How do Urban Climate Adaptation Strategies differ between Amsterdam and Rotterdam, a Historic City and a Modern City?

How do Urban Climate Adaptation Strategies

differ between Amsterdam and Rotterdam, a

Historic City and a Modern City?

Name: Jason Jabroer

Student Number: 11309806

Institute: University of Amsterdam Location: Amsterdam, The Netherlands

Date: 18/06/2021

First Supervisor: Jannes Willems Second Supervisor: Rosa van Schaick

Abstract

Coastal cities are subjected to serious flood risk, which could cause much structural, economic and social damage. Due to climate change, sea levels rise, increased peak river discharge and an increase in extreme precipitation threaten a growing number of cities. These cities have to adapt in order to prevent their decline. Flood risk management is a way of doing this, and some cities already have many years of experience, such as Rotterdam and Amsterdam. Two Dutch cities, a modern one and a historic one, that also have to adapt to the consequences of climate change, such as flooding. These cities are already role models for other cities to follow, however one of these two cities might be more relevant to observe than the other due to their urban planning differences. Because of this, research conducted in the paper intends to answer the question: How do the modern and historic city characteristics of Rotterdam and Amsterdam respectively, affect the way in which these cities are subjected to flood risk and how does this lead to different flood risk management strategies?

To do this, a document analysis is conducted over a selection policy documents from the

municipalities of Rotterdam and Amsterdam. The results suggest that the city characteristics do not have a significant impact on the flood risk that Rotterdam and Amsterdam are subjected to, and this also seems to be the case for their flood risk management strategies. The flood risks between the cities appear to be too similar to warrant flood risk management strategies that are very different.

Content

2.2 Flood Risk Management 8

2.3 Resilience 8

2.4 City Characteristics / Urban Form 9

2.5 Conceptual Framework 11

Methodology 12

Analysis 17

4.1 History and Urban Form 17

4.1.1 Amsterdam 17

4.1.2 Rotterdam 20

4.2 Flood Risk Management 25

4.2.1 Amsterdam 25

4.2.2 Rotterdam 27

4.3 Flood Risk Management Going Forward 28

4.3.1 Amsterdam 28

4.3.2 Rotterdam 32

Discussion and Conclusion 35

1. Introduction

Over half the world’s population lives within cities. Coastal cities are at serious risk of flooding, which can cause a large amount of damage, both structurally and economically, but also many lives could be lost. Climate change is expected to increase the risk of flooding in coastal cities due to rising sea levels, increased peak river discharge and an increase in both intensity and frequency of precipitation events. Many cities realize the need for adaptation. For a long time, flood management was focused on preventing floods from occurring through technical implementations such as dikes and storm surge barriers. Presently, the focus has largely shifted to more integrated and adaptive systems of flood management (Ward et al., 2013).

Figure 1: Churchillplein in Rotterdam (Ben Housing, 2021)

Documents from the municipality of Rotterdam, such as Gemeente Rotterdam (2013), show that Rotterdam has implemented standard interventions following the old philosophy of building dikes, levies and storm surge barriers to protect the city from the water from the North Sea and rivers through the city. Though the city also has significant parts of it not protected by these structures, roughly forty thousand people live in these areas, which are situated on slightly higher ground, about three to six meters above sea level, Normaal Amsterdams Peil (NAP). Rising sea levels and increased frequency of intense precipitation, however, could become problematic in the future (Gemeente Rotterdam, z.d.-b). In a city document that preludes the new City Vision, Verkenning Omgevingsvisie Rotterdam, Rotterdam acknowledges that adapting to climate change requires a change in mentality in how to deal

with water in the future (Gemeente Rotterdam, 2018). The municipality of Rotterdam collaborates with Rotterdams Weerwoord on implementing measures that should protect the city (Rotterdams Weerwoord, 2019). They point out that interventions such as green roofs and changes to the sewer system are ways that the city intends to become more resilient to the consequences of climate change (Gemeente Rotterdam, 2018). The city and Rotterdams Weerwoord realize that every neighbourhood is different and therefore have their own needs and vulnerabilities, each requiring a customized approach to make them more climate resilient (Rotterdams Weerwoord, 2019).

Figure 2: Canal with two streets in Amsterdam (ANWB, z.d.)

Rotterdam is, however, not the only city in the Netherlands that has to face the consequences of climate change. In the City Vision of Amsterdam, this city also acknowledges that it is in a vulnerable position due to potential flooding from sea level rise, extreme precipitation, increased river discharge as well as sinking soil. All of these factors lead to new challenges regarding flood risk, while Amsterdam’s current water system limits, including those of the sewers, are close to being reached. Amsterdam, like Rotterdam, aims to become more resilient in order to handle these threats (Gemeente Amsterdam, 2021a). In order to do this the municipality collaborates with Waternet and Amsterdam Rainproof to implement measures to improve the city’s resilience, for example by implementing water infiltration sites such as green roofs, wadies and strips of green for delayed water infiltration (Rainproof, 2021; Waternet, z.d.).

Both Dutch cities have a long water management history and are in the top three of the Sustainable Cities Water Index (Dutch Water Sector, 2016). They also both face similar challenges regarding climate adaptation in terms of sea level rise, an increase in precipitation intensity and frequency, and increased river discharge. These cities have a number of urban planning differences, however. Where Amsterdam is a city that maintains much of its historic urban form, such as the canals and the centuries

old houses that stand along these canals, wooden poles forming their foundation. Rotterdam is in a different situation after having been destroyed in bombardments by the Germans in 1940 (Amsterdam, 2020). Rotterdam is as a result a more modernist city after having been rebuilt in the post-war years, following the urban planning trends that were dominant at that time (Rooijendijk, 2005). As a result, Rotterdam shows the presence of more flat roofs and wider roads (see Figure 1), which can be prone to flooding, but also offer opportunities for climate adaptation.

Both of these cities serve as a role model for the rest of the world in how other cities can effectively implement urban climate adaptation strategies (Gemeente Rotterdam, 2013; Dutch Water Sector, 2016). It could however be interesting to explore how the differences between modern Rotterdam and historic Amsterdam lead to different flood risk management strategies, so that other cities in the world can judge which of these strategies would suit them best and could be used as a starting point for their own formation of flood risk management strategies. Therefore the following research question and subquestions have been formulated:

● How do the modern and historic city characteristics of Rotterdam and Amsterdam respectively, affect the way in which these cities are subjected to flood risk and how does this lead to different flood risk management strategies?

○ What are the differences between Rotterdam and Amsterdam regarding urban form? ○ What are the differences between Rotterdam and Amsterdam regarding flood risk? ○ What are the flood risk management strategies that Rotterdam and Amsterdam have

2. Theoretical Framework

The following chapter discusses and describes the concepts with which the climate adaptation strategies of Amsterdam and Rotterdam will be analyzed, using mostly secondary data from scientific papers. The concepts addressed will be Flood Risk, Flood Risk Management, Resilience and City Characteristics / Urban Form. The conceptual framework explains how the concepts are expected to relate to each other.

