Green Infrastructure and Low Impact Development
By Mara Dias, Rick Wilson and Colleen Henn
Stormwater runoff causes one of the greatest threats to water quality in this country. Contaminated runoff degrades coastal waters and habitats. Polluted Stormwater is responsible for most of the beach closures and swimming advisories issued at our beaches across the nation.
As cities and towns expand and become more developed, large portions of our watersheds are being paved over with concrete and other impervious surfaces. These hard surfaces interrupt the normal water cycle by preventing rainwater from soaking into the ground. Rain instead runs across rooftops, parking lots and roadways, picking up pollutants such as oil, fertilizers, and animal waste along the way. Marshes and wetlands are capable of cleaning many of the nutrients and pollutants in stormwater, but in many cases this natural vegetation has been lost as communities build out to the water's edge.
Stormwater is often channeled directly into streams, rivers and coastal waters through storm drain systems. Particularly problematic are combined sewer systems that exist in many of our older cities. Combined systems easily become overwhelmed and overflow raw sewage into receiving water bodies during storm events. While the consequences of stormwater runoff are most apparent in highly urbanized areas, it takes only a small increase in the percentage of impervious cover in a watershed for negative water quality impacts to occur.
Green Infrastructure, also sometimes referred to as Low Impact Development (LID), is a sustainable approach to urban planning and site design that aims to maintain and restore the water cycle in developing watersheds. This technique uses site-specific engineering designs that utilize Best Management Practices (BMPs) to infiltrate, filter, store and treat stormwater close to its source. Green Infrastructure construction and landscaping plans allow water to infiltrate into the ground, recharging local water supplies and protecting the water quality of nearby waterways. Green Infrastructure techniques are most effective when they are incorporated into the design for new development, but both commercial and residential properties can be retrofitted to hold more rainwater on-site.
Green Infrastructure Techniques
There are many different methods of Green Infrastructure that can be used to maintain a site's pre-development hydrology while still accommodating new development. The success of each is dependent on the specific conditions of a site such as soil type, topography, local precipitation and weather patterns.
Photographs of the successful installation of many of the following techniques can be viewed in a PowerPoint presentation posted online by Orange County Coastkeeper (California).
Bioretention areas are vegetated depressions that collect and filter runoff. Vegetative strips, rain gardens, grassy swales, shallow surface ponds, tree box filters, and underground drainage systems are all examples of bioretention areas that increase the amount of rainwater a property can absorb. Bioretention areas are often advantageous to conventional stormwater techniques, such as rentention ponds, because they are not installed in large development projects, require less space, and provide an added ecnomic incentive.
Rain gardens are a very popular bioretention technique that are being incorporated into residential, municipal, and commercial property landscaping plans. Designed to hold and infiltrate rain water, rain gardens also increase property values by adding to the aesthetic quality of the landscape, especially when planting native plant species that better tolerate standing water. Many cities are offering mini-grants to homeowners to install rain gardens on their properties. For example, the city of Owatonna, Minnesota began the Rain Garden Cost Share Program in order to promote the number of residentail rain gardens. The program provides cost share grants of 50% to residents who plant a rain garden in their yard.
The Surfrider Foundation offers a coastal twist on rain gardens and uses its nationwide chapter network to implement an Ocean Friendly Gardens program that employs CPR (conservation, permeability and retention) techniques to protect the ocean and our beaches by reducing urban runoff.
The bioretention capabilities of a site can also be preserved during construction by saving and amending topsoil. Often during construction, topsoil is scraped away and the remaining soil becomes hard and compacted as large machinery and building materials weigh down on the ground. At the completion of the project, many builders roll out turf on top of the compacted soil, making it very difficult for subsequent rain to percolate into the ground. Saving and replacing the topsoil or amending the soil with organic matter can help retain the site's ability to absorb water and prevent runoff.
Green Streets also provide source control of storm water, and are increasingly becoming more popular in cities all over the nation. On green streets, plants and soils are used to filter, slow, and cleanse storm water from nearby streets. This innovative form of Green Infrastructure manages rainwater from exactly where it falls.
Permeable Pavement offers an alternative to asphalt and concrete and allows rainwater to percolate into the ground. Most appropriate for lower traffic flow areas, permeable pavements have been used successfully to build parking lots, driveways, fire lanes, horse trails and bicycle paths. Although typically more expensive to construct than traditional asphalt pavement, their installation costs may be offset by a reduction in traditional curb and gutter systems.
