Consider the Source: Sustainable Means Keeping Water Close to Home
When it comes to considering a sustainable world, what we do with water has to be a central concern. Just one agency of the United States government spends hundreds of millions of dollars each year to predict when water will fall from the sky and how much will fall. We spend many more millions on flood insurance to deal with the consequences of that rain when it falls on human-built structures and infrastructure and suddenly becomes too much water in the wrong place. And none of those millions of dollars has any influence on when, where or how much rain falls.
To have sufficient water in the right places at the right times, we have to look at what we can influence. The rain water that runs off our roofs, that sweeps across parking lots and down storm drains, that overflows stream banks and washes out roads — all this rain water could nurture an apple tree or be a home for trout. To allow water to be a life-sustaining element rather than a rushing, roiling, destructive force, we have to look at what we do with the water we can control.
As landscape architect Mark Boyer says, “We haven’t been very successful in controlling when it rains, but we can be pretty successful in controlling what happens to the runoff when it does rain.”
Boyer is an associate professor of landscape architecture in the School of Architecture. He and his colleague, Carl Smith, a landscape architect from the United Kingdom who recently joined the faculty, are particularly interested in improving design and adoption of systems that are sustainable.
Some choices for handling rain water runoff don’t help and often have made the problem worse. When we shelter ourselves beneath a snug sloped roof, we stay dry while water funnels down a drainpipe to the street and eventually to a stream. When we pave our streets and parking lots with asphalt, we create a smooth, impervious surface that directs rain water into drains or ditches and eventually to a stream. These widely accepted ways of constructing our homes and infrastructure move water but also have some unintended consequences — polluting our streams, for one.
“The storm runoff in the first hour of rainfall has the same pollution index as raw sewage,” says Steve Luoni, director of the University of Arkansas Community Development Center.
Wasted water is another consequence. On days the water isn’t falling from the sky, we hook up a hose and water the grass and flowers.
“Less than one percent of the earth’s water is potable — it’s ridiculous that we spray potable water on our grass” says Boyer. “When we use a rain barrel, for example, we’re using the water that falls from the sky, and we’re putting it on our plants. It’s a much better system.”
On top of increased pollution and wasted water, the ways we build and grow have increased the likelihood of flooding by ignoring the natural dynamics of streams. Luoni explains that flood plains serve “the natural metabolism of that river by absorbing excess water during heavy storms.” And flood plains, he adds, are usually the first thing that gets sacrificed when urbanism encroaches on streams.
“Most streams want a flood plain that’s 10 to 30 times the width of the stream,” Luoni says. “If a stream is 30 feet wide, it’s going to want a 900-foot flood plain. Where the Mississippi River is a mile wide, it needs a 30-mile flood plain. When we sacrifice flood plains, we get into trouble.”
Designing to accommodate and manage water is nothing new. Fran Beatty points to the work of Frederick Law Olmsted, who designed Boston’s Emerald Necklace parks in the late 1800s. A century later, Beatty directed the redevelopment and reconstruction of the Emerald Necklace for the city of Boston. The Emerald Necklace, she says, is emblematic of the way that Olmsted worked.
“He looked at it in a holistic manner,” Beatty says, “and that is part of his genius.”
Much of Boston sits on marshland, and designing the linked parks of the Emerald Necklace involved redirecting rivers and restoring marshlands that had been used as dumping grounds. Olmsted considered entire watersheds in his planning and worked closely with the city’s engineer, a partnership that was not typical of such projects. During the 20th century restoration project, the engineers were impressed by what Olmsted had been able to accomplish in terms of effective storm water management and enhanced ecology.
Olmsted designed pragmatic solutions to problems of flooding and sanitation that enriched the lives of Bostonians with restful landscapes and opportunities for recreation. That is, his design contributed to the sustainable handling of water as well as to what Beatty calls “sustainability as cultural relevancy.”
While Olmsted tackled problems in a way that contributed to both a healthy environment and a healthy civic life, the lessons of his work seemed to have been forgotten in the building booms of the second half of the 20th century. The renewed emphasis on sustainability suggests a kind of amnesia, Luoni observes, “our own cultural ignorance about what has gone on before us.”
Sustainability, Beatty points out, is not about pristine wildness. The very presence of people changes a natural area, and human settlement means that some degree of management is necessary to ensure we continue to have such vital resources as water.
“Sustainability requires personal responsibility and advocacy,” Beatty says. “It’s hard, because it means we will have to change how we think and we have to change some habits.”
