Abstract

Urban expansion is one of the patterns of urban growth that causes the expansion of the central core of the city towards the peri-urban areas and the destruction of agricultural lands, gardens and natural resources and the negative effects of the environment. The purpose of this research was to investigate the pattern of physical-spatial expansion of Shiraz city and to analyze and identify factors affecting its expansion. Therefore, it is considered as one of the applied researches that used the descriptive-analytical research method. The required data and information have been collected through documents and library as well as field research, and to measure the physical growth of the city, two quantitative models, Heldren and Shannon entropy, have been used. The results show that the metropolis of Shiraz has had an inappropriate and large growth, which can be imagined as a scattered growth pattern. According to Holdren's model, about 59% of the physical growth of the city was related to population growth and 41% was related to the horizontal and spiral growth of the city. Also, the entropy index for the years 1365 and 1395 is 2.3 and 2.95, respectively, which shows its horizontal growth. This horizontal growth has taken place on agricultural lands and gardens, and as a result, it has caused the reduction of productive activities and the destruction of agricultural lands and productive gardens in peri-urban areas. Therefore, it is necessary to find a solution to preserve natural spaces and remaining resources.

Keywords: Urban growth, Holdren model, Entropy model, spatial expansion, urban sprawl

Urbanization is a universal and growing trend. Urban expansion is basically another concept for urbanization, which refers to the migration of population from densely populated cities and towns to low-density residential development in suburban and suburban areas. The final result of the expansion of the city and its peri-urban suburbs is marginalization. In other words, urban sprawl is defined as low-density residential and commercial development on undeveloped land. (Mokhtari, 1385). Urban sprawl, which is also called suburban sprawl or sprawl, is the rapid expansion of the geographical extent of cities and towns, which is often characterized by low-density housing and increased reliance on private cars. Economists consider three basic forces involved in urban growth that interact with land values to create urban spatial expansion. First, population growth leads to the outward expansion of urban areas. Second, increased income allows residents to afford larger living spaces. Third, there is a reduction in commuting costs. Therefore, dispersion is the result of a complex set of socio-economic and cultural forces related to each other (Mouratidis, 2019). The expansion of the scale of urban areas, especially in metropolises and their suburbs, especially in big cities, is increasing, the extraordinary growth of the region and the increase in the urban population in the last four decades is a global phenomenon, especially in the developing countries of the world, as For example, a city like Shiraz has experienced rapid development in the last two decades. Shiraz is the fourth city of Iran and the most populous and largest city in the south of the country, which was determined according to the estimate of 1400 (Housing Census, 1390). Looking at the satellite maps of the city of Shiraz and the detailed plan of the urban area between the years 2000 and 2022 It shows that the city of Shiraz, both horizontally and vertically, has experienced density and increase in size in all different directions, this expansion is most evident especially in the direction of the main and exit routes of the city and residential areas in the suburbs. Unprecedented urbanization in development leads to this expansion. Continuous development of urban land with rapid transformation of changes in economic activities, huge increase in the number of urban migrations and pressure of rapid urbanization has led to development. One of the important points in growth and change The population and urban expansion of Iran is noticeable, the change in the composition of the population in terms of urban and rural is noticeable, so that the rural population decreases and the urban population increases every year. In 2016, the country's rural population was 20 million and 749 thousand. The urban population was 60,304,000.Thus, in this year, 74.4% of the country's population lived in urban areas and 25.5% lived in villages. But in 2019, we see a significant change in this demographic composition. In this year, out of the country's population of 83 million and 409 thousand people, 20 million and 353 thousand people lived in rural areas, which indicates a significant drop compared to 2016. On the other hand, this year the urban population has increased to 63 million and 56 thousand people. Therefore, the share of cities in the country's population has increased to 75.5% (Iran Statistics Center, 2019).