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Adaptation and mitigation strategies against the
urban heat island effect A comparative study on Amsterdam and Rotterdam
Author: Marijn Fennema ([email protected])
Student no. 11054670
Word count: 17301
Course name: Bachelor Scriptieproject Sociale Geografie en Planologie
Bachelor Thesis Project Human Geography and Urban Planning
Course no.: 734301500Y
Coordinator: Drs. J. K. Maiyo
Second reader: Dhr. J.V. Rothuizen Date: June 25, 2018.
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Acknowledgements First of all, I would like to thank Drs. Josh Maiyo, my bachelor’s thesis supervisor for guiding
me through the process of writing my thesis and doing research as a human geographer. He has
also given me insight about what doing academic research is really like, which made me realize
that although I will soon have my bachelor’s degree, I still have a lot to learn.
Secondly, I would like to thank all the interviewees for helping me with my thesis by
interviewing them, sharing information I would not have obtained otherwise. More specifically, I
would like to thank Alexander Wandl and Jeroen Kluck for sharing their knowledge and insights
about heat stress in the Netherlands. Besides that, I want to thank the people interviewed at the
municipalities, municipal health services housing corporations for sharing their current views on
the urban heat island effect as well as their strategies to cope with it. I would also like to thank
De Groene Stad (the green city) for sharing their vision.
Finally, I would like to thank my family, and my friends in particular for their support and
positivity during the thesis writing process.
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Abstract Background. Human interference with the climate system is occurring, which leads to changes
in human and natural systems. These changes have caused impacts on natural and human
systems around the globe in the past and will continue to do so in the future. One of these effects
is the urban heat island effect, which is a phenomenon that occurs in urban areas, where the air
temperature is usually higher than in the surrounding countryside. This is caused by three
phenomena. The first being urbanization, population growth and urban sprawl, the second being
more manufactured materials and the third being an increase in heating and cooling needs. The
Netherlands has experienced negative effect from the urban heat island effect. The 2006 head
wave for instance led to an estimated 1000+ fatalities in the Netherlands, for a large part those
living in urban areas.
Research goal. This research is aimed to find out the current situation of heat stress in the
Netherlands, and Amsterdam and Rotterdam in particular. This study also looks into how
Amsterdam and Rotterdam are trying to cope with heat stress and implementing adaptation and
mitigation strategies.
Research Methods. The urban heat island adaptation and mitigation strategies in Amsterdam and
Rotterdam are researched by analyzing existing scientific literature as well as in-depth interviews
with people that are linked to heat stress and the urban heat island.
Results. Although heat stress does not receive the attention it deserves, heat awareness in both
cities is rising at an institutional level, which could eventually lead to the implementation of
more adaptation and mitigation strategies specifically aimed at reducing heat in cities. The
public, on the other hand, does not seem to be aware of heat stress. Adaptation strategies against
heat stress include the use of air conditioning and acting according to the national heat plan.
Vegetation is the primary mitigation strategy in both cities in the outdoor space as well as
applied on the built environment (mainly via green roofs). Many adaptation and mitigation
strategies are applied through co-benefits strategies, are often (but not always) top-down and
applied generically.
Conclusion. When comparing the two municipalities in heat awareness, it seems that Rotterdam
is more aware of the urban heat island and its implications than Amsterdam. This is on the levels
of heat awareness, as well as heat-oriented adaptation and mitigation strategies. The key
difference in adaptation and mitigation strategies is that Amsterdam is overall a greener city, and
Rotterdam is applying more adaptation and mitigation strategies that are aimed at the urban heat
island effect. The reason for this might be that in Rotterdam, there is more need for heat-specific
adaptation strategies, because it can become warmer in summers due to Amsterdam being a
much greener city
Recommendations. This study recommends making more use of the polycentric approach in
order to become resilient against the urban heat island effect, or resilient cities in general. Similar
future research should include interviews with urban planners, urban architects and urban
engineers, as well as interviewing or surveying residents to investigate public heat awareness.
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Table of contents
1 Introduction 5
1.1 Research topic 5
1.2 Scientific relevance 6
1.3 Research questions 6
2 Theoretical framework 7
2.1 The urban heat island effect 7
2.2 Causes of the urban heat island effect 7
2.3 Adaptation and mitigation strategies 9
2.4 A polycentric approach to the urban heat island effect. 9
2.5 Urban Resilience 10
3 Operationalization 13
3.1 Heat awareness 13
3.2 Adaptation and mitigation strategies 13
3.3 Implementation of adaptation and mitigation strategies 14
4 Background 16
5 Study area 18
5.1 The Netherlands 18
5.2 Amsterdam 18
5.3 Rotterdam 20
6 Methodology 22
6.1 Research design 22
6.2 Data collection methods 22
6.3 Reliability and validity 23
6.4 Ethical considerations 23
6.5 Data analysis 24
6.6 Limitations 24
7 Results: heat awareness 25
7.1 Institutional awareness 25
7.2 Public awareness 27
7.3 Concluding remarks 28
8 Results: adaptation and mitigation strategies 29
8.1 Adaptation strategies 29
8.2 Mitigation strategies 33
8.3 Concluding remarks 36
9 Results: implementation of adaptation and mitigation strategies 37
9.1 Heat stress adaptation and mitigation as primary or secondary objective? 37
9.2 Policy: top-down or bottom-up? 38
9.3 Area-oriented or generic adaptation and mitigation? 39
9.4 Concluding remarks 39
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10 Discussion 40
10.1 Co-benefits, the only way to adapt? 40
10.2 Rising heat awareness 40
10.3 Differences in adaptation and mitigation between Amsterdam and Rotterdam 41
10.4 A polycentric approach to the urban heat island effect? 42
11 Conclusion 43
12 References 45
13 Appendix 52
13.1 The heat stress framework by Hatvani-Kovacs et al. (2018) 52
13.2 Screenshots of the Extrema Rotterdam weather app 53
13.3 Infographic municipality of Amsterdam 54
13.4 Positions of the interviewees 55
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1 Introduction
1.1 Research topic
Urbanization is a rapidly growing form of land use change that is mainly driven by the
population and the economy in a country (Ma et al., 2005). Although it is considered as an
emerging phenomenon that can lead to many environmental problems in developing countries
nowadays, urbanization has played a big role in the economic development of the now
“developed” countries in the 20th century (Davis & Keating, 2015).
One of the countries that has experienced rapid urbanization in the 20th century is the
Netherlands. The number of urban inhabitants in the Netherlands has grown substantially over
the past decades, with 59,8% living in urban areas in 1960 and 76,8% living in urban areas in
1990 (United Nations, 2014). According to the United Nations World Urbanization Prospects
report (2014), the Netherlands is currently one of the world’s most urbanized countries, with
90,5% of its inhabitants living in urban areas (United Nations, 2014). This trend of urbanization
is expected to continue until at least 2050, where an estimated 96,4% of the inhabitants in the
Netherlands will live in urban areas, which will make the Netherlands the 13th most urbanized
country in the world (United Nations, 2014). Almost one sixth of the Dutch population resides in
Amsterdam and Rotterdam, the two largest cities in the Netherlands, with 1,1 and 0,9 million
inhabitants living in both urban agglomerations respectively (United Nations, 2014).
Urbanization can lead to various effects. These effects range from an increase in air pollution
(Barbera et al., 2010) to an increase in surface temperature and a decrease in humidity (Wang et
al. 2013). In the Netherlands, many cities have experienced expansion in the 20th century, which
in many cases has led to urbanization-induced temperature increase (Koopmans et al., 2015).
One of the most significant effects caused by urbanization closely related to urbanization-
induced temperature increase is the urban heat island effect, which means that urban areas
experience higher temperatures than rural areas (Peng et al., 2012). The urban heat island effect
leads to higher surface temperatures due to mainly an increase of impervious surfaces, which is
one of the effects of urbanization (Yao et al., 2017). The urban heat island effect is considered as
a threat because of its many negative effects, the most substantial negative effect being the
influence on human life by increasing the risk of exposure to health threatening heat (Zhou et al.,
2015). This has led to an increase in mortality rates (Tan et al., 2010). The urban heat island
effect is not a problem that only occurs in tropical climates. In fact, it also occurs in countries
with a cooler climate like the Netherlands. Here, cities such as Rotterdam can experience an
urban-rural temperature difference of 7 oC in the summer (Keuning, 2009).
Although the urban heat island effect can lead to threatening situations for humans, there are
many strategies that help to adapt or mitigate the urban heat island effect. This includes strategies
such as increasing green areas and open spaces (Rushayati et al., 2016) or increasing the albedo
(surface reflectivity) with the usage of reflective pavements (Synnefa et al., 2011). In this thesis,
I will compare the adaptation and mitigation strategies against the urban heat island between
Amsterdam and Rotterdam.
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1.2 Scientific relevance
Some research has already been done on the urban heat island effect in Amsterdam, Rotterdam
and the Netherlands in general (Van der Hoeven & Wandl, 2013; 2015; Koomen et al., 2013,
Heusinkveld et al., 2014). Most research that has been done regarding the urban heat island is
remote sensing research on mapping the urban heat island. Many of these researches do mention
some adaptation and mitigation strategies, such as that tree capacity mitigates the urban heat
island (Rafiee et al, 2016). However, most of the reports do not mention the possibilities and
opportunities for mitigating the urban heat island. Other reports mention urban and regional heat
island adaptation measures in cities in the Netherlands (Icaza, 2017) but do not compare these
cities with each other directly. This is why this research will be scientifically relevant, because
according to available knowledge, a research study that compares the current state of adaptation
and mitigation measures against the urban heat island effect in the two largest cities of the
Netherlands has yet to be done.
1.3 Research questions
The Netherlands is one of the world’s most urbanized countries, and notwithstanding its
flattening population rate, it is still expected that the Netherlands is becoming even more
urbanized. This urbanization can have various climatic side effects that need to be adapted or
mitigated. In this research, I am going to compare the effectiveness of adaptation and mitigation
strategies against the urban heat island effect due to urbanization in Amsterdam and Rotterdam.
Hence the following research question:
How do Amsterdam and Rotterdam apply adaptation and mitigation strategies against the urban
heat island effect?
This will be examined through the following sub-questions:
How aware are Amsterdam and Rotterdam of the urban heat island effect?
What are the main adaptation and mitigation strategies against the urban heat island in
Amsterdam and Rotterdam?
How are adaptation and mitigation strategies for the urban heat island effect implemented in
Amsterdam and Rotterdam?
In the literature review, I will examine the urban heat island effect in Amsterdam and Rotterdam,
and the municipal reports that mention heat stress or the urban heat island effect.
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2 Theoretical framework
2.1 The urban heat island effect
Although this study focuses on urban heat island adaptation and mitigation, the urban heat island
effect itself should be described before elaborating on the adaptation and mitigation strategies.
There is not much debate about the exact definition of the urban heat island effect. Oke (1987)
describes the urban heat island effect as a phenomenon that occurs in urban areas, where the air
temperature is usually higher than in the surrounding countryside (Oke, 1987). This definition
has been used in many different reports related to the urban heat island effect (Kleerekoper et al.,
2012; Taleghani, 2018; Ketterer & Matzarakis, 2014). Although this concept has been well
researched and documented, the understanding of the topic was quite limited (Mohajerani et al.,
(2017); Yow, 2007). This has changed in the past decade due to the greater focus on global
warming and climate effects, the greater prevalence of hotter cities, and changes in technology
for measurement and analysis (Mohajerani et al., 2017).
The urban heat island effect is not the same as the surface heat island effect. Whereas the urban
heat island effect is about the temperature of the atmosphere (Oke, 1987), the surface heat island
effect is about land surface temperature (Li et al., 2017). These concepts are related, however,
because a high land surface temperature has a direct influence on the urban heat island effect (Li
et al., 2017).
The urban heat island can lead to various negative side effects, such as heat stress. Heat stress
can be described as a leading cause of weather-related human mortality, with the high-risk
groups being the elderly, the very young and individuals with health problems (Oleson et al.,
2015). Although heat stress is a common natural phenomenon, it is expected that global warming
will lead to more population fractions experiencing heat stress (Sherwood & Huber, 2010). It is
expected that next to global warming, the urban heat island effect will exacerbate extreme heat in
urban areas, leading to even more heat stress (Stone, 2012). Extreme heat temperatures are most
known for the health risks it leads to, but extreme heat also affects water quality, outdoor spaces
(fire hazard), livability (urban comfort) and networks (increasing need for electricity) (Kluck et
al., 2017).
