Potential of offshore wind energy in Japan is enormous, but the potential in sea water depth of 50m or more accounts for the majority. To take advantage of this huge potential, the practical use of floating offshore wind power generation is required. However, floating offshore wind power is a demonstration phase still in the world; thus, in order to achieve early commercialization of floating offshore wind power generation in Japan, floating offshore wind power demonstration project has been kicked-off by the Ministry of the Environment from FY 2010. In this paper, the main achievements so far and outline of the demonstration project are introduced.

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 This paper introduces results of field study using Ocean Observation Tower system constructed off the Kita-Kyusyu city, aiming for establishment of future offshore wind farm design. Not only observed abnormal offshore winds and waves characteristics due to the the passage of low pressures and the typhoons, but also analyzed results of offshore vertical wind profile, simultaneous winds and waves characteristics, and accessibility wave criteria of the maintenance vessels to the offshore tower, were introduced in this paper.

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 In January 2013, The Choshi Offshore Wind Power Station started generation in the Pacific Ocean as the first in Japan. This power station was built as the test plant for investigating offshore wind power technology in severe natural conditions in Japan, including performance tests for turbine, evaluations of offshore wind and environmental assessment. According to 47 months observations of wave height and period, the average wave height is relatively high and swell frequently happens. And, in the typhoon 1326 in 2013, observational maximum high wave and spilling wave hit the gravity foundation. Based on these observations, in order to increase offshore wind power stations in Japan, it is important to procure high seaworthiness vessels for construction and maintenance.

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 Auatic environment in Miyako Bay, Iwate, Japan after the Great East Japan Earthquake has been still unknown because no field observation of it has been conducted after the earthquake. Therefore, we conducted field observations of water temperature, salinity, turbidity, dissolved oxygen and chlorophyll a at 0.1 m vertical intervals for 24-28 locations in the bay in September and December, 2013 using a portable multi-item water quality analyzer.
 The observed results revealed the characteristic feature of aquatic environment in the bay including the existence of low salinity water masses around Hei and Tsugaruishi rivers due to freshwater inflow and around the center-east part of the bay. The results also showed that sea surface distributions of chlorophyll a and turbidity have changed greatly within 6 hours.

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 This study investigates the morphology changes of Gamo Lagoon, located in Sendai City, due to the Great East Japan Tsunami in 2011 and its recovery process. Frequenly captured aerial photograph are effectively utilized to analyze detailed morphological change in response to wave action after the tsunami. The lagoon area was greatly changed due to the 2011 tsunami. The gradual process of river mouth changes and reformation of the lagoon was observed using aerial photographs. As compared with the shoreline position before the tsunami, retreat of the shoreline 40m can be confirmed even now after three years. Meanwhile, the water area shows distinct reduction by 40% as compared with the pre-tsunami situation. Further investigation is highly required to understand future state of the coastal environment destroyed by the deverstating tsunami waves.

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 We here report impacts of the 2011 great earthquake and tsunami on water quality and eelgrass beds in Matsushima Bay which locates on the coast of Miyagi Prefecture. The water quality of the bay was deteriorated due to severe damages of a sewage plant, but recovered rapidly after temporary repairs and start of primary treatment. This highlights that the temporary measure was significantly effective to improve the water quality deterioration caused by the disaster. Meanwhile, eelgrass beds of Matsushima Bay were severly damaged by the tsunami, and their total area decreased significantly. Even 2 years after the tsunami, eelgrass beds had not recovered. Our analysis based on a Habitat Suitability Index model indicates that the significant gound subsidence and consequent increase of water depth potentially hamper recovery of eelgrass beds in the bay. The recovery process of eelgrass beds in the bay needs to be monitored taking account of effects of other factors potentially affecting the competition between phytoplankton and eelgrass (e.g., nutirents, turbidity).

