Impulse wave generation: Comparison of free granular with mesh-packed slides

Slides generating impulse waves are currently generated using either block models or free granular material impacting a water body. These procedures were mainly developed to study plane impulse waves, i.e., wave generation in a rectangular channel. The current VAW, ETH Zurich, research is directed to the spatial impulse wave features, i.e., waves propagating in a wave basin. The two wave generation mechanisms mentioned above complicate this process for various reasons, including experimental handling, collection of slide material in the wave basin, poor representation of prototype conditions for the block model, and excessive temporal duration for free granular slides. Impulse waves originating from slides with free granular material and mesh-packed slides are compared in this paper. Detailed test series are presented, so that the resulting main wave features can be compared. The results highlight whether the simplified procedure involving mesh-packed slides really applies in future research, and specify advantages in terms of impulse wave experimentation.ISSN:2077-131

Traces of a prehistoric and potentially tsunamigenic mass movement in the sediments of Lake Thun (Switzerland).

Mass movements constitute major natural hazards in the Alpine realm. When triggered on slopes adjacent to lakes, these mass movements can generate tsunami-like waves that may cause additional damage along the shore. For hazard assessment, knowledge about the occurrence, the trigger and the geomechanical and hydrogeological mechanisms of these mass movements is necessary. For reconstructing mass movements that occurred in or adjacent to lakes, the lakes's sedimentary record can be used as an archive. Here, we present a prehistorical mass-movement event, of which the traces were found in an alpine lake, Lake Thun, in central Switzerland. The mass movement is identified by large blocks on the bathymetric map, a chaotic to transparent facies on the reflection seismic profiles, and by a mixture of deformed lake sediments and sandy organic-rich layers in the sediment-core record. The event is dated at 2642-2407 cal year BP. With an estimated volume of ~ 20 × 106 m3 it might have generated a wave with an initial amplitude of > 30 m. In addition to this prehistorical event, two younger deposits were identified in the sedimentary record. One could be dated at 1523-1361 cal year BP and thus can be potentially related to an event in 598/599 AD documented in historical reports. The youngest deposit is dated at 304-151 cal year BP (1646-1799 AD) and is interpreted to be related to the artificial Kander river deviation into Lake Thun (1714 AD). Supplementary Information The online version contains supplementary material available at 10.1186/s00015-022-00405-0

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

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 >1km2. 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

Videometric water surface tracking of spatial impulse wave propagation

ISSN:1343-8875ISSN:1875-897

Spatial Propagation of Landslide Generated Impulse Waves

ISSN:0374-005

Spatial impulse wave

ENGLISH Landslides and avalanches in natural lakes and reservoirs may generate so-called impulse waves. The run-up effects of these waves at the shore are similar to those of tsunamis. Hydraulic experiments in the laboratory help to estimate key wave characteristics, including the wave height and celerity. The picture presents two images of an experiment in the wave basin of the Laboratory of Hydraulics, Hydrology and Glaciology (VAW) at ETH Zurich. At the upper left, the moment shortly after the slide has hit the water surface is shown. The slide transfers its kinetic energy to the water and generates a wave. In the section on the lower right, the waves have propagated circularly from the impact location. The water is dyed white so that a grid can be projected onto the surface. During the experiment, this raster projection is simultaneously filmed by several cameras and the analysis of the image data allows for an accurate determination of the wave height decay. GERMAN Erdrutsche und Lawinen in natürliche Seen oder Stauseen können sogenannte Impulswellen auslösen. Die Auswirkungen beim Auflaufen dieser Wellen am Ufer sind mit denen von Tsunamis vergleichbar. Hydraulische Experimente im Labor helfen dabei, massgebliche Welleneigenschaften, wie beispielsweise die Höhe oder die Ausbreitungsgeschwindigkeit, abzuschätzen. Das Bild stellt zwei Aufnahmen eines Experiments im Wellenbecken der Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie der ETH Zürich zu unterschiedlichen Zeitpunkten dar. Oben links ist der Moment kurz nach dem Auftreffen des Rutsches auf die Wasseroberfläche zu sehen. Der Rutsch überträgt dabei seine Bewegungsenergie auf das Wasser und erzeugt eine Welle. Im Ausschnitt unten rechts haben sich die Wellen kreisförmig von der Eintauchstelle weg ausgebreitet. Das Wasser ist weiss eingefärbt, damit ein Raster auf die Oberfläche projiziert werden kann. Diese Rasterprojektion wird während des Experiments gleichzeitig von mehreren Kameras gefilmt und die Auswertung der Bilddaten ermöglicht eine genaue Bestimmung der Wellenhöhenabnahme

