The East Japan great earthquake and tsunami disaster which occurred on March 11, 2011 seriously dameged even port facilities.
 Assuming two levels of tsunami, "the maximum class" and "the comparatively high frequent class", and "disaster reduction" were proposed through the discussion repeated in some councils, committees, etc., meanwhile a concept of "persistence or persistent structure" was suggested.
 In this paper, the present situation of consideration and discussion, etc. on a way to design correspondding to "disaster reduction" and a view of "redundancy, toughness and ductility" are reported mainly on breakwaters and seawalls among port facilities, also introducing the information about the damage mechanism obtained by subsequent examination.

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 A series of hydraulic model experiments was systematically and carefully carried out to estimate the stability of various types of armor units for harbor-side rubble mound of composite breakwater against tsunami flow overtopping the crest of the caisson.
 As a result, the following points were carified: Damage to armor units is strongly dependent on the position of the flow. Armor stones of weight 1 ton are easily removed by the tsunami flow. Flat type concrete blocks with well-arranged holes showed high stability. Fixed armor units placed on the toe of the slope enhanced the total stability of the armor layer.

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 Hydraulic experiments were conducted to estimate tsunami wave pressure acting on an onshore structure, namely a vertical wall. Wave pressures were measured at some points on the wall. The existing hydrostatic formula tended to overestimate tsunami wave pressure in the experiment. The experimental results revealed that there is time lag in the occurrence between the maximum wave pressure near the ground and the maximum inundation depth caused by splash.
 Estimation method of tsunami pressure using inundation depth and horizontal velocity in front of a structure was proposed based on the laboratory experiment. It was confirmed from the comparison with the experiment that the vertical distribution of the maximum tsunami wave pressure can be reproduced by employing the proposed method in this study.

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 The north coast area of Iwate Prefecture was attacked by Tunami due to the 2011 Off The Pacific Coast of Tohoku Earthquake. This study mainly surveyed the tunami wave vestige in the coast area of Iwate Prefecture. Firstly, this study surveyed the heights from sea surface to the top of the wave vestige, there are remained on the wall of the house and on the ground slope due to wave run up. Secondary, the observed values are changed to the height of the Tokyo datum line by the tide prediction model.
 In results, the heights in this area are about 17m to 20m. However the wave increased over 30m due to the wave interference in the middle area of Noda Bay. In the many bay, example for Miyako Bay, the wave heights decreased at the inner area. However the heights increased in Hirota Bay.

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 On March 11, 2011, a magnitude 9.0 earthquake occurred off the coast of northeast Japan. This earthquake caused a tsunami which attacked mainly Tohoku District. The 2011 Tohoku Earthquake Tsunami Joint Survey Group consisting of the members of several related academic societies was organized immediately after the disaster. From March 26, the first six 6 teams entered the Tohoku district. The present study shows the field survey results across five major bays in the south part of Iwate prefecture performed by a joint team of Yokohama National University and the University of Tokyo. The measured tsunami heights range from 7.7 m to 30.1 m. A large difference of tsunami heights was observed between in Kamaishi Bay and in Ryouishi Bay, which situation may be attributed to the presence or absence of the offshore breakwater. In Ofunato Bay, the damage is considered to be intensified due to the existence of landward low flat grounds. Further, in Ofunato Bay and Kamaishi Bay, where offshore breakwaters existed, it was assumed from the eyewitness testimony that the water flow inside the bays were comparatively small, and the speeds of the water level raise were also reduced.

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 On March 11, 2011, a great earthquake and tsunami attacked the Ibaraki coasts. In this period, the seawalls of the Narita and Kamigama coasts, where sand was transported toward the wave shelter zone of Oharai Port and severely eroded, were severely damaged and collapsed mainly due to the ground vibration and their function was lost before the tsunami. The function of the seawall against tsunami was reconsidered.

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 On March 11, 2011, a great earthquake occurred off the northeast Japan's coast, and a great tsunami generated by this earthquake attacked the Pacific coasts. On Kujukuri Beach, tsunami invaded through small river mouths and several access ways between the inland and the shoreline, causing severe damages. These phenomena were investigated at the Yasashi River mouth flowing into the Iioka coast and the Hasunuma and Ichinomiya coasts.

