Landscape contractors often underestimate the critical importance of drainage when installing new features in landscapes. Nightmare scenarios can flood into any newly designed landscape when drainage factors are not assessed and there are no plans in place for proper drainage.Where land is flat, soils are dense with clay or water tables are high, a well-designed drainage system is priority.
Ryan Larsen (aka Dr. Drainage) is a civil engineer and drainage pro at NDS Inc., which manufactures products for stormwater management, residential drainage and landscape irrigation. He says, “In new landscapes, new water flow patterns are difficult to predict, and it’s even harder to predict how the new flow patterns will develop over long periods of time. This can lead to soil erosion and may create low spots or direct pathways to the home’s foundation, which could be as minor as a yellow lawn spot or as extensive as a crack in the building’s foundation.”
These photos showcase the effects of poor drainage. Photo: Tom Barrett, Green Water Infrastructure
Tom Barrett, principal of Indianapolis-based Green Water Infrastructure, agrees that drainage is an important element for any landscape design or renovation. “When you change the topography of the landscape, you’re bound to alter the course of rainwater runoff,” he says. “The volume of water from even a small rainfall event can be enormous.”
While proper grading is an effective technique to redirect water away from the property, without a drainage system, grading alone can lead to erosion of the landscape and deterioration of the plant life. “As the expert, the landscape contractor should be combining a drainage system with proper grading to achieve optimum drainage of excess water and to ensure the homeowner’s property is protected from water damage,” Larsen states.
Barrett says many problems can result from poor drainage. These include:
- Downspout runoff could potentially create basement flooding.
- Pool and patio runoff could create a slipping hazard.
- Driveway runoff could create erosion issues and a flooded garage.
- Improperly drained planter beds next to a home could create a wet basement.
- Standing water on walkways could create surface discoloration and a slipping hazard.
- Neighborhood runoff can contribute all of the problems associated with an improperly drained landscape.
When renovating or installing a new landscape, consider surface water drainage as well as subsurface water drainage, “shooting the grades” to establish the exact topography no matter how flat the site may seem.
“There are two critical drainage elements to assess when designing a landscape project,” Barrett explains. “The first element is the volume of rainfall generated from landscaped areas, roofs and paved areas. The second is to assess the slope. The steeper the slope, the faster the stormwater will be removed.”
He believes the most overlooked elements in assessing drainage are water runoff from adjacent properties and understanding the potential impact of water runoff onto adjacent properties.
Don Clark, principal project manager for Rain Bird, recommends landscapers use the Universal Formula, or “Rational Method,” equation to determine a property’s peak flow.
Low spots in the landscape benefit from the installation of a catch basin that has a sump area to prevent clogging of the drainage system by catching debris before it enters the drainage pipe, Clark points out. When creating drainage systems, he recommends creating at least two water collection points, so that if one has backflow problems for any reason, the other is there as a backup.
Every downspout should safely discharge the water into a catch basin and away from the building’s foundation. “Using a catch basin in downspouts, instead of connecting the downspout directly to the drainage pipe, prevents debris from the roof from entering and clogging the drainage system by catching it before it enters the drainage pipe,” Larsen explains.
PHOTOS: RAIN BIRD
When a landscape is mired with low-lying areas and a high water table, even the best laid plans for proper drainage may be stymied. That’s when plant selection is important. Certain plants that originate in river bottoms and wetlands do well in high-water landscapes. The best choices will be riparian species from local bogs, fens and swamps, which are naturally adapted to the climate and soils found there. Another solution is to raise the planting areas.
Proper drainage: a service solution
Clark sees drainage solutions as a key service for increased revenue potential for contractors. “You already have a crew in place to do landscaping work, so why not offer a value-added service at the same time,” he suggests.
Clark also stresses the importance of addressing drainage in all landscape contracts to help prevent liability issues. “Properties may be subject to excess water from heavy rainfall or drainage issues. If you address drainage in your overall contract (e.g., creation of a percolation basin, running special pipe into the sewer system), it should help absolve responsibility later if the result of your landscape work creates drainage problems that the client claims were not previously there,” he explains.
When drainage is recommended by the landscape contractor as a preventive measure, most homeowners accept this recommendation without hesitation, according to a press release from Ewing Irrigation. “Homeowners rely on the expertise of the landscape contractor to ensure their landscape and property will be well protected from water damage and less susceptible to water damage in the future,” says Sharon M. Vessels, director of marketing for NDS Inc.
In addition to providing customers with an effective drainage plan, landscape contractors can save on costs and increase profits by installing a drainage system in conjunction with other landscape projects. Larsen explains: “It’s much more cost-effective than installing a drainage system as a stand-alone project for a number of reasons. First, the contractor’s crew and equipment are already on the site. Second, the same trenches used for other aspects of the landscape project may sometimes be used for the drainage system. Finally, the drainage materials can be purchased in the same place as the other materials for the landscape project, which saves time and reduces transportation costs.”
Editor’s note: This article was originally published in August 2014 and has been updated.