2.2 Causes of the urban heat island effect
According to Mohajerani et al. (2017), the urban heat island has three main causes. The first
being urbanization, population growth and urban sprawl, the second being more manufactured
materials and the third being an increase in heating and cooling needs (Mohajerani et al., 2017).
Urbanization, the most significant cause of the urban heat island, has many different factors
contributing to the urban heat island effect. These effects range from increasing absorption of
solar radiation due to high density building (Santamouris et al., 2011) to increasing city density
due to urban growth (Doulos et al., 2004) to a decrease in vegetation (Akbari et al. 2001)
Increasing population growth leads to many global environmental changes, including
deforestation and biodiversity loss (Grimmond, 2007), which contribute to the urban heat island
effect because they lead to a decrease in surface and air temperature. An increasing population
often leads to an increase in anthropogenic heat release (Mohajerani et al., 2017).
8
There is still some debate if sprawl, the decentralization and geographical expansion of cities
over large areas (Stone et al. 2010) leads to an increase of the urban heat island effect. Previous
studies have shown different results about the effect of sprawl on the urban heat island effect
(Kohler et al, 2017; Stone et al. 2010).
Manufactured materials often have a lower albedo and greater heat storage compared to regions
with native vegetation, which is a major influence on the development of the urban heat island
effect (Golden & Kaloush, 2006). The changing materials can lead to new surfaces and
atmospheric conditions, altering the airflow, as well as an exchange of energy and water
(Mohajerani et al., 2017).
An increase in heating and cooling needs, as well as many other technological developments in
society, contribute to the urban heat island effect (Mohajerani et al., 2017). An increase in
temperature in cities leads to an increasing demand for cooling techniques such as air
conditioning. Although air conditioning provides cooling for human comfort, air conditioning
services itself generate more heat, which has an effect on the nearby, local-scale external climate
(Grimmond, 2007). An increasing outside temperature thus leads to an intensification in energy
consumption for cooling mechanisms (Santamouris et al., 2015), which leads to a hotter outside
temperature due to the heat generated by air conditioning.
Another influencing factor on the urban heat island effect is surface water. Rivers, lakes,
fountains and other bodies of water experience evaporation during warm periods, which leads to
cooling its surrounding area. However, due to its low albedo rate, water absorbs heat, which
contributes to the nocturnal heat island effect (Van der Hoeven & Wandl, 2015).
Figure 1 adequately visualizes the causes of the urban heat island effect.
Figure 1: How the urban heat island effect occurs (Yamamoto, 2006).
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2.3 Adaptation and mitigation strategies
In order to defend society against the negative effects of environmental issues, measures need to
be taken. These measures can range from building dykes to prevent floods due to sea level rise,
installing solar panels to one’s roof to reduce the use of fossil fuels or installing particulate filters
on diesel cars to reduce air pollution.
These kinds of strategies can be classified among two categories: adaptation and mitigation
strategies.
Adaptation strategies include avoiding hazardous locations and taking measures to counteract or
reduce the dangers of environmental phenomena (Dietz et al., 2008). The IPCC distinguishes
adaptation in human systems from adaptation in natural systems. In human systems, adaptation
strategies seek to moderate or avoid harm or exploit beneficial opportunities, whilst in some
natural systems, human intervention may facilitate to expected climate and its effects (IPCC,
2014b). An example of an adaptation strategy is building dykes in order to prevent flooding in
the Netherlands (Keessen et al., 2013). This is as a prime example of an adaptation strategy
because dykes reduce the chance of flooding, but the cause of flooding is not tackled.
Whereas adaptation strategies are more about preventing or controlling the outcomes of
environmental problems, mitigation strategies are more focused on combatting the causes of the
environmental problem (Dietz et al., 2008). In other words, mitigation strategies strive to tackle
the source of the problem, instead of reducing its consequences (IPCC, 2014a). Using sustainable
energy sources instead of non-sustainable energy sources are considered mitigation strategies,
because these strategies reduce CO2 emissions by using energy sources such as hydrogen, that do
not emit fossil fuels (Wang & Naterer, 2014), thus tackling the source of the problem instead of
reducing its consequences.
Instead of focusing solely on one strategy while neglecting the other, the future of climate policy
will have to consider a combination of adaptation and mitigation strategies (Brasseur & Granier,
2013). Because mitigation strategies tackle the source of the problem instead of its
consequences, one might think that mitigation strategies are always preferred over adaptation
strategies. This is confirmed in the article of Brasseur and Granier, who claim that mitigation
should be the first objective of international agreement, but that adaptation will probably become
necessary (Brasseur & Granier, 2013). However, sometimes it is not possible to carry out both
adaptation and mitigation strategies at the same time, which can happen due to constraints (Klein
et al., 2007: 749). These constraints include financial constraints, political constraints,
environmental constraints and so on. When these constraints occur, tradeoffs between adaptation
and mitigation strategies have to be made (Klein et al., 2007).
Although adaptation strategies tend to be near-term and mitigation strategies tend to be viewed
as more long-term solutions, there is a direct overlap between these strategies. This is because in
reality, both adaptation and mitigation strategies will interact with each other for the duration
they are implemented, regardless of the level they are initiated (Moser, 2012). This is why in this
research report, both adaptation and mitigation strategies will be considered in order to create a
clear image of the current situation in Amsterdam and Rotterdam.
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2.4 A polycentric approach to the urban heat island effect.
The urban heat island effect is not the same in each urban area. Instead, the urban heat island is
dependent on the regional atmospheric and geographic conditions. The location, climatic
conditions and seasonal variations all should be considered while analyzing the urban heat island
effect in a particular city (Mohajerani et al., 2017).
The intensity of the urban heat island effect is also affected by the built environment of an urban
area. As mentioned before, urban sprawl is linked to the urban heat island effect, which might
suggest that cities with more urban sprawl have a stronger urban heat island effect than denser
cities (Stone et al., 2010; Mohajerani et al., 2017). The urban heat island effect is affected by
other factors as well, and urban heat is present in both sprawled as dense cities (Debbage and
Shepherd, 2015). This suggests that the urban heat island is an irregular phenomenon, and an
issue that is best tackled with localized research and mitigation efforts, and mitigation strategies
need to be tailored to individual cities (Mohajerani et al., 2017, Debbage and Shepherd, 2015).
This suggests that regarding the urban heat island, there is no one-size-fits-all strategy, which is a
common phenomenon within environmental science. This is best explained by Hansen & Bi
(2017): “adaptive capacity varies greatly between different populations, communities, and
individuals, depending on levels of vulnerability, resilience, and available resources” (Hansen &
Di, 2017:353). Approaching adaptation strategies from a collectivist viewpoint fails to
acknowledge such differences. Instead, adaptation strategies must be considered through local
decision makers because there is no one-size-fits-all (Hansen & Bi, 2017).
I also support an approach that is more focused on local knowledge. Ostrom (2010) introduced
the polycentric approach for coping with collective action and global environmental change.
According to Ostrom, “polycentric systems are characterized by multiple governing authorities
at differing scales rather than a monocentric unit” (Ostrom, 2010:552). An advantage of a
polycentric system is that participants can use local knowledge, which is often not considered in
monocentric systems. Furthermore, the polycentric approach has considerable advantages due to
the mechanisms for mutual monitoring, learning, and adaptation of better strategies over time
(Ostrom, 2010).
In relation to the urban heat island effect the polycentric approach can be beneficial because of
the different actors involved, as well as local knowledge. A polycentric approach can possibly
prevent large top-down strategies that do not take local situations into account. It also supports
collaborative planning, which could lead to adaptation and mitigation strategies that are more
local-oriented.
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2.5 Urban Resilience
A subject that is gaining increasing prominence across many studies on cities and climate change
is (urban) resilience. Urban resilience emphasizes the idea that cities, urban systems, and urban
constituencies need to be able to quickly bounce back from climate related shocks and stresses
(Leichenko, 2011). Although there are some literary disagreements on resilience, there is a broad
consensus that cities must become resilient to a wide range of shocks and stresses, and efforts to
foster climate change resilience must be bundled with efforts to promote urban development and
sustainability (Leichenko, 2011). The urban heat island effect falls within this ‘wide range of
shocks and stresses’ in order to prepare for climate change, as many studies show the relation
between addressing the urban heat island effect and resilience (Emmanuel & Krüger, 2012;
Shafique & Kim, 2017; Leal Filho et al., 2018)
In order to become resilient, cities should not aim to maintain stability. Instead, cities, or systems
in general, should aim for flexibility (Nelson et al., 2007). A resilience approach recognizes that
vulnerabilities are an inherent part of any system. This means that resilient systems should
identify acceptable levels of vulnerability and respond when vulnerable areas are disturbed
instead of trying to eliminate vulnerability (Nelson et al., 2007).
For this research, the heat stress resilience framework by Hatvani-Kovacs et al. (2018) will be
taken into account (figure 2). In this framework, four sectors related to urban heat stress are
considered: public health services, the building and construction industry, urban planning and
infrastructure services and utilities (Hatvani-Kovacs et al., 2018).
Social and ecological systems need to be understood as related, coupled systems instead of apart
from each other (Nelson et al., 2007). This is the case in the heat stress resilience framework,
which consists of strategies aimed at social systems (increasing the accuracy of health alerts),
strategies aimed at ecological systems (green space ratio) and strategies aimed at both systems
(building cool public spaces) (Hatvani-Kovacs et al., 2018).
The heat stress framework includes some factors that are irrelevant for this research. This is
because the heat stress framework is based on heat stress in Australia, whereas this research
analyzes heat stress in the Netherlands, which has completely different atmospheric and
geographic conditions. Although I have stressed the importance that the urban heat island is best
tackled with localized research and mitigation efforts, I still believe that the heat stress
framework is also applicable on the Netherlands to a large extent. There are some suggestions
that are solely focused on Australia, but overall, the framework addresses many aspects of heat
stress risk and resilience that are applicable in the Netherlands as well.
The entire heat stress framework can be found in the appendix.
12
Figure 2: The policy framework to increase urban heat stress resilience (Hatvani-Kovacs et al., 2018).
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3 Operationalization
3.1 Heat awareness
The first concept that will be researched is heat awareness. As mentioned earlier, heat awareness
could lead to making the necessary step to adapt to heat stress (Klok & Kluck, 2018). For this
research, heat awareness will be divided into two types of heat awareness: institutional and
public awareness.
Institutional awareness will be analyzed at the municipalities, municipal health services and
housing corporations. In addition to that, the experts on the urban heat island effect will also be
asked about their thoughts on institutional heat awareness. Some strategies, such as heat warning
systems, are specifically aimed at informing the public about heat stress. Study shows that
although municipalities can be aware of heat stress and even make substantial efforts to prevent
heat-related morbidity and mortality, it could still be that the public might be unaware of the
dangers of hot weather in urban areas (Lane et al., 2014). The “public” will not be interviewed
for this research. Instead, the interviewees will be asked about their experience with public heat
awareness. For instance, the municipal health services will be asked about their experiences with
public heat awareness.
3.2 Adaptation and mitigation strategies
There are different kinds of adaptation and mitigation strategies against the urban heat island
effect. These strategies range from applying vegetation in the open space to constructing green
roofs to warning the public via television. Adaptation and mitigation strategies will be covered
separately. First, I will look into the adaptation strategies that are applied in both cities, followed
by the mitigation strategies in both cities.
Adaptation and mitigation strategies will be divided into three types of strategies: outdoor space,
built environment and social adaptation. Many scientific reports analyzing heat stress distinguish
strategies aimed at reducing outdoor temperatures from those reducing indoor temperatures
(Franck et al., 2013, Ashtiani et al., 2014). This does not mean that these strategies are not
interrelated. In fact, there are many adaptation strategies applied in the outdoor space that
influence the indoor space and vice versa. For instance, applying vegetation can lower the
outdoor air temperature (Taleghani, 2018), which directly affects the indoor temperature (Franck
et al., 2013). However, the indoor temperature is dependent on more factors than solely the
outdoor temperature, such as the urban structure. Adaptation and mitigations strategies that are
applied in the outdoor space include planting trees and increasing the albedo (Taleghani, 2018).
