Since 1970, the Port and Airport Research Institute (PARI) has been cooperating with the Ports and Harbours Bureau, Ministry of Land, Infrastructure, and Transport, and its associated agencies, on the Nationwide Ocean Wave information network for Port and HArbours (NOWPHAS). This study examined a long-term variability of wave characteristics, such as mean and maximum significant wave, calmness and wave power, around the Japanese coasts using observed wave data. Seasonal and annual average of significant wave period is increasing at almost points around the Japanese coast. The relation between the variation of significant waves and indexes was examined. The relation of correlation between a wave and sea water temperature is the highest.

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  We conducted nationwide survey on damage of coastal dike and revetment which occurred between 1999 and 2009. The results of analysis on 321 damage cases showed that coastal erosion was a major origin of facility damage, and that the number of damaged facilities with gentle seaward-slope was larger than that with upright or steep seaward slope. Major failure patterns of coastal dike and revetment were classified into 13 types.

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  Severe coastal disasters by storm waves have occurred even many breakwaters and seawalls have constructed with progressive researches and techniques of design for structures. For examples, 10 typhoons attacked Japanese coast in 2004 and these storm waves damaged a lot of structures at any harbors and costal lines in Japan. In addition, long period swells categorized as an unexpected wave penetrated to several coasts and overtopped in 2006, 2007 and 2008. Such waves would become high waves on shallow water due to shoaling, especially on a root of submerged cape due to concentration of refracted waves on deeper bathymetry. In this study, these coastal disasters are classified focusing to characteristics of high waves with re-composing a few papers studied on mechanism of damage to each breakwater or seawall in coastal area.

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  Extensive efforts have been made to remediate environment in enclosed bays since 1970s. Nevertheless, water quality standards have not fully achieved, anoxic water and associated mass mortality of fish and benthos have occur several times a year, and decrease of fish catch is ongoing matter. Targets of environmental remediation have been changed time to time. Water quality control, fishing reef and landscape had been major issues in the ocean engineering research since 1970. Issues have been increased diversity on sediment quality, load management, habitat creation.
To clarify updated targets and a strategic planning of studies, a special session on "enclosed bay's environmental remediation techniques" has been organized since the 35th Ocean Engineering Symposium. This paper is a review of the session activities.

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  Recently, the creation of the tidal flat is executed to improve the marine environment in various places as a habitat enhancement. However, it is difficult to obtain a good quality material as ea sand that is appropriate for creation of the benthos habitats. It is expected to implement a new material for the habitat creation such as recycling materials. On the other hand, the function of the dam has degraded by an increase of the accumulated soil. It also becomes a big problem that the removal of the soil accumulated at dam and the disposal of it in Japan.
  This study aims to use the soil accumulated at dam effectively as a material for benthos habitats enhancement on constructed tidal flat. Soil properties, chemical characteristic and acute toxicity had been checked by indoor test. Habitat creation processes had been checked by meso-cosms and the field experiments at onsite. As a result, the soil accumulated at dam has shown good applicability for a material for benthos habitats creation.

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  In order to improve the performance of the water exchange breakwater, an intake type water exchange breakwater consisting of double curtain walls was newly proposed in this study. To enhance both the wave energy dissipation by the breakwater and the water exchange function due to wave motions for the wide range of wave period, a double- curtain walled breakwater with a submerged water channel was adopted. Special considerations have been given to solve the contradictory problem. Typically, on one side, it is required to seek an effective cross section of the breakwater for reducing both the reflected and transmitted waves for extreme wave conditions. However on the other side, the effective cross section for the water exchange through the breakwater for nominal wave conditions is required. It was found out that the double curtain walled breakwater proposed in this study was a possible solution for solving the contradictory problem.

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  Oxygen deficiency in closed waters seems to induce serious problems. The authors have been trying to solve the problem utilizing liquid membranes of bubbles cluster formed by aeration in the h-shaped pipe located near the water surface, which enables to improve DO condition in the water at high efficiency and low energy cost. In this paper experimental results are given for DO improvement of the above system. The oxygen transfer rate N₍₂₀₎ and the efficiency E_P defined as the transfer rate per unit work rate required for aeration are examined for various values of the aeration depth H_A, flow rate of supplied air Q_g, and the height of the pipe H_U. As the results, both N₍₂₀₎ and E_P take high values when H_U is small and H_A is large. Also there is some optimum Q_g for a given diameter of the pipe.

