tech location in particular for the automobile industry. Daimler Chrysler and Porsche have their headquarters situated in Stuttgart. History of urban climatology in ...
In PGBCSym06Booklet_2ndEdition Implementation of climatic aspects in urban development – the example Stuttgart – Prof. Dr. Juergen Baumueller, Department of Urban Climate, City of Stuttgart
Introduction Considering the global climatic change and the fact that more and more humans will live in cities in the future world-wide, the implementation of climatic aspects in city planning gains more significance. By the example of the city of Stuttgart, which has already over 70 years experience in this field, it will be pointed out how climatic concerns can be integrated in city planning. Stuttgart is a metropolitan city with 590,000 inhabitants and is the centre of a region with 2.6 million inhabitants. Stuttgart is the capital of the federal state of Baden-Wuerttemberg in South Germany. The total area of Stuttgart is 207 km² with a settlement part of 102 km², which is about 50%.The forest areas cover about 25%. The region has one of the highest growth levels in Germany and has to deal with continual pressure in terms of settlement areas. In order to preserve one of its key characteristics as a “city in the green” the land use plan to 2010 focuses primarily on inner urban development. Therefore the priority for current urban development is to support large and small projects which contribute to a structural transformation within the city area. Stuttgart is not only “a Metropolis between vine and forest” but also a well-known industrial and hightech location in particular for the automobile industry. Daimler Chrysler and Porsche have their headquarters situated in Stuttgart.
History of urban climatology in Stuttgart Urban climatology has a long tradition in Stuttgart. Already in former times ventilation and air quality were a point of discussion in Stuttgart, especially in 1900 due to the expansion of the city by population growth. (Fig.1). In the year 1938 the municipal council decided already to employ a meteorologist, to investigate the special climatic situation in order to draw a conclusion for city planning. Since that time urban climate is of importance for city planning in Stuttgart. It is interest to mention that the mean wind speed in Stuttgart is very low as a result of the mountains shield like the Black Forest and the Schwabian Alps in the surrounding. In the city centre the mean annual wind speed is only 1.5 m/s (5.4 km/h) due to the special ‘basin’ topography.
City Planning in Germany and Stuttgart Not only because of the heat wave disaster in Europe in the year 2003 with more than 35 000 deaths (7000 in Germany) but also because of the problems caused by the global climate change and the need to find sustainable ways to develop our cities, in Germany a new way of thinking about urban development has emerged. To understand city planning in Germany it is necessary to mention the spatial and landscape planning system, which takes place on different scales, levels and responsibilities (federal, state, regional and municipal) as a legal base of urban development (Fig. 2). It is important to point out that within the planning levels legally binding plans like local development plan are approved on municipal level by administration and city council. The power in decision-making of the city council is high and therefore it is important to strengthen political awareness but also to create legally binding laws on climatic aspects.
Figure 1: The development of Stuttgart since 1900
Figure 2: System of landscape planning and spatial planning in Germany (Source: adapted from Federal Ministry for Environment 1998: Landscape Planning Contents and Procedures, Bonn)
The German Federal Building Code (BAUGESETZBUCH – short BauGB) is the legal framework of city planning on municipal level. The BauGB defines ecological issues as basic necessity for urban development. According to the BauGB the urban development has to be sustainable, integrating the social, economic and ecological demands. Further urban development plans have to contribute to an environment fit for human beings and to the protection and development of natural resources. In this law there are requirements of environmental protection, of nature protection and of the preservation of the countryside, of ecological balance in nature and water, air and climate. In preparing land-use plans and in legally-binding development plans public and private interests must to be duly weighed. A very important demand since 2004 (as well European wide) is to involve the public more into urban planning processes and to produce environmental assessment reports for each plan. Climatic aspects in urban planning To implement climatic aspects in urban planning it is necessary at first to investigate the local climate and especially the urban climate of the city. Urban climatologists already have a lot of data, calculations and maps of the city. In most cases they also have the tools on mesoscale and microscale to calculate the effect of planning on climate and air quality. It is important to look carefully to the main climatic problems in the cities like heat islands, air pollution, ventilation, bio-climate and may be shadowing. We know that the heat island effect is depending of the city size but you can find different zones of overheating in the city mainly depending on the sealed ground without green. This can be seen in the surface radiation temperature image of Stuttgart in the evening on summertime (Fig. 3).
Figure 3: Radiation surface temperature of Stuttgart (22:00) on August 29, 2005
City of Stuttgart – planning policy The preparing land use plan of Stuttgart up to the year 2010 (FNP 2010) has the following guiding principle: “compact, urban, green” and one major aim is to prefer inner urban development in the city more than development on green areas at the city’s edge. Therefore local planning focuses on infill
development, urban regeneration, and on the reuse and reactivation of brownfields as potential sites for building. This is the first step to prevent further damage to any existing unsettled and green area. The land use plan is developed by taking into account the Landscape Plan with general functions of the landscape like forest protection, recreation etc.. Many different measure e.g. conservation of forest areas and vineyards, establishing of green roofs and green rails further ventilation corridors contribute to a greener and climatic-friendly city.
Figure 4: Land use Plan 2010, Stuttgart
Figure 5: Landscape plan – general function
Forest and vineyards Around 25 % of the city area in Stuttgart are forest areas. The use of forest areas for urban development is out of question in Stuttgart. One reason for this is the climatic importance for the city to reduce urban heat islands, to gain thermal comfort, to produce cold air production and to filter air pollutants. But there are also other benefits: habits for animals, place for recreation and function for commerce (wood). In the past Stuttgart was an important city of wine production and till today 400 ha are vineyards. Vineyards are protected and are regarded as a cultural heritage.
