The authors have proposed a method of installing intersecting anti-rolling tanks at the top of the caisson to reduce the motion of the rotating system of a floating caisson and have confirmed its effectiveness in reducing the rotating motion through laboratory hydraulic experiments and numerical calculations. However, these studies were mainly based on regular waves, and it can be said that there was a small-scale effect. In this study, intersecting anti-rolling tanks were installed on an actual giant caisson (dead weight class 8000 tons) used for the eastern breakwater of the Hitachi-Naka Port Area of Ibaraki Port in Japan. The motion reduction effect was confirmed in real sea conditions where irregular waves act on the caisson. When the floating caisson without these tanks was subjected to head-on irregular waves in the actual sea area, it resonated with component waves close to its natural period, resulting in a larger pitch. However, the installation of the intersecting anti-rolling tanks reduced the frequency response of the pitch near the natural period more, and the floating caisson showed a high damping effect.

 In order to promote the decarbonization of port construction, it is important to consider CO₂ emissions at the design stage, but the CO₂-oriented design method has not yet been established. Although there are some reports to calculate the CO₂ emissions of port construction, there is no case to compare the CO₂ emissions of different structural types designed to meet the structural stability requirements under the same conditions.

 This paper is a feasibility study to deal with the trade-off relationship between cost and CO₂ emission of some structural types of quay walls. Firstly, three structural types were selected to meet the requirements under the same design conditions. Then, the construction costs and the CO₂ emissions were calculated to investigate the trade-off relationship between cost and CO₂ emission for the selected structural types with shadow carbon pricing. The results suggest that the structural type selected may vary depending on the decision indicator (mainly construction cost and CO₂ emissions) in the design.

 The Vertical Line Source Green's Function method (VLG method) has been shown to be effective for estimating wave height distributions in harbors with arbitrary configurations. This method has also been extended to cases where there are variations in water depth, such as navigation channels and sea ponds. In this study, we focus on how to apply the boundary integral equation analysis to multiple connected water depth regions in a harbor, using the extended VLG method. We show that for a complex harbor region with separated water depth areas, the boundary integral equation of the analysis can be applied as if these areas were interconnected by narrow passes, treating the domain as a simply connected one. Additionally, we consider the wave transmission through detached breakwaters and jetties to examine the sheltering effect in a harbor. Our numerical examination provides insights into the effectiveness of the VLG method for modeling wave behaviors in complex harbor environments.

 In TOMAKOMAI Port West District, the sedimentation of channel is an important problem. However, it is necessary to consider the effect of calmness for sand transport countermeasures, since there is also a problem of tranquility due to long-period waves. For this reason, we investigated countermeasures using a submerged breakwater with a small reflected wave. It is important to accurately model the sediment transport behavior around the submerged breakwater with a multi-layer model, since the suspended sediments partially pass with the flow on the submerged breakwater. Therefore, in this study, develop an evaluation model of the flow and the SS around the submerged breakwater, after reproducing the flow and SS of the field observation. Next, using this model, we clarified the effect of submerged breakwater on reducing sand drift.

 The stability of seaweed blocks using coal ash placed on the sandy seabed was examined by hydraulic model experiments. The coal ash mixture has a lower density than ordinary concrete, which is disadvantageous for the stability of seaweed blocks. However, the stability was ensured by devising the block shape. The following blocks were used in the experiment. (1) Rectangular blocks with normal density, (2) Rectangular blocks with low density, and (3) Two types of seaweed blocks with holes, slopes, legs and with same low density as (2) that have the same representative lengths as the rectangular blocks. As a result of the experiment, rectangular blocks with normal density were stable. Rectangular blocks with low density were not stable. Seaweed blocks devised shape with low density were stable. The legs of the block contributed greatly to its stability.

 In order to identify inundation risks due to storm surge and high waves, and to plan disaster prevention and mitigation measures, it is desirable to utilize storm surge and high wave inundation analysis. However, the increase in computational cost of analyzing the wave field, including the wave direction in the vicinity of the port, is a practical challenge. The purpose of this study is to propose a storm surge and high wave inundation analysis method that reproduces the inundation traces by combining a low computational cost wave calculation method targeting Shimizu Port, which was affected by Typhoon No. 19 in 2019. The study also aims to clarify the influence of wave direction in inundation analysis. It was confirmed that a simplified estimation method for wave direction by the line of sight angle, approximately reproduces the incident wave direction calculated by the Boussinesq model. In addition, when considering the wave direction based on the line of sight angle in the storm surge and high wave inundation analysis, it was confirmed that the vector division method reproduces the range of inundation traces most accurately. The proposed method provides useful insights for practical storm surge and high wave inundation analysis.

