The characteristics of morphological variation on the northern Kaetsu Coast, Ishikawa, Japan, have been investigated using a set of annual field surveys collected over 13 years for an alonghore stretch of approximately 32 km. Spatiotemporal variation of cross-shore profiles, shoreline location, and sediment volume has been examined for 12 survey lines. The alongshore variability on the study area was substantial: Significant retreat of shoreline was recognized on the middle and north part, while an accelerated accretion occurred on the south end near Kanazawa Port.

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 Artificial beach nourishment method as the defence work against beach erosion has been conducted. However, it was very difficult to estimate the shoreline and volumetric changes after nourishment and also the moving of the nourished sand is not clarified. On the other hand, recently, coarser sand nourishments have been noticed as effective favored work. In this study, in order to investigate the behavior of the fill sand, laboratory experiment was carried out. By tracing of the fill sand movements, the moving velocities of the fill sand can be related to to the characteristics of the wave.

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 This research is to develop the model that evaluates cross-shore and alongshore sand transportation simultaneously: cross-shore and alongshore sand transportation integrated model, aiming to evaluate the size of shore structures and its effect as beach protection on beaches where cross-shore sand transportation is dominated.
 To understand the characteristic of topographic change, we focused on the relation between wave height and cross-shore sand transportation. Waves which wave height is over 3 meters provoke cross-shore sand transportation, and its direction is inverted (from onshore to offshore) when wave height is over 4m. To simulate this characteristic, 4 models (SBEACH, Carmen and Magnus., Watanabe et al., and Van der Werf et al.) were tested using observed wave data, and the model developed by Van der Werf et al. showed the best application. In this research, modifications on wave height calculation and grain size were introduced to the Van der Werf model and the model that evaluates cross-shore and alongshore sand transportation simultaneously was developed.

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 The coastal erosions lead to serious problems in sandy beaches around the world. The artificial beach nourishment method has been accepted as an effective work for the restoration of shoreline in eroded area. As the coast facing the Sea of Japan tends to repeat seasonal variation, that is, the shoreline is eroded from autumn to winter and is restored between spring and summer. Therefor, a numerical N-line model which takes into account the characteristisc of wave condition after the beach noutishment is suggested.

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 In a slender water body with a small aspect ratio, the angle between the direction normal to the shoreline and the wave direction exceeds 45 degrees, resulting in the emergence of cuspate forelands and the subdivision of a lake, because of long wind fetch along the principal axis. In this study, the BG model (a model for predicting three-dimensional beach changes) was applied to this problem. Three-dimensional subdivision process of a long slender water body was predicted.

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 Large-scale land reclamation was carried out on the Yugawara coast in Kanagawa Prefecture. After this reclamation, the area north of the reclaimed land was eroded due to the wave-sheltering effect of this new land. In addition, the foot depth of the seawall of the reclaimed land increased, resulting in severe overtopping. As a measure against beach erosion, artificial reefs were constructed. In this study, a method to restore sandy beach north of the reclaimed land by beach nourishment was shown. The optimum method was investigated using the BG model.

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 We have developed a local remote sensing system that allows the quantification of nearshore morphology. In this system a network camera is installed on a high building. The camera is connected to a laptop computer which controls the data acquisition procedure. Image processing such as averaging (time exposure) and rectification are conducted in order to examine the morphological variation. The system has been applied to the field observation of Hachigasaki Beach, Ishikawa, Japan. Continuous observations have been conducted since November 2007. The comparison between image analysis and ordinary field survey shows good accuracy of the measurement. Various morphological features have been captured such as the formation of cuspated features of shoreline. These results show the high capability of the developed system to remotely measure the coastal morphology on sandy beaches.

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 Beach changes of northern Kujukuri Beach were investigated on the basis of the aerial photographs. The shoreline positions and the seaward marginal line of the coastal forest, which had advanced seaward by excess planting of pine trees, were read and the beach width between them was calculated and compared. It was found that the beach width in this area rapidly decreased. Aerial photographs of the regions where severe beach erosion occurred were closely compared.

