This paper presents a method of utilizing 3D data for wave-dissipating works aiming for more efficient and advanced design and construction. In the design phase, by calculating the required quantity of the wave-dissipating blocks from the volume directly obtained from the 3D data, the time required for the work is remarkably shortened. It is also possible to calculate required quantity of the blocks considering the engagement with the existing blocks by utilizing the 3D printer. In the construction phase, by using an installation system which guides the position of the blocks based on the 3D data created beforehand, the operation time of the crane is shortened. In addition, a method to optimally arrange the block shape 3D data into the point cloud is developed. The method was verified that it can create a 3D model including the position information of individual blocks in a short time with high accuracy. By utilizing this method, further improvement in efficiency of design and construction of wave-dissipating works can be expected.

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 In the midst of the increasing Port Structures that have crossed the in-service period of 50 years after construction, there is also deterioration in the number of divers carrying out the underwater investigation. In future, it is essential to develop a technique capable of carrying out wider area investigation in a short time as an alternative of current method of steady inspection of port structures. In order to improve the inspection efficiency of investigation while using surveying equipment and the divers, the technology of real-time surveying equipment becomes indispensable.
 In this paper, revetment surveying experiment was carried out with the Real-time Underwater Sonar capable of visualizing underwater in real-time and the results have been compared with the actual survey results of the Divers in order to check the measurement accuracy of the Real-time Underwater sonar and to confirm the investigation results based on the check points for substitution of items as mentioned in the Guidelines on Inspection and Diagnosis for Port Structures and reported.

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 This paper introduces the development status of sensor monitoring technique which is making an attempt to innovate as a supplementary tool of the inspection and diagnosis for piers. A pier is composed of a number of metal and RC members. The authors developed the support system for providing port managers with “the continuing collected data from various sensors placed in and/or on the members for evaluating the deterioration progress” and “the advice of professional engineers based on the sensor information” simultaneously by using internet technology. In addition, the effectiveness of this support system was examined by applying a long term sensor monitoring to a real pier or specimens exposed under marine environment. As a result, it could be proven that sensor monitoring was quite effective in the early detection of deterioration. However, it was considered that the professional engineers' participation with much knowledge of the sensor's characteristics and the deterioration of piers was very important for the appreciation of sensor information since the variation of temperatures etc. influences data from the sensors. Moreover the use of this system for unifying the management of sensor information was very useful for the port managers and the professional engineers to perform the preventive maintenance of piers.

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 By the utilization of NSR (Northern Sea Route), more efficient logistics service might be provided because the route will shorten sea transport distance between Europe and Asia by 40%.
 Regarding container transport, an intermediate service between the current sea transport via Suez and air transport will be possible. In this paper firstly, service levels of such service are examined by the actual vessel sailing record and other cost estimation. Then future use and benefits of container transport via NSR are examined from shippers' point of view, focusing on the effects brought by the shorter transit times.

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 Relationship between ship speed along the Northern Sea Route and sea ice condition is analyzed by implementing Ice Index. Ship speed is detected by satellite AIS. Ice Index along the actual ship track is calculated from sea ice concentration and thickness, which is derived from the data assimilation system TOPAZ4. The ships sailed independently until Ice Index decreases to be 15, then they sailed under ice-breaker assistance. Navigable speed reached 10~12knots under icebreaker assistance until the Ice Index decrease to -10, then it tends to decrease with decrease of Ice Index.

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 A block mound seawall, constructed on a reef that follows a steep slope of 1/7 at K-Port in M-Island, was strongly damaged by storm waves in 2009. Most wave dissipating blocks were scattered by the action of plunging breaking waves, and the apron behind the seawall was collapsed by the overtopping waves. Hydraulic model tests using random waves were conducted with the model scale of 1/50 to reproduce the damage of the block mound seawall. The wave overtopping flow rate at the site of the damage was found to be more than 10^-2 m³/m/s, which is the stability limit of port facilities. The relationship between the number of wave actions and the block damage ratio on the reef was discussed based on the results of block stability tests, and the correction factor for Hudson's formula was newly proposed for several reef width conditions. In order to decrease the wave overtopping flow rate, it is necessary to raise the upright section of the seawall by 2 meters. It was also shown that the present block size of 20 tons was insufficient, and the necessary block size was 80 tons.

