Thanks to more examples of successful implementations, new technology and a steadily increasing body of evidence about benefits, there is growing interest in the use of green infrastructure to manage issues such as stormwater, pollution and rising temperatures, as well as to improve the look and feel of our cities.
There isn’t a universal definition of green infrastructure but it’s broadly agreed to refer to green features that help to solve urban and environmental challenges.
Architect Stefano Boeri is passionate about green infrastructure and demonstrates the art of the possible with his fantastical-looking plant-covered buildings. He is famed for his tree-clad Bosco Verticale (vertical forest) skyscraper complex in Milan and is now working on urban forestation projects in countries around the world, including Switzerland, Holland, Brazil, Albania and France.
“Cities are two per cent of the entire Earth’s land surface, but they are producing 70 per cent of CO2,” Boeri said. “If we seriously want to deal with climate change, we have to study where climate change is produced. Forests absorb approximately 40 per cent of (man-made) CO2, so increasing the number of trees and plants inside a city is a crucial issue.”
Boeri’s now has a vision for “forest cities.” This ambitious plan will start with Liuzhou Forest City, which will be built in the north of Liuzhou in China, a country with one of the most chronic air pollution problems in the world. Construction is expected to begin before 2020 and will see offices, houses, hotels, hospitals and schools that are entirely covered by plants and trees.
Once completed, Boeri said the new city will be home to 30,000 people, absorb almost 10,000 tons of CO2 and 57 tons of pollutants per year, and produce approximately 900 tons of oxygen. It will have 40,000 trees and almost 1 million plants of over 100 species.
Beyond ‘bigger pipes’
Not all green infrastructure initiatives are quite so radical but they are still making a big difference. Aaron Koch is Chicago’s first chief resilience officer, appointed last year.
One of the challenges he is tackling is storm water management.
“In Chicago, like most big cities, we have lots of buildings, roads, hard surfaces…so water runs into our sewer system,” he said. “Our sewer system often can’t handle that rainfall and it either ends up as an overflow into our rivers, which causes pollution, or it backs up into people’s basements. In Chicago, many of our homes have basements.”
Chicago is making major investments in the city’s local sewers, but at the same time recognizes “we can’t just solve this problem by building bigger pipes.”
Green infrastructure, Koch said, can reduce the impact on the sewer system and keep the water from entering the sewer altogether. At the same time, it provides other benefits such as improving public spaces and air quality, absorbing heat and more.
One example is Chicago’s “streetscapes,” such as Argyle Street, which opened late last year. It’s intended to be a “shared street” between pedestrians, cars and cyclists. As well as raising the level of the roadway, eliminating curbs, adding decorative pavement and creating a plaza-like effect, the project incorporated a number of green infrastructure elements, including use of permeable pavers and infiltration planters that soak up rainwater.
Space to Grow is another Chicago initiative. Often, schoolyards are paved with asphalt, meaning they’re not ideal for playing in and they generate a lot of storm water run-off. So far, as part of Space to Grow, a dozen playgrounds have been updated to include green infrastructure such as rain gardens, bioswales, plants and permeable pavements, as well as play features and benches. Thirty-four Space to Grow playgrounds will be built by 2019.
“These spaces function as green infrastructure but also provide better environments for the children to play, as well as connecting to the science curriculum so they can learn about environmental issues,” Koch said.
Cities that want to expand their green infrastructure investment or kick-start initiatives will need to demonstrate results. Experts agree that this is an emerging area, but more research is needed to prove the case.
Chicago is working with UI Labs’ City Digital to pilot technology incorporating sensors and cloud-based analytics to evaluate the performance of green infrastructure for storm-water management.
Through the Smart Green Infrastructure Management Pilot, sensors at sites around Chicago measure how much moisture is held in green infrastructure, such as biosoil, permeable pavement, roadside planters and tree-grade infiltration beds. The sensors feed into a communications module which also collects information from a small weather station installed at each site. The data is transmitted back to a Microsoft Azure cloud data platform and made available through an online dashboard and the city of Chicago’s open data portal.
“That data’s alive and open to anyone interested in accessing it,” said Alex Frank, program manager, City Digital, UI Labs. “We think this program is unique in its ability to provide continuous monitoring data in an efficient manner. It’s something that can be useful both to the city of Chicago and their thinking about further investments in green infrastructure, but also provide data and understanding for green infrastructure and developments anywhere across the world.”
As well as demonstrating how well each type of intervention works, this real-time approach could also help cities shift green infrastructure from being a passive to an active resource, Frank said.