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URBAN STRUCTURE MODELS. CENTRAL BUSINESS DISTRICT. A central business district (CBD) is the area of a city where retail and office activities are clustered. The CBD is usually in the center of the city and we usually refer to it as “downtown.”
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CENTRAL BUSINESS DISTRICT • A central business district (CBD) is the area of a city where retail and office activities are clustered. • The CBD is usually in the center of the city and we usually refer to it as “downtown.” • All of the urban structure models start with the CBD in the center of the city.
CONCENTRIC ZONE MODEL • This model was created in 1923 by E.W. Burgess. • The model assumes that if the city is viewed from above a series of rings (like a tree trunk) can be seen. • The model is made up of five rings.
CZM: RING ONE • The inner-most ring is the central business district. • The model assumes a process called “invasion and succession” in which new arrivals to cities tend to move first into inner rings. Eventually, these people are pushed out into farther rings.
CZM: RING TWO • This ring is known as the “zone of transition” that forms just outside the CBD. • This ring never becomes developed because investors know it will constantly be changing. • This zone contains some industry and poor-quality housing (i.e. slums or ghettos)
CZM: RING THREE • This ring is the zone of working-class homes. • It contains modest older houses occupied by stable, working-class families. • These people can usually afford the commute to the CBD.
CZM: RING FOUR • This is the zone of better residences. • It has newer more spacious houses for middle-class families.
CZM: RING FIVE • This is the commuters’ zone that is outside the continuously built-up area. • It is a low-density suburban area.
THE SECTOR MODEL • The sector model was developed in 1939 by economist Homer Hoyt. He argued that cities develop in sectors, not in rings. • Geographers observed that there were urban land use zones based on transportation routes, such as roads, canals, and railroads.
THE SECTOR MODEL • Examples of different sectors: • Factories and industries follow rail lines. • Lower socioeconomic housing follows lines of public transportations. • Visitor service sectors are located near major highways.
MULTIPLE NUCLEI MODEL • The multiple nuclei model was created by C.D. Harris and E.L. Ullman in 1945. • The first two models focused on a strong CBD. • This model suggests that growth occurred independently around several major nodes, or focal points. • Examples of focal points are airports, universities, ports, and neighborhood business centers.
MULTIPLE NUCLEI MODEL • The theory states that some activities are attracted to particular nodes, whereas others will try to avoid them. For example, heavy industry will rarely exist near high-class housing. • It does not suggest that the CBD is unimportant, but it does show that new areas of growth (the nuclei) can grow around key nodes.