Landslide Hazard Zonation with Frequency Ratio Method (Case Study: Forest of Mazandaran Wood and Paper Industry)

The Landslide is one of the natural hazards that causes a lot of mortal and financial losses in high-altitude and seismic mountainous areas annually. Considering the importance of roads as a pillar of sustainable forest management in this study, we have tried to estimate the sensitivity of landslide occurrence in 8 forestry series with using frequency ratio approach. Initially, the slip position in the series occurred with ground scrolling by GPS, then the effective factors in the occurrence of landslides were determined for the study area. Raster maps of the effective factors were prepared and classified. Considering the distribution of landslides recorded in the field and the categories of effective factors, the frequency ratio for each class of each factor was calculated and their relationship with the occurrence of landslide was investigated. The results of the relationship between positioning and slipping showed that the highest amount of landslides occurred on the lower side of the road, and by increasing the age of the roads, the amount of landslides is reduced. The relationship between soil and slip occurred on the class with the code 2.2.3, which represents the soil texture of loamy, loamy clay and clay that the highest number of slides was observed. Elevation class 300 to 600 meter has the highest number of landslides. The relationship between the slope and slip showed that with increasing the slope up to 40%, the number of landslides was increased, but then the trend was decreasing. The relationship between geological and landslide showed that the highest number of landslides was observed in the class with L-PLL2 ​​code representing relatively high peaks with moderate slope, average soil depth, stability and permeability. The relationship between rainfall and landslide factors showed that the greatest slip is occurring between 600 and 800 mm. In the northern, northeastern and northwest directions, the highest slip occurred. The evaluation results of the model with the ROC method indicated that the area under curve (AUC) was 0.688 (68.8%).