 Elemental technologies have been developed to convert 2D design drawings of bridges and tunnels into 3D models by using a technology that automatically converts and integrates various data with different description formats (DPP). In this study, in order to apply this technology to the field of ports and harbors, the elemental technology was implemented using caisson structural drawings. As elemental technologies, we have implemented a program to read information on caissons (height, width, footings, etc.) and bulkheads (depth, width, center position, etc.), which are necessary for accurate representation of the external shape of caisson structural drawings, from line information in sectional and side views, and a function to output detailed models using the read data. In addition, a function to output a finite element model for seismic response analysis software, which is often used in the port and harbor field, has been implemented. This enables engineers who are not familiar with the program to automatically create a 3D model of a caisson with a standard shape.

 We developed an unmanned aerial vehicle (UAV) with a small electric winch that raises and lowers water quality sensors for coastal environmental surveys in very shallow water areas. The usefulness of the UAV was investigated through its application to estuarine areas with large spatial gradients of water temperature and salinity. The UAV equipped with a highly accurate sensor can measure the vertical distribution of water temperature and salinity at 13 points in the coastal waters within about 1 km of a home point in about one hour. UAV observations of water temperature and salinity agree with shipboard observations, indicating the UAV can survey water temperature and salinity distributions as an alternative to shipboard observations. For more accurate observations using the UAV, mainly in the near sea surface area, the measurement procedure should be improved by adjusting the ascent and descent speed of the sensor.

 The scope of offshore construction work, such as floating offshore wind power and submarine resource development, is expanding into deep water areas. Waves and wind are important design and construction conditions, but the influence of ocean currents cannot be ignored from the perspective of construction safety for work vessels and navigational safety to the construction area in deep water. However, offshore current observation data is scarce, and JCOPE reanalysis data is effective for this purpose. In this paper, we examine the characteristics of ocean currents in the large water depth region of more than 100 m where offshore construction will be deployed in the future using JCOPE2M.

 As a result, it was confirmed that JCOPE2M, which is a daily mean current, can sufficiently grasp the characteristics of offshore currents due to its high correlation with JCOPE-T. The maximum currents were about 0.5 to 1.0 m/s on the Pacific Ocean side north of Fukushima-oki and the Sea of Japan side, and more than 2 m/s on the Pacific Ocean side south of Fukushima-oki. Vertical profiles in the middle and lower troposphere were found to be overestimated by the 1/7 power law recommended by the guideline.

 One of the key issues in protecting the coastal sandy beach environment is to prevent erosion, sediment runoff, and loss of coastal dune surfaces from daily waves and wind. Although coastal vegetation is effective in preventing blowing sand, it is unclear to what extent it is effective in preventing erosion and sediment runoff from tsunamis and the storm surges and torrential rains caused by typhoons, which have become increasingly large in recent years. Numerical risk assessment requires clarification of the sediment runoff control effect of vegetation and its mechanism.

 This study focused on the sediment runoff control effect of vegetation and conducted hydraulic experiments to clarify the effects of coverage and placement. The effects of two types of waves (bore waves and steady flow) and different grain sizes of sand (silica sand and actual beach sand) on the amount of sediment transport were considered. In addition to the amount of sediment transport, the location of scour was also found to be different for the different waves. Based on these results, the sediment runoff control effect of vegetation was formulated. In addition, the results suggest that the placement, as well as the vegetation coverage, is a major factor influencing the conditions that increase the risk of localized sediment runoff.

 Microplastics adsorb highly toxic chemicals, and there are concerns about their impact on marine organisms. Under these circumstances, the actual status of MPs pollution is being investigated in Japan. In this study, we focused on Tokyo Bay and grasped the actual condition of MPs pollution in the ocean surface. The purpose of this study was to understand the seasonality of the number and size of MPs drifting on the sea surface. As a result, it is possible that the numbers, types, and sizes of MPs detected in Tokyo Bay vary greatly depending on the sea area, and that the number increases with increasing rainfall, and that the number, types, and sizes of MPs detected differ depending on the sea area due to differences in inflow sources. It was suggested that there was a tendency for the size to decrease with an increase in the number of MPs, and that there might be differences in the fragmentation mechanism depending on the polymer.

 In this study, semantic segmentation based on deep convolutional neural networks was applied to aerial images taken after the 2011 tsunami event for detecting tsunami debris. With both of SegNet and U-Net, tsunami debris area has been successfully extracted from the images with 75% of IoU at maximum. In the conditions tested in this study, SegNet shows better accuracy than U-Net, and the recall and IoU get higher with larger input image sizes while the precision doesn’t show clear trends with image sizes. Although the total accuracy can be higher with larger image sizes, the reproducibility of the boundaries of debris area seems better with smaller image sizes. The accuracy of debris detection with both of SegNet and U-Net is higher than object-based analysis and also simple CNN based segmentation. For further discussions of optimal learning conditions and architectures, more sample images should be included for the learning and testing processes.

