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Water oriented city planning as key impulse for sustainable urban development

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Since the beginning of industrialization urban areas have been rapidly growing. Recently, a paradigm shift has become noticeable, away from undamped economic and city growth towards more sustainable solutions. However, in the light of numerous
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  Water oriented city planning as key driver for sustainable urbandevelopment S. Koester*, koester@isa.rwth-aachen.de, M. Siekmann*, siekmann@isa.rwth-aachen.de, P. Staufer*,staufer@isa.rwth-aachen.de, S. Beier*, beier@isa.rwth-aachen.de, J. Pinnekamp*, sekretariat@isa.rwth-aachen.de* Institute for Environmental Engineering of RWTH Aachen University ABSTRACT Since the beginning of industrialization urban areas have been rapidly growing. Recently, a paradigm shift has become noticeable, away from undamped economic and city growthtowards more sustainable solutions. However, in the light of numerous negative trends of urban development there is still a bride gap between the ideal of sustainable development andreality. We suggest a far-reaching redefined approach of city planning predominantlyfocusing on water. By merging both modern urban water management and city planning weshaped a convincing idea which provides both a positive guiding principle and an operationalframework including concrete measures which will considerably facilitate decision making processes. Thus, the suggested sector approach of water oriented city planning (WOCP) hasthe promising potential to be the key driver for an overall sustainable development of urbanareas. WOCP includes a comprehensive bundle of different measures such as modernrainwater management, innovative urban surface design, new greening concepts, urbanrainwater harvesting and water reuse, an urban hydraulic cross-linking system, and finallycompletely new types of housing and architecture. However, the described approach has to besustained by an integrated and trans-disciplinary network of all relevant stakeholders as wellas by further financial and legislative measures and instruments. Keywords : city planning, global change, rainwater harvesting, sustainability, urban water cycle, water reuse INTRODUCTION Since the beginning of the industrialization we have had to cope with fast growing urbanareas. This development leads also to a still rising number of megacities worldwide. At the present time, approximately 3% of the earth’s land surface is occupied by urban areas. Morethan ever, the 21 st century will be an urban age. The world is projected to continue tourbanize. Thus, 60% of the global population is expected to live in cities by 2030. For quitesome time, there has been a change away from well established paradigms of economic andundamped city growth and the sustainable development of cities has become more and moreimportant. Essential criteria and indicators for a sustainable urban development have beenrepeatedly but also differently described (for many: KEIRSTEAD and LEACH, 2008).Considering multidimensional (social, economic, cultural, technical, environmental etc.(compare also HELLSTRÖM et al., 2000)) criteria the main objectives should be to combatthe environmental problems and to stop the non-reversible degradation of the naturalenvironment (BITHAS and CHRISTOFAKIS, 2006). If truth be told, between the ideal of sustainable development and reality – manifested by numerous negative trends of urbandevelopment – is still a bride gap. Because numerous urban trends currently fully move in thewrong direction, cities can still be regarded as antipode within the context of sustainability.For example, we have to recognize that there is still an increase of land use bysuburbanization, surface sealing, personal living space consumption, energy demand, noise pollution, as well as of traffic and transport volumes. Furthermore, we have to cope withmajor global trends which potentially unfold immense impact on urban areas. Accordingly,we inevitably have to handle a rising world population, to mitigate the negative impacts of   climate change and adapt to changing climatic conditions. However, the world-wide climatechange will definitely have a significant impact upon the environment and especially upon thenatural and urban water cycle. Last but not least, our welfare is massively influenced by thevolatile financial markets and their economic risks. The pressure to rethink, reiterate andmodify the standards and principles for urban development is mainly generated by thementioned global trends. Especially, the predicted dramatic impacts of climate changeinevitably harbour a growing threat for urban areas. To come closer to the vision of asustainable urban development we urgently need new approaches and starting points. METHODS Water plays a particular role in urban areas. The extreme forms of urban climate together withthe agglomeration of people and values lead to a very high vulnerability of cities in terms of water quantity (heavy rainfall, flooding, drought) but also water quality (water-relateddiseases and their dreadful consequences). The need for a reliable urban water cycle requiresus to thoroughly assure that not just only the supply and disposal infrastructures keep pacewith urban growth. The WOCP