Integrated Stormwater Management for the Water-Sensitive Retrofit of Cites

Transcription

1 Modern Environmental Science and Engineering (ISSN ) December 2015, Volume 1, No. 6, pp Doi: /mese( )/ /002 Academic Star Publishing Company, Integrated Stormwater Management for the Water-Sensitive Retrofit of Cites Elke Kruse Hafen City University Hamburg (HCU), Germany Abstract: The consequences of climate change present cities across the globe with new challenges. The increased frequency of heavy rainfall events in particular, leads to combined sewer overflows and urban flooding, which induces immense damage and thus results in substantial costs in the urban area. Consequently, numerous local administrations are developing concepts to adapt their cities through the implementation of structural measures. However, only few simultaneously utilize the transformation of their drainage system as an opportunity to revitalize the existing urban fabric. Investment resources, which might otherwise go towards the renovation of the existing combined sewer system or road construction, could be used to make the city more liveable by implementing a network of blue or green elements and providing residents with a new variety of open spaces. Proper foresight is required to adapt to the consequences of climate change in cities around the world. The following article describes how this can be achieved. Key words: climate change, adaptation, stormwater management, water-sensitive urban development, open space, quality of life, green infrastructure 1. Introduction Dense urban areas are especially sensitive to the consequences of climate change because of their high density and high ratio of impervious surfaces [1]. In future, these areas should be retrofitted in a water-sensitive way. High building density, a high ratio of impervious surfaces and, typically, small plot sizes offer limited space for the management of stormwater on individual plots [2]. For this reason, public open spaces have to become the focus of local administrations. Public open spaces can be retrofitted to both protect dense urban areas from flooding and reduce combined sewer overflows. An analysis of this topic forms the core of the dissertation upon which this article is based [3]. Corresponding author: Elke Kruse, Dr.-Ing., research areas/interests: integrated stormwater management. elke.kruse@hcu-hamburg.de. 2. Ideal Approach: Integrated Stormwater Management (ISWM) In order to retrofit the municipality in a water-sensitive way, an integrated city-wide perspective is required to develop interdisciplinary solutions for dealing with stormwater. This includes not only drainage engineering topics, but also urban, landscape and transportation planning issues. Solutions should not be limited to technical measures, e.g., the implementation of sewers with storage capacity and overflow; rather, the entire network of public open spaces should be kept in focus. Only then can the retrofitting of the urban drainage system be understood as a chance to enhance the existing urban fabric. This requires the adoption of Integrated Stormwater Management (ISWM) 1, understood as the ideal 1 Although the term Integrated Stormwater Management has already been used by experts [4], [Web-1], an official definition

2 Integrated Stormwater Management for the Water-Sensitive Retrofit of Cites 287 approach, which relies on an interdisciplinary planning culture. ISWM synchronises water management planning with urban, landscape and transportation planning, i.e., all concerned planning professionals in a municipality work together to develop planning strategies and design guidelines for water-sensitive urban development. Various fields of action play a roll: legislation, the development of sustainable urban drainage measures, the adaptation of planning instruments, financing and public relations (see Fig. 1) [7 8]. The aim of this article is to make planning and design recommendations for the implementation of Integrated Stormwater Management (ISWM). In the following, the strategies and working steps of three international reference cities, which have already implemented advanced adaptation concepts, will be analysed. The analysis is based on the evaluation of corresponding plans, interviews conducted with local experts and site visits to implemented pilot projects. At the end of this article, a practice-oriented guidance for municipalities will be presented based on the results. 3. Learning from New York City, Rotterdam and Singapore New York City, Rotterdam and Singapore are among the cities that have already embarked on innovative paths toward the renewal of their urban sewer or drainage systems. They have developed city-wide integrated approaches to stormwater management, which include public open space. Funding for drainage system renovations was partially reallocated and used for the water-sensitive design of streets and open spaces. The approaches of these cities serve as exemplary models and were thus evaluated for this study. The following research question does not exist. For this reason, the term will be defined within this article. The definition used by HCU is based on findings from different research projects, particularly SWITCH Managing Water for the City of the Future [5], Leitfaden Dachbegrünung für Kommunen [6] and RISA Rain InfraStructure Adaptation in Hamburg [Web-2] [8]. resulted: What design strategies, planning tools and procedures did municipalities employ to achieve their objective? 