Emerging urban centrality: An entropy-based indicator of polycentric development and economic growth

This study moves in the debate on polycentric development in Europe proposing an entropy-based indicator of urban centrality based on local-scale diversity in soil sealing levels. This indicator reflects a progressive transition from a mono-centric and hyper-compact morphology towards polycentric agglomerations, with formation (or consolidation) of sub-centres structurally and functionally distinct from central cities. The proposed approach was tested in three metropolitan regions (Barcelona, Rome and Athens) with the aim to provide a comparative analysis of recent urbanization patterns in European countries affected by rapid processes of urban spillover. The local socioeconomic structure underlying urban expansion was investigated using descriptive, correlation and multivariate analysis of 52 contextual indicators. Results of this study shed light on long-term urbanization patterns in the examined cities, providing evidence of a progressive settlement scattering in Rome and Athens. Early signals of polycentrism were observed in Barcelona. Diversification in the level of soil sealing decreased with the distance from central cities. The article finally debates on the use of composite indexes of diversification in the level of soil sealing when assessing polycentric urban development.