Helmfinal dissertationredsize

What Are The Benefits of Retrofitting Green Infrastructure Into The Existing Urban Fabric of The UK?

Jacob Helm

A thesis submitted in partial fulfilment of the Master of Arts in Landscape Architecture

Manchester School of Architecture August 2013

Contents Page 1

Introduction.

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The environmental problems associated with existing high density urban landscapes within the UK.

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The potential for retrofitting green infrastructure within existing high density urban landscapes.

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Retrofitting green infrastructure: methods, benefits and values.

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Case studies.

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Conclusion.

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References.

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1

Introduction.

At present urban landscapes experience and contribute to a wide range of well documented environmental problems within their own boundaries ranging from flooding through to the ‘heat island effect’ (RCEP. 2007), but urban areas have environmental impacts that can be felt globally. The unprecedented rates of urban population growth over the past century have occurred on <3% of the global terrestrial surface, yet the impact has been global, with 78% of carbon emissions, 60% of residential water use, and 76% of wood used for industrial purposes attributed to cities (Grimm et al. 2008).

The notion of achieving sustainability within urban landscapes is a relatively recent concept within urban planning. Local Agenda 21 (1992) a non-binding, voluntarily implemented action plan of the United Nations with regard to sustainable development and the Charter of European Cities & Towns Towards Sustainability (1994) were the first international policy agreements to highlight the need for achieving sustainability within urban environments.

These documents laid the foundation for government planning policy which is included within the 2012 National Planning Policy Framework (NPPF). The NPPF includes a ‘presumption in favour of sustainable development’ and sets out core planning principals including:

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Support the transition to a low carbon future in a changing climate, taking full account of flood risk and coastal change, and encourage the reuse of existing resources, including conversion of existing buildings, and encourage the use of renewable resources.

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â&#x20AC;˘

Promote mixed use developments, and encourage multiple benefits from the use of land in urban and rural areas, recognising that some open land can perform many functions (such as for wildlife, recreation, flood risk mitigation, carbon storage, or food production).

Urban sustainability requires minimizing the consumption of space and resources, optimizing urban form to facilitate urban flows, protecting both ecosystem and human health, ensuring equal access to resources and services, and maintaining cultural and social diversity and integrity (Wu J. 2009). This approach can be achieved with relative ease within developments on previously undeveloped land, but within the UK the rate at which land use alters is slow (0.7% over the period 1995-98 in England; White I. 2008) and according to some estimates at current rates of turnover an average dwelling in the UK would have a lifetime of around 1,000 years (ECI. 2005).

Consequently designers, engineers and planners now face the challenge of transforming existing urban landscapes into sustainable models. The retrofitting of green infrastructure within these environments is one method through which this aspiration can be achieved.

Green infrastructure can be considered as a planning and design concept that is: â&#x20AC;&#x153;principally structured by a hybrid hydrological/drainage network, complementing and linking relict green areas with built infrastructure that provide ecological functions, applying key principles of landscape ecology to urban environments, specifically: a multi-scale approach with explicit attention

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to pattern: process relationships, and an emphasis on connectivityâ&#x20AC;? (Ahern J. 2007).

This paper will concentrate the on the small scale practical elements of green infrastructure that have potential to be retrofitted within existing urban environments and schemes that illustrate the principle that modest, incremental and decentralized green infrastructure can have a significant cumulative effect to improve the urban ecology.

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The environmental problems associated with existing high density urban landscapes within the UK.

There have been significant environmental improvements in urban areas over the past 150 years. As part of the reform movement the Victorians’ created areas of public open space and introduced sanitation measures into towns and city’s to overcome the deleterious environmental effects of the industrial revolution (Ashley et al. 2011). The Clean Air Act of 1950 and the decontamination of rivers during the 1980s and 1990s combined with the replacement of heavy industry within towns by light manufacturing and the service sector show that it is possible to bring about radical environmental improvements in urban areas. Nevertheless urban landscapes still experience and contribute to a wide range of well documented environmental problems ranging from flooding through to air pollution (RCEP. 2007).

These problems have four major biophysical effects. “Firstly, urbanisation affects climate; cities tend to be hotter than the surrounding countryside and create what is known as an urban heat island. Second, urbanisation affects hydrology; cities shed more water as run-off into streams and rivers. Third, cities are net produces of carbon dioxide and have lower amounts of stored carbon. Fourth, cities are widely regarded as having lower biodiversity” (Whitford et al. 2001). Figures 1 and 2 illustrate the affects of urbanisation on the transfer of energy in relation to the heat island effect and the affects of urbanisation on hydrology. These problems can be primarily attributed to the massive reduction in vegetation urban areas experience in comparison with rural areas of a similar geographical location (Bridgman et al. 1995).

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Figure 1. The simplified effects of urbanisation on the transfers of energy that contribute to the build-up of an urban heat island. (A) the situation in rural areas; (B) the situation in urban areas.

Urban areas absorb and store more heat than rural areas due to the increase in buildings and roads that have a higher thermal storage capacity and a lower albedo. Thus, the urban heat island effect may result in the ambient temperatures of towns and cities being 1ยบ to 6ยบC higher than those in the surrounding countryside (RCEP. 2007).

Figure 2. The simplified effects of urbanisation on hydrology.(A) the situation in rural areas; (B) the situation in urban areas.

Within urban areas infiltration is reduced due to the increase in impermeable surfaces and evaporation is reduced due to the reduction in vegetation. Consequently surface runoff is increased placing increased pressure on urban drainage systems at times of peak flow.

Within the UK 80,000 properties are at risk of flooding caused by heavy rain overwhelming urban drainage systems (Evans et al. 2004).

A study by a multidisciplinary team from the University of Manchester (Whitford et al. 2001) demonstrates that there is a direct relationship between urban density and ecological performance, with high density urban landscapes experiencing increasingly severe environmental problems in comparison with less dense areas with a higher percentage of green space.

The study used ecological performance indicators to measure the four major 5

quantifiable ecological effects of urbanisation; surface temperature, hydrology, carbon storage and sequestration, and biodiversity. These indicators were applied to four residential urban areas of Liverpool: Sherdley Park (Fig 3), an affluent area dominated by detached and semi-detached houses, Claughton (Fig 4), an area of Victorian villas with established tree cover (both have a high percentage of green space and low urban density), Wavertree (Fig 5) an area of terraced housing and Scotland Road (Fig 6) an area of low-rise flats. (both have a high urban density and little or no green space). These areas are typical of many of the residential urban landscapes found throughout the UK.

