In this study, the occurrence characteristics of swell are investigated on the basis of a wave data set created by performing one year wave hindcasting for the Pacific Ocean using the wave model WAVEWATCH III. By applying a partitioning technique to the directional spectra of the data set, swell components are classified into the ones with short and long decay distances, respectively. As a result, it was found that the swell with short decay distance mainly comes from the southeast due to typhoons and low pressures, while the dominant swell with long decay distance comes from northeast, which originally developed in the northern North Pacific. Furthermore, we trace the swell by applying Wave System Tracking, and show the results of long period swell propagation to the Pacific coast of Japan, which originated from the South Pacific and the trade wind zone.

 A survey has been carried out on characteristics of seiches with periods of several hours observed in Mutsu Bay and Sendai Bay. In Mutsu Bay, this seiche occurs throughout the year, but is particularly large in winter. The seasonal change in seiche amplitude variation correlates well with that in wind speed. Spectrum Analysis shows that there are two dominant periods around five hours. The seasonal changes of the energy of these two components are different. In Sendai Bay, seiche with about three hours develops when tidal deviation increases. The phases of vibration are well matched in Sendai, Ishinomaki and Ayukawa in Sendai Bay, but such seiches are not observed at points outside the bay. The amplification factor of the component with three hours is larger than other components when tidal deviation is large.

 In this study, we investigated the predictability and accuracy of high wave estimation at Toyama Bay using the neural network (NN) with the Japanese 55-year Reanalysis data (JRA-55). A hierarchical NN that outputs significant wave height or period from the atmospheric data compiled from multiple 10 days’ events including Yorimawari-wave is developed. The NN model is optimized by the error of peak wave height and the correlation coefficient of the time series of wave height. In addition, the process of high wave generation is extracted and discussed from the results of the sensitivity coefficient method to the NN model optimized to reproduce Yorimawari-wave on February 23, 2008. As the results of analysis, the optimum learning conditions of Yorimawari-wave have 5 units at hidden layer, 4 to 6 events (a total of 160 to 240 hours of weather data), 13 hours lead time, and teacher data including the cyclones passing through the Japanese Islands. Optimized NN model reproduces the significant wave height and period of the large Yorimawari-wave on February 23, 2008.

 In the ocean surface, there are currents generated by ocean winds. Therefore, ocean wind observation was important to understand the ocean currents. The examination about the technique to estimate ocean wind was performed for a long time by wave data. Various data were included in measured wave data. The swell that a period was big and wave steepness was small. The swell affects the estimation of the ocean wind in previous study.

 In this study, ocean winds were estimated by obtained wave height and period from NOWPHAS and SMB method and Toba 3/2-power law. Therefore, wave steepness was lower than 0.02 and a wave with more than 8s of period was the factor that measured value was different from the estimate of ocean wind. The estimation of ocean wind was improved by excluding the wave of the condition mentioned above.

 The numerical models developed in previous our study are improved to simulate the influence of in- and exfiltration flow on swash sediment transport under the coarse grain condition. The interaction between runup wave transformation and seepage flow and the effect of in- and exfiltration flow on effective weight of coarse sand are considered in this models additionally. Through the comparison between present model results and previous experimental data, the influence of saturation in the beach slope becomes weaker according with increment of sand grain diameter. The characteristics of sediment transport under coarse grain condition can be evaluated by considering wave-induced infiltration-exfiltration flow.

 When impermeable objects such as beach rocks are buried under the beach face, the return flow and seepage flow during wave run-up may change, causing the change in sand deposition and erosion of the foreshore. In this study, such examples were shown, taking the beaches on the Komesu coast in Okinawa and on Hithadhoo Island in Maldives as examples. On the Komesu coast, coral reef well develops, and a sandy beach composed of gravel extends on the basement rocks. On the beach on Hithadhoo Island, beach rock with a slope of 1/7.5, the same slope as the foreshore slope of the coast, halfly exposed on the beach face because of erosion. Taking these examples into account, 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. It was found that seaward sand transport may accelerate when rocks exist under the foreshore.

