Green Infrastructure or Blue-green infrastructure is a network providing the “ingredients” for solving urban and climatic challenges by building with nature. The main components of this approach include stormwater management, climate adaptation, less heat stress, more biodiversity, food production, better air quality, sustainable energy production, clean water and healthy soils, as well as the more anthropocentric functions such as increased quality of life through recreation and providing shade and shelter in and around towns and cities.
Ideas for green urban structures began in the 1870s, with concepts of urban farming and garden allotments.
Green Infrastructure is a concept originating in the United States in the mid-1990s that highlights the importance of the natural environment in decisions about land-use planning. However, the term does not have a widely recognised definition. Also known as “blue-green infrastructure”  or “green-blue urban grids”  the terms are used by many design-, conservation- and planning related disciplines and commonly feature stormwater management, climate adaptation and multifunctional green space.
The term "green infrastructure" is sometimes expanded to "multifunctional" green infrastructure. Multifunctionality in this context refers to the integration and interaction of different functions or activities on the same piece of land.
The United States Environmental Protection Agency (EPA) has extended the concept of “green infrastructure” to apply to the management of stormwater runoff at the local level through the use of natural systems, or engineered systems that mimic natural systems, to treat polluted runoff. This use of the term "green infrastructure" to refer to urban "green" best management practices (BMPs), although not central to the larger concept, does contribute to the overall health of natural ecosystems.
However, it is apparent that the term “blue-green infrastructure” is applied in an urban context and places a greater emphasis on the management of stormwater as an integral part of creating a sustainable, multifunctional urban environment.
Context: The Role of Water
Today, many cities are facing severe water uncertainties, such as floods, droughts and upstream activities on trans-boundary rivers. The increasing pressure, intensity and speed of urbanisation has lead to the disappearance of any visible form of water infrastructure in most cities.
One fifth of the world’s population, 1.2 billion people, live in areas of water scarcity. Climate change and water-related disasters will place increasing demands on urban systems and will result in increased migration to urban areas. Cities require a very large input of freshwater and in turn have a huge impact on freshwater systems. Urban and industrial water use is projected to double by 2050.
In 2010 the UN declared access to clean water and sanitation a Human Right. New solutions for improving the sustainability of cities are being explored. Good urban water management is complex and requires not only water and wastewater infrastructure, but also pollution control and flood prevention. It requires coordination across many sectors and between different local authorities and changes in governance that lead to more sustainable and equitable use of the urban water resources.
The Green Infrastructure approach analyses the natural environment in a way that highlights its function and subsequently seeks to put in place, through regulatory or planning policy, mechanisms that safeguard critical natural areas. Where life support functions are found to be lacking, plans may propose how these can be put in place through landscaped and/or engineered improvements.
Within an urban context, this can be applied to re-introducing natural waterways  and making a city self-sustaining particularly with regard to water, for example, to harvest water locally, recycle it, re-use it and integrate stormwater management into everyday infrastructure.
The multi-functionality of this approach is key to the efficient and sustainable use of land, especially in a compact and bustling country such as England where pressures on land are particularly acute. An example might be an urban edge river floodplain which provides a repository for flood waters, acts as a nature reserve, provides a recreational green space and could also be productively farmed (probably through grazing). There is growing evidence that the natural environment also has a positive effect on human health
In the United Kingdom
In the United Kingdom, Green Infrastructure planning is increasingly recognised as a valuable approach for spatial planning and is now seen in national, regional and local planning and policy documents and strategies, for example in the Milton Keynes and South Midlands Growth area.
In 2009, guidance on green infrastructure planning was published by Natural England, and can be accessed online at  This guidance promotes the importance of green infrastructure in 'place-making', i.e. in recognizing and maintaining the character of a particular location, especially where new developments are planned.
In North West England the former Regional Spatial Strategy had a specific Green Infrastructure Policy (EM3 - Green Infrastructure) as well as other references to the concept in other land use development policies (e.g. DP6). The policy was supported by the North West Green Infrastructure Guide. The Green Infrastructure Think Tank (GrITT) provides the support for policy development in the region and manages the web site that acts as a repository for information on Green Infrastructure.
The Natural Economy Northwest programme has supported a number of projects, commissioned by The Mersey Forest to develop the evidence base for green infrastructure in the region. In particular work has been undertaken to look at the economic value of green infrastructure, the linkage between grey and green infrastructure and also to identify areas where green infrastructure may play critical role in helping to overcome issues such as risks of flood or poor air quality.
In March 2011, a prototype Green Infrastructure Valuation Toolkit was launched. The Toolkit is available under a Creative Commons licence, and provides a range of tools that provide economic valuation of green infrastructure interventions. The toolkit has been trialled in a number of areas and strategies, including the Liverpool Green Infrastructure Strategy.
