Warming up for the cooling down: The integration of adaptation strategies to the Urban Heat Island effect into urban design

Field: Environmental Science (Physical Sciences)

Predictions from the Royal Netherlands Meteorological Institute (KNMI 2014a) show that high temperatures and heat waves will occur more frequently in the future. Warm weather leads to even higher temperatures in the city, because of the Urban Heat Island (UHI) effect. This is not without risks, since heat can affect the health of people. Especially among elderly, poor, and minorities many extra deaths are reported because of heat. Heat does not only have a negative effect on people, but also on the economy and environment of a city. When the UHI effect is present, there is a temperature difference between the city and its surroundings. This is caused by the structure of the city, in which five characteristics play an important role. Together the amount of shadow, reflection (albedo value), perviousness, openness to the sky (sky-view factor), and fraction of vegetation/water, determine whether a city retains much heat or not. Since these heat related characteristics can be measured, an indication can be given of how heat proof a certain area is. Also, measuring these characteristics can give insight in how effective an adaptation strategy to heat can be. This is done in a case comparison for two locations in the cities of Antwerp, London and Copenhagen. In this case comparison, the heat related characteristics are estimated for before and after a given development. From the comparison of these results, it has become clear that interventions on a small scale and large scale both can have a positive effect on the local environment. The existing body of knowledge on adapting to the UHI effect, shows a gap in how to integrate adaptation strategies into urban design. Therefore, design elements are used in this graduation project to make this integration possible. The design elements combine the heat characteristics and adaptation measures, which can become part of a design. This leads to a design that is both good for the city and against heat. The mentioned design elements are described in a pattern language. The pattern language focuses on adaptation to heat, and is generically applicable in (Dutch) cities. In the Netherlands the UHI effect occurs in many cities, from which Rotterdam shows one of the largest temperature differences. The air temperature difference can be up to 8°C (Heusinkveld et al. 2010), while the surface temperature difference is 4,9°C (E. J. Klok et al. 2012). When looking closer at the temperatures, it becomes clear that the UHI effect of Rotterdam is mainly present in the central, western and southern part of the city. Two neighbourhoods in this area, called Bospolder-Tussendijken and Cool, are chosen as design locations for the implementation of the patterns. They both are vulnerable to heat, but in a different way. In Bospolder-Tussendijken there are many young children, and it is a poor neighbourhood with a weak social cohesion. In Cool we can find many working people, who are influenced by heat in terms of labour productivity. The developed patterns are implemented as test cases in urban designs for Bospolder-Tussendijken and Cool. It has become clear that focusing on the weaker heat related characteristics of the design location, has more effect than implementing patterns without focus on specific characteristics. Furthermore, it is not important how many patterns are used in a design, but the fraction of implementation should be as large as possible. Integrating adaptation strategies against heat in urban design, with the use of patterns, helps to create spots in the urban environment where people can cool down.