For example, to design, build and live in a sustainable manner, Boyer says we have to completely rethink how we look at storm water, and we have to use low-impact techniques that reduce storm water runoff, such as green roofs, bioswales or rain gardens, and pervious pavement.
“Instead of storm water being a problem or a liability that we deal with at the end of the development project, we have to deal with it at the beginning as an inspiration for design,” Boyer says.
He believes that if storm management systems were incorporated into the design, people would become more aware of the implications of development. Furthermore, if utilities charged based on the amount of storm water runoff generated, there would be more incentive to use sustainable methods to retain water at the source.
Storm water can be treated at the source — whether the source is a residential lot or parking lot. Low-impact technologies such as green roofs and rain gardens can retain water and slow its flow so that water has time to filter into the soil and recharge the aquifer. Or plants and trees can take up the water by their roots and release it slowly through their leaves.
“It’s really using the carrying capacity of the landscape to manage the water according to the landscape’s metabolism,” Luoni says, “which is what Olmsted did. He understood the metabolism and carrying capacity of the landscape and designed accordingly.”
In fact, Boyer says, “It’s a whole lot easier to deal with storm water at the source than dealing with it at the site or at the city scale.”
One example of a way to deal with water at the source is a constructed wetland — an artificial wetland created to deal with water runoff in a place that was never a wetland before. Constructed wetlands offer some important benefits on site by allowing some of the water to soak in, some of it to evaporate off and some of it to transpire through the plants. These natural actions improve water quality and reduce the volume of storm water runoff. At the same time, a constructed wetland creates a living natural habitat. The alternative is to drain water away with a pipe.
“What the pipe does is just send the problem someplace else,” Boyer says. “A pipe doesn’t do anything for the water quality or water volume — pretty dramatic difference between the two systems.”
To handle water at the source, Smith noted the importance of “maintaining unsealed space at the source.” That is, rather than covering the earth with acres of asphalt, designers and builders can choose to use permeable paving that allows water to seep through to the land. Landscaping using bioswales, also known as rain gardens, and systems like green roofs all contribute to keeping water from tearing across the land as a destructive force.
Keeping it Open
Here’s how a bioswale or rain garden works. Vegetation is planted in what would be commonly called a ditch. When rain falls and water runs off buildings, streets or parking lots, the vegetation in the ditch does some of the same things that wetlands do. It improves water quality, slows the flow and reduces the volume, the key elements in handling water in a sustainable manner.
“The great thing about bioswales is that they’re often associated with impervious surfaces — parking lots and buildings — where we’re going to plant things anyhow,” Boyer explains. “We just have to reverse — instead of building up for the planting area, we actually go down so that the water has someplace to go.”
Once the water runs off the parking lot into the bioswale, the pollutants that are picked up from the parking lot are trapped, taken up by the plants or allowed to volatize off. The water soaks into the ground to recharge aquifers. In a natural system it can take days or weeks for rainfall that hits the earth to make it into a stream.
“We’re killing our ecological systems with our development,” Boyer says.
With development that uses impervious surfaces, the water can get to the stream ten times faster. The rushing water carries all the pollutants and floods and erodes stream banks.
This is the problem the University of Arkansas Community Design Center faced with planning for campus improvements related to Mullins Branch, a stream running through the west side of campus and eventually draining into the White River. Much of the 40-acre site is covered by a parking lot. During storms, water runoff far exceeded the carrying capacity of the stream and produced major flooding that engulfed a campus foot bridge and threatened a highway overpass. The stream carried the highest sediment load in its entire watershed.
The Community Design Center, in collaboration with Audubon Arkansas, came up with three strategies to handle Mullins Branch. The design package for Mullins Branch received the 2008 Institute Honor Awards for Regional and Urban Design from the American Institute of Architects. The design was guided by an approach that Olmsted would have understood.
“Olmsted did something that is very difficult, that is to design what I call recombinant infrastructure,” Luoni says. “Recombinant design addresses social, economic, aesthetic, as well as ecological criteria all at once. So the infrastructure is not just fulfilling one function. It’s a multi-tasked infrastructure.”
In the case of Mullins Branch, recombinant design meant returning the stream to a healthy condition, returning sinuosity and a healthy bank to facilitate the return of a diverse aquatic wildlife natural to a stream of its size. At the same time, to
accommodate the parking lot, they had to devise ways to retain storm water. The designers suggested three strategies that are, Luoni says, “progressively aggressive.”
The designers called the most modest approach “hydrology pixilation.” It involves small bioswales and other water treatment facilities distributed equally across the site in much the way islands typically dot parking lots. In this case, the pixilated bioswales are vegetated dips, rather than mounds, that collect runoff. The entire site acts as a large sieve for groundwater recharge, diverting parking lot runoff away from the stream and holding floodwaters.
