If you're concerned about basement floods due to heavy rains, there's a relatively inexpensive and environmentally friendly way to prevent them, a volunteer with the David Suzuki Foundation says.

It's called a rain garden.

Marc Yamaguchi built one in his front yard last year to stop what he calls a slow leak. On Monday's edition of CBC Radio's Metro Morning, Yamaguchi said rain gardens are stormwater interventions by homeowners that not only can prevent pooling of water but also help to bring biodiversity back into a neighbourhood.

"By putting in that rain garden, you are basically putting in a living sponge around your home and building a little line of defence that again really helps to offset the stormwater that flows in the lake with a great force," Yamaguchi said.

Rain garden

Marc Yamaguchi's rain garden took about a weekend to build. One day to dig out, another day to fill in. It collects stormwater that flows out of a downspout. Plus, it's pretty. (Marc Yamaguchi)

According to Toronto and Region Conservation Authority (TRCA), a rain garden is a "landscaped feature" on a lawn that is designed to collect stormwater, which is rain and melted snow. It is carved out of the lawn. It usually contains loose, deep soil that soaks up runoff, helping to stop it from running into the storm drainage system and waterways.

"It puts in some biodiversity that didn't exist before. So we have a self-sustaining ecosystem, Yamaguchi said. 

"It doesn't require much watering because the downspout feeds it. Basically, we are collecting water to prevent the stormwater from entering our waterways that would otherwise go in with pollutants."

Rain gardens could be useful for some Toronto homeowners on Tuesday, when parts of the city are forecast to receive between 25 mm to 40 mm of rain. Some areas could receive up to 60 mm.

Environment Canada has issued a special weather statement for Toronto, saying the "significant widespread rainfall event" is expected to begin early Tuesday and end in the evening. A slow-moving low pressure system from Texas is being blamed for bringing the heavy rain.

Rain garden in a bowl

A cross section of a rain garden in a glass container while residents build one in the background. ( Kat - photographer with Evergreen Cityworks)

Yamaguchi's rain garden, which is about two metres by one and half metres, features an array of flowers, from purple coneflowers to butterfly weed and red cardinal flowers to Black-eyed Susan's. It is three metres from the foundation of his home. It cost him about $1,000 to build, an amount that includes his labour.

"It's very pretty. It's resilient," he said.

"A rain garden replaces a patch of lawn with a soil mix that is deep and loose and there's these beautiful hardy native plants that go in its place," Yamaguchi said. "Basically, it collects the storm water that flows out of your downspout."

Rain garden

A rain garden installed in Danforth East with the help of a city grant. (Kate Leuschen )

Yamaguchi attended a workshop at a Toronto public library run by the TRCA and learned how to build a rain garden. He then applied for a $10,000 grant from the Toronto Foundation for a pilot project, the Rain Gardens of Danforth East Village-East York, to install 10 rain gardens in the east end. Now, there are fourteen in all in the area. It began with a demonstration at his house.

"The concern is overland flooding," he said. 

He said his own rain garden took him a day to dig out and a day to fill it back in. He had a landscaper help with the excavation. Each one requires four elements: a source of stormwater runoff, such a downspout; an absorbent soil mix: full or partial sun: and native plants that are water tolerant and drought resistant.

Yamaguchi said the rain gardens are a great way to green the city.