Appropriate maintenance should be conducted for harbor structures due to their vulnerability towards chloride induced deterioration. We have already proposed an evaluation method of residual structural performance based on the judgement result of deterioration by versatile structural analysis software. On the other side, a simple evaluation method without structural analysis is also demanded when deciding the maintenance priority of several piers. In this study, evaluation methods of residual structural performance introducing artificial intelligence to estimate the damaged area ratio towards assumed external force are proposed. The estimation accuracy of artificial intelligence models are verified and damage estimation for piers with random deterioration distribution are conducted. As a result, for both models utilized numerical information and image showed high estimation accuracy, and the image model can also grasp the damage distribution as well as the damaged area ratio.

 In fishing port and fishing ground construction, the serviced coefficient of the work vessel is a very important factor to calculate the construction cost properly. For important ports in Japan, the serviced coefficient is stipulated with the observation wave height according to the "Service coefficient setting" (1997 Ministry of LIT notification). However, in other harbors, fishing ports and fishing ground constructions, the serviced coefficient is applied mutatis mutandis. But its value is not accurate. In this study, the authors built a web application that calculates the service coefficient. In the web application, the serviced coefficient is calculated with wave height, rainfall, and wind speed for a specific period. It was clarified that the definition of stormy day and the construction period will cause a difference in the serviced coefficient. In addition, it was clarified that the construction in bad weather conditions greatly increases the serviced coefficient.

 For the effective use of dredged soil, we newly developed a large block-shaped artificial rock which is made by placing mixed slurry composed of soil, steelmaking slag and cement into the CAGE MAT directly and hardening it. Since the artificial rock uses a large amount of dredged soil of high water content, it is necessary not only to consider a quality control method applicable for changes in soil properties in mass production but also to check the existence of drying shrinkage cracks and the safety during lifting the block. Therefore, a field demonstration test was conducted and the flowability control was proposed where the flow value of the dredged soil was adjusted to be about 300mm by adding water to ensure workability during kneading the slurry. In addition, based on the load tests carried out on the full-scale size test pieces, the compressive strength was shown to be 0.81 N/mm² required for lifting the block.

 Cement or lime are widely used for ground improvement. However, on exposure to seawater, it deteriorates due to elution of calcium. Previous studies have proposed the countermeasure using Microbial Induced Carbonate Precipitation (MICP); however, most MICP studies have been laboratory based and for sand, not clay. Therefore, this study involves the preparation of samples of cement-treated clay. And seawater exposure tests were conducted in both the laboratory and actual environments. As a result, 1) the eluted calcium ions are re-fixed, 2) the crystals fill the gaps associated with deterioration, 3) the deterioration mitigation method can be applied to cement treated clay, 4) possibility of long-term preservation of strength of cement treated soil in seawater environment, were be clear.

 The mixture with dredged soil and converter steelmaking slag has the solidification property. However, the solidification strengths vary according to the differences in the clayey soil. The important factor of the strength improvement of the dredged soil mixed with steelmaking slag was considered as calcium silicate hydrate causes, C-S-H, which was formed by the reaction between portlandite in the steelmaking slag and amorphous silica in the clayey soil. This study aims to determine the effect of the amorphous silica contents in clay on the undrained shear properties of clayey soil mixed with steelmaking slag. The clayey soil containing different ratios of amorphous silica content were prepared by mixing kaolin clay and metakaolin. As a result, where the amorphous silica content ratio in clayey soil was 20% or less, the q_max increased as the amorphous silica contents in clay increased at the same curing time. In addition, when the mixture was solidified, the residual angle of internal friction φ_0’res was 49 to 52 degrees.

 Authors have developed a technique called the cement-treated and mechanical dehydration method (CMD) as one of recycling techniques for dredged soil. Cement-treated soils have been developed in the field geotechnical engineering, and cement-mixing has been widely utilized as a recycling technique. The CMD technique is able to manufacture high-strength soil block. This paper examines the long-term strength of the CMD soil block, which are set different preparing, and curing conditions such as summer/winter season and underwater/air environment. The results obtained from this study are summarized below.

 (1)The water content of CMD soil block decreases about 10 % in 2 years with increasing curing periods.