 Laboratory experiments are conducted in a small 2D wave flume. A 4.7-cm transient wave height is used in the experiments. A certain amount of mixed sediment d₅₀ = 0.64, 1.59, 4.05 mm) is placed near the shoreline of the land side, and these sediments are pushed landward due to the inundation flow of the wave. The mixing ratios of the three sediments are changed, and 11 cases are conducted. The analysis focuses on the sediment transport of fine gravel (d₅₀ = 4.05 mm). From the results, regardless of the mixing ratio, the peak location of the fine gravel is nearly the same for all cases. Moreover, the fine gravel is likely to gather at the peak location, combined with fine sediment, and the shape of the spatial distribution can be expressed using a logistic peak distribution.

 In this study, movable bed experiments on topography change caused by large-scale tsunami eddy were implemented to understand the influence of the grain size ratio of bed material on the topography change. Measurements were performed changing the mixing ratio of sand with two kinds of grain sizes.

 The experimental results revealed that the amount of topography change is different depending on the grain size although the difference of the grain size has little influence on the spatial distribution of the erosion and deposition. It was also found that the smaller the content rate of coarse sand is, the larger the amount of topography change is. The results implied that the topography change for mixed grain size sand could be estimated by conducting linear superposition of the amount of topography change for each single-size sand based on the mixing ratio of sand. Coarse sand was confirmed to tend to deposit in the area where deposition occurs near sediment sources.

 In recent years, sea conditions are becoming severe due to climate change. In addition, it is required to cope with the action of multiple forces. There are cases where the conventional hydraulic model experiment facilities can not cope with these changes in the situation in recent years. Therefore, it is intended to organize the existing hydraulic model experiment facility and propose a hydraulic model experiment facility to clarify the mechanism of response to climate change and complex disasters.

 In this study, we considered wave power characteristic by plane hydraulic model experiment in case more than 60 degrees of sharp-angled incident wave against a caisson having breakwater with low crest wave dissipating blocks in the part of the trunk of breakwaters under construction. The main conclusions are as follows. (1) The shock pressure of breaking wave does not occur by low crest wave dissipating blocks. On the other hand, 1) The wave height increases by growth of meeting wave from upper side area with no wave dissipating blocks. 2)The wave pressure exceeds Goda value in most of the erect part by occuring a heavy disturbance in the space between the low crest wave dissipating blocks and the caisson wall. (2) The peak wave power which acts on the whole caisson is restrained because the action time of the wave is delayed from upper side to down side. (3) The peak horizontal wave power is restrained because the push back power generates from back face of caisson when the waves in the front face of caisson and diffracted waves going around to the back face becomes in phase.

 In developing countries, there is a breakwater or groin which employs the concrete cellular caisson with filled stones covered by the concrete blocks as economical type of structure. The cover concrete blocks are often just put on filled stones without sealing concrete to consider the instability of the concrete cellular caisson due to uplift force. On the other hand, there is a possibility that the cover concrete blocks are sometimes moved by wave action. It is quite few to study the stability of concrete block at the water surface level. In this study, physical model test using 2-dimentional flume was carried out to know the difference on stability of cover concrete blocks due to difference of water level and type of blocks. Furthermore, measurement of wave force using the 3-component load cell was conducted to know the relation between acting wave forces and stability of cover concrete blocks. It was known that stability is increased by increasing hole rate of block or making surface of block slope.

 A series of hydraulic model experiments was conducted to grasp the fundamental characteristics of the Isbash number of armor units against tsunami-induced current. From the experimental results of various slope angle of the mound, it became clear that the Isbash formula overestimates the influence of the slope angle. It was found that the armor units on the shoulder are structurally weak in the case of trapezoidal shaped mound. In the case of the breakwater head, the armor units near the corner of the caisson and the armor units on the mound ridge line on the downstream side were easily damaged, and the Isbash number decreased slightly compared to the two-dimensional experiments using trapezoidal shaped mound. Regarding the definition of the flow velocity in the Isbash formula, it is better to evaluate the Isbash number by using the cross-sectional average flow velocity from the viewpoint of consistency with the design method.

 For the objects of safety cargo-handling operations and economic management in ports, it is important to reduce long-period waves that cause a problem of cargo-handling. Tanaka et al. (2012) proposed a submerged wave absorbing mound structure covered with wave-dissipating blocks as a method of suppressing long-period reflected waves in a port, and showed that the structure is effective. However, only one type of wave-dissipating block is used in the study, the suppression effect of different type blocks have not been clarified. This study conducted the hydraulic model experiments using different types of wave-dissipating blocks and frame blocks covering the submerged wave absorbing mound structure to verify the effect of suppressing the reflected waves.

