Often in geography models are used to try to explain something that we can see in the physical environment. During the 20th century a number of models were developed to try to explain how urban areas grew. Although models show a very general idea of the shape of the city, all of the ones described here have aspects that can be seen in most cities in the developed and developing world.
Burgess's concentric ring model:
Burgess based his model on the city of Chicago
At its core is the CBD, or Central Business District. This is the area with the highest land price, which could only be afforded by businesses.
Around this is the zone of transition, which is where industry located. In many cities in the UK, such as Birmingham, this zone can be quite easily identified. However in most cases the industry has moved out, leaving the zone empty and in need of renewal.
Beyond the zone of transition are the rings of residential housing. As people became more wealthy they could afford to live further out of town, in bigger houses, with larger gardens.
The houses closest to the centre originally would have housed the workers for the inner city industries. Many British cities still have many of these terraced houses remaining.
As people moved away from the CBD, the houses closest to the centre would be taken by newly arrived immigrants to the city, either from elsewhere in the country or abroad.
Hoyt's sector model:
The sector model has a similar idea of a CBD to Burgess. This is still the area with the highest land price.
Hoyt then used transport routes to determine where his other sectors would be located. He still had a zone of transition around the CBD, but he also had industry fanning out from the centre along major transport routes. He assumed that "Like would attract like", which is why he decided that land-uses would concentrate to form sectors, rather being in rings, like Burgess thought.
The lowest class housing would be closest to the industry, and probably be located where the prevailing winds would blow the pollution towards them (and away from the higher class housing).
The high class housing also is in a sector of its own, running all the way from the CBD, where many of the residents would work, to the outer suburbs.
Harris & Ullman's multiple nuclei model:
This model was aimed at being more specific than the other two, however it also has become more complicated.
Harris and Ullman still have a central CBD, but they also have other smaller centres performing specific functions that Hoyt and Burgess decided would have been found in and around the CBD. Thus Harris & Ullman also havea business centre, and industrial parks.
Large cities do display some of these characteristics. London has different areas of its centre that have different functions: the City, Westminster, Oxford Street and the West End all have differing specific functions.
London has also grown to engulf other towns and villages, which have become smaller CBD's within the whole of Greater London. These CBD's act as growth poles, meaning that the city does not just grow from one central point, but from many spread around its area.
Waugh's model of a developing world city:
Based on cities of the developing world, using some of the ideas found in the MEDC models, but also incorporating the urban features only foundi n LEDC cities.
The CBD is still central to the urban area, and is the area of highest landprice. However around it is the most expensive residential areas. In someplaces, such as Sao Paulo, this means huge luxurious high-rise apartment blocks, whilst in others, such as Delhi, the former colonial areas are the most lucrative in which to own property.
Industrial development is along major transport routes, whilst there are also sectors of high-class housing.
The most striking difference between the LEDC model and the MEDC models is the remaining residential areas. They have been divided into three sections.The periferia are low class, poor quality houses. However they do have limited amenities and are permanent homes.
The favelas or shanty towns are illegal settlements, where the houses are built from what ever the people can find, and there are no basic amenities.In some cities, such as Sao Paulo, schemes have been introduced to help the residents of the favelas, and these people can be found in the sector of housing improvements schemes. (see section on Shanty Towns)
By drawing a transect of a city, you can quite easily identify the different zones, in much the same way as Burgess and the other theorists did. Transects help you to identify and classify zones, enabling you to compare the characteristics of each area. You can identify the CBD, the older terraced housing, and as you move further from the city centre the newer housing of the suburbs. The main zones to concentrate on are:
The CBD: The focal point of the city, with the highest land prices. The CBD is where shops will locate as they know it is the most accessible point for the people of the city. The high land prices mean that buildings tend to grow upwards, and this is why CBD's often have tall skyscrapers, particularly in American cities. The main functions of the CBD will include retail, entertainment, financial services and other professional services.
The Inner City:This is Burgess's zone of transition. The inner city in the 19th Century would have been the centre of industry for most cities. Low paid workers would have lived in the many rows of terraced houses that were built beside the factories. Nowadays, although the factories have gone, many of the terraced houses remain.The Inner city of many urban areas has undergone great changes. These are covered in detail in a later section. However once the industry moved out,the inner cities became areas in need of redevelopment. The first plan was to build tall blocks of flats to replace the terraces. This occurred in the 1960's and 1970's. During the 1990's Inner City redevelopment has taken the form of gentrification schemes aimed at rejuvenating the area, producing more of a community spirit, whilst trying to keep some of the old architecture.
The Suburbs: Many suburban houses were built in the period between the two World Wars, during the first half of the 20th century. Estates full of detached and semi-detached houses grew rapidly as public and private transport improvements allowed people to live further away from their place of work. During the 1960's and 1970's these areas also continued to grow.
The Rural-Urban Fringe: The rural-urban fringe is where most of the post war housing has been built. Usually in estates of mainly detached and semi-detached houses, the emphasis has often been on making the houses as spacious as possible. Again these housing developments were only possible thanks to the fact that most families now own at least one car.