The benefits of permeable pavements include better infiltration, ground water recharge, reduction in runoff volume and treatment of stormwater for pollutants. For example, one of the University of North Carolina's commuter parking lots was built with permeable pavement and actually produces less stormwater runoff than a grass field. In contrast, traditional parking lots produce up to 16 times as much runoff as a grassy meadow of the same size. Here's a driveway example from Houston, Texas.
Homeowners and local communities can see further reductions in stormwater runoff by employing alternative driveway and parking lot designs that reduce impervious surfaces and include bioretention strips or cells. Grass parking is also a good option for seasonal or temporary, event-related parking.
Green roofs are another innovative Green Infrastructure technique being employed to reduce runoff from the rooftops of both commercial buildings and private residences. These roofs are built with plants that can tolerate drought and extreme temperature conditions, and work effectively to absorb rainwater, improve air quality, reduce noise pollution, increase biodiversity, regulate the internal temperature of the building, and add an aesthetic appeal to any building. According to Green Roofs for Healthy Cities, green roofs retain 70-90% of precipitation. A great example of the energy reduction benefits is the Green Roof on the American Society of Landscape Architects building in Washington, DC. An engineering analysis showed that the green roof's extra insulation lowered the building's energy usage by 10% in the winter, and up to 2-3% in the summer.
Rooftop farms are increasing in popularity in the realm of Green Infrastructure due to their environmental benefits. They also have the potential to capture millions of gallons of storm water, which is diverted from sewer systems, avoiding the potential of overflow during rainfall. This also reduces the carbon footprint in food transport by narrowing the distance between the producer and the consumer. New York City has recently altered their zoning regulations and encourages rooftop farms as an integral part of sustainable development.
Roof rainwater collection systems are another example of Green Infrastructure that serve dual purposes. In arid areas, rainwater harvesting conserves water resources, while during wet weather, rainwater collection systems minimize the amount of stormwater running off rooftops. Particularly suited for retrofits, rain barrels and cisterns can easily be hooked up to homes and buildings. Channeling roof runoff to dry wells also keeps water out of the streets and storm drains.
Historically, Seattle has struggled with frequent sewer system overflows due to stormwater. In response, cisterns were created to collect runoff and filter the water before it reaches local watersheds. Growing Vine Street is a project that solves two problems: reduces urban runoff into surrounding watersheds, and captures water for outdoor irrigation. Not only is Seattle incorporating green roofs and cisterns into their green infrastructure techniques, but they embrace greenscapes as an effective and aesthetically pleasing way to reduce runoff and filter water before it is released into surrounding watersheds.
Green Infrastructure was first promoted by environmental organizations and tested on university campuses, and today the success of these low-impact development techniques in controlling stormwater runoff is now being recognized by municipalities across the country. Today, we see green infrastructure requirements incorporated into local code, ordinances, regulations and stormwater management plans.
In California, the Central Coast Regional Water Quality Control Board requires municipalities under the jurisdiction of their Municipal General Storm Water Permit to minimize negative impacts on aquatic ecosystems and degradation of water quality to the maximum extent practicable. Under this permit, cities are required to incorporate green methodology into new and redevelopment ordinances and design standards, unless they are able to demonstrate that the cost of low impact development practices would be prohibitive and exceed any resulting water quality benefits.
Ventura is one city that is affected by the Central Coast Water Board's ruling. The Ventura Chapter of the Surfrider Foundation is taking advantage of this opportunity by promoting Ocean Friendly Gardens in Ventura and proposing Green Infrastructure applications to solve specific water quality problems that are affecting the beaches in Pierpont Bay, including Surfers' Point.
The Washington Pollution Control Hearings Board ordered the State's largest local governments to begin using Green Infrastructure techniques to control stormwater ‘where feasible'. This decision affects stormwater permits for the Cities of Seattle and Tacoma, and Clark, King, Pierce, and Snohomish Counties.
In the Metro Bay Region in Rhode Island an Urban Coastal Greenway has been designated around the northern reaches of Narragansett Bay. Within this highly urbanized waterfront, all proposals for new development and redevelopment projects must manage 100% of stormwater on-site and maintain 15% vegetative cover. Applicants must incorporate LID techniques to the maximum extent practicable to meet the stormwater containment requirement.