Figure 3. Typical street scene: Sherdley Park

Figure 4. Typical street scene: Claughton

Figure 5. Typical street scene: Wavertree

Figure 6. Typical street scene: Scotland Road

The results of the study (Figures 7 â&#x20AC;&#x201C; 10) illustrate that there is a direct correlation between ecological performance and urban density. The areas of highest urban density (Wavertree and Scotland Road) showed the poorest

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ecological performance with higher maximum and minimum temperatures (Fig 7), higher run-off coefficients (Fig 8), lower carbon storage and sequestration (Fig 9), and lower proportion and diversity of green space (Fig 10).

Figure 7. Variation of surface temperature with area of greenspace at the four sites.

The graph illustrates the relationship between urban density, greenspace and temperature.

The areas with the highest urban density and lowest proportion of greenspace (Wavertree and Scotland Road) have the highest minimum and maximum temperatures. The variation in o landscape conditions results in a maximum temperature difference of 7 C between Sherdley Park and Wavertree. The higher temperatures can result in an increased demand for air conditioning and hence greater energy use and enhanced CO2 emissions. Public health can also be effected. The heat wave of 2003 is estimated to have contributed to 2091 excess deaths, the majority of which occurred in urban areas (HSQ. 2005).

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Figure 8. Variation of runoff coefficient with area of greenspace at the four sites.

The graph illustrates the relationship between urban density, greenspace and surface runoff.

The runoff coefficient within the area of highest urban density and lowest proportion of greenspace (Wavertree) is 0.3 higher than the area with the lowest urban density and highest proportion of greenspace (Sherdley Park). The increase in surface runoff can have serious effects within urban areas resulting in higher peak flows within drainage systems and rivers.

This can lead to increased likelihood of flooding and bank erosion.

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Figure 9. Carbon stored and sequestered at the four sites.

The graph illustrates the relationship between urban density, greenspace and, carbon storage and sequestration. Claughton, an area with mature tree lined streets has the highest levels of carbon storage and sequestration indicating that it is the level of tree cover that has the greatest influence over carbon storage and sequestration. The areas of high urban density (Wavertree and Scotland Road) achieve all most no carbon storage and sequestration.

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Figure 10. Comparison of green area, structural diversity and a combined index as indicators of biodiversity potential at the four sites.

The graph illustrates that the areas with the highest urban density (Wavertree and Scotland Road) have approximately 50% less area of green space and structural diversity than the areas of low urban density(Sherdley Park and Claughton).

The study highlights that the dominant influence on ecological performance is clearly the proportion of green space, which is in turn related to urban density.

The study also emphasises the relationship between affluence and ecological performance, as affluent areas generally have a lower urban density and a greater proportion of green space resulting in better overall ecological performance.

A study by the Engineering and Physical Sciences Research Council (Gill et al. 2007) calculated the proportional surface cover of high, medium and low density residential urban morphology types within Greater Manchester (Fig

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11). The study focuses on residential urban morphology types as residential areas are the dominant landscape category within most towns and cityâ&#x20AC;&#x2122;s urban mosaics (Forman et al. 1986) and therefore have a greater impact on the environmental performance of conurbations (Gill et al. 2007). Of the three residential morphology types the high density landscapes have double the level of impervious surfaces compared to low density areas and a much lower percentage of tree cover with only 7% of the total area compared to 27% in low density areas.

Figure 11. Proportional surface cover in high, medium and low density residential urban morphology types within Grater Manchester.

The results of the studies show that within urban landscapes there is a link between density, area of impermeable surface and the proportion of green space. Within high density urban landscapes it is the increased levels of impermeable surface and lack of vegetation that results in them becoming disconnected from the processes that regulate â&#x20AC;&#x153;naturalâ&#x20AC;? ecosystems (Gill et al.

2007) and it is this disconnection that leads to many of the environmental problems they currently experience (Whitford et al. 2001). If currant trends continue the environmental problems associated with high density urban

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landscapes are set to increase. The average building density for new developments in the UK has increased from 25 to 44 dwellings per hectare between 2001 and 2007 (DCLG. 2006), and in some areas up to 47% of front gardens have been paved over (RHS. 2006).

Climate change will also amplify the environmental problems faced by high density urban landscapes. The UKCIP02 Scientific Report predicts average annual temperatures may increase by between1째C and 5째C by 2080, with summer temperatures expected to increase more than winter temperatures.

There will also be a change in the seasonality of precipitation, with winters up to 30% wetter by the 2080s and summers up to 50% drier. These climate change scenarios do not take urban environmental conditions into account and it is likely that without intervention urban environments will experience significantly higher temperatures (Wilby RL. 2003) and increased levels of flooding in the future (RCEP. 2007). The biophysical features of green infrastructure in urban areas, through the provision of cooler microclimates, reduction of surface water runoff, carbon storage and sequestration, and the provision of habitat therefore offer the potential to adapt cities for climate change and reduce the environmental problems they currently experience.

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The potential for retrofitting green infrastructure within existing high density urban landscapes.

The majority of the long-established urban areas within the UK originate from the time of the industrial revolution with subsequent additions and modifications (Ashley et al. 2011). At the time of the industrial revolution the built urban environment of the UK experienced a rapid expansion as people migrated to the towns and cityâ&#x20AC;&#x2122;s to find work. This triggered the building of low cost high density housing with little consideration given to public health and sanitation (NECR079. 2012). The deleterious conditions of towns at the time of the industrial revolution led to the spread of diseases and life expectancy was around thirty-five years (CPRE. 2009). In order to improve the living conditions and public health sanitation measures were introduced and a philosophy of getting all storm and foul drainage rapidly away from towns was adopted in most urban areas by the early 1900s (Chocat et al. 2007).

The legacy of development in this pattern has left many towns and cityâ&#x20AC;&#x2122;s with areas of high density, impermeable landscapes that are disconnected or detrimental to the wider ecosystems and environments to which they are linked (Dakers A. 2000). These areas can be identified using GIS methods such as high-resolution orthophotos to identify surface cover and estimate the proportion of evapotranspiring surfaces (Akbari et al. 2003). Figure 12 identifies the proportion of evapotranspiring surfaces in Greater Manchester.

The areas with the lowest proportion of evapotranspiring surface (20 â&#x20AC;&#x201C; 40%) are areas that can be considered to be high density urban landscapes and could be considered to have the greatest impact on the environmental performance of the conurbation, with the greatest localised environmental 13

issues (as explained in chapter 1). Therefore it is these areas that would benefit the most from being retrofitted with green infrastructure.

Figure 12. Proportion of evapotranspiring (i.e. vegetated and water) surfaces in Greater Manchester.

The origins of green infrastructure.

Green infrastructure is a term being used to describe environmental or sustainability goals that cities are trying to achieve through a mix of natural approaches and technology (Foster J. 2011) and is being applied to landscape and sustainability initiatives ranging in scale from regional masterplans through to small scale adaptations of individual buildings (GISS. 2012).

