Fast assessment of landslide-generated tsunami risks by coupling SLBL with shallow water model

Martin Franz

Dans les comptes rendus d’articles de la conférence: GeoVancouver 2016: 69th Canadian Geotechnical Conference

Session: GEOHAZARDS - VI Climate Change Floods & Landslides

ABSTRACT: We developed a 2.5D numerical model that is able to simulate the landslide propagation (Bingham rheology and granularflow), the tsunami propagation and the run-up. By coupling it with the SLBL method,we obtain an efficient tool forlandslide-generated tsunami assessment. Its capacities are demonstrated on two case studies: the Nicolet landslide,QC, Canada, and the Oeschinensee case, Switzerland.R•SUM•Nous avons d†velopp†un mod‡le num†rique en 2.5D qui a la capacit† de simuler la propagation du glissement(rh†ologie Bingham et flux granulaire), celle du tsunami et le run-up. En le couplant avec la m†thode SLBL, nousobtenons un outil efficace pour l…†valuation des tsunamisg†n†r†spar glissement de terrain. Ces capacit†s sontd†montr†e avec deux cas d…†tude: Le glissement Nicolet, QC, Canada, et le cas d…Oeschinensee, Suisse.1INTRODUCTIONWater bodies located in mountainous regions aresusceptible to be reached by mass movement, whichcould lead to an impulse wave.This phenomenon isparticularly threatening as an infrastructures and highpopulation density are often located on the shore of thoselakes, fjords or rivers. A lot of researches are nowadaysfocusing on this phenomenon (Wieczorek et al., 2007;Ward and Day, 2011;L—vholt et al., 2015; Wang et al.2015) but few models are developed focusingonapplication and ease of use. Moreover, the landslidetsunamis assessment requires different capacities suchas the determination of the landslide geometry, thesimulation of the landslide propagation and its interactionwith the water body, as well as the wave propagation andrun-up modelling.This study aims to demonstrate that our model is ableto do all ofthese tasks in a user friendly manner, as it ispurposely developed for quick hazard assessment.2GOVERNING EQUATIONSOur model integrates three different modules. The firstone aims torecreate the geometry of the landslide usingthe SLBLmethod(Jaboyedoff et al., 2004;Jaboyedoff etal., 2009b;Fig.1).2.1Landslide propagationThe second module concerns the propagation of thelandslide. This latter provides three choices for thepropagation. The first one is the simple translation of arigid block, the second one uses the Bingham rheologyand the last one is granular flow.Figure 1: A: Linear SLBL for a spur. B: SLBL computationprocedure. C: Curved SLBL assuming a tolerance leadingto a rotational-like surface (modified after Jaboyedoff etal., 2009b).The Bingham rheology model is suitable to simulatethe propagation of material such as snow, volcanic lava,marine, and river sediments(Imran et al., 2001;Skvortsov2005;Glimsdal et al., 2013). We used the equationdevelopedby Skvortsov,2005.Thelandslide model isbased on the onedimensionalshallow water equation(SWE)[1]whereQthe solution vector, FxandFythe flux vectorsare defined as[2] 2, 2[3]whereDis the water depth, u and v are thecomponents of the depth averaged velocity vectors, g…is

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