 (2)Unconfined compressive strength of CMD soil block cured in underwater increases to about 10MPa in 2 years.

 (3) CMD soil block with low water-cement ratio shows high unconfined compressive strength. The block cured in underwater, and manufactured in winter season have the following relationship. q_u=14.608×(W/C)^-1.592.

 As support for infrastructure export, it is an effective method to export Japanese technical standards and its system to developing countries. The technical standards in Vietnam have been being established jointly by Vietnam and Japan. The standards for design and construction were already issued while a draft of maintenance standards is at the stage of the final review.

 This paper presents the outline of the maintenance standards in Vietnam established based on Japanese standards, with a consideration of the legal system and actual condition of maintenance practice in Vietnam. Finally, the finding obtained from the process of establishing Vietnam's maintenance standards is summarized, which will be a reference for applying Japan's standards to other developing countries.

 The camera mounted on unmanned Aerial Vehicles (UAVs) for sea surface evaluation has recently attracted attention because it is flexible for moving and easy to use. However, it is known that the absence of measurement occurs when image quality is strongly affected by sun glitter. In this study, we develop a method to evaluate wave propagation from different oblique aerial video images. Ortho-images were created from video frames by using the collinearity equation and perspective transform. Time-averaged images were created by the average of frames during the time after that the grayscale images were calculated. The relationship between the time-averaged grayscale image and light environment was investigated by considering the reflection properties of the sea surface and the radiance distribution of incident light. This model emphasized the best observation angle. The significant wave period and the wave celerity can be evaluated from the gray-scale images. The wave spectrum, wave direction, and long-component wavelength were handled by using 2D Fourier transform and low-pass filter. As a result, applying the present method to data acquired in the Tateyama coast, the wave propagation characteristic was successfully evaluated.

 The unconfined compressive strength (UCS) of the sandy ground improved by the Permeable Grouting Method is usually set to about 100 kN/m² of the UCS. Since the strength reveals rather lower value than that of the clayey improved ground, it is concerned that the strength could be underestimated due to the disturbance of samples during sampling. To avoid the effect of disturbance, in-situ tests, as alternative methods, are proposed to use for estimating the unconfined compressive strength. However, in actual application, the conditions to select the method for quality assurance have not been clarified so far. In this study, an analysis on the UCS of core samples is carried out to study the conditions for selecting methods in quality assurance. The results show that the unconfined compression test using undisturbed samples is applicable to the evaluation of the improved ground with the gravel content of 15 % or less and the average particle size of 1 mm or less. In this case, it is noted that the specimen obtained from the sample with the sampling rate of 75 % or more should be used.

 Quasi-high-resolution open satellite images were collected from the Internet to extract seasonal variation of wide-area shorelines positions. The target area of this study is the eastern part of the Enshu-nada Coast in Shizuoka Prefecture extending 20 km from the mouth of the Tenryu River. The shoreline positions were read every 10 m from 78 scenes taken between 2010 and 2019. The result shows wavy distribution of shoreline position in the vicinities of break water and jetty, and also variational tendencies (accumulation or retreat) which are consistent with previous studies. Further, comparison with survey results shows that the mean error of shoreline position was similar to the spatial resolution of the satellite.

 It is difficult to tell the difference between the background and the wave splash in the rough weather, since both of splash and cloud is gray. In this study, we proposed a method that can analyze time series of maximum wave run-up heights automatically from the video frame instead of reading the maximum wave run-up heights respectively by measuring the video images. As a result, the calculated run up heights seems accurate since it draws a smooth parabola with respect to time. It is confirmed that time series of wave run-up height can be automatically obtained including the characteristic of spatial distribution of wave run-ups in this method.

 Wave monitoring at marine construction sites is of great importance in maintain the safety of workers and construction quality. In particular, a ship wave generated near a construction site hits ships and floating structures immediately and potentially causes a severe accident. A simple and low-cost monitoring system using buoy image analysis has been previously developed for a ship-wave warning system. However, this method cannot identify the wave direction, and thus, the measured wave may not reach the construction site. The purpose of this study is to propose a method of estimating wave direction using buoy image analysis. We conducted ship-wave tests in marine construction sites and confirmed that the accuracy of estimated wave direction was within ±22.5 degrees from the true value. The results confirmed the method’s capability of predicting a wave attack on a construction site.

