|This article needs additional citations for verification. (July 2006)|
Urban structure is the arrangement of land use in urban areas. Sociologists, economists, and geographers have developed several models, explaining where different types of people and businesses tend to exist within the urban setting. Three models are described in this article. Urban structure can also refer to the urban spatial structure, which concerns the arrangement of public and private space in cities and the degree of connectivity and accessibility.
The grid plan, grid street plan or gridiron plan is a type of city plan in which streets run at right angles to each other, forming a grid. In the context of the culture of Ancient Greece, the grid plan is called Hippodamian plan.
This model was the first to explain distribution of social groups within urban areas. Based on one single city, Chicago, it was created by sociologist Ernest Burgess in 1924. According to this model, a city grows outward from a central point in a series of rings. The innermost ring represents the central business district. It is surrounded by a second ring, the zone of transition, which contains industry and poorer-quality housing. The third ring contains housing for the working-class and is called the zone of independent workers' homes. The fourth ring has newer and larger houses usually occupied by the middle-class. This ring is called the zone of better residences. The outermost ring is called the commuter's zone. This zone represents people who choose to live in residential suburbs and take a daily commute into the CBD to work.
A second theory of urban structure was proposed in 1939 by an economist named Homer Hoyt. His model, the sector model, proposed that a city develops in sectors instead of rings. Certain areas of a city are more attractive for various activities, whether by chance or geographic and environmental reasons. As the city grows and these activities flourish and expand outward, they do so in a wedge and become a sector of the city. If a district is set up for high income housing, for example, any new development in that district will expand from the outer edge.
To some degree this theory is just a refinement on the concentric model rather than a radical restatement. Both Hoyt and Burgess claimed Chicago supported their model. Burgess claimed that Chicago's central business district was surrounded by a series of rings, broken only by Lake Michigan. Hoyt argued that the best housing developed north from the central business district along Lake Michigan, while industry located along major rail lines and roads to the south, southwest, and northwest.
Calgary, Alberta almost perfectly fits Hoyt's sector model.
Multiple nuclei model
Geographers C.D. Harris and E. L. Ullman developed the multiple nuclei model in 1945. According to this model, a city contains more than one center around which activities revolve. Some activities are attracted to particular nodes while others try to avoid them. For example, a university node may attract well-educated residents, pizzerias, and bookstores, whereas an airport may attract hotels and warehouses. Other businesses may also form clusters, sometimes known locally as Iron Triangles for automobike repair or red light districts for prostitution, or arts districts. Incompatible activities will avoid clustering in the same area, explaining why heavy industry and high-income housing rarely exist in the same neighbourhood.
Irregular pattern model
Irregular pattern model is an arrangement of Public space that characterizes the stage of "Transition from village to city" especially in Third World. This urban model is due to lack of planning or construction and illegal without a specific order. This urban model is very suitable for ancient cities, particularly in Africa, South America or Asia and some few places in Europe.
Central business district
A central business district (CBD, also called a central activities district) is the commercial and often geographic heart of a city. In North America this part of a city is commonly referred to as "downtown" or "city center". "City centre" is commonly used in Britain and Canada. In big cities or Metropolis, "Secondary Central business districts" develop alongside the Central business district.
An industrial park is an area zoned and planned for the purpose of industrial development. In Hong Kong, industrial parks are usually known as industrial estates. In the United Kingdom small industrial parks containing multiple units all of the same style are known as trading estates. A more "lightweight" version is the business park or office park, which has offices and light industry, rather than heavy industry.
Urban open space
In land use planning, urban open space is open space areas for “parks”, “green spaces”, and other open areas. The landscape of urban open spaces can range from playing fields to highly maintained environments to relatively natural landscapes. They are commonly open to public access, however, urban open spaces may be privately owned. Areas outside of city boundaries, such as state and national parks as well as open space in the countryside, are not considered urban open space. Streets, piazzas, plazas and urban squares are not always defined as urban open space in land use planning.
The arrangement of streets and large thoroughfares in cities can be further divided into various arrangements throughout the different regions of the world. The structure of the roads themselves is usually representative of the dominant culture of the region. Roads and Streets are used as a Skeleton of the city.
- Europe: A ringed weblike structure is typically found in European cities. Medieval European towns were typically constructed around a church or cathedral. Cities founded prior to Christian influence were built around temples and other structures of cultural significance. Roads usually radiate outward from this central nucleus. The very centre of towns dating back to Roman times can be based on the grid pattern of a Roman Castra. This is the case for Vienna.
- North America: A gridlike pattern is common in North American cities, which unlike European Cities, are typically built around a central business district. Early colonial cities such as Boston show a hybrid of the central nucleus structure and the grid structure. In Southwestern cities such as Phoenix, this grid structure is astoundingly apparent in aerial photographs of the urban area.
- Burgess E.W. (1924)"The growth of the city: an introduction to a research project" Publications of the American Sociological Society, 18:85-97
- Hoyt H (1939): "The structure and growth of residential neighborhoods in American cities" Washington DC; Federal Housing Administration
- Harris C D and Ullman E L (1945), "The nature of cities" Annals of the American Academy of Political and Social Science 242: 7-17