Green Infrastructure & Nature-based Solutions Overviews

Climate change is fueling more intense weather and compounding the impact of hazards that communities are dealing with already, such as flooding and heat waves.  Aging infrastructure and stronger, more frequent storms are a rising challenge to communities around the globe as they seek to rapidly adapt to a changing world.  This “new normal” is constantly testing traditional ideas on hazard mitigation and how communities recover from natural disasters.

Knowing that every $1 spent on mitigation at the local level saves $6 on recover efforts, communities are looking for economically viable mitigation solutions.

Nature-based solutions refer to managed landscape strategies designed to mimic nature by creating holistic and integrated solutions that provide essential services like a clean water supply, drought mitigation, and flood control. Research shows that nature-based solutions can provide more co-benefits to a community than traditional forms of gray infrastructure, while also reducing overall costs to build and maintain over the life of the system.

Projects that restore and/or emulate natural systems to increase human, ecosystem, and infrastructure resilience to climate impacts­­––often referred to as nature-based solutions or Green Infrastructure ––can reduce damage from natural hazards as well as (or better than) traditional engineered projects, often at less cost.


What is Green Infrastructure?

In the past, the main goal to manage stormwater was to drain it as quickly as possible. With the advent of Low Impact Development (LID) and Green Infrastructure (GI), rainwater is treated as a resource and not as a waste product. This approach reduces the impact of development on receiving streams and on increasing flood risk.

In its simplest terms, green infrastructure is an approach to stormwater management and flood mitigation that provides areas for water to soak into the ground, or evaporate back into the air, rather than forming runoff and leading to flooding. 

As communities historically developed, the amount of impervious surfaces such as roads, sidewalks, and parking lots within the community increased.  These surfaces are referred to as impervious because they do not allow rainwater to soak into the ground.  Community flood risk increases as the area of impervious surface increases.  Since rainwater falling on impervious surfaces is not able to soak into the ground, it must either run off of that surface or collect in low-lying areas.

LID/GI uses natural features and engineered controls to reduce runoff volume through infiltration, evapotranspiration, or rainwater harvesting. Also, stream buffer plantings slow down and infiltrate runoff, keeping streambanks stable. Healthy vegetation, groundwater recharge, and wildlife habitat are side benefits that create more livable communities.


Why the Need for Green Infrastructure

Most communities have some type of stormwater collection system comprised of storm drains and pipes.  These systems are referred to as grey infrastructure because they are constructed of man-made materials and are engineered and designed to collect water and move rainwater rapidly out of the community.  However, these systems are often undersized and outdated compared to the increases in impervious surfaces within the community over time.  As these grey infrastructure systems become overwhelmed, they are no longer able to collect additional stormwater runoff.  That excess runoff then flows across the surface of the community and collects in low-lying areas, leading to localized flooding.

Stormwater runoff in urban areas is also a major cause of water pollution.  As rain water runs off the ground, it can collect and carry trash, bacteria, and heavy metals.  These pollutants are ultimately carried to local streams and rivers.  As high volumes of runoff enter local streams, there is also a rapid increase in the water levels in those streams.  This increases the impacts of localized flooding, streambank erosion, destruction of property, and in some cases flash flooding. Increases in impervious surface area means that even smaller storm events can lead to flooding because the overall volume of stormwater runoff increases.

  • Natural infrastructure — These projects restore or use existing natural systems and landscapes (such as forests, floodplains, and wetlands) to increase resilience to climate impacts.  Natural infrastructure projects often support habitat restoration as described below.
  • Urban focus — Nature-based solutions, such as increasing tree canopies, can be incorporated into urban environments to improve resilience to climate impacts such as extreme heat and flooding.
  • Habitat restoration — Natural habitats preserved or restored to protect biodiversity and improve habitat health can mitigate climate impacts. 
  • Flood prevention — Nature-based solutions can help mitigate flooding cost-effectively by absorbing and reducing runoff..
  • Water quality — Nature-based solutions that reduce runoff and increase filtration minimize pollution and improve water quality.  In addition, clean water improves the effectiveness of nature-based solutions along riverine areas, which allows the solutions to better support climate adaptation and mitigation.
  • Pollution abatement — Several types of pollution, especially air, water, and soil pollution, can be reduced through nature-based solutions.  Pollution abatement with nature-based solutions, such as planting and maintaining trees and enhancing soil quality, also serves as a mechanism for climate adaptation (i.e., water storage) and mitigation (i.e., carbon sequestration).
  • Disaster mitigation — Nature-based solutions aid in disaster mitigation by helping “communities prepare for, cope with, and recover from disasters, including slow-onset events such as droughts.”