The European Commission White Paper on adapting to climate change (EC. 2009) states: â&#x20AC;&#x153;Evidence suggests that working with natureâ&#x20AC;&#x2122;s capacity to

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absorb or control impact in urban and rural areas can be a more efficient way of adapting than simply focusing on physical infrastructure. Green infrastructure can play a crucial role in adaptation in providing essential resources for social and economic purposes under extreme climatic conditions”.

Examples include green, blue, and white roofs; hard and soft permeable surfaces; green alleys and streets; urban forestry; green open spaces such as parks and wetlands; and adapting buildings to better cope with flooding.

Consequently green infrastructure can be seen to challenge popular conceptions about urban green space as it places emphasis on the importance of the ecological benefits they provide (Ashley R. 2011).

The term green infrastructure was “first coined in Florida in 1994 in a report to the governor on land conservation strategies and was intended to reflect the notion that natural systems are equally, if not more important, components of our “infrastructure.” Since it is generally accepted that we have to plan for grey infrastructure, the idea of also planning to conserve or restore our natural resources, or "green infrastructure," helped people to recognise its importance to planning” (Firehock K. 2010).

Although the term “Green Infrastructure” is relatively new, the concepts which underpin it can be traced through the beginnings of environmentalism, landscape architecture and planning, and can be seen within the evolution of parks, Garden Cities and the earlier New Towns (Ashley et al 2011). It is the

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interdisciplinary roots of green infrastructure that give it its multifunctional strengths and adaptability (NECR079. 2012).

The Biotope Area Factor.

One of the earliest government initiatives in relation to the retrofitting of green infrastructure within a high density urban landscape was the Biotope Area Factor (BAF) developed as part of Berlins Landscape Program in the 1980s.

West Berlin was isolated from the Federal Republic of Germany from 1945 until 1990. This unique isolation and lack of access to rural areas motivated research and public interest in urban ecology (GISS. 2012). The interest in urban ecology combined with governmental policies, such as the National Environmental Protection Law, which empowered local authorities to develop landscape plans for urban areas resulted in the development of the Landscape Program for West Berlin (1984). One of the fundamental objectives of the Landscape Program was â&#x20AC;&#x153;to find fair planning solutions which, without losing the urban character of the city, integrate open spaces and vegetation around developments thereby making the most of the limited space available in the cityâ&#x20AC;? (Kazmierczak et al. 2010). This approach resulted in the development of the Biotope Area Factor program (BAF), which after reunification was introduced as a binding document in 1994 and is now applied as a legally binding Landscape Plan to 16% of Berlin in 21 distinct areas. Outside of these areas the BAF is voluntary.

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The BAF aims, through the retrofitting of green infrastructure to address the environmental issues found within the high density urban landscape of Berlin’s city center. The BAF standardises and puts into concrete terms the following environmental quality goals: •

Safeguarding and improving the microclimate and atmospheric hygiene.

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Safeguarding and developing soil function and water balance.

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Creating and enhancing the quality of the plant and animal habitat.

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Improving the residential environment.

The BAF is implemented at the parcel or building scale. Under the program, each parcel must mitigate its environmental impacts on-site. A primary goal of the program is that new or renovated buildings achieve a prescribed biotope factor rating or BAF. The BAF expresses the area portion of a plot of land that serves as a location for plants or assumes other functions for the ecosystem (SDUDE) and is expressed as the ratio of the ecologically effective surface area to the total land area covered by the development. Similar to urban planning parameters used in development planning, such as the gross floor area and the site occupancy index, which regulate the dimensions of structures.

BAF = Ecologically-effective surface areas / total land area

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The BAF recognises that targets must differ in response to land use intensity and formulates ecological minimum standards for structural changes and new development accordingly. The objective is to achieve the BAF target values listed in Figure 13.

Figure 13. BAF targets values in relation to land use.

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The prescribed ecologically effective surface area can be achieved through a number of methods (Figure 14). Each technique is assigned a weighting in according to their evapotranspiring qualities, permeability, ability to store rain water, relationship to soil functioning and provision of habitat for plants and animals. This is then calculated as a percentage of the total site area.

Figure 14. BFA Weighting factor / per m² of surface type in accordance to "ecological value".

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The BAF leaves the fine design details to the developer and the target values can be achieved in a combination of ways (Figures 15 -21) giving designers and property owners room for individuality, creativity and flexibility.

Figure15. Current situation.

The courtyard is mainly covered with asphalt. There is gravel with grass coverage on the periphery, and the tree stands in a soil bed that measures 1 m².

The site as it exists has a BAF of 0.06 and needs to achieve a BAF value of 0.3 to meet the requirements of the legislation.

Figure16. Planning variant 1.

Achieving the targeted BAF will require measures that amount to a BAF of 0.24. By reducing the area covered by asphalt and changing the type of surfacing, as well as by significantly expanding the area covered by vegetation, a BAF of 0.3 can be realized on this plot of land.

Figure17. Planning variant 2.

Building a covered bicycle stand means that the portion of partially sealed surfaces must be increased. It is therefore necessary to utilize roof and fire wall surfaces in order to achieve the required BAF.

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Figure 18. Inner courtyard of building from the late 19th century in Prenzlauer Berg prior to implementation of the BAF.

Figure 19. Inner courtyard of building from the late 19th century in Sonnenalle after the implementation of the BAF.

Figure 20. The retrofitting of green roofs in accordance with the BAF to a building historical monument status.

Figure 21. Facades covered with greenery as an ecosystem and species preservation measure accordance with the BAF.

The Biotope Area Factor demonstrates a decentralised approach to the retrofitting of green infrastructure. It uses targets and emphasises the beneficial aspects of green infrastructure without the use of an explicit spatial concept. The adaptive nature of the program has received positive feedback from architects and property owners, as it is easy to use and results in immediate visual improvements and energy savings (Kazmierczak et al.

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2010). City planners also appreciate that it is formed in the same logic as other planning indices and ratios, making it simple to understand and evaluate (Ngan. 2004).

The Biotope Area Factor method demonstrates how a neighbourhood scale approach to retrofitting green infrastructure can make a meaningful contribution to overall green infrastructure provision (GISS. 2012) and it has now been adopted unchanged or in a modified version within several countryâ&#x20AC;&#x2122;s around the world including Canada, Denmark, Finland, Italy, Puerto Rico, Sweden and the USA (Cloos I. 2009).

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Retrofitting green infrastructure: methods, benefits and values.

Green infrastructure uses a hybrid of natural and engineered systems to utilise precipitation at its source. Natural systems, such as plants and soils are combined with engineered solutions to create swales, rain gardens, street planting and green roofs, enabling rain water to be managed onsite and replicating the natural processes of infiltration and evapotranspiration that would have occurred within the area pre-development. Green infrastructure is more than just ground water infiltration. The incorporation of vegetation into drainage systems increases their capacity to absorb wastewater as root action and biomass accumulation stimulate and maintain soil structure increasing infiltration capacity. The process of transpiration by the plants also replenishes the soils absorption capacity. Green infrastructure can be seen as being more subtle and sophisticated than hard engineering solutions (Evans.