3.1 New York City From Grey to Permanent Green New York City lies directly on the Atlantic and has a growing population of over eight million inhabitants. Because of its coastal location and outdated sewer system, the city is highly vulnerable to the impacts of climate change [9]. The aim of the municipal government is, therefore, to make the city both more resilient to extreme weather events as well as to improve the quality of life for its growing population. The planyc 2030, published in 2007, acts like an integrated planning vision, which includes the greening of the urban area as one of the guiding principles. The aboveground green infrastructure is meant to supplement the underground sewer system. Green infrastructure includes different, more natural measures, which are primarily used for the infiltration and evaporation of stormwater runoff. These include roadside vegetated swales, the so-called Greenstreets, as well as the infiltration of stormwater in tree pits, in green areas and parks. The connection between ecology and economy, as well as the involvement of the public in the concretization of the plan and the implementation of projects, are central guidelines of planyc [10]. The City Council started by performing a comprehensive cost-benefit analysis, which is summarised in the Sustainable Stormwater Management Plan (SSMP). The plan compares the cost of a conventional sewer system with more natural methods of infiltration, retention or storage of stormwater. The plan is the product of interdepartmental collaboration, the so-called Best Management Practices Task Force, which included the Departments of Environmental Protection, Transportation, Parks & Recreation, Buildings and City Planning [11].

3 288 Integrated Stormwater Management for the Water-Sensitive Retrofit of Cites Fig. 1 Fields of Action for Integrated Stormwater Management (Source: Author). The first step of the process was the identification of catchment areas in the city that urgently needed retrofitting. These areas are often affected by local flooding or have polluted water bodies as a result of combined sewer overflows. This applies primarily to areas in Queens and Brooklyn, but to some extent also in the Bronx. In the second step, a city-wide analysis of the soil composition, infiltration and storage capacity was performed. In addition, in 2010 the City Council adopted the NYC Green Infrastructure Plan, which functions as a kind of implementation strategy for water-sensitive retrofits [12]. Because the implementation of water-sensitive retrofits on private lands in built-up areas proved difficult, the City concentrated on public land, including the so-called public rights-of-way. These areas make up approximately 30% of the catchments concerned. Here, the implementation of green infrastructure is relatively easy and cost-effective to achieve when included at the start of road reconstruction or maintenance. A Street Design Manual (2013) presents the range of possible retrofits that are appropriate depending on road typology and site conditions [13]. The size and design of Greenstreets varies depending on local site conditions and space availability. To maximize cost efficiency, installations are dimensioned to capture 90% of annual precipitation. With the help of special sub-bases the infiltration potential of the soil is improved. Excess water is directed via overflows into the sewer system [Int.-1]. Maintenance is an important topic in the implementation concept when it comes to ensuring the long-term effectiveness of the infiltration bed. For cost reasons, the local authority cannot take on the on-going comprehensive maintenance of Greenstreets, so private partners and volunteers are found. For this purpose, maintenance agreements with residents are finalised and necessary information about maintenance procedures is shared in the context of informational meetings. Fig. 2 A completed Greenstreet in Brooklyn (left) and the overflow into the sewer system (right). The Greenstreet was installed as a retrofit in an existing urban quarter. (Source: Author)

