The third intervention focuses on increasing public green spaces. Here too, we are not talking about great new parks or large green areas; these are micro interventions that can be applied in a city with a consolidated infrastructure. Practically speaking, it is about creating new traffic islands and planting new trees. These interventions necessitate an innovative approach based on a new public space management vision. At present, for most Italian cities to add new trees and traffic islands in urban areas where everything has already been built could involve an increase in maintenance costs and a loss of needed urban space (for car, bicycle, and pedestrian traffic, parking, etc.). This is why this new approach would have to be adopted as part of a strategic paradigm shift in the general management of city spaces. Creating new green spaces inside the context of a built up city entails changing one's perception of street space as just for transit, parking, and car maneuvering. A new paradigm for the use of public green spaces requires a strategic rethinking of urban greenery, insofar as what it can offer in terms of the urban ecosystem adapting to climate changes. Going down this road means understanding and valuing the gamut of services that green spaces can offer to mitigate the heat island effect in addition to other negative externalities due to weather phenomena: lamination for the containment of

water during extended rainfall, reducing air pollution, helping to reduce the speed of urban traffic, and even a general improvement in the environmental and aesthetic quality of public spaces. New traffic islands were added inside the pilot area along the streets whose width could reasonably be reduced or that could be switched from two-way to one-way traffic. We also added a green area on a space used as a square along Via Guizza.

#### *8.5.3 Private Outdoor Spaces*

The management of private outdoor spaces is also a major factor in determining the occurrence and intensity of urban heat islands. Depending on the type of settlement, a significant portion of Veneto's cities that is not covered by buildings is private property; in the case of Padua's pilot area, private property covers more than 1\3 of the total surface.

It is obvious that the management of these surfaces is greatly relevant to the mitigation of the heat island effect. However, in this case, even a simple technical solution (increasing the green surface and the reflectance of impermeable surfaces) must be justified at the management and legislative level; a cogent response is necessarily based on a general strategic vision that can harmonize individual management needs with the understanding of the importance of adapting to climate changes. Private outdoor spaces can easily be handled when it comes to new buildings, where building codes can set new extension and surface type parameters, but they require a much more thorough consideration for consolidated urban areas, as is the case of the pilot area, since it is more difficult to find legislative levers or incentives to modify already built property.

In these cases, implementation can be achieved through the following:

Within the pilot area, we proposed to modify only the reflectivity of the private surfaces currently impermeabilized by asphalt, concrete or the like with intervention 4, whereas with intervention 5 we proposed to replace them with greenery (Figs. 8.13 and 8.14).

#### *8.5.4 Post-scenario Intervention*

The last project intervention on the pilot area takes a step beyond the interventions encompassed by the feasibility study, proposing a more incisive transformation that involves buildings as well.

**Fig. 8.13** Intervention 4+summary of intervention 4 Albedo on private paved surfaces. Modify the reflectance on private surfaces

**Fig. 8.14** Intervention 5+summary of intervention 5. Put greenery on private surfaces Add green areas on private surfaces

**Fig. 8.15** Intervention 6+summary of intervention 6. *Green roofs*: extra scenario intervention

This intervention pictures a gradual transformation of the roofs of private buildings, first by modifying the reflectance of flat surfaces and then by turning them into green roofs. A real expansion of green roofs can only occur if our cities will understand and assess their value in terms of the services that they can offer to the community: mitigation of the heat island effect, lamination of rainwater, improvement of air quality, and last but not least, recreational use.

This final scenario is not meant to offer a new utopian vision of what a city should be like, but it is rather an attempt to propose the application of solutions that would adapt the current state of affairs to a no longer so remote future of rapid climate changes.

To increase concretely the resilience of our urban system to climate changes, such as in the case of heat island mitigation demonstrated by this project, we must utilize several approaches: in-depth climate evolution studies on the regional and local scale, the use of climate modeling, the use of new technologies as a support for urban planning, the research of new building materials, the revision of the urban governance system, and above all the creation of a new strategy to review and harmonize all the aspects of the matter (Fig. 8.15).

#### **Bibliography**

#### **Focus A: Energy and Urban Form**

Filippo Magni Department of Design and Planning in Complex Environments, IUAV University of Venice, S.Croce, 1957, 30135, Venice, Italy<EMAIL_ADDRESS>
**Keywords** Urban form, Energy planning, Design and UHI, Climate change

Nowadays, the population which can be considered an urban population exceeds 50% of the total with areas where the percentage reaches 80%. This process of urbanization of the population, combined with the potential impacts of climate change induced by the anthropogenic component (IPCC 2007), provides a new impetus to efforts to understand how the forms, functions and resources interact within urban environments. In some cities, energy consumption per capita has grown at approximately the same rate as spatial growth (Baynes and Bai 2009). From a point of view of urban metabolism, energy therefore represents one of the most critical resource flows for the life of a city, since it is a primary factor in supporting physical and economic systems (Alberti 1994). Considering then that the growing global contribution to GHG emissions of cities (Bai 2007), addressing global climate change bringing it down to an urban level acquires strategic interest, as it provides greater effectiveness of intervention: energy consumption, urban form, density and morphology if correctly associated, may provide the opportunity to address the issue of climate locally. Much of the literature available, for example, Williams et al. (2000), Jenks and Burgess (2000) and Foley (2005), Oke (2006), focus on the issue of mitigation considering it a driver of urban sustainability. Better planning, better design of spaces and urban forms, should be able to both mitigate climate change, and ensure a gradual process of adaptation to reduce the direct and indirect impacts of climate change on cities.

The approach to mitigation carried out so far to reduce GHG emissions, has been focused primarily on the production of energy from renewable sources, energy savings of buildings, "green" technologies for industrial production, alternative fuels with a higher efficiency for vehicles, and an increase in public transport. It has focused less on the study of urban form and the role it plays in an energy strategy for the conservation and efficient use of this resource.

The globalization of the construction industry and the total delegation of the indoor systems and plants has in fact determined, in the last century, an increasingly pervasive realization of approved buildings and urban structures barely related to their climatic context, cultural material. "The same buildings can be found from Stockholm to Nairobi, from Shanghai to Sao Paulo, with age-old design principles simply eliminated" (Butera 2004): a challenge for nature set by man, to prove that he can live indifferently in any context and in any climate.

If we take a broader view, which embraces and considers the territory as a geometric area of energy consumption (Olgyay 1951), we must consider that urban planning aimed at energy saving and sustainability must be sensitive to local conditions and able to exploit the resources that the environment provides. The end result of this approach is expressed naturally in architectural forms and urban structures, contextualized by morphology, type, use of materials. This does not necessarily mean that they should be vernacular or traditional, given that typological, morphological and technical-constructive solutions evolve over time as new requirements emerge and new materials and new building systems are introduced. We must also take into account on the fact that the use (and waste) of energy does not only depend on the use of the individual buildings and their systems, but often on the way in which these have been designed and arranged in relation to each other. For example, the layout of a building on the land, its position in relation to the prevailing winds, the path of the sun and the reciprocal relationship with other surrounding buildings can prevent the sunlight needed from reaching it, creating barriers to hot winds and vice versa channelling the cold winds, leading to an inefficient use of energy. It is very rare that building regulations or urban-building standards for the implementation of planning regulations contain directives aimed at ensuring environmental conditions which are conducive to energy saving for temperature regulations.

Therefore, urban planning policies that are sensitive to reducing energy consumption and comfort, related to the use of the spaces within a city, must be based on a bioclimatic approach, which aims to simultaneously control three interconnected levels: environmental-climatic, typological and

technical-constructive which, if studied in sufficient detail, can provide the following information:

It is therefore the designer and/or planner who, on different levels, who is called upon to deal with the issues related to the regulations, the shape of the urban structures, the orientation of the buildings, the cladding and systems, and therefore work towards reducing energy consumption and ensuring suitable living comfort.

Therefore, designing buildings today, with a climate which is changing constantly, means understanding the reasons related to the microclimate, resources and local materials. Planning in these geographical areas does not require a strict adherence to architectural shapes of traditional buildings, but rather an innovative reinterpretation of the reasons which have "naturally" driven construction for centuries.

#### **Bibliography**

London: Spon Press, Taylor and Francis Group.

Williams, K., Burton, E., & Jenks, M. (2000). Achieving sustainable urban form.

#### **Focus B: Using Aerial Photogrammetry for Urban Sustainability Analysis**

Denis Maragno

Department of Design and Planning in Complex Environments, IUAV University of Venice, S.Croce, 1957, 30135, Venice, Italy<EMAIL_ADDRESS>
**Keywords** Forecasting UHI, Monitoring climate change, Digital surface model

The ongoing climate change and energy issues are among the most important challenges that city planning, zoning, and architecture are now facing.

Limited resources and the economic crisis aggravate the difficulties of intervention, forcing one to identify multifunctional interventions for combined solutions to different problems and needs (Musco et al. 2013).

In recent years, there has been considerably growing interest in alternative and renewable forms of energy supply (Pearce 2002); at the same time, the difficulties experienced by cities in resisting the effects of climate change are steering Public Administrations toward formulating integrated policies in order to decrease CO2 production and simultaneously increase the land's resilience to climate change (Musco 2008).

The ensuing difficulties lead one to analyze urban environments using the most advanced technology and the best tools available.

We introduce an example of applied methodology, where, using a point cloud generated by a photogrammetric technique, we will consider what buildings are most suitable for installing a PV system and which areas are most affected by solar incidence (Wilson et al. 2000).

Thanks to recent advances in photogrammetry Hardware and Software (Hirschmüller 2008), by using stereoscopic techniques it is possible to make 3D point clouds3 and digital models of a terrain comparable in definition to those produced by active sensors (e.g., LiDAR). But unlike LiDAR data,4 a

3These point clouds consist of geo-referenced and dimensioned points, with an average density of 12 points per m2 , which thus render the photographed area (or detected, in the case of LiDAR processing) in digital form and in three dimensions. Available algorithms, including through open source software, are able to analyze both geographically organized and dimensioned points, and render an exact 3D urban composition in numerical form.

4LiDAR (Laser Imaging Detection and Ranging) performs remote sensing to determine the distance of an object or surface through the emission of high frequency laser pulses by a flying sensor (plane or drone). The distance of an object is given by the length of time elapsed between emission and reception. Very high frequency pulses bouncing from objects or the ground are converted into geo-referenced and dimensioned points, thus giving rise to a "point cloud" from which the exact reconstruction of an area can be created in the form of three-dimensional digital models.

point cloud created with the Dense Image Matching (DIM) method has a much lower cost, making it more accessible to Public Administrations.

To assess the solar incidence impacting the slopes of buildings and horizontal urban surfaces, we trace a methodology composed of three steps.

#### *Step One*

In order to transform the point cloud generated by the stereoscopic technique, the first step is to transform it into a DSM5 (Digital Surface Model), which is a raster file whose pixels contain the average dimensions of the points of the cloud.

The very high density of the cloud has allowed us to create a DSM with a 0.5 m2 per pixel resolution. The conversion can take place with the aid of various software tools; for the prototype we used LAStolls. This application has a very simple command line interface, developed by Martin Isenburg for LiDAR data, but which could be used for this specific operation on photogrammetric data in the LAS format.

The command for the operation is the following:

las2dem -i name\_file\_input.las -o name\_file\_output.tif -step 0.5

By using this command on Command Prompt, the software automatically transforms the point cloud into the desired DSM.

#### *Step Two*

The second step consists in producing information pertaining to solar incidence and the inclination angles of roof slopes. This operation was performed with the Open Source Software System for Automated Geoscientific Analyses (SAGA GIS). SAGA GIS has many algorithms, one of which can calculate the inclination angles of surfaces (by Olaya 2004), and another the potential solar incidence of surfaces (by Conrad 2010).

The information layer pertaining to the inclination angles of roof slopes will be crucial in the classification of roofs, as for the study in question it is important to distinguish flat roofs from sloping roofs. The inclination angles of roofs are also essential in selecting and suggesting an installation type.

5DSM is a digital elevation model in raster format. Each cell of the model, called pixel, holds a height number. Therefore, DSM represents the spatial distribution of the dimensions of an area or surface.

The calculation of the solar incidence uses the three-dimensional knowledge acquired automatically by SAGA GIS from the input raster file: knowing the latitude and longitude supplied by the georeferenced raster file, the algorithm simulates the height of the sun and considers the dimensioned urban elements, projecting shadows, and thereby calculating the potential solar incidence for each pixel.

The output will therefore still be a raster file with a 0.5 m2 per pixel resolution, where each pixel contains the information in kWh. The process has the option to choose the time of year to be analyzed (January rather than July), and the number of days (1–365).

