This paper describes the resonance of fully-nonlinear internal solitary waves by using fully-nonlinear and strongly-dispersive internal wave equation model. The 3rd order theoretical solutions for internal waves in a two-layer system was used for the initial conditions. Two different wave amplitudes were given, in which four different incident wave angles were given for each wave amplitude. The length of stem was confirmed to increase faster in the larger wave amplitude conditions. The 'stem' was found to keep the characteristics of internal solitary waves though the wave amplitude was three times as large as the original incident internal wave. Furthermore, it is found that amplified internal wave amplitude can be modeled by using the theory of Mach reflection, regular grazing reflection and regular non-grazing reflection.
Mach stems generated by the oblique interaction of waves were numerically simulated using a set of nonlinear equations derived on the basis of a variational principle without any assumptions concerning wave nonlinearity and dispersion. The Mach stems showed a larger amplification rate defined along the nondimensional time as the incident wave height to water depth ratio was larger and the water depth to incident wave length ratio was smaller. When the Mach stem reflected at a vertical wall, its wave height became remarkably large without wave breaking. A new method was proposed to consider the boundary conditions on a vertical wall which was set diagonally across computational grids. The wave amplification at the head of a bay depended on not only the incident-wave parameters but also how large the Mach stem was amplified.
Advanced numerical model is required in order to accurately simulate the breaking phenomenon. However, it is not suitable for practical application. Simultaneous coupling method (SCM) was developed by combining the efficiency of SWE with k-ω model for better bed stress assessment. Moreover, SCM employs FORCE-MUSCL shock capturing scheme to handle breaking wave. In this study, SCM is verified by simulating a breaking wave run up case. SCM provides a good agreement with the observed wave breaking sequence from the experiment by Sumer et al. (2011). Bed stress comparison shows that SCM with its boundary layer approach has successfully assessed bed stress under breaking wave run up, showing a better agreement than the Manning method. Further verification was given by the estimated turbulent intensity from SCM which shows good comparison to the measured bed stress fluctuation.
This study examined the application capability of high-order nonlinear Boussinesq wave model (BWM) which can calculate wave run-up for wave transformations in field shallow sea areas such as reef. In a simple example for uniform slope beach, it was found that BWM's outputs of irregular wave runups agreed well with the estimations by an existing runup formula. In cases of field coastal area of reef topography, the outputs by BWM were also good in agreement with observations and predicted wave heights by a coupled parabolic wave model. Thus, it is indicated that BWM can be applied to estimation of irregular wave transformations in complicated sea area such as reef accompanying with very shallow water area.
To examine eddies around solids in multi-phase flow, a high-resolution calculation is needed. But, it is difficult to calculate the unsteady flow with solid phases, in particular, there are few methods that can simultaneously deal with free surface comprehensively. MPS method is effective to capture interface between phases and free surface even in violent flow. Despite of this advantage, MPS method doesn't have enough schemes to treat flow around solid with high resolution. In this study, three new schemes of DEM-MPS method for high resolution calculation of solid-liquid multi-phase flow are proposed and their validities are verified by comparing their results with an experiment of 2D multi-phase dam-break with cylinders.
Wave breaking model composed of the time dependent bore model and one-equation turbulence model has been proposed for Boussinesq-type wave transformation model. The validity of the model has already been evaluated on the calculated wave profiles in many reports, but the production and dissipation process of turbulence during calculation of wave breaking have not been discussed well yet. In this report, the appropriate turbulence scale which is required in calculation of them is estimated with comparison between the calculated and measured distribution of wave height in surf zone. Moreover, the calculation process of spatial distribution of the turbulence energy and the eddy viscosity in the model is grasped on a regular wave breaking on a slopping beach.
Three-dimensional surface shapes of breaking waves were quantitatively measured using a novel imaging technique with a projector and digital camera. With a measure of relative surface length, three-dimensional transitions of the deformed wave shapes have been characterized for spilling and plunging breakers. Two kinds of jets, a so-called finger jets, deformed due to sub-surface turbulence, and preceding smaller jet, governed by surface tension, have been observed to predominate the splash-up cycle in the surf zone, which have distinctive lateral and longitudinal length scales as well as deformation velocity scales evolving in breaking process.