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 On March 11, 2011 a great earthquake with a magnitude of 9.0 occurred off the Tohoku Japan, and great tsunami attacked the coasts in Sanriku Region and Sendai Bay, causing large disaster. Although the tsunami height was different from place to place, many shrines built near the coasts were escaped from being destroyed by tsunami except several cases and they were used as an effective area for the evacuation of the people. We investigated the reason in terms of the tsunami height and the ground elevation of the shrines.

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 In this research, we compare the results of video analysis of the 2011 Tohoku tsunami in Kesennnumaand the results of simulation. Based on the comparisons, we consider the validity and improvement of the simulation model. As the result of this research, simulated water velocity gives a good agreement with recorded real water velocity at land area. Inundation simulation also shows good estimation. It appears that embankment had a big influence on the rise of water elevation in land.

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 This work aims to ascertain the wave behavior and possible damage in a lake or a bay caused by the effect of long-period ground motion using the same numerical analysis. The generation of waves which are affected by long-period ground motion is a new concept. In general, when an earthquake occurs in a marine area, tsunami disaster is of special concern as water can damage coastal regions. However, in fact, not only tsunami but also high waves caused by long-period ground motions were generated at Sai Lake in Yamanashi Prefecture about 470km far from the epicenter of the Tohoku earthquake (Mw9.0) and this phenomenon has not received sufficient attention up to now. According to the field survey, there is evidence that waves of up to 1.0m height were generated. These 1.0m height waves were accurately simulated by the numerical model, whose governing equations are the non-linear shallow water equations. Furthermore, this model was applied to Tokyo Bay against the possible future Tokai and Tonankai earthquakes which are forecasted to take place within the next 20 years. As a result, the wave height generated by the long-period ground motion is less than 1m. These waves, although they will not lead to inundation of coastal areas, are irregularly generated and can shake small boats or float bridges, and it is important for people in the area to pay attention to this following the earthquake.

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 A full-scale three-dimensional numerical analysis is carried out to quantitatively determine whether rigid buildings located along coasts reduce inundation water volume due to run-up tsunamis. For investigation, a run-up tsunami propagating through impermeable rigid buildings on an impermeable horizontal flat land behind an impermeable vertical quay wall is simulated and analyzed in terms of inundation water volume beyond the buildings using a three-dimensional coupled fluid-structure-sediment interaction model. Numerical results show that the inundation water volume decreases with an increase in the ratio of the longshore length of the buildings to the total length of the coastline (building-coastline ratio), and conversely slightly rises with an increase of the height of the tsunami and the cross-shore distance of the buildings from the quay wall. On the other hand, the inundation water volume is insensitive to the period of the tsunami, the height of the quay wall, the initial sea water level, the cross-shore length of the buildings, and the number of gaps between the buildings. Based on the numerical results, approximation equations are proposed to predict the reduction rate of the inundation water volume from the building-coastline ratio. As a result, it is demonstrated that rigid buildings located along coasts are effective as one of the countermeasures against run-up tsunamis in terms of inundation water volume.

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 Local wisdoms such as a tradition, land-use system and etc. had sometimes mitigated tsunami damages in Indonesia. The effective use of those local wisdoms is strongly desired especially in developing countries, because it is quite difficult for those countries to allocate enough budgets for constructing hard type countermeasures against tsunami. Among local wisdoms against tsunami hazard, this study evaluates the efficiency of a hollow topography which can be seen on the beach along Lampon village in Indonesia Artificial hollows are arrayed on the beach as one of the local wisdoms in Lampon village to reduce the intensity of inundated tsunami flow. The numerical simulation of tsunami inundation is conducted to evaluate the efficiency of this hollow topography. Furthermore, this study evaluates the efficiency of some contrivances, such a combination of vegetation area and a multiple-use of hollow and embankment topography, in order to enhance the performance of countermeasure based on the local wisdom.

