A Multi-Scale (Multi-Fractal) Approach for a Systemic Planning Strategy from a Regional to an Architectural Scale.

摘要

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 order to reduce urban sprawl, numerous authors recommend going back to the concept of compact cities. However, policies favoring the compact city concept turned out to be less efficient than expected. Indeed, a large number of households choosing these areas reject urban density since they prefer living in individual houses surrounded by a garden and enjoy a green and calm environment. Hence, instead of rejecting urban sprawl it seems more reasonable to find solutions for better managing the dynamic aspects of cities, in order to reduce traffic costs and pollution, and to avoid undermining natural and agricultural resources. Frankhauser (2004) first proposed reflections onto what extent planning concepts referring to fractal geometry could be of interest for reducing negative impacts of urban sprawl. In a recent research project, financed by the French Ministry of Ecology, Energy, Sustainable Development and Sea in the framework of the PREDIT research program, a planning concept was developed concretizing this basic idea. A planning support system was developed which allows testing the efficiency of the concept (Frankhauser et al 2007, 2008). Let us recall that fractal geometry is based on a hierarchical principle, which has been to be an essential element of urban structures. The hierarchical ordering principle is a cascade of similar elements on different levels of detail: house, block, quarter, district - or: path, residential road, side street, main road, freeway, and highway. According to Read (Read 2000), different scales of hierarchy are distinguished by scales of mobility, and are designed to convey different scales of movement. The spatio-functional pattern describes everyday space use and movement. The above-mentioned fundamental systematic of the built environment requires a structural-analytical approach on all interwoven scales (global to local) for future developments (regional, urban and architectural). The multi-scale logic allows the articulation of residential areas and leisure areas across scales, introducing different levels of service centres according to their frequency of use. These service centres are localized in the nodes of the transportation system thus improving their accessibility with respect to residential areas. This paper addresses a further development of this theoretical model, extending it to be a holistic, comprehensive system. The idea of an "urban" hierarchy (street network, green areas, building blocks, building heights, and urban centres), generated as a multi-scale urban planning model for developing scenarios (regional, urban, architectural scale - 2D & 3D) for metropolitan areas, allows the implementation of highly efficient, functional and sustainable transport networks, masterplans and mass models. The comprehensive system presented here can not only simulate growth scenarios but also assesses the quality of an existing area for consolidation and revitalisation (masterplan, urban fringe) or to identify areas with low overall access for a sustainable negative growth scenario (inverse model for shrinking cities and quarters).