In addition, impervious surfaces increase the urban heat island effect. By removing impervious
surfaces, the urban heat island effect could reduce (Van der Hoeven & Wandl, 2013).
There are some strategies applied on or in buildings that affect the indoor temperature as well as
the outdoor temperature, such as green roofs and green façades (Taleghani, 2018). Although both
of these strategies influence both the indoor and the outdoor environment, they will be covered
by “built environment” because these strategies are applied on or in the built environment. Other
adaptation strategies, such as the use of air conditioning, cool the temperature inside buildings
and thus reduce mortality rates, but can on the other hand lead to an increase in the outdoor
temperature (Tremeac et al., 2012).
14
Adaptation and mitigation strategies that are applied on the built environment include air
conditioning, green roofs and green façades. Isolation will also be considered. Although well-
isolated buildings tend to warm up slower, thus staying cool for a longer period of time, well-
isolated buildings also tend to retain heat for a longer period of time, thus giving the building less
opportunity to cool down (Van der Hoeven & Wandl, 2013; Parag, 2008). Rising building
temperatures often lead to more use of air conditioning (Yamamoto, 2006).
Next to strategies that are applied in the outdoor space and the built environment, there are
adaptation strategies that are not covered by these categories but are still considered adaptation
strategies against the urban heat island effect. Strategies such as heat wave warning systems
(Kim et al., 2014) and drinking water (Lane et al., 2014) help people adapt to heat stress, even
though these strategies do not have implications for the indoor and outdoor temperature. Other
social adaptation strategies, or behavioral adaptation strategies, are adapting sleeping habits to
reduce sleep time exposure to intense heat (Hendel et al., 2017).
The heat stress framework by Hatvani-Kovacs et al. (2018) is divided into four sectors related to
the urban heat stress; public health services, the building and construction industry, urban
planning and infrastructure services and utilities. These sectors will be sorted into the three sub-
groups stated above; Social and behavioral adaptation will include the public health services, the
built environment will include the building and construction industry and the outdoor space will
include urban planning as well as infrastructure services and utilities.
3.3 Implementation of adaptation and mitigation strategies
“Implementation of adaptation and mitigation strategies” will be analyzed separately from
“adaptation and mitigation strategies”. This is because these concepts are approached differently.
The latter looks into what is implemented, whereas the former looks into its decision-making
context. The three main topics within the decision-making context are heat as primary or
secondary objective, top-down or bottom up approaches and area-oriented or generic approaches.
Climate change adaptation is place and context-specific (IPCC, 2014a), which means that not
only that some strategies are more effective in one place than in another, some climatic problems
are more present in one place than in another as well. In order to analyze if the urban heat island
is considered a primary or secondary objective, I will investigate if both cities have heat-specific
adaptation reports. If heat-specific strategies have yet to be implemented, it could still be that the
urban heat island effect is combatted through co-benefit strategies. This means that strategies can
include actions with co-benefits for other objectives (IPCC, 2014a). Green roofs, for example,
have multiple benefits, including the reduction of greenhouse gases, prevent water runoff during
peak precipitation and reducing the surface temperature of roofs (Moghbel & Erfanian Salim,
2017).
According to the IPCC (2014a), all adaptation and mitigation strategies can be sorted into two
broad categories: top-down and bottom-up approaches. Both approaches can be understood from
a development studies perspective: “In most cases, resettlement planning is based on this kind of
top-down centre outwards approach to planning. Planners assume that their expertise allows
them to ‘understand and manage the interests of the farmers better than the farmers do for
themselves” (Lightfoot 1979, p. 30 in Adams, 2009, p. 312). The bottom-up approach suggests
15
that “for success, developments must be not only innovative and research based, but locally
conceived and initiated, flexible, participatory and based on a clear understanding of local
economics and politics” (Adams, 2009, p. 328). Translated to environmental studies, these
approaches stay more or less the same, and revolve around the level of involvement of the
public. Top-down, the public is lesser involved than in bottom-up. Examples of bottom-up
approaches are citizen participation and neighborhood initiatives (Niederer & Priester, 2016).
Top-down strategies can range from the public having hardly any influence on the project to the
public being consulted by the strategy-implementing party (Skarp et al., 2017).
Previous studies have shown that the urban heat island effect is not equally dispersed over both
cities, but that some neighborhoods experiences higher temperatures than others during hot
periods (Van der Hoeven & Wandl, 2013; 2015). The IPCC also mentioned that adaptation is
place- and context-specific, and there is no single approach for reducing risks appropriate across
all settings (IPCC, 2014a). Hence, I will analyze if Amsterdam and Rotterdam use more area-
oriented strategies, or more generic adaptation and mitigation strategies.
This will be done by asking the interviewees if the strategies are implemented generically or
area-oriented, as well as looking into policy reports.
Concept Dimensions Indicators
Heat awareness Institutional awareness Heat awareness and risk perception at the
municipalities (Runhaar et al., 2012).
Public awareness Experiences with public heat awareness. Questions
from the public at municipal health services.
Adaptation strategies Outdoor space Creating shading (Runhaar et al., 2012).
Built environment Air conditioning (Tremeac et al., 2012). Sun
Screens, creating shading (Runhaar et al., 2012).
Social/ behavioral
adaptation
Warning systems (Kim et al., 2014), adapting
sleeping habits (Hendel et al., 2017), drinking water
(Lane et al., 2014).
Mitigation strategies Outdoor space Applying vegetation, increasing the albedo
(Taleghani, 2018). Removing impervious surfaces
(Van der Hoeven & Wandl, 2013).
Built environment Green façades, green roofs, increasing the albedo
(Taleghani, 2018).
Strategy implementation Primary objective
Reports aimed at adapting or mitigating to the
urban heat island effect or heat stress.
Secondary objective Co-benefits strategies (IPCC, 2014a), no reports
aimed at combating to urban heat.
Top-down approaches
Lack of citizen participation and neighborhood
initiatives (Niederer & Priester, 2016), Consultation
(Skarp et al., 2017)
Bottom-up approaches Citizen participation, Neighborhood initiatives
(Niederer & Priester, 2016).
Area-oriented strategies
Specific strategies on city-district or neighborhood
level.
Generic strategies No specific strategies on city-district or
neighborhood level.
Table 1: Operationalization table.
16
4 Background Human interference with the climate system is occurring, which leads to changes in human and
natural systems. These changes have caused impacts on natural and human systems around the
globe in the past and will continue to do so in the future (IPCC, 2014b). One of these effects is
temperature rise. The average temperature in the Netherlands is expected to rise between 1,3 oC
and 3,7 oC by 2085, depending on the climate scenario. In addition to that, more extreme weather
events are more likely to occur (KNMI, 2015). In urban areas, climate change will lead to
increased frequency, intensity and/ or duration of extreme weather events such as heavy rainfall,
warm spells and heat events, drought and intense storm surges (IPCC 2014a).
There are many examples of urban areas experiencing such extreme weather events. An example
closely related to this research is the Paris heat wave in 2003. In August 2003, France, and Paris
in particular, experienced a devastating heat wave, which killed nearly fifteen thousand, mostly
elderly, people in France, and over a thousand in Paris alone (Keller, 2013). After this disaster,
heat awareness raised. France developed a national “Plan Canicule” (heat wave plan), which
resolved around responsibility, prevention and solidarity during heat waves, with measures such
as count at-risk persons, cooled rooms and support emergency medical services and personnel
(Poumadère et al., 2005). The “Plan Canicule” is still relevant and updated regularly.
Although mostly known for its effects on the residents of Paris, the Netherlands also experienced
negative effects from the 2003 heat wave, with an estimated 1700 deaths (Van der Hoeven &
Wandl, 2013). The Netherlands experienced its second heat wave of the decade in 2006, which
led to an estimated 1000+ fatalities in the Netherlands (Statistics Netherlands, 2006). The 2006
heat wave led to the highest temperature ever recorded in Rotterdam (27,8 oC). In addition, the
2006 heat wave led to the highest death ratio among people over 75, with 385 fatalities. This
means 75 extra deaths among people over 75 in July compared to the average amount of deaths
in July in Rotterdam (Van der Hoeven & Wandl, 2015). Although the amount of extra fatalities
is unknown for Amsterdam, the land surface temperature of Amsterdam was 10 to 20 oC warmer
than its rural surroundings. (Van der Hoeven & Wandl, 2013).
It was not until 2006 that the Netherlands was developing national adaptation strategies against
heat stress. In 2007, the first Dutch heat wave plan, the “Nationaal Hitteplan” was released due
to the 2006 heat wave (RIVM, 2014). This late development of heat plans in comparison to Paris
can be explained from the fact that the water-related issues instead of heat stress is seen as the
predominant climate-related issues (Van der Hoeven & Wandl, 2013) as well as the position of
the Netherlands in a mild maritime climate zone close to the sea in which high temperatures have
not been a concern for a long time (Van Hove et al., 2011).
Heat plans like the “Nationaal Hitteplan” mainly revolve around social adaptation, being vigilant
as the government and warning the people on time. This is one of many forms of heat adaptation
and should not be the only form to adapt to heat. Other examples are cool roofs that due to
reflectivity keep roofs, and thus the indoor temperature cooler in Athens (Synnefa et al., 2012),
pavement-watering to reduce maximum outdoor daily heat stress in Paris (Hendel et al., 2016)
and constructing parks as well as tree planting in cities have a cooling effect on its urban
surroundings (Yang et al., 2016).
17
Urban heat can lead to many negative effects. Increased temperatures lead to damaged
ecosystems, more pollutants in the air, can lead to deaths by heat stress and will likely cost
tremendous amounts of money for both residents and governments (Susca & Pomponi, 2018). As
mentioned above, there is enough knowledge about adaptation strategies that can be
implemented against the urban heat island. However, it is a mixed picture when it comes to
taking these steps and implementing these adaptation strategies in order to prevent or reduce
urban heat (Susca & Pomponi, 2018). In this research, I will try to find out the current situation
of heat stress in the Netherlands, and Amsterdam and Rotterdam in particular. I will also look
into how Amsterdam and Rotterdam are trying to cope with heat stress and implementing
adaptation and mitigation strategies.
18
5 Study area
5.1 The Netherlands
Situated in a temperate maritime climate zone, the climate of the Netherlands is characterized by
mild summers, cool (but not cold) winters and overall high precipitation (KNMI, 2015). The
average temperature in the summer months is 17 oC, and the average winter temperature is 3,4 oC
(KNMI, 2015). There are many different climate scenarios for the Netherlands in the 21st
century, in which there are many differences. There are some general predictions for the
Netherlands that are likely going to occur no matter the climate scenario, such as rising
temperature in both summer and winter and more high-intensity precipitation (KNMI, 2015). In
particular the temperature rises will be of great importance for this research, because temperature
rise and climate change in general influence the urban heat island intensity (Corburn, 2009).
One of the most important city regions in the Netherlands is the Randstad area, which is a
megapolis with a population of 7,1 million inhabitants consisting of the four largest cities in the
Netherlands; Amsterdam, Rotterdam, The Hague and Utrecht and their surrounding areas. In this
research, I am going to compare the two largest cities in the Randstad areas; Amsterdam and
Rotterdam.
5.2 Amsterdam
Amsterdam has a population of approximately 811.000 and an urban agglomeration of 1,1
million inhabitants, which makes Amsterdam is the largest city in the Netherlands (Municipality
of Amsterdam, 2017a; United Nations, 2014). As the capital of the Netherlands, Amsterdam is of
great global importance in many areas. Schiphol airport is the third airport in Europe in terms of
market share and is one of the most visited tourist destinations in Europe (Schiphol, 2018;
Rawding, 2000). Amsterdam is also home to many headquarters of large companies, and the port
of Rotterdam is the fourth largest port in Europe (Port of Amsterdam, 2013).