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 Questionnaire researches were carried out three times in the same beach. These researches were carried out in August of 2006, August just after the Tohoku Earthquake Tsunami in 2011, and August in 2013 when two years passed after the Tsunami. Using these data, time variation in tsunami awareness of beach users is discussed in this paper. From the results, it is found that the awareness of them became better just after the Tohoku Tsunami, but it has deteriorated with years. Therefore, stakeholders have to consider these results and be planning educational campaigns and so on.

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 The number of foreign tourists who were invited from domestic or overseas exceeds 10 million people in Japan. On the other hand, the serious damage assumed by the massive earthquake and its tsunami has been a social problem. The disaster prevention for tourists is one of the factors that need to consider for the regional disaster prevention plan of a tourism city. Although several approaches against the ways of evacuating safely tourists have been examined by a part of tourism organizations, its importance is not well understood. In this study, the significance of tourism disaster prevention in Hakodate is verified through the current situation of the tourism characteristics and the inundation prediction of the scenario earthquake tsunami of level 2 in Hokkaido. The countermeasures and problems of the tourism disaster prevention are summarized from the results of the educational activities toward the tourism industry.

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 Tsunami numerical simulations are performed. The selected tsunamis are caused by Keicho, Genroku and the northen bay of Tokyo earthquakes. These tsunamis cause big disasters around Tokyo bay in the future. The damage of tsunami and the cost of protection measures against tsunami are calculated. By using these results, the cost and the benefit are compared. As a resut, the damage of Keicho tsunami is 6.95 trillion yen, for Genroku tsunami it is 5.04 tillion yen and for the northern Tokyo bay tsunami it is 4.54 trillion yen. The cost of protection including seawall and water gate are 1.05 trillion yen. The cost of building with pilotis is 15.0 trillion yen The probabilities of occurrence of earthquakes and cost-benefit ratios are calculated. As a result, B/C is 9.97 if we protect by using seawall and water gate. B/C is above 1.0 if we protect by offering public support to house owners up to 60 percent of the cost of construction of pilotis.

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 A real-time tsunami hazard mapping system has been developed to estimate tsunami inundation before tsunami arrival afther earthquake occurfrence in order to support disaster preventive activities before tsunami arrival such as evacuation guiding and closing of land lockes, and emergency responses for relief and restoration after disaster occurrence. This system uses tsunami waveform data measured offshore to estimate a tsunami source which is emplyed to calculate tsunami propagation and inundation. Developing a pototype of the system and applying it to Nagoya port hit by a tsunami generated by an expected megathroust earthquake along Nankai trough, it confirmed that the system can produce inundation estimation in Nagoya port within 8 minutes after the earthquake ooccurrence. Using a graphic processing unit, it takes totally 80 seconds to estimate a tsunami source based on tsunami waveforms measured by 8 offshore GPS-mounted bouys and calculate tsunami propagation and inundation from the tsunami source.

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 In response to a eleventh report of the Transport Policy Council of July 1981, we started the data offer of the NOWPHAS (Nationwide Ocean Wave information network for Ports and HArbourS) from April 1995 and developed the COMEINS (Coastal Oceanographic and Meteorological Information System). The first system started official use in February 1997, enabled interactive communication by the dedicated line and the terminal. In correspondence with the spread of Internet technologies, we started a Web version as a second generation system formally, and also started Mobile version using the cellphone. In correspondence with diversification and advancement of coastal oceanographic and meteorological information, we developed the third generation system which pursued convenience of the operability and started official use now from October 2012.

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 Tidal and ocean currents in the Tsugaru Strait are considered as one of the potential marine-renewable-energy sources in Japan. Wake behind a tidal turbine modifies the physical environment around the turbine through velocity deficit as well as vortex generation. This study proposes a computational procedure to incorporate the resistance by a tidal turbine in a computation using a three-dimensional ocean circulation model, MITgcm. The resistance force due to a turbine is calculated by the Blade Element Momentum method which has been used for determining a flow around a wind turbine. The residence is distributed into a few grids around the turbine location using the Immersed Boundary Method, which enables to evaluate the effects of a turbine in a large scale computation by the circulation model. Velocity difference originated at the turbine location was found to spread over a wide area in the strait.

