Geomorphological Assessment of Land Suitability for the Physical Expansion of Sanandaj City Applying Restricted Areas

Introduction The Third World cities, in recent years, are faced with numerous problems, including population growth, uncontrolled migration and consequently increasing disproportionate construction with environmental capabilities. This heterogeneous development has multiplied the vulnerability of cities to the risks involved. The fact is that the structure of the spatial and physical development of cities is very complicated. This problem prevents many attempts to analyze and communicate useful and effective policies and approved plans of the city. Therefore, understanding the natural structure of the area, on the one hand, could have the breadth of vision and knowledge of the environment and, on the other hand, provides a measured and considered the possibility of any movement in the environment by humans in the form of a regular system. Establishment and creation of a city, more than anything else, depends on the conditions of its geographic location, because the natural phenomena have a decisive effect in location, sphere of influence, urban physical and morphological development. Natural phenomena act as sometimes positive and sometimes negative factors and inhibitors. Therefore, any development in natural areas should be done with appropriate programs and management plans and zoning so that, along with the people use of the region, it is possible to preserve its natural values and, thereby achieve continuous operation of the area. To achieve this objective, urban land-use planning is considered as one of the main aspects of building the city. Due to the turmoil, the problems of the cities have been considered. In this connection, environmental and especially geomorphological features, in the direction of optimal management of this process are very significant and have important role and should be considered and evaluated as a necessity in connection with the selection and development of environments settlements and especially urban areas.   Methodology In this study, to investigate and zoning favorable areas for urban development, 8 different factors of slope, aspect, elevation, geology, land use, distance to fault, distance from the river and distance from urban areas have been used as factors of this research. In order to analyze the data and locating suitable areas for respective objectives, restricted areas method and fuzzy logic with AHP models have been used. The restricted areas method is for site selection of the settlements appropriate for all criteria. For this purpose, restricted areas have been identified that are fit for the purposes of urban development. Then, for the areas that are off-limits, zoning action is taken by using a combination of fuzzy logic and AHP. In the present study, in order to prioritize the criteria and determine the weights of each of them, the AHP model is used. For this purpose, the opinions of relevant experts are used. Moreover, the final weight of each criterion is obtained after comparing test criteria. In order to increase the accuracy of the study and comparison, fuzzy logic model associated with linear membership function is used to layers.   Results and discussion For site selection of suitable areas for urban development in the study area, eight parameters were used. After gaining weight factors and identifying restricted area, the layers of fuzzy data were collected and have become comparable. Then, according to the final weight of the criteria and the restricted areas, data layers are combined and integrated in GIS. Gamma fuzzy operator is used to adjust the sensitivity of the very high multiplication sensitivity and very low phase addition operator fuzzy. The results obtained from integrating layers as well as restricted areas (Figure 12) indicates that a large portion of the study area is restricted areas and unsuitable for its respective purpose. Unlike marginal and peripheral areas, central areas of the study area have fair potential for urban development goals. In fact, many of these areas are off-restricted areas.   Conclusion In this study, different aspects of urban development in Sanandaj city were examined in different directions and using natural parameters. Finally, the total area of 208 square km under study were evaluated and placed in three categories of relatively good, good and very good. Mountainous areas, high-altitude regions and consequently high slope regions with crossing streams and multiple faults, and restricted areas for urban development have the greatest area (36%) of the map. Relatively good areas for development are in second place, 25.1%, and located mostly in southern and eastern parts of the map. The 23.7% of the total area under consideration is allocated to the good fields in the northern parts of urban development. Moreover, 15.2% of map area is allocated to very good lands for urban development. This covers much of the center of the map and the current location of Sanandaj City. Finally, the results of this research are in a borderline management state for the present situation and provide management horizon for urban development patterns in the future.