Tsunamis and other extreme hydrodynamic events have the potential to transport large debris that, along with the flow, are capable of causing severe damage to coastal structures and infrastructures. Therefore, modelling such processes is essential when assessing the multiple hazards associated to this type of events. In harbour areas, transport inland of shipping containers and subsequent impacts are relevant examples of waterborne debris hazards. The present work addresses two gaps in the scientific research of this problem using numerical methods; the understanding of the effect of containers initial layouts and that of the flow impact angle on the transport and diffusion. To fill these gaps a numerical study was carried out using idealised flow conditions. To this end a Smoothed Particles Hydrodynamics solver (DualSPHysics), coupled with a Discrete Element Method model (Project CHRONO), was used and initially validated with experiments published in the literature. Subsequently, four layouts commonly used in shipping containers yards were simulated, including incident flow depth and impact angle variability, resulting in 76 total simulations. The results were analysed in terms of normalised standard deviation and normalised range differences with respect to the initial values of both parameters. These parameters were related to the flow impact angle, water depth to containers height ratio DhR, and normalised displacement of the container clusters centroids. Standard deviation and range are shown to reach, for almost all results, a quasi-steady state by the end of the simulations. It is shown that the standard deviation and range are more sensitive to the impact angle for DhR <= 1.7. In this case, the configurations with flow impacting orthogonally to one of the containers axes show larger values of the two parameters than for intermediate angles. For larger values, DhR drives the standard deviation and range, independently from the impact angle. DhR is shown to be a physical parameter that well describes the relative importance of dispersion and advection of containers transported in extreme hydrodynamic events. Finally, existing relationships, that assume an infinite growth of the range, are shown to overestimate numerical results at the stage in which dispersion does not grow further. Two new regression formulae are numerically derived to predict the dispersion parameters at this stage. They include the effects of the cluster layout, impact angle a and DhR making them a valid alternative to existing relationships.

The dynamic interaction between cliff, beach and shore-platform is key to assessing the sediment balance for coastal erosion risk assessments, but this is poorly understood. We present a dataset containing daily, 3D,colour LiDAR scans of a 450 m coastal section at Happisburgh, Norfolk, UK. This previously para-glaciated region comprises mixed sand-gravel sediments, which are less well-understood and well-studied than sandy beaches. From Apr-Dec 2019, 236 daily surveys were carried out. The dataset presented includes: survey areas, transects LiDAR scans, georeferenced orthophotos, meteorological- and oceanographical conditions during the Apr-Dec observation period. Full LiDAR point-clouds are available for 67 scans (Oct-Dec). Hourly time-series of offshore sea-state parameters (significant wave height, mean propagation direction, selected spectral periods) were obtained by downscaling the ERA5 global reanalysis data (global atmosphere, land surface and ocean waves) using the numerical model Simulating Waves Nearshore (SWAN). We indicate how to obtain hourly precipitation time-series by interpolating ERA5 data. This dataset is important for researchers understanding the interaction between cliff, beach and shore-platform in open-coast mixed-sand-gravel environments.

Subaerial landslide-tsunamis (SLTs) are generated by mass movements such as landslides, rockfalls, glacier calving and snow avalanches impacting into lakes, reservoirs, fjords and the sea. Past SLTs reached runup heights of up to 524 m and are responsible, in combination with associated phenomena and tsunamis generated by partially submerged landslides, for a cumulative death toll in excess of 58000. Generic experimental research into SLTs, i.e. studies intended to predict SLTs for a range of scenarios, is ongoing for many decades. However, the advancement in the physical understanding, the wave prediction accuracy between similar studies and the reliability of hazard assessments does not fully reflect the large number of published generic peer-review work, particularly after 2005. A step change in generic SLT research is therefore needed. This article critically reviews SLT research with a focus on generic empirical equations from laboratory and numerical tests. Key features of past SLT cases are presented, relevant parameters affecting SLTs are reviewed and the most relevant conditions of 76 studies involving 6481 experiments, are listed including 10 milestone studies. This article further reviews findings into the effects of the mass movement type and slide model, slide to wave energy transfer, wave types, the effects of the water body geometry and non-uniform bathymetry, frequency domain analysis, edge waves and analytic achievements. Research gaps and shortcomings around generic empirical equations are also highlighted. Options to contribute to a step change are then suggested. These include the Korteweg-de Vries and Kadomtsev-Petviashvili equations, a generally applicable numerical code, machine learning and combinations.

