A GEOGRAPHIC INFORMATION SYSTEM GIS ASSESSMENT OF URBAN SPRAWL
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, and planning documents to measure sprawl. The study area includes the jurisdictions that comprise the Metropolitan Statistical Area (MSA) of Lekki of Lagos. Urban land cover increased by one-fourth, from approximately 559 square kilometers to approximately 746 square kilometers from 1992 to 2001. This study analyzes urban land cover data as well as interviews with local developers and planning documentation to understand development trends in Richmond from 1992 to 2001. These dates reflect the availability of National Land Cover Data (NLCD), which I reclassified in the GIS to show only those classes that represent urbanized land. I then compared the two years to show the level of urban growth over the nine year time period. Next, I analyze patterns of urban expansion by using mapping capabilities within the GIS and neighborhood statistics in order to show the density and connectivity of patches of new growth. Based on the density and connectivity of new growth areas, I classify patterns as one of three types of sprawl: linear along highways, cluster, and leapfrog. My threshold densities are; 0 to 400 30 meter pixels per square kilometer for low density, 401 to 700 for medium density, and 701 to 1200 for high density. I also interviewed local developers and planners to gauge their opinions on the issue of urban sprawl versus urban growth. Developers do not see themselves as contributors to sprawl while planners see their roles as buffers between unfettered growth and market forces. The results indicate that Lagos MSA did experience an increase in urban land from 1992 to 2001 and that urban growth in the study area can be classified as urban sprawl with the use of GIS mapping, neighborhood statistics, and analysis of jurisdictional planning documentation coupled with interviews with developers, land owners, and local planners. The density of new development is greatest in VIP and LEKKI, but the pattern and character with which development has occurred in Idomuta Lagos is synonymous with sprawl. Sprawl is also facilitated by inexpensive land with available infrastructure (water, sewer lines).
The Urban Sprawl Debate
As urban development takes place within Nigerian cities and around their fringes, urban sprawl or the lack thereof will continue to be a by-product of development practices and policies. Population increases and the consequences of unplanned urbanization are directly related to recent growth management practices that seek to influence the way in which built-up land can proliferate. The pattern, density, and rate at which built-up land develops are the basis for one contemporary debate: urban sprawl versus urban growth. As a contemporary planning issue, the debate over sprawl is framed by different disciplines and their understanding of how and why urban areas grow. Although urban sprawl is a type of urban growth, sprawl is dependent on the way in which development occurs.
Issues related to Urban Sprawl
Sprawl has been criticized for eliminating agricultural lands, spoiling water quality, and causing air pollution (Allen et al 2003). As population increases, so does the need for new housing, schools, and transportation networks. In the urban world today, industrial, commercial, and residential districts are markedly different from years past. Decentralization is a trend indicative of urban sprawl and present day industrial, commercial, and residential areas are no longer necessarily a part of the urban core (Nechyba et al 2004). Rather, these types of development are often found in low-density areas that are separated from the major urban area by large tracts of homogeneous land. Hence, the needs for larger transportation networks and in turn a greater dependency on automobiles, which produce more air pollution. As new roads are put in place, precious farmland is often left unprotected from commercial or residential developers (Hathout 2002). The greater the imperviousness of an area the more water runoff one can expect, which is the catapult for water pollution (Wilson et al 2003). Without regulations on urban growth, consequences of urban sprawl are likely to continue.
Visualizing Urban Sprawl
Before the introduction of Geographic Information Systems, mapping any phenomenon took an extremely long time. Maps produced through manual cartography for comparison were planned well in advance of a due date. Computer aided maps without GIS were very rudimentary and were not very aesthetically pleasing to say the least. The availability of different types of spatial data allows a GIS user to map virtually any phenomena with a geographic dimension applied to it. In addition, large amounts of data are processed before the creation of a map with much less work than with manual cartographic techniques. With a GIS, maps can be compared in a fraction of the time and can be done at variable scales with ease.
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.