Newsbulletin Story

No. 186 - September 11, 2009

Climate change check up for Canadian cities

Researchers at the University of Toronto are looking into how urban drainage systems might perform in various climate change scenarios.

One key question according to Dr. Barry Adams, a Natural Sciences and Engineering Research Council (NSERC)-funded civil engineer involved in the project, is whether the historical rainfall conditions currently used in stormwater drainage designs will be valid in the long term, especially given changes in precipitation patterns already observed. He looks at the topic in detail in a recent paper written in conjunction with researchers from Golder Associates Ltd. and McMaster University.

The paper concludes that “a 20 percent increase in rainfall intensity would reduce the capacity of a system such that components previously designed to handle one storm event every ten years would be exceeded during an event every four years.”

All aspects of stormwater infrastructure could be affected, including pipes, ditches, streams, green roofs, ponds, infiltration devices and sewers.

Dr. Adams’ general fields of research are environmental decision making, and sustainable infrastructure and water resources. Sustainable urban drainage systems planning falls under both these areas. It involves studying how increasing population in urban areas, more paved surfaces, changes in the landscape and increased precipitation affect stormwater infrastructure.

It is an important field of study, given that failed drainage systems increase the risk of flooding. Urban runoff—rainwater that cannot be absorbed due to impervious surfaces such as asphalt—is also a negative side-effect of inadequate drainage. This runoff is a major contributor to water pollution, and can contaminate drinking water as well as wildlife areas. 

There are also major cost implications, as cities spend billions of dollars on urban infrastructure. A 2004 Infrastructure Canada study estimates that the cost of maintaining existing drainage infrastructure over a 15-year period ranges from $38–39 billion, with the cost of new or upgraded water and wastewater systems reaching $88.4 billion.

According to Dr. Adams, his research aims to develop formal methodologies, or mathematical models, for decision making which can be used to identify the most effective systems at the lowest cost. These models depict and predict how infrastructure systems will perform under a range of conditions, as well as the economic and social costs of these systems.

To put the importance of good decision making in context, Dr. Adams cites the city of Toronto’s Wet Weather Flow Management Master Planning exercise, the first phase of which will cost about $1 billion.

“Although this may seem like small potatoes relative to Wall Street bonuses, I am sure that the Canadian taxpayer would want to see such large sums well spent,” writes Dr. Adams. 

But he recognizes that when it comes to water infrastructure and climate change, it’s more about weighing the risk rather than defeating it. He says it’s not always possible to exactly predict what will happen, especially when dealing with something as variable as rainfall.

“In this business there is always risk. You’re working with nature, and nature has a lot of variability. It’s about finding the appropriate levels of risk. Nothing can be failsafe.”

Contact :

Barry Adams
Tel.: 416-946-0164
E-mail: adams@civ.utoronto.ca