In Japan the numbers of port calls by large cruise vessels have been increasing. It is becoming more and more significant to prepare adequate spaces in ports for safe navigation. While the sizes of cruise vessels are getting larger, it is known that recent cruise vessels tend to be equipped with pod propulsion systems and strong thrusters, in order to secure good navigability.

 The purpose of this study to obtain relevant information for port planning and safety assessment, by examining the trends in vessel sizes and propulsion systems, and by analyzing the use of water areas by large cruise vessels focusing on turning at ports, under the utilization of AIS data.

 If the Tokyo Metropolitan Earthquake occurs, a massive amount of disaster waste will be generated. As the first step for disposal of the waste, the waste is collected into temporary storage close to the places that generated said waste. After that, it is necessary to transport the waste to secondary temporal storage locations and perform intermediate treatment, disposal, and recycling promptly.

 Therefore, focusing on the ports that have vast land and sea space in the center of the Tokyo Metropolitan Area, we studied the process of transporting waste to secondary temporal storage locations. We then studied the storage, treatment, disposal, and recycling of the disaster waste in the port areas. Then, we grasped a concept model for disposing of and recycling disaster waste by using the port areas. To measure the validity of the concept model, we assessed transportation, storage, disposal, and recycling of the disaster waste by using Tokyo Port’s area in the event that occurs. The study results showed that each examination item was expected to fit on a realistic scale.

 We conducted questionnaire surveys on cruise passengers of eight cruise callings to Japanese ports to clarify the difference of consumption by characteristics of passengers, and calculated the economic impact precisely. It was revealed that the average consumption varied by the nationality of passenger, cruise class, and the number of ports of call in Japan, and that the nationality of passenger also influenced on the participation percentage of optional tour at the calling ports and the percentage of staying before/after cruising. In addition, we calculated the percentage of numbers of passenger sightseeing spots within or outside the port manager's municipalities, and estimated the respective economic impacts.

 East Asian ports have increased their container volumes based on rapid economic development in recent years. Thereby, the numbers of direct services calling at Japanese ports have decreased. Shipping alliances/companies arrange their container services, such as TEU capacity and frequency, based on the target cargo volume. This study analyzed the relation between ship capacity and container volume of each shipping alliance in North American route. The result indicated that ship capacity had strong correlation with cargo volume and the average load factors (L/F) were around 50 to 70%. L/Fs of Japanese ports were almost below the averages of whole East Asia; however, they were reversed or in the same level if the containers were restricted to west bound or direct services. In addition, the target container volume to maintain and increase direct services were calculated.

 In recent years, there has been an increasing interest in food safety and security, and sanitary management type fishing ports have been developed in many production areas.

 The purpose of this study is to conduct a “difference-in-differences” analysis, which statistically analyzes causal relationships, in addition to the conventional data analysis, to clarify the effects of sanitation management measures on fish price changes. We were able to quantitatively evaluate the effects of hygiene management measures.

 Automobile industry occupies a vital position in the Japanese economy. In recent years, due to intensification of competition in the automobile industry, improving of efficiency in manufacturing has been demanded. Therefore, management integration among auto makers and consolidation/relocation of factories are progressing.

 In this study, we grasped the change of maritime transport of auto parts due to the change of the production volume of assembling factories and the progress of modal-shift, and considered the future trend of maritime transport based on the expected changes in automobile industry and the surroundings. As a result, it was revealed that import auto parts by containers from overseas increased remarkably, and that domestic transport by unit load system such as ferry, RORO ship and by railway increased in some areas. In addition, to promote maritime transport, the direction of relaxation of container terminal and access road congestion and the reducing of imbalance in maritime unit load transport was considered.

 Singularity is a day on which a particular weather phenomenon is more likely to appear than before and after. For example, singularity of strong wind is empirically known. If there is singularity of the wind, there must also be singularity of the waves generated by the wind. If the characteristics of singularity of the waves becomes clear, it will be useful information in setting up a large port construction process. In this study, wind and waves were focused on and existence of singularity of them was examined. As a result, what was known empirically as singularity of strong winds and weak winds was confirmed with observed data. On the Sea of Japan side, singularity of the high wave corresponds to that of the strong wind, but not necessarily on the Pacific side. Singularity of low waves corresponds to that of weak winds in both sea areas. Regarding the waveform gradient, the singularity of high(low) wave corresponds to that of large(small) waveform gradient.