4 Integrated Stormwater Management for the Water-Sensitive Retrofit of Cites Rotterdam From Grey to Temporary Blue The Dutch harbour city of Rotterdam is the second largest city in the Netherlands. The majority of the city lies below sea level. Due to the high groundwater level and the City s dense urban structure, stormwater infiltration is often not possible. Thus, Rotterdam is one of the areas in the world most vulnerable to flooding [14]. The effects of climate change are already being felt today in the form of extreme rainfall events. In future, the city will be confronted with increasingly heavy rainfall, summer droughts, an overall increase in annual precipitation as well as rising sea levels. In 2005, Rotterdam addressed these challenges as part of the second international Architecture Biennale with the topic The Flood. The Biennale presented the opportunity to examine a topic, which has traditionally been considered technical and engineering-oriented, from an interdisciplinary perspective in order to develop innovative ideas and explore new approaches. Instead of focusing on the technical solution to a problem, the search for appropriate urban planning strategies was the basis for further discussion [Int.-2]. As background for the assessment, a calculation was performed to determine the water storage capacity needed to protect the city from uncontrolled urban flooding up to the year 2050 [Int.-3]. The necessity to expand storage capacity simultaneously presented the opportunity for the re-imagination of the former industrial city. Existing urban quarters were to be strategically upgraded to counteract the current decline in urban population. Inspired by the Biennale, these interdisciplinary considerations were incorporated in the Waterplan 2, which was published in Measures in the Waterplan are closely tied to the urban development of Rotterdam and are similarly based on a timeline up to the year Water plays a central role. Due to space limitations, high-density urban quarters in particular require innovative solutions [15]. The ideas and concepts summarized in the Waterplan were developed in a series of interdisciplinary working groups and six design workshops, which were attended by urban planners, landscape architects, drainage engineers, traffic planners and various specialists for the topics of water management, ecology, water quality, safety, design and management. For implementation, the Waterplan presents an action plan with scheduled projects. Depending on existing urban structure types (e.g., industrial parks, city centre, old city districts, or garden city) the Waterplan proposes different retrofitting measures for the retention, storage and drainage of stormwater runoff, and presents them in a catalogue style. The retrofitting measures are chosen based on the ratio of impermeable surfaces, space availability, property ownership and flood risk, among other variables. Particularly in densely built-up urban areas it became clear that the retrofitting of open spaces is an important component to adapting to the effects of climate change [15, 16]. Like New York, Rotterdam emphasizes the greening of the city. But due to the dense urban structure of the city centre and high groundwater levels, which limit potential for infiltration, the city made an unusual move. In addition to building more canals and lakes, the city presents the temporary flooding of sealed surfaces in public open spaces as a complementary retrofitting measure. A small-scale network of streets designed to collect water temporarily, and open drainage channels, direct excess stormwater runoff to so-called Waterpleins, water plazas. This reduces pressure on the existing sewer system during extreme rainfall events. Public squares, as well as playgrounds and outdoor recreational facilities, are set below the surrounding street level. These deep plazas are designed to meet the required retention capacity and can be flooded during heavy rainfall events. The Benthemplein, located near the train station, is one of the pilot projects (see Fig. 3).

5 290 Integrated Stormwater Management for the Water-Sensitive Retrofit of Cites During the design phase, future users were invited to take part in several workshops. This allowed for the consideration of user desires, safety requirements, as well as concerns of neighbourhood residents from the start of the planning process [Int.-2]. Fig. 3 The Benthemplein after completion in September The plaza consists of three basins which can be used by teenagers for basketball and football, skating or to see and be seen if the basin is not temporarily filled with stormwater runoff following a downpour. (Source: Author) 3.3 Singapore from Grey-Blue to Permanent Blue-Green Singapore is an island city-state, which lies between Malaysia and Indonesia, and is home to the largest container port in the world. In terms of area, the city is comparable in size to the City of Hamburg, but with triple the population density. The island is predominantly flat and consists primarily of wetland, which is drained by three main rivers: Kallang, Rocher and Sinapore Rivers. The development of the city has always been closely connected to water infrastructure. In the 1970s, natural watercourses were converted to an underground drainage system and open drainage canals [17]. The vast, largely empty concrete canals were designed to prevent flooding caused by tropical rainfall. This enabled both conditions for economic growth as well as the creation of new land area for settlement, helping meet the needs of Singapore s rapidly growing population [18, 19]. Even today, the city is faced with problems like periodic droughts and flooding. Furthermore, while