Extreme hydrodynamic events, such as those driven by tsunamis, have a significant impact on coastal environments. The Smoothed Particle Hydrodynamics computational method gained popularity in modelling these phenomena. However, high resolution is needed in areas of interest, making coupling techniques popular to reduce computational costs. Herein, a new two-step offline coupling method was developed and validated in DualSPHysics. In step 1, the simulated velocity field and water depth are measured over a two-dimensional meshed surface of a generating domain. In step 2, the interpolated flow variables are used as boundary conditions in a receiving domain with equal or higher resolution. The method was validated by using two different laboratory experiments that are representative of tsunami propagation and inundation inland. The results show a reduction of computational time of up to 17.6 times, with decreasing savings for increasing resolution in the receiving domain. The validation tests showed that the developed method allows to simulate flows in the receiving domains at nearly the same accuracy of the generating domain while also decreasing computational time. When including debris transport, improvements in accuracy occur when doubling the resolution of the receiving domain with respect to the generating domain.

Extreme hydrodynamic events, such as tsunamis, can transport debris of a very wide range of dimensions, from cohesive sediments to debris such as trees and cars. Large sized floating debris are particularly hazardous for two main reasons: (i) they can accumulate in narrow passages, such as the case of log jams at bridges, and obstruct the flow, creating potential for further flooding; (ii) they can impact directly on structures transferring significant energy to them, due to their mass and velocity, which can lead to damage and even failure. The transport and the interactions of this type of debris is studied experimentally, often in the context of tsunamis and flash floods. However, numerical studies on large floating debris impact on structures are rare. Therefore, the present study aims to address this gap by numerically modelling of the flow-debris-structure interactions. First, the experiments of Stolle et al. (2018) are simulated numerically. These experiments involve a single positively buoyant container impact a structure as a result of being transported by a dam-break flow. The numerical simulations are carried using the open source DualSPHysics model based on the Smoothed Particle Hydrodynamics method. First, the hydrodynamics results were validated with data from Stolle et al. (2018). Subsequently, DualSPHysics was coupled with the Multiphysics engine CHRONO to simulate the container and its impact on the structure. The dam break event described in Stolle et al. (2018), was generated by modelling the movement of a swing gate using the experimental time series, with the container and the structure positioned at 3.2 m and 7.03 m, respectively, downstream of the reservoir consistently with Stolle et al. (2018). The trajectory as well as the velocity of the centroid of the container were tracked throughout the simulation. The agreement between the model and the experiment results is quantitatively assessed and it is shown that the model is accurate in reproducing the floating container trajectory, impact velocity and, in turn, force. In a second stage, numerical simulations beyond the conditions tested by Stolle et al. (2018) are used to investigate the role of the flow velocity, impact angle and location.

Landslide-tsunamis are generated by masses, such as landslides or icebergs, impacting into water bodies. Such tsunamis resulted in major catastrophes in the recent past. Generic research into landslide-tsunamis has widely been conducted in idealised water body geometries at uniform water depths. However, varying bathymetries can significantly alter landslide-tsunamis. This article investigates this effect in a 2D flume using selected idealised bathymetries to provide methods to predict the transformed wave characteristics downwave of each feature. The selected bathymetries are: (a) linear beach bathymetries, (b) submerged positive and negative Gaussian bathymetric features and (c) submerged positive and negative step bathymetries. The hydrodynamic model SWASH, based on the non-hydrostatic non-linear shallow water equations, was used to simulate 9 idealised landslide-tsunamis (1 approximate linear, 2 Stokes, 2 cnoidal and 4 solitary waves), for a total of 184 tests. The analysed parameters include the free water surface, wave height and amplitude. Shoaling in (a) is represented by either Green's law or the Boussinesq's adiabatic approximation up to wave breaking with an accuracy of −7% to +10% for cnoidal and solitary waves, respectively. The results are then analysed with an (i) Artificial Neural Network and (ii) a regression analysis. (i) shows a smaller Mean Square Error (MSE) of 0.0027 than (ii) (MSE =0.024) and good generalisation in predicting the transformed wave characteristics and, after defining the best dimensionless parameters, (ii) provides empirical equations to predict transformed waves. In addition, simulations were conducted in a 3D basin to investigate the combined effect of the bathymetry and geometry. The efficient use of the developed prediction methods is demonstrated with the 2014 Lake Askja landslide-tsunami where a good accuracy is achieved compared to available numerical simulations.

