Considering and Analyzing changes of urban hierarchy in the sixth decade (1335-1395)(case study: Semnan province)

Urban hierarchy survey is the most effective way to recognize the organization of the city system and helps to manage its space. The lack of attention to the urban hierarchy system and the distribution and distribution of urban centers in the area of one region on the one hand and the growth of urbanization on the other hand will lead to imbalance and rupture in the spatial structure ofcities. This research is a descriptive-analytical method and a method for collecting information as a library. In this regard, the cities of the province based on the results of general census surveys of population and housing during the years 1335 to 1395 using the models (urban hierarchy profiles) ) ((Rank-size)) ((stratified difference limit)) have been analyzed and analyzed. The results indicate that the existence of two superior cities of Shahrood and Semnan, the hierarchy of the province from the rank of the rank - size did not follow, and the result of the stratified difference model showed that the division of cities in the province is not harmonious and systematic failure and a significant statistical failure in It is there. About 71 to 80 percent of the city's provinces are in the fifth-order population group. Graphs drawn from the urban hierarchy graph model over the past six decades show that the population of cities has not been balanced in different censuses and imbalances It is quite evident in the number of cities and their populations.