Models applied to case studies
Thus at the end of the third final stage the innermost band one is 100 %
developed, band two 50 %, band three 37.5 %, band four 25 %, and the outermost
band five is 12.5 % developed. The innermost band in this dispersed model is
completely urbanized after the third stage, just as the equal-sized inner zone of
theconcentric model is fully developed after the first stage.
Models applied to case studies
What can we discover by applying the four urbanization models just
described to the patterns of real cities? Which is the best way to spread outward --
as concentric zones, satellite cities, transportation corridors, or dispersed sites?
Which is worst? The answers here must be based on sustaining natural systems
and their human uses. To answer these questions, this section examines two
urban regions in some detail, and the following section compares all 38 urban
regions more broadly.
Mosaic sequences generated by the four models are first mapped on the urban
regions of Mexico City and Nantes (France). Mexico City has a large population
(8 590 000) and a metropolitan area of 1606 km^2 .Nantes is relatively small in
both population (278 000) and metro area (171 km^2 ). Then the four major urban-
ization options are directly compared by recording the amount of key sites or
areas (Color Figures 22 and ) affected at each stage for each model. Two of
themany nature-and-people variables on the urban region maps are selected
forevaluating the urbanization models for these cities: (1) biodiversity sites,
and (2) rivers/major streams. Biodiversity sites (described in Chapter5)aresim-
ply counted. The second variable refers to the total length of rivers and major
streams in the region that are surrounded (toc.3kilometers on each side) by
natural vegetation. In short, the urbanization options are evaluated using four
alternative models times three stages of urbanization times two urban regions
times two variables of importance for natural systems and human uses.
Maps of the four mosaic sequences in the Mexico City region are strikingly
different (Figure8.3). Development in the concentric model completely covers
thearea close to the city. The satellite-model development covers four small outer
areas. The transportation-model development covers four long radial spokes or
finger-like areas. And the dispersed-model development extends at low density
across a large area around the city. The same results are evident for Nantes, a
relatively small city (Figure8.4).
Chicago was originally included as a case study because, worldwide, it is a
medium-size city in population (2 896 000), has the largest metropolitan area
of all 38 regions analyzed (3993 km^2 )(seeTable5.1), and contains consider-
able sprawl. However, the huge metro area posed problems for applying the