 For the objects of strengthen the stability of the breakwater against the tsunami, the method of raising the mound behind the breakwater is adopted. The required mass of armor blocks covering the mound is calculated by the proposed formula. The stability numbers of various armor blocks have already been shown. However, this number is in conditions where the mounds top end is submerged during tsunami overflow, and research on the high rubble mound is inadequate. In this study, the stability of armor blocks on reinforcing high rubble mound for breakwaters was examined. As a result of the experiment, it was found that the stability number of armor blocks was lower than the stability number of submerged conditions, and the influence on the stability of the shape of armor blocks was considered.

 Until now, seismic-resistant design of sheet pile quay walls at fishing ports has been done with seismic coefficients table which roughly consider area classification and ground characteristics. However, those coefficients do not reflect seismic behavior of soil and walls. On the other hand, sheet pile quay walls in deep water depth at commercial or industrial ports are now designed using a new coefficient and its calculation method which reflects seismic behavior and allowable deformation amount.

 This paper aimed at an application of new coefficient and its calculation method for sheet pile quay walls in shallow water depth at fishing ports. For that reason, two-dimensional seismic analysis is carried out to identify the parameters for calculating seismic coefficients suitable for water depth of quay walls at fishing ports and its standard design method. On the premise of application of a new method, stress characteristics of structural members are also verified.

 In 2007, material factor approach of level 1 reliability design method (partial factor design method) was introduced to "Technical Standards and Commentaries for Port and Harbor Facilities in Japan", which was revised in 2018. The revised technical standard has employed "load and resistance factor approach" instead of "material factor approach", for the stability of port facilities, such as quay wall and breakwater. Partial factors are applied in performance verification in both approaches, though those have different roles in equations for performance verification of each approach. Therefore, partial factors were required to be readjusted and suitable to the new approach. In this study, reliability analysis was conducted to obtain the partial factors appropriate to the load resistance factor approach, for the stability in permanent situation of port facilities with foundation ground improved by Sand Compaction Pile Method and Deep Mixing Method.

 This paper describes the motion characteristics as the Large-Scale Floating Coal Transshipment Station (LFTS) System considering the effects by motion of LFTS and large bulker. Because the topography of the seabed near East Kalimantan Island, Indonesia's main coal production area, is shallow, it is difficult for bulk carriers to reach the coast.

 Therefore, LFTS is proposed, which will be used as a relay base between coal-barging barges from land and bulk carriers offshore. However, LFTS and bulker are both large structures, and their motion are considered to affect each other through mooring ropes. Also, LFTS is affected by long-period wave drifting force. Therefore, grasping the motion characteristics of the LFTS system consisting of LFTS and bulker will be a very important issue for its realization.

 And then, in this study, the characteristics of the movement response of the LFTS system were also considered, which also considered the influence of the movement of the two floating bodies of LFTS and bulker on the movement response of each other through the mooring rope.

 The effectiveness of flume-type anti-oscillation tanks installed on a floating caisson in the pitch and roll directions under regular waves and multi-directional irregular waves was investigated from hydraulic experiments, and a simple numerical method for estimating the effect of the anti-oscillation tanks was developed and applied to the hydraulic experiments. From experimental results, it was revealed that the anti-oscillation tanks can reduce the pitch of the caisson increased at around the natural frequency and its double frequency under the regular waves. Furthermore, the anti-oscillation tanks were found to be effective against not only the pitch but also the roll under the multi-directional irregular waves. From numerical results, it was found that the effect of the anti-oscillation tanks can be estimated reasonably well in terms of the amplitude of the pitch. This suggested the usefulness of the developed method in estimating the most effective water volume in anti-oscillation tanks.

 This study aims to propose a new prediction formula of the effective height of a hanging curtain in steady water flow. According to the hydraulic experiments and numerical calculations, the more practical calculation formula of the effective curtain height was obtained using the ratio of dynamic pressure and weight and the ratio of the effective curtain height to the curtain length. Our formula is characterized in that the experimental coefficient is without user specification, and the weight is included in the formula, and the parameter using the ratio of the initial curtain height to the water depth is used.