#### *Step Three*

The final step of the analysis compares the information obtained so as to identify the urban areas vulnerable to strong solar radiation, in order to come up with more accurate mitigating and/or adaptive solutions.

Making use of any GIS Software (for this example we used Quantum GIS) it is possible to analyze quantitatively the two dimensions under study.

As for identifying the roofs most suitable for a photovoltaic or solar thermal installation, one can simply evaluate information such as solar incidence, inclination angle, and slope size.

As for identifying hot urban areas (with greater solar incidence), one can simply ask Quantum GIS for the location of areas vulnerable to solar incidence (it will be better to convert the raster file into vector format for this purpose). The resulting zoning information will be of great help in choosing an intervention, where, depending on land area type (square, parking lot, sidewalk, intermodal station, etc.), this can be done with greater accuracy and solutions pertaining to shading in conjunction with renewable energy production can be easier to find.

#### **Bibliography**

Musco, F., Maragno, D., Gariboldi, D., & Vedovo, E. (2013). Remote Sensign e Cambiamenti Climatici: rischi e opportunità nel riuso e riciclo delle città. In *Il Governo della Città nella Contemporaneità: La città come motore di sviluppo* (pp. 187–189). Rome: Edizioni INU, Salerno.

#### **Focus C: Urban Sprawl and Measures for Environmental Sustainability**

Laura Fregolent Department of Design and Planning in Complex Environments, IUAV University of Venice, S.Croce, 1957, 30135, Venice, Italy<EMAIL_ADDRESS>
**Keywords** Urban sprawl, Urban growth, Carbon dioxide emissions, Welfare policies

#### *Urban Sprawl: Characteristics and Impacts*

The contemporary city has increasingly been characterised by certain distinctive features, in particular by a progressive urban fragmentation and by a polarisation and specialisation of some functions and services outside the urban centres, which resulted in a growing increase of mobility.

The phenomenon, known as *urban sprawl*, is generalised and extended and has been studied extensively in its social, economic, cultural, political and institutional components6 as well as in its causes, impacts,7 formal expressions and local specificities, which have led to different manifestations of the phenomenon according to the different territorial and geographical contexts.

6About the effects of local scale regulations and sprawl and about the relationship between administrative fragmentation and sprawl increase, see: Pendall R. (1999), "Do Land-Use Controls Cause Sprawl?", *Environment and Planning B*, vol. 26/4, pp. 555–571.

7Between the various studies, see Ewing R., Pendall R., and Chen D. (2002), *Measuring Sprawl and Its Impact*, Smart Growth America/U.S. Environmental Protection Agency, Washington, D.C.

Research has highlighted the close relationship between low-density of settlements and sprawl, as well as new needs, consumption and lifestyles impose high-impact territorial choices with high land use rates.

A topic that over time has become important in research on the effects of the sprawl is the one linked to the quantification of the collective8 and social costs related to mobility9 and more recently, the health care costs that the sprawl imposes. Some recent studies in fact highlight the connection between a sprawl and the health of individuals: «The study, *Relationship Between Urban Sprawl and Physical Activity, Obesity, and Morbidity*, found that people living in counties marked by sprawling development are likely to walk less and weigh more than people who live in less sprawling counties. In addition, people in more sprawling counties are more likely to suffer from hypertension (high blood pressure)»10 as well as the need to act, regulating and limiting the development of sprawling so as to allow improvement the people's quality of life.

Research on the sprawl is also characterised by an approach which takes ever more the form of planning and is ever more linked to identifying common tools, policies and measures that are primarily aimed at limiting land use. The latter is considered the most evident criticality and the one with the larger impact since it is associated with the erosion of natural, environmental and

8On this subject, reference should be made, by way of example, to the numerous studies conducted in the United States of America on the *social* and *environmental* costs of sprawl since the 70s: Real Estate Research Corporation (1974), "The Costs of Sprawl" (US Environmental Protection Agency, Washington, DC); Ladd H. (1992), Population growth, density, and the costs of providing public services, *Urban Studies*, 29; Carruthers J., Ulfarsson G.F. (2003), "Urban sprawl and the cost of public services", *Environment and Planning B: Planning and Design*, 30. In the case of Europe and Italy, the amount of research is more restricted: Camagni R., *et al.* (2002), *I costi collettivi della città dispersa*, Alinea, Firenze; Caperchione E. (2003), "Local Government accounting system reform in Italy: A Critical Analysis", *Journal of Public Budgeting, Accounting and Financial Management*, 15(1); Hortas-Rico M., Solé-Ollé A. (2008), "Does Urban Sprawl Increase the Costs of Providing Local Public Services? Evidence From Spanish Municipalities", *Urban Studies*, 47(7); Travisi C.M., *et al.* (2009), "Impacts of urban sprawl and commuting: a modelling study for Italy", *Journal of Transport Geography*, 18(3); Fregolent L., *et al.* (2012), "La relazione tra i modelli di sviluppo urbano dispersi e i costi dei servizi pubblici: un'analisi panel", in Cappellin R., Ferlaino F., Rizzi P. (editors), *La città nell'economia della conoscenza*, Franco Angeli, Milan.

9McCann B. (2000), *Driven to spend. The Impact of Sprawl on Household Transportation Expenses*, Surface Trasportation Policy Project, Center for Neighborhood Technology.

10McCann B., Ewing R. (2003), "Measuring the Health Effects of Sprawl: A National Analysis of Physical Activity, Obesity, and Chronic Disease", Smart Growth America and Surface Transportation Policy Project, Sep., p. 1.

landscape resources, and soil sealing.11 Waterproofing is the result of the strong anthropization caused by the urbanisation processes and leads to the degradation of the ecosystem functions, the alteration of ecological balance, and a series of negative impacts on the environment such as a strong pressure and water resources with consequent decrease in rainfall absorption; loss of biodiversity; impact on food safety; increase in solar energy absorption due to dark asphalt or concrete surfaces, which contribute significantly along with the heat generated by air conditioning and cooling systems, and the heat produced by traffic, to the so-called 'Urban Heat Island' effect.

The evolution of the sprawl phenomenon and the quantification of its impacts have therefore pushed scholars and researchers and then also administrators and politicians to search for the measures to adopt and the possible actions to be implemented through specific and sectoral policies as well as careful planning.

The urban and regional planning may limit the sprawl also by means of infrastructural and transport regulation measures which foster a reduction in greenhouse gas emissions and allow to direct the growth and form of the urban space. In fact, density, functional *mixité*, re-compaction of the urban space, infrastructure design and the promotion of public and collective transport are the principles for developing guidelines for sustainable planning that regulates the urban space in such a way to control and reduce CO2 emissions. This is how the form of the urban settlement and the planning aimed to regulate its growth that can make an important contribution to climate protection,12 and this is why even at a European level, one of the major pushes is heading for intervention on the urban form, the compaction of the urban space, and the re-use of abandoned and dismissed areas.

11On this subject, please refer to the documents produced by the EU, in particular the Soil Thematic Strategy (COM(2006) 231); and on the measures that may be adopted to mitigate the phenomenon: European Commission (2011), *Report on best practices for limiting soil sealing and mitigating its effects*, Technical Report, 2011-050, Apr., available at: http://ec. europa.eu/environment/soil/pdf/sealing/Soil%20sealing%20-%20Final%20Report.pdf

12See: Intergovernamental Panel on Climate Change – IPCC (2014), "Human Settlements, Infrastructure and Spatial Planning", in Edenhofer, O., R. Pichs-Madruga, Y. Sokona, E. Farahani, S. Kadner, K. Seyboth, A. Adler, I. Baum, S. Brunner, P. Eickemeier, B. Kriemann, J. Savolainen, S. Schlömer, C. von Stechow, T. Zwickel and J.C. Minx (eds.), *Climate Change 2014: Mitigation of Climate Change*, *Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change*, cap. 12, Cambridge, Cambridge University Press, United Kingdom and New York.

#### *8.1.1 Measures and Tools for Sprawl Containment*

The European Union has long been committed to the promotion of a culture of sustainability which over the past two decades has helped to increase attention towards environmental issues and is now a leader with respect to the major environmental issues, from combating climate change13 to the protection of biodiversity.

As for land and its protection – with special reference to the land use – the measures proposed by the EU collide again with the constraints stemming from the fact that land planning is a matter for the competence of the individual Member States. But other policies that affect to a greater or lesser degree, the land transformation processes and the issue of non-sustainable consumption and soil sealing, are the focus for a number of European Institutions (European Commission, European Environment Agency, and Eurostat), who initiated monitoring programs, research and awareness, although we continue to wait for a specific directive on land that is difficult to achieve.

As previously mentioned, planning is one of the strategic tools identified by the EU for a new enhancement of the city and the control of urban growth to take place in a sustainability manner, because sustainability means a transdisciplinary perspective on phenomena that requires different approaches, opinions and observations, which planning can combine and intersect in order so as to develop effective solutions. For this reason: «The majority of the EU Member States have established the principle of sustainable development in their key spatial planning regulations, referring to economic use of land resources and avoidance of unnecessary urban sprawl. However, the existence of relevant regulations does not give any insight on the effectiveness of implemented measures».14 In addition, the actions taken by several European

13On this subject, a first assessment can be made of the planning measures adopted in the USA: "The first generation of state and local climate change plans reflects increasing consciousness of this, and these plans have begun to take important steps, such as measuring emissions. But much stronger action is needed. Instead of pursuing slow, incremental policy changes, governments at all levels must adopt a *backcasting* approach, setting goals for both mitigation and adaptation based on the best available scientific knowledge, and working backward from these targets to develop plans and programs capable of achieving them. The initiatives would then be regularly reviewed and revised to ensure progress at an appropriate rate" (Wheeler S.M. (2008), "State and Municipal Climate Change Plans. the first generation", *Journal of the American Planning Association*, vol. 74/4, pp. 481–496).

14Soil Thematic Strategy (COM(2006) 231); and on the measures to be adopted to mitigate the phenomenon: European Commission (2011), *Report on best practices for limiting soil sealing and mitigating its effects*, Technical Report, 2011-050, Apr., available at: http://ec. europa.eu/environment/soil/pdf/sealing/Soil%20sealing%20-%20Final%20Report.pdf.

countries and aimed at sustainability-oriented planning are based on: «Quantitative limits for annual land take exist only in six Member States: Austria, Belgium (Flanders), Germany, Luxembourg, the Netherlands, and the United Kingdom. In all cases the limits are indicative and are used as monitoring tools",15 for example: «In England, 10% of the total land area, which includes country roads, is urban and, according to the Department for Communities and Local Government (2008), over 70% of new development is taking place on this previously developed land (i.e., brownfield) at high densities to conserve greenfield land. This is a highly restrictive land use policy, constraining the supply of new houses and limiting lifestyle choice».16 Similar rules have been adopted in other European countries: in Germany, measures were introduced for progressive control of land consumption with the goal of reaching zero consumption in 2050, by envisaging re-use of brownfield sites, requiring new urbanization to only occur in areas accessible by public transport and urban development plans to be designed in such a way to enhance compact urban centres and provide them with services, such as Active City and District Centres (2008). In France, the "Schémas de la Cohérence Territoriale" (SCOT) – large-scale plans which serve as a guide for the local plans - allow to determine perimeter of the protected natural and urbanized spaces. The SCOTs impose the principle of "extension limitée de l'urbanisation" which establishes limits to the urbanisation of non-anthropized areas and the realization of large commercial spaces.

Different regions in Italy are preparing urban regulations aimed to control land consumption: Regione Veneto is working on a draft law on the reduction of land consumption through urban regeneration; this work began at the end of 2013 but the draft law is still under discussion. Regione Toscana is engaged in reviewing its Regional planning law with the introduction of specific measures to contain land use; Regione Puglia, which has already passed a law to encourage and facilitate access of youth to agriculture and combat the abandonment and consumption of agricultural land.

In addition to planning, the most common tools for urban growth control are greenbelts and urban growth boundaries, applied in different cities around the world (London, Berlin, Portland, Beijing, Singapore, etc.) with the aim of defining and delimiting the physical boundary between the city and the countryside, with the contribution also of fiscal and regulatory measures and other indications such as the re-use of dismissed areas and buildings to encourage

15 op. cit.

16Echenique M.H., Hargreaves A.J., Mitchell G., and Namdeo A. (2012), "Growing Cities Sustainably. Does Urban Form Really Matter?", *Journal of the American Planning Association*, vol. 78/2, pp. 121–137.

the upgrade of that which is already in existence, and the start of urban regeneration processes in order to prevent consumption of non-anthropized land, to allow construction works to take place on free land only when all dismissed or under-used land is recovered, and when re-use of areas already compromised has been verified to be impossible. In any case the use of free land should be linked to real needs; regulating land use through regulatory restrictions and adopting different local taxation systems for the different areas and uses.