Singapore itself has hardly any groundwater resources, the city strives to develop an independent supply of drinking water. To ensure this supply, the increase in population needs to be considered alongside the effects of climate change. These issues were the basis for the development of a long-term sustainable strategy for the production of drinking water and the renovation of the existing drainage system. The head of the national water agency (Public Utilities Board) responsible for the municipal water supply was an important driver in the overall process. He made sure that the construction of measures for the retention, purification and delayed discharge of stormwater runoff was combined with the recreational features for the general population [Int.-4; Int.-5]. In 2006, the ABC Waters Programme was initiated with the guiding principle, active beautiful clean (ABC). This new approach to dealing with stormwater is a main component of Singapore s drinking water

6 Integrated Stormwater Management for the Water-Sensitive Retrofit of Cites 291 supply network: the entire city is regarded as a catchment area and stormwater is used for the production of drinking water. In addition to improving water quality and increasing the quantity of potable water, improving the aesthetic and functional qualities of watercourses for the benefit of residents is as an important aspect of the general programme. The programme also signifies a shift toward an interdisciplinary approach by the involved public agencies. In the first phase of the implementation process, an interdisciplinary team of water managers, urban and landscape planners developed area-wide master plans for the island s three main rivers and their tributaries. The Active, Beautiful, Clean Waters Master Plan 2008 combines the three plans [20]. Based on the three-part master plan, a total of 100 possible ABC Waters projects were identified for the redesign of concrete drainage canals. Priority was given to projects that provided the greatest benefit to residents. The first 28 projects were completed by the end of 2012 and are partly used for demonstration purposes. An extensive monitoring programme accompanies the projects. The remaining projects followed in the second phase. A successful example project is the restoration of the Kallang River. The 3-kilometre section of the largely channelized river was restored to a more natural form. The existing u-shaped profile of the canal was widened, fences were dismantled and the new watercourse was generously integrated into the adjacent park. Changing the profile of the river allowed for the riverbanks to be restored to a more natural form and created more space for water. The result was not only valuable from an ecological perspective; users and residents also benefited from the restoration of the river, which provides space for recreation and a more inviting atmosphere [Int.-4]; [Int.-6]. In Singapore, as in the other reference cities, the involvement of citizens in the planning process is a significant factor for the success of the implemented projects. Events for citizen participation as well as information sessions provide important opportunities to present information about the ecological aspects of water protection and the production of drinking water and, thus reacquaint Singapore s residents with the water. Fig. 4 Part of the canal that has not been restored (top). Centre and bottom: the widened profile of the Kallang River invites residents to interact with the river. (Source: Author)

7 292 Integrated Stormwater Management for the Water-Sensitive Retrofit of Cites 4. What Conclusions Can Be Drawn from the Examples? An increasing frequency of extreme rainfall events and increased flood risk require a change in the present sectoral planning culture. The examples of New York City, Rotterdam and Singapore make it clear that water management issues must be a central component of urban development and open space planning strategies. Water must be provided with both more space in the urban fabric as well as more time to infiltrate and drain. To achieve this, Integrated Stormwater Management is essential. The manner of implementation is determined based on natural and man-made site conditions, and can be carried out in different forms. In the planning process it is crucial that actors consider not only technical solutions, but also simultaneously use the creative potential of the modification of their existing drainage or sewer system strategically for urban and landscape development. 4.1 Design Strategies of the Reference Cities Are Transferable The reference examples showed that city-wide design strategies are an important component of Integrated Stormwater Management. Depending on site conditions, these strategies can be applied to other cities. Even in densely built-up areas it is possible to create a green, temporarily blue or blue-green network, while simultaneously improving quality of life First Strategy: Green Network A green network, like in New York City, can complement sewer systems in existing urban quarters and relieve pressure on the system, especially during extreme rainfall events. Thus, streets become so-called Greenstreets with the installation of roadside infiltration beds. Or, vegetated swales are constructed in parks and street trees are planted in tree pits that allow water to infiltrate into the soil. This strategy is suitable for cities with soil conditions that allow for infiltration. It is especially Fig. 5 The city-wide design strategy green network consists of roadside infiltration beds, tree pits as well as parks or open spaces in which stormwater can infiltrate. (Source: Author)