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 The flow velocity of tsunami wave was estimated by using Particle Image Velocimetry(PIV) and Particle Tracking Velocimetry(PTV). These methods have many advantages that can be used to measure velocity under limited data such as the 2011 off the Pacific Coast of Tohoku Tsunami. The results of video image analysis are evaluated by comparing with theoritical approach. The collected video image is stabilized and rectified in the pre-processing to enhance the accuracy of PIV method, whereas the proposed theoretical method is based on conservation equation. It is found that the estimated flow velocity range is consistent regardless of the method. The method is expected to perform well for analyzing videos and providing information in tsunami cases where there is no adequate measurement data.

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 The 2011 off the Pacific coast Tohoku Earthquake Tsunami caused serious damages to coastal protection facilities constructed on the land. In the present design for coastal protection facilities against tsunamis, the crown heights have to be designed in order to prevent the overflow by the tsunami whose return period is equal to the designed service lifetime of the facilities.
 On the other hand, more reasonable crown heights can be designed on the basis of the amount of damage by tsunami overflow. In this study, the method of determining the crown heights of parapets against tsunami is proposed in which the initial construction cost and the amount of damage are estimated. The applicability of the proposed method is discussed by introducing the index to express the extent of the damage and the appropriate estimate of the amount of damage.

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 Authors have advanced the research and development concerning the flaring shaped seawall. Hydraulic characteristics that the wave overtopping rate can be greatly decreased though this seawall is a low crown height have been clarified. The first local construction is executed the flaring shaped seawall as a shore protection works against storm surge and waves in 2004 and, up to now, has been constructed about ten seawalls. However, many seawalls had damaged by the 2011 Tohoku Earthquake off the Pacific coast and we had to evaluate hydraulic characteristics to tsunami of the flaring shaped seawall.
 In this study, we have verified hydraulic characteristics to tsunami of the flaring shaped seawall by using the numerical analysis and have compared with it of the upright seawall and the sloping seawall. As a result, the flaring shaped seawall is able to clarify that there is a possibility that the impact wave force given to the structure in seawalls back is able to be decreased greatly according to the condition of tsunami and others.

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 It originates in generating of the serious tsunami damage which is caused by the Tohoku-Pacific Ocean Earthquake. Need for the research and examination about several tsunami dameges is increasing.
 Although there are many researches about stability of wave absorbing blocks which are causing little action of them under wave conditions, there is few researchs about the great migration of the block groups and the usability of wave absorbing blocks after great migrations under tsunami condition.
 In this study, hydraulic model experiments remaking the groups of wave dissipation blocks which are set in front of the revetments facing the outer sea have been done. This paper aims to acquire the fundamental knowledge on the forms and mechanisms of extensive sufferings of the blocks due to the over-designed tsunami forces and influence on the vicinity.

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 The serious damage of coastal dikes and breakwaters occurred in the tsunami caused by the 2011 off the Pacific coast of Tohoku earthquake. It is important to reinforce these coastal structures with the concrete blocks and to give the function of tenacious structures. Hydrodynamic experiments had been performed to study the damage of concrete blocks armoring on slope and mound in the side of land of these coastal structures for the over flow in tsunami. In the case of coastal dikes, the stability of concrete blocks and the damage of these coastal structures are affected by the strength of foundation in spillway. The stability of blocks are also affected by the types of blocks and there geometrical arrangement. In the case of breakwater, the critical values of the total head above the crest of breakwater, in which the damage of concrete blocks occurs, are affected by the height of breakwater above the still water level and the water depth from still water level to the foundation of breakwater. The positions where the damage of armor concrete blocks occur on the foundation change with the total head above the crest of breakwater.

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 Coastal area in Tohoku district was devastated by Tsunami at the East Japan Earthquake Disaster, and resulted that large volume of sediments of Tsunami were still accumulated. Now, public work, sediments removed and construction of soil structures as the dike for Tsunami, was in rehabilitation process. If large volume of sediments could be used for material of soil structures, it will contribute to the rehabilitation of the great earthquake disaster.
 In this study, granulated fly ash was mixed with soils as representative samples of devastated area, and laboratory test which was cone penetration test, odor test and germ culture test was tested. Granulated fly ash could be improved strength and could be restrained bad odor and culturing bacteria. By the field test with blending machine, those improvement effects were evaluated.

