Go Green! We hear that so often now, but while our intentions are good, beyond changing out our light bulbs and recycling, many of us are unsure what difference we can make as an individual. Find out about one easy and fun way you CAN make a difference by minimizing your contribution to water pollution in your own home landscaping as Blue Max Materials' Mike Bishop and WBTV Meteorologist Jim Lytle explore Rain Gardens.
Rain gardens are just what the name implies - first and foremost, they are beautiful gardens, but their design allows them to serve as miniature water treatment plants. They capture rain water that runs off of your roof, driveway or patio, filters it, and allows it to soak into the ground instead of running into storm drains or streambeds.
Why do we need rain gardens?
Nature's cycle has rain falling on pervious natural areas like woodlands or meadows where the soil and plants slow down the water, filtering it and allowing it to soak into the ground. However, in our urban areas, rain falls on all kinds of impervious surfaces like rooftops, roads and parking lots where it can't soak into the ground; instead it rushes along collecting pollutants like fertilizer, pesticides, sediment, motor oil, litter and pet and yard waste. An acre of impervious surface results in about 26,000 gallons of runoff from a 1" rain compared to little to no runoff resulting from the same amount of rain in a natural area.
Where does this stormwater go? Not to the water treatment plant as you might expect - instead, it heads directly for streams, rivers and lakes where it pollutes the water (water that is ultimately the source of drinking water for someone downstream) and can cause flooding during heavy rainfalls. To prevent some of this massive runoff in the greater Charlotte area, you'll be seeing more and more rain gardens (or bio retention gardens) designed to capture this water and minimize runoff being built in such places as parking lot islands and sub-divisions.
Rain garden located at The Sanctuary in Lake Wylie.
Bio retention rain garden located at Wilmore Walk (design by Estes Design).
What does this have to do with you as a homeowner? Think about your yard - you may have a concrete (or other impervious) driveway, you certainly have a roof and you may have an impervious patio. Water runs off of all of these surfaces, collecting the fertilizer you put on your grass, the pet waste you didn't get a chance to pick up, the motor oil dripping from the car in your driveway - you get the picture! Some of it soaks into your grassy area, but during heavier rains, your ground can't keep up, so the water rushes along and may enter a stream behind your house or run onto the street and into the stormwater drain where it eventually ends up in another creek or body of water. A rain garden can absorb 30% more water than the same area of lawn, so by building a rain garden in your yard, you can minimize the water runoff originating on your piece of the earth and do your part to cut down on water pollution.
What is a rain garden?
A rain garden is simply a shallow depression in the ground that captures your water runoff and allows it to soak into the ground. Plants and soil work together to filter pollutants through absorbtion or chemical breakdown, delivering cleaner water through the ground to nearby streams. A rain garden is not a pond or a wetland; it is dry most of the time and holds water after a rain. When properly located and designed, water filters into the ground in less than 48 hours. Because water doesn't sit for more than a couple of days, you don't have to worry about the rain garden becoming a breeding ground for mosquitoes!
Where do you put your rain garden?
First, you need to choose a site by observing the water flow in your yard during a rainfall, watching to see where the water is flowing from (e.g., roof, downspout, driveway)and flowing to (e.g., low spot, drain, street). You'd like to position the rain garden somewhere between these two places, for instance in an area where your downspouts will drain into it. Keep in mind these considerations:
What kind of plants should you use in a rain garden?
Plants that are native to the area are the first choice for use in rain gardens because of their disease resistance and tolerance in local conditions. There are plenty of native choices for the Charlotte area, so use your imagination! You may want to choose plants that attract hummingbirds or butterflies, or that flower most of the season. Some people are even trying edible rain gardens with plants that produce fruit and nuts!
Consider the different wetness zones in your rain garden; plants around the outside edges can handle more typical landscape plants, but those in the center, deeper area will need to be able to withstand a couple days of flooding at a time. Lists of suitable native plants can be found online at various sources, including the NC Cooperative Extension Service at http://www.bae.ncsu.edu/topic/raingarden/plants.htm and Natives, Inc. at http://www.plantnative.net/.
Use container-grown versions of the plants you choose; their well-established root systems work far better than trying to grow plants from seeds in a rain garden. You will need to water your plants about every other day for the first 2-3 weeks or until they show signs that they are growing and doing well. Once established, your native plants won't require additional watering!
Rain garden information included here was compiled from:
NC Cooperative Extension Service (http://www.bae.ncsu.edu/topic/raingarden/index.htm),
Catawba Riverkeeper Foundation (http://www.catawbariverkeeper.org/issues/stormwater/rain-gardens),
Alabama Cooperative Extension Service (http://www.aces.edu/waterquality/nemo/Fact%20Sheets/rain%20garden,%20mg,%20final.pdf),
West Michigan Environmental Action Council (http://www.raingardens.org/Index.php).