Above: Downtown Calgary during the Alberta floods of 2013 (Ryan L.C. Quan)
Did you know? The term “urban” refers to cities. It’s often used to describe development, culture, or trends related to highly populated areas.During the summer of 2013, both Calgary and Toronto were hit by rainstorms bigger than anything recorded in recent history. Catastrophic floods filled local and international newscasts with images of people stranded in the streets, abandoned cars, and inundated homes. No one seemed to expect that storm water could cause so much damage. Even worse, climate scientists who study long-term weather patterns warn that these kinds of storms will happen even more often in the future.
So just how much more can our cities handle? An even better question might be: How can our cities better take advantage of the ecosystem services provided by natural landscapes? By favouring green infrastructure (also called “low-impact development”), we can make our cities more resilient.
Did you know? Aquifers are underground layers of water-filled rock. They are an important source of drinking water.Cities are typically built with materials that are essentially waterproof: concrete, asphalt, metal, and bricks. These surfaces often seal off land that, only decades ago, was covered by forests, farms, and wetlands. As urban populations grow, so does the extent of these water-repellent surfaces.
So instead of being transpired by plants or absorbed by spongy soils, rainwater runs directly off roadways and into gutters and storm sewers, which are connected to rivers and lakes.
But even the most extensive sewer system has its limits. When it has nowhere else to go, storm water is diverted to the nearest low-lying areas. Often, this results in flooded roads, homes, and businesses. Meanwhile, flood water can become dangerously unhealthy by picking up toxins, harmful bacteria, and other pollutants.
Urban stream syndrome and ecosystem services
Did you know? “Green infrastructure” describes a way of designing cities that incorporates plants, soils, and other natural elements to help absorb water. Scientists have used the term urban stream syndrome to describe the damage done to streams and rivers by growing cities. Symptoms include higher water levels, frequent flooding, and increased contamination.
In other words, the same ecosystems that have been replaced by city streets and buildings could help avoid floods like the recent ones in Toronto and Calgary.
In fact, nature typically provides a range of important benefits to cities and their residents. These benefits are called ecosystem services, and they include fresh air, clean water for drinking and recreation, and flood protection for our rain-drenched cities.
Cities can reap the benefits of ecosystem services by including more open green spaces like parks, lawns, gardens, forests, and wetlands. As part of a city’s ecosystem, these natural landscapes are key to preventing severe floods. They allow the soil to soak up storm water and help channel water to underground water sources called aquifers.
Did you know? The Insurance Bureau of Canada has described the 2013 Alberta floods as the costliest natural disaster in Canadian history.Continued urban growth and more storms like those experienced by Calgary and Toronto should help us recognize the value of nature’s services. The more green infrastructure in our neighbourhoods, the stronger and more resilient our cities will become in the face of powerful storms.
By giving water more chances to enter soils and fill up aquifers, we can also help keep drinking water healthy and safe, not to mention keep our lakes, rivers and beaches clean for recreation. If we take better care of nature in our cities, it will take better care of us.
Calgary hit with flash floods from heavy rain (CBC News) Toronto storm causes chaos throughout the city (USA Today)
The urban stream syndrome (US Environmental Protection Agency)
Photos and videos
Flooding in the GTA: Your photos (The Weather Network)
Environmental websites and blogs
Working with nature can protect us from floods (David Suzuki Foundation)
Daily GC et al. 2009. Ecosystem services in decision making: time to deliver. Frontiers in Ecology and the Environment. 7:21-28. http://scholarship.law.duke.edu/cgi/viewcontent.cgi?article=3030&context=faculty_scholarship Daily GC, Matson PA. 2008. Ecosystem services: From theory to implementation. Proceedings of the National Academy of Sciences of the United States of America. 105:9455-9456. http://www.pnas.org/content/105/28/9455.full Millenium Ecosystem Assessment. 2005. Ecosystems and Human Well-being: A Framework for Assessment. Island Press, Washington, DC. Walsh CJ et al. 2005. The urban stream syndrome: current knowledge and the search for a cure. Journal of the North American Benthological Society. 24(3):706-723. http://clear.uconn.edu/projects/tmdl/library/papers/walsh_etal_2005.pdf