In 2012, the Greater London Authority published the All London Green Grid Supplementary Planning Guidance (ALGG SPG) which proposes an integrated network of green and open spaces together with the Blue Ribbon Network of rivers and waterways. The ALGG SPG aims to promote the concept of green infrastructure, and increase its delivery by boroughs, developers, and communities, to benefit areas such as sustainable travel, flood management, healthy living and the economic and social uplift these support.
Green Infrastructure is being promoted as an effective and efficient response to projected climate change.
In the United States
Green infrastructure programs managed by EPA and partner organizations are intended to improve water quality generally through more extensive management of stormwater runoff. The practices are expected to reduce stress on traditional water drainage infrastructure--storm sewers and combined sewers—which are typically extensive networks of underground pipes and/or surface water channels in U.S. cities, towns and suburban areas. Improved stormwater management is expected to reduce the frequency of combined sewer overflows and sanitary sewer overflows, and provide other environmental benefits.
For example, the City of Philadelphia has installed or supported a variety of retrofit projects in neighborhoods throughout the city. Installed improvements include:
- permeable pavements in parks, basketball courts and parking lots
- rain gardens and bioretention systems at schools and other public facilities
- constructed wetlands for management of stormwater runoff.
Some of these facilities reduce the volume of runoff entering the city's aging combined sewer system, and thereby reduce the extent of system overflows during rainstorms.
Another US example, the State of Maryland, has promoted a program called GreenPrint. GreenPrint Maryland is a first in the nation web-enabled map showing the relative ecological importance of every parcel of land in the State.
Combining color-coded maps, information layers, and aerial photography with public openness and transparency, Greenprint Maryland applies the best environmental science and Geographic Information Systems (GIS) to the urgent work of preserving and protecting environmentally critical lands. A valuable new tool not only for making land conservation decisions today, but for building a broader and better informed public consensus for sustainable growth and land preservation decisions into the future.
The program was established in 2001 with the objective to “preserve an extensive, intertwined network of land vital to the long term survival of our native plants and wildlife and industries dependent on clean environment and abundant natural resources.”
In April 2011, EPA announced the Strategic Agenda to Protect Waters and Build More Livable Communities through Green Infrastructure and the selection of the first ten communities to be green infrastructure partners. The communities selected were: Austin, TX; Chelsea, MA; the Northeast Ohio Regional Sewer District (Cleveland, OH); the City and County of Denver, CO; Jacksonville, FL; Kansas City, MO; Los Angeles, CA; Puyallup, WA; Onondaga County and the City of Syracuse, NY; and Washington, DC.
Since 2009, two editions of the ABC (Active, Beautiful, Clean) Waters Design Guidelines have been published by the Public Utilities Board (PUB), Singapore. The latest version (2011) contains planning and design considerations for the holistic integration of drains, canals and reservoirs with the surrounding environment. PUB encourages the various stakeholders — landowners, private developers to incorporate ABC Waters design features into their developments, and the community to embrace these infrastructures for recreational & educational purposes.
The main benefits outlined in the ABC Waters Concept include:
- Treating stormwater runoff closer to the source naturally, without the use of chemicals through the use of plants and soil media, so that cleaner water is discharged into waterways and eventually our reservoirs.
- Enhancing biodiversity and site aesthetics.
- Bringing people closer to water, and creating new recreational and community spaces for people to enjoy.
In Fragile States
A 2012 paper by the Overseas Development Institute reviewed evidence of the economic impacts of green infrastructure in fragile states.
Upfront construction costs for GI were up to 8% higher than non-green infrastructure projects. Climate Finance was not adequately captured by Fragile states for GI investments, and governance issues may further hinder capability to take full advantage.
GI Investments needed strong government participation as well as institutional capacities and capabilities that fragile states may not possess. Potential poverty reduction includes improved agricultural yields and higher rural electrification rates, benefits that can be transmitted to other sectors of the economy not directly linked to the GI investment.
Whilst there are examples of GI investments creating new jobs in a number of sectors, it is unclear what the employment opportunities advantages are in respect to traditional infrastructure investments. The correct market conditions (i.e. labour regulations or energy demand) are also required in order to maximise employment creation opportunities.
Such factors that may not be fully exploited by fragile state governments lacking the capacity to do so. GI investments have a number of co-benefits including increased energy security and improved health outcomes, whilst a potential reduction of a country’s vulnerability to the negative effects of climate change being arguably the most important co-benefit for such investments in a fragile state context.
There is some evidence that GI options are taken into consideration during project appraisal. Engagement mostly occurs in projects specifically designed with green goals, hence there is no data showing decision making that lead to a shift towards any green alternative. Comparisons of costs, co-benefits, poverty reduction benefits or employment creation benefits between the two typologies are also not evident.
