The average residential property provides only limited opportunity for rainwater to soak in to, or "infiltrate" the soil. Your roof, driveway and patio are all waterproof surfaces. Even your lawn quickly becomes waterlogged at the surface, leaving rain to run downhill and find its way into storm drains as runoff. This wastewater carries many contaminants into waterways, from pet and bird droppings to silt and weed killer residues. You can limit runoff in several ways, even on a sloped lawn. Two of the least intrusive are planting trees or shrubs, or creating a rain garden.
Trees and Shrubs
Consult with local nurseries about native shrubs and small trees that grow well in your area with minimal maintenance. Consider their year-round appearance and choose varieties that offer colorful blossoms and attractive foliage, or that attract desirable wildlife (see References 1, 2).
Stand in front of your house or at the front window and select locations on the lower portions of your property where those varieties will enhance your view.
Mark out each planting area with stakes. Dig it up with shovels and a rototiller or a rented excavator. Ensure that the excavated area is deep enough for the roots of your selected trees and shrubs.
Improve your soil, if it is heavy or compacted, by adding sand and compost, peat or other organic materials.
Plant the trees and shrubs in an esthetically pleasing arrangement. Include some native grasses and wildflowers, if you wish, to crowd out weeds and make a more natural appearance. Mulch around the planted areas with wood chips or bark mulch to prevent erosion and further slow runoff.
Select one or more sites for rain gardens. Each should be at least 100 square feet to work properly; 300 square feet will drain an average lawn capably. Select a site at least 10 feet from the house to capture rain from a downspout or 30 feet away to drain a portion of the lawn as well (see References 3).
Mark out the bed or beds with stakes. An oblong boomerang shape with the curve facing downhill is effective at retaining and infiltrating rainwater.
Dig the bed with shovels and a rototiller or a rented excavator. If the soil is too heavy or compacted to absorb water well, incorporate sand and organic material such as compost or peat.
Level the bed, leaving a small raised berm on the downhill side. Plant the garden in an attractive variety of native plants and hardy perennial wildflowers that will crowd out any weeds and generate deep roots to slow runoff.
Run a length of PVC drainpipe from your drain spout to an area just above the water garden, when possible. This maximizes the rain garden's ability to capture runoff from that portion of your roof.
Items you will need
- Wooden stakes
- Excavator (optional)
- Compost or peat
- Native shrubs and small trees
- Native grasses and wildflowers
- Wood chips or bark mulch
- PVC drainpipe (optional)
- Many communities offer subsidized prices on rain barrels, which can also help limit runoff.
- "Swales" work much like a rain garden, but aren't as visible. Dig up a section of lawn as you would for a rain garden and level it or leave it slightly concave, with a small berm on the downhill side to trap water. Replace your sod or re-seed with grass. During rainfall, the swales will help slow runoff and increase infiltration (see References 1).
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