1. URBAN STRUCTURE MODELS

2. 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.

3. 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.

4. 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.

5. 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)

6. 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.

7. CZM: RING FOUR This is the zone of better residences.
It has newer more spacious houses for middle-class families.

8. CZM: RING FIVE
This is the commuters’ zone that is outside the continuously built-up area.
It is a low-density suburban area.

12. 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.

13. 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.

16. 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.

17. 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.