Urban Environmental Quality: Exploring and analysing nature-based design solutions for Brussels. by Marie-Caroline Kawa

Urban Environmental Quality:

Exploring and Analysing Nature-Based Urban Design Solutions for Brussels. Proposal For a Common Typological Classification. Marie-Caroline Kawa

Master thesis submitted under the supervision of Prof. Ahmed Khan, the co-supervision of Philip Stessens, in order to be awarded the Master’s Degree ’MSc. in Architectural Engineering’. 2019-2020

Urban Environmental Quality:

Exploring and Analysing Nature-Based Urban Design Solutions for Brussels. Proposal For a Common Typological Classification. Marie-Caroline Kawa

PREFACE This Master's thesis is the result of an extensive research on Nature-Based Solutions (NBS) for a sustainable urban regeneration and their potential to respond to societal and environmental challenges, within the specific context of Brussels. It contains a proposal for a common typological classification of NBS and factsheets of multiple NBS that were investigated by means of in depth case studies.

**All graphic material is produced personally, unless indicated otherwise. I

AKNOWLEDGEMENTS First and foremost, I would like to thank my supervisor Ahmed Khan for changing my view on architecture and urban planning and sparking my interest in the possibilities of nature-based urban design solutions. I would similarly like to thank Phillip Stessens, my co-supervisor, for his guidance during the entire process, the encouraging discussions and invaluable input. My gratitude goes to Ellis Dupker from Rooftop Revolution and Elise Candry from Bureau Bas Smets for their time and transparency and their introduction to the design processes of advanced projects. The interaction between theory and practice and the information they provided was a valuable input in this research. Finally, I would like to thank my boyfriend, family and friends for for proofreading this thesis and for their eternal patience and constant support throughout the past five years. This is, to the extend valid for all the architecture engineering students, the Bruface-program and the entire department of Architectural Engineering. III

ABSTRACT A changing climate in combination with an expected demographic growth in the Brussels Capital Region, translates into environmental and societal challenges. This gives rise to a growing interest among local authorities and policy makers to encourage the use of design tools and strategies for building resilience for climate change and improving environmental impact of urban projects. Nature-based solutions (NBS) present a sustainable approach for addressing these challenges. They have the potential to regulate urban micro climates, improve air quality, enhance biodiversity, balance the urban hydrological cycle and thus can significantly contribute to the well-being of inhabitants and local green economy. Nonetheless, here still exists a discrepancy between the theoretical framework of NBS, their benefits, and the planning and decision-making policy. This Master thesis aims to identify and explore NBS for ecologically sensitive urban regeneration and their potential to respond to environmental and societal challenges, as supporting design tools for architecture and urban planning to enhance Brusselsâ&#x20AC;&#x2122; urban resilience. As a result, a comprehensive typological classification of NBS is proposed and factsheets are created of multiple NBS by means of two in-depth case studies. These tools gather and promote knowledge on NBS and their effectiveness for addressing urban challenges, while narrowing the gap between theory and practice. V

TA B L E O F C O N T E N T S PREFACE I

AKNOWLEDGEMENTS III ABSTRACT V LIST OF FIGURES

VIII

I N T R O D U C T I O N

LIST OF TABLES

1.1 Problem statement

1.2 Research question & Objective

2 5

1.3 Outine & Methodology 7

S TAT E - O F - T H E - A RT 9 2.1 Ecosystem services

2.2 Nature-based solutions

10 13

2.3 Classification of Nature-Based Solutions 21

2.4 Parameters for the classification 24

B R U S S E L'S U R B A N C H A L L E N G E S

F R A M E W O R K F O R A T Y P O LO G I C A L C L A S S I F I C AT I O N

4.1 Defining categories and types

4.2 Defining parameters 38

Scale

Degree of intervention

Investment and maintenance

38 38

4.3 Defining (co-) benefits 46 4.4 Factsheet template 48 VI

I N - D E P T H C A S E S T U D Y A N A LY S I S

5.1 Case 01: Resilio 53

5.1.1

Urban challenges

5.1.3

Technical design requirements

5.1.2 Context

5.1.4 Monitoring

5.1.5 Discussion

5.2 Case 02: Nieuw-Zuid 65

5.2.1

Urban Challenges

5.2.2 Context 5.3.2 Design 5.2.3

Technical design requirements

5.2.4 Discussion

66 67

CO N C LU S I O N 83 B I B L I O G R A P H Y 87 A N N E X 95 DATA B A S E 101 FAC T S H E E T S 109

VII

LIST OF FIGURES

FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 FIGURE 9 FIGURE 10 FIGURE 11 FIGURE 12 FIGURE 13 FIGURE 14 FIGURE 15 FIGURE 16 FIGURE 17 FIGURE 18 FIGURE 19 FIGURE 20 FIGURE 21 FIGURE 22 FIGURE 23 FIGURE 24 FIGURE 25 FIGURE 26 FIGURE 27 FIGURE 28 FIGURE 29 FIGURE 30 FIGURE 31 FIGURE 32 VIII

(left) Visual representation of the research methodology. 7 Classification of Ecosystem Services (Millennium Ecosystem Assessment, 2003a). 10 The relation between Ecosystem Services and human well-being (Haines-Young & Potschin, 2010). 11 (left) Timeline: use of the term 'NBS'. * funded under Grant Agreement by Horizon 2020 Programme. Adapted and updated from (Somarakis et al., 2019). 13 Schematic representation of the classification structure. 32 Icons of types falling under the category: Building scale measures 34 Icons of types falling under the categroy: Green measures for public space. 35 Icons of types falling under the category: Measures for linear grey infrastructure 35 Icons of types falling under the category: Measures for water bodies and drainage. 36 Icons of types falling under the category: Measures for natural urban areas. 37 Schematic representation of the range of level and type of intervention (Eggermont et al., 2015). 38 Overview of incorporated (co-) benefits. 40 Template for the NBS Factsheets. 48 (left) Amsterdam. The neighbourhoods in which RESILIO is implementing a smart bluegreen roof network. 1. Slotermeer 2. Kattenburg, 3. Oosterparkbuurt, 4. Rivierenbuurt , 5. Indische Buurt . Water is represented in black. 53 Smartroof 2.0 on the Marineterrein, Amsterdam. 55 Schematic section of the RESILIO roof: green roof with a storage and capillary irrigation system. Adapted from RESILIO. 56 The lightweight HDPE crate system for water storage with capillary irrigation (rockwool cone visible). (© De Dakdokters) 57 Smart flow control system with an automatically controlled valve. Closed state: rainwater retaining. (© Eva Krol) 57 Smart flow control system with an automatically controlled valve. Open state: rainwater discharge. (© Eva Krol) 57 Schematic sections of the three research plots. The left and right plot are equipped with the Permavoid drainage and capillary irrigation system. Adapted from (Cirkel et al., 2018). 58 Top view of the Smartroof 2.0 setup with the three research plots (green squares) (Cirkel et al., 2018, p. 4). 58 Smartroof 2.0. The three reasearch plots and the measurement set-up is visible. 58 Picture of the conventional extensive green roof after a period of 1 year (Municipality of Amsterdam, 2018). 60 Picture of the extensive blue-green roof after a period of 1 year. (Municipality of Amsterdam, 2018) 60 RESILIO Cargo bike transformed into a smart blue-green roof mockup. Photo taken by Eva Krol. Obtained from Rooftop Revolution. 62 (left) Map of Antwerp. The Nieuw-Zuid project site is indicated. Water bodies are represented in black. 65 Schematic representation of the plot and Striga division. 67 Nieuw-Zuid: reinforced quay under construction. Photo taken in Novemeber 2019. 68 (left)Nieuw-Zuid construction site. Photo taken from the quay. Novemeber 2019. 68 (right)Schematic representation of the plot and the different types of streets and paths. 68 (right) Isometry of the internal street. (© Bureau Bas Smets) 70 (left) Nieuw-Zuid Internal Street. Photo taken November 2019. 70

FIGURE 33 FIGURE 34 FIGURE 35 FIGURE 36 FIGURE 37 FIGURE 38 FIGURE 39 FIGURE 40 FIGURE 41 FIGURE 42 FIGURE 43 FIGURE 44 FIGURE 45 FIGURE 46 FIGURE 47 FIGURE 48 FIGURE 49

(right) Schematic drawing of the water management system between streets, paved squares and the flood plains in the park. 70 (right) Section of the internal street. (© Bureau Bas Smets) 70 (right) Isometry of a residential street. (© Bureau Bas Smets) 72 Plan view of the residential street. 72 (left) Nieuw-Zuid residential street. Photo taken in November 2019. 72 (right) Schematic section of the residential street. (© Bureau Bas Smets) 72 (right) Isometry of the Residential path. (© Bureau Bas Smets) 74 Plan view of the residential path. 74 (right) Schematic drawing of the water management system between green roofs, bioswales, infiltration basins and the flood plains in the park. 74 (left) Nieuw-Zuid residential path. Photo taken in November 2019. 74 (right) Schematic section of the Residential path. (© Bureau Bas Smets) 74 (right) Nieuw-Zuid: manipulated topography forming flood plains in the park. Photo taken in November 2019. 76 (left) Nieuw-Zuid elevated topography forming a sound barrier to block noise from the ring road. Photo taken end November 2019. 76 (right) Schematic representation of the water management system on the Nieuw-Zuid Site. 76 Newly constructed bio-swale. Photo taken in November 2019. 78 Perforated concret tiles, both employed as pavement and for securing drainage pipes in the swale. Photos taken in November 2019. 78 NBS integrated in Nieuw-Zuid Antwerp. 80

LIST OF TABLES

TABLE 1 TABLE 2 TABLE 3 TABLE 4 TABLE 5 TABLE 6 TABLE 7 TABLE 8 TABLE 9 TABLE 10 TABLE 11 TABLE 12

Definitions of Nature-Based Solutions found in literature. Goals and Research & Innovation Actions (EC, & DG Research and Innovation, 2015). Set of labels employed by the Naturvation Atlas. . Impact valuation framework employed by the Groentool (Vranckx et al., 2016). Scale levels used in literature and classifications concerning Nature-Based Solutions. Challenges used in the literature and classifications relating to Nature-Based Solutions. Brussel's urban challenges. Categories of NBS. Incorporated scale levels. Incorporated cost levels. Resilio: facts. Nieuw-Zuid: facts.

14 17 18 19 22 24 28 32 38 38 54 67 IX

INTRODUCTION This chapter explains the field in which this thesis is situated, the main objectives of the thesis and the research methodology.

1.1 Problem statement

We live in a time of great opportunities for addressing societal and environmental challenges, such as increasing urbanisation, economic and social inequalities, and climate change (Faivre et al., 2017). Over the past year many climate manifestations have been organised not only in Brussels but all over Europe. The various activist groups that have arisen are a solid indication of an increased interest to tackle these challenges (Hagedorn et al., 2019). According to the European Commission nearly three quarters of the European population live in urbanised areas and numbers are predicted to increase up to 83.7% by 2050 (Koceva et al., 2016; Kostovska, 2018). Demographic expansion due to combined internal growth and migration increases pressure exerted on urban planning and infrastructure, and consequently challenges sustainable growth and development of cities (Jiang & Oâ&#x20AC;&#x2122;Neill, 2017). Urbanisation is inextricably linked with conversion of rural to urban landscapes, accompanied by an increase in impervious artificial surfaces and a reduction of natural capital. The augmented stress on urban environments increases vulnerability for climate change effects and occurrence of extreme phenomena, such as increased heat stress due to the Urban Heat Island effect, biodiversity loss, extreme precipitation events, urban pluvial flooding and droughts. These effects have severe, and in some instances, irreversible environmental impacts resulting in economic damage, social vulnerability and negative effects on human health and well-being (Eggermont et al., 2015; Kabisch et al., 2017). The Federal Planning Bureau (2017) anticipates a strong demographic growth of 28,1% by 2060 for the Brussels Capital Region (Federaal Planbureau, 2017). This will entail hardships when it comes to public and private open space, urban infrastructure, biodiversity, citizenâ&#x20AC;&#x2122;s health and the circumstances of ecosystems and their benefits in general (Tzoulas et al., 2007). Urban green spaces are an essential source of contact with nature for citizens, and the myriad benefits provided by natural capital are increasingly recognized as important constituents for quality of life. Urban green space provision and quality in Brussels however, is unbalanced and consequently negatively affects the physical and psychological health of inhabitants (Cox et al., 2018; Engemann et al., 2019; Stessens et al., 2017). The prospect of simultaneous densification and the need for increasing green infrastructure challenge urban planners and policymakers to move beyond solely managing the urban landscape (Pulighe et al., 2016). Kabisch (2017) explains that conventional engineered systems may no longer be an adequate solution to the increased pressures on urban areas, as they might not be sufficient, sustainable or cost-effective (Kabisch et al., 2017). 2

There is a growing interest among city councils and policy makers to support and encourage the use of design tools and strategies that will build urban resilience for climate change and improve the environmental impact of urban projects. This can be seen from initiatives as Antwerp’s Groentool, Brussels’ Plan Nature and Plan Canal and the engagement of many European cities and researchers to contribute to the knowledge base of NBS (Bruxelles Environnement, 2016; Chemetoff, 2014; Groentool—Groenmaatregelen, 2014; Lafortezza et al., 2018). Nature-based solutions (NBS) present a sustainable approach to address environmental and societal challenges arising from climate change and urbanisation. NBS are innovative actions that employ nature or are inspired or copied from complex natural processes. They are cost-effective, resource-efficient, enhance natural capital and simultaneously produce myriad environmental, social and economic benefits, which can address a variety of urban and societal threats in the long-term. The concept’s potential lies in the integrated approach for building urban resilience, relying on the implementation of solutions that deliver ecosystem services or benefits. They have the potential to regulate urban micro climates, improve air quality, enhance biodiversity, balance the urban hydrological cycle and thus can significantly contribute to the well-being of inhabitants and local green economy (Eggermont et al., 2015; Faivre et al., 2017; Kabisch et al., 2017). Although the NBS concept is fairly recent, multiple initiatives and 3

research groups have focused their attention on the subject and have shown efforts to contribute to the evidence base of NBS (Lafortezza et al., 2018; Somarakis et al., 2019; UNaLab, 2019; URBAN GreenUP, 2018; Vranckx et al., 2016). The European Commission has launched the Horizon 2020 programme and is substantially investing in exploration of NBS to tackle environmental and societal challenges (Maes & Jacobs, 2017). Accordingly, several projects have been initiated by different institutions and research groups (Almassy et al., 2018; Kabisch et al., 2016; Somarakis et al., 2019; UNaLab, 2019; URBAN GreenUP, 2018). Nonetheless, there still exists a discrepancy between the theoretical framework of NBS, their benefits, and the planning and decision-making policy (Kabisch et al., 2016; Lafortezza et al., 2018). Since it is a relatively new field, a lot of research is still needed to fill the current knowledge gaps and erase the barriers in relation to NBS, their ecosystem services and the co-benefits they deliver. While a broad definition of NBS has been established, it is still unclear which specific solutions exist, which are their (co-) benefits and how they address urban challenges. A missing link remains between the theoretical framework of NBS, their benefits, and the planning and decision-making policy. There is insufficient awareness of (co-) benefits of urban green infrastructure and limited understanding of NBS among architects, urban planners and decision makers. (Kabisch et al., 2016). Hence, there is a lack of evidence base for urban planners in Brussels to develop and compare NBS. The limited amount of currently available NBS catalogues is also incoherent, in the sense that they employ different parameters, use other nomenclature for similar NBS, do not include the same NBS and apply other classification methods. First, there is need for a thorough classification system recognizing that NBS are complex measures and often simultaneously provide multiple services and co-benefits for human well-being. Secondly, additional and detailed knowledge is required on co-benefits of NBS. Finally, elaborating knowledge on the implementation of NBS in urban design is necessary to bridge the gap between theory and practice.

1.2 Research question & objective

“What are NBS for an ecologically sensitive urban regeneration, which are the (co-) benefits they provide and how can they respond to Brussels’ urban challenges?” The aim of this master thesis is to make a meaningful contribution to the current planning debate by, firstly, establishing a framework for the classification of NBS that recognizes the complexity of NBS with specific attention for the Brussels Capital Region. It is necessary to create this framework in order to organise and compare different results and impacts over time and through different disciplines. The second objective is to provide valuable input to the existing evidence base of NBS by creating an in-depth inventory and typological classification of existing and innovative NBS recognizing their complexity and their broad range of societal and environmental benefits. This inventory will be placed within the established framework, and will gather and promote state-of-the-art knowledge regarding NBS and their (co-) benefits. Finally, this paper intends to expand detailed knowledge on the implementation of specific NBS in urban design to bridge the gap between theory and practice. To this aim, following additional research questions arise:

• Which are the existing classification schemes of NBS? • Which parameters are relevant when considering NBS? • What is the relationship between NBS and the benefits they provide? • What are the urban challenges that the Brussels Capital Region is facing? • Which practical examples exist and what can we learn from case studies?

