## 3 Materials and Methods
### Landslides  
The landslide process is one of the many forms of geological matter evolution. The causes of landslides are divided into two groups: random (scholastic) and expected. The first group includes such fast-moving factors as precipitation, abrasion, erosion, earthquakes, and man-made factors. The regularity of the landslide process reflects the features and mode of rocks occurrence, tectonic disturbances that gradually develop in these rocks, and the appearance of stress fields in them. The ratio of both factors leads to the accumulation of anomalous stresses in rocks, which causes landslides. Among 350 landslides explored in the mountains of North Ossetia, the following are distinguished by size: small (up to 1 thousand cubic meters), medium (up to 10 thousand cubic meters), large (up to 1 million cubic meters), and very large (with a volume of more than 1 million cubic meters). Examples of very large landslides are the Luar, Donifars, and N. Nar landslides. The main factor of landslide processes activation is the excessive watering of the slopes, which occurs during snowmelt and heavy rains (Figure 6). A sharp increase in river runoff contributes significantly to the activity of landslides; as a result, the erosion and destruction of the frontal parts of landslides occur, which often leads to the displacements of the overlying masses, as was observed on the Luar landslide in 1984 and on the Matsuta landslide in 1991. A noticeable increase in landslide activity is caused by seismic impacts associated with modern tectonic movements. In particular, the movements of the Matsuta and Donifars landslides in 1990 and the Ursdon landslide in 1993 are associated with tectonic movements. A retrospective analysis of the formation and large activation of landslides in the 20 th century indicates that some of them are directly related to earthquakes (Dallagkau landslide, 1905; Korinskiy landslide, 1915; Turmonskiy landslide, 1981). Slope stability was assessed for the territory of North Ossetia on a scale of 1:200,000. The average values of rock properties were used to identify the most hazardous zones for further detailed analysis. There was used the Scoops3D program, which makes it possible to assess the stability of slopes in a three-dimensional setting based on digital elevation models. The elevation model was built on the basis of SRTM satellite data. To perform  
Figure 6: Monthly precipitation and the number of landslides in the Alagir region of North Ossetia-Alania in 2019–2020. calculations throughout the entire territory, a digital elevation model was compiled, the resolution was reduced to 200 m.  
Scoops3D is a computer program developed by the United States Geological Survey (USGS) for analyzing slope stability across the entire digital landscape, represented by a digital elevation model (DEM). It detects large numbers and calculates the stability of 3D potential landslides covering a wide range of depths and volumes. Scoops3D uses a three-dimensional \"column method\" of limited equilibrium analysis to calculate the resilience of potential slope failures (landslides) with a spherical potential slip area. The approach was originally described in the work of [51]. The results of Scoops3D analysis show the minimum safety factor (stability index) for potential slip areas affecting each DEM cell throughout the landscape, as well as for volumes or areas associated with these potential damages of slopes. Scoops3D allows the user to choose between two well-known geotechnical methods of the moment equilibrium for calculating the stability of a rotating surface. [PERSON]'s method was used in our calculations. When performing a slope stability analysis, Scoops3D calculates the shear strength s on the test surface using the Coulomb-Terzaghi linear fracture rule [52]. Scoops3D calculates the safety factor F for a given test surface using moment equilibrium [52].