*5.2. Model Selection*

In the DAN-W software, the accuracy of the calculation result depends on three important factors: Sliding body motion trajectory, rheological model, and parameter selection. First, based on multi-period remote sensing images, aerial imagery of drones, and field geological surveys, topographic lines before and after landslides were determined (Figure 6). Second, the Panjinbulake loess landslide was divided into the sliding source area, debris flow area, and accumulation area (Figure 5). According to the hazard characteristics of different regions, it is critical to select suitable rheological models for different regions. Since the sliding source area started from the shearing exit, there are signs of scratch on the exposed area of the bedrock. According to the existing research results [23,49–51], the Frictional model(F) was suitable for the sliding source area. The Frictional model and the Voellmy model(V) were used in the debris flow area and the accumulation area, respectively. According to the landslide path sequence, four sets of the rheological model combinations, Frictional–Frictional–Frictional, Frictional–Frictional–Voellmy, Frictional–Voellmy–Voellmy, and Frictional–Voellmy–Frictioanl, were used to simulate the dynamic hazard effects of the Panjinbulake loess landslide, so as to select the most suitable rheological model combination to simulate the movement process of the loess landslide (see Table 1). The simulation results calculated from a combination of the four rheological models were compared to the features of the actual loess landslide. According to the results, we could find that the Frictional–Voellmy–Frictional model fit the above characteristics. From Equation, the Voellmy model is proportional to the velocity of the sliding body, and it could simulate the huge scraping force which removed the surface loess soil. Thus, the Voellmy rheology model had a better fit than the Frictional model in the debris flow area. Finally, we intended to simulate the movement characteristics of the Panjinbulake loess landslide using the Frictional–Voellmy–Frictional rheological model.

**Table 1.** Hydrodynamic model of the Panjinbulake landslide.

