## 2 Materials and Methods
### Determination of the Probability of Landslide Occurrence in Cluj County
In this respect, territories characterized by a medium amount of precipitation, as well as catchments in the mountain and hilly areas generally controlled by the precipitation at the level of their area, have an average probability of landslide occurrence, receiving a value of probability coefficient between 0.1 and 0.3. Territories characterized by moderate amounts of precipitation and mature valleys that have tributaries affected by floods, presenting sectors with active vertical erosion, have a medium-high probability of landslide occurrence and a value of probability coefficient between 0.3 and 0.5. Territories receiving an amount of precipitation higher than 850 mm/year have a high probability of landslide occurrence and a value of probability coefficient between 0.5 and 0.8 (Figure 4). Figure 3: Landslide probability based on geomorphology (\(K_{b}\) coefficient). The impact of hydrogeology on the probability of landslide occurrence was determined using a hydrogeological map of Europe. Areas characterized by a depth of over 5 m for the phreatic water level correspond to a low probability. An average-high probability of landslide occurrence was considered for areas where phreatic waters flow on steeper slopes or at the feet of slopes where springs occur. These areas received a value of probability coefficient between 0.3 and 0.5. The areas with a high permeability of the upper deposits correspond to a high probability of landslide occurrence and received values of probability coefficient between 0.5 and 0.8 (Figure 5). Figure 4: Landslide probability based on the hydro-climatic coefficient (\(K_{d}\)). Cluj County is mostly located in a VI seismic area on the MSK seismic scale for earthquakes that have an intensity higher than 6 degrees on the Richter scale. As a consequence, in terms of this triggering factor, there is an average probability of landslide occurrence for about 80% of Cluj County, which received a value of probability coefficient between 0.3 and 0.5 (Figure 6). The probability of landslide occurrence induced by the seismic factor is average-high only in the South-East of the county, receiving a value of probability coefficient between 0.5 and 0.8, because this area is located in a VII seismic area on the MSK seismic scale according to STAS 11100/1993 and the parameters for the zoning of seismicity according to act P100/1992 for earthquakes that have an intensity higher than 7 degrees on the Richter scale. Figure 5: Landslide probability based on hydrogeology (\(K_{e}\) coefficient). Regarding the stabilizing role played by the vegetation in case of landslides, previous studies have shown that there is a lower density of landslides on forested slopes [53; 54]. Data from the Copernicus Land Monitoring Service EEA were used to model this coefficient. Therefore, territories characterized by forest cover on more than 80% of their area correspond to a low probability of landslide occurrence, receiving a coefficient of 0-0.1. These are mainly mountain areas, where about 55% of the territories correspond to this description and the density of landslides is low. Territories covered by between 55% and 80% forest present an average probability of landslide occurrence and a value of probability coefficient between 0.1 and 0.3. Agricultural lands, as well as transition (deforested) lands, are characterized by a high and very high probability of landslide occurrence, and therefore received a value of probability coefficient between 0.3 and 0.5, as the stabilizing effect of the vegetation is extremely low (Figure 7). Figure 6: Landslide probability based on the seismic coefficient (\(K_{\gamma}\)). In order to stress the influence of construction on the overloading of slopes and the high density of infrastructure elements, the territories without constructions were characterized with a low probability of landslide occurrence and a minimal value of probability coefficient, 0.1. In contrast, overloaded slopes have a high probability of landslide occurrence and a coefficient of 0.9 (Figure 8).