 We have devised the on-site reforming method to improve a seabed clay ground by mixing with a steelmaking slag at the original position. In order to substantiate the usefulness of this method, we have been carried out field experiments of construction. As a result of experiments, it was found that it was possible to mix the steelmaking slag uniformly enough for the seabed clay ground with a natural water content, and the strength of the improved clay soil exceeded that of the indoor mixing with the hand mixer. It was also confirmed that 2.5m of the surface layer of the ground could be reformed to the improved clay soil and that an underwater embankment could be constructed. In addition, the difference in the concentration of suspended solids between before and during construction was within 10 mg/L. This confirmed that the method was capable of suppressing turbidity during construction.

 This study examines the behavior of small vessels drifting in a tsunami and the impact force of the drifting vessels on a seawall built behind a sand dune by means of a 1/100-scale hydraulic experiment. As a result, it was determined that the likelihood of a ship colliding with the seawall increases when the non-dimensional initial location (distance from the shoreline) becomes less than 0.6. The bouncing water mass of a tsunami generated in front of the seawall tends to reduce the impact power of a ship on a seawall. When there is a structure in front of the seawall, the influence of the bouncing water mass on the impact force can be estimated by considering the ship's drifting speed and the time lag between the tsunami and the ship reaching the seawall.

 The authors investigated the consolidation properties of dehydrated treated soils as they change with the consolidation effect.The authors also estimated the hydraulic conductivity from the exchangeable cation using the theoretical evaluation equation for hydraulic conductivity. In this paper, fall cone tests, constant strain consolidation tests, and flame atomic absorption tests were conducted using solidified treated soil, which is a mixture of dredged clay and solidifier, near the NewKitakyushuAirport in Kitakyushu City, Fukuoka Prefecture, Japan. In the fall cone test, the undrained shear strength and liquid limit were examined. In the constant-strain consolidation test, e-log p curves and the relationship between pore ratio and hydraulic conductivity were obtained. The exchangeable cation of the solidified treated soilafter consolidation was measured bythe flame atomic absorption test, and the hydraulic conductivity was estimated. The results showed that (1) the relationship between the liquid limit, e-log p curve, pore ratio and hydraulic conductivity varied with increasing curing time as the solidified treated soil solidified, and (2) the relationship between the exchangeable cation, e-log p curve, pore ratio and hydraulic conductivity varied with increasing curing time. (2) Comparing the estimated hydraulic conductivity from the exchangeable cation and the measured hydraulic conductivity from the constant strain consolidation test, the estimated value/measured value was estimated to be in the range of 0.05-9.02.

 A three-dimensional experiment was conducted to examine the effective width for increasing the power generation efficiency of the pendulum-type wave power generator by the width of the reflection wall installed behind it. From the pendulum's equation of motion, the amount and efficiency of energy generated by the pendulum were calculated. As a result, it was revealed that the natural period of the pendulum in three-dimensional conditions was shorter than in two-dimensional conditions, indicating the need to calculate the natural period in three dimensions. When the reflecting wall is installed, the power generation efficiency is maximum at the position of the standing wave's node, and it is high for relatively short incident wave periods, the same as in the two-dimensional case. When the width of the reflecting wall decreased, the development of the standing wave in front of the reflecting wall weakened, and the influence at the node and antinode positions was small. If the position of the antinode of the standing wave is avoided, the power generation efficiency can be increased when the width of the reflecting wall is greater than 1.5 times the width of the pendulum.

 The sand compaction pile (SCP) method, which constructs sand piles in sandy ground, is widely used for ground improvement such as liquefaction countermeasures and bearing capacity improvement. In this paper, numerical analysis was performed to understand the seismic behavior of SCP improved ground with spatial variability in liquefaction strength. Monte Carlo simulation was performed to evaluate the characteristics among seismic response, seismic settlement, and excess pore water pressure.

 In sediment transport analysis for port burial, it is essential to understand the model error and the external force level of the waves to evaluate the calculation results. In this study, the results of sedimentation analyses of ports in Hokkaido show the importance of indicating the area where the model reproducibility was confirmed and also statistically show that the error of the calculated sedimentation rate from the measured value is about 20% with a standard deviation of σ and about 40% with a standard deviation of 2σ. We also found that in ports, where relatively high correlations between sedimentation rate and wave energy can be obtained, these relationships enable the estimation of sedimentation rates from wave observations without sedimentation analysis. Furthermore, using the first-order correlation between sedimentation rate and wave energy from the Wave Weather Prediction Dataset 2022, which is the result of wave estimation associated with future climate change, we found that the amount of sedimentation at navigation and anchorage areas in ports on the Pacific side of Hokkaido would decrease with future changes in external forces of waves.

