Rain Gardens and Why They Are Important

 

 

The city I work for, and many other cities here in the Lower Mainland, are starting to develop roadways and other hardscapes with rain gardens. You may have noticed these in your travels or even in your community. They certainly add beauty to the area in which they are installed, but they also serve another very important function. These rain gardens are engineered in such a way to accept water flow off roadways, parking lots and sidewalks, while preventing the water from flowing into the storm drains. By diverting excess water from travelling down our storm system a great deal of wear and tear on the system is reduced. Less wear and tear on our infrastructure means less frequent repairs and ultimately a longer life span for the pipes. 

This rain garden is located off a large parking lot located at the back of one of the recreational facilities. This particular parking lot tends to flood a fair bit during rain storms, and is also the site where the fire department has practice sessions with fire hoses. That's a lot of water on the regular basis. As you can see, the garden is lower than street level and the concrete in front of intakes (cut into the curb) is graded so that the water will pour into the garden.

 

 

The garden has been planted with native plant material such as Deer Fern (Blechnum spicant), Sword Fern (Polystichum munitum), Spreading Wood Fern (Dryopteris expansa), Snowberry (Symphoricarpos albus), Vine Maple (Acer circinatum) and Low Oregon Grape (Mahonia nervosa). The plants are planted directly into the soil and the entire bed has
been mulched with arborist woodchips.

The drain that you see in the middle of the bed is actually raised quite high, thus giving the water time to be absorbed by the surrounding soil. It is only in the case of severe rain storms (such as a 1-in-10 or 1-in-20 year storm) that the water level would actually get high enough to start draining into the pipe and into the storm system.