If current effects on waves (CEW) are considered, the offshore extent of rip currents can be significantly suppressed by wavenumber modulation associated with wave ray bending (Weir et al., 2011). In the present study, a two-dimensional shallow-water model based on Regional Oceanic Modeling System (ROMS) with wave effects on slowly-evolving littoral currents through a vortex-force formalism, coupled tightly with WKB refraction equations, is used to examine dynamic effects essential to development of rip currents. If CEW is taken into consideration, wave ray bending occurs with a modified wavenumber field that changes the alongshore pressure gradient force and the cross-shore component of acceleration due to wave breaking through wave shoaling, leading to the reduction of the extent of rip current.
An imaging technique to measure advection-diffusion velocity of heat and materials in arbitrary flows, which is based on calculus of variations for the advection-diffusion equation, is proposed in this paper. The estimated results are verified through a variety of numerical and physical tests: numerical advection and diffusion experiments for determining the expected errors, physical heat transfer measurements using Infrared images and water temperature data of ocean surfaces as well as comparisons with PIV measurements.
Air flow distributions and turbulent properties in the boundary layer over wind waves have been investigated by using PIV. Two regions adapted a logarithmic law were found in a vertical distribution of stream wise mean air flow. One of the logarithmic law regions is close to wavy surface and another called the middle layer is located upon the lower logarithmic law region. The friction velocity calculated from the middle layer corresponded to the Reynolds stress in a constant stress layer close to wavy surface region. The mixing length, l calculated from the experimental data showed that there were larger vortices than Prandtl's mixing length hypothesis, l = κy close to wavy surface for Case03 and 04. It was considered that the larger vortices were generated by air flow separation from wave crests.
We investigate wave height change on the coral reef which has steep front slope. Data of both regular and irregular wave experiments were used in order to study characteristics of wave deformation including wave breaking. By using a parameter Hrms/d, properties of energy loss by wave breaking on the reef can be obtained. We modified wave energy balance equation model developed by Tajima and Madsen (2005) in order to estimate wave energy on the coral reef. Calculation results show good agreement with experimental data.
Fundamental features of transitional distributions of velocity and shear in a run-up wave have been experimentally identified in this paper. In the run-up front, vertically uniform shore-ward velocity is predominant, while typical free-surface shearing flow with a bottom boundary layer is formed behind the front. Depending on local surface gradients and fluid acceleration, reverse streaming occurs within the boundary layer despite the shore-ward flow still dominates above the layer. In the later stage, another shear layer has also been formed beneath the surface.
Numerical simulation of tsunamis due to a landslide has been performed using a MPS method, where the water surface is indicated based on the spatial gradient of number density of particles. In comparison with the water surface displacements through hydraulic experiments, the calculation results are accurate when the inflow can be assumed as a fluid. The larger the initial potential energy of the inflow is, the larger the tsunami height becomes, although the tsunami height is not large when the initial position of inflow is below the water surface since the initial relative potential energy of the inflow is lower, as well as without impact of plunging. Due to the inflows of the assumed initial values for mass, shape, and velocity caused by a sector collapse of Sakurajima Island, the tsunami height shows more than ten meters in Kagoshima Bay.
Because debris flow which can become a trigger of landslide-induced tsunami is solid-liquid multiphase flow, its configuration varies with concentration and density of solid phase. As a model of debris flow, a rigid body, higher density fluid and non-Newtonian fluid have been treated in previous simulations. While in the previous studies by the MPS method, a non-Newtonian fluid model have applied to only single phase flow analysis. Therefore, in this study, a non-Newtonian fluid model coupled with Newtonian fluid model is developed. This model is applied to landslide-induced tsunami simulation and its validity is examined.
Sensitivity of turbulence models and grid resolution are investigated in the simulation of collapse of a water column by a three-dimensional tsunami analysis with VOF method in comparison with the previous experimental results. LES turbulence model is found as an effective model in simulation of tsunami wave run-up on shores. High mesh resolution or mesh refinement need to be adapted around walls to simulate the collision of tsunami wave on buildings and structures. The performance of the tsunami analysis is also confirmed in comparison with a tsunami run-up water tank test. A large-scale simulation is carried including a wide urban area with complex terrain. Local concentration of high wave height distribution in narrow steep terrain and inhibitory effect of buildings and structures on tsunami run-up have been found.
