On the evening of December 22, 2018, the coasts of the Sunda Strait, Indonesia, were hit by a tsunami generated by the collapse of a part of the Anak Krakatau volcano. Hundreds of people were killed, thousands were injured and displaced. This paper presents a preliminary modeling of the volcano flank collapse and the tsunami generated based on the results of a 2D depth-averaged coupled model involving a granular rheology and a Coulomb friction for the slide description and dispersive effects for the water flow part.With a reconstructed total volume (subaerial and submarine) of the landslide of 150 million m 3 inferred from pre and post-collapse satellite and aerial images, the comparison of the simulated water waves with the observations (tide gauges located all around the strait, photographs and field surveys) is satisfactory. Due to the lack of information for the submarine part of the landslide, 2 Alexandre Paris et al. the reconstructed submarine slope is assumed to be approximately constant. A significant time delay on the results and particularly in the Bandar Lampung Bay could be attributed to imprecisions of bathymetric data. The sensitivity to the basal friction and to dispersive effects is analyzed through numerical tests. Results show that the influence of the basal friction angle on the simulated wave heights decreases with distance and that a value of 2°gives consistent results with the observations. The dispersive effects are assessed by comparing water waves simulated by a shallow water model and a Boussinesq model. Simulations with frequency dispersion produce longer wave periods and smaller wave amplitudes in the Sunda Strait and particularly in deep waters.

No abstract

Abstract. In this paper, we present new results on the potential La Palma collapse event, previously described and studied in Abadie et al. (2012). Three scenarios (i.e., slide volumes of 20, 40 and 80 km3) are considered, modeling the initiation of the slide to the water generation using THETIS, a 3D Navier–Stokes model. The slide is a Newtonian fluid whose viscosity is adjusted to approximate a granular behavior. After 5 min of propagation with THETIS, the generated water wave is transferred into FUNWAVE-TVD (Total Variation Diminishing version of FUNWAVE) to build a wave source suitable for propagation models. The results obtained for all the volumes after 15 min of Boussinesq model simulation are made available through a public repository. The signal is then propagated with two different Boussinesq models: FUNWAVE-TVD and Calypso. An overall good agreement is found between the two models, which secures the validity of the results. Finally, a detailed impact study is carried out on La Guadeloupe using a refined shallow water model, SCHISM, initiated with the FUNWAVE-TVD solution in the nearshore area. Although the slide modeling approach applied in this study seemingly leads to smaller waves compared to former works, the wave impact is still very significant for the maximum slide volume considered on surrounding islands and coasts, as well as on the most exposed remote coasts such as Guadeloupe. In Europe, the wave impact is significant (for specific areas in Spain and Portugal) to moderate (Atlantic French coast).

No abstract

In this paper, we analyze the relevance of the use of the shallow water model and the Boussinesq model to simulate tsunamis generated by a landslide. In a first part, we determine if the two models are able to reproduce waves generated by a landslide. Each model has drawbacks but it seems that it is possible to use them together to improve the simulations. In a second part we try to recover the landslide displacement from the generated wave. This problem is formulated as a minimization problem and we limit the number of parameters to determine assuming that the bottom can be well described by an empirical law.

No abstract

In this paper, we present a new source assessment of the La Palma collapse scenario previously described and studied in Abadie et al. (2012). Three scenarios (i.e., slide volumes of 20, 40 and 80 km 3 ) are considered, from the initiation of the slide to the water waves generation, using THETIS, a 3D Navier-Stokes model. The slide is considered as a Newtonian fluid whose viscosity is adjusted to approximate a granular behavior. After 5 minutes of propagation with THETIS, the generated water wave is transferred into FUNWAVE-TVD for 15 minutes of Boussinesq model simulation. Then, four different depth-averaged 5 codes are used to propagate the wave to the Guadeloupe area, Europe and French coasts. Finally, the wave impact in terms of run-up is evaluated through direct computations in specific areas or using theoretical formulas. Although the wave source appears reduced due to the rheology used compared to former works, the wave impact is still significant for the maximum slide volume considered on surrounding islands and coasts, as well as on remote most exposed coasts such as Guadeloupe. In Europe and in France, the wave impact is moderate (for specific areas in Spain and Portugal) to weak (Atlantic French coast). 10The comparison between the different wave models in overlapping computational regions shows an overall agreement in terms of first wave amplitude and time of arrival, but differences appear in the trailing waves.

