## 4 Results and Discussion
### Application of the VR Model  
In order to study, in detail, the relationship between each factor and the scale of the landslide, each factor is divided into several classes. The results of the spatial relationship between landslide volumes and the classes of landslide conditioning factors using the VR model are shown in Table 1. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Independent Variable** & **Classes** & \(\mathbf{V_{jk}}\)**\({}^{\star}\)/\(\mathbf{V_{jk}}\)** & \(\mathbf{T^{\prime}}\)/\(\mathbf{T}\)** & \(\text{VR}_{jk}\) \\ \hline \multirow{4}{*}{Slope angle (\({}^{\circ}\))} & 0–15 & 0.7294 & 0.8629 & 0.8453 \\  & 15–25 & 0.2427 & 0.1272 & 1.9089 \\  & 25–35 & 0.0259 & 0.0094 & 2.7538 \\  & \textgreater{}35 & 0.0019 & 0.0006 & 3.5264 \\ \hline \multirow{4}{*}{Elevation (m)} & \textless{}1000 & 0.1448 & 0.9991 & 0.1450 \\  & 1000–1100 & 0.0947 & 0.9874 & 0.0959 \\ \cline{1-1}  & 1100–1200 & 0.1886 & 0.9946 & 0.1896 \\ \cline{1-1}  & 1200–1300 & 0.5719 & 0.9937 & 0.5755 \\ \cline{1-1}  & \textgreater{}1300 & 0.0000 & 0.0000 & 0.0000 \\ \hline \multirow{4}{*}{NDVI} & no cover & 0.0000 & 0.0004 & 0.0000 \\  & very low cover & 0.1478 & 0.0263 & 0.1778 \\ \cline{1-1}  & low cover & 0.7124 & 0.2459 & 0.3451 \\ \cline{1-1}  & medium cover & 0.1398 & 0.5355 & 3.8301 \\ \cline{1-1}  & high cover & 0.0000 & 0.1919 & 0.0000 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Spatial relationship between landslide conditioning factors and landslide by volume ratio model. Figure 3: Amount and frequency of landslides in the Yangou watershed. In the case of slope angle, the results showed that the VR values also increased as the slope increased, indicating that the slope angle has a good positive correlation with the probability of the landslide volume. The slope is a major factor in landslide occurrence because it relates to drainage, fault line, and road networks [2]. In the Yangou watershed, the 0\({}^{\circ}\)-15\({}^{\circ}\) slope area constituted 20.34% of the total area, the 15\({}^{\circ}\)-25\({}^{\circ}\) area accounted for 35.49%, the 25\({}^{\circ}\)-35\({}^{\circ}\) area accounted for 36.57%, and slope areas of more than 35\({}^{\circ}\) were 7.61% of the total area. The findings revealed a wide range of slope changes across the whole research area. According to the survey, 78% of the landslides occurred on slopes greater than 15\({}^{\circ}\) in the study area. Generally, the mass movement shifts from sliding to slumping with an increasing angle [30; 31]. Thus, landslides are created in a hilly region or mountainous areas with steep slopes. The slope affects the scale and intensity of surface material flow and energy conversion. For example, the slope affects the area and amount of rainfall on the slope, thereby affecting the magnitude of runoff, infiltration, and runoff kinetic energy [32].Thus, the greater the slope, the greater the gravity erosion [20; 33]. There is no correlation between landslide volume and elevation rise in terms of elevation. There are many reasons for the influence of elevation on the development of landslide disasters, such as that different elevation ranges have different climatic characteristics and local depressions are due to slope differences, whether there is a sliding surface and an intensity of human activities in different elevation ranges [34]. Thus, elevation has no direct impact on the distribution of gravity erosion disaster points in the region. The 1200-1300 m area had the highest VR value of 0.5755, followed by 1100-1200 m (0.1896), and \(<\)1000 m (0.1450). The 1000-1100 m area has the lowest value of 0.959. In the Yangou watershed, 96.3% of the landslides occurred on the altitude ranging from 1000 m to 1300 m. This showed that landslides usually occurred at intermediate elevations. The results can also be