## 1 Introduction  
Landslide disasters occur frequently in the southwestern areas of China due to the alpine landforms and rainy climatic conditions [1; 2; 3]. Landslides are events in which the originally stable slope or geologic mass becomes unstable and undergoes shearing because of external influences, ultimately resulting in a complete or partial slide occurrence [4; 5; 6]. Landslides have many characteristics, such as prediction difficulty, abruptness of occurrence, magnitude of impact, and the possibility of causing secondary hazards [7; 8]. Landslides can also produce a landslide dam with a large reservoir capacity, which increases the risk of flooding downstream [9; 10; 11]. For example, the Wenchuan earthquake in 2008 triggered numerous landslides, many of which led to the formation of large dammed lakes, including the Tangjiashan dammed lake with a reservoir capacity of 300 \(\times\) 10\({}^{6}\) m\({}^{3}\) and the Laoyingan dammed lake with a dam height of 130 m [12; 13]. More than 30 dammed lakes of significant sizes that posed a great security threat to downstream areas were produced by the Wenchuan earthquake. In 2000, peak flow from the breakage of the Yigong landslide dam reached 124,000 m\({}^{3}\)/s, which forced more than 6000 people to evacuate and washed away a large number of roads, bridges, and additional infrastructure [14]. River blockagestriggered by landslides affect larger areas and produce greater hazards than those impacted by and resulting from the landslides directly. The study of river blockage processes caused by landslides is of great importance to reveal the blockage characteristics, including blockage type and dam-break mode, as well as to identify hazard warning techniques and expand the understanding of landslide dams [15]. Research on landslide-induced river blockages is mainly focused on the prediction and assessment of landslide risk [16], the mechanisms of landslide movements and river blockage [5; 17], and the use of numerical simulations [18; 19]. At present, the research methods used to investigate the formation of dammed lakes mainly include on-site investigations, physical model tests, and numerical simulations [3; 20; 21; 22; 23; 24; 25; 26]. Landslide disasters are difficult to predict and monitor, especially large-scale landslides, and it is also difficult to precisely deduce the landslide movement process through on-site investigations. Tests using physical models are of substantial significance for the study of these types of river blockages. The distribution of the debris in the landslide dam is affected mainly by the roughness of the sliding surface [27]. The landslide volume and the discharge area can be used to assess the damming capacity of rock slides [22]. For the study of the mechanism and characteristics of river blockage caused by landslides, these three aspects are particularly important: (1) the possibility of river blockage after the occurrence of landslides; (2) the volume of debris sliding into a river that may block the river and form a dammed lake [28]; and (3) the morphological characteristics and types of river blockage. The study of dams produced after a landslide requires the integration of geotechnics, hydraulics, material mechanics, sediment movements, etc. Although numerical simulation studies have been carried out extensively, there is still a lack of conventional experimental tests [29]. Experimental studies are a useful method to reveal the characteristics of river blockages caused by landslides [27]. The material type, source volume, and slope angle are some of the predominant factors in landslide movement [27; 30]. However, the influences of natural material characteristics involved in river blockage, such as slope topography and dynamic water flow during the blocking process, are seldom taken into account in physical model tests [31]. Moreover, whether the river flow conditions are put into the model will substantially affect the final deposition of landslide dams.