Nature-based Solutions Approach

Nature-based solutions are locally appropriate, cost-effective practices that mimic or support natural processes (like restoring floodplains to help store excess flood waters) while simultaneously providing economic, social, and environmental benefits.

Why take a nature-based approach? 

With the increase in frequency and duration of severe weather events becoming the new normal, communities are facing growing pressure to develop strategies that protect vulnerable populations and infrastructure from flooding and other water quantity issues.

Extreme rain events can exacerbate runoff of water quality-degrading pollutants, such as sediments and nutrients.  Nature-based solutions that provide filtration of pollutants from stormwater runoff may also slow quick flowing water and improve water infiltrating into the soil, thereby reducing erosion and flooding while simultaneously protecting water quality and controlling water quantity.

By supporting the natural sponge-like function of soils, for example, such actions can also help combat drought conditions by maintaining moisture in the ground.  

Living shorelines, restored wetlands, reforestation projects, and green (vegetative) roofs are just a few examples of nature-based solutions.  They provide multiple environmental, economic, and social benefits, including carbon sequestration, which is a key tool for reducing greenhouse gas emissions.

Green Infrastructure Examples

Green infrastructure — Typically, green infrastructure is a built or engineered solution such as a green roof or bioswale.  See examples below.

  • Downspout disconnection – This simple practice reroutes rooftop drainage pipes from draining rainwater into the storm sewer to draining it into rain barrels, cisterns, or permeable areas. It can be used to store stormwater and/or allow stormwater to infiltrate into the soil.
  • Rainwater harvesting – systems collect and store rainfall for later use. When designed appropriately, they slow and reduce runoff and provide a source of water. This practice is particularly valuable in arid regions, where it could reduce demands on increasingly limited water supplies.
  • Rain gardens – are versatile features that can be installed in almost any unpaved space. Also, known as bioretention, or micro-bioretention cells, these shallow, vegetated basins collect and absorb runoff from rooftops, sidewalks, and streets. This practice mimics natural hydrology by infiltrating, evaporating, and transpiring stormwater runoff.
  • Bioswales – are vegetated, mulched, or xeriscaped channels that provide stormwater treatment and retention as it moves from one place to another. Vegetated swales slow, infiltrate, and filter stormwater flows. As linear features, they are particularly well suited to being placed along streets and parking lots.
  • Permeable Pavement – infiltrate, treat, and/or store rainwater where it falls. They can be made of pervious concrete, porous asphalt, or permeable interlocking pavers. This practice could be particularly cost effective where land values are high and flooding or icing is a problem.
  • Green roofs – are covered with growing media and vegetation that enable rainfall infiltration and evapotranspiration of stored water. They are particularly cost-effective in dense urban areas where land values and stormwater management costs are likely to be high.
  • Urban tree canopy – a Trees reduce and slow stormwater by intercepting precipitation in their leaves and branches. Many cities have set tree canopy goals to restore some of the benefits of trees that were lost when the areas were developed. Homeowners, businesses and community groups can participate in planting and maintaining trees throughout the urban environment.
  • Planter Boxes – are urban rain gardens with vertical walls and either open or closed bottoms. They collect and absorb runoff from roofs, sidewalks, parking lots, and streets and are ideal for space-limited school sites in dense urban areas.

Learn about Green Infrastructure

EPA has many resources to implement green infrastructure in your community.  Learn more:

Visit EPA’s Green Infrastructure Website.   The website provides a variety of information on planning,
constructing, and maintaining green


Green Infrastructure Wizard Connects Communities to Resources

EPA released a new web-based tool, the Green Infrastructure Wizard (GIWiz), to help local officials and community members find tools and resources more easily. GIWiz offers quick, direct access to Green Infrastructure tools and resources that can support and promote water management and community planning decisions.