Floods can transport debris of a very wide range of dimensions, from cohesive sediments to large floating debris, such as trees and cars. The latter increases the risk associated with floods by, for example, obstructing the flow or damaging structures due to impact. The transport of this type of debris and their interaction with structures are often studied experimentally in the context of tsunamis and flash floods. Numerical studies on this problem are rare, therefore the present study focuses on the numerical modelling of the flow-debris interaction. This is achieved by simulating multiple laboratory experiments, available in the literature, of a single buoyant container transported by a dam-break flow in order to validate the chosen numerical approach. The numerical simulations are carried using the open source DualSPHysics model based on the smoothed particle hydrodynamics method coupled with the multi-physics engine CHRONO, which handles the container–bottom interactions. The trajectory, as well as the velocity of the centroid of the container, were tracked throughout the simulation and compared with the same quantities measured in the laboratory. The agreement between the model and the experiment results is quantitatively assessed using the normalised root mean squared error and it is shown that the model is accurate in reproducing the floating container trajectory and velocity.

Landslide-tsunamis are caused by mass movements such as landslides and rockfalls impacting into a water body. This phenomenon has caused catastrophes in recent history that significantly affected both human lives and the economies of countries. Landslide-tsunamis also need to be assessed in high risk countries such as China with 87000 reservoirs. For this reason, reliable hazard assessment methods are required. Next to landslides generating the tsunamis, two additional water body characteristics affect their propagation before reaching the shore. These are: the water body geometry affecting the landslide-tsunami energy spread, and the bathymetry affecting phenomena such as shoaling and reflection. Landslide-tsunamis research under idealised conditions, is essentially based on the two idealised water body geometries (i) wave flume (2D, laterally confined wave propagation) and (ii) wave basin (3D, unconfined wave propagation). The wave heights in 2D and 3D can differ by over one order of magnitude in the far field and the wave characteristics in intermediate geometries are currently not well understood. Further, under idealised conditions, the majority of the studies use a uniform water depth to better isolate other effects. However, it has been demonstrated that also the bathymetry can considerably affect tsunami propagation via shoaling and other depth and shore related effects. This study focuses on how these two described aspects affect landslide-tsunami propagation. The numerical model SWASH, based on the non-hydrostatic non-linear shallow water equations, was used to simulate approximate linear, Stokes, cnoidal and solitary waves. The effect of the water body geometry was investigated in 6 different idealised water body geometries including 2D, 3D and intermediate geometries with water body side angles of θ=7.5°, 15°, 30° and 45° at uniform water depths. The effect of the bathymetry was mainly studied in 2D using a wide range of potential conditions representing real cases namely beach, positive and negative Gaussian and positive and negative step bathymetries. This resulted in a total of 184 numerical tests. In addition, the combined effect of the water body geometry and bathymetry was investigated in selected bathymetries with wave conditions spanning from deep to shallow water. The wavefront length, i.e. the arc length of the circle sector formed by the wave front, e.g. a semi-circle in 3D, was found to be an excellent parameter to correlate the wave decay along the slide axis in all investigated geometries in agreement with Green's law and diffraction theory in 3D. Semi-theoretical equations to predict the wave magnitude of the idealised waves at any desired point in the water bodies are also presented. Further, simulations of experimental landslide-tsunami time series were performed in 2D to quantify the effect of frequency dispersion. This process may be negligible for solitary- and cnoidal-like waves for initial landslide-tsunami hazard assessment but results in approximations in deeper waters. The results of landslide-tsunami propagation over different bathymetries showed that shoaling on beaches follows either Green's law or the Boussinesq's adiabatic approximation up to wave breaking with an error of -7% to +10% for cnoidal and solitary waves. The results were then analysed with an Artificial Neural Network (ANN) and a regression analysis to find the transformed wave characteristics downwave of the investigated bathymetries with the first showing better performance. In addition, the combined effects of the water body geometry and bathymetry were studied revealing that relations derived for a 2D geometry result in under-predictions of the wave characteristics for deep-water waves while they are more appropriate for shallow-water when θ>0°. The 2014 Lake Askja case, Iceland, was used to validate and define a prediction procedure to calculate the wave characteristics for a real case with variable geometry and bathymetry. The derived semi-theoretical equations resulted in an error of 10% for the wave height and 1.5% for the amplitude when compared with the detailed numerical simulations of Gylfadottir et al. (2017). This is under the condition that only the effect of the water body geometry is relevant. When both the effect of the water body geometry and bathymetry are relevant then additional prediction methods were employed with the ANN resulting in the best performance with errors of 23.4% and 1.0% for the wave height and amplitude, respectively. Note that the lower agreement found when combining the two effects can be attributed to non-linear superposition effects which are highly dependent on the wave type. The findings herein are expected to significantly improve the reliability of preliminary landslide-tsunami hazard assessment in water body geometries between 2D and 3D and with variable bathymetries. However, the combined effect showed that the water body geometry and bathymetry play an important role. Therefore, future developments should investigate this combined effect for both idealised and real cases using numerical simulations and laboratory experiments. Also, the impact on defense structures and buildings should be investigated by using inundation models to improve design equations to mitigate future risks.

