Impulse wave modelling and corresponding underwater landslide deposition

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Helge Fuchs, Willi H. Hager

Monday 29 june 2015

16:00 - 16:15h at Amazon (level 1)

Themes: (T) Water engineering, (ST) River and coastal engineering

Parallel session: 3C. Coastal engineering

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Impulse waves are considered a severe danger amongst natural hazards in mountainous regions. They are generated in lakes or reservoirs following a landslide, rockslide, rockfall, avalanche or glacier impact. The resulting long waves are of cnoidal-, solitary, Stokes or bore type. The usually short propagation distance and the corresponding negligible wave attenuation lead to a massive damage potential. Damages at the opposite shore are generated due to direct wave impact on buildings and structures, driftwood and float, and their deposits after water retreat. Possible dam overtopping may lead to structural damages or even a total failure for a reservoir. The generated flood wave may then propagate downstream endangering distant settlements. The latter scenario occurred in 2010 near Carhuaz, Peru. A _ 300,000 m3 rock-ice avalanche impacted a glacier lake leading to wave overtopping of _ 1 × 106 m3 of water. The generated flood wave caused significant damages to the village of Carhuaz, located 15 km downstream to the glacier lake. In the course of global warming, glacier retreat creates additional glacier lakes increasing the hazard risk for mountainous regions. Using the VAW impulse wave computation guideline a possible event can be assessed in advance. However, valuable information following a back-analysis of past slide events applies to calibrate the calculation procedure. Video recordings of 41 slide-generated impulse wave tests in a two-dimensional wave channel were therefore analyzed regarding the underwater slide dynamics and their final deposition patterns. Correlation equations for specific slide deposit features e.g. its length and thickness were defined. This work thus contributes to the estimation of risk assessment and to safety aspects relating to wave-shore interaction.