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 Damages due to wave overtopping occur frequently under strong wind conditions. On the other hand, parameters such as wind speed and wind direction are not included in a seawall design. In order to promote a highly integrated land use on coastal areas, a seawall design method that includes wind parameters should be developed. This study investigated the effect of wind speed on each individual wave overtopping that was generated by waves in an irregular wave train. Three types of seawall, upright seawall, wave dissipating type seawall and flared type seawall, were tested in a series of hydraulic experiments that were conducted with two-dimensional wave tank that had a wind blowing tunnel. The volume of water in each individual wave overtopping tended to increase with wind speed. The characteristic of this increasing tendency differed depending on the seawall type and wave condition. Furthermore, this study presented an equation to estimate the ratio of wave overtopping quantity at windy condition to the quantity at no wind condition.

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 A coastal area in Hokkaido has damage due to wave overtopping during the winter season. In some regions, a protect fence for wave overtopping is temporarily installed. Although such preventative measures have been taken, damages due to wave overtopping have continued to occur. As a result, permanent measures against wave overtopping must be realized as soon as possible. This study was discussed on the characteristics of wave overtopping with shape condition of wave dissipating structure by using numerical analysis. Although wave dissipating structures are effective in reducing the wave overtopping rate, it may increase the wave run-up height, depending on the particular wave conditions.

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 In coastal construction, we have developed a wave absorbing breakwater using buttress in order to secure a desired work space with reduced wave height and secure a stage of heavy machinery etc. to be used for the work space on the sea. It is an earth retaining structure that buried a buttress which is an L-Type wall structure in the rubble mound breakwater, and stabilized against sliding and overturning by the weight and frictional resistance of the rubble stone. In order to contribute to the design of this wave absorbing breakwater using buttress, a hydraulic model test was carried out.
 As a result, we clarified the estimation method of the wave force and the wave overtopping rate.

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 Further maintenance should be conducted for pier due to its vulnerability towards chloride induced deterioration. However, research for residual structural performance and seismic performance of corroded pier is still limited. Since significant cost and time is needed for regular detailed survey to evaluate the residual structural performance of corroded pier, relatively simple evaluation method becomes necessary, especially for private businesses. In this research, load tests for specimens with different deterioration degrees are conducted, relationship between deterioration degree and residual structural performance is clarified. Introducing the results of the tests to versatile structural analysis software, simple evaluation method of residual structural performance is proposed. By reflecting the judgment result of deterioration degrees of a real corroded pier to structural analysis model, seismic damage area and level could be relatively easily and quantitatively shown.

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 It is not realistic to carry out preventive maintenance repair simultaneously for all coastal revetments which are deteriorated. Therefore, it is necessary to set priorities of countermeasures and conduct inspection and repair systematically. In this research, we classified the deterioration confirmed in the periodical inspection conducted in Nagasaki Prefecture. In addition, we examined the priority of maintenance management and selected preventive maintenance for each classification. The maintenance management policy was set in consideration of the possibility of performance degradation of the structure in the future based on the deterioration chain concept.

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 Structural performance and durability performance of the structure strongly depends on corrosion of the reinforcing bars and corrosion reduction amount. Normally, deterioration diagnosis is made visually. If it is possible to estimate the corrosion amount of the reinforcing bars from the cracks on the concrete surface, it is possible to perform advanced maintenance management. In this research we have adopted a damage model based on fracture mechanics developed in recent years. Simulation of crack propagation of concrete due to corrosion expansion of deformed reinforcement and round steel muscle by finite element scheme which can reproduce fine crack growth of concrete will be carried out and the influence of corrosion expansion of reinforcing bar on crack width will be examined.

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 The progress of the chloride induced deterioration in the superstructure of an open-type wharf is not homogeneous. The chloride ion penetration in a slab of the superstructure of an open-type wharf is also not homogeneous. It is important to reveal the influence factors on heterogeneous distribution of chloride ion penetration in order to discuss where is the critical inspection points or areas in an open-type wharf.
 The aim of this study is to reveal the factors underlying heterogeneous chloride ion penetration into concrete. The chloride ion contents of two slabs obtained from an open-type wharf that was about 30 years old were measured. The average chloride ion contents of each measurement depth from the surface of concrete in two slabs differed greatly. From the distributions of chloride ion content in each measurement depth in two slabs, it was found that the chloride ion contents at the land side of each slab was relatively higher than that at the middle and sea-side of the slabs.
 In conclusion, it was found that the distribution of the chloride ion penetration was affected by factors including the location of the slab, the environmental conditions such as the sea level, and the other structural members surrounding the slab.

