Identification of Suitable Areas for the Physical Expansion of the Urban and Suburban Areas of Divandarreh Using Geomorphological Documents and Integrated Models

Introduction

Iran’s geographical and geological setting places the country among the ten most disaster-prone regions in the world in terms of natural hazards. Hazards such as earthquakes, floods, droughts, soil erosion, and landslides continuously threaten cities and human settlements, causing extensive damage. Among Iranian provinces, Kurdistan Province, due to its diverse geomorphological characteristics, mountainous structure, and numerous drainage basins, is considered one of the country’s most sensitive areas with respect to hydro-geomorphological hazards. Studies indicate that a significant portion of the province’s land is exposed to seismic risk, severe soil erosion, and destructive floods, with the increasing trend of flood occurrence in recent decades resulting in substantial social and economic losses. Divandarreh city, as one of the major cities of Kurdistan Province, has experienced rapid physical expansion due to its geographical location, residential attractiveness, and rural-to-urban migration. If such development proceeds without adequate consideration of natural and geomorphological conditions, it may lead to increased urban vulnerability and the intensification of hazards. Flooding, landslides, slope instability, and soil erosion, combined with uncoordinated physical development, highlight the necessity of revising urban planning and management approaches in Divandarreh. Geomorphology, through its focus on landforms and governing processes, plays a crucial role in guiding sustainable urban development and provides a scientific basis for site selection, hazard zoning, and risk reduction. Given that urban development in Iran—particularly since the 1960s—has often occurred with limited integration of environmental sciences, many cities, including Divandarreh, face serious environmental and hazard-related challenges. Therefore, examining the physical development of Divandarreh through a geomorphological and hazard-oriented approach, aimed at identifying suitable, restricted, and prohibited development areas and preparing a realistic environmental framework, is essential for achieving sustainability and enhancing urban resilience.



Materials and Methods

To achieve the research objectives, a diverse set of data and tools was employed. Library-based data were used to compile the theoretical framework and identify regional natural hazards through the review of theses, scientific articles, books, and relevant research projects. Statistical data included climatic and demographic information, collected from relevant organizations and institutions. Visual and spatial data consisted of Google Earth and Landsat satellite imagery, geological maps, and a 12.5 m resolution ALOS PALSAR digital elevation model, which were utilized for spatial and geomorphological analyses. Field surveys were conducted to validate and complement the collected data and to assess the actual conditions of the study area. Regarding research tools, physical instruments such as GPS devices and digital cameras were used for field data collection, while conceptual tools included various software platforms and analytical models. Google Earth Engine was applied to generate vegetation density maps; ArcGIS was used for spatial mapping and analysis; TerrSet software was employed to implement the WLC model; SuperDecisions was used to execute the ANP model; SPSS was applied for statistical calculations; and Google Earth was utilized for monitoring and visual assessment of the study area. The research was conducted in two main stages: first, the preparation of a comprehensive geomorphological and hazard framework for Divandarreh city and its suburban area, and second, the identification of areas suitable for physical urban development.



Discussion and Results

The results of geomorphological and spatial analysis indicate that the natural structure of Divandarreh city plays a decisive role in shaping the physical development pattern of residential areas. The dominance of steep hilly terrains over more than 94% of the study area, together with the presence of deep river valleys and floodplains, reflects unstable geomorphological conditions and a high level of natural hazard risk. These characteristics increase the sensitivity of the urban area and its suburbans to hazards such as flooding and slope movements, significantly limiting the availability of land suitable for sustainable development. The outputs of multi-criteria decision-making models, including fuzzy gamma, WLC, and ANP, reveal that parameters such as slope, lithology, and distance from watercourses exert the greatest influence on land suitability for physical development. Accordingly, the northern parts of the urban area and sections along the Divandarreh–Saqqez transportation corridor exhibit the highest development potential due to gentler slopes, more favorable elevations, and greater distances from high-risk zones. In contrast, the southern parts of the city, steep valleys, and floodplains were identified as highly vulnerable areas where physical development would entail serious risks. The consistency among the results of different models confirms the reliability of the findings and demonstrates that the integrated application of geomorphological analysis and spatial decision-making models provides an effective approach for identifying safe zones for urban development.





Conclusion

The findings of this study demonstrate that physical expansion of residential areas in Divandarreh city, if undertaken without adequate consideration of geomorphological characteristics and natural hazards, may result in undesirable consequences such as increased risk, environmental damage, and urban instability. The high diversity of landforms, the predominance of steep terrains, and the presence of flood-prone and landslide-susceptible areas underscore the necessity of adopting a preventive, science-based approach to urban planning. The integration of remote sensing data, GIS techniques, and multi-criteria decision-making models revealed that only a limited portion of the urban area and its surroundings—particularly the northern part and areas along the Divandarreh–Saqqez axis—possess relatively suitable conditions for physical development. Consequently, concentrating urban expansion within these areas can reduce natural hazards while promoting safer and more sustainable development. Moreover, the preparation of a geomorphological and hazard-based framework, as the main outcome of this research, serves as a strategic tool for urban managers and planners by facilitating informed development guidance, controlling physical expansion, and reducing urban vulnerability. Ultimately, this study emphasizes the importance of integrating geomorphological assessments and risk evaluation into higher-level urban planning documents and offers a practical model applicable to other cities with similar natural conditions.