The dynamics of urban expansion : a model for planning
Creators: name: Mathieson, Ronald Arthur
Publisher: name: University of British Columbia
Year: 2011

description: The implications of urban expansion as a dynamic, evolutionary process are far from self evident. Such problems as the ecologically sound allocation of land resources and the orderly provision of essential services in urban fringe areas, are not being solved. The importance of the rural-urban land conversion process, in long range planning for metropolitan regions, requires that a method be found for describing the likelihood of the rate, extent and location of urban expansion. Within this context the study is concerned with firstly, the shortcomings of present methods for examining and forecasting urban expansion. It is pointed out that the regional planner needs to understand the dynamics of land assignment, in the urban expansion process, if he is to know in advance the probable consequences of his actions and be able to fulfil planning objectives. That this elementary point is frequently ignored or misunderstood can be seen in the attempts to prescribe how a process should behave, instead of first trying to discover how it does behave. This is most noticeable where techniques are used which entail optimization or conditional prediction, based on generalized and unrealistic assumptions of human values and behaviour. As a result, the dynamics of change, including the influence of chance events, are usually left unaccounted for in actions subsequently taken. Restrictive zoning is an example, which more often than not seeks to force rather than fit or guide urban development. Secondly, a simulation model of rural-urban land conversion is developed for the Vancouver Regional Simulation Project, to demonstrate the advantages of experimental strategies and synthetic models in regional planning. The viewpoint is taken that urban expansion can be represented as a spatial diffusion process. When formulated stochastically, spatial diffusion processes account for uncertainty in land assignment practices. The model is organized in a regional systems framework, with structural properties (i.e., thresholds, boundaries, and lags), and feedback interactions, represented, to reflect the complex and dynamic nature of urban expansion. It is emphasized that the future cannot be forecast, on the basis of past and present conditions, with sufficient reliability for long range planning purposes. While it is implicit in the model formulated that emerging patterns of rural and urban land use bear some functional relationships to historical patterns, they are not constrained from evolving into new and different forms. Special attention is paid to change and chance mechanisms to avoid indiscriminate extrapolation of present trends. The experimental nature of the model is considered its greatest strength. Because it facilitates experimental monitoring and regulation of process behaviour, we are made more aware of critical thresholds and capacity limits within metropolitan regional systems. Consequently, planning policies, compatible with the dynamic urban expansion process, can be devised with greater assurance of their success, and regional planning goals can be achieved more readily. Thus the approach is submitted as a progressive step beyond the traditional reliance on specific predictions, as a primary basis for regional planning.