The outcomes of these measures in the various contexts of application were different, and this demonstrates that there is no solution or single measure able to minimize the sprawl but that the measures to be taken must be different and applied in different ways, but all within an unambiguous reference framework to be determined by the planning.

The adjustment and implementation of policies aimed at governing urban transformation must take place at different scales of intervention with a focus on the large-scale and/or metropolitan scale, because this allows understand, contextualize, and find solutions to phenomena that occur on a local scale.

Planning plays a key role, especially on a vast or regional scale, since the processes of urban sprawl affect large areas of land - several municipalities and provinces mutually adjacent. This scale also enables to address issues such as pollutant gas emissions, resource management, reduction of land consumption, protection of natural ecosystems, and also enables to implement welfare policies17; and an integrated approach to urban development policies is the only key to implementing the *European strategy for environmental sustainability*.

The images or other third party material in this chapter are included in the work's Creative Commons license, unless indicated otherwise in the credit line; if such material is not included in the work's Creative Commons license and the respective action is not permitted by statutory regulation, users will need to obtain permission from the license holder to duplicate, adapt or reproduce the material.

17Wheeler S. (2009), "Regions, Megaregions, and Sustainability", *Regional Studies*, vol. 43/6, pp. 863–876.

**Open Access** This chapter is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, a link is provided to the Creative Commons license and any changes made are indicated.

## **Chapter 9 Pilot Action City of Vienna – UHI-STRAT Vienna**

#### **Doris Damyanovic , Florian Reinwald , Christiane Brandenburg , Brigitte Allex , Birgit Gantner , Ulrich Morawetz , and Jürgen Preiss**

 **Abstract** The article presents the results of the pilot action "Urban Heat Islands– Strategy Plan Vienna" (UHI-STRAT Vienna). It sets out by determining what potential consistent consideration of urban climate aspects at different levels of action and decision-making has and how to implement such consideration. In a second step it looks at today's and future development of UHI and the urban climate. The report goes on to explain the three fi elds of action identifi ed, i.e. awareness building, information and public relations for UHI, as well as urban infrastructure and large-scale and more detailed technical and structural measures to support strong consideration of the issue. It shows up the levels of action in planning from the master plan to the actual project and the options available in the course. Two feasibility studies reveal how UHI-relevant measures can be implemented in designated areas of the city. They make a clear distinction between measures in the development of new city quarters and measures in adapting existing ones, and they also identify two different levels of planning, the strategic master plan on the one hand and the planning of legal provisions, i.e. the land-use and building development plans on the other hand. The "Master Plan for Nordbahnstraße – Innstraße" in Vienna's 20th municipal district is used as an example to show how measures can be introduced at different stages of the master plan process. Proposed measures can be embedded in land-use and building development plans, as demonstrated in the case of the quarter surrounding the Vienna University of Technology (Karlsplatz) in the 4th municipal district. The studies were assessed as to the feasibility of the measures proposed, which involved participation of different agencies of the Vienna

 D. Damyanovic • F. Reinwald • C. Brandenburg • B. Allex • B. Gantner Department of Landscape, Spatial and Infrastructure Sciences, Institute of Landscape Planning , University of Natural Resources and Life Sciences , Vienna , Austria

U. Morawetz

J. Preiss (\*)

Department of Economics and Social Sciences, Institute for Sustainable Economic Development , University of Natural Resources and Life Sciences , Vienna , Austria

Vienna Environmental Protection Department, Municipal Department 22 , Unit of Spatial Development , 1200 Wien, Dresdner Straße 45 , Vienna , Austria e-mail<EMAIL_ADDRESS>
City Administration. The summary points out the project's added value for the city, indicating that the journey Vienna has taken to protect the climate while at the same time adapting to the consequences of climate change is bound for success.

#### **9.1 Introduction**

 The pilot action "Urban Heat Islands – Strategy Plan Vienna" (UHI-STRAT Vienna) is meant to trigger discussion processes, to make the problems entailed in UHI visible for political decision-makers and the city administration, as well as to offer assistance and clearly defi ned solutions. The results of the pilot action UHI-STRAT Vienna are helping to put the issue of Urban Heat Islands in the focus of future urban development. Increasing heat stress and a rising temperatures during the summer months as predicted for the City of Vienna can be mitigated by putting into place the strategic and technical measures proposed. Protecting and expanding the city's green infrastructure, for example, can effectively reduce the consequences of UHI while at the same time improving people's quality of life and boosting urban biodiversity. The pilot action UHI-STRAT Vienna helps the participating administrative agencies identify the measures relevant for their work, the measures they can implement in their own areas of competence, the steering tools and levels at their disposal, and the potential of the different measures. The pilot action UHI-STRAT Vienna was developed in close coordination with representatives from the Vienna City Administration and outside experts on the basis of autonomous yet interlinked discourses (Hubo and Krott 2012 ).

#### **9.2 A Consistent Strategy for UHI in Urban Planning**

 The objective of the UHI-STRAT Vienna is to integrate consistent consideration of urban climate aspects at different levels of planning. There is a wide range of tools where the (urban) climate already features strongly, along with a number of strategies and rules on how to tackle the phenomenon of Urban Heat Islands. The subject matter includes contracts under international law, such as the UN Climate Change Convention, Austrian wide approaches, such as the Austrian Strategy on Adaptation to Climate Change, regional approaches, such as the Climate Protection Programme of the City of Vienna, as well as federal and provincial laws, guidelines, planning tools and planning assistance. Mitigating the effects of UHI combined with forwardlooking urban planning for the prevention of Urban Heat Islands has become a very integrative task. Different fi elds of action, steering levels and planning processes are either infl uenced by the implementation of measures or infl uence the latter in turn. It is important in the context to bear in mind the hierarchy of the planning tools and the chronological order the different tools are used in the course of planning.

 This is why many aspects of adaptation to climate change have found their way into programmes and activities pursued by the City of Vienna, mostly in conjunction with objectives of environmental protection:

 The Municipal Department for Environmental Protection has been promoting roof and façade greening for many years, measures to this end ranging from presentations, international congresses, publications and consultation with individual projects. It even has its own test area with several types of roof greening on the Department's offi ce building. Numerous studies, expert meetings and public relations activities are dedicated to forward-looking use of rainwater (rainwater management), particularly with a view to raising the rate of evaporation. There is positive interaction with "ÖkoKauf" (EcoBuy Vienna) , a programme for sustainable procurement, and "Öko Businessplan" (EcoBusinessPlan Vienna), a cooperation initiative with the economic chamber to consult businesses on ecological measures.

 The ecological criteria set out in UHI-STRAT are in line with the Environmental Department's wildlife conservation programme "Netzwerk Natur" (network nature), a topic which is also addressed in the project "Nachhaltiger Urbaner Platz" (sustainable urban space), a checklist for sustainable design of urban spaces.

 "Microclimate" constitutes a separate assessment category along with other environmental goods incorporated into the "strategic preliminary assessment of environmental impacts caused by housing projects". This tool is to make different locations and projects for the creation of housing more easily comparable and comprehensible with regard to their environmental impact at the urban development level already. It is to ensure that all environmental aspects are duly considered when choosing from different planning options.

 All of the above programmes and projects are brought together in the city's Smart City Strategy and the Climate Protection and Adaptation Programme (KliP II).

 Implementation of UHI-STRAT Vienna must be addressed both in the different fi elds of action and at the various levels of planning. The UHI effect needs to be considered with measures relevant to the city as a whole, as well as with those that have a bearing on individual lots or buildings. It means acting strategically and setting specifi c measures within one's own competence. Aside from large-scale urban planning approaches it is also important to build public awareness and make members of different Municipal Departments and agencies with the Vienna City Administration sensitive to today's and tomorrow's challenges in tackling the UHI phenomenon.

 The city administration, builders and developers, private ones too, have the right to set measures of their own accord for the purpose of reducing the UHI effect.

 Circumstances and concepts for reducing or preventing the UHI effect may vary depending on the location and occasion. Each development task (e.g. planning a new city quarter, adapting and enhancing existing buildings or project-related processes) has its own set of actions and measures. Political and legal settings, as well as planning instruments provide the basis for realising urban planning and development that is sensitive to UHI. Adjustment measures to reduce Urban Heat Islands are positioned at various political and legal levels and provide the frame for UHI-STRAT Vienna.

#### *9.2.1 Consolidation at the European and the National Level*

 The "EU Strategy on Adaptation to Climate Change" (2013) is based on the premise that climate protection measures must be paired with adaptation measures if Europe is to master the challenges of climate change. From the point of view of the EU Commission "it is cheaper to take, early, planned adaptation action than to pay the price for not adapting" (COM 2013 , 2). The objective must be to raise climate resilience in Europe. The adaptation options are threefold: "gray" and "green" infrastructure approaches, as well as "fl exible" structural approaches (COM 2009 ). Promoting functions and services within ecosystems is considered imperative as these are considered more cost-effective and sometimes more viable than simply trusting grey infrastructure (COM 2009 , 6). The "Austrian Strategy on Adaptation to Climate Change" (2012) adopted by the Council of Ministers also makes it clear that along with measures to limit the global rise in temperature it also takes suiTab. and timely adaptation measures. This second pillar of climate policy constitutes a major complement to climate protection seeing as it reduces greenhouse gases. More specifi cally, the Austrian strategy emphasises the negative effects of heat waves on people's health and the importance of measures to reduce these (Federal Ministry of Agriculture, Forestry, Environment and Water Management 2012a , b , 5). The rise in hot days and the heat stress they create are considered tomorrow's challenges which adaptation measures are required for. Land-use planning is addressed as one of 14 main fi elds of activity (Federal Ministry of Agriculture, Forestry, Environment and Water Management 2012a , b , 16). "Prevention of overheating and heat islands and compensation of bioclimatic stress for people's health" is to be made possible by providing, in development plans, "green" and "blue" infrastructure for built-up areas, as well as "measures with an impact on bioclimate" (Federal Ministry of Agriculture, Forestry, Environment and Water Management 2012a , b , 117f). The strategy also calls for a 'Climate Proofi ng' of spatial planning and tools "to systematically consider the impact of climate change" (Federal Ministry of Agriculture, Forestry, Environment and Water Management 2012a , b , 118f).

#### *9.2.2 Strategic Approach to UHI-Relevant Aspects in Vienna*

 The City of Vienna has taken a strategic approach to climate-sensitive action and measures to adapt to climate change.

 The objectives and results of the individual aspects were combined to form the " **Smart City Vienna Framework Strategy** " adopted by the Vienna City Council in 2014. It is an umbrella strategy for the period up to 2050 to be implemented step by step, individual objectives being subject to continuous monitoring. The overriding goal is to reduce CO 2 emissions from currently 3.1 tons per head to approximately one ton (minus 80 % from 1990 to 2050). Unlike comparable strategies in other cities it encompasses environmental protection goals beyond that, such as reducing the share of motorised private transport from currently 28 to 15 % by 2030, or maintaining the high share of green areas of 50 %.

 The current *Climate Protection Programme of the City of Vienna (KliP II)* encourages strong consideration of the UHI effect in tools of spatial planning, nature conservation plans, as well as informal tools. The "Climate Protection Programme of the City of Vienna (Klip II) – update 2010–2020" adopted by the Vienna City Council has coined as its key goal the reduction of greenhouse gases and proposes measures to adapt to and mitigate the impact of climate change. It contains a separate fi eld of action dedicated to "mobility and urban structure". Again the focus is primarily on reducing energy consumption. The set of measures, however, clearly addresses urban planning measures that are to help reduce the UHI effect. Objectives for the fi eld of action "urban structure and quality of life" include "pursuing integrated sets of measures to raise the quality of life in built-up urban areas (greening street space, courtyards and roofs, reducing soil sealing, upgrading green and open space,…)" (Vienna City Administration 2009 , 93). Specifi c measures are "green paths, multiple use, activating green and open spaces already dedicated, roof greening, neighbourhood gardens and succession gardens" (Vienna City Administration 2009, 100). Regional cooperation must ensure "green and open space for the long term, linking green space (regionally) and strengthening awareness for agricultural products from the city region (Vienna City Administration 2009, 105et seq.). KliP II also for the fi rst time stimulates Vienna's measures to adapt to global climate change.