Although these factors are good economically, there are many downsides to these factors when
linked to climate change. It has been proven scientifically that tourism affects climate change
(Amelung & Moreno, 2012). Amsterdam Schiphol Airport is responsible for noise, air and odor
pollution, as well as greenhouse gas emissions (Staatsen et al. 1994). Shipping in Amsterdam
also leads to severe air pollution of nitrogen dioxide, sulfur dioxide and fine particles (Van
Zoelen, 2017). In other words, the activities that are of great importance for Amsterdam
economically can lead to many climatic downsides that could be linked to temperature rise and
the urban heat island effect.
Not the entire metropolitan area of Amsterdam will be investigated in this research. Instead, this
research will focus on the following city districts in Amsterdam: Amsterdam city center
(Centrum), Noord, Oost, Zuid, West, Nieuw-west and Zuidoost. The Westpoort port area of
Amsterdam will be excluded in this research, because with 192 inhabitants (OIS, 2017), this area
has barely any residents that will be affected by the urban heat island. The research area of
Amsterdam is shown in figure 3.
19
The urban heat island in Amsterdam
Overall, the urban heat island is
present in Amsterdam, especially in
the summer months. In the summer,
the urban heat island effect in
Amsterdam when compared to its
surrounding countryside can lead to an
increase of over 3 oC on moderately
warm summer days with a daytime
maximum temperature of 20 oC, and
up to 5 oC on hot summer days
(Koomen & Diogo, 2017). On these
summer days, the temperature
differences between urban Amsterdam
and its surrounding rural areas
increases by 0,15 oC for each degree
increase in maximum daytime
temperature (Koomen et al, 2013).
This temperature difference is much of
a problem on moderately warm
summer days. On hot summer days
and during heat waves however, the
urban heat island can lead to risks.
In the past, Amsterdam has experienced some heat waves, with the heat wave in 2006 being the
most significant. Heat waves can lead to health risks such as fatigue and headaches, and even
fatalities in extreme cases (RIVM, 2012). During heat waves, the urban heat island in
Amsterdam can be quite substantial. The land surface temperature in residential areas with
impervious surfaces can be 10-20 oC higher than its surrounding rural areas by day during heat
waves (Van der Hoeven & Wandl, 2013). During the night, the urban heat island effect in
Amsterdam is not only 7-9 oC warmer than its surrounding rural areas, Amsterdam also cools
down to a lesser extent than its surrounding rural areas (Van der Hoeven & Wandl, 2013). By
analyzing these heat waves, it seems that the urban heat island effect in Amsterdam is in the
upper range of what could be expected in European cities (Van der Hoeven & Wandl, 2013).
The urban heat island effect affects every city district in Amsterdam. Nevertheless, the urban
heat island differs between, and even within each city district. The urban heat island effect
affects the entire city of Amsterdam, but Amsterdam West and the city center in particular
(Rombouts & Van Zoelen, 2015). This is because of the lower quality of life of the neighborhood
and the poorer energy efficiency of the buildings (Van der Hoeven & Wandl, 2013). Amsterdam
Noord, Zuid and Zuidoost (with the exception of the Amstel III/ Bullewijk district) are relatively
cool when compared to the rest of Amsterdam (Van der Hoeven & Wandl, 2013). The urban heat
island effect strikes Amsterdam the hardest on the most urbanized locations, most of these
locations lying around the city center. The areas where the urban heat island has the least
significant effect are Waterland (Noord), Lutkemeer/Ookmeer (Nieuw-West) and Nellestein and
Driemond (Zuidoost).
Figure 3: The research area in Amsterdam (the Westpoort Area will not be
investigated in this research). Source: OIS Amsterdam (2016) and ESRI
Nederland (2018), map made by the author.
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5.3 Rotterdam
Although less important economically and globally than Amsterdam, Rotterdam is still one of
the most important cities of the Netherlands. With a population of around 618.000 (Municipality
of Amsterdam, 2017) and an urban agglomeration of 0,9 million inhabitants (United Nations,
2014), Rotterdam is the second-largest city in the Netherlands. The Port of Rotterdam is
Europe’s largest port and industrial complex (Port of Rotterdam, 2017). In corporation with The
Hague, Rotterdam is also linked to the Rotterdam The Hague Airport, which is a small airport
compared to Schiphol. Although having less of a business climate in comparison to Amsterdam,
Rotterdam is also home to some headquarters and branches of domestic and international. Like
in Amsterdam, these generally positive economic factors do have some negative downsides that
are related to climate change and the environment.
Some regions in the
municipality of Rotterdam will
be excluded for this research.
This applies for the following
city districts: Hoek van
Holland, Rozenburg, Pernis,
Hoogvliet and the port and
industrial areas. This is because
most of these areas are too far
away from the city center, or do
not have a significant number of
inhabitants in order to be
investigated properly. The areas
that will be examined in this
research are: Rotterdam city
center (Centrum), Delfshaven,
Overschie, Noord,
Hillegersberg-Schiebroek,
Kralingen-Crooswijk, Prins
Alexander, Feijenoord,
IJsselmonde and Charlois (figure 4).
Regarding sustainability, Rotterdam is known for its movable storm surge barrier, the
Maeslantkering. Since its opening in 1997, the Maeslantkering has closed twice, during storms in
2007 (Volkskrant, 2007) and 2018 (NU.nl, 2018), which has led to the prevention of possible
floods. Rotterdam is also part of the Rockefeller 100 resilient cities program, which is set up by
the Rockefeller foundation to help more cities build resilience to the physical, social and
economic challenges that are a growing part of the 21st century (Rockefeller foundation, 2018).
Figure 4: The city districts that will be investigated in this research in Rotterdam.
Source: Statistics Netherlands (2016) and ESRI Nederland (2018), map made by the
author.
21
The urban heat island in Rotterdam
Like Amsterdam, the urban heat island effect in Rotterdam is the most significant in the summer.
On windless summer days with a temperature of over 30 oC, the maximum urban heat island
intensity can lead to a temperature difference of over 8 oC in comparison to the surrounding
countryside in the densest city areas of Rotterdam (KVK, 2011). Studies have shown that the
pre-war districts in Rotterdam (North, South and West) are warmer and thus more vulnerable to
the urban heat island effect in comparison to the other areas of Rotterdam, mainly the low-rise
districts with many green spots (Van der Hoeven & Wandl, 2015; Municipality of Rotterdam,
2013). More specifically, the areas with a high surface temperature due to the urban heat island
effect in Rotterdam are mostly highly urbanized areas with impervious surfaces that are located
near industrial activities.
During the day, Delfshaven, Feijenoord and IJsselmonde are affected the most by the urban heat
island effect. During the night, the harbor and industrial areas of Rotterdam, as well as Pernis,
are most affected by the urban heat island effect. The areas that are affected the least by the
urban heat island effect are districts with many low-rise buildings such as Kralingen. The city
center itself, including the Kop van Zuid area, is also greatly affected by the urban heat island
effect (KVK, 2011).
22
6 Methodology
6.1 Research design
This study’s research design will be the comparative design, where two (or more) cases are
studied by using the same methods (Bryman, 2012). In this research, the two cases that will be
compared are the built-up areas of Amsterdam and Rotterdam. A comparative research can be
either quantitative or qualitative, depending on the context and the methods used. This research
will be using mainly qualitative data, making it a qualitative comparative study. Although this
research is mostly about the urban heat island as a natural phenomenon, the social factors that
influence and are influenced by the urban heat island effect will also be examined. The
epistemological approach in this research is the interpretive theory, or interpretivism, in which
the subject matter of social sciences is treated as fundamentally different from that of the social
sciences (Bryman, 2012).
This research will be based on the inductive theory. With an inductive approach, a theory will be
formed as the outcome of the research and its findings (Bryman, 2012). Hypotheses are not
needed in order to implement an inductive research. This is the opposite of a deductive approach,
where hypotheses are formed before collecting data and analyzing results (Bryman, 2012). The
research question will be answered by taking interviews and analyzing existing scientific
literature regarding the urban heat island effect in Amsterdam and Rotterdam.
6.2 Data collection methods
The research methods in this research will be a combination of a literature review and interviews
with people that are linked to the heat stress.
Scientific literature that has already been written will be the base for this research. From the
literature, I will use the data for examining the existing situation for both cases. Existing data has
also been used for constructing the theoretical framework. Some scientific research has already
been done regarding urbanization, the urban heat island effect and adaptation and mitigation
strategies in Amsterdam, Rotterdam and the Netherlands in general. In addition, I have also
made use of scientific articles that revolve concepts related to urban heat island adaptation and
mitigation, mainly urban resilience.
For this research, I have done in-depth interviews with people that are linked to heat stress in one
way or another. The interviewees for this research are sampled through purposive sampling. This
means that the research participants are not chosen on a random basis, but strategically with the
research goal in mind (Bryman, 2012). The samples are chosen from establishing criteria
concerning the kinds of cases that need to be addressed for the research questions, which Bryman
describes as the generic purposive sampling approach (Bryman, 2012). The units of analysis for
this research are adaptation and mitigation strategies.
The criterium used for deciding the research group are that they have to be somewhat linked to
urban heat island adaptation and mitigation, preferably in Amsterdam and Rotterdam. I have
tried to interview people that are active in one of the four subgroups related to urban heat stress
by Hatvani-Kovacs et al. (2018). The people interviewed at municipal health services fall within
the public health services, the housing corporations are included in the building and construction
industry, and the municipalities include urban planning and infrastructure services and utilities.
23
Parties linked to urban heat island adaptation and mitigation include municipalities, housing
corporations and municipal health services. From each of the previously mentioned parties, I
have interviewed someone who is linked to heat stress in some form. Besides that, I have
interviewed two experts that have done research on the urban heat island effect in the
Netherlands. I have also interviewed an employee at De Groene Stad (The Green City), a
company that aims to inform and stimulate the interest with authorities, organizations and
companies which are professionally involved in planning and developing the urban area,
ensuring green will be applied appropriately (De Groene stad, 2018). I have tried to make the
interviews as balanced as possible, which means that I have tried to interview the same amount
of people in Amsterdam as in Rotterdam. There is some sampling error in this research. This is
because I have interviewed three people who work at the municipality of Rotterdam, and just one
employee from the municipality of Amsterdam. The other interviews are without any sampling
error.
Each interview held is a semi-structured interview, which means that I have set up a list of
questions or topics for each interview beforehand, but I have had a great deal of leeway in how
to reply (Bryman, 2012). In each interview, I have asked questions that were not set up
beforehand in order to get more information from the interviewees on specific topics.
6.3 Reliability and validity
This study has taken place in Amsterdam and Rotterdam. Only a small sample of people
involved in the urban heat island effect in both cities have been interviewed. One housing
corporation per city, one employee per municipal health service, a few employees from both
municipalities, two researchers and one external company are interviewed. However, only a
small amount of people in both cities that are invloved in the urban heat island effect is also quite
low. The external validity, the degree to which findings can be generalized across social settings
(Bryman, 2012) is low. This study gives insight and possibly develops theoretical ideas
regarding urban heat island adaptation and mitigation across various parties. This means that it is
not possible to generalize the results in both cities, but that the internal validity is high in this
research.
The external reliability, the degree to which a study can be replicated (Bryman, 2012) is also low
for this research. Both the urban heat island effect as well as the adaptation and mitigation
strategies against it can change over time, which will likely lead to different results than the
results of this study.
6.4 Ethical considerations
All interviewees have been informed about the aim of this study before each interview in order to
avoid misconceptions. The respondents agreed for recording their interview for transcribing
reasons. A week before handing in the thesis, I sent each respondent their quotes as well as other
information related to them or their organization. This is again done in order to avoid
misconceptions.
24
I have asked each respondent for their permission to use their identity. I have only used the
identity of the respondents that agreed with using their identity. The respondents who preferred
to be anonymous or from whom I have not received an answer will remain anonymous. The
anonymous respondents are referred to as abbreviations of their function and city they live in.
For instance, AM1 means Amsterdam Municipality 1, RHS1 means Rotterdam Health Service 1.
The list of interviewees can be found in the appendix.
6.5 Data analysis
The interviews have been coded manually. The interviews have been coded directly after
transcribing each interview. Quotes were sorted into different themes (some of the quotes in
multiple themes) such as heat awareness, adaptation strategies and strategy implementation. I
have used the Grounded Theory in order to come to conclusions from the collected data. This
means that the theory is derived from data and is systematically gathered and analyzed through
the research process (Bryman, 2012).
