Influence of rheology on debris-flow simulation

Abstract

Abstract. Systems of partial differential equations that include the momentum and the mass conservation equations are commonly used for the simulation of debris flow initiation, propagation and deposition both in field and in laboratory research. The numerical solution of the partial differential equations can be very complicated and consequently many approximations that neglect some of their terms have been proposed in literature. Many numerical methods have been also developed to solve the equations. However we show in this paper that the choice of a reliable rheological model can be more important than the choice of the best approximation or the best numerical method to employ. A simulation of a debris flow event that occurred in 2004 in an experimental basin on the Italian Alps has been carried out to investigate this issue. The simulated results have been compared with the hydrographs recorded during the event. The rheological parameters that have been obtained through the calibration of the mathematical model have been also compared with the rheological parameters obtained through the calibration of previous events, occurred in the same basin. The simulation results show that the influence of the inertial terms of the Saint-Venant equation is much more negligible than the influence of the rheological parameters and the geometry. A methodology to quantify this influence has been proposed.

Applications of simulation technique on debris-flow hazard zone delineation: a case study in Hualien County, Taiwan

“…It was found that the yield stress, roughness coefficient n and volumetric sediment concentration have a relatively large influence on the simulated results as compared with other testing parameters. The result is identical to that of other researches (Lin et al, 2005;Arattano et al, 2006;Sosio et al, 2007).…”

Rheological investigation and simulation of a debris-flow event in the Fella watershed

“…Their flow characteristics depend on the water content, sediment size and/or sorting, and on the dynamic interaction between the solid and fluid phases (Pirulli et al, 2008). In particular, the rheological properties naturally change, even during a single debris-flow event (Remaitre et al, 2005) or still for debris flows taking place in the same torrent (Arattano et al, 2006). Even if there are so many variabilities and uncertainties in the choice of the rheological parameters, they are generally required by numerical models to replicate debris-flow events, and the models outcome are very sensitive to the wide variability of them (Arattano et al, 2006).…”

“…In particular, the rheological properties naturally change, even during a single debris-flow event (Remaitre et al, 2005) or still for debris flows taking place in the same torrent (Arattano et al, 2006). Even if there are so many variabilities and uncertainties in the choice of the rheological parameters, they are generally required by numerical models to replicate debris-flow events, and the models outcome are very sensitive to the wide variability of them (Arattano et al, 2006). This implies that, for purposes of hazard prediction and assessment on a debris fan, different simulations have to be performed assuming different rheological behaviours and exploring the related consequences (Arattano et al, 2006).…”

Rheological properties and debris-flow modeling in a southern Italy watershed

“…It is based on the solution of the conservation of mass and momentum equations and uses a quadratic rheological model defining the flow pattern of the mixture both for a viscous fluid and for a turbulent/dispersive fluid. The resistant term of the Saint Venánt equations has a higher influence on reproducing debris-flows than the other terms (Arattano et al [20]), so it should be adequately estimated. The rheological behavior of a debris-flow containing coarse particles cannot be assessed considering exclusively the contribution of the finer matrix (silt and clay) and thus neglecting the effects of direct grain contacts (Sosio et al [21]).…”