The paper presents power generation characteristics of the proposed wave energy converter based on the bottom-hinged pendulum. The pendulum behavior becomes unstable and the power generation efficiency decreases when the wave energy is small, and the pendulum is installed at the position of D/L ≈ 0.5, which is the antinode of the standing wave. When the initial water depth was deeper than the pendulum, it was found that larger wave energy was required to rotate the pendulum stably. The maximum power generation efficiency (k_e = 0.77) was obtained at the position of D/L ≈ 0.32.

 Sea ice floe distribution and their fractal dimensions on Okhotsk Sea coast of Hokkaido were analyzed from images taken by UAV in the ranges of 300m by 300m near shoreline. The floe sizes in this study had the mean of 2.14m and the median of 1.19m, and were widely distributed up to 65m. The floe sizes up to 5m accounted for 90% of the total number, and its frequency distribution had strong skewness. Although an unified fractal dimension which can be applied to the whole range of the floe size was not found, fractal dimensions were able to be defined in three divisions. Simulation methods of the floe sizes using plural fractal dimensions and a theoretical probability distribution (log-normal) were also discussed. Fundamental knowledges useful for engineering issues such as an occurrence prediction of ice jam formation considering non-uniformity of ice floe size were obtained.

 Standing silt curtains would be used to reduce the diffusion of turbidity generated during mining of methane hydrate on the deep sea floor. The purpose of this study is to simulate the flow field around these curtains in a slow and uniform flow in the deep sea by numerical calculation as a basic research for the development of these curtains that can be applied to the unique environmental conditions of the deep sea. Hydraulic experiments were carried out at a finite depth for the same slow steady-state flow as in the deep sea, and the boundary conditions between the bottom surface of the numerical calculation and the curtains surface were determined from the results. Numerical calculation shows that the drag coefficient of the curtain does not change with water depth when the depth-to-curtain height ratio is more than 20 times (preferably more than 30 times), resulting in an external flow where the drag coefficient of the curtain does not change with water depth. The external flow simulations confirm that the flow returns to the lower layer in front of the curtain.

 Water traffic users can enjoy wonderful Maritime-scape that can not be expected in inland areas. In order to promote the use of water traffic, it is important to show photo information using the homepage and social media services. However, the content and quality of the photos depends on each tourism company, and the characteristics of the Maritime-scape and composition are not clarified. This paper analyzed Maritime-scape from both tourism companies and user of water traffic. As a result, it clarified seven composition types and their compositional characteristics of the Maritime-scape that were evaluated by tourism companies and user of water traffic.

 The harmfulness of UV rays has been focused on in recent years. However, crisis awareness is low in Japan compared with that in other countries. Also, the number of beach users at the bathing beach decreases to avoid sunburn. In order to save the health of beach users at the beach, an understanding of the characteristics of the UV strength at the beach and suitable preventable measures are required. In this study, we investigated quantitative UV strength which changes under different conditions such as sandy beaches, sea and concrete ground under the direct or reflection sunlight as time changes. As a result, there is a different sequence of the UV strength of the direct sunlight condition compared with that of the reflection condition, and the UV strength of reflection on the sea is from 1.6 to 3.3 times to that on the beach. Also, although a main factor of the UV strength is the importance of solar altitude, cloud amount, and humidity were also considered. Finally, we suggested the UV measures on the beach based on these results.

 In order to verify the mechanism of upheaval control and the effect of improvement in a new CPG involving expansion of the mortar improved body, visualization tests using the transparent ground and shaking table tests were performed. As a result, the following findings were obtained.

 (1) The behavior of the ground around the mortar improved body showed upheaval in the case of injection, but it showed subsidence when the injection pipe moved Up and Down. The subsidence was larger in the upper part of the soil layer, and the upheaval was greatly suppressed.

 (2) It was clarified that the mortar improved body expanded and contracted by moving the injection pipe Up and Down.

 (3) A maximum of about 3% of sand was taken into the mortar improved body by moving the injection pipe Up and down, and the mortar improved body expanded.

 (4) A high upheaval control can be obtained quickly with a small number of moving injection pipe Up and Down.

 (5) The liquefaction strength of the U/D method in a new CPG was more than twice that of the conventional method.

