The G3 approach uses a variety of green street practices to:

·         Reduce stormwater runoff,

·         Capture and infiltrate stormwater on site,

·         Improve water quality,

·         Reduce energy use (lighting, heating, cooling),

·         Increase pedestrian safety

·         Improve community aesthetics and walkability


These practices include using a Green Infrastructure approach to green stormwater management. Green infrastructure uses engineered systems that mimic natural processes to increase infiltration or filtration of runoff, reduce flows, and enhance watershed health.  Examples of green infrastructure includes pervious pavements, planted stormwater infiltration areas (curb bumpouts, rain gardens, bioinfiltration areas, bioswales), and increasing street trees / urban tree canopy.  Along with addressing stormwater, Green Streets reduce energy costs through the use of solar lighting, help reduce urban summer temperatures (reduced heat island effect) which means less energy use to cool buildings, and incorporate recycled materials.  Examples of these practices are provided below.


Stormwater is one of the largest water challenges in urban and suburban areas.  Rainwater falling on impervious surfaces such as roads, sidewalks, and parking lots is not able to soak into the soil and quickly runs off the surface.  As the water runs across these surfaces it collects pollutants such as oil and grease, animal waste, metals, and nutrients.  Most of this water is directed to streams and rivers untreated.  In many areas this pollution concern is even greater because the rainwater entering the sewer system causes untreated sewage to be discharged to rivers.  The increased water pollution from stormwater impacts human health, fish ha In the Chesapeake Bay the only growing source of water pollution is from stormwater.

Along with pollution concerns, the increase in impervious surfaces leads to increase flooding.  Even small rain events can lead to flooding in highly impervious areas.  High volumes of water suddenly entering streams and rivers can lead to stream bank erosion, sedimentation, and loss of stream stability.  This can mean loss of property and important infrastructure such as pipes, road, bridges, and culverts.

Addressing the stormwater from streets, roads, and alleys helps reduce impervious surface which reduces pollution, reduces flooding, and the impacts of high volumes of stormwater.  For instance, in the Anacostia Watershed alone there are a total of 2,574 lane miles of roadway or impervious surfaces with approximately 1,809 miles of local, neighborhood & rural roads and city streets.  


EPA –What is Green Infrastructure and Green Infrastructure Elements

Downspout Disconnection


Downspout disconnection refers to the rerouting of rooftop drainage pipes to drain rainwater to rain barrels, cisterns, or permeable areas instead of the storm sewer. Downspout disconnection stores stormwater and/or allows stormwater to infiltrate into the soil. This simple practice may have particularly great benefits in cities with combined sewer systems.


Toronto Homeowners' Guide to Rainfall: Downspout Disconnection
Water Environment Research Foundation

Demonstration of Downspout Disconnection Effectiveness
Ontario Centre for Municipal Best Practices: Best Practice Summary Report

Los Angeles Downspout Disconnection Program
Milwaukee Downspout Disconnection
Portland Downspout Disconnection Program

Web Sites
Mid-America Regional Council
Blue Water Baltimore

Rainwater Harvesting


Rainwater harvesting systems collect and store rainfall for later use. When designed appropriately, rainwater harvesting systems slow and reduce runoff and provide a source of water. These systems may be particularly attractive in arid regions, where they can reduce demands on increasingly limited water supplies.


Portland Stormwater Solutions: Rain Barrels
Portland Stormwater Solutions: Rain Cisterns
Build it Green (PDF) (3 pp, 43K, About PDF)

Capturing Rainwater to Replace Irrigation Water for Landscapes (PDF) (4 pp, 39K, About PDF)
Reducing Mains Water Use Through Rainwater Harvesting (PDF) (4 pp, 1.5MB, About PDF)

Technicians for Sustainability: Water Harvesting
New York City Rain Barrel Giveaway Program

Web Sites
Rainwater Harvesting at North Carolina State University
American Rainwater Catchment Systems Association


Rain Gardens


Rain gardens (also known as bioretention or bioinfiltration cells) are shallow, vegetated basins that collect and absorb runoff from rooftops, sidewalks, and streets. Rain gardens mimic natural hydrology by infiltrating and evapotranspiring runoff. Rain gardens are versatile features that can be installed in almost any unpaved space.

Bioretention Literature Review
Urban Design Tools: Bioretention

Burnsville, MN Stormwater Retrofit Study
12,000 Rain Gardens

Web Sites
Rain Gardens for the Bays
Rain Garden Network
Rain Garden Design Templates


Planter Boxes


Planter boxes are urban rain gardens with vertical walls and open or closed bottoms that collect and absorb runoff from sidewalks, parking lots, and streets. Planter boxes are ideal for space-limited sites in dense urban areas and as a streetscaping element.

Performance Assessment of Three Types of Rainwater Detention Structures (PDF) (71 pp, 5MB, About PDF)
See Rain Gardens and Green Streets

Michigan Avenue Streetscape
Philadelphia Water Department

Web Sites
See Rain Gardens and Green Streets

How a Stormwater Planter Box Works





Bioswales are vegetated, mulched, or xeriscaped channels that provide treatment and retention as they move stormwater from one place to another. Vegetated swales slow, infiltrate, and filter stormwater flows. As linear features, vegetated swales are particularly suitable along streets and parking lots.