This paper aims to understand the characteristics of a tsunami propagating over a wide reef platform, which was observed during a field survey of the 2009 Samoan Islands Tsunami, by using a turbulence model. A Large Eddy Simulation (LES) model was used to simulate wave breaking and energy dissipation. The results of the numerical simulations were shown to reproduce well the results of the field survey of the 2009 Samoan Islands Tsunami. In particular after the 2004 Indian Ocean Tsunami, tsunamis propagating over coral reefs were observed in many countries, such as the Maldives, the southwest coast of Sri Lanka and Solomon Islands. The present method may also apply to these countries and contribute to considering regional tsunami mitigation strategies.
Swash zone range is the area between the max run-up and the max run-down. Here the max run-down is defined as the most offshore-ward position being dried during the specified period. Field data of USWG deployed near the shoreline at Hasaki were analyzed to evaluate both values for one hour during storms. Comparison of max run-up height from the mean water level with Van der Meer·Stam(1992) show that the filed values are much larger during high waves as the large long waves are predominant near the shoreline. Crude model to calculate the max run-up and run-down from the power of the long waves and short waves near the shoreline are proposed and compared fairly well with the observed ones. It is shown that the max run-up from MWL is roughly twice as large as the max run-down from MWL both in the model and the observation.
A numerical simulation is performed to evaluate the influence of wave-driven coastal seepage on sediment transport in swash zone. The tractive velocity of swash motion and infiltration-exfiltration rate are estimated using a Navier-Stokes model coupled with a porous flow model incorporated the unsaturated region. The tractive force under the influence of seepage is quantified through a permeable Shields parameter, which is concerned with both the effective weight of sediment and swash boundary layer thickness. The comparison between model results and previous experimental data shows that the direction of sediment transport changed from onshore to offshore can be evaluated by the infiltration-exfiltration process.
Ocean wave in-situ measurement is limited only to measure temporal sea surface information. In order to measure spatial surface information a radar system is suitable; however, radar image includes many noises. In this study both temporal and spatial ocean surface characteristics were measured by a X-band radar and a wave buoy. Radar scattering waves were analyzed by WaMosII (Wave Monitoring System II) system which gives spatial surface elevations in a measuring region. Wave parameters such as significant wave height, maximum wave height, peak wave period, wave age were estimated and verified by the X-band radar. It was shown that the radar measurements gave narrower directional spectra than the buoy observations.
Extrapolation plays such an essential role for evaluating sea extremes frequencies that the return period has been introduced. But we use it without being aware of the hidden double meanings. The return period employed in handling the past record has been substituted for the period of the coming successive event in the future. Thus, we obtain the design force, as the return level against a return period, by extrapolation of the observed data in the past years, while we may employ it also for the future to extend the estimation along the time axis, which should be recognized as another extrapolation. Durability is applicable to give the confines of these double extrapolations.
At the three GPS buoys off the Sea of Japan coast of Tohoku Region, Japan, the monthly-mean wave height is higher than 2.5 m, the most frequent wave direction is WNW or NNW, and the mean wave energy flux exceeds 20 kW/m in December and January, while the wave height is lower than 1 m between June and August. The seasonal variation in the wave height is wider and that in the wave direction is narrower, compared with the GPS buoys off the Pacific coast. The ratio of the significant wave height and period at a coastal wave gauge to those at the nearby GPS buoy varies with the wave direction. An energy balance equation model with the significant wave height, period, and direction at the GPS buoy off the Yamagata Prefecture coast can estimate precisely the wave height at the coastal wave gauge site in Sakata Port.