 In this study, we investigated the occurrence characteristics of the swell along the Pacific coast using the NOWPHAS wave observation data, and discussed the improvement of the swell estimation accuracy by verifying the accuracy of waves hindcasted for a case of Typhoon LAN(1721). As a result of analyzing the observation data using partitioning, it was confirmed that swell as well as multimodal waves occurred frequently on the eastern Pacific coast, and various swell overlapped are rushing to the coast. The hindcasted data for Typhoon LAN(1721) showed that the long period swell peculiar to Kashima Port were generated due to the influence of the seabed topography off Inubozaki. In addition, in order to improve the estimation accuracy, the effects of the nonlinear interaction terms and the number of directional divisions on the estimation accuracy were investigated. It was found that when GMD was used for the nonlinear interaction term, the overestimation of swell was slightly improved. It is expected that such comparative verification of each swell component will lead to improvement of swell estimation accuracy.

 Coastal wind speeds retrieved from Sentinel-1 synthetic aperture radar (SAR) was compared with in-situ data observed in five coastal waters to develop more reliable methods for offshore wind assessments. All SAR images was resampled with a resolution of 100 m and 500 m to reduce speckle noise. As a result, Biases and RMSEs of SAR retrieved wind speeds with the 500 m spatial resolution are -0.62 to 0.88 m/s and 1.31 to 1.75 m/s, respectively. Additionally, the SAR wind speeds with the 500 m spatial resolution have higher accuracies than those with the 100 m spatial resolution in all coastal waters. That is why the 500 m spatial resolution can reduce an effect of strong backscatters from artificial structures (e.g. observation masts, buoys and ships) in SAR images. It is also found that breaking waves, which often occur in shallow waters, lead to the strong backscatter in SAR images. Consequently, the SAR wind speed shows higher than the in-situ wind speed in such coastal waters though the effect of breaking waves does not appear when the wind speed is more than 12 m/s.

 In ports, breakwater planning against waves should be conducted by the condition of ship motion in suspending cargo loading and unloading, but the characteristic of ship motion is not being sufficiently observed. In this study, the ferry motion by waves in Tomakomai Port are studied and the prediction method of that is proposed. The ship motions are caused by wind waves and long period waves and predicted by wave height and period off the coast.

 This study proposes a new method for offshore and upper wind speed estimations in a coastal area: The method is based on 16-secotor steady-state wind simulations using the mesoscale model WRF with the LES mode and in-situ wind measurement data available near the coastline. The study area is the coastal area of Hazaki, Kamisu-shi, Ibaraki Prefecture, and the accuracy of the method was validated with measurements from a buoy and a vertical Doppler LiDAR. As a result, it was found that the proposed method can estimate wind speed with a similar accuracy to those reported in previous studies with WRF. On the other hand, it was also found that this method exhibits underestimation tendencies for the horizontal gradient and vertical shear of wind speed, especially when wind blows from the land sector. The result also indicated that the estimation accuracy of this method can be improved by conducting additional simulations for each stability class and by re-examining the dynamical processes and parameters over land surface.

 It is necessary to collect wave data for evaluations of costs of installations and maintenances, which are important for decision making of offshore wind farm site selections. Authors had carried out wave hindcast for 1957-2010 by using sea surface wind evaluated by long-term meteorology hindcast for the same period. However, underestimation trend of wave heights of high waves for typhoons had been a technical issue, and it was caused by prediction accuracy of typhoons by the meteorology hindcast. The sea surface winds for typhoons were evaluated by the combination of traditional empirical typhoon model and global reanalysis data, and waves for typhoons were evaluated again by using the new sea surface wind data, resulting in good accuracies of predicted waves for typhoons. Accuracies of predicted waves for normal sea state and extreme waves for non-typhoons and typhoons were evaluated by comparison with measurement data using GPS buoys. By using the long-term hindcast wave data, database which provide valuable wave information for decision making of site selections for offshore wind farms were developed.

 On estimating reliable harbor tranquility in the port of which a part of offshore composite breakwaters has sunk in a sea, it must be required to calculate wave transformation on and behind the submerged caisson-type breakwater instead of the missed composite breakwater. In this study, the harbor tranquility analysis is conducted by using a Boussinesq-type wave model which can consider wave fission, refraction and breaking on a sea-bed gap to estimate cargo handling rates on a target berth in cases of the submerged breakwater existing and the offshore breakwater missing.