Users can produce customized reports that include links to the resources they want to use.

Click to Use the Wizard to search for resources for your community.


Building Community Resilience with Nature-Based Solutions – A Guide for Local Communities

August 2020

The focus of this FEMA guide is local communities, but many of the ideas and advice may also apply to state, territorial, and tribal governments.  Natural hazards such as flooding, high wind, drought, and landslides pose major threats to communities across the U. S. Reducing the threats they pose to lives, properties, and the economy is a top priority for many communities.  The National Mitigation Investment Strategy identifies nature-based solutions as a cost-effective approach to keep natural hazards from becoming costly disasters.  The promise of nature-based solutions comes from the many benefits they offer and the many partners they can draw to the table.

Nature-based solutions weave natural features and processes into a community’s landscape through planning, design, and engineering practices.  These practices can be applied to a community’s-built environment (for example, a stormwater park) or its natural areas (for example, land conservation).  While nature-based solutions have many hazard mitigation benefits, they can also help a community meet its social, environmental, and economic goals.  Communities across the country are finding nature-based solutions to be a highly effective way to provide public services that were traditionally met with structural or “gray” infrastructure. 

The key goal of this guide is to help communities identify and engage the staff and resources that can play a role in building resilience with nature-based solutions.  Planning and building cost-effective nature-based solutions will require collaboration.  Many departments may need to be involved in planning and carrying out the strategies in this guide.  Consider including the following local government partners:

  • Parks and Recreation
  • Public Works
  • Planning and Economic Development
  • Environmental Protection
  • Utilities
  • Transportation
  • Floodplain Administration
  • Emergency Management

In addition, non-governmental community partners like civic associations, watershed groups, and non-profit organizations should be involved in the planning process.  They may have the capacity to customize and implement nature-based solutions.

Download the Building Community Resilience with Nature-Based Solutions – A Guide for Local Communities


Step-by-Step Guide to Integrating Community Input into Green Infrastructure Projects

April, 2018

Many communities are turning to “green infrastructure” to reduce flooding, clean and conserve water, and provide recreational and other benefits.  But how can local governments ensure they’re meeting the needs of the community?  The Step-by-Step Guide to Integrating Community Input into Green Infrastructure Projects shows how.

The guide provides details and tips to help local governments as they move through the decision making process in eight, easy-to-digest steps.  While the guide is directed largely at local governments, it could also be a useful resource for other groups such as community and nonprofit organizations that are looking to implement green infrastructure projects in their communities.

Download the Step-by-Step Guide to Integrating Community Input into Green Infrastructure Projects.

For additional information, visit ELI’s Green Infrastructure Program.


Flood Avoidance Green Infrastructure

December 14, 2015

To address the impacts of excess stormwater, the U.S. Environmental Protection Agency (EPA) evaluated potential scenarios for managing stormwater from new development and redevelopment.  The purpose of this study is to examine one of these impacts: flood loss avoidance.  This study generated an estimate of the monetary value of flood loss avoidance that could be achieved by using distributed stormwater controls to capture a specified volume of runoff. 

This stormwater management approach retains on-site small storm events in an attempt to simulate predevelopment runoff conditions.  This approach is referred to as Low Impact Development (LID) or Green Infrastructure (GI) for stormwater management and is an integrated approach that uses site planning and small engineered stormwater controls spatially distributed throughout a development site to capture runoff as close as possible to where it is generated.  In this document, the term Green Infrastructure is used for bioretention filters, landscaped roofs, rainwater cisterns, and infiltration trenches are examples of stormwater controls commonly found in GI applications.  These controls infiltrate and evapotranspire runoff, or capture and store rain for beneficial uses like landscape irrigation and other non-potable uses.  The approach in this study considered the application of GI only to new development and redevelopment, not as retrofits to mitigate the impact of existing imperviousness.

