Wave formation, propagation and run-up in natural mountain lakes from a cascade hazard perspective - analysis and modeling of triggering processes, lake´s morpho-dynamics and potential downstream hazard effects

Andrea Franco
Supervising board members: Bernhard Gems, Barbara Schneider-Muntau , Jasper Moernaut, Markus Aufleger, Michael Strasser

 

Funding

University of Innsbruck

 

Involved research institutions at the University of Innsbruck

Unit of Hydraulic Engineering, Department of Geotechnical Engineering and Tunneling, Institute of Geology

 M.A. concept

Overview

The management and the analysis of the hydrological and geological risk in mountain regions is considered nowadays as a priority for human and territory safety. The study of phenomena that affect these regions, like landslides or flash floods, has been and is still a challenge in continuing evolution for a better comprehension for reliable natural hazards assessment. In the last centuries the consciousness of phenomena like tsunamis in lakes or in artificial basins (also known as impulse waves) has spread since several catastrophes happened. In fact, landslides either subaquatic or subaerial can trigger devastating tsunami waves. The generation of impulse waves in lakes is often triggered by an amount of material, collapsing in the water body, with a sufficient energy in terms of mass and velocity to allow the formation and propagation of a wave. Often, large landslides, or rockslides, are triggered by intense rainfall events or earthquakes.

The study of landslide generated impulse waves in natural mountain lakes, or reservoirs, in a forward analysis, represents a hard challenge for the science world. For that purpose, a multidisciplinary approach is needed to analyze the complexity of these kinds of phenomena where different science disciplines as geology, geotechnics and hydraulics are strictly related. A detailed geological, structural, geo-morphological and geo-mechanical investigation of an area allows the realization of a good geotechnical model of an unstable slope. A topography with high resolution and an accurate bathymetry of the lake floor are necessary for a good simulation of a landslide generated impulse wave. The purpose is to see the effects and the damages along the shoreline and the surrounding areas.

Application of this approach means also to analyze this kind of phenomena from a cascade hazard perspective, since we are talking about a “domino effect”. Like a chain reaction of triggers and consequences, a quake could destabilize a slope that at the end of its collapsing process impacts a water body, like a lake, generating an impulse wave, whose propagation damages the banks surrounding the impact area. A good knowledge of the possible triggers (e.g. in terms of rainfall or seismic hazard) concerning a specific mountain area is needed. Information, like the local acceleration if an earthquake is taken into account, can be used as input for stability and stress-strain analysis of a slope to understand the possibility of an unstable volume to collapse in a lake or in a reservoir. Starting from the outputs obtained from the previous analysis, a landslide run out simulation is considered as process boundary condition of the hydraulic model simulating formation and propagation of the impulse wave and any related hydraulic consequences.

Recently, the most used commercial-available software for the simulation of impulse waves in alpine lakes and reservoirs is the computational fluid dynamics (CFD) model Flow-3D. A task of this project is also to test the capacity of Flow-3D and its limits with regard to the extent of the computational domain, the grid resolution, the corresponding computation times and as well the accuracy of modelling results.

Lituya Bay 1958 Landslide generated - impulse wave simulation

Video - Lituya Bay Tsunami 1958 


Project Results - Recent Journal Publications

Franco, A., Moernaut, J., Schneider-Muntau, B., Strasser, M., Gems, B. (2020): The 1958 Lituya Bay tsunami – pre-event bathymetry reconstruction and 3D numerical modelling utilising the computational fluid dynamics software Flow-3D.
In: Natural Hazards and Earth System Sciences, 20, 2255-2279. https://doi.org/10.5194/nhess-20-2255-2020

 

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