Building a water drainage system for your yard is not optional. When you start to plan your landscaping, most plants, be they ornamentals, vegetables or shrubs and trees, demand "well-drained" soil. Drainage affects buildings on the property, too; a sound drainage design carries water away from foundations and basements, not into them. Professional landscapers follow a few positive steps and call upon a number of strategies to address problems when developing drainage systems. Recognizing these basics can make the difference between a thriving landscape and a bog garden.
Consult your local building inspector to get advice on what type of grading exists in your neighborhood. She may also have advice on how to direct the flow of water in your yard and know the location of natural springs or wetlands that may impact your plans.
Contour soil to drain with your neighborhood's storm runoff system. Add soil near buildings; the surface of your yard's soil should fall away from buildings at a rate of 6 inches every 10 feet. Check to make sure downspouts drain away from buildings, not back toward them.
Locate any specific problems, such as low spots, areas that drain slowly or heavy soil. Correct heavy soil first---you'll never grow great grass, gardens or trees on clay soil. Build in compost and organic matter until you have 8 or more inches of fertile top soil that can drain an inch of water an hour.
Dig dry wells in slow-draining spots. Use an auger or post hole digger to dig straight down until you hit the gravelly subsoil, then back fill with coarse gravel a few inches. Test for drainage; dig deeper if necessary to get to a point where your well drains at the rate of an inch an hour. Fill the well with gravel and replace topsoil.
Install French drains to draw water in specific directions. These drains may be as simple as a subsurface "stream" of gravel or may contain perforated PVC pipe. Since water follows the path of least resistance, it drains from the heavier soil into the gravel and follows it whichever way it tilts.
Raise garden beds in areas with soil that is too heavy. Building up areas and filling them with fertile, well-draining soil will lead to successful plants---which will absorb water that may otherwise end up as runoff.