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 In the previous studies on beach changes around Oharai Port in Ibaraki Prefecture, the beach changes in areas north and south of the port were separately investigated and the overall comprehensive studies were not carried out. This area was damaged by the 2011 Great Tsunami occurred on March 11, 2011. In this study, recent beach changes occurred in this area between Naka River mouth north of Oharai Port, and Narita and Kamigama coasts were investigated, including the effect of the great tsunami.

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 Field observations on the seasonal variation of the river mouth bars were carried out at the Choja River mouth located on the Emi-Wada coast and the Yonaga and Tenjin Rivers on the Kamogawa coast. The change in the river mouth bar was measured using aerial photographs and GPS. A method estimating longshore sand transport at a river mouth was proposed using the change in river mouth bar and the foreshore slope.

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 Although sand colors have influences on a variety of functions, such as coastal landscapes and beach ecological systems, they have never been research subjects in the coastal engineering area. The purposes of the present study are to clarify color characteristics of sands which were collected at 23 beaches in Japan and to examine relationships between the color characteristics and geological features of river drainage areas which are adjacent to the beaches. PCA ordinations showed that the 23 beach sands colors can be well ordinated in a coordinate plane which has axes of brightness and of black to brown. It was confirmed that the brightness of the sand is well explained by area ratios of the felsic rock and of mafic rock, by examining the relationships between the beach sand colors and the igneous rocks.

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 Beach has been severely eroded on Akaehama Beach extending between the Oyodo River mouth and Aoshima Island with a stretch of approximately 11 km in Miyazaki Prefecture. To investigate the cause, aerial photographs were compared and shoreline changes were obtained. Past condition of erosion with the formation of scarp during Typhoon No. 16 in August 2004 was shown. Furthermore, topographic changes around the Oyodo River mouth were investigated based on the records of dredging.

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 Topographic changes of Ajigaura Beach caused by the wave sheltering effect due to the offshore breakwater of Hitach-naka Port were investigated. Aerial photograph was taken on November 5, 2010 using an unmanned aerial vehicle. Shoreline changes were investigated using seven sets of aerial photographs taken between 1984 and 2010, including the photograph taken on November 5. In addition bathymetric survey data taken in 1996 1999 and 2002 were compared. Finally it was concluded that the beach changes at Ajigaura Beach was triggered northward longshore sand transport, which was caused by the wave sheltering effect of the offshore breakwater.

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 The Mabushi coast located on Izu-oshima Island and being a pocket beach with a 650 m length had been eroded. To investigate the cause of the beach erosion, aerial photographs and bathymetric survey data were gathered and analyzed as well as the field observation on February 4, 2011. It was found that the beach erosion was triggered by offshore mining in the past, but recently it reached equilibrium state.

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 The BG model (a model for predicting three dimensional beach changes based on Bagnold's concept) was applied to the investigation of the effect of beach nourishment on the Hasse coast in Kanagawa Prefecture. The southward longshore sand transport was induced due to the wave sheltering effect of the breakwater of Hasse fishing port, resulting in erosion north of the fishing port. As a soft measure against beach erosion, sand back pass from behind the breakwater to the north part was considered. The results showed that the sand back pass with a rate of 500 m³/yr was effective to recover sandy beach.

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 A large amount of sand was deposited in the wave shelter zone of Ohtsu fishing port, resulting in difficulty of the navigation at the port entrance. The BG model (a model for predicting three-dimensional model for beach changes based on Bagnold's concept) was applied to this problem. Measures against sand deposition inside the port were investigated and most appropriate measure was the extension of the jetty with a 100 m length at the tip of the west breakwater.

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 A preventive measures of the littoral drift inflowing in the Ishikari Bay New Port from the west coast is described by the simulation of near-shore current and the observational data of wave, bottom sounding ,etc. in this paper.
 Consequently it was clear that the inflowing sand in the Ishikari Bay New Port was the littoral drift of the west coast, so that the west breakwater was effective means.

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 For the purpose of planning a effective dredging against burial, characteristics of the long-term depth variation of the Kanmon route was examined based on the annual bathymetry data having benn measured since 1995. From the data, it was shown that the whole area of the route has been kept deeper than 12m depth due to dredging. Moreover, it is also shown that a mid of the strait have a tendency of accumulation, though the depth variation due to sediment transportation at Kanmon Strait is small compared with the sea of the Suo area.