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  In order to identify the relationships between ocean current fields and coral habitat environment in Amitori Bay, Iriomote Island, Japan, water mixing process of tidal flow and river flow are investigated by field survey and numerical analysis. The temperature, salinity, and illumination intensity are observed at several points in the bay during a 2-month period. The field survey indicates that the river water mass of lower temperature and lower salinity is likely to flow selectively into the eastern side of the bay, especially under the conditions of nocturnal low tide and calm weather. Furthermore, an idealized numerical analysis based on the coastal current model is realistically capable of representing the water exchange process between tidal flow and river flow in the bay, and reproduces the asymmetric distributions of the surface salinity as seen in the observations. The remarkable asymmetry is considered to be induced by the complex topographic effects and to affect spatial heterogeneity in the coral habitat distribution in Amitori Bay.

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  This paper presents a summary of the second part of special session "Preservation, Development and Natural Resources Exploitation around Remote Islands" which was held in Kagoshima City on June 24, 2010. Presented topics were concerning nissology versus engineering, island policies for border areas, marine litters at remote islands, port service activity in Amami Island and port construction policy at remote islands in Kagoshima Prefecture. A panel discussion among panelists who made presentations was also conducted with the audiences.

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  Residual currents around submerged asymmetrical structures, known as BaNK blocks, are quantitatively estimated in wave fields. Komatsu et al. (2001) proposed 'BaNK system' in order to cope with beach erosion and shoaling of fairways. The system is a method to control sediment transport using residual currents which are produced by plural submerged asymmetrical structures in a wave field. In this study, three kinds of dimensionless parameters which are the Keulegan-Carpenter number, Reynolds number and structure height relative to water depth are regarded as main dimensionless parameters for producing residual currents. Velocity distributions around half cylinder type BaNK blocks are measured in various wave conditions and structure heights in a wave tank. As a result of this study, the relationships between vertical residual current distributions around asymmetrical structures and the dimensionless parameters are found. Furthermore some empirical formulas are established to calculate residual currents generated by the BaNK system in a wave field.

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  Wind effects on wave overtopping are essential in designing seawalls. However, the relationship between wind and wave overtopping rate has not been clarified quantitatively. A numerical wave flume based on a two-dimensional numerical model `CADMAS-SURF' is proposed in this study so that wave overtopping analysis can be conducted considering wind external force. Moreover, a TimerDoor method, which is a computational method for water particle motion, was improved to represent acceleration motion by wind. The proposed method was validated by comparing with a hydraulic model experiment. As a result, numerical results showed that the wind speed affects wave deformation such as wave breaking and mean water level. Furthermore, the dimensionless wave overtopping rates obtained by the numerical computations were in reasonable agreement with the hydraulic model experimental results. It was found that the proposed method is useful for wave overtopping simulation considering wind effects.

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  In recent years, particle numerical methods which can simulate wave pressure on coastal structures have been developed. Especially, WCSPH method is excellent in repression ability of numerical pressure fluctuation and its light computational load, because the basic equations of WCSPH consider weekly compressible fluid and need not to solve Poisson's equation which generally uses in other particle numerical methods. However, less computation using WCSPH method for coastal structures has been reported and further inspection is required.
  In this study, we compared the results computed by WCSPH method to those of experiments for the permeable detached breakwater which has some slits and sloping top. We confirm that the wave pressure and the surface water elevation simulated by WCSPH method well agree with the experimental results. It turns out that the computing particle size needs less than 1/7.2 for the slit size of the structure to realize accurate calculation.

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  Large-scale submerged breakwater, jetties and nourishment has been constructed as shore protection facilities. The facilities of 1,630m long within the 2,540m overall length have been constructed. A belt-shaped scour is formed behind the submerged breakwater, and fill sand is flow out through the end section of the facilities. The remainder section 910m long will be constructed in the near future. The present study is, therefore, considering the adoption of the submerged breakwater of two rows and the plane configuration of end section of facilities to prevent or reduce the belt-shaped scour and outflow of fill sand at the remainder section. Three-dimensional hydraulic model test and two-dimensional numerical model test were carried out to decide the standard section and the configuration of the end section. As a result, it is confirmed that submerged breakwater of two rows is more effective than conventional submerged breakwater. And the plane configuration of the end section of the facilities is decided.

