The measure against erosion of sandy beaches on the ocean is one of urgent national issues in view of the predicted sea level rise. Some of the authors have been studied a permeable breakwater with slotted walls supported by piles for last several years. Although the characteristics of wave attenuation of the breakwater with vertical slits has been examined by numerical calculation so far, enough validity has not been verified yet. In this study, comparison between calculated results by CADMAS-SURF/3D and experimental results on wave attenuation and flow in the visinity of the permeable breakwater is presented. As a result, it is shown that the CADMAS-SURF/3D is a useful tool to design the permeable breakwater in practical use. According to the results of the calculation and PIV measurements, it is implied that upward flow in front and back of the breakwater will be direct relation with local scour and the vertical circulation flow in the chambers of the permeable breakwater will affect sand transfer.

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 The curved front face of Flared Shape Seawall returns incoming waves to offshore with ejecting a volume of water at the tip of the seawall. A landward wind transports this ejected water to inland, and it increases the quantity of wave overtopping and splash over the seawall rather than a calm condition. This study evaluates the effects of the wind on wave overtopping and splash generated at the Flared Shape Seawall through hydraulic experiments with changing wind speed, wave period and seawall crest elevation. The augmented water over the seawall increases in proportion to the volume of run-up water above the seawall crest. The ratio of wave overtopping against the volume of run-up water increases exponentially with wind speed. The coefficients included in this exponential function depends on an incident wave steepness and crest elevation. The characteristics of wave overtopping and splash under the wind depend on the incident wave steepness, the ratio between wave height and crest elevation and wind speed. This study confirms good correlation between experimental data and calculated ones that are obtained from regression equation what include those parameters.

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 Local scour behind coastal dikes by tsunami overflow is a main factor of their destruction by the 2011 tsunami. However, the local scour is also considered to have reduction effect on velocity of tsunami flood. In order to design optimum coastal dikes against tsunami, velocity reduction by the local scour is required to be quantitatively evaluated in addition to the toughness of coastal dikes against tsunami overflow.
 In this study, characteristics of velocity field behind coastal dikes were discussed through hydraulic experiments with measurement of velocity field around local scour models by Particle Tracking Velocimetry (PTV). The models of the local scour were made of acrylic boards as fixed bed based on previous moveble bed experiments by authors. And the reduction effect by the scour hole were discussed through comparison of the landward velocity with and without the scour behind the coastal dike model.
 Some different flow patterns were observed in the cases with different overflow depths and sizes of scour holes. With relatively larger scour hole, large vorteces and separation of the flow were observed in the scour, while flow was along the bed without no large horizontal vorteces and separation of the flow with the smaller scour. Reduction rate of the landward velocity by the scour hole was about 60 % with the former flow patterns, while it was less than 30% with the latter flow patterns.

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 The flow induced by an horizontally-oscillating circular cylinder in stationary fluid was measured by the PTV technique and the relationship of turbulent flow and mean flow was investigated on the basis of the measured data. Transverse velocity of time-mean flow was large in the area that vortexes shed from a circular cylinder distributed. Although turbulent intensity was small in the area that vortexes shed from a circular cylinder did not distribute, the one was large in the area that vortexes shed from a circular cylinder distributed. In the area that time-mean turbulent energy was large, transverse velocity of time-mean flow was also large. It was suggested that turbulence induced by vortexes shed from a circular cylinder contributed to occurrence of mean flow generated around a circular cylinder.

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 For the precise evaluation of tsunami generated flows around coastal structures, the development of analyzing techniques to represent such three dimensional flows is necessary. Recently, various advanced numerical programs have been proposed, however, the experimental validations using a three dimensional wave basin are indispensable for the practical applications. As the resolving ability of the numerical program is considered to be dependent on the flow complexity/transiency, detailed comparisons with three-dimensional experiments for the various flow conditions are necessary. In this study, three dimensional flow measurements are conducted to investigate the flow characteristics where a solitary wave collides and overtops model structures possessing square and trapezoidal cross-section. Next, the numerical analyses using CADMAS-SURF/3D are conducted under the same wave-structure condition as the experiments. By comparing both results, the three dimensional characteristics of the tsunami flows with different temporal intensity around the model structures are investigated, and applicability of the numerical model is discussed.