6.6 Limitations
This study has some limitations. I could only interview 11 participants related to the urban heat
island effect. I wished to have interviewed more people related to the urban heat island effect,
but this was not possible due to time limitations. I have not interviewed the residents in both
cities. This means that public awareness is solely based on the experiences of the interviewees,
which could be misleading. I also have not interviewed urban designers and architects in both
cities. This is a limitation, because urban designers and architects might have more knowledge
on urban heat island adaptation and mitigation in the outdoor space as well as the built
environment. As mentioned earlier, only one housing corporation in each city has been
interviewed. Although the housing corporations interviewed have a relatively large housing
stock, they still cover a small amount of the total housing stock in each city. Finally, this research
is done from a social-scientific perspective. I have analyzed the different measures that are
currently used in both cities, but I have not measured the how the adaptation and mitigation
strategies affect the urban heat island effect in both cities.
25
7 Results: heat awareness
The urban heat island effect is considered in many countries as one of the top climate-change
related threats in urban areas. In the Netherlands, however, water-related issues such as an
increase in precipitation, flooding and sea level rise are considered as the predominant issues
caused by climate change (Van der Hoeven & Wandl, 2013). This combined with the fact that
the Netherlands is situated in a mild maritime climate zone close to the sea is the reason that high
temperatures have not been a concern in the Netherlands for a long time, and why the urban heat
island effect is often not considered when analyzing climate scenarios for the Netherlands
(Van Hove et al., 2011).
7.1 Institutional awareness
The Dutch ministry of Rijkswaterstaat (part of the Dutch Ministry of Infrastructure and water
management and responsible for the design, construction, management and maintenance of the
main infrastructure facilities in the Netherlands (Rijkswaterstaat, 2018)) acknowledges that the
negative health effects of heat stress, especially in urban areas, must be addressed. This is why
heat stress is included in the Dutch National Adaptation Strategy for 2018-2019 (NAS, 2018).
The NAS focuses on three components: the implementation of local heat plans in municipalities,
doing research on heat and smog during events, which leads to advice on how to handle during
such circumstances and the development on heat vulnerability maps (NAS, 2018). In June 2018
“Congres Hittestress”, the first national heat stress congress will take place. This congress
resolves around how the Netherlands will cope with a warmer climate and focuses on raising
awareness around heat scenarios in the Netherlands (Congres Hittestress, 2018;
NAS, 2018).
Within the institutions interviewed, heat stress is not considered a priority climate-wise. Both
municipalities primarily focus on water stress, municipal health services prioritize issues such as
air quality over heat stress and housing corporations focus on making houses more sustainable,
mainly by isolating them. According to Alexander Wandl, the institutions do not put heat stress
on a more primary position due to the lack of awareness.
“I think there is not enough awareness on the level of the developers. So, it may be in the municipal plans
and so on, but if you are talking about the real implementation, that tends to disappear, because you
cannot make a lot of money” (Alexander Wandl).
This is substantiated further in the article by Runhaar et al. (2012). Although heat stress is not a
new phenomenon in the Netherlands, urban planners do not seem to be aware of it, or even
perceive it as a problem. This might be because of the rather abstract knowledge on heat stress
due to the limited information on local heat stress projections (Runhaar et al., 2012). The lack of
heat awareness in the Netherlands is mainly takes place on a local level (Klok & Kluck, 2018).
The article by Runhaar et al. shows that there is a substantial difference between the
municipalities of Amsterdam and Rotterdam regarding heat stress awareness. Amsterdam did not
expect heat stress to occur due to the low building density and the presence of much open space
and open water. Rotterdam, on the other hand, was one of the few municipalities that was active
in the area of heat stress in 2012, and the only municipality that had made estimations about the
health impacts of heat stress (Runhaar et al., 2012).
26
Amsterdam: institutional awareness
Amsterdam does not have a specific heat policy. This does not mean however, that there is no
heat awareness in Amsterdam. In fact, AM1 mentioned that heat is the next thing they want to
address in Amsterdam. The municipal health service in Amsterdam has more adaptation
strategies against heat stress compared to the municipality. This is in order to prevent health
issues in risk groups that will be affected by heat stress. Mainly the elderly, the chronically ill
and people who work outside, but also children and event visitors can experience health issues
due to heat stress, according to Ben Rozema. However, if you look at the priority of heat within
the municipal health service of Amsterdam, heat is not at the top. Other issues, mainly aerial
pollution get the priority over heat. Eigen Haard, one of the largest housing corporations in
Amsterdam, is not focusing on heat stress in particular, but more on general climate adaption
strategies that make houses more energy-efficient, according to Wim de Waard.
Rotterdam: institutional awareness
The municipality of Rotterdam acknowledges that Rotterdam will experience more and longer
warmer periods (in 2050, Rotterdam will experience twice as many hot days compared to 2010).
This in combination with a city that is getting more compact, will probably lead to a drastic
increase in the urban heat island effect (KVK, 2011). This is why the municipality of Rotterdam
has included heat as one of the main subjects in the adaptation strategy of Rotterdam
(Municipality of Rotterdam, 2013). In the adaptation strategy the consequences of heat waves,
such as health issues, thermal comfort, infrastructural issues and consequences for flora and
fauna are taken into account (Municipality of Rotterdam, 2013). This will be further elaborated
upon in the adaptation and mitigation chapter.
The interviews as well as well as climate adaptation reports have shown that the municipality of
Rotterdam is currently more aware of the consequences of urban heat compared to Amsterdam.
Heat stress and its effects are included in the national adaptation strategy of Rotterdam, and
according to RM2, heat is an important theme within the adaptation strategy of Rotterdam.
Considering health services, the attitude of the municipal health service Rotterdam is comparable
to Amsterdam.
“Heat stress has a relatively low priority. This is partly because we have programs such as the national
heat plan, which national and local media cover once it is activated. This gives the image that heat stress
is covered” (RHS1).
Within housing corporation Woonstad Rotterdam, the urban heat island is an upcoming issue.
For the past decade, Woonstad Rotterdam mainly focused on making its housing stock more
energy efficient. Besides that, Woonstad has recently recruited a sustainability specialist who
mainly focuses on circularity and climate adaptation. The two main subjects within climate
adaptation are water nuisance and heat stress.
27
7.2 Public awareness
For this research, no surveys or interviews have been taken to investigate the public awareness.
The results in this section are retrieved from interviews, when asked about their experience with
public heat awareness.
The experts have the opinion that there is hardly any public awareness at all concerning heat
stress. According to Jeroen Kluck, heat stress is not considered a threat by many people in
comparison to water stress. When elderly people were asked about heat stress, a common answer
was that they would not think they would experience negative effects from heat. Some people
even see hotter cities as a beneficial effect.
“What you hear a lot among citizens is: we will get the temperature of Marseille, that would be great”
(Jeroen Kluck).
Hot weather is indeed seen as something positive among citizens, as RM2 points out:
“People are used to a rainy climate. When the sun shines, people go to terraces and drink beer because
we are glad the sun is finally shining again. This is actually the worst thing to do” (RM2).
Because of the lack of public awareness, the implementation of adaptation and mitigation
strategies can be delayed. Alexander Wandl argues as well that due to the lack of public
awareness, it is more difficult to “get things through” and implement heat-focused strategies.
Amsterdam: Public awareness
The fact that people do not consider heat stress as a threat is confirmed by both municipal health
services. According to Ben Rozema, the municipal health service in Amsterdam receives
relatively few questions and reports on heat stress. The municipal health service does receive
questions from schools that want to organize school trips and events such as marathons or dance
festivals. Ben Rozema also states that heat measures are generally known.
“The heat measures are generally known because of the previous campaigns that were held. Most people
know that you have to drink more water, prevent that the sun does not shine inward and to ventilate in the
evening” (Ben Rozema).
Wim de Waard mentions that most of the tenants at Eigen Haard care about other issues than
climate change or the urban heat island effect. However, it seems that the tenants care about the
indoor temperature.
“Simply said, our tenants do not care much about sustainability ideals such as carbon neutrality. At first,
the tenants notice factors such as the temperature, it should not be too hot or cold. Also, the presence of
mold. Secondly, they care about the energy bills. The residents care about other issues than carbon
neutrality and climate change” (Wim de Waard).
28
Rotterdam: Public awareness
The municipal health services of Rotterdam seems to have the same views on public heat
awareness compared to Amsterdam.
“Within our discipline, we have the image that people worry a lot about low-risk issues and hardly worry
about high-risk issues. I expect that heat stress is generally seen as a low-risk issue, but heat stress
actually has many risks” (RHS1).
Woonstad Rotterdam has a large housing stock that is used for social housing. These houses have
affordable rent and are intended for people from lower income groups. According to Hanneke
van der Heijden, many of the tenants at Woonstad Rotterdam do not prioritize climate-related
issues, and often do not have the knowledge of these issues.
“For many tenants, sustainability is not a priority in their lives. It already takes a lot of effort to increase
awareness about tenants’ behavior in energy use. A topic like heat stress is even more difficult to relate to
since the effects are less obvious in peoples’ daily lives. Where the energy bill drops when you are saving
energy, this direct benefit is lacking in terms of climate adaption strategies like coping with heat stress.”
(Hanneke van der Heijden).
7.3 Concluding remarks
Although heat stress does not receive the attention it should get, heat awareness is rising, which
could eventually lead to the implementation of more adaptation and mitigation strategies
specifically aimed at reducing heat in cities. Rotterdam has started to include heat stress in its
policies more than Amsterdam, but even in Amsterdam, the expectations are that heat will be one
of the next things that will be addressed. Considering both housing corporations, Eigen Haard
has yet to implement heat-specific strategies, whereas Woonstad Rotterdam recently is putting in
some work in order to do more about climate adaptation, including heat stress.
It seems that the public is not very aware of heat stress in both cities. The municipal health
services hardly receive questions from citizens about heat stress, and experts on heat stress also
agree that most citizens are unaware of the dangerous effects of heat waves. The same goes for
housing corporations in both cities, where it seems that most of the tenants care more about other
issues than heat stress.
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8 Results: adaptation and mitigation strategies
8.1 Adaptation strategies
8.1.1 Outdoor space
Most strategies applied in the outdoor space are mitigation strategies. There are some exceptions,
however. Water tapping points are scattered over both cities, which means that people have the
possibility to stay hydrated without spending money during warm summer days. In addition,
both municipal health services encourage events such as dance festivals and marathons to
implement heat-stress reducing strategies. Strategies include handing out free or low-priced
water bottles at events during summer in order to prevent visitors from dehydration.
8.1.2 Built environment
Isolation
Every housing corporation in the Netherlands is working on becoming more sustainable.
Housing corporation Eigen Haard focuses specifically on becoming carbon neutral in 2050. In
order to become carbon neutral in 2050, measures need to be taken, with isolation being one of
the most important measures. Improving isolation in houses is the most used strategy in order to
become sustainable at housing corporation Eigen Haard. This is done through façade isolation,
roof isolation and insulated glazing. However, if you isolate a house, you also have to improve
its ventilation, Wim de Waard notices.
Woonstad Rotterdam also has worked on making the houses more energy efficient for the past
couple of years.
“In order to become more sustainable, some interventions have to be prioritized. (…) A couple of years
ago, Woonstad made their portfolio more energy efficient by decreasing energy loss (by improving
isolation) and generating sustainable energy, mainly solar energy” (Hanneke van der Heijden).
The experts on urban heat also agree that making buildings more energy efficient needs to be
done in combination with good ventilation, and not only isolation.
“With proper isolation, it will take a while before a building is warmed up. But once a building is warmed
up, it will stay warm for a longer period of time. Concerning heat stress, ventilation is much more important
than isolation” (Jeroen Kluck).
“It is important how you make buildings more energy efficient. Don’t look only at isolation. Because if you
follow only the aim of energy efficiency through insulation, the result is that buildings become and stay
very hot inside” (Alexander Wandl).
Furthermore, becoming energy-efficient is one of the biggest tasks of the 21st century, and
isolation buildings is one of the most effective adaptation strategies. However, especially during
summer months, isolated buildings will get hotter. Hence, ventilation systems are needed.