GOAL: defining relevant parameters for the classification of NBS

MEANS: literature study and analysis of existing classifications

GOAL: enable a focussed selection of NBS and case studies

MEANS: study Brusselsâ&#x20AC;&#x2122; urban challenges

GOAL: establishing a typological classi-

fication that recognizes the complexity of NBS by including all relevant parameters and the effectiveness of NBS to a broad range of societal benefits.

MEANS: collection of data from litera-

ture study, contacting contractors and case studies

GOAL: gaining detailed knowledge on the design and implementation of NBS

MEANS: in-depth case study analysis

through meetings, photographical material and additional research on technical desingn and requirements.

GOAL: presenting NBS in a comprehen-

5 6

sive way, to help architects & planners in decision-making

MEANS: creating a template for NBS factsheets + creating factsheets for NBS occurring in the case studies

1.3 Outline & Methodology

The first phase of the research consists of an in-depth literature study regarding NBS and existing inventories of NBS and classification schemes. Through a comparative analysis key parameters that will be meaningful for establishing a typological classification are defined. Information is gathered from literature, currently available catalogues and online platforms (Almassy et al., 2018; Groentool— Groenmaatregelen, 2014; Nature-based solutions | Oppla, 2018; Kabisch et al., 2016; Millennium Ecosystem Assessment, 2003a; Somarakis et al., 2019; UNaLab, 2019; URBAN GreenUP, 2018). Subsequently, Brussels’ urban design and climate-related challenges are studied to enable a selection of NBS and case studies relevant for Brussels. This information comes forth from several policy papers comprising environmental and societal goals, such as Plan Nature, Quiet.Brussels, their Water Management Plan, Plan Canal and additional publications of Brussels’ climate goals (Bondt & Claeys, 2013; Bruxelles Environnement, 2016, 2017, 2019; Chemetoff, 2014; Hitte-eilanden in steden, 2019). Following, a framework for a common typological classification of NBS is developed. Followed by establishing a database of existing and innovative solutions organised with parameters derived from the elaborate literature review. The data is collected from literature study, existing catalogues and contacting contractors to obtain detailed information about parameters such as investment and maintenance of specific NBS. Additionally, two relevant projects are selected for an in-depth case study to gain detailed knowledge on the design and implementation of NBS. The information is gathered through interviews with the (landscape) architects and project partners, on-site visits, photographical material and additional research on technical design and requirements for implementing these NBS. Finally, a template is proposed for the representation of NBS in the form of ‘Factsheets’.

Figure 1 (left) Visual rep-

resentation of the research methodology.

STATE OF THE ART This chapter introduces the state of affairs in research relevant to Nature-Based Solutions. First, important concepts at the base of NBS are clarified and the evolution of the concept is studied in order to facilitate an understanding of the NBS framework. Subsequently, available literature and classifications concerning NBS are discussed and analysed thoroughly to determine the key parameters for the classification of NBS which are investigated in the final part of this chapter. 9

2.1 Ecosystem Services

An ecosystem is a dynamic complex of biological communities of interacting organisms and their physical environment. The products or final outputs of these systems are referred to as Ecosystem Services (ES), which are considered the benefits that humans obtain from ecosystems. The Millennium Ecosystem Assessment defines ES as the direct and indirect contributions of ecosystems to human wellbeing. (European Environment Agency, 2011; Millennium Ecosystem Assessment, 2003a). Several organisations and research groups have shown efforts to examine ES and multiple classifications are available. The ones most widely acknowledged and frequently used can be consulted in Ecosystems and human well-being: a framework for assessment (Millennium Ecosystem Assessment, 2003a), in The Economics of Ecosystems and Biodiversity: Ecological and Economic Foundations (Kumar, 2012) and in Common International Classification of Ecosystem Services (CICES, 2011). These classification schemes organise ES into the four same categories including provisioning, regulating and cultural services. An overview of the benefits is illustrated in Figure 2. Haines-Young and Potschin (2010) have studied the correlation between ES and the constituents of human well-being and found various linkages of different intensity, illustrated in Figure 3 (HainesYoung & Potschin, 2010).

Figure 2 Classification

of Ecosystem Services (Millennium Ecosystem Assessment, 2003a).

Figure 3 The relation be-

tween Ecosystem Services and human well-being (Haines-Young & Potschin, 2010).

first use of the term 'NBS'

2002

2005 Millennium Ecosystem Assessment

2008 World Bank Report

2013

Groentool

IUCN Programme

Biodiversa Workshop*

2014

IUCN Research Horizon 2020 Conference*

2015

H2020: NBS and Re-naturing cities*

2016

URBAN GreenUP*

IUCN results publication

NBS2017 Conference Tallinn *

2017

NATURVATION*

2018 Oppla*

Nature4Cities* ThinkNature*

2019

ThinkNature NBS Handbook* UNaLab Handbook* 12

2.2 Nature-Based Solutions

To establish a framework for the classification of NBS it is important to outline the definition of the term and its origin. A timeline displaying the use of the term ‘NBS’ in the research field and the most relevant events over the past twenty years are illustrated in Figure 4. Over the past decade, the notion of NBS has become familiar in the European research field and a few definitions have been proposed, illustrated in Table 1 on page 14. In the next paragraph a definition, in line with the literature, that will be employed in this thesis is proposed. “Nature-based solutions (NBS) in an urban context are measures that employ natural capital or are inspired by, supported by or copied from complex natural processes. They are cost-effective and simultaneously produce environmental, social and economic benefits, which can potentially address a variety of urban and societal threats and challenges in the long-term. “ This definition implies that preserving and enhancing urban natural capital is crucial as it establishes the foundation for solutions. These NBS are, if possible, resilient to climate change, as well as energy and resource efficient. In order to comply with these criteria it is essential that they are adapted to local environmental settings. (European Commission & Directorate-General for Research and Innovation, 2015)

Figure 4 (left) Timeline: use

of the term 'NBS'. * funded under Grant Agreement by Horizon 2020 Programme. Adapted and updated from (Somarakis et al., 2019).

Eggermont et al. (2015) state that NBS are often seen as a concept, a flagship term, employed to encourage development of innovative strategies integrating nature in policy and planning. The concept of NBS was originally presented by practitioners from the IUCN (International Union for Nature Conservation) in 2013 and was rapidly picked up by policy (European Commission) referring to sustainable use of nature to address societal challenges. The concept of NBS is aimed at relocating the focus on humans by including environmental and societal aspects (Eggermont et al., 2015). The concept's potential lies in the integrated approach for building urban resilience, relying on the implementation of solutions that deliver ecosystem services or benefits. They have the potential to regulate urban micro climates, improve air quality, enhance biodiversity, balance the urban hydrological cycle and thus can significantly contribute to the well-being of inhabitants and local green economy (Eggermont et al., 2015; Faivre et al., 2017; Kabisch et al., 2017). 13

Table 1 Definitions of Na-

ture-Based Solutions found in literature.

2.3 Classification of Nature-Based Solutions

Exploration and analysis of existing literature and classification schemes regarding NBS, will allow to detect important aspects and missing links in the existing evidence base. As has been alluded to earlier, recent initiatives have shown several efforts to contribute to the evidence base of measures for urban resilience and climate change adaptation and mitigation. On the behalf of the City of Antwerp the Groentool (www.groentool.antwerpen. be, 2014) has been created. The online platform functions as a tool promoting the understanding of green measures and the effects of greenery on the surroundings. Concurrently, several research projects have been initiated in response to the conference “Renaturing Cities: Addressing Environmental Challenges and the Effects of the Economic Crisis through Nature-Based Solution” in May 2014 (European Commission, 2014). In response first preliminary classification of NBS was proposed (European Commission & Directorate-General for Research and Innovation, 2015). The two-day conference was organised by the European Commission in context of the European Union’s Horizon 2020 Research and Innovation Programme, with the aim to position Europe as a world leader in the NBS field (Eggermont et al., 2015). To this end, a funding programme under Grant Agreement was launched for initiatives exploring NBS. Three main types of EU funded initiatives can be distinguished. First, platforms such as Oppla (www.oppla.eu, 2018) and Naturvation (www. naturvation.eu, 2017) provide a broad overview and classification of case studies that implement NBS. Secondly, projects such as Nature4Cities (www.nature4cities.eu, 2017), Grow Green (www. growgreenproject.eu, 2017), URBAN GreenUP (www.urbangreenup. eu, 2018) and UNaLab (www.unalab.eu, 2019) have been initiated to collect information on and test the implementation of NBS in cities, some of these projects have established a preliminary catalogue with the purpose of creating an overview of possible measures. Finally, platforms such as ThinkNature (www.thinknature.eu, 2018) provide a platform that is aimed at supporting the understanding and the promotion of NBS. They have equally established a framework for classifying NBS (Somarakis et al., 2019). Following paragraphs assemble an overview of the existing documents and classifications schemes relevant for NBS. 15

2.3.1 Research and Innovation agenda on Nature-Based Solutions and Re-Naturing Cities* A first preliminary classification was suggested in 2015 by the European Commission in the context of its Horizon 2020 Framework Programme to set the foundation for a discourse on NBS. The catalogue distinguishes four principal goals that could be addressed and seven ‘Research and Innovation Actions’ relying on NBS to achieve those goals. Table 2 provides an overview (EC & DG for Research and Innovation, 2015). In addition, a preliminary list of 310 NBS (Sutherland, et al., 2014) is included in the Horizon 2020 report. The solutions are divided into 11 sections, referring to ES: air quality regulation, climate regulation, water flow regulation, erosion regulation, water purification and waste treatment, disease regulation, pest regulation, pollination, disaster risk reduction, soundscape management and health. Each section is subdivided according to geographical setting. Although many potential services provided by NBS are listed, it is worth mentioning that only 35 in total are aimed towards urban settings. Hence, the list obtained for this specific research is rather still limited, as the document is primarily aimed at encouraging research in the field of NBS (European Commission & Directorate-General for Research and Innovation, 2015). This type of classification however does not clearly reflect the complexity of one NBS, that can provide multiple benefits at once (Raymond et al., 2016). When NBS are categorised under benefits or ES, one NBS appears multiple times and it is difficult to have a clear overview of benefits provided by one solution. To illustrate, a nature-based urban design strategy, that implements rain gardens in the streetscape for improving water management while accommodating a variety of carefully selected vegetation, could be placed under multiple sections. Firstly, it contributes to Air Quality Regulation (Section 1): ‘planting trees alongside roads to trap particulates’ (NBS 6). It could equally contribute to Climate Regulation (Section 2): ‘create urban green spaces to store carbon’ (NBS 44). Then it also fits under Waterflow Regulation (Section 3): ‘implement raingardens’ (NBS 79). Furthermore, this NBS equally contributes to Disease Regulation (Section 6): ‘vegetated permeable surfaces in a hard landscape that allow runoff water to infiltrate and prevent disease populations to form’ (NBS 174). Raingardens as a strategy can similarly contribute to Pollination (section 8): ‘careful selection of appropriate species for pollination in municipal areas’ (NBS 251). Finally the NBS also has the potential to promote Health (section 11): ‘make green space accessible and attractive’ (NBS 308). The example fits the description all of these actions. Additionally, the classification does not take into account the extent to which NBS contribute to said benefits, which makes it impossible to analyse the effectiveness of implementing the NBS. 16

Table 2 Goals and Research

& Innovation Actions (EC, & DG Research and Innovation, 2015).

2.3.2 Oppla* Oppla is an abbreviation of and describes itself as an open platform intended for a broad range of users with diverse interests concerning NBS. Their objective is to establish a channel that facilitates obtaining, sharing and creating knowledge with an interface organised in three core sections. Firstly, a “Marketplace” makes all kinds of ‘products’ available to be consulted by the user, such as reports or tools, concerning NBS. A second part includes a broad “Case Study” collection organised according to their location, scale and type. Finally, an online “Community” is established which is accessible for members and enables communication among users. It is a valuable tool for accessing research on the topic of NBS as the platform is updated regularly. It even displays real-time Twitter posts relevant to the topic. However, the overload of available information is not optimally organised and is overall rather policy oriented, hence no detailed list or explanation of NBS is presented. Likewise, the numerous case studies include many policy documents related to sustainability goals related to NBS benefits, rather than actual implementation examples of NBS. The examples of implemented projects that are included in the collection, do not contain any detailed information on the NBS that were used.

2.3.3 Naturvation* A more thorough classification of case studies implementing NBS is established on behalf of the Naturvation initiative. “NATure-based URban innoVATION” is a four-year project involving fourteen European institutions in the disciplines of innovations studies, economics, geography and urban development. The programmes' main objective is to develop an understanding of the potential effects of NBS in urban settings, examine by what means innovation can be encouraged in the field, and above all, encourage implementation of NBS to address urban sustainability challenges. The objectives are approached by analysing a large amount of case studies in various European cities. Since the launch of the project in 2017 a large database of case studies has been established. Following, a comparative analysis has been conducted in order to define some parameters that allow to group case studies and draw conclusions (Naturvation, 2017). 17

The classification of case studies is achieved by defining a set of parameters that are assigned to each case in the form of ‘tags’ or ‘labels’ covering 11 themes, listed in Table 3. The catalogue is made accessible through an online “Atlas” and includes a broad range of over 100 case studies promoting the implementation of NBS. The organisation with labels facilitates navigation through the cases and the search for specific scenarios. The labels that relate to financing and project management allow to gain insight on the organisation and set-up of projects addressing numerous challenges. In addition to the “Atlas”, the programme includes creating an assessment framework for the valuation of NBS, which is still under construction (Assessment, 2017). While the Naturvation Atlas may be very useful tool, it has its limitations. It is clear that emphasis was placed on the quantity of case studies, which makes that the case studies do not explain the projects in detail. While key challenges are assigned to each project, little explanation is given on how exactly these challenges are addressed nor is there a valuation that indicates to which extent the NBS contribute to addressing these challenges.

2.3.4 Groentool Antwerp Another relevant tool for the topic on NBS was established on behalf of the City of Antwerp in collaboration with Vito n.v. and the University of Ghent. Groentool is an online platform that allows interested parties to gain insight on the effects of greenery on the surroundings. The tool is focused on the city of Antwerp and its surroundings by providing location related information based on GIS-data. The area-analysis tool allows users to determine the effect of a green measure on a specific location within the city of Antwerp. Moreover, a webpage named “Groenmaatregelen” provides an overview of possible green measures, illustrated in Annex 2. The measures are grouped into ten classes based on their typology, although there seems to be some overlapping. For instance, “shrubs” as a green measure are included in both “Shrubs, hedges and wooded banks” and “Forest and park-related green forms”. An interesting feature of Groentool are the seven themes referring to benefits which are quantified for each measure with scores ranging from zero to five, with the exception of the impact on air quality. Depending of the context, the implementation of trees can have a negative impact on air quality. For instance, when trees are planted in a heavy traffic narrow streets, called street canyons, they can reduce ventilation of the canyon and therefore an accumulation of fine particles (Vranckx et al., 2016). Groentool includes 49 green measures in total with for each a brief description and a quantification of its effectiveness in terms of each theme.

Table 3 Set of labels em-

ployed by the Naturvation Atlas. .

Table 4 Impact

valuation framework employed by the Groentool (Vranckx et al., 2016).