 In present study, tsunami risk assessment in Niigata urban area was conducted by using numerical modelling of tsunami hazards associated with Niigata earthquake (1964). Tsunami inundation simulations considering uncertainty with regard to fault model and slip amounts provide an estimate of flooded area and affected people in the present ground elevation. According to the results of the simulations, the total inundated area is nearly 6.6 ~ 15.3 km² and roughly 27 ~ 81 thousands people are directly affected by tsunami inundation in the case where uncertainty related to four fault models was included into the simulations. In addition, inundation area increases as 12.3 ~ 28.7 km² and the amount of the affected ranges from 47 to 127 thousands in the case where the slip amount was added by 4.5 m on the fault models. As a summary, it can be said that the current Niigata urban area is highly vulnerable to tsunami hazards caused by the fault models of Niigata earthquake.

 Sandy beach and dune were significantly eroded in Katoku coast by Typhoon 1418 and 1419 in October 2014. Part of private properties on the dune were lost. The local residents were afraid of losing their cemetery on a dune into the sea because a distance from the cemetery to a crest of dune scarping was nearly 4 m after these typhoons. Therefore local residents requested proper shore protection. However, the area has been nominated as the World Natural Heritage Site after the typhoon damage, thus synthetic shore protection concerning environmental issues and utilization of dune and beach was necessary. To conduct an optimized shore protection for a local community, cause of beach and dune erosion as well as coastal processes were studied by using aerial photographs and drone technology. It was shown that significant dune scarping was generated by typhoon 1418 and 1419, thus a part of dune area should be protected by hard structure but may be requested to cover the hard structure by sand and vegetation as much as possible.

 A train of H line facing the Pacific Ocean was stopped by a driftwood which had run up on the railway track due to high waves between the T and K stations on September 5, 2006. It is estimated that the driftwood was run up by overtopping waves through the opening area of damaged seawall due to wave action with a swell condition. This study clarified the wave pressure characteristic acting on a seawall parapet by random waves with an experiment at a scale of 1/30 that reproduced sea wave and tidal conditions when the traffic disturbance happened. The wave overtopping rate, as well as run up rate of driftwood for different lengths and specific gravity, were measured for the damaged parapet portion of the seawall. In addition, the driftwood run-up pattern on the railway track was analyzed due to flow velocity of wave overtopping by a dam-break wave in a large experiment of a scale of 1/10. As a result, it was shown that the specific gravity of the driftwood which caused traffic disturbance on site was about 0.7.

 The problem of traffic disturbances due to wind waves has become obvious on the lakeside road of Lake Shikotsu and urgent measures are required. This study estimated the wind in the lake through the mass-consistent model taking into consideration the impact of the terrain and used Wilson's method to obtain the probability wave to be used for the design. In the hydraulic model test, we reproduced the 1/2 scale slope of the lake bottom and obtained the height of waves passing over the present embankment to compare it with the results of field observation. Then we showed that the height of waves passing over the embankment could be reduced by 50 percent if wave-dissipating concrete blocks were installed in front of the embankment. In the case of high waves equivalent to the design wave, the transition of the foot of the slope toward the offshore side of the wave-dissipating concrete blocks is apparent. Thus, we discovered offshore flows unique to the steep slope condition and the characteristics of wave power applied to foot protection blocks through the analysis using a numerical wave channel. In addition, through results of a stability experiment, we showed that flat blocks (7-ton type) were necessary as foot protection to secure stability of wave-dissipating works. Subject to implementation of such enhancement of shore protection, we made proposals for non-structural measures to ensure safety of passing vehicles.

 In this study, we validated the debris model included in the tsunami simulator T-STOC by the hydraulic experiments that a container landed after drifting under the tsunami backwash. We measured the friction coefficient on the container model bottom and ground under wet and dry condition, and the drag coefficient of the drifting container model. We investigated the effect of each coefficient on the calculation of the acting force, drifting velocity and position. As a result, it shown that the calculated drifting position using the friction coefficient measured under the wet conditions was consistent with experimental results. Although the measured drag coefficient was slightly larger than the general drag coefficient of rectangular solid, the drifting speed and position were roughly reproduced by numerical calculations using the drag coefficient obtained from the measurements.