2011), as to replicate the processes of green infrastructure artificially would be both technically challenging and expensive.

The case studies will demonstrate that the technology used within green infrastructure is not â&#x20AC;&#x153;cutting edge, untested, risky technology, but something that is well established, tried and tested and liked by those living and working in the area if it is done properlyâ&#x20AC;? (Evans T. 2011).

Green infrastructure is also compatible with other sustainability measures.

Photovoltaic panels have been demonstrated to work more effectively at roof level when installed on green roofs when compared with conventional surfaces. This is due to the ability of the green roofs to reduce sensible heat 23

flux (Scherba et al. 2011). This is attributed to the green roofs thermal mass which prevents the roof from cooling below ambient temperatures at night and reduces peak daytime temperatures, providing more effective operational conditions for the panels which operate more efficiently at low temperatures.

Figure 22. Combination green roof and solar plant, Unterensingen Primary and Secondary School, Germany.

The combination green roof and solar plant contains two hundred photovoltaic panels with an output of 23 kW(p) producing enough electricity to power the entire school.

The hybrid nature of green infrastructure results in multiple benefits that go well beyond water management. By weaving natural processes into the built environment, green infrastructure helps to take pressure off underground drainage networks and reduces the risk of sewer and storm water flooding. It reduces the climate change emissions of wastewater management because with less water entering the underground network less energy is used in pumping and treating. Evapotranspiration leads to evaporative cooling by the elements of green infrastructure which then counteracts the heat island effect of cities, which improves the quality of life, reduces stress and reduces the need for air-conditioning. Where trees are used within green infrastructure they can intercept more than 35% of rainfall and reduce runoff by some 17% (Ashley et al. 2011), remove particulates from the atmosphere and reduce wind chill and heat loss in winter, which reduces energy consumption for space heating (Evans T. 2011).

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These benefits can be seen in terms of savings in energy and water resources, but green infrastructure also has social and economic benefits.

Green infrastructure changes the aesthetics of urban landscapes providing habitat for wildlife, increasing levels of recreation, and improving property prices (CNT 2010). Research by Sheffield University has shown that greener streets â&#x20AC;&#x153;have a profoundly positive influence on socio-economic behaviour, with at least a 35% drop in crime, fewer absences from the workplace and an increased awareness of the environmentâ&#x20AC;? (Diamond R. 2009), and the CABE report Future Health: Sustainable Places for Health and Well-being states that there can be a 300% Increased likelihood of residents being physically active in residential areas with high levels of greenery (CABE 2009).

Figure 23 produced by The Centre for Neighbourhood Technology (CNT) illustrates the multiple benefits associated with the primary methods of green infrastructure suitable for retrofitting within high density urban landscapes.

Figure 23. Green infrastructure benefits and practises.

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The individual performance of each method of green infrastructure can vary depending on the specification of the product used, the scale and location of the application, and the climatic conditions of the site. These variables make it difficult to give specific details on overall performance and benefits. The following information is based on research conducted by the CNT, RHS and CIRIA gives a overview of the primary retrofitting methods and their associated benefits.

Green Roofs.

A green roof is an assembly of materials, including plants, that can replace a traditional roof system . They typically consist of a growing medium and vegetation planted over a waterproof membrane. They may also include additional layers such as a root barrier, drainage layer and irrigation system (Fig. 24). Green roofs are classified by their depth of growth medium.

Figure 24. Green roof components.

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Extensive green roofs require a depth of 5-15cm of growing medium and generally use a artificial materials such as perlite, leca, sand, rockwool and crushed tiles or concrete. Mat-forming species of Sedum, Sempervivum, moss and in shady conditions ferns are suitable types of vegetation for extensive green roofs.

Figure 25. Extensive green roof, Dusseldorf.

Semi-extensive green roofs require a depth of 10-20cm of growing medium, enough to support perennials but not shrubs and trees.

Dry habitat perennials and grasses are suitable types of vegetation for semi-extensive green roofs.

Figure 26. Semi-extensive green roof, Dusseldorf.

Intensive green roofs require a depth of at least 30cm of growing medium, much of which needs to be organic matter. Drought tolerant plants are suitable for intensive green roofs but they can support perennials, grasses, shrubs and trees. They can also be used for rooftop farming.

Figure 27. Roof-top potato farm, Tokyo.

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Associated benefits of green roofs.

Reduced surface water runoff: • Green roofs store water in their growing media. This water is then used by the plants or released back into the atmosphere through evaporation or transpiration. Reducing the amount of surface runoff entering sewer systems and waterways.

Reduced energy consumption: • The presence of plants and growing media provides additional insulation and reduces the amount of solar radiation reaching the roof’s surface.

This insulates the building in winter and cools the building in summer reducing energy consumption.

• Evaporative cooling from water retained in the growing medium reduces roof surface temperatures, thus reducing air conditioning requirements.

Improved air quality and reduced atmospheric CO2: • The vegetation absorbs air pollutants and intercepts particulate matter improving local air quality.

• Green roof vegetation directly sequesters carbon.

• The cooling effect of the vegetation lessens smog formation and groundlevel ozone by slowing the reaction rate of nitrogen oxides and volatile organic compounds.

• By reducing energy use, green roofs lessen the air pollution caused by electricity generation.

Reduced urban heat island effect: • The local evaporative cooling provided by green roofs can reduce elevated temperatures present in urban areas.

• The total area of heat-absorbing surfaces is reduced, decreasing the overall albedo of urban conurbations.

Improved habitat: • The increase in vegetation helps to support biodiversity and provides habitat for flora and fauna.

• If green roofs are applied over a large area they can contribute to the formation of wildlife corridors.

Social and educational: • Their visibility can improve local aesthetics and awareness in green infrastructure.

• Soil and vegetation help reduce sound transmission, thus reducing local noise pollution levels.

• They increase recreational opportunities by providing outdoor areas for people to use.

• Green roofs may be used for food production increasing urban agriculture.

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Urban Tree Planting.

Urban tree planting provides many services which have ecological, economic and social implications.

These benefits are increased when tree planting is combined with measures such as bioretention tree pits or tree pits that are connected through the soil to the water table.

Figure 28. Bioretention tree pits, Washington.

Associated benefits of urban tree planting.

Reduced surface water runoff: • Trees intercept and absorb precipitation through their canopies and root action, which reduces surface runoff.

• Transpiration by the trees reduces soil moisture and recharges the ground’s ability to absorb precipitation.

