Analyzing the changes in the pattern of urban systems of Kohgiluyeh and Boyer-Ahmad Province

The sharp rise in urban population of the world, especially in developing countries in recent decades, caused prime city in them. Iran, as one of the developing countries, in recent decades, particularly from 1345 onwards, has balanced out of the trend. The aim of this paper is to analyze the situation and the pattern of urban systems in Kohgiluyeh and Boyer-Ahmad, during the years 1335 to 1390. The research methodology is analytical, library and documentary method of data collection.. Models used in this study include: the first indicator of a city, city index, the index of a fourcity, four-city index Mehta, MoMA and Alvesaby index, the Herfindahl concentration index, dispersion index and Henderson Entropy Coefficient. In order to do data analysis, EXCEL software; & to map the study area ARC GIS9.3 software is used. The findings of this study manifest that in the temporal period of the studied population settlement in urban centers are not balanced and are of homogeneous distribution. In the cities of Yasuj, Gachsaran and Dehdasht, the urban systems were almost stable, and the other cities of the province are far beyond these cities, in the matter of population. The prime city of Yasuj has overtaken the rest of the cities over time, and urban network is heading toward instability.