واکاوی الگوهای رشد شهری در بازه زمانی 20 ساله بر اساس فنون تحلیل فضایی؛ نمونه موردی: شهر شیراز

شهرنشینی پدیده‎‌ای بسیار رایج در سرتاسر جهان به‌ویژه در کشورهای درحال‌توسعه است و تاثیر بازگشت‎‌ناپذیری بر محیط‎‌زیست و کاربری اراضی دارد. ازاین‌رو، شناسایی و درک الگوهای رشد شهری به‌منظور هدایت الگوهای رشد شهری آینده به سمت توسعه پایدار از طریق سیاست‌های فضایی مناسب، ضروری است. باتوجه‌به این نیاز، هدف مطالعه حاضر محاسبه نرخ رشد شهری، شناسایی الگوهای رشد و تغییرات حاصله در الگوی منظر شهرنشینی در شهر شیراز در بازه زمانی 1380 تا 1402 است. با استفاده از تصاویر ماهواره‎‌ لندست، نقشه طبقه‎‌بندی تصاویر ماهواره‎‌ای در سال‎‌های 1380، 1392 و 1402 به‎‌دست آمد. پس از آن به منظور افزایش دقت سنجش الگوهای رشد شهر شیراز، از ترکیب 4 معیار فضایی شاخص شدت گسترش شهر، آنتروپی شانون، شاخص‎‌های منظر و شاخص گسترش منظر، در مقیاس‎‌های کلی و فرعی (در 8 جهت جغرافیایی و فواصل 2 کیلومتری از مرکز) استفاده شد. نتایج نشان داد الگوی رشد شهر شیراز پراکنده بوده و با گذشت زمان تشدید شده است. همچنین مشخص گردید میزان و الگوی رشد شهر شیراز در جهات و فواصل مختلف، متفاوت است. شاخص شدت گسترش نشان داد بیشترین سرعت گسترش در این بازه 22 ساله مربوط به محدوده‎‌های جنوب، جنوب‎‌غربی و شمال‎‌غربی بوده است. آنتروپی شانون و شاخص‎‌های منظر نشان‎‌دادند محدوده‎‌های شمال‎‌غربی و جنوب بیشترین مقدار پراکندگی را دارند. در نهایت شاخص گسترش منظر الگوی غالب رشد شهری در شهر شیراز را الگوی رشد لبه‎‌ای شناسایی کرد. همچنین مشخص گردید بیشترین درصد گسترش بیرونی نیز در نواحی جنوب و شمال‎‌غربی رخ داده است.

analysis of the urban growth pattern during the last two decades through spatial metrics; case study: shiraz city