 In recent years Japan has experienced a decrease in the number of container ports at which trunk route vessels call, due to economic growth in the other Asian countries, increasing vessel sizes, and development of shipping alliance. This paper aims at analyzing detailed trends of container cargo transshipment in the transpacific route, in order to provide necessary information to parties concerned, such as government bodies or shippers in making their responsive actions.

 As a result, several significant points have been found. First, decrease of the ratio of direct shipment at Japanese ports was led by the decrease of the number of container services between Japan and East Coast of North America. Second, the major route of container cargo transported from and to Japan via other Asian countries is Japanese major container ports – Busan port – North American ports. Finally, potentially Japan can target at cargoes from/to countries in South East Asia to/from North America as cargos transshipped at ports of Japan, in order to increase the total cargo volume of transpacific route.

 In this study, to acquire and utilize wave data at all points, the accuracy of the Sentinel-6 satellite wave data was verified, and the validity of the satellite data and specific utilization methods were examined. The Sentinel-6 wave height data tended to be larger than the actual values (NOWPHAS wave heights). Therefore, we also derived a correction formula for the Sentinel-6 observations. As a result, it was found that the accuracy was improved by applying the correction formula. The wave energy around Japan was calculated and mapped, and it was found that the difference in wave energy from point to point was small on the Sea of Japan side.

 The improved ground has a large spatial variability due to the spatial variability of naturally deposited ground and construction. A seismic deformation analysis considering the spatial variation of the premixing treated ground is conducted by Monte Carlo simulation using FLIP. The unconfined compressive strength of the improved elements with spatial variability was calculated from the mean strength, coefficient of variation, and autocorrelation distance based on a log-normal distribution, from which the cohesion, initial shear modulus, and bulk modulus were calculated as input values. The main conclusions of this paper are as follows,

(1) The allowable residual horizontal displacement is satisfied with 100 % of reliability when the percent defective is less than about 33 %, regardless of the mean strength of the improved elements.

(2) The improved elements with unconfined compressive strength of less than 100 kN/m² are treated as equivalent to untreated soil, which is on the safe side analysis for residual displacement after earthquake.

(3) This analysis method can be applied to any type of solidification ground improvement.

 In this study, various tests were performed on the anchoring structure of Tsunami breakwaters. For the anchorage structure using reinforcing bars and cement milk, it was confirmed that the bond strength of the anchorage structure of the reinforcing bars had a margin of safety equivalent to the bond strength between reinforcing bars and concrete compared with the bond strength of Standard Specifications for Concrete Structures. Although limited cracking occurred on the edge surface, pull-out load did not decrease, confirming that there was no effect on the anchoring performance of the reinforcing bars under the experimental conditions. Also, to elucidate the load-bearing capacity of the anchoring structure between a steel H-beam as a shear keys and the bed-rock, a shear loading test using a full-scale physical model was conducted. Although cracks appeared in the concrete due to the behavior of the H-beam under the load, the load gradually increased until reaching its maximum value. Strain measurements on the H-beam confirmed that their behavior under the load was generally within the elastic range on this experiment.

 Petroleum products such as gasoline are one of the essential resources in disaster periods as well as normal periods. However, many petroleum storage facilities are vulnerable to the effects of earthquakes and tsunamis since they are located in waterfront areas which are susceptible to these hazards. In the case of the Great East Japan Earthquake, Akamatsu et al. analyzed how the supply of petroleum products to storage facilities through oil tankers helped alleviate the shortage in the affected areas. This study examined the problems and solutions related to the supply of petroleum products to storage facilities after an earthquake and tsunami disaster. It involved analyzing the impact of the Nankai megathrust earthquake and tsunami on these facilities and critical resources in business processes, from the tanker’s entry into the port to the delivery of petroleum products from the facilities. Additionally, the study addressed the necessary clearance work of navigation channels for tanker supply. For detailed analysis, we focused on four petroleum storage facilities along Ise bay, where the Nankai megathrust earthquake and tsunami potentially cause severe impacts.

 Rare earth mud and manganese nodules exist near the seafloor around Minami-torishima Island, which is within Japan's EEZ. The Pulp-lift method is being considered as one of the development methods. The Pulp-lift method is a transporting manganese nodules using a high-viscosity working fluid made by mixing rare earth mud and seawater. To realize this method, it is essential to estimate the yield of seafloor resources under various conditions. However, the viscosity characteristics of the working fluid were unknown, and the reliable estimation of the yield was not possible. In this study, the viscosity characteristics of the working fluid of the pulp lift system were clarified through experiments, and a simulation model was constructed for estimating the lifted yield.

 The effect of suspended sediment on inundation, run-up, wave pressure, and wave force caused by a black tsunami was investigated using hydraulic experiments with clear water and turbid water containing kaolin as bottom sediment. From experimental results, it was found that tsunami inundation can be locally accelerated in kaolin mixed water. Furthermore, the maximum value of surge-front wave pressure was reduced on average by mixing the kaolin. However, large surge-front wave pressure could occur at high concentration due to the high variability. The maximum value of quasi-steady wave pressure increased proportionally to an increase in the apparent fluid density due to the kaolin.