 The *Urban Development Plan 2025* (STEP 2025 ) in particular broaches the issues of urban climate and climate protection. Its aim is to make "climate protection and adaptation to climate change integral elements of planning, implementation and further development of city quarters and open spaces"(STEP 2025 , 85). This involves, amongst others, creating open and green spaces that can contribute towards reducing the UHI effect. Specifi c measures include the greening of roofs and facades, as well as planting trees and avenues (STEP 2025 ). The chapter on open spaces in STEP 2025 has a separate focus on "adaptation to climate change". Green and open spaces in this context are granted a major role in adapting to climate change while special emphasis is placed on their positive infl uence on the urban climate. A network of open space is to improve the microclimate in individual city quarters. The initiative "urban green instead of air conditioning" wants to identify the areas concerned and reduce UHI.

 The *Vienna Nature Conservation Act* wants to protect and "take care of nature in all its forms across the city and to ensure urban ecology functions" (Nature Conservation Act §1). Protection of green and natural areas includes urban climate aspects considering that climate is part of the landscape balance (section 3, para. 2). "All measures must be planned and implemented in such a way as not to endanger or seriously impair 1. the balance of the landscape, 2. its structure or 3. its recreational effect on human beings" Vienna Nature Conservation Act §4 para 2). Site protection as provided for in the Nature Conservation Act essentially ensures that green spaces and their role for the climate in Vienna are maintained for the long term.

 The *Building Regulations for Vienna* (Vienna Urban Development, Urban Planning and Building Code) set out the principles of urban planning, land use and construction engineering. The fi rst part lists the objectives for determining or amending land-use and building development plans. These refer to climate-relevant aspects only indirectly, e.g. the objective "to (4.) preserve or create environmental conditions that will ensure a healthy environment, in particular with a view to housing, work and leisure time " (Building Code for Vienna, §1, para 2 Z4).

 Protection of the urban climate has been embedded in the strategic and legal tools to enable targeted measures for reducing the UHI effect.

#### **9.3 UHI and the Urban Climate in Vienna – Status Quo and Future Developments**

 Building up natural permeable surfaces is considered the main culprit in the development of Urban Heat Islands (Kuttler 2011 ). The UHI effect is further enhanced by both a steady decrease and fragmentation of urban green spaces and the waste heat produced by industrial processes, air conditioning and motor vehicles. Construction developments also increase the surface roughness, slowing down wind speed in the course. They prevent cold air fl ows generated in undeveloped "cold air production sites" from entering the densely built-up city. Building developments in many cases act as an additional blockade for cold air fl ows from undeveloped environs to agglomeration areas. Generally speaking temperatures are expected to rise from the periphery to the city centre (see Fig. 9.1 ).

 The isothermal map highlights the Urban Heat Islands, the outlines of the built up area, as well as the "hot spots", such as sealed car parks or industrial areas, and "cold spots", such as parks, agricultural areas and bodies of water in Vienna.

 Forecasts for climate development are subject to a certain amount of uncertainty. From today's point of view temperatures in Vienna are reckoned to increase. "The 2040ies in the eastern parts of Austria will likely see an increase in temperatures of 1.3–1.8 °C in winter, 1.8–2.5 °C in spring, 2.0–2.5 °C in summer and 2.5–.0 °C in autumn, compared to the 1980s. Heat waves will be on the rise. Between 1961 and 1990 there were an average of 5.1 heat wave days per year (also known as "Kysely days"), between 1976 and 2005 there were as many as 9.1 already, and the current forecast for the period between 2010 and 2039 in the centre of Vienna is an average 17.7 Kysely days per year, the inner districts, because of the UHI effect, being more affected by the heat stress than the periphery" (Vienna City Administration 2009, 196) (Fig. 9.3 ).

 The Central Institute for Meteorology and Geodynamics in Vienna (ZAMG), during the project "Focus I" (Zuvela-Aloise et al. 2013 ), calculated high-resolution, climate simulations of future heat stress in Vienna and examined the effectiveness of adaptation strategies in urban planning aimed at reducing heat stress in densely populated areas. The simulation showed how to improve buildings and open spaces by raising the amount of green and water surfaces, as well as the level of desealing, and by exploiting the Albedo (refl ection coeffi cient) effect on surfaces and roofs.

 **Fig. 9.1** Thermal image of Vienna and surroundings by night. There is a noticeable difference between the urban agglomeration and the cooler rural areas (Source: City of Vienna, MA 22)

 **Fig. 9.2** The Fig. shows the average hourly temperature distribution on a given day in the summer of 2012 – pictured here are two selected areas in Vienna (see Sect. 9.6.2) compared to a rural area in Seibersdorf. Results clearly reveal signifi cant differences in the microclimate of the areas studied, with conspicuously high temperatures in the city centre (Source: Vienna University of Technology, Mahdavi et al. 2014 )

 **Fig. 9.3** Average annual number of summer days 1981–2010 ( *far left* ) and possible climate scenarios 2071–2100 (Source: Zuvela-Aloise et al. 2013 )

The aim was to create a scientifi c foundation for urban planning to build on. The MUKLIMO\_3 experiments, for the purposes of urban development strategies, arrived at the conclusion that there is a great need for adaptation measures if heat stress in the city is to be reduced signifi cantly. Targeted small-scale measures, when combined with each other, such as increasing the share of green space (+20 %), reducing building density (−10 %) and desealing (−20 %), also have a decidedly positive effect (Zuvela-Aloise et al. 2013). All of the above can compensate the impact of climate change at least to some extent. Model results also revealed that because of the topography, the prevailing atmospheric circulation (NW and SE winds) and the different urban structures adaptation measures will not be felt the same throughout the city. Raising the share of green space (+30 %), for example, has a higher cooling effect in the city centre than it does in districts on the outskirts.

#### **9.4 Fields of Action for UHI-STRAT Vienna – City-Wide Actions and Actions for Individual Lots and Buildings**

 UHI-STRAT Vienna identifi es three fi elds of action to enhance consideration of the UHI effect, i.e. (1) awareness building, information and public relations for UHI, (2) urban infrastructure and large-scale strategic measures (3) and more detailed technical and structural measures.

#### *9.4.1 Awareness Building, Information and Public Relations*

 This fi eld of action covers measures aimed at making heat a major issue for future urban planning and development and at building awareness among people and planning experts in general.

 It is primarily about providing information, whereby a distinction has to be made between information for residents and visitors to the city on the one hand and information relevant for planning purposes on the other hand. Information on (impending) heat stress for the city has been available since 2010. The Vienna Health Board in cooperation with the Central Institute for Meteorology and Geodynamics provides preventive information on expected heat waves on its website and via the local media (http://www.wien.gv.at/gesundheit/sandirektion/hitzebericht.html). This site, as well as that of the Public Health Services of the City of Vienna (MA 15) (www. gesundheitsdienst.wien.at), also explains about what to do in the event of a heat wave.

 Implementing the UHI-STRAT also means building awareness and competences for the UHI issue and its impacts among the departments responsible for planning and projects at the City Administration. Spatial research and research projects on climate change are already generating information relevant for planning to some extent.

#### *9.4.2 Urban Structure, Large-Scale Strategic Measures*

 When implementing measures a distinction is made between long-term strategic measures and the more specifi c technical and structural ones, the difference being the scale – from the city as a whole down to individual buildings and open spaces – and the time horizon. Building an interconnected network of open spaces to generate and distribute cold air and expanding the tree population in the city are strategic measures with a long-term effect.

#### *9.4.3 Specifi c Technical and Structural Measures*

 This fi eld of action describes different approaches for implementing the strategic goals of UHI-STRAT Vienna, as well as large-scale strategic measures for the planning and project stages. The 24 specifi c technical and structural measures are divided into fi ve different areas, (1) green and open spaces (incl. streets), (2) water bodies in the city, (3) shading, (4) mobility and (5) buildings. The measures prepared take into account suitable courses of action with both existing and planned new structures.

#### **9.5 Level of Action – From Master Plan to Project**

 Bearing in mind the overarching signifi cance of Urban Heat Islands, the environmental and climate policy approaches for the protection of the (urban) climate and the rules and regulations associated with them the following main levels of action were identifi ed for UHI-STRAT Vienna: (1) master plans and urban development guidelines; (2) strategic environmental assessment (SUP) and environmental impact assessment (UVP); (3) land use and building development plan; (4) planning and development of public green and open space; (5) developer competitions, housing initiatives and public housing construction; (6) planning and development of public utility buildings and (7) subsidising measures.

 When implementing measures it is important to take into account the hierarchy of planning levels and the chronological order different tools are employed in during the planning process. Interfaces with the various tools call for integrated planning and harmonisation across departments and agencies if the measures employed against the UHI phenomenon are to be successful.

#### *9.5.1 Master Plans and Urban Planning Mission Statements*

 Urban development mission statements and master plans have a major bearing on subsequent steps of planning and development in city quarters (MA 21B, 2010 ). They harmonise public and private interests and create the foundation for further planning. Urban development structures, building density and distribution of open spaces are determined right here. While this planning level is not legally binding it is usually confi rmed by a City Council decision to be used as a guiding principle for further development.

 Urban development master plans, as a rule, are developed through a number of processes, e.g. citizen participation and competitions, and take into account the challenges planning entails, such as planning of new buildings, the development of former railway locations or branches of industry. Major subject matter and strategies are incorporated into this planning level to weigh up (partly) contradictory urban development objectives, such as densifi cation vs. expansion of open space.

#### *9.5.2 Strategic Environmental Assessment and Environmental Impact Assessment*

 Major projects require various testing methods, more specifi cally the environmental impact assessment (UVP) and strategic environmental assessment (SUP). UVP is used for the approval of specifi c projects that have a major impact on the environment while SUP is implemented as early as the planning stage to set the course for decisions relevant to the environment. Both assessment methods investigate the impact of projects on the following protected goods: human beings, animals, plants and their habitat, soil, water, air and climate, landscape, material goods and cultural assets, as well as the interactions between them. Climate already ranges high with the assessment methods and projects are currently run to fi nd our whether, how and to what extent climate change is considered in these methods.

#### *9.5.3 Land Use and Building Development Planning*

 Land use and building development planning sets out legally binding conditions for all subsequent planning and development processes. Here is where building types, building heights and their orographic alignment are decided. Special Conditions also determine a number of UHI measures at this stage. Aside from building alignments and size, rules may be defi ned to determine the amount of green space on a given parcel of land, as well as the size and location if windows. Details on roof and façade greening may also be provided at this point.

#### *9.5.4 Planning and Development of Public Green and Open Space*

 Planning and development of public streets, squares, green and open spaces is vital for the implementation of UHI-reducing measures, because here is where qualities are determined for the long term. Major emphasis is placed on incorporating UHIsensitive criteria into design competitions. Internal guidelines and checklists, some of which contain climate-sensitive aspects, facilitate implementation of measures at this level.

#### *9.5.5 Developer Competitions, Housing Initiatives and Public Housing Construction*

 Approximately 60 % of households in Vienna live in subsidised apartments (Kolbitsch and Stalf-Lenhardt 2008 ). This level of action is therefore relevant for many parts of the city. Developer competitions have proven successful in Vienna since 1995. The competitions help to promote quality in subsidised apartments. Four main criteria are used to assess the quality of drafts: architecture, economy, ecology and social sustainability. In addition there are "theme" competitions for low-energy and passive houses or car-free housing developments. Competitions to date have considered microclimate for the design of open spaces and have also included the vision of "climate neutral cities" (e.g. Aspern Urban Lakeside).

 The housing initiative launched in 2011 has contributed to ensuring quality based on a two-tier cooperative planning process. Both programmes have always emphasised climate protection but have not paid much attention to adaptations to climate change. Evaluation of these instruments (Liske 2008 ) shows that new and quite specifi c topics can be integrated into urban development at this level and turned into pilot projects for other projects to copy.

#### *9.5.6 Planning and Development of Public Utility Buildings*

 Being a "model" in its own sphere of competence allows the City of Vienna to infl uence commercial developers and participants in competitions. This applies to all Viennese kindergartens, schools and campuses (Vienna Model where different school levels, from kindergarten to secondary schools, share the same building), as well as administrative buildings and other city-owned buildings. The "Space Book" (Municipal Department 34 – Building and Facility Management) and the "Criteria for Energy-conscious Building for Service Buildings in Vienna" (Municipal Department 20 – Energy Planning) defi ne quality standards for the purpose. These guidelines contain a number of UHI-relevant aspects and measures, such as effective sun protection, reducing the externally induced cooling energy provided for in the building code or avoiding large glass constructions to prevent overheating.

#### *9.5.7 Subsidising Measures*

 Subsidies are a way of infl uencing private persons and institutions. Municipal Department 42 (Parks and Gardens) has been subsidising roof greening, courtyard and vertical greening successfully since 2003. Subsidies for roof greening are calculated on the basis of the thickness of the rooting substrate. The example shows how subsidies can promote quality-assuring aspects and measures for the reduction of UHI.