urbanization is a widespread phenomenon worldwide, especially in developing countries, and it has an irreversible effect on the environment and land use. therefore, it is necessary to identify and understand urban growth patterns to guide future urban growth patterns toward sustainable development through appropriate spatial policies. according to this need, the present study aims to calculate the urban growth rate and identify the growth patterns and the resulting changes in the urban landscape pattern in shiraz metropolitan in the period from 2001 to 2023. using landsat satellite images, satellite image classification maps were obtained in 2001, 2013, and 2023. after that, to increase the accuracy of measuring the growth patterns of shiraz metropolitan, from the combination of 4 spatial criteria of urban expansion intensity index, shannon entropy, landscape indices, and landscape expansion index, in general, and sub-scales (in 8 geographical directions and 2 km distances from the center) was used. the results showed that the growth pattern of shiraz metropolitan is scattered and has intensified over time. it was also found that the growth rate and pattern of shiraz metropolitan areas are different in each direction and distance. the urban expansion intensity index showed that the highest speed of expansion in these 22 years was related to the south, southwest, and northwest regions. shannon’s entropy and landscape indices showed that the northwest and south regions have the highest amount of dispersion. finally, the landscape expansion index identified the dominant pattern of urban growth in shiraz metropolitan as the edge expansion pattern. it was found that the highest percentage of outlying expansion also occurred in the south and northwest regions. extended abstract1-introduction urbanization is a widespread phenomenon worldwide, especially in developing countries, and it has an irreversible effect on the environment and land use. the expansion of urban areas is often at the cost of productive agricultural lands, forests, and vegetation, and this expansion is the cause of many environmental problems, such as climate change, loss of animal habitats, reduction of biodiversity, land fragmentation, air pollution, and heat islands. in light of these global challenges, guiding future urban growth patterns through effective spatial policies is considered key to achieving global sustainability, and towards this, a better understanding of the current urban growth patterns is essential. to increase the accuracy of measuring the growth patterns of shiraz metropolitan, the present research is based on the combination of 4 spatial criteria, urban expansion intensity index, shannon’s entropy, landscape indices, and landscape expansion index, in general, and sub-scales (in 8 geographical directions and 2 km distances from the center) was used. 2-materials and methodsthe case study is the political boundary of shiraz metropolitan with an area of about 1100 square kilometers. this area includes the city of shiraz along with 43 rural areas and some garden village complexes. the current research is descriptive-analytical and in terms of purpose, it is an applied type of research. the data used in this research are landsat 7 etm+ and landsat 8 oli satellite images in 2001, 2013, and 2023. the research method includes two main stages of data pre-processing (satellite images) and their analysis. after performing pre-processing using envi software, in the first step, using the maximum likelihood classification technique, the images were classified and validated into 4 categories: bare land, built-up areas, vegetation, and water bodies. after land use change detection, built-up areas were considered as urban categories and the remaining categories (barren, vegetation, water) were considered non-urban categories the map of the case study was divided into 8 geographical directions and concentric circles with a radius of 2 km from the center of shiraz was separated. finally, the city expansion intensity index, shannon’s entropy and landscape expansion index using arcgis software, and 4 landscape indices including the largest patch index, number of patches, area-weighted mean of the fractal dimension index, and the area-weighted mean of the contiguity index in fragstats software was calculated. 3- results and discussionthe results showed that the built-up areas increased by 52% during the 22 years (from 2001 to 2023). the growth pattern of shiraz metropolitan is sprawl and the amount of its sprawling is increasing over time. also, the rate of growth and urban sprawl is different in each direction and distance. the urban expansion intensity index showed that the highest intensity of growth in the investigated period was in the distances of 6 to 12 kilometers from the southwest, 6 to 18 kilometers from the south, and 30 to 32 kilometers from the northwest. also, the intensity of the expansion of the southeast region increased from 1392 to 1402, and after the south region, it ranked second in terms of the increase in the speed of expansion. shannon’s entropy showed that the northwest, south, and southeast regions experienced the highest sprawl development respectively. the landscape indicators identified the sprawl growth pattern of the north-west and south-east regions. finally, the landscape expansion index (lei) showed that the dominant pattern of development in both periods was edge expansion, and the highest percentage of outlying expansion in both periods was investigated in the south and northwest areas.in this study, the technique of combining panchromatic and multispectral bands (pan-sharpening) of satellite images was used to increase the clarity of the images. similar to the results of previous research, the gram-schmidt technique showed better clarity than other band composition techniques. in this research, the landscape expansion index (lei) was preferred simple urban growth index (s) because the use of a buffer in the analysis reduces possible errors and provides more favorable results. the current study did not evaluate the factors that led to such growth. urban growth is often driven by a combination of different development-driving factors. therefore, while such factors may well be responsible for the observed changes in shiraz metropolitan, they were beyond the scope of the current study and their identification provides a fruitful path for future research. 4- conclusionurban growth dynamics and patterns identified in this paper provide essential information for land use management and planning authorities. in general, the result of all the spatial techniques used in this research shows that the north-western and southern regions of shiraz metropolitan had the largest share in sprawl development in both periods and in providing strategies to guide the growth pattern of shiraz metropolitan and they should be prioritized towards sustainable growth in the future. the north-west area has the highest rate of sprawl and the sprawling trend in this area is still increasing. the creation of garden complexes and the development of villages in this area is the most important factor for the sprawl development of this area due to good economic efficiency and favorable weather conditions.the southern region has also had sprawl growth in recent years. one of the most important reasons for the sprawl development in the south of shiraz is the existence of the industrial town and the special economic zone of shiraz. the industrial sector has been built in the peri-urban area of shiraz and close to its fringe villages and has exposed this area to rapid and extensive job migration. in addition to the spatial expansion of industrial areas, this causes the spatial expansion of fringe rural areas.another reason for the sprawling growth of this area is the planning of government housing projects. these government projects, in addition to their direct impact on spatial development, cause an influx of private investments, mostly with the purpose of personal construction in the direction of economic efficiency. finally, the results showed that in the south-eastern area, which has a lower expansion and sprawl rate than the previous two areas in the last ten years, there has been an increasing trend, and it is predicted that without proper planning, in the future, this area will reach a critical level like the north-west.