 In case that the top of breakwater near the harbor entrance has sunk by 2 meters below the sea level, the wave period of transmitted wave is shortened by about 20% in a relative wide area behind the submerged breakwater due to wave fission while the incident wave height is 1 meter. In addition, the cargo handling rate in the case of the submerged breakwater existing is at least 10% higher than one of the offshore breakwater missing because of reduction of wave heights due to breaking, and so on.

 A follow-up computation of the hydraulic model experiment of Noguchi et al. (2015) was conducted by three-dimensional coastal current and beach change model. The numerical model reproduced the experimental outputs of current and beach changes around the artificial reef system to confirm the applicability of the model which consists of SWAN for wave computation, POM for three-dimensional coastal current field, and the Van del Werf sediment transport formulation under wave and current coexisting field. The calculation results reproduced the surface and bottom layer current patterns around the artificial reef and the velocities relatively well. Although the topographic change calculation has a problem in the reproducibility of the sedimentation near the shoreline, a certain amount of topographic change tendency can be reproduced in the case of a high incident wave. It was confirmed that the three-dimensional beach current and beach deformation model had generally good applicability.

 When it is difficult to raise seawalls due to a building height restriction such as for airport facilities, wave-dissipating works with a notch are adopted between the wave-dissipating works and seawalls. Although studies on wave overtopping of wave-dissipating works with a large retarding pool have been carried out, there are few studies of stability and overtopping of wave-dissipating works with a notch at the rear end of the crown. Then, the hydraulic model experiments were conducted to clarify the stability and overtopping characteristics. It was clarified that the blocks at the shoulder area of the crown rear were susceptible to damage due to the effect of the water mass that had passed over the wave dissipating works from the experimental results and that the amount of overtopping with there was a notch increased compared to without notch.

 Wave dissipating works using concrete blocks has been widely used for reducing the wave overtopping rate. In general, wave over topping rate is calculated by using Goda’s diagram. However, it is pointed that the calculated value is quite different when the profile of wave-dissipating works change caused by the damage of wave-dissipating concrete blocks. The aim of this study is to investigate the effects of deformation of wave-dissipating works on the overtopping rate. Several cross sections of wave-dissipating works defined based on the previous study. When the crown of wave-dissipating works down to near the still water level, the overtopping rate increases with progress of wave-dissipating works deformation. When the crown of wave-dissipating works settles under the still water level, the increase of overtopping rate is suppressed.

 Nakatani et al.(2019) proposed a simple method for the wave-overtopping prevention. The method utilizes a cylindrical body for the vertical seawalls, the both ends of the cylindrical body are moored using rope to the front face of the seawalls. The mooring allows that the cylindrical body moves following the wave motion in front of the seawall. This method has several merits, e.g., low cost, ease of construction and maintenance, and so on.

 In this study, hydraulic model experiments were conducted using a two-dimensional wave flume in order to investigate the performance of the new wave-overtopping prevention method, i.e., the reduction of wave-overtopping quantity. Furthermore, the tension acting on the mooring ropes, which is very important factor for the design of the prevention method, was investigated. From the experimental results, it was confirmed that the wave-overtopping prevention method for the vertical seawalls is efficiently able to reduce the wave-overtopping quantity. Both the maximum tension and the average one acting on mooring ropes linearly increase with the significant wave height. The increase rate, however, is markedly different. While the increase rate of the average tension is very small, the maximum tension drastically increases as the significant wave height increases. When the wave height is small, the probability density distribution of the tension can be expressed by the normal distribution. As the wave height increases, however, the shape of the PDF is distorted like a heavy-tailed distribution. In other words, the occurrence probability of strong tension greatly increases.

 Generally, harbor water region should be effectively sheltered from incoming stormy waves by outside breakwaters. However, as a secondary effect of such a breakwater system, it often causes the water pollution problem in a harbor. In order to solve such a problem, various types of water exchange breakwater have been proposed and applied to the real harbor sites. In this study, we have examined the performance of a newly proposed slotted breakwater that has a water channel on the bottom side for water exchange. The basic functions of the breakwater, such as wave reflection and transmission, are also examined simultaneously.

