Heat stress: a growing problem in cities

As a result of climate change and urbanisation, heat stress is becoming increasingly common. It is a complex problem involving many factors. What can we do about it and how can digital models help?

Hard surfaces in cities

Heat stress is particularly a problem in cities. Hard surfaces play a major role in this, as the sun’s heat is absorbed by materials such as tiles and concrete. These materials then give off heat all day long. As a result, the heat remains in the city both day and night. This is known as the urban heat island.

Local differences in heat stress

There are also factors that influence urban heat at a very local level. Shade, wind and evaporation reduce heat stress. This is why it is important to have sufficient green spaces and water in cities. It ensures that not the entire city heats up, and that there are enough cooler areas.  

Impact of heat stress

Whether and how heat stress is experienced varies from person to person and from area to area. Often the function of an area is considered in relation to heat stress. This involves questions such as: Do many people work outside? Do old people live there? Are there many children playing in the street?

Digital models

Witteveen+Bos works with various models. Through the clever use of data, these models can help make heat stress easier to understand.

One of these models is the Heat Stress Map [link]. This model can show very specifically per urban location how high the perceived temperature is. To a certain extent, perceived temperature is dependent on the individual. Elderly people, for example, experience higher perceived temperatures because they are less able to shed heat. As well as this, perceived temperature is affected by sun, shade, wind, trees and buildings. The model takes all these factors into account.

Another model – the UCAM model – calculates the urban heat island and provides insight into the relationship between buildings and vegetation on a larger scale. Read here how this model has been deployed in Ghent.

Measures against heat stress

If you know where the hot spots are, various measures can be taken. The effects of these measures can also be calculated beforehand, allowing informed choices to be made. Cooler areas can be created, such as parks, shaded walking routes, or pleasant rest spots. Or the layout of buildings can be examined: How are they cooled? Is solar protection in place? And: What kind of building materials have been used?