 The method to pile up stones behind a caisson is gathering attention after Great East Japan Earthquake for reinforcing breakwaters against a tsunami. Past experiments and analyses showed that piled stones could increase the sliding resistance and bearing capacity of foundation mound. The assessment method was also proposed. However, there is few research that investigated subgrade reaction acting on the bottom of a caisson backfilled with stones. Large edge pressure might damage the corner of a caisson and crush stones. In this study, subgrade reaction of a caisson was examined by centrifuge model tests. The edge pressure was comprehensively examined on the basis of the test results of the present and past studies. Simplified model calculating the subgrade reaction could successfully simulate the model tests.

 The present study investigated the sustainability of the effects of wave force reduction and prevention of collapse by a new wave reduction method through caisson joints by a buffer material proposed by the authors. The results of the measurements of caisson joint waves at aging facilities show the prolonged effect of the wave reduction such that the wave transmission coefficient was as low as 10% even one year after installation despite some configuration changes of caisson joints due to continuing wave impacts as well as the chages in surrounding environments. The results of the investigation further revealed the effects on preventing the cycles of collapse in the field. Hence, the propose method is expected to significantly contribute to such disaster prevention and mitigation as well as to sustainable coastal infrastructures.

 Field investigation on collapsing and scouring of the seawall on the Kenbutsu coast in Tateyama Bay was carried out, where a seawall was constructed at an excessively seaward location by land reclamation. Because of the protrusion of the seawall, severe wave overtopping has occurred. Although wave overtopping over the seawall was first confirmed on January 5, 2017, the seawall itself maintained its original form. In the field observation on November 2018, the seawall was severely damaged along with the scouring behind the seawall. Field conditions of collapsed seawall and scouring were investigated in the field investigation, and the mechanism of the collapsing of the seawall was studied on the basis of these field observations.

 The coastal areas of the Pacific Ocean suffered extensive damage by the tsunami of the 2011 off the Pacific Coast of Tohoku Earthquake. Installing steel pipe piles behind the caisson with filling the space between the caisson and piles is proposed as one of the reinforcing methods against tsunami, called “Steel Pipe Method”. In order to establish the design method of this structure, the design of the steel pile is the most important. In this study, the effect of the shape of filling soil and rigidity of foundation ground on pile was examined by model loading experiments. The model ground was prepared by dry silica sand #5 with relative density of 80% or 10%. As a result, it was found that the smaller the width of the inner filling soil, the larger the maximum bending moment generated in the pile. In addition, when the rigidity of the foundation ground is low, the external force at pile was acting to a deep depth.

 When it is assumed that steel sheet piles are used as foundation structure to improve a revetment against earthquake and tsunami, the vertical bearing capacity is not cleared in case constructed by press-in method such as installation by static hydraulic load. In this study, vertical load test of a Hat Type Sheet Pile (SP-50H) constructed by press-in method was carried out to obtain the property of vertical bearing capacity. The measured vertical capacity is compared with estimated value of a existed design code installation by vibratory hammer. We proposed that the equation of estimating bearing capacity of sheet pile foundation installation by press-in method.

 The reduction effect of earth pressure at the time of earthquake by using heavy-weight solidified block was examined by the calculation and the experiment. It was shown that the 45 % reduction of earth pressure can be obtained in the case of horizontal seismic intensity 0.25 by the use of the heavy weight solidified block at the bottom and the lightweight block at the top, by using the slice method. The heavy weight solidified block (density 2.45 g / cm³) was placed behind the gravity type quay-wall in the model and the effect on the reduction of earth pressure was examined by the centrifugal shaking table test. Through the experiments, it was confirmed that there was a significant earth pressure reduction effect on the front side of the solidified block.

 In the gravity-type quay wall supporting the earth pressure behind the structure by the self-weight, an increase of the horizontal earth pressure due to liquefaction result in damage of the caisson. As a countermeasure against the quay damage, a method of solidifying the back-filling layer behind the caisson has been proposed. In this research, the seismic response of gravity-type quay wall with different improved area has been investigated by experimental simulation using geotechnical centrifuge. As a result, it was confirmed that the displacement of the caisson can be reduced by solidifying the backfill at the same height as the caisson.

