Concentric Zone Model
For example, one of the first models created for use by academics was the concentric zone model which was developed in the 1920's by the urban sociologist Ernest Burgess. What Burgess wanted to model was Chicago's spatial structure with regards to the usage of "zones" around the city. These zones radiated from Chicago's center, The Loop, and moved concentrically outward. In the example of Chicago, Burgess designated five different zones that had separate functions spatially. The first zone was The Loop, the second zone was the belt of factories that were directly outside of The Loop, the third zone included homes of laborers who worked at the factories, the fourth zone contained middle-class residences, and the fifth and final zone hugged the first four zones and contained the homes of the suburban upper class. Keep in mind that Burgess developed the zone during an industrial movement in America and these zones worked mainly for American cities at the time. Attempts at applying the model to European cities have failed, as many cities in Europe have their upper classes located centrally, whereas American cities have their upper class mostly at the periphery. As a summary, listed here are the five names for each zone in the concentric zone model for reference:
Central business district (CBD)
Zone of transition
Zone of independent workers
Zone of better residences
Since the concentric zone model isn't applicable to many cities, some other academics attempted to further model the urban environment. One of these academics was Homer Hoyt, a land economist who was mostly interested in taking a look at rents within a city as a means of modeling the city's layout. The model (also known as the Hoyt model or sector model), developed in 1939, took into account the effect of transportation and communication on a city's growth. His thoughts were that rents could remain relatively consistent in certain "slices" of the model, from the downtown center all the way to the suburban fringe, giving the model a pie-like look. It has been found that this model works especially well in British cities.
A third well-known model is the multiple-nuclei model. This model was developed in 1945 by two geographers, Chauncy Harris and Edward Ullman, to try and further describe a city's layout. Harris and Ullman made the argument that the city's downtown core (or CBD) was losing its importance in relation to the rest of the city and should be seen less as the focal point of a city and instead as a nucleus within the metropolitan area . The automobile began to become increasingly more important during this time which made for greater movement of residents to the suburbs. Since this was taken into consideration, the multiple-nuclei model is a good fit for sprawling and expansive cities.
The model itself contained nine differing sections that all had separate functions. They are as listed:
Central business district
Outlying business district
These nuclei develop into independent areas because of their activities. For example, some economic activities that support one another (for instance, universities and bookstores) will create a nucleus. Other nuclei form because they'd be better off far from one another (e.g., airports and central business districts). Finally, other nuclei can develop from their economic specialization (think of shipping ports and railway centers).
As a means of improving upon the multiple nuclei model, the geographer James E. Vance, Jr. proposed the urban-realms model in 1964. Using this model, Vance was able to look at San Francisco's urban ecology and summarize economic processes into a sturdy model. What the model suggests is that cities are made up of small "realms" which are self-sufficient urban areas with independent focal points. The nature of these realms is examined through the lens of five criteria:
The topological terrain of the area, including water barriers and mountains.
The size of the metropolis as a whole.
The amount and strength of the economic activity taking place within each of the realms.
The accessibility internally of each realm in regards to its major economic function.
The inter-accessibility across the individual suburban realms.
This model does a good job at explaining suburban growth and how certain functions that are normally found in the CBD can be moved to the suburbs (such as shopping malls, hospitals, schools, etc.). These functions diminish the importance of the CBD and instead create distant realms that accomplish approximately the same thing.