 In order to meet a goal of putting abalone circulating land-based aquaculture into practical use, labor cost saving is essential. We replaced the electrolytic device to reduce the accumulated chromaticity with an ozone aeration treatment that requires less maintenance work. We conducted beaker reaction examinations in laboratory and empirical study in demonstration facility to clarify the ozone concentration level resulting in reduction of the breeding water and verify whether or not useful microorganisms including abalone and nitrifying bacteria are affected adversely by ozone or free chlorine generated through the ozone treatment.

 The examinations and the study show the followings. It is possible to reduce chromaticity with low-concentrated ozone of 1 mg/L or less. Ozone below 3 mg/L in the breeding water does not affect microbial treatment adversely. Furthermore, free chlorine generated through the ozone treatment can be detoxified by microorganisms that nitrify ammonium and nitrous acid in the breeding water.

 It is important to understand wave information in coastal management. In this study, a wave estimation model with high accuracy was constructed at the heavily eroding Shichiri-Mihama-Ida beach by applying deep learning to orthomosaic images and meteorological information. It is shown that the third-generation wave estimation model SWAN can estimate the waves at the NOWPHAS observation point off the coast of Mie-Owase, and that a CNN can be applied to both the SWAN estimation results and coastal images to obtain a good estimation of significant wave heights. The results also showed that applying the CNN to both the waves estimated by applying LSTM to the wind speed data and the coastal image improved the accuracy of the significant wave height and wave direction and gave the good estimation of the significant wave period compared to the results obtained by applying the CNN only to the coastal image.

 Akita Port is one of the most important ports on the Sea of Japan side, playing an important role as a logistics hub in Akita Prefecture. In 2023, thirteen landing-type offshore power generators were installed in the port. However, the power generation facilities are located around breakwaters, which are relatively close to container groups and anchored vessels in the port. In this study, a hydraulic model experiment was conducted to investigate the speed and load of drifting debris impacting the offshore wind turbines. As a result, the behavior of the drifting object model was different for the first wave and the second and subsequent waves of the assumed tsunami. The maximum load on the structure model tended to increase as the difference between the storage depth and the inundation depth increased, but this was not the case for the drifting object model.

 Carbon neutralization is a global issue that needs to be implemented immediately, but the use of energy resource is not fully explored. In this study, we examine the carbon negative resources that can be used in the coastal areas as a tool for realizing carbon neutral ports. Deterioration of coastal water environment is mainly due to long-term accumulation of enormous energy of organic carbon, thus energization of soil organic carbon in reduced sediments leads to improvement of carbon circulation. In addition, energization of soil organic carbon simultaneously reduces emissions of CO₂ and other greenhouse gases such as CH₄. In this paper, the potential of reduced coastal sediments as a negative carbon resource is quantified, and the electrochemical characteristics of soil organic matter in the electric fields are revealed experimentally.

 Suitable sites for eelgrass can be evaluated from the range of parameters such as depth and Shields number. Using existing data where the eelgrass distribution and physical conditions in the same mesh, line graphs for each parameter for coverage and leaf length, and regarded HSI number string as a set of genetic information. Although the coverage and leaf length distribution could be reproduced qualitatively by 100,000 trials, there were many eelgrasses non-distribution areas, and quantitative problems were observed in the coverage and leaf length.

 The purpose of this study was to quantitatively evaluate the relationship between the distribution characteristics of birds and tidal levels on a small artificial tidal flat in the Hyogo Canal. We used a time-lapse camera to capture images of the artificial tidal flat and analyzed the images using machine learning to detect the number and location of birds. As the tide level increased, birds were detected in the upper part of the intertidal zone, and especially birds were located near the shoreline. The number of birds detected staying on inter tidal flat areas was about twice that of birds resting the masonry. No correlation was observed between tidal level change and the number of birds, and birds changed their distribution position depending on the tidal level between low and high tides, which allowed quantitative evaluation of bird use and distribution characteristics.

 This study aimed to obtain basic information regarding methods for promoting increases in feed organisms by supplying sea floor substrate. Onsite experiments were conducted by using net sacks filled with gravel as simple specimens. The ultimate aim of the authors is to use the surface of the blocks and other structures in fishing ports to increase the sea floor space that is habitable by benthos on which fishes feed. The specimens were left on concrete foot protection blocks for one year or longer, up to two and a half years. The number and the wet weight of macrozoobenthos, particularly of annelids on which fishes feed, collected from inside the specimens were greater inside the port than outside the port. The number and the wet weight of macrozoobenthos collected were similar to those on the sea floor at the anchorage in the port. It is likely that the specimens began to provide a habitable environment for macrozoobenthos during the years these specimens were left on the blocks. Thus, it is suggested that the placement of gravel or other sea floor substrate on structures in sea areas promotes increases in organisms on which fishes feed and enhances the fishing port’s ability to serve as a feeding ground.