2.1 Flood Risk

Floods are defined by Schanze (2006) as land being temporarily covered by water that is outside of its regular confines. They tend to happen in areas such as estuaries, at the coast and in river basins. Schanze (2006) also mentioned that floods can be systematized according to the cause of events, like snow-melt floods, winter rainfall floods, sea surge and tidal floods, rising groundwater floods, tsunamis, etc. Certain factors characterise a flood, such as flow velocity and water depth. Floods can be dangerous if they occur in areas where humans are present.

Risk can be described as the likelihood, or probability, of an unwanted event occurring, multiplied by the impact or damage caused by this unwanted event, like it is an equation. If monetary value is attributed to the impact, then the risk can be calculated by multiplying the probability with the impact (Kent, 2016).

Apel et al. (2004) says flood risk is the combination of flood hazard and the consequences of flooding, or vulnerability, while according to Merz et al. (2010), flood hazard is the probability of the occurrence of potentially damaging floods, which means that some elements are exposed to flooding and could be harmed (Schanze, 2006). The damage done to these elements by the flood hazards depends on their vulnerability. Three areas of vulnerability can be distinguished according to Schanze (2006): economic, ecological and lastly social and cultural vulnerability. Economic vulnerability refers to direct and indirect financial losses due to damage to property, material and goods, reduced productivity and relief efforts. Ecological vulnerability refers to the pollution of  soils, waters and ecological systems. Social and cultural vulnerability refers to loss of life and vitality, stress, loss of personal possessions and cultural heritage and health impacts (Schanze, 2006).

Merz et al. (2010) claim that over recent years the notion of flood risk being the basis for flood risk management decisions has become widely accepted.

2.2 Flood Risk Management

According to Plate (2002), risk management is a procedure to deal with risks of both natural, environmental and man-made hazards, which includes floods. In this article they explain that risk management has three distinct action levels: the operational level, the project planning level and the project design level. The operational level is the level that is considered to be operating an existing system. The project planning level is used when a new project is planned, or when an existing project is to be revised. The project design level is a part of the project planning level and should describe how an optimal solution for the project is attained. The process of transition from the operational level to the project planning level is dynamic. When the value system of a country changes, and the natural boundaries are also changed by the actions of humans or global change, the existing system will then no longer be meeting the demands of the contemporary society, and then actions on the project planning level will be initiated. The changes in options available to address a flood situation, and also the changes in the perception of risk and the attitudes towards it, are important criteria that influence the decisions for change. On the project design level, design costs and benefits are evaluated and compared to the benefits that have been obtained from the planned project. The residual risk is also taken into account, the risk which still remains after the completion and operationalisation of a project (Plate, 2002). Schanze (2006) describes flood risk management as a procedure that deals with a wide array of tasks and issues that range from the prediction of flood hazards, through their consequences to society to measures and instruments for risk reduction. Because of this, he argues that flood risk management needs systematisation and integration.

The paper by K.M. de Bruijn (2004), describes flood risk management in a new way by applying a systems approach. This approach might be better suited to the different socio-economic contexts in which flood risk management is implemented, compared to the other approaches. The systems approach is supposed to allow the definition of resistance and resilience strategies. Resistance strategies are designed to prevent flooding, whereas resilience strategies should minimize the impacts of flooding and enhance the subsequent recovery, resilience strategies are also supposed to be able to better cope with uncertainties compared to resistance strategies.

The risk equation that has been described in the Flood Risk paragraph, suggests that there are two ways in which risk can be mitigated. Namely reducing the likelihood or probability that an unwanted event occurs is an option. Reducing the impact that such an unwanted event could have is the other option.

2.3 Resilience

Resilience comes from the Latin word of resilire, which means to spring back. It is now often used to mean that something has the ability to bounce back or rebound. The term resilience has become a regularly used term in the academic world (Davoudi, 2007). Herrman (2011) describes resilience as

referring to positive adaptation, the ability to regain and maintain health despite experiencing damage. Masten (2002) describes resilience as positive adaptation in the presence of significant adversity. The IPCC (2007) defines resilience as ‘the ability of a social or ecological system to absorb disturbances while retaining the same basic structure and ways of functioning, the capacity of self-organisation, and the capacity to adapt to stress and change.’ Resilience requires flexibility, change and learning (Adger et al., 2005). Tyler & Moench (2012) claim that regarding urban climate adaptation, a resilience based approach encourages the practitioners to change and innovate to help recovery from disturbance or adversity that might be predictable, or not. They (Tyler & Moench, 2012) add that the strategic approach of resilience building has many advantages over more standard system management for social-ecological systems which are complex, dynamic and facing high uncertainty. Restemeyer, Van den Brink & Woltjer (2018) note that resilience is considered a concept which could produce a paradigm shift from flood control to an integration of flood risk management and spatial planning. The core is that ‘nothing is certain except uncertainty itself’ and adaptability is crucial in dealing with the unknown. This terminology is increasingly used, even though they (Restemeyer, Van den Brink & Woltjer; 2018) consider it fairly unclear, therefore they researched how it is used in planning practice. Their case studies of London and Rotterdam show that uncertainties are a main concern, leading to strategic plans that are more adaptive. While London and Rotterdam use differing approaches, ‘scientific pragmatism’ and ‘joint fact finding’ respectively, there are striking similarities. In both cases methods like scenario planning and monitoring to manage uncertainties are used. A technical-rational way is used to accommodate the resilience narrative, and therefore the policy strategies are resulting in the maintenance of the status quo instead of starting a paradigm shift, like in previous turns of flood risk management (Restemeyer, Van den Brink & Woltjer; 2018).

2.4 City Characteristics / Urban Form

The modern city can be perceived as a source for environmental problems. Urban form directly affects ecosystems, habitat and water quality due to land consumption, replacement of natural cover with impervious surfaces, and habitat fragmentation. Urban form also influences travel behaviour, affecting air quality, loss of farmland, wetlands and open space, as well as soil contamination, noise and climate (Jabareen, 2006).

Sustainable development as a concept has reignited the discussion about urban form. It encouraged practitioners and scholars to search for forms of human settlement that would meet the requirements of sustainability and enable the built environments to function more constructively (Jabareen, 2006).

Jabareen (2006) has identified seven design concepts of sustainable urban form.

● Compactness: a widely accepted strategy that could help achieve more sustainable urban forms. It includes contiguity and connectivity, suggesting that further urban development should take place adjacent to existing urban structures. Further sprawl is supposed to be

prevented this way when applied to existing urban fabrics. Though it does not reduce the sprawl that had already occured. The compactness of an urban space minimizes the transport of water,

materials, energy, people and products.

