Evaluation of Urban Growth and Its Impact on Vegetation and Environmental Sustainability (Case study: Zahedan City)

unplanned urban physical development inflicts irreparable damages such as Land use change causes, vegetation loss, an increase in the temperature of the earth's surface, an increase in the price of residential land, and the tendency to marginalization becomes unplanned. In this research, To investigate urban changes during a 25-year study period from 1995 to 2020 to prevent the mentioned damages due to physical development without a plan three Landsat images for analysis were obtained from the USGS website.  Pre-processing and processes to identify the changes on the images to estimate the physical development were done in ArcGIS and ENVI software, the surface temperature was extracted, the marginal areas were determined, the change map was obtained and finally the results were validated. The results showed that in 2020 and 2015, the temperature of the earth's surface in the northern and northeastern regions is higher than in other directions of the city, during 2020-1995, about 1850 hectares have been added to the area of urban areas. The main reason for the physical development of Zahedan city in the east and northeast direction is the expansion of marginalization in agricultural lands. Also, one of the reasons for the expansion of the city of Zahedan in the south and southwest direction is the presence of industrial towns and administrative centers such as universities. Therefore, due to the increase of built-up lands (marginal areas), the agricultural land in the north and northeast of Zahedan City has decreased and its temperature has increased. It is necessary to continuously monitor urban changes so that urban managers can carefully plan for the physical development of cities to prevent uncontrolled urban physical development and its possible future risks.
 
Extended Abstract
1-Introduction
Today, one of the important characteristics of urbanization is the rapid physical development of cities due to new urban developments, and these developments are manifested in the form of rapid population growth and physical growth of the city. In Iran, the physical development of cities has been due to reasons such as the integration of villages with cities, migrations from villages to cities, etc. These factors have influenced the physical development of cities and have caused many problems, which have manifested themselves in the form of marginal settlements around big cities are like unplanned and unbridled informal constructions. In this study, considering issues such as marginalization and the temperature of the earth's surface, the phenomenon of urban expansion is discussed, and it is one of the main reasons for unbridled urban expansion in Zahedan City. In this research, it has tried to address this issue by using remote sensing, and to some extent, it can prevent urban expansion without a plan. Unbridled physical development of cities causes land use change that causes irreparable damage such as the loss of vegetation on the surface of the earth, increase in the temperature of the earth’s surface, increase in the price of residential land and tendency to marginalization. For this reason, in this research, to prevent the mentioned damages, using Landsat 5 and 8 images for 25 years, the physical development of Zahedan City has been examined.
 
2-Materials and Methods
First, Landsat satellite images were obtained from the USGS website, and radiometric and geometric corrections were applied to the images. Corrected images for 1374, and 1399 were classified by support vector machine method. For the classification of built-up lands, lands with vegetation, built-up lands, and educational samples were taken. About 100 didactic samples were selected for each class. Then the state of vegetation, wasteland, and built-up lands was determined. Based on the classification done from 1374 to 1399, about 1850 hectares were added to the urban area, and the areas with vegetation and barren areas were reduced. Then the obtained results were validated using satellite images and Google Earth images. To evaluate the accuracy of the classified maps, the indices of overall accuracy, user accuracy, produce accuracy, and Kappa coefficient based on 40 correct points of pixels related to vegetation, built-up uses, and wasteland in different directions for review. The accuracy of the classified maps of Zahedan city for the years 1374 and 1399 was taken and calculated from Google Earth and the maps in which the built-up lands, vegetation, and barren lands are completely clear and are also clearly visible in Google Earth. The amount of each index of overall accuracy, user accuracy, producer accuracy, and Kappa coefficient were determined. The validation results showed that the images classified using the support vector machine algorithm have high accuracy.
 
3- Results and Discussion
Based on the obtained results, the built land in Zahedan city has grown increasingly from 1374 to 1399, and built land has increased from 33729300 to 18503100 square meters. From this amount of built land, 6478200 square meters are marginal areas. So the land with vegetation has started a downward trend since 1374. Agricultural land has decreased from 4,410,900 in 1374 to 735,300 square meters in 1399 and barren lands have also experienced a negative growth from 2014 to 2019. With the loss of vegetation-covered lands, the surface temperature of the northern and northeastern areas of Zahedan city has taken a rising trend, even though during the study period, there was a general downward trend in the surface temperature of the ground, from 49 degrees Celsius since 1374 reached 42 degrees Celsius.
 
4- Conclusion
The results of this research showed that by examining the urban expansion of Zahedan City using remote sensing about surface temperature and marginalization, according to the maps, it can be concluded that urban expansion in Zahedan City is unbridled and in all directions has happened. The urban expansion of Zahedan city is more in the north, northeast, northwest, and south directions, and no plan has been adopted to prevent urban expansion in the north and northeast directions, which are considered high-risk areas due to their proximity to the Zahedan fault. Agricultural lands have turned into built-up lands as a result of marginalization, and this has caused the temperature of the earth's surface to rise in these areas. One of the main reasons for the expansion of the city to the north, northeast, and northwest is the phenomenon of marginalization, which is the result of indiscriminate migration to Zahedan city. The lands located in the south of Zahedan have been converted into built-up lands due to the favorable climate and the existence of administrative centers such as universities and industrial towns. One of the main reasons for the expansion of the city to the south and southwest was the presence of university industrial estates and administrative centers. According to the obtained results, the growth of the city of Zahedan was unplanned and caused the loss of land with vegetation and instability in the environment. The results of this research show that the further expansion of the city towards the Zahedan fault and areas with vegetation should be prevented. This can be possible by adopting policies to reduce the immigration of Zahedan city or planning for settlement in non-sensitive areas. To avoid Unplanned urban growth is suggested that city managers use remote sensing for urban expansion in the right direction to prevent the expansion of the city towards quality lands, agricultural lands, faulted land, etc.