2.3.5 Urban Greenup* URBAN GreenUP is another one of the initiatives receiving funding from the European Union’s Horizon 2020 programme to explore NBS. The project’s intention is to develop a strategy for ‘Renaturing Urban Plans’ and to have the strategy applied, improved and replicated in a number of participating cities. The main objective is the mitigation of climate change, the improvement of air quality and water management as well as increase of the city's sustainability through implementation of NBS. (Urban GreenUP, 2017) Twenty-five partners and nine countries are participating in the URBAN GreenUP programme which is coordinated by the CARTIF Technology Centre. The project was initiated in June 2017 and is planned to end in May 2020, which implies that it is still ongoing at the moment. Within the framework of the project a catalogue of NBS was constructed with the purpose of facilitating the selection and introduction of the most appropriate NBS in the development of the 'Renaturing Urban Plans' (NBS Catalogue, 2018). The strategy is currently being tested in three ‘runner cities’: Valladolid (ES), Liverpool (UK) and Izmir (TR). The idea is that, based on the experiences in those cities, five ‘runner-up’ cities will establish their own plan to replicate the URBAN GreenUP strategy. Within the catalogue 46 NBS are documented and categorized into 14 groups based on their type. They are listed and described with a set of parameters and characteristics. Additionally, NBS cards were created for each group including a more elaborate description, a listing of ES and a quantification of the effectiveness of the NBS in terms of the challenges that it addresses (URBAN GreenUP, 2018). 19

2.3.6 UNaLab* A similar project is UNaLab, also having received funding from the EU. Through the establishment of an Urban Living Lab in three front-runner cities (Eindhoven (NL), Tampere (FI) and Genova (IT)) the cities become trial projects for experimenting, demonstrating and evaluating a series of NBS that respond to climate and water-related urban challenges. The approach is inclusive in the terms that solutions are co-created with and for local stakeholders and citizens. Active collaboration and sharing of experiences between the front-runner cities and the seven follower cities is meant to facilitate creating a European reference base for NBS built on a few factors such as type of intervention, benefits, cost-effectiveness, economic viability, performance and replicability of NBS. The future document is intended to function as a guide for other cities in and beyond Europe to develop and implement their own co-creative NBS. For the project a first draft classification of NBS has been completed and published in September 2019. UNaLab has defined a structure to represent 39 NBS in order to provide an elaborate understanding of a broad range of potentially applicable NBS. Scale, cost and maintenance have not been included in this version of the catalogue. The handbook displays an overview of NBS that are, above all, useful for addressing the UNaLab citiesâ&#x20AC;&#x2122; challenges related to water and climate adaptation. A final version is expected to be published towards the end of the UNaLab project (UNaLab, 2019).

2.3.7 ThinkNature* The recently published ThinkNature handbook is an overarching policy focussed document on the NBS framework. A classification scheme is established that includes various parameters: NBS approaches referring to (European Commission, 2014), challenges addressed, scale, and ES. Somarakis et al. (2019) highlights the importance of equally considering potential risks of some NBS benefits. For instance, while a NBS can provide the benefit of increasing the value of an area, the risk of creating inequality among different societal groups arises. (Somarakis et al., 2019, p. 66) The classification scheme displayed here, is very broad and not specifically focussed on urban settings. It comprises mostly governance and management actions, while few solutions are aimed at engineered measures. Additionally, while the ES provided by the NBS are presented, the classification does not reflect the extent to which they occur.

2.3.8 Discussion Some of the abovementioned projects have been initiated to encourage and facilitate the implementation of NBS in participating cities. Within this vision, tools and classifications have been developed with the intention of creating an overview and understanding of NBS. However, the available catalogues are incoherent, in the sense that they each employ different parameters, use other nomenclature for similar NBS, do not include the same NBS and apply other classification methods. Some of them provide a valuation of challenges, benefits or ecosystem services of NBS, but most sources merely list a few services without elaborating on their effectiveness. Nonetheless, the analysis reveals the importance of several factors related to NBS, such as the degree of intervention, the scale of the intervention, the (local) challenges to address, the ES and co-benefits of NBS, valuation of these benefits, the cost-efficiency and finally detailed information about the NBS, which allows educating designers and planners on NBS. These parameters are elaborated upon in following paragraphs.

2.4 Parameters for the classification

2.4.1 Scale Former research on potential classification methods for ES suggests the use of scale qualifiers. According to Fisher et al. (2009), classifying ES whilst taking into consideration a scale factor recognizes the spatio-temporal dynamics of ecosystems (Fisher et al., 2009). Three of the previously discussed classification schemes include a scale factor. In the URBAN GreenUP catalogue a total of five scale levels referring to the size of the NBS measure are distinguished and assigned to each NBS by the means of a letter code. When a NBS is viable on multiple scale levels, it is given more than one letter. For instance, one of the NBS is a â&#x20AC;&#x153;Floodable Parkâ&#x20AC;? which could be potentially implemented on Regional, Metropolitan or Urban scale. In this case the Floodable Park is assigned R, M and U as scale levels. Alternatively, the ThinkNature Handbook includes a scheme relating NBS benefits to relevant NBS types at different scales (Somarakis et al., 2019, p. 59). Three scale categories are distinguished; regional, local and fine scale. Then again, Oppla differentiates a set of six scale levels in the classification of their case studies (Global, Continental, Sub-Continental, National, Subnational, Local) (Case studies | Oppla, 2018). These scales however, seem to be quite unspecific for local urban settings and therefore will be disregarded in this research. Finally, Nature4Cities also employs a scale parameter in the organisation of their case studies, including three levels, illustrated in Table 5 (Nature4Cities, 2017).

Table 5 Scale levels used in

literature and classifications concerning Nature-Based Solutions. 22

2.4.2 Degree of Intervention Eggermont (2015) distinguishes three types of intervention regarding NBS. A first level consists of protecting existing ecosystems to preserve biodiversity of natural areas and therefore requires minimal intervention. The second type entails new management methods that focus on improving sustainability and enhancing the ES delivery, which is equally important for maintenance. Finally, the last type entails NBS that consist of the establishment and management of novel ecosystems (Eggermont et al., 2015). These types were equally employed in the UnaLab Handbook.

2.4.3 Benefits and Co-Benefits Nature-based solutions provide direct benefits or ES. Both the European Commission (2016) and Raymond et al. (2016) state that NBS simultaneously provide environmental, social and economic benefits. In addition, NBS are said to provide benefits for biodiversity and human well-being (IUCN World Conservation Congress, 2016). Co-benefits are the added indirect benefits. Jiang et al. (2016) defines them as the various benefits that can be provided by a NBS simultaneously over a certain time frame (Jiang & O’Neill, 2017). They result from the direct benefits or services obtained from ecosystems. Sometimes they are referred to as “multiple benefits” or “synergies” (Co-benefits of climate policy, n.d.). For instance, green spaces implemented to reduce heat stress, naturally improve air quality as well, which in turn positively affects human health and well-being. Differences exist in how relations between NBS, ES and co-benefits are identified. In the Millennium Assessment of Ecosystem Services framework (MAES) emphasis is placed on assessing biodiversity and ES. The Nature-Based Solutions impact assessment framework however, highlights the relationship between NBS, ecosystem services, co-benefits and diverse forms of impact at various scales (Raymond et al., 2016). Earlier discussed classification schemes, such as Urban GreenUP, Naturvation and ThinkNature, define the benefits of NBS in terms of ES. In Groentool, the ‘Themes’ on which green measures have an impact, equally relate to ES and their co-benefits. It is interesting how Somarakis et al. (2019) also identifies a link between the benefits of NBS and the potential unwanted impacts that could occur as a result of inconsiderate implementation of NBS (Somarakis et al., 2019, p. 66).

2.4.3 Investment and Maintenance Among the investigated classifications, only two include a cost parameter. On one hand, the Urban Nature Atlas which is a classification of case studies by Naturvation, identifies a range of 6 cost levels: < 50 K, 50 K - 100 K, 100 K – 500 K, 500 K – 2 M, 2 M - 4 M. These prices are all expressed in euro and refer to the total initial project cost, which often includes indirect costs which can vary depending on the country. It is interesting to point out that many projects include more than one NBS, making it difficult to evaluate the investment required for a specific solution (Urban Nature Atlas, 2017). On the other hand, the Urban GreenUP catalogue provides a list of NBS, with for each solution an estimated budget and maintenance expressed in exact prices. The data is collected through a collaboration between various institutions in the European Union, resulting in prices being taken from different markets and possibly varying between countries (Urban GreenUP, 2017).

2.4.4 Challenges Multiple catalogues refer to potential challenges that can be addressed by NBS. In other words, the implementation of one single naturebased measure can possibly contribute to tackling various challenges. Strategies combining multiple NBS could have the potential to maximise the amount of benefits produced and challenges addressed. Groentool defines seven “themes”, which in reality come down to Antwerp’s environmental challenges concerning the city’s water management, heat stress, air quality, noise pollution, biodiversity loss and the shortage of accessible green space. However one could easily relate them to the ecosystem services defined by the Millennium Ecosystem Assessment, illustrated in Figure 2 on page 10. The challenges that have been distinguished by nearly all of the projects under Grant Agreement of the Horizon 2020 programme, including URBAN GreenUP, ThinkNature and Naturvation, all are in line with the seventeen Sustainable Development Goals (SDGs) (European Commission, 2016b). The set of challenges employed in UNaLab Technical Handbook however, are based on the climate and water related threats that the collaborating cities are facing. Unfortunately, no explanation is provided regarding these challenges (UNaLab, 2019).

Table 6 Challenges

used in the literature and classifications relating to Nature-Based Solutions.

BRUSSEL'S URBAN CHALLENGES This chapter identifies Brussel's environmental, social and economic challenges challenges in order to allow a focussed selection of Nature-Based Solutions and Case Studies.

3. Brussel's Urban Challenges In order to define suitable measures for ecologically sensitive development and regeneration of the Brussels Capital Region, it is essential to focus on the urban challenges that the city is facing. Defining these challenges enables decision-makers to outline which NBS and corresponding (co-) benefits are needed in Brussels. Bruxelles Environment [NL: Leefmilieu Brussel] outlines several goals in planning reports, such as Plan Nature, Quiet.Brussels and their plan for water management. In Plan Nature the main challenge is enhancing accessibility and connectivity of green spaces in the metropole to reduce social division and improve biodiversity and physical and psychological well-being of inhabitants. Plan Nature identifies the cities priority greening zones. The aim is to include natural features in all future urban planning and decision-making, also beyond protected areas. Thus, additional insight is required on the functioning, implementation and management of polyvalent green space, which provide a broad range of benefits. Furthermore, the organisation intends to invest in raising general awareness regarding biodiversity to ensure respectful use of green infrastructure (Bruxelles Environnement, 2016). Equally important are the challenges related to noise pollution. The city’s sound management approach, Quiet.Brussels, concentrates mostly on mitigation strategies for noise reduction. However, the plan also includes a paragraph promoting the use of green space and natural elements to create comfort zones where residents can enjoy a quiet sound environment. The planning authority aims at strengthening local authorities and encouraging citizen participation in decisions-making processes relating to their environment (Bruxelles Environnement, 2019, p. 40). Multiple water related objectives are summarised in Bruxelles Environnement’s Water Management Plan. Most goals focus on connecting, reopening and renaturing Brussels’ natural waterways and ponds, including the Senne and its effluents. In line with these measures, the Canal’s hydraulic function is planned to be extended as it plays a role in the drainage of rainwater overflow from the Senne (Bruxelles Environnement, 2017). Plan Canal equally mentions ambitions for reopening the Senne-Canal crossings along with the implementation of healthy public spaces (Chemetoff, 2014). Actions re-naturing waterbodies and thus restoring and enhancing natural ecosystems and their potential ecological richness are aimed at enhancing biodiversity, improving quality of surface water, building resilience for urban flooding and over time, re-establishing the recreational function of these spaces. Additionally, the entire Brussels Capital Region is vulnerable to recurrent episodes of pluvial flooding due to more frequently occurring heavy precipitation events causing sewer overflows. An increasing amount of impervious surfaces prevents runoff water from infiltrating and channels it towards the unitary sewer system. Although mitiga28

Table 7 Brussel's urban

challenges.

tion measures are being taken, they are often designed for merely one type of rain intensity and duration and do not suffice in capacity for the current changing climate. Additional measures to address urban pluvial flooding are necessary (Bondt & Claeys, 2013). Similar to other metropolitan areas, Brussels is an Urban Heat Island (UHI). Due to the UHI effect, urbanised areas experience elevated temperatures compared to the surrounding rural zones. Typically, surface temperatures in urban areas show a difference of 15 °C in comparison with green areas on a sunny summer's day (Vranckx et al., 2016). The differences are even more noticeable at night, as the urban surfaces with a low albedo or solar reflectance absorb the sun’s energy and release it in the form of heat radiation. Darker surfaces tend to have lower solar reflectance values than light coloured surfaces (U.S. Environmental Protection Agency, 2008). Consequently, during periods of recurring high temperatures, the UHI effect results in heat stress, which can lead to negative health impacts, increased energy consumption, etc (Lauwaet & De Ridder, 2018). The effect is clearly visible in Annex 1 on page 96. The Federal Department for Public Health defines a heat wave as a period of at least three consecutive days with an average minimum temperature higher than 18,2 °C (over the three days) and an average maximum temperature higher than 29,6 °C (Hitte-eilanden in steden, 2019). Plan Canal argues in favour of keeping economic activity in the city through local job creation. The plan aims to address the existing economic paradox in Brussels. Many tertiary jobs exist for highly educated individuals, while there is insufficient employment for low educated citizens, although they are more heavily represented (Federale Overheidsdienst Economie (ADSEI), 2018; Onderwijsniveau | Statbel, n.d.). Additionally the plan promotes social justice through the creation of an urban fabric that is open to everyone and inclusive and that serves the needs of local citizens instead of being car-oriented (Chemetoff, 2014). Abovementioned challenges can be subdivided into environmental, social and economic challenges. They can easily be related to challenges in the literature, resulting in following list.

FRAME WORK FOR A T YPOLOGICAL CL ASSIFICATION This chapter establishes the framework for a common typological classification of Nature-Based Solutions that recognizes their complexity by including all relevant parameters and the effectiveness to a broad range of societal benefits.

4. Framework for a typological classification of Nature-Based Solutions

Table 8 Categories of NBS.

In this chapter a framework is established for a common typological classification of NBS. The aim is to gather knowledge and to establish an overview of existing and innovative NBS and to promote detailed understanding of the relationship between NBS and their (co-) benefits, to aid in decision-making. A total of 69 NBS are included in the database, specifically aimed at the Brussels Capital Region, but widely applicable. The selection is a combination of NBS found in aforementioned literature and innovative nature-based measures obtained from two in-depth case studies (Chapter 5). Relevant literature sources include Groentool, URBAN GreenUP, UNaLab, Nature4Cities, Naturvation and ThinkNature (Almassy, Pinter, Rocha, Naumann, et al., 2018; Groentoolâ&#x20AC;&#x201D;Groenmaatregelen, 2014; Nature4Cities, 2017; Somarakis et al., 2019; UNaLab, 2019; URBAN GreenUP, 2018). Based on their typological characteristics, the measures are grouped into five categories, displayed and briefly clarified in Table 8, and subsequently organised in types and sub-types. The established framework recognises the complexity of NBS by including parameters for scale, degree of intervention, estimated required investment and maintenance cost, and the effectiveness regarding possible (co-) benefits of NBS. These benefits have been clustered under three core themes: social, economic and environmental, referring to ecosystem services and societal challenges. This organisation allows to easily determine the challenges to which the NBS respond. The database consists of information gathered from aforementioned tools and catalogues, contacting contractors and in-depth case study analyses. Methods for assessing and evaluating benefits do not fall within the scope of this thesis. The scoring system for the (co-) benefits consists of scores ranging from 0 to 5, where 0 indicates that the NBS does not have any impact regarding the concerned benefit and a score of 5 indicates a high impact. Exceptionally a negative score is attributed when the NBS has a potential negative impact. For some NBS a negative score has been given regarding air quality. For example, implementing â&#x20AC;&#x2DC;Street Treesâ&#x20AC;&#x2122; in a street canyon, a narrow heavy traffic street, reduces street ventilation and therefore has a negative impact on local air quality. However, implementing the NBS in any other context has a positive effect on air quality. Additionally, when a clear indication of positive performance regarding a benefit was found in literature, but no quantification of its impact was given, the potential effect is indicated with a dot. Finally, when no impact-information was found regarding a specific benefit, the space is left blank. 32

Figure 5 Schematic rep-

resentation of the classification structure.

NBS CHALLENGES

SCALE

N B S C AT E G O R Y DEGREE OF INTERVENTION

NBS TYPE INVESTMENT & MAINTENANCE

(C O -) B E N E F I T S

The classification is displayed in the form of a visual database facilitating a comprehensive overview of 69 NBS and their parameters, in order to facilitate comparison. The visual database is included in chapter 9. The following pages illustrate the included categories and types of NBS. Subsequent paragraphs elaborate on the employed parameters and clarify the potential (co-) benefits. 33

4.1 Defining categories and types In this section an overview is provided of the NBS categories and types that are included in the database. The categories are defined based on the typology or applicability of the solution, built upon the Klimatek case study for NBS in the Basque Country (GutiĂ¨rrez et al., 2017). For instance, "Building Scale Measures" are NBS that are implemented on a building or plot. However, they can be combined into a large scale network to maximise effectiveness. The types often group multiple sub-types. For instance, Green Roof's sub-types include extensive, semi-intensive and intensive green roofs as their impact regarding to benefits varies.