 Evacuation in the event of a tsunami attack is an important issue for fishing boat services. In addition, fishing boat services need to consider many kinds of risk to their business continuity. To understand the thoughts of such service operators with regard to business continuity, we conducted a questionnaire survey of fishing boat services in high risk areas for the Nankai Trough earthquake. The results of our survey showed that many fishing boat services had considered measures for evacuation in the event of a tsunami. However, almost none of these fishing boat services had prepared a business continuity plan. It was also found that depletion of fishery resources was feared. Thus, not only tsunami disasters but also fishery resources are an important problem for them.

 The objective of this study was to quantify the biodegradability of organic matter in sediments from 13 tidal flats in the coastal area of Osaka Bay. Sediment organic carbon (SOC) ranged from 0.35 to 30.7 mg/g. Refractory organic carbon and labile organic carbon ranged from 0.32–23.2 mg/g (25–91%) and 0.03–9.37 mg/g (9–75%), respectively. Labile organic carbon showed statistically significant correlations with AVS and ORP, no correlation with carbon dioxide emission rate. Multiple regression analysis was used to identify three factors that affect the labile organic carbon: SOC, carbon stable isotope ratios and water content. These results indicate that organic carbon of marine and terrestrial origin is deposited on tidal flats in the urban coastal areas of Osaka Bay, and that organic carbon sequestration in the sediments on the tidal flats.

 The purpose of this study is to clarify the designation and development requirements for tsunami evacuation facilities focus on the coastal area of Enshunada, Shizuoka Prefecture, where severe tsunami damage is foreseen due to a Nankai Trough earthquake. As a result, this paper clarified the five types of location environment types and the selection/development requirements of tsunami evacuation facilities based on the characteristics such as the installation position, the location environment and the land use around the tsunami evacuation facilities in the tsunami flooded area.

 Medium-scale experiments on the collision applied by timber on a flat plate along with sea ice as a kind of tsunami debris were performed to investigate the applicability of the prediction method for sea ice collision force to other materials. At high collision speeds, sea ice caused brittle failures, but there was no fracture / separation of the timber, and the maximum collision forces by the timber were greater and their duration time were shorter than those by sea ice. The maximum collision forces of both sea ice and timber, which were normalized by the factors included in the prediction equation, were directly proportional to the collision speed, and they were roughly equal to each other. Therefore, it was presumed that the prediction equation could be used regardless of the physical properties and the failure mode. We also proposed a very simple method for estimating tsunami force and a tsunami fragility curve with tsunami debris such as sea ice floes and verified their validities from some trial calculations.

 During the construction of an offshore wind power generation facility, a SEP vessel lands its four lifting column legs (legs) on the seabed and jacks up its hull above the sea surface. At this time, ground pressure of more than 900 kN/m² acts on the ground through the legs, so a bearing capacity study is necessary. However, in soft ground such as cohesive soil, the leg penetrates several meters into the ground due to fracture, making it difficult to evaluate the bearing capacity using conventional methods. In addition, if the bottom of the leg is close to a structure, there is concern that the leg may affect the structure. Therefore, We conducted a centrifuge model experiment to simulate the penetration of a leg into the ground to understand the deformation of the ground and the stress state in the ground, with the final objective of proposing a method to evaluate the bearing capacity and the impact on the surrounding ground. This paper reports the results of the centrifuge model tests.

 In the case of temporary road construction along the coast, cases of protecting offshore slopes by laminating bags filled with crushed stones are increasing. The method of packing cobblestones in a bag is a material in which a filling material is packed in a synthetic fiber net. This construction method has the advantage of being able to perform rapid construction. In addition, the authors have developed a highly constrained bag that can be expected to have higher stability against waves than conventional ones. In this study, the wave resistance stability of a temporary road slope covered with the highly constructed bag is investigated.

 Experiments on the cross section of the dike confirmed K_D values of 12 to 13 and wave reflectance K_R of 0.25 to 0.45. In addition, it was confirmed that the high-restriction type bag exhibits higher stability against waves than the conventional type. Wave height is the only parameter in calculating the K_D value. However, in this study, it was suggested that there was a difference in stability depending on the period. Therefore, as a result of evaluating the irregular wave energy and damage rate, a good relationship was obtained.