 This paper discusses the experimental findings pertaining to the build-up of residual pore pressures around an offshore monopile foundation leading up to liquefaction and the effects of gravel cover replacement around the pile on the stability of the foundation. A range of wave tests using a drum centrifuge was performed under a centrifugal acceleration of 70 gravities. It was found that liquefaction firstly occurred at the side of the monopile against the direction of progressive waves, which indicates the significance of the rotation of principal stress axes as well as the restriction of the partial drain in the sand. The gravel layer replacement with a range of 2 times of usual scour protection could not prevent the occurrence of liquefaction and the collapse of monopile under severe wave conditions. This indicates the significance of embedment of the monopile in the dense layer in addition to the scour protection.

 Steel pipe piles have been used for a long time in Japanese port facilities. Nowadays deep embedded and large diameter steel pipe piles have been widely used in the port facilities for supporting the large vertical load, as growing size or changing structural types of port facilities. Therefore, an estimation method of the bearing capacity of steel pipe piles is not consolidated. In this paper, a series of pile penetration experiments were conducted using a double-pipe model pile by which inner friction resistance, R_fI, and the annular part resistance, R_p can be separately measured. From the measured data, unit resistance of inner friction, q_in and the annular part, q_out were calculated. As a result, the unit annular resistance, q_out was widely changed according to the plugging of inner friction.

 In order to use the premises of the offshore waste disposal site highly, it is necessary to construct piles into the bearing layer. In such a case, piles penetrate through impermeable layer. At that time, the pile is thought to bring the waste below the impermeable layer. In this study, the large-size granular waste in the waste disposal site was easily simulated on a flat metal plate, and the penetration characteristics of flat plate subjected to eccentric vertical load was investigated. As a result of experiments, it was confirmed that the flat plate was penetrated while rotating gradually, it was separated from the pile at shallower depth as the eccentricity of the vertical load was lager. In particular, when the flat plate was separated from the pile, it is considered that the reaction force from the ground is in a state close to the limit state. In addition, it was confirmed that when the thickness of the flat plate is large, the moment to resist the rotation of the flat inclination angle of the flat plate to the increase of the penetration amount is small.

 Artificial tidal flats are constructed using dredged soil with high silt-clay content at port channels and anchorages, but the way of constructing as habitats of short-necked clam hasn’t been established. Experimental tidal flats were constructed in Ariake sea to investigate the positive effects of these habitats on short-necked clam populations. Temporal variations in survival rates could be estimated from the monthly total sulfide in the bottom sediments and the condition factor of clam.

 The object of this study was to reveal the role of attached organisms on oyster shell in Osaka Bay. In this study, we focused and clarified quantitatively organic matter decomposition by attached organisms on oyster shell. Attached organism carbon weight of animals and microorganisms were 1.3-67.6 gC/m² and 2.0-47 gC/m², respectively. Oxygen consumption rate by attached organisms on oyster shell by dark chamber method was 4.59-239 mgO₂/m² /hour. Oxygen consumption rate of microorganisms occupied 47-97% in all oxygen consumption. Oxygen consumption rate by attached organisms on oyster shell was 2.45 times higher than that with respiration. In addition, the oxygen consumption rate by the attached organic matter was 5.63 times higher than that of the attached animal. It was found that oyster shells provided habitat to attached organisms to promote the organic matter decomposition.

 In recent years, it is reported that the catch of short-neck clams Ruditapes philippinarum shows a decreasing trend year by year. The aim of this research is to develop a method to estimate suitable habitat for juvenile short-neck clams in a short period from multiple perspectives. As well as drone aerial analysis using UAV, grain size and X-ray fluorescence analyses of sediments were conducted to develop this method. A UAV camera with 20,000,000 pixels was used for drone aerial shooting, and a 3-dimensional model was made for GIS analysis to obtain ground information. Also, results of grain analysis were added to assure ground information. X-ray fluorescence was used to obtain sediment information. As a result of a multiple regression analysis by setting population of juvenile short-neck clams as the objective variable and ground and sediment information as the explanatory variable, correlation more than 0.6 was shown. According to these results, this method shows possibilities to estimate the population of juvenile short-neck clams in a short period from multiple perspectives.