<p class="Standard"><span lang="EN-GB">Coasts are hosting most of the human population worldwide and hosts a large part of the economic activities. Among the various types of coastal environments, sandy beaches represent one third of the global shoreline of which a large proportion is eroding (Luijendijk <em>et al.</em>, 2018). This phenomenon is accelerating under the effect of climate change and the understanding and mitigation of the shoreline erosion is a fundamental issue in coastal engineering.</span></p> <p class="Standard"><span lang="EN-GB">In this contribution we analyse survey data from two well-documented Atlantic beaches: Duck (North Carolina, USA), a microtidal East-exposed beach and Truc Vert (Aquitaine, France) a meso/macrotidal West-exposed beach. A statistical analysis of the waves data over 2 to 3 decades provides useful information to evaluate the various possible morphodynamic beach states following Masselink & Short (1993) classification. This classification is based on the Dean number and the relative tidal range. Using the measured bathymetries, it is possible to verify the Masselink and Short classification. For example, using Duck data, a morphological analysis is performed on the 18 available bathymetries from the year 2019. These data illustrate the up-state and down-state sequences between reflective (summer) and dissipative (winter) states. In particular, the variability of the beach morphology increases significantly during intermediate beach states.</span></p> <p class="Standard"><span lang="EN-US">Applied to the two datasets, a modeling approach combining a one-line model, ShoreFor (Splinter<span class="apple-converted-space"> </span><em>et al.</em>, 2014), and 2D depth-averaged process-based model, XBeach (Roelvink<span class="apple-converted-space"> </span><em>et al.</em>, 2009), is envisaged. ShoreFor is run to predict<span class="apple-converted-space"> </span>shoreline and bar location (Splinter<span class="apple-converted-space"> </span><em>et al.</em>, 2018) and<span class="apple-converted-space"> </span>XBeach simulations are used on specific subsets of the entire computational window for intermediate 2D morphological state predictions.</span></p> <p class="Standard"><span lang="EN-GB"> </span><span lang="EN-GB"> </span></p> <p class="Standard"><span lang="EN-GB"> </span></p> <p class="Standard"><span lang="EN-GB"> </span></p> <p class="Standard"><span lang="EN-GB">Luijendijk, A., Hagenaars, G., Ranasinghe, R., Baart, F., Donchyts, G. and Aarninkhof, S. (2018), The State of the World’s Beaches, <em>Scientific Reports</em>, <strong>8</strong>(6641).</span></p> <p class="Standard"><span lang="EN-GB">Masselink, G. and Short, A. (1993), The Effect of Tide Range on Beach Morphodynamics and Morphology: A Conceptual Beach Model, <em>Journal of Coastal Research</em>, <strong>9</strong>(3), 785–800.</span></p> <p class="Standard"><span lang="EN-GB">Splinter, K.D., Turner, I.L., Davidson, M.A., Barnard, P., Castelle, B. and Oltman-Shay, J. (2014), A generalized equilibrium model for predicting daily to interannual shoreline response, <em>Journal of Geophysical Research: Earth Surface</em>, <strong>119</strong>, 1936–1958.</span></p> <p class="Standard"><span lang="EN-GB">Splinter, K.D., Gonzalez, M.V.G., Oltman-Shay, J., Rutten, J., Holman, R. (2018), Observations and modelling of shoreline and multiple sandbar behaviour on a high-energy meso-tidal beach, <em>Continental Shelf Research</em>, <strong>159</strong>, 33—45.</span></p> <p><span lang="EN-GB">Roelvink, D., Reniers, A., van Dongeren, A., van Thiel de Vries, J., McCall, R., and Lescinski, J. (2009), Modelling storm impacts on beaches, dunes and barrier islands, <em>Coastal Engineering</em>, <strong>56</strong>(11–12), 1133–1152.</span></p>