Physical Development Patterns of Urmia City and Providing an Optimal Pattern to Increase Compression

Introduction One of the vital issues of the 21 century for urban scientists is urban form (Compression or distribution) and urban stability. Therefore, knowledge of the urban spatial form and its shape can have an important role in the success rate of urban planners and help us improve the urban environment. As urban growth pattern is related to one of the most accessible human resources of the earth, so it is important to consider the main criteria for sustainable urban development. Urban population growth and rapid expansion of cities has faced most countries in the world with numerous problems. The problems affected not only urban policy but also the socio-economic and environmental issues in most of the urban areas.Among these problems, we can point to sprawl, spatial imbalance, development without planning, increased infrastructure costs, loss of agricultural land with good quality, expansion of urban areas, formation of low-density tissue in the margins of the city and the difficulty of service. The purpose of this study is to evaluate the situation of urban density and compression in Urmia and the process of its growth and development. By using the results, we can achieve a suitable pattern and strategy for the future development of the city. In order to solve negative effects of the widespread distribution of cities, we have proposed different suggestions, solutions, ideas and opinions.Sustainable development as the theory of the third millennium and a replacement for the previous school ideas represents  the necessary condition for the balanced development in social, economic, administrative and physical space. One of the fundamental functions in urban planning is paying attention to the physical growth and development of the city. Therefore, the necessity of planning and urban appropriate design is to use the methods of development required to prevent construction of agricultural lands around the cities and urban sustainability.Therefore, we have calculated the degree of distribution and compaction of Urmia based on quantitative indicators in different periods with the mixed land use.   Methodology Research Methodology in this study is Analytical-descriptive. The population is the residents of Urmia and its four regions. The information has been collected through detailed results of General Census of Population and Housing, Comprehensive Plan and the maps of current situation. To investigate the process of urban development we used Heldern, Shannon entropy and accumulation index in order to solve the problems related to urban sprawl. Mixed land use policy is offered for urban compression. To review and assess the state of mixed land use, we used Balance Index, Herfindahl-Hircshman, Dissimilarity Index and Atkinson.   Results and discussion The results of Heldern model showed that only 59 percent of urban expansion has been due to the Population growth and 41 percent has been related to horizontal growth and sprawl. This can result in a decrease in population gross density and increasing gross per capita in urban land. The amount of entropy for the year 1989 has been 1.362, While the maximum value is Ln= 1.386. Proximity to the maximum amount of entropy can represent urban sprawl. For year 2007, this amount has been 1.312. This shows that during 20 years, Physical expansion has been scattered and non-condensing. Moran coefficient was -0.16 for population and -0.01 for job. Gary coefficient was 1.4 for population and 0.94 for job. These coefficients have represented Urban Sprawl for population and pattern of random agglomeration or multipolar for job. In the second part of the study, to determine diversity and mixed land use, we have employed the balance, heterogeneity, Hirschman and Atkinson models. The results of these models show that among the Urmia districts, the district 4 has the best conditions due to having a variety of uses with useful distribution and district 3 has the worst of these conditions.   Conclusion The results showed that the city of Urmia has expanded sprawl. Therefore, the mixed land use is offered as one of the ways of urban compression. The housing and leisure together are the components of basic needs. While each of these sectors have certain and separate scale  at the same time separation, it is necessary and essential to continue living. As the results of the study showed the district 4 is located in the Urmia City Center. Compared with other areas, the district has more diversity and incorporation. That is because of centralization of this area and the existence of market and business sectors. The ownership  is another factor that influences urban development. Great owners around the urban aras has sold their lands in the north-western and south. Thus, from the direction of the Northwest and south of the city (region 1 and 3), the areas have the lowest level of concentration and the incorporation. The existence of the villages close to the city has caused growth of the city. For evaluation of the mixed land use, we have used the models of diversity to determine balance, heterogeneity, Hirschman and Atkinson. According to these indicators, district 4 has the best and district 3 has the worst.