## 4 Conclusions  
This paper described two sets of code, ravaflow and GeoFlow-SPH, which are similar in mathematical formulation and differ by numerical implementation method. The two programs have been used to back-analyze two real cases that occurred in New Zealand in ancient history and Hong Kong in 1999. In previous works, the former has been back-analyzed with the ravaflow code to validate the implemented depth-integrated, two-phase model, and the latter has been back-analyzed through the GeoFlow-SPH code to evaluate the two-phase model while considering the space-time evolution of pore-water pressure. The best fit values of geotechnical parameters, which were achieved through one of the programs in the previous works, were used in another program in this study.  
The aims of the research were (1) to evaluate the prediction capabilities of programs, which are based on a depth-integrated two-phase model, by comparing the numerical  
Figure 9: The distribution of relative pore–water pressure at (**a**) 0 s, (**b**) 10 s, (**c**) 20 s, and (**d**) 60 s.  
results with available field data, and (2) to investigate whether the same geotechnical parameters calibrated in the one numerical code can be transferred to other numerical sets of code.  
The numerical results were compared to the field data, and they evidenced that both sets of code were capable of reproducing the run-out distance, deposition thickness, and shape for the real cases, although some parameters are considered in one numerical code but not in another, such as internal friction angle, earth pressure coefficients, and excess pore pressure evolution. Thus, the results of both sets of code can be considered satisfactory. The first numerical analyses showed that the same values of rheological parameters can be used for different sets of code based on similar mathematical formulae. However, the mathematical formulations used for the second case study were different due to the implementation of a consolidation equation in the Geoflow-SPH code for considering the space-time evolution of pore-water pressure.  
There were also considerable differences between the numerical results obtained by the two programs. In the first case study, the GeoFlow-SPH code underestimated the maximum propagation thickness compared to the ravaflow code. In the second case study, the ravaflow code underestimated the maximum propagation velocity compared to the GeoFlow-SPH code, which considers the pore-pressure evolution. These results confirm that using more than one simulation code is necessary to predict specific events to assess potential risks and design possible countermeasures.  
S.A.M.T. conceptualization, formal analysis, writing--original draft, and investigation. S.M.T.: formal analysis, visualization, writing--original draft, and investigation. M.P: methodology, writing--review and editing, supervision, and resources. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Spanish Ministry MINECO under project P-LAND (PID2019-105630 GB-I00).  
Not applicable.  
All measured data can be obtained by contacting the authors.  
The authors gratefully acknowledge the support of the Geotechnical Engineering Office, Civil Engineering and Development Department of the Government of the Hong Kong SAR in the provision of the digital terrain models for the Canada landslide case.  
The authors declare no conflict of interest.