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  A slit-caisson is known as a typical wave-absorbing-structure with a vertical front face. The design wave force on the slit caisson is usually estimated by the empirical formula, for instance the modified Goda formula. In this study, the perforated wall type caisson consisting of angular members in it's front was adopted as a model caisson. We have carried out the experiment on wave forces on the model caisson very precisely to rationally estimate the design wave forces. Characteristics of local wave force on each member of the model caisson, say wave forces on the front wall etc., were examined experimentally. For the practical design, the similar wave force analysis to the previous method for a slit caisson was also applied to specify the modification coefficient of the wave force given by the Goda formula.

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  A time dependent 2DV numerical model for behavior of flexible curtain structure was proposed, which is composed of two-way coupling of fluid flow calculation by SMAC method and catenary model of curtain structure. The curtain structure is described as a chain of tracers traveling on flow field creating restoring force which is taken into account for flow field calculation. Trials of numerical applicability were made on behavior of curtain structure in uniform flow and sediment dumping driven flow.

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  The rise of sea levels and the increase of wave forces which has been caused by global warming will cause the failure of breakwaters. The ground anchor for reinforcement is proposed as an anti-sliding method of caisson breakwaters. In this study, we conducted hydraulic model experiments with a scale of 1 to 30 model in order to investigate the sliding stability of caisson breakwaters with the ground anchor for reinforcement against wave forces. The results show that the caisson breakwater with the ground anchor for reinforcement increases the sliding resistance and reduces the sliding distance, and the larger the initial tension of the anchor is, the more effective as an anti-sliding method.

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  In this study, static lateral loading tests in a centrifuge for L-shape breakwater subjected to tsunami were conducted in order to discuss the external stability. In case that the foundation was embedded, FE analyses were also performed. As results of tests, the bearing capacity was depended on the condition of the contact surface, the characteristics of ground. In particular it was revealed that the bearing capacity was significantly influenced by the weight of structure and the embedment of the foundation. In addition, the bearing capacity was evaluated with high accuracy by the equation of failure surface proposed in a past study. From FE analyses, it was indicated that the residual strength provided the good agreement with test results. Furthermore it was revealed that the earth pressure around the foundation was generated due to the motions of slip and rotation of the breakwater. In this study, the simple method of evaluation for the stability by assuming the earth pressure was suggested.

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  It is important to know the threshold of the cross-section area of a beach to which a coastal dike and a seawall will come to suffer damage. Therefore, the actual conditions on coastal damage are investigated about 33 beaches in Japan and Thailand. Then, the marginal sizes of the beach required in order that those coastal facilities will not suffer damage to each incident wave are clarified. Moreover, since there are many cases that the fracture mechanism of the dike and the seawall in a sand area or a very shallow area cannot be explained by only the stability calculations of these facilities, scour and suction also need to be taken into consideration. Hence, a practical method of predicting the destruction of the dike or the seawall by using the wave overtopping rate to it and the net effective shearing resistance force in its sucking part is proposed. In addition, the availability of a countermeasure which strengthens the net effective shearing resistance force by using small stones as material of the sucking part is confirmed.

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  Monte Carlo simulation is often used for the evaluation of failure probability of breakwaters in view of cumulative sliding displacement. Although wave distribution characteristic in front of breakwater is often assumed to be constant during the design working life of breakwater, recent study points out that wave height tends to increase according to the cumulative sliding displacement of breakwater. This study aims at evaluating the failure probability of breakwater in view of sliding displacement considering wave height increase according to sliding of breakwater. Failure probability considering wave height increase is compared with that without considering wave height increase.

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  In recent yeas, `permeable' breakwaters have been constructed in closed seas such as inner bays for the improvement in water quality; however, these breakwaters permit high transmitted waves compared with normal breakwaters. This study, therefore, installed the model of the vertical wave-dissipating block breakwater with permeate holes, with a scale ratio of 1/30 and 1/18, in a wave flume and then measured the transmitted flow velocity and wave height at the backward of the breakwater. The effect of the permeate holes in exchange of the water at the forward and backward sides of the breakwater became most significant at LWL. The transmission coefficient at LWL was larger than that at HHWL when wave-overtopping rate was large.