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 In order to dispose debris generated by the 2011 off the Pacific coast of Tohoku Earthquake Tunami, we have thought to break pieces of wood and to use it as fuel. And, we have thought to construct waste repository for radioactive waste and dump radioactive waste into the repository. We estimated cost for the projects and CO2 emission associated with the projects. The results showed that to use pieces of wood using as fuel at cement factory cost and emitted CO2 less than incineration disposal as waste. And, sea repository case cost and emitted CO2 less than land repository case.

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 Laboratory experiments were performed to study wave transmission and wave reflection capacity of mangroves and trees as coastal protection from waves. Drag forces on a live pine in small scale open channel flow were measured by using a load cell. Drag forces on a circular cylinder in rapid flow were also measured. A theoretical analysis based on application of the continuity and energy equations to flow through the rows of trees were made to evaluate wave transmission and wave reflection capacity of mangroves and trees in coastal area. The significant wave reflection from mangroves with large and dense canopy was estimated.

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 The 3.11-Tohoku tsunami caused severe damages on not only houses but windbreak forestry along the north east coast of Japan. In Sendai coastal area, pine trees were planted along the coast with around 500m width against storm surges. People had believed that the windbreak forestry would act as filter against any tsunami. But, almost all of the windbreak forest trees were washed away from the roots in the region during the 3.11 tsunami. In this study, the distribution of the pine trees were washed away by tsunami into landward is revealed by GIS analysis. The total number of the drowned tree reached 21,054. The pine trees were mostly scattered around 1km - 3km from the coastal line. Some houses in the damaged area were protected by the trees those stood against tsunami.

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 Recently, utilizing coastal forests as a countermeasure against tsunamis attracts coastal engineers and practitioners, because they have concurrent benefits both for disaster mitigation and environmental preservation. If tsunami force exceeds the physical strength of trees, breakings of the trunk and branches occur, which may reduce the mitigation ability against tsunamis. This paper conducts numerical analyses on the dynamic response and internal stress of the tree elements under tsunami fluid forces.

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 The counter measures for preventing tsunami disaster have been targeted to local inhabitants, therefore the effect of mitigating disaster in the seaside resorts where many tourists visit is not adequate at the present. In this study, the questionnaire surveys concerning on the beachgoer's awareness of tsunami disaster were conducted in six seaside resorts where the raid of gigantic tsunami could be expected when the Tonankai and Nankai earthquake would be happened near future.
 The result shows that the evacuation awareness is directly related to the uncertainly of tsunami. The covariance structure analysis carried out is able to find the effect of the Tohoku-Pacific Ocean earthquake on evacuation decision.

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 A questionnaire survey was undertaken for residents' evacuation against tsunami attack and factors of their dicision making on the tsunami warnings in Okinawa main island. These are warning on near-by origin at this island and distant origin at Chiri . Factors about residents' evacuation are analyzed by Cramer's coefficient of association. quantification method of the second type and logistic regression analysis. The following things became clear from these analysis. Resident who is making effort to prevent disasters have a high refuge rate. In order to raise residents' evacuation rate, it is important not only the announcement from a local government but tocall from neighbor.

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 Since the 2011 off the Pacific coast of Tohoku Earthquake occurred, it has been pointed out that Tokai, Tonankai and Nankai massive earthquakes with a magnitude of 9.0 could attack the Pacific Ocean coasts. This paper discusses tsunami propagation characteristics caused by Tokai, Tonankai and Nankai massive earthquakes on the coast of the Pacific Ocean and three major bays (Tokyo Bay, Ise Bay and Osaka Bay). The numerical results showed that the tsunami heights of M9.0 were about twice comparing to those of M8.7 on the coast of the Pacific Ocean and the tsunami arrival time was faster at some areas distant from the source of tsunami. Moreover, high water level in the bays was also found to continue for a long time because the bay mouths are narrow.