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Air conditioning
When considering ways for ventilating a building, the consideration between air conditioning
systems and natural ventilation often is made. Using air conditioning systems is one of the most
commonly used ways of ventilation. However, although air conditioning leads to a cooler
temperature inside buildings, due to its energy use, it will heat the public space (Grimmond,
2007).
“By adapting to the urban heat island effect, especially with elderly people, using air conditioning sounds
as a logical solution. However, it can be the most disastrous solution. It uses enormous amounts of energy.
It has a cooling effect indoors, but it will lead to an even hotter outdoors environment. The electricity
networks will also not be able to manage all the air conditioning systems. Using air conditioning can lead
to all kinds of unwanted repercussions” (Roland van der Heijden).
On the other hand, applying air conditioning systems use as an effective adaptation strategy
against the people that are more vulnerable to heat stress. This is why at both municipal health
services, air conditioning is seen as a mainly positive solutions that help the more vulnerable
population groups.
“If you look at the outcome of less fatalities during heat stress due to air conditioning, you should look at
how you can apply air conditioning, but under certain conditions, for instance linking them to solar panels
or to only use them during heat periods” (Ben Rozema).
“For the people that do not have the possibility to search for cool places elsewhere, air conditioning is a
good solution, because it limits the negative effects of overheating, such as dehydration, headaches, nausea
and even extra fatalities. So, from a healthcare perspective, I have no issues with air conditioning, but I
understand the argument that it is not a proper solution, and we only make the city warmer by using air
conditioning” (RHS1).
There are more sustainable ventilation alternatives in comparison to air conditioning. This is
called natural ventilation. Examples of natural ventilation are heat/ cold pumps, but also
constructing houses in such a way that you can control the wind coming into your house on
specific moments.
When asked about applying natural ventilation instead of air conditioning, most of the
respondents replied that air conditioning is the main ventilation system that is applied in both
cities. Although the respondents from both municipalities were aware of the negative impacts of
air conditioning, air conditioning is still the dominant ventilation system, and natural ventilation
systems have yet to be constructed on a large scale.
Housing corporation Eigen Haard does not use air conditioning, but both natural and carbon-
driven ventilation. Air conditioning is not used because it is not sustainable and leads to higher
energy bills.
“We are such a large municipality, we are active with sustainability, reducing energy, and make use of
energy that is as green as possible. Natural ventilation is needed for that” (AM1).
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Although the respondents from the municipality of Rotterdam indicate that they want natural
ventilation to be applied in the city, carbon-driven ventilation is also the most dominant form of
ventilation in Rotterdam.
“I indicate that I want more natural ventilation systems in the city, because with our current plans, we
make use of electricity, which uses energy. Natural ventilation is more favorable. It is something we want
to develop, because using air conditioning isn’t everything” (RM2).
“It is something we have in picture and we want to develop, but we have yet to come up with a specific
policy” (RM1).
Woonstad Rotterdam does not own many houses with air conditioning. Most houses are
ventilated via mechanical suction, heat recovery ventilation or natural ventilation. There are
some examples of housing blocks owned by Woonstad Rotterdam that have heat pumps, but the
maintenance of these heat pumps is not the responsibility of the housing corporation.
8.1.3 Social/ behavioral adaptation
National heat plan
As mentioned in the background chapter, the Dutch National Institute for Public Health and the
Environment (RIVM) developed a national heat plan “Nationaal Hitteplan” in 2007 because of
the 2006 heat wave. This heat plan aims to alert the country on time to take measures in order to
reduce and prevent heat stress (RIVM, 2014). The national heat plan tries to communicate on
time to the risks groups such as elderly people, obese people, small children and homeless
people, but also healthcare providers (RIVM, 2014). In order for the national heat plan to operate
as adequate as possible, the RIVM has collaborated with parties such as the Dutch ministry of
public health, well-being and sport (VWS), the Royal Dutch Meteorological Institute (KNMI),
municipal health services, healthcare institutions and the media. The Nationaal Hitteplan makes
agreements with event organizations in order to make events during summer heat-proof and
inform the parties linked to the Nationaal Hitteplan.
The national heat plan has three phases. The first phase is the watchful phase, which runs from
June 1 to September 1. Before this phase, organizations have to prepare themselves for a period
of persistent heat and its risks (RIVM, 2014). The second phase is the pre-warning phase, which
occurs when there is a small chance of 4 consecutive days with a maximum temperature above
27 oC. During this phase, organizations are informed about the possible chance of a heat wave,
which rises awareness. Residents are not informed, because the risk of a possible heat wave is
too small. Besides that, if the public is warned too often, the credibility of the warning will
decrease (RIVM, 2014). The warning phase, which is the third phase occurs when there is a high
chance of 4 consecutive days with a maximum temperature above 27 oC. When this phase starts,
the RIVM sends a warning mail with informative content and up-to-date weather information to
organizations such as the municipal health service. These organizations have the task to
communicate this information to their regional contacts and followers. The Dutch residents will
be informed by press releases from the RIVM. Organizations that have set measures in the
watchful phase can perform these measures during the warning phase (RIVM. 2014).
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Extrema Rotterdam heat stress app
In June, the municipality of Rotterdam in collaboration with the municipal health service
Rotterdam will launch a mobile app in which they record the experiences within the city
regarding the weather. By filling in your personal information, the app will calculate the risk
group you are in regarding heat stress.
By collecting satellite data in combination with your personal information, the app gives you
advice about adapting to heat, such as drinking enough water and showing the water tapping
spots in Rotterdam, but also showing where the coolest spot in a radius of 500 meters is. This
way, people who have downloaded this app can always seek out to cooler spots and prevent heat
stress. The app also allows users to create extra profiles for others, which can be beneficial for
caregivers who help the elderly.
According to Jeroen Kluck, the cool spots in the city could be the solution to coping with heat
stress in a city.
“I do not know if we will succeed, but if we are smart enough, we should invest in enough cool spots in
the city where one can stay. This way, the city will get more pleasant due to the cooling” (Jeroen Kluck).
Screenshots from the Extrema app can be found in the appendix.
Infographic
Amsterdam does not have an app that helps people adapt to heat stress. However, Amsterdam
has created an infographic that informs vulnerable groups to heat stress about measures they
should make.
“One of our spin-offs is a project on our department in collaboration with the Red Cross, we have developed
an infographic in which the vulnerable groups are mentioned, the phenomena of heat stress and how you
can prevent heat stress” (Ben Rozema).
The heat stress infographic can be found in the appendix.
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8.2 Mitigation strategies
8.2.1 Outdoor space
Vegetation
When the experts were asked about most effective strategies against heat, they seemed to agree
that applying vegetation is the most important strategy in the open space. Alexander Wandl
argued that in the public space, green is the most dominant strategy. Jeroen Kluck agrees with
this.
“Greening is the most effective. Wind is also effective, but wind is not always present. Shading is very
important. It does not matter if it is shading by trees or buildings. But there are large differences between
temperature in shadow spots and in spots where no shadow is present” (Jeroen Kluck).
The two experts on the urban heat island both mention that making the city greener is the most
effective adaptation strategy in the public space. According to Alexander Wandl: “ “In the public space, it is all about green, green, green. Less impervious and more pervious surfaces and
more vegetation.” (Alexander Wandl).
Amsterdam profiles itself as a city of trees. It is estimated that there are a million trees in
Amsterdam (from which there are 270.000 street trees), which is quite special (Municipality of
Amsterdam, 2018). The municipality is applying green and vegetation in various forms. One of
the most prominent forms is just by planting trees, but the municipality is also applying
vegetation on school playgrounds, tramlines, small parks and gardens (AM1). The municipality
is also investing in “postzegelparkjes” which are
“small parks, often in collaboration with residents from a specific neighborhood, in which also trees are
present” (AM1).
In addition to that, Amsterdam is investing in a green network, which are recreative cycling and
walking routes that go in and out the city that are as green as possible (AM1). In these strategies,
the greening of school yards in particular, tiles are being removed, which leads to less
impervious surface.
With 160.000 trees in the city and 450.000 trees in its surrounding green areas and forests,
Rotterdam has significantly less trees than Amsterdam (Municipality of Rotterdam, 2018). The
municipality of Rotterdam is trying to make the outdoor spaces of the city greener:
“Rotterdam is applying vegetation in the city. This is primarily for other reasons, but it does address the
urban heat island” (Roland van der Heijden).
According to Livien van de Ven, vegetation has benefits in many sectors, including biodiversity,
climate, economy social cohesion and health. Instead of looking for adaptation strategies that
reduce heat stress, she sees applying vegetation as the strategy that has the most benefits,
including reducing heat stress.
34
“Climate change leads to negative effects such as water stress and more precipitation. Last week, you
saw a lot of water nuisance in South-Limburg. Partly by planting trees, the water storage capacity gets
bigger. Concerning heat stress, more vegetation leads to temperature decrease in urban municipalities”
(Livien van de Ven)
Other strategies in the outdoor space
It seems that applying vegetation is the only mitigation strategy that is implemented in the
outdoor space. Although this is the primary strategy to reduce urban heat, removing impervious
surfaces is also an important strategy. According to Alexander Wandl, large parts of the outdoor
space is private land, which is often tiled. Both cities do not have programs that encourage to
remove impervious surfaces in backyards. Eigen Haard and Woonstad Rotterdam have discussed
this with other parties but have yet to start such programs.
8.2.2: Built environment
Green roofs
Both cities have green roof plans. According to AM1, Amsterdam has a total of 300.000 square
meters of green rooftop surfaces, based on aerial photographs, which is around 2600 buildings
with a green roof. When compared to the total of 12 square kilometers in Amsterdam, 300.000
(2,5%). This does not seem as much. However, the construction of green roofs is a phenomenon
of the past decade.
“The past 3 years, 40.000 square meters of green rooftop surface has been constructed. Most of the green
rooftop surface has been constructed in the past 10 years” (AM1).
In addition to that, Amsterdam has been giving out subsidies for eight years to people who
construct green roofs, partially to make the indoor climate more heat-proof. Housing corporation
Eigen Haard does help with the construction of green roofs occasionally, but this is definitely not
the norm. Woonstad Rotterdam is in the process of starting a pilot green roofs program. If this
pilot works out well, the program could be extended.
Rotterdam mentions that applying green roofs, green façades and more reflective materials will
help making the built environment more heat resilient (Municipality of Rotterdam, 2013).
Rotterdam has a high number of flat roofs, and many of these roofs are unused. From the 14,5
km2 of flat roof surface in Rotterdam, 220.000 m2 is used as a green roof (Rotterdam Climate
Initiative, 2018). Rotterdam is encouraging its citizens to construct green roofs with a subsidy
program (Kleerekoper et al. 2012). The subsidy is currently €20 per square meter but will
decrease to €15 per square meter of green roof (Rotterdam Climate Initiative, 2018). The
municipality of Rotterdam has been actively greening flat rooftop surfaces since 2007, primarily
out of water measures, according to RM2.
“In 2007, the goal was set to have 160.000 square meters of green roof top surface in 2014, and a long-
term goal to have 800.000 square meters of green rooftop surface in 2030, and more than half of the real
estate owned by the municipality” (RM2).
The municipality is also giving out subsidies per square meter of green rooftop surface.
However, the contribution per square meter has been decreased slightly since 2018.
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Furthermore, the development of green roof surface in both Amsterdam and Rotterdam is an
upcoming trend. Most of the green roofs in both cities have been developed for the past decade,
and it seems that both cities will continue the construction of green roofs. However, this does not
mean that green roofs are always mitigating heat.
“In order for it to function as a mitigation measure against the urban heat island effect, a green roof needs
to be irrigated, so that the evapotranspiration is functioning. That is important. It doesn’t help if you have
a green roof, and that everything is brown when it’s hot. It needs to stay green, wet, evapotranspiration
needs to function. Otherwise it doesn’t have a cooling effect.” (Alexander Wandl).
Moreover, if you have a green roof that dries out during hot, dry summer periods, it will not have
any cooling effect. This is why the irrigation of green roofs has to be stimulated. Fact sheets
from organizations that commit to greener cities, such as “De Groene Stad” (the green city)
mention that green needs to be irrigated. Otherwise, it will dry out, and will have less effect.
