Topography effects on landslide dynamics, generated tsunamis and seismic waves
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Landslides and generated tsunamis represent some of the costliest geo-hazards and a growing threat to human life across the globe as a result of climate change and population growth. The trajectory and dynamics of gravitational flows such as landslides or debris flows is mainly controlled by topography variations, channeling the flow within valleys or placing obstacles in their way. Describing accurately these effects in landslide and tsunami simulations requires huge computational cost but is necessary to build accurate hazard maps. For these reasons, approximate models have been developed based on depth-averaging of the equations and the shallow layer approximation. However, the formal derivation of shallow equations for general topographies is not straightforward. The curvature of the topography results in a force that maintains the velocity tangent to the topography and a curvature term appears in the bottom friction force (Peruzzetto et al. 2021). With the SHALTOP numerical model, we quantify here their influence on flow dynamics and deposits over synthetic and real topographies. Our simulations show that neglecting the curvature force increases the simulated travel times by up to 30%. When the curvature in the friction force is neglected, the travel distance may be increased by several hundred meters on real topographies. We observe similar effects on synthetic channels with a 50% increase of the kinetic energy. Comparison of the simulated force generated by landslides with the force inverted from low frequency seismic data also shows the strong effect of topography related forces in landslide dynamics (Moretti et al. 2015). Using the code HySEA that does not incorporate these curvature terms we estimate their impact on the generated tsunami waves (Poulain et al. 2023). Curvature effects can thus have significant impact for model calibration, overflows prediction, and for generated tsunamis all being critical for hazard assessment. References Moretti, L., Allstadt, K., Mangeney, A., Capdeville, Y., Stutzmann, E., and Bouchut, F., 2015. Numerical modeling of the Mount Meager landslide constrained by its force history derived from seismic data, J. GEOPHYS. RES. Solid Earth, 120(4), 2579-2599. Peruzzetto, M., Mangeney, A., Bouchut, F., Grandjean, G., Levy, C., and Thiery, Y. 2021. Topography curvature effects in shallow-water models, J. GEOPHYS. RES. - EARTH SURFACE, 126(4), e2020JF005657 Poulain, P., Le Friant, A., Mangeney, A., Viroulet, S., Fernande