 In a design of seawalls, it is important to keep wave overtopping discharge below an allowable value, whereas it is desirable to keep a crown height of seawall as low as possible from viewpoint of water affinity and landscape.When there is a limit to expansion of seawalls to front sea area, vertical block masonry seawalls are sometime employed. Although authors compared the overtopping characteristics of two types of block masonry seawalls with those of vertical seawall, the shore slope is limited in 1/30. This study carries out a series of hydraulic model experiment with 1/10 shore slope and the overtopping characteristics were compared with the results of different beach slope. Results of experiment show the reduction of wave overtopping was improved when a lid was attached to the top of the seawall with the diamond-shaped opening. As the shore slope gradient increased, the reflection rate in front of the seawall decreased and the overtopping discharge increased. We proposed empirical formulas and figures which enable to estimate overtopping and wave runup for block masonry seawall with different slopes.

 Numerical simulations are now being applied in place of the physical model experiments that have been used in the design of maritime structures. In this paper, the transition from model experiments to numerical simulations in the field of design of maritime structures is investigated. For wave deformations such as wave shoaling and wave breaking and reflected waves of long-period waves, it is now possible to shift from physical model experiments to numerical simulations. Numerical simulations can be performed on wave pressure, wave overtopping, and transmitted wave, but when applied to actual design, accuracy verification is required and calculation speed is desired to be improved. At present, it is difficult to apply numerical simulations for phenomena accompanying movement of objects such as caisson sliding and wave dissipating block movement to actual design.

 The breaking wave pressure can cause seawall and hinterland vibrations. In this study, to clarify the mechanism of this vibration, we conducted a hydraulic experiment. As a result, the followings were clarified. 1) An impulsive breaking wave force caused the seawall to vibrate, and the maximum acceleration was 6 m/s². 2) The acceleration of the hinterland just behind the seawall was 1/10 of that of the seawall and decreased with the distance from the seawall. 3) Only the vibration with the natural frequency of the hinterland propagated. In contrast, other components besides this frequency attenuated with the propagation. 4) The phases of the horizontal and vertical components differ by half a period. This characteristic indicates that the vibration was a Rayleigh wave. 5) The trench to prevent the propagation of vibration was not very effective.

 In the seawall with high rubble mounds, the surface of rubble was covered with asphalt mat and measures were taken to remove landfill sand from foundation rubble. Three years after the completion of the landfill, the road behind the revetment swelled, and from the results of the field survey, it was assumed that wave pressure was the cause. As a countermeasure, in order to provide an opening for depressurization of on the apron of the seawall, on-site observations were conducted to investigate the relationship between waves and pore water pressure, and a numerical model for the interaction between waves, ground and structures was used. The required width of the opening was studied by numerical calculation.

 The monopile gravity-type foundation, which is the foundation type of offshore wind power generation facilities, was examined when the shape of the RC bottom slab was circular or octagonal, which is lighter than rectangular and lower cost. In order to obtain information on the stability and the uplift pressure acting on the bottom slab under the eccentric inclined load due to wind and waves, a cross-sectional hydraulic model test of a 5 MW wind turbine and a numerical analysis with a numerical wave tank CADMAS-SURF / 3D were performed.

 As a result, it was stable up to 7-11 % above the overturning limit on the design, and the bearing capacity of the rubble foundation was not destroyed at the time of the overturning, so that the conventional stability and bearing capacity checking method can be applied mutatis mutandis. Furthermore, regardless of the plane shape of the bottom slab and the wave conditions, the uplift pressure distribution is almost uniform in the direction orthogonal to the wave direction, and the contribution rate of the vertical wave force moment during the design wave action is about 8 to 14 % at the maximum.

 With the increasing demand for renewable energy in the world, research contributing to the improvement of the technology level of wave power generation is essential. The authors have been developed a wave power generation system using port facilities in inner bays with high energy-consuming cities. In this study, the relationship between the rotational characteristics of a Savonius water turbine and the water particle velocity was quantitatively evaluated under the calm conditions of the inner bay, such as wave motion, flow, and coexistence of wave and current. According to the experimental results, it is found that the relationship between the rotational circumferential speed and the water particle velocity of the water turbine installed in a wave field tends to be different from that in a flow field and is evaluated by different equations. In addition, the relationship between circumferential velocity and the water particle velocity has also been formulated when installed in a wave-current coexistence field.