 We examined the accuracy of the 3D image analysis for floating model experiments, the effect of imaging conditions on measurement accuracy, and labor saving for long-term measurements. The 3D image analysis was able to measure with high accuracy for the floating model experiment. To get high quality data, two cameras should be installed line-symmetrically with the object so that the ratio of the height to the horizontal distance from the object is 0.4 to 0.7, and the distance to the object in the long case, it was effective to secure the resolution with an optical zoom lens. Data containing white noise could be improved by low-pass filtering. Labor saving was achieved by using a commercial video camera instead of a high-speed camera. This method maintained the measurement accuracy and realized a significant labor saving of data analysis capacity. In the future, this method is expected to be applicable to irregular wave experiments that require long-term measurement.

 Wave runup height is important indices to be grasped for shore protection and storm surge damage reduction. However, the field observation methods for wave runup height have not been established.

 In this study, the field observation using ultrasonic-type water level gages was carried out to obtain the data of the wave runup height on the seaward slope of coastal dike.

 As the results, it is necessary to remove noise from the obtained data, and noise was removed using two devices considering the wave runup characteristics. It was confirmed that most of the runup height was detected from noise removal data. And the accuracy of the wave runup height measured by ultrasonic-type water level gages was almost the same as that measured by the capacitance-type wave gage.

 There are some existing studies on the relationship between the set values of 3D models and the accuracy or the arrangement of reference points and the accuracy for the purpose of improving the accuracy of UAV surveying. In this study, the relationship between and the condition related to field work and the accuracy was evaluated for the purpose of verifying the applicability of beach monitoring by UAV survey. As a result, it was shown that the field work could be simplified depending on the purpose of the beach monitoring survey.

 UAV Photogrammetry plays a major role in labor saving by unmanned operation, ensuring work safety and this survey method has been widely used in the land construction sites. According to the Survey Manual published by Geospatial Information Authority of Japan, it is required to set up Reference Control points in the target survey area for geo-referencing. However in case of the survey of wave dissipating blocks, one of the widely used harbor structures, it is difficult to set up the reference control points on the wave dissipating blocks because of the safety management issues. In this paper, the measurement accuracy of the wave dissipating blocks by UAV Photogrammetry without the Reference Control Points is verified by the applicability of the results of UAV Measurement Survey.

 As a result, this suggested method has an error of 10cm or less and measurement results could be expected to be used for surveying the output forms during construction and the disaster damage assessment.

 In order to investigate applicability of estimation for strength information of improved soil with small cohesive force by shear wave velocity measurement, some soil shear tests were carried out. In addition, we compared estimated value of shear wave velocity by conventional proposed equation with test results. These results showed that shear wave velocity of sands improved by chemical grout is determined by mainly effective confining pressure, void ratio and base material unit weight. And, shear wave velocity and effective confining pressure of normally consolidated cohesive soil has positive correlation. For the specimens using in this research, obvious relationship between cohesive force, shear strength and shear wave velocity couldn't be found.

 The objectives of this study are to validate SST (Sea Surface Temperature) of GCOM-C SGLI (commonly known as "Shikisai") in Tokyo Bay and to investigate the characteristics of monthly average SST. SGLI-derived SST was compared 210 samples with in-situ SST at three station in Tokyo bay from January 2019 to August 2019 at 11:00 AM synchronized with satellite within 30 minutes. As a result, the accuracy of SGLI SST in the bay was calculated with a standard deviation of 0.90 °C and a bias of - 0.27 °C when cloud removal was performed using the quality flag. The SST data derived from SGLI had an acquisition rate of 9 to 33% each month. Furthermore, as a feature of the monthly mean SST distribution, SGLI data well captures the front, especially at the bay mouth in January and February.

