One of the important strategies that have been taken into consideration in the last half-century to counter regional imbalances, caused by the increasing growth of large cities, is the creation of small cities. Due to the availability of some facilities and services, small cities are considered as one of the important centers for bringing balance to regional development. The method of the present research is a descriptive-analytical one, and the purpose of this research is to study the status of changes in the urban system of the small cities of Alborz province in order to bring balance to the regional sustainable development. In order to find out the status of small cities in the urban system in a 30-year period (1986-2016), rank-size models, as well as entropy and balance sheets models were used, and then their role in bringing balance to the regional development was evaluated. The results of the study show that the Entropy coefficient without counting the small towns, will still have imbalances. The rank-size logarithmic model, by counting small cities with the slope of the line amounting to -1.94 and without counting small cities reduced to -1.21, indicating the undeniable role of small cities in the urban system. Also, the results of the balance sheet model show that component changes are mainly intra-class and are due to the growth of cities. Moreover, concerning the process of changing villages to cities, changes resulted from the formation of new cities can be seen only in 2006.

Due to the consequences of globalization, regional development, which has always been highly important in macro planning, requires new approaches that are flexible about regional change. Among these consequences is the emergence of powerful regional economies with high GDP that have drawn the attention of many planners to the concept of competitiveness. Using recently proposed approaches and the important aspects of the global economy, this study set out to explore this concept at the area level. The purpose of this study was to analyze movements and structural-functional relationships in order to develop a local pattern of clusters in Tehran province. This study was a developmental-applied research project in terms of purpose and an analytic-descriptive one in terms of methodology. The data collection was based on document analysis and library studies and the data was collected through note taking, available statistics, and documenting. Data analysis was carried out using cluster analysis and specialized index methods, and the results were used in identifying activity clusters after examining the natural capability of each county. The results of the analysis show that the pattern of activity in Tehran province is the metropolis-dominated cluster pattern, and the counties which are located in the province can be identified in the form of 5 regional-local clusters. The above mentioned clusters of activities can provide the basis for regional development in Tehran province by joint and purposeful planning based on the priorities offered in this article.