 **Fig. 9.4** Planning levels in the city relevant for the reduction of the UHI effect (source: from top to bottom: Stadtentwicklung Wien, Magistratsabteilung 18 – Stadtentwicklung und Stadtplanung, 2014, STUDIOVLAY; Stadtentwicklung Wien; Büro tilia; Jürgen Preiss, MA 22)

#### **9.6 Feasibility Studies**

 The feasibility studies described below want to demonstrate how UHI-relevant measures can be put into practice using two selected areas in the city as examples (Fig. 9.5 ). They make a clear distinction between measures in the development of new city districts and measures in adapting existing ones, and also identify two different levels of planning, the strategic master plan on the one hand and the planning of legal provisions, i.e. the land-use and building development plans on the other hand. The "Masterplan Nordbahnstraße – Innstraße" in Vienna's 20th municipal district is used as an example to show how measures can be introduced at different stages of the master plan process. Proposed measures can be embedded in land-use and building development plans, as demonstrated in the case of the quarter surrounding Vienna University of Technology (Karlsplatz) in the 4th municipal district. Workshops were held with different agencies at the Vienna City Administration to assess how the UHI catalogue of measures can feasibly be implemented at these planning levels. The Institute for Building Physics and Building Ecology at Vienna University of Technology simulated measures for both selected areas (e.g. tree planting, roof greening) to fi nd out what impact these measures have on air temperature (Figs. 9.10 and 9.12 ).

 The results of a survey carried out for the case study UHI STRAT Vienna are presented here to set the scene for the description of the feasibility studies. The

 **Fig. 9.5** Location of the two pilot areas in the city (Source: Vienna GIS)

survey refl ects people's attitude towards heat in the city, their behaviour during heat waves, as well as their assessment of the measures employed to reduce the UHI effect.

#### *9.6.1 People's Attitude Towards Heat in the City*

 385 answers were collected during this postal survey among people in Vienna to assess their perception and attitudes towards heat in the city.

 The survey was done in August 2013. Questionnaires were sent to 3792 households in Vienna, which approximately 10 % of the addressees replied to. 27 blocks of fl ats were picked out randomly from different areas in Vienna, some more densely built-up than others, and the responses were weighted to arrive at as representative as possible a sample. Almost everyone in Vienna has witnessed at least one heat wave already. Three quarters consider this a negative experience. Heat is felt particularly strongly in the streets and in people's homes (Fig. 9.6 ).

 People in their homes try to adjust to the heat and fi nd ways to reduce its effect. Most frequently cited measures to fi ght heat are: open windows during the night (88 %), make sure to take in more liquids (86 %), keep blinds and curtains closed (80 %). A negligible number of people considered leaving the city or working fewer hours an option during the last heat wave. Only 6 % of the respondents used airconditioning in their homes. Approximately half of the respondents used fans.

 Most frequently perceived public measures against the heat are air-conditioning in public transport (64 %), drinking fountains in the city (59 %) and trees in the streets (51 %). Respondents have hardly noticed measures, such as brightening of street surfaces, shading of pavements or greening of rail or tram tracks.

 A vast majority (86 %) believes that trees are a suiTab. measure for reducing heat stress in the city. An even greater number agrees that trees have a positive effect on

 **Fig. 9.6** Responses to: how did the last heat period affect your wellbeing? (Source: INWE)

 **Fig. 9.7** Responses to: attitude towards measures against heat development, weighted values (Source: INWE)

the streetscape. Most respondents would like to see more trees in their neighbourhood (70 %) and across the city (87 %). A majority of 54 % endorses the claim for "more trees and fewer parking spaces in my district". Only 24 % are not in favour of this measure (Fig. 9.7 ).

#### *9.6.2 Feasibility Study for the Urban Development Master Plan*

 Planning and realisation of large-scale urban expansion and urban development projects can take years and even decades which is why it so important to fi nd ways of reducing heat in city quarters at this strategic level. Urban development master plans and guidelines require intensive planning processes, usually in combination with participation processes. To implement UHI sensitive planning and development means to involve experts early on in the process, ideally when preparing the strategic objectives for the master plan.

#### **<IP_ADDRESS> UHI-Relevant Links in the Master Plan Process**

 The following description of ways to incorporate UHI-relevant issues into the different stages of developing an urban development master plan or guideline is based on the study "planning as a process" commissioned by Municipal Department 21B – District Planning and Land Use – to collect experience with master plan processes in Vienna and internationally. Master plan development is characterised by the four stages of "opening, setting the programme, consolidating and implementing" (MA 21B 2010 ), during which UHI-relevant issues may be introduced and put into practice.

 During the opening stage political and planning requirements, as well as the various expectations with regard to future development are identifi ed. Process structures and participants are determined at this point so it is imperative to include persons knowledgeable in climate-sensitive urban planning. This stage also determines what basic information, plans, expert reports and studies will be required for the process. The master plan process has to specify what basic information on climate conditions in a city quarter must be obtained (e.g. main wind directions, signifi cance of the area as a cold air production site, link with major cold air corridors etc.).

 Setting the programme for actual planning usually means drawing a rough urban development guideline to give the project direction. The interests of politics, investors, landowners and representatives from the administration are translated into functional and structural specifi cations for the development of an area.

 Structural and urban development criteria to prevent heating in future city quarters may be introduced at this stage. The objectives, challenges and general framework defi ned here provide the setting for further development. Analysing the planning area also reveals links that UHI-relevant aspects can be attached to. This means, amongst others, assessing the availability of green and open space in neighbouring quarters, wind corridors, air fl ows and water permeability of the soil.

 The most important step towards incorporating UHI-relevant issues and measures (see below) at this stage is to defi ne the requirements for preparing qualifi cation processes and urban development competitions. The actual urban development qualifi cation process rounds off this phase.

 The "consolidation" phase in the planning and development process is about turning the competition results into specifi c guidelines, preparing feasible concepts and developing detailed implementation projects. By transferring the requirements to the land-use plan and preparing the environmental assessments and environmental impact assessments as needed UHI-relevant strategic objectives and clearly defi ned measures are introduced to the process. Issues, such as the effect of planned construction on the microclimate, must be dealt with in detail at this stage.

 The phase is completed by an interface with the legally binding land-use and building development planning "Not every urban development aspect in the master plan requires binding regulations. By the same token it would be negligent to waive binding and reliable regulations in favour of informal agreements " (MA 21B 2010 , 51). Ways of embedding UHI-relevant measures in the land-use and building development plan are described extensively in the second example.

 The implementation stage is about developing individual projects for the social and technical infrastructure provided by the public authorities, about implementing public space and building development. Technical and planning measures to reduce the UHI effect are put into practice at this stage (Fig. 9.8 ).

#### **<IP_ADDRESS> UHI Measures in the Master Plan for "Nordbahnstraße – Innstraße"**

 "Nordbahnstraße – Innstraße" is located on the premises of the former Nordbahnhof (a railway station in the 20th municipal district) developed gradually over the course of the past few years. Employees of the Vienna City Administration acted out a

 **Fig. 9.8** Stages of the master plan process and links to implementation of the measures (Source: MA 21B 2010 )

 **Fig. 9.9** Feasibility Study "Nordbahnstraße – Innstraße" – section from an aerial view ( *left* ) and measures discussed ( *right* ) for the winner in the urban development competition (Source: City of Vienna)

scenario to transfer competition results into an urban development mission statement that encompasses UHI-relevant measures (Fig. 9.9 ).

 To spark the discussion objectives were defi ned for the "competition inviting urban development ideas for Nordbahnstraße – Innstraße". Additional competition documentation defi ned quality objectives along with "hard" project requirements, such as gross fl oor area, the mix of residential areas/offi ces/retail/commerce in percent, as well as social infrastructure. Following spatial analyses and information campaigns for the public the "general conditions and objectives for the competition inviting urban development ideas" (MA 21A 2011 ) were drawn up. It was during this early planning stage that the fi rst UHI-relevant goals and criteria were drafted. A number of solutions mentioned in the collection of measures were strategically positioned at this point already. The objectives for the urban development competition reveal modalities of how these measures may have a bearing on subsequent implementation stages. One of the requirements, for instance, was to create a system of green and open spaces with a high quality of use for everybody, another was to link the new city quarter with the surrounding main green and open spaces. Other requirements included minimising the degree of soil sealing, as well as considering and integrating urban climate aspects (sun/shade/wind/humidity) in competition submissions across the board (MA 21A 2011 ).

 There was general agreement among staff from the relevant departments that most UHI-reducing measures at this planning level can be introduced during the phases of opening and setting the programme for the master plan process. It is important if not imperative to coin UHI-relevant propositions in the urban development guidelines already. Participatory development during the feasibility study and cross-agency discussions about chances and restrictions have proven successful. These negotiating processes can set the frame for addressing confl icting objectives and challenges and thus support the process of weighing up individual objectives. Attention also needs to be paid to bringing on board the "implementers", e.g. Vienna Public Transport for matters relating to designing and placing bus or tram stops, or coordinating green and open spaces across construction sites to minimise overheating in a quarter. Listed below are the points and issues that can and ought to be addressed and fi nalised during this early stage of urban planning and development: (1) What impact will the planned project have on climate? (2) Which measures for reducing the UHI effect can be implemented in the urban development scenario proposed? (3) Who is responsible for implementation? (4) Which tools will be employed and which planning processes applied to implement the measures? Which challenges does or may implementation pose?

#### **<IP_ADDRESS> Modelling Measures and Their Impact with the Example of "Nordbahnstraße – Innstraße"**

 The Department of Building Physics and Building Ecology at Vienna University of Technology (Mahdavi et al. 2014 ) was commissioned to simulate the impact of the master plan on microclimate based on the results of the winner in the competition inviting ideas for development of the former brownfi eld Nordbahnstraße – Innstraße.

 As soon as the buildings were simulated the mean night air temperature in the area under investigation was seen to rise. This may be explained by a reduced sky view factor, an increase in thermal mass in the area and an increase in the long-wave radiation emitted as a result. In the daytime, however, a signifi cant reduction in mean air temperature was noted (see Madhavi et al. 2014) (Fig. 9.10 ).

 **Fig. 9.10** ENVI-met model before and after building development plus a comparison of average hourly temperatures in the course of a reference day before and after building development (Source: TU Vienna, Mahdavi et al. 2014 )

#### *9.6.3 Feasibility Study at the Level of Land-Use and Building Development Planning*

 Permissible utilisation and development on individual sites are made legally binding for owners and developers during land-use and building development planning. As a rule sites are zoned for building purposes, as green areas or as traffi c areas. Aside from this classifi cation the land-use and building development plan also defi nes the building categories, building methods and building regulations, height and cross-section of traffi c areas (§5 Vienna Building Code), as well as additional defi nitions and "Special Conditions".

#### **<IP_ADDRESS> UHI-Relevant Links in the Land-Use and Building Development Plan**

 In principle a distinction has to be made between new developments and structural improvements to existing buildings. Of course, there is more scope for implementing UHI-relevant measures with new developments. However, there is a wide range of regulations that can be implemented for future projects in existing buildings as well. Where major changes are made to existing buildings these must be adapted to the land-use and building development planning valid at the time. Again, this proves the long-term strategic signifi cance of this planning level.

 Essentially there are two areas where UHI-relevant topics and measures can be incorporated: in the drawn and in the written part. The drawn part sets out rules for escape routes, conditions for use or building classes, i.e. rules to do with the urban structure and the shape of buildings, as well as measures aimed specifi cally at reducing the UHI effect, such as various greening measures, or at mitigating the impact, such as requirements for shaded pathways and arcades. "Special Conditions" (BB) in the written part of the building development plan contain specifi cations for the defi ned area, offering additional suggestions for integrating measures to reduce the UHI effect. This includes, in particular, targets for garden design, roof greening, façade greening, desealing, greening of courtyards and tree planting.

 Measures in the drawn part may range from directions of the streets to the geometry of a building. Streets heat up more in the course of a day than their environment. It is recommended that street layout and adjacent buildings with a shading effect on the streets are considered at this level. The width of streets is connected to the height of buildings with relevant regulations set out in the Vienna Building Code (§75 para. 4). These regulations are generally applicable with the exception of protected zones or areas designated "urban development hotspots". There is little point in narrowing the cross sections of streets as this would necessitate a reduction in building heights to avoid diffi culties with lighting and exposure to light. Wider cross sections combined with green infrastructure can help to reduce the UHI effect. Depending on the direction of a street (E-W, N-S) measures, such as planting rows of trees or utilisation of surfaces may have more or less of an impact. Alignment of streets must take into account the main wind direction so as not to hinder the exchange of air. The height of buildings, their position in relation to each other and the shade they subsequently produce must be coordinated separately for each location. There is no rule of thumb here as the local wind situation, topography and supply of green space vary widely. For complex urban development situations or where climate challenges, such as strong winds, prevail microclimate simulation with different building scenarios is recommended. The drawn part can set the scene for "public pathways" and "arcades" for sun protection along major pedestrian axes. Measures may also be specifi ed in the written part, i.e. the special conditions, as demonstrated in the second, inner-city example below.