Intensification is a major strategy to achieve compactness. The urban land is used more efficiently by increasing the density of developments and activities. It also includes the development of land that had not been developed yet, and the redevelopment of already existing buildings, conversions, sites, subdivisions, additions and extensions (Jabareen, 2006).

● Sustainable transport: One of the biggest issues for environmental debates regarding urban form is transport. The form of cities reflect the transport technologies that were dominant during its different development stages. Sustainable urban form should be a form and scale which are appropriate for cycling, walking and public transport while also offering enough compactness to encourage social interaction. Access to the city’s facilities should be enabled while the resulting costs are minimized (Jabareen, 2006).

● Density: In determining sustainable urban forms, density is crucial. Density is the amount of people or dwelling units within a certain land area. Density and urban character are in a relationship which is based on the concept of viable thresholds. This means that at certain densities, the number of people within an area becomes sufficient for generating enough interaction to make urban activities and functions viable (Jabareen, 2006).

● Mixed Land Uses: This allows compatible land uses to locate within close proximity, thereby travel distances are decreased. This includes mixing commercial, residential, industrial, institutional and transportational uses. This encourages the use of transportation modes such as walking and cycling (Jabareen, 2006).

● Diversity: Sustainability of cities requires diversity of activity. Diversity promotes further desirable urban features such as a larger variety of household sizes, housing types, cultures, building densities, ages and incomes. Diversity can represent the social and cultural context of the urban form (Jabareen, 2006).

● Passive Solar Design: This is supposed to reduce the demand for energy and it should provide optimal use of passive energy in sustainable ways through specific design measures. These measures affect the form of the built environment through urban densities and the orientation of buildings. There is an assumption that orientation, design, siting, layout and landscaping can optimally use microclimatic conditions and solar gain to minimize the need for space cooling or heating of buildings by using conventional sources of energy generation (Jabareen, 2006). ● Greening: Green space has the ability to provide a positive contribution to several urban areas

like sustainability. Greening intends to embrace nature as an integral part of the city and the experience of life within the city through a diverse array of open landscapes. Urban and suburban places become more pleasant, appealing and sustainable as the city becomes greener. There are also other benefits mentioned that greening is supposed to have. Namely the increase

in economic attractiveness, improvement of urban image and quality of life, contributions to maintenance of biodiversity, contributions to sustainable development and moderating extremes of urban climate (Jabareen, 2006).

2.5 Conceptual Framework

Figure 3: Conceptual Framework

Both cities of Rotterdam and Amsterdam are at significant risk of flooding due to their low lying locations and proximity to surface waters such as rivers and the North Sea. Also due to climate change these cities are increasingly exposed to higher and more frequent peak discharge and heavy precipitation. These phenomena can be extreme enough to cause damage to capital, infrastructure and people. The increasing flood risk is increasingly hard to avoid, if at all possible. Rotterdam and Amsterdam need to adapt to the changing situation, meaning they have had to increase their focus on flood risk management. One of the most important aspects of flood risk management is the increased implementation of resilience in the urban planning of these cities, whereby damage is limited when flooding occurs, and recovery from flooding is easier, quicker and cheaper. By increasing their resilience as part of their flood risk management, the cities will also be affecting some of their city characteristics, which will in turn affect the flood risk these cities are subjected to.

3. Methodology

In this research paper the Dutch cities of Amsterdam and Rotterdam are compared regarding their urban form, flood risk and flood risk strategies. This is done because these cities are of similar size population wise, being the two largest Dutch cities housing around 835.000 and 635.000 people respectively, as well as because of their close proximity to each other of just 60 kilometers (Entzinger, 2019). Both cities face similar challenges regarding climate change and its consequences, both cities are located near the North Sea, both cities have one or more rivers running through them and both cities face an increase in precipitation frequency and intensity, as has been mentioned in the Introduction. There are also differences between the cities that should be mentioned. The municipality of Rotterdam collaborates with Rotterdams Weerwoord and the three different regional water authorities of Waterschap Hollandsche Delta, Hoogheemraadschap van Delfland and Hoogheemraadschap van Schieland en de Krimpenerwaard (Gemeente Rotterdam, z.d.-a). While Amsterdam is in collaboration with Amsterdam Rainproof and Waternet (Gemeente Amsterdam, 2020). Waternet is a water company that is responsible for the entire water cycle, with tasks including the provision of drinking water, while also being responsible for the maintenance of dykes and clean water. The company was created by the municipality of Amsterdam and the regional water authority called Waterschap Amstel Gooi en Vecht (Waternet, z.d.). Another difference between Amsterdam and Rotterdam is their urban form, Rotterdam being a city with more modernist influences compared to Amsterdam (Rooijendijk, 2005). This paper researches how these differences affect the flood risk in Amsterdam and Rotterdam, and how these cities intend to adapt to this flood risk.

To acquire the relevant secondary data for answering the research questions, several different data sources are to be consulted, this mainly includes policy documents from the municipalities of Rotterdam and Amsterdam that are accessible through the World Wide Web, as well as online documents from Rotterdams Weerwoord and Amsterdam Rainproof. Acquired data is always referred to using the APA reference system in order to adequately credit the sources that have been consulted. The research is conducted by using the qualitative method of document analysis by analysing the data using the programme Atlas.ti, using codes that can be found in Table 2. This is done in order to gain the empirical knowledge and meaning of the studied policy documents by comparing these documents between Amsterdam and Rotterdam, and to be able to answer the research question and subquestions that are hereby recalled as:

How do the modern and historic city characteristics of Rotterdam and Amsterdam respectively, affect the way in which these cities are subjected to flood risk and how does this lead to different flood risk management strategies?

○ What are the differences between Rotterdam and Amsterdam regarding urban form? ○ What are the differences between Rotterdam and Amsterdam regarding flood risk?

○ What are the flood risk management strategies that Rotterdam and Amsterdam have created in order to adapt to flood risk, how do they differ?

A document analysis is described as an effective and efficient method of gathering data due to documents being practical and manageable resources. Documents are widespread and diverse, which makes them reliable and accessible (Triad 3, 2016). Answering the aforementioned questions should provide clear insight for other cities to use in their efforts to adapt to climate change in the future. What should be kept in mind when conducting a document analysis however is that they can be open to interpretation, so from the same data that is analysed, different researchers could potentially draw different conclusions (Triangle Admin, 2018). Also, not all documents provide as much relevant data as others, or even none at all (Triad 3, 2016).

In Table 1 below, a list can be found of the documents that are analysed in this paper. These documents have been selected because their contents should be able to provide sufficient data to answer the research questions. All of the documents are publicly available on the World Wide Web and can be found via google searches or using the websites of the municipalities of Amsterdam and Rotterdam, or Amsterdam Rainproof and Rotterdams Weerwoord.

Amsterdam Rotterdam

Gemeente Amsterdam. (2021a, januari).

