The New Favourite Colour of North American Cities

Green Infrastructure

Urban planners are increasingly looking to build partnerships between nature and the construction industry. In finding solutions to stormwater runoff and other challenges, they are discovering that there are economic and social benefits to be had too…

Whether the rain falls in the forest or in the plains, it’s absorbed into the earth, directly nourishing the vegetation and the living creatures that feed on it or finding its way to streams and rivers, lakes and ocean, home to myriad forms of marine life.

But when rain falls on the city it’s very different: deep in the concrete jungle, which houses 81 percent of the U.S. population and 74 percent of the Canadian population, there’s just nowhere for stormwater runoff to go.

Here, rather than nourishing the urban landscape, stormwater becomes an agent of pollution, carrying trash, bacteria, and heavy metals through storm sewers, where it’s flushed out into the nearest waterway, on its way to lake or ocean.

This is particularly troubling for Canada, which has 243,000 km of coastline, the longest in the world, and the U.S., which, with almost 20,000 km, ranks fourth. In addition, the two nations share a border along one of the largest inland waterways in the world, comprising the St. Lawrence River and the Great Lakes.

Both nations are beginning to recognize the critical importance of conserving marine and freshwater environments, crucial both for natural ecosystems and for developing a ‘blue economy’—opportunities for sustainable economic growth through resources such as energy, food, and the tourism associated with rivers, lakes, and oceans.

In addition to the impact stormwater runoff has on waterways, heavy rainstorms can cause flash flooding when storm sewers overflow, which in turn damages property and infrastructure.

So apart from a healthy blue economy, which benefits both nations, it’s in the self-interest of municipal governments to mitigate the issues created when “they took away the trees and put ‘em in a tree museum, then they paved paradise and put up a parking lot.” (Joni Mitchell, “Big Yellow Taxi”, 1970.) Clearly the type of greywater infrastructure—a system of gutters, pipes, and tunnels to move stormwater to treatment plants or dump it straight into the nearest body of water—that urban areas have used for over 100 years is not working.

But there are green solutions that can work if there’s a political will, investment from stakeholders, and willingness from the construction industry to participate in implementation.

In 2019, the U.S. Congress enacted the Water Infrastructure Improvement Act, which falls under the auspices of the United States Environmental Protection Agency (EPA). It defines green infrastructure as “the range of measures that use plant or soil systems, permeable pavement or other permeable surfaces or substrates, stormwater harvest and reuse, or landscaping to store, infiltrate or evapotranspirate stormwater and reduce flows to sewer systems or to surface waters.”

Meanwhile, the Canadian Government has included the development of green infrastructure among its Sustainable Development Goals under an umbrella that includes five priority areas: public transit, green infrastructure, social infrastructure, trade and transport, and rural and northern communities.

Commenting on the launch in 2021 of Canada’s first National Infrastructure Assessment, “Building the Canada We Want in 2050,” Thomas Mueller, President of the Canada Green Building Council, says that this assessment will establish a long-term vision for the country and provide ways to fund infrastructure projects as they move toward a net-zero emissions future and finally get onboard with green infrastructure.

“For the first time, both buildings and natural systems are actually acknowledged as being part of the ‘infrastructure’ and with that comes federal funding for sustainable, resilient infrastructure,” he told participants on a Blue Economy webinar ( and quoted in “Blue Economy: Implementing green infrastructure” by Jen Smith, May 15, 2022 (

In the same webinar, Roy Brooke, Executive Director of the Municipal Natural Assets Initiative, noted that green infrastructure includes three things: “Natural assets, so think your forests, riparian areas, wetlands. And then enhanced natural assets. So, for example, bioswales, and rain gardens. And then engineered natural assets. Think permeable pavers, green roofs, and the like. It’s a broad category, a grand continuum.”

Thirty years ago, long before North American cities began considering green infrastructure initiatives, Staten Island, one of the five boroughs of New York, developed an engineered solution to deal with the stormwater runoff that would otherwise flow into New York Harbour and Raritan Bay.

Named the Bluebelt, since it was devised to solve problems associated with water, it comprises more than 14,000 acres on the 59-square-mile island that is home to close to half a million people. Its 19 sites temporarily hold and filter as many as 350,000 gallons of rainfall, and have saved tens of millions of dollars that would have been spent on conventional storm sewers—all while “hiding in plain sight, disguised as parkland.”

Instead of the stormwater being carried directly into the harbour by pipes that run beneath the streets, it is diverted to engineered systems designed to mimic natural streams and ponds, which help control flooding, pollution, and erosion. By diverting the stormwater to meandering streams and rocky ponds, with tiny waterfall-like features, the movement of the water is slowed down, allowing sediment to settle, which can be emptied to avoid build-up.

The Bluebelt project also works to preserve, restore, and enhance the land around these waterways by developing healthy ecosystems. Native plants which contain helpful bacteria that clean the water were planted together with others that support wildlife such as fish and dragonflies, both of which provide chemical-free mosquito control.

