Stormwater Management the Natural Way
April showers may bring May flowers, but they also bring a lot of water in the process. And, as ideal flat or gently sloping building lots become harder to find, homebuilders now must pay greater attention to how that water will move across a potential home site. Working with the lot's natural drainage patterns will help limit future problems for both the homeowner and the larger community.
Rain, Rain, Go Away
In the past, suburban developers typically developed site plans with the goal of making unwanted stormwater simply disappear. Underground drainage systems forced runoff into storm sewers that eventually made their way into municipal water treatment plants — or simply dumped the untreated runoff into area waterways. Growing environmental awareness, along with stronger local ordinances, is forcing a change in this see-no-evil approach.
"It's become much more popular to deal with stormwater in a way that's visible and reduces the impact on local hydrology" says Stan Jones, head of the Department of Landscape Architecture at the University of Oregon in Eugene, Ore. "If you move it from your backyard to a city system, you're asking that system to deal with your water and move it someplace else."
This doesn't mean homeowners have to resign themselves to backyard floods after every heavy rainstorm. But it does mean builders need to take another look at previous grading and landscaping strategies and consider new ways to handle onsite stormwater.
"We still create yards, but now, instead of looking at stormwater as something we get rid of, we think of ways that we can use it creatively," Stan says. "All the water coming off your downspout and yard ends up in a stream somewhere. The better we can mitigate that, the better off our water resources are going to be."
The most important goal of any landscape plan from a homeowner's viewpoint is to minimize water pressure against the foundation. Poor grading can direct water against basement walls, requiring expensive workarounds or future repairs. To minimize such troubles, Stan suggests grading so that water is pushed away from the foundation for at least five feet.
How well that water you push away from the house drains into surrounding soil is directly related to that soil's composition, whether it is primarily fast-draining sand or slow-draining clay. To determine how quickly water will infiltrate in a particular area Jay Blue, a landscape architect with Brodhead, Wis.-based Applied Ecological Services, Inc., suggests a simple test: Dig a one-cubic-foot hole, fill it with water and then watch the water level over time.
"If it doesn't change at all in an hour, you know you have very poorly draining soil," he says.
In such situations, low areas in a yard may develop small ponds during heavy rainstorms. In the past, builders may have sought to fill in such areas, or install drainage systems directing the runoff to the street. Today, though, municipal officials frown on such measures, which can stress water-treatment systems and add to pollution woes. Instead, Stan and Jay suggest more natural solutions, working with the site's natural drainage patterns and incorporating native species.
"Rain gardens" are one approach to stormwater management gaining favor among both homeowners and environmentalists. These beds group native perennials, which have adapted to thrive in a region's specific soil and water conditions, in the path water would naturally take traveling through a site.
Jay says native species, including various types of grasses and wildflowers, develop very deep root systems that improve water infiltration in two ways. The plants themselves absorb more water, and, as the roots grow and die back over time, they create channels in even clay-based soil, speeding water drainage and minimizing runoff.
Using new permeable asphalts for driveways and other surfaces is another strategy for limiting stormwater runoff. But Jay cautions that these materials are not appropriate in all settings. In the Midwest and Northeast, for example, winter snowplowing can fill the pavement's pores, limiting its water-absorption effectiveness. Instead, he recommends the two-track approach to driveway design common in older homes, in which two parallel concrete-paved tire tracks are poured, with the space in between planted in ground cover.
"Adding that vegetation helps capture any oil or sands that might be coming from the vehicle," Jay says.
Whether builders use one or some combination of these techniques, they're ensuring happier homeowners, dryer yards and healthier water systems. Not a bad return for a little bit of planning.
Chuck Ross is Cape Cod-based freelance writer who has first-hand experience with soggy backyards.