Most landscape features have a border that defines their shape and fulfills a practical purpose. For example, lawn edging keeps the edges of grass looking crisp and clean while preventing the turf from invading adjoining flowerbeds. Edging along a driveway sets off the driveway from the surrounding landscape, framing the surface with an attractive border, and the edging slows the surge of storm-water runoff if it is designed and installed with that function in mind.
Driveway in Rain
As an impermeable surface, a paved driveway collects a tremendous amount of water whenever rain occurs. In a heavy rainfall event of 1 inch of rain per hour, a 10-by-20-foot parking surface sheds 125 gallons of water. The water runoff needs to go somewhere, and often driveway edging is used to direct it. If no edging is present, the water simply drains to the driveway's lowest point, where the concentrated runoff probably will cause erosion.
A driveway benefits from a curb similar to the kind found on city streets. The curb directs the water to a drainage system that carries it to where it can safely percolate into the ground or enter a natural waterway. Curbs made of poured concrete, brick, landscape timbers, cobblestone edging or concrete blocks are all possible. Choose a material that fits with the appearance of your home, the driveway and the surrounding landscape. Building a curb in the form of a low stone wall makes an especially dramatic addition to an entryway.
River Rock Edging
River rock is a less formal approach to driveway edging and is a suitable material for a do-it-yourself project. It works well with relatively flat driveways, where the runoff spills into the landscape across a wide area. River rock comes in many sizes, but a minimum of 2 inches per rock is necessary to ensure the rocks won't be dislodged by a torrent of storm water. Install river rocks in a strip adjacent to your driveway to diffuse the runoff's impact, causing the water to spread and filter into the ground. Remove a 3- to 4-inch depth of soil along the driveway's edge, creating a trench, and lay a sheet of weed fabric in the trench before installing the river rocks. The ultimate height of the river rock edging should be just below the driveway's surface so water drains freely into the edging.
On sloped a driveway, "weep holes" should be built into the curb every 10 to 15 feet to serve as mini-drains. Otherwise, substantial drainage structures are needed to deal with a large volume of runoff in one place. Trenches filled with river rocks should flow to larger basins, where the runoff can collect and percolate slowly into the soil. Alternatively, install a network of box drains at the low points in the river rock edging to collect the water runoff in underground piping.
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