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by Lynn Richards
Imagine a vibrant neighborhood, with apartments and condos above offices and stores, sidewalks filled with people walking and sitting at cafés, shaded by street trees. At first glance, this scene could be played out in almost any neighborhood that has incorporated smart growth principles. Looking closer, however, you see that this neighborhood has additional features that aren't as common. For example, the street trees are surrounded by native grasses. At one café, the tables are arranged around a waterfall that is fed by rain water from the roof and empties into a small pond filled with water-loving plants. The roofs of the higher buildings are partially or entirely covered with grasses and flowers. Buildings are set back three feet from the sidewalk and, every 15 feet, there is a small patch of native grasses fed by downspouts from the roof. The main retail street enters a roundabout, the center of which is a large grassy area filled with wildflowers. While calming traffic and adding to the overall attractiveness of this neighborhood, the roundabout retains and filters stormwater from the surrounding streets. Curb cutouts filled with grasses also serve to calm traffic and absorb and filter stormwater.
This vision—the transformation of stormwater runoff into a community amenity—is the next step for smart growth neighborhoods and can make them even greater places to live. A stormwater community amenity meets multiple objectives. It is a site-level stormwater management technique that also can calm traffic, enhance the pedestrian environment, increase fiscal performance for local retail outlets, help create a more distinctive community, and, in some cases, help save taxpayers money.
There is considerable urban planning precedent for considering runoff as a community amenity. For example, some older buildings are now preserved as historic because they serve to enhance community character. Cars parallel-parked along streets are now considered vital for protecting pedestrians. Street lamps are no longer viewed as a utilitarian feature to provide light—there are numerous specifications for how high and how big street lamps should be to create various street atmospheres. The next change for creating great places is adding function to stormwater runoff management. Architects, town planners, and developers need to start imagining how a community's runoff can be harnessed to create a more inviting, dynamic, and vibrant neighborhood.
Runoff as a Community Amenity?
Addressing the increased impervious cover associated with growth and development has been problematic for some communities. To help clarify this issue, EPA recently released "Protecting Water Resources with Higher-Density Development," which discusses new research that can help communities better understand the impacts of high- and low-density development on water resources.
The report concludes that, while increasing densities regionally can better protect water resources at a regional level, higher-density development can create more site-level impervious cover, which can increase water-quality problems in nearby or adjacent bodies of water. Numerous site-level techniques are available to address this problem. When used in combination with regional techniques, these site-level techniques can prevent, treat, and store runoff and associated pollutants. Many of these practices incorporate low-impact development techniques, such as rain gardens, bio-retention areas, and grass swales. Others go further by changing site-design practices, for example, by reducing parking spaces, narrowing streets, and eliminating cul-de-sacs.
Some site-specific strategies can enhance a neighborhood's sense of place, increase community character, and save taxpayers money. The strategies that meet multiple community objectives are generally not the traditional engineered approaches, such as detention ponds, which are often difficult to install in urban areas or on sites where available land is limited, such as infill sites.
Nontraditional approaches work best in dense urban areas because they use the existing elements of a neighborhood, such as roads, roofs, abandoned shopping malls, or courtyards, and add some engineering and design to landscaping elements to help retain, detain, and treat stormwater on site. When done correctly, these approaches manage stormwater and add value to a community to help to make the neighborhood a more desirable place to live. In short, they become a community amenity.
Within the arena of site-specific strategies, architects, town planners, developers, and community designers can, and indeed, should get creative. Addressing stormwater runoff has traditionally been the responsibility of engineers. State or local requirements dictate that a certain percentage of runoff must be detained or retained on site, and engineers address that problem as efficiently as possible. Recently, that dynamic has broadened to include environmental scientists, who discuss the environmental benefits of using pervious pavement or installing a grass swale next to a sidewalk. However, a communication gap still exists between the experts who handle stormwater runoff and those responsible for creating great neighborhoods, which results in stormwater management practices that fill no other function than that of managing runoff.
What would happen if runoff was viewed as a community amenity? Architects and town planners could get creative, implementing a wide range of site-specific techniques to use stormwater in communities ranging from one or two blocks of a vibrant main street to several miles of dense, urban environment. Some communities have already begun or are planning developments that embrace this idea. For example:
- High Point Redevelopment, Seattle, Washington. A new 1,600-unit, mixed-income development will replace 716 subsidized housing units on 120 acres in the West Seattle neighborhood. The site's previous infrastructure directed polluted street, sidewalk, parking area, and building runoff through a series of underground pipes directly into the creek, damaging the ecosystem and reducing local salmon populations. Now, narrow streets, sidewalks, and a traditional grid system make it easier for people to get around the neighborhood while also reducing stormwater runoff through site design. Water-specific strategies are actively incorporated to further mitigate runoff. In place of curbs and gutters, swales and check dams are shaped into the land alongside the street. These wide, landscaped swales buffer pedestrians from traffic, as well as slow, filter, and direct street runoff into a detention pond that doubles as a park area. Parking areas are constructed with pervious gravel cover, and sidewalks with porous pavement. Together with the housing units, these features create a comprehensive system that will cover all 120 acres of the site.
- Stapleton Airport, Denver, Colorado. One of the largest redevelopment undertakings in the country, the Stapleton project will over 20 years convert a 7.5-square mile former airport site into a mixed-use community that includes 12,000 homes, 13 million square feet of office and retail space, six schools, and 1,100 acres of open space (increasing the total acreage of Denver's city parks by 25 percent). The site redevelopment uses natural corridors to improve water quality. Visitors and residents enjoy walking, biking, and relaxing in these natural areas. Constructed wetlands channel stormwater through the development to nearby creeks and create wildlife habitat. Natural landscaping and sculpted hills help create a natural transition and manage runoff from the 80-acre groomed central park area to area creeks. The surface stormwater system harvests runoff to irrigate landscaped areas and can retain flows associated with a 100-year storm. By using natural stormwater controls instead of building major subsurface infrastructure, the developer saved an estimated $20 million in storm sewer outfall costs.
As these two examples illustrate, using stormwater runoff to create community amenities can add attractive features to a vibrant, high-density, mixed-use neighborhood. And even more can be done. Architects and designers can think up new ways to incorporate runoff into the everyday life of a neighborhood, from creating a water feature for a group of restaurants to being creative with the small spaces between buildings and sidewalks. If an area can be landscaped, it can be landscaped in a way that treats and minimizes runoff. Can runoff be a community amenity? Absolutely. It's where smart growth planners, designers, implementers, and everyone else should be headed. It's the next big wave.
Lynn Richards is a Senior Policy Analyst in the U.S. Environmental Protection Agency's Office of Policy, Economics, and Innovation - Smart Growth Program. She may be reached at 202-566-2858 or richards.lynn@epa.gov.
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