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Stefan Fina Patterns of Urban Sprawl Geographical Analysis
Table 2 Sensitivity tests for relevant properties of the Dispersion Index
DI increases with disconnected greenfield developments Var. 1: small town
(n=4, DI=0,8)
When new urban entities are developed disconnected from
existing entities, DI goes up. This is the case even if the spacing
of new urban entities is as dense as for the existing. The
relation to the added number of entities in the nearest neighbor
ratio of actual versus artificially distributed entities ensures
that this property is always true.
DI decreases with infill development Var. 3: greenfield
(n=16, DI=3,2)
Additional disconnected greenfield developments can be
considered as dispersed when compared to a single compact
development (variation 3 vs. variation 1). However, if infill
development occurs in existing urban areas, average distances
between urban entities decrease, and accordingly, DI goes
down.
DI increases when restricted areas are taken into account Var. 5: dispersed
(n=24, DI=2,78)
In a randomly dispersed configuration of entities, DI is quite
high. When geographical restrictions are considered (=
undevelopable land) for the same configuration, remaining
open spaces cannot be used for the artificial distribution of
entities, and consequently, DI goes up.
DI takes feature weights into account Var. 7: equal entities
(n=32, DI=0,95)
For each urban entity, a feature weight can be applied to
distance calculations to give effect to different densities and
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thus likely levels of interaction between entities (e.g. number of
households, number of people). The artificially dispersed
entities carry an average weight. With this technique, density
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variations are included in DI and higher concentrations of
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interacting agents in an urban center reduce DI.
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DI gives effect to urban concentration Var. 9: leapfrogging
(n=36, SR=5,17)
Urban area configuration can be considered dispersed if
entities are isolated from each other and cannot share
infrastructure provisions. When they grow together, economies
of scale allow for joint use of services and infrastructure, thus
increasing efficiency. DI considers this effect by counting the
number of entities in the artificial distribution that intersect
existing urban areas and using the result as a weighting factor.
Var. 2: disconnected
(n=8, DI=1,14)
Var. 4: infill
(n=20, SR=1,75)
Var. 6: restricted
(n=24, DI =2,9)
Var. 8: weighted
(n=32, DI=0,51)
Var. 9: amalgamation
(n=36, SR=1,48)
The results cannot be shown in detail in this research note, the positive aspects, however, can be
summarized as follows:
- DI allows for comparative analysis of any type of administrative or geographically defined area,
regardless of their areal size, topographic setting, and no matter how many entities they are made
up of.
# Actual !.
Distributed urban entities Open space Urban areas with "central place status"
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