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Salat S.,Urban Morphology and Complex Systems Institute
International Journal of Urban Sustainable Development | Year: 2017

Resilient historical cities are the product of evolution and they have been shaped by incremental adaptation to fluctuations and by shocks of various magnitudes. Adaptive complex cities operate as systems and they obey certain universal laws: the distribution of elements reflects organic growth processes, such as the ones described by allometric growth and inverse power laws in biology. Their elements and connections organization does not obey Gaussian laws (concentration around averages). They are not aggregates of inert elements but integrated highly differentiated self-organized wholes. They exhibit a hierarchical configurational order characteristic of complex adaptive systems, with nested subsystems ordered in a hierarchy of scales united by mathematical regularities. Planners need to be aware of these laws of adaptive complexity and plan with rather than counter to these emergent properties in order to enhance resilience. Understanding the universality of complex systems order, which characterizes living systems, and which modernist city planning has violated, would allow planning more resilient cities. © 2017 Informa UK Limited, trading as Taylor & Francis Group

Salat S.,Urban Morphology and Complex Systems Institute | Bourdic L.,Urban Morphology and Complex Systems Institute | Labbe F.,Urban Morphology and Complex Systems Institute
Archnet-IJAR | Year: 2014

The challenge of a science of cities is to understand the links between urban morphogenesis, efficiency and resilience. Mathematical regularities emerge in resilient cities, coming from the scale-free properties of complex systems that present the same level of complexity across their different scales. They take the form of inverse power laws that are the « signature » of complexity. In living cities, these mathematical regularities derive from historical layering over millennia (Paris) or from intense market forces (New York). In complex, living and resilient cities, the distribution of elements and connections does not obey Gaussian laws but scale-free inverse power laws. Understanding the universality of this structure which also characterizes natural phenomena and living systems, and which has been violated by modernist city planning, would allow planning more efficient and resilient cities. The paper shows how initial breaks of symmetry fostered the emergence of scale-free structures in Paris and New York, with long-range time correlations, and how a break of symmetry in the spatial layout created a highly differentiated socio-economic structure in Barcelona. © 2014 Archnet-IJAR.

Salat S.,Urban Morphology and Complex Systems Institute | Bourdic L.,Urban Morphology and Complex Systems Institute
International Journal of Sustainable Building Technology and Urban Development | Year: 2014

Chinese cities are hovering in their average density close to the threshold of 5000 inhabitant/km2, with highly dense congested cores and a vast suburban expansion where the suburban area has been multiplied by 1.8 every 10 years for the last 2 decades. If the present trends continue, Chinese suburban density will be around 2500 inhabitant/km2 in 2030, with suburbs 36 times bigger in surface than the core, as the Shanghai case exemplifies. It would notably lead to a tripling of energy demand for transportation and contribute to increasing the infrastructure costs per capita. China needs an urgent and ambitious shift toward infill urban development to avoid the current trend of edge and leapfrog growth that feeds de-densification and urban sprawl. National and local policies must promote and foster compact urban development and high levels of articulated density: high residential density, high job density, neighbourhood scale mixed use, and high density of urban amenities to improve accessibility. © 2014 © 2014 Taylor & Francis.

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