SHADES

Different

of green

at the U.S. Environmental Protection Agency

GREEN INFRASTRUCTURE RESEARCH
The Problem with Water Runoff

Conventional stormwater infrastructure, 

or gray infrastructure, is largely designed 

to move stormwater away from urban 

areas through pipes and conduit. Runoff 

from these surfaces can overwhelm sewer 

systems and end up contaminating local 

waterways. When stormwater runs off 

impervious streets, parking lots, sidewalks, 

and rooftops, it moves pollutants such 

as motor oil, lawn chemicals, sediments, 

and pet waste to streams, rivers, and 

lakes. Runoff flows can also cause 

erosion and flooding that can damage 

property, infrastructure, and wildlife 

habitat. In addition to runoff problems, 

impervious surfaces also prevent water 

from penetrating the soil and recharging 

groundwater supplies. 

What is Green Infrastructure?

Green infrastructure uses plants, soils, 

landscape design, and engineered 

techniques to retain, absorb, and reduce 

polluted stormwater runoff. Green 

infrastructure prevents or reduces the 

amount of runoff that flows directly into 

storm drains and can be a vital tool for 

cities to address combined sewer overflows 

and nutrient impairment. It provides many 

environmental, social, and economic 

benefits that promote urban livability, such 

as improved surface water quality, water 

conservation, and improved aesthetic 

and property value. EPA is developing 

innovative tools for communities to use for 

planning and installing green infrastructure 

for achieving its many benefits. 
Types of Green Infrastructure Practices

Permeable Pavements are porous paved surfaces that allow rain to 

infiltrate into soils. Permeable pavements can be constructed from various 

materials such as pervious concrete, porous asphalt, and permeable 

interlocking pavers.

Rain Gardens are depressed areas in the landscape, planted with grasses, 

flowers, and other plants, that collect rain water from a roof, driveway, or 

street and allows it to infiltrate into the ground. Rain gardens can also help 

filter out pollutants in runoff and provide food and shelter for butterflies, song 

birds, and other wildlife. More complex rain gardens with drainage systems 

and amended soils are often referred to as bioretention cells.

Bioretention Cells (or Bioswales) are depressions that contain vegetation 

grown in an engineered soil mixture placed above a gravel drainage bed 

which slow, infiltrate, and filter runoff. They provide storage, infiltration, and 

evaporation of both direct rainfall and runoff captured from surrounding 

areas. As linear features, bioretention cells are particularly well suited to 

being placed along streets and parking lots.

Vegetative Swales are channels or depressed areas with sloping sides 

covered with grass and other vegetation. They slow down the conveyance of 

collected runoff and allow it more time to infiltrate the native soil beneath it.

Infiltration Trenches are narrow ditches filled with gravel that intercept runoff 

from upslope impervious areas. They provide storage volume and additional 

time for captured runoff to infiltrate the native soil below. 
Green Roofs are a variation of a bioretention cell. Green roofs have a soil 

layer laying atop a special drainage mat material that conveys excess 

percolated rainfall off of the roof. They contain 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 are likely 

to be high.

Planter Boxes are structures with vertical walls and open or closed bottoms 

filled with gravel, soil, and vegetation that collect and absorb runoff. They are 

ideal for space-limited sites in dense urban areas.

Rainwater Harvesting systems, such as rain barrels and cisterns, collect and 

store rainfall for later use. These systems provide a renewable water supply 

and can slow and reduce runoff. Rainwater harvesting can reduce demands 

on increasingly limited water supplies in arid regions.

Rooftop (Downspout) Disconnection allows rooftop rainwater to discharge to 

pervious landscaped areas and lawns instead of directly into storm drains. 

You can use it to store stormwater and/or allow stormwater to infiltrate into 

the soil. Downspout disconnection could be especially beneficial to cities with 

combined sewer systems. 

Urban Tree Canopies intercept rain in their leaves and branches, thereby 

reducing and slowing stormwater runoff.
Integrating

Green Infrastructure Practices

Green Parking integrates green infrastructure elements such as permeable 

pavements and rain gardens into a parking lot design. Such structures 

manage stormwater on site, mitigate urban heat islands, and create a more 

pedestrian-accessible environment.