Shallow water wave hindcasting under the SDP measurement data-based wind condition is conducted for each of the 20-selected strong typhoons during the year period of 1911-1959 in Tokyo Bay and for each of the 12-selected strong typhoons during the year period of 1921-1960 in Ise Bay. Extreme value analyses are made using the samples of the annual maximum wave height data produced by combination of the above-mentioned data with the data during the year period of 1961-2005. Extension of data year-length yields a significant increase in a re-estimate of 100-year return wave height H100 in each bay. The largest H100 ranges from 10 m in the outer area to a little over 4 m in the inner area of Tokyo Bay and from 15 m in the outer area to 6.5 m in the inner area of Ise Bay.
Benjamin-Feir Index (BFI) and directional spread are measures of nonlinear four-wave interactions and resultant indices of possible potential conditions for freak waves. Temporal-spatial distributions of BFI and directional spread are examined by numerical simulations using a spectral wave model with analysis data of ERA-40. The spatial distributions of wave characteristics such as significant wave height, wave period, BFI and directional spread are simulated in a global scale. Freak waves resulting from nonlinear four-wave-wave interactions have a greater potential of occurring in the western edge of ocean basin. Furthermore, dependence of BFI on wave age in short fetch can be observed.
Coastal and maritime structures around Japan have been occasionally damaged by the long period waves ranging from 15 to over 20 seconds. The mechanism of their generation and development has not been clarified yet. Hence, their predictability and reproducibility accuracy of the existing wave models have been hardly discussed so far. In this paper, we therefore numerically investigate the characteristics of frequency downshift of directional spectrum caused by the nonlinear energy transfer considered to be one of their generation and development mechanisms. Numerical simulations are carried out with an improved WAM implemented with SRIAM proposed by Komatsu (1996). The characteristics of the nonlinear energy transfer were discussed in relation to the various shapes of directional spectra.
The system for long swell prediction at Fushiki-Toyama Port has been made as a test operation. During the test operation, predicted value using current assimilation method had almost detected swell. But this method had some biases and errors in 2 cases. New assimilation method was applied in consideration of property of long swell propagation by NOWPHAS data. As a result, accuracy of assimilated value obtained using new method was improved compared with current method.
For the preservation of a tourist coast, the Ibusuki coast located at the mouth of Kagoshima Bay, wave characteristics as a driving force of sediment transport should be made clear. It is necessary for this purpose to investigate the wave fields of storm waves developed in the Pacific Ocean, swells intruding into the bay, and local wind waves developed inside the bay. The shielding effects of ocean wave penetration into the bay by the Osumi Islands and the Satsuma-Osumi Peninsular were discussed with the outputs of SWAN wave simulation and WRF meteorological simulation for the case of Typhoon T0416 that is the severest case for beach erosion of the Ibusuki coast.
This study conducted the statistical analysis on frequency-banded wave components acquired by the GPS buoys and their nearby coastal wave gauges on the Pacific coast of Tohoku to Shikoku District, Japan. A high correlation was found between the frequency-banded wave height at a GPS buoy and its nearby coastal wave gauge, particularly in long period components. The correlation between the long-period wave height and the significant wave height is high, while the ratio of the swell height to the significant wave height varies with the wave direction and the meteorological condition. The swell direction sometimes differs from the wind wave direction, and the ratio of the swell height to the significant wave height differs between before and after the peak of the significant wave height.
Large scale fluid motion due to the 2011 Tohoku Tsunami was investigated by decomposing the water surface elevation computed by the linear wave theory through spectrum analysis. Dominant periods of nearshore fluid motion are extracted from the water surface elevation at the depth of 10m. The power spectra and phases at the alongshore points are compared. From these results, cross-shore and alongshore long-period oscillations are described in Sendai Bay, which appear to be consistent with the large runup height especially at the center and the both ends of the Sendai Bay. It appears that the long-period motion with period of 80 minutes propagates southward alongshore as edge waves. Standing alongshore wave motion which is not consistent with the dispersion relationship of edge wave is also detected.
A survey has been carried out on the characteristics of propagation of slight atmospheric pressure changes concerning the seiches which developed in wide areas in Kyushu and the western part of The Sea of Japan in February and July in 2009. The typical propagation direction of slight atmospheric pressure changes is eastward and the typical propagation speed is 2 km/min. When slight atmospheric pressure changes develop, they do not develop just once. Some components of various frequencies with different propagation speeds come over repeatedly. From the dispersion relation equation of atmospheric gravity waves, the vertical propagation speed is estimated to be about 1/10 of horizontal one.
