Evaluation of Intra-Urban Capacities with Emphasize on Infill Development Strategy (Case Study: Ardabil City)

Introduction
Most urban areas have faced to sprawl growth due to rapid population growth and immigration expansion in the last three decades, and a strong tendency toward urbanism and, consequently, an increase in the need for land to live. These cities have grown with no explicit plan and urban areas have expanded to several times their original size in a short period of time or their development has been in separate parts without planning. This challenge has become known as the pattern of urban sprawl and has been the source of many problems in developing and developed cities. Ardabil city, along with other cities in the country, has undergone a serious change in the urban planning system after the recent developments. This city became the center of the province in 1993, which intensified the process of physical and demographic growth of the city, so that the population of the city in 1997 was 340386 thousand people, which in 2017 reached 527264 thousand people. Simultaneously with population growth, urban sprawl also occurred with the integration of villages and the change of agricultural land uses on the outskirts. Despite this problem, so far in urban plans, no serious attention has been paid to the control of urban physical development and intra-urban capacities. This article is a research to answer the questions as follow; whether the city of Ardabil has internal capacity for development? and this strategy could be one to prevent the physical growth of the city? In order to answer these questions, first, the rate of urban sprawl was determined and then the internal capacities of the city were identified and finally the feasibility of the ability of these capacities to estimate the lands required for the future development of the city has been examined.

Methodology
The research is an applied one. The required data and information have been collected by documentary-library method and official statistical reports of the country and the city of Ardabil. To investigate the physical growth of the city and the spatial distribution of the city's internal capacities, the Shannon and Heldren models and Average Nearest Neighbor in ARC GIS software were used, respectively.

Results and discussion
According to the calculation of entropy method, the rate of ln (n) was obtained 1.38, which in comparison with the rate of entropy coefficient of the city, which is 1.37, indicates the urban sprawl. The results of Heldren's method also showed that physical growth has been 90.31 percent due to population growth in Ardabil city during the last 20 years, from 1997 to 2017, and only 9.69 percent has related to urban sprawl which has led to decrease population gross density and increase of land gross per capita. The findings of the study of the city's internal capacities also showed that more than 917 hectares of the proposed land uses of the detailed urban plan have not been realized yet. According to a comparative study, the amount of land uses in infill development has been higher than the amount of internal capacity for this city, which is equivalent to 2408 hectares. Finally, the results of VIKOR calculations indicated that third region of the city has the highest internal capacity due to the importance of each of the studied land uses and based on the numerical average of the nearest neighborhood that was measured at -27.85, the inner capacities of the city are distributed in clusters across the city.

Conclusion
The findings of the project confirm that the lands and internal areas of Ardabil have the necessary features and quantitative capacities for the policy of infill growth. The extent of areas combined with thematic diversity and different perspectives, the local pattern, and the system of establishing urban infill areas enables urban growth planning by resorting to infill growth policy. However, the policy of infill growth is a multifaceted and very complex one; Not only because of the extent of the concept and the inclusion of a wide range of urban real estate or the variety of goals and methods of implementation, but also because of the multifaceted and fundamentally controversial nature of planning due to the presence of multiple actors in this urban growth policy. As a result, any planning to develop an infill growth plan should be based on understanding the social and cultural characteristics of the population, monitoring the demographic changes of urban residents, the size of existing land plots, and observing the priorities of function (priority for exit and transfer of disturbing activities and inconsistent land uses, priority of revitalization of problematic and inefficient textures and activities with environmental pollution or social harm), observance of the dynamics of the limitations of the natural environment (faults, canals, and other natural features areas) and most importantly, in line with the zoning of land uses permitted to be established on the basis of the city's zoning system, which is guiding criteria for the policy of urban infill development.