Figure 6 Icons of types

BUILDING SCALE MEASURES

GREEN ROOFS

B LU E-G REEN RO O FS

COOL ROOFS

B LU E RO OFS

GREEN WA LL S

RE-N AT U RIN G G A R D ENS

falling under the category: Building scale measures

Figure 7 Icons of types

falling under the categroy: Green measures for public space.

GREEN MEASURES FOR PUBLIC SPACE

CO N N E CT ING G REEN S PACE S

UR B A N PA R K S A ND FO R E S T S

GREEN SHADING STRUCTURES

UR B A N FA R M ING

URBAN B I O - F I LT E R A R E A

Figure 8 Icons of types

falling under the category: Measures for linear grey infrastructure

MEASURES FOR LINEAR GREY INFRASTRUCTURE

G REEN NO IS E B A RRIE RS

S T RE E T T RE E S

GR E E NING S T RE E T S

Figure 9 Icons

MEASURES FOR WATER BODIES AND DRAINAGE

RESTORIN G WAT ER B ODIES

FLOATING G A R DEN S

RA IN G A RDENS

S USTA IN A B LE DR A IN AG E SYSTEMS (SUD s)

RE-N AT U RING WAT ER B O DIE S

B IO -SWA L E S

F LO O D P L A INS

P ERV IO U S PAV E M E NT

of types falling under the category: Measures for water bodies and drainage.

Figure 10 Icons

of types falling under the category: Measures for natural urban areas.

MEASURES FOR NATURAL URBAN AREAS

N AT U RA L H E RR ITAGE P ROT EC T IO N

W E T L A ND S FO R WA S T E WAT E R T RE AT M E NT

GR E E N FIE L D S

4.2 Defining parameters

Scale The first parameter is a scale factor with five possible levels: Building (B), Street (S), Neighbourhood (N), Urban (U), and Regional (R) scale. In several instances one NBS can be implemented at different scales, in this case multiple scale levels are assigned.

Degree of intervention

The second parameter refers to the degree of intervention in biodiversity and ecosystems and is in line with Eggermont’s (2015) typologies. Three types are distinguished. A first level consists of minimal intervention and protection of existing ecosystems to maintain biodiversity of natural areas. The second type refers to novel management approaches that improve sustainability and enhance the delivery of services. Finally, the last type entails NBS that consist of creating and managing new ecosystems, which allows to maximize the amount of services produced (Eggermont et al., 2015). The NBS comprised in this classification mostly rely on the design of a new ecosystem. The selection is based on solutions that could address Brussels’ urban challenges, which often require implementation of new green and blue infrastructure, with the result that the majority matches the third type. This emphasises Brussel's current shortage of green and blue infrastructre.

levels.

Table 10 Incorporated cost

levels.

Investment and maintenance

Each NBS is assigned a cost parameter related to the initial investment and the maintenance required by the system. It should be noted that defining an exact price for each NBS is challenging since it depends on the selection of systems, materials and/or plant species. For instance, the price of a green roof system varies depending on the choice of drainage system, substrate type and thickness, vegetation species and even the contractor. Similarly, maintenance of various green roof systems differs. Another example can be illustrated with the price of one single tree, which varies between € 4 and € 12 000 depending on the species. Moreover, each species has specific characteristics and will perform differently and perhaps even have different impacts regarding benefits. The price data selection consists of values found in case studies (Chapter 5), values obtained through contacting contractors, and values retrieved from the Urban GreenUP catalogue which are based on multiple European markets. These values are translated into three investment levels referring to the price per square meter. 38

Table 9 Incorporated scale

Figure 11 Schematic

representation of the range of level and type of intervention (Eggermont et al., 2015).

4.3 Defining (co-)benefits

The benefits defined in this framework include both direct and indirect services and are identified based on the ecosystem services provided by NBS, the co-benefits they deliver, and the urban challenges that they address from environmental, social and economic perspectives. A total of fourteen benefits have been included and quantified in the database. The data collection is a combination of values obtained from Groentool, Urban GreenUp, UNaLab, ThinkNature and values obtained from two in-depth case studies (Chapter 5). Monitoring the actual impact of NBS in terms of these benefits does not fall under the scope of this thesis, but could be a focal point of future research. It should be noted that NBS performance primarily depends on geographic conditions such as local climate and geomorphology. Selection of vegetation species also affects the effectiveness of a solution. For instance, the effectiveness of implementing Street Trees regarding carbon sequestration strongly fluctuates with the selection of species, age and height of the tree. Nonetheless, performance varies for each species. This should be taken into account when designing NBS.

Water balance

Water balance consists of several flows. Water entering the system through precipitation (P) is transferred into either evaporation (E), surface runoff (R) or stored in the soil or a basin (S). P=E+R+S Urban areas consist of an increasing percentage of impervious surfaces. Moreover, urban drainage systems are often not designed to support the increasingly intense precipitation events. This causes an imbalance in the urban hydrological system where precipitation cannot be drained stored nor infiltrated in the soil with the risk of pluvial flooding. Increasing the amount of green space and pervious surfaces in urban areas reduces surface water runoff as well as water scarcity and increases precipitation retention, infiltration into the soil, evaporation and evapotranspiration (Vranckx et al., 2016). Implementing NBS, such as pervious pavements or rain gardens, will allow to slow down precipitation runoff so that it can be captured, retained, drained and/ or infiltrated into the soil. Additionally, water retained by the soil and absorbed by vegetation can be released in periods of drought through evapotranspiration. The effectiveness in terms of water balance is expressed through the retention coefficient given in litres of water retained per square meter (l/mÂ˛). The composition of the soil and flora selection is equally important for the effectiveness. 40

Figure 12 Overview of incor-

porated (co-) benefits.

E N V I R O N M E N TA L

S OC I AL

E CONOM I C

water balance

recreation & proximity

local employment

water quality

health & well-being

lowering energy consumption

heat stress reduction

participation

air quality

urban regeneration

carbon sequestration soil quality biodiversity sound

Water quality

Clean water supply is a basic requirement for many fundamental uses that humans rely on, such as consumption, agriculture, industry and recreation. Quality of surface and groundwater is equally important for ecosystems and biodiversity (Carr & Neary, 2008). Monitoring water quality however, depends on many variables. In Flanders following variables are measured to determine water quality: temperature, dissolved oxygen concentrations, chemical oxygen demand, nitrogen (NH₄-N, NO₂-N, NO₃-N), phosphate, total phosphorus, chloride, conductivity and acidity (pH) (Surface Water Quality Monitoring— Summary: Belgium., 2008). NBS including vegetation have the potential to ameliorate water quality by filtering out pollutants, sediments and debris. Additionally, vegetation slows down the stream flow and establishes ecosystems contributing to the water’s health (Liquete et al., 2016). While multiple sources agree that specific NBS contribute to water quality improvement, none of them have quantified the impact. Therefore the current version of the database does not include exact values on the effectiveness of NBS in terms of water quality improvement. However, when a positive effect is agreed, the benefit is not quantified but indicated with a dot (URBAN GreenUP, 2018) (Somarakis et al., 2019) (UNaLab, 2019). 41

Heat stress reduction

Due to the UHI effect, urbanised areas experience elevated temperatures compared to the surrounding rural zones. Typically, surface temperatures in urban areas show a difference of 15 °C in comparison with green areas on a sunny summer's day (Vranckx et al., 2016). The differences are even more noticeable at night, as the urban surfaces with a low albedo or solar reflectance absorb the sun’s energy and release it in the form of heat radiation. Darker surfaces tend to have lower solar reflectance values than light coloured surfaces (U.S. Environmental Protection Agency, 2008). Consequently, during periods of recurring high temperatures, the UHI effect results in heat stress, which can affect a community’s environment and quality of life, as it contributes to discomfort, and other heat related complaints. (Lauwaet & De Ridder, 2018; U.S. Environmental Protection Agency, 2008). Elevated temperatures result in an augmented energy consumption for cooling and exert pressure on the power network during peak periods of demand. An increase in energy consumption is generally associated with an increase in air pollution concentrations and greenhouse gas emissions, which have a negative effect on air and water quality. Poor air and water quality can cause diseases and thus have an indirect negative effect on human health (U.S. Environmental Protection Agency, 2008). NBS provide an opportunity to reduce the Urban Heat Island (UHI) effect by increasing the amount of water bodies and green cool spaces and surfaces in cities. Firstly, vegetation and specifically trees, green roofs and green facades provide shade and prevent hard surfaces, such as building roofs, facades and grey infrastructure, from absorbing solar energy and warming up. Simultaneously they create cool environments that protect humans from direct solar radiation. Secondly, cool surfaces with a high reflection coefficient have a low albedo and limit the absorption and radiation of solar energy. Finally, water bodies and green areas have cooling properties through evaporation and evapotranspiration (D. Li et al., 2014). The effectiveness of NBS regarding heat stress abatement is expressed in surface and air temperature reduction (°C).

Air quality

Poor air quality caused by pollutants has a significant negative impact on human health (Landrigan, 2017). NBS relying on the creation, enhancement or restoration of green space in urban areas can play an important role in air quality. First of all, they can aid in filtering air pollutants such as fine particles (PM2.5) and removing carbon dioxide (CO₂) from the atmosphere. Secondly, they reduce air temperature, which impedes the creation of secondary contaminants, such as ozone (O₃). Finally, they contribute to the oxygen concentration through photosynthesis and improve the atmospheric composition for humans (Raymond et al., 2016). 42

Groentool expresses the impact on air quality in differences in fine particulate matter concentrations in the atmosphere (% PM2.5) before and after application of the NBS (Vranckx et al., 2016). These values have been included in the NBS database. However, when a positive effect is agreed in other sources, but not quantified, it is indicated with a dot (URBAN GreenUP, 2018) (Somarakis et al., 2019) (UNaLab, 2019).

Carbon sequestration

The increasing amount of atmospheric carbon dioxide is primarily caused by the universal use of fossil fuels and has significant global health implications (Landrigan, 2017). Vegetation has the ability to capture carbon dioxide (CO₂) from the atmosphere and store it as carbon, while oxygen (O₂) is released through photosynthesis. Hence, it affects the air quality positively. However, there is little data on the effectiveness of urban vegetation to reduce concentrations of airborne pollutants such as carbon (Velasco et al., 2016). The Groentool has quantified the performance of different vegetation types regarding carbon sequestration (Vranckx et al., 2016). However, it should be noted that these values are generalized and in reality vary per species. Vranckx (2016) expresses the impact of carbon sequestration in kilograms of carbon captured in one year per square meter (kg C/year/m²).

Soil quality

Urbanisation and rapid industrialization negatively affect urban soil quality due to large discharges of contaminants, which in turn have negative implications on ecosystems and human health (G. Li et al., 2018). Similarly to its potential for improving water quality, appropriately selected vegetation has the potential to improve soil quality by filtering out pollutants. The performance of NBS regarding to soil quality is unfortunately undocumented. While various sources acknowledge that some NBS contribute to improving the quality of the soil, their effectiveness has not yet been monitored. In this case, the benefit is not quantified but indicated with a dot in the visual representation of the NBS database (Somarakis et al., 2019; URBAN GreenUP, 2018).

Biodiversity enhancement

Decrease in urban biodiversity both results from and affects humans. Our survival depends on benefits from ecosystems, which in turn depend on a broad range of living organisms. Biodiversity is often used to measure how healthy a particular ecosystem is. In other words, an ecosystem occupied by a wide variety of species will translate 43

into a high biodiversity index. Urban biodiversity is threatened by an increase in non-natural materials, such as concrete and asphalt, and a higher rate in greenhouse gas emissions. Biodiversity loss can affect human health and well-being as it results in decreased resilience to climate change and extreme weather, and reduced quality or quantity of ecosystem services (Pedersen Zari, 2018; The Importance of Biodiversity in Urban Areas, 2018). Implementing NBS can aid in protecting and enhancing biodiversity, through improved maintenance of existing ecosystems and creation of new urban ecosystems. To illustrate, parks, cemeteries, gardens, green roofs and vegetated facades are potential urban biodiversity hubs. Enhancing the quality of gardens by increasing the variety in species and creating green corridors connecting green spaces to establish a network can improve biodiversity (Groentool—Groenmaatregelen, 2014). The values included in the NBS database originate from values defined by Groentool and Urban GreenUp. However, when a positive effect is stated in other sources, but not quantified, the benefit is indicated with a dot (Groentool—Groenmaatregelen, 2014; Somarakis et al., 2019; UNaLab, 2019; URBAN GreenUP, 2018).

Sound Noise pollution caused by increasing urbanisation, industrialization and rapid growth affects ecology, human health and quality of life, because it distracts, disturbs and interferes with sleep (Gandhi et al., 2019). NBS can contribute to noise reduction in multiple ways. First of all, vegetation can be used as an acoustic barrier to block out street noise. Secondly, selecting a pavement with sound attenuating properties can aid in muting traffic noise. Finally, green roofs and facades provide an additional layer to the building structure, which aids in noise attenuation through absorption by the substrate (Galbrun & Scerri, 2017). It is worth mentioning that different physical processes are responsible for the sound muting effect of plants: scattering, absorption and shielding. Tree trunks and branches scatter and block the sound, which is the most effective way to reduce the noise level as fewer direct soundwaves are able to traverse. Leaves however, are too frail and do not contribute to attenuation. They are inclined to vibrate with the soundwaves, which can conceal the original sound. Coniferous trees with closely spaced needles however, display a higher sound absorption. Green shielding is only effective for noise reduction with a dense layer of vegetation. The noise can also be attenuated indirectly, through absorption by unpaved soil and through reduced wind speed. Hence, sound attenuation depends on a few NBS related variables: density, height, surface of the vegetation and appropriate selection of plants (Groentool—Themas, 2014). Noise reduction can be monitored by measuring the difference in sound level (dB) before and after the implementation of the NBS. 44

Recreation and proximity

Studies have shown that accessibility to qualitative green space positively affects human well-being, as it provides many benefits including social cohesion, recreation and environmental education. Many citizens however have limited access to green space due to limited or non-existing availability of green infrastructure in their proximity. Implementing NBS can increase the amount and improve the distribution of accessible green space in the urban tissue (Groentoolâ&#x20AC;&#x201D;Groenmaatregelen, 2014; Stessens et al., 2017). The values, quantifying the effectiveness of NBS for this indicator, included in the current database were obtained from Groentool and Urban Greenup. The valuation system employed by Groentool is based on the potential of particular NBS to provide visible and accessible green in urban areas. A range of zero to five is established, illustrated in Table 10 (Vranckx et al., 2016).

Health and well-being of inhabitants

Many of the abovementioned benefits have significant impacts on human health and well-being. NBS can contribute to a broad spectrum of positive psychological and physiological benefits through providing opportunities for physical activity, relaxation and stress relief and through the provision of ecosystem services, such as heat stress reduction and decrease in air pollution. In other words, NBS can contribute to improving overall human health and well-being. The data included in the classification originates from Urban GreenUP, which is based on expert judgement (URBAN GreenUP, 2018).

Participatory planning and governance

Involving citizens in planning, management and monitoring of projects allows them to become committed in their neighbourhood and promotes general awareness. Through monitoring inhabitants can easily contribute to data collection from implemented NBS (Kallus, 2016; Kusters et al., 2018). The values for participatory planning and governance included in the NBS database originate from Urban GreenUP, and are based on expert judgement (URBAN GreenUP, 2018).

Urban regeneration

Urban regeneration refers to improvement in the economic, physical, social and environmental conditions of an urban area that has experienced negative change and is considered non-resilient. NBS supporting the implementation and optimisation of green, blue and grey infrastructure can contribute to urban regeneration and sustainable growth (European Commission, 2014; Raymond et al., 2016). When implementing NBS it is crucial to consider the correlations between urban regeneration, urban planning and development, urban design and aesthetical value, urban ecology and sustainable energy and water use. For instance, well managed landscapes generally have a lower crime rate and enhance social capital. However, it should be noted that urban regeneration comes with a potential risk of issues concerning gentrification and social justice. For instance, housing prices often rise with urban regeneration which can result in social division (Raymond et al., 2016). The data included in the classification originates from Urban GreenUP, which is based on expert judgement (URBAN GreenUP, 2018).

Improving local employment

The implementation of NBS, on one hand, creates new economic opportunities for “Green businesses” and on the other hand, generates “Green-Collar Jobs” that can range from low-skill positions to highskill jobs and enhance local employment (Maes & Jacobs, 2017; Raymond et al., 2016; URBAN GreenUP, 2018). The values for NBS effectiveness in terms of local employment included in the current database equally originate from Urban GreenUP, and are based on expert judgement (URBAN GreenUP, 2018).