Increased groundwater recharge: • If the trees pits are connected to the water table through the soil they can contribute to local aquifer recharge and to the improvement of watershed system health, from both quantity and quality standpoints.

Reduced energy consumption: • When properly placed, trees provide shade, which can help cool the air and reduce the amount of heat reaching and being absorbed by buildings.

In warm weather, this can reduce the energy needed to cool buildings.

• Trees reduce wind speeds. Wind speed, especially in areas with cold winters, can have a significant impact on the energy needed for heating.

• Trees release water into the atmosphere through transpiration, resulting in cooler air temperatures and reduced building energy consumption.

Improved air quality and reduced atmospheric CO2: • Trees absorb air pollutants including ozone, sulphur dioxide, nitrogen dioxide, carbon monoxide and particulates.

• Trees directly sequester and store carbon.

• Trees reduce energy consumption, which improves air quality and reduces the amount of greenhouse gases, including N2O and CH4.

Reduced urban heat island effect: • The various cooling functions of trees help to reduce the urban heat island effect.

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Improved habitat • Planting trees increases wildlife habitat, especially when native species are used.

Social and educational: • Trees shade and shelter pathways, improving local microclimate.

• Trees help to reduce sound transmission, reducing local noise pollution levels.

• Tree planting may provide opportunities for urban foraging and food production.

• Studies have shown that property values increase between 2-10% when new street tree planting has been introduced (Wachter et al. 2008).

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Bioretention and Infiltration Practices.

Bioretention and infiltration practices come in a variety of types and scales, including rain gardens, planter boxes and bioswales. Native plants are recommended for bioretention and infiltration practices because they are generally more tolerant of local climate, soil, and water conditions, and are more beneficial to local flora and fauna.

A rain garden is a planted depression or a hole that allows rainwater runoff, from a roof downspout or adjacent impervious surface the opportunity to infiltrate into the ground. They perform best if planted with long-rooted plants like native grasses.

Figure 29. Retrofitted rain garden, Islington.

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.

Figure 30. Planter box, Portland, Oregon.

Bioswales are vegetated, mulched, or xeriscaped channels that provide treatment and retention for surface water.

Vegetated swales slow, infiltrate and filter surface water flows. Effectively trapping silt and other pollutants that are normally carried in runoff from impermeable surfaces.

Figure 31. Retrofitted bioswale, Augustenborg, Sweden.

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Associated benefits of bioretention and infiltration practices.

Reduced surface water runoff: • These practices store and infiltrate stormwater, which mitigates flood impacts and prevents the stormwater from polluting local waterways.

Improved water quality: Bioretention shows the following removal rates: • Total Phosphorous: 70%-83% • Metals (Copper, Zinc, Lead): 93%-98% • Total Kjehldahl Nitrogen (TKN): 68%-80% • Total Suspended Solids: 90% • Organics: 90% • Bacteria: 90% Increased Groundwater Recharge: • Bioretention and infiltration practices mimic natural hydrology and have the potential to increase groundwater recharge by directing precipitation into the ground instead of drainage systems.

Improved air quality and reduced atmospheric CO2: • Similar to other vegetated green infrastructure features, infiltration practices can improve air quality through direct carbon sequestration and the uptake of air pollutants and particulates.

• By minimizing the amount of water entering drainage systems infiltration practices reduce the amount of greenhouse gases emitted as a consequence of water treatment.

Reduced urban heat island effect: • Through evaporative cooling these practices work to mitigate the urban heat island effect, reducing energy use.

Improves habitat: • Bio-retention and infiltration practices provide a diversity of habitats within urban areas increasing biodiversity.

Social and educational: • Bioretention and infiltration practices improve local aesthetics by introducing vegetation in to hard landscapes.

• The visible disconnection of bioretention and infiltration practices from the drainage network promotes awareness and understanding around the importance of sustainable water resource management.

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Permeable Paving.

Permeable paving is a term used for a range of materials and techniques that allow precipitation to infiltrate through their surface. In addition to reducing surface water runoff, this effectively traps suspended solids and filters pollutants. Methods include pervious or porous concrete, porous asphalt and interlocking permeable pavers. From a construction point of view there are two main types of permeable paving systems; infiltration - surface water is directed via voids within areas of solid paving and porous - water is drained directly through the surface.

Figure 33. Permeable macadam surface, visibly similar to conventional bitmac.

Figure 32. Infiltration concrete supported grass paving.

Associated benefits of permeable paving.

Reduced surface water runoff: • Permeable paving reduces surface runoff by allowing precipitation to infiltrate into underlying soils, reducing water treatment costs and the risks of flooding and bank erosion.

Increased groundwater recharge: • By allowing precipitation to infiltrate into the water table, groundwater systems are recharge within urban areas.

Reduced salt use: • Permeable paving retains less surface water, thus reducing ice and frost formation in winter which mitigates the need for salt spreading.

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Improved air quality and reduced atmospheric CO2: • Similar to infiltration practices, permeable paving reduces the amount of water entering drainage systems, thus reducing the amount of greenhouse gases emitted as a consequence of water treatment.

Reduced urban heat island effect: • When vegetation is incorporated into permeable paving installations the total area of heat-absorbing surfaces is reduced, decreasing the overall albedo of urban conurbations.

Social and educational: • Similar to infiltration practices, permeable paving introduces vegetation into hard landscapes and can increase awareness of green infrastructure methods.

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Water Harvesting.

Water harvesting is the redirection and capturing of precipitation for use onsite. Thus treating precipitation as a resource for irrigation and sanitation (toilet flushing). Methods include downspout disconnection and the use of storage containers such as rain barrels, cisterns and geocellular methods.

Figure 34. Downspout disconnection into planter box street planting.

Figure 35. Geocellular storage and treatment linked to multiple green infrastructure methods.

Associated benefits of water harvesting.

Reduced surface water runoff: • By capturing and utilising water on site, harvesting methods reduce the amount of water entering urban drainage systems.

Increases available water supply: • The RHS estimates that at peak times up to 70% of potable water supply is used for garden irrigation and up to 24,000 litres of water could be collected from the average roof each year. Given these estimates, using rainwater for irrigation purposes can substantially reduce the amount of potable water used residentially, effectively increasing supply.

Increased groundwater recharge: • Water used for irrigation purposes will infiltrate into the water table replenishing groundwater systems.

Reduced energy consumption: • Rain water harvesting reduces water treatment and potable water supply demands. These savings result in less energy being used by water companies and the associated production of atmospheric pollution.

Social: • Onsite reuse of rainwater helps to reduce water treatment needs, which allows communities to save on costs associated with potable water conveyance, treatment and use.

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The financial value of green infrastructure.

