Assessment of Vulnerability of Communication Lines and Rural Settlements against Landslide Hazard in Mountainous Areas (Case Study: Mianeh to Bostanabad Road)

Landslides are one of the most significant hazards causing considerable damage annually in mountainous regions. Among the vulnerable areas is the communication corridor between the cities of Mianeh and Bostanabad. Given the importance of this issue, this study focuses on identifying landslide-prone areas and analyzing the vulnerability of rural settlements along this route. The research utilized key datasets including MODIS satellite imagery, the 30-meter resolution SRTM Digital Elevation Model (DEM), and a 1:100,000 scale digital geological map of the region. The main tools employed in this study were Google Earth Engine, ArcGIS, and TerrSet software. Additionally, the WLC, OWA, and AHP models were applied to identify landslide susceptibility zones. According to the results, approximately 27.8% of the study area identified by the WLC method and 27.6% by the OWA method fall within high and very high landslide susceptibility classes, mainly located in the western and central parts of the study area, coinciding with the slopes adjacent to the Mianeh–Bostanabad road. Moreover, the results of this study have shown that at least 10 villages in the region are at risk of landslides, making it essential to take necessary measures such as managing land-use changes and monitoring compliance with proper principles in the development of transportation routes.
 
Extended Abstract
 
Introduction
Natural hazards refer to environmental phenomena and events that can cause human casualties, financial losses, and environmental damage to people and infrastructure. The increasing population growth, expansion of human activities, and lack of attention to environmental capacities have intensified the likelihood of natural hazards in recent years. Landslides are among the most dangerous and common natural hazards in mountainous and sloped areas, caused by the downward sliding of large volumes of soil and rock. This phenomenon is usually triggered or exacerbated by heavy rainfall, earthquakes, human activities such as deforestation, and unstable construction, and can lead to road blockages, destruction of buildings, and harm to human lives. Therefore, identifying and managing landslide hazards is crucial for reducing damages and increasing the safety of local communities. In countries with rugged topography like Iran, landslides can cause significant human and financial losses and threaten vital infrastructures such as roads, bridges, and civil installations. The occurrence of landslides is influenced by various factors. In addition to natural factors such as topography, geology, and hydroclimatic conditions, human activities including construction development and land-use changes contribute to landslide occurrence in many regions. Among the vulnerable areas is the road corridor between Mianeh and Bostanabad located in East Azerbaijan Province. Given the importance of the issue, this study aims to identify landslide-prone areas along this rout.
 
Methodology
In this study, satellite images from MODIS, the 30-meter SRTM Digital Elevation Model (DEM), and the 1:100,000 scale digital geological map of the area were used as the primary data sources. The main tools employed in this research included Google Earth Engine, ArcGIS, and TerrSet software. Additionally, the WLC, OWA, and AHP models were utilized. Given the objectives of the study, the research was conducted in several stages. In the first stage, after identifying the relevant parameters and preparing their informational layers, each data layer was assigned an intra-layer value ranging from zero to one to enable evaluation; these layers were standardized based on their intra-layer values, where landslide-prone areas were assigned values close to one, and non-prone areas values near zero. In the second stage, using the Analytic Hierarchy Process (AHP) model and Expert Choice software, weights were assigned to the data layers, and these weights were then applied. In the third stage, using the WLC and OWA models, the data layers were combined, and the final landslide susceptibility map was produced. In the fourth stage, the vulnerability status of the villages within the study area against landslide hazards was evaluated.
 
Results and Discussion
The assessment of area and percentage of landslide susceptibility classes indicates that areas with high and very high landslide potential cover approximately 178 and 171 square kilometers (equivalent to 27.8% and 27.6% of the total area) in the WLC and OWA methods, respectively. A significant portion of these areas adjoin the main Mianeh–Bostanabad road, thus possessing high importance and sensitivity. Conversely, areas with low and very low landslide potential cover about 291 and 242 square kilometers (equivalent to 46.9% and 38.9% of the area) in the WLC and OWA methods, respectively. These areas are mainly located in the eastern parts of the region, particularly near Mianeh city, where the elevation and slope are low, resulting in lower landslide susceptibility. After producing the final landslide susceptibility maps, the spatial distribution of 49 village points within the study area was analyzed according to susceptibility classes. The results showed that 9 and 11 villages (representing 18.4% and 22.4% of all villages in the area) are situated in high and very high landslide potential zones according to the WLC and OWA methods, respectively. Additionally, 30 and 28 villages (61.2% and 57.1% of all villages) fall within low and very low susceptibility zones in the WLC and OWA analyses.
 
Conclusion
The results indicate that topographical factors such as elevation and steep slopes, lithology type, and proximity to faults play significant roles in increasing landslide risk. According to the analyses, about 27.8% of the total area in the WLC method and 27.6% in the OWA method fall within high and very high susceptibility classes, primarily located in the western and central parts, mostly corresponding to slopes adjacent to the Mianeh–Bostanabad road corridor. Areas with low and very low susceptibility are mainly in the eastern region, especially around Mianeh city. The vulnerability assessment of 49 villages indicated that at least 10 villages are in high-risk zones, necessitating special attention and management actions to reduce potential damages. Based on the findings, it is recommended that land-use planning and developmental projects in high susceptibility zones be limited and based on detailed geotechnical studies. Implementing slope stabilization projects, constructing retaining walls, and applying surface water control engineering methods can effectively reduce landslide hazards. Moreover, installing monitoring and early warning systems in critical points, particularly in villages at risk, is essential. Educating and raising awareness among local residents about early signs of landslides and preventive measures plays a crucial role in minimizing human and financial losses. Continuous updating of landslide susceptibility maps with new data and employing remote sensing and GIS technologies can enhance the accuracy of management decisions.