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 The depth of closure in Sendai Port is estimated using 10 years bathymetry data and proposed as a longshore variation. The hydrodynamic condition is simulated using Boussinesq equation (Peregrine, 1967) which was modified by applying long wave theory. Using wave data from 1991 to 2003, 20% wave height in deep areas is applied as a representative wave. From the modeling, bottom velocities in the x and y directions are obtained. The result is used to calculate the maximum bottom velocities just outside the boundary layer. The effect of wave reflection is observed using the velocity distribution and maximum bottom shear stress. By integrating the velocities in the x and y directions, the area that is influenced by reflected waves can be observed. The results are depicted as a spatial map. The longshore variation of the depth of closure is overlaid on the results to confirm the influence of wave reflection for its variation.

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 A sand pack is sand filled geotextile bag and it is used for coatal protection. Ultraviolet rays and hydrolysis degradation of geotextile is unsolved quantitatively. This study investigates reduction of geotextile tensile strength through light and water exposure apparatus(Open-flame carbon-arc type) and natural weathering test. And we suggest methods for estimating remaining tension of geotextileby daylength.

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 A literature review of 47 cases of applications of geosynthetics to shore protection in 16 countries was conducted. A fault tree for coastal structures constructed using geosynthetics was proposed based on 14 cases of bad practice. Important bottlenecks against which countermeasures need to be taken were identified as being the following: instability of sand bags, a scour on the tip of the sand tube, expansion of water channels and rupture of geosynthetic material. Wave tank experiments were conducted for assessing the process of collapse of submerged coastal structures by wave attack. Experimental results showed that the stability of a submerged sand-bag depends on both the extent to which the sand-bag is filled and the direction of wave attack. This result suggests the need for a new method for determining the stability of submerged coastal structures constructed using geosynthetics.

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 Measures against erosion of Ohmi-shirahama Beach located west of the Kamogawa River flowing into northern Lake Biwa were investigated using the contour-line-change model. On the basis of the plan, two groins were newly constructed as well as the beach nourishment of 800 m³ of sand. Monitoring results after the construction showed that the predicted and measured results were in good agreement. The stabilization method of the lakeshore change was confirmed, which was caused by decrease in sand supply from rivers.

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 The development of a cuspate foreland on a steep coast with abrupt change in coastline orientation was investigated by a movable bed experiment. After 8-hour wave generation, a groin was installed at the cuspate foreland and the effect of obstructing continuous longshore sand transport was also experimentally investigated. The results of the experiment were reproduced using the BG model which was proposed by the present authors. The beach changes around the cuspate foreland were successfully predicted. The experimental and numerical results were in good agreement. The installation of a detached breakwater on a steep coast with abrupt change in coastline orientation was also predicted using the model and both results were compared.

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 About the pile-supported wave absorbing breakwater with a low crown height, we have examined the characteristics of local scouring around the structure in mild-slope conditions. In this study, we conducted the hydraulic model test with steep-slope movable-bed for scour around the structure, that the increase in scour depth is around the pile side of the onshore, and a similar trend in mild-slope conditions was found. In addition, in a large wave height condition, due to the influence of plunging breaker, scour has occurred in the onshore, and deposition has occurred in the offshore. By installing the countermeasure against local scour, we confirmed the effectiveness of measures to reduce the flow velocity in the sediment.

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 Hakata Bay is located in nothern part of Kyushu Island. The area has been reduced by large reclamation since the beginning of twentieth century. Changes of the coastal line could have affected tide, tidal amplitude and sediment transport in an inner bay. We tried to clarify the effect using two approaches: (1) harmonic analysis of observational water level data at Hakata and Izuhara and (2) numerical experiments using a three-dimensional Princeton Ocean Model (POM). As a results of this study, it was clarified that tide, tidal current and sediment transport have changed near the Island City.

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 Ministry of Land, Infrastructure, Transport and Tourism is conducting the investigation of environmental characteristics in Ariake Sea and Yatsushiro Sea by using the ship "KAIKI". As a result of environmental monitoring, we obtain three results from this project of 2010; 1) the DO value of 3mg/L has been observed for the first time off Miike port and estuary of Kumagawa river, 2) the classification of seven patterns in Ariake Sea by combination of bottom sediments and benthos cluster analysis.