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 Marine Renewable Energy(MRE) is expected after The Great East Japan Earthquake. The consideration for MRE is also progressing and the field test has also begun on the sea. Some types are considered also about wave power converter. It becomes important to predict wave power with high precision for wave power converter.
 In this research, the wave power around Japan is rearranged using the wave observation data whose observing point increased. And the local characteristic of wave power is considered. Furthermore, the trial calculation of the wave power was made at the breakwater of the Habu fishing port in the Oshima and the Miike fishing port in the Miyake-jima.

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 Japan is the maritime state surrounded by the sea, effective use of the ocean energy which exists abundantly is an important issue, and the realization is desired. Tidal current is the periodic energy which can be predicted, therefore it can expect to supply energy stably. In Seto Inland Sea, many straits and Seto regions exist, and it is known that tidal current energy will be amplified because a tidal current becomes quick. Therefore, the power generation technology which utilized current energy attracts attention. This study estimated the possibility of the tidal current power generation in Seto Inland Sea by performing local observation. At first time, the amount of maximum energies was calculated by observing the tidal current of Seto Inland Sea. Next, the amount of maximum energies obtained when a dynamo is built was calculated.

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 For the purpose of using wave energy as a renewal energy, a wave power generation caisson with wave absorb function is being developed for last several years. In this paper, a wave power generation caisson which consists of impermeable vertical water and an array of savonius-type watermills is proposed. Energy acquisition performance from wave energy and wave attenuation ability were examined by conducting laboratory experiment. Experimental results on the effect of diameter of the watermill, the distance between impermeable wall and the center of watermills, and load torque on them are presented.

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 A purpose of this study is to improve a performance of a vertical axis marine turbine with variable pitch blades. The study investigated how pitch angle controlled and the roter solidity effect on the turbine efficiency and conducted flume tank experiments using a turbine model. Besides, numerical experiments with CFD calculations were performed. The turbine model has 0.5m in diameter of turbine, 0.6 m length of a blade and removable from 1 to 6 blades with a section of NACA0018, which has an arch camber line. As a method of pitch control system, the cyclic mechanism was applied so pitch angle was absolutely mechanically determined. As a result, when the solidity of 0.293 and setting angle of blade - 7 degrees were set, the model showed the highest performance, which was the turbine efficiency of 55% in 2.0 TSR (λ).

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 Six private companies and research institutes & universities jointly started a consortium research for practical use of the oscillating water column system (OWC) in 2011. Hydraulic experiments with small and large scales (S:1/25 – 1/7) were conducted to improve the primary conversion from wave to air flow. Projecting-walls (PW), installed both side of the opening, were found out to make frequency dependency reduced. At the same time, hydraulic experiment for the single OWC facility installed on the line of breakwater showed sudden drop down of the efficiency of the primary conversion against a certain wave period . This occurred due to the interposition with reflection waves from the ambient surface of breakwater. Reduction of wave reflection improved this drop significantly.
 The consortium also tried a new application of PW-OWC system to coastal embankment with air chambers inside. Numerical analysis was applied to this wave-absorbing type embankment to examine the response of the primary conversion against incident wave period.
 The PW-OWC system installed on the existing breakwater is expected a possible design of the practical application

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 In the previous study, we have already presented an effective structure of tidal current power plant, typically a vertical turbine with guide vanes around it. In this study, in order to be able to carry out rational designs of the tidal power plant, hydrodynamic forces on the structures have been examined mainly from experimental points of view. Natural environmental conditions, such as waves and tidal currents as well as coexistence of waves and currents, were adopted for external loading conditions. In the same way as the previous study, a vertical Savonius turbine with guide vanes was used as a tidal current power conversion facility. It was confirmed that not only the tidal current force but also the wave force on the conversion facility are equally important.

