## 3 Experimental Results
### River Blockage Induced by Landslide Dams  
The different types of river blockage are summarized in Figure 7, where three characteristic heights are marked as the stable water depth \(h_{\text{w}}\), the maximum dam height \(H_{\text{max}}\), and the minimum dam height \(H_{\text{min}}\). According to the relationships between these three characteristic heights, river blockages are characterized into six types, as listed in Table 2.  
Based on the images of the landslide dams recorded by the cameras, only five types of river blockages were observed in these experiments, as listed in Table 2. Because the chute exit is lower than the stable water surface, type 2-2 was not observed in these experiments. Typical experimental landslide dams for the five types are presented in Figure 8. The landslides entered into the flume, and the heads of the landslides slowed the rear landslides. Large volumes of landslide material will accumulate in the chute. If the height of landslide deposition on the side where it enters the flume surpasses the height of the chute's exit, then further landslide movement could be prevented by this outcrop  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**River Blockage** & **Degree of Blockage** & **Relationships of Characteristic Heights** & **Representative Experimental Test** \\ \hline Type 1-1 & & \(H_{\text{min}}\) \textless{} \(h_{\text{w}}\) & \\ Type 1-1 & & \(H_{\text{max}}\) appears in the middle of the river. & A1-1, A3-1 \\ \hline Type 1-2 & Partially blocked & \(H_{\text{max}}\) \textgreater{}  
of material; thus, not all landslide material could enter the flume. In this case, the landslide dam is highest on the landslide side and lowest on the opposite side, which is characteristic of blockage types 1-3. The main reason for the difference between types 1-2 and 1-3 is the difference in velocity entering the flume. As the slide angle and particle size increase, the cross-section type of the landslide dam will gradually transform to type 1-2. When a large volume of landslide material moved at a slow velocity, the landslide formed a complete blockage dam of type 2-3, in which \(H_{\text{max}}\) appeared on the landslide side. With a steeper slope, larger particle size, and larger material volume, landslides are more likely to result in dam type 2-1, which presents as a completely blocked channel with \(H_{\text{max}}\) near the center axis of the dam.  
According to the experiments conducted in this study, the proportions of the five blockage types are illustrated in Figure 9. Type 1-3, which has the highest deposition on the landslide side of the river, is the most common. All the sliding masses enter the flume and form the landslide dam in the experiments. In most tests, the maximum dam height \(H_{\text{max}}\) is observed on the landslide side of the river because the landslide materials slide into the flume at a low velocity. \(H_{\text{min}}\) is almost always on the opposite side because the final volume of the landslide materials has lower speeds and moves slowly across the surface of the deposition near the landslide side. The influence of slide angle, particle size, and landslide volume on the characteristics of deposition geometry and blockage type will be analyzed in the following sections.  
Figure 8: Photographs of typical river blockages by landslides. The red line marks the shape of the landslide dam.  
Figure 7: Different types of river blockages are caused by landslide dams.