Omgevingsvisie 2050 Een Menselijke

Metropool.

https://assets.amsterdam.nl/publish/pages/96

1463/ontwerp-omgevingsvisie_amsterdam_2050.pdf

Gemeente Rotterdam. (2020, juni). Aanpak

Omgevingseffectrapportage.

https://www.rotterdam.nl/wonen-

leven/omgevingsvisie-nrd/Nota_reikwijdte-en-detail.pdf

Gemeente Amsterdam. (2020, februari).

Strategie Klimaatadaptatie Amsterdam.

https://www.amsterdam.nl/wonen-

leefomgeving/duurzaam-

amsterdam/publicaties-duurzaam-

groen/strategie-klimaatadaptatie-amsterdam/?PagClsIdt=15442988#PagCls_1

5442988

Gemeente Rotterdam. (2018, maart).

Verkenning Omgevingsvisie Rotterdam.

https://commissiemer.nl/projectdocumenten/

00007301.pdf

Gemeente Amsterdam. (2021b, mei).

Verordening van de gemeenteraad van de

gemeente Amsterdam houdende regels

omtrent het bergen van hemelwater

Gemeente Rotterdam. (2007). Water Krijgt

een Grotere Rol in Rotterdam.

(Hemelwaterverordening Amsterdam).

https://www.rainproof.nl/sites/default/files/h

emelwaterverordening_gemeenteblad.pdf

Gemeente Amsterdam, Waternet, &

Amsterdam Rainproof. (2019a).

Regenbestendige Gebiedsontwikkeling

Katern 1. Gemeente Amsterdam.

https://www.rainproof.nl/sites/default/files/d

ef_katern_1_beleidskader_en_programma-klein.pdf

Gemeente Rotterdam. (2021, februari).

Gemeentelijk Rioleringsplan.

https://www.rotterdam.nl/wonen-leven/grp/Gemeentelijk-Rioleringsplan.pdf

Gemeente Amsterdam, Waternet, &

Amsterdam Rainproof. (2019b).

Regenbestendige Gebiedsontwikkeling

Katern 2. Gemeente Amsterdam.

https://www.rainproof.nl/sites/default/files/d

ef_katern_2_regenwaterbestendige_gebieds

ontwikkeling-klein.pdf

Gemeente Rotterdam. (2013). Rotterdamse

Adaptatiestrategie.

https://ruimtelijkeadaptatie.nl/publish/pages/

120068/edepotlink_t54902ab0_001.pdf

Gemeente Amsterdam & Waternet. (2016,

januari). Gemeentelijk Rioleringsplan

Amsterdam 2016–2021. Waternet.

https://www.waternet.nl/siteassets/ons-

water/gemeentelijk-rioleringsplan-amsterdam-2016-2021.pdf

Rotterdams Weerwoord. (2019).

Urgentiedocument Ruimtelijke Adaptatie.

https://klimaatadaptatienederland.nl/publish/

pages/158605/rapport.pdf

Table 1: List of Analyzed Documents

To help with the analysis of the research questions, the core concepts have been operationalised into codes in Table 2, below. The codes help label and organise the relevant information in the policy documents for subsequent analysis.

Concept Concept Definition Category Code

Flood Risk The combination of flood hazard and the consequences of flooding. Economic damage

Ecological damage

Social and Cultural damage Flooding “Plants / Green”, “Biodiversity”, “Ecology”, “Ecosystems” “Environment”,

This category was addressed very little in the analysed documents, therefore the codes have been removed. “Peak/Heavy Precipitation”, “High Groundwater Level”, “Threat/Risk”, “Flooding” Flood Risk Management Strategies

A procedure that deals with the prediction of flood hazards, their consequences to society and measures and instruments for risk reduction.

Spatial Interventions “Water Protection”, “Water Storage”, “Water Drainage / Infiltration” “Plants / Green”

City Characteristics Differences in which Rotterdam and

Amsterdam are located and built.

Urban Form “Parks”,

“Infrastructure”, “Buildings”, “Density”,

Water System

“Functions”, “Plants / Green”

“Surface Water”. “Sewer”

Resilience Something (the city) has the ability to bounce back or rebound after major disruption. Recovery Flexibility Adaptability “Repaired”, “Withstood”, “Restructuring” “Proactive”, “Anticipatory” “Learning’, “Change”

Table 2: Operationalisation of Concepts

In Table 2 can be seen that the code “Plants / Green’ is found both in the category City Characteristics, as well as Spatial Interventions because this code can be used to describe aspects or interventions both in both these categories respectively.

The research that is conducted is to follow the ethical rules of research described by the University of Amsterdam guide of ethics version 1.2 (Universiteit van Amsterdam, 2016).

The acquired data is to be stored in four separate digital locations. The primary location for data storage is the personal laptop of the researcher responsible for writing this thesis, this laptop is  primarily used for academic purposes. The second location for data storage is the Google Drive digital environment belonging to the same researcher.  The third storage location for the data is Atlas.ti, where the data is also analysed. All of the data storage locations that have been mentioned so far are only accessible by the researcher through password protection.

4. Analysis

The analysis chapter aims to provide an answer to the research question, through providing answers to the sub-questions in the order that they have been formulated. Firstly, by providing an answer to the question: What are the differences between Rotterdam and Amsterdam regarding urban form? Secondly, by providing an answer to the question: What are the differences between Rotterdam and Amsterdam regarding flood risk? Thirdly, by providing an answer to the question: What are the flood risk management strategies that Rotterdam and Amsterdam have created in order to adapt to flood risk, how do they differ? And finally the main research question: How do the modern and historic city characteristics of Rotterdam and Amsterdam respectively, affect the way in which these cities are subjected to flood risk and how does this lead to different flood risk management strategies?.

4.1 History and Urban Form

4.1.1 Amsterdam

Amsterdam has been dealing with water and its management for centuries. This is due to the location where the city is situated. The construction of the dam along the Amstel river was the starting point for continued efforts to transform the surrounding area, which consisted of swamps, into a place where people could live and work. During the sixteenth century buildings would start to be constructed by brick instead of wood. To prevent the sinking and collapse of these buildings because of the soft swampy soil, they would be built on a foundation of wooden poles that would be placed deep into the ground. The canals were built in the seventeenth century to cope with the city’s growing population. The city formed a plan in which the soil was raised and canals were dug for drainage. Dykes, sluices and windmills were subsequently constructed and used to manage water levels. With the construction of the sluices calles ‘Oranjesluizen’ in the nineteenth century, the ebb and flow in the canals of Amsterdam was ended. Further expansion of the city was executed without much consideration for water and green. Raising of buildings was done using rubble and waste, this cheap method led to buildings sagging even before people had moved in. Integral raising of soil by the municipality would start after the introduction of the leasehold system in 1896. Initially dredged material would be used for the Van der Pekbuurt and the Vogelbuurt. Around 1925 the municipality however decided to switch to using clean sand without sludge and clay, the Rivierenbuurt was built on this type of soil. After the Second World War, Amsterdam planned and built new neighbourhoods to the West and South. During these times flood risk from the North Sea was considered low enough to significantly reduce the requirements to the raising of soil for new developments, this was due to the construction of the Afsluitdijk and the sluices near IJmuiden. Amsterdam still benefits from the investments in water defences and the raising of soil. The city however also faces extra challenges due to cost saving measures having prevented some areas from being raised, worse building materials being used and inferior drainage being put into place. The effects of climate change make these challenges more significant (Gemeente Amsterdam, 2020).