 In recent years, social interest in Eco-DRR (Ecosystem-based Disaster Risk Reduction) has been increasing as a disaster prevention and mitigation measure utilizing ecosystems. This Eco-DRR is not to consider both the development by hardware measures accompanying disaster prevention and the environmental protection as the opposing axes, but to take advantage of both, and to show the significance of green infrastructure development. It is considered that the sandy beach has a potential expression function. In this study, we conducted a liquefaction experiment using artificial vegetation on the sandy beach along Awaji Island, and examined the liquefaction characteristics of the sandy beach depending on the existence and type of vegetation.

 The characteristics of wave overtopping with rubble stones were analyzed on three coastal roads by field observations. The cases of vehicle damage and traffic hindrances were also investigated for a coastal road based on the records prepared by the police and the road administrator. Hydraulic model experiments with a scale of 1/15 were conducted in order to obtain the relationship between wave run-up height and wave overtopping rate for typical seawall conditions. The wave force was measured due to random waves for three different stone diameter conditions using a one-component dynamometer, and the critical run-up height of rubble stones was shown using non-dimensional wave force, which was measured wave force divided by stone weight. The movement patterns of rubble stones were determined by video analysis for four specific gravity conditions and three diameter conditions. Based on the experimental results, the stone run-up height can be calculated as a function of wave height. Furthermore, the effectiveness of the calculation method was also confirmed by the field observation data.

 At the quay of the ferry terminal in the Okinosu area of Tokushima Komatsushima port, even if storm surge did not exceed the quay height, wave overtopping caused by high waves induced inundation damage at the time of typhoon No. 1821 coming. Because wave overtopping was also observed at Tsuda breakwater and Okinosu breakwater at this time, it was anxious that the transmitted waves from the breakwaters increased wave overtopping at the quay caused by the incident waves from the port entrance.

 In this study, the reproducibility of the transmitted waves generated by using Boussinesq-type wave model which could calculate wave overtopping was confirmed through the comparison with the results of cross-sectional experiment at first, and then, the wave deformation calculation in the port was performed. Through the comparison of the maximum inundation depths calculated at several points on the quay with the ones observed in the field, it was confirmed that the calculation almost reproduced the inundation on the quay although it was underestimated behind the quay, where the incident waves from the port entrance were much more dominant than the harbor transmitted waves.

 A field survey on damage caused by Typhoon Hagibis in 2019 was conducted in Shimizu and Yaizu ports. The highest sea levels observed in both ports were 1.7 m above the mean sea level, and the sea level rise by the typhoon in Shimizu was about 1 m, which was twice as high as the estimated pressure-driven surge. The survey showed that waves riding on storm surge caused damage to facilities on wharves even protected by breakwaters, while smaller waves hit wharves that could not be directly seen from an opening section of breakwaters especially in Shimizu. To investigate the effects of storm surge and waves on port facilities is important for enhancing port resilience to typhoon disasters.

 The radii of maximum wind (RMW) of Typhoons Faxii and Hagibis in 2019 were approximately half and twice, respectively, compared to the mean values of past typhoons according to an analysis referring to the typhoon bogus installation procedure developed by the Japan Meteorological Agency. In the case of Typhoon Faxii having a small RMW, the JMA’s GPV, MSM, gave higher sea level pressure within the radius and lower 10m wind speed near the radius. The downscaling of MSM with WRF improved the wind field alone significantly. The parametric typhoon model based on the mass balance on the moving coordinate with super gradient wind, ETM, could give the useful pressure and wind fields. The storm surge hindcast with ROMS concluded that the WRF and ETM meteorological fields gave better estimations than MSM. Contrarily, in the case of Typhoon Hagibis having a large RMW, the storm surge hindcast showed better results than the case of Typhoon Faxii even though MSM meteorological fields was given.

 Due to giant typhoons in recent years, the development of a land gate open-close status confirming system is urgently required in order to alleviate storm surge damage, and to take immediate and wide-ranging evacuation activities and emergency measures. In this study, an image AI model using deep learning was constructed to confirm the open-close status of land gates installed as part of maritime embankments or levees, and its applicability was examined. Size and RGB of the images were examined, and the conditions of the image AI were assessed in order to develop the model for confirming land gate open-close status. As a result, the quality of the model was confirmed with 98% correct status designations. Examination of the image AI model using Grad-cam revealed that the status confirmation was judged from the land gates edges.