Slide-induced Impulse Waves in the Context of Periglacial Hydropower Development: Ondes d’impulsion générées par glissements dans le contexte du développement del’hydroélectricité périglaciaire

Due to retreating glaciers, new potential locations for the construction of dams for hydropower and other purposes will open up in the near to long-term future. The periglacial environment of these facilities is increasingly affected by mass wasting processes. In addition to snow avalanches and glacier break-offs, unstable slopes previously supported by glacier ice and the thawing of permafrost due to rising mean air temperatures pose a risk to future reservoirs: If these landslides enter a reservoir at high speed, tsunami-like impulse waves are generated. The dam structure as the lowest situated shore area is particularly endangered and can be overtopped by relatively small waves. Impulse waves therefore represent a risk that must be taken into account when planning new facilities. About a decade ago, the Laboratory for Hydraulics, Hydrology and Glaciology (VAW) proposed a computational procedure for the assessment of impulse wave events with a special focus on reservoirs. Recently, a second updated edition of this ‘impulse wave manual’ was published. This contribution presents a procedure for the hazard assessment of impulse waves in reservoirs. A special focus is given to the potentially wave-generating forms of mass movement in the periglacial environment and the hydraulic characteristics of small impulse wave events.En raison du recul des glaciers, de nouveaux sites potentiels pour la construction de barrages hydroélectriques et autres s’ouvriront à l’avenir proche et à long terme. L’environnement périglaciaire de ces installations est de plus en plus affecté par des processus de gaspillage de masse. Outre les avalanches de neige et les débâcles de glaciers, les pentes instables auparavant soutenues par la glace de glacier et le dégel du permafrost dû à l’augmentation des températures moyennes de l’air constituent un risque pour les futurs réservoirs : Si ces glissements de terrain pénètrent à grande vitesse dans un réservoir, des vagues d’impulsion de type tsunami sont générées. La structure du barrage, en tant que zone côtière la plus basse, est particulièrement menacée et peut être submergée par des vagues relativement petites. Les vagues d’impulsion représentent donc un risque qui doit être pris en compte lors de la planification de nouvelles installations. Il y a une dizaine d’années, le Laboratoire d’hydraulique, d’hydrologie et de glaciologie (VAW) a proposé une procédure de calcul pour l’évaluation des vagues de choc, en mettant l’accent sur les réservoirs. Récemment, une deuxième édition mise à jour de ce "manuel sur les ondes de choc" a été publiée. Cette contribution présente une procédure pour l’évaluation des dangers des vagues de choc dans les réservoirs. Une attention particulière est accordée aux formes de mouvement de masse potentiellement génératrices de vagues dans l’environnement périglaciaire et aux caractéristiques hydrauliques des petites vagues à impulsions

Impulse Wave Runup on Steep to Vertical Slopes

Impulse waves are generated by landslides or avalanches impacting oceans, lakes or reservoirs, for example. Non-breaking impulse wave runup on slope angles ranging from 10° to 90° (V/H: 1/5.7 to 1/0) is investigated. The prediction of runup heights induced by these waves is an important parameter for hazard assessment and mitigation. An experimental dataset containing 359 runup heights by impulse and solitary waves is compiled from several published sources. Existing equations, both empirical and analytical, are then applied to this dataset to assess their prediction quality on an extended parameter range. Based on this analysis, a new prediction equation is proposed. The main findings are: (1) solitary waves are a suitable proxy for modelling impulse wave runup; (2) commonly applied equations from the literature may underestimate the runup height of small wave amplitudes; (3) the proposed semi-empirical equations predict the overall dataset within ±20% scatter for relative wave crest amplitudes ε, i.e., the wave crest amplitude normalised with the stillwater depth, between 0.007 and 0.69

Impulse Wave Runup on Steep to Vertical Slopes

Impulse waves are generated by landslides or avalanches impacting oceans, lakes or reservoirs, for example. Non-breaking impulse wave runup on slope angles ranging from 10° to 90° (V/H: 1/5.7 to 1/0) is investigated. The prediction of runup heights induced by these waves is an important parameter for hazard assessment and mitigation. An experimental dataset containing 359 runup heights by impulse and solitary waves is compiled from several published sources. Existing equations, both empirical and analytical, are then applied to this dataset to assess their prediction quality on an extended parameter range. Based on this analysis, a new prediction equation is proposed. The main findings are: (1) solitary waves are a suitable proxy for modelling impulse wave runup; (2) commonly applied equations from the literature may underestimate the runup height of small wave amplitudes; (3) the proposed semi-empirical equations predict the overall dataset within ±20% scatter for relative wave crest amplitudes ε, i.e., the wave crest amplitude normalised with the stillwater depth, between 0.007 and 0.69.ISSN:2077-131