شناسايي عوامل موثر بر پراكنده‌روييِ شهري، و ارتباط آن با ساختار فضايي شهر؛ نمونه مورد مطالعه: شهر اروميه

Identification of Factors Influencing Urban Sprawl and Its Relationship

پراكنده‌رويي پديده‌اي است كه در نيمه دوم قرن بيستم شكل گرفته و امروزه به‌عنوان يكي از موضوعات محوري در بسياري از كشورها مطرح است. پراكنده‌رويي پيامدهاي مثبت و منفي فراواني را به‌همراه داشته است و مي‌توان گفت كه با توجه به ساختارهاي گوناگون و ويژگي‌هاي متفاوت جغرافيايي، اقتصادي، اجتماعي، سياسي و جز اينها، دلايل پراكنده‌رويي از شهري به شهر ديگر متفاوت است. اروميه از شهرهايي است كه در سال‌هاي اخير با سرعتي شتابان گسترش يافته است. به‌منظور بررسي ميزان پراكنده‌رويي در اروميه، پس از مروري بر متون نظري و تجربي مرتبط، بر اساس تلفيقي از نظريات اوينگ و ديگران (2002)، تورنس (2008) و فرنكل و اشكنازي (2007)، با استفاده از 19 متغير نشانگر پراكنده‌رويي و انجام تحليل عاملي در 30 ناحيه اروميه، در نهايت اين شش عامل، كه پراكنده‌رويي را در اين شهر تبيين مي‌كنند، معرفي شده‌اند: اختلاط كاربري، تراكم، بي‌قاعدگي نواحي ساخته‌شده، مركزيت، دسترسي، و فضاي فعاليت. مقايسه پراكنده‌رويي با روند گسترش كالبدي اروميه در سال‌هاي مختلف، نشان مي‌دهد نواحي‌اي كه در دوران آغازين شكل‌گيري شهر به‌وجود آمده‌اند، پايين‌ترين ميزان پراكنده‌رويي را دارند؛ و با هرچه نزديك‌تر شدن به نواحي ساخته‌شده در سال‌هاي اخير، مي‌توان ديد كه عمدتاً روند گسترش شهر به سمت پراكنده‌رويي بيشتري ميل مي‌كند. همچنين بررسي ساختار تك‌مركزي ـ شعاعي اروميه و مقايسه آن با پديده پراكنده‌رويي، مشخص مي‌سازد كه گسستگي ايجادشده در ساختار فضايي اروميه باعث شده است كه عمدتاً در نواحي خارج از ساختار شهر پراكنده‌روييِ زيادي مشاهده شود.

Disharmonic growth of Cities and urban sprawl are among the most problematic issues of current cities which have led to destruction of farm lands around them and other destructive consequences. Therefore, it has doubled the importance of conscious leading and controlling expansions of cities. Urban sprawl, which was initiated in the second half of the 20th century, is propounded as one of the main issues in most of the countries. Urban sprawl is accompanied by several positive and negative consequences and is caused by various reasons in different cities with different geographical, economical, political and social characteristics. The Iranian cities are no exceptions to this norm; although they have had slow expansions over the last centuries. However, as the time goes by, most of them are faced with sprawl phenomenon. Moreover, specific formal characteristics of the cities act as effective factors in urban expansion, and lacking specific forms and structural patterns. Meanwhile, structural tools, which have formed the city and caused the integration of spatial organization of it, are kinds of instruments that through them the urban planners, as well as the decision makers, can help the urban management to control the expansion of the city. Urmia is one of the cities that has confronted with rapid growth in recent years. In order to measure the sprawl in this city, after reviewing the related theoretical as well as empirical literature, based on the findings of Ewing et al (2002), Torrens (2008), Frenkel and Ashkenazi (2007) on sprawl, 19 variables were selected to study the sprawl phenomenon in this city. A factor analysis in 30 districts of the city was run to identify the underlying dimensions of sprawl in the city. Six factors were extracted, named: mix land use; density; irregularity of the built up area; centrality; access; and activity spaces. The combination of these 6 factors in a GIS map illustrates that the central areas of the city are the least affected areas by sprawl, and the further it goes from the center, the more intensive the sprawl becomes, whereas the most sprawl could be seen in the northwestern, southern, eastern and western parts of the city. Moreover, comparing sprawl and expansion process of the city in different periods of time shows that the earlier formed districts have the lowest sprawl and as a person reaches to the newly built areas, the city expansion process tends to have more sprawled. Also the investigation of the Radial-Concentric form of Uroumieh and the characteristics of development in location and time aspects and comparison of them with the sprawl in various parts of the city indicates that the rupture created in the city form have led to a high sprawl at the out-of-form areas. Consequently, in order to control the sprawl, some proposals were presented by making use of structural tools and creation of integration in the spatial organization of the city.