Analysis of landslide occurrence time via rainfall intensity and soil water index ternary diagram
Document Type
Article
Publication Date
12-1-2022
Abstract
This study introduces the soil water index (SWI) approach, the sum of water depths in the three-layer tank model, with rainfall data to understand landslide occurrence in Taiwan. A total of 236 historical instance data were compiled to investigate the characteristics of different types of landslides: debris flows (DF), shallow landslides (SL), and large-scale landslides (LL). The data shows that most DF occurred near the time of maximum rainfall intensity. However, several SL and LL events indicate that the occurrence of SL and LL has correlations with more than just rainfall intensity or rainfall amount. The SWI and the water depth in the tanks (from top to bottom: H1, H2, H3) provide an intriguing approach to correlate soil moisture content at occurrence time with the landslide types. DF events show the highest H1/SWI value, which indicates the correlation with water content in the surficial soil. LL events after rainfall have the highest H3/SWI ratio, indicating that prolonged rainfall events cause rainwater to infiltrate a deeper soil layer and trigger these LL. We developed a ternary diagram of the water depth-to-SWI ratios to show characteristics of the three landslide types. This study found that the H2/SWI value is typically in the range of 0.2–0.4. In this range, the landslide type gradually shifts from DF to SL, and then to LL, along the H3/SWI axis. Therefore, the ternary diagram can explain landslide type changes with the water depth-to-SWI ratios and better understand landslide occurrence.
Publication Source (Journal or Book title)
Landslides
First Page
2823
Last Page
2837
Recommended Citation
Liu, Y., Chiu, Y., Tsai, F., & Chen, S. (2022). Analysis of landslide occurrence time via rainfall intensity and soil water index ternary diagram. Landslides, 19 (12), 2823-2837. https://doi.org/10.1007/s10346-022-01944-1