Process-based, wave-resolving models are essential tools to resolve the complex hydro-morphodynamics in the swash zone. The open-source Non-Hydrostatic XBeach model can solve the depth-averaged wave-by-wave flow in the nearshore region up to the shoreline and the intra-wave bed changes during time-varying storms. However, validation and testing of its morphological response are still limited in the context of sandy beaches. This work aims to assess the performance of the wave-resolving sediment dynamics modelling within Non-Hydrostatic XBeach for different sediment transport formulations. The sediment transport modelling approaches considered in this study were tested and compared to laboratory experiments involving wave trains over an intermediate beach. Numerical results show a better performance in the prediction of the intra-swash sediment dynamics when the newly implemented wave resolving transport equation is applied compared to the existing approach within the model.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/2sy-Dr8iJ1M

This paper analyzes the modeling of the hydro- and morphodynamics of bichromatic wave groups on an intermediate beach with an initial 1 : 15 slope. The nonhydrostatic version of XBeach was used to simulate two incident wave conditions of the experiments carried out within the HYDRALAB-IV Coupled High Frequency Measurement of Swash Sediment Transport and Morphodynamic (CoSSedM) project. The chosen forcing conditions have different strengths of swash-swash interaction. A procedure was developed to generate boundary conditions for the model that are able to fully account for both the bound and free long waves measured during the experiments. Using the normalized root-mean-squared error as a measure, this paper finds a higher accuracy of the nonhydrostatic version of XBeach in simulating swash-swash interaction from the hydrodynamics point of view, and worse performances in capturing the details of intragroup sediment transport. Nevertheless, the model is able to distinguish the relative difference in offshore swash sediment transport among different types of swash-swash interaction, and it is overall more successful in simulating beach morphodynamics when the swash sediment transport is of the same order of magnitude as the surf zone one. (c) 2019 American Society of Civil Engineers.

Large landslide-tsunamis are caused by mass movements such as landslides and rock falls impacting into a water body.Landslide-tsunami research is essentially based on the two idealised water body geometries (i) wave flume (2D, laterally confined wave propagation) and (ii) wave basin (3D, unconfined wave propagation).The wave heights in 2D and 3D vary by over one order of magnitude in the far field and the wave characteristics in intermediate geometries are currently not well understood.This article focuses on numerical landslidetsunami propagation in the far field to quantify the effect of the water body geometry.The wave model SWASH, based on the non-hydrostatic non-linear shallow water equations, is used to simulate Stokes and solitary waves in 6 different idealised water body geometries.This includes 2D, 3D as well as intermediate geometries consisting of "channels" with diverging side walls.The wavefront length was found to be an excellent parameter to correlate the wave decay along the slide axis in all these geometries in agreement with Green's law.Semitheoretical equations to predict the wave magnitude of the idealised waves in any desired point of the water bodies are also presented.The findings herein significantly improve the reliability of preliminary landslidetsunami hazard assessment in water body geometries between 2D and 3D, as demonstrated with the application on the 2014 landslide-tsunami event in Lake Askja.

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.