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  Breakwaters have been frequently constructed in Japan as one of countermeasures against coastal disasters, for instance, shore erosions, overtopping waves and so forth. However, breakwaters have been viewed with suspicions that bring about various problems. These problems are water pollution in harbor and impairing scenery. Therefore, a breakwater combining submerged breakwater and horizontal plate was chosen as a permeable breakwater, and the wave effacing effects of the breakwater were researched using transmission coefficient to know degrees of the wave effacing effects of the breakwater in this study. As a result, we found that the wave effacing effects of a breakwater depend on size and position of submerged breakwater and horizontal plate: horizontal plate set at higher level make a breakwater more effective.

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  To introduce the performance design into the decision making problem of the repair or renewal of the damaged armor block on seawall, a performance evaluation system of seawall with the accumulative damage of armor is necessitated. In this study, numerical experiments and model tests are conducted to investigate the reflection coefficient of the seawall under condition of the damage progression of armor blocks on crown and slope of seawall. The regressive prediction properties between the reflection coefficient and the damage parameter could not be recognized from those results. The performance evaluation system is developed using a neural network system, which evaluates the causal relation of the reflection coefficient and the accumulative damage parameter. The neural network with a three-layer calibrated by the numerical experiments can predict the reflection coefficient of seawall under the damage progression of armor layer within about 10% errors.

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  A series of laboratory experiment was carried out in order to examine the effect of wave-dissipating section on wave reflection characteristics of a vertical caisson covered with artificial blocks. Based on the experimental results for regular wave, two simple estimation equations of reflection coefficient were derived. One equation was represented as a function of wave steepness and relative wave height. The other was represented as a function of offshore wave length, the length of the section of wave-dissipating blocks which still water surface crossed, and water depth.

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  Evaluation of the amount of the deformation is necessary for the performance-based design of caisson type composite breakwaters. However, the evaluation method of the deformation except for the sliding failure mode has not been established yet.
  In this study, authors obtained a past hydraulic model experiment result and discussed the deformation characteristic of breakwaters. As a result, it was shown that the deformation of breakwaters is not as simple as mere sliding but is accompanied by the deformation in the rubble mound even in the range of small deformation. Difference of the penetration angle of the edge of caisson into the rubble mound is discussed.

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  In this study, the dynamic behavior of a floating panel, which is installed in front of an upright seawall for wave overtopping reduction, was numerically investigated by utilizing a multiphase flow model `DOLPHIN-3D' with solid-gas-liquid phase interaction. The validity of the model was confirmed through the comparison between the numerical results and experimental ones in terms of the water surface elevation in front of the seawall and the floating panel motion. A good agreement between the numerical results and experimental ones revealed that the model is capable of reproducing the interaction of waves and a floating body with high accuracy. A POV-Ray interface system was also developed as a three-dimensional computer graphics system which makes it easy to understand wave-structure interaction phenomena.

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  In recent years, the floating facilities for the ocean space utilization such as the marine disaster prevention base and the floating restaurant are planned and some of those facilities are actually built. Most of these facilities are the pontoon type floating structure, and the mooring system is a mooring dolphin. In the design of such facilities, the forecast of the movement of the pontoon type floating structure supported by the mooring dolphin is important. In this research, the 3D-MPS method is applied, and the solitary wave and the bore like wave are applied as an assumed tsunami. The heaving motion on floating body in the tsunami is paid to attention, and it reports on the result of examining the detaching from mooring dolphin of floating body.

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  In this study, experiments were conducted on the effects of a container drifted by wind, wind-driven current and wave of a wind-wave channel. The channel is 28.5 m in length, 1.3 m in height and 1.5 m in width. The wind blown into the channel drives the wind-driven current and wave. In the case that the blower operated at 300 rpm, the kinematic eddy viscosity K_Z was measured as 3.46 cm²/s at the fetch x=18 m and 0.475 m above the water surface.
  The container model is 1/20 scale of 40 feet container. At the middle of the channel, the container model is floated on the surface of the water and is stilled at its initial position by a rigid steel base. The container model is forced by wind-drag, wind-wave and drag of the wind-driven current. The drag force and force of wind driven current acted on the container model were estimated by calculation in balance of the forces. The result is compared to the drag force coefficient and coefficient of force of wind driven current proposed by the previous researches.