Green Streets and Alleys integrate green infrastructure elements such as 

bioswales, planter boxes, and trees into street and alley design. Green streets 

and alleys are designed to store, infiltrate, and evaporate and transpire 

stormwater while adding aesthetics to landscapes.
Protecting Existing Green Spaces

In addition to green infrastructure practices, 

communities can also address water quality 

and flooding impacts of urban stormwater 

by protecting open spaces and sensitive 

natural areas within and adjacent to a city 

while providing recreational opportunities 

for city residents. Natural areas that should 

be a focus of these land conservation 

efforts include riparian areas, wetlands, and 

steep hillsides.

Environmental and Economic 

Benefits of Green Infrastructure 

Introducing green infrastructure to 

communities has many environmental and 

economic benefits. Green infrastructure 

can be a cost-effective approach to improve 

water quality and help communities stretch 

their infrastructure investments further by 

providing multiple environmental, economic, 

and community benefits.

Examples of environmental benefits:

● Improved water quality and increased 

water supply

● Reduced flooding

● Improved air quality

● Greater resilience to climate change

● Increased habitat improvement and 

connectivity

● Healthier communities

Examples of economic benefits:

● Increased property values

● Reduced filtration costs

● Infrastructure cost savings

● Reduced private and public costs
EPA’s green infrastructure research 

supports the increased adoption of both 

constructed and natural green infrastructure 

into communities. 

Models and decision support tools

EPA researchers are analyzing and refining 

existing models and tools designed to 

increase green infrastructure practices in 

communities. This research will support 

decision-makers and allow further 

inclusion of green infrastructure practices 

into management plans that support 

sustainability goals. 

Impacts of green infrastructure on 

groundwater resources 

EPA is researching the impacts of green 

infrastructure on groundwater resources to 

provide the basis for long-term research on 

the efficacy of green infrastructure as a best 

management practice for water resources 

enhancement, particularly in arid and 

semiarid regions.

Assessment of risks posed to natural 

wetlands used for wastewater and 

stormwater management 

EPA is reviewing the impacts of wastewater 

and stormwater on natural wetlands and 

riparian areas. This research will help guide 

decisions by regions, states, tribes, and local 

municipalities when incorporating green 

infrastructure with natural wetlands and 

riparian areas as part of stormwater and 

wastewater management plans.

Green Infrastructure Research
EPA Research in Action

Urban Soil Assessment 

Sewer system overflows can put cities in violation of the Clean Water Act. 

EPA researchers developed soil survey assessment protocol to identify the 

urban imprint on major US soils. The research helps urban planners, land 

managers, and sewer districts understand the potential for soils to support 

green infrastructure applications. It provides an overview of urban soils and 

offers recommendations for how soils can be rehabilitated to support green 

infrastructure or urban agriculture.

Transforming Cleveland’s Vacant Lots

Based on technical guidance from EPA experts, Cleveland, Ohio has 

incorporated a green infrastructure pilot program into their CSO control plan. 

This program takes advantage of the city’s excess vacant land, turning that 

land into green spaces that can soak up stormwater and keep excess water 

out of the sewer system.

The transformation of urban vacant lots into park-like gardens that catch 

stormwater runoff not only helps remedy the CSO problem, but also improves 

the social and economic fabric of neighborhoods lacking green spaces.

Daylighting Streams to Improve 

Water Quality

Researchers compared the effectiveness of buried streams (streams that are 

paved over or routed into underground pipes during urban development) and 

open-air or daylighted streams at removing harmful nitrogen. The research 
shows daylighted streams are more effective at removing nitrates due to 

interactions with plants and other organic matter that feed on nitrates. 

Daylighting streams could prove to be a sustainable method for removing 

nitrogen and improving water quality.

Green Infrastructure at Fort Riley

Researchers with EPA’s Net Zero Program are working with the U.S. Army, 

U.S. Army Corps of Engineers, Kansas Unified School District 475, and other 

partners to demonstrate and assess green infrastructure technologies and 

performance at Fort Riley, an Army base in Kansas. EPA researchers are 

testing a permeable parking lot at Seitz Elementary School, which is located 

on Fort Riley. Researchers will measure how much rainwater passes through 

the pavement, how fast the permeable pavement clogs with debris, and 

changes in groundwater chemistry. They are also monitoring the school’s 

existing stormwater-capture-use system, which is a set of storage tanks that 

capture rain runoff. For this part of the study, researchers are measuring 

the amount of rooftop runoff that is captured and the chemistry of the water 

stored in the tanks.