8 Integrated Stormwater Management for the Water-Sensitive Retrofit of Cites 293 For which urban settings is the green network strategy appropriate? 2 Criteria critical for the implementation of this design strategy are summarized in the following list: for urban areas with high groundwater levels or limited soil infiltration potential. SITE CONDITIONS: Infiltration potential + available space permeable soil, adequately low groundwater level and adequate distance from buildings, no soil contamination, potential for the removal of paved surfaces (e.g., through the optimization of transportation infrastructure) or combination with structural retrofitting measures in exiting green spaces. SUITABLE SPATIAL TYPES: streets (including impermeable pavement or parking spaces) existing street trees + tree pits or existing roadside vegetation green spaces (with a quality deficit) Design elements of the network: roadside infiltration beds or vegetated swales tree pits which allow for stormwater infiltration green spaces with surface infiltration, vegetated swales or infiltration beds) applicable in cities with generously dimensioned roadways, including pavement and roadside parking spaces. The strategy is also applicable in cities that already have green elements within the public right of way, which have not yet been used specifically for stormwater infiltration, i.e., roadside vegetation and street trees, or existing green spaces Strategy: Temporary Blue Network If the green network cannot be realised as is the case in Rotterdam a temporary blue network presents an alternative. Especially in historic city centres or urban quarters built atop former industrial areas, the realisation of a green network can be problematic. Reasons for this are the lack of space available for green elements as well as possible soil contamination. In addition, this strategy is appropriate 2 Possible runoff loads depending on the source and any additional cleaning procedures that may be required before the water is allowed to infiltrate, were not included in these systematics. These factors are to be investigated on-site. This also applies to the other two networks included in this study. Fig. 6 The city-wide design strategy, temporary blue network, for the retention of stormwater as flood prevention (Source: Author, based on a concept by DE URBANISTEN).

9 294 Integrated Stormwater Management for the Water-Sensitive Retrofit of Cites For which urban settings is the temporary blue network strategy appropriate? Criteria critical for the implementation of this design strategy are summarized in the following list: SITE CONDITIONS: Limited infiltration potential or no space available for the implementation of a green network. Main reasons for this include: impermeable soil or semi-impermeable soil area with high groundwater levels soil contamination no potential for the removal of paved surfaces (e.g., because the existing use requires a paved surface) SUITABLE SPATIAL TYPES: public squares play areas and outdoor recreational facilities parking spaces or streets where selected sections can be flooded Design elements of the network: multifunctional paved surfaces that are set lower than the surrounding area and designed with suitable topography streets that function as temporary water basins and drain into the water plaza The temporary blue network consists of a combination of streets designed for temporary stormwater retention and so-called water plazas, which can host a variety of uses. For this purpose, portions of paved areas, e.g., public squares, play areas and outdoor recreational facilities as well as streets and parking spaces, are temporarily flooded in a controlled way until the sewer system has sufficient available capacity to allow the areas to drain. As the network only appears temporarily, it is essential to inform residents from the beginning about how to deal with safety requirements and to involve them in the design process. Also, adequate maintenance measures should be established so that the actual use can be resumed as soon as possible after a flood event Strategy: Blue-Green Network Blue-green networks involve, as in the example of Singapore, the restoration of watercourses once channelized or buried underground. They should be designed to be as natural as possible. Restoring the Fig. 7 The design strategy blue-green network involves the restoration of formerly convered or chanalised watercourses (Source: Author, based on a concept by Atelier Dreiseitl).