 Three high school students drowned at Zenibako Beach in August 27th 2017. Firstly, we check the past newspaper articles about the disaster accident at Zenibako Beach. As the result, some accidents occurred at this area. Secondary, we made the field survey and acquired the topographic information. At the field survey, we got the topographic information and current information due to use ADCP. ADCP attached to a water motorcycle. During field survey, we pigmented the rip current by the sea water colorant, and the pigmented current was recorded as the aerial photography by the UAV. The photographed were used to make grid topographic data and calculated the average current velocity. When we made the field survey, Japan Coast Guard, Hokkaido Prefectural Police and Otaru Fire Defense Headquarters offered the information about the accident.

 Grain size distribution is a fundamental information for sandy beach management and is essential for predicting the future sandy beach environment with climate change. However, it is difficult in terms of time and cost to make high-frequency monitoring over the entire beach. In this study, we aimed to develop a simple method to estimate grain size distribution from images taken by a smartphone, which is widely used by the general public, and examined the applicability of the calibration method using the virtual sediment images and effect of photographic conditions. A comparison between the conventional median grain size and that of defined by area percentages was conducted.

 It is desirable to effectively use clayey soil for reclamation from the viewpoint of sustainable development of society. In use of clayey soil, the stability against slip and future settlement should be examined, and it is important to understand the soil properties in advance. In this study, we introduce artificial intelligence technology to estimate soil properties such as consolidation constants based on information such as soil source, wet density, and picture. It is confirmed that the machine learning model developed by using the Convolutional Neural Network (CNN) can accurately estimate the consolidation constants, the liquid limit, etc. This paper proposes a landfill management system that integrates the AI model to estimate soil properties with the sedimentary shape analysis model and settlement analysis model.

 In use of clayey soil as reclamation material, the stability during construction and future consolidation settlement should be examined, and it is important to understand the sedimentary shape for each layer. In this study, we conduct centrifuge tests to evaluate the sedimentary shape and propose an analysis method which can get the composition of soil layers simultaneously. We also introduce artificial intelligence technology to estimate soil properties such as the liquid limit based on information such as soil source, wet density, and picture. It is confirmed that the proposed analysis model can reproduce the sedimentary shape accurately by comparing with the on-site data. The distribution of soil property based on artificial intelligence also showed high accuracy compared with the cone penetration test result.

 This study aims to quantify people and vehicles in a fishing port by using AI image recognition, and to examine how to use it to improve objectivity in planning and project evaluation which is conventionally conducted based on interviews from users. A demonstration test held at a fishing port with one of the largest catches in Hokkaido. In the fishing port, facilities have been improved for hygiene control and work efficiency. We quantified the use condition before and after commencement of new facilities.

 We developed an object detection model and an object tracking model using CNN （Convolutional Neural Network）, which is a kind of deep learning. The object detection model captured temporal changes in the number of workers, forklifts, and birds by using AI image analysis. These highly objective data such as total work hours, can be used as a basis for project evaluation.

 It is important to grasp the wave during marine construction. Conventionally, wave monitoring has been carried out by visual observation or measurement instrument. And the wave measurement using image analysis is attracting attention due to cost and real-time performance. The measurements using the image analysis and measuring instrument were performed on-site. The results of image analysis and measurement instrument were comparable. Also, if was found that the method based on image analysis is suitable for the monitoring of the wave due to cost, installation and real-time performance during marine construction.

 In Tokyo Bay, there exist deep depressions by the large-scale excavations for coastal reclamation, or as the natural topography of the seabed. Typical one of them is located off Futtsu coast, Chiba Prefecture with T.P.-15~-16m depth. The bottom sediment had become an area of poor fishing ground due to the progression of hypoxia and the accumulation of fine organic mud. Since 2013, a new attempt for the environmental restoration has been applied by beneficially using the land soil, generated in the Tokyo metropolitan area. Earth fill was conducted to raise the ground level of the depression, followed by sand covering (up to T.P.-11~-13m depth). Field monitoring has been carried out continuously to check the improvement of the marine benthic ecosystem. Healthy system was found to appear on the newly created ground surface. The results is reported on the long-term environmental monitoring from 2013 to 2019.