The Rivierenbuurt, the Bellamybuurt and Watergraafsmeer are among the lowest lying neighbourhoods of Amsterdam with many elevation differences. An overabundance of water causes disruption after heavy rain showers (Gemeente Amsterdam, 2020).

Figure 4: Groundwater challenges in Amsterdam (Gemeente Amsterdam, Waternet & Amsterdam Rainproof; 2019b)

In figure 4 can be seen where the groundwater level compared to the ground level is considered lower than the ideal measure of 0,90 m. In the orange areas drainage is possible. Drainage is however not possible in the red areas, which are therefore more at risk of flooding. The infiltration methods of Amsterdam Rainproof are therefore not suitable for use in the red areas (Gemeente Amsterdam, Waternet & Amsterdam Rainproof; 2019b).

Figure 5: Vulnerable areas in Amsterdam (Gemeente Amsterdam, Waternet & Amsterdam Rainproof; 2019b) The figure above shows the areas in Amsterdam that have a higher chance of being flooded and damaged during events of extreme precipitation intensity. This is at the intensity of 60 mm of rainfall per hour or 120 mm per hour in the model that was used to create this map. The red areas cover both public as well as private property (Gemeente Amsterdam, Waternet & Amsterdam Rainproof; 2019b).

Amsterdam is currently in a position where its ability to withstand extreme precipitation is not sufficient. The amount of water that can be drained or temporarily stored determines the chance of damage and disruption. Water drainage and storage are dependent on the sewers, as well as the physical layout and land use of public and private property. The sewers were not designed and built to discharge extreme amounts of water in short periods of time. Simultaneously was the city’s layout and land use not designed to store large amounts of water. This can be seen in the predominantly impervious surfaces covering the city, water that falls on buildings and pavement cannot infiltrate into the soil and therefore runs off into the sewers and surface waters or flood streets and buildings, causing damage and disruption to these buildings and essential functions and infrastructure such as the power supply, which can be identified as the economic and social and cultural vulnerabilities of the city (Schanze, 2006). Another consequence in extreme cases of precipitation is the death of local plant life due to drowning (Gemeente Amsterdam, 2020), the ecological vulnerability (Schanze, 2006).

Figure 6: Polders and Ground Water Levels within the Municipality of Amsterdam (Waternet, 2012).

Historically Amsterdam is prone to flooding the North Sea, the Lek river, the Marker Lake and regional water systems. Amsterdam’s water system is reaching its limits, leaving little flexibility to successfully drain extreme amounts of water. The deepest polders in Amsterdam are the most vulnerable to flooding, these areas can be seen in Figure 6. While the chances of flooding are low, if a flood does occur the consequences would be severe. The risk would be citywide disruption by making certain areas temporarily unreachable, including emergency services, the failure of essential functions, damage to infrastructure and buildings and the economy, as well as long recovery times (Gemeente Amsterdam, 2020). The description of risk by Kent (2016) can be seen here, the chance of flooding in Amsterdam is currently low, but in the event that it does occur, the damage would be severe, thus multiplying the chance with the potential damage led Amsterdam to believe that the risk is large enough for action to be taken. In the following paragraphs it is explained how the city is doing that, by not only reducing the chance of flooding, but also the potential damage a flood could cause.

4.1.2 Rotterdam

Rotterdam is a city that has been partly destroyed at the start of World War Two in 1940 by the Germans. As a result, the city had to rebuild itself after the war, and this was done using the more modernist urban planning trends that were dominant at the time (Rooijendijk, 2005). This can be seen today with the

many tall and flat-roofed buildings, as well as wider roads compared to Amsterdam. Though some older neighbourhoods did survive the war, there still are pre-war buildings with wooden pile foundations which require the groundwater levels to not drop too far. The more modern buildings, without the wooden pile foundations but with concrete foundations and/or basements, are more vulnerable to higher groundwater levels (Rotterdams Weerwoord, 2019).

Figure 7: Buildings at risk of flooding (Rotterdams Weerwoord, 2019).

The figure above shows which parts of Rotterdam are the most vulnerable to damage caused by flooding in the event of extreme precipitation in excess of 70 mm per hour. The darker blue areas have a higher percentage of buildings at risk of flood damage compared to areas that are indicated in lighter shades of blue. The main roads indicated in orange become unnavigable in such a flooding event, the yellow main roads remain accessible to traffic from emergency services. The ‘wateropgave oppervlaktewater’ shows the areas in which extreme precipitation could harm the surface water system (Rotterdams Weerwoord, 2019).

Figure 8: Flood risk inside and outside of areas that are protected by dikes (Rotterdams Weerwoord, 2019). In figure 8, the areas that are protected by the dykes, and the areas that are not protected by the dykes, are highlighted in blue and red respectively, whereas the dotted and ragged lines respectively indicate the locations of the regional and primary dykes. The yellow ragged lines show where the dykes could potentially be strengthened. The darker red areas lay below 3,6 meters above sea level, whereas the lighter red areas lay above 3,6 meters above sea level. The 3,6 meters is the height at which new developments behind the Maeslant barrier are to be built. The areas indicated in a darker shade of blue show a higher flooding depth in the event flooding occurs due to dyke breaches (Rotterdams Weerwoord, 2019).

Figure 9: Vulnerable areas to low and high groundwater levels (Rotterdams Weerwoord, 2019).

In the figure above is shown where in Rotterdam groundwater levels can become too low or too high. When the difference between the ground level and the open water level, the ‘drooglegging’, is smaller than 80 cm there is a higher chance of high groundwater levels causing damage, indicated in blue. Buildings that are not built upon wooden pile foundations are bearing the most risk when groundwater levels are high. When the groundwater levels are low, the wooden pile foundations are at risk of rotting away, causing the buildings on top of these wooden piles to sink, their location can be seen in the figure in dark purple. The replacement of the sewers could cause a change in groundwater levels, therefore the areas containing buildings with wooden foundations where sewer replacement is a priority, are shown in the figure in the lighter shade of purple. The foundations on sand are indicated in orange (Rotterdams Weerwoord, 2019).

Figure 10: Sinking soil in Rotterdam (Rotterdams Weerwoord, 2019).

During long term dehydration, the peat soil is susceptible to uneven sinking, leading to damage to buildings and infrastructure. The groundwater level is an important factor herein. In the figure above can be seen different areas in Rotterdam with different rates of soil sinking. From orange to brown the soil sinks by a larger average amount of mm per year. The blue and green circles are the priority areas in which the buildings are vulnerable to uneven soil sinking and where action needs to be taken to ensure that these neighbourhoods continue being liveable to their inhabitants. The priority areas are ranked into three distinct categories depending on which areas the municipality prioritises (Rotterdams Weerwoord, 2019).

