Coastal Services Center

---

Pollutant Runoff Indicator Information

---

In the Scenarios | What Effect Does Site Design Have on Pollutant Runoff? | What Can I Do?| References and Resources

Related Indicator Information Open Space Vegetated Buffers Clearing Costs Impervious Surface

In the Scenarios

This project used the SGWATER application, a component of the U.S. EPA's Smart Growth Index, to estimate the potential impacts of each design on local water quality. SGWATER estimates the amount of total suspended solids, phosphorus, and nitrogen leaving the site but does not model impacts on receiving waters. The application is intended for use in planning-level analyses and should not be substituted where more detailed and technically rigorous studies are appropriate.

All of the development alternatives increase runoff volume and pollutant loads in comparison to the undeveloped site. The indicator results for development-induced changes in runoff show the greatest impact from the conventional development, next greatest impact from the new urbanist design, and least impact from the conservation scenario. Note that the scenarios are not drawn in sufficient detail to include stormwater management components, so the SGWATER results are modeled based on no stormwater mitigation measures being in place. An engineering-level assessment would incorporate any required measures for each site design. Note too that any required structural measures would add to infrastructure costs for the design.

To access more information on the SGWATER software used to calculate the runoff estimates for each scenario, refer to the Indicator Methods section.

What Effect Does Site Design Have on Pollutant Runoff?

Populations in coastal areas continue to increase and fuel development. The challenge is to determine how to best accommodate the needs of growing communities without destroying the natural resources and quality of life that make coastal areas attractive places to live.

Runoff is stormwater that runs off the land and into streams, rivers, and other water bodies. Stormwater picks up many types of pollutants as it rushes along: lawn fertilizers, herbicides, pesticides, oil from paved surfaces, animal wastes, and even soil. In their proper places, none of these are considered harmful. But once these substances enter local water bodies, they can be deadly to aquatic life and affect human health.

When a site is developed, several factors make stormwater runoff leaving the site likely to increase. First, trees and other vegetation that once intercepted a portion of precipitation are removed to make room for homes, streets, and parks. The soil is compacted as a result of grading and its ability to absorb water is reduced. Grading also removes natural variation and depressions in the topography that allow water to collect in pools and return to the atmosphere through evaporation. An increase in impervious surfaces also typically accompanies development. The result of these changes to the local hydrology and impervious surface is that a greater portion of the total precipitation falling on the site leaves the site as runoff, carrying with it atmospheric and surface pollutants.

The issues surrounding stormwater runoff in urban areas stem from two sources: increased water quantity and decreased water quality. Reduced capacity for infiltration and storage leads to larger and more rapid discharges to receiving streams. Downstream flooding, changes in stream morphology (straightening, downcutting, etc.) and erosion are a few of the problems resulting from too much water leaving a site too quickly. Stormwater runoff from developed areas also tends to carry higher pollutant loads than runoff from undisturbed sites. Nutrients such as phosphorus and nitrogen, suspended solids or sediments, hydrocarbons like oil and grease, and metals (zinc, copper, lead) are all commonly found in stormwater runoff from developed sites (Schueler 2000). Storm sewers are not connected to wastewater treatment plants, but instead convey everything that flows or is poured into them to the nearest water body. Pollutants in runoff can cause fish kills, beach closures, and pollution of shellfish beds, which in turn affect fishermen, tourists, and the community as a whole.

What Can I Do?

Citizens are encouraged to learn more about local stormwater runoff and water quality. Some activities citizens could undertake to promote watershed health are

• Organizing a stream cleanup event
• Stenciling storm drains
• Participating in the political process
• Participating in public education and outreach about the potential impacts of lawn care, pet waste, etc.

Local governments can do many things to reduce pollutant runoff. A first step is to avoid filling or developing in isolated wetlands, which act as nature's flood control and filtration system. Next, local governments can reduce impervious surface coverage by encouraging "better site" design. The Center for Watershed Protection defines better site design as a collection of "techniques that employ a variety of methods to reduce total paved area, distribute and diffuse stormwater, and conserve natural habitats" (Watershed Protection Techniques). One technique that could be encouraged is clustering, which may reduce imperviousness by 10 percent to 50 percent depending on lot size and road configuration (Schueler 2000). During construction, other techniques can be used: silt fences help control sediment transport, and limits on clearing and grading allow the site to retain more of its natural hydrology. To allow clustering and other innovative techniques, local governments may need to revise their zoning ordinances.

Local governments can use and promote stormwater best management practices (BMPs) to lessen the negative effects of development. Nonstructural BMPs are a preventative approach to stormwater management that can include land use controls, maintenance efforts (street sweeping), and public awareness campaigns (drain stenciling). Structural BMPs focus on reducing the impacts of existing development. Some examples of structural BMPs are detention ponds, vegetated buffers, swales, and constructed wetlands.

