Landslide and debris flow risk analysis in Haraz and Lavasanat roads

Introduction
Landslide occurrence is caused by severe ground movement and fault fractures that lead to structural damage, road blockage, human death, and significant damage to other features. Landslide is one of the most destructive natural phenomena that can cause great damage to property and human loss. One of the basic measures to reduce potential damage is to identify landslide-prone areas. Due to the location of most cities in the mountainous and foothill areas and the topographic, geological, and geomorphological features, the natural conditions are vulnerable to a wide range of landslides. Tehran, as the largest city in Iran, has almost 12% of the total population of the country and is partly located in the foothills and mountainous areas. Tehran, has many important infrastructures, including crowded roads, and a large population, therefore, determining areas prone to future landslides is an important management issue. Also, debris flow is one of the main factors that cause serious damage to properties. Thus quantitative assessment and management are required to reduce the possible damages. In addition, technologies are needed to assess disaster prevention facilities and structures in disaster-prone areas. Therefore, using combined methods for landslide susceptibility areas can be very effective in managing the risk of reducing casualties.
Materials and Methods
In this study, the effective factors on landslide occurrence such as rainfall, earthquake, vegetation, land use, geology, river, fault, slope and aspect, and roads are employed using an integrated approach. Then, spatial analysis was performed in ArcGIS using Euclidean distance and Curvature functions. The Haraz and Lavasanat roads were selected as a case study, and each of the criteria was examined and classified using the Euclidean distance method and inverse distance weighted (IDW) technique.
Results and Discussion
The results showed that the areas facing northeast and southwest parts were ranked 1st and the rest of the area was ranked 0. The areas with slope values higher than 50%, had a higher risk of landslide. The curvature of the selected main and secondary roads was located in convex hillslopes indicating the areas at a high-risk level. These Haraz and Lavasan roads are at risk of slipping during rain, earthquakes, and other hazards. According to the area obtained from the regional statistical properties.
Conclusion
The mountainous roads of Tehran are vulnerable to landslide and debris flows due to the geographical location, and the existence of faults. The excessive interference in the nature and increase of additional load on the slopes and excessive influence on agricultural and road use are important reasons for instability in the slope and increasing the debris flow in these land uses. The controlling of landslide and debris flow phenomena depends on a comprehensive management plan. Factors such as population growth, land-use change, and climate change are intensifying the landslide and debris flow occurrence. Since rainfall is one of the accelerating the occurrence of natural disasters, the existence of a management system such as an early warning to the endangered population is necessary.