 The authors propose a method of unitizing steel members by using perforated I-beams as a substitute for steel bars in the upper slab of port road piers. In this study, concrete filling tests were conducted on a composite concrete structure using perforated I-beams to confirm the presence of filling defects just below the web of the I-beam. In addition, pull-out and bending load tests were conducted to confirm the adhesion performance to concrete and the bending load capacity of the composite structure. In the filling test, it was confirmed that concrete filled the area directly under the web by the perforated I-beam. The perforated I-beams were shown to have adhesion performance equivalent to that of I-beams with studs in the pull-out tests, and bending load tests showed that the perforated I-beams had bending load capacity and deformation performance equivalent to that of I-beams with studs.

 There is concern about the risk of inundation caused by wave overtopping and surge overflow due to storm surge, and the countermeasures for the risk is an important issue. The authors focused on an impermeable double parapet seawall as a countermeasure against storm surge flooding, and proposed an estimation equation to calculate the wave overtopping discharge through the double parapet seawall based on the hydraulic experiments for regular waves. In this study, the estimation equation was partially modified, and validated for irregular waves according to the results of hydraulic experiments under irregular waves. Moreover, numerical experiments were conducted using OpenFOAM to confirm the applicability of the estimation equation on a wide range of conditions. The results of the numerical experiments agreed with the hydraulic experiments in terms of qualitative characteristics, however, there was a tendency to underestimate the quantity of wave overtopping compared to the hydraulic experimental results.

 The present finished form measurement for floor digging is mainly conducted by single beam or multibeam echo sounding. However, echo sounding takes considerable time for setting of equipment, navigation, and data processing. This study aims to improve work efficiency by utilizing the construction history data of a grab dredger for the finished form measurement. The location and depth of floor digging are estimated at each grid by the horizontal coordinate of the top of a crane boom and the length of hoisting wire rope. Field experiments are carried out at three different construction sites of floor digging to compare the finished form measurement between construction history data and echo sounding. The result shows that the finished form measurement by construction history data is in good agreement with echo sounding and the design depth. At over 90% of all the grids with 1 m by 1 m size, the finished form measurement by construction history data satisfies the shape control criteria for floor digging.

 Mixture of dredged clay generated during navigation channel maintenance and steel slag from steel mills (hereinafter referred to as "modified soil") is being utilized. In this study, as a basic investigation, the effects of specimen size and different maximum particle sizes of steel slag on the unconfined compression strength of the modified soil were investigated for two different addition rates, which are relatively low.

 As a result, the following properties were obtained. A linear approximation of the relationship between the ratio of the amount of slag to clay mass, which affects the strength of the modified soil, and the unconfined compression strength showed that the coefficient of determination, R², was about 0.53 for the total amount of slag added, but when the maximum grain sizes were matched and the ratio of the amount of slag below a certain maximum grain size to the clay mass was taken, the R² improved to about 0.9. Thus, it was found that the unconfined compression strength of the modified soil can be estimated by aligning the maximum grain size.

 Sediment quality of riverbank tidal flats was investigated before and after the covering of granulated coal ash (GCA). This study focused on the formation of recalcitrant organic carbon by GCA, and n-hexane extraction, fatty acid analysis, and combustion tests were carried out. The results showed that extraction of more fatty acids than oils and fats in the GCA layer, suggesting the polymerization of fatty acids by forming complexes with cations dissolved from GCA. In conclusion, GCA promoted the formation of recalcitrant organic carbon and production of organic matter by biological activities. Therefore, tidal flats using GCA create an environment that polymerization of fatty acids produced by animals by making metal complexes.

 The Ino map is a map created by Japan's first modern surveying technology based on the results of the 1st to 10th surveys (1800-1816) conducted by Tadataka Ino in the latter half of the Edo period. In par-ticular, with the intention of capturing the entire country, information on the coastal areas of the whole country is literally enriched. In this study, we investigated the transition of the coastal environment over the past 200 years by linking the spatial information (coastline and coastal place names) of the Ino map with the current environmental information by spatial information analysis. As a result, it was possible to grasp the changes in the coastline from the time of making the Ino map, the degree of disappearance of sandy beaches in the coastal area, and the degree of reduction in the risk of tsunami damage due to de-velopment in all the coastal prefectures to be analyzed.

 As a technology of protecting harbor facilities and hinterlands from tsunamis, high waves, and storm surges, a movable port entrance floodgate installed on the seabed has been developed in recent years. These floodgates are designed, constructed at two locations and put into service in Japan: Ofunato Fishing Port in Iwate Prefecture and Fukura Port in Hyogo Prefecture. By closing the port entrance, it also has the advantage of reducing the need to build protective walls inside the port. We proposed a new type movable gate which is different from the above two structures. The calculation is based on 2D FLIP analysis, which can calculate the interaction between the structure and nonlinear behavior of the ground during earthquakes. The contact phenomenon between the lift gate and the foundation was analyzed using the three-dimensional FEM analysis LS-DYNA, and it was confirmed that the proposed structural form almost satisfied the required performance.