The quality of green roofs in both cities is unknown. In the case of Amsterdam, AM1 said the
following:
“We have 300.000 square meters of green rooftop surface, but we do not know its quality. Hence, we do
not know how many square meters are functioning adequately and how many square meters are not”
(AM1).
The green roofs program in Rotterdam is derived from sewage charge and is currently more
focused on reducing water stress and prevent the flooding of streets, not on reducing heat stress.
Both RM1 and RM2 argue that the green roofs have to be focused on reducing both heat stress
and water stress, and not only focusing on water.
Both cities are currently experimenting with new types of green roofs as well. This is mostly out
of water stress issues, but this can improve the city’s resilience during heat waves as well.
According to RM2, most green roofs in Rotterdam have a water storing capacity of 15 liters per
square meter. To make investing in green roofs more interesting for market operators, green
roofs need additional functions, RM1 states. To promote this, the Rotterdam roof program
focuses on four colors: blue (water storage), green (vegetation), red (recreation) and yellow
(energy). For example, placing a coffee bar or café on a green roof makes it worthwhile to invest.
The municipality of Rotterdam is also trying to improve the water storing capacity, which is
done from a collective perspective to reduce water stress. Smart roofs and polder roofs are
examples of roofs that are interesting for investors, but there are many different types of green
roofs in Rotterdam.
“Smart roofs have a water storage capacity that is 7 times higher than a traditional sedum roof. There are
also sensors that can deflate the roof if heavy rainfall is predicted” (RM2).
“There is also the polder roof system in Amsterdam, in which the stored water is directly used for the
irrigation of plants, which leads to more possibilities” (AM1).
These two types of green roofs are much better adaptation strategies against the urban heat
island, because the roofs stay wet for a longer period of time, which is needed in order for it to
function against heat stress. However, there are not many of these roofs in both cities.
Concerning smart roofs, there is only one smart roof in each city. The shift towards polder roofs
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is gradually happening, but the vast majority of green roofs that are being constructed are sedum
roofs.
Green façades
According to AM1, there are thousands of green façades in Amsterdam. Amsterdam has a green
façade program and is also giving out subsidies to residents who are constructing green façades
and façade gardens on their house. Most of the green façades in Amsterdam are grounded.
Amsterdam also has some non-grounded green façades that are irrigated via a particular system.
However, there are only around 10 non-grounded green façades in Amsterdam, because these
façades cost a lot of maintenance. Most of the green façades in Amsterdam can be found within
the city ring.
“We subsidize green façades, and although this is not always the case, green façades regularly provide
shadows and cooling” (AM1).
Unlike Amsterdam, Rotterdam does not have a green façade program. Hence, green façades in
Rotterdam are not eligible for subsidies. Rotterdam does have a few green façades, but it is a
very small amount in comparison to Amsterdam.
Other mitigation strategies in the built environment
There are many more mitigation strategies that can be applied in the building environment.
Strategies such as cool roofs, or painting roofs white are discussed in the interviews, but there are
no examples of other strategies in the built environment that are being applied.
8.3 Concluding remarks
In both cities, vegetation is the primary mitigation strategy in the outdoor space. Vegetation has
many benefits against the urban heat island effect, such as creating shadows and cooling down
the city. In comparison to Rotterdam, Amsterdam is a much greener city. However, both cities
have various programs that lead to more vegetation in the city, which could mitigate the urban
heat island effect to a large extend.
The main mitigation strategies applied on the built environment are the greening of houses. Both
cities have green roofs programs, and Amsterdam has a green façade program. Isolation of
houses is happening a lot in order to make the houses more energy efficient. However, this could
lead to an increase of the indoor temperature, which is unfavorable. In order to prevent the
indoor temperature rise, some sort of ventilation is needed. The indoor temperature rise is often
adapted by using air conditioning. Within municipal health services, air conditioning is seen as a
positive adaptation strategy, because it could prevent health risks in vulnerable groups. However,
despite the advantages of air conditioning, air conditioning can lead to an average increase of the
outdoor temperature. Both housing corporations are doing a good job regarding the use of air
conditioning, which is barely used.
Regarding social adaptation strategies, Amsterdam and Rotterdam have to act according to the
national heat plan when a heat wave occurs. Amsterdam has created an infographic that informs
people how to act during warm periods. Rotterdam has launched an app that calculates if you are
at risk based on your location, personal data and temperature, and shows the cool spots near you.
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9 Results: Implementation of adaptation and mitigation strategies
9.1 Heat stress adaptation and mitigation as primary or secondary objective?
Both municipalities have yet to implement physical adaptation or mitigation strategies that are
directly aimed at reducing heat stress and its effects. The only strategies that are directly aimed at
heat stress are social adaptation strategies, such as the heat app in Rotterdam or the infographic
and mailing in Amsterdam. When looked at all the physical adaptation strategies in both
municipalities, you can conclude that all the strategies are primarily intended for other purposes
than the urban heat island effect. The two most common primary purposes are to reduce water
stress and to improve the livability of the city. As described earlier in this report, this is called
co-benefits, where heat stress is mainly adapted through strategies aimed at reducing heat or
improving livability.
In Amsterdam, there are many co-benefits strategies that reduce heat stress. From a health
perspective, green does not only mitigate the urban heat island effect, but also improves the air
quality and is better for one’s mind, Ben Rozema argues. Removing impervious surfaces and
greening schoolyards also has many co-benefits. Trees in schoolyards create shadows, absorb
water, improve the playing environment for children, and also reduces heat stress, according to
AM1. However, Amsterdam primarily focuses on other effects than heat.
“Actually, for the past four years, heat stress has been free riding on a variety of measures. So, we do not
aim specifically on heat, but on water stress, which we are trying to address with Amsterdam Rainproof
since 2013/ 2014. Back then, heat was not such a focal point to address with climate adaptation. But now,
in many public space designs, heat stress adaptation is applied. (…) But we do not have a specific heat
policy” (AM1).
In Rotterdam, this is practically the same phenomenon. According to RM1, almost all the
measures that are taken that have an effect on reducing heat stress are in the context of water
issues. The green roof program in Rotterdam also originates from water storage but has as co-
benefit strategy that also reduces heat stress, RM2 argues. Roland van der Heijden mentions that
he has the idea that the urban heat island is free riding on several other policy themes, such as
water, energy and elderly care through which the urban heat island effect is reduced as well.
Adapting or mitigating to heat via co-benefits is seen as beneficial. Some experts see this as
beneficial because of the lack of interest otherwise:
“You should combine the urban heat island measures with other measures, otherwise there is not enough
interest. (…) And maybe the urban heat island becomes a lot more apparent. As you can see now, it is not
much of an issue” (Alexander Wandl).
“It could be that we can agree on this. We have recently started a research. On one hand, we have to look
at the heat goals and issues. What measures suit this? How effective are these measures? It could be that
it will be all about greening. Green has many benefits for the city, including cooling the city” (Jeroen
Kluck).
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In addition to this, although adapting to heat stress is often viewed as a secondary benefit when
applying adaptation or mitigation strategies, some adaptation strategies can be described as
primary strategies. For instance, green roofs, if irrigated, serve as a primary mitigation strategy
against the urban heat island effect.
“If it’s an accessible rooftop that improves the quality of space, any kind of improvement is good. In
order of it to function as a mitigation measure against the UHI, it needs to be irrigated, so that the
evapotranspiration is functioning” (Alexander Wandl).
9.2 Policy: top-down or bottom-up?
The vast majority of adaptation and mitigation strategies against heat that implemented in both
cities, are implemented from a top-down perspective, with often some consultation with the
inhabitants.
“The majority of strategies in the city are implemented top-down. With every project we do, the
neighborhood is involved, but often, it is initiated from the municipality” (AM1).
The same goes for Rotterdam, where most projects are indeed implemented top-down. This does
not mean that there are no bottom-up projects in both cities. There are many projects set up by
residents in Amsterdam in Rotterdam. In Rotterdam, for instance, the Zomerhof neighborhood
has goals to become a climate neutral neighborhood in Rotterdam. This district has also applied
strategies to mitigate heat stress, for instance with removing impervious surfaces and making
roofs greener.
“The inhabitants of Zomerhof have contacted us that they want to improve their neighborhood” (RM1).
“Resilience is not something we do for the city, but together with the city. So here, we have a more
facilitating and framework-setting role. This is to look how we can ensure that the people want to
participate in our program” (RM2).
The same trend in Amsterdam is happening, where bottom-up initiatives are increasing, or where
Amsterdam only plays a facilitating role.
“Many initiatives are bottom-up. When an initiative set up by residents is presented, it often needs
collaboration with the municipality. So, there are all kinds of initiatives where we collaborate with residents
as the municipality. Besides that, due to our subsidy scheme, initiatives can request subsidies at the
municipality” (AM1).
Bottom-up strategies are not always the best solution. According to AM1, top-down strategies
are sometimes needed because some neighborhoods are not taking action by themselves.
However, it is important that citizens who live in the neighborhood where strategies are applied
will be involved in the decision making, Livien van de Ven argues.
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9.3 Area-oriented or generic adaptation and mitigation?
As shown in the literature review, the urban heat island effect does not occur equally over both
cities. Some neighborhoods, such as the Amsterdam city center and Delfshaven in Rotterdam
experience the urban heat island effect in a heavier form, whereas neighborhoods such as
Amsterdam Zuid and Kralingen in Rotterdam experience less heat stress.
Currently, both cities apply strategies that are not area-oriented. The municipality of Amsterdam
currently applies generic adaptation because it would not be fair if some neighborhoods are
prioritized over others. In other words, every citizen has to be treated equally. AM1 states that
this could change in the upcoming period due to to new plans revolving around green in
Amsterdam.
The municipality of Rotterdam also applies generic strategies. The municipality is aware that
mainly the pre-war districts are more vulnerable to heat stress than the post-war districts, but
currently, the municipality applies generic policies. According to RM1, the municipality of
Rotterdam is currently revisiting the ideas of changing to more area-specific adaptation and
mitigation strategies.
The fact that only generic policy is applied, could be because the current policies against heat
stress are primarily focused on issues such as water stress. On the other hand, area-oriented
policy could be seen as disadvantageous because it could lead to undesirable situations in other
areas.
“This is debatable in my opinion. If you have one neighborhood with many vulnerable residents, and an
adjacent neighborhood with a few vulnerable residents, you would think the neighborhood with many
vulnerable residents should be prioritized. But, the neighborhood with less vulnerable residents should get
attention as well. It could be that the less vulnerable neighborhood will get more vulnerable residents in
the future and vice versa” (Jeroen Kluck).
9.4 Concluding remarks
The urban heat island is mainly adapted and mitigated through co-benefit strategies, where heat
mitigation is often seen as side effect. An example is the construction of green roofs. Green roofs
serve as a water buffer in order to prevent water stress, but if irrigated, green roofs also serve as
mitigation strategy against the urban heat island effect. This could be seen as beneficial, because
multiple issues are addressed simultaneously. However, it might be necessary to mitigate the
urban heat island effect through co-benefit strategies because there could be not enough interest
otherwise.
Although the majority of the adaptation and mitigation strategies are applied through top-down
policy, there are also some examples of strategies that are applied bottom-up. For instance, there
are some initiatives set up by residents where the municipality has a more facilitating role.
Overall, both cities apply adaptation and mitigation strategies through generic policy that is not
area-oriented. It is debatable if this is the right way to implement strategies. On one hand, some
neighborhoods deserve more attention than others, but on the other hand, it might be unfair if
some neighborhoods are getting less attention than others.
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10 Discussion
10.1 Co-benefits, the only way to adapt?
In general, co-benefits might sound as the ideal solution because multiple issues are mitigated at
the same time. As Roland van der Heijden argues it is important that all climate goals will be
reached.
“Eventually, we should succeed work on all the climate goals that are set. If we are using strategies that
reduce water stress or lead to energy neutrality, it is beneficial is we could mitigate the urban heat island
simultaneously” (Roland van der Heijden).
