Flooding is a critical issue facing Canadian municipalities that will only become more challenging as we continue to experience the effects of climate change. A 2019 Council of Canadian Academies report quotes damage to physical infrastructure caused by extreme weather as Canada’s top risk and in 2019, for the first time in history, the Bank of Canada listed climate change as one of six vulnerabilities to Canada’s financial system. Considering that extreme weather, including floods, is Canada’s primary climate change risk, stormwater and flood management is an important strategy for enhancing our climate resiliency.
Urban centres like Toronto are particularly vulnerable to flooding, and with a seasonal bombardment of news headlines warning of rising flood costs and impending infrastructure damages, this seems impossible to ignore. And rightly so—the Greater Toronto Area has seen a significant increase in flooding over the past ten years, coinciding with rising average temperatures. In 2019, the Insurance Bureau of Canada reported that insured losses from severe weather in Ontario reached $1.3 billion in 2018, after exponential increases since the early 1980s, when average insured losses were only $400 million per year for all of Canada.
There are many reasons why urban areas across Canada are seeing more flooding. Older neighbourhoods were constructed in floodplains and some regional topography shows development in low-lying areas prone to flooding, simply due to the nature of how water flows. However, three important factors are the main drivers of increased flooding in urban centres like Toronto: more precipitation as a consequence of climate change, aging and insufficient infrastructure capacity and the abundance of concrete, asphalt, and other hard surfaces.
These impermeable areas prevent water from seeping into the ground as it naturally should, forcing it to flow overland into storm sewers, many of which are old and have limited capacity. To reduce these effects, introducing permeable features like plants and soil to soak up water would help protect cities from floods—like taking a step towards re-establishing the power of the forest or wetland that once stood where our cities do now. This is natural infrastructure; the use of vegetated systems to manage stormwater and restore some of the hydrological functions of natural areas.