Thus what are the differences between Rotterdam and Amsterdam regarding urban form? Both cities seem to be facing similar challenges. They both have areas that are more vulnerable to high groundwater levels, and low groundwater levels, as is the case with flood risk. Both cities have areas that are below sea level, and they both have areas that are above sea level. The cities each have one or more rivers running through them, though not all of Rotterdam is protected by dykes, compared to Amsterdam, which does seem entirely to be protected. A part of Rotterdam has been rebuilt following more modernist trends after the Second World War, leading to wider streets and taller, flat-roofed buildings, whereas Amsterdam maintained its more historic center and canals.

4.2 Flood Risk Management

4.2.1 Amsterdam

An important part of Amsterdam’s water management in Amsterdam Rainproof. This is a network approach which consists of more than 90 parties. Their goal is to improve the city’s resilience against the increase in extreme precipitation events. Furthermore, they aim to utilize as much of the precipitation as possible. Amsterdam Rainproof is involved in both public and private space. The network was initiated by the municipality of Amsterdam and Waternet; among the previously mentioned 90 parties there are people involved from every part of society, such as housing corporations, gardeners, residents, entrepreneurs, local green initiatives, knowledge institutions and others. This way knowledge and practical experience are supposed to come together and drive innovation and diversity. Rainproof is involved in resolving water issues that have been identified in certain areas of the city. Resolving these issues by making them rainproof requires communication with, and participation from the neighbourhood that is to receive a rainproof intervention. For example, Amsterdam Rainproof was involved when in the Bellamybuurt the ageing sewer system was to be replaced. They decided to use this opportunity to improve the entire neighbourhood’s resilience to heavy precipitation. Amsterdam Rainproof did this by redirecting the flow of rainwater towards the Bellamyplein, by using thresholds. On the Bellamyplein they had created lower lying strips of green to temporarily store the excess water (Gemeente Amsterdam, 2020). The previously described intervention can be seen as an example of the systems approach with a resilience strategy as has been described by K.M. de Bruijn (2004).

Rainwater Ordinance

The municipality is responsible for the drainage of precipitation. In the Municipal Sewer Plan Amsterdam 2016-2021 it is described how the municipality of Amsterdam acts to fulfill this responsibility. The starting points are as follows (Gemeente Amsterdam, 2020; Gemeente Amsterdam & Waternet, 2016):

● The property owner is responsible for the drainage of precipitation on his property. ● The preference is to discharge excess water immediately.

● The municipality is responsible for the arrangement of public space and the temporary storage of excess water from extreme precipitation.

The Municipal Sewer Plan states that rain showers of 60 millimeters per hour should not be able to damage properties and essential infrastructure, both private and public property, though the Sewer Plan is not enforceable for private property. New rules have yet to be developed to change this.

The core of the rainwater ordinance is (Gemeente Amsterdam, 2020; Gemeente Amsterdam & Waternet, 2016; Gemeente Amsterdam, 2021b):

● To prevent or minimize damage or hindrance due to water, it will become mandatory for new developments to feature water storage.

● At least 60 liters of rain water should be able to be stored per square meter of built up surface. Within 60 hours this water should then be completely discharged, with a maximum discharge into the sewers of 1 liter per square meter of built up surface.

● There are exceptional systems of water reuse, centrally operated systems and permit free developments.

To prevent an overabundance of precipitation from causing damage or disruption, and in order to use this water to improve the liveability and attractiveness of the city, Amsterdam has already implemented measures in pursuit of these goals. These measures include (Gemeente Amsterdam, 2020):

● Collecting and storing as much precipitation as possible in the location where it lands. This water should then be reused or it should slowly drain into the soil, surface water or sewer. ● Using stored rainwater for hydrating urban green, cooling the city and hydration of the soil,

which should help during heatwaves and drought.

● Rainproof planning, meaning that every future physical change to the city should be designed rainproof. The city should be able to tolerate rain showers of 60 millimeters per hour without damage to property and essential infrastructure.

● Rainproof measures implemented in new area developments, starting in the first initial phase. Implements such as temporary water storage and thresholds to direct water flow. The Hemelwaterverordening is developed to make water storage and slowed drainage mandatory additions to new buildings.

● The strengthening and expansion of the Amsterdam Rainproof network in order to connect all parties in the city that can contribute to making Amsterdam more rainproof. When they are connected they can subsequently be activated and facilitated.

● Stimulating housing corporations, businesses and private individuals to store rain water on their properties by removing hard surfaces such as tiles and replacing them with greenery.

● Streamlining water drainage in Amsterdam, for example: Five bridges between the Amstel river and pumping station Zeeburg are to be modified to improve drainage in order to prevent the water levels in the Amstel, the canals and the areas South of the city from rising too far during wet periods.

To reduce the chances of flooding in the city and reduce the consequences when flooding does occur, thus reducing flood risk using the equation described by Kent (2016), the city manages the following measures to enhance water safety (Gemeente Amsterdam, 2020):

● The inspection, maintenance and potential replacement of the water defences such as sluices and weirs.

● The prevention of defects in the sewer system, drinkwater system and surface water management resulting from extreme precipitation or flooding, as far as this is possible within reasonable cost. Otherwise damage to the assets should be minimized when defects cannot be reasonably prevented, the time it takes to repair should also be minimized.

● There should also be a focus on climate adaptation in the wider metropolitan area of Amsterdam. The Adaptation Strategy Waterproof Westpoort has received approval for continuation and is directed by the province of North-Holland. An important link is made between climate adaptation and the challenge of building new housing on a large scale.

4.2.2 Rotterdam

The new Sewer Plan (2021-2025) of Rotterdam recaps what the city has managed to achieve according to the plans of the previous Sewer Plan (2016-2020). They are listed below (Gemeente Rotterdam, 2021):

● Replacing 200 kilometers of sewers.

● Renovated several large and small pumping stations. ● Renovated pressure pipes.

● Laid several kilometers of separate sewer pipes for the discharge of precipitation. ● Laid several hectares of permeable surfaces that let water seep through.

● Placed a dozen special amenities to store water from precipitation, spread over the city. This was often done using innovative solutions such as Urban Waterbuffer at Sparta.

● Increasing the robustness of the water system while increasing the quality of the sewer system. These improvements were carried out in cooperation with several stakeholders. Among these stakeholders are housing corporations, utility companies and RET. Rotterdam also works closely together with the three regional water authorities in which the city is located, as well as the neighbouring municipality of Capelle aan den IJssel and water company Evides. Other parties involved were local residents and businesses. By working integrally the costs managed to stay within the prognosis. Another advantage of working integrally was the prevention of having to open up certain parts of the city with construction works, which reduced nuisance (Gemeente Rotterdam, 2021).

