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Local scour and wave loading are two key factors that affect the safety of seawalls under tsunami attacks. In this study, the scouring process at the toe of and wave impact force on a vertical seawall under consecutive solitary wave attacks are simulated using a quasi-three-phase (air, water, and sediment) flow model, which models the air and water as a fluid mixture phase and sediment as a solid phase. The air and water interface is modeled by a VOF method and the sediment–fluid interaction is modeled using the Eulerian two-phase flow method. A comparison between the beach profiles with and without the seawall shows that, with a seawall, a deeper scour hole is generated at the toe of the seawall. Besides, the presence of the seawall causes the eroded sediment to be deposited further offshore. The numerical results are then analyzed in detail regarding the flow field and sediment transport process to reveal the mechanisms of the above eroding/depositing patterns. The wave impact force on the seawall is also analyzed to understand the effect of scouring on the wave loading. It is shown that the wave impact force, despite being stochastic for a specific wave, increases in general with the deepening of the scour hole because the latter increases the exposure of the seawall to wave slamming. • A numerical model capable of tracking air, water and sediment is used to simulate sediment transport in front of a seawall. • The seawall is found to cause sediment loss at its toe. • The wave impact force exerted on the seawall is found to be enhanced by the scour hole at the toe. [ABSTRACT FROM AUTHOR]

Submarine landslides are one of the major causes of tsunamis but less understood due to complicated dynamics involved and the lack of observational data. In this study, the collapse of a submerged granular column is used as an idealized submarine landslide model. A three-phase (solid–liquid–gas) continuum model is used to study the effect of the column’s initial packing on the collapse process and the resultant waves. Numerical simulations reveal that the initial packing can have significant effect on the duration of the collapse process and the characteristics of the resultant waves. Pore pressure, velocity field of the fluid phase, the volume of the sliding granular mass, and the sliding velocity are calculated and used to understand the effects of initial packing condition. Our results show that it is important to consider the initial packing effects in numerical simulations of submarine landslides and the resultant waves. Our result also show that the large vortex generated by the moving front of the granular flow can affect the form of the waves generated by the landslide. [ABSTRACT FROM AUTHOR]

Destructive tsunamis can destroy coastal structures and move huge amounts of tsunami debris. Our current understanding of motion of tsunami debris in tsunami flows is limited. In this paper, we present a preliminary laboratory study of motion of model debris under the action of solitary waves running up a beach. The difference between the waterline of maximum inundation and the final position of debris was examined under various conditions. Effects of solitary wave height, water depth, and the distance of debris source to the shoreline on the maximum inundation, the debris limit, and the final position of debris were examined. In general, the final positions of the debris are different from the waterline at maximum inundation and there is a low possibility that a large amount of debris can be carried by retreating water offshore into the sea. [ABSTRACT FROM AUTHOR]

Some challenging issues in tsunami disaster mitigation and risk management are raised at the AIWEST-DR2011 in Conjunction with SCSTW-4. Currently there is no enough attention given to potential tsunamis in South China Sea due to the lack of data for historic tsunamis in the area, therefore there is a need to have a joint effort among the countries bordering the South China Sea to collect scientific evidence of historic tsunamis along the border of the South China Sea. [ABSTRACT FROM AUTHOR]

Abstract: The subduction megathrust under the Manila Trench has been accumulating strain over a period of 440 years or more, and could be the source for a giant earthquake of M w ∼9. We present a plausible earthquake rupture model constructed from seismic and geodetic data, together with hydrodynamic simulations of the potential tsunami with COMCOT (COrnell Multi-grid COupled Tsunami model). Results indicate that this megathrust poses a risk of devastating tsunami for the Philippines, southern China, Vietnam and other population centers bordering the South China Sea. [Copyright &y& Elsevier]