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 Radioactive materials were released from the Fukushima Daiichi Nuclear Power Plant as a result of the reactor accident after the 9.0 earthquake and subsequent tsunami of 11 March 2011. In this paper, amount of inflow radioactive material released from the Fukushima Daiichi Nuclear Power Plant were estimated in Tokyo Bay. The inflow route made into the object are descent out of the atmosphere and inflow from some rivers. As a result, the sum total of the amount of inflow of two routes was about 12TBq in ten months from March, 2011 to December.

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 This paper describes the relationship between wind and salt wedge intrusion in Lake Abashiri. Intrusion discharge is correlated closely with water level difference between sea and lake, but may be affected in winds. This study thus aims to reveal the relationship between intrusion discharge and water level difference, wind velocity and its direction by applying statistical approaches to observed data. It shows that strong wind affects intrusion discharge secondarily by Principal Component Analysis (PCA), and observed data classified with a diagram of 1^st principal component score against 2^nd on PCA have better correlation. By multiple regression analysis with that data, estimation accuracy of intrusion discharge is improved on.

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 In the Yatsushiro Sea, the harmful algae Chattonella antiqua red tides is becoming a major threat to the fishing industry, with damages exceeding 10 billion yen. In this study, CCA was used to determine the relationship between the growth of C.antiqua and factors of the water quality environment. Factors involved in the growth of C.antiqua include degree of stratification, O₂ saturation of bottom water, water temperature, DIN/SiO₂-Si and DIN/PO₄-P were raised. The fact that the degree of these factors differs in areas where outbreak occurs could be clarified. From now, the factor extraction technique by CCA is expected to be effectively applied for development of a prediction model for red tide using the HSI model, etc.

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 The aim of this study is to examine the effect of the various density currents on wave-current interaction with various density differences using an improved model including three-dimensional advection-diffusion equations and the equations of state on salinity and temperature of water. Then, using the numerical results the characteristics of coexisting fields between wave and current are examined in relation to density differences. Based on the numerical results, the wave height, turbulence intensity and mean flow under wave-current interaction have been discussed in relation to the density of water.

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 The distributions of wave overtopping discharge along the coastal seawall next to Murotsu harbor in Kochi prefecture occurred by Typhoon SONGDA (No.0418) and TOKAGE (No.0423) are reproduced with the horizontal 2D Boussinesq model. Their validity for the locations and quantities of wave runup and overtopping is confirmed with not only the records of regulation of traffic along the Route 55 behind the coastal seawall but also the results estimated with the modified imaginary gradient method and CADMAS-SURF/2D on the several representative cross sections.
 The condition of wave overtopping evaluated with the Boussinesq model can explain the records of regulation of traffic as the allowable wave overtopping discharge is set to 1.0E-05 m³/m/s for the traffic. And their values correspond to the results estimated with the above methods on the cross sections without the armor blocks covered with seawall and the horizontal wave transformations. In addition, they can suppose appropriate results on the other cross sections with such conditions.

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 Recently, coastal disasters due to long period swell induced by heavy storms and catastrophic typhoons increase in the Japanese coasts and harbors. However, it is important to optimize the use of the protective effect of existing seewalls like the drainage canal in cases where it is difficult to take countermeasures in the same as before.
 In this study, the numerical simulations with Boussinesq-type wave transformation model are conducted to clarify the process of the drainage of wave overtopping and inundation for long-period swell. A part of water mass of wave overtopping are drained away though the drainage canal, the rest flood the backland and the areas of inundation spread extensively. Moreover, it is indicated that the simplified counter-measure has a great effect on the reduction damages of the inundation.

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 This paper focuses on difference of breaking wave models especially in terms of their different predictive skills of the current field around the surf zone. Widely-used modified Boussinesq equations were applied to the newly conducted experimental conditions with different breaking wave models, i.e., dispersion type, friction type and surface roller-type models. Predicted osscilating current velocity and depthaveraged undertow velocity were compared to the measured data. Comparions clearly demonstrated the advantages of the surface roller-type model in that the model succsessfully explains the increase of the undertow velocity inside the surf zone. While all the models showed excellent predictive skills of the wave heights, none of these models successfully represent the profiles of near-bottom orbital velocity.