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 This study numerically investigates tsunami inundation characteristics due to Tokai, Tonankai and Nankai massive earthquakes on the coast of the Pacific Ocean and three major bays (Tokyo Bay, Ise Bay and Osaka Bay) in Japan. As a result, the inundation depth in some regions along the Pacific Ocean enlarged with the increase of the magnitude of earthquake, but there was little difference in terms of inundation area. Flat areas below sea level were strongly damaged by tsunami inundation in the case that all the riverine and coastal structures were completely destroyed just after the earthquakes. On the other hand, they were recognized to be slightly damaged in the case that all riverine and coastal structures worked. Thus, it is necessary to take hard countermeasures against tsunami disaster in areas below sea level. Furthermore, the comparison of historical tsunamis and numerical results suggests that tsunami induced by Tokai, Tonankai and Nankai massive earthquakes with a scale of M9 is important to be discussed.

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 Next future Tokai-Tonankai-Nankai earthquake is predicted by the Headquarters for Earthquake Research Promotion with a high probability of more than 60%. This study has evaluated the inundation risk against various tsunami magnitudes over the estimated tsunami source by the Central Disaster Prevention Council. In the Wakayama Prefecture, variation of tsunami-induced inundation areas and heights depends on each area's topography. Inundation risks in the middle and south areas gradually increase with the increase of tsunami magnitude, while the inundation risks in the north low-lying areas increase drastically.

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 The 2011 off the Pacific coast of Tohoku earthquake, Mw 9.0, occurred on March, 11, 2012. Faulting near the axis of Japan trench produced extraordinarily large tsunamis which do devastating damages to the coastal area in Tohoku.
 In this study, we have examined the applicability of the nonlinear hydrostatic model to the giant tsunami, by comparing the calculated results with the waveform observed at offshore of Choshi city, Chiba prefecture, Japan. The pattern of the observed temporal variation was successfully reproduced for both the surface displacement and horizontal velocities. On the other hand, the magnitude of the temporal variation was underestimated. It is suggested that the underestimate results from the assumption of an instantaneous rupture. We also examined the characteristics of tsunami propagation near Choshi area.

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 The tsunami height in Tokyo Bay caused by the interrelated-type earthquake near the Nankai Trough was simulated to examine the influence of the slip distribution among faults and the slip generating time lag between faults. About the time lag of slips, the maximum tsunami height in case that the slips occur having the time lag which the tsunami maximum height by each fault overlaps becomes more than twice of the case that all of the slips occur simultaneously. Moreover, it turned out that slip distribution which makes the tsunami height mathematically maximum is widely different from with the distribution using the knowledge of seismology.

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 A set of field survey including airborne laser mapping, sea bottom sounding, boring, Swedish weight sounding was conducted to measure topographical change induced by the 2011 Tohoku Earthquake and Tsunami in Takada Coast, Okirai Coast, Ryoishi Fishing Port Coast, Kanahama Coast and Otsuchi River in Iwate Prefecture. Tsunami overtopping caused scouring landward of coastal dike deeper than the height of the ground at the time of the survey. It shows that backfilling occurred with a thickness of several meters after the scouring. Scour depth at dike break was larger than that in adjacency. In Takada Coast, large-scale topographical change resulted in sediment loss of about 1.86 million cubic meters.

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 In Kesennuma Bay, the study area, the sea bottom was scoured, the geography and sediments were altered, and much debris, oil, and chemical materials flowed into the sea from land as a result of the 2011 0311 tsunami. Highly precise information for the change of geography and sediment distribution by this tsunami applicable to the reduction of tsunami damage can be obtained by this investigation. We collected data on water depth, refraction intensity by acoustic systems, and four sediment samples, interpreted the intensity related to the physical properties of the sediment, made a three-dimensional topographical map and distribution map of the sediment and debris, and evaluated the marine environmental change based on a comparison with a chart published before this earthqueick.
 The geographical changes by impact of the tsunami restricted to the inner bay, such as a north-south geographical rise (< 8 m water depth) on the east side and a depression (> 16 m water depth) on the west side.
 Acoustic reaction is strong in the uneven geography present in the dune field which intersects perpendicularly with the bay axis in the joint area between the inner and central area of the bay. Coarse sediment and woody material are present in the area.
 Three clusters composed of many dunes are also distributed in the southeast area of the bay. The reflective intensity is strong at the top of the dune and is weak at its bottom. Fishermen stated that muddy sediment was widely distributed in the bay before this earthquake and that the sea bottom in the southwest area of the bay was exposed at the time that the water surface reached its lowest point during the tsunami. Thus, the evidence suggests that much debris and clastic particles were transported and the dune was formed by the tsunami's backwash.