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 The characteristics of tidal currents at the Oshima Strait were examined in relation to tidal current power generation using the data of direct current measurement and numerical simulation with FVCOM. We found the strong tidal currents with a maximum speed of 2 m/s in the eastern area of the strait. Moreover, it was shown from the output data of the simulation that the daily mean value of tidal power potential in the strong current area is about 170 MW.

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 Although the information of wind state on land around Japan is provided, the detailed wind information around offshore sea is not given. Offshore wind and wave information are necessary when planning an offshore wind farm for the use of natural renewable energy. The present study made mappings of detailed wind and wave conditions around Japan. It becomes clear that the annual averaged wind speeds at a height of 10 m from the sea surface, economical criterion of wind energy utilization, are greater than 6 m/s except near coastal regions. The average wind speeds for each of the four seasons and twelve months are also obtained. A user friendly information system was developed to indicate the values of wind speed and wave height at the same location.

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 The purpose of this research is to establish the stand-alone power generation system by means of wind power generation in ports and coastal area. It is necessary to know the variance characteristics of demand of electric power in port facilities. This paper shows investigated data of electric power usage in a port that is located at the west coast of Hokkaido. The deferences of demand and supply by wind generation and hybrid system with solar generation are analyzed and the contermesures to reduce the energy gap of demand and supply also discussed.

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 The proving research of the offshore wind power has been continuing at the offshore of Choshi. The foundation of the offshore wind turbine is the gravity foundation. The wave pressure acting on the foundation of the wind turbine has been measured to examine the validity of the evaluation method of the wave force. The linear relationship between the siginificant wave height and the maximum wave pressure has been revealed by using the observed data, and it has been confirmed that the evaluating method of the probability distribution of the wave pressure is appropriate.

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 Redevelopment of old piers and yards aims at reconstructing old isolated area into new commerce and business zone. It is a private sector that develops new commerce and business zone.
 Private sector usually worries about suffering from uncertainties of redevelopment as follows.
 1. Uncertainty of completing construction of infrastructures by public sector and on schedule.
 2. Uncertainty of changing land use control on the basis of negotiation with interested parties
 3. Uncertainty of accomplishing the first stage development in certain extent of area in cooperation with developers of neighboring blocks.
 In order to eliminate the uncertainties and let private sector participate in redevelopment, public sector should construct infrastructures with their own budget, carry out negotiation for changing land use control by himself and form multiple developments of neighboring blocks into one unit development. This wide range of roles of public sector is particular characteristic of redevelopments of old piers and yards and should be authorized in master plan of redevelopment so that public sector may take a leading part in PPP and accomplish redevelopment by PPP.

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 Since the 19^th Century, Nemuro city located in eastern part of Hokkaido, has developed as the hinterland to nortern ocean in Japan. Nawadays, Nemuro city plays the role of the important site of fishing idustry, however, has the problem of Aging, Emigration, Population Decrease, as with other port cities.
 This study is aimed to analyze current social situation, using the port - hinterland theory, to clarify characteristics of the social structure in Nemuro. Changing lifestyle to be modernized , consumption activities to be supported information technology complicates port-hinterland relations in Nemuro.

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 In recent years, security measures have been strengthened in maritime transport and port area. On the other hand, container transport vehicle is congestion in container terminals of the Japanese major ports.
 In this study, we surveyed the actual situation of Honmoku-BC terminal of Yokohama port, and calculated waiting time and numbers of waiting by the simulation if the security measures were strengthened.
 At the BC terminal, maximum number of trucks waiting gate open is about 300. Queue line was freed up about 1 hour after gate open.
 If strengthening security measures caused the processing time of the container carrying-in five minutes longer, the simulation would overflow at present equipment. But it could be processed within the same day by the improved gating process. Even in cases that gate open during the lunch time if the security measures were strengthened, would also overflow at present equipment.

