Comparison of Two Depth Averaged Numerical Models for Debris Flow Runout Estimation

Abstract

This paper analyses an important aspect of the continuum numerical modeling of rapid landslides as debris flows: by using the same rheological parameter values, are the results, obtained with codes that implement the same constitutive equations but a different numerical solver, equal? In order to answer this question, the two numerical codes RASH3D and GeoFlow_SPH are here used to back-analyze the debris flow event occurred in the Nora stream (Northwestern Italian Alps) in October 2000. Comparison of results evidenced that the RASH3D best fit rheological values for the Nora event back analysis overestimated both the final depositional heights and the simulated flow velocities if used in GeoFlow_SPH. In order to obtain thickness values comparable with those measured in situ, it was necessary to re-calibrate GeoFlow_SPH rheological parameter values. In this way, with the exception of a larger lateral spreading of the sliding mass given by RASH3D, both thickness and velocity values were similar for the two numerical codes.