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 To confirm the applicability of multi-level wave model for linear scattering problem by step-like bathmetry, characteristics of the eigenvectors obtained by dispersion relation of model equations were investigated. In the case of equally divided layers, the shape of the eigenvectors turned out to converge to that of the small amplitude wave theory, by the increasing number of layers. Although the eigenvectors of non-uniformly divided layers do not converge to that of the small amplitude wave theory, the results of scattering analysis with the eigenvectors have shown sufficient accuracy in the transmission and reflection coefficients.

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 In estimating significant wave heights with satellite remotely sensed data, a joint probability density function of water surface elevation and slopes is usually used to be Gaussian distribution. However, the effect of the nonlinearity of waves becomes stronger, the distribution does not satisfy the Gaussian distribution. A Gram-Charlier series distribution has been used for the probability density function of the surface elevation and slopes but has a disadvatage that may take a negative value. In this study, the relationship between the wave nonlinearity and higher-order moments such as skewness and kurtosis is investigated. Then we developed a new estimation method of a joint probability density function by applying the two-variate maximum entropy principle method. Through the comparison between the distributions of the present study, Gram-Charlier series, and observed data, the present method shows a relatively good agreement with measured distribution.

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 Frequency components of infragravity waves whose periods are more than 600s are called 'meteorological tsunami'. It is known that the characteristics of these components are different from those of shorter components. In this paper, we analyzed mainly seasonal changes of infragravity waves of various frequencies. The main conclusions of this paper are written below.
 1. Components whose periods are less than 600s are maximum in winter and minimum in summer in the Sea of Japan, on the other hand, they are large in spring and autumn in the Pacific Ocean.
 2. Seasonal changes of components whose periods are more than 600s are different from those of shorter components. But, in the Sea of Japan, they are more similar than in the Pacific Ocean.
 3. There is no correlation between the components whose periods are less than 600s at the two stations which are located almost in the same latitudes. But there are clear correlations between the components whose periods are more than 600s.

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 In many ports, it has been reported that long-period waves cause trouble in cargo handling. As a countermeasure to this, a wave absorbing mound installed on the harbor-side of the breakwater is proposed. The crown height of the mound is almost equal to that of the caisson. However, because of the low wave absorbing performance of such conventional structures, the required width to absorb the long-period waves becomes more than 30m. It is important therefore to reduce the size of the structure to apply to various site conditions. In this study, a submerged mound type long-period wave absorbing structure is proposed. A series of hydraulic model experiments was systematically and carefully carried out to evaluate the wave absorbing performance of the proposed structure.
 Throughout this study, it became clear that submerged structures display a higher wave absorbing performance compared with those of conventional structures. In particular, the wave absorbing performance of a two-layer covering of concrete armor blocks is significant. For example, under conditions where the water depth is 10m and the wave period is 60s, a 16m width submerged structure is equivalent to a 30m width conventional structure from the standpoints of wave absorbing performance. As a result, it can be expected that the proposed submerged structure would contribute to cost reduction. Such mound structures are particularly applicable to middle- and small-sized harbors.

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 Irregular Regular wave data over the shallow reef with steep slope were analyzed using data of experiments conducted by Sekimoto et al.(2011). Occurrence distribution of wave height is investigated. Statistical parameter, such as maximaum wave height, Significant wave height, rms wave height, rms value oflong period wave were also investigated. Condition of the reborn of waves on the reaf is studied. Upper limit of maximum wave height corresponds to breaking condition of solitary wave on the reaf is found.

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 Regular wave data over the shallow reef with steep slope were analyzed using data of experiments conducted by Nakajima et al.(2011). We selected root mean square wave height H_rms as wave height in our analysis for wave energy evaluation. By using a parameter H_rms/d, d is mean water depth, we estimate the parameter for the reborn wave height on the reef as 0.28±0.1. We investigate wave energy decay process using the parameter. We also study wave characteristics after wave breaking under the condition of flow existance.