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 Recently, coastal forests have received much attention because they have concurrent benefits both of tsunami disaster mitigation and of coastal environment preservation. The important point when coastal forests are utilized as a countermeasure against tsunamis, is that the properties of individual trees and the forest stand vary with age. As the results, the performance to mitigate tsunamis is time-dependent reflecting the changes of tree topography and stand density. Depending on the stage of growth, not only the trunk part but also the tree crown part may contribute the flow resistance. Since a forest in field grows on a sandy dunes with a certain distance from the shoreline, such topographic effects on tsunami run-up also should be considered. This study aims to assess the tsunami reduction ability of coastal forests by considering the temporal developments of trees and forest stands, and by incorporating realistic beach topographies.

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 Tsunami wave force acting on storage tanks are measured in a two dimensional wave flume. Bores are generated as tsunamis in the wave flume. Cylindrical and spherical tanks are used for the measurement. Measured tsunami wave force are analyzed for each of the first and second crests of the bores because the bores generated in the wave flume has several crests. For the cylindrical tanks, measured tsunami wave forces are compared with existing equations for estimating them. For the spherical tanks, measured tsunami wave forces are considerably scattered and the mechanism of the tsunami wave force is very complicated.

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 In the Great East Japan Earthquake, it was confirmed that the damage scales of immediate buildings within a block are different respectively. The evaluation method for tsunami force acting on the building group in the block will be required. To clarify the tsunami force for the buildings, the model experiments were performed using the model building group in the block reproduced by 3 D printer. The method for evaluation of tsunami force acting on the buildings are investigated using the area and the shape of the building group.
 As a result, the tsunami force acting on the buildings in the back of the building of sea side has decreased markedly. The forces for the rear buildings also become small and uniform, regardless of the conditions of incident wave. Furthermore, it is proposed that the parameters used the area ratio and the circularity of the building group are new means for evaluation of tsunami force.

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 It is necessary to take measure for flowing out the stores and drifting the storage tanks during tsunami, because the storage tanks store usually the dangerous contents. In this paper a method of countermeasure of drifting the storage tank during tsunami is proposed and its effectiveness is examined by the analytical and experimental methods. The analytical method in this examination is able to take into account the drifting behavior of storage tank during tsunami and consequently can evaluate the effectiveness of the proposed countermeasure. The hydraulic experiment carried out to confirm the drifting behavior.

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 In order to estimate drifting and run-up sea ice floes, we developed a quasi-3D DEM in which phenomena unique to granular solids such as the arch action, jam and pile up of such solids can be simulated with a small computation load. Hydraulic experiments using synthetic ice were performed to evaluate the simulation method. The run-up ice floes driven by a tsunami was also simulated. We confirmed that the simulation results could estimate risk areas where ice pile up and jam form as well as hazardous areas showing damage states for structures. The simulation was also expected to be applied to drifting and run-up large amounts of tsunami-related debris, such as containers, vehicles and timber.

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 RC buildings with piles had been expected to be resistant to tsunamis. However, pile-supported RC buildings were pulled up and toppled by the 2011 Off the Pacific Coast of Tohoku Earthquake Tsunami. Damage mechanism of the pile-supported RC buildings due to tsunami has to be found out for tsunami evacuation countermeasures with tsunami evacuation buildings. In this study, we focus on one of the pile-supported RC buildings in Onagawa town, Miyagi Prefecture that was pulled up, toppled and moved during the 2011 tsunami and find out the effect of three dimensional tsunami analysis for damege mechanism. As a result it was shown that caluculation result of two dimensional tsunami analysis is 12.1% bigger maximu tsunami at horizontal force, 3.2m lower at its point of action, and 40.9% smaller at the overturnign moment than that of three dimensional tsunami analysis.

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 A large number of slips and overturns of breakwaters and scouring of rubble mounds foundation were confirmed in fishing ports due to the Great East Japan Earthquake. It is urgently necessary to construct performance assessment method of breakwaters against tsunami. In this research, physical model tests were conducted in a wave flume to investigate characteristics of tsunami wave pressure on breakwaters under overflow conditions and stability of armor units as a measure against scouring due to waterfall from the top end. As a result of the tests, tsunami wave pressure on breakwaters under overflow conditions can be assessed as 1.1 times in front of breakwaters and 0.9 times behind them as much as hydrostatic pressure, and this method is applicable to the case of not only vertical incident waves, but the time of tsunami undertow and breakwaters with wave dissipating blocks. It was suggested that stability of armor units can be enhanced by changing positions of waterfall due to improving shapes of parapets.