#### **<IP_ADDRESS> UHI for the Land-Use and Development Plan for Karlsplatz and Surroundings**

 The second example is located in the area surrounding Vienna University of Technology in the 4th municipal district of Vienna. An analysis was made as to how to incorporate requirements when revising the land-use plan to make sure that new constructions with and renovations of existing buildings take into account the phenomenon of UHI. Most of the area was developed during the Gründerzeit (in the late nineteenth century) with an utilisation mix of apartments, offi ces and commerce and is comparable to many quarters in the city centre of Vienna.

 Special Conditions are particularly suitable for determining how UHI-relevant measures can be implemented in areas already developed. The Fig. 9.11 shows the potentials staff from the Vienna City Administration gathered during an experimental game based on the requirements set out in the Special Conditions for land-use and building development planning. The Special Conditions proposed are concerned primarily with tree planting, roof and façade greening, landscape design of surfaces, as well as with requirements that have a bearing on the level of soil sealing, both in public and in private areas. Qualities, such as substrate thickness with roof

 **Fig. 9.11** Feasibility Study "Karlsplatz" – section from an aerial view ( *left* ) and the measures discussed ( *right* ) (Source: City of Vienna)

greenings, or accessibility of roof gardens may also be defi ned in the Special Conditions. Other issues addressed may include taking the necessary steps to enable tree planting along streets and in public squares, determining the permissible percentage of sealing on a plot of land to reduce the level of soil sealing in park areas or specifying whether arcades are to be built in the area (Fig. 9.11 ).

#### **<IP_ADDRESS> Modelling Measures and Their Impact with the Example of Karlsplatz and Surroundings**

 Three adaptation measures were modelled for assessment of the city centre. The scenarios include: a base case without measures, (1) tree planting, (2) roof greening and (3) a combination of tree planting and roof greening. The fi gures below show the difference in climate conditions between the current building stock and the simulated implementation of individual measures on a reference day. The models were built by the Department of Building Physics and Building Ecology, Vienna University of Technology using ENVI-met 4.0 (Mahdavi et al. 2014 ). Clearly visible are the differences in air temperature between the current situation and after the simulated impact of the measures selected.

 Results reveal that adaptation measures have the potential to reduce air temperature in the research areas on hot summer days. As expected different adaptation measures also have different levels of impact. Roof greening in the city centre has no noticeable effect on air temperature in the open spaces of streets (scenario 2), while trees do (scenario 1). The combination of the two selected measures proved particularly effective (scenario 3). Looking at the time patterns showed that differences in air temperature are more distinct in the evening and during the night (see Fig. 9.12 ).

 **Fig. 9.12** The research area in the ENVI-met model and after implementation of selected adaptation measures, as well as average hourly temperature on a reference day, shown for the current building stock and for the three adaptation scenarios (Source: Vienna University of Technology, Mahdavi et al. 2014 )

 **Fig. 9.13** Cover of the UHI-STRAT Vienna; Download (in German): https://www.wien.gv.at/ umweltschutz/raum/pdf/uhi-strategieplan.pdf

#### **9.7 Conclusion**

 The pilot action UHI-STRAT Vienna shows how measures for reducing the UHI effect can be implemented in urban planning and urban development in Vienna. There is in fact a wide range of tools to trigger action at various levels of planning and to make urban planning climate-sensitive, from strategy planning to development and completion. Close cooperation with the administrative agencies relevant for planning confi rmed that existing tools of urban planning, formal and informal, are quite capable of reducing the UHI effect. Many examples revealed during the project process are proof that urban climate is an issue already for many administrative agencies in their day-to-day business. The examples can help to make sure that Vienna will continue its successful venture of protecting the climate while at the same time adapting to the impact of climate change. This must be considered at an early stage at the strategic level and then broken down to the various levels of planning and fi nally development.

 "Green" measures proved especially effective for Vienna. A growing city where densifi cation of built-up areas is necessary to keep distances short can employ these measures to create green and recreational areas for residents, while at the same time reducing the UHI effect. There are strong synergies between measures to reduce the UHI effect and other strategies pursued by the City of Vienna, e.g. reducing (leisure time) traffi c, promoting biodiversity, improving water retention and establishing a network of open space. UHI-STRAT Vienna provides the setting for the implementation of these measures Fig. 9.13 .

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#### **References**

### **Chapter 10 Pilot Actions in European Cities – Stuttgart**

 **Rayk Rinke , Rainer Kapp , Ulrich Reuter , Christine Ketterer , Joachim Fallmann , Andreas Matzarakis , and Stefan Emeis**

 **Abstract** The fi eld of urban climatology has a long tradition in Stuttgart. It exists as discipline in Stuttgart since 1938. Stuttgart was the fi rst city to establish its own Department of Climatology to research ways of improving the fl ow of fresh air into the city and to reduce thermal stress in most populated city districts. The specialist department of Urban Climatology, within the Environmental Protection Offi ce, deals with tasks relating to environmental meteorology within the scope of air pollution control and also relating to urban and global climate protection. So in Stuttgart the urban heat island phenomenon (UHI) is studied for several decades, leading to a high level understanding of the UHI and the problems which it causes. The UHI causes an increase in air temperatures and thermal stress, that are identifi ed as most negative impacts on human health and urban living. In the view of global climate change and the predicted temperature rise for the Stuttgart region of 1.5–2 K in this century, the negative impacts of UHI on human health and urban living will become more problematic in the future. According to the results of climate models the frequency of very hot days is expected to jump by nearly 30 % at the end of the century. The rising temperatures due to the global climate change in combination with the temperature shift as a result of the UHI will intensify the heat stress in

R. Rinke (\*) • R. Kapp • U. Reuter

iMA Richter & Roeckle , Eisenbahnstrasse 43 , 79098 , Freiburg , Germany

 J. Fallmann UK Met Offi ce , Exeter

 A. Matzarakis Albert-Ludwigs-University of Freiburg , Werthmannstr. 10 , D-79085 , Freiburg , Germany

 Research Center Human Biometeorology , German Meteorological Service , Stefan-Meier-Str. 10 , D-70104 , Freiburg , Germany

S. Emeis

Section of Urban Climatology, Offi ce for Environmental Protection, Municipality , Gaisburgstraße 4 , 70812 Stuttgart , Germany e-mail<EMAIL_ADDRESS>
C. Ketterer Albert-Ludwigs-University of Freiburg , Werthmannstr. 10 , D-79085 , Freiburg , Germany

Head of Research Group "Regional Coupling of Ecosystem-Atmosphere" , Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research , Atmospheric Environmental Research (IMK-IFU) , Garmisch-Partenkirchen , Germany

urban areas, that leads to a signifi cant increasing risk to human health, in particular to the very young and elderly. Not least due its importance for the human health and the quality of urban life in Stuttgart, the UHI is focussed by urban planners and is noticed by the future development of the city.

 Within the pilot action study in Stuttgart several measure for reducing the UHI and the impacts on urban living and human health are analysed by the use of micro- scale and macro-scale simulations. With the help of these analysis realisable measure are selected. The most useful measures are implemented into a development outline plan for the redevelopment of the city district Stuttgart-West by the municipal urban planners.

 **Keywords** Climate change • Urban climatology • Urban heat island (UHI) • Urban planning • Restructuring • Air ventilation • Thermal stress • Development outline plan • Green roofs • Heat warning system

#### **10.1 The City of Stuttgart**

 In the following chapter a short overview of the urban and climatic conditions in Stuttgart is given. Especially the basics of the complex topographic situation and the city structure, that infl uence strongly the urban climate in Stuttgart is described. Also the urban heat island phenomenon in Stuttgart is presented. More information can be found at the website: http://www.stadtklima-stuttgart.de

#### *10.1.1 Urban and Climatic Situation in Stuttgart*

 Stuttgart is the capital of the state of Baden-Wuerttemberg located in south-western Germany. As the sixth-largest city in Germany, Stuttgart has a population of about 590.000 and is the centre of a densely populated area, the Greater Stuttgart Region, with a population of 2.6 million. Stuttgart covers an area of 207 km 2 thereof 49 % are settlements. The population density is about 5410 person/km 2 .

 Stuttgart's area is characterised by a complex topographic situation with local distinctions (Fig. 10.1 ). It is one of the greenest cities in Germany. The land use distribution of Stuttgart is shown in Fig. 10.2 . Greenery in the form of vineyards, forests, parks, etc. is prevalent throughout the city. In Stuttgart 39 % of the surface area has been listed as protected green belt land or nature conservation area; a record in the whole of Germany. Despite this greenery populated, industrial and commercial areas are densely built-up. The city's location, building and topographical characteristics have a negative impact on urban climate and cause an intense urban heat island (City of Stuttgart 2010 ).

 The city is located in a river valley (the Stuttgart basin), nestling between vineyards and thick woodland. Stuttgart's centre is situated close by, but not on the River Neckar in a Keuper sink. The city area is spread across a variety of hills and valleys.

 **Fig. 10.1** Topographic map of Stuttgart's city area and Stuttgart's location within Europe

Steep hill slopes surround the city centre on three sides. The elevation ranges from 207 m above sea level by the Neckar River to 549 m on Bernhartshöhe hill. The complex terrain has a signifi cant infl uence on all climatic elements like radiation, air temperature and wind, resulting in large climatic distinctions within the city area. Stuttgart's overall climate is mild with an average annual temperature of about 10 °C in the Stuttgart basin (city centre) and about 8 °C in the more elevated outskirts situated about 400 m asl. Figure 10.3 shows the annual mean temperature distribution in the city area). Besides the Upper Rhine Valley, Greater Stuttgart is one of the warmest regions in Germany. The month of July is the hottest month with an average temperature of 18.8 °C, while temperature in January averages 1.3 °C.

 A major element of Stuttgart's climate is the light wind, that causes a lack of adequate air exchange. The light wind results not only of the city's position between two bights of the Keuper plains. The whole Neckar Valley is known for low wind speeds and very frequent lulls. This is the result of small air pressure differences common to Southern Germany and of Stuttgart's sheltered position between the Black Forest, the Swabian Alb, the Schurwald and the Swabian-Franconian Forest. Due to orographic conditions, it is impossible to indicate a consistent wind rose for the whole of Stuttgart. The sheltered position between the surrounding mountain

 **Fig. 10.2** Land use map of Stuttgart

ranges leads to a frequent development of local wind systems, especially at the slopes and in the valleys. In addition, over large green areas in the surrounding and the city area especially at the higher altitudes, in the nighttime cold air is produced, that generates cold air streams. Even if these winds have no high wind speeds, they play a signifi cant role for the ventilation and local fresh or cold air supply in some city districts. Preserving these local winds and streams is an important objective in the urban planning process in Stuttgart with focus on environmental and urban climate protection since decades. It becomes apparent that primarily cold air fl ows effectively reduce UHI caused thermal stress in nighttime.

#### *10.1.2 UHI in Stuttgart*

 The lack of adequate air exchange in combination with high building density and a huge amount of sealed surfaces, especially in most populated and industrial city districts, facilitate the development of an intensive UHI. Quantifying the intensity of

 **Fig. 10.3** Annual mean temperature in Stuttgart. The city area is marked with a *grey line*

UHI in Stuttgart is complicate, because of the differences in altitude, which infl uence the air temperature and overlay the temperature shift due to the UHI. However, the overall temperature raise due to the UHI phenomenon (UHI Ta ) in Stuttgart is identifi ed within several studies by 1–2 K in annual mean, but locally the UHI Ta intensity can reach more than 5 K. The UHI phenomenon modifi es the climate in Stuttgart. For example in the surrounding of Stuttgart, the Filder region, there are 28–32 summer days (days with more than 25 °C daily maximum temperature) as compared with 40–47 summer days in the Innercity region and the Stuttgart bight. The UHI turns Stuttgart's inner city into a region with high heat stress (about 32 days, Fig. 10.4 ) and only occasional cold stress.

