Investigating the development of settlement system in the central region of Iran between 1956 and 2016

Easy access to goods and services is one of the most important issues in planning. This will lead to a hierarchy of settlements in the context of national, regional and district planning. Since the central region of ​​Iran is very large, the issue of balance in the hierarchy between the settlements of this region is very important. Therefore, the purpose of this research is to investigate the changes in the settlement system of the central region of Iran between 1956-2016. The research method is descriptive-analytics using a number of urban and regional planning models. In this research we use urban primacy index, 2-city primacy index, 4-city primacy index or Ginsberg index, Mehta's four city primacy index, Moomav and Alwosabi index, entropy index, Henderson decentralization index, Herfindahl concentration index, Elshakhas index and zipf coefficient to investigate settlement system of central region of Iran. Findings show that the settlement system of the central region of Iran has shifted towards imbalance until 1976 and then to balance until 1996 and from 1996 to 2016 towards imbalance. Also central region of Iran has been facing the Urban Primacy phenomenon and Isfahan metropolis dominates the whole system, but from 1996, indicators indicate formation of a new metropolis of Yazd in this region. In order to improve the balance status of the settlement system of the central region of Iran, decentralization of the metropolitan area of ​​Isfahan with respect to the principles of land preparation and equitable distribution of facilities in small and medium cities is necessary.