As cited in the previous chapter, Alexander Wandl argues that co-benefit strategies are not
advantageous, but necessary. This is because there would be not enough interest if adaptation
and mitigation strategies would solely aim to reduce the urban heat island effect. Throughout
their interviews, both Alexander Wandl and Jeroen Kluck stressed that there is not enough heat
awareness on the side of the developers as well as citizens in the Netherlands. This is a primary
reason for applying co-benefit strategies against heat stress. Moreover, it is expected that heat
will primarily be adapted through co-benefit strategies as long as awareness is not rising.
10.2 Rising heat awareness
Although heat awareness is starting to rise, it could be that heat awareness will not reach the
point it should be. As shown earlier, water-related issues are often seen as the biggest threat for
the Netherlands, whereas heat stress, especially among citizens, it not taken as seriously as it
should be. This could mean that the urban heat island effect is not mitigated enough, which could
eventually lead to unwanted consequences.
Alexander Wandl is also quite skeptical about the current urban heat island awareness. He argues
that heat awareness could rise to the point it should be if a catastrophic summer takes place in the
Netherlands. This is relatable to the catastrophic summer in France in 2003, which encouraged
the French government to introduce adaptation and mitigation strategies against heat stress
(Poumadère et al., 2005).
While Jeroen Kluck argues that heat awareness is slowly rising, he agrees with Alexander Wandl
that a catastrophic summer will lead to more awareness.
“A heat wave will help, preferably a very long heat wave, so that the city will get really unpleasant. This
way, we can really think about the urban design of cities” (Jeroen Kluck).
To summarize, it is likely that a “catastrophic summer” or long heat wave is needed in order for
heat awareness to rise. However, this is a quite worrying prospect, because this means that the
thousands of people, mainly those who are in vulnerable population groups will experience
negative effects from heat stress which could eventually lead to fatalities.
41
10.3 Differences in adaptation and mitigation between Amsterdam and Rotterdam
In this research, I looked into the different adaptation and mitigation strategies applied by
Amsterdam and Rotterdam to combat heat stress. From analyzing the interviews, it turns out that
there are actually a lot of similarities in adaptation and mitigation strategies between Rotterdam.
Applying vegetation is the primary mitigation strategy in the outdoor space, both cities have
green roof programs, and both cities have to work according to the national heat plan when a
heat wave occurs. There are also many similarities between the cities regarding the way
adaptation and mitigation strategies are applied. Co-benefit strategies are used a lot in both cities,
and most strategies are implemented top-down. There are some differences in adaptation and
mitigation between Amsterdam and Rotterdam. Amsterdam has more green façades than
Rotterdam, but Rotterdam has introduced an app specifically aimed at adapting to heat stress.
It seems that Rotterdam is applying more adaptation and mitigation strategies that are aimed at
mitigating the urban heat island. An example is the heat app, but Rotterdam also has more policy
reports that describe future strategies that are aimed at reducing the impacts of the urban heat
island effect. Amsterdam currently only applies heat strategies through co-benefits, mainly by
applying vegetation in the outdoor space and on the built environment. This might be because
Rotterdam needs to apply more adaptation and mitigation strategies than Amsterdam.
Amsterdam has a lot more trees and significantly more green façades than Rotterdam. Besides
that, Rotterdam has much more flat roof surface than Amsterdam, which often leads to more heat
stress indoors. According to Roland van der Heijden, this is why Rotterdam has set strategies
such as having 800.000 square meters of green rooftop surface in 2030, because the need for
improvement is bigger in Amsterdam.
“I can imagine that the average housing stock in Amsterdam is better prepared against the urban heat
island than in Rotterdam. But I think Rotterdam is currently doing more than Amsterdam, because there
is more need for improvement” (Roland van der Heijden).
Hence, it is difficult to conclude which municipality is doing better on urban heat island effect
adaptation and mitigation. What is certain, is that the urban heat island despite the rising
awareness does not receive the attention it deserves in both cities. In other words, there is a lot of
work to do in both cities to reduce heat stress. However, even if more strategies are going to be
applied in both cities, it is still possible that the urban heat island effect will not be reduced.
“I think there will be change. More green, more imperviousness. I am not sure if this will lead to a
decrease in the urban heat island. You can mitigate the urban heat island, but if the temperature rises, the
city will still get hot” (Alexander Wandl).
42
10.4 A polycentric approach to the urban heat island effect?
In the theoretical framework, I introduced the polycentric approach for coping with collective
action and global environmental change by Ostrom (2010) as a prime example how
environmental change should be approached. Both Amsterdam and Rotterdam have implemented
plans that can be considered polycentric. The “postzegelparkjes” in Amsterdam and the
Zomerhof district in Rotterdam both include collaboration on multiple levels and sharing joint
goals and wishes for the neighborhood. This is a good start, but (in my opinion) not enough in
order to become resilient cities, let alone mitigating to the urban heat island effect.
In order to become a resilient city, more effort has to be put in the polycentric system by Ostrom.
Hence, more effort has to be put in bottom-up initiatives and collaborating with locals, as well as
implementing area-oriented adaptation and mitigation.
43
11 Conclusion The aim of this research was to compare the way Amsterdam and Rotterdam apply adaptation
and mitigation strategies against the urban heat island effect. Before comparing both cities, I
analyzed heat awareness, the adaptation and mitigation strategies as well as the way both
strategies are implemented in each city.
When comparing the two municipalities in heat awareness, it seems that Rotterdam is more
aware of the urban heat island and its implications than Amsterdam. In 2012, Rotterdam was one
of the few municipalities than acknowledged heat stress as an issue where Amsterdam, had yet to
view heat stress as an issue. Rotterdam also has implemented heat adaptation and mitigation
strategies in its policy reports. In the policy reports from the municipal reports of Amsterdam,
heat stress remains absent. However, it seems that institutional heat awareness in both
municipalities is slowly rising, and that it might be the next subject on the climate change
agenda. The municipalities, municipal health services and housing corporations are putting more
effort in combatting heat stress by adaptation and mitigation strategies. This could eventually
lead to the implementation of more adaptation and mitigation strategies against the urban heat
island effect. However, the pace in which the heat adaptation strategies are taken might be too
slow.
The public, on the other hand, seems not to be very aware of the urban heat island effect and its
implications on one’s health. The interviewees agree that that most citizens are unaware of the
dangerous effects of heat stress, mainly because they care more about other issues than heat
stress. The experts agree that a hot, catastrophic summer could lead to an increase of adaptation
and mitigation strategies.
A common adaptation strategy in both cities is the use of air conditioning in houses, because it
makes the inside temperature more pleasant during hot periods. This is not an optimal adaptation
strategy, because the energy use of air conditioning leads to an increase in the outside
temperature. Other adaptation strategies include informing citizens through the media due to the
national heat plan. Both municipalities have also worked on other adaptation strategies, such as a
heat app and an infographic.
Mitigation strategies that are applied often include vegetation, which is seen in both open spaces
and the built environment. In the built environment, this is mainly seen in green roofs, which are
practiced in both Amsterdam and Rotterdam, and green façades, which are mostly seen in
Amsterdam.
Mitigation strategies against urban heat are often applied through co-benefit strategies where
heat mitigation is often seen as a side effect. Strategies such as green roofs and vegetation often
have as main purpose mitigating water stress or improving the living environment. Although
there are some examples of heat that is mitigated bottom-up, most mitigation strategies are
applied through top-down policies. Concerning scale, most mitigation strategies are applied
through generic policy, and not area-oriented policy.
44
As shown in the results, there are many similarities between urban heat island adaptation and
mitigation in Amsterdam and Rotterdam. However, there are some significant differences
between both cities. The key difference in adaptation and mitigation strategies is that Amsterdam
is overall a greener city, which is visible in the outdoor space as well as the built environment.
Rotterdam, on the other hand is applying more adaptation and mitigation strategies that are
aimed at the urban heat island effect. Examples are the extrema heat app and the fact that heat
stress is considered a threat within municipal reports from Rotterdam, whereas it is not
mentioned in the municipal reports of Amsterdam. The reason for this might be that in
Rotterdam, there is more need for heat-specific adaptation strategies, because it can become
warmer in summers due to Amsterdam being a much greener city.
In order for both cities to become a resilient city, or at least resilient to the urban heat island
effect, I suggest making use of the polycentric approach by Ostrom. Interviews have shown that
the municipalities are happy with the initiatives such as the “postzegelparkjes” in Amsterdam
and the Zomerhof district in Rotterdam. Hence, I suggest that more effort has to be put in
bottom-up initiatives, collaborating with locals and implementing area-oriented adaptation and
mitigation.
For this research, I have tried to interview as many actors as possible that are related to heat
stress adaptation and mitigation in Amsterdam and Rotterdam. There are some actors that have
to be covered in order to create a more accurate image of the current state of urban heat island
adaptation and mitigation in both cities.
Firstly, I have not included urban planners, urban architects and urban engineers. These actors do
have the knowledge about urban heat island adaptation and mitigation, especially in the built
environment. Although I have collected enough data about heat adaptation and mitigation
strategies through interviews with the municipalities, I suggest having interviews with urban
planners, urban architects and urban engineers for more in-depth results regarding urban heat
island adaptation and mitigation applied on the built environment. Moreover, I suggest that
future research using the same methods should consider the heat-stress framework by Hatvani-
Kovacs et al. (2018) by interviewing people that are more active in one of the four following
sectors: public health services, the building and construction industry, urban planning and
infrastructure services and utilities.
Secondly, I have covered public awareness in this research. However, I have only investigated
this through the knowledge of experts. For a more accurate analysis of the public awareness in
relation to heat stress and the urban heat island effect, I suggest having a quantitative research
where inhabitants of both cities are surveyed on heat stress.
Finally, this research is done from a social- scientific perspective. I have not measured the effects
of the adaptation and mitigation strategies on the urban heat island effect in both cities. In order
to do a more accurate analysis on the impact of the adaptation and mitigation strategies, I suggest
doing a more natural scientific approach.
45
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13 Appendix
13.1 The heat stress framework by Hatvani-Kovacs et al. (2018)
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13.2 Screenshots of the Extrema Rotterdam weather app
The extrema app shows your location. On the basis of satellite data, the app calculates the
outside temperature and the humidity. In combination with your personal data, the app
calculates your personal risk, and shows the cool spots in Rotterdam (for instance cinema’s,
public libraries, fountains) where you can cool down.
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13.3 Infographic municipality of Amsterdam
This infographic shows the groups that are the most vulnerable during heat waves, the dangers
of overheating and the measures to take in order to prevent negative effects during hot periods.
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13.4 Positions of the interviewees
Amsterdam
Municipality of Amsterdam: - AM1: advisor climate adaptation, green in the city,
Amsterdam rainproof at the municipality of Amsterdam.
Municipal health service: - Ben Rozema: doctor health and society, working at the
municipal health service Amsterdam (GGD) at the
department of the living environment.
Housing corporation: - Wim de Waard: head communication at housing
corporation Eigen Haard in Amsterdam.
Rotterdam
Municipality of Rotterdam: - Roland van der Heijden: urban planner, product manager
digital city at the municipality of Rotterdam, has worked on
sustainability topics.
- RM1: advisor at the sustainability program at the
municipality of Rotterdam, specialized in the adaptation
strategy of Rotterdam and energy transition.
- RM2: advisor city development for multifunctional
rooftops and specialized in heat within the adaptation
strategy for the municipality of Rotterdam.
Municipal health service: - RHS1: environmental medical advisor at the municipal
health service in Rotterdam (GGD), specialized in heat.
Housing corporation: - Hanneke van der Heijden: sustainability specialist at
housing corporation Woonstad Rotterdam.
Extern parties:
Researcher 1: - Alexander Wandl: researcher at TU Delft at the
department of environmental technology and design, co-
author of scientific reports Amsterwarm, Hotterdam and
other reports on the urban heat island effect. Researcher 2: - Jeroen Kluck: lector water in the city at Amsterdam
University of Applied Sciences, co-author of research
reports about climate-proof cities and neighborhoods.
Greening company: - Livien van de Ven: Junior communication advisor at De
Groene Stad (The Green City), a company that aims to
inform and stimulate the interest with authorities,
organizations and companies which are professionally
involved in planning and developing the urban area,
ensuring green will be applied appropriately.
