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RESEARCH PRODUCT

Stratégie d'aménagement pour le développement durable d'aires métropolitaines par un système multi-scalaire d'aide à la décision : l'exemple de Vienne

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A sustainable and sustaining planning strategy is globally important for metropolitan areas. Sustainable planning addresses the development of strategies to reduce the use of resources, increase economic efficiency and improve integration of social aspects (e.g. pedestrian-friendly environments, well-balanced public and private transport modes, efficient street networks, land use, movement economy; access for all to jobs, retail, services; healthcare, culture and leisure). In contrast, splinter development (e.g. urban sprawl) involves damage to nature and generation of an increasing volume of traffic (these are the main criticisms following a study by Newman and Kenworthy (1989) on the relationship between settlement density and energy consumption). Interestingly, the overly compact city also has this effect as it may generate traffic flows for accessing green and leisure areas, or changes of residence due to a favouring of sites that lie farther away from the centre than the inhabitants current places of residence. Households not only consume urban amenities integrated into densely populated areas, but also aspire to have access to green and leisure areas. Schwanen et al. (2004) showed that households usually optimize their residential choice with respect to accessibility to various types of amenities, which is inherently linked to the frequentation rate of these amenities (daily, weekly, monthly, and occasional) (c.f. spatial practice of people). Moreover, on an urban scale, over-compactness causes ecological problems such as a lack of green wedges for supplying the city with fresh air (urban microclimate).Thus, we aim to find a solution for managing dispersed development which marries the twin elements of green and built-up space in a highly efficient manner. This solution also needs to incorporate dynamic aspects of a city as well as minimizing traffic costs and emissions. Based on the observation that urban space is founded on the principle of fractal geometry, it seems interesting to explore to what extent fractal geometry may be drawn upon for solving the spatial antagonism of compactness and urban sprawl.The decision support system Fractalopolis developed herein allows an articulation of green areas and urbanised space based on the underlying hierarchical concept, thus providing leisure areas in the neighbourhood of urbanised space but avoiding fragmentation of open landscape. In addition, this concept introduces hierarchy of centres and sub-centres on a metropolitan scale, allowing accessibility to daily, weekly, monthly and occasionally frequented facilities to be improved. Larger distances are accepted for less frequented amenities.