approach is mainly based on the synthesis of our findingsreaped of our projects dealing with the adaptation to climate change such as KLIMANET I,KLIMANET II and DYNAKLIM. In DYNAKLIM the impact of global warming on an entirewatershed with regard to water quantity and water quality as well as their biological functionsare assessed in order to identify the most promising adaptation scheme. The wide range of aspects and stakeholders such as energy production, traffic, etc. are unified by the mutualtopic of sufficient water availability. KLIMANET I&II developed and demonstrated atransdisciplinary approach focusing on a resilient adaptation scheme that involves all relevantstakeholders (SIEKMANN et al., 2008). In particular, water management, city planning, andresidents were involved to select measures to adapt inner cities to increased storm precipitation. By incorporating city planning and water management it was demonstrated thatmulti usage of areas can significantly reduce the probability of surcharges of the sewer system. This article brings together the results from these projects and - mirrored to the resultsof a comprehensive literature review - outlines our ideas for innovative solutions for the urbandevelopment in the future. System analysis of the urban water cycle and the urban heat island effect  Mainly influenced by the urban heat island (UHI) effect cities are characterized by a specificlocal climate (figure 1). Due to the interrelation of temperature, humidity, and the feeling of well being, the management of water is very important to the livelihood within a city(ARNFIELD, 2003). Compared with the surrounding countryside we have to deal with larger fluctuations of humidity, higher concentrations of condensations cores, and even more heavyrainfall events. Not only for this reason, water has played a crucial role in urban areas for along time – particularly as factor with high damage potential. The urban water balance is alsosubject to many influences and factors mainly determined by humans (equation 1). Especially,the terms piped water (W) and “anthropogenic” water vapor (F) are sources and sinks whichare directly influenced by anthropogenic interventions. In addition, evapotranspiration (ET),net runoff ( Δ R), and the change in water storage ( Δ S) can be indirectly controlled byanthropogenic interventions (compare ARNFIELD, 2003, MITCHELL et al, 2008). 0   AS R ET F W P (Eq. 01) P = precipitationW = piped water F = „anthropogenic“ water vapor ET = evapotranspiration Δ R = net runoff  Δ S = change in water storage Δ A = net advection of moisture    Figure 1: Urban water cycle and the urban heat island effect City planning and prerequisites for sustainable urban development  City planning and development primarily focuses on the economic development supportingthe local factors to generate economical growth. In modern planning other pending interestsof course are considered, e.g. traffic, the environment, emergency services. These haveevolved guiding principles such as the “city of short distances” or densifying inner cities. Inthe long term mainly the initiation of a permanent so called re-urbanization process will be anessential prerequisite for the sustainable urban development. To re-urbanize mainly means toinitiate the reversal of the current urban trends as described above. In the end, this trendreversal inter alia implies the reduction of the expenditures for public services and for damage prevention: e.g. flood protection. The proximity of living and working will lead to significantreduction of traffic and in an overall view we will generally save precious resources such assurface, energy and water. Thus, a benefit from the general upgrading of quality of life in highdensity urban areas due to the improved urban climate and the availability of an extensivegreen infrastructure has to be anticipated. Further impact would be a decreasing vulnerabilityespecially with regard to climate change. Then, the improved quality of urban life willadditionally disturb the process of the urban sprawl and will further support the process of re-urbanization. The Water Oriented City Planning approach Considering already existing options such as “best management practices” (BMP), or “lowimpact development” (LID) in the US, sustainable urban drainage systems (SUDS) in the UK,and “water sensitive urban design” (WSUD, compare also COOMBES et al, 1999; WONG,2007; MITCHELL et al., 2008) in Australia worldwide first steps in the right direction weredone and relevant interfaces between city planning and water became obvious. Water as wellas greening are broadly accepted and perceived as “creative elements” for urban areas andtheir increased use can be legitimized by actual threats e.g. driven by climate change. Thus,our suggestion is to merge both urban water management and conventional city planning intoa comprehensive sector approach of Water Oriented City Planning (WOCP) as shown infigure 2. Thus, this article intends to prove that this sector approach has the promising potential to be essential key driver for an overall sustainable development of urban areas.    