چکیده:
یکی از مباحث مهم در حیطة تخصصی مسائل شهری، سازمان فضایی شهر و افتراق‌ها و جدایی‌‌گزینی‌‌های فضایی در آن است. به‌طورکلی، ساختار فضایی شهر تا حد زیادی تعیین‌کنندة عملکرد آن است و تأثیر زیادی بر دسترسی، پایداری زیست‌محیطی، اقتصاد، رفاه، عدالت اجتماعی، سرمایة اجتماعی و نوآوری فرهنگی دارد.یکی از عوامل تأثیرگذار بر چگونگی شکل‌گیری این ساختار، نحوة توزیع و سطح سرویس خدمات شهری و رابطة متقابل آن با شبکة راه‌های شهری است؛ به‌‌طوری‌‌که توزیع نامتناسب هزینه‌ها و ایجاد زیرساخت‌های شهری به ارائة خدمات و تسهیلات شهری، به سطوح افتراق‌های فضایی به‌ویژه پراکنده‌‌رویی در شهر دامن می‌زند. در شهر یزد، با گسترش افقی 15 برابری در سال‌های 1345- 1385 و رشد جمعیت 6/4 برابری در همین دوره، شاهد ازهم‌گسیختگی زیادی در سازمان فضایی شهری بوده‌ایم. در این راستا هدف از این پژوهش، تبیین افتراق‌های فضایی در شهر یزد، مبتنی‌‌بر پراکنش خدمات عمومی و ساختار فضایی شبکة راه‌های شهری با استفاده از تحلیل شبکه و چیدمان فضاست. مقایسۀ این دو تحلیل، نشانگر ساختار فضایی منسجم در مناطق مرکزی، همراه با سطح خدمات‌رسانی مناسب شهری است. همچنین تحلیل خوشه‌بندی امتیازهای فضایی با استفاده از آمارة گتیس- آرد جی، نشان‌دهندة تمرکز مناطق با امتیاز بالا در فضاهای میانی در امتداد شمال به جنوب شهر است و با فاصله‌‌گرفتن از آن‌ها، تمرکز فضاها با امتیاز پایین شکل می‌گیرد.
چکیده انگلیسی:
Introduction
One of the critical issues associated with sustainability in the twenty-first century is how cities are growing and developing in the space. Rapid urban growth and physical development of cities cause disintegration of the spatial organization of cities and consequently spatial inequality between urban spaces. This phenomenon can be considered as spatial segregation or fragmentation in the urban space. To accept the principle of sustainable development requires a coherent and balanced spatial structure of cities. Our modern cities have been faced with imbalance service and fragmented urban growth. This can show instability in the cities, such as poverty and informal settlements, spatial and social gaps and a lack of cohesion, the excessive density, traffic and environmental pollution. Urban spatial structure is affected by road network and the main urban landuse, particularly Urban Public Services. The objective of this research is to find spatial fragmentation based on distribution of public services and the spatial structure of urban road network in Yazd city.
Methodology
To perform this analysis, we have used polygon layer of Yazd block and street network layer in GIS 10. To analyze the level of public services, we also employed network analysis technique with 10 variables including educational and cultural, health, sporting, shopping centers, urban facilities, office services, parks, police, and passenger terminals. To analyze the spatial organization of urban spatial structure, Space Syntax technique have been employed with 5 variables including global and local integration, connection, control, and intelligibility. This analysis has been made by using axwoman6 extension in ArcGIS 10 software. The method of Space Syntax is a suitable technique for analysis of urban spatial structure permeability. Integration is the main concept of configuration space. Integration of a point indicates its connection to the general structure or a subset of it.
Since the value of the variables is different, the Fuzzy Delphi technique has been used for weighting of them. The Fuzzy Delphi is the combination of Delphi method and Analytic Hierarchy Process (AHP) in fuzzy environment. In this method, AHP weighting process is done based on the Pairwise Comparison Matrix. The indicators are weighted by 10 urban professionals who have knowledge of the physical space.
Finally, we have also used Kernel Density analysis to analyze patterns of spatial fragmentation and Hot spot analysis to understand the spatial clustering and focused fragmentation or integration in spatial structure of Yazd.
Results and Discussion
Overlapping Space Syntax parameters in Yazd city indicates that both north-south and east-west crossing, that almost cover the entire city, are the most integration crossing in the city. As a result, these streets form the city backbone and considered the main factor of the urban spatial organization coherence. Thus, it can be argued that the more spaces between these structures and other urban spaces, the more is the isolated areas or spatial separation in the urban space. The results of Kernel Density analysis of space syntax results represent the spatial coherence in downtown and away from the downtown towards the periphery. This reduces spatial integration and increase in spatial segregation and greater disintegration, especially in margin neighborhoods southwest of the city.
Simultaneously, the results of network analysis indicate that rich areas are developed in inner urban spatial areas and deprived regions in the newly developed part of the city. The old and historical districts are in the central city of Yazd and much of the city has worn out neighborhoods in these districts. The old districts are at higher level of service than other urban areas in this part of the city. These are the reasons for scattered development, especially on the South West and West edge of the city. Thus, the level of service is zero in these parts of the neighborhoods.
In hot spot clustering, although the central area of the city and the historical context have formed hot spots in terms of service level, but they have low and middle scores in terms of the spatial structure of the spatial concentration. Also, some marginal neighborhoods in terms of service levels are at low level, but in terms of the integration of the spatial structure they have formed hot spots. This phenomenon may be caused by organic fabric of historic neighborhoods and checked fabric of marginal areas. The checked fabric is more permeable than the organic fabric.
Conclusion
Distribution of urban services as one of the main indicators of citizen welfare and shaping urban spatial structure and activity is one of the important problems in most of the developed and developing countries. The results of this study indicate that while some downtown neighborhoods are parts of historical and worn-out textures, but in terms of service levels they have higher scores in comparison with other places around the city. However, this is due to lack of quality of life suffering from time-warning. Lack of coherence and integration of the internal structure of these neighborhoods with the whole structure of the city is the reason for lack of space quality in urban central neighborhoods. Perhaps the historic fabric neighborhoods are isolated socially from the rest of the city, but due to both physical and spatial relationships and integration with the main structure of the city they have no significant difference (although regeneration is necessary, particularly in the internal space areas). Thus, the spatial organization of historical fabric is not the cause of exhaustion in these districts. But the main reasons are social and economic problems. The spaces, which are separated from the spatial organization and formed in cold spots, are populated neighborhoods.
On the other hand, disintegration in the spatial structure of the city is the influential factor in the high horizontal development of the city. Hence, the creation and redefining integration of urban spatial organization is essential to prevent the scattered development in the city.
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