The valuation of green infrastructureâ&#x20AC;&#x2122;s monetary benefits is still a developing field. The construction costs can be easily compared with grey infrastructure equivalents but this does not take into account the cumulative multiple benefits of reduced water treatment and positive impacts on energy consumption, air quality, carbon reduction and sequestration, property prices, recreation and other elements of community health and vitality that have monetary or other social value. Cost-benefit analysis comparing grey infrastructure with green infrastructure would be incomplete without factoring in the multiple benefits green infrastructure can provide, but as many of these services are not directly bought or sold nonmarket valuation methods such as revealed preference methods, stated preference methods and avoided cost analysis (CNT 2010) have to be used.

These methods have been used to develop evaluation tools, including online calculators, spreadsheet models and desktop software to assess the performance and value of green infrastructure practices. The Building Natural Value for Sustainable Economic Development: Green Infrastructure Valuation Toolkit, a free open source resource available from Green Infrastructure North West is the most comprehensive green infrastructure valuation tool available in the UK and is endorsed by CABE and DEFRA.

The following case studies selected from regions with similar climatic conditions to the UK highlight the potential monetary savings and associated benefits with green infrastructure retrofitting projects.

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5

Case studies.

Portland, Oregon.

Portland, Oregon is considered to be one of the leading pioneers in the application of green infrastructure retrofitting. The city has gained numerous awards for its sustainability measures including the American Society of Landscape Architects General Design Award of Honour in 2006 for its innovative Green Streets Project. The primary motivation for adaptation within Portland came from the need to protect salmon in the Willamette and Columbia rivers. The salmon became the symbol of green infrastructure within Portland, used on kerbs and interpretive boards to educate and promote the benefits associated with the projects (Fig 36 & 37). This resulted in green infrastructure gaining wide scale backing from both the City Council and the public. The city of Portland receives an average annual rainfall of 1.2m, similar to the average conditions found in the UK (Met office. 2012), therefor the methods they have developed could be applied to the UK.

Figures 36 & 37. branded kerbs and interpretive boards used to increase awareness and educate people of the benefits of green infrastructure.

Portland developed its green infrastructure initiatives as part of its Combined Sewer Overflow Abetment Program (CSOAP). The program included grey infrastructure approaches, but the City Council recognised early on that green

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infrastructure could play a crucial roll in its overall strategy. Since 1977 Portland charged a separate utility fee for surface water management and in 1993 under the CSOAP the city began providing incentives for residents in selected neighbourhoods to disconnect downspouts from the combined sewer system and redirect the roof water into their gardens. Since its inception the scheme has resulted in more than 50,000 homes disconnecting downspouts, removing approximately 3.8 million m3 per year of surface water from the combined sewer system. The program has now been expanded and under the Clean River Rewards scheme, launched in 2006 private and commercial ratepayers can claim a 30% discount for managing their surface water runoff using green infrastructure methods.

Portland Green Streets Project.

The Green Streets Project uses planter boxes (Fig 38 & 39) and curb extension rain gardens (Fig 40) to capture surface water runoff, allowing the water to soak into the ground as plants and soil filter pollutants before it enters groundwater supplies. They also create attractive streetscapes and urban green spaces, provide natural habitat, and enhance pedestrian and bicycle safety.

Figures 38 & 39. A chain of planter box rain gardens in down town Portland, demonstrating that green infrastructure can be retrofitted within congested areas.

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Figure 40. Siskiyou Green Street curb extension rain gardens. The rain gardens absorb 80% of the surface runoff from the street.

In 2009 there were 900 green street facilities throughout the city. Combined they have reduce peak stormwater flows by as much as 85 percent, stormwater volume by 60 percent and pollution in runoff by up to 90 percent.

They have also contributed to the refreshing of groundwater supplies and have reduced urban heat islands that cause air pollution inversions.

Glencoe Elementary School parking lot swale, Portland.

To combat localised flooding within the parking lot at Glencoe Elementary School 1350 m2 of impervious surface was converted to landscape areas incorporating green infrastructure methods (Fig 41 & 42).

Figures 41 & 42. The parking lot at Glencoe Elementary School before and after the application of green infrastructure.

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Two speed bumps intercept sheet flow from the parking lot and direct it to the swale; raised parking stripes also help direct flows into the swale. Most of the runoff enters the swale at three entry points while log check dams help retain stormwater passing through the swale. In larger storm events when the system reaches capacity, excess flows drain through a standpipe in the bottom compartment of the swale. The grey infrastructure solution was estimated at costing $144 million, by incorporating green infrastructure into the design the project ended up costing $86 million. A saving of $58 million was achieved through the use of green infrastructure methods.

Portland green roofs.

As part of Portland’s “Grey to Green” program developers are permitted additional floor space if they install green roofs and there is also a payment of $5/m2 to encourage retrofitting. By 2011 there were 271 green roofs in the city totalling 5.2 hectares. The program aims to achieve a total area of 17.5 hectares within the city and calculations estimate this will generate an annual energy saving of 63,400 kWh. Figure 43. Hamilton Ecoroof.

The Hamilton ecoroof was installed in 1999; monitoring data from 2002 to 2010 shows on an average year, the roof manages about 3,500,000 litres of precipitation, assuming an average retention rate of 53.5% and on an average annual rainfall of 94cm.

The data within this case study was provided by the City of Portland and the CNT.

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Seattle, Washington - Street Edge Alternative.

Seattle's pilot Street Edge Alternative (SEA) Project was completed in the spring of 2001 (Fig 44 & 45). It is designed to provide drainage that more closely mimics the natural landscape prior to development. The scheme reduced impervious surfaces by 11% through the use of bioswales, and added over 100 evergreen trees and 1100 shrubs to the street. Two years of monitoring show that SEA Street has reduced the total volume of surface runoff leaving the street by 99%. The Seattle Public Utilities agency estimates that a local street converted to the SEA street design saves $100,000 per 100 linear metres compared to a traditional street design achieving the same level of porosity (35% impervious area).

Figures 44 & 45. Seattle Street Edge Alternatives project before and after retrofitting.

The data within this case study was provided by the City of Seattle and the CNT.

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Germany - Luckenwalde Temporary Park

Figure 46. Luckenwalde Temporary Park.

The Luckenwalde Temporary Park is an innovative approach to urban wasteland.

The site is immediately adjacent to the main shopping street and a major public park. It had been vacant for 10 years and the city council could not find anyone willing to invest in the site. As an alternative the council proposed a creative temporary solution which would leave future development options open. This involved a contract with the site owner including regulations regarding the temporary use of the site as a public park and an annual, symbolic lease.

The owner has the option of developing the property if necessary. The park is linked into the local park path network and uses plant species suitable for transportation to other sites if necessary, providing additional green space within the inner city.

The information within this case study was provided by Werkstatt-Stadt and the Landscape Institute.

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i-Tree.