Cincinnati Green Infrastructure Efforts 

The Lick Run stream in Cincinnati, Ohio is a part of a combined sewer system 

that spills its polluted mixture into the nearby Mill Creek during storm events. 

EPA researchers collaborated with the local sewer district to monitor and 

adjust several green infrastructure early success projects that are designed 

to reduce the amount of stormwater entering combined sewers and put it to 

good use elsewhere. 

Images above: vacant lot before and after 

transformation to green space and pervious pavement.
EPA Models and Tools 

EPA is developing innovative tools, technologies, and strategies for 

communities to manage water resources with green infrastructure to move 

toward more natural hydrology and increased resilience to future changes 

such as climate and extreme events.

Green Infrastructure Wizard (GIWiz) 

GIWiz is an interactive web application that connects communities to 

EPA green infrastructure tools and resources. GIWiz provides users with 

customized reports containing EPA tools and resources they select, direct 

links, and overview information about each. 

Watershed Management Optimization Support Tool (WMOST) 

WMOST is a software application designed to facilitate integrated water 

resource management across wet and dry climate regions. The tool allows 

water-resource managers and planners to screen a wide range of practices, 

including low impact development or green infrastructure, across a watershed 

for cost-effectiveness as well as environmental and economic sustainability. 

Visualizing Ecosystems for Land Management Assessment 

(VELMA)

VELMA is a computer software eco-hydrological model used to quantify the 

effectiveness of natural and engineered green infrastructure management 

practices for reducing nonpoint sources of nutrients and contaminants in 

streams, estuaries, and groundwater.

Storm Water Management Model (SWMM) 

SWMM models hydrology and hydraulics to simulate the movement of 

water through the landscape and into and through sewer systems. A 

green infrastructure module was added to SWMM in 2010 to simulate 

the integration of green infrastructure practices, ranging from green roofs 

to permeable parking lots, into a community’s stormwater management 

plan. SWMM is widely used throughout the world and considered the “gold 

standard” in the design of urban wet-weather flow pollution abatement 

approaches, and allows users to include any combination of low impact 

development/green infrastructure controls to determine their effectiveness in 

managing stormwater and sewer overflows. 
SWMM Climate Adjustment Tool (SWMM-CAT)

SWMM was updated to include a software utility that allows future climate 

change projections to be incorporated into modeling. SWMM-CAT provides 

a set of location-specific adjustments derived from World Climate Research 

Programme global climate change models. SWMM-CAT accepts monthly 

adjustment factors for climate-related variables that could represent the 

potential impact of future climate changes. 

National Stormwater Calculator (SWC) 

SWC is a desktop application that estimates the annual amount of 

stormwater runoff from a specific location in the United States (including 

Puerto Rico), based on local soil conditions, land cover, and historic rainfall 

records. It is used to inform site developers on how well they can meet a 

desired stormwater retention target with and without the use of green 

infrastructure. It also allows users to consider how runoff may vary based 

both on historical weather and potential future climate. SWC is a resource for 

all Rainwater Management Credits in LEED by the U.S. Green Building 

Council for all project types in all rating systems.

Greening EPA

EPA has buildings in over 40 locations across the country that are committed 

to promoting the Agency’s mission to protect human health and the natural 

environment by incorporating sustainability wherever possible. To support 

this commitment and provide an opportunity for needed research, EPA 

constructed an experimental parking lot with rain gardens as part of a longterm research project to quantify the effects of different permeable surfaces 

on stormwater runoff and the ability of rain gardens to accept, store and 

infiltrate stormwater.
Additional Information:

Green Infrastructure Research:

https://www.epa.gov/water-research/green-infrastructure-research

Green Infrastructure Overview: 

https://www.epa.gov/green-infrastructure

Greening EPA: 

https://www.epa.gov/greeningepa

Contact: 

EPA’s Office of Research & Development, Safe and Sustainable Water 

Resources Research Program, sswr@epa.gov