Nya Krokslätt, Sweden
The site of former factory “Nya Krokslätt” is situated between a mountain and a stream. Danish engineers, Ramboll, have designed a concept of slowing down and guiding storm water in the area with methods such as vegetation combined with ponds, streams and soak-away pits as well as glazed green-blue climate zones surrounding the buildings which delay and clean roof water and grey water. The design concept provides for a multifunctional, rich urban environment, which includes not only technical solutions for energy efficient buildings, but encompasses the implementation of blue-green infrastructure and ecosystem services in an urban area.
Since 1991, the city of Zürich has had a law stating all flat roofs (unless used as terraces) must be greened roofed surfaces. The main advantages as a result of this policy include increased biodiversity, rainwater storage and outflow delay, and micro-climatic compensation (temperature extremes, radiation balance, evaporation and filtration efficiency). Roof biotopes are stepping stones which, together with the earthbound green areas and the seeds distributed by wind and birds, make an important contribution to the urban green infrastructure.
In the old industrial area of the Ruhr District in Germany, Duisburg-Nord is a landscape park which incorporates former industrial structures and natural biodiversity. The architects Latz + Partner developed the water park which now consists of the old River Emscher, subdivided into five main sections: Klarwasserkanal (Clear Water Canal), the Emschergraben (Dyke), the Emscherrinne (Channel), the Emscherschlucht (Gorge) and the Emscherbach (Stream). The open waste water canal of the “Old Emscher” river is now fed gradually by rainwater collection through a series of barrages and water shoots. This gradual supply means that, even in lengthy dry spells, water can be supplied to the Old Emscher to replenish the oxygen levels. This has allowed the canalised river bed to become a valley with possibilities for nature development and recreation. As a key part of the ecological objectives, much of the overgrown areas of the property were included in the plan as they were found to contain a wide diversity of flora and fauna, including threatened species from the red list. Another important theme in the development of the plan was to make the water system visible, in order to stimulate a relationship between visitors and the water.
New York Sun Works Center, US
The Greenhouse Project was started in 2008 by a small group of public school parents and educators to facilitate hands-on learning, not only to teach about food and nutrition, but also to help children make educated choices regarding their impact on the environment. The laboratory is typically built as a traditional greenhouse on school rooftops and accommodates a hydroponic urban farm and environmental science laboratory. It includes solar panels, hydroponic growing systems, a rainwater catchment system, a weather station and a vermi composting station. Main topics of education include nutrition, water resource management, efficient land use, climate change, biodiversity, conservation, contamination, pollution, waste management, and sustainable development. Students learn the relationship between humans and the environment and gain a greater appreciation of sustainable development and its direct relationship to cultural diversity.
Hammarby Sjöstad, Stokholm, Sweden
In the early 1990s, Hammarby Sjöstad had a reputation for being a run-down, polluted and unsafe industrial and residential area. Now, it is a new district in Stockholm where the City has imposed tough environmental requirements on buildings, technical installations and the traffic environment. An ‘eco-cycle’ solution named the Hammarby Model, developed by Fortum, Stockholm Water Company and the Stockholm Waste Management Administration, is an integral energy, waste and water system for both housing and offices. The goal is to create a residential environment based on sustainable resource usage. Examples include waste heat from the treated wastewater being used for heating up the water in the district heating system, rainwater runoff is returned to the natural cycle through infiltration in green roofs and treatment pools, sludge from the local wastewater treatment is recycled as fertiliser for farming and forestry. This sustainable model has been a source of inspiration to many urban development projects including the Toronto (Canada) Waterfront, London's New Wembley, and a number of cities/city areas in China.
The continued development of Geographic Information Systems (GIS) and their increasing level of use is particularly important in the development of Green Infrastructure plans. The plans frequently are based on GIS anaysis of many layers of geographic information.
A 2012 study found that 44% of green infrastructure projects reduce costs compared to 31% that increased costs. The study focused on 479 green infrastructure projects from across the US. Reduced stormwater runoff and decreased heating and cooling costs are the most notable cost savings.
- European green infrastructure
- Low-impact development
- Sustainable urban drainage systems
- Watershed Central
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- PaveShare - Permeable Paver Design
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- Save the Rain - Onondaga County, NY
- Maryland's Green Infrastructure- Maryland Department of Natural Resources
- Sonoran Desert Conservation Plan - Pima County, Arizona
- The Center for Green Infrastructure Design - The Center for Green Infrastructure Design
- Green Infrastructure Wiki
- Low Impact Development - The Low Impact Development Center
- Green Infrastructure Resource Center - American Society of Landscape Architects