The i-tree process is a state-of-the-art, peer-reviewed software suite developed by the United States Forestry Service that provides urban forestry analysis and benefits assessment (Fig 47). It is increasingly being used through out the world and Torbay District Council conducted the UK’s first iTree Eco project. Torbay District Council used the software to estimate total value of carbon stored by its urban tree stock and not sequestered annually; the pollution removal of a number of greenhouse gases including sulphur dioxide, nitrogen dioxide, carbon monoxide and particulates; and the structural values of the tree stock. Natural England have surmised that the value of carbon stored by Torbay’s trees is worth £5 million, and of sequestration around £0.2 million. Air pollution removal by the trees is suggested to be worth £1.3 million per year.

Figure 47. Annual benefits of public street trees in Fond du Lac, Wisconsin estimated using the i-tree process.

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6

Conclusion.

Given the uncertainties in understanding how climate change may affect precipitation and temperature in the future (UKCP09. 2013), and how these climatic conditions are amplified within high density urban landscapes (Whitford et al. 2001), it is evident that flexible and resilient approaches are required to enable towns and cityâ&#x20AC;&#x2122;s to adapt for future environmental problems (Defra. 2010). The retrofitting of green infrastructure offers solutions to many of these existing and predicted problems by reconnecting urban landscapes to natural ecological systems (Dakers A. 2000) reducing temperatures, air pollution and the risk of flooding within the urban landscape.

The case studies demonstrate that the UK is along way behind the international standards set by leading practitioners of green infrastructure within Europe and America. These projects demonstrate that green infrastructure practises can be successfully retrofitted within high density landscapes with similar climatic conditions and environmental pressures as found in the UK. Several recent studies (Ashley et al. 2011; GISS. 2012; Evens T. 2010) highlight that it is not the landscape or climatic conditions that are hindering the development of retrofitting green infrastructure within the UK, but rather institutional resistance to new approaches and unfamiliar practises and a lack of cooperation between regulatory bodies. Within the UK responsibility for drainage, highways, housing, biodiversity and open space is split between different institutions, each with its own accountabilities and agendas (Evens T. 2010). The Highways Agency for example has no responsibility for surface runoff once it has left the street, it becomes someone

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elseâ&#x20AC;&#x2122;s problem. In countries that have a progressive approach to green infrastructure these functions often fall under the responsibility of municipal authorities.

The NPPF and the Localism Act 2011 should redress this lack of cooperation and accountability between governmental organisations. The acts enable neighborhood forums and parish councils with the power to shape there local communities through the process of neighborhood planning. This should increase the use of infrastructure methods that have multifunctional benefits (GISS. 2012), such as green infrastructure solutions, if communities and professionals are made aware of the overall benefits and cost savings that can be achieved through their application.

The review of current knowledge â&#x20AC;&#x201C; surface water management and green infrastructure report (Ashley et al. 2011) highlights that a lack of education and awareness within professionals involved in the planning and design process is one of the barriers to green infrastructure becoming established within the UK. For example green infrastructure is not taught in many relevant degree courses (e.g. Civil Engineering), so engineers are not familiar with the practices and are therefor less likely to implement them. The progression of valuation methods such as i-Tree, the BAF (as recommended by the LI) and the Green Infrastructure Valuation Toolkit with in the UK will play a vital roll in increasing awareness within professionals, as these methods convert the values and benefits of green infrastructure into terms governmental organisations are used to understanding and applying to grey infrastructure

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projects, i.e. money and resources. This will allow planners and councils to make informed decisions based on overall performance.

Water utility companies can also be seen to have a vested interest in green infrastructure, as they would benefit financially from the reductions in surface water treatment and the increase in potable water supply that would result from the retrofitting of green infrastructure within urban landscapes. The water industry in England and Wales loses 3.36 billion litres of water a day in leaks and water companies are continually investing in improvements to their networks (BBC. 2012). Increased public, professional and governmental awareness in green infrastructure could act as a driver to encouraged utility companies to replace failing grey infrastructure with green alternatives.

The challenge now is how to implement the retrofitting of green infrastructure within the existing urban fabric of the UK. If we are to rely on the normal building and development process it would take more than 50 years to adapt the urban environment (Ashley et al. 2011). Financial incentives have been shown to increase demand for green infrastructure applications (see Portland, Oregon case study) and in Germany surface water runoff is classed as a pollutant, therefore a charge is applied for its disposal. This charge can be avoided if a property is disconnected from the drainage system. Giving people direct financial motivation to apply alternative methods, such as rain gardens or water harvesting.

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Within the UK there have been moves to encourage the development of green infrastructure, but few of these are focused on the existing urban landscape.

The Red Rose Forest Project is promoting â&#x20AC;&#x2DC;Green Streetsâ&#x20AC;&#x2122; as part of its regional strategy for Greater Manchester and seeks to reintroduce street trees, planters, public art and street furniture back in to the street scene. The Urban Greening in London: Mayoral Strategies has also set targets for increasing tree cover, green space and green roofs within the city of London, but the UK lacks any unified governmental strategy in relation to the application of green infrastructure within existing urban landscapes. The Green Infrastructure Portfolio Standard (GIPS) currently being developed and tested by the CNT in America could hold the potential to rectify this situation.

The GPIS is a program specifically focused on increasing green infrastructure practices in urban areas that are unlikely to see new development or redevelopment in the near future. The GPIS is based on the Renewable Energy Portfolio Standards adopted by over 30 U.S. states. The goal of Renewable Energy Portfolio Standards is to gradually but deliberately increase the use of electricity from renewable sources over twenty or thirty years (CNT. 2012), setting annual goals for local and regional authorities to achieve (Fig 48). By applying the principles of renewable energy targets to green infrastructure (Fig 49) realistic goals can be set and achieved.

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Finger 48. Illinois Renewable Energy Portfolio Standard Schedule.

Figure 49. The application of renewable energy targets to green infrastructure.

If this approach is shown to be effective and is adopted within the UK the cumulative affect over many years would be substantial, stimulating the widespread application of green infrastructure within urban landscapes, resulting in radical environmental and ecological transformations within the urban fabric of the UK.

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References Chapter 1

Introduction.

Ahern J (2007) Green infrastructure for cities: The spatial dimension.

Environmental Change Institute (2005). 40% House. University of Oxford.

Grimm NB, Faeth SH, Golubiewski NE, Redman CL, Wu J,Bai X, Briggs JM (2008) Global change and the ecology of cities.

RCEP (2007) Royal Commission on Environmental Pollution, 26th Report: The Urban Environment White I. (2008) The absorbent city: urban form and flood risk management.

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Chapter 2

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Health Statistics Quarterly (2005) The impact of the 2003 heat wave on mortality and hospital admissions in England.

