# Correlation between Soil Moisture Change and Geological Disasters in E'bian Area (Sichuan, China)
## 2 Materials and Methods
### Study Area
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{3}{c}{**Geological Disaster Distribution Statistics (by Elevation)**} \\ \hline Type & \textless{}600 m & 600–1500 m & 1500–2400 m & 2400–3300 m & \textgreater{}3300 m \\ Landside & 49 & 27 & 16 & \\ Collapse & 24 & 17 & 2 & \\ Debris flow & 3 & 9 & 1 & \\ Dangerous rock & 5 & 3 & 2 & No survey data \\ Terrain subsidence & 0 & 3 & 1 & \\ Geomorphology unit area & 280.72 km\({}^{2}\) & 518.43 km\({}^{2}\) & 1017.87 km\({}^{2}\) & \\ Disaster point density & 0.378 & 0.147 & 0.032 & 0 \\ \hline \hline \multicolumn{5}{c}{**Geological Disaster Distribution Statistics (by Slope)**} \\ \hline Type & \textless{}15\({}^{\circ}\) & \(15^{\circ}\)–\(30^{\circ}\) & \(30^{\circ}\)–\(45^{\circ}\) & \(45^{\circ}\)–\(60^{\circ}\) & \textgreater{}60\({}^{\circ}\) \\ Landside & 3 & 8 & 82 & 4 & 0 \\ Collapse & 2 & 2 & 51 & 3 & 4 \\ Debris flow & 4 & 3 & 6 & 8 & 2 \\ Terrain subsidence & 0 & 3 & 11 & 0 & 0 \\ Slope area & 681.75 km\({}^{2}\) & 765.31 km\({}^{2}\) & 441.72 km\({}^{2}\) & 288.65 km\({}^{2}\) & 64.09 km\({}^{2}\) \\ Disaster point density & 0.012 & 0.021 & 0.312 & 0.079 & 0.083 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Geological disaster statistics (topographic factors). Figure 4: Flow chart. an important factor affecting surface temperature. Larger gradients can cause some areas to be more exposed to direct sunlight, making them relatively warm and able to change soil texture. At the same time, the distribution of vegetation on different slopes may also affect the TVDI value. In this paper, the slope of the study area is divided into \(<\)10.6\({}^{\circ}\), 10.6\({}^{\circ}\), 10.6\({}^{\circ}\)-17.22\({}^{\circ}\), 17.22\({}^{\circ}\), 17.22\({}^{\circ}\)-23.18\({}^{\circ}\), 23.18\({}^{\circ}\), 23.18\({}^{\circ}\)-28.81\({}^{\circ}\), 28.81\({}^{\circ}\), 28.81\({}^{\circ}\)-34.11\({}^{\circ}\), 34.11\({}^{\circ}\), 34.11\({}^{\circ}\)-39.07\({}^{\circ}\), 39.07\({}^{\circ}\), 39.07\({}^{\circ}\)-44.37\({}^{\circ}\), 44.37\({}^{\circ}\)-50.66\({}^{\circ}\), 50.66\({}^{\circ}\), 50.66\({}^{\circ}\)-58.94\({}^{\circ}\), 58.94\({}^{\circ}\), 58.94\({}^{\circ}\)-94.42\({}^{\circ}\). The relationship between vegetation cover and slope was analyzed by superposition (Figure 5). In the field of geological disaster prevention and monitoring, slope orientation has important early warning significance for surface sunlight exposure. The orientation of a slope determines its exposure to sunlight. Southern slopes, which receive more direct sunlight, tend to have higher surface temperatures. Conversely, northern slopes, which receive less direct sunlight, are typically cooler [33]. The temperature difference caused by slope orientation can directly impact the occurrence and evolution of geological hazards. Higher surface temperatures on southern slopes can increase the risk of localized debris flows. On the other hand, lower temperatures on northern slopes can make them more susceptible to freeze-thaw action, increasing the likelihood of landslides [34; 35]. At the same time, slope aspect plays a crucial role in the field of geological hazards and is a key factor in the study of ecosystems and climate change. For instance, slope aspect can  
Figure 5: Slope map of study region from 2018 to 2023.  
influence vegetation patterns, which can in turn affect soil stability and susceptibility to erosion. In this paper, the slope direction is divided into flat (\(-1^{\circ}\)), north slope (\(0^{\circ}\)-\(22.5^{\circ}\), \(337.5^{\circ}\)-\(360^{\circ}\)), northeast slope (\(22.5^{\circ}\)-\(67.5^{\circ}\)), east slope (\(67.5^{\circ}\)-\(112.5^{\circ}\)), southeast slope (\(112.5^{\circ}\) and \(157.5^{\circ}\)), south slope (\(157.5^{\circ}\) and \(202.5^{\circ}\)), southwest slope (\(202.5^{\circ}\) and \(247.5^{\circ}\)), west slope (\(247.5^{\circ}\)-\(292.5^{\circ}\)), and northwest slope (\(292.5^{\circ}\)-\(337.5^{\circ}\)) for superposition analysis (Figure 6).