Lowering Energy Consumption

As mentioned earlier, elevated temperatures and heat stress result in an augmented energy consumption for cooling and an increase in air pollution concentrations and greenhouse gas emissions, negatively affecting air and water quality which has negative health implications (U.S. Environmental Protection Agency, 2008). NBS such as (blue-)green roofs and vegetated facades reduce energy consumption in buildings, as they perform as an additional insulating layer. Performance depends strongly on the set-up of the system and varies with substrate thickness and vegetation type (Susca, 2019). The impacts related to lowering energy consumption included in the database were obtained from Urban GreenUP and are based on expert judgement (URBAN GreenUP, 2018). 46

4.4 Factsheet Template In order to present NBS in a concise and comprehensive way, a factsheet template is made up containing relevant aspects of the considered NBS. This is done in order for future NBS to be incorporated within the framework in a clear and straightforward manner. The factsheets have the potential to facilitate decision-making by displaying all relevant information concerning one NBS in one single location. The left-side banner is dedicated to the type-icon of the NBS along with a visual representation of its parameters and its impact in terms of (co-) benefits. The valuations are taken from the database, displayed in chapter 9, as are the scale, degree of intervention and investment which are schematically represented above the (co-)benefits. In the upper center part, the (sub-) type of the NBS is displayed right under its category. Subsequently, a brief description of the NBS is given, where it is specified how the NBS will interact with different environmental and societal challenges. Next to the description, an image of a representative case is provided along with additional references of case studies. Consequently, parameters or factors that influence investment and maintenance cost are discussed. In order to facilitate future urban planners, architects and other decision-makers, a technical design paragraph is included emphasising critical technical requirements or attention points during design, ideally accompanied by a technical drawing. If special attention should be given during the implementation of the NBS, it is stated here. Finally, additional notes on important factors are included.

Figure 13 Template for the 48

NBS Factsheets.

N B S C AT E G O R Y

N AT U R E - B A S E D S O L U T I O N

ICON

DESCRIPTION

Brief description of the solution and how it contributes to climate change adaptation

€€

Image of a representative case .

REFERENCES Reference projects that have successfully implemented the NBS INVESTMENT & MAINTENANCE

N OT E S

Short description of the required initial investment and further maintenance of the NBS.

Important factors for the performance of the NBS.

TECHNICAL DESIGN Clarification of the technical details and design requirements.

Technical drawing to illustrate the set-up.

IN - DEPTH CASE STUDY ANALYSIS In this chapter, two practical examples that have implemented NBS are investigated to explore the full potential of NBS in practice. The selection of cases is built on challenges relating to those of the Brussels Capital Region. The carefully chosen cases both address multiple urban challenges simultaneously. 51

5. 3.

5.1 Case 01: Resilio

A SMART BLUE - GREEN NET WORK

5.1.1 Urban challenges Urban Flooding Four future climate scenarios for The Netherlands have been investigated by the Royal Dutch Meteorological Institute (KNMI). The scenario effects show minor variations, but the general trend is that the global warming effect will cause milder winters and warmer periods in summer. Winters will experience an increase in both the intensity and frequency of precipitation, while summers will be characterised by a reduction of rainfall events but a significant increase of their intensity. As a result, summers will have longer and more extreme periods of drought (KNMI, 2015). Since 1901, the annual average precipitation rate has increased with a percentage of 25, and is predicted to continue rising (KNMI, 2018). Urbanised areas such as the municipality of Amsterdam are vulnerable for urban pluvial flooding, caused by a combination of heavy rainfall events and the limited capacity of sewer systems. The latter experience additional pressure caused by a decreasing area of pervious surfaces, limiting the infiltration of rainwater, in combination with more frequent heavy rainfall events (Cirkel, Voortman, van Veen, & Bartholomeus, 2018). The policy programme Amsterdam Rainproof has conducted a vulnerability analysis for the region of Amsterdam. The results were translated into an online map illustrating critical areas with a high risk for flooding and damage caused by extreme precipitation. The critical areas vary in severity and size (‘Amsterdam Rainproof’, 2017). Analysis results indicate that the neighbourhoods Kinkerbuurt, Rivierenbuurt, Indische Buurt West, Betondorp and Oosterparkbuurt are most vulnerable. This is due to the fact that the critical areas are situated topographically lower than their surroundings, meaning that stormwater runoff naturally flows towards them.

Figure 14 (left) Amsterdam.

The neighbourhoods in which RESILIO is implementing a smart blue-green roof network. 1. Slotermeer 2. Kattenburg, 3. Oosterparkbuurt, 4. Rivierenbuurt , 5. Indische Buurt . Water is represented in black.

Additionally, Amsterdam currently lays largely beneath sea level and the worst climate scenario predicts a sea level rise of one meter before 2100, which could be catastrophic for the canal city. Urban Heat Island & Heat Stress The average annual temperature in The Netherlands has known a rise of 1,6°C since 1950. The KNMI climate scenario’s indicate that the temperature will continue this rising trend and result in a significant increase of tropical nights (>20°C) and Urban Heat Island (UHI) effect in high-density built areas (KNMI, 2018). 53

5.1.2 Context The most effective nature-based solution to decrease UHI and high stress on public sewer systems would be implementing permeable green areas in the city, which are known to decrease stormwater runoff by capturing, retaining and evaporating rainwater (Foster, Lowe, & Winkelman, 2011). However, space on ground level is scarce in many metropolitan areas, while urban rooftops form a large unused area. RESILIO is installing a total of 10.000 m² smart blue-green roofs that are connected with sensors and collectively form a water buffer capable of retaining 560 000 litres of rain water. The innovative roofs are being installed in the neighbourhoods Kattenburg, Oosterparkbuurt, Indische Buurt, Slotermeer and Rivierenbuurt, some of which are highly vulnerable to urban pluvial flooding and damage due to heavy downpour. The selected neighbourhoods are illustrated in Figure 14. Particular buildings were selected based on participation of the owners, the location and current roof state, ideally requiring replacement. Currently participating landlords are social housing companies Stadgenoot, the Alliance and De Key. Private proprietors can also have a smart blue-green roof installed, which will be subsidized by the municipality of Amsterdam starting from March 2020. The smart blue-green roof system, developed by MetroPolder Company, is based on water storage with a capillary irrigation system (Permavoid). The water is stored in a layer beneath the substrate and vegetation, equipped with an integrated fibre technology for capillary irrigation. Water travels up and is evenly distributed for absorption, ensuring that the plants have permanent access to water and nutrients. The roofs are equipped with smart sensors and valves controlled by Waternet, Amsterdam’s water managing company. Data collected from sensors measuring the water level in the sewer system, on the roofs and in the soil combined with accurate weather forecasts allows to determine the exact amount of water to be retained or discharged when suitable with automatically controlled valves. By connecting the roofs with each other a largescale smart network for rainwater management is established. The system allows to use the collected data to investigate the amount of rainwater drained in the neighbourhoods and analyse the information to maximize performance and for further research. Preliminary to the RESILIO project, blue-green roof systems have been tested and researched with pilot project Smartroof 2.0 on the Marineterrein in Amsterdam to determine the performance in terms of energy balance and thermal cooling for heat stress reduction, which proved to be significantly higher in comparison to conventional extensive green roofs (Cirkel et al., 2018). Additionally, positive effects were observed in terms of the roof’s thermal insulating properties and biodiversity enhancement. The RESILIO project is the first large scale implementation of smart blue-green roofs forming a integrated water managing network. This offers many opportunities for future research. The Hogeschool van Amsterdam and the Vrije Universiteit Amsterdam are monitoring the effects on building, neighbourhood 54

RESILIO is an abbreviation for “Resilience nEtwork of Smart Innovative cLImate-adapative rOoftops” and is a interdisciplinary collaboration between the municipality of Amsterdam, Waternet, MetroPolder Company, Rooftop Revolution, Hogeschool van Amsterdam, Vrije Universiteit Amsterdam, Consolidated and social housing companies Stadgenoot, the Alliance and De Key. Financing of the project is partly covered by the ERDF fund of the European Union through the Urban Innovative Actions programme. The initiative has received a grant of € 4.8 million as an innovative project in the field of climate adaptation, covering 80% of the costs. The remaining 20% are invested by the participating housing companies.

Table 11 Resilio: facts.

Figure 15 Smartroof 2.0 on

the Marineterrein, Amsterdam.

and urban scale. Furthermore, the effects of green space on human health are being studied by the Municipal health organisation (GGD). Gained knowledge and results however, will be shared on European level with the aim of encouraging European cities to implement bluegreen roofs to address climate related urban challenges. . (RESILIO: 10.000 m2 aan slimme blauw-groene daken | Amsterdam Rainproof, 2019)

5.1.3 Technical design requirements RESILIO’s smart blue-green roofs are constructed on the existing roof structure, that needs to be able to bear the additional load of the nature-based system. Exact calculations are made by partner Consolidated, but usually if the roof is already covered with a layer of gravel, it is supposed strong enough to bear the load of an extensive bluegreen roof. The system weighs 90 kg/m² when dry and up to 170 kg/ m² when the storage layer with water. A root repelling waterproofing (5) is applied on top of the existing roof structure (6) to protect it from penetrating roots and leakage. On top, the buffer layer for water storage (4) is placed, consisting of a lightweight crate system with a height of 85 millimetres that allows to collect and retain 80 litres of water per square metre. A “smart” valve (7) is installed between the storage and the roofs’ drainage system (8), responding to weather forecasts and automatically controlling the rainwater discharge (Figure 18). An integrated fibre technology based on capillary irrigation allows for the water in the buffer layer to travel up and be absorbed by the plants’ roots. This system consists of rockwool cones that are placed in dedicated perforations in the crate system (Figure 17) and is covered with a water absorbing geotextile. One rockwool cones suffices to irrigate one square metre of vegetation. The geotextile functions as a filtering layer (3) , separating the substrate from the water storage and preventing erosion and particles from entering and clogging the drainage system, while simultaneously providing a uniform water distribution for absorption. The substrate (2) is the soil in which the vegetation (1) is rooted, providing support and nutrients. It usually consists of a mixture of shale, pumice, lava rock, crushed bricks, clay, and compost. Substrate thickness depends on vegetation type. Various species can grow on the roof, such as moss, sedum, herbs, grasses, ferns, shrubs or a combination of those.

Figure 16 Schematic section

of the RESILIO roof: green roof with a storage and capillary irrigation system. Adapted from RESILIO. itategev )1((1)

)7(

artsbus )2((2) m retlfi )3((3) ts retaw )4((4) & toor )5((5) trts foor )6((6)

)8(

Figure 17 The

lightweight HDPE crate system for water storage with capillary irrigation (rockwool cone visible). (© De Dakdokters)

Figure 18 Smart flow con-

trol system with an automatically controlled valve. Closed state: rainwater retaining. (© Eva Krol)

Figure 19 Smart flow con-

trol system with an automatically controlled valve. Open state: rainwater discharge. (© Eva Krol)

Figure 20 Schematic

sections of the three research plots. The left and right plot are equipped with the Permavoid drainage and capillary irrigation system. Adapted from (Cirkel et al., 2018).

Figure 21 Top view of the

Smartroof 2.0 setup with the three research plots (green squares) (Cirkel et al., 2018, p. 4).

Figure 22 Smartroof

2.0. The three reasearch plots and the measurement set-up is visible. 58

5.1.4 Monitoring Prior to the RESILIO project, a test project was implemented on the Marineterrein in Amsterdam to determine the performance of different green and blue-green roof systems. Green roofs are often promoted as measures for climate change adaptation to address heat stress and improve water balance and thermal comfort. However, there was still much debate on the solution’s actual performance. The effectiveness of blue-green roof systems is investigated with Smartroof 2.0. The project’s aim is to study the cooling properties and the water and energy balance of various green roof types. The study is performed by a team of researchers from various academical institutes. In order to assess the benefits of a storage and capillary irrigation system, they set up and performed lysimeter measurements to quantify the evaporation on the roofs. Additional measurements were performed to quantify the surface and air temperature. Furthermore, the effects on biodiversity were observed. Results show that the presence of water enhances cooling and biodiversity on green roofs (Cirkel et al., 2018). The measurement set-up consists of three different plots on the roof of a two storey building on the Marineterrein. The first plot is a conventional extensive green roof system with a drainage mat of 25 mm and a substrate thickness of 4 cm vegetated with sedum plants. The two other plots are equipped with a Permavoid storage and capillary irrigation system. One has a substrate thickness of 4 cm and is covered with sedum while the other’s substrate thickness reaches 8 cm covered with vegetation consisting of a mix of sedum, herbs and grasses. Unfortunately the original roof structure posed some limitations to the system. The maximum storage level of the buffer layer is 8 mm, but due to the roof’s maximum allowable static load of 90 kg/m², a storage level of only 30 mm could be allowed, requiring discharge of all excess water to the sewer system.

HEAT STRESS REDUCTION

The cooling properties of blue-green roofs are attributed to the evaporation of the vegetated surface as the sum of three fluxes: evapotranspiration and evaporation of captured water. Whereas conventional green roofs only rely on evapotranspiration. The results prove that extensive green roofs equipped with a storage and capillary irrigation system have a significantly larger evaporation rate than conventional green roof systems. During a two week heat wave in June 2017, the conventional green roof showed an evaporation of 18 l/m², while the blue-green roof exhibited a notably higher evaporation of 42 l/m² in that same period. When equipped with a thicker substrate and covered with herbs and grasses the evaporation rate is even higher. Additionally, the capillary irrigation system through a water storing layer showed to be significantly more effective than regular manual irrigation. The presence of water in the roof system enables maximal cooling efficiency, since there is more evaporation potenial. Surface temperature difference between a reference roof covered with black bitumen and a blue-green roof rises up to 40°C on warm summer days (Cirkel et al., 2018). 59

Figure 23 Picture

of the conventional extensive green roof after a period of 1 year (Municipality of Amsterdam, 2018).

Figure 24 Picture of the ex-

tensive blue-green roof after a period of 1 year. (Municipality of Amsterdam, 2018)

BIODIVERSIT Y IMPROVEMENT

In addition to measurement results, observations were made relating to biodiversity. Plant roots have continuous access to water, resulting in visible vegetation differences. While the conventional green roof plot does not develop further than an early stage of Sedum plants, the equivalent blue-green roof shows a mixed vegetation of Sedum, herbs and grasses. Moreover, a vibrant population of multiple spider species and a notable amount of flying insects were observed during an ecological study. A total of 42 species were spotted in a time span of 24 hours in August 2018. The presence of these insects indicates an ecosystem of multiple prey-predator cycles (Municipality of Amsterdam, 2018).

LOWERING ENERGY CONSUMPTION

Ever since the construction of Smartroof 2.0, building users claim not to have needed nor used the air-cooling system in the rooms on the upper level, under the roof. Covering the original non-insulated roof with the blue-green roof system seems to have increased the roof’s thermal performance. This can be confirmed by the measurement result, which indicate that water in the storage layer never reached a higher temperature than the maximum of only 24°C on the warmest days. Additionally, (Blue-) green roofs enhance the performance of solar panels due to their cooling properties. Solar panels exhibit optimal performance when the sky is unclouded in combination with a temperature below 25°C. Performance declines with rising temperature. Conventional black bitumen or gravel roof surfaces warm up to 70°C, causing solar panels to lose performance. The Permavoid water storage layer has been developed in such a way, that the perforations permit the installation of solar panel supports before placement of the substrate and vegetation layer (Municipality of Amsterdam, 2018).

INVESTMENT & MAINTENANCE

Within the project two types of roofs are distinguished: extensively vegetated and intensively vegetated roofs. The first type consists of light vegetation with moss and sedum and costs â&#x201A;Ź60 per square meter without including the smart valve, sensors nor installation. Maintenance consists of fertilizing twice a year and additional irrigation in dry periods of summer by supplying tap water to the storage layer through a controllable valve. In other words, the systems uses natural irrigation without requiring artificial irrigation and the associated pumps, tubes or energy. Evidently, the more intensively vegetated, the higher the price and the more maintenance is required, but also the more and higher the benefits in terms of water storage, biodiversity and cooling through evaporation. Currently captured water is only used to nourish plants and discharged water is unfortunately released into the sewer system, but other options are being researched. The prospective would be to connect the smart roofs to a larger water managing system, such as infiltration buffers under the street and recessed parks that allow for the rainwater to infiltrate.

