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List of Discussions



1960 Chilean tsunami survey in Chile and in Hawaii (20 min)


June 14, 2005 Tsunami Warnings - Lessons Learned to Application (Download this presentation)


Pitfalls of translating inundation modeling and mapping into rational evacuation plans

I would like to talk about the difficulty in implementing evacuation plans that realistically account for the effects of a local tsunamigenic earthquake on evacuation routes. Citizens and emergency managers commonly plan evacuations by car without consideration of the capacity of highways expected to be evacuation routes. For instance, highways such as those exiting the Long Beach and Ocean Shores peninsulas have a capacity of 400 cars/hour but a tsunami arrival time of 30 minutes or less. These plans typically don't anticipate liquefaction or landslide damage to roadways or failures of bridges. Some jurisdictions have also planned to use the police and fire departments to provide traffic control instead of responding to emergencies arising from earthquake damage. It is generally necessary to do at least a tabletop exercise to begin to insert realism into these plans.


Tsunami Warning/information with the real time observation in Sanriku

Tsunami meters with GPS buoy type meter have been widely installed by local and central autonomies along the Sanriku coast that has been hit and damaged by tsunamis. The purpose of installation is mainly the watching of the abnormal change in water level when a tsunami warning is issued. Most of tsunami meters are installed at and in the neighborhood of the shoreline and measure the tsunami height in the shallow sea. We propose the idea to exchange and share the measured data, and to add real time data in GPS meter for warning and prediction. Firstly, quick information on tsunami based on the earthquake magnitude and location can be issued. Secondly, the real time observation off the Sanriku coast can provide information on initial tsunami with the height of the first wave and 1/4 wave period, which should be used to modify the fault parameters in the early stage. Thirdly, the observed data at each tsunami meter along the coast can be again used for estimating proper parameters. The data base will be discussed at each stage after generation of a tsunami until reach to the coast.


Tsunami flooding protection by erodible sand dunes

Based on field survey in Sri Lanka, sand dunes were found to be effective in protecting flooding. Considering financial limitation in the Asian countries, tsunami countermeasures by using artificial sand dunes is investigated on the basis of laboratory measurements and numerical modeling.



Swash morphodynamics and its relation to tsumamis


The interpretation of grading and lamination in tsunami deposits (Download this presentation)

Discuss the interpretation of sedimentary structure in tsunami deposits, possibly bringing in some links to models if time permits. Sedimentary structure is primarily vertical and horizontal grading, layering, and lamination, but might also include bedforms in some cases. I think there are some particularly interesting bits around grading and lamination with some detailed example data from Thailand.


The relative importance of suspended vs. bedload in formation of tsunami deposits

The relative importance of suspended vs. bedload transport in tsunami must change with size the tsunami waves and the grain size of the particles being transported. The aim of this discussion is to explore evidence for relative importance of suspended vs. bedload in formation of tsunami deposits.


Influence of pore pressure on sand movement due to waves

It is important to understand the influence of pore pressures on sand movement mechanism since the sand movement under tsunami is highly unstationary. Oscillatory flow tunnel experiments revealed a difference in sand movement rate between round-shaped sand and angular sand. The intergranular friction as well as transmission of pore pressures in the void between sand particles are found to be essential.


Stationary vortices in wall flows - how to laminarize a turbulent boundary layer by adding stationary vortices

Water tunnel experiments reveal that when stationary vortices are added to a turbulent boundary layer, the flow becomes laminar. In accord with a model originally developed by Cotel for stratified entrainment, the results support the notion that the ratio of rotational to translational speed of a vortex near a surface is a fundamental parameter of the physics, called the "persistence" parameter. When the surface is a wall, this intrinsic velocity ratio determines whether the wall fluxes are laminar or turbulent. Flow visualization and heat flux measurements show that when large, streamwise vortices are added to a turbulent boundary layer over a wall with streamwise grooves to stabilize the vortices, the flow becomes laminar over most of the surface. Another example of the universal importance of this velocity ratio is the starting jet, where Gharib et al. found that the physics was described by a "formation number", which is identical to the persistence parameter.



