Rain Gardens

Improving water quality with nature as a guide

GA JClifford 7384

When you think of things designed to help consumers and homeowners reduce their environmental footprint, chances are some of the first to come to mind are of the high-tech variety: solar PV systems, spray-foam insulation, electronic monitoring equipment, and other, costly investments. However, the last two decades have seen a considerable uptick in another eco-conscious application, the rain garden, which demands far less in the way of both maintenance and materials.

What exactly are rain gardens? In a nutshell, they are planted depressions, which help filter harmful elements and contaminants out of water runoff from pavement, roofs, and other man-made surfaces. In so doing, these natural fortifications can significantly curb the number of pollutants reaching aquifers, rivers, and other water sources. Since their first mass application in the early 1990s, rain gardens have been used primarily as a way for commercial and residential areas to replace the natural buffers eliminated during development. And with water-diverting infrastructure such as sidewalks and gutters costing much more than rain gardens, it is no surprise that the efficacy and cost effectiveness of these gardens continues to grow.

Since their modern reintroduction, rain gardens have become an increasingly common and sought-after avenue for property owners looking for ways to responsibly deal with excess rainwater. Not only are rain gardens cheaper than other, more complex storm-management systems; they are also much more low maintenance, requiring little more than an annual weeding and the occasional new planting. More importantly, they serve as a natural filter for the wholly unnatural chemicals and other man-made materials that might otherwise end up back in the water supply—things like pesticides, fertilizers, and volatile organic compounds (VOCs).

GA Penny 1853Photo Courtesy of the Indianapolis Museum of Art

Unlike with regular gardens, however, one’s choice in plants must be aimed more at effectiveness and durability than aesthetics. Because they are often employed to deal with both copious amounts of water as well as extended dry periods, it is suggested that rain gardens reflect as much in their botanical makeup. Luckily, New England is teeming with various species of hardy plants well suited for the task. Still, that does not mean visual appeal must be ignored completely. New England rain gardens could include popular shrubs such as winterberry and summersweet and herbaceous plants such as New England aster, lobelia species, and panic grass.

“The main purposes of the rain garden is to effectively treat and purify the water before it goes back into the aquifer, and to hold off surges of water from storms,” Shannon Alther of Portsmouth-based TMS Architects explains. “But the vegetation itself can also add a nice visual element to the site, and can help attract things like birds and butterflies that can add to its look and feel.”

You would not think a project seemingly suited for a seasoned landscaper would fall under the purview of an architectural firm like TMS. Lately, however, the company has found itself involved in a number of projects—residential as well as commercial—involving rain gardens. In early 2012, TMS partnered with fellow Portsmouth firm Altus Engineering in lending their design expertise in the construction of a massive rain garden adjacent to Regeneration Park, a newly renovated business campus located in the old Toyota dealership on Route 1 near the Portsmouth-Rye border. In the process, the park was able to reduce the amount of pavement by an astounding 16,000 square feet. What is more, the new rain garden was positioned to allow filtered water to be let back into the sprawling wetlands adjacent to the complex.


In 2009, TMS and Altus Engineering teamed up to craft a common rain garden for three, LEED Gold certified faculty houses at the Phillips Exeter Academy. The resulting banana-shaped depressions, which employ layers of sand and mulch to help filter runoff, are designed to collect water from both the nearby driveways as well as the roofs. Eager as they were to foster projects reflecting their long-held commitment to environmental stewardship, the renowned preparatory school leaders—eager to minimize water discharge to the surrounding town—found in both companies an enthusiasm for green that resembled their own. The results have vindicated that mutual green-leaning perspective. “So far, the rain garden is working as intended, and has been 100 percent effective,” notes Mark Leighton, Associate Director of Facilities Management at Phillips Exeter. “We’ve worked with both TMS and Altus on a number of projects, and once again they were both great to work with and did an outstanding job.”

How outstanding? The project, which includes both faculty housing as well as the adjacent rain garden, was honored by the U.S. Green Building Council’s New Hampshire Chapter with LEED Gold certification, the program’s second highest honor.

Yet despite their many noted successes, rain gardens are not without the occasional detractor. One common criticism is that the space required for proper implementation precludes their use in tighter, more congested urban areas. Not so, says Altus Engineering’s Jeff Clifford. “From my perspective I’d rather see some treatment in the form of rain gardens than no treatment at all,” says Clifford, whose civil engineering-focused firm has been installing rain gardens for over a decade. “Regardless of the application, I think they’re a great best management practice, and it’s been shown that they’re one of our better tools to use for regulatory compliance.”

According to Clifford, as regulations relating to managing storm water have become more strict, the popularity of rain gardens—be it in commercial, residential, or municipal applications—has only grown. “For a long time all people were looking at was the peak rate of runoff, and not necessarily the water pollutants themselves,” Clifford explains. “But eventually regulations were developed that kind of forced everyone to focus more on the contaminants and how to mitigate them.”

Here on the Seacoast, several organizations, including the New Hampshire Coastal Protection Partnership (NH Coast), have spearheaded tutorial workshops for homeowners interested in going the rain garden route. One such installment, located at Newcastle’s Great Island Commons, includes engaging educational signage for curious passersby. “People are definitely starting to look at how to harness runoff water responsibly, be it with rain gardens or with simpler things like rain barrels” says Dave Anderson, Project Coordinator for NH Coast. “There’s definitely a growing interest from homeowners in building rain gardens, but they’re looking for people capable of designing and installing one the right way.”

As Shannon Alther explains, just because the materials used to create rain gardens are simple and accessible to most homeowners does not necessarily mean the task itself should be undertaken with anything less than responsible planning. “For homeowners, it’s about finding the right balance between roof or pavement surface area and the size of the garden,” Alther explains. “If your garden is a lot smaller than your surface area, the water will end up overwhelming the garden; and if you’re garden is too big, it can become cost prohibitive.”

Still, Alther and Clifford agree that, with the right planning and materials, these multi-faceted, multi-purpose, green constructs can do wonders for a home or business’s yard, to say nothing of the surrounding environment. “The beauty of having a rain garden is that you can conceivably do it yourself,” says Alther. “It might involve retrofitting gutters or doing some research, but as long as you maintain certain principles, there’s no reason why a home or business can’t take that step.”

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