PARTICIPATION AND PL ANNING

Project partner Rooftop Revolution is in charge of raising awareness among owners and residents. With this aim in mind they collaborated on making a mock-up of the RESILIO blue-green roof on a cargo bike to showcase the system at promotion events. . Their goal is to inspire and enthuse property owners and residents to install the system on their roofs. Furthermore they are exploring in what sense residents of the participating social housing blocks could be involved.

Figure 25 RESILIO

Cargo bike transformed into a smart blue-green roof mockup. Photo taken by Eva Krol. Obtained from Rooftop Revolution.

5.1.5 Discussion In this study a few noteworthy factors regarding the implementation of the NBS stand out. In this case the main goal is to increase resilience of multiple neighbourhoods for climate change induced urban pluvial flooding. The challenge is addressed with an integrated approach and a large collaboration between many partners on various levels. In order to achieve a desirable water balance on neighbourhood or urban level, it is crucial that the problem is addressed at this level and that solutions are designed and calculated accordingly. Implementation of individual blue-green roofs would not be as effective as a smart bluegreen network. In this case the performance is enhanced by reacting on actual weather forecasts and water-related information obtained through data collection. Additionally, performance of blue-green roofs varies depending on multiple factors. Firstly, the capacity of the buffer layer determines and limits the amount of rainwater that can be collected and stored. The greater this volume, the higher the effectiveness in terms of thermal cooling, but it also increases the weight of the roof system. Consequently, the substrate can also store a significant amount of rainwater by saturation of the soil. A thicker substrate layer will therefore be better for the cooling properties. Substrate thickness equally defines the type of vegetation species that can be sustained. A thin layer only supports succulents and moss, while a ticker layer (from 8cm) can support additional species such as herbs and tall grasses. The vegetation selection has a significant influence on the ecosystem that is created on the roof and on its biodiversity. The more variation in vegetation species, the more insects and spiders and therefore birds it attracts. However, a higher performance is accompanied by a greater investment and more maintenance. The case of RESILIO also highlights some limitations. Currently, discharged rainwater flows straight to the public sewers. From the interview with partner Rooftop Revolution it became clear that there were intentions for rainwater recovery, but at this stage of the pilot project a sustainable urban drainage system would require too much investment. In the future, connection to other NBS such as a residential park with an integrated flood plain can be considered if the pilot project proves successful. This case study allows to incorporate (smart) blue-green roofs in the established NBS database and to create Factsheets (see chapter 10) with relevant parameters, technical design requirements and potential benefits provided by the system.

BLU E- G REEN ROO FS

5.2 Case 02: Niew-Zuid

A SUSTAINABLE NEIGHBOURHOOD

5.2.1 Urban Challenges Green space provision and accessibility One of the city’s main challenges is balanced green space provision and connectivity of these green spaces. Ecological connections on city scale need to be enhanced while also providing a diverse range of open spaces on neighbourhood scale to ameliorate accessibility for all inhabitants (Groen, 2018; Secchi & Viganó, 2012). For this purpose, Antwerp has created a Groenplan and accordingly the Groentool, to promote the positive impacts of greenery in the urban environment (Groen, 2018). Urban Pluvial Flooding Water management equally plays an important role in Antwerp’s future policy plans. The city invested in a precipitation model, which predicts a future scenario with higher intensity precipitation events resulting in rainy winters, while in summers more dry periods are envisioned. Including water bodies in urban areas is beneficial for thermal cooling, but it is equally a challenge to prevent flooding and shortage. Therefore, Antwerp is investing in sustainable and naturebased water catchment and management, through combinations of measures such as open basins, green roofs and green facades, in exemplary projects such as Nieuw-Zuid (Groentool—Themes, 2014; Water, 2018). Air Pollution The city is dealing with air pollution due to fine particulates (PM2.5), carbon dioxide (CO₂) and nitrogen dioxide (NO₂) as a result of emissions from vehicles and industry. In addition to mitigation strategies, such as establishing a low-emission zone, providing city bikes and improving cycling paths, green infrastructure is employed to address the issue. Moreover, no new residential projects are permitted in highly polluted areas (Lucht, 2018).

Figure 26 (left) Map of Ant-

werp. The Nieuw-Zuid project site is indicated. Water bodies are represented in black.

Noise Pollution Noise has an impact on public health, as it causes negative health effects. When people are exposed to excessive noise periods and amounts issues can arise such as stress, high blood pressure, heart problems, sleep disorders and concentration difficulties. Antwerp’s Sound Action Plan is aimed at noise reduction in problem zones and protection of quiet natural areas (Geluid, 2018). 65

5.2.2 Context Studio Secchi-Viganó created a masterplan for Nieuw-Zuid Antwerp in 2012 in response to the open call organised by the city of Antwerp on behalf of plot owner and Antwerp based developer, Triple Living. The masterplan establishes an overall philosophy for the site to create a new sustainable residential neighbourhood and to achieve a resilient urban fabric. Bureau Bas Smets was involved by the client at very early stage after the creation of the master plan. The landscape architecture office is put in charge of the project’s landscape design and environmental quality. According to Bas Smets the image and identity of the neighbourhood is created by the landscape and not by the buildings. The landscape design is developed based on Secchi-Viganò’s masterplan and subsequently the buildings are designed in consultation and collaboration with Bureau Bas Smets. In order to improve air quality, mitigation strategies are employed. A sustainable mobility policy is persued, in which the presence of the Antwerp South railway station and tramway access are assets. The applied STOP-principle works by focusing on a strongly fordable fabric for pedestrians and cyclists, by providing opportunities for the expansion of the public transport network and the realisation of cluster car parks. This ambition is reflected in the layout of the public domain with its residential streets and paths (Secchi & Viganó, 2012).

Studio Secchi-Viganò was founded by Bernardo Secchi and Paola Viganò in 1990 in Milan, Italy. The office specializes in urbanism and works at different scales of urban planning. Studio Secchi-Viganò has visibly left its mark on the Antwerp cityscape. Before winning the international design competition for Nieuw-Zuid they had already designed the Theatre square (2009) and Park Spoor Noord (2008) (Studio associato bernardo secchi paola viganò, n.d.).

Bureau Bas Smets is a Brussels based landscape architecture office, founded in 2007 by Bas Smets. Their projects vary in scale and in type, but each project is seen as part of an encompassing research into the possible roles of landscape projects for building urban resilience in a changing climate. Their objective is to create ‘augmented landscapes’, by using the logics of nature, while crereating inviting atmospheres for their visitors and inhabitants (“Bureau Bas Smets”, 2019).

5.3.2 Design The projects location is enclosed between the river Scheldt, the southern node of the Antwerp ring road and the palace of justice. Bridging the transition between the dense city and the open river, the masterplan aims to combine high density housing with a large park piercing the streets and reaching between the building blocks. Bas Smets refers to this continuity of public space as “living in the park”. Each building is required to have some qualitative views towards open spaces. Due to the large scale of the project, the design of each building or block is assigned to a different architecture office, resulting in a visually and typologically diverse neighbourhood. The plot is subdivided into 8 parts, called Strigas (Figure 27), that serve a function as operational units for the phasing of the project, which is completed in three successive phases. The first phase involving the first three strigas has been completed. Currently the second phase concerning strigas three to five, is in execution. As for the last phase, regarding the last two strigas, the conceptual design is in development. The ‘Striga’ concept is an ancient town planning principle and can be traced back to roman military sites. By following the rhythm of the train tracks and facing the river perpendicularly, the strigas organise a habitat for approximately 2500 homes. The site’s location poses some challenges in terms of connectivity and water management, as it is vulnerable for urban flooding due to extreme percipitation events, as well as due to river overflow. Annex 3 on page 97 displays zones in the Antwerp regio that are susceptible to flooding due to overflow of the Scheldt.

Figure 27 Schematic rep-

resentation of the plot and Striga division.

The landscape model focusses on a few main principles. Firstly, creating a rainwater neutral neighbourhood, meaning that all precipitation and stormwater runoff is infiltrated on site with an overflow to a floodplain in the park area and an additional overflow to the Scheldt in case of a large storm, predicted once every twenty years (T20). Furthermore the project has a closed earth loop, meaning that all excavated soil is reused on site to create a sculpted landscape allowing to channel runoff water and attenuate noise from southern ring road. Finally, the design attempts to preserve the largest possible number of original trees. The project site can be reduced to three main elements; the river quay, the built area and the swale landscape.

Table 12 Nieuw-Zuid: facts.

QUAY To enhance the site resilience to river overflow due to stormwater runoff, the quay is reinforced and elevated one meter as part of the Sigma plan (“Nieuw Zuid”, n.d.). The existing quay is demolished and substituted by a sturdier construction, moulds of the historical style elements are then restored on the surface. The quay is still under construction. Currently, the structure has been reinforced but the ground level must still be elevated and the surface covered.

BUILT AREA One Striga always consists of a residential street and a residential path that are connected to the quay and merge into the residential area. Within this area, internal paths form the connection between different Striga’s. Additionally, one wider internal street, parallel with the river, cuts through the residential area and connects to the adjacent urban plot. The main difference between residential streets and residential paths lays in the street set-up. Every residential path comprises a linear bio-swale that is designed to capture rainwater and infiltrate it locally. Since the project is a new construction in Antwerp, all roofs are required to be either green roofs or to be connected to a rainwell per building. Depending on the vegetation and substrate thickness on the roof, a percentage of the precipitation is absorbed by the plants and stored in the substrate. The excess water is drained into linear bioswales together with all surface water runoff from paved impervious surfaces in the project.

Figure 28 Nieuw-Zuid: re-

inforced quay under construction. Photo taken in Novemeber 2019.

Figure 29 (left)Nieuw-Zuid

construction site. Photo taken from the quay. Novemeber 2019.

Figure 30 (right)Schematic

representation of the plot and the different types of streets and paths.

Internal Street The internal street connects to the Waalsekaai and includes a wide pedestrian strip and street trees that were selected specifically for their effectiveness in removing fine particulate matter from the air. The two species (Ginko Biloba and Metasequoia Glyotostroboïdes) grow easily in sandy soil, are not susceptible to diseases and have a long lifespan (respectively over 120 and 150 years). Furthermore, the trees have a different growth rate: the Metasequoia grows twice as fast as the Ginko, which creates a dynamic atmosphere in the streetscape.

Figure 31 (right)

Isometry of the internal street. (© Bureau Bas Smets)

The street surface is slightly sloped towards the middle strip where rain water runoff is drained through pipes towards an infiltration buffer that can temporarily store large amounts of water before it infiltrates into the soil. An infiltration buffer is constructed from high density poly ethyleen (HDPE) plactic crates with perforations, covered with a permeable membrane and buried under the street. The system is connected to the entire water management on site and has an overflow to the flood plains in the park area for extreme rainfall events. Figure 32 (left) Nieuw-Zuid

Internal Street. Photo taken November 2019.

Figure 33 (right) Schematic

drawing of the water management system between streets, paved squares and the flood plains in the park.

Figure 34 (right) Section of

the internal street. (© Bureau Bas Smets) 70

Residential Street Residential streets are accessible by car and provide the access point to the underground parking lots beneath the residential buildings. These streets are paved and, just as in the internal street, precipitation runoff is guided along the slightly sloped street surfaces towards the middle of the road where it is drained through pipes and lead towards larger underground infiltration basins with an overflow to the floodplains in the park. The basins are constructed from plastic crates covered with a permeable textile (geotextile) functioning as a filter membrane that allows water to enter the crate while dirt and soil particles are filtered out. The rainwater is retained in the basin while it slowly infiltrates in the soil. Most residential streets are designed for one-way traffic and have vegetated patches and front yards. These patches increase the pervious surface area of the street and equally aid in managing storm water runoff. Additionally by implementing the patches on alternating sides of the street, they function as natural speed bumps since cars have to make small turns. Vegetation was carefully selected based on local climate and native species, resulting in a mix of ornamental fruit trees, flowering Lilacs shrubs and Ferns. This combination of plants exhibits a flowering period from March to June and colours deep red in autumn.

Figure 35 (right)

Isometry of a residential street. (ÂŠ Bureau Bas Smets)

Figure 36 Plan view of the

residential street.

Figure 37 (left) Nieuw-Zuid

residential street. Photo taken in November 2019.

Figure 38 (right) Schematic 72

section of the residential street. (ÂŠ Bureau Bas Smets)

Residential Path Residential paths are intended for pedestrian use and cycling. Their set-up is very different from the streets. A pedestrian and cycling path is separated from the buildings entrance and front yard by a linear bio-swale. Swales are topological depressions that facilitate collection and infiltration of stormwater runoff. The system is similar to a river valley, where excess rainwater is stored and slowly sinks into the ground. When vegetated with plants the system is called a bio-swale (Soorten wadi’s | Gids Duurzame Gebouwen, n.d.). As mentioned earlier, all impervious surfaces such as paved streets and rooftops are connected to the linear bio-swales. The infiltration process is equally beneficial to soil fertility, which enhances vegetation growth and improves biodiversity due to the new ecosystem established in the swale. The selection of species to vegetate the residential streets and paths is aimed at increasing the overall ecological value and biodiversity on site. In the residential paths the vegetation concept is aimed at creating a wild, green and cool environment by a selection of hydrophile species with strong cooling properties. Access to the buildings is provided by small bridges crossing the vegetated swale. To ensure fire safety, residential paths require exceptional car accessibility. Hence, a combination of pervious and impervious pavements has been selected. A grid of two by two meters sets the base for the paths’ design. Two types of pavement with different permeability are chosen. Adjacent to the swale the designers opted for a highly pervious pavement consisting of a perforated concrete base that is subsequently filled up with substrate and allows for grass to grow. The second strip is covered with large concrete tiles of two by two meters.

Figure 39 (right)

Isometry of the Residential path. (© Bureau Bas Smets)

Figure 40 Plan view of the

residential path.

Figure 41 (right) Schematic

drawing of the water management system between green roofs, bio-swales, infiltration basins and the flood plains in the park.

Figure 42 (left) Nieuw-Zuid

residential path. Photo taken in November 2019.

Figure 43 (right) Schemat74

ic section of the Residential path. (© Bureau Bas Smets)

FLOODABLE PARK The linear bio-swales between buildings form a system of green-blue corridors that infiltrate runoff water locally with an overflow to the flood plains in the park, occurring twice a year. These sunken areas are large natural basins that can fill up with excess water runoff in case of heavy precipitation events. The water is collected and gradually infiltrated in the soil. An additional overflow to the Scheldt is provided in case of an extreme storm, predicted once every twenty years. The network of green roofs, pervious pavements, bio-swales, flood plains and overflows prevents other parts of the site and surroundings from being flooded.

Figure 44 (right)

NieuwZuid: manipulated topography forming flood plains in the park. Photo taken in November 2019.

Trees in the park are planted in undulating rows as a reference to the former train tracks and the Scheldt. The tree waves flow, metaphorically speaking, towards the river. The trees were carefully selected based on their characteristics and the location of the site. The team opted for black birch and European aspen, two fast growing species, and pedunculate oak, a slow growing tree. Mixing these native tree species with colourful flowers and herbs suitable for the dry and calcareous soil creates a strong and dynamic atmosphere. On sunny days, the vegetated flood plains form ideal sunbathing areas with their slightly sloped topography. The southern part of the park is elevated and forms an acoustic barrier between the Antwerp Ring Road and the Nieuw-Zuid site.

Figure 45 (left) Nieuw-Zuid

elevated topography forming a sound barrier to block noise from the ring road. Photo taken end November 2019.

Figure 46 (right) Sche-

matic representation of the water management system on the Nieuw-Zuid Site. 76

5.2.3 Technical design requirements For the dimensioning of the linear bio-swales, infiltration basins and floodplains a few criteria must be met. First of all, the buffering and infiltration system is designed based on large precipitation volumes as a result of low intensity rainfall over a longer time span. Subsequently, the drainage capacity is dimensioned for peak flowrates during precipitation events of short duration but high intensity (T20: 230l/s.ha during 15 minutes). At last, organizing the drainage by Striga allows to simplify the water managing system, and reduces the dimensions of the individual elements.

Figure 47 Newly construct-

ed bio-swale. Photo taken in November 2019.

The dimensions are determined per Striga, based on the surface area of impervious surfaces that will be connected to the system (S). This area is then multiplied with the precipitation intensity of a heavy storm (T20: 230l/s.ha during 15 min) which gives the flowrate (Q) that allows to determine the section and slope of each part. Q= S x T20 [l/s]

To determine the required buffer volume of the swales and basins the infiltration flowrate (Qi) is calculated based on the connected impervious surface (S), the envisaged infiltration surface (Si), the infiltration capacity of the soil (I) and the allowed recurring overflow period, in this case (T20).

