Abstract
This study presents a numerical landslide-tsunami hazard assessment technique for applications in reservoirs, lakes, fjords, and the sea. This technique is illustrated with hypothetical scenarios at Es Vedrà, offshore Ibiza, although currently no evidence suggests that this island may become unstable. The two selected scenarios include two particularly vulnerable locations, namely: (i) Cala d’Hort on Ibiza (3 km away from Es Vedrà) and (ii) Marina de Formentera (23 km away from Es Vedrà). The violent wave generation process is modelled with the meshless Lagrangian method smoothed particle hydrodynamics. Further offshore, the simulations are continued with the less computational expensive code SWASH (Simulating WAves till SHore), which is based on the non-hydrostatic non-linear shallow water equations that are capable of considering bottom friction and frequency dispersion. The up to 133-m high tsunamis decay relatively fast with distance from Es Vedrà; the wave height 5 m offshore Cala d’Hort is 14.2 m, reaching a maximum run-up height of over 21.5 m, whilst the offshore wave height (2.7 m) and maximum inundation depth at Marina de Formentera (1.2 m) are significantly smaller. This study illustrates that landslide-tsunami hazard assessment can nowadays readily be conducted under consideration of site-specific details such as the bathymetry and topography, and intends to support future investigations of real landslide-tsunami cases.
Highlights
Landslides are a main source of impulse waves in reservoirs [1,2], lakes [3,4], fjords [5], and the sea [6]
Such impulse waves are better known as landslide tsunamis if they occur in the open sea, and for simplicity, this term is adopted irrespectively of the type of water body in question
Landslide tsunamis from nearshore to offshore involve multiple time and length scales such that more than one numerical code is required in order to reliably deal with all of these scales, e.g., DualSPHysics for the nearshore [7,8] combined with SWASH (Simulating WAves till SHore) [9,10] for the offshore region
Summary
Landslides are a main source of impulse waves in reservoirs [1,2], lakes [3,4], fjords [5], and the sea [6]. An approximately 20 million m3 large landslide initiated a 50-m large tsunami resulting in a run-up height of 60–80 m on the opposite shore [4]. Another example is a 270 million m3 landslide impacting into the Vajont reservoir in Italy, on 9 October 1963. The resulting wave overtopped the dam crest, resulting in approximately 2000 casualties [1] Such cases demonstrate the need for reliable landslide-tsunami hazard assessment methods to prevent similar catastrophes from the large number of potential landslides in proximity of a water body all around the world [11,12]
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