10 Integrated Stormwater Management for the Water-Sensitive Retrofit of Cites 295 For which urban settings is the blue-green strategy appropriate? SITE CONDITIONS: Space availability alongside human-impacted rivers (to alter the watercourse profile or implement small-scale design elements in urban areas) + limited soil permeability. It is also possible to daylight watercourses, which are buried underground as part of the urban drainage or sewer system. This should be done when the system is shown to have insufficient capacity or is in need of repair. Again, space availability is essential in order to be able to daylight watercourses. In particular, urban quarters with considerable urban design deficits can be enhanced by the creation of a blue-green network. SUITABLE SPATIAL TYPES: In addition to the water body or channel sections, the following spatial types are suitable: green spaces (with a quality deficit) street sections to be relocated, or public or private land that can be integrated into the design or purchased in order to make room for the blue-green network Suitable types should be located either in the flood zone alongside the watercourse or canal, or above covered watercourses, sections of rivers or formerly open drainage systems. For additional small-scale design elements, streets and green spaces are suitable. Design elements of the network: restoration of channelized watercourses daylighting of covered watercourses reactivation of formerly open drainage systems additional small-scale elements: reservoirs, ponds, ditches, wetlands, cleansing biotopes (e.g., floating wetlands) watercourse to a more natural profile and integrating neighboring open areas can result in ecological benefits and improved user experience. For this strategy, it is important that the various water levels of the river are taken into account by considering both seasonal variation in rainfall patterns and increased water levels following heavy rainfall events. Stretches of watercourses that suffer from inland flooding or low precipitation levels in summer can benefit from this design strategy. Provided, however, it is possible to change the profile of the watercourse, e.g., by integrating riparian green space or acquiring strategically located property. Small-scale design elements in the form of ponds, ditches and wetlands complement the network. In the inner city the implementation of a blue-green network is often not an easy task, as the surrounding transportation infrastructure or adjacent residential quarters limit available space. In the long term, relocating streets and residential blocks, especially in areas at risk of flooding, is conceivable in order to achieve sufficient space. If no space is available, so-called floating wetlands can be used, which provide cleansing biotopes or the greening of concrete embankments in urban areas. 5. Recommendations for the Implementation of ISWM Based on the knowledge gained, the following recommendations can be made for municipalities that intend to implement Integrated Stormwater Management. 5.1 Forming an Interdisciplinary Task Force As the implementation of Integrated Stormwater Management represents an additional task for the municipal administration, it is difficult to integrate into normal daily operations. It makes sense to create an ISWM Task Force : i.e., an interdisciplinary working group, equipped with sufficient financial and human resources, which is responsible for creating a network of relevant municipal departments and is firmly anchored in the respective administrative structure. Thus, professional exchange can be secured and binding planning guidelines can be developed. 5.2 Attract Key Management Personnel as a Driver During the analysis of the reference cities, it quickly became clear that the implementation of Integrated Stormwater Management is centrally dependent on the people who initiate the process. Engagement, persuasiveness, vision and staying power are important characteristics in order to

11 296 Integrated Stormwater Management for the Water-Sensitive Retrofit of Cites convince all stakeholders of the new ideas. Additionally, ISWM should be supported by persons in political key positions, because the implementation of a city-wide network requires financial support over the course of many years, and in some cases, decades. 