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 In order to clarify characteristics of bore pressure and propose its evaluation method, we carried out hydroaulic experiments in which bores were impacted on a vertical wall on a dry-bed, and the vertical distribution of the bore pressures on the wall were measured. The height under which positive bore pressures were significantly measured were lower than water depths of inflows, and on the other hand, higher than weter depths of local water rising observbed just in front of the wall. This phenomenon would show that the bore pressures were generated by the momentum transfer from the flows in the streamwise directioin in the turbulent bore to the upstreams in front of the wall. Based on this concept, evaluations of bore pressures are tried by applying the turbulent bore theory proposed by Madsen and Svendsen (1983). The predicted bore pressures are in agreement with measured ones.

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 It is known that piloti-type structures, which have open space on the ground floor, have an advantage for tsunami hitting because tsunami can pass through the ground floor. There is a basic guideline for the design of piloti-type structures for tsunami forces but detailed information such as tsunami forces acting on the elevator hall or the ceiling is not speculated. It was also reported that tsunami forces acting on members of piloti-type structures such as the elevator hall or the ceiling estimated by the existing guideline were occasionally smaller than the tsunami forces measured by the hydraulic physical model tests.
 In the present study, hydraulic physical model tests were performed by using the tsunami wave generator in the wave basin in order to investigate the characteristics of tsunami force acting on the elevator hall and the ceiling of the piloti-type structures. As a result of the physical model tests, the tsunami forces acting on members of the structure depended on the shape of tsunami waves such as a speed of water level rise of tsunami. It was also found that the tsunami forces acting on members of the piloti structure could be estimated by the hydrostatic pressure corresponded to the maximum inundation depth in front of the piloti-type structure when the speed of water level rise of tsunami was relatively slower.

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 There are still many issues about characteristics of tsunami wave force acting on a piloti structure, especially on the components such as column structures and ceiling slabs, which are subjects for designing. Hydraulic experiments are effective measure to investigate those subjects, but its trial cases for wave profiles, model configurations and scale are limited, and numerical simulations can be useful tools to reveal the hydraulic characteristics of tsunami acting on the structure with complex shape. In this study, the applicability of numerical simulations to evaluate the tsunami wave force was examined regarding several sizes and arrangements of column structure. First, OpenFOAM were applied as the CFD code and the results of the existing hydraulic physical mode tests were reproduced to confirm the applicability. Then, the we also examined the change of water pressure characteristic by size parameter of columnar structure model by numerical analysis which we didn't do in the experiment. As a result, the differrence of width and height of columnar structure on the first floor influenced on wave force, but it depends on characteristics of the wave. As columnar structure is wider, or its height becomes lower, wave force is likely to become stronger. But distance of columnar structure from center line has no effect on wave force.

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 The oblique incident tsunami acting on a breakwater which has abrupt change of the breakwater width causes an extreme complex phenomena, such as a complex velocity field and the resultant complex damage of the breakwater. In order to clarify this phenomena, a 3D large hydraulic experiment simulating the 1/25 model of S port tsunami breakwater was conducted. In addition, a 3D numerical simulation was conducted as well. As the results, followings were clarifiled. The oblique incident tsunami changes the current direction perpendicular to the breakwater because of the strong overflow. At the abrupt change point of the breakwater width, the overflow current accumulates resulting in the damage of the mound cover layer behind the breakwater.

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 Based on the observed results of tsunami due to the Tohoku earthquake, wave period of tsunami was over 8 mins, which was longer than the wave period from former bore wave and solitary wave. From physical experiments, the time history waveform of girder acting force, the change in the steep waveform, such as the impulsive bore force caused by the tsunami tip portion is not seen, continuous sustainable force in the quasi-steady state had been excellence. Moreover, from the experimental results of former and this study, it was confirmed that horizontal acting force was impulsive bore force when tsunami period was in 1 min; and it was sustainable force when tsunami period was bigger than 1 min.

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 Some concrete bridges have been damaged and failed by Tsunami. One of the reasons of the damage was lack of useful method for evaluating the action of the concrete bridges subjected to the water flow. The vertical fluid force on concrete bridges caused by Tsunami is important for evaluating the flow out of concrete bridges. The calculation method for vertical fluid force on concrete bridges caused by Tsunami is not established.
 In this study, the vertical fluid force on the condensed railway concrete girders caused by uniform water flow is measured by the hydraulic experiment. The distribution of water level and fluid velocity around the condensed railway bridges are investigated by the fluid analysis. The calculation method for vertical fluid force on the condensed railway bridges caused by uniform flow is considered by the fluid analysis. This calculation method is based on Bernoulli's theory considered the submerged condition, the distribution of water level and fluid velocity. This calculation method can estimate the vertical fluid force acting the condensed railway bridges caused by uniform flow in the hydraulic experiment.