 Suitable physical characteristics associated with wave and current for rearing juvenile Manila clam, Ruditapes philippinarum (artificial seeds) using a suspended culturing system was investigated in the field survey within a live fish preservation in Era Fishing Port (Matsumae Town), southwestern Hokkaido, Japan and laboratory experiments. The results indicated that the use of fixed cage and the placement of substrate were important for their growth as well as different types of substrate such as gravel and pumice, depending on the different life stages of the clam.

 In 2016, widespread coral bleaching occurred in Amitori Bay, Iriomote Island, Okinawa, Japan. In this study, the coral coverage, spawning rate, number of juvenile coral colonies, water temperature, and other data were measured in 2017 and 2018 to determine the state of the coral communities after intense bleaching and predict their future recovery. The following principle results were obtained: (1) The coral coverage significantly reduced in 2017 than in 2016 and remained constantly low in 2017 and 2018. (2) No bleaching was observed in 2017 or 2018 owing to the decrease in the water temperature by the typhoons. (3) The spawning rates in 2017 and 2018 were 37.5% and 65.9%, respectively, exhibiting a certain degree of recovery from bleaching damage to a certain level in 2018. (4) Several juvenile coral colonies were observed, particularly at the mouth of the bay. (5) The coverage recovery was considered from the perspective of survey results of this study and the physical field. A nonuniform pointwise recovery was suggested, and recovery was initiated at the mouth and the Amitori side of the bay center.

 To reduce the impact of global warming, “blue carbon” has been received attention as carbon stocks which can be captured and stored by marine plants and animals. With the growth of eelgrass, Zostera marina, carbon dioxide can be absorbed, and the captured carbon can be stored at the sea bottom due to the renewal of eelgrass. When considering how eelgrass meadow efficiently absorb carbon, it is important to evaluate deflected vegetation height (DVH) in a uniform flow field since it affects the absorption rate of carbon by photosynthesis of SAV. This study thus aims to examine DVH based on conditions of water depth and flow rate. It was found that the ratio of the length of SAV and water depth is an important factor to control deflected vegetation height. It was found that completely submersion limit can be presumed by using Ca and B.

 The eelgrass beds are important for coastal ecosystems, and there are many researches on monitoring. The authors are engaged in research to analyze the area of eelgrass beds from aerial photographs. The authors (2018) have shown that CNN can learn eelgrass field images and perform image discrimination with 94% accuracy. CNN is an algorithm that learns outline features and performs image discrimination in general. However, the eelgrass field image has few outline features, and the examination about the fact that the identification accuracy of the eelgrass field was high was not enough. In this study, we focused on pattern of feature map and verified discrimination.

 The purpose of this study is to evaluate the effects of long-term distribution and biodiversity of trans planted eelgrass bed in breakwater by comparing with surrounding natural eelgrass beds in Shimokamagari Island, Kure city, Hiroshima prefecture.

 The distribution area of eelgrass inside the breakwater became more than twice the transplanted area in Dec. 2001 however, it decreased significantly from 0 to 37% since 2006. There was no significant change in Natural bed (NB) between Dec. 2001 until Nov. 2015. The shoot density of Inside breakwater (IB) increased with seasonal variation after transplantation, but then it declines with 0 to 12 shoots, and all the eelgrass disappeared during the fall decline period, and the eelgrass beds were formed again by the seeds in spring. It became the annual eelgrass bed. The light transmittance was calculated from the amount of sediment deposition on the leaves. The light intensity of IB was about 15% more than NB.

 In the breakwater, the eelgrass community species diversity was lower in both the phytal animal on the leaves and macrobenthos in the sediment than in natural eelgrass surrounding. After eelgrass transplantation in 15 years, it shows that there is similar genetic diversity for eelgrass community in the breakwater and also natural eelgrass.

 The aim of this study was to confirm the effect of magnesia mortar and Shochu distillation lees on the growth of microalgae in the sea. Cylindrical blocks made of four different materials, namely cement mortar (C_M), magnesia mortar (M_M), and cement and magnesium mortars containing Shochu distillation lees fermented by lactic acid bacteria (C_S, M_S) were used for experiments conducted in summer and winter. The blocks were placed in the sea covered with a net to prevent fish from eating the microalgae growing on them. Seawater temperatures were recorded with a temperature meter at 10-min intervals. Ten blocks were collected after three days, one–six weeks in the summer experiment, after one–three weeks in the winter experiment, and placed in an N, N-dimethylformamide solution. The concentrations of chlorophyll a were measured to determine the density of chlorophyll a in the microalgae on the blocks.

