Forests, wetlands and grasslands: The superheroes of flood control

Minesing Wetlands (Photo by NCC)

Each year, especially spring and fall, Ontario residents grapple with flooding. Wet basements, flooded waterside properties, and encroaching shorelines seem to be more and more common. With climate change, flooding events are predicted to worsen, in both severity and frequency.

So what is the solution to all this water? Well one way to help control flooding is the use of natural landscapes or ecosystems. Forests, wetlands and even grasslands help slow erosion, absorb water and provide a natural buffer to lakes and rivers.

Unfortunately, many of Ontario’s natural ecosystems are badly fragmented and degraded, especially in cities and suburban areas.

That’s where the Nature Conservancy of Canada (NCC) comes in. NCC protects and restores forests, wetlands and grasslands so that they can do their job: act as giant sponges against rising water levels throughout the province.

These restored or protected ecosystems offer effective flood control services thanks to their complex structure, something that human-made flood control measures have a hard time replicating.

Complex root systems

Roots of an old American beech tree at Clear Creek Forest (Photo by NCC)

The root systems of trees and other plants in forests, wetlands and grasslands absorb water and help hold soil in place. These natural spaces act like sponges, absorbing water and releasing it gradually. This reduces the violence of storms and snowmelt events, as the slowly released water is less likely to overwhelm rivers and streams, and the water is distributed evenly over the landscape.

Without this gradual release, rivers and streams would flood, causing damage to neighbouring communities. The complex root systems also prevent river and stream bank erosion by holding the soils in place.

Effects of urban development

Toronto Islands (Photo by Céline Chamiot-Poncet)

Unlike forests, wetlands and grasslands, the concrete jungles of urbanized areas are mostly impermeable to water. Without the help of natural ecosystems, storm water has no place to go but our public drainage systems, which can become overloaded so that untreated water rushes back into nearby creeks and streams.

Today, urban planners are seeing the benefits of incorporating natural spaces into residential areas by creating naturalized parks, native wildflower gardens and green roofs. The more plants and trees we have around us, the more water can be slowed down and absorbed. These natural spaces have the added bonus of storing carbon and providing us with places to enjoy the outdoors.

Harnessing the power of nature in our own backyards

Residential gardens can help provide some of the same flood control services that forests, wetlands and grasslands do. Think about doing away with a traditional lawn and replacing it with a native garden. Planting native trees, shrubs and grasses in gardens, as well as allowing for mulch and leaf litter to accumulate, “intercepts” rainfall, which means water evaporates faster and percolates more slowly through the soil, reducing runoff. The runoff that does make it to the public drainage systems is filtered by the plants in your garden, which helps reduce stormwater pollution. The benefits to creating a native garden include:

• limiting the amount of water that enters the local storm drain system;
• reducing the potential for flooding, drainage problems and stream bank erosion;
• reducing pollutants that run from your yard and road straight into waterways; 
• restoring and recharging our groundwater system; and 
• encouraging native species, such as pollinators, to thrive!

Since 2018, Intact Financial Corporation has been supporting NCC’s work to create and restore natural ecosystems in order to mitigate the effects of climate change.