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 Bridges are playing a vital role in the post-tsunami reconstruction process providing access to the damaged areas. Therefore, as it is costly to reconstruct the bridge itself, a damaged bridge is also a huge setback for the mobility of resources. In the current study, tsunami flow over three types of bridge sections was numerically simulated to assess the behaviour of tsunami-induced loading, and results are compared with the existing physical experiment results. Failure of bridge girder by the lateral movement was well reproduced in the three-dimensional numerical simulation. The temporal variation of the reaction forces at the girder bearings was also agreed well with the physical experiment results and discussed in the paper.

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 Based the tsunami of same wave height and wave shape, parameter study on different level of bridge girder location has been conducted by experiment. During the experiment, the pressure being act on the bridge model has been measured in detail, by which the effect of girder location on wave force with the assumed wave height has been evaluated. As a consequence, compare to the situation when the girder is attacked near the wave crest, the rapid force is greater when the girder located close to the static water level; this is caused by the increment of pressure from the variation of water level under the girder.

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 Three hundred and nineteen fishing ports were damaged due to the Great East Japan Earthquake. Though the collapse of the facilities like breakwaters, quaywalls, aprons, seawalls and so on by the earthquake and tsunami was confirmed, but the open-type wharves stopped at the damage slight in comparative way such as sinking of deck blocks and disappearance of connection plates. In this research, physical model tests were conducted in a wave flume to investigate the tsunami-induced forces including pressures acting on the open-type wharves on vertical piles under stationary flow condition. As a result of the tests, the wave pressure of the deck block surface fell significantly compared with the hydrostatic pressure, and it was revealed that the wave pressure difference in the faces at the top and the bottom of the deck block brings lift and that lift excels to the horizontal force of the wharves. The lift of the deck block was different depending on presences of connection plates, but the lift coefficient could admit a downward trend with increase of a Froude number together. We made it clear that it's able to regard the coefficient as a constant value on the practical use. More wave pressure distribution of the face at the top and the bottom of the deck block and lift were formulated, and the validity was indicated more than relationship with measurement lift.

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 In this study, hydraulic model tests and numerical simulations were conducted in order to investigate the effects of bore pressure on structural integrity of a seawall. As the results, the bore pressure generally had smaller effects on that structural integrity than sustainable one. However, under specific conditions, such as when the seawall stands near a shoreline and wave-breaking occurs just in front of the seawall, the bore pressure may have larger effects on the seawall. Even under such circumstances, it is confirmed that the method provided in MLIT's interim guideline is applicable in evaluating the load of the bore pressure.

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 This study aimed to know the tsunami situation from Pacific Ocean to Kuji bay. And the tsunami propagation progress to Kuji bay was gotten by the observed results of GPS-mounted Buoys and aerial photographs. From the results of GPS-mounted Buoys of Iwate North at the position 25km far from coastline and wave gauge of Kuji bay at the position 6km far from coastline, it was observed that 1/4 wavelength of tsunami were 5600m and 1800m; and maximum water level were 4m and 5.1m respectively. In addition, for the first tsunami impact, small wave crests occurred at the position about 3200m far from the coastline and fission of solitons appeared at the front of tsunami with a very short wavelength whose 1/4 wavelength was 150m. After that, with tsunami propagation, wave shape deformed from fission of solitons to breaking wave at the position 2400m far from the coastline. And it could be found that the maximum water level of the first tsunami impact near coastline was about 5m, however wave level didn't change from 6 km far from coastline.

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 Resistance force of reinforcing mound using wave-dissipating concrete blocks against tsunami was investigated. Resistance forces of the reinforcing mounds of various cross-sections were measured by loading experiments in the air. Hydraulic model experiments on tsunami wave pressure acting on a caisson and experiments on caisson sliding under the tsunami overflow were also conducted. These experiments clarified that the wave-dissipating concrete blocks behind caisson significantly contribute to the increase in the resistance force. It is also found that the wave pressure on the rear-side of the caisson tends to increase by the placement of the reinforcing mound. Estimation method for the resistance force of the reinforcing mound with wave-dissipating concrete blocks was proposed. The validity of the method was confirmed by comparing with the experimental results.