Based on the obtained infiltration rate and the allowed recurring overflow period of 20 years, the buffer capacity can be found in the table for buffervolumes (Vaes & Berlamont, 2004). (Annex 4) It should be noted that soil samples need to be taken and tested to determine the infiltration capacity of the soil on site. In this specific case the soil has a sandy consistence and which is beneficial for infiltration. In the case of a soil with lower permeability, larger basins are required to store the runoff water due to a lower infiltration rate. In this case, the bio-swales are 4 m wide on top level, have a depth of 80 cm, and a minimal width of 1,6 m on the bottom. The maximum allowed water level is 50 cm. If exceeded, the overflow will be used. The excess rainwater from the rooftops is drained through pipes ending perpendicularly in the swale. Their position is secured by reinforcing the soil with pervious concrete tiles to avoid movement and damage caused by erosion. 78

Figure 48 Perforated con-

cret tiles, both employed as pavement and for securing drainage pipes in the swale. Photos taken in November 2019.

5.2.4 Discussion In this specific case various NBS were combined into a Sustainable Urban Drainage system. These NBS include street trees, green pervious pavements, green roofs, bio-swales, residential green streets and flood plains. This analysis allowed to create factsheets of specific these NBS. They can be found in Chapter 10. The study allows to determine some important aspects for the implementation of NBS. These kinds of large scale projects rely on an integrated approach. In this case the whole site is owned by one proprietor, Triple Living, which facilitates the design process and excecution. Additionally, the client decided to involve the city of Antwerp in the development of the site in the initial stage, which enables the planning process to take place at urban level and react to the cityâ&#x20AC;&#x2122;s challenges by implementing NBS in an early stage. The design process is carried out in different stages and is a collaboration between different planning entities, engineering firms, landscape architecture and architectural offices. Ideally, water management schemes are designed at the scale of the sewer system. However, designing a connected water management scheme for an entire existing urban area is practically challenging. The Nieuw-Zuid site offered an opportunity to create a whole new neighbourhood and implement an integrated nature-inspired management of water flows based on the infiltration of all rainwater on site, without putting additional stress on the urban sewer system. When dealing with nature-based water management of a neighbourhood, importance lays in connecting the different solutions, such as green roofs, bio-swales and flood plains, to ensure site resilience and prevent flooding. The systems require to be specifically designed and dimensioned according to precipitation rate and frequency. The infiltration rate of the soil is equally important. Hence, local climate conditions and site properties are crucial and should be considered. Some other factors are also essential for the design of specific NBS. For instance, vegetation selection is decisive for the performance of multiple NBS such as street trees for air purification, bio-swales and green roofs. Street trees should consist of species that are effective for removing pollutants from the atmosphere. Subsequently, bio-swales require a specific selection of hydrophile species, preferably with high cooling properties. Finally, the vegetation choice for green roofs will equally affect their performance in terms of heat stress reduction and biodiversity. In addition, substrate thickness and soil composition will affect the water storing capacity of the system as it depends on saturation of the soil. The Nieuw-Zuid case highlights some limitations. Due to its large scale, the project cannot be completed in one single stage. Therefore temporary drainage solutions for the swales must be provided until they can be connected to the flood plains in the park area, which will only take place in the last stage. Unfortunately, no monitoring took place or is planned for mapping the performance of the implemented NBS and no additional information is available on this topic. 80

Figure 49 NBS integrated in

Nieuw-Zuid Antwerp.

G REEN RO O FS

B IO - S WA L E S

PER VIO U S PAV EM EN T S

FLO O D PL A INS

ST REE T T REES

S US TA INA B L E URB A N D RA INAGE S Y T E M S

G REEN IN G ST REE T S

CONCLUSION

A changing climate in combination with an expected demographic growth in the Brussels Capital Region, translates into environmental and societal challenges. This gives rise to a growing interest among local authorities and policy makers to encourage the use of design tools and strategies for building resilience for climate change and improving environmental impact of urban projects. This research aimed to identify and explore Nature-Based Solutions (NBS) for ecologically sensitive urban regeneration and their potential to respond to societal and environmental challenges as supporting design tools for architecture and urban planning to enhance Brusselsâ&#x20AC;&#x2122; urban resilience. As a result, a comprehensive typological classification of NBS is proposed and factsheets were created of multiple NBS that were investigated by means of two in-depth case studies. These tools gather and promote knowledge on NBS and their effectiveness for addressing urban challenges, while narrowing the gap between theory and practice. Relevant parameters for categorising NBS were identified through an extensive literature study and comparative analysis of existing tools and classification schemes. To ensure a focussed selection of NBS and case studies, Brusselsâ&#x20AC;&#x2122; urban challenges were investigated. Consequently, a framework for a common typological classification of NBS was established including parameters for scale, degree of intervention, estimated required investment and maintenance cost, and effectiveness regarding possible (co-) benefits of NBS. These benefits have been clustered under three core themes: social, economic and environmental, referring to ecosystem services and societal challenges. The classification is displayed in the form of a visual database facilitating a comprehensive overview of 69 NBS and their parameters, in order to facilitate comparison. To explore the full potential of implementing NBS in practice, two case studies have been investigated. Through an in-depth analysis, it could be concluded that in order for NBS to address urban challenges, an integrated approach and planning on municipal or higher authority level is required to maximise effectiveness. Additionally, local climate conditions and site specifications are crucial and each NBS should be carefully designed. Although an overview of NBS and their effectiveness in terms of (co-) benefits is a valuable tool, it is worth noting that performance may vary with scale, substrate and vegetation selection, as each species have unique properties. 84

The research field of NBS is growing in Europe and there are many opportunities for further investigation. Closer examination on multiple aspects of NBS is still necessary as only a general framework and classification is provided. This inventory is a work in progress and the tools certainly need to be tested in practice and further developed. Future research opportunities entail adding to the list of NBS and further exploring their applicability and performance in practice. This could be done through in depth theoretical research or monitoring innovative projects in urban settings. It should be noted that during this research, bias should be avoided, as to not only focus on the positive effects, but also possible negative implications. All relevant social, environmental and economic effects should be measured ideally. An integrated approach is thus not only applicable for NBS design and implementation, but also for monitoring and NBS research. Up until now, little research is available on the implementation of NBS and monitoring of actual performance and assessment of the (co-) benefits provided. Thus there is definitely incentive in investigating the impacts of NBS and methods for the assessment of (co-) benefits.

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Urban GreenUP. (2017). https://www.urbangreenup.eu/

79.

URBAN GreenUP. (2018). Urban GreenUp: D1.1 NBS Catalogue. CARTIF Technology Centre.

80.

Urban Nature Atlas. (2017). NATURVATION. https://naturvation.eu/atlas

81.

U.S. Environmental Protection Agency. (2008). Reducting Urban Heat Islands: Compendium of Strategies. In Urban Heat Island Basics. https://www.epa.gov/sites/production/files/2017-05/documents/reducing_urban_heat_islands_ch_1.pdf

82.

Vaes, G., & Berlamont, J. (2004). Het ontwerp van bronmaat-regelen gebaseerd op continue langetermijnsimulaties. Water. (p. 13). K.U. Leuven.

83.

Velasco, E., Roth, M., Norford, L., & Molina, L. T. (2016). Does urban vegetation enhance carbon sequestration? Landscape and Urban Planning, 148, 99–107. https:// doi.org/10.1016/j.landurbplan.2015.12.003

84.

Vranckx, S., Brabers, L., Hendrix, R., Nocker, L. D., & Janssen, S. (2016). Uitwerken van een aanpak om vegetatiestructuren in te zetten met het oog op de verbetering van het stedelijk leefklimaat Literatuuroverzicht (p. 68). VITO.

85.

Water. (2018). Antwerpen Morgen. Retrieved 18 November 2019 https://www.antwerpenmorgen.be/toekomstvisies/water/over

ANNE X

8.3 Brussels' urban challenges Annex 1 Map of Flanders indicating the number of heat wave days (Hitte-eilanden in steden, 2019).

8.5 In-depth case studies Annex 2 Vulnerability of Amsterdam regarding urban pluvial flooding illustrated with critical areas (Bottle-

necks) ranging from extremely urgent (red) to very urgent (orange) and urgent (yellow) (Amsterdam Rainproof, 2017).

Annex 3 Schematic drawing of zones vulnerable for flooding in the proximity of Antwerp. Adapted from

(Sechhi & Viganรณ, 2012).

Annex 4 Required buffervolumes based on the maximal infiltration flowrate and reccuring period of extreme

percipitation over a time span of 10 minutes. (Vaes & Berlamont, 2004)

100

DATABASE

101

NATURE-BASED SOLUTIONS

DATABASE

Building Scale Measures Green Roofs

Extensive

€

Semi-Intensive

€€

Intensive

€€

B|U

€

B|U

€€

€

€€

Smarrt Blue-Green Roofs Extensive Semi-Intensive Blue Roofs Cool Roofs Green Walls

Ground Connected Green Facade Independent Green Facade Planter Green Facade

Evergreen Hedge

€

Deciduous Hedge

€

Vegetated Fence

€

Re-naturing Gardens

Green Measures for Public Space Connecting Green Spaces Green Shade Structures Urban Farming

N|U Climate-Smart Greenhouses Urban Orchards

Urban Parks & Forests

Bio-Filter Areas

102

€€

N|U

Community Composting

B|S|N|U

€

Small Scale Urban Livestock

B|S|N|U

€

Residential Parks

N|U

Deciduous Forests

U|R

Coniferous Forests

U|R

Mixed Forests

U|R U

€€

scale B = building S = street N = neighboorhood U = urban R = region

E N V I R O N M E N TA L

degree of intervention minimal intervention & protection of exisiting ecosystems low impact intervetion & novel management approaches creating & managing new ecosystems

investment & maintenance cost € €€

(co-) benefits no effect

= low cost

excellent performance

= medium cost

€€€ = high cost

S OC I A L

negative effect positive effect, impact unknown

E CONOM I C

** **

When implemented in a street canyon ( = narrow heavy traffic street) the NBS reduces street ventilation, which has a negative impact on air quality.

103

NATURE-BASED SOLUTIONS

DATABASE

Measures for Water Bodies and Drainage Restoring Water Bodies

U|R

Re-naturing Water Bodies

S|N|U|R

€€€

€€

Bio-swales

S|N

€

Rain Gardens

S|N

€

Flood Plains

U|R

€

Floating Gardens

Sustainable Urban Drainage Systems (SUDs)

N|U|R

Pervious Pavements

Hard Drainage Pavement

S|N|U

€

Green Pavement

S|N|U

€

B|S|N|U

€

B|S

€

Permeable Concrete

S|N|U

€

Porous Asphalt

S|N|U

€

€€

Single Tree (>12m)

S|N|U

€

Single Tree (6m-12m)

S|N|U

€

Single Tree (<12m)

S|N|U

€

Multiple Trees (>12m)

S|N|U

€

Multiple Trees (6m-12m)

S|N|U

€

Multiple Trees (<12m)

S|N|U

€

Vegetated Parklets

€€

Cycle and pedestrian green route

€

Green residential street

Green two-way street with front lawns

Vegetated Grid Pave Wood Chips

Measures for Linear Grey Infrastrucutre Green Noise Barriers Street Trees

Greening Streets

104

scale B = building S = street N = neighboorhood U = urban R = region

E N V I R O N M E N TA L

degree of intervention minimal intervention & protection of exisiting ecosystems low impact intervetion & novel management approaches creating & managing new ecosystems

investment & maintenance cost € €€

(co-) benefits no effect

= low cost

excellent performance

= medium cost

€€€ = high cost

S OC I A L

negative effect positive effect, impact unknown

E CONOM I C

** ** ** ** ** **

When implemented in a street canyon ( = narrow heavy traffic street) the NBS reduces street ventilation, which has a negative impact on air quality.

105

NATURE-BASED SOLUTIONS

DATABASE

Measures for Linear Grey Infrastrucutre Greening Streets

Green-blue one-way street

Green-blue two-way street

Green-blue two-way street with central reservation and parking Green-blue two-way street with central swales Green tree lane with front yards Green-blue wide street with water element Green roundabout with multiple trees

S S S S S

Green crossing with adult trees

Green car-free neighborhood

Green tram infrastructure

Green residential streets

S|N

Measures for Natural Urban Areas Natural Herritage Protection Wastewater Treatment Green Fields

106

N|U|R

Natural Wetland

N|U

Electro Wetland

N|U

Grass Fields

U|R

Flower Beds

U|R

Meadows

U|R

Tall Herb Vegetation

U|R

Heath

U|R

Agrarian

U|R

€€

scale B = building S = street N = neighboorhood U = urban R = region

E N V I R O N M E N TA L

degree of intervention minimal intervention & protection of exisiting ecosystems low impact intervetion & novel management approaches creating & managing new ecosystems

investment & maintenance cost € €€

(co-) benefits no effect

= low cost

excellent performance

= medium cost

€€€ = high cost

S OC I A L

negative effect positive effect, impact unknown

E CONOM I C

** ** **

When implemented in a street canyon ( = narrow heavy traffic street) the NBS reduces street ventilation, which has a negative impact on air quality.

107

108

FACTSHEETS

109

BUILDING SCALE MEASURES

SMART BLUE-GREEN ROOFS DESCRIPTION

B | U

€ - €€

Space on ground level is scarce in many metropolitan areas. Urban rooftops collectively form a large unused area with great potential for climate adaptation. The smart blue-green roof system is based on water storage with a capillary irrigation system. Percipitation is captured and stored in a specific layer beneath the substrate and vegetation, equipped with an integrated fibre technology for capillary irrigation. Water travels up and is evenly distributed for absorption, making that the plants have permanent access to water and nutrients. The roofs are equipped with smart sensors and automatically controlled valves. Data collected from sensors measuring the water level in the sewer system, on the roofs and in the soil combined with accurate weather forecasts allows to determine the exact amount of water to be retained or discharged when suitable. Linking a series of blue-green roofs with each other establishes a large scale smart network for rain water management to prevent urban pluvial flooding. The permanent water supply equally increases the green roofs’ performance regardging Urban Heat Island mitigation by providing natural cooling through evaporation and evapotranspiration.

INVESTMENT & MAINTENANCE The roof system costs about € 60/m² in case of an exensive covering with substrate thickness 4 cm and Sedum vegetation. However, this price does not include the smart sensors and valves nor placement. The price will vary with the selection of species and substrate. Maintenance varies with vegetation selection. In the case of moss and sedum, no additionall irrigation is required. In periods of drought it suffices supply the storage layer with tap water. Intensively vegetated roofs might require additional irrigation and nutrient treatments.

TECHNICAL DESIGN

Smartroof 2.0, Amsterdam

REFERENCES RESILIO: https://resilio.amsterdam/ Smartroof 2.0: www.projectsmartroof.nl

NOTES

• This NBS should be planned on municipal level or higher to maximize effectiveness, since data collection from public sewers and and weather forcasts is involved. • Potential for participatory planning with concerned parties and inhabitants. • When freezing temperatures are forecasted all stored water is discharged to prevent damage.

( 1 ) Vegetation: should be adapted to local climate conditions and species • extensive system: moss and sedum • semi-intensive system: moss, secculents, herbs, grasses, ferns, shrubs ( 2 ) Substrate: mixture of shale, pumice, lava rock, crushed bricks, clay, and compost • extensive system: 4 cm • semi-intensive system: 8 cm When saturated, the substrate itself can store between 32-150 l/m² of rainwater. ( 3 ) Filter membrane + integrated fiber technology: permeable geotextile + rockwool cones (1/m²) ( 4 ) Water storage: lightweight crate system with a height of 85 mm and capacity of 80 l/m² ( 5 ) Root repellent waterproofing: impervious bitumen or plastic cover ( 6 ) Roof structure: needs to be able to bear the additional load of the nature-based system ( 7 ) Automatic valve for smart flow control ( 8 ) Exisiting drainage system W E I G HT Dry weight: 90 kg / m² Saturated weight: >170 kg / m²

(7)

(1) vegetation

(2) substrate (3) filter membrane (8)

(4) water storage with smar

(5) root & water repellent c

(6) roof strtucture with exis

110

BUILDING SCALE MEASURES

EXTENSIVE GREEN ROOFS DESCRIPTION

€

Space on ground level is scarce in many metropolitan areas. Urban rooftops collectively form a large unused area with great potential for climate adaptation. The extensive green roof systems is relatively lightweight and usually does not entail much maintenance. It can be installed on both flat and sloped roof structures up to 45 °. The substrate thickness between 4 and 15 cm accommodates vegetation ranging from moss to succulents and other herbaceous species. The low minimum weight of the extensive green roof (60 kg/m² in saturated state) makes it a feasible option for both new and renovated constructions. An extensive green roof will perform as a rainwater buffer, allowing the substrate to saturate and store rainwater (32-150 l/m²). The vegetation absorbs a part of the water and another part evaporates and cools the air, potentially reducing the urban heat island effect (UHI). Additionally, the green layer prevents the roof from heating up in summer and adds an extra layer of thermal and acoustic insulation to the building.