Placing more and larger sewer pipes is no longer sufficient to keep the city’s water system robust and climate resistant. Climate change increases the odds of damage and disruption occurring due to extreme precipitation, heat, drought and flooding. This leads to concerns for health, safety and the economy. Excess water can damage buildings and infrastructure, drought can cause low groundwater levels, extreme heat can cause decreased productivity, health issues and death to the elderly and other vulnerable people (Gemeente Rotterdam, 2021).

In the paper by Restemeyer, Van den Brink & Johan Woltjer (2017) the authors observed that the Dutch policy makers in their case study of Rotterdam were torn between adaptability and controllability.

Therefore they (Restemeyer, Van den Brink & Johan Woltjer, 2017) suggested a stronger focus on monitoring and learning to improve the adaptability of long-term water policies. To increase the capacity to adapt, the engagement with local stakeholders such as the inhabitants and businesses should be improved. It seems that Rotterdam has started to follow these suggestions and implemented them in the city’s recent plans. This falls in line with the systems approach from K.M. de Bruijn (2004), in which Rotterdam is increasingly utilising resilience strategies on top of resistance strategies. The city cannot stop using resistance strategies entirely due to its vulnerable position in a river delta.

4.3 Flood Risk Management Going Forward

4.3.1 Amsterdam

Amsterdam wants to increase their efforts to adapt to climate change and reduce flood risk. These efforts are subdivided into five categories (Gemeente Amsterdam, 2020):

● Structural integration in activities and management ● Participation between different stakeholders and the city

● Stimulating and supporting promising climate adaptation projects ● Communication and knowledge sharing

● To research and to monitor

Structural integration in activities and management

Climate adaptation is to become a normal aspect regarding relevant developments and activities. To achieve this a change in methods is required in which climate adaptation plays a permanent central role alongside climate mitigation. When new information becomes available and new standards become the norm, they have to be integrated as quickly as possible into the working processes of area development, maintenance and replacement. This should lead to clear standards that projects and activities have to meet in order to always include climate adaptation. The city lists three courses of action which must be taken to achieve this (Gemeente Amsterdam, 2020):

● Create a dialogue with relevant parties to discuss in which direction to go, and figure out what the ‘new normal’ is supposed to look like.

● Creating a list of requirements that projects and activities must meet and compliance should be promoted. The requirements can differ depending on the domain, weather circumstances and type of project.

● Mapping overlapping urban dossiers e.g. ‘Autoluw’ and ‘Circulair’ and processes such as ‘Groenvisie’ and ‘Omgevingsvisie’.

Restemeyer, Van den Brink & Johan Woltjer (2017) are of the opinion that to increase a city’s capacity to adapt, engagement with the local stakeholders is important. The city of Amsterdam shows in the

paragraph above that they are willing to collaborate with residents and businesses to improve the city’s adaptability to climate change, this is necessary because only around 50% of land within the municipal borders is owned by the municipality.

Participation between different stakeholders and the city

The municipality argues that urban climate adaptation is a group effort and that everyone in Amsterdam could contribute to the city’s ambition of preparing against the consequences of climate change. The frontrunners will continue to be actively involved by Amsterdam. But the city has its aim also on those businesses and residents that would like to be involved but need extra support or advice. Dialogue should lead to an enhancement of the Strategy Climate Adaptation (2020) and sketch an image of the city’s priorities. Another three courses of action are listed to achieve the above mentioned description (Gemeente Amsterdam, 2020):

● Establish a relationship with other planned rounds of talks within the city.

● Creating an implementation agenda based on these talks and financial frameworks. ● Organizing collaboration by setting up partnership and expanding them.

This paragraph shows as well that the city of Amsterdam is committing to collaboration between the city and the relevant parties within it. Once again following the opinion of Restemeyer, Van den Brink & Johan Woltjer (2017) to increase the city’s ability to adapt to climate change.

Stimulating and supporting promising climate adaptation projects

Amsterdam considers it important that every resident takes their responsibility in the challenges posed by the changing climate, but recognizes that the municipality can take the initiative. They should also stimulate the businesses and residents to contribute to making the city climate resilient. To stimulate technological innovation, pilot projects need to be started up and supported to test certain climate adaptive solutions and measures in practice. They need to be as effective as possible and therefore receive clear objectives and guidelines.

It is important to consider implementing climate adaptive measures with projects that are already ongoing, and subsequently monitor them. If the necessary requirements have not been announced yet or if the required tools are not yet available with which the project can identify their challenge themselves, then the project would at least have to confirm in which ways it is contributing to the climate adaptation of the city.

Existing projects that contribute to the city’s climate adaptation should also be upscaled to increase the range in and impact on the city. Three courses of action are listed below to achieve this (Gemeente Amsterdam, 2020):

● Stimulating everyone in Amsterdam to help further develop the strategy for climate adaptation and to create a learning environment where innovative climate resilient solutions can be tested. ● Use a network approach in which the government actively collaborates as a partner.

The Adger et al. (2005) resilience requirement of learning is shown to be used by Amsterdam in the stimulation of climate adaptation projects.

Communication and knowledge sharing

By sharing knowledge about the risks and chances for the city, it creates a realization about shared ownership of climate change and climate adaptation. It is important to convey a consistent message that is in line with other internal programmes such as ‘Autoluw’ and ‘Circulair’, and is in line with external partners like other cities and Ministries. A balance is to be found between informing about risks and preventing unrest while simultaneously offering a positive perspective that invites action. Four courses of action are listed below to achieve this (Gemeente Amsterdam, 2020):

● Creating a communication strategy.

● Mutual knowledge sharing between different climate programmes.

● Informing employees and residents, educating and helping with implementing climate adaptation.

● Focused collaboration with other cities in the Netherlands, as well as foreign cities that could be of added value to Amsterdam.

These courses of action show that Amsterdam intends to grow the self-organisation and the ability to adapt to stress and change within the city. This indicates Amsterdams commitment to improve its resilience as it is defined by the IPCC (2007). To inform and educate inhabitants and other relevant parties within the city, the resilience requirement of learning (Adger et al, 2005) is being addressed

To research and to monitor

It is not precisely known how the climate is changing, new information is constantly produced. Because of this it is important to have access to the right information at the right time. The city has to regularly confirm which information it needs and it then needs access to this data, as well as the other involved parties. By using an iterative approach with continuous development, all parties involved should be simultaneously maturing in the theme of climate change and climate adaptation. This way the city and the parties involved know better what they can expect and how to react. Four courses of action are listed below to achieve this (Gemeente Amsterdam, 2020):

● In collaboration with knowledge institutions more research is to be conducted in the form of stress tests to improve the understanding of the impact on the city.

● Monitoring the effects of implemented measures and pilots.

● Organizing measuring points in the city itself, so that the stress tests are not predictions based on data from other parts of the Netherlands.