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 Due to the climate change, big storms increasing occur with significant disasters, which are possibly caused by high tide compounded with big waves. Despite that such a complex disaster may cause unexpected damage to coastal structures, the detail of the mechanism has not been studied sufficiently. Therefore, in this study, we implemented hydraulic experiments targeting on a breakwater suffered the by mixture phenomenon with overflows and overtopping waves. This study focuses on the wave power exerted on the caisson and the mechanism of suffering processes of armor units, which cover the mound behind breakwater. The experiments show that mixture phenomenon gives inclement of wave force comparing with an overflow boundary, which has a similar overflowing depth to that of the mixture phenomenon. Through the experimental results, it is found that the tendency of the increment quantity of the wave force depends on states of wave shoaling on the breakwater. In addition, the suffering process of the armor process is examined focusing on suffering area and pressure force.

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 In the Tohoku Pacific Ocean earthquake, not only an earthquake, the possibility that the damage of the structure spread by a tsunami and the flotsam is pointed out. Until now, study of the single disaster such as an earthquake or the tsunami has been actively carried out. But study of the influence of the structure by the complex disaster such as an earthquake and a tsunamis and the flotsam is extremely few. Therefore, in this study, the numerical analysis of the viaduct catching the complex disaster was performed, and a damage degree of the viaduct was evaluated. As a result, there was no great difference in a impact power between the complex disaster than a case not to consider an earthquake. However, a meaningful difference occurred in the displacement of the viaduct.

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 The recent 2011 off the Pacific coast of Tohoku Earthquake earthquake and tsunami generated huge tsunamis, and many protective facilities were destroyed. Most of the damage was caused by the tsunami overflow. On the other hand, many aftershocks occurred after the main shock and attacked the coastal facilities combined with tsunami. In order to clarify the superposition phenomenon of an earthquake and the tsunami, large haydraulic experiments were conducted. As a result, it was clarified that the hydraulic pressure acting on the caisson is basically expressed as a superposition pressure of earthquake and tsunami.

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 The 2011 Tohoku Tsunami severely damaged river mouth areas protected by seawalls and dikes. In a river mouth area, the defense structures are usually meandering as they are aligned along complex coastlines and river channels. The purpose of this study is to clarify the tsunami force exerted on curved seawalls. Laboratory experiments were conducted to measure wave pressure distribution along seawalls which are convex to indicent waves. The results show that the impact wave pressure rapidly decreases with the local angle of wave incidence, whereas the standing wave pressure reduces with a relatively lower rate. It was also found that the local curvature of seawall tends to enhance the impact pressure, while relaxes the standing wave pressure.

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 Land run-up waves caused and accelerated by overflowing sea-walls may give crucial damages on land structures. In particular, since parapets are set in front of the sea, they have a risk that they could suffer a huge impact by a direct attack of such a high-speed flow. Despite the fact that many studies focus on prediction of wave forces acting on the parapets, in addition, it is general to suppose setting of some optional structures such as wave-dissipating blocks for in-water structures, e.g. breakwaters and seawalls, insufficient studies consider possibility of the optional structures. For efficient design of resilient parapets, optional structures should be effective to reduce wave forces. In this study, targeting some optional structures, e.g. slit, porous, and net set in front of the parapet, their reduction effects of wave force acting on the parapet is verified by implementing hydraulic experiments targeting dam break problems. From the results of experiments, their characteristics as a dissipating structures are shown.

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 In the 2011 Tohoku Earthquake Tsunami, the tsunami disasters occurred in many vessels moored along the terminals inside the harbor basins. It is required how to express and estimate the tsunami wave force on those vessels. An experimental study on the tsunami wave force for a vessel which is modeled as a 90,000DWT class coal carrier has been conducted in two-dimensional water tank during a tsunami bore. The surface elevation, current and wave forces acting on the fixed vessel in head seas have been measured in several established bores. The property of the tsunami bore and wave forces are investigated, and a practical estimation method of tsunami wave force of the vessel is also demonstrated by using Morison's formula, and compared with that of observed one.

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 Japan's energy policy has been changed after the Great East Japan Earthquake. Marine renewable energy is increasing. An advantage of tidal current energies is hardly influenced by weather conditions. Energy can be generated both day and night. During the installation work of tidal power generation device, the vessel and the suspended load are moving by the waves and tidal currents. As a result, the installation accuracy of the suspended load is reduced. Therefore, it is important to understand the motion characteristics of the vessel and the suspended load. This study examined the characteristics of movement during installation of tidal power generation device using a crane vessel in the hydraulic model experiment.