 Inclined capillary barriers (CB) are an efficient slope disaster prevention technology to control rainfall infiltration, which using an upper finer soil layer and a lower coarser soil layer to compose layered grounds. Therefore, CB has the function to block rainwater infiltration and to act as a drainage function in grounds. Moreover, it has been found that crushed shell particles can be used instead of general coarser soil layers in CB. The purpose of this paper is to study the stability of embankments under short-time heavy rainfalls. To investigate the additional effects of using crushed shell particles in CB, laboratory experiments have provided to examine the effect in preventing rainwater infiltration and scour on surface soil layers. Under limited experimental conditions, the following two conclusions were reached based on the results of crushed shell particles in the shallow layer of the embankment slope. I：effect of infiltration control in the embankment was realized after breakthrough, II：the soil scour due to surface flow on the slope were prevented.

 Typhoons No. 15 and No. 19 in 2019 passed from southwest to northeast of Tokyo Bay, and ships were significantly affected by dragging anchors and clashing with structures.We compare and analyze the sheltering plan in Tokyo Bay and the sheltering conditions during the 2019 typhoon, and examine safe anchoring and mooring. This paper analyzes the anchoring in Tokyo Bay due to the 201915 typhoon and the 201919 typhoon, and reports a case study of the safe anchoring area during a typhoon considered from a dragging anchors.

 In the case of tsunami hazard at snow covered area is concerned that snow will be an obstacle to evacuation and increase the risk of disaster. The influence of snow during the evacuation, assuming that the vulnerable people such as elderly and disable people evacuate not only foot but also by car. In this study, the route was analyzed in Hakodate City, the which is snow-covered and underpopulated area, by architecture road network with consideration of traffic and tsunami evacuation characteristics in the snow-covered area on GIS. As a result, there was delay about 7 min at Yunokawa and Minato in snow season. In addition, proposed to review the Hakodate snow removal plan, because some of the facilities with narrow roads in the vicinity were delayed due to snow removal conditions.

 There are from 2,000 to 3,000 rescues every summer season on the beaches of Japan. The lifesavers have to do speedy rescues of the drowning victims to reduce the number of drowning accidents. However, it is difficult because the number of lifesavers is small at around 1 lifesaver compared to the thousands of beach users. In order to reduce drowning accidents, immediate detection of the drowning victim is required. In this study, we tried to develop the Artificial Intelligence (AI) using YOLOv3 for detection of a drowning person which performs the "help signal". The training data was made at three situations including the laboratory, outdoors, and the beach. As a result, it was found that drowning people victims were detected at F-values of about 0.7 to 0.9, indicating the possibility of drowning person detection.

 There are approximately 10,000 to 25,000 first aid responses per year at about 200 beaches in Japan. Injuries or emergency conditions at the beach such as heat stroke, disorientation, and intoxication are also included in first aid. In order to save the injured person, a prompt first aid response is required. In this study, outbreak characteristics of injuries and emergency conditions regarding the rescue and first aid at the beach were investigated using the statistical analysis at Onjuku Beach as an example. As a result of this study, the rescue and first aid were happening when a large number of beach users used the beach in either permitted or unsafe swimming conditions. Furthermore, a new system for prompt first aid was proposed based on the field experiment. The proposed system was verified to enable a 7-10% improvement in survival rates.

 In Japan, there are many beaches which are supervised by lifesavers. However, it is difficult to prevent drowning accidents completely because the number of lifesavers is small at around 1 lifesaver compared to the thousands of beach users. In order to prevent drowning accidents, flexible changing of monitoring systems by lifesavers depending on the number of beach users is required. On the other hand, the main factor of outbreak drowning is the rip current, however, the relationship between an increase or decrease in the number of beach users and their entering the rip current areas that cause drowning accidents is not investigated. In this study, we calculated the number of beach users using AI from beach images of fixed-point shooting and, revealed that the relationship between fluctuations in the number of beach users and probability of their entering rip currents areas.

 The threat of storm surges caused by typhoons is likely to increase further due to the effects of rising sea levels and intensifying typhoons due to global warming. Therefore, it is important to understand future changes in typhoon characteristics in considering coastal disaster risk reducation in the future. In this study, the typhoon paths extracted from d4PDF were classified into patterns using the Self-Organizing Map in the Ariake Sea, which is a typhoon-prone area and has experienced many floods in the past. By analyzing typhoon intensity for each pattern, future changes in typhoon path and intensity were examined. As a result, it was found that the typhoon path pattern became more diversified and the central pressure and wind speed increased as the warming progressed. In addition, a storm surge simulation was performed to clarify future changes in the maximum storm surge in the Ariake Sea for each path pattern.

