## 2 Study Area and Data Sources
### Landslide Conditioning Factors
#### 2.3.1 Topographic Factors  
Topographic factors include altitude, slope degree, slope aspect, Topographic Wetness Index (TWI), plan curvature, and profile curvature. These factors are all calculated based on digital elevation model (DEM) data with a 30 m resolution. The DEM data used in this study are SRTM, obtained from NASA's Earth data Search platform ([[https://search.earthdata.nasa.gov](https://search.earthdata.nasa.gov)]([https://search.earthdata.nasa.gov](https://search.earthdata.nasa.gov)), accessed on June 2024). The spatial analysis and extraction of topographic factors from the DEM data were performed by using ArcGIS. The gravitational force on a slope generates a downward pressure on slope materials, making it a critical triggering factor influencing landslide susceptibility [30; 31]. As shown in Figure 2b, the slope degree in the study area ranges from 0\({}^{\circ}\) to 79.54\({}^{\circ}\). The influence of the slope aspect on landslides has shown contrasting results, as it indirectly affects vital attributes such as moisture retention, vegetation cover type, and vegetation distribution [32] (Figure 2c). The Topographic Wetness Index (TWI) quantitatively describes the distribution of soil moisture. A higher TWI value means more soil moisture, making the soil more likely to become saturated and produce runoff, which increases the possibility of landslides [33]. The TWI ranges from 1.66 to 30.10 (Figure 2e) and is calculated by using the following formula:  
\[\text{TWI}=ln\left(\frac{A}{tan(Slope)}\right) \tag{2}\] \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Category** & **LCFs** & **Type** & **Scale/Resolution** & **Source** & **Min.** & **Max.** \\ \hline \multirow{8}{*}{Topographic factors} & Altitude & Raster & 30 m & DEM & 363 & 4242 \\  & Slope degree & Raster & 30 m & DEM & 0 & 79.54 \\  & Slope aspect & Raster & 30 m & DEM & — & — \\  & Plan Curvature & Raster & 30 m & DEM & \(-\)20.45 & 26.18 \\  & Profile curvature & Raster & 30 m & DEM & \(-\)22.21 & 20.09 \\  & TWI & Raster & 30 m & DEM & 1.66 & 30.10 \\  & NDVI & Raster & 30 m & Landsat 8 satellite images & 0.32 & 0.90 \\  & soil types & Vector & 1:1,000,000 & & & ([[http://www.ncdc.ac.cn](http://www.ncdc.ac.cn)]([http://www.ncdc.ac.cn](http://www.ncdc.ac.cn)), accessed on June 2024) & — \\  & & & & & National Earth System Science Data Center, & \\  & & & & & National Science \& Technology Infrastructure of & \\ Environmental factors & Distance from rivers & Vector & 1:250,000 & & China ([[http://www.geodata.cn](http://www.geodata.cn)]([http://www.geodata.cn](http://www.geodata.cn)), accessed on June 2024) & 0 & — \\  & & & & & National Earth System Science Data Center, & \\  & & & & & National Earth System Science Data Center, & \\  & Distance from roads & Vector & 1:250,000 & & National Science \& Technology Infrastructure of & 0 & — \\  & & & & & China ([[http://www.geodata.cn](http://www.geodata.cn)]([http://www.geodata.cn](http://www.geodata.cn)), accessed on June 2024) & — \\  & Lithology & Vector & 1:1,000,000 & & ISRIC ([[https://data.isric.org/](https://data.isric.org/)]([https://data.isric.org/](https://data.isric.org/)), accessed on June 2024) & — & — \\ Geological factors & & & & & Data Sharing Infrastructure of Seismic Active & & \\  & & & & & Fault Survey Data Center & \\  & & & & & ([[https://www.activefault-datacenter.cn](https://www.activefault-datacenter.cn)]([https://www.activefault-datacenter.cn](https://www.activefault-datacenter.cn)), accessed on June 2024) & 0 & 0.40 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Information on landslide conditioning factors. where \(A\) represents the catchment area and the slope is measured in radians [34]. Plan curvature and profile curvature are necessary for describing terrain shape and modeling flow patterns and velocity, both critical in building landslide susceptibility mapping. Plan curvature (Figure 2d) refers to the curvature of contour lines, indicating whether the terrain is concave or convex, influencing water's convergence or dispersion.