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 The purpose of this study is to clarify the effect of the overflow falling height on the scour depth using physical experiments. Small-scale physical experiments were performed. The results indicate that the maximum scouring depth increases when the falling height of the overflow increases up to a given height. However, the maximum scouring depth decreases if the falling height is greater than the critical height because the diameter of the vortex decreases at such falling heights. The relation between the diameter of the vortex and the maximum scour depth is compared to the formula used in two previous studies. The scour depth determined in this paper is smaller than that estimated by the previously published formula. Thus, it is important to evaluate the velocity on the bottom for accurate estimation of the maximum scour depth.

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 In a design of a hydroplane tsunami barrier, it is required to pay attention sufficiently to the tensile strength of a belt to control the motion of a flap gate. If tsunami attacks cut the control belt by a tensile force exceeding its critical strength, a flap gate could not keep standing posture and the protection function of the barrier for a tsunami would be lost. In the worst case, a flap gate could drift and collide with neighboring coastal structures. Therefore, the prediction of tensile force acting on the belt is a significant issue in a design of a hydroplane tsunami barrier. This paper presents the investigation of the applicability of accurate particle methods to the prediction of the tensile force. The tensile forces for the cases of two types of pressure gradient models such as CMPS and GC methods are compared with an experimental result. The GC method shows superior performance to CMPS method in the prediction of tensile force acting on the belt.

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 The Hydroplane Tsunami Barrier is a kind of the movable breakwater. The main body is fixed to the pedestal by special rubber belts, and it rises by hydraulic force due to tsunami and storm surge. The effectiveness of this breakwater for tsunami countermeasures is indicated through experiments of response characteristics for hydraulic force, wave force acting on the main body and the damping effect for a wave height. This study aim to evaluate the performance of the Hydroplane Tsunami Barrier by using the full-scale model. As a result, it is revealed that the damping effect increases with the height of tsunami. Response characteristics evaluated by this study had good quantitative agreement with experiment results of 1/50 and 1/200 models.

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 This research had grasped stability characteristic of wave dissipating blocks by plane hydraulic model experiment and obtained the underlying data of the future design to caisson breakwater covered with wave dissipating blocks against the various conditions by about 60 degrees of sharp-angled incident wave. The main conclusions are as follows. (1) The wave height ratio front of wave dissipating blocks is influenced by generation status of meeting wave and is highest in case of wave dissipating blocks to start from the middle when meeting wave attack from the stage up side. (2)A sharp-angled incident wave is transmitted to lower direction on the wave dissipating blocks crest while breaking and is making blocks in the shoulder part fall to down side. The damage mechanism is different during vertical incidence. (3)As a result, the increasing coefficient of wave dissipating blocks to about 60 degrees of sharp-angled incident wave is guessed at 1.7-2.7.

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 This paper presents a stability estimation method of armor units to cover a rubble mound at the rear side of a caisson breakwater against tsunami overflow while taking account of the influence of the shape of superstructures of the caisson. In this method, the required mass of the armor units is obtained from the impinging velocity onto the rear side mound which is calculated by using overflow depth. Accordingly, the influence of the shape of superstructure is taken into account directly. This method also takes the influence of the slope angle into account properly by using the formula by Isbash. In addition, the influence of the impingement position of the overflow nappe and the influence of the thickness of the overflow nappe are considered. The validity of this method is confirmed by comparing with the results of hydraulic model experiments conducted in a wide range of conditions.

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 An enhanced fully-Lagrangian coupled solver is developed for modeling of Fluid-Structure Interaction (FSI) phenoma. The fluid solver provides solutions to the continuity and Navier-Stokes equations on the basis of the projection-based Moving Particle Semi-implicit (MPS) method. The structure solver is founded on the description of a non-linear hyper-elastic structure in the frame of a Hamiltonian system based on Hamilton's principle of least action. The fluid and structure solvers are properly coupled through a consistent coupling algorithm. Performance of the proposed solver is examined, by reproducing a dam break with an elastic gate and a dam break with an elastic plate. The results obtained from Hamiltonian MPS FSI model are also compared with those by a MPS FSI model that incorporates a linear-elastic structural solver.

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 Based on the experimental results for profile change of wave-dissipating blocks covering a caisson breakwater, the model profiles for the damaged block layer are made and the relation between the damage progression and change of performance is investigated. The results of the numerical experiment using the model profiles show that the overtopping rate increases by a factor of 1.5 compared to that of the initial profile with damage progression. Furthermore a statistical model based on the Markov chain is applied to the damage progression process and the total cost for the maintenance of wave-dissipating blocks is estimated by using an assumed repair cost and loss. This method can be applied to find a policy of repair that minimizes the total (life cycle) cost, however, it is necessary to evaluate the practical amount of repair and loss reasonably.