Lightweight green roof in Grimbergen

KLBS Gent www.canopy-greenroofs.be/blogPost/ sedumdak-klbs-gent LWGR Grimbergen www.ecoworks.be

INVESTMENT & MAINTENANCE

NOTES

The extensive green roof costs € 75/m².

• In Belgium, many municipalities subsidize the installation of green roof systems.

Maintenance varies with vegetation selection, but in general an extensive green roof requires to be fertilized once a year, which comes down to a cost of €5/m². Usually no additional irrigation is needed.

• When installed on a sloped roof structure, an additional mesh layer is required on top of the substrate to secure the system and prevent it from slipping. • A structural analysis should be performed to define whether the existing roof structure can bear the additional load.

TECHNICAL DESIGN

( 1 ) Vegetation: should be adapted to local climate conditions and species • extensive system: moss, secculents and herbs. ( 2 ) Substrate: mixture of shale, pumice, lava rock, crushed bricks, clay, and compost thickness: 4 - 15 cm water storing capacity: 32 - 150 l/m² ( 3 ) Filter membrane: geotextile ( 4 ) Drainage layer: HDPE 25 mm ( 5 ) Protection mat with absorption properties: felt fabric ( 6 ) Root repellent waterproofing ( 7 ) Roof structure: flat roof or sloped up to 45° W E IG HT Dry weight: 60 kg / m² Saturated weight: >90 kg / m²

(1) (2) (3) (4) (5) (6) (7)

111

BUILDING SCALE MEASURES

SEMI-INTENSIVE GREEN ROOFS DESCRIPTION

€€

Space on ground level is scarce in many metropolitan areas. Urban rooftops collectively form a large unused area with great potential for climate adaptation. The semi-intensive green roof system supports a variety of vegetation ranging from secculents and herbs to tall grasses. The system is relatively low maintenance but plant selection and roof design strongly affect this aspect. The larger substrate thickness increases the overall performance of the roof system in terms of water retention, cooling, carbon sequestration and sound retention. The cooling performance of the green roof system can help address the UHI and heat stress. The green roof performs as a rainwater buffer, allowing the substrate to saturate and store rain water (32-150 l/m²). The vegetation absorbs a part of the water cools the atmosphere through evapotranspiration and another part is evaporated from the soil. Additionally, the created ecosystem consisting of various species aids in improving urban biodiversity.

REFERENCES

LAAD Heverlee www.canopy-greenroofs.be/blogPost/ semi-intensief-groendak-laad-heverlee

INVESTMENT & MAINTENANCE

NOTES

The semi-intensive green roof costs approximately € 250/m², depending on the substrate thickness and choice of vegetation.

• In Belgium, many municipalities subsidize the installation of green roof systems.

Maintenance varies with vegetation selection, but in general the semi-intensive green roof requires to be fertilized once a year, which comes down to a cost of €5/m². Additional irrigation may be needed in warm periods.

• A structural analysis should be performed to define whether the existing roof structure can bear the additional load.

TECHNICAL DESIGN ( 1 ) Vegetation: should be adapted to local climate conditions and species • semi- intensive system: moss, secculents, herbs and tall grasses. ( 2 ) Substrate: mixture of shale, pumice, lava rock, crushed bricks, clay, and compost thickness: 15 - 20 cm water storing capacity: 40 - 150 l/m² ( 3 ) Filter membrane: geotextile ( 4 ) Drainage layer: HDPE 40 mm ( 5 ) Protection mat with absorption properties: felt fabric ( 6 ) Root repellent waterproofing (1) ( 7 ) Roof structure: flat roof W E IG HT Dry weight: 90 kg / m² Saturated weight: >150 kg / m²

(2)

(3) (4) (5) (6) (7)

112

BUILDING SCALE MEASURES

INTENSIVE GREEN ROOFS DESCRIPTION

€€€

Space on ground level is scarce in many metropolitan areas. Urban rooftops collectively form a large unused area with great potential for climate adaptation. The intensive green roof is the most advanced type of green roof supporting a broad range of species from herbs to small size trees. The minimum substrate depth for an intensive green roof system is 20 cm but can go up to over one meter and mostly depends on the type of vegetation. Roof gardens and agriculture are equally intensive green roof systems and entail higher nutrient applications and intensive maintenance. The elevated substrate thickness increases the overall performance of the roof system in terms of water retention, cooling, carbon sequestration and sound retention. The cooling performance of the green roof system can help address the UHI and heat stress. The green roof performs as a rainwater buffer, allowing the substrate to saturate and store rain water (70-150 l/m²). The vegetation absorbs a part of the water cools the atmosphere through evapotranspiration and another part is evaporated from the soil. Additionally, the created ecosystem consisting of various species aids in improving urban biodiversity.

EU Parliament -Wilfried Martens www.ecoworks.be

INVESTMENT & MAINTENANCE

NOTES

The intensive green roof costs approximately € 350/m², depending on the substrate thickness and choice of vegetation.

• In Belgium, many municipalities subsidize the installation of green roof systems.

The system requires advanced irrigation and professional maintenance. Plant selection and roof design strongly affect the amount of maintenance and irrigation required, therefore the maintenance price varies depending on the project.

REFERENCES

• A structural analysis should be performed to define whether the existing roof structure can bear the additional load.

TECHNICAL DESIGN ( 1 ) Vegetation: should be adapted to local climate conditions and species • intensive system: moss, secculents, herbs, tall grasses, flowers, small trees ( 2 ) Substrate: mixture of shale, pumice, lava rock, crushed bricks, clay, and compost thickness: 15 - 20 cm water storing capacity: 70 - 150 l/m² ( 3 ) Filter membrane: geotextile ( 4 ) Drainage layer: HDPE 60 mm ( 5 ) Protection mat with absorption properties: felt fabric ( 6 ) Root repellent waterproofing (1) ( 7 ) Roof structure: flat roof W E IG HT Varies too much per case

(2)

(3) (4) (5) (6) (7)

113

G R E E N M E A S U R E S F O R P U B L I C S PA C E

GREEN RESIDENTIAL STREETS DESCRIPTION

S | N

Greening streets is a key action in urban regeneration plans that creates mutually beneficial relationships between city dwellers and their environments. Including vegetation in the streetscape increases livability and promotes well-being of residents. Green residential streets are one-way traffic streets with vegetated patches, including front lawns and street gardens. By alternating the positioning of the of the street gardens, they can simultaneously function as natural speed tresholds, while improving the aesthetics of a neighbourhood. The street's set-up encourages pedestrian and bicicle access, as there is no physical division between the street and the sidewalk. The streets are paved and precipitation runoff is guided along the slightly sloped street surfaces towards the middle of the road where it is drained through pipes and lead towards larger underground infiltration basins. The basins are constructed from plastic crates covered with a permeable layer (geotextile) functioning as a filter membrane that allows water to enter the crate while dirt and soil particles are filtered out. The rainwater is retained in the basin while it slowly infiltrates in the soil. The vegetated patches equally aid in managing storm water runoff, due to the soil's quality to store and infiltrate water. Nieuw-Zuid Antwerpen

INVESTMENT & MAINTENANCE

REFERENCES

Maintenance of green residential streets consists of keeping the street clean and managing the vegetated patches through weed control, reseeding of bare areas, and clearing of debris and accumulated sediment.

Nieuw-Zuid Antwerpen See Case 02 in this thesis.

TECHNICAL DESIGN To ensure that surface runoff water is drained correctly, the street surface is sloped towards the gutter. Providing drainage in the center of the street, prevents walkways and buildings from being flooded. Vegetation is carefully selected based local climate, native species and desired performance. For instance, while all plants are benefical for cooling, some have higher evapotranspiration rates and will be more effective. The same applies for removing air pollution. Trees like the Ginko Biloba and Metasequoia Glyotostroboïdes perform well in this regard.

114

MEASURES FOR LINEAR GREY INFRASTRUCTURE

S I N G L E S T R E E T T R E E S ( 6m - 12m ) DESCRIPTION

S|N|U

€

https://streetandgarden.com/project/ flinders-street/

**It should be noted that trees can have a negative impact on air quality when they are implemented in a high traffic narrow street, or street canyon. In this case they obstruct ventilation flow and keep pollutants in the street.

INVESTMENT & MAINTENANCE The price of trees varies a lot depending on the species. **

REFERENCES

Nieuw-Zuid Antwerpen See Case 02 in this thesis.

Maintenance of street trees consists of clearing debris and accumulated sediment.

TECHNICAL DESIGN The implementation of street trees is relatively straightforward. The trees are planted in pits in the streetscape. It is important that the roots have sufficient space to grow. Vegetation should be carefully selected based on local climate, native species and desired performance. For instance, while all trees are benefical for cooling, some have higher evapotranspiration rates and will be more effective. The same applies for removing air pollution. Trees like the Ginko Biloba and Metasequoia Glyotostroboïdes perform well in this regard.

115

M E A S U R E S F O R WAT E R B O D I E S A N D D R A I N A G E

( B I O - ) S WA L E S DESCRIPTION

S | N

€

Swales are linear topological depressions facilitating collection and infiltration of stormwater runoff. The system is similar to a river valley, where excess rainwater is collected and slowly sinks into the ground. When vegetated with plants the system is called a bioswale. Two main types can be distinguished: an infiltration swale and a buffer swale. An infiltration swale consists of a shallow infiltration basin often combined with an underground permeable filter bed consisting of coarse grained soil. The filter layer functions as an additional water storage and filters out pollutants, which is beneficial for soil fertility and enhances vegetation growth. Hence, it improves biodiversity due to the new ecosystem established in the swale.

In case of an impermeable soil (infiltration flowrate <1mm/h) or due to environmental issues (risk of soil or groundwater contamination) a buffer swale is chosen. The system is similar to an infiltration swale, but instead of infiltrating the rainwater runoff the soil, it is drained through pipes underneath the swale. Optionally the pipes can be places under a filter bed.

Nieuw-Zuid Antwerpen See Case 02 in this thesis.

INVESTMENT & MAINTENANCE

NOTES

The initial cost lays between €10-€60/m³, depending on the plant selection.

• The groundwater level should be at least 1 m under the lowest point of the swale and the soil may not be polluted to avoid ground water contamination.

Bio-swales require moderate maintenance which costs about €1 - €5/m². Maintenance of a dense and healthy vegetated cover consists of weed control, reseeding of bare areas, and clearing of debris and accumulated sediment.

REFERENCES

Best Management Practices https://www.guidebatimentdurable.brussels/fr/types-de-noues.html?IDC=9008

• The soil on site need to be tested to determine the infiltration capacity in order to chose the correct type of swale.

TECHNICAL DESIGN The dimensioning of the required buffer volume is quite technical and requires a professional approach. Parametes to consider in the equation: • Surface of the impervious area that is drained into the swale • Desired infiltration surface • Infiltration capacity of the soil • The allowed recurring overflow period For detailed information, please consult (Vaes & Berlamont, 2004). The vegetation is preferably a selection of native hydrophile species with strong cooling properties.

Infiltration Swale

116

M E A S U R E S F O R WAT E R B O D I E S A N D D R A I N A G E

FLOOD PL AINS DESCRIPTION

U | R

Flood plains are sunken areas forming large natural basins covered with grass that can fill up with excess water runoff in case of heavy precipitation events. The rain water is temporarily stored and gradually infiltrated in the soil. The flood plains are often combined with an underground permeable filter bed consisting of coarse grained soil. The filter functions as an additional water storage and filters out pollutants, which is beneficial for soil fertility and enhances vegetation growth.

€

Implementing flood plains in urban areas, for instance in a park, increases resilience and aids in preventing urban pluvial flooding. Combining the nature-based solution with other solutions such as bio-swales and green roofs can be part of a water management plan for a whole urban area or neighbourhood.

REFERENCES

Nieuw-Zuid Antwerpen See Case 02 in this thesis.

INVESTMENT & MAINTENANCE

NOTES

The initial cost lays between €15-€25/m².

• The groundwater level should be at least 1 m under the lowest point of the flood plain and the soil may not be polluted to avoid ground water contamination.

Maintenance of a dense, healthy vegetated cover consists of periodic mowing, weed control, reseeding of bare areas, and clearing of debris and accumulated sediment.

• The soil on site need to be tested to determine the infiltration capacity and whether infiltration is possible at all.

117

M E A S U R E S I N WAT E R B O D I E S A N D D R A I N A G E

G R E E N PAV E M E N T S DESCRIPTION

S | N |U

€

Urban areas consist of an increasing percentage of impervious surfaces and urban drainage systems are often not designed to support the increasingly heavy precipitation events. This causes an imbalance in the hydrological system where precipitation cannot be stored nor infiltrated in the soil with the risk of urban pluvial flooding. Increasing the amount of green space and pervious surfaces in urban areas reduces surface water runoff as well as water scarcity and increases rainwater retention, infiltration and evaporation. Green pavements exist in various forms, but usually consist of a perforated concrete base. They are an excellent solution for surfaces requiring permeability and stability. The tiles protects the soil from erosion without while preserving a natural appearance. The perforations are filled with substrate with seeds, which in time will transform into a green cover.

Nieuw-Zuid Antwerpen

Nieuw-Zuid Antwerpen See Case 02 in this thesis.

INVESTMENT & MAINTENANCE

NOTES

The initial cost lays between €60 -€100/m², depending on the type of tile and the transportation distance from the contractor.

• These types of pavement are often selected to create paths or access to buildings for the fire brigade.

Maintenance of green pavements consists of weed control, reseeding of bare areas, and clearing of debris and accumulated sediment.

TECHNICAL DESIGN From top to bottom the set-up consists of: ( 1 ) Perforated concrete tiles filled with soil and grown with grass. ( 2 ) Root zone consisting of stabilized sand soil ( 3 ) Structural layer consisting of coarse grained soil, such as gravel. ( 4 ) Existing soil One tile measures approximately 40 cm x 60 cm and weighs almost 54 kg.

(1) (2) (3)

(4)

118

Newly placed pervious pavement. Nieuw-Zuid Antwerpen

M E A S U R E S I N WAT E R B O D I E S A N D D R A I N A G E

S U S TA I N A B L E U R B A N DRAINAGE SYSTEMS (SUD'S) DESCRIPTION

N|U|R

A sustainable urban drainage system (SUD) is a collection of water management practices that aims to align modern drainage systems with natural water processes. SUD's can be achieved by connecting various NBS for a sustainable water management that does not solely rely on urban sewers for drainage and reduces sewer overflows. For instance, combined elements such as green and blue roofs with pervious pavements, bio-swales, infiltration basins and flood plains or constructed wetlands can be considered a SUD. Other combinations are equally possible. Since SUD's consist of various natural surface solutions that include vegetation and pervious surfaces, they result in additional benefits besides a desirable water balance. The interconnectedness of the systems allow for the establishment of large ecosystems with a great potential biodiversity. Vegetation also has the ability to filter out contaminants from surface water and therefore also contributes to improving water quality. Additionally, implementing natural water bodies and vegetation in urban areas can aid to reduce the Urban Heat Island, since cooling will occur due to a combination of evaporation and evapotranspiration. SUD's increase the amount of accessible green space and enhance the environmental quality of neighbourhoods or urban spaces. Ultimately, they can contribute to health and well being of residents with the multiple benefits they provide.

INVESTMENT & MAINTENANCE Usually SUD's components are on or near the surface and most can be managed using landscape maintenance techniques. Additionally, sensors and control systems could be implemented to measure water flows and increase effectiveness.

Nieuw-Zuid Antwerpen

ÂŠ Marie-Caroline Kawa REFERENCES

Nieuw-Zuid Antwerpen See Case 02 in this thesis. Many examples https://www.susdrain.org/

TECHNICAL DESIGN The design of SUD's should consider local climate conditions, urban challenges and site specific properties such as the soil's infiltration rate. Since SUD's are integrated solutions, that can be composed of a large variety of NBS, the techinical design requirements for the individual solutions should be considered. In order for the SUD to respond to local climate conditions, the whole system of NBS requires coordinated dimensioning according to local percipitation rates, infiltration capacities, etc.. These calculations are quite technical and require a professional approach. Vegetation selection will equally have impac on the performance of the system. A selection of hydrophile species with high cooling properties is preferable.

119