The second design, called “riparian bands,” alternates strips of bioswale with strips of parking, creating a green parking lot that handles storm water even more efficiently than the pixilated version.
The “total marsh” plan comes closest to what engineers originally advocated — that the entire site becomes a retention basin. With this plan, much of the site becomes a constructed wetland for a flood plain and storm water retention. Other uses — parking and visitors center — are moved to one edge of the wetlands in a parking garage that floats above the wetlands.
Another way to deal with water at the source is to use green roofs. While roof gardens are considered a form of green roof, an extensive green roof puts less load on the building, requires less maintenance and is commonly referred to simply as a green roof. Green roofs have been used in Germany and Scandinavian countries for generations.
A green roof replaces tiles or shingles with a minimal depth of growing medium and a hardy planting, often sedum. Green roofs reduce the amount of storm water that washes off the roof. In fact, Boyer says, with a green roof “it’s not uncommon for them not to have any water come off them in storms of one half-inch rain or less.”
Green roofs also insulate buildings, demanding less heating and air-conditioning and releasing less carbon dioxide into the atmosphere, thus reducing the urban heat island effect and cooling cities. Green roofs mitigate acid rain and other pollutants.
Boyer installed a green roof as a demonstration project on three storage buildings on the south side of campus. One purpose of the project was to test whether a green roof would survive. While the roofs have done well in the maritime climate of Europe, no one had looked at their viability in the continental climate of Arkansas, which can be hotter, colder and drier.
With the help of student volunteers, Boyer planted 32 species of plants. After installation, Boyer did nothing — no water, no cultivation, no weeding. Subtracting those that didn’t survive the first year, at least 20 species have thrived on neglect.
Landscape architecture professor Mark Boyer has been studying the effects of green roofs, such as the one shown here in various stages of growth.
The cumulative effect of green roofs in a city can be dramatic, which is why Mayor Richard Daley of Chicago is promoting green roofs in his city. Daley visited Germany, saw green roofs, and, Boyer says, “got the bug.” Daley’s goal is to reduce the urban temperature in Chicago by one degree to save $150 billion a year in utilities. The city is offering small grants as incentives to offset the cost of installation.
Boyer notes that nationally most green roofs are installed on industrial or institutional buildings. The most dramatic growth in impervious surfaces is in residential construction, where the use of green roofs has lagged.
In his work in the United Kingdom, Smith followed an inner-city rehabilitation project in Liverpool, England, in which green roofs were among the sustainable practices proposed by landscape architects. While public housing officials have “embraced environmentalism,” Smith observed that residents sometimes have other ideas. The Liverpool residents, who accepted solar panels, vetoed green roofs. In part, they didn’t want to live in a building “that was so radically different visually that they felt they were in some strange experiment.”
Smith also found that developers of higher-end homes objected that green roofs were “out of place” in their developments. At the same time, he points out, there are aspects of green housing that are appealing to developers. The green development accreditations — known as LEED in the United States and BREEAM in the United Kingdom — convey marketing benefits. In the abstract, people like the idea of green housing and are willing to pay more for some green elements, such as the use of less-polluting paints or sustainably sourced wood. Yet, Smith said, there’s still a question of how much this openness to green “will be mitigated by an unusual aesthetic.”
Although there are major problems with flooding in the United Kingdom due to intensive urbanization, Smith said that local building regulations in the United Kingdom, as in the United States, often don’t allow for unsealed green space. “Low-rise” development of conventionally designed, one-to-two-story buildings contributes to the problem.
“Oddly enough,” he said, “high-density development that demands that we build upwards can potentially leave more room on the ground for permeable surfaces.”
Talking 21st Century
In his new book, Residential Landscape Sustainability: A Checklist Tool, Smith offers designers and developers a resource “to develop design solutions sympathetic to the environment and improve the sustainability of residential landscapes.” Smith shows landscape architects and urban designers how to conserve resources, minimize pollution and enhance ecological diversity, “without significant capital outlay.”
In recent articles in the magazines Green Places and Sustain, Smith and Boyer discuss examples of reluctance to use one element of sustainable design, green roofs and the need to better understand public perceptions of a system that has proved effective in Europe.
They ask a question that applies to all the changes necessary for sustainable landscapes: “Should respecting local identity and vernacular be about preservation alone? What is a vernacular if not a physical manifestation of the technical, political and artistic climate of the day, and what better or more appropriate vernacular for the 21st century than one that is environmentally responsible and socially ethical?”