Generation of cavitation bubbles at the air-water interface


Tsunami impact experiments video in the large wave flume at PHRI, showing the destruction of model house wall by a broken bore (15 min)


Wave Loads on Breakwaters, Sea-Walls, and Other Marine Structures (Download this presentation)

An attempt will be made to critically review and analyse the present state of knowledge related to the loading induced by non-breaking, breaking and broken waves on:

    (1) Monolithic breakwaters and seawalls, including the dynamic response of the foundation
    (2) Innovative surface piercing and submerged wave absorbers
    (3) Crown-walls of rubble mound breakwaters
    (4) Single vertical and inclined slender piles
    (5) Vertical slender pile within a pile group with different arrangements
    (6) Sloping sea dikes, including dike response (breach initiation)
    (7) Submerged bodies as a function of the submergence depth, including the effect of neighbouring bodies in different arrangements

Focus will particularly be put on the involved physical processes and the problems associated with a reliable modelling, including laboratory and scale effects as well as the difficulties to amene the problem to analytical solutions particularly for the extreme loading cases which are most relevant for structural design. Moreover, the major weakness of most available design wave load formulae is also stressed as they do not account for the time dependence of the loading. In fact, the rise time and the total duration of the wave load, together with the dynamic properties of the loaded structure and its foundation (generally summarized by the eigenperiod), will determine whether a wave load should be considered as “dynamic” or “static”. Ignoring this issue may result in both underdesign or overdesign depending on the approach used.. The importance of taking into account load duration and time sequencing will also exemplarily be illustrated by two types of “stepwise failure”: the sliding process of a monolithic structure and the erosion process of an earth structure by a series of single wave loads. The addressed issues, suggestions, recommendations and illustrations will essentially be based on the results of research projects performed under the lead of the author which are related to wave forces on structures as well as on the results of related ongoing projects. If the time will allow, the hydraulic performance of protective structures will also be addressed, because differences between storm waves and tsunami are expected to be even more important than the loading.


Measurement of wave force acting on buildings

We measured the wave force acting on structures on land. Of course, the wave force acting on the structure near coastline is large and the wave force acting on the structure in second or third row is small. The impulsive force was not clear in our experiments, the numerical simulations with staggered leapfrog scheme and hydrostatic pressure was succeeded to reproduce the force acting on the structure in the front row on average. However, the wave force on structure in second and third row was underestimated, if the grid spacing was not small enough. It is possible that the flow behind the structure was not reproduced appropriately in numerical simulations.


Shallow water equation

The use of adaptive mesh refinement to be able to zoom in on coastal structures and perhaps couple the fluid dynamics to calculations of forces on the structures.


Damage due to the drifting ships and its modeling by using EDEM

When large earthquakes such as Tokai and Tonankai in Japan happen, followed by a tsunami, the coastal area particularly in industrial zone should suffer great damage due to tsunami, including the effect of floating materials such as ships and vessels, because, as seen in 2004 Indian Ocean Tsunami, drifting/floating bodies together with tsunamis attacked to coastal area and increased the force to destroy the offshore and land structures more. This will be significant in tsunami induced damages at industrial area. Firstly this study try to complete data related with the floating material and categorize them recorded in past tsunamis. Secondly, we aim to develop the model of drifting bodies with Extended Distinct Element Method, EDEM, in the sea and on the land. The EDEM consist of several elements forming a body, connected by spring, dash pot and slider with particular parameters. When the size of bodies and material become large, the distribution of the drifting force acting on them should be considered precisely, which the EDEM can take into account. Tsunami simulation with Nonlinear long wave theory give temporal velocity on each element which enable to estimate horizontal force on drifting bodies calculated by Morrison eq. and vertical motion considering buoyancy, gravity and drag force. The feasibility of EDEM will be discussed through comparisons with the result of hydraulic experiments.


Very-fine grained-, very-coarse grained-, and internally stratified-tsunami deposits: Geologic constraints on flow conditions (Download this presentation)


Inverse modeling of tsunami deposits to determine tsunami flow speed

Tsunami deposits reflect the sediment transport that created them. By making assumptions about the contribution of sediment transport convergence and sediment falling out of the water column from suspension, the thickness and grain size of the deposit can be used to estimate tsunami flow speed. These assumptions can be checked using the vertical and horizontal characteristics of the deposit. The aim of this discussion is to critically evaluate the assumptions currently being used for inverse modeling of tsunami deposits.