The paragraph above shows that Amsterdam also realizes that constant learning is important, which, once again, according to Adger et al. (2005) is one of the requirements of resilience.

Amsterdam more rainproof

The city strives to prevent damage or disruption being caused by events of extreme precipitation and to simultaneously use rainwater to contribute to a desirable, comfortable and liveable city. To do this, the city aims to accelerate the adaptation of areas that are at most risk of suffering damage or disruption due to extreme precipitation by capturing, storing and reusing rainwater where possible to ensure that the surface waters are left with enough space to safely discharge the excess amount of water. Models are to be used to identify the possibilities and impossibilities of buffer networks of the groundwater system. Meanwhile Amsterdam intends to improve their insight into the relation between damage and vulnerability to an excess of rainwater on the scales of neighbourhoods, streets and individual buildings. Improving the buffering capacity of the outdoor area by coordinating building levels and ground levels is also one of the priorities (Gemeente Amsterdam, 2020).

Amsterdam being better prepared to deal with flood risk

The chance of flooding is to be reduced, as well as the effects in the event that a flood does occur. Thus the equation or risk described by Kent (2016) can once again be recognized in the plans by Amsterdam. This risk reduction is done using spatial design as well as crisis management. Therefore it is necessary to further develop the following solutions (Gemeente Amsterdam, 2020):

● Increasing awareness among spatial planners, designers, area managers, area developers, administrators of essential functions and other parties of flood risk and the functioning of the water system.

● Establish a thematic study of water safety for the purpose of developing knowledge in the context of area development, spatial choices and utilities.

● Increasing the role of flood risk and sea level rise with regard to location choices and area development using stress tests. This should be on the level of the city vision as well as on the level of the individual projects.

● Generating attention for robust development of the city facing sea level rise and subsidence. Actively searching for chances with which the city could increase its water robustness by advising during projects how they could best be shaped.

● Identifying and developing linkage opportunities with other current challenges such as the energy transition and the lack of housing.

● Collaborating with the security and crisis management domain to build a solid link between spatial adaptation and crisis management e.g. evacuation routes and shelters.

● Developing a plan of action for the enforcement and maintenance of primary flood protection within the city and for reserving space for future expansion of the water system and the water defences.

Once again the learning aspect (Adger et al., 2005) can be found in the climate adaptation plans of Amsterdam for increasing resilience, as well as the city’s willingness to engage in collaborations, as is recommended by Restemeyer, Van den Brink & Johan Woltjer (2017).

4.3.2 Rotterdam

In the preparatory city vision of Rotterdam (Gemeente Rotterdam, 2018), the municipality states that a resilient port city has to continuously adapt to new developments and should be able to quickly recover after an incident or crisis, which follows the IPCC’s (2007) description of resilience. Also Rotterdam intends to implement further climate adaptation measures. Just like Amsterdam, the city of Rotterdam wants to prepare for an increase in precipitation and the rise of sea levels (Gemeente Rotterdam, 2018).

It is a big challenge for Rotterdam to combine the programmes and investments to provide fitting solutions for many developments. Among these programmes are the mobility transition, increasing urban density, the energy transition and climate adaptation. By combining the work that has to be done, the city intends to reduce nuisance. Rotterdam wants to keep using integral methods and include the groundwater system, the surface water system and the entire outdoor space within the municipality (Gemeente Rotterdam, 2021).

Rotterdam notes that its sewers cannot always handle the increase in precipitation due to the increase in precipitation not only being in rain frequency but in rain intensity. This has already led to flooded streets, squares and parking garages, showcasing the economic, as well as the social and cultural vulnerabilities (Schanze, 2006). Rotterdam wants to improve 2.500 kilometers of the sewer system with an emphasis on reuse and adaptation. They intend to collaborate with regional water authorities, housing corporations, inhabitants and utilities, which is in line with the opinions of Restemeyer, Van den Brink & Johan Woltjer (2017). The city mentions water storage as an important measure to mitigate these issues, water storage would be arranged in both public spaces as well as private properties, where the inhabitants should also disconnect their gutters from the sewer system and add green to their yard while removing non-permeable surfaces so water can infiltrate into the ground, the city meanwhile implements similar interventions in the public spaces. The water storage provides a place for water to go when there is an excess of it, therefore providing protection to economic, ecological and social and cultural vulnerabilities. (Gemeente Rotterdam, 2021; Gemeente Rotterdam, 2013; Rotterdams Weerwoord, 2019; Schanze, 2006). To improve water storage in the city, Rotterdam also plans on

adding more green in the city and experimenting with brown roofs (see figure 11), roofs that are covered with debris that should accommodate plant growth, also attracting insects and birds, which reduces the ecological vulnerability (Schanze, 2006). Another advantage is of water storage through these means is the cooling effect during hot and dry periods (Gemeente Rotterdam, 2021; Gemeente Rotterdam, 2013; Rotterdams Weerwoord, 2019).

Figure 11: Urban Climate Interventions (Gemeente Rotterdam, 2013).

To protect itself against the rising sea levels, Rotterdam recognises that it has to ensure that the quality of its dykes and levies are kept adequate to protect the city, while also not neglecting parts of the city which are not protected by dykes or levies, which includes the harbor and most of Kop van Zuid (Gemeente Rotterdam, 2018).

Rotterdam owns only 40% of the land within the municipal borders. So just like Amsterdam a large part of the city is owned by private individuals, businesses and housing corporations. And like in the case of Amsterdam, it is necessary that these parties implement their own climate adaptation measures to make the city climate resistant. Initially this responsibility falls solely on the land owners. New building projects will have to adhere to new uniform regulations regarding water storage and water drainage (Gemeente Rotterdam, 2021; Rotterdams Weerwoord, 2019).

The groundwater system is influenced by precipitation, water levels of surface waters, the soil conditions and the local infrastructure. The groundwater levels are not manipulated by mechanical tools like pumps in public areas. When it comes to the management of the groundwater it is important to communicate with local residents, this is due to different residents having different needs in this aspect. Some people need a higher groundwater level to keep their foundation consisting of wooden poles hydrated. Others need lower groundwater levels to prevent flooding of their basements and yards (Gemeente Rotterdam, 2021).

Thus what are the differences between Rotterdam and Amsterdam regarding flood risk? And what are the flood risk management strategies that Rotterdam and Amsterdam have created in order to adapt to flood risk, how do they differ?

The cities of Rotterdam and Amsterdam appear to be subjected to similar flood risks, both cities protect themselves from flood from the North Sea and from their respective rivers. Flood risk from an increase in precipitation intensity and frequency is a more recent threat with which both cities are not as experienced with. Though despite the fact that there are some differences in urban form, the cities appear to be using similar strategies to adapt to the consequences of climate change. Both cities intend to involve every relevant party within the city to participate in the cities’ climate adaptation. They intend to continuously learn how to adapt better and become more resilient.