Portland, Oregon has been a leader in promoting Green Infrastructure and green building practices through regulations and financial incentives. The city's code requires on-site stormwater management for new and redevelopment projects, and new city-owned buildings are required to install green roofs on at least 70% of the total roof area. The city also offers zoning incentives for privately owned buildings to install green roofs and will allow up to a 35% discount in stormwater utility fees for properties with on-site stormwater management. Portland also has a progressive green streets program to meet many different community health objectives including stormwater management.
New Jersey and Maryland have both taken action on the state level to codify stormwater management rules. In 2004, New Jersey passed new stormwater rules requiring that sites maintain 100% of the average pre-construction groundwater recharge or allow for any increase in stormwater runoff to be infiltrated. The Maryland Stormwater Act of 2007 identifies Green Infrastructure practices as the preferred stormwater control method in the State and stipulates their use as the first control option for new development projects.
Given the growing acknowledgement of the benefits of Green Infrastructure, there is an increased opportunity for Surfrider members and activists to push local governments to include Green Infrastructure strategies in stormwater management plans and community planning and zoning codes. Many smaller cities are now developing stormwater management plans to meet Phase II NPDES permit requirements of the Clean Water Act, and the public is invited to participate in these planning processes. Local planning and zoning boards and environmental commissions hold public hearings before approval of development projects. These hearings give the public the opportunity to ask for Green Infrastructure alternatives to be considered during the review of building permit applications.
The Center for Watershed Protection has posted several online Better Site Design publications. Another great resource which outlines how citizens can become involved in local rulemaking and planning to implement solutions to stormwater pollution in their community is the American River's Local Water Policy Innovation; A Road Map for Community Based Stormwater Solutions. Growth and development can move forward in ways that do not disturb the water cycle we depend on for clean water and beaches.
Following is an index of Green Infrastructure and Low Impact Development online resources.
Green Infrastructure and Low Impact Development Reference Websites
California. California LID Portal. California Stormwater Quality Association.
Great Lakes. Lake Superior Streams. Site Design Toolkit. Site evaluation, policy, LID methods, case studies.
Low Impact Development (LID) Center Urban Design Tools Website. Bioretention, green roofs, permeable pavement, rain barrels and cisterns, soil amendments, tree box filters.
Low Impact Development Center. General Information, techniques, handbooks & manuals.
Massachusetts. Boston Metropolitan Area Planning Council. LID Toolkit. Case studies, fact sheets, explanation of techniques, regulations and codes.
Natural Resources Defense Council. LID definitions, benefits, case studies.
New England. University of New Hampshire Stormwater Center. LID Case studies.
North Carolina. NC State University. Stormwater and LID publications.
USEPA. Green Infrastructure.
USEPA. Low Impact Development "Barrier Busters" Fact Sheet Series. These fact sheets explain the benefits of LID in clear terms and through examples. Specific fact sheets in this series directly address specific concerns that have been raised about adopting LID, thereby busting barriers.
West Coast. West Coast LID Portal - intended to serve as a community clearinghouse, providing information on funding sources, incentive programs, training opportunities, and technical resources.
Handbooks, Manuals & Guides
California. San Diego County Department of Planning and Land Use. LID Handbook.
California. City of Salinas Development Standards Plan Low Impact Development Designs and Practices for Urban Storm Drainage Management.
California. Southern California LID Manual, California Stormwater Quality Association.
Great Lakes. Center for Neighborhood Technology. Upgrade Your Infrastructure: A Guide to the Green Infrastructure Portfolio Standard And Building Stormwater Retrofits.
Hawaii. Coastal Zone Management. A Practitioner's Guide to Low Impact Development.
Maryland. Department of Environmental Protection, Montgomery County. What are RainScapes?. RainScapes Project Manual. Environmentally-Friendly Landscapes for Healthy Watersheds. Rain Gardens for RainScapes. Technical Design Manual.
Massachusetts. Massachusetts Bay Estuary Association. Greenscapes Guide.
New Jersey. New Jersey Department of Environmental Protection. Stormwater Best Management Practices.
Oregon. Portland Bureau of Environmental Services. Stormwater Solutions Handbook.
US Department of Housing and Urban Development. The Practice of Low Impact Development.
US EPA. Tools, Strategies and Lessons Learned from EPA Green Infrastructure Technical Assistance Projects (PDF), summarizes results from EPA’s green infrastructure technical assistance program for communities looking for solutions to their unique challenges. This quick reference guide matches problems with real world, tested solutions and offers readers resources for further information. The report also includes a handy guide to technology and a table of benefits that you can share with potential collaborators and stakeholders.