In addition, many communities have created stormwater utilities that fund stormwater management programs by collecting a fee from local landowners. Typically, projects funded include the maintenance and upgrade of existing storm drain systems, development of drainage plans, flood control measures, and coverage of administrative costs (Kaspersen 2001). Local governments can also benefit through better management of scarce public resources by starting a green builder program.

However, local governments need not work alone to address stormwater runoff. Builders for the Bay (BFB) is an example of a voluntary program aimed at reducing environmental impacts from residential and commercial construction within the Chesapeake Bay watershed. This program is encouraging the adoption of 22 better site design principles under the leadership of the Alliance for the Chesapeake Bay, the Center for Watershed Protection, and the National Association of Home Builders.

References and Resources

The Center for Watershed Protection. "An Introduction to Better Site Design." Watershed Protection Techniques. Volume 3, Issue 2. Pages 623-632.

The Center for Watershed Protection provides many resources, tools, and publications on watershed management including resources on runoff. The Center is a nonprofit that provides local governments, activists, and watershed organizations around the country with the technical tools for protecting streams, lakes, and rivers.

The Environmental Protection Agency's Watershed Information Network provides free training in the on-line Watershed Academy, information on its watershed grant program, a watershed atlas, summaries of urban stormwater best management practices, a homeowner's guide to reducing runoff, and many other resources through its water issues Web site.

EPA low impact development resources.

The Georgia Stormwater Management Manual is available for download in two volumes — the Stormwater Policy Guidebook and the Technical Handbook — from the Atlanta Regional Commission.

The Green Affordable Housing Coalition (GAHC) provides numerous resources on green building programs, including a list of cities and counties with green programs, tools, financing, fact sheets, and case studies. The GAHC is a coalition of San Francisco Bay Area public-sector and private-sector professionals committed to incorporating green building practices into the design, construction, operation, and maintenance of affordable housing through education and outreach.

Hoag, Grant. 2004. "Developing Equitable Stormwater Fees: Setting Rates that Reflect the Cost of Providing Service." Stormwater: The Journal for Water Quality Professionals. January/February 2004.

An Internet Guide to Financing Stormwater Management Web site is provided by the Center for Urban Policy and the Environment at Indiana University-Purdue University Indianapolis (IUPUI) in cooperation with the Watershed Management Institute, Inc.

Kaspersen, Janice. 2000. "The Stormwater Utility: Will It Work in Your Community?" Stormwater: The Journal for Water Quality Professionals. November/December 2000.

Keating, Janis. 2002. "Trees: the oldest new thing in Stormwater Treatment?" Stormwater: The Journal for Water Quality Professionals. March/April 2002.

Low-Impact Development (LID) Urban Design Tools Web site provides watershed managers with a new set of tools and techniques that can be used to meet regulatory program goals and receive water protection program goals for urban retrofits, redevelopment projects, and new development sites.

The Natural Resources Defense Council has many free resources available for download such as Stormwater Strategies: Community Responses to Runoff Pollution, which contains strategies to control urban runoff pollution, case study examples, and information on low-impact development.

National Education for Municipal Officials (NEMO) provides case studies on pervious constructing materials and pervious landscape elements. Other resources provided include planning, regulatory, and design guidance for stormwater programs. NEMO is a University of Connecticut educational program for local land use officials that addresses the relationship of land use to natural resource protection.

The NOAA Coastal Services Center provides water quality tools and resources like the impervious surface analysis tool (ISAT).

The North Carolina Cooperative Extension Service provides a guide for homeowners called Stormwater Management for Homeowners.

Schueler, Thomas R. 2000. "Why Stormwater Matters." The Practice of Watershed Protection. Pages 365 to 370.

— "Use of Open Space Design to Protect Watersheds." The Practice of Watershed Protection.

South Carolina National Education for Municipal Officials SC (NEMO) provides several presentations about impervious surfaces: best management practices, better site design, zoning options, and others. These were presented at the Taming Stormwater Workshop and are available for download.

The Stormwater Manager's Resource Center (SMRC) provides various resources on stormwater management, including model ordinances on erosion and sediment control, criteria for stormwater operation and maintenance, and much more. SMRC is maintained by the Center for Watershed Protection.

The University of Georgia Marine Extension Service provides water quality education and resources through its Nonpoint Education for Municipal Officials program.

The University of Georgia's River Basin Science and Policy Center provides research on land use and water quality.

The U.S. Department of Agriculture's National Resources Conservation Service (NRCS) provides water quality assessment and monitoring guidance documents and technical assistance, mostly through local conservation districts. NRCS fosters partnerships to help people conserve, maintain, and improve our natural resources and environment.

The U.S. Geological Survey provides a variety of information on the following topics: a primer on water quality, Water Quality Data for the Nation and Nonpoint and Point Sources of Nitrogen in Major Watersheds of the United States.

Return to top