Investigating the Role of Small towns in Balancing Population in Kermanshah Province (Case study: sarpol-e Zahab City)

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.