## 1 Introduction  
Every year, hundreds of landslide-related phenomena, including rock avalanches and debris flows, cause loss of human life and the destruction of much else [1]. The risk analysis of this kind of natural hazard requires the evaluation of the stabilization of the source area and the prediction of propagation behavior (runout distance, velocities, thickness, and shape of deposit). In this study, we dealt with the latter issue by using reliable tools for investigating the dynamics of these flows. Once the flow characteristics are predicted, we can develop more precise hazard maps and design more effective countermeasures. There exist many different debris-resisting structures to cope with the threat related to debris avalanches and debris flows, such as bottom drainage screens [2] and artificial barriers [3].  
Once unstabilized areas where mass flows are likely to release have been identified, existing programs based on dynamic numerical models are employed to predict flow behaviors and identify possible impact areas. Nowadays, there exists a large number of numerical models [4; 5; 6] developed to be useful for risk assessment and runout analysis, and the choice of the most suitable simulation code, given the advances in computational capabilities, has raised another important issue. It is always recommended to use more than one simulation to predict specific events or a detailed back-analysis. This allows us to compare numerical results, understand the main differences, and assess potential risks more precisely. Regardless of the selected simulation code's capabilities, many other factors, including the choice of rheological law [7], the pore-water pressure evolution [8], the presence of erosion [9], and accurate definitions of parameters, affect the results significantly.  
This research's motivation was the significant challenges researchers and users face when attempting to obtain the same results from two different sets of code. We also aimed to evaluate the performance of a depth-integrated, two-phase model implemented in two different sets of code, and investigate the capabilities of these two widely validated sets of code, GeoFlow-SPH [10] and ravaflow [11], which are based on the same mathematical model have with fundamentally different numerical solvers. The most important thing was to comprehend the methodologies behind the two sets of code, in order to choose an appropriate rheological law and appropriate geotechnical properties, rather than using the same rheological and empirical laws for both sets of code. This is because engineers will use the numerical results obtained for mapping dangerous areas and designing structural countermeasures.  
The paper is structured as follows. The first section is dedicated to introducing the two different continuum-based programs and briefly describing the implemented depth-integrated, two-phase mathematical model consisting of the balance equations of mass and linear momentum, and suitable rheological and empirical equations. In the next section, we report the simulations of two different real events. The simulations used the selected sets of code while aiming to evaluate the ability of the depth-integrated two-phase model to reproduce rapid, large-scale landslides. Finally, the obtained numerical results are compared and discussed.