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 Colombo Port Expansion Project was initiated with the recognition of increment in demand for container throughput in future. Construction works of the project are in progress. The toe of the main breakwater contains 8 - 12 T large boulders. Whilst the construction of main breakwater is in progress, contractor faced difficulties to find the 8 - 12T rock boulders from queries for toe. Hence, application of 20 T CORE-LOC instead of 8-12T was proposed by the contractor. Two dimensional (2D) physical model testing was carried out to assess the stability of toe in main breakwater with two or three CORE-LOC (20T) rows instead of 8 - 12T boulders. Model scale was determined considering flume dimensions, sea bed profile, available CORE-LOC miniatures and wave heights to be tested and dimensions of the breakwater section etc. Scaling down of the prototype to model was done according to the Froude's Similarity and model units (armour units, CORE-LOC) were scaled down based on Hudson's Stability Criterion. Several alternative design sections were subjected to the testing and higher emphasis was set to maintain the specified rock gradations. Study determined the adequate number of CORE-LOC rows to replace the existing 8 - 12T large boulders layers while considering overall stability of the breakwater.

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 Tenacious structures for mitigating devastating disaster of tsunami overflows have been recently required for coastal dikes in Japan. As one of the hard countermeasures, it is suggested to install landward toe protection works. However, hydrodynamic characteristics of impulsive forces acting on the works in tsunami overflows have not been clarified thoroughly in previous studies.
 In this study, we experimentally investigated the impulsive forces affecting on failures of the works, which occur at an early stage of tsunami overflows. In the experiments, four types of concrete blocks were used for the landward slope and toe protection works, and we systematically changed the tsunami height and the block type used for the works. For each experimental case, we took videos of the corresponding failure. We also measured drag, lift forces, and moments acting on the blocks.
 Results showed that the upward force observed during a very short time after tsunami flow lands on the blocks is the key factor triggering the washout of the toe protection works. The results also showed that the location of the block flowing out firstly from the works is approximately determined by the tsunami height and the block type.

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 Most of coastal structures, especially coastal dikes were destroyed by the 2011 Tohoku Tsunami. It was reported that one of the most important causes was the failure of back slope of dikes due to scouring.
 It was effective to drain into the landside as possible smoothly in examining the robustness of the dike for the tsunami. In this study, a numerical model using CADMAS-SURF/3D has been applied to clarify the difference of tsunami external force toward back slope of dikes due to structure specification and to make suggestions for mechanism of robustness and design of coastal dikes. As a result, in order to restrain scouring at back slope of dikes, excepting method of moderating the back slope, streamline at top of inner slope and back slope were proposed.

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 The development act and industrial activity by man has caused heavy coastal erosion in the world, and the global warming is deteriorating the coastal safety. Therefore, the research on safety of a coastal dike and a seawall is becoming very important. Because the suction by small waves in the shallows causes the break of those, Ioroi et al. presented two methods for predicting the suction rates of backfilling materials
 In this paper, an empirical formula which can evaluate the suction rate in consideration of the influence of the uniformity coefficient and the dry density of backfilling materials is presented. Moreover, Ioroi et al's methd for simulating the suction rate using CADMAS SURF (a numerical model for simulating fluid motion in a porous media) and empirical equations of the suction rate is improved in order to raise the accuracy.

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 Numerous amount of wreckages may increase various risks and hazards of the inundated area under the severe flooding events. The purpose of this research is to capture the behavior of the flood with numerous wreckage by a hydraulic experiment and to investigate the characteristics of the movement of wreckage and surrounding inundating flow. The experiment was first conducted on a plain basin with a wide dam-break type wave generator. Through the analysis of the experimental results, we found that the locally accumulated wreckage had significant impact on the inundating flow and locally elevated the inundation depth. A numerical model, accounting for such interactions of flooding water and accumulated wreckage, was verified through the comparisons with experiments and it was also found through the numerical analysis that interactions of flow and wreckage affect not only the flow charcteristics but also the predicted behaviors of wreckage.

