Landslide Hazard Zoning by Density Area Model and Hierarchical Analysis to Assess the Pathway Designed for the Chellir District in the Khayrud Forest

As one of the most important pillars of the land organization, the Forest Road Network plays a key role in the management of forest resources, and on the other hand, roads have the highest rate of administrative and environmental costs. Road construction on unstable forest soils will increase road maintenance costs in the future, as well as irreparable environmental damage, including soil erosion. The aim of this study is to assess the risk of landslides in the Challeir Forest in the Khairud Forest in order to study the design of forested roads, to high-risk road distances as part of a linear complication, identified and with double attention, from irreparable damage to environmental repairs and costs. In this study, designed and projected roads in the Chellir district of Khairud forest with an area of more than 1720 hectares have been studied, in the study area, 38 km of roads have been predicted and 14 km of which have been constructed. Initially, slope factors, direction, distance from the fault, distance from the road, distance from the streams, geological structure, and soil type were identified as effective factors in landslides and with the help of the hierarchical analysis process, were evaluated and weighted according to experts. In the next step, the required maps were prepared in the Arc GIS and classified according to previous studies, and the slips in the area, which were harvested using the field study (GPS), were compared. Then, the sub-maps of the sub-criteria were weighted according to the characteristics of the slips (according to the slip area in each floor) by the density area model, then the map of the sub-criteria was weighted according to the sub-criteria measured by the hierarchical analysis process. The Arc GIS was integrated with each other and the landslide hazard zoning map of the study area was prepared on five classifications from high risk to low risk. Finally, by placing the road map made and designed on the obtained zoning map, the distance of the roads on different classes of the hazard was extracted. The prioritization results of the factors showed that the slope and distance from the waterway with weights of 0.22 and 0.19 they had the greatest impact and distance from the fault and distance from the road with weights of 0.096 and 0.085 had the lowest effect on landslides. Also, the results of road analysis showed that out of about 38 km of road designed, about 21 km is located in high and very high-risk classes and 11 km is in low and very low-risk classes, a distance of about 6 km from this road network is also in the middle-risk class, indicating the importance of domain sustainability studies in this area, including grain seeding, soil kneading rate, and other mechanical properties, before any construction operations.