Broadly called “green infrastructure,” this new set of strategies seeks to manage stormwater, reduce urban heat island effects, improve air quality, and promote economic development and other sustainability goals. Green infrastructure provides an attractive alternative to traditional concrete (or “gray”) infrastructure by making paved and hard surfaces vegetated or permeable. Permeable pavements and green roofs both capture rainfall and retain it on site, keeping it out of the stormwater system. Green infrastructure also provides wildlife habitat and greenhouse gas reduction benefits. While vanguard communities are innovating, most others are struggling to know where to begin. And while the professional design community has explored a new generation of best design practices, municipal policy frameworks have not incorporated these practices appropriately. In addition, limited resources are available to help jurisdictions develop technical expertise and share best practices. This Green Infrastructure Toolkit was developed in collaboration with leading cities to help them identify and deploy green infrastructure approaches in their communities.
This toolkit is powered by the Georgetown Climate Center's Adaptation Clearinghouse. For a full list of resources on green infrastructructure in the Adaptation Clearinghouse click here.
Local governments across the country face serious challenges in managing urban stormwater (surface water runoff resulting from rainfall or snowmelt). Aging infrastructure, changes in precipitation patterns, watershed deforestation, and impervious surfaces such as roadways and parking lots cause urban flooding that pollutes waterways. Climate change will exacerbate these flood risks in many places due to more intense storms that could overwhelm existing infrastructure systems. If we fail to adapt these systems, severe repetitive flooding will increasingly affect community health, safety, and welfare, and the consequences of flooding often impose a disproportionate toll on the most vulnerable and disadvantaged populations and communities.
Innovative local communities and regions are beginning to implement a wide array of new “green infrastructure” measures, which retain and treat stormwater where it falls instead of relying on traditional, concrete-based systems largely underground. In order to ensure effective implementation, this toolkit identifies the best green infrastructure practices from cities across the country to guide those still designing their programs.
Conventional development and drainage techniques, also known as gray infrastructure, include man-made, constructed assets like roads and sewers.See footnote 1 “Gray surface infrastructure” covers natural landscapes with impervious surfaces such as concrete, asphalt, tile, or compacted gravel that increase the rate and volume of stormwater runoff. Stormwater runoff carries trash, bacteria, heavy metals, and other pollutants from the urban landscape to nearby waterways. Gray stormwater infrastructure generally uses large tunnels or other underground conveyances to move or store stormwater to treatment facilities.See footnote 2
Green infrastructure, in contrast, includes techniques such as using permeable pavements and green roofs to both capture rainfall and retain it on site, keeping it out of the stormwater system.
These techniques also provide a multitude of benefits. Green infrastructure can:
- reduce urban heat island effects through evaporation of infiltrated water and through shade provided by urban forests;See footnote 3
- improve air quality through increases in vegetation to filter pollutants, as well as indirectly from lowering temperatures (smog forms more easily at higher temperatures);See footnote 4
- absorb carbon, because vegetation uses carbon dioxide as part of photosynthesis;See footnote 5
- improve water quality by reducing runoff and filtering pollutants from the runoff that infiltrates or gets stored;See footnote 6 and
- provide urban recreational and open space.See footnote 7
Building green infrastructure is not without challenges, however. In past years stormwater managers have struggled to quantify the effectiveness of green infrastructure, especially as compared to gray infrastructure. Ongoing monitoring programs are detailed in the Getting Started chapter of this toolkit. Green infrastructure can require collaboration by multiple local agencies that do not always work closely, such as transportation, stormwater, and public health. Successful collaboration efforts are also detailed in the Getting Started chapter. Last but not least, green infrastructure requires different, ongoing maintenance than traditional stormwater infrastructure. Coordinating and paying for that ongoing maintenance can be difficult to plan and implement. The Scaling Up chapter and Funding chapter describes how local governments are beginning to solve the maintenance challenge.
While vanguard communities are innovating, many others are struggling to know where to begin. And while the professional design community has developed a new generation of best design practices, municipal policy frameworks (land-use regulations, street design, etc.) have not institutionalized these practices appropriately. In addition, limited resources are available to help jurisdictions develop technical expertise and share best practices. This toolkit therefore has a chapter dedicated to incorporating green infrastructure practices into jurisdiction-wide plans and processes, from comprehensive plans to zoning and building codes.
Green infrastructure also has to operate within legal and regulatory frameworks at the federal, state, and local level. The Clean Water Act, for example, requires the US Environmental Protection Agency (EPA) to address stormwater runoffSee footnote 8 in its effort to “restore the chemical, physical and biological integrity” of the waters of the nation.See footnote 9 In doing so, EPA has created consent agreements with many municipal governments. These agreements legally require cities to come into compliance with the Clean Water Act’s requirements including controlling overflows from combined sewer systems. Local governments can incorporate green infrastructure practices in addition to gray infrastructure; cities from Louisville, KY to Chicago, IL, have incorporated green infrastructure into those formal agreements.See footnote 10
State and local legal authority questions also affect implementation of green infrastructure at the local level. For example, some local governments have funded green infrastructure by setting up a stormwater utility or charging stormwater fees. However, to do so, local governments need specific authority delegated from their state legislatures authorizing the creation of a stormwater utility and the collection of those fees. The absence of the legal authority to establish a stormwater utility or to establish a stormwater fee can hinder a local government’s ability to implement and pay for green infrastructure. Finally, constraints in some states on local authority over zoning or building codes can diminish a city’s ability to change policy to require or encourage green infrastructure. This toolkit addresses these legal constraints and requirements where appropriate throughout.
The next tab in this introductory chapter introduces different green infrastructure techniques and their various applications.