Computational Flow Modeling for Long-Runout Landslide Hazard Assessment, with an Example From Clapiere Landslide, France

Abstract

Use of a computational continuum dynamic flow model for the hazard assessment of catastrophic landslides is illustrated for a site in southern France. The continuum method has the advantage of including such site-specific details as the precise geometry of the initial failure mass, as well as variations of the topography in the runout zone. The method assumes two-dimensional transient flow of an incompressible biviscous fluid; two viscosity coefficients and a yield stress term comprise the relevant model material parameters, and can be set to approximate Bingham flow behavior. Judgment is necessary in the selection of these rheologic parameters; the procedure recommended involves choice of an analog landslide from a calibrated database of rheologic parameters. This general approach possesses some advantages over alternative methods for hazard evaluation involving fall-to-reach (H/L) ratios, or point-mass or slide block models, in which the uncertainties involving rheology and geometry are lumped indiscriminately together. The continuum method has been applied to a large potential slope failure at “la Clapiere” in southern France. Landslide runout, velocity, and debris thickness were predicted for this case example, for several potential travel paths, with the aim of aiding hazard management decisions involving areas hazardous to debris runout, inundation behind a landslide dam, and down-stream flooding with breaching of the landslide dam.