What’s also notable about the Bluebelt project, devised in the 1990s, is that it owes its very existence to urban planners back in 1964. At the time people were flocking to Staten Island because the land was cheap, but on the advice of urban planners, the municipal council refused permission for developers to drain the swampy land and pave it over. Today it’s proof that land conservation, combined with engineered green infrastructures, does work and stands the test of time.

Across North America, cities are turning to green solutions, presenting many opportunities for the construction industry to get involved in projects from small-scale residential to large-scale municipal ones.

For example, Philadelphia, Milwaukee, and Portland have implemented Downspout Disconnection programs which reroute rooftop drainage pipes from draining rainwater into the storm sewer and instead into rain barrels, cisterns, or permeable areas. Backyard rain barrels, commercial building cisterns, ground-level pits, and aquifers are also used by the District of Columbia, Philadelphia, Milwaukee, and New York in rainwater harvesting programs. Syracuse, Los Angeles, and Chicago are among the cities implementing green streets and alleys, by integrating green infrastructure elements into their design to store and filter rainwater, including permeable pavement, bioswales, planter boxes, and trees, while Toronto has developed guidelines for greening of surface parking lots.

Rain gardens, shallow sunken areas of plantings also known as bioretention cells, are collecting stormwater runoff from roofs, streets, and sidewalks in Montgomery County, Maryland, Hillsborough County, Florida, and Puget Sound, where 12,000 have been planted in residential areas.

Bioswales, essentially long narrow rain gardens, are filling the spaces between sidewalks and curbs, and in the medians and perimeters of parking lots, using vegetation and mulch to slow and filter stormwater flow. A positive side effect is that they also reduce the urban heat island effect.

Meanwhile, planter boxes, with either open or closed bottoms, located on downtown streets in many cities and towns, not only beautify the streetscape but collect and absorb runoff.

Permeable pavements, made from pervious concrete, porous asphalt, or permeable interlocking pavers, slow and filter rainwater where it falls and are cost-effective where land values are high and flooding is a problem. And for municipal councils who are concerned that green solutions are expensive, the City of Sultan, Washington has issued a report indicating that the use of pervious concrete eliminated over $260,000 in construction costs.

A green roof system covered with vegetation enables rainfall infiltration and evapotranspiration of stormwater and is beneficial in dense urban areas on large commercial buildings where stormwater management costs are high. Urban tree canopies, meanwhile, absorb water while providing shade, making walking in urban areas more pleasant, an initiative Chicago and Philadelphia have taken on.

On a grander scale is land conservation. By protecting open spaces and sensitive areas, such as wetlands and steep hillsides within and on the perimeter of cities, urban stormwater issues can be addressed using engineered solutions such as Staten Island’s Bluebelt, while offering healthy recreational spaces for city dwellers.

Indeed, city-wide comprehensive green infrastructure programs offer numerous benefits to the ever-increasing numbers of urban dwellers. In addition to managing flooding, green infrastructure, including urban forests and vegetation, improves air quality and absorbs and stores greenhouse gases, while tree canopies on streets lower the temperatures in city centres, making them more walkable. Vegetation also reduces the urban heat island effect and can lower air conditioning costs or act as a wind break to lower heating costs, while community gardens provide food.

A team of researchers at the University of Toronto’s Scarborough campus “noted that during the pandemic, communities most impacted by COVID-19 were also most likely to lack access to nature.” (“Living Cities: U of T researchers develop framework for green infrastructure” by Alexa Battler, November 15, 2022.

Battler goes on to say that the researchers found that “the communities lacking green spaces—and now feeling the worst impacts of climate change—are often racialized populations… a living city requires identifying the areas that need [green infrastructure] most and putting them first, while ensuring decision-making is driven by collaborating with the people it will impact.”

Recommendations such as this are at the heart of the report “Pathways to Living Cities,” a document produced by a team of University of Toronto researchers with the environmental organization Green Communities Canada ( It’s a document that will provide decision-makers, and those advising them, with the information and resources they need to make GI a fundamental part of their communities, describing its vision of a living city “as a place where GI is widespread, well-maintained, and prioritizes underserved communities.”

Although this framework was only released to the public late in 2022, it has been at the centre of a pilot project to create living cities across Canada, working with five communities of varying sizes in Ontario, Alberta, and New Brunswick.

In the words of Christine Mettler, Green infrastructure expert at Green Communities Canada, “Green infrastructure can be aligned with addressing the everyday concerns of a community. It not only helps increase our resilience to climate change, but it also supports biodiversity, community health, and well-being, all while delivering critical municipal services, like stormwater management.”



Cladding and Exteriors

Read Our Current Issue


A Concrete Foundation

December 2023

Elegant and Eco-Friendly

November 2023

From Beautiful Bridges to Breathtaking Buildings

October 2023

More Past Editions

Featured Articles