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  Interaction of surface/internal waves with a floating flexible structure has been numerically simulated using a set of nonlinear equations derived through vertical integration in each fluid layer to satisfy the nonlinear boundary conditions on the surface, interface, and seabed. Calculation results of surface displacements are compared with the existing experimental data, where a tsunami in terms of a solitary wave propagates across an area with a floating thin-plate. Surface and internal waves due to a point load moving on a floating thin-plate are also simulated. The wave height of the surface or internal mode is amplified when the moving velocity of point load is equal to the surface or internal wave celerity, respectively, in shallow water.

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  Wind forces acting on a ship that harbors behind a big building is studied experimentally using an open channel instead of a wind tunnel. For the purpose of safety mooring, the effect of this wind force must be investigated sufficiently. The flow profile of 1/7 law are made in a channel by means of roughness set on floor. Then, a ship and a building of a fence or a warehouse are set in a flow. A ship is allowed sway only.
  Measurements show the following. The length of regurgitation area of a wake of fence is about double of that of a warehouse. When the position of ship is near the building behind, time-averaged wind forces on a ship are pulling forces and when a ship leaves from a building, wind forces change to pushing forces. As the distance between a ship and a building becomes large, time-averaged wind forces become large and fluctuating wind loads become large as well as ship motions do. In addition, in case of a fence, pushing forces of wind on a moored ship is found to be larger a little than on a ship fixed.

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  The wave power generation system which consists of wire(s), float(s), counterweight(s), driving pulley and ratchet mechanism is set on a Curtain-Wall-Type Breakwater at Shiranui Bay in the Yatsushiro Sea. The device can take advantage of the existing onshore or offshore structures reducing the installation cost significantly. Next, since all the mechanical and electrical components except the float and the counterweight are set well above the water level, supervision and maintenance are convenient.
  In this paper, several examinations for setting the device are introduced. Firstly, the energy gain, the maximum wire tension on the float side, and the maximum torque that the driving pulley receives from the generator in anticlockwise direction are evaluated from the mechanical dynamics model for stable operation of the device. After satisfactory completion of the setup, the device is brought into operation. This paper presents the sea trial results of the electrical power output.

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  The application of a constant torque resistance is proposed. The effect of this resistance in addition to that proportional to the angular velocity of the rotation of the driving pulley on various physical quantities of the floatcounterweight wave energy converter has been examined. The main objective of this research is to keep the device stationary in small-amplitude waves frequently present in the real sea condition.

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  In order to develop an efficient water turbine for extracting tidal current energy at Kurushima Strait in Imabari, Japan, three different types of turbine, including a Darrieus Turbine and a Savonius Turbine, have been examined experimentally. In this study, considering the multi directional streaming of tidal current at Kurushima Strait, the vertical axis turbine was adopted as a possible energy extraction device. An additional current controlling device was newly proposed to power up the extraction efficiency of the vertical axis turbine. It was found out that the additional current controlling device is very useful to increase the efficiency of the vertical turbine, typically by about three times. For the practical design of vertical axis turbine at Kurushima Strait, tidal current forces and wave forces on the vertical axis turbine were experimentally examined.

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  The Kurushima Straits is known as a sea area where the tidal current is very swift from old days, and is a dangerous place for the marine navigation. Power generation from tidal flow is noticed as one of the ocean energy utilization. In this research, abundance of the tidal current energy in the sea area around the Shimanami Sea Road including the Kurushima Straits was shown based on the 3-D numerical simulation result. We also indicated the representative sea area where suitable for the construction of the power generation facilities considering tidal current power map and submarine topography.

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  This paper discussed the results of field tests conducted using a wind turbine installed at a plant located in the Tokyo Bay area. Special emphasis will be given to the examination of wind speed and the properties of power output as well as the properties of wind turbulence in strong wind conditions. Additionally, we discussed the feasibility and challenges of using medium-sized wind turbines for stand-alone power generation at commercial ports and fishing ports, based on surveys conducted in coastal areas of Hokkaido along the Sea of Japan.

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  Two-dimensional earthquake response analysis is the standard checking method for seismic performance of open-type wharves against Level-two earthquake ground motion. As iterative calculation is necessary until the appropriate wharf profile is obtained, it is very important to assume an adequate initial wharf profile before conducting the two-dimensional earthquake response analysis. This study proposes the optimal setting method of initial wharf profile for two-dimensional earthquake response analysis in the case that the influence of the bending moment of piles generated by the ground deformation is large.

