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A Geographic Information System Gis Assessment Of Urban Sprawl
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The use of Geographic Information Systems modeling has
become quite prevalent within the field of urban sprawl research. Some
research on urban sprawl uses GIS as a tool in understanding the effects
of urban sprawl on the natural environment. GIS reveals spatial
patterns of urban sprawl by measuring distances of new urban growth
areas from town centers and roads for example (Gar-On Yeh et al 2001).
Because urban development is irreversible, GIS simulates future land
development (Lee et al 1998). A Geographic Information System is a
decision support system that can facilitate urban planning.
Because
there is a lack of a universal definition of urban sprawl, a map of
urban or built land is an adequate starting point in studying
urbanization. A map provides the visual aspect from which studies on
urban sprawl can begin in relation to urban growth. A Geographic
Information System is useful for mapping the spatial distribution of
urban areas. Unlike traditional cartographic methods, GIS allows for the
manipulation of different types of data in one map frame. Mapping urban
phenomena is a crucial part of quantifying urban sprawl. While many
layers of data are used to create a map of urban growth, ultimately it
is the map that tells the story about the level of urban sprawl over a
given landscape. This type of mapping involves a temporal signature in
which two or more time periods are used for comparing amounts of
urbanization. One base map shows urban or built-up land in a starting
year and another map shows the developed land from the end year.
Therefore, mapping the extent of urbanization over a given period of
time is an essential part of understanding urban sprawl.
The Distinction between Growth and Sprawl
As
urban growth occurs, that growth is often confused with urban sprawl.
However, there is a distinction between urban growth and urban sprawl.
Cities often experience growth either physically, by population, or by a
combination of both. Urban sprawl is much more complicated because it
may or may not qualify as urban growth. How a city grows can create the
appearance of sprawl. Such urban growth may appear as a low-density
leapfrog pattern, a linear or strip development pattern along highways,
or a tightly condensed pattern of new development around pre-existing
built-up landscapes (Nechyba et al 2004). Without urban growth there
would be no appearance of urban sprawl.
The patterns represented by
sprawling landscapes are aligned with the definition of the word sprawl.
If I lay out on the floor in an awkward way, I am sprawling out. This
idea coupled with urban development gives a good visualization of what
urban sprawl may look like. A formal entry reads this way: "Sprawl v.
sit or spread out in a relaxed or awkward way - n. sprawling position"
(Goldman, 1993, p. 279). This definition coupled with the phrase urban
growth is one example of the difference between simple growth and urban
sprawl. Urban growth may have more of a planned appearance while the
pattern of sprawl often appears awkward, uncontrolled, and haphazard.
Perhaps there is a new development very similar to an urban landscape in
the middle of a seemingly rural area broken up by many other rural
landscapes such as farmland or forested areas. Perhaps the timing of
this development closely follows the completion of a new road network or
major highway.
The debate over urban sprawl is relatively new, yet
there are many definitions of urban sprawl. This is due in large part
because there is no consensus on what sprawl is and what is simply urban
growth. Despite vivid examples of what some may classify as sprawl over
a given landscape, there is no clear definition of urban sprawl that is
shared by all who study urban phenomena. There are definitions based on
characteristics of urban sprawl, effects of urban sprawl, and factors
leading to urban sprawl. Further, definitions of urban sprawl are also
influenced by the people that create them. Many definitions of urban
sprawl may include bias towards being pro or con urban development.
It
is important to note a few of the definitions from different time
periods. Here I will present those definitions in a chronological manner
in order to show a progression in the concept of urban sprawl.
Ottensmann (1977, 389) defines urban sprawl as "the scattering of new
developments on isolated tracts, separated from other areas by vacant
land." Ewing (1997, 108) characterizes urban sprawl as "leapfrog land
use patterns, strip commercial development along highways, and very
low-density single-use developments." Zhang (2001, 221) states that
"urban sprawl results from poorly planned, large scale new residential,
commercial and industrial developments in areas previously not used for
urban purposes."
For the purposes of my research, I will use a
combination of all of the previous three definitions in my
conceptualization of urban sprawl. In operationalizing sprawl, I will
use many of the techniques found in the literature review section of
this paper. I will begin operationalization by isolating only urban land
within the GIS for 1992 and 2001. I will incorporate road data at this
point. Then, I will use neighborhood statistics to measure the density
and connectivity of new patches of urban growth. After quantifying how
dense and connected patches of new growth are, I will classify those new
growth areas as one of three types of sprawl: linear along highways,
cluster, or leapfrog. I will also incorporate responses to interview
questions from developers, land owners, and local planners and analysis
of planning documentation to gauge opinions and perceptions of sprawl as
well as planning practices.
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ABSRACT - [ Total Page(s): 1 ]In Nigeria, the urban sprawl debate has closely paralleled urban growth trends over the past few decades. Many studies indicate that it is the pattern, density, and rate of new urban growth that create the appearance of sprawl. Population dynamics are often cited as a driving force behind urban sprawl. This thesis uses Geographic Information Systems (GIS) mapping and land cover change analysis, neighborhood statistics, community surveying, key-informant interviews with planners and developers, a ... Continue reading---
