**2. Sustainability concept and sustainable urban development**

The history of sustainability concept dates back to 1970s. Sustainability concept arose when environmental degradation and economic bottlenecks were increased and developed countries started suffering from these conditions. Therefore, it becomes a necessity being aware of the common future of the humankind. The concept of "Sustainable Development" gained importance after the Work of the World Commission on Environment and Development known as the Brundtland Commission in 1987. The final product is known as the Brun‐ dtland Report. This is also the first milestone that sustainability concept starts to reflect itself on urban planning. Sustainable development is a continuing and balanced development model. As cities are the basic elements of contemporary civilization, it can easily be claimed that sustainability concept is an urban-based concept. Sustainable urban areas are the key factors for the success of sustainability approach. This situation is emphasized and gained more importance after the Earth Summit or the UN Conference on Environment and Development in Rio in 1992 and Habitat II Conference held in Istanbul in 1996. After the Habitat II Conference, sustainable development became a necessary strategy that countries have to adopt as a requisite.

"Local Agenda 21 accepted in Rio Conference has a special importance that it could be accepted as the primary mechanism for the application of sustainable development at the local level. This shows that urban areas have become the focus of sustainable development policies starting from the 1990s" [2].

Substantially, the sustainability concept can be adapted to all components, sectors, and institutions of any society. Sustainable city, sustainable economy, sustainable mining, sustainable education, and sustainable environment are some of the examples of this state‐ ment. However, sustainable development has a framework that contains five stages as political and supervisory (related to decision making, participatory processes, use of resources, etc.), physical (spatial relations, land use, etc.), environmental (eco systems, artificial urban systems, land, air, water, etc.), economic (production, consumption, employment, etc.), and social (equity, security, life quality, etc.) stages [4].

Sustainable development and sustainable society are urban-based concepts. Though there is a concept of rural sustainability in the literature, it is not wrong to assimilate the sustainable development concept within urban sustainable development as the basic determinants of the civilization are the urban concept and urban life. In addition, urban areas are against the nature and natural ecology as built-up environment of cities invades natural land in a very fast manner. Even you built up a cabin in the woods, you can give damage to the microenviron‐ ment and ecology on the area you built up your cabin. The concept of city and urban sys‐ tems is naturally against the ecological sustainability concept. That is why the urban areas have become the key factors of the sustainable development. Not only the environmental and ecological concerns are the focus of the problems, but also economic and social problems arise from urban systems and mechanisms become the source of global anxiety of future. Especial‐ ly, as cities of developing world are overgrowing, environmental, social, and economic problems are not remaining as local problems but they are seen as global problems and tried to be solved. In this respect, sustainable urban development takes place at the heart of the sustainability concept. Sustainability of urban areas becomes the key factor in sustainability debates.

Definitely, planning is the main director of urban development and urbanization. Planning not only deals with the physical development of the cities but also affects the social, econom‐ ic, and cultural future. For this reason, a sustainable urban planning model is very essential for the sustainable urban development and a sustainable society.