 Previous tsunami hazard assessments evaluated the stability of submarine slopes during earthquakes by using pseudo-static limit equilibrium methods. However, the applicability of this method to submarine slopes has proved to be unreliable. In this study, we evaluated the collapse behavior of a submarine slope during an earthquake by performing a series of dynamic and static centrifugal model tests. Additionally, the applicability of the modified Fellenius method was also investigated. The results of this study can be summarized as follows. (1) The slip surface initially formed at a relatively shallow depth and then became deeper as the shaking intensity increased, (2) the horizontal seismic coefficient when the slip surface formed is equal under static and dynamic loading conditions, and (3) the modified Fellenius method was applicable for the evaluation of submarine slope stability with certain variation during an earthquake.

 In the design of ports, to understand the behavior of tsunami acting on the various structures in the port during few hours is important. Therefore, in general, tsunami simulation with multiple nesting boundaries in the area from the large area including the tsunami source to the small area around the port structure is performed. In the minimum area targeting ports, 10 m resolution mesh and line boundaries which are insufficient to reproduce the structural shape such as breakwaters are often used. In this study, we performed numerical experiments with different spatial resolutions and shape of breakwaters and examined the characteristics of flow and bathymetry changes around breakwaters. As a result, it was clarified that there was no difference in flow and bathymetry change at the opening area of breakwaters and that the flow velocity and the scouring amount at the head of the breakwater were significantly different depending on the difference between the mesh resolution and the shape of the breakwater.

 For facilitating the risk assessment of submarine landslides and associated tsunamis, this study analyzed the seafloor ground dynamics based on the water depth survey conducted by Imperial Japanese Navy. The observed data represent the depth change in the case of 1923 Kanto Earthquake tsunami in/around Sagami Bay and Tokyo Bay mouth. From the results, it was found that submarine sediments were deposited at the foot of submarine scarp, and significantly outflowed on a gentle slope. The study also predicted and assessed the liquefaction risk of the seafloor focusing on the area where the sampling core data was abundant under presumed huge earthquakes. The results highlight the importance of earthquake-induced landslide tsunami risk assessment.

 Coastal areas are facing more severe storms and flooding worldwide. These storms create significant morphological changes to coastlines. Coastal engineers have made several efforts to assess and predict the strength of coastal storms and morphological changes. Recently, several parameters for predicting storm impact have been proposed. In this study, the Coastal Storm Impulse (COSI) parameter is used to predict volume changes from coastal storms using the data observed in Japan. The wave height and storm duration were used to define and pull out the storms. The volume change from each storm was calculated for two areas, i.e., the entire beach profile and nearshore area (Zone 1). The correlation coefficient, R², between the COSI parameters and the volume change for the entire profile and Zone 1 were 0.34 and 0.32, respectively. The storm events were classified into two groups based on the surge contribution, i.e., with and without the surge momentum effect for Groups 1 and 2, respectively. From the regression analysis, the correlation coefficient, R², between Group 2 of the COSI parameters and the volume change of Zone 1 was 0.62. Moreover, the shoreline position was included in the estimation of the volume change in Zone 1, and the predicted result improved by up to R² = 0.71. From the analysis results, although there is a relatively low correlation between the COSI parameter and the volume change at Zone 1, the relationship will increase when we focus on the storms that include surge momentum and consider the shoreline position. Thus, we considered the seasonal shoreline location to improve the prediction results.

 In the 2011 off the Pacific coast of Tohoku Earthquake, many oil storage tanks located in the coastal area were found to be damaged severely. Approximately 90 percent of the damaged oil storage tanks are small-scale tanks which are less than 1,000 kL, and countermeasures for those tanks are urgent. Authors proposed countermeasure for tsunami drifting by fixing the tank base and the RC slab by CFRP sheet. However, the peeling characteristics between tank and CFRP, RC slab and CFRP remain unclear. In this study, element experiment and reproductive analysis are conducted to clarify the peeling characteristics. Thus, applicable limit of tsunami heights and countermeasure effectiveness are evaluated by conducting finite element analysis with consideration of peeling characteristics.