 For the longterm characterisation of UHI meteorological values such as temperature, solar radiation and humidity are measured continuously at about ten sites in the city area, operated by German Weather Service (DWD), municipality Stuttgart (MS), University Hohenheim (UnH) and the environmental protection agency of Baden-Württemberg (LUBW). In this study the UHI is analysed using air temperature and also the thermal index Physiologically Equivalent Temperature PET (Mayer

 **Fig. 10.4** Annual number of days with high heat stress in Stuttgart. The city area is marked with a *grey line*

and Höppe 1987 ; Höppe 1993 , 1999 ; Matzarakis et al. 1999 ) measured at the sites Schwabenzentrum (MS), Schnarrenberg (DWD), airport station Echterdingen (DWD) and at University Hohenheim (UnH). Average annual UHI Ta intensity (based on air temperature) at Schwabenzentrum is 2 K and at Schnarrenberg 1.6 K. In the Neckar valley, the mean UHI Ta is 0.9 K. At the suburb Hohenheim, the UHI Ta of 0.3 K is not pronounced as the suburb is surrounded by agricultural areas and has a higher elevation as the rural reference station Echterdingen. The urban-rural differences in PET are higher with 4.1 K (3.1 K) between Schnarrenberg (Schwabenzentrum) and Echterdingen.

 During summer, the UHI PET (UHI Ta ) is by 15.2 % (8.1 %) higher than 6 °C in the city center. However, a UHI between 0 and 6 °C is most frequent at the other measuring sites. The UHI effect is stronger and more frequent during summer than during winter, increasing the already existing heat load. The minimum UHI Ta occurs in the late morning, whereupon the rural air temperature is often higher than the urban, especially during warm seasons. The UHI Ta peaks at 6:00 p.m. in the winter and 9:00 p.m. during spring, summer and autumn at Schwabenzentrum. At Neckartal, the amplitude of the diurnal cycle is weaker and UHI Ta is maximal in the early morning. The monthly maximum UHI Ta occurs in winter in the city center due to anthropogenic heat production. However, considering hourly averages, the maximum UHI is experienced in summer. It can be observed that air temperature differences are largest at nighttime, but the PET differences are highest at daytime. The urban heat island intensity was compared to the air pressure as well as fl ow patterns. The UHI is more pronounced during periods with anticyclonic weather situation (Ketterer and Matzarakis 2014a ).

#### **10.2 Pilot Action Study Stuttgart**

 In this chapter the pilot action study in Stuttgart is presented. For the pilot action area the city district Stuttgart-West is chosen. The area was selected in view of a problematic climatic situation with high thermal stress caused by the structure of building. An important point for the selection of the area is an initiative launched by the municipal urban planners for restructuring the district in the next decades. Expected changes in urban living, the predicted increase in urban population, within the district existing brownfi elds and also the poor climatic situation are facts for a necessary restructuring of the district. The objective of the pilot action study is to fi nd out realisable options for improving the local climatic situation in the district mainly due to better the air ventilation and the reduction of thermal stress. The results of these study should be integrated into a development outline plan of the district, which is under development by the municipal urban planners. In Stuttgart development outline plans are an established pathbreaking helpful urban planning tool for the sustainable future development and restructuring of single city districts weighting residental, economical, public, natural, environmental and climatical aspects. Reducing the negative impacts of the UHI on urban living will be a topic of the development outline plan. For the implementation into the development outline plan, fi rst the UHI intensity and hotspots of high thermal stress in the district have to be known. As a second the effectivity of measures must be analysed to set up the most valuable ones. Within the pilot action study, the UHI intensity and its impacts on urban living is analysed using meteorological measurements and micro- and macro-scale simulation tools. Micro-scale simulation tools are also used to verify the local effectivity of thermal stress reducing measures. To estimate the potential of measures for a city wide reduction of the UHI intensity, macro-scale simulation tools are used.

#### *10.2.1 Pilot Action Area*

 The pilot action area Stuttgart-West (valley fl oor) is located in a small valley close to the city centre in the western inner-city region (Fig. 10.5 ). The area is surrounded by steep hills at three sites (South, West and North). Stuttgart-West is the most densely populated district in Stuttgart and has a population of about 33,000 and a

 **Fig. 10.5** City map of Stuttgart with the location of the pilot action area Stuttgart West ( *red marked area* )

 **Fig. 10.6** Airviews of Stuttgart-West, which illustrate the typical building structure

population density of 18,370 person/km 2 . About 10 % of the inhabitants are younger than 15 years and about 15 % are older than 65 years, that means 25 % of the inhabitants are in early danger by thermal stress. The area is characterised by a high building density with predominant residental buildings. A high number of historical buildings, that have to be preserved, limit the redeployment of the district. Green areas and places for the recreation of the inhabitants are sparse available. The

 **Fig. 10.7** UHI classifi cation in Stuttgart-West ( *left* ) and number of days with high thermal stress in Stuttgart-West (annual mean, *right* )

typical building structure in the district are blocks with additional buildings in the inner areas of the blocks (Fig. 10.6 ). These characteristics causes poor ventilation of the district and a high UHI intensity with increased thermal stress (Fig. 10.7 ). In addition the air pollution is on a high level. Due to these atmospheric conditions the pilot action area is less attractive for living with potential risks for human health.

 The average UHI Ta intensity is about 2 K, but can be many times higher on local hotspots depending on daytime and season. On hotspots an UHI Ta intensity of more than 6 K is measured frequently. At the surrounding hill slopes local wind systems arise and at nighttime cold air fl ows are induced at the hill slopes. Because of the high building density in the valley fl oor, these local streams are blocked and mostly don't reach the inner district area. The pilot action area is the most thermally stressed area in Stuttgart. Based on case studies an optimized building structure for the pilot action area to reduce the thermal stress is developed.

 **Fig. 10.8** Different scenarios for the Olga Hospital site as input for the micro-climate simulations. *Panel A* depicts the current state of the Olga Hospital (also with green roofs for every building with fl at roofs), *Panel B* the park scenario, in *Panel C* one building is replaced by a small pond (shallow water) and in *Panel C* the number of trees along the streets was increased

#### *10.2.2 Case Study Olga Hospital (Stuttgart-West)*

#### **<IP_ADDRESS> Quantifi cation of Mitigation and Adaptation Possibilities**

 For the case study the area of the Olga Hospital in Stuttgart-West is chosen. The Olga Hospital is a hospital, that is not longer in use and should be redesigned into a residental area in the next years. The human thermal comfort conditions of the case study area and different scenarios (Figs. 10.8 and 10.9 ) were analyzed using microscale models RayMan (Matzarakis et al. 2007 , 2010 ) and ENVI-met 3.5 (Bruse and Fleer 1998 ; Huttner 2012 ). The input parameters for the ENVI-met simulations are based on the measurements of the 24th July 2010 (wind speed 2.6 ms −1 , wind direction: 250°, no clouds, shortwave radiation adjustment factor 0.83, relative humidity and potential temperature were forced). So, these case studies are representative for hot summer days with a high amount of solar radiation. The average

 **Fig. 10.9** Physiologically Equivalent Temperature (PET) of different scenarios (see Fig. 10.8 ) of the Olga Hospital area. The basic meteorological variables were simulated by ENVI-met 3.5 and PET was calculated by TIC-ENVI-met (Ketterer and Matzarakis 2014b ). Finally, the data were averaged from 10 a.m. to 4 p.m. for the height of 1.5 m above ground

mean radiant temperature in the whole area is 57 °C; ranging from 23.8 °C to 75.6 °C. The lowest mean radiant temperature was calculated in the shadow of trees in green areas. The mean radiant temperature is at least 3 K higher in the shadow of buildings and 45 K higher in sealed courtyards. The mean radiant temperature has the greatest infl uence on PET in the daytime on a sunny summer day. PET rises up to 58 °C above sealed surfaces with low albedo, high solar irradiation and low wind speed. In green areas, PET ranges between 18 and 28 °C in shaded, but does not exceed 35 °C in unshaded areas. Streets which are parallel to the wind direction (e. g. Bebel and Bismarck Street), featured lower PET (ΔPET ≤ 10 K) than other streets (Senefelder Street). The difference in PET between sealed and non-sealed areas is at least 10 K (Ketterer et al. 2013 ).

#### **<IP_ADDRESS> Micro-scale Simulations**

#### <IP_ADDRESS>.1 Surface Types

 Thermal conditions over green areas, paved and water surfaces are quantifi ed using ENVI-met simulations. PET rises up to 58 °C above paved, unshaded surfaces with low albedo. Above green areas, PET does not exceed 35 °C in unshaded areas and 25 °C in shaded areas. The difference between paved and green areas is at least

 **Fig. 10.10** Frequency distribution of the Physiologically Equivalent Temperature (PET) for following different urban morphology: courtyards, street canyon with aspect (H/W) ratio of 0.5 and 3.5 and rotation of 90° (E–W) and 345° (NNE–SSW), under a group of trees and the original data of the measuring station Schwabenzentrum (city center) for the period 2000–2010

10 K. Considering the assessment scale of Matzarakis and Mayer ( 1996 ), the thermal stress can be reduced from strong heat stress above paved surfaces to light heat stress above green surfaces (Fig. 10.9 ).

 The installation of a small pond has no signifi cant impact on the spatial average of the studied Olga Hospital area, but a local impact on the air temperature. Air temperature is decreased due to the smaller Bowen ratio and enhanced latent heat fl ux. Additionally, water has a very high specifi c heat capacity. However, small and shallow water surfaces heat up relatively fast, so that they can have a warming effect during evenings and nights in mid-summer as well as in early autumn.

 ENVI-met simulations of the current scenario with the Olga Hospital and for a scenario with a park were done for a calm, hot summer day and compared for 14 LST. The specially averaged PET value decreases by 2.6 K in the park scenario. The wind speed increases due to lower roughness in the lee (east) side of the park and decreases PET, too. The PET value was decreased by maximum 7.0 K an on average by 1.7 K in the street east of the park. On the streets in the north and south of the park, PET is 0.4 and 0.8 K lower than in the current state. A park with a continuous green area is 1–20 K PET colder then green areas on the built-up area. The more trees in a park, the cooler PET on a hot summer day and the smaller the diurnal amplitude of the temperature. However, the air temperature differences between different scenarios are below 2 °C (Ketterer et al. 2013 ; Ketterer and Matzarakis 2014b ).

#### <IP_ADDRESS>.2 Trees

 PET in 1.5 m height was found to be around 10 K lower under trees compared to green areas and 25 K lower than over asphalt (Fig. 10.9 ). Therefore, shading by trees could reduce the frequency of daytime heat stress signifi cantly (Fig. 10.10 ).

 The increasing number of trees in the Olga Hospital area has no signifi cant impact on the averaged air temperature during moderate warm conditions. However, during hot summer days it could reduce the air temperature in this area by 3.0 K (spatial average).

#### <IP_ADDRESS>.3 Green Roofs

 The effect of green roofs was quantifi ed using ENVI-met and by changing all roofs of the hospital scenario into green roofs. The effect of green roofs on the local thermal conditions experienced by humans on street level are on a very low level (ΔPET < 0.06 K). The local air temperature differences on street level are even lower. However, green roofs signifi cantly reduce the warming of urban roof surfaces in daytime. Inside green roofs the accumulation of heat is decreased, resulting in a lesser heat emission in nighttime. A large-scale revegetate of roofs is an effectively measure for the mitigation of UHI intensity especially in nightime.

#### <IP_ADDRESS>.4 Urban Morphology

 The urban morphology is analyzed using RayMan Pro (Matzarakis et al. 2007 , 2010 ). The morphology of street canyons infl uences solar access and radiation and therefore thermal comfort. The importance of solar access for city dwellers depends on the climate zone. While south of the Alps sun is considered as harmful, solar access is favored in northern cities such as Stuttgart. East-west oriented street canyons do not have solar access during winter months due to the low zenith angle of the sun. But during summer, the street canyon and especially the northern façade is illuminated during the whole day. Accordingly high is the frequency of heat stress in this E-W oriented street canyon. A N-S oriented street canyon is accessed by sunshine during the midday hours throughout the year (Ketterer and Matzarakis 2014b ).

 The daily maximum value of PET could be reduced by 10 K due to a changing H/W ratio from 0.5 to 3.5 and an orientation of 120° on a hot summer day. Throughout the year, the frequency of heat stress can be reduced by 477 h (4.3 %). Additionally, the occurrence of thermal comfort conditions could be increased by 10 %. However, a change in H/W ratio from 0.5 to 1 (2.5) could already reduce the frequency of heat stress by 192 (333) hours per year (Fig. 10.10 ).

