## 3 Analysis of Temporal and Spatial Distribution Characteristics of Landslide Surge
### Characterization of Surge Waveforms  
Since factors such as diversion area and curved area existed in the physical experimental model, these factors were also taken into account when considering the arrangement of the testing points of wave gauges. Nine testing points were divided into a diversion area (h01-h03), a topographically similar area (h03-h07), and a curved area (h07-h09) according to their respective locations. The experimental data of the reference group MLS2 were analyzed. Figure 6 shows the wave height gauge data of the nine testing points within 40 s after low-pass filtering processing; the red line depicts the time of head wave occurrence at each point. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Testing Point** & **MLS1** & **MLS2** & **MLS3** & **MLS4** & **MLS5** \\ \hline h01–h02 velocity (m/s) & 2.38 & 2.59 & 2.27 & 2.05 & 2.78 \\ h02–h03 velocity (m/s) & 2.50 & 2.78 & 2.94 & 3.26 & 2.46 \\ h03–h04 velocity (m/s) & 3.00 & 2.78 & 2.5 & 2.72 & 2.72 \\ h04–h05 velocity (m/s) & 3.00 & 3.45 & 3.57 & 2.88 & 3.00 \\ h05–h06 velocity (m/s) & 2.67 & 2.42 & 2.54 & 2.08 & 3.33 \\ h06–h07 velocity (m/s) & 2.31 & 2.27 & 2.34 & 3.54 & 2.11 \\ h07–h08 velocity (m/s) & 2.78 & 2.34 & 2.63 & 2.86 & 2.38 \\ h08–h09 velocity (m/s) & 2.42 & 3.06 & 2.05 & 2.80 & 2.63 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Wave velocity of adjacent testing points under different volumes. Figure 4: Fitting curve of head wave velocity. Figure 7 shows that the waveform changes greatly after 20 s. It is due to the fact that, during wave propagation, subsequent waves are affected by the wave reflections that the head wave encounters from the riverbanks, so only the waveforms in the 20 s after the head wave are analyzed. For the diversion area of 0 m\(\sim\)6 m away from the testing point h01, the waveforms are greatly affected by the significant changes in terms of river course width, average water depth and cross-sectional area of the river course during the surge propagation. Testing points h01 and h02 are only affected by the diversion area, so for the head wave, the waveforms are basically the same, with some differences in wave height. When the surge propagates to the testing point h03, the topography of the testing point h03 has been changed. The number of wave peaks at testing point h03 appear to decrease compared with testing point h02 in the same period of time; this is due to the superposition of the reflected wave and other waves, apart from head wave. The number of peaks of the surge changes considerably, so the number of peaks will be a big change for the surge propagating in the diversion area. In the physical model, there are also some areas where the topographic factors such as river course width and water depth are almost  
Figure 5: The ratio of wave velocity deviation. Figure 6: Landslide surge wave height curve at nine testing points of test MLS2. **(a)** Diversion area; **(b)** topographically similar area; **(c)** curved area. unchanged; these areas are called topographically similar areas, so the waveforms of the wave propagation are less affected. The area in the testing points h03-h07 belongs to the topographically similar area; waveforms are basically the same in the region of the testing points h04, h05 and h06. In 20 s, these waveforms all appear in five peaks, and the trend of change is also relatively close, so that the waveform can be considered to be similar when the wave propagates in the topographically similar area. There are also some curved areas in the river; in this kind of area, the direction of the water flow in the river changes a lot. So, for the surge, the propagation direction is also affected by the influence of the curves; then, the waveforms in these areas are greatly affected. The range of testing points h07-h09 belongs to the curved area, because in the wave propagation the river topography appears to turn, and the direction of the water flow appears to be a big change, so there is a more obvious change in the waveform.