Cellular Dynamics: Modelling Urban Growth as a Spatial Epidemic

Contemporary urban growth consists of three interrelated problems of spatial dynamics: the decline of central or core cities which usually mark the historical origins of growth, the emergence of edge cities which both compete with and complement the functions of the core, and the rapid suburbanization of the periphery of cities — core and edge — which represent the spatially most extensive indicator of such growth. Our understanding of these growth processes is rudimentary, notwithstanding at least 50 years of sustained effort in their analysis. Our abilities to ‘control and manage’ such growth or ‘sprawl’ as it is colloquially and often pejoratively referred to, is virtually non-existent despite occasional but short lived successes through planning instruments such as green belts. The suburbanization of cities and methods for the control of such growth go back to the origins of cities themselves. Urban history reveals a succession of instruments used to separate the growing city from its suburbs. Documented examples refer to Ur in Sumeria, ancient Rome, to Elizabethan London, where edicts were in place to ensure the quality of life in the core city by restricting overbuilding and access (Morris 1979). However the concept of suburb has changed through history. Jackson (1985) sums this up quite cogently when he says: ‘... the suburb as a residential place is as old as civilization... However, suburbanization as a process involving the systematic growth of fringe areas at a pace more rapid than that of core cities... occurred first in the United States and Britain, where it can be dated from about 1815’ (p. 130).