 Wave forces acting on caisson-type quay walls by undertow of overflowing tsunamis have not been studied sufficiently. Here, hydraulic experiments are performed to examine the tsunami forces and arrange compensating parameters for an estimation formula of the forces. In addition, a solidification method is proposed to enhance the stability of the caissons against the tsunamis. Its good performance is shown by the experiments, and influences of damages of the surrounding structures, e.g. a crack of the solidification part or a tilt of the caisson, are clarified. From the experiments, it was found that the water level inside the solidification part was decreased, and as a result, the tsunami forces on the caisson were effectively reduced by the solidification treatment. Moreover, it was shown that the solidification treatment maintained a more tenacious structure even when the damages of the surrounding structures occurred.

 In the coastal environments, detailed understanding of current or wave-induced bottom shear stresses, which are often associated to the steady friction law and wave friction law respectively, is essential to evaluate quantitatively the sediment transport and coastal morphological changes. Many previous studies have indicated that there was an influence of unsteady characteristics in the boundary layer beneath a long-period wave. Therefore, the bottom shear stress under shoaling tsunami should be considered the unsteady wave-like effects. A new correction approach has been proposed by comparing the wave friction factor to the steady friction factor. The current study aims to implement the new correction method for assessing the bed shear stress to the conventional model for tsunami. Application for a solitary wave, which propagates from the tsunami source to the shore, shows that bottom shear stress by the new method is ten times larger than the conventional method in a deep water and become smaller in shallow area. In addition, the location of the critical Shields parameter of 0.05 by the new method is situated in deeper water than the conventional method.

 Tsunami-induced force acting on an inland building located at the landward side of a coastal protection facility with resilient structure combined with a coastal dike and an embankment was investigated numerically. Numerical results showed that the relationship between the tsunami force considering the erosion of the embankment and that assuming the constant profile of the embankment was affected by the scale of the erosion. This suggested that it is essential to take into account the erosion process of an embankment in assessing tsunami force acting on inland buildings.

 After the Great East Japan Earthquake, countermeasures against tsunami overflowing on seawalls caused by expected tsunami are required. For PRA, one of the analysis methods, the relationship between tsunami height, seawall height and inundation depth are required. And, behind the seawall area, some phenomena that cannot be reproduced by the generally applied long-wave approximation, such as supercritical flows, occur. In this study, hydraulic experiments were carried out to clarify the inundation characteristics of the overflow behind the seawall and to develop the evaluation model based on the inundation depth of the passing wave without seawall. The results of this study are expected to be used for efficient implementation of PRA and safety examinations of structures installed at the back of the seawall.

 Permeable wave barriers consisting of perforated metal plates and supportive pillars are placed on coastal revetment to mitigate wave splash and spray overtopping induced by storm surges and high waves. This study examined mitigation effects of perforated barriers on wave overtopping and wave forces to evaluate the hydraulic performance of perforated barriers under a wide range of relative crest freeboard corresponding to various site-conditions. Laboratory experiments of wave barriers mounted on vertical seawall and wave-dissipating seawall were carried out to investigate characteristics of maximum wave force acting on the barrier and mean wave overtopping rate. The experimental results indicated that the perforated barrier with a porosity of 30 % reduced the wave force acting on the barrier by at least 30 % when the seawall crest freeboard relative to wave height was ranging between 0.3 and 0.9 (i.e. low-crested seawall). The wave overtopping rate of the barrier decreased by 40 – 60 % in the case of low-crested seawalls. In the case of wave-dissipating seawall on steep sea bottom, the mitigation effects of the barrier on wave overtopping rate and wave force varied due relative positional relationship between wave breaking point and wave-dissipating blocks.

 In this study, hydraulic model experiments were conducted in order to understand the characteristics of suspended sediment transport due to tsunami at a water intake facility. Tsunami and suspended sediment flowed into the facility by opening a gate installed at the end of a reservoir. Sea area and the water intake facility, which consists of an intake tunnel and a pump room, were set up in an experimental equipment. The concentration of suspended sediment transported by tsunami inflow and water intake due to a pump was measured using turbidimeters.

 It was confirmed that the water intake has a strong effect on flow field in the tunnel and pump room. The time-averaged and maximum concentration distributions of suspended sediment from the water inlet to the water tunnel to the pump room were also found to be greatly influenced by the intake flow rate.