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RCEP (2007) Royal Commission on Environmental Pollution, 26th Report: The Urban Environment Royal Horticultural Society (2006) Gardening Matters. Front Gardens: Are we Parking on our Gardens? Do Driveways cause Flooding?

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Wilby RL (2003) Past and projected trends in London’s urban heat island.

Whitford V, Ennos AR, Handley JF (2001) “City form and natural process” – indicators for the ecological performance of urban areas and their application to Merseyside, UK. The UKCIP02 Scientific Report (2002) Climate Change Scenarios for the United Kingdom.

Images Figure 1 & 2 - Adapted from Whitford V, Ennos AR, Handley JF (2001) “City form and natural process” – indicators for the ecological performance of urban areas and their application to Merseyside, UK. Figure 3,4,5 & 6 - https://maps.google.co.uk/maps Figure 7,8,9 & 10 - Whitford V, Ennos AR, Handley JF (2001) “City form and natural process” – indicators for the ecological performance of urban areas and their application to Merseyside, UK. Figure 11 - Gill SE, Handley JF, Ennos AR, Pauleit S (2007) Adapting Cities for Climate Change: The Role of the Green Infrastructure.

Chapter 3

The potential for retrofitting green infrastructure within existing high density urban landscapes.

Ashley R, Nowell R, Gersonius B, Walker L (2011) A review of currant knowledge – Surface water management and green infrastructure.

Akbari H, Rose LS, and Taha H (2003) Landscape and Urban Planning 63 Analysing the land cover of an urban environment using high-resolution orthophotos.

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Firehock K (2010) A Short History of the Term Green Infrastructure and Selected Literature.

Foster J, Lowe A, Winkelman S (2011) The Value of Green Infrastructure for Urban Climate Adaptation.

Gill SE, Handley JF, Ennos AR, Pauleit S (2007) Adapting Cities for Climate Change: The Role of the Green Infrastructure GISS (2012) Green Infrastructure Scoping Study WC0809 Undertaken by the Landscape Institute (LI) and the Town and Country Planning Association (TCPA) for the Department for Environment, Food and Rural Affairs (DEFRA) Kazmierczak A, Carter J (2010) Adaptation to climate change using green and blue infrastructure. A database of case studies.

Natural England Commissioned Report NECR079 (2012) Green Infrastructure: Mainstreaming the Concept.

Ngan G (2004) Green Roof Policies: Tools for Encouraging Sustainable Design.

SDUDE (no date) Senate Department for Urban Development and the Environment. http://www.stadtentwicklung.berlin.de accessed August 2013.

Images Figure 12 - Gill SE, Handley JF, Ennos AR, Pauleit S (2007) Adapting Cities for Climate Change: The Role of the Green Infrastructure.

Figure 13,14,18,19,20 & 21 - SDUDE (no date) Senate Department for Urban Development and the Environment. http://www.stadtentwicklung.berlin.de accessed August 2013.

Figure 15, 16 & 17 - Adapted from SDUDE (no date) Senate Department for Urban Development and the Environment. http://www.stadtentwicklung.berlin.de accessed August 2013.

Chapter 4

Retrofitting green infrastructure: methods, benefits and values.

Ashley R, Illman S, Stephenson A (2011) Engineering Natureâ&#x20AC;&#x2122;s Way: A Guide to

SuDS in the Urban Landscape.

Commission for Architecture and the Built Environment (2009) Future Health: sustainable places for health and wellbeing.

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CNT (2010) The Value of Green Infrastructure: A Guide to Recognizing Its Economic, Environmental and Social Benefits Diamond R (2009) Forgotten fabric. Green Places.

Evans T (2011) Report by the Foundation for Water research, wastewater Research & Industry support Forum: Retrofitting green infrastructure for rainwater – what’s stopping us?

Scherba A, Sailor D, Rosenstiel T, Wamser C (2011) Modelling impacts of roof reflectivity, integrated photovoltaic panels and green roof systems on sensible heat flux into the urban environment Wachter S, Wong G (2008) “What is a Tree Worth? Green-City Strategies, Signaling and Housing Prices.” Real Estate Economics.

Images Figure 22, 25 & 26 - http://www.greenroofs.com Figure 24 - http://dcgreenworks.org Figure 27 - http://www.cityfarmer.info Figure 28 - http://greatergreaterwashington.org Figure 29 - CIRIA (2012) Retrofitting to manage surface water.

Figure 30 - http://www.museumofthecity.org/portlands-green-streets Figure 31 & 35 - Ashley R, Illman S, Stephenson A (2011) Engineering Nature’s Way: A Guide to SuDS in the Urban Landscape.

Figure 32 – CNT (2010) The Value of Green Infrastructure: A Guide to Recognizing Its Economic, Environmental and Social Benefits.

Figure 33 - http://pavingexpert.com Figure 34 - http://water.epa.gov

Chapter 5

Case studies.

Met office (2012) - http://www.metoffice.gov.uk/climate/uk/2012/annual.html Images Figure 36 - Evens T (2010) Retrofitting Green Infrastructure For Rainwater What's Stopping Us?

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Figure 37 - Ashley R, Nowell R, Gersonius B, Walker L (2011) A review of currant knowledge – Surface water management and green infrastructure Figures 38, 39 & 40 - http://www.museumofthecity.org/portlands-greenstreets Figures 41, 42 & 43 - http://www.portlandoregon.gov Figures 44 & 45 - http://www.seattle.gov Figure 46 - GISS (2012) Green Infrastructure Scoping Study WC0809 Undertaken by the Landscape Institute (LI) and the Town and Country Planning Association (TCPA) for the Department for Environment, Food and Rural Affairs (DEFRA) Figure 47 - http://www.itreetools.org

Chapter 6

Conclusion.

Ashley R, Nowell R, Gersonius B, Walker L (2011) A review of currant knowledge – Surface water management and green infrastructure.

BBC (2012) How much does your water company leak? http://www.bbc.co.uk/news/uk-17622837 CNT (2012) Upgrade Your Infrastructure: A Guide to the Green Infrastructure Portfolio Standard And Building Stormwater Retrofits Defra (2010) Defra’s Climate Change Plan.

Evens T (2010) Retrofitting Green Infrastructure For Rainwater - What's Stopping Us? GISS (2012) Green Infrastructure Scoping Study WC0809 Undertaken by the Landscape Institute (LI) and the Town and Country Planning Association (TCPA) for the Department for Environment, Food and Rural Affairs (DEFRA) Whitford V, Ennos AR, Handley JF (2001) “City form and natural process” – indicators for the ecological performance of urban areas and their application to Merseyside, UK. UKCP09 (2013) UK Climate Projections http://www.ukcip.org.uk Images Figures 48 & 49 - CNT (2012) Upgrade Your Infrastructure: A Guide to the Green Infrastructure Portfolio Standard And Building Stormwater Retrofits.

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