عنوان مقاله [English]
Analysis of urban growth using multi-temporal data is topic that have great importance in urban studies and planning for the future of cities. The city as a dynamic phenomenon has an spatial- temporal identity which is changing during the time result from human activities and it is expanding. Generally, the city growth is affluence by different human and physical factors thereby the extent, dimensions and directions of expansion and growth are affluence by those factors. The first consequence of a city expansion and sprawl is land use and land cover change of peripheral lands. According to this, depends of where and how urban sprawl is took place, it might have positive and negative impacts. Planning for the future of urban expansion and directing it to a proper and sustainable direction, awareness about urban expansion, urban growth and urban sprawl in different periods is totally necessary nowadays. One of the most important ways to analyze and study the expansion and growth of a city is using the data and methods of remote sensing.
The city of Mashhad, second largest city in Iran, has experienced a big migration from villages and towns result from, millions of tourist yearly, more attention of the government, increment of investments and creating more employment opportunities. This factors has grew the population first and then expansion and sprawl of the city. Mashhad’s growth has been taken place without any attention to environmental potentials, thereby, many problems in parts of socio-economic and environment has been emerged. Therefore, this paper aimed to study and analyze the physical growth and sprawl of Mashhad from 1987 to 2013 using satellite images and change detection algorithms and detect land use / cover change. In addition to this, the proper and appropriate direction for the next growth has suggested.
The aim of this study is to Assessment of the physical expansion of the city of Mashhad, Identify the nature of changed lands to urban uses, determining the main directions of growth and also examine growth pattern of this city. Thus using Landsat satellite images (1987, 2000 and 2013), were extracted land use and land cover classes for city of Mashhad and its surroundings. Using changes detection technique by post-classification comparison method, were identified changes from agricultural lands and barren lands to urban land uses. Then using zonal statistic techniques, were obtained extent and nature of changes in different geographical directions.
Results and Discussion
According to the results, from the 1987 to 2000, the amount of 3,344.67 hectare of agricultural lands and amount of 6,964.11 hectares of barren lands are converted to urban land uses. The main directions of expand of the city at this time, respectively is northwest, west and east directions. The northwest, east and north directions respectively is directions that had been highest amount of agricultural land change to urban land uses. On the other hand, in the directions of northwest, west and south, change from barren land to urban land is higher than in other directions. Examine the density and distribution of urban growth show that expansion of city has followed the sprawl growth pattern. According to the results, provided maps and satellite images of the city of Mashhad, the most appropriate direction for the future development is the northwest. Because in this direction, the proportion of barren lands into agricultural lands compared to the other direction is further. Also there is not any natural barrier limiting in this direction.
According to what has resulted from the data and analysis, Mashhad has a very rapid rate of population growth in last decade. This phenomenon has a lot of causes like tourism, job opportunities, and amenities and so on. But the more interesting phenomenon is its urban sprawl and physical expansion that it is much more rapid than population growth. So that, from 1987 t0 2013, the expansion of this city has increased more than two times. The most changed uses are barren lands and agricultural lands. About 3344 hectares of agricultural and grand spaces has converted to urban land use in a short period (26 years). The growth this city is so much rapid that it is possible to say that it has all conditions of urban sprawl in a developing country, growth toward villages and along roads and highways very scattered and fragmented. The restled showed that the growth won’t stop but urban managers and planners must direct it to the optimism direction that the least productive lands change. It is said that the best direction for the next growth of this city is North West. We have to use and implement some strategies to strengthen the city growth to this site.