 In this study, we carried out numerical simulations using a three-dimensional numerical wave tank “CADMAS-SURF/3D” in order to estimate tsunami inflow process at a water intake facility with high accuracy. We also conducted parameter study changing wall boundary condition, the discretization scheme of advective term, and turbulence model. As a result, wall-function boundary condition, first-order upwind scheme and standard k-ε model were found to be reproducible in the present study. The experimental and numerical results also revealed that pump intake volume has a strong effect on tsunami inflow process. The application of a three-dimensional numerical model is said to be important to figure out tsunami inflow process at a water intake facility since three-dimensional complex flow including turbulence is formed by tsunami inflow.

 Tsunami wave forces acting on seawall are divided into the impulsive forces and the hydrostatic forces, and the evaluation method of the impulsive forces has not been established. If the impulsive forces can be reduced less than the hydrostatic force, the hydrostatic force becomes dominant in tsunami force. In this study, the countermeasure to reduce impulsive forces was proposed, and its effect was confirmed by hydraulic experiments and numerical simulations. It was found that the impulsive force caused by falling to the water surface is reduced because the run-up water is dispersed by the countermeasures, and therefore the countermeasures work effectively. On the other hand, the length and shape of the countermeasure should be properly determined in consideration of the tsunami wave form and the scale of the tsunami run-up.

 Reinforced gravity type breakwater with steel pipe piles have proposed to increase ability of tsunami resistance of breakwater. In this study, effect of the length of piles under the ground on the behavior of reinforcing piles are considered by model loading experiments. As a result, effect of reinforcement of pile’s behavior and breakwater’s behavior are different when length of piles are changed. A range of this study, it is proved that breakwater with short piles is reinforced as effective as one of long piles when there is a proper length of piles.

 In this study, we aimed at building a system which can forecast coastal distribution of wave overtopping and wave runup with the precision of block unit. At first, we performed a surge and wave simulation that can reproduce observation data at Suruga Beach. Then we constructed DNN model which can reproduce results of the simulation. We built the system to calculate wave overtopping and wave runup by IFORM using output of the DNN model and astronomical tide. We applied this system to the case of typhoon No. 19, 2019 and verified its validity

 Recently, the intense typhoons passed around Japan every summer. Accordingly, the severe damages caused by storm surges have been increasing. By seeing these situations in these days, the importance of prevention against storm surges got to be recognized in society more and more. Thus, the need for storm surge prediction has been growing. In general, storm surge is strongly affected by the typhoon track which is difficult to estimate accurately in advance. Therefore, in this study, some trial storm surge simulations were performed with ensemble weather forecast. Besides, the problems for operating the storm surge prediction system were investigated. The one of the main goals of this system is that every process have be completed within 30 minutes. By this study, it was known that the storm surge simulation itself can be performed within approximately 3 minutes hence even if other processes were included, the goal had high feasibility. Besides, the worst storm surge could be estimated 3 days before typhoon making the closest approach to the objective sea area. On the other hand, there is a still room for improvement about the reproducibility of the storm tide as well as the wind fields.

 Typhoon-induced wave overtopping is a combined result of astronomic tide, storm surge and wave runup. However, in present practice the cause and the extent of damage due to typhoon is investigated using storm surge simulation models and wave simulation models independently where there is no consideration of tide-wave interaction. Hence, the application of a coupled model is expected in future practice to obtain more realistic results and thereby to determine the exact cause and the extent of damage. In addition, it is important to increase the spatio-temporal resolution of input forcing to accurately reproduce the typhoon phenomenon. Hence, the objective of this study is to analyze the typhoon-induced storm surge with COAWST (Coupled-Ocean-Atmosphere-Wave-Sediment Transport) modeling system which is forced by three different types of modelled forcing with three different spatio-temporal resolutions.

 The COAWST model with ROMS (Regional Ocean Modeling System) as the ocean model and SWAN (Simulating Waves in Nearshore) as the wave model was used to analyze the typhoon-induced storm surge due to a number of strong typhoons struck Japan in the recent past. WRF (Weather Research and Forecasting) model was used independently as the atmospheric model. Computed model results were compared with the tidal observational data and wave observational data with respect to each forcing. Thereby, the significance of sptio-temporal resolution of forcing on model results were discussed at the end of this study. COAWST model could well reproduce the typhoon phenomenon and model results were consistent while the results were highly sensitive to the spaio-temporal resolutions of input forcing.