 Terrestrial soil excavated during construction is expected to be utilized as environmental improvement materials in marine area. However, it is a problem that soil generated by shield tunnel excavation often contains surfactants. With focusing on polyoxyethylene alkyl ether surface (AES), which is a typical main component in the surfactants, we considered the experimental methods to assess the natural degradation of AES in soil and the adsorption to soil. As the results regarding the degradability experiment, the following points to note were suggested to be considered: keeping the moisture content of the soil to the liquid limit; the shaking operation is performed in a dark place at 5 °C; shaking the soil in water at least for two hours, etc. Regarding the adsorption experiment, the following points were needed to be considered; a stirrer-type operation is applicable instead of shaking-type operation for the stirring processing; the solid-liquid ratio is appropriate 1:50 for black clayey soil.

 As a result of active dredging activities during the postwar high growth era, many borrow pits are located in enclosed bays in Japan. Borrow pits have been identified as sources for anoxic water masses and hydrogen sulfides that adversely impact the nearby ocean and borrow pits in various locations are being filled. Obtaining material to fill borrow pits is important for environmental restoration of enclosed bays. As the amount of dredged spoil from harbor construction work is inadequate, it will be necessary to effectively use soil and sand from sources including river and road construction works. However, schemes for quality control of materials from various sources have not been established. Based on the results of borrow pit filling in Osaka Bay, this study proposes a quality control scheme for the beneficial use of materials from various sources as well as an overall methodology for the adaptive management.

 Most Japanese littleneck clams (Rudiapeshi plilppinarum) are caught off Konagai, the northern part of Isahaya Bay in Nagasaki Prefecture, Japan. However, the catch is stagnant. On Shimabara Peninsula, adhering of suspended larvae is reported, but their survival rate is too low to increase the catch. In this study, transplantation tests of adult clams and natural seed (young clams) collection and growth tests were conducted using net bags containing gravel, which prevents ‘damage caused by predation and escape’. Laboratory tests using the net bags to identify the factors causing the main summer decrease were also conducted. As a result of the tests, the possibility of stable production increased through use of a series of processes from natural seed collection, conservation and growth, transplantation, to the catch of adult clams were demonstrated. It is also highly possible that decreased summer catch is influenced by water temperature. It was concluded that further discussions are necessary for the application of appropriate measures to further increase clam production in summer.

 To improve the environment of the Amagasaki Canal, a method for moving nutrients out of the system using a food web pathway derived from attached algae to fishes was investigated and field experiments were conducted. It was found that Tridentiger obscurus with bottom-dwelling properties gather in structures with some gap spaces installed near the water's surface. During the summer when water quality deteriorated, T. obscurus used the structures as a refuge. Such a structure would also reduce intraspecific competitions and allow for smaller T. obscurus to coinhabit around the shelter with the larger fish occupying the interstices of the structures. The stomach contents of T. obscurus suggested that they were feeding on attached algae and the shrimp in the structures. In addition, the T. obscurus were laying their eggs in the gap space of the structure.

 The Maldives with low elevation and narrow land, which was formed by the accumulation of coral sand and gravels owing to long-term wave action, has been experiencing the vulnerability against the climate change. On the other hand, various artificial modifications on shore and coral reefs have been undertaken, especially on residential islands in accordance with recent active economic development. However, actual conditions of artificial modifications and their impact have not been discussed. This paper is to clarify the current conditions of artificial modifications on shore and coral reefs and to examine their impact on the basis of the field investigation on several residential islands in Maldives.

 Internal solitary waves are likely to be excited by the external forces such as wind in stratified lakes and coastal areas. When the internal solitary waves break on a slope, potential energy (E_p) of the internal solitary wave tends to be lost completely. The previous studies showed that hypoxia recovers on sloping bottom boundaries in Tokyo Bay when a strong wind is given. However, E_p of internal solitary waves cannot be included in a real-scale simulation because of the hydrostatic pressure approximation. Therefore, this study aims to model the energy loss to take account the breaking of internal solitary waves on a slope. As a result, the energy loss of internal solitary waves can be modeled under hydrostatic pressure approximation successfully by using friction-type energy loss not only in laboratory scale phenomena but also in real scale phenomena, Tokyo Bay.

 Global warming induced sea level rise can cause various impacts to coastal regions of many countries specially islands. Effects of sea level rise in various aspects for coastal communities in Japan has analysed in many areas. This paper discusses the effects of sea level rise on estuarine hydrodynamics specially salinity intrusion along the river. A simple three dimensional model was used for the analysis. Tone river estuary was selected as an example location due to the availability of field survey data.