 The seawater temperature was 26–31°C in the summer experiment and 17–21°C in the winter experiment. The density of chlorophyll a increased for one to two weeks after setting in the sea during the summer experiment and decreased gradually from three until six weeks after setting. The density of chlorophyll a in M_S was significantly higher than in C_M at one, three, and six weeks after setting in the summer experiment and one and two weeks after setting in the winter experiment. Magnesia mortar and Shochu distillation lees contributed to the growth of microalgae in the sea.

 In this study, it was intended that we evaluated stability of the stratification for an index quantitatively about the current control function by the artificial reef in a fishery ground constructed in Osaka bay. After field research, we calculated Ri (Richardson number) which was the index of the stability of the stratification, ME (mixed effect), UE (upwelling effect) and compared those values in a fishery ground with control area that set for the downstream side. As the results of investigation of Ri in the fishery ground was smaller than control area and UE>0. It was confirmed upwelling and mixture of lower water mass in the constructed fishery ground.

 It was concluded that mixture of the seawater, upwelling occurred by located artificial reefs, and the knowledge for quantitative evaluations of the current control function were successfully obtained by field research.

 In this study, we considered how releasing red spotted grouper seedings have worked and how artificial reefs contribute with their growth at the coast of Ehime Prefecture. Interrelationships in the amount of seedings, underwater observed information and catch statistics are investigated. Young and semi-adult tended to observe more often at the reef areas with total seedings increasing, and the grown-sized were caught at some years later. In summer, breeding colored individuals were also confirmed. Accordingly, it is suggested that the role of artificial reefs is not only their early shelter, but also growing and breeding sites, all life cycle bases.

 Shallow bottom was constructed by using granulated coal ash (GCA) as a material in the inner harbor where benthic organisms can not live due to the influx of organic matter from sewage.Based on thesurvey results of benthic animals for about 3 years on the tidal flat implemented in advance, the condition of animal regeneration in the shallow bottom was evaluated, and the organic matter purification capacity to the sewage load by shallow bottom was calculated.In addition, the influence of the bottom sediment condition formed by GCA on the habitat of benthic animals was verified.As a result, it has been revealed that the organic matter of about 10g-COD/m² is consumed by benthic animals. It is shown that GCA can reduce H₂S, NH₄⁺ concentration, etc., and the amount of deposited sludge.

 There were changes in the cross-shore distributions of the peracarid crustaceans, associated with the storm-induced morphological changes. The changes in the cross-shore distributions were consistently and quantitatively accounted for by the variations in the developed suction, caused by event-induced morphologic changes in the beach profiles.

 Recently, precast concrete is expected to be used in port structures such as piers in order to improve productivity. The authors propose a new connection structure of pile top using loop joint in the construction of pier. In this study, in order to evaluate the influence of the difference in the type of vertical construction joint or connection structure on the mechanical properties of the structure, the loading test with the beam specimen was conducted. The present result suggested that the difference in the type of vertical construction joint has little influence on the flexural capacity and shear capacity of the beam specimen, the beam using new connection structure called separate type loop joint has flexural capacity and shear capacity that is equal to or higher than that of beam with reinforcing bars placed in one row without joint. Furthermore, it suggested that these mechanical properties can be estimated using Standard Specifications for Concrete Structures and equations proposed by F, Leonhardt.

 The authors have already proposed “Sleeve tube type” as a pile head connection which is suitable for precast superstructure of vertical pile pier. However, for the case of raking pile pier, which is also widely used as port pier for its high lateral rigidity, “Sleeve tube type” is difficult to be applied for the concern of lower rigid connection of precast concrete due to larger sleeve tube diameter. In this paper, the authors proposed another “Socket rebar type” as a new type of pile head connection for raking pile pier, and cyclic loading tests are carried out to confirm the rigid connection of pile connection for both methods. As a result, under test conditions with a raking angle of 10 degrees, “Sleeve tube type” was almost the same with conventional pile head connection, and “Socket rebar type” was better in terms of rigid connection and lateral rigidity.

