from impermeable material and water is funneled into drains towards an end point like lakes and rivers.
“But now people are starting to talk about the fact that maybe these highly engineered systems, designed to get water out of city very quickly, are not serving us that well anymore.”
Wolff says that municipalities need to integrate “soft engineering” elements into development plans such as encouraging green roofs and porous parking lots, increasing the number of trees in highly urban areas, and using vacant suburban land as reservoirs during storm events to “slow the flow of rainwater down and ease the pressure on sewer systems that are being overwhelmed by intense, unpredictable storms.”
‘The government of Canada has not been engaged enough in this problem, and what’s happened over the past few weeks will be enough to get them engaged again.’—Paul Kovacs
But while all of these solutions will help land absorb water in a much more predictable fashion, “soft engineering will not solve the fundamental problem of old infrastructure that can’t handle the kind of storms we saw in Calgary and Toronto,” says Gail Krantzberg, a professor of civil engineering at McMaster University.
“We need to combine traditional engineering approaches with new kinds of thinking, like reducing the amount of paved surfaces in our cities.”
A public health issue
Many cities in Canada, especially those with aging downtown cores, have combined sewers in which storm water and sewage is carried in a single pipe.
In Toronto, for example, 23 per cent of the sewers in the downtown are combined, according to Lou Di Gironimo, general manager of Toronto Water.
The problem, however, is that combined sewers are very easily overwhelmed during big storms and the overflow is discharged into the environment, releasing solid human waste into lakes and rivers to prevent it from ending up in people’s homes and buildings and overwhelming waste water treatment plants, says Di Gironimo.
The resulting water quality problems can lead to illness.
“If people are swimming, for example, in Lake Ontario following a major overflow event then eye, ear and throat infections and fecal coliform problems can become a significant issue for people,” says Krantzberg.
“I think the human health impacts of that: hospitalization, medical treatment and all of those things add ammunition to the argument that we need to deal with overflows better than we are.”
Political leadership
The city of Toronto is investing $680 million over the next 10 years to reduce the number of combined sewers in the downtown core, but smaller municipalities who generate less tax revenue will need help from other levels of government.
Following several big urban floods in the late 1940s and 1950s throughout Canada, including Hurricane Hazel in 1954, the federal government, along with provincial authorities, took a strong lead in addressing flood management, says Kovacs.
By 1975, the Flood Damage Reduction Program was established, in which the federal and provincial governments shared the cost of creating flood risk assessment and also mapped floodplains.
The program dissolved in 1990, and since then flood-risk management has been neglected at the federal level, according to Kovacs.
“The government of Canada has not been engaged enough in this problem, and what’s happened over the past few weeks will be enough to get them engaged again,” he predicts.
Krantzberg points out that taxpayers can feel removed from infrastructure that is often buried deep underground and out of sight.
“Unless the taxpayer understands that this is for their health and safety, and support taxes going into water management infrastructure, it’s a hard sell,” she says.
But experts seem to agree that these recent dramatic flood events will likely catapult water infrastructure into the public dialogue.
“It’s absolutely awful, what has been happening,” says Wolff at the University of Toronto. “But I think an upside is that this has been a problem below the level of public consciousness for a long, long time and it’s a really important wake-up call for all of us.”
http://www.cbc.ca/m/touch/news/story/2013/07/10/f-floods-rain-engineering.html#