5.3 Implement ISWM in Working Steps Even though the working process and the approaches of the references cities differ to a certain extent, and the cities did not follow a fixed schedule from the beginning of the planning process, the experience gained can still be used as a basis to define ideal working steps for the implementation of ISWM. The author has summarized the procedure in thirteen Table 1 ISWM working steps (Source: Author) Ideal Working Steps for the Implementation of Integrated Stormwater Management 1. Start planning based on a policy decision for water-sensitive urban development; 2. Bring together an interdisciplinary team of water managers, urban and landscape planners; this may include professionals from further disciplines, as necessary (i.e., traffic planners); 3. Identify areas on a city-wide scale, which have water management and open space deficiencies, and determine interdependencies; 4. Consider different urban structure types, given the fact that, for example, different measures can be implemented in the inner city than can be implemented in an area with detached houses; 5. Overlay data from different planning professions and decide on priority areas which should be retrofitted as soon as possible; 6. Carry out initial site analyses, especially determine soil permeability and analyse available open spaces on public land in order to assess which of the three networks might be feasible; 7. Develop and decide on a collective vision for water-sensitive urban development with all relevant actors and determine which networks should be realised; 8. Ensure the course of action through political resolution; 9. Implement city-wide integrated plans and expand the interdisciplinary team; 10. Carry out pilot projects and allow for public participation; 11. Monitor the projects and use the experiences gained to continuously improve the measures. 12. Develop an action plan with specific aims and projects, and create a schedule for implementation; 13. Gradually retrofit priority areas and keep the public informed about the status of the planning and implementation process, involving them in specific retrofit projects. optimized working steps and created a practical guide to action (see Fig. 8). The working steps should serve as guidance and checklist for other cities to follow. It should be noted that the sequence of the steps depends optimized working steps and created a practical guide to action (see Table 1). The working steps should serve on the current situation in the respective municipality and can be adapted according to pressing needs. Some steps can be done in parallel. However, it is important that working steps are eventually addressed and implemented. 6. Conclusion: Green and Blue Networks to Complement the Municipal Sewer System As the reference cities showed, public space in existing high-density urban quarters offers great potential for water-sensitive retrofits. Many local governments have not yet recognized this potential. The premise is that the topic should be approached on a larger scale than previously done. The city-wide planning approach offers many advantages over the currently employed small-scale, often problem-oriented approach. With the help of design strategies, in the long-term a coherent, functional and effective network can be achieved in public spaces. This replaces the previous fragmented patchwork made up of projects with different drainage concepts. As part of the overall network, individual projects can still make an important contribution. If water management issues are integrated into the early phases of the overall urban and landscape planning process, they contribute to the creation of a liveable and sustainable city, which is simultaneously adapted to extreme weather events. Particularly in view of global competition between cities, this aspect, as a soft locational factor, is gaining significance. For this purpose, city-wide planning instruments are necessary. These instruments should be prepared in an interdisciplinary way and should complement existing urban, landscape and water planning instruments. They present one, or if necessary more, suitable

12 Integrated Stormwater Management for the Water-Sensitive Retrofit of Cites 297 city-wide design strategies and ideally provide a vision for water-sensitive urban development, which has been developed and agreed upon by all community stakeholders. Thus, the design strategy can affect all planning levels through to project completion. On the project level, specifications appear in the form of design manuals and handbooks, which should be prepared by the municipality. These should include detailed plans and present an operational pilot project as necessary. By taking an interdisciplinary approach to processing and implementation, funds otherwise set aside for the expansion of underground sewer or drainage systems or for road construction projects could be used for water-sensitive retrofits in cities. Moreover, national urban development goals could be combined with the goals of water-sensitive development by setting appropriate priorities or by integrating water-sensitive development strategies into the framework of urban revitalization projects. References [1] J. Fink, N. Klostermann, T. Zimmermann and E. Kruse, Klimaanpassung