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  The study follows the investigation of the structure of the pile-supported wave absorbing breakwater with a low crown height, reported in 2009. In the present paper, wave scour around the structure is studied. The investigation was performed by movable-bed models. The equilibrium scour depth was larger than that of piles and the maximum scour was generated at offshore pile near the gap of the structure where the velocity of fluid was very high due to the contraction. Normalized maximum scour depth by incident wave height was in inverse proportion to Shields number. Also, the morphology in front of the structure showed as N-type scour which occurs in standing waves region. Moreover, a countermeasure against local scour was proposed and the validity was verified by hydraulic tests.

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  This paper presents a fundamental study to establish the evaluation method of seismic performance of slope-type revetment against Level-one earthquake ground motion. As it was found that settlement is the governing failure mode of slope-type revetment, we proposed a method using one-dimensional earthquake response analysis loading initial vertical stress of soil layers estimated by elastic theory. Calculation accuracy of the proposed method was discussed in comparison with the result of two-dimensional earthquake response analyses. The proposed method led to the vertical displacement corresponding to that of two-dimensional earthquake response analysis though it is underestimation.

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  The present study understands the behavior of the foot protection concrete block of the plunging breaker on the steep coast of bottom slope 1/5 through the hydraulic model experiment and we propose the method of calculating the required mass of the foot protection concrete block of the plunging breaker. At first, we confirmed that the movement and scattering of the block is triggered by sliding by the wave force. The next, we calculated hydraulic quantity and evaluated stability for the sliding of the block, in the CADMAS-SURF. In the study, we show that the required mass for stability of the block is calculated with good precision in the CADMAS-SURF.

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  The damage of armor blocks occasionally occurs at the toe of a mound foundation of a breakwater although the block weight is larger than the one calculated by the Hudson's formula. This paper aims to elucidate the factors that influence on the stability of armor blocks at the toe of the mound foundation by conducting 3D hydraulic model experiments with field topography. The 3D experimental results revealed that the change of flow induced by the existence of the armor block has a great effect on the stability of the block in the same way as the previous 2D experimental results. The incident wave angle and a tidal level was also found to affect the block stability.

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  A floating breakwater has various wave-dissipation mechanisms such as reflection, wave breaking of the incident wave, resonance of radiation wave due to motions of floating body, vortex formation and shedding around the structure. The understanding of these fundamental wave dissipation mechanisms is essential in designing a new-type floating breakwater. In this study, basic wave-control performances for rectangular and circular floating bodies, which are anchored to the bottom with inclined-tension mooring line, were investigated using experimental models. Furthermore, the motions of floating body and flow fields were examined through image analysis. Experimental results show that the motions of floating body and flow fields greatly depend on the geometry of a floating breakwater and its crown depth, and they are closely related to wave control performance.

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  The earlier work on the dynamics of floating structures largely depends on the potential theory based on the assumptions of non-viscous and irrotational flow. However, these models might be faced with several difficulties in modeling the wave-structure problems. The main purpose of this study is to investigate the applicability and validity of the numerical model based on the Navier-Stokes solver in simulating the dynamics of a submerged floating breakwater with impermeable mooring plate. Another objective is to attempt to analyze the performance of the newly developed wave energy converter. The favorable agreement between numerical estimation and experimental data proves the capacity of proposed model in mimicking the dynamics of a submerged rectangular floating breakwater anchored to the bottom using plates.

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  Hydraulic model test has been carried out in order to study the characteristics of wave breaking, wave fission and wave regeneration on coral reefs which have steep slope in front. The two types of coral reef model, which have single and double step-like topography, are installed in wave flame. The wave transformation on coral reef is investigated in detail. The broken wave height and period on the coral reef are varied spatiotemporally due to wave breaking and wave fission.
  In this study, we found that wave regeneration point can be estimated by ratio of distance from reef edge to wavelength of deepwater wave. The wave regenerated under the condition that the ratio was almost unity in these experiments.

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  Wave transformation in shallow water can be underestimated in generation for a representative incident wave spectrum (Hirayama et.al, 2010). The damage wave called Yorimawari-nami which causes many caissons of the offshore breakwater slide widely in Fushiki-Toyama port in 2008, however, are usually estimated with the representative single wave spectrum in shallow water. In this paper, the characteristics of wave height distribution in front of the damaged breakwater are investigated by reproducing wave transformation on complex bathymetry in generation for several incident wave spectra in Boussinesq model. In addition, the same numerical simulation is carried out for the shorter period wave appeared in the storm due to 23th typhoon in 2004, in order to make comparison with them. The wave height distributions at the wave observation station and along the damaged breakwater become gentle around the peak for Yorimawari-nami in generation for several wave spectra at incident boundary, though they still correspond to the Rayleigh distribution at the foot.