 In this research, we focused on developing an economical seismic retrofit method for pile supported wharf by retrofitting a buckling restrained brace as a damping member. The effective setup for damping member such as its layout, axial yield force and axial stiffness, and effect of frequency characteristic of input wave was examined through the non-liner finite element method. The targeted wharf have depth of 13 meters with five rows of steel pipe pile. The model consists of two types of sandy soil layer on the foundation as ground conditions, on which a rubble mound, L Shape Retaining Walls and backfill soil. The buckling restraint braces were installed between piles as its angles of 45 degrees, and the layout of installation were set between all the piles and between only two piles of the sea side. The effect of the retrofitting damping member was to reduce the maximum displacement of the wharf about 25% to 30% by sharing the bending moment of pile head with its energy absorption and reduction of rigidity. By appropriately selecting the axial yield force and rigidity against pile bending stiffness, we showed that reinforcement was obtained through balanced distribution of force on an existing structure.

 Intermediate soil improvement method of coupled piles is to construct cement consolidation improvement on the ground around the piles, and is a new method devised with an expectation of increasing lateral resistance of coupled piles. The purpose of this study is to confirm the effect by large-scale model test toward the implementation of the improvement method. Therefore, the cross section assuming the actual structure was reproduced on 1/30 scale, and the dynamic model test was conducted with a underwater shaking table. The experimental results show that the improvement method reduces horizontal displacement of coupled piles even when the surrounding ground moves to the sea side with the sheet pile, and show that the effect is expected even in actual structures.

 Basement parts of breakwaters at fishing ports are constructed underwater, and it is mostly difficult to functionally diagnose deterioration of the submerged basements by visual observation from land. Therefore, a diagnosis method by evaluating natural vibration frequencies obtained from free vibration measurements of the upper parts of breakwaters (the breakwaters above water) is examined. However, by using free vibration, it is difficult to evaluate natural vibration frequencies on site. In this study, a method to evaluate natural vibration frequencies from resonant curves by forced vibrations is proposed. Its applicability was examined by laboratory and on-site tests, and its effectiveness for functional diagnosis at fishing port facilities was discussed. As a result of the laboratory test, it was confirmed that natural vibration frequencies were dependent on the number of compression springs, and it highly correlated with the theoretical values. The result of the on-site test showed that the forced vibration method was easier and certain to evaluate natural vibration frequencies, and was applicable to functional diagnoses including defect estimation by differences of natural vibration frequencies.

 It is not easy to predict sedimentation by numerical simulation for channel and port area situated along river mouth to costal area especially because of complex behavior of advection-diffusion of siltation by waves and flow, and drift sand at shallow area by waves. Therefore, in this research, studies of channel sedimentation such as the relationship between turbidity and external forces, changes of sedimentation trend with varies of location as river mouth area and channel area, and seasonal effect to the sedimentation etc. were carried by long-term bathymetric surveys and field monitoring such as wave, current and turbidity at -14m channel dredging site. As the results, significant increase of turbidity and sedimentation in the channel was occurred during rainy season with frequent high waves. Therefore, dominant effect to sedimentation in this channel was suggested as waves by this study results.

 One of the causes of the beach erosion is due to the disruption of continuous longshore sand transport by artificial structures. In developing countries including Vietnam with a rapid economic growth, beach erosion that was experienced in Japan in the 1960s‒1970 is now occurring. Various artificial facilities for the economic development have been rapidly constructed on a coast with insufficient adjustment of their plan, and once erosion occurs, the stop-gap measures against erosion have been widely taken, resulting in further downcoast erosion. In this study, these erosion problems were investigated by comparison of aerial photographs together with the field observations on October 23, 2016 and November 9, 2017, taking beach changes in Phan Thiet as an example.

 Golden Beach in Taiwan is a famous sandy beach attracting many people because of a wide sandy beach and beautiful sunset. In recent years, however, this beach has been eroded. As a measure against beach erosion, groins were constructed as well as the beach nourishment on the beach. Despite these efforts, their effect was insufficient in recovering sandy beach. In this study, the beach changes in a widespread area including the Erren River, Golden Beach, and Anping Harbor were investigated using the satellite images and bathymetric survey data. Field observation was also carried out on May 25, 2018 near Anping Harbor and Golden Beach. On the basis of these field data future measures were discussed.