Compactness-sprawl and urban growth patterns: a spatial metrics approach

Abstract

The disorderly expansion of cities is a global challenge that impacts urban development. In this paper, we analyse the urban growth in a medium-sized city over five decades, focusing on urban form and employing more than 20 spatial metrics associated with the geometry of physical-territorial expansion in the built environment. We examine the growth patterns in the context of the urban sprawl phenomenon and the Diffusion-Coalescence theory perspective. We discuss the inherent limitations of existing metrics and raise alternatives that simultaneously address the properties of Compactness, Fragmentation, Complexity, and Dispersion. The results reveal distinct phases in urban growth over the decades, from diffusion of an initially compact form into smaller parts on the periphery; to a transition towards more compact growth. This oscillation suggests adherence to the Diffusion-Coalescence theory, with urban sprawl occurring between 1966 and 1976, followed by increased compactness in subsequent decades (1976-2006). After 2006, the results became ambiguous, possibly due to intervening planning factors. The discussion of the findings underscores the importance of quantifying urban growth using metrics and introduces concepts that have been hitherto limited to international literature.

Keywords:
Spatial metrics; Urban growth; Urban sprawl; Coalescence-diffusion