The study approach consists of estimating flood depths and the associated flood losses with and without GI.  The benefits are the losses that are avoided by watershed-wide implementation of GI.  In this report, the terms “damages” and “flood losses” are used interchangeably.  The timeframe of analysis is from 2020 to 2040.  The extent of GI application assumed for this study is small initially, because the assumption in this study is that GI would be implemented only on new development and redevelopment starting in 2020.  The extent of GI application, and the associated benefits, would increase with development over time.  Therefore, maximum benefits are realized in 2040, the last year of this study period.  At the time of this report, several states have already adopted on-site retention practices; therefore, benefits of wider adoption nationwide are the focus of this study (i.e., the study focuses on areas that have not adopted retention policies to date).

Download the Flood Loss Avoidance Benefits of Green Infrastructure for Stormwater Management.



Community Funding

Communities can easily integrate green infrastructure initiatives into other community improvement or capital projects such as

  • transportation corridor upgrades,
  • pedestrian safety upgrades,
  • neighborhood revitalization efforts,
  • road repaving, and
  • utility work.

By integrating green infrastructure into these planned projects, communities can achieve significant cost savings as compared to retrofit projects focused solely on installing green infrastructure practices. Education for private developers can help them include green infrastructure into their designs.


Financing Green Infrastructure Projects

December 2017

Municipal budget officers have long been familiar with the intricacies of capital improvement planning, which allows governments to align infrastructure investments with their communities’ long-range comprehensive plans.

Conventional stormwater management systems (often called “gray”) contain stormwater runoff in reservoirs and massive underground pipes and tunnels—large scale public works projects—to pre­vent polluted runoff from draining directly into waterways.  

Read more, link to the APA and NRPA Financing Green Infrastructure Projects.


Using Low Impact Development and Green Infrastructure to Get Benefits From FEMA Programs

EPA promotes the use of Low Impact Development (LID) and Green Infrastructure (GI) as a cost-effective and resilient approach to stormwater management.  LID/GI provides many community benefits including cleaner water, wildlife habitat, enhanced aesthetics, and can be designed to supplement localized or watershed flood protection.

LID/GI projects that reduce flood losses to properties insured under the NFIP may be eligible for grant funding through FEMA.  In addition, LID/GI projects may allow a community to claim points toward flood insurance discounts.

LID/GI ordinances and other environmental planning may allow a community to claim points toward flood insurance discounts under the Community Rating System (CRS) developed by FEMA.  LID/GI projects that reduce flood losses to properties insured under the NFIP may be eligible for grant funding through FEMA.



Working with the Markets: Economic Instruments to Support Investment in Green Stormwater Infrastructure 2017

By Seth Brown, Storm & Stream Solutions, LLC and Carrie Sanneman, Williamette Partnership

Urban stormwater runoff is one of the most significant environmental issues facing communities today.  Flooding, water supply, water quality, habitat degradation, and other impacts associated with runoff are increasing due to urbanization, more episodic climatic regime, and rising temperatures.

Communities are in need of cost-effective and innovative ways to drive investment and implementation of green infrastructure for stormwater management.  This report summarizes how stormwater managers can work with market forces, applying “economic instruments” to address these critical issues and meet their program goals.  Economic instruments recognize and deliberately work within the economic system to create action or drive investment that meets environmental goals.  They include the use of rebates, subsides, trading, and mitigation.  Economic instruments are a useful tool for stormwater managers because they can:

  • Increase the coverage of green infrastructure on both public and private lands, for new development and urban retrofits;
  • Provide flexibility for regulated entities trying to meet stormwater requirements;
  • Provide a vehicle for both public and private investments; and
  • Enhance the efficiency of delivering benefits associated with stormwater infrastructure.

Incentives-based approaches motivate the installation of stormwater controls by offering cost avoidance, financial gain, or program/project support.  Stormwater programs often use rebates, subsidies, or project/logistical support as an incentive for private parties to install green infrastructure.  Mitigation or credit-based approaches are those in which stormwater benefits are quantified as a currency or “credit” and traded between parties to mitigate or offset regulatory requirements.  This creates an incentive for pollution controls to occur where it is most cost-effective to do so.  These programs provide flexibility for regulated parties and create an incentive to develop new, more cost effective methods to reduce pollution and/or control stormwater volume.

Read more about Willamette Partnership publications resources.


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