US EPA. Case Studies Analyzing the Economic Benefits of Low Impact Development and Green Infrastructure (PDF, 2 MB). A technical report to help utilities, state, other municipal agencies, and other stormwater professionals understand the potential benefits of low impact development and green infrastructure programs. The report highlights 13 case studies of selected public entities throughout the United States that have conducted economic evaluations of these programs.
US EPA. Flood Loss Avoidance Benefits of Green Infrastructure for Stormwater Management (PDF, 13 MB). This modeling study estimates the flood loss avoidance benefits from application of small storm retention practices for new development and redevelopment nationwide. Twenty HUC8 watersheds were modeled in areas where significant growth is expected between 2020 and 2040, using the FEMA Hazus model and national-scale datasets. The results show that, over time, the use of green stormwater infrastructure can save hundreds of millions of dollars in flood losses, while just applying the practices to new development and redevelopment only. If retrofitting were to occur, the avoided losses would be even more significant.
US EPA. Green Infrastructure Wizard. EPA’s Green Infrastructure Wizard, or GIWiz, provides access to tools and resources that can support and promote water management and community planning decisions. GIWiz is an interactive web application that connects communities to EPA Green Infrastructure tools & resources.
Washington. Puget Sound Partnership. Technical Guidance Manual for Puget Sound.
Low Impact Development Center. Low Impact Development (LID) Urban Design Tools Website. Tree box filters.
University of Maryland. Bioretention and Stormwater Research. Rain gardens.
Oregon. City of Portland. Soakage Trenches (infiltration trenches) fact sheet.
Oregon. Oregon State University Extension. Stormwater Planters fact sheet.
USEPA. Office of Water. Bioretention.
USEPA. The Low Impact Development Center. Low Impact Development and Sustainable Landscapes: Bioretention.
Green Streets: Vegetative Strips, Buffers & Swales
Great Lakes. Lake Superior Streams. Site Design Toolkit. Grassed swales.
Oregon. Oregon Sea Grant Extension. Vegetated Filter Strips fact sheet.
Oregon. Oregon Sea Grant Extension. Swales fact sheet.
Virginia. Virginia DEQ Grass Channels.
Ocean Friendly Gardens and Rain Gardens
Surfrider Foundation. Ocean Friendly Gardens.
Florida. Florida DEP. Rain Gardens for Watershed Protection.
Georgia. Clean Water Atlanta. Rain gardens for home landscapes.
Hawaii. Surfrider Foundation Maui Chapter. A Turn For the Better For A Maui Beach Park
New Jersey. Native Plant Society of New Jersey. Rain garden manual and case studies.
New Jersey. Ocean County Soil Conservation District. Rain garden fact sheets, brochures and manuals. Low maintenance landscaping manual.
North Carolina. NC Cooperative Extension. Rain garden installation and maintenance.
Oregon. American Society of Landscape Architects. Mount Tabor Middle School Rain Garden. Art, education, and ecological function.
Oregon. Oregon Sea Grant. The Oregon Rain Garden Guide.
Oregon. Oregon Sea Grant Extension. Rain Gardens fact sheet.
Virginia Department of Forestry. Rain Gardens.
Washington. Surfrider Foundation Northwest Straights Chapter. Native Garden Project. Improve water quality, support ecosystem health, and scenic beauty.
Center for Watershed Protection. How to install a rain barrel.
Delaware. Delaware Soil and Water Conservation District. Rain barrels.
Georgia. Atlanta Department of Watershed Management. Rain Barrel Workshops.
Nebraska. Alternative Stormwater Best Management Practices. Rain Barrels and Cisterns.
Texas. Texas Commission on Environmental Quality. Rainwater Harvesting with Rain Barrels, A Take Care of Texas Guide.
Green Roofs and Green Infrastructure
Greenscapes Urban Gardening. Urban Gardening Instructions.
Oregon. Oregon Sea Grant Extension. Green Roofs fact sheet.
Oregon. Oregon Sea Grant Extension. Stormwater Planters fact sheet.
New York, New York. Urban Rooftop Farming.
USEPA. Using Green Roofs to Reduce Heat Islands.
USEPA. Managing Wet Weather with Green Infrastructure.
USEPA. Green Infrastructure Wizard.
Washington D.C. American Society of Landscape Architects. Green roofs.
California. Grass Parking.