#### <IP_ADDRESS>.5 Courtyards

 The micro-climate of courtyards was studied using the micro-climatic models RayMan and ENVI-met. The human thermal comfort conditions in two courtyards (Schlossstrasse and Senefelderstrasse) in the Olga Hospital area were compared to the conditions in street canyons (Breitscheidstrasse, Senefelderstrasse) and on a green area (Elisabethenstrasse – Hasenberstraße) over 11 years. Therefore, the micro-scale RayMan model employing fi sh-eye photos was used to describe long term conditions. In the courtyards, the frequency of heat stress (PET > 29.1 °C) and thermal comfort is between 45.5 % and 51.6 % from May to September. Whereas the frequency of thermal comfort is between 3.6 % and 13.8 % higher in east-west and NNW – SSE oriented street canyons. Additionally, PET is also higher at nighttime than during daytime due to the smaller sky view factor in courtyards. Multiple refl ections can also increase PET in courtyards. Another factor is the low wind speed in these sheltered locations, triggering a further increase in PET. ENVI-met simulations for a hot summer day show that PET is up to 25 K higher over a paved courtyard compared to a park area covered with plants and grass.

#### *10.2.3 Macro-scale Simulations*

 Specifi c urban planning strategies, like green roofs or facades and highly refl ective materials are able to reduce the UHI. Taha ( 1997 ) demonstrated that increasing the albedo by 0.15 can reduce peak summertime temperatures for the urban area of Los Angeles by up to 1.5 °C. During the DESIREX Campaign 2008, Salamanca et al. ( 2012 ) stated that a higher albedo leads to about 5 % reduction in energy consumption through air conditioning during summertime periods for the area of Madrid. The regional energy saving effect of high-albedo roofs can also be found in Akbari et al. ( 1997 ) and on a more global perspective in Akbari et al. ( 2009 ).

 In the course of the project UHI – Development and application of mitigation and adaptation strategies and measures for counteracting the global "UHI phenomenon" (3CE292P3) – CENTRAL Europe. (2011–2014), these kinds of scenarios are conducted for the urban area of Stuttgart. Due to its geographical location in a valley, the weak mountain – valley circulation leads to increasing potential for natural heat trapping in the urban region. Modelling work of the environmental agency of Stuttgart shows, that the area with more than 30 days/year heat stress is anticipated to increase from 6 % (1971–2000) up to 57 % (2071–2100). This refl ects the calculations of the Intergovernmental Panel on Climate Change (IPCC) on global climate change.

 The Karlsruhe Institute of Technology (KIT) conducts simulations using the numerical mesoscale Weather Research and Forecasting Model WRF Skamarock et al. ( 2005 ) on regional scale, coupled to urban parameterization schemes (Kusaka et al. 2001 ; Martilli et al. 2002 ). The results refl ect the effects of certain urban planning strategies on near surface air temperature and on UHI intensity.

 **Fig. 10.11** Difference in potential 2 m air temperature for the four scenarios: ( **a** ) changed albedo for roofs and walls, ( **b** ) modifi ed proportion street width/building height and the two urban greening scenarios with one big park ( **c** ) and a number of smaller parks ( **d** ); projected time is August 13 2003 8:00 p.m

 **Table 10.1** Impact on UHI formation expressed as the difference between mean urban and mean rural temperature, August 13 2003 8 p.m

The control run indicates 'real' conditions

Four case studies were applied representing different mitigation measures.

 The difference in 2 m temperature between scenario- and base case ('reality') run refl ects the effi ciency of the mitigation procedure (Fig. 10.11 ). To refer to an extreme case scenario, a period during the European Heat Wave 2003 (August 11th–18th 2003) was chosen, where summertime temperatures exceeded the annual average.

 Table 10.1 presents the mean and maximum urban temperature as well as the UHI, calculated from mean urban and mean rural temperature with regard to Aug 13 2003 8:00 p.m. The difference between Control run and Scenario is calculated for both temperature and UHI.

 Referring to Table 10.1 , a changing of the albedo of wall and roof surfaces has the strongest effect on temperature, causing a decrease of the UHI intensity by nearly 2 °C.

 Both vegetation scenarios show a decrease of about 1–1.3 °C. With 1.2 temperature reduction, the effect is similar for the 'Density' case.

 Because of insuffi cient observation data in the rural surrounding, it is diffi cult to retrieve the UHI intensity from measurements. The difference between air temperatures observed at 'Stuttgart Schwabenzentrum' (37.4 °C) and at Stuttgart Hohenheim in the near surrounding (33.1 °C) accounts for 4.3 °C, for August 13 18:00 UTC. Assuming a height dependent temperature decrease of 1 °C per 100 m between urban (250 m NN) and rural (400 m NN) location, the adapted observed UHI amounts to 3 °C. The second parameter in Table 10.1 describes the mean temperature for the whole modelling period for one single urban grid cell in the centre of the city, whereas all other parameters treat aerial statistics for one temporal snap-shot.

 The above fi ndings describe the climatological and meteorological background for the forthcoming mitigation and adaptation actions to reduce the urban heat islands and its impacts. Besides the modeling results it is now of great importance to fi nd the best urban planning strategy for the specifi c urban area of interest, considering a mixture of different mitigation strategies. However, due to the coarse resolution it is diffi cult to directly apply the measures proposed by that study. Rather, these kinds of modelling studies can be used as a decision support and provide meteorological boundary conditions for high resolution street scale models.

#### **10.3 Transfering the Findings of the Pilot Action Study to Urban Planning Process in Stuttgart**

 The fi ndings of the studies within the pilot action Stuttgart, have shown, that several measure can be effectively reduce the UHI intensity and the impacts on urban living and human health. However, reducing UHI intensity in a city, which is growing over the centuries, requires deep changes in the city and building structure. Changing a city to improve the urban climate is a hard and challenging transaction, which needs a sustainable future-oriented urban planning. Most of the measures for reducing UHI in a city are only effective by large-scale implementation, but changing a city due to urban planning are mostly concentrated on single buildings or small areas like existing brownfi elds. Additional diffi culties are a low awareness for the problems caused by UHI by the public and political boards, existing national and internation strategies for the future development of urban areas, which potential forces the UHI intensity (for example the European sustainable development strategy, which supports the development of more compact and more densed cities), a low number of free available areas to set up measures like parks, contrary interests of public, industry and economy and the ownership structure. Also, in Germany a legal basis for the consideration of UHI related aspects in the urban planning process is currently not available.

#### *10.3.1 Legal Basis for the Consideration of UHI Related Aspects Within the Urban Planning*

 To date in Germany no independent "Urban Climate Protection Act" exists in its own right. Also planning measures for Urban Heat Island specifi c requirements are not directly regulated. Instead, these concerns have been integrated into the structure of existing environmental legislation. This is due to the circumstance that many of the classical disciplines of environmental protection or rather ecology simultaneously exercises positive repercussions for climate change and that a fi rm foothold can be provided for climate protection within the framework of existing legislation. Examples of this include the Federal Building Code (BauGB), the Federal Nature Conservation Act (BNatSchG) and a variety of regulations issued by the Federal Immission Control Act (BImSchG). Also rulings given by a series of laws and regulations such as the Energy Saving Act (EEG) and the Energy Saving Ordinance make a specifi c contribution to global climate protection, as well as the "Greenhouse Gas Emissions Trading Act" (TEHG).

 The German Building Code is the most powerful act in Germany for the municipal administration to arrange measures for urban planning in respect to environmental, nature, urban and global climate protection. The code offers differentiated possibilities for urban development that is urban and global climatically just.

#### *10.3.2 Development Outline Plan*

 The development outline plan (DOP) constitutes a non-formalized level of spatial planning. It is not codifi ed by the Federal Building Code and non-obligatory. In practice, however, the DOP proved to be a valuable and fl exible tool to steer urban development within built up areas. It is an essential function of the DOP to defi ne the municipality's development and planning goals for those parts of the city that show tendencies of urban change. In practice, the planning intentions for public spaces and streets can be described more precisely than those for private building sites. This is why the DOP often also functions similarly to a local design plan. The DOP is not subject to legal regulations.

 In Stuttgart development outline plans are used to set up the urban planning strategy for the sustainable future development and restructuring of single city districts weighting all aspects of urban living, economy and nature, environment and climate protection.

 For the pilot action area Stuttgart-West a development outline plan is under progress by the municipal urban planning department. Within the development outline plan Stuttgart-West the strategy for the future development of the city district is ascertained. One aspect of this strategy is to improve the climatic situation and to reduce the negative impacts of the UHI inside the district. Based on the analysis simulation results, done within the pilot action study, hotspots of high thermal

 **Fig. 10.12** Map based on the analysis of areas with high thermal stress. The *grey shaded blocks* are characterised by high thermal stress mainly due to a prevented ventilation of the inner area and due to high building density and unavailable greening. The *grey blocks* should be redesigned according the development outline plan. The purple surrounded blocks are currently under reconstruction

stressed areas in the district are indentifi ed. Also effective and realisable measure for reducing the thermal stress on the hotspots are choosen for the implementation into the development strategy and the development outline plan for the district.

 Hotspots, which are high thermal stressed are located mostly in the inner region of the district (Fig. 10.12 ). These areas are characterised by a high building density with additional buildings inside the blocks, a high degree of sealing and a lack of greening. The high building density prevents a ventilation of the block inner area, which forces the accumulation of heat. For these blocks an optimised building structure (Fig. 10.13 ) for the potential reconstruction is developed based on the micro-scale simulation done in the pilot action study (Olga Hospital, see Chap. 2.2). These optimised building structure supports a better ventilation of the block and the thermal stress is reduced compared to the existing building structure due the greening of the block in form of greened courtyards, green roofs and green facades or the use of cool materials for roofs and facades. However, the optimised building structure is

 **Fig. 10.13** Optimised building structure, which is offered to reduce the thermal stress inside the block. These building structure is part of the development outline plan is not obligatory for potential reconstruction of existing blocks, but gives a reference to improve the local climatic situation. Gaps between the buildings facilitate the ventilation of the inner area. The courtyard of the block ( *green marked area* ) is greened. Buildings inside the blocks ( *red-green marked* ) must be equipped with green roofs and the height of these buildings is limited. Buildings around the block ( *orange marked* ) should be equipped with green roofs, but it is not compulsory. Facades which are orientated to the south ( *dark green marked* ) have to be greened or designed with cool materials

 **Fig. 10.14** Optimised design of street canyons in Stuttgart-West. *Green lines* marking street canyons, where the thermal stress is reduced due to facade greening of the use of cool materials for facades. *Green circles* marking possible positions for trees

 **Fig. 10.15** Possible creation of green connections ( *green lines* ) in Stuttgart-West

not obligatory for the redevelopment of a block, but gives a reference to improve the climatic situation. If the suggested building structure is absolutely the optimum has to be checked from case to case under consideration of the ambient conditions. But setting up green roofs on new buildings can only be prevented for a comprehensible reason. Green roofs on new buildings are a standard in Stuttgart.

 Beside the optimised building structure also suggestions for the design of public spaces are offered (Figs. 10.14 and 10.15 ). The design of public spaces to reduce the thermal stress is relatively easy realisable, there no ownership structure must be respected. The measures offered for the design of public spaces mainly strive the improvement of the sojourn quality, due the reduction of thermal stress in street canyons, squares and parks. To reduce the thermal stress in street canyons, especially possible tree positions inside street canyons, which are orientated from east to west are identifi ed and implemented into the development outline plan. Also for building facades along east to west orientated street canyons a design with cool materials and/or a facade greening is offered. The greening of existing brownfi elds mainly due to parks are also part of the development strategy of the district. The creation of connections between existing green areas (Fig. 10.14 ) are an utmost concern, which is considered within the strategy for the improvement of the climatic situation inside the district.

 Also the ventilation of the district due to local wind systems and cold air streams is analysed (Fig. 10.16 ). To improve the ventilation of the district, reducing the

 **Fig. 10.16** Major cold air streams in Stuttgart-West. The *yellow shaded areas* mark areas with restriction to buildings to reduce the obstruction of existing streams

obstruction of existing streams, due to the enlargement of the major stream axes (mostly street canyons) is implemented into to development outline plan for Stuttgart-West. For the enlargement of the stream axes in the concerned areas, a maximum building high, an optimal building axes orientation and the reinstatement of buildings are offered.

#### **10.4 Stuttgart's Heat Warning System HITWIS**

 The increase in the number of days exposed to high temperatures and high humidity will result in heat stress for the population. This can pose a danger, particularly for the elderly and those in poor health. In the summer of 2003, the extreme conditions accounted for an estimated 2000 additional deaths. So it is necessary to inform and to warn respectively. Additionally a customized behaviour must be advised different target groups.

 To improve the more or less existing heat warning system in Stuttgart HITWIS was constituted a working group "Heat waves/heat stress" including some parts of the municipality (health care, urban climate, social welfare offi ce etc.). This working group is well connected to external institutions like ambulance services, housing societies, social services etc..

The following measures are recommended and have been partly realised: