As tsunami deposit, sand layer is found in many coastal areas. Tsunami deposit is treated as an evidence of tsunami run-up. And it is considered that tsunami deposit contains hydraulic information. In this study, two different hydraulic experiments are conducted about sand deposit by tsunami run-up on a slope. One experiment is related on the effect of grain size for sand deposit. By the experimental result, it is shown that the distribution of tsunami deposit is influenced by the grain size. In the case of large grain sand, that sand was stopped and accumulated near shoreline. Another experiment is on the initial area of movable sand. By the hydraulic experiment with different initial areas, the main origin of sand deposit on a slope is shown near shoreline.

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This study investigates the influence of topographic characteristics on Tsunami disaster and its reduction. Firstly, the Digital Elevation Model (DEM) with 5m resolution around Nakatajima dune was developed and inundation area by expected Tokai-Tonankai earthquake was estimated. The results show the recent topography has higher risk than past topography. Secondly, effectiveness of dune height on Tsunami inundation protection was investigated by 1-D simulation on the representative cross section in Nakatajima dune. The inundation process there was affected by dune height. It is pointed out by the simulation results and past 10-year survey of dune height that suitable monitoring and maintenance of dune height is necessary for Tsunami disaster mitigation.

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The damage due to tsunami has been mainly estimated for the water level and velocity so far. However, it is possible that a great volume of sediment transported during tsunami causes damage. In this study, numerical simulations for the sediment transport due to tsunami by To-nankai and Nankai Earthquake, for the port of Wakayama-Shimotsu and Osaka where the sediment characteristic is different, were carried out to examine the influence of the port facilities by the sediment transport due to tsunami. The calculated results showed that the erosion is remarkable in the breakwater head and narrowed part, the maximum erosion of -6.4m in the port of Wakayama-Shimotsu and -4.5m in the port of Osaka. On the other hand, the sediment widely deposit in the inside the harbor with slow velocity, the maximum deposition of 1.9m in the port of Wakayama-Shimotsu and 0.4m in the port of Osaka.

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Authors carried out hydraulic experiments to clarify a tsunami wave load on a bridge deck subjected to surging breaker bores(SBB) and plunging breaker bores(PBB), focusing on the relationship between the position of a bridge deck to wave height and the occurrence of vertical force acting on a bridge deck. Experimental results show that the vertical force occurs when the value of the height from lower level of a bridge deck to the crest of a wave (a-h_c) divided by wave height a, (a-h_c)/a, becomes 0.39 for PBB to 0.41 for SBB. The magnification factor of vertical force compared with hydraulic pressure of the wave height λ(=F_Z/ρgaA) becomes 0.37 for SBB to 0.48 for PBB when (a-h_c)/a varies from 0.75 to 1.00.

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The paper describes the damage assessment of confined-masonry and concrete-block houses due to the recent three earthquake tsunamis. The authors analyzed 13 damage data, focusing on the evaluation of strength of houses subjected to the tsunami wave loads. Concrete-block houses and masonry houses which are one-story ones, and located near the coastlines at Peru, Samoa and Chile are analyzed. Based on the theory of by Asakura et al (2000) previous research, we identify the strength of a wall by computing the distribution of the tsunami wave pressure on the wall exposed to an inundation height.

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Drifting behavior of a container on an apron due to tsunami run-up and drawdown is investigated using hydraulic experiments and numerical simulations. When a container and a wall on the apron are set parallel to the seawall, the container can drift to the sea for the large relative overflow height of an incident tsunami and the small relative position of the container. It is consequently suggested that it is not always effective to move containers landward before tsunami attack to prevent the containers from drifting to the sea. When a wall with an opening is set oblique to the seawall, a container parallel to the seawall can rotate toward the normal to the seawall as drifting through the opening. As a result, it is necessary to consider various drifting patterns of container in dealing with the container drifting landward through the opening.

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The main purpose of this study is to develop a numerical analysis code for the prediction of a flapgate breakwater behavior during a huge tsunami. The features of this code are that the FAVOR method and the VOF method are applied. The code is applied to a hydraulic experiment of flapgate breakwater. As a result, the obtained numerical solutions agree well with the result of the experiment. Furthermore, through applying the code to a prediction of the flapgate breakwater behavior during the 1993 Hokkaido-Nanseioki tsunami, the applicability of the code to a real-scale simulation and the effectiveness of the breakwater to a huge tsunami are discussed.

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DONET, i.e., the dense ocean-floor network system for earthquakes and tsunamis has started in operation in the Nankai Trough in the early of 2010. DONET consists of various sensors such as broadband seismometer, seismic accelerometer, tsunami meter, etc. This paper focuses on bottom pressure sensors being used as tsunami meters. Long-term sensors' stabilities have been evaluated before/after the deployment into the deep-sea, and tide assimilation has been carried out in order for detection of crustal deformation with high accuracy. As a result, sensor drift of ~20 hPa per month could be measured in the laboratory experiment, and it may continue after the deployment. This paper also reports that the tsunami from the Tohoku-oki earthquake on 11 March 2011 could be detected by DONET with those peak-to-peak amplitudes of 20~40 cm.

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Results of a field survey of the 2010 Chile Earthquake tsunami in Chile are reported. After outlining the general state of tsunami heights, the aspects such as the tsunami-trace distribution around a building, the inundation flow velocity, the variation coefficient of inundation flow velocity and the countermeasures to floating objects are discussed. Field data on the tsunami inundation in a housing complex area are, for the first time, indicated. Remarkable tsunami damage observed along a small river which almost runs parallel to a coastline is also discussed. The upper end level of reef whitening after the uplift due to the earthquake is proved to correspond to the low tide level before the earthquake.

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A post-tsunami survey was conducted to clarify impacts of the 2011 Tohoku Pacific Ocean tsunami on sandy coasts of Chiba and Ibaraki prefectures. The measured tsunami height varies from 4 to 8 m above the mean sea level at respective sites and shows a general tendency to slightly decrease southward. Analysis of tide data from nearby stations reveals that tsunami waves of same amplitude repeatedly attacked the coasts for several hours. A large portion of the coasts was protected from the tsunami by seawalls and/or high vegetated dunes while some areas without dunes or around river mouths were severely damaged by tsunami floods. Detailed damage analysis was carried out for some representative locations on the basis of high-resolution topography data.

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Coastal tree failure conditions such as the lodging, uprooting and breaking are necessary to estimate tsunami energy reduction due to coastal forest. A field test on the lodging and uprooting conditions of Sea casuarinas is carried out on the west coast of Central Sumatra, Indonesia. Based on the field test results, empirical lodging and uprooting conditions of Sea casuarinas are presented. The validity of the conditions is checked through comparison with those data obtained through a field survey of the 2010 Mentawai Earthquake tsunami. It is confirmed that more than 40% of the data satisfy the conditions. Based on the geometric and dynamic characteristics of Sea casuarinas, its scale model in the hydraulic experiments is examined considering the similarity laws for trunk and branches.

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In the area in front of Nankai trough, tsunami wave height may increase if tsunamis attacking from some wave sources overlap because of time-lag of seismic event on Nankai trough. To evaluation tsunami risk of the important facilities located in front of Nankai trough, we proposed the probabilistic tsunami hazard assessment considering uncertainty on time-lag of seismic event on Nankai trough and we evaluated the influence that the time-lag gave to tsunami hazard at the some representative points.

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Inundation flow with floating objects was witnessed and videotaped in Banda Aceh, Indonesia at the 2004 Indian Ocean Tsunami. With this background, a simple model for estimating such a flow was developed by the authors with a fixed bed in mind, where the model adopted the notion of the conventional bore theory regarding the floating objects as a hypothetical fluid, and took account of the resistance force due to the floating objects piling up at the surge front of the flow. However, as the flow is under the condition of a movable bed in most cases, laboratory experiments are newly carried out under its condition. Through the examination of experimental results and solutions of the model, whether the model is useful and basic characteristics of the inundation flow are discussed.

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This study improved the debris model (STOC-DM) including wind load to trigger the debris drift in typhoon attack. Through the model tests with considering the drag and inertia forces due to water current and the drag force due to wind, the influence of the wind drag force was confirmed and the drift velocity was verified theoretically. Prototype numerical simulations with freight containers as debris of Mikawa port in typhoon 0918 were implemented, and the containers were moved to the wind direction not to the water flow direction. This phenomenon was also confirmed in actual site, Mikawa port. From the results, considering wind load as the external force is necessary to grasp behavior of the drifting debris in a strong wind.

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There are several bulk flux models for an ocean surface boundary layer, such as surface roughness and TKE fluxes at the ocean surface. However, these bulk flux models have not been calibrated in detail.The validation for the parameterization of bulk flux models is carried out analyzing correlation of temperature and velocity vertical distributions between numerical results and observed data. The numerical experiments were conducted during the Typhoon Melor in 2009 at Tanabe Bay, Wakayama Prefecture, Japan. It was found that the parameterization for the TKE flux has significant influences on temperature and velocity in the nearshore region.

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In the west coast of Japan wave-current interaction is important factor for predicting wind-driven currents during winter season. The present study examined the performance of radiation conditions for open boundary when using a coupled numerical model of surge, wave and tide where wave-current interactions on surface and bottom boundary layers were taken. The performance of radiation conditions was examined with regard to a fixed or changeable phase speed on simplified and real test cases. We proposed an equation of the radiation condition based on Flather's model and confirmed that the proposed open boundary condition gives stable water levels and currents' outputs and contributes the reduction of the spin-up calculation.

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Recently, there are many researches on sea level rise due to global warming. Various problems on aquatic environment and disaster prevention will be caused by the sea level rise. However, variations of high water level (H.W.L.) and low water level (L.W.L.) are important to discuss countermeasures against these problems rather than that of mean sea level (M.S.L.). Changes in H.W.L. and L.W.L are determined by a combination of variability in M.S.L. and tidal amplitude. We tried to clarify long term global changes of oceanic tidal amplitudes by usung the harmonic analysis. From the results of this study, we found that tidal amplitudes changed during 20th century. The trends were increase in most part of the world.

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Around a river mouth at open coastal zone, complicated flow fields arise from interactions between waves, tidal and fluvial currents. To estimate sediment budget around river mouth, it may be important to investigate the current field. In this study, spatio-temporal properties of the currents off the Tenryu River mouth on the Pacific Ocean are discussed based on field data and numerical simulation. The field data were obtained in five-year observation in summer from 2006 to 2010. The westward component is significant in the vertical profile of time-average current. The bottom layer currents are developed in long-term under the influence of a flood discharge. Also from the numerical simulation with 3D hydrodynamic model, seasonal variations of the current field in wide coastal area have been roughly reproduced.

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In recent years, marine products industry has been damaged seriously by red tide in the Yatsushiro Sea. Furthermore, the coastline of the Yatsushiro Sea has been changed by land reclamation is the case in the Ariake Sea. In this research, we tried to reveal the behavior of low-salinity water masses in summer season and the shift of physical fields triggered by the change of coastline. As a result, the followings were clarified: 1) In case of large discharge such as over 1000 m³/s from Kuma River is happened, surface layer's salinity across the Yatsushiro Sea falls to a low level; 2) The change of coastline caused by land reclamation from1900s to 2000s, so that 30 % decrease of tidal current in closed-off section and 10 % decrease of tidal current in the southern part of the Yatsushiro Sea are caused.

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The study was carried out to investigate the dynamics of the fresher-water plumes by Fuji River outflow by using the field measurements in the inner pert of Suruga Bay. The Fuji River water spreads over a deep continental slope as a surface-advected plume and extends several km. According to the three dimensional current data collected using shipboard acoustic Doppler current profiler (ADCP), anticyclonic eddy at the river mouth is not generated. It was found that the intrusion of Kuroshio warm water prevented the spreading of the Fuji river water to east area of inner part of bay. Residual current, such as wind driven current or intrusion of the oceanic current, have a strong effect to the fresher-water plume.

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Mixing process between the river flow and sea water at the Tenryu River mouth was investigated based on the infrared camera imagery. Three times field surveys were carried out to evaluate the influence of various physical factors, e.g., nearshore topography, tide, river flow, and waves. Infrared camera was deployed to monitor the spatiotemporal distribution of river flow movement during the spring tide event. Assessment was conducted with respect to the temperature difference between the river flow and sea water. It was confirmed that the river flow went eastward after filling into the ocean. Vertical distribution of the temperature and salinity was measured. Numerical simulation in terms of a heat conservation equation was performed to model the mixing process, in which waves and currents were simulated based on the energy balance equation and quasi-3D nearshore current model, respectively.

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Intensive field measurements of water quality and current were carried out in summer 2010 off the Toyogawa river mouth located at the head of Mikawa Bay. Structures of water density and dissolved oxygen concentration and their variations were discussed based on the data. The residual currents were compared with wind data and freshwater discharge from the river. The estuarine circulation observed in the measurement seemed to be caused mainly by wind action, but large amount of freshwater discharge may cause current toward the river mouth near the bottom. Dissolved nutrients especially phosphorus may be transported upstream by the bottom flow and used in the primary production in shallow waters.

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This study analyzed the movement of river front at Tone River by using the echo data observed with X band radar network from January to June of 2010. Relationships between intensities and the propagation speeds of the front, and water level of Tone River, tide level and wind velocity and direction measured at Fishing Port of Choshi were analyzed. Front intensity tends to strengthen when tide level is descending. The alongshore propagation speed and the arrival point of front increase when the alongshore component of wind increases.

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The mechanism of formation and the wind response of low salinity water mass in Isahaya Bay have been investigated by using the 3-D flow simulation model incorporating time-varying wind stress on the water surface. The northerly wind and the southerly wind are prevailing in Isahaya Bay and are repeated at the period of several days. The analytical results show that the change of the prevailing wind direction induces the appearance and disappearance of low salinity water mass. When the southerly wind blows, the low salinity water mass near the water surface is swept out Isahaya Bay and the salinity stratification is gone with the wind. On the other hand, the inflow of low salinity water mass to Isahaya Bay is accelerated by the northerly wind and the salinity stratification is formed.

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We propose a procedure to calculate the latent heat of vaporization of sea sprays in the meteorological model in order to investigate the effect of the sea sprays on the air temperature field above the sea surface. The air temperature locally decreased 0.1-0.5℃ when we consider latent heat flux due to sprays than the results without sprays. The numerical experiments varying `spray generation function' revealed that the sea sprays with its radii of O(10-100 μm) have influence on the temperature field the most. This suggests that the local meteorological field around the surf zone, where the number of the sea sprays of (O10-100 μm) is known to be greater than that above the ocean, is well affected by sea sprays.

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Hourly wind distributions on 3 regional sea areas which include the Kanto Sea Area, Ise Bay and the Seto Inland Sea are estimated using the measurement data of sea level pressure around the areas over a 45-year period form 1961 to 2005, after which a 45-year wave hindcasting is conducted station by station. For monthly- and yearly-highest 1/3-averaged wind speeds and wave heights, hindcasts are in reasonable agreement with measurements. Trend and jump analyses for yearly-highest 1/3-averaged atmospheric pressures, wind speeds and wave heights yield the following results : 1) Pressure does not exhibit any trend or jump. 2) Both wind speed and wave height show a statistically significant increasing trend and positive jump putting a pivotal year at around 1986, and their intensities become weaker toward the western area.

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This paper deals with statistics of wave climate. NOWPHAS data from 7 observatories along the Sea of Japan are analyzed. Fourier spectrum of the significant wave heights shows that it can be divided into three frequency regions; (A) f<0.007 d^-1, (B) 0.007 d^-1<f<0.2 d^-1 and (C) f>0.2d^-1 in which d^-1=1/day. Simple but appropriate spectrum modeling for individual regions is proposed in this study. From numerical simulations with the models, frequency distributions of significant wave height for arbitrary specified period including one year is derived. It is also shown that the maximum wave height distribution in these periods can be approximated with the Gumbel distribution. Examples for application of the present study in maintenance of a coastal structure are shown in the last.

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On 15 July 2009, a meteotsunami occurred at Tsushima Strait and with the flood damage at Sasuna community area in the west of Tsushima Island. This study analyzed the meteorological conditions in relation to the meteotsunami event. The baiu front system moved south from Korean Peninsula to the north Kyushu and San-in area in the morning of 15 July, accompanied with the strong cold downdraft. The pressure disturbance occurred by the acoustic gravity mode 100-120 km west from Tsushima Island in the middle of the strait, where the surface moist air from the southwest was lifted by cold downdraft. The cycle of the pressure disturbances were around 10 minutes, which is nearly same as the eigenoscillation of the small bays of the Tsushima.

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Abiki is a kind of meteotsunami (a large amplified seiche) reached to west Kyushu coastal area. This study is aimed to clarify the characteristics of the atmospheric disturbance forcing the tsunami-like ocean long wave. The sea-level pressure disturbance observed and modeled over the East China Sea had its source over the southeastern China mountains and was then propagated by a jet stream toward western Japan with a help of both wave-duct and wave-CISK (conditional instability of the second kind) mechanisms. The backward trajectory analysis also showed that the atmospheric gravity wave propagated with its phase speed of aroung 30 ms^-1, and it took 8-12 hours from atmospheric wave source to Kyushu coastal area. Hence, the forecast of the midtroposhere instability can be useful for the meteotsunami prediction.

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In this study, a climate in September of 2099 based on the SRES A1B scenario was assumed as the future climate affected by the global warming. 50 cases of potential typhoons striking Tokyo Bay under the assumed future climate were estimated by using potential vorticity bogussing scheme of a tropical cyclone. Then, distributions of the possible maximum storm surges and high waves generated by the 50 potential typhoons were predicted by using an atmosphere-ocean-wave coupled model. The results show that the potential storm tide in Tokyo Port reaches 3.4 m and the maximum storm tide of 4.1 m height in Tokyo Bay is caused in Katunan located at the most inner part of Tokyo Bay. The heights of these storm tides remarkably exceed the largest storm tide 2.3 m ever recorded in Tokyo Bay.

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Re-analysis and reproduction of storm surges and waves due to the Isewan Typhoon were tried using the detailed re-analysis meteorological data that agreed with the meteorologocal observations. In the simulations a coupled model of surge, wave and tide was used. The predictions using the coupled model agreed well with the observed surges, but not for the uncoupled model's predictions that are much smaller than the observations. Predicted waves were comapred with previous estimations since there are no observations. The magnitudes of wave heights were constistent each other.

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This study aims at investigating space and time-distributions of possible maximum storm surges and high waves in Ise Bay caused by potential typhoons based on the SRES A1B scenario. Initial fields of 50 potential typhoons were provided by using potential vorticity bogussing scheme of a tropical cyclone. Then, the distributions over the whole area of Ise Bay under the 50 initial fields were predicted by using an atmosphere-ocean-wave coupled model. The results show that all storm tides in Nagoya Port caused by the 50 potential typhoons exceed 3.5 m which is the largest storm tide ever recorded in Japan and that its maximum value reaches 6.9 m. Moreover, it was found that the storm surge of 3.6 m and the significant wave height of 6.0 m occur in Chubu Centrair International Airport at the same time.

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In this study, the typhoon potential vorticity bogussing system (TYPVB) and high-resolution mesoscale meteorological model (MM5) are utilized to estimate the maximum potential wind speed in the bay of Tokyo. TYPVB can initialize the 3-dimensional well-matured typhoon structure for MM5 entirely consistent with the atmospheric dynamics, and MM5 can make it strike the arbitrary geographical area wherever powerful measures to prevent storm surge disaster are demanded. As a result of the appropriate settings of typhoon environment in TYPVB, it becomes obvious that well-matured typhoons which are modeled as Typhoon Vera (1959) causes a resultant wind speed of about 40m/s in the bay of Tokyo, where the worst wind speed is weakened by about 5m/s owing to the shadow effect of the upstream peninsula.

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In order to dynamically and precisely estimate the future typhoon change caused by the global warming, the method of setting typhoon environment in the typhoon potential vorticity bogussing system (TYPVB) developed by Yoshino et al. (2009) is substantially revised in this study. In TYPVB, the future climate change evaluated by the CMIP3 multi-model ensemble is strictly included in the environment of Typhoon Vera (1959) which is selected to represent the typical well-matured typhoon environment for the present climate, so that the future climate change can be reflected appropriately to atmosphere and ocean. A number of MM5 simulations initialized by TYPVB indicated that the maximum potential wind speed in the bay of Ise is enhanced by 10% to 50 m/s in the future climate.

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This paper focuses on the part for studying an attenuation of surface waves propagating through frazil/grease ice and pancake ice in a wave tank in a cold room. The tank is equipped with a wave maker of plunger type. The air temperature is kept around -8 degrees during the whole experiment. Regular waves of eleven different frequencies are generated in during 50 sec to avoid the reflection waves. The portion of the wave signals before the arrival of reflections is used to measure the wave number and the attenuation rate. As a result, it is found that the wave attenuation decreases with increasing frequencies. For the incident wave of marginal ice zone, the attenuation rates of the high frequencies side become 70 %. Further, to estimate the wave attenuation in grease-pancake ice, it is necessary to consider not only frequency but also wave height.

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One of the important procedures for Disaster Prevention Plan is to determine accurately the window condition of an approaching typhoon. By using the Meteorological Model, it enables the aforementioned situation to be specified. The purpose of this study is for the method application to the Disaster Prevention Plan. The effect examined is due to the difference of several computational condition by Typhoon 0416 and 0418. This reveals the property model of WRF. In addition to that, we enumerated the problem issued from the model utilization in order to make the application easy. According to the study, it is proved that Four Dimensional Data Assimilation greatly influences reproducibility of typhoon path. The magnitudes of central pressure and wind velocity speed are susceptible to the parameters of microphysics scheme etc.

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In this study, we developed an oil spreading and diffusion particle model. The model can calculate oil spreading by particle model to use Fay's equations(1969) and the effectiveness was evidenced. We conducted hindcast simulation of oil spill incident of Hebei Spilit, South Korea in 2007 using the model. We compared calculation and observation of spilled oil, its applicability was verified. We discussed about vertical and horizontal eddy viscosity coefficients because their coefficients affected the simulation results. We proposed vertical eddy viscosity coefficient equal to 0.10m²/s and horizontal eddy viscosity coefficient equal to 30m²/s.

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In Japan, a wave observation network called NOWPHAS (Nationwide Ocean Wave information network for Ports and HAbourS) has been maintained since 1970's, and NOWPHAS has about seventy wave observation points. On the Pacific side in the Tohoku district, GPS-mounted buoy and coastal wave gauges observe ocean waves. Therefore, it is important to examine the correlativity of wave data observed by these wave gauges. This study examines the correlativity of observed wave data between GPS-mounted buoy and coastal wave gauge, and the estimation of wave height on coastal wave gauge on the basis of wave height observed by GPS-mounted buoy. As a result, it was confirmed that there is the correlativity of wave data observed by both wave gauges though it depends on wave direction.

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The flood models that employ an Euler type moving boundary technique has been used for analysis of flooding simulation. However, the Euler model is difficult to simulate the flow in flat area, because of dis- continuity of shoreline movement. Then, the quasi-Lagrange flood model that change nodes with Lagrangian only on the shoreline for applying to an unstructured grid analysis was developed. It was confirmed that the proposed model can simulate flood process accurately by comparing with the result of the hydraulic model test, whereas the Euler type model overestimated the flood area near the flooding point.

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Relationships between the topographic changes near the shoreline and the waves both offshore and just outside the swash zone are studied for some twenty storm events observed during years of 2003 to 2004 at Hasaki. All the storms which lasted long enough produced a kind of equilibrium beach profile of mildly sloping uniform one near the shoreline, irrespective of the initial profiles. It is shown that the slope may be predicted by the parameter by Sunamura(1984), employing either the offshore data of significant waves or the long wave properties near the shoreline.

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A sediment transport model taking into account laminar and turbulent resistance force due to infiltration/exfiltration is proposed in this study. A three-dimensional two-way coupled fluid-structure-sediment interaction model (FSSM) combined with the proposed model is applied to sediment transport in a steady uniform flow and local scouring due to tsunami run-up. As a result, the laminar resistance force due to infiltration/exfiltration affects the sediment transport rate, and it is consequently essential to take into account the laminar resistance force in assessing sediment transport in the presence of infiltration/exfiltration. The results also show that the FSSM with the proposed model predicts experimental data reasonably well, and demonstrate the validity of the FSSM with the proposed model.

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A model for predicting beach changes using a cellular automaton method was developed, in which sand transport under the ongoing and outgoing waves is separately calculated in accordance with the fundamental concept of the BG model proposed by Serizawa et al. The model was applied to the beach changes on the gently sloping revetment of the Katsuyama coast, and also applied to a model case, in which sand is trapped in the holes excavated on a reef flat by coral mining.

