Image Source: Chris Hamby. Source License: CC BY-SA 2.0. Adaptations: cropped.

Stormwater best management practices (BMPs) refer to strategies that utilize vegetation, soils, and natural processes to manage water and reduce stormwater runoff.

Why is this important to your community?

Stormwater contamination is a concern for many communities within the CONNECT region. Stormwater carries runoff from parking lots and gas stations, yard debris and chemicals, silt from development sites, and pollutants from wildlife and domestic animals, among other pollutants. Such “non-point-source” runoff and debris that enters streams leads to increased demand at water treatment plants and negative environmental impacts, such as flooding, and can affect water quality and impair watershed health. Instead of undertaking costly, and often unnecessary, expansions to existing stormwater conveyance and treatment systems, communities throughout the region can employ stormwater best management practices (BMPs) to manage stormwater at its source and reduce runoff. By minimizing the negative effects of unmanaged stormwater in the CONNECT region, we can make progress in improving water quality, one of the region’s top priorities.

How does it work?

According to the U.S. EPA, stormwater is precipitation that runs off streets, lawns, and other sites. Stormwater that is absorbed in the ground or other pervious surfaces is filtered before flowing into watersheds. However, in developed areas, impervious surfaces (e.g., sidewalks, roofs, roads, and other pavement) prevent the natural filtration of stormwater, causing water to flow into storm drains, sewer systems, and ditches. Overuse of and reliance on traditional grey infrastructure (piped networks that transfer water off-site for treatment) can lead to negative environmental and financial outcomes, including low water tables, flooding, stream bank erosion, wildlife habitat destruction, sewer overflows, damage to existing infrastructure (e.g., water treatment plants), and contamination of key watersheds—not to mention the cost to local taxpayers for infrastructure construction and maintenance.

BMPs aim to capture and treat stormwater naturally before it flows into watersheds or treatment facilities. BMPs can be designed to suit a variety of locations and stormwater loads – from an individual rain barrel at a residence to a green or blue roof on a public building, to swales and rain gardens throughout new neighborhoods. Regardless of the scale, each approach works to filter, transpire, capture, and reuse stormwater. BMPs (stormwater planters, tree trenches, rain gardens, green and blue roofs, swales, wetlands, rain barrels, and green gutters) typically capture water from a street, sidewalk, green inlet, or from rainfall (e.g., green and blue roofs) where plants, trees, or a stone media filter and transpire the water while enhancing the appearance of the environment. Water remaining after initial infiltration, seeps into the soil where stone or other storage media provides additional stormwater storage, or is transferred to storage for reuse (e.g., rain barrels, green and blue roofs).

Counties or municipalities can encourage the use of BMPs by adopting zoning or other regulations requiring developers to manage a certain amount of stormwater produced on site (see sample Stormwater Management regulation). The EPA’s National Stormwater Calculator (SWC) estimates the annual amount of rainfall and frequency for sites throughout the country based on soil conditions, land cover, and recorded rainfall averages. The SWC is a tool that developers, landscape architects, site designers, planners, and homeowners can use to determine the appropriate size and type of stormwater best practice.

Ready to get started?

Using the Tool

  • Convene a working group of representatives from county or municipality departments (water department, streets department, development, zoning and planning), developers, architects and landscape architects, engineers, and local schools and institutional partners to discuss strategies for employing stormwater best management practices (BMPs) locally.
    • Review any existing plans or guides to employing BMPs (North Carolina Division of Water Quality – Stormwater Best Management Practices Manual, 2007 and South Carolina Department of Health and Environmental Control – BMP Handbook)
    • Asses what regulations currently exist to address stormwater (e.g., zoning, Post-Construction Stormwater Ordinances, Long Term Control Plans, and state law). Consider revising existing zoning and regulations to require stormwater management for all new developments, or revising water rates to reflect the stormwater burden generated by properties.
    • See what SMPs and other green infrastructure projects have been employed in your area. This map, made by American Rivers, maps the nearly 2,000 examples found throughout North Carolina.
    • In rural areas, it may be appropriate to employ strategies to manage agricultural runoff, which may include harmful pesticides and other pollutants. Rain gardens, sediment ponds, or vegetation buffer strips can help manage water flow and reduce negative impacts on the local water supply. See NC State University’s Best Management Practices for Agricultural Nutrients for additional strategies and information.
    • In more developed areas, discuss the current stormwater infrastructure system. Determine if the system is currently overloaded, and if so, what areas present the greatest risk to water quality. Work with county or municipal departments to develop a strategy for employing BMPs. This could include a series of pilot projects, a BMP design manual for private homeowners and developers (e.g., Philadelphia Water Department’s Green Streets Design Manual).
    • Research federal, state, and local funding sources (e.g., Clean Water State Revolving Fund Programs, EPA’s Green Infrastructure Funding Program)
    • Explore the possibility of providing incentives for developers who manage more than the minimum amount of stormwater on site. For example, site design that manages more than the first inch of stormwater could receive a density bonus, reduced parking requirements, or expedited permitting.
  • Consider creating a public education campaign that details the importance of employing BMPs to manage stormwater and improve water quality. This could include public meetings, flyers or pamphlets, speaker series, or media campaigns. Storm sewer marking that shows where what goes into the storm sewer goes—untreated—is a very successful and inexpensive public education device.
  • Support legislation that works to improve water quality and reduce the cost of providing services. Legislation could include new zoning or regulations requiring developers to manage on-site stormwater or the approval of a municipal-wide project to install BMPs on certain streets to manage stormwater.

Where has it worked?

Drover’s Road Preserve - Buncome County, NC

Image Source: Eco Friendly Real Estate Blog.



David Tuch, Equinox Environmental Consultation & Design, Inc.

About the Program

Drover’s Road Preserve, located in rural Buncombe County, North Carolina near Asheville, is a large-lot residential conservation development situated on a 186-acre mountainside site. The developers made a commitment to protect the site’s natural heritage, resources, and scenic views. Overall site design focused on preserving the quality of the existing land and protecting the site’s water resources. Instead of installing traditional grey infrastructure (e.g., stormwater drains and gutters), the planning team utilized roadside swales, bioretention areas, forested riparian buffers, a stormwater wetland, and an infiltration meadow to manage stormwater on site. In addition to BMPs, Drover’s Road Preserve’s site planners furthered conservation goals by planning new roads and infrastructure to reduce stream crossings, impervious surfaces, and forest clearing and set aside land for permanent conservation in a Conservation Easement program. Planning consultants worked with developers to create a set of design guidelines and rules to ensure that the site was developed in accordance with the overall plan while allowing individual homeowners to build houses on individually purchased lots.

Why it works

At the time of planning and construction, Buncombe County had no post-construction stormwater requirements or other stormwater or conservation zoning. However, the developers and their planning team, recognizing the site’s unique natural character, made a commitment to conservation throughout the site. With help from the planning team and North Carolina Extension, the development team sized a number of BMPs, including swales, wetlands, and bioretention areas, to capture the first 1.25 inches of stormwater. Post-construction, the developers transferred long-term maintenance of open spaces including the stormwater BMPs to the homeowners’ association, while the land in the conservation easement is maintained by the Southern Appalachian Highlands Conservancy. This case illustrates a comprehensive approach to conservation development by successfully limiting site disturbance, preserving 59% of the site for open space and conservation, utilizing conservation easement tax credits, reducing impervious surfaces, and using BMPs to treat stormwater on site.