 In the Great East Japan Earthquake, unexpected tsunami caused enormous damage along the coast and lost the production and distribution functions of marine products. Despite the confusion, stakeholders made efforts to restore the functions, but it took a long time to resume the functions.

 In this study, we proposed a method to evaluate the early resumption of marine product production / distribution functions as the value of marine product production from the damage status of facilities and equipment over time. By using this method, it is possible to clarify the facilities and equipment that should prevent the restoration of production value after the disaster and to implement measures with priority, and to confirm the effects of implementing the measures. It is expected to contribute to the formulation of the business continuity plan (BCP) and the resumption of effective production and distribution functions of marine products after the disaster.

 It was received tsunami damage in The Great East Japan Earthquake, tsunami wave height of two levels were sets by Central Disaster Prevention Council. "The tsunami of the greatest class where the outbreak frequency brings the damage that is serious although it is extremely low" was tsunami more than assumptions conventionally. Then, it was only high place refuge and it may not protect human life. So, it became important that establish the measures to the tsunami more than evacuation sites. There was the tsunami refuge that utilized a floating type of tsunami evacuation shelter as tsunami measures after the high place refuge. However, it may not become clear about the characteristics of floating type of tsunami evacuation shelter.

 In this study, the motion of shelter examined using wave force and Froude number at the tsunami. As a result, angle of the water to hit the shelter influenced it by difference in inundation depth, and it turned out that was greatly different in wave force.

 Liquefaction prediction of the mixed sandy soil containing fines content is conducted based on the liquefaction strength derived from the N-value. The N-value is corrected depending on the fines content (Fc) and plasticity index(Ip). The previous research shows that the sand’s uniformity coefficient affects the correlation between the N-value and liquefaction strength. This research aims at thoroughly investigating the influence of particle size distribution and fines content on the accuracy of liquefaction prediction in mixed sandy soil. A series of undrained cyclic torsional shear tests and prototype-scale standard penetration tests were conducted using 5 base materials having different particle size distributions. The quantity of Fc and Ip was also changed in each stage under the tests. By comparing the experimental results, it is found that the accuracy of liquefaction prediction varies by the quantity of Fc in cases of mixed sandy soil containing silt. The particle size distribution of the base material has also been shown to influence the accuracy of liquefaction prediction in cases where the mixed sandy soil contains clay.

 There are few studies of long-term predictions of storm surges at the regional scale required for planning coastal disaster prevention. In this study, we performed high-precision numerical simulations of storm surges using large-scale ensemble climate prediction data for the Suo-nada Sea, and examined long-term changes in storm surge characteristics. As a result, a storm surge with a return period of 1,000 years in the Suo-nada Sea increases by 1 m or more in the inner part of the bay in the future climate and the storm surge exceeds the tidal deviation of the current embankment design height, therefore, it causes an increase in the possibility of floods in the future. Storm surge anomalies have large differences between the future change patterns in sea surface temperature, and the difference is greater than the future change due to climate change, thus, storm surges will be greatly affected by the uncertainty of future climate change. Furthermore, spatial distribution of storm surge in the Suo-nada Sea change will have the tendency to change.

 This paper presents the case of Yamada Bay with a narrow entrance in Iwate prefecture to elucidate the true state of fishing boat evacuation by a survey on the fishermen who stood out to sea at the time of Great East Japan Earthquake. We calculate the flow velocity distribution in the inside and outside of the bay by simulating the tsunami caused by the 3.11 earthquake, and verify the possibility of drifting or capsize of a fishing boat by comparing the speed of the tsunami with that of the fishing boats evacuated at sea during the 3.11 earthquake etc. As a result, we found that a flow velocity of a tsunami equal to or exceeding the maximum speed of the fishing boat was generated in the bay entrance. This result elucidates that fishermen ought not to evacuate the fishing boats to the deep-water bay uniformly, but need to confirm both the maximum flow velocity of a tsunami near the bay entrance and the sailing speed of the fishing boats using the tsunami simulation to clarify whether the fishing boats can sail safely. Furthermore we elucidate the necessity of making it public the comparatively safe sea area inside the bay beforehand to the fishermen who may fail to escape in a bay with a narrow entrance in the event of tsunami.