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 In the near future, it is expected that the number of decrepit fishing port facilities will be increasing. So far, simple investigations by visual checks are used as a major diagnosis method for fishing port facilities, however, visual checks are considered to be time-consuming and cost-ineffective. Also, the accuracy of visual checks is highly dependent on the judgements made by respective technicians.
 In this study, we used the measurement technique deploying the input points and measurement points face-to-face to understand the inner defects of fishing port facilities and examined the availability for soundness diagnosis. In the laboratory experiment, we prepared specimens with inner defects and measured elastic waves in both sound and unsound parts of the specimens. The results showed that the elastic wave velocity and power transmission ratio significantly changed with or without inner defects. We confirmed that inner defects of the specimens were detectable at the intersection when the elastic wave velocity was 4,400m/s and the power transmission ratio was 10.0dB. We also confirmed that the applicability of the method based on the results of the on-site experiment using the same method as the laboratory experiment.

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 In sea areas covered with ice where active sea ice movement is seen, the degradation and deterioration of marine and coastal structures of concrete has been caused by freeze and thaw, salt damage and ice abrasion. So far, although the test methods of the ice abrasion on concrete have been developed, such methods have had common faults.
 For instance, one problem is that thin ice film grows gradually on the concrete surface to inhibit further abrasion of the concrete. For this reason, it was difficult to conduct an abrasion test between ice and concrete for a long period.
 In this study, we developed a new method of the abrasion test under water to prevent ice film from forming on the concrete surface. We used flouorinert as antifreeze, which has a freezing point of -127 deg. and is considered harmless in the concrete, in order to make it possible to perform the test under water. As results under various test conditions, we confirmed that the test method using by flourinert could prevent ice film from forming on the concrete surface and made it possible to conduct the ice abrasion test for a long time.

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 After rust layer at the surface of corroded steel is removed due to sea ice action in winter time, the bare mild steel is appeared. This phenomenon, which is repeated every winter time, subsequently leads to promotion of wear due to increase of corrosion. Damage to training levees made of steel-sheet-pile-type seawalls on the Sea of Okhotsk occurred earlier than expected, since larger wear rate of steel structure had not been considered in their design. In the paper, a simple method is proposed to estimate wear thickness depending on elapsed year through wear rate in steady (mild) wear region obtained by sliding wear tests. Taking this wear thickness as the additional thickness to original steel wall for expected life time of structure will lead to rational countermeasure as a sacrificial steel wall.

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 To investigate the performance of steel with a heavy-duty coating (polyurethane) against sea ice friction as an anticorrosive measure, a sliding wear test and an exposure test for the material in an ice-covered area were performed to reveal the characteristics of wear mechanisms and the wear rates, and to give some suggestions from a practical point of view. In the sliding wear test, ice caused severe adhesive wear of the resin coating (TPU) and a wear rate one order of magnitude greater than the abrasive wear rate of carbon steel; however, ice containing particles caused even more severe abrasive wear, with a rate that was a few times greater than the adhesive wear rate. From the exposure test, it was confirmed that the separation of the coating progressed from the edge to reach greater deterioration in the fourth year. It was concluded that the application of such a heavy-duty coating, which has been used under normal sea areas, to ice-infested waters would be inappropriate, otherwise it requires special care and proper management for its application in ice-infested waters where active sea ice movement is seen.

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 Simplification and efficiency of diagnosis methods are essential for appropriate management of fishing port facilities. Especially, we should note that visual inspections are not always available for detecting structural inner defects of fishing port facilities such as breakwaters. Submersible surveys are required to detect defects of the invisible parts, however, it is pointed out that submersible surveys are cost-ineffective and dangerous.
 In this study, we examined a natural vibration measurement method for diagnosis of the invisible portion (basements) in fishing port facilities by using a breakwater model. The diagnosis method was examined through comparison of the theoretical and measured values of rocking vibrations (vibrations in vertical and horizontal directions). The results of the laboratory experiment showed that both the theoretical and measured values were almost identical, and natural frequencies decreased when the supporting surface of the basement became smaller. We applied this assumption to the on-site structures and confirmed that the measured natural frequencies were consistent with the theoretical values.

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 The concrete superstructure of piled pier is generally exposed to the severe corrosion environment. In the general periodic inspection, that plays a crucial role in the series of maintenance works of superstructures, the undersides of all concrete members were visually inspected for corrosion of reinforcing bars. Inspectors generally access to the underside by boat, therefore, the tidal and wave conditions have a large influence on performing the visual inspection safely. To ensure the safety and efficiency of inspection works, the authors are working to develop the visual inspection device using semi-submergible-type remotely operated vehicles equipped with upward cameras. This paper reports the demonstration test results of the visual inspection of a superstructure by the developed device. Moreover, the diagnostic imaging support software for a superstructure was proposed to achieve the efficient inspection and diagnosis work.

