Prioritization of factors and zoning susceptibility of landslide in Karaj Dam Watershed

Identification of the areas prone to landslides and the risks arising from them is one of the primary measures in natural resource management and development and construction planning. Considering the loss of lives, financial losses and environmental effects, landslides have been one of the most important natural disasters in the world and especially in our country, which every year plays an increasing role in the destruction of communication roads, pastures, gardens, residential areas, cause erosion and produces a high volume of sediment in the watersheds of the country. These issues have led to the use of data mining models in geological and geotechnical studies. In recent years, the use of geographic information systems and remote sensing along with machine learning methods has created a new step in landslide occurrence zoning and landslide susceptibility maps with appropriate accuracy. The watershed of Karaj Dam is one of the areas prone to landslides due to mountainous and rainy conditions and many construction due to suitable weather conditions and non-standard road construction. The purpose of this research is to prioritize the factors affecting landslides using the maximum entropy model (MaxEnt model) and to determine areas with landslide susceptibility potential.

The Karaj Dam watershed is located in the east of Alborz Province. The highest and lowest average annual rainfall is calculated as 1099 and 608 mm, respectively. In this research, in order to determine the areas with landslide susceptibility, among 11 factors affecting the landslide potential of the area, including height, slope, slope direction, distance from waterway, lithology, rainfall, land use, topographic moisture index, surface curvature, distance from the waterway and the distance from the road, the factors were selected and tested for collinearity with the Variance Inflation Factor (VIF) test in SPSS software. From the total of 477 landslides, 70% were randomly classified as test data (334 points) and 30% as validation data (143 points). In this research, the maximum entropy model is used. To determine the most important parameters, the jackknife diagram and the Relative Performance Detection Curve (ROC) were used to determine the predictive power of the model. Landslide points of the studied area were prepared from the database of the General Directorate of Natural Resources and Watershed Management of Alborz Province and field visits.

The results showed that there is no co-linearity between the used factors. According to the Jackknife diagram, rainfall layers, distance from the road, lithology and land use were respectively the most important factors influencing the occurrence of landslides in the study area. The relative performance detection curve showed the accuracy of 90% (excellent) of the maximum entropy method in the training phase and 83% (very good) in the validation phase. According to the final landslide susceptibility map, more than 35% of the study area has high and very high landslide susceptibility potential.

According to the obtained results, it can be said that the MaxEnt model has a high ability to determine landslide-susceptible areas, and due to the high speed and accuracy of the model, it is suggested that it be used in similar research, especially in developing countries. The reason for the lack of facilities and financial resources, as well as the time-consuming nature of identifying landslide sensitive areas, should be used. In addition to natural factors, some human factors such as road construction play an important role in the occurrence of landslides, and in order to reduce the relative risks, it is necessary to avoid changing the ecosystem as a driver of natural disasters. In general, it can be stated that the watershed of Karaj Dam has a high potential for landslide susceptibility, that most of the susceptible areas are located near roads, and because there are many human interventions in these areas. Landslide sensitivity has increased. It is suggested to combine geographic information systems with maximum entropy method in order to determine areas with landslide susceptibility, especially in developing countries like Iran, where access to landslide information and data is limited by time and cost. The results of this research can be used in decision-making and preparation of provincial land as well as urban planning and will play a significant role in preventing and reducing damage caused by landslides.