عنوان مقاله [English]
The imbalance in the world's urban hierarchies has created problems, especially in developing countries, such a situation that is intensity and weak, but is most commonly seen in most parts of Iran. Because of existence of the first urban phenomenon in Kermanshah, this fact has caused that more than half of the population to be concentrated in the first city. The method used in this research is applied research. Rank-size model, rank-size-adjusted law model, Lorenz curve, mean annual growth, Gini coefficient and entropy coefficient model were used for data analysis. The results show that during the census period from 1991 to 2016, the city of sarpol-e Zahab is one of the medium-sized cities and the results revealed that due to the first presence of Kermanshah city, the urban hierarchy has not complied with the law of size and the inconsistency and lack of equilibrium in the urban hierarchy of the province has been determined. Studying the trends of urban changes and urban population during the five censuses from 1991 to 2016 in Kermanshah province and analyzing them shows that urban growth has gradually intensified and the ratio of urban to rural population has increased, Survey of urban hierarchy in the province shows that in this province as in most of the provinces in the country has a heterogeneous and unbalanced urban network. The case study in this research was sarpol-e Zahab which, looking at the demographic and physical developments of these cities to achieve the optimal urban and spatial hierarchy, to ensure equity in the distribution of facilities and services as well as to create equal opportunities for small and medium-sized cities of the province, including the city of sarpol-e Zahab, is needed.
Keywords: Small towns, Lorenz Curve, Gini Coefficient, Kermanshah Province, sarpol-e Zahab City.
The existence of a regular urban hierarchy distributes goods and services to the whole community and a balanced distribution of facilities and services to all parts of a region. With regards to the increasing trend of rural migration and increasing of citis populations, studying the pattern of spatial distribution of population in the urban system of each region is an inevitable necessity. By examining the five censuses (1991-2016) in Kermanshah province, sarpol-e Zahab is home to about 50% of the population in Kermanshah. Increasing and concentration of the more population in Kermanshah and, consequently, the first urban phenomenon provides numerous problems. Therefore, it is necessary to examine the hierarchy and urban developments of the province. One of the most important reasons for attention to small towns is the emergence of metropolises, which has created decentralization, causing imbalances and resulting in problems and anomalies.
This research analyzed the urban hierarchy of Kermanshah province with using quantitative models and statistical methods such as rank-size law, adjusted size rank model, Lorenz curve, Gini coefficient and entropy coefficient in sarpol-e Zahab urban network during several census periods. Given the characteristics of Kermanshah province, planning to militarize the hierarchy of settlements and especially small towns can bring regional balance. The spatial imbalances between foci, surfaces, zones, and functional subregions are already in evidence. The most effective way to balance the province's urban system seems to be to prevent the monopoly process from continuing to become the province's first city. Decentralization policies and limiting economic, social and cultural potentials are policies that are effective in creating a balanced urban network.
The purpose of this research is an applied research that analyzes and evaluates the structure of urban hierarchy in Kermanshah (about sarpol-e Zahabcity). The method of data collection is library and documentary using several censuses of the General Population and Housing Organization (1991-2016), comprehensive plan, internet resources, tables, charts, and computer applications such as GIS and Excel have been used. This study classifies the urban population data of the province and using quantitative models and statistical methods such as rank-size law, modified size rank model, Lorenz curve, Gini coefficient and entropy coefficient are analyzed.
One of the most important features of the urbanization system in Kermanshah province is the large cities growth and population density. Surveys show that only the metropolis of the province (Kermanshah) is out of order of the urban system and retains its superiority as the premier or prime city, if we consider the distribution of the cities according to population categories and different urban groups (metropolis, big cities, medium-sized cities, and small cities) can be likened to a pyramid, with many small towns at the base of the pyramid, gradually decreasing their number in the upper classes until in the pyramid remains only one city, which is the prime city.
Studying the trends of city and urban population changes during the seven census periods from 1991 to 2016 in Kermanshah province and analyzing them and the findings of the study show that urban growth is gradually intensifying and the ratio of urban population to the rural population has increased, the results of the urban hierarchy survey show that the province, like most provinces in the country, has a heterogeneous and unbalanced urban network. This requires presenting policies and strategies to achieve the desired urban hierarchy. The case study in this study is sarpol-e Zahab city which survey of statistical periods shows that during different decades the population of sarpol-e Zahab city is increasing. It has reached the fifth most populous city in the province. This means that if sarpol-e Zahabis given the facilities and resources, it can be economically and economically attractive to the population and many migrations are prevented to the center of the province
According to the studies, the highest population growth was in the period from 1991 to 2016 and the lowest growth was in the period 2006 to 2011. The results obtained from entropy coefficient decreased from 1991 to 2016, indicating an imbalance in the distribution of urban population in the cities of Kermanshah province. According to the distribution and classification of United Nations, sarpol-e Zahab in considering the tables of 2016 was ranked 5th in the list of middle cities and was the fifth city in Kermanshah province which there is a shortage of population according to the adjusted rank-size model of its population and comparison with the population of sarpol-e Zahab. The main causes of instability in the urban hierarchy include lack of adequate government resources and budgets, lack of proper policy making, inequality in distribution of income and assets, rural structure of the city and rural population density, lack of health facilities, problems in the urban infrastructures (sewage, water and electricity, etc.), social problems, and so on.