California. Sea Grant. Permeable Paving.
California. Sea Grant. Fact Sheets. Home Water Conservation: Rain Gardens, Drought Tolerant Plants, Green Building & Low Impact Development.
Oregon. Oregon Sea Grant Extension. Porous Pavement fact sheet.
Maryland. University of Maryland Extension. Permeable Pavement Fact Sheet.
New York. Green Streets Program.
USDA. Natural Resources Conservation Service. Pervious Paving.
USEPA. Green Parking Lot Resource Guide.
Green Infrastructure Retrofits
California. UC Cooperative Extension. Water Wise demonstration project, typical residence, retrofitted residence & LID designed residence.
Center for Watershed Protection. Urban Subwatershed Restoration Manual Series.
Washington, DC. Chesapeake Stormwater Network. Stormwater Management and runoff prevention.
Saving and Amending Topsoil
California. Sea Grant. Saving & Amending Topsoil.
Low Impact Development Center. Soil amendments.
North Carolina. North Carolina Cooperative Extension Service. Amending Clay Soils.
Oregon. City of Salem. Soil Amendment.
USEPA. Resource Conservation. GreenScapes.
Fact Sheets & Educational/Outreach materials
California. Sea Grant. Green Building Info Sheets. Residential LID methods, bio swales, alternative driveway design, porous pavement, natural landscaping, saving and amending topsoil, tree cover.
Low Impact Development Center. Builder's guide to LID.
Michigan. Landscaping for water quality: the LID approach. Michigan State University Extension.
USEPA. Green Infrastructure. Grassy swales, green roofs, porous pavement, rain gardens, bioretention, vegetated filter strips, rain barrels, cisterns, downspout disconnection, green parking, open space design.
Washington. Puget Sound Action Team. Low Impact Development Manual.
Local Ordinances & Regulations
California. Central Coast Regional Water Quality Control Board. LID requirements for new construction and redevelopment projects.
New York. New York City Parks. Green Infrastructure.
Portland, Oregon. Green Street Program.
Rhode Island. Urban Coastal Greenways Policy. Metro Bay Special Area Management Plan. RI Coastal Resources Management Council. Vegetative cover and LID requirements.
Washington. Puget Sound Partnership. Low Impact Development. Technical Guidance Manual for Puget Sound.
American Rivers. Local Water Policy Innovation. A Roadmap for Community Based Stormwater Solutions.
Center for Watershed Protection. Better Site Design: A Handbook for Changing Development Rules in Your Community. Model Ordinances.
California. State Water Resources Control Board. A Review of Low Impact Development Policies: Removing institutional barriers to adoption.
U.S. Navy. LID policy.
Green Infrastructure Regional Examples & Case Studies
- Featured are over 400 case studies of Green Infrastructure techniques controlling rainfall. The link includes the project description, design features, costs, benefits, the number of jobs created by the project, and more.
District of Columbia.
- Office of Energy and Environmental Affairs. Smart Growth/Smart Energy Toolkit. LID Case Studies.
- Preventing CSO Contamination through Green Infrastructure.
- Portland Bureau of Environmental Services. Case studies.
- USEPA. Case Studies Analyzing the Economic Benefits of Low Impact Development and Green Infrastructure (PDF, 2 MB). A technical report to help utilities, state, other municipal agencies, and other stormwater professionals understand the potential benefits of low impact development and green infrastructure programs. The report highlights 13 case studies of selected public entities throughout the United States that have conducted economic evaluations of these programs.
- USEPA. Reducing Stormwater Costs through Low Impact Development (LID) Strategies and Practices. Cost and benefits evaluation. Fact sheet.
- USEPA. Bioretention Applications - Inglewood Demonstration Project, Largo. Maryland and Florida Aquarium, Tampa, Florida.
- NRDC Rooftops to Rivers and Stormwater control case studies.
- Chicago, Illinois
- Milwaukee, Wisconsin
- Pittsburgh, Pennsylvania
- Portland, Oregon
- Rouge River Watershed, Michigan
- Seattle, Washington
- Toronto, Ontario, Canada
- Vancouver, B.C., Canada
- Washington, D.C.
- Seattle Public Utilities. Completed Green Stormwater Infrastructure Projects.
Cooperative Institute for Coastal and Estuarine Environmental Technology (CICEET). Tools for Clean Water and Healthy Coasts.
Bioretention cells. Product. Stormwater filter in urban and parking areas.