Investigating the impact of urban land expansion on the spatial form in the Tehran metropolitan region

Metropolitan regions as a new form of urbanization are expanding rapidly and under the influence of different factors, have different growth patterns. The main purpose of this article is to investigate the evolution of form in the metropolitan area of Tehran under the influence of urban land expansion during the years 1986 to 2016 using the urban land density function. The results of this study show that the trend of urban land expansion in recent years has shifted the shape of the region to a scattered and decentralized pattern. The results of the study of the expansion of urban land in the form of the region at the middle and micro level show that other cities around the metropolis of Tehran have become wider and more scattered over time. Findings show that over time, urban density in urban areas and rural areas and around the metropolis of Tehran has increased under the influence of urban expansion waves.  In the metropolitan area of Tehran, the increase in the boundary between the urban edge and the surrounding areas over a period of thirty years describes the vast urban expansion. In the metropolitan area of Tehran, in recent years, the slope, changes in barren lands, distance from built-up areas, changes in agricultural use, and distance from main roads have had the greatest impact on the expansion of urban land. The rapid growth and urban sprawl in a metropolitan area in metropolitan areas, above all, affect the peripheral areas and cause a disruption of the spatial order, the destruction of natural lands around, increasing marginalization and informal settlement and integration of areas. It becomes a village in the urban space.