The Swamp in your Backyard – Flood Protection and Clean Water


 |  Biodiversity/Conservation

If you live in a newer subdivision in Canada, there is a good chance that there is a marsh in your neighbourhood. This alone may not be surprising – both the forests and prairies that have been replaced with towns and farms were full of small swamps and sloughs, popular with ducks, muskrats and mosquitos. What may be more surprising to learn is that property developers and cities have intentionally been creating completely artificial wetlands, digging up prime real estate for an unappreciated ecosystem.

Redwing Blackbird, a common sight in city wetlands (Image Credit: Steve Smith (Unsplash))

Marshes and other wetlands like swamps, bogs and fens, can be incredibly productive ecosystems, hosting a wide variety of plants and animals. Their preservation is certainly important, but it seems uncharacteristic for property developers, who are often considered to be at odds with environmental protection goals, to want to contribute to this conservation. In fact, one of the priorities of Ford’s Ontario government was removing regulations that protected wildlife from development and lessened the requirements that had brought wetlands into subdivisions in the first place. So, why is their conservation so important to developers, cities, and governments? 

See, those muddy ponds ringed with reeds and full of blackbirds have a very specific purpose, one unrelated to conservation. They keep your basement from flooding. The suburbs are very different from the natural forests and prairies they replaced. Instead of there being lots of thirsty plants and porous soil, we have shingled roofs and driveways that water runs right off, and then into the streets.

For most people, this is a given. They’ll watch rivulets run down the sides of the streets and down into metal grates where the water disappears below ground into the drainage system beneath the city, with storm sewers usually running untreated into creeks and rivers. Untreated rainwater would not usually be a problem, but along the way it picks up oils, rubber, asphalt and other pollutants, carrying them into natural waterways and contaminating the water. 

Storm sewers are also imperfect, designed to handle regular rainfall events, but can easily be overwhelmed by a 1-in-100 storm, or what meteorologist predict to be the biggest rainfall event in a century.With more extreme weather events brought on by climate change, these stormwater systems are overwhelmed with increasing regularity, resulting in flooding of households and infrastructure.

Mallard ducks, another widespread bird species (Photo credit: Kristjan Kotar (Unsplash))

Stormwater ponds exist to address these two major concerns. Short drains around the neighbourhood deliver runoff into these ponds or marshes that are equipped to handle the runoff for hundreds of hectares. In the ponds, sediments including oils and other pollutants settle into the mud at the bottom of the wetlands, keeping it from freely flowing downstream and into the environment. They can also retain massive volumes of water in the event of a flood, protecting the surrounding environment.

Flood control and water purification are two examples of ecosystem services. Ecosystem services are measurable economic benefits humans gain from natural ecosystems. Without these stormwater ponds, municipalities would have to spend more money on stormwater drains, rebuilding damaged structures, and cleaning contaminated water. By integrating marshes and other wetlands within the city and suburban neighbourhoods, cities avoid these future costs. 

Urban flooding, a common disaster (Image Credit: Saikiran Kesari (Unsplash))

Damage control isn’t the only benefit that these spaces offer to us. Ponds and other “blue infrastructure” or water features are great at combating the urban heat island effect that contributes to heat waves and higher average temperatures in cities. Water alone tends to absorb heat, but aquatic vegetation cools the air during photosynthesis, releasing water vapor into the air. Additionally, green spaces provide  recreational areas for residents to exercise and play, which has enormously beneficial psychological effects on mental health, reducing stress and anger and making people happier. They also provide habitat for plant and animal species, including attractive wildflowers and songbirds.

These relatively small wild spaces within our cities confer many direct economic benefits, and contribute significant social benefits as a side effect. When combined with traditional urban infrastructure, they make cities more resilient to storms, pollution and the ravages of climate change. Their adoption is a great step towards recognizing and incorporating the benefits of ecosystem services into our modern lives – a lesson we can expand to other issues such as desertification, pollution, climate change and food and water insecurity.