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 Shipping cost of iron ore and LNG from the Arctic to Japan via the Northern Sea Route is examined. At the same time, compatrative shipping scenarios and costs from actual production sites are also investigated. Via the Northern Sea Route, shortened distance and sailing time reduce fuel cost, operational costs and overhead expenses. And this could cancel out additional cost of the Northern Sea Route such as icebreaker fee and ice pilot fee.

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 In this study, we made a landscape map of Tottori Prefecture using the open data, and determined the landscape indicator from landscape composition index. Next, we analyzed the new quantitative coastal landscape evaluation method by comparing the landscape design system, and would like to report the results.
 According to the analysis, the new evaluation method and the landscape design system showed nearly identical results. Consequently, it demonstrated the effectiveness of the new method.
 The landscape design system needs a large amount of energy to have questionnaire survey. In contrast, the new evaluation method by using the open data has an advantage which is easy to conduct by the use of GIS.

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 Sea Bottom environment in ports and harbors becomes hypoxic or anoxic condition by formation of density stratification during summer season. It is necessary to understand the mixing effect of jet in density stratified field before applying water mixing technologies in actual site.
 In this study, we carried out laboratory experiments on the water mixing under density stratified field and we measured the spatial distribution and temporal changes of density by using a LIF method. The results of this study were as follows: (1) It is suggested the possibility that the mixing effect will be able to be prediction by Richardson number about a jet acting on the density stratified field. (2) It is found that to supply a jet in such a way that the extent of the impact of jet becomes widely was effective for the relaxation of density stratified field.

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 This study carried out field observation and numerical simulation for the purpose of clarifying the actual situation of the vertical mixing over artificial mound reef. From an observation result, a layer of a density reversal and the density equality was confirmed in a range of below the mixed layer from sea bottom in the direct above and the down stream of the structure. A value grew big about the energy dissipation rate that it estimated based on an observation result in the same layer, and it was confirmed that vertical mixing occurred. In addition, from a numerical simulation result based on an observation result, the vertical mixing that was similar to an observation result was grasped.

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 Field observations of wave, flow, water temperature and salinity were conducted in some areas in Okinawa, Naha port, Urasoe and Shiraho coasts. Observational durations are 30 days in winter and summer. This report shows the following three topics. (1) Semidiurnal fluctuation of water temperature are apparent offshore areas of Naha port and Urasoe coast in summer. (2) Variations of flow patterns in winter and summer are revealed in Shiraho coast, typical fringing reefs. The reef currents are driven by gradient of elevation caused by wave setup. The difference of wave direction between winter and summer varies the reef currents. (3) Variations of water temperature are shown in Shiraho coast. Semidiurnal variation of water temperature is dominant under the calm condition. In the disturbed durations, vertical mixing is enhanced and the vertical distribution of water temperature is homogeneous.

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 The topographical features of Okinawa Islands and Sakishima Islands, it is typhoon-prone area and the coral reefs are well developed. Therefore, it is necessary to improve the accuracy of calculating the high wave and storm surges. In this study, as a method capable of calculating the wave height with high accuracy in the area, we have proposed a method of setting the wind field and air pressure field which is the external force conditions of storm surge forecasting and wave hindcasting. In addition, We make a selection of wave breaking model that allows the estimation of appropriate wave on the leaf terrain.

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 Various kinds of approximate and explicit solutions(AESs) to the wave length in the Airy wave theory have been made because of analytical insolvability of the basic dispersion relationship. In this paper, 25 kinds of 1 step-AESs and their 2 step-AESs based on Newton's method using each AES for an initial estimate are respectively classified into 7 groups according to the maximum relative errors ε⁽¹⁾_max associated with the 1 step-AESs. Then a range of relative error ε and behavior of ε with relative water depth are investigated as to each of grouped AESs as well as a Combined Piecewise AES (CPAES) for separate usage in shallow water and deeper water. Main findings are (1)1 step-AES-based ε⁽¹⁾_max widely distributes from 0.0012 % to 5.2 %, (2)2 step-AES yields an ε⁽²⁾_max smaller than 1 step-AES with a ratio from 10^-2 to less than 10^-5, (3)the CPAES gives higher accuracy than the best of 1-step AESs, and (4)selection of the AES or CPAES properly meeting the requested conditions may be possible from the candidates by taking ε_max and computation load into account.

