عنوان مقاله [English]
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.
Keywords: Settlement System, Central Region of Iran, Balance, Concentration, Urban Primacy
Since the industrial revolution that took place in the late 18th century, the world's population has grown dramatically at an astounding rate, reaching from one billion in 1830 to seven billion in 2013. In this explosive world population growth, the share of the urban population is increasing day to day. So that For the first time in human history, in 2007 the share of the world's urban population exceeded 50% of the world's population and is projected By 2030, 2 billion people will be added to this. But what led to the most important scientific and social challenges in population planning was the rapid growth of the population and its intensive concentration in one or more urban areas, that lead to imbalances and inequalities in the distribution of opportunities and cause inefficiencies of the settlement system. This is much worse in developing countries. because developed countries have a more balanced settlement system due to the relative homogeneity of socioeconomic and spatial capacities. In the last half century, Iran has also been experiencing rapid growth of urbanization and increasing number of cities and urban population, so that Iran had only 13.67% of urban population in 1956 and Iran's urban population in 2011 reached to 71.39%. increasing in the urban population of Iran led to changes in the urban system, so that several major cities gradually emerging and dominating the entire urban system. The unbalanced urban system resulted in spatial inequalities and uneven distribution of resources. Therefore, it is important to study the evolution of the urban system in Iran, so by knowing the balance process of the system, can help to eliminate inequalities and imbalances. This issue is very important for the central region of Iran, including the provinces of Isfahan, Yazd, and Chaharmahal and Bakhtiari, due to the large area and the relatively long distance betwean settlements; Therefore, the main question in this study is as follows:
Has the urban system in central region of Iran moved toward balance and decentralization?
And the main hypothesis is defined as follows:
The urban system in the central region of Iran is moving towards balance and decentralization.
Regarding to the desired purpose, this study is an applied-descriptive study in which the developments of the urban system of the central region of Iran (including Isfahan province, Yazd province, Chaharmahal and Bakhtiari province) will be studied from 1956 to 2016. The data required for analysis were extracted from statistical yearbooks of this region in 1956 to 2016. In order to evaluate developments in the urban system of the central region of Iran, balance and concentration indices were used as follows:
Primacy Urban Index: Whatever the value of this index being more, the largest city has larger primacy.
Two City Index: Whatever the value of this index being more, the largest city has larger primacy.
Four City Index or Ginsberg: Whatever the value of this index being more, The desired urban system has more urban primacy.
Mehta's Four City Index: Whatever the value of this index being more, The desired urban system has more urban primacy.
Moomav and Alwosabi Index: Whatever the value of this index being more, The desired urban system has more urban primacy.
Herfindahl concentration index: Whatever the value of this index being more, The desired urban system will be more concentrated.
Entropy index: Whatever the value of this index being more, The desired urban system is moving towards balance.
Henderson decentralization index: Whatever the value of this index being more, It indicates a decrease in the concentration in the urban system.
Taghvaee Index: Whatever the value of this index being more, the urban system will be more concentrated and more unbalanced.
Elshakhas index: Whatever the value of this index being more, the urban system will be more concentrated and more unbalanced
zipf coefficient: whatever the value of this coefficient being more, the urban system is more balanced.
Results and Discussion:
Due to the upward trend of all primacy urban indicators during the period 1956 to 1976, there is a strong concentration in the first city of the region, Isfahan, in this period. But from 1976 to 1996, all indicators have declined. In other words, from 1976 to 1996, second-class cities such as Yazd, Shahrekord, Kashan and Najafabad also experienced rapid growth compared to Isfahan, and to some extent, the region was freed from the excessive domination of the first city; But after 1996, the primacy urban indicators have risen again. According to the values of Herfindal concentration and Henderson decentralization indicators, we find that from 1956 to 1976, concentration has been occurring in the urban system of the region. but, from 1976 to 1996, the concentration decreased and after 1975, it increased again with very mild intensity. The Taghvaee index shows that the concentration of the entire urban system has increased from 1956 to 1976 and has decreased sharply from 1976 to 1986 and there has been a very slight decrease in concentration from 1986 to 1996. From 1996 to 2016, the concentration of the entire urban system has also increased dramatically. Among the balance indices based on the Pareto rule, three indexes of Zipof coefficient with OLS method, Zipof coefficient with HILL method and Zipof coefficient with Alperovich method were calculated for the region. The results of the Zipf coefficient in all three methods, indicate that the urban system of the region has moved toward unbalance first, then to balance and finally to unbalance again.
The purpose of this study was to investigate the evolution of urban system in the central region of Iran. In order to test the research hypothesis, primacy, concentration and balance indices were calculated for the central region of Iran between 1956 and 2011. The findings show that the urban system in the central region of Iran has urban primacy and tends towards imbalance and concentration, so the main hypothesis of the research is rejected