## 3 Results
### Rainfall Data Analysis for Each Typhoon Event  
Two data sources of rainfall data were individually analyzed for this study. CHIRPS daily precipitation was obtained for the 19 typhoon events selected, where the highest daily precipitation registered on the day of the typhoon passing over Taiwan was 208 mm for typhoon Fung-Wong, while the lowest daily precipitation registered was 43.7 mm for typhoon Sarah. The mean daily precipitation for the selected events was 120 \(\pm\) 48.2 mm. Nevertheless, a comparison of this satellite-derived data with rain gauge data from the CWB showed that the CHIRPS dataset under/overestimates the rainfall amount for different events (Figure 6). This observation is supported by the findings of [PERSON] et al. [24], who found that remote sensing rainfall products underestimate rainfall compared to rain gauges for typhoon Morakot over Taiwan. Given that the CHIRPS data are freely available and span the entire study period, we decided to include it in the study. However, the correlation results of the mapped landslide area with CHIRPS daily precipitation data should be interpreted carefully. For the CWB station data, we analyzed rainfall event parameters derived from hourly precipitation records for three separate rain gauges. Several studies used spatial interpolation for the analysis of rainfall parameters in comparison to landslide area [8; 75; 76]. These studies investigate several landslide locations but do not focus on a detailed analysis of the progressive evolution of one major landslide. Given that spatial interpolation can introduce uncertainty to the resulting rain measurements [77] and that the rain gauges were located within a range of 2.8-8 km from the landslide area, we decided to analyze the three closest rain gauges separately. The rain gauge data are available since 1992, and thus cover only 17 of the selected 19 typhoon events. In addition, rainfall data for the Longwang and Haitang typhoons were not available for station Xiaoguanshan. Cumulative rainfall, duration and mean intensity were derived for each rainfall event within the typhoon period for each station. Summary statistics of the derived parameters are presented in Table 6. In general, station Xiaoguanshan recorded the highest cumulative rainfall, duration and intensity during rainfall events, which could be explained by the altitude of the station, as well as its location downstream of the valley. Table 7 presents the individual parameters per typhoon event next to the semi-automated mapping results. For every station, the maximum cumulative rainfall and duration correspond to typhoon Morakot, whereas the maximum intensity corresponds to typhoon Toraji, and the minimum duration corresponds to typhoon Nepartak. Minimum cumulative rainfall and intensity varied between typho  
Figure 6: Comparison of daily precipitation for Climate Hazards Group Infrared Precipitation with Station (CHIRPS; orange) and CWB (blue palette) data for the selected 19 typhoon events. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Cumulative Rainfall (mm)**} & \multicolumn{4}{c}{**Duration (h)**} & \multicolumn{4}{c}{**Intensity (mm/h)**} \\ \cline{2-10}  & **M** & **F** & **X** & **M** & **F** & **X** & **M** & **F** & **X** \\ \hline Mean & 419.39 & 423.01 & 514.25 & 26.3 & 25.9 & 27.9 & 13.97 & 14.37 & 16.97 \\ SD & 425.41 & 440.16 & 508.47 & 16.0 & 16.5 & 15.3 & 6.24 & 6.08 & 8.33 \\ Min & 69.00 & 56.50 & 132.00 & 7 & 7 & 10 & 6.31 & 4.71 & 7.76 \\ Max & 1818.50 & 1914.00 & 2185.50 & 76 & 78 & 76 & 28.86 & 27.34 & 36.93 \\ Count & 17 & 17 & 15 & 17 & 17 & 15 & 17 & 17 & 15 \\ \hline \hline \end{tabular} Note: CWB station symbols: M = Station Meishan, F = Station Fuging, X = Station Xiaoguanshan.  
\end{table} 
Table 6: Summary statistics for rainfall parameters derived from rain gauges at three CWB stations.