 The simultaneity and the duration of high waves and storm surge on the coast of Okinawa Island are estimated by using a coupled ocean-wave model. The peak of the wave height and that of the tide anomaly sometimes appear simultaneously in a typhoon event on the Pacific coast, and the peak of the wave height tends to follow that of the tide anomaly on the East China Sea coast. In Naha, the time difference between these peaks is related to the typhoon forwarding angle to the island. Swell can travel for a long distance from a typhoon to the island; consequently, the duration of high waves is long compared with the coast of Tokyo Bay. The duration of the storm surge is more constant than that of the high waves. The suction effect of depression, the wind-drift effect, and the wave setup, of the storm surge varies with location and affect the duration of the storm surge.

 Buildings would have an effect on the inundation process of storm surge at densely built-up areas. In this study, we constructed a numerical model with 2m-grid mesh considering building configuration and layout, and calculated three-dimensional storm surge inundations due to potential maximum typhoon. As a result, inundation process behind coastal structures was found to be strongly affected by building configuration. It was also confirmed that flow velocity on narrow roads between buildings becomes faster. Opening or closing condition of tide gates was revealed to have a strong impact on the spatial distribution of velocity. A three-dimensional inundation simulation of storm surge with building configuration and layout would provide useful information on the examination of hazard maps and evacuation planning.

 In this paper, scour prevention region was designed reasonably using numerical simulations about submerged multi-port diffuser of Fukushima Natural Gas Power Plant. By numerical simulations using energy balance equation model, it was shown that the wave propagated mainly from northeast or east-northeast direction and its wave height was about 3.9m at the point of the submerged multi-port diffuser. Numerical simulations with 3D-VOF method were also conducted, and it was found that the flow field was disturbed by the shape of multi-port diffuser and it was shown that especially the flow induced by discharged water from the nozzles increased velocity around seabed. Finally, the area with the flow velocity of 1.0 m/s or more, where bedload and suspended load coexist, was determined as the scour prevention region.

 The An Du Estuary is located in Binh Dinh Province that is in the southern part of the Central of Vietnam. The location of An Du River mouth has been changing remarkably that caused a lot of problems for the navigation activities in this area. However, there was very limited data availability in this area making difficult to quantify the mechanism of sand spit growth or providing suitable countermeasure plans. In this study, the long-term morphological evolution of An Du sand spit was quantitatively examined by using the satellite images for about 30 years from September, 1988 to April, 2019. The analyzed results indicated that the southern sand spit was elongating to the north at an average speed of 140 m/year. Besides, the northern sand spit was retreating at almost the same speed. The sand spit was breached twice in the year of 1998 and 2005. The longshore sediment transport rates, that estimated by multiplying the changing rate of the sand spit area to the depth of active motion, are varying from 1.1 to 2.3x10⁵ m³/year depended on the breaching periods. These results show good agreement with the Delft3D numerical simulation results for this study area.

 Morphology of sand dunes formed on the Hamamatsu-shinohara coast facing the Enshunada Sea was investigated by field observation. The development of sand dunes was numerically predicted using a model predicting the effect of both waves and windblown sand. In the field observation, development of sand dunes of a rhythmic shape similar to a sand spit was observed in the backshore area. It was found that pine trees were died in the area with a narrow sand dune owing to wave run-up or the dispersion of salinity during storm wave condition. In the numerical simulation, sand dunes were successfully reproduced when wind blew at a large angle relative to the direction normal to the shoreline.

 When impermeable objects such as rocks or beach rocks are buried under the beach face, the return flow and seepage flow during wave run-up will change, causing the change in sand deposition and erosion of the foreshore. A two-dimensional movable bed experiment was carried out to investigate foreshore changes under the condition that rocks are buried under the foreshore composed of gravel, while changing the location of the model rock and the thickness of gravel layer over the rock. From the experiment of 25 cases, it was found that that the direction of the cross-shore sand transport strongly depended on the location and thickness of the gravel layer.

 On the Oiso-kitahama coast where westerly wind prevails in winter, field observation on the deposition around the multiple fences for preventing windblown sand were carried out in June and July, 2019. On this coast, 17 fences were built at an angle of 40° relative to the direction normal to the seawall with gradually increasing length of the fence. In each fence, sand mound with a maximum height of 0.85 m on upwind side of the fence has formed owing to the prevailing wind, and the cross-shore distribution of the mound was asymmetry and the elevation rapidly decreased because of the passage of wind through the opening between the fence and seawall. On the most downwind site, sand was deposited up to the top of the fence.