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 The 2011 off the Pacific coast of Tohoku Earthquake caused catastrophic damage along coastal area in Fukushima Prefecture, Japan on March 11, 2011. The big tsunami generated by the earthquake was as high as 14m and caused significant change in sediment and bathymetry in Matsukawaura inlet in Soma city, Fukushima. The Matsukawaura is scenic and important fishing area. Therefore, sediment samples were collected at 147 points and water depths were measured at 268 points as an emergency environmental assessment. In general, sediment becomes coarse in the most of area except northwest and southeast parts of the inlet. In addition, it is observed that large quantity of finer sediment in Matsukawaura were transported and deposited inland. Water depth become deeper and the most of tidal flat were lost.

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 A massive earthquake with a magnitude of 9.0 occurred on March 11, 2011, at 14:46 with an epicenter 130 km offshore of Oshika Peninsula in Miyagi Prefecture. After the earthquake, a large tsunami was generated owing to the abrupt crustal subsidence and elevation and inundated east Japan's coastline. We carried out field observations to investigate the deformation of the previous river mouth bar by the comparison of oblique photographs as well as the investigations of the damage of the seawalls and tsunami inundation depth on the Iwama-sanuka coast, located north of the Same River in the southern Fukushima Prefecture. The results of the field observations on the deformation of sandy beach and the inundation of the Iwama-sanuka coast were reported.

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 The 2011 off the Pacific coast of Tohoku Earthquake caused catastrophic damage along coastal area in Tohoku and Kanto regions, Japan on March 11, 2011. The big tsunamis generated by the earthquake caused beach and dune erosion as well as destructions of coastal structures. The tsunamis also scoured and breached significantly just behind a crest of frontal dune and shore protection structures such as sea wall and mild slope revetment which exist along a shoreline but not perpendicular to. The dune and coastal structures are usually expected to play a role as a sort of the last defense against massive tsunami force. Therefore, the size of scouring and breaching by the tsunami are studied by using aerial photographs and field survey.

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 A massive earthquake with a magnitude of 9.0 occurred on March 11, 2011, at 14:46 with an epicenter 130 km offshore of Oshika Peninsula in Miyagi Prefecture. Due to the earthquake, sea cliffs were collapsed at many coasts. In this study, three examples were briefly introduced: sea cliff at Point Kunosaki south of Hirakata fishing port, sea cliff at the Akahama coast 1.5 km north of Point Takadobana and sea cliff at the Osawa coast facing Uraga Strait. Topographic changes due to waves were monitored after the collapse at the Osawa coast. The scale of the collapse of sea cliff increased over time.

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 To keep the lives safe against run-up tsunamis, it is important to study the forces due to driftage which collides on refuge towers in the area near the seashore. Colliding forces, therefore, on a column by an object of the size of small boat which drifts by run up tsunami onto a plain coast are investigated with focusing on the momentum change, i.e. the impulse, and compared with the results by tsunamis of solitary waves.
 The following emerge: In comparison with the solitary wave's case, as the front of run-up tsunami has strong power and strong turbulence, the impulse becomes large although the added mass becomes small, and the values are scattered. The colliding acceleration is important parameter because the impulse and the added mass are large when the acceleration is positive and small when negative.