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 UAV is an effective tool in the surveying of structures after large-scale disasters. For safer UAV manipulation, we developed a technology to manipulate UAV with visible light communication by LED panels on the ground to support GPS autonomous flight and manual radio control generally used.
 In this study, we firstly examined a possibility of applying UAV and the problems for the research in the port and coastal area. And we made a prototype of UAV by visible light communication to carry out indoor tests for flight control. As a result, the flying UAV recognized the signs of LED panel on the ground such as turning, lifting, descending, etc. and successfully carried out specified actions. In addition to reporting the result, this study shows the cause of not detecting the panel, the solution, the methods and effectiveness of inspecting structures and disaster investigation using such technology.

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 As a survey method to promptly and efficiently judge availability of mooring facilities at the time of seismic disaster occurrence, a method of residual displacement measurement using photographed images by unmanned aerial vehicles(UAV) was examined. In the method using the UAV, accuracy varies greatly depending on the conditions such as the type of the UAV and camera, the conditions of flight and photographing and location and shape of the target facility. In this research, for the purpose of confirming the accuracy of the displacement measurement method using UAV and extracting issues during measurement, the verification experiment was performed. In the experiment, as a situation close to the actual measurement condition, quay wall models were installed at a mooring facility, and by moving them, the residual displacement at the time of the earthquake was simulated. When the earthquake is large scale and the movement of the ground reference point due to the displacement of the ground behind the quay wall and the crustal movement are concerned, it turned out that the measurement method using UAV which can utilize Real Time Kinematic positioning is superior.

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 The accident that three children and two adult males who tried to rescue the children died occurred at Jogehama beach in 2014. The beach was known in the around area for the small cusp topography and steep slope. Therefore, the beach was the swimming prohibited area, and they played on the beach when the accident occurred. However, the big wave suddenly run up to the beach, and the children were swept out to sea. Our group reproduced the wave run up condition by the numerical simulation. We used the vertical two dimensional model, CADMAS-SURF2D. In this case, we changed the wave height, the period and the bottom slope. The result was compared with other beaches. According to the results, we considered the safety degree about the wave run up on the beach, and we tried to extract the same beaches that the same phenomenon occurs in Niigata prefecture.

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 Due to noticeable subsidence of ground occurred in the wide area of the Tohoku district caused by the 2011 off the Pacific coast of Tohoku Earthquake, necessary measures including level raising of quay walls were undertaken. Long-lasting post-seismic crustal movement is affecting fishing port facilities: several years after the main shock, quay walls became too high for fishermen due to the increased ground elevation associated with recovery from the crustal movement, thus, quay wall lowering construction followed the level raising construction. During the reconstruction, continuation of fishing was an important issue. One method for resolving the problem was step-by-step recovery of the fishery quay walls, which was effective for areas where immediate ground elevation occurred after the subsidence during the main shock. In order to obtain beneficial knowledge for the next predicted mega subduction-zone earthquake, such as Nankai Trough earthquake, this study carried out hearing survey with local governments and with those concerned with the fishing industry. Special note should be made of the involvement of high accuracy geodetic data (GEONET data) provided by the Geospatial Information Authority of Japan as well as corresponding recovery process of the fishing port facilities in this study.

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 The coastal area of the Sendai coast was suffered expensive damage from the tsunami that followed the Great East Japan Earthquake in March 2011. In the case of a large-scale disaster, monitoring the recovery process over the long term will contribute largely to improving the efficiency of shortening the disaster recovery period and readjustment of the disaster recovery plan. In this study, the recovery and reconstruction process of coastal embankments and reconstruction roads and coastal woods on the Sendai plains were evaluated using high-resolution satellite images of five periods with superior characteristics for time series and high-detailed investigation. In addition, we evaluated the change process of the vegetation environment and the land cover characteristics in the coastal area by the change process of the normalized vegetation index by using high-resolution spectral characteristics. It was considered that this monitoring methods was effectively used from these results to evaluate the long-term and continuous change processes in large-scale disaster.

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 For estimating long-term sea level variation, periodical corrective adjustments by measuring the degree of ground deformation are required which are done by surveyors' levelling from the 1st class benchmark to the levelling spot at the tidal station. However, due to the issues of increasing costs of such manual levelling works and shortage of young surveyors, finding a simpler method of measuring ground deformation has become an urgent issue. In this study, we estimated sea level variation using a GNSS (i.e. global navigation satellite system) survey to grasp the level of ground deformation. At the Port of Mikawa, annual sea level variation was estimated to be -3.20 (mm/year) based on the tide observation record, while the same decreasing tendency was observed at the Ports of Toba, Nagoya and Onizaki which are all located along Ise bay.
 However, due to ground deformation, the GNSS survey shows that the height of the levelling spot at the tidal station at the Port of Mikawa increased by 68.4 mm in 5 years (13.7 mm/year) while the ground elevation estimation using the semi-dynamic correction of the geodetic framework shows that the area of Port of Mikawa rose by 120 mm in 19 years (6.32 mm/year). Based on the magnitude of the ground deformation, the sea level at the Port of Mikawa is estimated to be rising at a rate of 3.12 mm per year.
 Furthermore, the authors proposed a method to control the height of the levelling spot at the tidal station when recovering from the disasters.

