A Simplified Classification of the Relative Tsunami Potential in Swiss Perialpine Lakes Caused by Subaqueous and Subaerial Mass-Movements

Abstract

Historical reports and recent studies have shown that tsunamis can also occur in lakes where they may cause large damages and casualties. Among the historical reports are many tsunamis in Swiss lakes that have been triggered both by subaerial and subaqueous mass movements (SAEMM and SAQMM). In this study, we present a simplified classification of lakes with respect to their relative tsunami potential. The classification uses basic topographic, bathymetric, and seismologic input parameters to assess the relative tsunami potential on the 28 Swiss alpine and perialpine lakes with a surface area >1 km 2. The investigated lakes are located in the three main regions "Alps," "Swiss Plateau," and "Jura Mountains." The input parameters are normalized by their range and a k-means algorithm is used to classify the lakes according to their main expected tsunami source. Results indicate that lakes located within the Alps show generally a higher potential for SAEMM and SAQMM, due to the often steep surrounding rock-walls, and the fjord-type topography of the lake basins with a high amount of lateral slopes with inclinations favoring instabilities. In contrast, the missing steep walls surrounding lakeshores of the "Swiss Plateau" and "Jura Mountains" lakes result in a lower potential for SAEMM but favor inundation caused by potential tsunamis in these lakes. The results of this study may serve as a starting point for more detailed investigations, considering field data.

Hazards from lakes and reservoirs: new interpretation of the Vaiont disaster

“…The displacement of reservoir water produced an impulse wave or tsunami around eight times higher than predicted. There are three types of tsunamigenic scenarios: (i) differential movements of the Earth's crust during earthquakes, (ii) submarine landslides involving fine sediments on relatively gentle slopes (Løvholt et al 2015) including lacustrine sediments (Strupler et al 2020), (iii) large or very large subaerial landslides moving rapidly into bodies of water (Couston et al 2015) including volcanic sources (e.g. pyroclastic flow and/or flank collapse: Freunt et al 2007).…”

“…(d) Of the major controls on wave height identified by Strupler et al (2020), the slide width at Vaiont (~1800 m) was probably significant, but neither the impact velocity nor the impact angle were relevant as there was no 'impact' (point (a) above).…”

“…Franco et al 2020;Waldmann et al 2021); (ii) evidence of previously unknown historical and prehistorical events continues to be found and assessed, such as in Swiss lakes (e.g. Spinney 2014;Strupler et al 2020); and (iii) recent events such as at Chehalis Lake, Canada in 2007 (Wang et al 2015) and Lake Askja, Iceland in 2014 (Gylfadóttir et al 2017) can be investigated almost immediately. In addition to some factors not relevant to the Vaiont case, the height of an impulse wave depends strongly on the balance between the angle and velocity of impact of a large rockslide entering a lake, with the width of the sliding mass being a highly significant factor (Strupler et al 2020).…”

“…Spinney 2014;Strupler et al 2020); and (iii) recent events such as at Chehalis Lake, Canada in 2007 (Wang et al 2015) and Lake Askja, Iceland in 2014 (Gylfadóttir et al 2017) can be investigated almost immediately. In addition to some factors not relevant to the Vaiont case, the height of an impulse wave depends strongly on the balance between the angle and velocity of impact of a large rockslide entering a lake, with the width of the sliding mass being a highly significant factor (Strupler et al 2020). If the volume of the landslide is very large compared with the volume of water in the lake, high waves can be generated even from shallow water and may exceed the breaking-wave height threshold if the travel distance to an opposite shore is short (Freunt et al 2007).…”

Geometry-Based Preliminary Quantification of Landslide-Induced Impulse Wave Attenuation in Mountain Lakes

“…Strupler et al [18] suggest a classification of mountain lakes based on their impulse wave potential, which they derived from both subaerial and subaqueous mass movements at Swiss perialpine lakes >1 km 2 . Their method relies on parameters calculated from digital elevation data (using geospatial software), for instance, topographic surfaces and bathymetry, together with seismologic data (e.g., the local acceleration), considered as an external factor for landslide initiation.…”