 Velocities were analysed for the present condition under different tidal phases and found a comparative match with the field survey data. Then the several scenarios of sea level rises were analysed for the different tidal phases ebb tide and flood tides. An increased salinity intrusion along the river was observed for sea level rise scenarios. Quantitative estimate of salinity values were obtained for each sea level rise conditions. Further, various inflow conditions caused for different salinity intrusion conditions.

 Intertidal flats play an important role on the maintenance of water quality and ecosystem of inner bays. Sediment transports on intertidal flats have not been clarified yet. In this study, a regional sediment transport was discussed by using high quality bottom survey, bottom sediment analyses and numerical simulations by gRSM and WDM-POM. In conclusion, a remarkable erosion/deposition tendency was not recognized, but a remarkable siltation due to a flood of the Yamakuni River was confirmed. Tidal and coastal currents of the Suo-nada Sea and the Nakatsu Intertidal Flat were calculated and discussed.

 Development of in-situ device to determine the model parameters for erosion in numerical modeling of bottom sediment transport in coastal areas was carried out. In the present research, two model parameters for erosion, namely, critical shear stress τ_cr and erosion rate parameter M can be estimated by the in -situ measurement using the device. In-situ experiment using the device was attempted at 19 sites in Minamata Bay, Japan, in 2019. We succeeded to determine the two parameters through the in-situ measurement effectively. From the comparison between the present result and the results from references, our results are included in the suitable range, but τ_cr shows smaller and M is higher than the previous researches because of the possibility of generation of fluid mud on the bottom surface in the bay.

 This study focus on the long-term improvement effect of sediment and water quality using granulated coal ash as sand covering material. To understand the effect, a field experiment and a laboratory experiment of the same scale and same time were conducted to compare the amount of sediment deposition, the ion concentration of pore water, and the change in the properties of the sediment.

 From the field experiment, we revealed that sediment flows out of the granulated coal ash layer when the water temperature difference between the inside and outside the layer reverses and the amount of sediment deposition was smaller than in the gravel layer. The calcium ion concentration in the pore water and the amount of adsorbed calcium ion of sediment were high in both field and laboratory experiments. From these results, it is suggested that the decreasing of the amount of sediment deposition in the granulated coal ash layer was caused by local scale phenomena such as density inversion and tide level change in addition to sediment property change.

 Artificial tidal flat utilizing dredged sediment have been developed and the case studies to show its effectiveness have been reported. However, it is hardly to say that the artificial tidal flat has solved the problem of the decreasing in catch of asari clam in these days. It is desired to develop new technology of high puroduct of asari clam using dredged sediment for the estuary with severe decreasing in catch them. I Nutrient supply from dredged sediment and II high productovity of algae for feed are emphasized as the function of artificial tidal flat for asari clam. In this study, we have investigated the applicabilities of glanulated coal ash (GCA) as the tidal flat material to enhance the productivities of asari clam using dredge mud for the shallow place worring about the low neutrialnt condition. Aiming to develop the design method of tidal flat with the supply sourse of algae as the feed for asari clam, test tidal flat was installed in the inner area of Hiroshima bay and we evaluated the function of I and II of captioned tidal flat

 The Mukawa coast is a good fishery of Japanese surf clam. The main food of clam in this sea area is a microphytobenthos. On the other hand, the turbid waters temporarily increase the dissipative modulus of this fishery. However, the finding of microphytobenthos is few in an openhearted littoral region. Therefore, the culture examination of microphytobenthos was executed. Consequently, the proliferation of microphytobenthos has the water temperature dependency. If it is as much as 5 degrees in the water temperature, the growth speed is high. Therefore, the growth rate that depends on water temperature and light quantum was modeled. The time change of the growth rate was calculated in spring.

 The effect of carbon storage by seagrass meadows has been recognized. In the present study, an attempt was made to create a Zostera japonica bed in the intertidal zone. Our results showed that eelgrass can grow and reproduce around the middle between Low Water Level and Mean Water Level even in the Keihin Canal where the water quality is not good. We compared the growth conditions of the eelgrass with sedimentary physical characteristics and found that the eelgrass distribution was affected by the wave conditions when the wake wave of the ship acts.

