Simulating spatial urban expansion based on a physical process

Urban expansion as a dynamic process of land use change is a complicated social/economic phenomenon. It may be linked with details related to topography, transportation, land use, social structure and economic type, but it is generally related to demography and economy in a city. It is helpful for macro-planning and decision-making to have a simulation model available which considers these two factors. Since the spatial appearance of urban expansion is similar in some degree with a physical diffusion process, one easy way to model urban expansion under various scenarios is to build a simulation model based on basic diffusion. In this way, a clear mechanism of urban expansion is demonstrated. Population density is regarded as an internal driving factor and economy as an external push on urban expansion. Because of its computational features, this model is implemented with cellular automata. These have an advantage in that they allow the model to be extended and to be incorporated with other geographical systems. By applying the model to an actual example for scenario studies, we have shown that it can produce some valuable results through simulations at various scenarios.