Urban centres are particularly unprepared for the increased storms, floods, heat and drought that climate change is bringing. In the years to come, cities in Canada will feel the extremes of climate more and more: hotter, drier summers punctuated by storms; wetter and stormy winters.
Green City, written by University of Calgary Professor Bev Sandalack, advocates for a landscape approach to parks planning that recognizes and enhances the important ecological services provided by parks. Parks not only increase natural habitat in cities and provide space for recreation and social connection (which improve our physical and mental well-being); they also provide a critical aspect of stormwater infrastructure and climate resilience. Green spaces soak up and filter rain, acting as buffers for intense rainstorms and run off. Runoff from paved roads and parking lots carries garbage, bacteria, heavy metals and other contaminants directly into our waterways through the storm sewers. Functional parks reduce intensity of storm events and associated contamination.
An old engineering approach to dealing with stormwater and flooding has been to capture it and direct it through drains and underground pipes in what is called “grey infrastructure.” Grey infrastructure uses a combined sewer overflow (combined sewage and stormwater in the same pipes). When heavy rain overwhelmed the system, it was designed to release partially treated sewage and stormwater into our waterways as a safety valve to protect the system from flooding.
The alternative to this archaic method of dealing with increasing storm events is to create “green infrastructure”—essentially naturalizing our urban and suburban settings and what I call “wilding”; bringing Nature back in to where we work, play and live. Examples include daylighting streams, creating rain gardens and constructing wetlands that filter pollutants, hold water and help transport it naturally.
A park must be more than green to slow down, soak up and clean water where it falls. Soil compaction from heavy use, such as grassy open spaces, will not filter water well. For a park to effectively capture, retain and treat stormwater, it must be designed to act as a “sponge.” Parks need to be intentionally designed as climate-resilient infrastructures. They must be designed with ecological function in mind. This is not the engineer’s purview; it is the ecologist’s. For cities to become resilient we must adapt to our changing environment.
For too long, urban design has bowed to the architect and engineer to create a vision for and solve challenges in human functionality. This has given us the modern and post-modern world of humanist existentialist efficiency; an existence and expression based on a stable environmental paradigm. Climate change is changing that. It is ushering in a new paradigm informed by natural phenomena. We must look to the landscape architect and the ecologist for our answers now.
In his article in Park People, Jake Tobin Garrett, provides a list of common “green infrastructure” features that will help create resilient parks and ultimately more climate-adaptive cities.
Examples of Green Infrastructure
Rain garden. A depression filled with vegetation, trees, and rocks that collects and stores stormwater, using it as a water source for plants and allowing it to filter into the ground. These can be found in strategic locations within a park or along the edges of roadways where a drain allows stormwater from the curb to drain into the rain garden. New York City has invested heavily in creating rain gardens as part of their overall green infrastructure plan, resulting in the spin-off benefit of street beautification and increasing urban nature.
Stormwater management pond. An area designed to hold stormwater during heavy rainfalls. These can be designed as both wet and dry. A wet retention pond, like a wetland, is designed to always contain water, while a dry detention pond, like a basketball court or playing field, is designed to fill and hold water only during storms.
Daylighted streams. The practice of bringing streams that have been buried in pipes, back to the surface and renaturalizing them. For example, Vancouver is currently working on a plan to “create an ecologically diverse stream” through Tatlow and Volunteer Parks that will feed into English Bay.
Bioswale. A depression or groove like a miniature stream, sometimes filled with vegetation and rocks, that channels stormwater to a drain, water body, or retention area, like an underground tank or aboveground pond.
Bioretention storage areas. Underground stormwater treatment and storage areas using soil mixes designed to hold and infiltrate water. These can be used to create healthy conditions for trees, with engineered systems called soil cells to support paving above.
Permeable paving. Pavement that allows water to infiltrate to the ground below, rather than runoff of it, including materials like porous concrete and permeable interlocking concrete pavers. One study noted that permeable pavement is helpful in winter as it allows snowmelt to filter through, reducing the amount of freezing ice on the actual surface. Ideally these paving solutions are also designed to provide water for trees and planting areas through underground bioretention areas, expanding their benefit.
Benefits of Green Infrastructure
The benefits of green infrastructure for water control are multi-layered and go way beyond an engineer’s concept of simply moving water in a pipe from one place to another. In his article, Garrett provides the following benefits of green infrastructure:
- Perform important environmental functions. This includes decreasing water runoff, improving water quality, mitigating and preventing erosion, and cleaning the air. It can also reduce the urban heat island effect by increasing green areas that don’t absorb heat like hard surfaces—an important cooling benefit to cities as climate change results in hotter weather.
- Improve and expand urban nature and habitat. Green infrastructure can include native plants that provide critical habitat and food for pollinators, such as native bees and butterflies, and other wildlife that are under threat, helping to promote urban biodiversity and healthier ecosystems.
- Create new community gathering and recreational spaces. Green infrastructure can increase public space and recreational areas in cities. These projects can enhance existing parks, but they can also be opportunities for creating new green spaces and plazas from underused areas like roadways and traffic islands.
- Save money.By reducing the amount of money a city spends on expensive infrastructure like pipes, green infrastructure can help save money. For example, Copenhagen estimated that its green infrastructure approach to stormwater management was estimated to cost half the price over time of a more traditional “grey” infrastructure-only approach.
- Create safer roads. If included within traffic calming measures such as traffic islands and bump-outs that increase pedestrian space or separate bike lanes with planting areas, green infrastructure can help slow down cars and improve traffic safety. Toronto’s new Complete Streets guidelines, for example, contain a section on green infrastructure.
Nina Munteanu is an ecologist, limnologist and internationally published author of award-nominated speculative novels, short stories and non-fiction. She is co-editor of Europa SF and currently teaches writing courses at George Brown College and the University of Toronto. Visit www.ninamunteanu.ca for the latest on her books.