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 Installing porous wave barriers at the top of a composite breakwater can be expected as an economical and effective method to realize a resilient breakwater against tsunami by reducing scour due to tsunami overflow. This study clarified the reduction effect of scour and the characteristics of tsunami force acting on a caisson by installing porous barriers by a series of hydraulic model experiments. The test results show that the stability of the armor blocks against tsunami overflow improve according to the height and the porosity of the barriers. From the viewpoint of the scour reduction effect, the barriers should be installed avoiding the vicinity of the rear face of the caisson. On the other hand, from the viewpoint of the tsunami forces acting on the caisson, it is better to place the barriers avoiding the vicinity of the front face of the caisson.

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 Sendai Bay area in Miyagi Prefecture has been seriously damaged by the 2011 Tohoku Earthquake Tsunami, which propagated inland up to about 5km in Sendai Plane. Along the Sendai Bay Coast, there are historical canals such as Teizan Canal, Tona Canal and Kitakami Canal connecting the Abukuma River and the Old Kitakami River mouths with a total length of 49km. It is said that the canals had reduction effect of tsunami disaster during the 2011 devastating tsunami. Hence 2-D numerical simulation has been made in this study to evaluate tsunami mitigation effects of Teizan and Kitakami Canals in expectation of their role as a part of multiple defense system in the Sendai Bay area. Results of numerical simulation show their effectiveness with respect to tsunami energy reduction and tsunami arrival time.

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 For tsunami mitigation, arrangement of multiple tsunami measures structures is very important. The objective of this study is to estimate effect of a tree crown of coastal forest on tsunami flow pattern behind sea-embankment by the hydraulic model experiment.
 In submerged overflow, the flow velocity becomes large at the upper layer of the flow, and the effect of tree crown on tsunami flow becomes large. However, In incomplete overflow, the flow velocity becomes large at the lower layer of the flow, and the effect of tree crown on tsunami flow becomes small.

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 In adaptation to the impact of climate change, knowing the increase in disasters due to sea level rise is important in determining coastal adaptation measures. In this study, as adaptation measures, the tsunami damping effect by combining mangrove forest and embankment, and an increment of tsunami disaster caused by rising sea level for the tsunami which is not related to global warming were arranged by one-dimensional cross section calculation. As a result, the increase in disasters due to sea level rise showed a case where the increase range increased when mangrove forest and levee were combined. In the calculation using one-dimensional numerical model, it shows that appropriate vegetation and embankment placement and scale make it effective to delay the arrival of the tsunami regardless of the distance from the target point. Furthermore, it suggested the possibility of a best mix that the delay effect will reduce the construction volume of evacuation facilities.

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 It is expected that coastal forest reduce tsunami height and velocity and mitigate its acting force on a structure behind the forest, but the characteristic of reducing effect depending on tsunami form, e.g. wavelength and steepness, is not revealed. In this study, hydraulic experiments were conducted to examine the effect of coastal forest, which was modeled with simple cylinders, concerning the passing inundation tsunami and its force acting on the structure behind. And 3D-numerical simulation, which becomes practical to estimate tsunami force by improving computing devices, was applied to reproduce the experimental results to discuss its applicability.
 As a result, it was confirmed that the reducing effect on inundation height is remarkable during early phase of run-up tsunami because of the large velocity, and the effect was small in a case of long period tsunami because the velocity when the maximum inundation height occurs is small. In addition, numerical simulation accurately reproduced the reducing effect by coastal forest and its availability was confirmed.

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 After the Great East Japan Earthquake, research and development on the massive tsunami countermeasures technology with high resilience is under way. The massive tsunami continued for several tens of minutes, and the water level and flow velocity changed over time complicatedly. For this reason, it has been difficult to make a massive tsunami in the experimental flume. The authors are developing a new tsunami generator using the electric sluice gate that can control the flow rate continuously. In this research, we tried reproducing the tsunami waveform of the Great East Japan Earthquake and control the dispersion wave by controlling the opening and closing speed of the electric gate.