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Modeling of key processes for fine sediment transport dynamics near the sea bed with fluid mud layer has been studied for the inner Tokyo Bay considering the mud characteristics of the site. Field monitoring data have revealed some specific features of the muddy sediment around the study site such as high water content at the bottom surface and fluid mud transport. Resuspension flux is estimated as turbulent diffusion flux between the sea water and fluid mud layer and estimation results show fairly good agreement with observed data. For the estimation of horizontal mass flux in the fluid mud layer, velocity profiles are analytically calculated using the relationship between shear stress and deformation rate for Bingham fluids considering the vertical structure or yield stress profile in the observed fluid mud layer.

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A series of mud mass transport experiments were conducted under the irregular waves and currents co-existing field in a two-dimensional wave flume. Results were compared to theoretical values that were calculated by the visco-elastic-plastic model. As a result, mud mass transport under irregular waves and current can be well evaluated by using visco-elastic-plastic model. The model was applied to each element of irregular wave classified by the joint distribution of wave heights and wave periods. This method gives evaluation with good accuracy for different conditions of current and spectrum shapes. It has been found out that spectrum shapes don't give significant influences on the mud mass transport.

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Large eddy simulation is performed to investigate the mechanism of the vertical sorting of sediments under sheet-flow regime particularly from a viewpoint of interacting between eddies and sediment based on the solid-liquid multiphase turbulent flow model. The agreements between experimental results and numerical results are reasonable with choosing the model parameters in the distinct element method for simulating movable bed. The developing process of the vertical sorting is discussed through the distribution of the phase-dependent turbulent energy production.

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To investigate size distributions of suspended sediments, the field measurement using LISST (Laser In-Situ Scatter and Transmissometer) was conducted on a sandy beach. The time-series of suspended sediment concentration (SSC) of a grain size in the sand range (63 to 500 μm) had strong correlations with those of other sand grain sizes, and the same trend was observed for silt (3 to 28 μm). However, the time-series of SSC of sands had little correlations with those of silts. The comparison between the estimated and measured grain size distributions of suspended sediments suggested that the assumption that SSC is inversely proportional to the sediment fall velocity can be applied to estimation of SSC of various grain sizes. With the increase in median sediment diameter, the sorting coefficient decreased and the skewness increased.

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Field observation on sand deposition on the gravel beach was carried out on the Jinkoji and Akashi coasts facing the Pacific Ocean. On the basis of the contour-line-change-model, a model for predicting sand deposition on the gravel beach under the calm wave conditions was developed, taking into consideration that the equilibrium slope of sand is increased due to the percolation effect of gravel bed and its effect depends on the thickness of sand layer. Furthermore, landward movement of gravel due to storm waves was explained by the model. Predicted results were in good agreement with measured values.

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Laboratory experiments were performed on the sediment transport on backshore, which was caused by solitary waves as well as cyclic waves. Measurements were conducted for overtopped volume of water and sand, temporal variations of horizontal water particle velocities, surface elevations and suspended sediment concentration. Meyer-Peter-Muller's formula and Lane-Kalinske's formula were found to be consistent with the sand transport rate caused by long waves but inconsistent for solitary wave. Sediment suspension and convection on the foreshore due to breaking was found to be important to estimate the sand transport due to solitary wave. The saturation of suspended sand concentration was observed when the height of the incident solitary wave exceeded 7cm.

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A model for predicting not only the change in longitudinal profile but also the change in grain size composition was developed using the contour-line-change model. In the model, the information of the grain size composition in a sand layer of the deposited beach is memorized as well as its position, and in the erosion process such information can be used for the calculation. The seasonal profile and grain size changes can be well predicted using the present model.

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Beach profile model taking into account the time-space variations of sediment density has been developed and compared with the movable bed experiments in the laboratory wave flume. Concretely, the conventional sediment transport load using the velocity moments with use the fluid acceleration is revised considering the time-space variations of underwater specific gravity of sand particles in the activation depth based on the X-ray CT scanning. Conducting the numerical experiments, the fluid acceleration (horizontal pressure gradients) is found to have an inverse proportion to the underwater specific gravity of sand particles in the activation depth. Preliminary attempts to parameterize the time-space variations of underwater specific gravity of sands appear promising.

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