Measurement and evaluation of urban sprawl (Case study: Sari city)

The accelerated and uneven physical spatial development of Iranian cities in the last few decades has brought adverse social, economic and physical effects and consequences. The exorbitant costs of city transportation and services, energy waste, waste of material and social capital in the city are considered to be the most important problems of cities in the discussion of unfavorable development of physical space and low density of cities. The purpose of the current research is to investigate the phenomenon of scattered urban sediments and to measure the amount of dispersed sediments in Sari city. In terms of the type of method, it has a quantitative methodology of the factor analysis type. Exploratory factor analysis was done to identify the correlation and hidden structure between each of the research variables. The research showed that 16 effective indicators in urban sprawl in Sari city can be categorized into 6 factors: density, accessibility, net density, irregularity of built areas, activity space and construction parts. Also, the total scattered index in the areas of Sari city showed that 176.60 hectares of the area and 18124 people of the population from the city of Sari are in the scattered area, and also 598.31 hectares of the area and 74540 people from the city of Sari are in the scattered area. There are too many. The two factors of density and accessibility have a high effect on scattered land and also in the areas that have witnessed the highest amount of land scattered from the social and economic point of view, they have drawn a vision of poverty, illegal land use change, lack or shortage of infrastructure services and public services and caused the formation of and the expansion of inefficient urban tissues.
Extended Abstract
Introduction
The accelerated and uneven physical spatial development of Iranian cities in the last few decades has brought adverse social, economic, and physical effects and consequences. The exorbitant costs of city transportation and services, energy waste, and waste of material and social capital in the city are considered to be the most critical problems of cities in the discussion of unfavorable development of physical space and low density of cities. The city of Sari is one of the cities of Iran whose rapid and accelerated growth and development in recent decades due to population growth, rapid migrations, urban land policies, parts of urban land remaining unused, low density, expansion of peripheral suburbs and centralized urban system have led to the breakdown of the spatial organization and the traditional neighborhood system. In addition, until a few decades ago, it was formed in a limited, organic, and coherent space, but today it has expanded a lot and is caught in a porous, unbalanced, and scattered structure. Based on this, the current research seeks to measure the amount of scattered precipitation at the level of the districts and identify the most important factors that cause it in the whole city so that it can provide a favorable ground for creating a spatial balance and expanding the city in a guided way. The current research aims to measure the amount of scattered water in Sari. This research is descriptive-analytical and practical in terms of purpose and applying the results.
 
Methodology
This research is descriptive-analytical in terms of its purpose and practical in terms of applying the results. Also, in terms of methodology, it is quantitative and a factor analysis type. In order to analyze the data, the factor analysis method was exerted. For this purpose, 16 effective indicators in urban sprawl were determined using background, research, and library studies. In the following, each of these 16 indicators was calculated using the data of the statistical blocks of Sari city as well as the data of the master plan of Sari in 2017 in the GIS software environment. Then, using the extracted data, exploratory factor analysis was performed to identify the correlation and hidden structure between the research variables. Moreover, each of these 16 indicators should be presented in a more limited number of indicators and in the form of a general category. These categories were examined according to each urban area. Finally, by combining these indicators, the amount of scattered sediment was calculated according to the areas.
 
Results and discussion
Based on the results of the current research by conducting factor analysis, 16 research indicators were placed in the majority of 6 general factors of density, access, gross population density, activity space, construction parts, and irregularity, which explain a total of 89% of the variance of the urban sprawl phenomenon. In other words, each of these factors explains 26, 21, 15, 11, 9, and 7.5 percent of the urban sprawl phenomenon's variance. Among the factors, density and access have a high effect on urban sprawl, which should be considered more in the formation and rooting of this phenomenon. In District 2, the highest amount of dispersal zone can be seen, which covers an area of 535.545 hectares with a population of 28,624 people. Then District 4, which includes the city's central core, with an area of 184.79 hectares and a population of 14,740 people, and also in District 3, an area of 166.227 hectares and a population of 15,257 people, are located in a very dispersal zone. In general, 176.60 hectares of the area and 18124 people of the city of Sari are in the very low dispersal zone, and 31.598 hectares of the area and 74540 people of the city of Sari are in the very high According to the final map, out of a total of 20 districts, 15 districts have high and very high dispersal.
 
Conclusion
According to the results, the urban sprawl of Sari city can be presented based on three different spatial patterns, which include:

The pattern of continuous low-density development can be seen in areas 3 and 4 of District 2 on the eastern edge of the Tajan river and in the areas of Imamzadeh Abbas and Zoghalchal. These areas were rural areas that had recently been added to the city limits.
The marginal development pattern is seen in District 1 of District 4 in the area of Dokhaniat and adjacent to the famous area of Rahband with a unique and inefficient texture.
The pattern of internal development that can be seen in District 4 and the city's central district.

The fields of formation and creation of each of these patterns have been different, so each of them has different characteristics, and different approaches should be taken to organize them.