Performance of Engineered Soil and Trees in a Parking Lot ale (PDF) (7 pp, 5.7MB, About PDF)
Water Quality Benefits of Grass Swales in Managing Highway Runoff (PDF) (10 pp, 218K, About PDF

Wisconsin Department of Natural Resources Technical Standard

Web Sites
University of New Hampshire Stormwater Center
See Rain Gardens and Green Streets

Source: Philadelphia Green Streets Manual


Permeable Pavements


Permeable pavements are paved surfaces that infiltrate, treat, and/or store rainwater where it falls. Permeable pavements may be constructed from pervious concrete, porous asphalt, permeable interlocking pavers, and several other materials. These pavements are particularly cost effective where land values are high and where flooding or icing is a problem.

Long-Term Stormwater Quantity and Quality Performance of Permeable Pavement Systems
Reducing Urban Heat Islands: Cool Pavements (PDF) (39 pp, 6.2MB, About PDF)

Use of pervious concrete eliminates over $260,000 in construction costs
Minnesota city eschews storm drains, uses pervious streets

Web Sites
National Ready Mix Concrete Association: Pervious Concrete
Interlocking Concrete Pavement Institute
National Asphalt Pavement Association: Porous Asphalt

How Permeable Pavement Works


 Source: Philadelphia Green Streets Manual

Green Streets and Alleys


Green streets and alleys integrate green infrastructure elements into the street and/or alley design design to store, infiltrate, and evapotranspire stormwater. Permeable pavement, bioswales, planter boxes, and trees are among the many green infrastructure features that may be woven into street or alley design.

Portland Vegetated Curb Extension Flow Test Report
Demonstrating the Benefits of Green Streets for Active Aging (PDF) (81 pp, 2.8MB, About PDF)

Seattle Public Utilities Natural Drainage Projects
Syracuse Green Street: Concord Place (PDF) (2 pp, 220K, About PDF)
Los Angeles Green Street: Elmer Ave
The Chicago Green Alley Handbook (PDF) (24 pp, 3.7MB, About PDF)

Web Sites
Low Impact Development Center: Green Streets
Green Street Initiatives Around the United States
Creating a Successful Green Street Program


Green Parking


Many of the green infrastructure elements described above can be seamlessly integrated into parking lot designs. Permeable pavements can be installed in sections of a lot and rain gardens and ales can be included in medians and along a parking lot perimeter. Benefits include urban heat island mitigation and a more walkable built environment.

EPA Case Study: Bioretention Applications (PDF) (3 pp, 133K, About PDF)
Reducing Urban Heath Islands: Cool Pavements (PDF) (39 pp, 6.2MB, About PDF)

Ipswich River Watershed Demonstration Project
Toronto Design Guidelines for Greening Surface Parking Lots (PDF) (40 pp, 9.6MB, About PDF)

Web Sites
EPA Experimental Stormwater Parking Lot (40 pp, 9.6MB, About PDF)


Green Roofs


Green roofs are covered with growing media and vegetation that enable rainfall infiltration and evapotranspiration of stored water. Green roofs are particularly cost effective in dense urban areas where land values are high and on large industrial or office buildings where stormwater management costs may be high.


EPA Stormwater Menu of BMPs
Charles River Watershed Association (PDF) (2 pp, 622K, About PDF)
Portland Ecoroofs

EPA's Green Roofs for Stormwater Runoff Control (PDF) (81 pp, 2.8MB, About PDF)
Green Roofs as Urban Ecosystems
The Monetary Value of the Soft Benefits of Green Roofs

King County Green Roof Case Study Report (PDF) (31 pp, 1MB, About PDF)
Green Roof and Wall Projects Database

Web Sites
Green Roofs for Healthy Cities
Portland Ecoroof Program


Urban Tree Canopy


Many cities set tree canopy goals to restore some of the benefits provided by trees. Trees reduce and slow stormwater by intercepting precipitation in their leaves and branches. Homeowners, businesses, and cities can all participate in the planting and maintenance of trees throughout the urban environment.

Sustainable Cities Institute: Benefits of the Urban Forest
US Forest Service: Urban Forest Data

Chicago Trees Initiative
Philadelphia Water Department: Stormwater Tree Trench

Web Sites
Watershed Forestry Resource Guide
i-Tree: Tools for Assessing and Managing Community Forests
US Forest Service: Urban and Community Forestry


Land Conservation

Protecting open spaces and sensitive natural areas within and adjacent to cities can mitigate the water quality and flooding impacts of urban stormwater while providing recreational opportunities for city residents. Natural areas that are particularly important in addressing water quality and flooding include riparian areas, wetlands, and steep hillsides.


Conservation Fund: 10 Green Infrastructure Case Studies
Using Smart Growth Techniques as Stormwater Best Management Practices
EPA's Protecting Water Resources with Higher Density Development

Greenways & Blueways

Green Seams: Flood Management in Milwaukee
Alachua County Green Infrastructure Investment Program (PDF) (8 pp, 233K, About PDF)

Web Sites
EPA Healthy Watersheds Initiative
The Conservation Fund
The Trust for Public Land


To learn more visit Philadelphia's Green Streets Design Manual

Alternative energy generation for street lighting