Central Place Theory

I

Introduction

Central Place Theory, spatial theory in human geography that attempts to explain the number, size, and distribution of settlements, and to provide a framework by which settlement structures all over the world may be studied. It was first developed by the German geographer Walter Christaller in 1933 and modified in 1954 by another German, August Lösch.

The essence of the theory is that settlements act as central places providing one or more services for their surrounding areas, and that they vary in their importance, or order, according to the number and type of other settlements dependent upon them, and according to the number and type of services, or functions, they provide. Services are also ordered: lower-order functions include the types of services provided by a village shop; higher-order functions include department stores and hospitals. Cities and large towns are classified as high-order settlements because they supply both low- and high-order services, the latter to both their own inhabitants and to those living further away. A village with one small shop would be of a very low order.

II

Market Areas

Central place theory also involves the distance people are prepared to travel to obtain particular functions. This distance, known as the range of the good or the range of services, determines the size of a settlement's market area, that is, the area inhabited by most of the people who use its services. The higher the order of a central place, the larger its range. Therefore, places with only lower-order functions will have a very limited market area and their residents will need to travel further to higher-order central places to obtain higher-order functions.

Christaller theorized that across a more or less flat landscape with evenly spaced settlements, or isotropic plain, market areas would be hexagonal in shape with the settlements in the centre of the hexagons. This is because hexagons interlock neatly, whereas circular areas would leave some parts of the plain unserved. However, in reality settlements are of different orders, with higher-order settlements competing to encompass lower-order ones within their market areas. Because of this, various, often complicated hexagonal structures of settlement patterns can develop. For example, a pattern consisting of just two orders of central places—rather than the seven that Christaller distinguished—would result in the central positioning of the higher-order settlements in relation to adjoining market-area hexagons. According to Christaller's theory they will each be surrounded by six lower-order settlements positioned according to three main patterns. Firstly, the lower-order central places may be positioned on the six points of the hexagon surrounding the higher-order central place; in the case of a landscape honeycombed with adjoining hexagons, this would mean that each lower-order place would be competed for by the three adjoining higher-order central places. Secondly, the lower-order central places could be positioned in the centre of the sides of the hexagon, which would mean they were in the market areas of the two adjoining higher-order central places. Finally, all the lower-order central places could be contained within the market-area hexagons of the higher-order central places. The kind of complicated pattern that can develop with more than two orders of central places is illustrated on the left-hand side of the diagram.

III

Central Place Hierarchy

This ordering of settlements according to the size of their market area creates what is known as a central place hierarchy. Each central place can be given a value, called a k value, according to how many lower-order places are dependent upon it. However, it is more usual to describe the overall settlement pattern in k-value terms. For example, a hierarchy based on the second settlement pattern described above—where lower-order central places are located on the sides of the hexagons around the higher-order central places—would have a k value of four. This is because each of the six lower-order central places is shared between the two adjacent higher-order places. Thus, each higher-order place has the equivalent of three (6 divided by 2) settlements dependent upon it plus itself, hence k = 4. Much higher k values are possible, especially when there are more than two orders of central place involved in a hierarchy.

IV

Modification by Lösch

In reality, market areas are very rarely neat and hexagonal. Physical features like valleys and mountains affect settlement patterns and market areas, as do factors that improve communications in one direction but not in another, such as motorways. Lösch sought to represent reality more accurately. He considered it unlikely that settlements would be distributed more or less concentrically around places of the next higher order. Instead, the highest-order settlements, such as large cities, would restrict the nearby development of high- and middle-order settlements because the cities would provide all their functions, and more. In a Löschian landscape, such as that illustrated in the right-hand side of the diagram, small, low-order central places are found close to very large settlements, such as metropolitan centres, whereas high- and middle-order settlements will only be found a substantial distance away. Even then they are more likely to be clustered in certain directions rather than distributed evenly around the metropolitan centre.