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 The behavior of a container drifting on an apron and moving to the sea due to tsunami run-up and sub-sequent drawdown reflected from a parapet is investigated using a three-dimensional fluid-structure-sediment interaction model. In terms of water surface elevation in front of the apron, inundation depth on the apron, and drifting behavior of the container, the predictive capability of the model is demonstrated against experimental data. Numerical results show that it can be determined from the vertical and rotational motion of the container with the landward velocity of zero whether the container finally moves to the sea. In addition, it is possible that a short wall placed in the vicinity of the parapet is effective as a countermeasure to prevent the container from moving to the sea.

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 Recently, with the 2011 Tohoku Earthquake occurred, it is becoming important to consider the influence by tsunami flotsam colliding with an important structure. Also, the collision analysis method is being received much attention. However, practical applications of the collision analysis have not been investigated yet. Therefore the purpose of this study is to develop and evaluate a collision analysis method capable of simulating the phenomenon to which large flotsam collides with an important structure like the long-span bridge. Moreover, the marginal size of tsunami flotsam which can avoid collapse to an object bridge is computed using this method.

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 The motion of a bridge deck due to a breaking bore is investigated numerically in terms of the horizontal and vertical components of tsunami force acting on the deck using a coupled fluid-structure-sediment interaction model. Numerical results show that the motion of the deck depends on the clearance below the deck and the weight of the deck because both horizontal and vertical tsunami forces acting on the deck are affected by the clearance below the deck and the static friction force acting on the deck is affected by the weight of the deck and the vertical tsunami force. As a result, the interaction between the deck, the horizontal tsunami force, and the vertical tsunami force is essential to assess the tsunami-induced motion of the deck. Furthermore, it is found that the horizontal tsunami force acting on the deck at the onset of the deck motion can be estimated from the horizontal flow velocity at the side of the deck when the deck begins to move by the bore hitting on the side of the deck.

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 The effect of structure geometry on tsunami wave load is investigated by hydraulic model experiment. The results reveal that pilotis configuration characterized by absence of walls at the first story can be effective to reduce the tsunami force. It is because, run-up tsunami can pass easily through the pilotis. Tsunami force acting on pilotis increases when drifting objects infill openings of pilotis. Thus, the application of counter measure for damage due to drifting objects is important. Moreover, it is observed that shock pressure distribution on front of structure is decided by frontal form of building but not rear form. Furthermore, tsunami force acting on building is affected by scale and position of openings. Influence of positioning of openings is important to reduce tsunami force than that of scale.

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 A Flap-gate breakwater is a new type coastal structure which lies down on the seabed usually and rises up as a continuous seawall with its buoyancy. Through previous studies and designs, availability of these structures was confirmed as tsunami/surge and wave protection barriers. Present study verifies fundamental capability of behaviors, characteristics of wave responses and effectiveness of maintenance of both structures by a field experiment. As a result, it was proved that influences of aged deteriorations did not occur and that these systems of operations and supports and processes of maintenance were appropriate.

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 The flap-gate seawall usually lies down on ground surface and rises up in buoyancy against inundation due to tsunamis or storm surges. It needs neither power machineries nor human operations, and perfectly protects a target important area against the inundation. In the Tohoku earthquake tsunamis, serious damages were caused by inundation from mouths of outer walls in several large buildings. The present study verifies both capability of disaster prevention and characteristics of hydrodynamics of the wall-attached type flap-gate in a series of hydraulic model experiments employed in a 50m wave channel. The experimental results demonstrate that the flap-gate type seawalls rise up immediately and prevent the inundation from openings. Moreover, characteristics of wave pressure induced in bore-type tsunamis were evaluated and the data necessary for prototype design was obtained.

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 A lot of breakwaters suffered damage by the great east Japan earthquake tsunami. The present study is, therefore, aimed at investigating the stability of armor units on the harbor side mound of common breakwaters against tsunami overflow. Two-dimensional model test is carried out to investigate the stability of armor units. Furthermore, numerical wave flume "CADMAS-SURF" is carried out to replicate the results of hydraulic model test. As a result, installing a parapet at the front side on the coping is effective against scouring of the harbor side mound by tsunami overflow.