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 If the earthquake occurs, the tsunami information will be offered by Japan Meteorological Agency via TV or the internet. However, for rapid evacuation, it is better that the every people can judge whether the tsunami will be occurred or not. Furthermore it is better that the people at coastal area can know the variation amount of the sea surface at the coastal area when the tsunami will occur. We remake the judge criteria whether the tsunami will be occurred or not when the earthquake will occur. In this case, we thought the relationship between the seismic energy and the hypocenter depth. Secondary, the response rate between the earthquake ground and the sea surface at the seismic center was calculated by the horizontal numerical simulation. This result were compared with the hydraulic experiment. According to the result, the response rate in the 100km scale was set as 50 % to 60 %. Furthermore, the sea surface change from the seismic center to the coastal area was calculated by the Green's law method. This result was compared by the CADMAS-SURF2D. Finally, we make the sea surface variation amount map around Niigata prefecture by the tsunami. In this case, the earthquake magnitude was set as 7.8. According to the result, the variation amount of the sea surface at Niigata city will be less than 3 m.

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 The distribution of tsunami height is an important quantity to estimate a magnitude of the earthquake and tsunami, and to predict a damage level. The present study proves that the distribution of tsunami height near the shoreline follows a log-normal distribution by wave deformations due to shoaling, refraction, diffraction, bottom friction and wave breaking on a complex bottom topography. A new tsunami height similarity index is proposed to estimate the location of earthquake together with the Aida's κ value. The moment magnitude of an earthquake in the Sea of Japan was determined using the relationship between tsunami and moment magnitude and average logarithmic values of the ratio of tsunami height.

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 Retrogressive landslides starting from the lower part of the slope were focused and the relationship between the number of divisions of the landslide and the difference in movement start time and the generated tsunami water level were analyzed. In addition, the sensitivity of the tsunami water level to the depth of water and landslide peak speed was also analyzed. For the analysis, a nonlinear longwave model based on a finite volume Godunov-type scheme was used, and the ocean bottom fluctuation at each time was taken into consideration. Regarding the relatively small landslide with a total length of 1 km, we evaluated the influence of retrogression, mainly by extension of the tsunami wavelength and reduction of the amplitud, and the tsunami level due to the rigid body motion of single block was the largest, but it was found that the time lag causes amplification of the water level of about 10% on the opposite direction of landslide movement. This is due to the superimposition of the tsunami generated by individual small blocks. Amplification due to the retrogression can be estimated according to the water depth, and it can be reflected in the estimation of tsunami caused by individual landslide.

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 At the heavy rain in Kyushu in northern Kyushu in July 2017, a large number of reservoirs were damaged, and they were destroyed. Even in the sea area, lakes and reservoirs, waves are generated by sediment inflow due to slope collapse. The wave may cause damage to surrounding structures and people. In this study, we use OpenFOAM to treat sediment as density flow. The validity of the model for the phenomenon due to the influx of earth and sand into the hydrostatic area was examined. We conducted experiments as accuracy verification and reproduced by numerical analysis. OpenFOAM needs reproducibility by tuning with the kinematic viscosity coefficient ν of sediment and density ρ, and the surface tension σ of interfaces related to sediment. From the analysis results, it was possible to grasp the flow velocity distribution around the sediment flow. We were able to grasp the formation process of nose and head at the tip of sediment flow.

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 Maximum wave force induced by a run-up tsunami containing suspended sediment was investigated using a numerical model considering change in fluid density and viscosity due to suspended sediment. Numerical results showed that the maximum tsunami force induced by quasi-steady wave pressure can be evaluated conservatively from that for no suspended sediment and fluid density considering assumed suspended sediment concentration in many cases. In contrast, it was found that an increase in the maximum tsunami force induced by surge-front wave pressure tended to be larger than that in fluid density due to suspended sediment. This suggested that investigation for tsunamis containing suspended sediment would be essential in assessing the maximum tsunami force induced by surge-front wave pressure.

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 Hydraulic experiments were conducted in order to analyze the influence of coastal sea area with narrow pass on sediment transport and bottom topography change under tsunami action. Numerical simulations were also carried out for confirming the validity of a depth-averaged numerical model.
 The experimental results revealed that erosion volume is affected by the width of the narrow pass. It was also found that local erosion depth is strongly influenced by the shape of the narrow pass. The depth-averaged sediment transport numerical model is said to be able to reproduce the laboratory experiment appropriately in the case that local erosion hardly occurs.

