Stormwater management as civic art
How to handle rainwater in ways that accentuate placemaking
In times past, engineers often integrated elements of civic art, architecture, and history into a city’s parkways, bridges, and other public necessities. In doing so, they enhanced the character of the urban environment. Today, when engineering often deals with the environment, there is an opportunity once again to serve civic purposes — by handling rainwater well.
Water is fundamental to human existence. Rain, however, can be both a blessing and a curse — either too much or not enough of it can cause big problems. Consequently, management of rain and water has become an integral part of caring for the built environment. We could be handling rainwater much better — using it to enhance our towns and cities.
In antiquity, water management contributed to the making of civic space. The fountains of Rome, the step wells of India, the lavoirs (public wash houses) of France all had elements that established places in the urban landscape. Many examples of ancient water-engineering skill, such as the Romans’ aqueducts, still exist and are widely admired.
Communities today can benefit from reestablishing the connection between civic space and water management. Besides improving the relationship of people to the natural environment, we can gain urbanistically by taking the typically mundane elements of stormwater infrastructure and using them to generate modern civic art.
The Water Budget
Every region — and each location within it — has a “water budget,” the result of processes that include rainfall, evaporation, absorption, overland flow, and transpiration. As a landscape becomes more developed, the components in the hydrological cycle change, often affecting the water’s volume, character, and disposition. As the amount of hardscape increases, the ability to absorb rainwater into the soil decreases. Groundwater recharge diminishes, which is important because recharge helps maintain aquifer and stream water levels. As recharge diminishes, ecosystems may suffer.
Rainwater, though it generally starts out clean, tends to gather pollutants as it comes into contact with a developed environment. Depending on the condition of ground cover, the water may become laden with sediment and excessively enriched with nutrients. It can transport pollutants and it can raise the temperature of streams, ponds, and lakes, harming the aquatic habitat. Combine those changes with an increase in the water’s velocity and volume, and you quickly have a big problem. These are the principal reasons for institutionalized stormwater management and for many state and federal water management laws.
In the face of those trends, Paul Hawken, author of Natural Capitalism and The Ecology of Commerce, says a nationwide hydrological reform is taking place. As Hawken sees it, modern culture has wasted, misused, and otherwise disrespected rainwater resources. Negative conventional practices are now being challenged — and in some instances replaced — by measures that are part of a broader design movement. For example, porous surfaces are being used — in everything from “green” roofs to tree-lined filter strips — to reduce both the immediate environmental impact and the long-term economic costs of development. The reforms are moving forward at multiple scales — those of the watershed, neighborhood, site, project, and rooftop.
One result of hydrological reform is the development of a broad palette of good management measures — specific interventions that, when used collectively, can improve environmental conditions across a watershed or drainage basin. A comprehensive management approach known as a stormwater master plan can not only serve the natural environment but can also integrate rainwater-oriented civic art into the urban landscape.
The stormwater master plan
A stormwater master plan must first concentrate on controlling the negative effects that ensue when a sizable volume of rainwater concentrates on impervious surfaces. The primary goal of the design team is reduction of the rate of runoff so that downstream impacts are mitigated. This can be done in a way that fits the neighborhood and contributes to placemaking.
Elements of modern stormwater engineering are not all that dissimilar from the ones our ancestors used. They include ponds, storage tanks, dry detention depressions, conveyance swales, and flow dissipaters, among others. They should be designed so that they do not confuse or detract from their surroundings.
The following principles make sure that all the design decisions support placemaking:
• Rainwater is a valuable resource.
• Stormwater design is integral element of neighborhood design.
• Engineering elements must not detract from character- or location-defining elements of the neighborhood.
• The foundation of a stormwater master plan is created at the lot scale.
• Streets play integral role in generating runoff and can be used to capture it and help it filter into the ground.
• End-of-pipe elements will be designed with as much care as the architecture or urban design components of the neighborhood.
• Vegetation and managed terrain must be supported by permanent management measures that provide long-term support for the ecosystems.
When the project team takes context into account, the resulting stormwater design solutions will likely be more creative — enhancing the architecture and strengthening the public spaces. Let’s consider a hypothetical stormwater management plan. True to the seven principles listed previously, the master plan calls for measures that begin at the source, the rooftops. The plan uses features at the lot level, such as cisterns and infiltration gardens, to reduce the site’s total runoff. Conveyance networks disperse stormwater into a shallow recessed green serving part of the neighborhood.
A minor network of channels, ridges, and runnels within the green slows the runoff and dissipates energy, preventing any avoidable erosion. The collected rainwater is spread over a planted area designed to control the rate at which it seeps into the ground. Plantings on the perimeter provide visual interest in addition to improving the water quality.
In the event that a storm is so large that the rainwater cannot be controlled by the recessed green, the plantings at the edge will help to reduce the velocity and provide another opportunity for filtration or separation. During dry weather the recessed green functions as a recreational space. To keep it in good condition, undesirable residue from the stormwater will have to be removed periodically, as is true of any stormwater device.
Conventional engineering wisdom often dictates using whatever solution is simplest to design, most efficient to build, and cheapest to maintain. Often the most efficient way of dealing with stormwater runoff is to pipe it to a large permanent pond or a detention element at some remote corner of the property. Conventional methods of that sort are satisfactory in some circumstances, but generally they don’t make the most of the context. Frequently, it would be better to employ a different method — using techniques that can be integrated into urban environments. Those techniques have the additional advantage of helping to create better addresses and greater real estate value.
One example of how to do this can be seen at the I’On development in Mt. Pleasant, South Carolina. I’On’s developers dug two small canals to help cleanse and control the flow of water in two man-made lakes. The canals improve circulation, helping to balance the water’s quality. The canals also offer an excellent vantage point for viewing I’On’s buildings (see photo on page 1). The view of the water itself is pleasurable as well. Though the canals offer little direct stormwater benefit, they improve overall conditions in I’On.
A second example is the “rose garden” at WaterColor, on the Florida Panhandle. There a small, semicircular grouping of cottages looks onto a recessed, landscaped green. In heavy rains, the rose garden collects water, which is then released gradually through infiltration into the ground. The combination of a grassy surface area and shallow slopes helps to clean the water, while the depression meets the need for stormwater detention.
At New Town at St. Charles in Missouri, stormwater is handled in a way that helps unify the urban landscape and create attractive scenery. Instead of relegating stormwater to ponds situated off-site or in a far corner of the 630-acre development, the water is carried through surface canals to lakes. The banks of the canals were designed to provide additional infiltration capacity throughout the site; they were also designed to handle “sheetflow” from water generated along streets and yards in the neighborhoods. The canals, capable of handling both small “rain events” and larger storms, have allowed the developers to avoid extensive installation of underground pipes or other costly infrastructure.
Comprehensive small-scale stormwater systems like these work in a variety of conditions. They can be customized and calibrated to suit the site, the neighborhood, the region. Amenities arise from otherwise mundane, overlooked, or wasted space.
Water can be more than just a decoration of the urban environment. Proper management of water serves multiple purposes, from public safety and environmental protection to aesthetic enjoyment. This is too important a task to be left solely to engineers or public works departments. Stormwater management, at its best, is part of the civic art that that makes a city great.
Milt Rhodes is an urban designer based in Raleigh, North Carolina. He is working on stormwater management plans throughout the Southeast that encompass the elements of placemaking and urban design.