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  In this study, the wave-current interaction and its mechanism are investigated in relation to its crossing angle using newly developed numerical model which is able to generate oblique waves smoothly.Numerical analysis has been conducted to analyze the wave height distribution and velocity field due to the wave-current interaction. First, numerical method has been verified in comparison with exiting experimental results on the wave-current interaction. It is shown that there is a good agreement between numerical and experimental results.Also, numerical results show that the wave height decreases with increasing current speed. It can be pointed out that current speed and incident wave period have a little effect on wave height as crossing angle between wave and current becomes smaller.

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  Wave overtopping on a seawall can be calculated in a numerical wave flume, such as CADMAS-SURF which solves Navier-Stokes equations with combination with VOF method. On the other hand, a two-dimensional Boussinesq-type wave transformation model has been expanded for evaluating overtopping discharge with applying the overflowing formula. The overflowing depth, however, is still underestimated because of limit of surface boundary condition, in addition to the weak-nonlinearity and the error in difference method. In this study, it is revised with amplifier coefficient which is evaluated in comparison with measured and calculated water surface elevations in front of a seawall. Moreover, wave overtopping and inundation on a seawall equipped some drains are calculated by using the Boussinesq-type wave transformation model.

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  Numerical analyses of the seawall overtopping phenomenon using a particle method (Smoothed Particle Hydrodynamics) are presented. To solve a problem of wave height losses occurring in a standard SPH, we applied the symplectic time integration scheme which is superior in the energy conservation. Using this scheme, simulated wave heights agreed well with experimental values. Also, it is found that the seawall overtopping flow rate can be predicted within 20% error for straight type seawalls. However, for flared type seawalls, simulated values became around 60% of experimental values.

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  A new judging method of free water surface of MPS is being proposed in this study. This method decreases the generation of the surface particle inside the fluid and improves the pressure distribution. The authors investigate a relation between the number of free surface particle and the hydrostatic pressure in the calculation of static water. The stable pressure is obtained in this new method compared to the original method. In the new method, high accuracy and computational stability are also obtained when applied to the calculation of the collapse of a water column.
  The study suggests that the new method is useful as the judging method of free water surface.

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  This simulation by the original MPS has a problem that is attenuation of progressive wave. This study shows that attenuation of progressive wave is due to the imprecise calculation method of the gradient operator. And to improve this problem, authors built a precise calculation method of the gradient operator into MPS. This MPS shows good results for the velocity vector and height of progressive wave on both condition of shallow and deep water wave.
  In addition other applications, such as run-up and wave breaking can be simulated. This study suggests that MPS with a precise calculation method of the gradient operator is useful to reduce the attenuation of progressive wave.

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  In recent years, CADMAS-SURF is being applied to the numerical simulation of the structurally resistive design against wave action by using irregular waves and turbulence model due to performance advances of computers. Fujiwara (2008) proposed the improvement method for input horizontal velocity in order to address the numerical divergence and the increase of total water mass in the flume. However, this method is complex and unexpected free short and long waves may be generated. To address these problems, Sekimoto and Takahashi (2010) proposed a simple method of irregular wave generation using the uniform horizontal velocity profile. In these methods, the time series variation of a mass transport is not considered. And, the example of the application of turbulence model in CADMAS-SURF is few. In this paper, we proposed the improvement method of the conservation of the total water mass in the flume and confirmed that the generated irregular waves have good accuracy and the turbulence model in CADMAS-SURF is effective.

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  Some seaweed beds, important components of the shallow water ecosystem, have disappeared by land reclamation of fishery harbours, power plants and other facilities and water quality declination in Japan.
  In this study, we attempt to evaluate seaweed beds formation on a submerged breakwater in the vicinity of Shimane nuclear power station. Calculation results are as follows;
  1. Seasonal changes in seaweed species composition are not estimated.
  2. A submerged breakwater works as grounds of seaweed beds, considering depth and angle of gradient.
  3. Herbivorous animal impacts on seaweeds are low.

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