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 When a tsunami acts on a breakwater, seepage flow occurs in the foundation mound due to the water level difference inside and outside the port of the breakwater. According to previous studies, the seepage flow reduces the bearing capacity of the foundation mound. In a general breakwater, decrease of bearing capacity is considered to be almost proportional to water level difference inside and outside the port, and be reduced by 20% at the water level difference of 10 m. However, the mechanism of the decrease in the bearing capacity and the influence of seepage flow on breakwater with reinforcing embankment have not been sufficiently revealed. Therefore, in this study, numerical calculations that can consider seepage flow in the foundation mound were performed for various types of breakwater, and the decrease in the bearing capacity was quantitatively evaluated. In addition, by considering the mechanism of the bearing capacity, in the case of a tsunami, it was shown that the influence of tsunami seepage flow should be considered and it showed that reinforcing embankment is effective as a countermeasure.

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 Characteristics of tsunami running up into rivers were discussed through analysis of observed tsunami profiles and numerical simulation. Tsunami form of the 2011 Great East Japan Earthquake Tsunami along Kitakami River, which was observed at Fukuchi Station (8.6 km from the river mouth) was compared with tsunami profiles observed along the coast and also on the ocean. River run-up of the 2011 tsunami along Kitakami River was simulated with Shallow-Water Equation model for more understanding on the characteristics of the observed tsunami form along the river.
 On the ocean and also along the coast, the first wave was the highest, while the maximum water level at Fukuchi Station was recorded during the third wave. The wave height of the first wave rapidly got smaller with running up along the river due to the overflow of river embankments. On the other hand, the following waves ran up with the raised water level by the first wave to have less reduction of the wave height, resulting in the higher water level in upstream area than the first wave.
 Due to the centrifugal force, the water level along the outer side of the curve of the river got higher to cause higher load and more overflow against the river embankment. Theoretical formula to calculate water surface slope based on the balance between pressure gradient and the centrifugal force shows good agreement with the simulated water surface slope around the breaching point of the river embankment of Kitakami River.

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 To precast superstructure of port piers, the connection method for precast concrete with steel pipe piles is required at the rigidity condition which is based on port design criteria. As a new method, sleeve tube with larger diameter than steel pipe is buried into superstructure in advance, and steel pipe is inserted into it during erection with the gap filled with grouting, named “sleeve tube type” has been proposed. In this study, authors conducted a three-dimensional nonlinear finite element analysis on cyclic loading experiment of “sleeve tube type”, examined the effect of shear key, the insert length of steel pipe pile into sleeve tube, and discussed the stress transmission mechanism of the connection.

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 Anchored sheet pile is often employed for shallow water quay walls of fishing port facilities in Japan. these facilities are often designed with a conventional static analysis method and regional seismic coefficient. However, safety and serviceability of these facilities is not examined in a seismic analysis. In this study, two-dimensional earthquake response analysis is carried out with the model of typical anchored quay wall of fishing port. The bending moment of wall and anchor, the tension of the tie rod and the deformation of those are investigated. As a result, any components of the facility hardly yield under the action of seismic vibration corresponding to the intensity of Level-1 earthquake. The result showed that recently developed seismic coefficient, which is reflecting frequency response characteristics and allowable deformation amount of structures, is applicable to anchored sheet pile at shallow water quay walls in fishing ports.

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 Natural period of open-type wharves with vertical pile is estimated from a spring constant of wharves calculated by frame analysis according to 2007 technical standards for port facility. But to this method it is pointed out that the calculation result deviates from the 2D-Seismic Response Analysis. In addition, this method is not affected by seismic motion, although natural period of wharves should be affected by strength of seismic motion because soil stiffness around piles decrease by seismic motion.
 In this study, we evaluate the natural period and decreasing rate of soil stiffness by Seismic Response Analysis, and organize the relationship between them. Thereby, we correct the current method to be consistent with the 2D-Seismic Response Analysis.

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 Holes and section defects were caused on the steel sheet pile wall near the low tide surface due to concentrating corrosion. There was concern about the collapse of the apron and a decrease in the sheet pile capacity. It is an urgent task to recover the mechanical performance of degraded parts. In this study, experiments and analysis were carried out in order to confirm capacity performance and the effectiveness of the joining by the method of patch plate.As a result, the stiffness and capacity of members after repair were able to obtain a great improvement effect compared with the case without repair. Moreover, through verification by numerical analysis, it was confirmed that the performance by the rib reinforcing to the patch plate was greater than when the thickness of the patch plate was increased.

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 In this study, 1/55.8-scale hydraulic experiments modelled on 1/4-scale large experiments in Suzuki et al. (2002) were carried out as a first step to organize what should be considered in determining the sizes of mound gravel and seabed sand for composite breakwaters covered with wave dissipating blocks. Experimental results showed that sand deposition was formed in the seaward part of the mound unlike the 1/4-scale large experiments and 1/16-scale medium-size experiments. This suggested that it would be important to pay attention to the type of sediment transport based on settling velocity, the size ratio of mound gravel to seabed sand, and the permeability of the mound based on hydraulic conductivity.