Figure 2 : Sector approach: Water Oriented City Planning (WOCP) as key driver forsustainable urban developmentRESULTS AND DISCUSSION Measures combining city planning and water management will result in common synergiesdecreasing the overall costs. Furthermore, WOCP affects the acceptance of sustainablemeasures and the social awareness as was shown by Siekmann et al. (2008). They reviewedthe impact of best management practices on city planning, acceptance, water quality issues,and costs. The positive effect of incorporating water as main element in city design andlandscaping will involve manifold synergies which enhance and prolong the intended positiveand actively prevents the “not in my back yard (NIMBY) effect” which often is the limitingfactor in environmental politics. However, decentralized systems which are not maintained professionally are more likely to fail. New housing and living forms will address cooperationschemes that enable the residents to take over responsibilities. Also, the centralizeddistribution and collection systems have service times which will still last for several decades.Since the capital costs are disconnected to the service load, substitution of services mayincrease the specific cost per service unit. Consequently, WOCP has to include modern waysthat are based on the polluters-pays principle and promote the capitalization of environmentalcosts. The main elements of the suggested WOCP strategy - as presented in figure 2 - should be based on the following measures as listed in table 1.  Table 1 Elements and measures of the water oriented city planning approach Element Measuresmodernrainwatermanagement Integration of facilities for a modern rainwater management (in any case necessary due toclimate change): specific rainwater treatment facilities according BAT standard,construction of intermediate rainwater storage systems urban rainwaterharvesting Application of Urban Rainwater Harvesting (RWH): use of new technologies for RWHand freshwater storage systems urban hydrauliccross-linkingsystem Implementation of a comprehensive urban hydraulic cross-linking system to connect freeurban spaces: including the target to use water as design element; urban irrigation system(link to RWH) water reuse Implementation of “hot spot wastewater treatment” (e.g. specific hospital wastewater treatment) and launching of adapted and decentralized water reuse solutions innovative urbansurface design Launching of an innovative urban surface design: avoidance or unsealing of impervioussurfaces, multi-use surfaces and buildings, rainwater treatment by active surfacecoverings; user-specificrestrictions Introduction of user-specific restrictions of land use for better water retention: e.g.reduction of areas for motorized individual transport (MIT); new greeningconcepts Realization of new greening concepts of urban areas / implementation of a green infra-structure: i.e. import of green / biological elements into cities, use of fallows new forms of living / housing Pursuit new forms of living / housing in high density districts: higher and denser constructions: additional shading and cooling, vertical extension of urban greening, higher resource efficiency and integration of renewable energies  Modern rainwater management  With regard to modern rainwater management the WOCP approach includes both sourcecontrol measures and the deceleration of the urban water cycle. The first bases on a detailedassessment of the specific loading rates of each surface type. Commonly used values may beobtained from literature. Polluted rainwater either is directed towards the waste water treatment plant or treated decentralized. Decentralized treatment options range from first flushtreatment over wet-ponds to ultra urban treatment facilities. Often a combination leads to themost economical solution (VILLARREAL et al. 2004). These kinds of treatment options arelabelled “best management practices” (e.g. KAISER, 1997) or “low impact development”(KRISTIN et al ., 2009) in the US, sustainable urban drainage systems (SUDS) in the UK (BUTLER and PARKINSON 1997) and The Netherlands (RIJSBERMAN et al ., 2000), aswell as “water sensitive urban design (WSUD)” in Australia. If biological treatment such as biofilters (HATT et al. , 2009) is the desired option, up to 6 % of the developed area has to beassigned to the treatment facilities straining the monetary success of the development.Furthermore, modern rainwater management uses infiltration and evapotranspiration to ruleout the short circuiting of the urban water cycle, hence also decreasing CSO emissions(MONTALTO et al ., 2007). Green areas and infiltration ponds that also contribute greatly tothe appearance of the development increase groundwater recharge, hence decreasing urbanrunoff. Urban rainwater harvesting In water scarce regions, where surface and groundwater sources cannot sustain the water needof its population, storage and consequently use of rainwater have always been used for irrigation, personal hygiene, and potable water (THOMAS, 1998). The sum of collection,storage, and treatment of rainwater is also referred to as rainwater harvesting (RWH). Infuture RWH will become more important in urbanized areas. Especially fast growingagglomerations and an increasing population density require a sustainable water supplysystem that embraces the potential of decentralized rainwater use (BALKEMA et al., 2002;SCHMIDT et al., 2007). Buildings equipped with smart water management systems allow todistribute water with respect to their quality requirements while maintaining highest standards
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