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

ABSTRACT
This study aims to identify suitable areas for the physical development of Divandarreh through the preparation of a geomorphological and hazard documentation framework. Due to its geographical location and diverse geomorphological and topographical conditions, the city faces both opportunities and constraints for spatial expansion. Geomorphological landforms not only shape the natural landscape but also directly influence settlement suitability and urban development decisions. In the first stage, a geomorphological document of the urban area was prepared focusing on landforms, dominant processes, and hazards. In the second stage, a comprehensive spatial analysis was conducted to identify development-prone areas in both urban and peri-urban zones. The study utilized Google Earth imagery, MODIS images, a 12.5-m ALOS PALSAR Digital Elevation Model, and a 1:100,000 geological map. Analytical tools included ArcGIS, TerrSet, and SuperDecisions software, along with field observations. Fuzzy Gamma and Weighted Linear Combination (WLC) methods were applied for spatial modeling.  Results indicate that low-slope hilly landforms, covering about 39.2 km² (47.2%) of the study area, represent the most suitable geomorphological unit for urban expansion due to minimal active processes and hazards, mainly located in the northern and northeastern parts of the city. According to the Fuzzy Gamma and WLC models, approximately 25.2% and 28.7% (equivalent to 9.1 and 10.2 km²), respectively, have high development potential. The strong quantitative and spatial consistency between the geomorphological document and model outputs confirms the validity of the research and highlights the effectiveness of geomorphological and hazard mapping in urban planning and resilience enhancement.
Extended Abstract
Introduction
Iran’s geographical and geological setting places the country among the ten most disaster-prone regions in the world with respect to natural hazards. disasters 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 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. The prevalence of floods, 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.
 
Methodology
A diverse set of data and tools was employed to achieve the research objectives. 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 utilized 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 surrounding area, and second, the identification of areas suitable for physical urban development.
 
Results and Discussion
The results of geomorphological and spatial analyses 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 core and its periphery 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 demonstrate that physical development 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 zones 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.
 
Funding
There is no funding support.
 
Authors’ Contribution

Sina Karami: Writing the initial draft, compiling the introduction, collecting data and sources, and final editing the text.
Mamand Salari (corresponding author): Research design, developing the methodology, analyzing and interpreting data, supervising the research process
Hamid Ganjaian: Processing spatial data, preparing maps and graphic outputs, implementing spatial models.

 
Conflict of Interest
Authors declared no conflict of interest.
 
Acknowledgments
We are grateful to all the scientific consultants of this paper.