Rain Gardens

What is a Rain Garden?

A rain garden is a type of green infrastructure landscape feature that collects rain and melted snow. The rain garden absorbs stormwater (rain and melted snow) that runs off your grass and impervious surfaces such as rooftops and driveways. The garden is designed to have a shallow depression that has deep, loose soil so that it absorbs and naturally filters stormwater, instead of water entering the storm sewer network. Although water is collected in rain gardens, they are not a breeding habitat for mosquitoes.

What are the benefits of a rain garden?

When it rains, urban runoff (stormwater) carries sediment and pollutants from vehicles, fertilizers, road salt, animal waste, litter, grass clippings, etc. into the Assiniboine River, polluting the natural habitat and our source of clean drinking water.

A rain garden is a simple and effective way of reducing the amount of urban runoff from your property while providing other benefits. They are aesthetically pleasing with low maintenance requirements.

A rain garden can also:

• Reduce the amount of water that enters the local storm sewer network
• Reduce flooding, mitigate drainage issues and prevent stream banks from eroding
• Restore and recharge our groundwater system replicating the natural hydrological cycle
• Attract birds, butterflies, pollinators and other beneficial insects, such as mosquito-consuming dragonflies
• Reduce the amount of pollutants that run from urban areas straight into our waterways

How Much Water Can My Rain Garden Collect?

1 inch of rain on a 1000 square foot roof yield 623 gallons of water.

To calculate the amount of stormwater your roof yields, take the square footage of your house and multiply by 623. Then divide that number by 1,000.

To calculate the average yearly amount of stormwater generated by your roof multiply the number above by the average amount of annual rainfall in our area. (Audubon, Sept. 2003 and Cumberland Conservation District 2006)

The average rainfall amount in our area is about 610mm (24 inches). That's a lot of stormwater, isn't it? Think about how much water can go back into our groundwater table by using raingardens!

What type of plants are best suited for a rain garden?

Rain gardens experience alternate flooding (during a large rainstorm) and drought (during low periods of rainfall) this means that what you plant in your rain garden needs to be tolerant of both wet and dry conditions. Planting native species is recommended as they are well suited to local growing conditions and support native pollinators and wildlife. It will take a few growing seasons before the benefit of your rain garden is achieved.

Students enrolled in the Land and Water Management Diploma Course at Assiniboine Community College created a suggested plant list for rain gardens.

View Plant List