 Simple but accurate methods to monitor temporal and spatial macroalgal coverage are in demand, accompanied by ocean warming affecting their distribution and species composition. In this study, we examined a simple method to evaluate macroalgal coverage by the relationship between macroalgal coverage and RGB value of aerial photography at Motoineppu fishing port (Ōmu-cho) located in northeastern Hokkaido, Japan. Sufficiently accurate coverage using the tested method was demonstrated in this study, suggesting a possible simple and inexpensive measure to evaluate macroalgal coverage.

 This paper reports on the construction method of large-scale shallows in coastal area using Calcia Improved Soil produced by mixing dredged soil and steelmaking slag products, and on the results of monitoring survey around them for over 3 years after construction. This project was implemented in collaboration with the local fishery cooperative, the orderer of private dredging work and the contractor of this work. The results confirmed that the created artificial shallows were stable without collapse even after the history of the typhoon, that the calcia improved soil did not adversely affect the surrounding marine environment, and that it had an algae and animal settlement effect. It was consequently demonstrated that the creation of such artificial shallows could contribute to the improvement of the coastal fishing ground environment.

 Large-scale coral bleaching occurred in August, 2016 in Amitori Bay, Iriomote Island, Okinawa, Japan. This study was conducted to clarify the situation of dispersion–retention of coral larvae before and after large-scale coral bleaching.

 Data of the coral coverage degree, the date and time of simultaneous spawning, spawning rate, and velocity/direction of the wind during 2016–2019 were obtained by field observation. Results demonstrate that the spawning rate, which once decreased to 37.5% in 2017 because of bleaching, recovered to 90.0% in 2019. Then, based on the data, analyses were conducted to assess the larva dispersion–retention numerically during coral spawning during 2016–2019. Results clarified that in 2016, before bleaching, the arrival rate of the larvae in the open sea was lower and that the retention rate within the bay was higher than in other years because more larvae were emitted than in other years. Additionally, the northerly winds were remarkable.

 The species of the genus Haustorioides (Amphipod) and Excirolana (Isopod), which are intertidal species inhabiting the surficial sediments of sandy beach, are distributed throughout the marginal seas of the Northwestern Pacific and the world’s oceans, respectively. Recently, it has been clarified that the geophysical environment represented by suction governs the distributions of H. japonicus and E. chiltoni. Against this background, in this study, we conducted field studies and an unified analysis to investigate whether there are universal linkages between the suction and the distributions of four Haustorioides species, namely H. japonicus, H. munsterhjelmi, H. koreanus, and H. nesogenes, and E. chiltoni, which occur in sandy beaches with different tidal ranges in Japan and Korea. The distributions of the four Haustorioides species and E. chiltoni were associated with particular suctions for the Haustorioides and Excirolana species. Namely, the four Haustorioides species and E. chiltoni became absent where suction exceeded about 2 kPa and 5 kPa, respectively, in all sandy beaches, despite more than 10-fold tidal range and its variations.

 Few studies have investigated the migration behavior of salmon around fishing ports and stationary nets along the Hokkaido coast. Migratory behavior is important when considering catching methods, where salmon are commonly caught using fixed nets. Using acoustic tags and receivers, we investigated salmon migratory behavior around the Port of Atsunai, and set nets up to the mouth of the Tokachi River. Salmon released at the port left that area quickly and could return even if other salmon entered the port. The individuals released from the fixed net returned offshore and likely searched for the mother river. The time from release to capture in the river or surrounding area ranged from 8.4 to 18 days. This study provides basic data for the management of chum salmon resources.

 In order to evaluate environmental impacts in tidal flats, it is desirable to accurately understand the interaction between living benthos and their habitats. In this study, the purpose of this study was to understand the relationship between burrows and topography of tidal flats for each season in Scopimera globosa that appeared in tidal flats. As a result, there is relationship between tideland topography and burrows.