A series of data set of ocean wave records observed at outside harbour and in offshore is analyzed for understanding long wave characteristics in lights of relationship between short and long waves in an effort to improve reliability of harbour tranquility. It is found that long wave is strongly dependent to short wave during high wave and that it is possible to evaluate long waves with an assumption that long waves propagate in the same direction as short waves. In addition, long wave at outside harbour has defferent characteristics from long waves in offshore in terms of developing process of free and bound long waves.
To investigate the propagation of the 1700 Cascadia tsunami, we simulated a trans-pacific tsunami using the linear long-wave and dispersive models. The model results suggest that the scattering of the tsunami excited by the Emperor Seamounts Chain causes the delay of the maximum tsunami along the Pacific coast of Japan. We further conducted simple numerical tests focusing on resolutions of bathymetry data to develop the modeling of the scattering waves. The results reveal that less than 2-min grid size of bathymetry data is required to represent the tsunami scattering waves. We simulated the 1700 Cascadia tsunami and compared the measured data with the computed tsunami heights. The computed results approximately consist with the measured data of "Lower height estimate". On the other hands, the doubling the fault model of Cascadia earthquake is required to conform the computed data to the measured data of "Upper height estimate".
The effect of breakwater on reduction of tsunami inundation is investigated for the tsunami caused by the 2011 off the Pacific coast of Tohoku Earthquake. Numerical simulations are conducted in the Port of Kamaishi and Port of Ofunato and Port of Soma in which bay-mouth breakwaters and offshore breakwater are installed. It is confirmed that the bay-mouth breakwater in Kamaishi and offshore breakwater in Soma reduced the area of tsunami inundation and its height, although they were damaged by the tsunami. The reason why they reduced tsunami impacts is that caissons remain partly and mostly. In addition, the numerical simulation indicates that the breakwater mound has the effect on reduction of tsunami intrusion for the bay-mouth breakwater in Ofunato.
In this study, the effectiveness of an offshore breakwater for the 2011 off the Pacific Coast of Tohoku Earthquake Tsunami was examined by quasi three dimensional (quasi-3D) and three dimensional (3D) numerical models. First, both 3D numerical models were applied to the behavior of tsunami inundation inside of Kamaishi bay where a baymouth breakwater installed against to assumed tsunami. The numerical results well agreed with the post-event tsunami survey on the land. The numerical simulations were performed without offshore breakwater. It is found that the offshore breakwater performed significant reduction of the tsunami height on the land. Furthermore, the velocity of tsunami inundation was discussed for understanding physical characteristics of tsunami around Kamaishi bay.
To understand the characteristics of tsunami propagation in the Seto Inland Sea, tsunami simulations for the largest earthquake on the Nankai trough were conducted. In this paper, we assumed three fault models with taking into account the latest findings after the 2011 earthquake off the Pacific coast of Tohoku. For the case of large fault slip along the plate boundary region, the tsunami height around the Seto Inland Sea was about the same as the value of the conventional assumption, because the tsunami components generated by the plate boundary regions were attenuated when passing through the straits. But we confirmed that the tsunami height around the Seto Inland Sea became higher in the case of delayed rupture with appropriate time lag, or in the another case that the fault region was expanded to north.
OKINAWA is in geographical condition to have active fault leading to big earthquake in Southwestern Ocean Trench, Okinawa Trough and etc. as well as having an experience of big TSUNAMI led by Yaeyama Earthquake in 1771. As logistics and people's flow in Okinawa greatly depend on sea and air routes, the immediate resolution of ports and airports functions shall be important issues at the time of earthquake and/or TSUNAMI disasters and it shall be very important to study for the TSUNAMI countermeasure related to the port function. This study is the study for TSUNAMI disasters at ports areas conducting TSUNAMI simulation with the TSUNAMI led by the Mw8.8 earthquake at the maximum.
