When it rains, water collects from the roof, parking lots, driveways, and other impervious surfaces. Instead of soaking back into the ground, this rainwater, called stormwater, gets funneled to a storm sewer drain. The sudden flash flood from the rain creates an incredible strain on the local water system.
Stormwater runoff is a large source of pollution. Rain falling on an acre of parking lot collects up to 4 gallons of oil and gas each year. Other pollutants include pesticides, fertilizers, and trash. When the rainwater runs off the parking lot, these toxic compounds end up in your groundwater (and the lakes, rivers, and oceans). Many cities and towns now require some form of stormwater management to treat and slow the rainwater before it floods into the storm sewer.
Plus, every time it rains, the water runs downhill and slowly erodes your landscape. To keep the water from leaking into your home, it must be directed around and away from your house. Although this is typically done with concrete or asphalt paving, in this section I fill you in on some natural options.
Gabions: Natural Erosion Control
A gabion is a large wire basket filled with stones. You place them along the edges of areas where water will flow, to prevent erosion. The wire baskets hold the stones in place. Instead of building concrete walls to control erosion, a gabion serves as a more natural and inexpensive method. Over time, sediments will get trapped between the stones, and plants will grow over the basket.
Carving the Land to Move Water
A swale is a ledge or depression in the landscape terrain to encourage water to flow in a specific direction. Using swales, you can manage the flow and direction of the stormwater around your site.
If too much water is sent in a specific direction, the water may cause erosion along the landscape.
Retention Ponds
A method to slow stormwater is to use retention ponds. Simply direct the rainwater to a depression in the ground. The plants and soils filter the water, slowing the rate the water soaks into the ground. For a house, a small retention pond can work well.
Be sure to keep children away from retention ponds, not only because they collect trash but because they can be drowning hazards after a rain.
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