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 The practicality of two-layered geotechnical filter for erosion protection in coastal facilities was investigated. Fist, the performance of geotechnical filters with a narrow grain size distribution was experimentally investigated and verified in view of the existing standard. Secondly, the mechanical stability of two-layered geotechnical filter was examined against earthquakes and traffic loads. Thirdly, the process of the internal erosion, cavity formation and collapse of reclaimed sand was observed by physical modelling tests and the effectiveness of the proposed geotechnical filter as the preventive measures was confirmed.

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 It is a problem that sediment flows out by rolling up the bottom mud. Based on the results of previous studies, the effectiveness of superficial solidification technology using enzymes derived from microbial functions has been clarified from the study of Lake Ichkeul in Tunisia. Therefore, in this research, for the purpose of evaluating the applicability of this technology to domestic and shortening the construction period, we examined the effectiveness of the proposed technology by the enzyme catalytic method for domestic surface sediments. In the test, two cases of specimens for long-term construction and short-term construction were prepared. According to the results of the test, it became clear that turbidity suppression by enzyme catalytic method for domestic sediments is possible. In addition, CT imaging revealed that as the thickness of the calcite membrane deposited on the surface layer of the sediment became thicker, the surface strength increased and gaps were formed between the calcite and the bottom mud.

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 One effective countermeasure to prevent salinization in semi-arid lands is capillary barriers (CB), where gravel layers meet sand layers. Dry sand in semi-arid lands easily mixes between gravel particles due to drying and vibration during construction, etc. It is extremely difficult to retain layered ground over the short or long term. The authors clarified that by using crushed shells as a substitute for gravel, it is possible to maintain the CB function as well as preventing the upper sand from mixing into the lower crushed shell layer at the same time. However, when crushed shells are used as a substitute for gravel, since the soil water characteristic curve varies greatly depending on the particle size of the crushed shell, there is the possibility that the salinity (moisture) blocking function of the CB may be significantly impaired. Therefore, in this study, by focusing on the particle diameter of the crushed shells, the influence of fine crushed shell particles of less than 2 mm on preventing salinization was clarified experimentally.

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 When material dredged from a dam reservoir is used for beach nourishment, such an operation is often feared among fishermen, because fine components contained in the material are considered to damage the fishery in coastal sea. To study this issue from the scientific point of view, the characteristics of the materials dredged from the reservoir and those sampled from sandy beach were compared, taking Takataki Dam in the Yoro River basin and Kujukuri Beach as the study areas. Materials were sampled from many points in Takataki Dam reservoir and on Kujukuri Beach, and sieve analysis was carried out. As a result, it was found that the silt content in the material dredged from Takataki Dam was as high as 18.4%, whereas that of the beach in Katagai fishing port was 3.9% at maximum; the content of silty material was five times greater than that on the beach.

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 On the Ichinomiya coast located near the south end of Kujukuri Beach, beach nourishment using 8,800 m³ of sand was carried out in early July, 2017. To investigate the effect of the beach nourishment, field observations were carried out on May 27, 2017 before the nourishment, July 14, immediately after nourishment, July 22 and August 3, 1 and 3 weeks after the nourishment, respectively, to measure the shoreline configuration and beach profiles. Furthermore, sampling of beach material was carried out along with photographing of the beach. Beach changes after the nourishment was calculated using the BG model proposed by Noshi et al. The measured and predicted shoreline changes were in good agreement. Out of the beach nourishment using 8800 m³ of sand, the volume of beach sand increased by 5400 m³, and 61% of sand remained.

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 Miyazaki Coast locates between the Hitotsuse River mouth and the northern side of Miyazaki Port. This beach has been suffering from severe beach erosion due to the shortage of sediment supply from rivers and the change of waves and nearshore currents by the construction of an offshore breakwater at Miyazaki Port. In order to preserve the sandy beach, a beach nourishment project has been implemented since 2008 in combination with the installation of Sand-Packed containers that were placed in front of the dune. A certain volume of nourishment sand has been installed for the sand fill work that covers Sand-Packed containers, and the rest has been dumped off the coast. The purpose of this research is to evaluate the effectiveness of the beach nourishment with using long-term bottom sounding data. This study discussed the effect of the beach nourishment on longshore sandbar evolution. The change of the sand volume in research area was also discussed in this study. Furthermore, the method of Empirical Orthogonal Functions, EOF, was applied to some cross sections in order to describe the spatial and temporal variability of longshore sandbars.

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