 Although the amount of wave setup has a large impact on evaluating the wave dissipation effect of artificial reefs, only the impact of the crest water depth and waves is considered in the desk study. In this study, the effect of some types of artificial reef including tandem type, which has few cases of construction, are confirmed by 2-dimensional cross sectional fixed-bed experiments, in addition to evaluating the effects and impacts of subsidiary wave-dissipating facilities. The results suggest that 1)wave overtopping discharge decreases although water level increases behind the artificial reef by installing artificial reef; 2)the wave setup tends to decrease as the wave overtopping discharge increases when the distance from the shore is about the same, while the wave setup tends to decrease as the distance from the shore increases when the wave overtopping discharge is about the same; 3)the wave-dissipating works could be suitable as subsidiary wave-dissipating facilities for reduction of wave overtopping discharge.

 The reduction of greenhouse gas (GHG) emissions is an important objective in the fight against global warming. In this study, we investigated the organic carbon content of dredged material used to make synthetic sediments composed of the dredged material and converter slag from steel-making to be deposited on the seafloor behind the breakwater at the Port of Hakodate. We estimated CO₂ emissions from the transport of materials, the construction itself, and alternative disposal of the sediments on land. CO₂ emissions when altered sediments were deposited on the seafloor were lower than those associated with land disposal if the residual organic carbon content of the dredged sediments after land disposal was less than 75%. If the distance required for sea transport of the converter slag was less than a certain threshold, CO₂ emissions were lower when the altered sediments were deposited on the seafloor, even if the residual organic carbon content of the dredged sediments after land disposal was 100%. The results of this study suggest that seabed disposal of synthetic sediments is a promising way to reduce CO₂ emissions. Furthermore, if the marine transport distance of converter steel slag becomes less than a certain threshold, there may be cases where the CO₂ emission is smaller than land disposal. These results suggested seabed disposal of synthetic sediments as one of the promising measures to reduce CO₂ emissions.

 3d-LiDAR enable to get wide range point cloud data without UAV. It is difficult to get water surface by using LiDAR that use near infrared rays. But can get a part of the surface like whitecap. If it becomes possible to measure water surface by using LiDAR, it can be used for wide range wave measurement and solid-liquid measurement such as wave and sand on the coast. Therefore, in this study we examined the applicability of water surface measurement using 3d-LiDAR by water tank experiment.

 As a result of regular wave experiment, it became clear that LiDAR provide water surface data right under them. Measurement accuracy of LiDAR is affected the number of point cloud data and by increasing integral time within one-fifth of the wave period, accuracy is improved. In addition, we developed a method that get point cloud data indirectly by projecting a laser reflected on the water surface onto the screen.

 Two types of transportation surveys were conducted using web questionnaires to determine the accessibility of sandy beaches to coastal users. Based on the survey results, recreation values of sandy beaches were evaluated using the travel cost method. A local survey was conducted on visitors at four crowded beaches, while a nationwide survey was conducted on visitors to all beaches around Japan, and the result was analyzed by prefecture unit. The recreation values estimated for Shirarahama, Kariyushi and Emerald beaches coincided well with those estimated based on the results of the nationwide survey. However, the recreation value estimated for the Katase-Nishihama-Kugenuma beach was smaller than the value estimated from the nationwide survey. The results of the local and nationwide surveys showed that while the railway was the preferred mode to access Katase-Nishihama-Kugenuma beach, most of the coastal users preferred cars to travel to other beaches. The difference in cost of travel to Katase-Nishihama-Kugenuma and other beaches was because of the specific choice of the transportation to Katase-Nishihama-Kugenuma beach. The findings that the nationwide survey is applicable to beaches where coastal users arrive by cars. The local survey results also revealed that sea coastal users visited with no particular purpose to beaches. Although most coastal users visited to have a walk, sea bathing was not a primary purpose of visit. These results suggest the importance of conducting surveys for evaluation of the number of visitors to assess the recreation value of sandy beaches accurately. Based on these results, few suggestions for utilizing web surveys and methods comparing travel costs are discussed.

 Recently, it has been revealed that coastal areas and lakes and mashes play a role in absorbing carbon dioxide, suggesting the necessity of establishing a carbon credit approach for the freshwater carbon system. We proposed and verified a new method for estimating carbon dioxide sequestration and reduction using the equation of DIC metabolism (DIC equation). The proposed method has the advantage of considering only vegetation density and length, indicating its potential for use as a new method. The estimated annual sequestration of carbon dioxide by eelgrass in Komuke Lagoon, located in Hokkaido, Japan, using the DIC equation was 1.41 tonnes CO₂ ha-1 year-1, which is close to the value estimated value obtained from the carbon content of eelgrass in Komuke Lagoon and also the estimated value obtained by leaf marking methods in Lake Akkeshi, located in Hokkaido, Japan.