Urban Regions : Ecology and Planning Beyond the City

Four urbanization models 207

Figure 8.2Four major spatial models of urbanization spread. Metropolitan area is

thecentral circle; small open circles in upper right are satellite cities including

their adjacent built area. As illustrated in a model, the total area urbanized after

each of three time stages equals approximately 1.5 times, 2 times, and 3 times the

initial metropolitan-area size. For illustration convenience in lower right, each new

developed area equals about 2.5 % of the initial metro area. See text for quantitative

rules (algorithms) of urban expansion.

parallels, both in mosaic sequence and analytic approach, to the edge, nuclei,
corridor, and dispersed models used to understand landscape change (Forman
1995). In the succeeding sections, these urbanization models will be applied in
some detail to two case studies (Mexico City, Nantes), and then more broadly to
all of the 38 cities.
Afewkeyassumptions or parameters apply to all four models. The mosaic
sequences or land-cover changes for each model are illustrated at three stages or
time periods, i.e., when the total urbanized area reaches: (1) 1.5 times, (2) 2 times,
and (3) 3 times the initial size of the metropolitan area (an increase in built area