It’s a rain garden, and it’s specifically designed to reduce the risk of flooding and stop runoff pollution.
But what is runoff, and why is it a problem? Runoff is excess water—usually rainfall or snowmelt—that runs over impermeable surfaces, collecting pollutants, dirt, and debris. It’s bad for rivers, streams, or really anywhere that it ends up.
Because of deforestation, development, and road construction, more and more areas are covered with paved surfaces – like rooftops and cement. So rain that would usually flow into the soil instead flows into storm drains or local waterways. This is a major problem, since runoff that comes from paved surfaces, like roads, can contain “dirt and dust, rubber and metal deposits from tire wear, antifreeze and engine oil that has dripped onto the pavement, pesticides and fertilizers, and discarded cups, plastic bags, cigarette butts, pet waste, and other litter,” according to the EPA. Not a nice cocktail.
Rain gardens can combat runoff pollution by filtering and slowing that flood of rainwater.
A rain garden is made up of two simple elements: a long shallow hole, and the right plants. The hole runs the length of the garden, and is deep enough to allow water-loving, deep-rooted plants to grow. Excess rainwater or snowmelt gets slowed down as it soaks into the ground surrounding the plants. And once there, the plants and microbes clean the water, dropping out debris and even capturing pollutants. The long roots of the rain garden plants provide space for a greater amount of water to be absorbed into the soil. And rain gardens also provide beautiful natural scenery and habitat, especially butterflies.
Check out this document (PDF) to learn to build your very own rain garden.
Photo credit: Wis. DNR, via flickr