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 In order to debevep the probabilistic damage evaluation method of the structure against tsunamni debis impact, behavior of debris which is initially set on the land due to tsunami inundation flow were investigated using hydraulic experiments. By setting a rectangular structure on the land, collision probability and collision speed of debris in the situation where effects of both tsunami inundation flow and refrected waves fenerated from the rectangular on the debris behavior should be considered, were investigated. Experimental results show that features of the trajectory and the streamwise and spanwise dispersion in the debris behavior on the tsunami inundation flow. The results also demonstrate that the specific gravity of the debris has considerable impact on the debris behavior. Moreover, decrease in collision probability and collision speed of the debris against the rectangular due to the generation of waves refrected off the rectalgular are quantitatively presented.

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 We used a hydraulic model to study the effects of a pump house's discharge tank space and of the tsunami wave height on the dissipation of tsunami energy. The model used direct measurements of the wave pressure obtained from a pressure gauge at a drainage pump station to support decisions about how to reduce tsunami damage by controlling operation of the water discharge tank.
 It was possible to decrease the wave pressure at the pump house by about 60% if the wave height was below the height of the discharge tank. Even when wave height exceeded the height of the water discharge tank, this approach could reduce the wave pressure by more than 40%. Tsunami energy dissipating effect was so small that discharge tank and a pump house interval became big, and when it was about 6 times of distance from the standard location, the effect was hardly obtained.
 The peak wave pressure occurs when the tsunami strikes land, when the downward flow velocity between the water discharge tank and the pump house is high, the wave force in the direction of movement of the tsunami wave was reduced.

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 This study deals with the wave reduction effect of a new type artificial reef that combines the conventional reef with flaring-shape block to find a possibility for contraction of the crest width. Two types of the flaring-shape block of unequal size were used in the numerical computation and the results were compared with that of the conventional reef which has a trapezoidal section. In the case of reef with the block, a rapid decrease of wave height occurs by the wave breaking around the top of the block in comparison with the conventional reef. The cases of the contracted reef with the block were also investigated. It was confirmed that the wave reduction effect in the case of contracted reef with the block was in the same level as that of the conventional reef. The result shows the possibility for contraction of the crest width by combining the flare-shape block.

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 Disaster prediction for upright seawall is examined subsequently to previous our research work in order to provide the possibility of index to explain the disaster occurrence. In this method, tidal variation is newly included and the significant wave height data from NOWPHAS each 2 hour is used to predict the flow rate of wave overtopping from the upright seawall. The accumulation value of the flow rate of wave overtopping with the time function are also carried out to judge of disaster.
 As a result, it makes clear that wave history duration is possible to expand 3 years and the power of the time function is enough 1.

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 A tencency of extension of construction work due to an increase in the frequency of high wave periods has recently been reported by some of the construction sites installing caisson breakwaters in Japan, which may lead to delay of improving infrastructure and an increase in cost. We analyzed trends of wave climate in the past 30 years focusing on the duration of workable condition for installation work and found that the wave climate is becoming more severe in the coasts of the Pacific Ocean side. We then performed a laboratory experiment to consider a measure for mitigating the effect of the changing wave climate on installation work and showed a promising method for osscilation damping of caisson during its installation work based on a minor modification of caisson structure using tuned liquid damper (TLD).

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 In this study, on-site surveys based on reports of damage to backshore slopes on coastal roads along the Sea of Okhotsk in Hokkaido were conducted, and an embankment fracture experiment with model high waves was performed in consideration of the survey results. In the experiment, ground with varying relative density and vane shear strength was used to simulate various states of soil suction dynamics. The results highlighted the collapse phenomenon that occurs when soil suction is reduced by high waves on a partially saturated and loosened slope, and scouring caused by high waves was observed on a partially saturated slope with medium-to-high density. The patterns of coastal road damage that follow changes in the relative density and degree of saturation seen in the field soils were clarified, and the mechanism behind high-wave-related failure on coastal roads was elucidated in relation to changes in soil properties. The volume of backshore slope collapse was also found to depend on the relative density and degree of saturation of the slope's soil.

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 In this paper, is discussed the scour phenomenon in the two-layers ground due to vertical jet flow. The geo-material in upper layer was used two type gravels and the Toyoura sand was used in the lower layer. The total height of deposited ground had setting 0.7 m and the thickness ratio: (= thickness ratio of upper layer: D_g / Total height of deposited ground: D) was changed. As an experimental result, scouring of the sandy ground was suppressed by laying the gravel on the sandy ground. Especially, we found that a property of gravel in upper layer and its thickness had an influence on the scouring scale of sandy ground in lower layer. In the future, in order to evaluate the loosening area and the blocking effect for scour of sandy ground of lower layer in two-layers, we necessary to clarify the mechanism of energy loss by gravel in upper layer.

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