Tsunami intrusion into river is investigated in this study. Investigation and analyses were conducted based on water level measurement data and bed slope at several rivers in Tohoku region during The Great East Japan Tsunami, 2011 and The Great Chillean Tsunami, 2010. These data were used to proposed an empirical method for estimating dissipation coefficient. The empirical method was used to approach the intrusion length by assuming that the furthest distance is given for the ratio of local tsunami wave height to the tsunami wave height at the river entrance of 0.05 (5%). The intrusion length from the proposed method in this study shows good comparison with measurement data.
The damage of infrastructures including railway due to the 2011 tsunami was remarkable, reporting that the damage on seven lines and total distance of approximately 325 km section caused by only the tsunami. The paper summarize the railway damage including damage to train cars with the simulation results of tsunami inundation and velocity. The evacuation guidance situation for each line and the damage mechanism on train cars using the computed inundation and velocity in time are discussed to improve the criteria of railway damage and estimation of them.
This study aims to develop a tsunami numerical model which is capable to include several grid systems and facilitate the process of assembling domains of different resolutions. The assembly of structured domains (inner and outer) is achieved by constructing an intermediate unstructured grid between them. The present scheme is able to diminish short period waves reflected on the boundary of a coarse grid domain. A numerical simulation consisting of a Gaussian-hump shape is used for validation by determining the energy transferred/retained in a finer grid domain. In addition a practical application, the 2010 Chilean Tsunami, is provided as a case study to confirm the validity of proposed model.
The 2011 off the Pacific coast of Tohoku Earthquake Tsunami caused massive overflowing of a structure, fast flow through an opening section of structure and wave deformation with soliton fission and breaking. These calculations are necessary for estimation of damage induced by the tsunami of the maximum level. The mathematical model of STOC that calculates tsunami propagation and inundation from the initial form and the tsunami interaction with structures is improved to precisely calculate the high tsunami. Especially, a wall boundary condition is improved to calculate the tsunami overflowing of a structure. It is confirmed that STOC-IC with tsunami breaking model newly installed can estimate wave deformation with soliton fission and breaking in comparison with physical model tests and actual wave deformation in the Port of Kuji.
High frequency ocean surface radar observation reveals the velocity fields of propagating tsunami waves and subsequent 30-40 minute period natural oscillation in the Kii Channel, Japan induced by the March 11, 2011 moment magnitude 9.0 Tohoku-Oki earthquake. Technical issues of the ocean surface radar system concerning the detection of tsunami waves and natural oscillation velocities are also discussed.
A lot of typhoons have often raged through the Kyushu district, causing a great deal of damage by storm surges. Additionally, due to global warming, there are growing concerns about possible tremendous disaster caused by furious typhoons more than ever. In order to cope with tremendous storm surge disaster, it is necessary to estimate storm surges caused by the typhoons that might happen in the future. In this study, five typhoons was extracted from the climate change prediction (MRI-AGCM3.2S) based on the global warming scenario (A1B), and storm surge simulations were conducted for the typhoons that approach Ariake Sea. The results show that the maximum storm tide anomaly reaches 5m in the most inner part of Ariake Sea, and the heights of these storm tides remarkably exceed the existing disaster prevention plan.
By the image taken from the helicopter, it was confirmed that the soliton fission caused the second wave to be the wave group, in 2011 Tohoku Tsunami. There is a possibility that amplification of wave height caused by soliton fission had expanded damage. In this study, we developed the nonlinear dispersive wave model which can be practicable to reproduce the soliton fission wave. And, the applicability of the developed model was verified by simulating the reproduction of the soliton fission in 2011 Tohoku Tsunami.
We examined how an array configuration of offshore tsunami stations affects accuracies of near-field tsunami forecasts provided by a tsunami forecast method based on an inversion of the offshore tsunami data. We simulated tsunami forecast of the 2011 Tohoku earthquake assuming several array configurations. As a result, an installation of bottom-pressure gauges to the outer sea of the trench contributes to improving the forecast accuracies, as well as deployment of the gauges at the seafloor between a source and a coastal point where forecasts will be provided. We also examined how rapidly accuracies of tsunami forecasts improve when a dense offshore observation network is installed, and found that the accurate forecasts can be obtained from the data of the dense network 10-15 min earlier than from those of the existing-array configuration.