 Beach changes around a seawall (gently-sloping revetment) were investigated, when the seawall was constructed on a coast with seasonally-changing wave direction, taking Horikawa-hama Beach on the Kujukuri coast and Habushigaura Beach as examples. Beach changes around the seawall under these conditions were predicted using the BG model (a model for predicting three-dimensional beach changes based on Bagnold’s concept). It was found that beaches on both sides of the seawall were eroded, forming scarp, even though the land behind the seawall could be protected by the installation of the seawall. Sand supplied from scarp erosion was transported offshore, implying that the construction of the seawall accelerates offshore sand movement.

 Field surveys were carried out at thirty-four beaches at Okinawa. Sediment samples were collected near the shoreline and beach face slopes were measured from the shoreline to the run up height. The sediment constituents were identified and counted visually or under a microscope. The properties of sediment sample such as grain size, roundness and color were analyzed by images of sand particles.

 Data shows that coral grains are the dominants constitutes, followed by foraminifera, shellfishes, minerals and sea ruinous. The coral beaches can be divided into 6 groups by the concept of entropy with the percent of sediment constitutes. The distance between the coral leaf and the shoreline was correlated with the percent of sediment constitutes. The magnitude of the exponent on simple power-low relationships between grain size and beach face slope at coral beaches is larger than that of sandy beaches. The sediment constitutes could be identified and counted by roundness, brightness and saturation of sediments.

 In Chatan Town in Okinawa, an artificial beach of 630 m length bounded by groins on both sides was constructed along with beach nourishment. After the beach nourishment, marked shoreline changes were triggered by obliquely incident waves. Immediately offshore of this artificial beach a deep channel was remained in the south-north direction owing to the past dredging of the reef bed, but a shallow reef flat was remained offshore of the northern part of the artificial beach. Because of the wave-sheltering effect of this shoal, northward longshore sand transport was induced, resulting in the shoreline recession in the south part and accretion in the north part. To investigate these beach changes, bathymetric survey was carried out, and the mechanism of beach changes were analyzed. Two stabilization methods were shown.

 At the mouth of the Maite River flowing into Nakatsu tidal flat, a river-mouth jetty of 54 m was constructed on the left bank of the river mouth by March 2019. After the construction of a jetty, monitoring surveys have been carried out. Due to the aerial photograph taken on September 18, 2019, using a UAV (Drone), this jetty was effective for the stabilization of the river course at the river mouth and to prevent sand from depositing at the river mouth and erosion on the west bank of the river mouth. Also, it was found that a sand mound appropriate for the spawning of horseshoe crab Tachypleus tridentatus was formed near the jetty, and a sandy beach was reformed in front of the sand dune.

 On the Akahama coast in Takahagi City, 35 km north of Hitachinaka Port, the seawall was severely damaged over 120 m length due to storm waves associated with T1919 which landed in the Kanto Plain on October 12, 2019. On October 27 after the typhoon, field observation was carried out and the causes of damage of the seawall were investigated. The direct cause was the rapid disappearance of the foreshore in front of the seawall due to erosion, and the earth material under the seawall was drawn out, causing a void under the front surface of the seawall.

 Gabions have been constructed as a measure against beach erosion on the Hitotsumatsu coast located in the south part of Kujukuri Beach. These gabions have been destroyed every time when storm waves hit the coast, and the recovery works to the original shape have been carried out. In 2019, these gabions were destroyed again. When investigating the cause of the collapse of these gabions, the steel covering the gravels inside gabion was broken by wave force against gravels, resulting in the scattering of the gravels. However, the gravel was stably deposited forming a steep slope near the shoreline, similarly to the gravel beach. It was concluded from this fact that it is better to carry out the gravel nourishment instead of the use of gabion with gravel inside.

 Sand bypass around a river mouth, an inlet as well as artificial coastal structures such as port and harbors and groin is important factor to consider a shore protection. Shoreline progress and retreats in updrift and down-drift side coasts, respectively, while the sand bypass system is changed by either natural or artificial reasons. Hitotuse River locates at northern terminal of Miyazaki coast where coastal erosion is significant. Two jetties were constructed at both side of the river mouth and thus could reduce the downside sediment transport, therefore the sand bypassing at the river mouth has been revealed by using aerial photographs and satellite images, and numerical modelling. It is shown that the sand bypass system partially recovered in ten to fifteen years period and supply sediment to down-drift side coast.