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 External forces, such as winds or tides, induce internal waves in a nearly enclosed bay that is stratified due to solar radiation and fresh water input. The Coriolis effects transform internal waves into internal Kelvin waves, which may induce horizontal circulation and mass transport through break of the waves. However, the influence of internal Kelvin wave breaking on horizontal circulation and mass transport has not been well revealed in previous studies. This study aims to investigate the currents induced by breaking internal Kelvin waves on slopes with different angles by using a three-dimensional numerical model. Numerical simulations show that larger slope angle induces higher run-up height. It is also found that the location of horizontal circulation is correlated with the wave breaking point.

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 Amplification factor of secondary undulations in western region of Kyushu was examined using sea leval data at five tidal stations during February 10 - March 31 in 2012. As a result, it was shown that the heights of shallow water waves at Fukue, Nagasaki, Koshiki Island and Makurazaki are amplified by factors of about 2.0, 6.6, 7.6, 7.0, respectively. Moreover, it was suggested that sea level variation with periods less than one hour at Meshima Island is a good index to forecast the large secondary undulation west of Kyushu.

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 In this paper, we investigated differences of frequency characteristics of infragravity waves observed at 20 coastal wave stations and 15 offshore GPS buoy wave stations. Shorter components whose periods are less than 150s exist only in shallow areas whose depth is less than 250m and their temporal variations are large depending on occurrence of meteorological disturbances. On the other hand, longer components whose periods are more than 300s exist in all areas and their temporal variations are small.

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 The long period waves observed in harbor inside may consist of free waves not only propagated from offshore but also generated on harbor entrance due to reduction of wave groups by diffraction and breaking. In this study, a harbor tranquility analysis for long period waves is conducted by using Boussinesqtype wave transformation model with model verifications. The offshore long wave heights are estimated from wind waves with a newly proposed relationship of them, and the generated long wave heights on harbor entrance are estimated from the results of calculation for wind wave transformation. A harbor tranquility analysis for the generated long waves on harbor entrance is more appropriate because the directional spreading of their component waves may be reproduced in calculation of wave transformations.

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 To give the calculated wave profile in upside region to the incident boundary in downside, a nesting method for Boussinesq model is proposed as an one-way connecting procedure, reffering the nesting method for a calculation of tsunami propagation from offshore to coastal area. The ratio of connecting time intervals can be selected at an optional positive number and the ratio of connecting grid sizes between upside and downside regions can be selected at 1:1 or 2:1. As for the 1:1 connection, the wave profiles calculated in upside and downside regions completely correspond with each other in case of linear and nonlinear wave transformations; moreover breaking. As for the 2:1 connection, in order to secure the calculation accuracy in downside region, an enough resolution on upside region is required.

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 This study investigated an application of wave dissipating blocks to reduce the wave overtopping at a joint corner between upright seawall and flare shaped seawall. A series of hydraulic experiments were conducted with using a plane basin to clear the effect of wave dissipating blocks on reducing wave overtopping at the joint corner. Furthermore, this study investigated the possibility of applying a partition wall, which is installed on the face of the flare shaped seawall, to reduce the wave overtopping instead of the application of wave dissipating blocks. The partition wall reduced the wave overtopping at the joint corner in the case of small incident wave angle. In the case of larger incident wave angle, wave dissipating blocks installed on the both side of the joint corner effectively reduced the wave overtopping.

