How green roofs can protect city streets from flooding

How green roofs can protect city streets from flooding

August 22, 2017 12.31am BST •Updated August 28, 2017 6.22pm BST

The Acros Fukuoka eco-building in Fukuoka, Japan boasts one of the world’s most famous green roofs. The GRIT Lab at the University of Toronto is working to bring green roofs to the city and beyond in order to combat climate change. (Shutterstock)

Authors

1. Catherine Howell
   Research Assistant, GRIT Lab, University of Toronto
2. Jennifer Drake
   Assistant Professor of Civil Engineering, University of Toronto
3. Liat Margolis
   Associate Professor of Landscape Architecture , University of Toronto

Disclosure statement

Catherine Howell works for the GRIT Lab and is a Master of Landscape Architecture student at the University of Toronto. 

Jennifer Drake receives funding from NSERC. She is affiliated with GRIT Lab at the University of Toronto. 

Liat Margolis receives funding from NSERC, Mitacs, Ontario Centres of Excellence, Connaught Fund, RCI Foundation, and Landscape Architecture Canada Foundation. She is the Director of the GRIT Lab at the University of Toronto.

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University of Toronto provides funding as a founding partner of The Conversation CA.

The Conversation UK receives funding from Hefce, Hefcw, SAGE, SFC, RCUK, The Nuffield Foundation, The Ogden Trust, The Royal Society, The Wellcome Trust, Esmée Fairbairn Foundation and The Alliance for Useful Evidence, as well as sixty five university members.

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Spring and summer 2017 have been among the wettest on record in eastern North America. And the world is watching Houston this week, where the remains of Hurricane Harvey have caused devastating flooding.

Rainfall amounts in the spring broke records in places like Toronto, where 44.6 millimetres of rain fell in 24 hours. The downpours earlier this spring caused the stormwater infrastructure in Canada’s biggest city to overflow, leading to flooding of busy downtown streets.

Urbanization in many North American cities has led to a rapid loss of permeable surfaces where water can freely drain. Coupled with the growing downtown core population in cities Toronto, this means that the stormwater and sewer systems in place must manage more water than in previous decades. 

Furthermore, global temperature increases have been linked to the rise in extreme weather events worldwide, a trend that could worsen if global warming is not brought under control.

Many cities are ill-equipped to deal with these unprecedented amounts of precipitation due to their insufficient and outdated stormwater infrastructure. 

A tow truck driver walks through flood waters after hooking up a car on the Don Valley Parkway in Toronto after a major rainstorm in July 2013. THE CANADIAN PRESS/Frank Gunn