200 Urbanization models and the regions
Common urbanization patterns
Twomajor factors, physiography and planning, provide constraints on
urbanization and lead to the characteristic spatial patterns of urban expansion
(Fainstein and Campbell1996,Simmonds and Hack2000,Antrop2000,Berger
2006). The prime physiographic constraints are mountains and water-bodies,
especially sea, estuary, major river, and large lake or wetland. Planning, using
legal and/or enforced constraints, creates diverse spatial patterns such as green-
belts, green wedges, and transportation corridors.
Withno major constraints, concentric growth is the archetypal form of
outward urbanization. From the rounded perimeter of a city or metropolitan
area a relatively equal amount of expansion over time occurs in all directions.
Three other common growth patterns should be mentioned in the context of
no constraints. Firstinfillbuilds on unbuilt spaces embedded in the metropoli-
tan area. Second, for metro areas with green wedges present (Chapter 4),
urbanization creates a compacting or rounding pattern that fills in the wedges
(e.g., Seoul, Melbourne). Third, a sequence of expansions in different directions
tends to maintain a rounded form with bulges (e.g., growth of London up to
1830 [Turner1992]). Thebulges patternor model of urbanization seems more
characteristic than the rounded pattern, because investment for development
is more likely targeted to a specific area on a metro-area perimeter than to a
narrow strip along the perimeter.
Still more common patterns result from urbanization in the presence of plan-
ning and physiographic constraints (Barker and Sutcliffe1993,Warren1998,
Pandellet al.2002,Ozawa2004,Ishikawa2001,Clark2006). Green wedges, green-
belt, urban growth boundary, or ring of parks may be present near a metropoli-
tan area.Green wedgesare unbuilt greenspaces projecting into the metro area
(e.g., Stockholm, Copenhagen, Melbourne). Agreenbeltis a protected band or
zone of greenspace around a city where urban growth is prohibited or permit-
tedatavery slow rate (London, Seoul). Anurban growth boundaryis a ‘‘lineinthe
sand” beyond which urbanization is prohibited or can only proceed at a much
reduced rate (Portland). Unlike an urban growth boundary, urbanization may
occur outside a greenbelt zone. Aring of parksis analogous to a greenbelt except
that transportation corridors and nearby development radiate outward from the
city leaving, for example, four to eight large parks in a ring and separated by
highway corridors (Budapest). The Seoul greenbelt might become a ring of parks
(Color Figure35)(Bengston and Youn2006).
More-distant patterns of urbanization are characteristically near transporta-
tion corridors (Figure 8.1)orsatellite cities (Browder and Godfrey 1997,
Simmonds and Hack2000,Antrop2000,Schneideret al.2003). Development