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 A low-crest seawall with a drainage, which is composed of a seawall and a backside parapet, has been constructed to reduce wave overtopping volume efficiently. In this situation, it is necessary to evaluate the influences of water elevation in a drainage on the wave overtopping volume into a land.
 The purpose of this study is to investigate the reduction effects of wave overtopping volume on a low-crest seawall with a drainage and to estimate the water elevation in a drainage by a one dimensional unsteady flow analysis and the experimental data. As results, it is found that it is important to control wave elevation in a drainage behind a low-creat sewall for reduction of wave overtopping volume on a backside parapet. Moreover, it is possible to estimate every temporal-spatial distribution of the water elevation in the drainage by a one dimensional unsteady flow analysis.

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 In order to understand effect on overflow rate caused by waves, we simulated with a 2D wave-simulating numerical flume that sea water flowed over seawall on complete overflow condition with waves. The flow rates from the simulations on no wave condition were considerably consistent with overflow rates calculated by Rao & Muralidhar's fomula. On wave conditon, surplus flow rate over seawall caused by waves was undetected when sea level height from top of seawall, h₁ was larger than 3m. When h1 was smaller than 3m, the flow rate on wave conditon was larger than on no wave condition. The surplus flow rate caused by waves increased with increasing wave height and height of seawall. And, we developed the formula to estimate surplus flow rate over seawall caused by waves based on the results of numerical simulations, and verified that outputs of the formula fit the simulation results considerably.

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 In July, 2004, an embankment behind a vertical seawall was damaged due to storm waves from Typhoon No. 8 on Hokkaido's Pacific coast, and railway services were suspended as a result. In this research, hydraulic model tests with irregular waves were conducted on a scale of 1/40 to clarify the characteristics of wave overtopping on vertical seawalls with replication of the wave and tidal conditions prevailing when the 2004 damage occurred. The patterns of rapid flow generated by wave overtopping were examined for the maximum condition of the irregular wave train. The velocity and thickness of the rapid flow was also reproduced by dumping water from an upper tank on a scale of 1/4. The scouring pattern was shown by the action of 30 instance of rapid flow onto the cement-reinforced model embankment. The test results showed that scouring of the model embankment was similar to that observed with the prototype.

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 A net type unit with rubble in it is proposed to prevent the scouring. The construction of unit could beThe unit easoly implementedin at a pilot site. The speed of construction of that is confirmed in the test. A test for exposition is done to investigate the variation of strength for tension. The results demonstrate the strength for tension is kept in about 60% of initial stage. Secondary experiment employs the model unit with 1/50 scale to measure the stability coefficient in wave and tsunami flow actions. The stability is much higher than the rubble used in the breakwaters. Finally the scouring test is carried out comparing the sedimentation volume.

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 In this study, hydraulic experiments were conducted to examine the influence of incomplete covering condition of wave-dissipating blocks to wave force acting on the superstructure and wave transmission due to wave overtopping at several cross sections. The incomplete coverge of sloping breakwater influences front wave force on the superstructure and therefore increase the possibility of the superstructure to slide. The influence of wave transmission coefficient due to wave overtopping was small due to the steel sheet pile wall installed at the harbor side of the breakwater. In addition, we examined a method of rearranging experiment datas using two cross section wave force measuring lines on the superstructure to evaluate the fluctuation of wave pressure data.

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 Laboratory experiments were carried out to investigate the stability of the wave-dissipating blocks of detached breakwaters against waves and tsunamis. The relationship between the stability number, relative damage level D and the number of waves N as well as the Iribarren number was proposed by modifying Van der Meer's formula. A stability number Ns is proposed that is suitable for the wave dissipating blocks and armor stones used in detached breakwaters. The required mass of the concrete blocks and armor stones was found to become large when the relative water depth and the height of the breakwaters increase.

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 Stability of tetrapod for breakwaters covered with wave-dissipating blocks was examined for steep and shallow foreshore conditions by two-dimensional hydraulic model tests. For the condition of 0.010≦Ho'/Lo≦0.048 and 0.35≦h/Ho'<0.85, the necessary mass of tetrapod becomes smaller than the calculated mass by Hudson type design formula. The stability number(Ns) for tetrapod was obtained experimentary in these conditions. Furthermore, the damage mechanism of wave-dissipating blocks at the end of slope was explained.