Sediment transport and resulting topographic change can be affected by bottom flow velocity on the surface of the seabed and pore-water pressure on the surface layer of the seabed. In this study, a sediment transport model considering pore-water pressure on the surface layer of the seabed is proposed and incorporated into a three-dimensional coupled fluid-structure-sediment interaction model (FSSM). For validation, the FSSM is applied to tsunami-induced local scouring around an inland square cylinder. As a result, numerical results show that the topographic change including the evolution of the local scour around the seaward corner of the cylinder is predicted reasonably well using the FSSM, and suggest that it is essential to take into account pore-water pressure for tsunami-induced sediment transport phenomena.
Chemical properties of tsunami-inundated soil and tsunami deposits were investigated using the samples obtained in Tohoku after the 2011 Tohoku-oki tsunami. The relative composition of water-soluble ions in the inundated samples obtained from Tohoku was similar to that of seawater and no significant difference was found between the tsunami deposits and the tsunami-inundated soils. Some soil samples show that the water-soluble ions in the surface may have been removed by rainfall, indicating that the layers of the tsunami-inundated soil and tsunami deposits could not be correspond to the layers containing rich chemicals.
Pacific coast of Tohoku Earthquake Tsunami gave terrible damage in all of Japan on 11th March 2011. The past studies showed this kind of big tsunami transported huge amounts of sea bottom sediment. In this study, we estimated the transportation of sea bottom sediment in a large region by this tsunami using the numerical model. The distribution map of the external force of this tsunami, such as the maximum velocity and the power of shear stress revealed the bottom sediment had a potential to move at the area where the velocity became large or continued. The attempt of an estimation of the pickup function indicated sand moved inside bays from Aomori prefecture to the north of Miyagi prefecture and the area between 20m and 30m depth in Sendai Bay.
We conducted a bathymetric survey at Kesennuma Bay in Miyagi-prefecture before and after the 2010 Chilean Tsunami and the 2011 Tohoku Tsunami, and measured detailed 3D bathymetric data. Based on the survey data, we confirmed geomorphic characteristic on Kesennuma Bay and geomorphic changes due to recent two tsunamis in 2010 and 2011. And we provide quantitative analysis of these geomorphic changes, analyzed the relation to the character of each tsunamis, and studied the sediment transport characteristic.
To study the effect of barrier against tsunami flowing over a mound, hydraulic experiments were carried out. The nearshore topographical were set up in a 205m long 2-dimensional flume to investigate tsunami force acting on the barrier and overflowing quantity due to tsunami flow. The scale of models was 1/40. A movable bed mound set up to measure deformation of it due to tsunami. It was found that the maximum tsunami force acting on a barrier was measured when tsunami overflew it. The vertical distribution of pressures at the maximum tsunami force could be expressed by a linear relationship which depended on the maximum water level at the barrier. A barrier controlled overflowing quantity and erosion of landward slope on a mound.
Tsunami wave force acting on the axisymmetric caisson foundations was investigated through the hydraulic model tests. Water surface profile of tsunami caused by the 2011 off the Pacific coast of Tohoku Earthquake observed 11m deep and 3km offshore of Choshi city (Fukumoto et al., 2012) was used as the incident wave. By using the pump-type tsunami wave maker the observed tsunami profile was well reproduced in the wave-basin. Tsunami wave pressure distribution and wave forces acting on the axisymmetric caisson foundations were measured. Based on these experiment data, a mathematical formula expressing peak wave pressure distribution with the parameter of the incident tsunami height was proposed.
When the Tohoku Earthquake occurred in March 11, 2011, the associated tsunami washed away a number of bridges. This resulted in difficulties such as transport disorder to rescue and recovery operations. Therefore it is necessary to estimate of tsunami force acting on a bridge. In this study, we applied the three-dimensional numerical analysis based on VOF method to two hydraulic experiments, each with a different type of bridge model. The results of the calculation are compared with those of the experiments in regard to the horizontal and vertical forces. As a result, the method well simulated each time series variation of tsunami force acting on the bridge beam.