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 In the East Japan Great disaster, a large number of people were dead and some number of persons were still missing, especially by giant tsunami attacks. One of the causes of the disaster was a significant amplification of tsunami height in a ria bay, typically Sanriku District, Tohoku area. In the last fifty years, in order to prevent and minimize the tsunami disaster in Sanriku Dsitrict, tsunami breakwaters have been constructed or under construction at the mouse of ria bays. However, in the last great disaster, almost all tsunami breakwaters were collapsed or partly destroyed. Consequently the disaster level was significantly expanded. In this study, effective layout of tsunami breakwaters at he mouth of ria bay has been exten-sively studied. The concept of a water wave resonator for reducing incoming tsunami waves is introduced. The new type of wave resonator developed in the authors' previous study has been adopted to reduce tsunami heights in the most shore side of a ria bay. The more practical layout of the breakwater deduced from the previous study is also examined.

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 The 2011 off the Pacific coast of Tohoku Earthquake Tsunami caused serious damages to a lot of composite-type breakwaters. The damage probably results from the water pressure acting on a caisson caused by the overflow of tsunami, which is not taken into consideration in the design method. In this study, wave flume experiments to measure the water pressure acting on the caisson caused by overflow of tsunami were conducted. The water pressure acting on the rear of the caisson decreased rapidly under the condition that the tsunami overflowed the crest of the caisson. The rapid decrease in the water pressure probably causes the falling down of the caisson.

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 The sliding distance of sloping top caisson breakwater with wave dissipating blocks was measured by hydraulic experiment. The sliding distance of the breakwater with a sliding safety factor by an irregular wave varied with the deformation in mound around the caisson toe as well as the wave period. This study presents the diagram to estimate the sliding distance of the caisson accumulated during a storm event, the rate of the subsided wave dissipating blocks, and the rate of increase in composite wave force for sliding the caisson, which are applicable to the operation and management of the breakwater.

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 This study estimates a sliding distance of a caisson covered with blocks considering the effects of coastal climate change, such as changes in the sea level, storm surge, and wave height. The sliding distance increases in 100-350 % influenced by the change of those factors at the end of 21^st century, depending on the condition of breakwater, compared to that in the present climate condition. The climate change effects on a sliding distance and a necessity width depend on not only the assumed wave height but also the wave height to water depth ratio. The climate change effects become more significant especially for a breakwater installed in a deep water.

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 In numerical analyses using particle methods, reappearence of wave dissipation effect has been realized through some methods as to duplicate 3-dimensional configuration of wave dissipation blocks accurately or to assume artificial forces. On the other hand, a concise model not to require high spatial grid resolution or complex presumption is necessary from the practical viewpoint. A simplified model of wave dissipation blocks in the 2-dimensional SPH method is proposed in this study. This paper aims to confirm the dupulicability of the model for permeabilities of wave dissipation blocks and wave forces exerting on the seawall behind the blocks in comparison with those obtained from the previous studies.
 Wave dissipation blocks are simply modelized as to provide total permeability appropriately by arraying some little square or triangle structures. Wave transmission coefficients of block mound breakwaters and wave forces exerting on seawalls with wave dissipation blocks by the simulation agree with those derived from the design formulae under the condition of no wave overtopping, which verifies the fine applicability of our model.

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 Evaluation of deformation is important for the performance-based design of caisson type composite breakwaters. However, evaluation method of deformation except for sliding failure mode has not been established yet.
 This paper presents a simple estimation method of deformation of breakwaters of the hydraulic model experiment results. Authors applied the regression analysis using a past hydraulic model experiment results and proposed a simple estimation equations for penetration angle, apparent friction coefficient, and rotation angle of caisson. It was shown that estimated deformation of breakwaters by the proposed method is in good agreement with that by the past hydraulic model experiment result.

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 This study discusses the influence of various conditions on the target safety level of composite break-waters in view of life cycle cost. Target safety levels of two ports corresponding to minimum life cycle cost differ considerably although the influence of tail length parameter and damage loss cost were small. Wave breaking condition was the governing condition on target safety levels within the scope of this study.

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