im Siedlungsbestand. Maßnahmen der dezentralen Regenwasserbewirtschaftung, PlanerIn 4 (2012) [2] E. Kruse and J. Ziegler, In Stadtentwicklung und Klimaanpassung. Klimafolgen, Anpassungskonzepte und Bewusstseinsbildung beispielhaft dargestellt am Einzugsgebiet der Wandse, Hamburg, in: Kruse E., Zimmermann T., Kittel A., Dickhaut W., Knieling J., Sörensen C. (Eds.), Hamburg, Germany, Chapter 2.3, 2014, pp [3] E. Kruse, Integriertes Regenwassermanagement für den wassersensiblen Umbau von Städten. Großräumige Gestaltungsstrategien, Planungsinstrumente und Arbeitsschritte für die Qualifizierung von Bestandsquartieren, Stuttgart, Germany, [4] British Columbia, Ministry of Water, Land, and Air Protection (Eds.), Stormwater Planning: A Guidebook for British Columbia (2nd draft), Canada, [5] J. Hoyer, W. Dickhaut, L. Kronawitter and B. Weber, Water Sensitive Urban Design: Principles and Inspiration for Sustainable Stormwater Management in the City of the Future, Berlin, Germany, [6] W. Ansel, H. Baumgarten, W. Dickhaut, E. Kruse and R. Meier (Eds.), Leitfaden: Dachbegrünung für Kommunen, Nutzen Fördermöglichkeiten Praxisbeispiele, Nürtingen, Germany, [7] E. Kruse, Integriertes Regenwassermanagement großräumig planen. Potentiale und Entwicklungsmöglichkeiten für Hamburg, Hamburg, Germany, [8] E. Kruse and S. Andresen, Integriertes Regenwassermanagement in Hamburg. Veränderungsnotwendigkeiten und Handlungsoptionen für die Planung und Verwaltung, S. Andresen, W. Dickhaut (Eds.), Hamburg, Germany, Chapter 1.4, 2013, pp [9] A. C. Loftus, B. Anton and R. Philip (Eds.), Adapting Urban Water Systems to Climate Change: A Handbook for Decision Makers at the Local Level, Freiburg, Germany, [10] City of New York, Mayor s Office of Long-Term Planning and Sustainability (Ed.), planyc: A Greener, Greater New York, New York, NY, USA, [11] City of New York, Mayor s Office of Long-Term Planning and Sustainability (Ed.), Sustainable Stormwater Management Plan 2008, New York, NY, USA, [12] City of New York, Department of Environmental Protection (Ed.), NYC Green Infrastructure Plan: A Sustainable Strategy for Clean Waterways, New York, NY, USA, [13] New York City Department of Transportation (Ed.), Street Design Manual, New York, NY, USA, [14] P. Dircke, J. Aerts and A. Molenaar (Eds.), Connection Delta Cities: Sharing Knowledge and Working on Adaptation to Climate Change, Rotterdam, Netherlands, [15] Gemeente Rotterdam, Waterschap Hollandse Delta, Hoogheemraadschap van Schieland en de Krimpenerwaard and Hoogheemraadschap van Delfland (Eds.), Waterplan 2 Rotterdam: Working on Water for an Attractive City, Rotterdam, Netherlands, [16] Gemeente Rotterdam, Waterschap Hollandse Delta, Hoogheemraadschap van Schieland en de Krimpenerwaard and Hoogheemraadschap van Delfland (Eds.), Waterplan 2 Rotterdam, Herijking. Rotterdam, Netherlands, [17] J. Read and G. Hauber, Singapurs Bishan-Park: Nach der Renaturierung des Kallang Rivers entsteht eine Fluss-Parklandschaft, Stadt + Grün 8 (2012) [18] G. Hauber and P. Geitz, Testanlage für ingenieurbiologische Bauweisen: Renaturierung des Kallang Flusses in Singapur, Garten + Landschaft 9 (2010)

13 298 Integrated Stormwater Management for the Water-Sensitive Retrofit of Cites [19] L. C. M. Lee and V. Kushwaha, Case study: Attractive, Beautiful and Clean waters programme of Singapore, Research study within the project Eco-efficient and sustainable urban infrastructure development in Asia and Latin America, Singapore, [20] Public Utility Board (Ed.), Active, Beautiful, Clean Waters Masterplan. Produced by Atelier Dreiseitl Asia, Singapore, [21] Int.-1: Compton, Jeanette: Landscape Architect and Director of Green Infrastructure in Forestry, Horticulture and Natural Resources Group, Department of Parks & Recreation, City New York; Interview: May 09, New York, NY, USA. [22] Int.-2: Boer, Florian: Environmental Designer and Founder of the Office De Urbanisten in Rotterdam; Interview: October 18, 2013, Rotterdam, Netherlands. [23] Int.-3: Jacobs, John: Civil Engineer and Senior Consultant at Climate Office for Sustainability and Climate Change of the City of Rotterdam; Interview: October 24, 2013, Rotterdam, Netherlands. [24] Int.-4: Baur, Tobias: Landscape Architect and Director at Atelier Dreiseitl in Singapore; Interview: November 18, Singapore. [25] Int.-5: Yau, Wing Ken: Chemical Engineer at Public Utility Board (PUB), Catchment & Waterways Department, Singapore; Interview: November 18, Singapore. [26] Int.-6: Tan, Shanny: Managerin des Bishan Parks beim National Parks Board (NParks), Singapore; Interview: November 22, Singapore. [27] Minnesota Pollution Control Agency 2014, accessed on April 04, 2014, available online at: ormwater_management. [28] Web-2: RISA Hamburg 2015, accessed on July 31, 2015, available online at: index.php/english.html.