 We investigated over tidal cycles in the 4 seasons, the diel behavior of the sand-crab, Scopimera globosa using 1 minute time-lapse interval infrared cameras on the tidal flat, in the intertidal brackish water area of the mouth of the Isumigawa river, Chiba Prefecture, Japan. As a result, it was confirmed that in June and July, S. globosa was feeding during both day and night. However, in October S. globosa activity outside the nest was confirmed in the light period, but not in the dark period. And in January no activity outside the nest by S. globosa was confirmed. Focusing on the diel behavior, in the light period S. globosa appeared out of the nest quickly on emergence with the receding tide. And when the temperature inside the sediment became 20℃ or higher, activity of S. globosa became active regardless of day and night.

 Thus, using the infrared camera with the interval function, it is possible to examine the diel behavior of S. globosa and its seasonal change by simultaneous visual observations at multiple points.

 In order to reveal the carbon uptake mechanism of eelgrass, the vertical distribution of dissolved inorganic carbon (DIC) was estimated by a conceptual model considering the stratification effect at Lake Komuke. The field observation show that the eelgrass meadows change stratification and the vertical distribution of DIC. The conceptual model was verified by comparing with the vertical diffusion coefficients obtained from the Submerged Aquatic Vegetation model (SAV model). As a result, the conceptual model results agreed with the SAV model when eelgrass exists densely in a strong stratified fluid. Additionally, SAV model was improved in order to reduce run-time cost by combining with a hydrostatic model. The improved SAV model shows high accuracy and the run time was reduced dramatically.

 The use of recycling materials in Tokyo Bay was examined for the purpose of reclaiming the aquatic environment. Therefore, a system for verifying the safety and efficiency of recycling materials for utilizing them for the construction of tidal flats and shallow field was developed. The safety verification process was conducted during the mesocosm experiment using the experimental aquarium, based on the concept of the whole effluent toxicity system. In the efficiency validation, seven ecosystem functions defined in tidal flats were scored based on the survey results of the test case with recycling materials and the control case with natural sand, and the functional difference between the test and control cases was quantified through multiple regression analysis. First-stage tests (coal granules and ferronickel slag) and second-stage tests (constructed soil) were conducted to establish the validity of the verification system.

 To lift up coarse and heavy ores from deep seafloor, new technology by using circulating carrier materials (mixtures of viscous fluid and fine particles, CMs) in riser pipe was proposed. For effective operation, CMs must not be separated from ores during lifting. In this paper, the results of sphere falling experiments conducted to study the non-separability of ores in CMs were reported. By RFID system, falling velocities of invisible spheres, i.e. ore models (OMs), were monitored in a vertical pipe which was filled with turbid CMs. By assuming the viscous characteristics of CMs as that of Bingham fluid, the rheological properties, i.e. the plastic viscosity and the yield stress, were estimated. The obtained results demonstrated that the plastic viscosity is dependent on the mixing proportions of both thickener and fine particles while the yield stress is dependent only on the thickener. Finally, the condition of nonseparability for spherical ores of certain diameters and densities was derived based on the rheological model for CMs.

 The Japanese technical standard for the offshore bottom-fixed wind power generation facility basically follow the international standard established by IEC, considering the natural conditions in the Northern Europe. Therefore, it is necessary to consider the oceanographic conditions such as the high waves and swell associated with the typhoon in the Japanese technical standard, appropriately. However, there are few studies on the effects of the above ocean waves on the dynamic response of the offshore bottom-fixed wind turbine. In this study, we investigated the characteristics on the dynamic response of the monopile-type offshore bottom-fixed wind turbine in operation under the winds and waves by using the load coupled analysis. As a result, it is found that the bending moment on the sea bottom follows the wave loads over the rated wind velocity at the hub height although it follows the wind loads under the rated wind velocity, mainly.

 In this research, we perform numerical analysis the tidal current using CFD targeting the Ohshima Ohashi bridge fourth bridge piers over Obatake Seto strait. Based on the numerical analysis results, the tidal current distribution and the turbulence intensity distribution near the bridge piers were analyzed in detail. In consideration of the influence of the tidal current and turbulent intensity near the bridge piers on the power generation device, the optimum installation position of the power generation device was selected.As a result, it was predicted that the total amount of power generated by the Oshima bridge No. 4 pier would be approximately 323.8 MWh per year, indicating the feasibility of tidal power generation in this area.