## 3 Results
### Landslide Volume and Change in River Channel Volume
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **UP3** & **UP2** & **UP1** & **EV** & **WV** & **YL** \\ \hline
**Date** & \multicolumn{6}{c}{**Change in Height Difference (m) *} \\ \hline
10 April 2009–6 November 2015 & \(-\)5.44 & 6.55 & 5.47 & 6.91 & 4.02 & 3.26 \\
10 April 2009–28 August 2009 & \(-\)2.33 & 13.79 & 11.10 & 8.14 & 2.84 & 2.54 \\ Ratio (\%) & 42.83 & 210.53 & 202.93 & 117.80 & 70.65 & 77.91 \\ \hline \hline \end{tabular}  
* negative value represents erosion and a positive value represents deposition.  
\end{table} 
Table 4: Topographic change in the river depth. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **UP3** & **UP2** & **UP1** & **EV** & **WV** & **YL** & **Total** \\ \hline  & & \multicolumn{6}{c}{**Area (M m\({}^{2}\))**} \\ \hline  & 1.2 & 1.45 & 1.19 & 0.8 & 0.17 & 0.17 & 4.97 \\ \hline
**Date** & \multicolumn{6}{c}{**Volume (M m\({}^{3}\))**} \\ \hline
10 April 2009–6 November 2015 & 11.73 & 10.07 & 8.47 & 5.50 & 0.22 & 0.18 & 36.16 \\
10 April 2009–28 August 2009 & 9.12 & 9.01 & 7.25 & 5.99 & 0.02 & 0.24 & 31.63 \\ Ratio (\%) & 77.75 & 89.47 & 85.60 & 108.91 & 9.09 & 133.33 & 87.47 \\ \hline \hline \end{tabular}  
\end{table} 
Table 3: Landslide volume. In this study, we did not have a field survey of landslide and channel depth, but the evaluation of accuracy provides centimeter to the meter-scale resolution of DEMs, and therefore the data should be expanded to support the observation results. As for a long-term topographic change in the river channel (after Typhoon Morakot), UP3 was the only river section that showed erosion. Due to the steep channel gradient, the landslide material after the typhoon was transported to the middle and lower reaches of the flood. Therefore, the erosion in UP3 was higher than the deposition. The channel area was approximately 0.09 km\({}^{2}\), average channel height difference was 5.44 m (Table 4), and the highest height difference was 30-35 m. The deposition at UP3 was  
was 1.33 M m\({}^{3}\) (Table 5). In EV, two large landslides near the upstream and above the residential area formed the largest deposition in the catchment. The river channel area was approximately 0.24 km\({}^{2}\), average height difference was 6.91 m (Table 4), the highest deposition depth was 15-20 m, deposition volume was 1.83 M m\({}^{3}\), erosion volume was 0.14 M m\({}^{3}\), and the total amount of deposition was 1.69 M m\({}^{3}\) (Table 5). In WV, the downstream section of the Laishe River, sediments from upstream had gradually slowed down, and there was no large-scale landslide. The channel area was approximately 0.18 km\({}^{2}\), average deposition depth was 4.02 m (Table 4), highest deposition depth as 8-10 m, deposition volume was 0.77 M m\({}^{3}\), erosion volume was 0.03 M m\({}^{3}\), and the total amount of deposition was 0.74 M m\({}^{3}\) (Table 5). In YL, the gentlest channel of the Laishe River catchment, the channel area was approximately 0.14 km\({}^{2}\), average height difference was 3.26 m (Table 4), highest height difference was 8-10 m, deposition volume was 0.45 M m\({}^{3}\), erosion volume was less than 0.01 M m\({}^{3}\), and the total amount of deposition was 0.44 M m\({}^{3}\) (Table 5). In addition, for the event-scale topographic changes of the river channel (Table 5) in UP3, the average height difference was 2.33 m (42.83% of the long-term average) and the total amount of deposition was 0.28 M m\({}^{3}\) (54.90% of the long-term average). At UP2, the channel showed accumulation, with an average height difference of 13.79 m (210.53%), and total depositional amount of 2.57 M m\({}^{3}\) (352.05%). From UP1 to YL, the decreasing average height difference was 11.0 (202.93%), 8.14 (117.80%), 2.84 (70.65%), and 2.54 m (77.91%), and the total deposition amount was 2.80 (210.53%), 2.40 (142.01%), 0.54 (72.97%), and 0.29 (65.91%) M m\({}^{3}\). Overall, compared to the long-term average, Typhoon Morakot almost doubled the sediment input.