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 In order to expand the effective range of wave frequency of a water chamber type breakwater, a double-water-chamber structure was newly proposed, and examined experimentally and theoretically. It has an additional function, such as a water exchange function , to an ordinal breakwater function. It was clarified that both the functions of wave energy dissipation and water exchange can be retained by installing a horizontal plate partly at the lower end of the second water chamber. In order to improve the stability of the new breakwater against stormy waves, performance of a new measure, typically an addition of a massive base to the breakwater, has been examined. It was confirmed that both the functions of wave energy dissipation and water exchange are also retained for this new breakwater.

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 Many wave energy absorption system proposed can absorb wave energy with high efficiency, regarding wave energy at a specified frequency band. But they have lower their absorption efficiency in irregular waves. This is due to the fact that while waves themselves are composed of wide-range frequencies. The natural frequency of the wave energy absorption system itself is basically a single one, and is so arranged that the wave absorption efficiency will become the greatest in the vicinity of its natural frequency. To overcome this discrepancy, ingenuity has been used to estimate the incident waves and functionally change the natural frequency, but this method has not yet been able to enhance the efficiency. This research verifies the existense of determining the natural frequency of the water column in the oscillating water-column-type wave energy absorption facility, using the same concept as that of the water column in the U-shaped tube. We comfirmed the absorption efficiency at the case of installing plural number of water columns which have different natural frequencies in the same facility. In addition, this facility was able to absorb the wave energy of an irregular waves in real marine area.

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 The 2011 Tohoku earthquake and tsunami caused widespread and serious damage especially to coastal areas in the Tohoku region. While a number of hydrographic observation facilities were damaged, there exist movies capturing tsunami propagation and inundation, which are considered to be useful for obtaining hydrographic properties of tsunami behaviors. In this study, we tried to estimate time series of velocities of the tsunami in Ofunato Bay, using a movie that captured the first tsunami wave attack. Time series of the original images were converted to separate images of brightness values and then their distortion corrections were made using our field survey data. Finally, we obtained temporal and spatial distributions of the tsunami induced currents in Ofunato Bay.

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 Nankai Trough earthquake is a massive earthquake which is estimated to occur in the near future in Japan. The elevation of vast reclaimed area located in the southern part of Okayama city is very low and the risk of liquefaction there is rather high. Therefore, an earthquake-triggered liquefaction and a severe tsunami inundation disaster are expected there. But, detailed information about tsunami inundation process on the land still has not been clarified at present state. In order to contribute to take evacuation countermeasures of Okayama city against tsunami inundation, 2-D tsunami inundation simulation was carried out. To clarify the tsunami inundation process, different numerical conditions of tsunami wave height and with or without a coastal levee's subsidence caused by liquefaction were investigated. Numerical results show that the levee's subsidence have a great influence on the expansion of tsunami inundation area. And the tsunami inundation progresses gradually in more than several hours by not only the first arrival of tsunami wave but also the second wave or coming several waves after.

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 This study simulated a tsunami runup in the virtual simple river and in Tone River using the generalized coordinate system and the Cartesian coordinate system models. The research's purpose was to understand the characteristics of the water level and to improve the simulation's precision of a tsunami runup in a river.
 The computed results of the virtual simple river indicated that the water level using the Cartesian coordinate system model is different from the actual phenomenon along the levee. Whereas, the calculated water level using the generalized coordinate system model is closer to the actual phenomenon.
 The results of the reproduction simulation of The 2011 off the Pacific Coast of Tohoku Earthquake Tsunami in Tone River showed that the water level using the generalized coordinate system model is more accurate than that of the Cartesian coordinate system model, based on the comparison of the computations and observations at 18.0 kilometer post (down the estuary barrage).

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