Dynamic modelling of entrainment in rapid landslides

TLDR

Entrainment of path material is a key feature of many rapid landslides, and the resulting volume increase and flow character changes can markedly affect mobility. The authors present a simple material entrainment algorithm, assuming natural exponential growth with displacement, to model rapid landslide motion across 3D terrain. The model permits user‑defined growth rates and rheology changes at entrainment onset, and a hypothetical example illustrates how mass and momentum transfer assumptions influence the dynamics. Back‑analysis of the 1999 Nomash River landslide shows that the model can reproduce the bulk characteristics of a complex event involving substantial entrainment. Keywords: landslides, debris flows, rock avalanches, entrainment, erosion, dynamic modelling.

Abstract

Entrainment of path material is an important feature of many rapid landslides. The associated increases in volume and changes in flow character can significantly influence mobility. A simple material entrainment algorithm, based on the assumption of natural exponential growth with displacement, has been incorporated into a new computer model designed to simulate rapid landslide motion across 3D terrain. The user controls the growth rate and can also implement a change in rheology at the onset of entrainment. A hypothetical example is used to demonstrate the influence of the mass and momentum transfer assumptions. A back-analysis of the 1999 Nomash River landslide is included to show that the simple model is capable of simulating the bulk characteristics of a complex event involving substantial entrainment.Key words: landslides, debris flows, rock avalanches, entrainment, erosion, dynamic modelling.