Brazilian urban porosity: Treat or threat?

Urban areas have spatial discontinuities, such as disconnected neighbourhoods, brownfield areas and leftover places. They can be captured by the metaphor of urban porosity. This paper aims to highlight the potential social consequences of urban porosity by creating a ‘porosity index’. The authors argue that these areas can provide capacity for flexibility, fluidity and absorption in major cities, but that they can also be a source of fragmentation, disconnection and isolation between different social groups, eroding the adaptive capacity of metropolitan systems. Porosity may thus have both positive and negative influences on the resilience of urban systems. Brazil's rapid process of urbanisation over the last 50 years shows both these sides of porosity, which create treats and threats for its urban systems. This paper develops an analytical framework within which to study how porosity manifests itself in Brazilian metropolises, which helps to identify porosity in the context of urban growth and decline. It uses statistical data from Brazilian Institute of Geography and Statistics relating to 12 Brazilian metropolises to generate the proposed porosity index. Additionally, the paper discusses the added value of the concept of urban porosity in addressing urban resilience and briefly elucidates the issues and opportunities caused by discontinuities in the urban fabric in Brazil's metropolises.