Figure 6: Forest and other green areas in Stuttgart
Green roofs To increase the green parts in Stuttgart normally houses for private and commercial use with flat roofs have to be built with green roofs. Since 1986 the renewal of roofs on private houses or garages are financially supported with nearly 1 Million Euro in 372 projects. An area of 53 000 m² was gained. The grant will consist of 50% of the actual cost, with a maximum of 17.90 € per m². The responsible parties must retain and maintain the grant aided roof plantings for a minimum period of 10 years. There is no support for new buildings because the Federal Building Code of Germany gives us the possibility to demand green roofs in new local development plans as well as to retain and maintain the roof plantings by the building owners. Obligatory green roof areas in local development plans are 1 500 000 m². Thereof 300 000 m² till now are realised. On municipal buildings in the last 20 years 90 000 m² green roofs were built. For green roofs there are many benefits partly similar to forest areas: aesthetic view; experience of nature, protection of the weatherproofing layer by thermal and mechanical damage, retention of rainwater and high evaporation, improving the microclimate, dust fixation and new living space for animals.
Figure 7: Downtown of Stuttgart with university and houses with green roofs
Figure 8: Sedum plants often are used for green roofs
Green rails Another way to enlarge green areas in the city is to built “green rails” The total rail length of the “Citytram” in Stuttgart and surrounding is 226 km. Thereof 32 km are built as green rails (Fig. 9). Green rails are standard by building new tracks in Stuttgart. The costs to construct green rails are a little bit higher but on the other hand cheaper in maintenance. The benefits of green rails are similar to green roofs but the work on another height level.
Figure 9: Rails built in the old way
Rails built as “green rails”
Skyscrapers Some years ago there was a discussion about high-rise buildings in Stuttgart. The result was that in the greater part of Stuttgart high-rise buildings are from now on forbidden. Only on a few locations high-rise buildings are allowed but a special audit for permission is necessary (Fig. 10/11)
Zone 1: protected zone Forbidden areas for skyscrapers because of topography, urban climate and townscape Zone 2: possible zones Higher buildings possible but special audit necessary because of urban climate and townscape
Figure 10: High-rise buildings in Stuttgart
Figure 11: Forbidden zones in Stuttgart for high-rise buildings
Ventilation corridors Ventilation in a city is necessary for better air quality but also for a better local bio-climate in the city. Thus air quality normally depends directly on wind speed and on the cooling power of the human body, too.
Kata-Value(mcal/cm² s)
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w ind velocity in m /s
Figure 12: PM10 in Stuttgart by different wind speed
Cooling power by different wind speed
Local wind systems, which mainly show up in areas of weak regional winds, can also be of importance to the movement of air in city areas. These are distinguished between systems that are dependent on topography and those that are determined by the built environment. The former of these, which includes slope winds as well as mountain and valley winds, are shaped strongly by the topographical relief at hand. This circulation is important above all for cities in valleys and "bowl" or "basin" locations, since it contributes to the removal of pollutants as well as to the supply of fresh air.
The development of cold air flows, which typically occur at night close to the ground, depends on the size of the surfaces that produce cold air and on the incline of the slope. Because of the complex topography in Stuttgart at night a local wind system is developing. This nocturnal cold air flow (mountain wind) occurs 40 percent of all nights in Stuttgart and is so important for the local climate in Stuttgart. The figure 13 shows the calculated wind field in Stuttgart th from July 19 2006 at 6:00 with very different wind speeds and wind directions influenced by the nocturnal cold air flow.
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Figure 13: Wind field in Stuttgart from July 19 2006 at 6:00
Based on the knowledge of the special wind situation in Stuttgart, it is one task for the urban climatologists to protect ventilation corridors in urban development. This can be achieved on the level of the urban land use plan as well as on the level of the legally binding local development plan. The example in Figure 14 and 15 shows a protected ventilation zone in the land use plan (Fig. 14) and in the local development plan (Fig. 15) by marking this zone to a green area as private and public green.
Figure 14: Ventilation zone as green area in the land use plan
Figure 15: Ventilation zone as green area in the local development plan
Figure 16: Ventilation zone in an aerial photo
Information of public, politicians and planners It is necessary to provide an information access to citizens, politicians and planners to the results of investigations about urban climate. For example Stuttgart established an municipal internet platform and urban climate information system on CD-ROM which is available for everyone. The intention is that discussions on climatic aspects on public and professional level should strengthened and also becoming part of the local political decision-making processes. http://www.stadtklima-stuttgart.de/ (only in German) http://www.staedtebauliche-klimafibel.de/ (also in English available) http://www.stuttgart.de/
Figure 17: CD-ROM Urban Climate 21
Climate Booklet for Urban Development (on Internet)
Conclusion - It is a need to analyse the local climate as base for planning decisions using different tools. - It is a need to develop and improve urban climate tools for application on the diverse scales. - Planners and climatologists should be better educated to understand their different “languages” and problems of each other. - Climate must be taken into account in all urban planning processes and we need legally binding rules and regulations to manage this. - Protection of ventilation zones (e.g. local wind systems) is very important, in combination with increasing the green parts in the cities - Do goods and talk about it! Information for the public is necessary!