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 This study numerically investigates how an artificial reef affects wavecurrent fields using a 3-d direct numerical model. The numerical results reveal that wave-current co-existing field is considered to investigate the effect of wave-current interaction on wave fields around an artificial reef installed at river mouth., Wave-current interaction greatly influence the energy flux with a resulting increase in wave height behind the artificial reef and the energy flux mechanism is significantly different between permeable and impermeable artificial reefs.

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 Characteristics of propagation of atmospheric pressure disturbance over the East China Sea were investigated using the output data from numerical weather prediction model, called meso-scale model (MSM), developed by the Japan Meteorological Agency. By applying the method of particle image velocimetry (PIV) to the consecutive images of sea-level atmospheric pressure based on the MSM outputs, we could find the atmospheric pressure disturbance travelling eastward at speeds of 115-150km/h and causing the occurrence of large secondary undulation at the west coast of Kyushu. It was suggested from the results that the MSM sea-level pressure data are useful for predicting the occurrence of the secondary undulation at the west coast of Kyushu.

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 This study aims at investigating space and time-distributions of possible maximum storm surges and high waves caused by potential typhoons in Mikawa Bay under a present climate. A meteorological field surrounding Typhoon Vera (1959) was assumed as the present climate which generates the potential typhoons. Under this condition, a potential vorticity bogussing scheme of a tropical cyclone initialized 200 cases of potential typhoons striking Mikawa Bay. Then, the spatial and temporal distributions of the storm surges and the high waves in Mikawa Bay under the 200 initial fields were predicted by using an atmosphere-ocean-wave coupled model.
 The results show that the potential storm tide over a large area of Mikawa Bay exceeds 2.75 m which is the largest storm tide ever recorded in Mikawa Bay. In particular, the storm tide in Takahama, located at the eastern inner part of Mikawa Bay, reaches 4.0 m in the maximum and exceeds 2.75 m during 70 minutes. Hence, there is a possibility of an occurrence of the storm surge disaster in Mikawa Bay under the present climate.

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 A storm surge and high wave-induced inundation model is used in this study, which consists of the Myers-based typhoon model, a depth-averaged flow model, the wave model SWAN and inundation model using a CIP method. The model was validated by comparing the numerical results with the observed ones. Moreover, this study numerically examined the temporal and spatial distributions of water elevation and flow strucutre in Tokyo bay as well as the inundation around Tokyo port induced by storm surge and high wave under the intensification of typhoon due to the global warming.

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 Recently, due to global warming, there are growing concerns about possible tremendous disaster caused by furious typhoons more than ever. It is therefore very important to develop an accurate numerical model for storm surge. Recently, some circulation models, e.g. Princeton Ocean Model (POM), Regional Ocean Modeling System (ROMS), etc. are applied to the storm surge simulations for enabling more accurate estimations. Among these existing models, Finite Volume Coastal Ocean Model (FVCOM) developed by Chen et al. (2003) has an advantage in that it employs unstructured grid system so as to compute tidal currents in complicated inner bays with high accuracy. Thus, the FVCOM seems to be superior to other models in storm surge simulations. In this study, first, the FVCOM was modified to deal with the spatiotemporal changes of pressure fields in the momentum equations. Second, in order to investigate the influence of computational conditions (e.g. domain size, grid size, etc.) on the computational results, the storm surge simulations were conducted for the past severe typhoons which actually caused the storm surges in Ariake Sea and Yatsushiro Sea. Then, computational results were compared with observed data as well as other results computed by the POM to clarify the advantages of the FVCOM in storm surge simulations.Unstructured Grids can re-create complex topography better than Structured Grids, hence FVCOM is more applicable to compute storm surges in inner bay.

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 In the study, an application of a neural network is examined in order to forecast a real-time storm surge at the Sakai Minato on the Sanin Coast. In the forecast experiments, sea level pressures, depression rates of sea level pressures, wind speeds, wind directions, tidal levels and storm surge levels during only one typhoon (T0418) and two typhoons (T0418 and T0314) were trained. A storm surge during Typhoon 0415 was forecasted using the neural network. From the results of the experiment, it is found that the forecasted storm surge level trained with the tidal level, the storm surge level, the depression rate of sea level pressure are close to the observed storm surge level. In addtion, the forecasting results are significantly improved in maximum storm surge level with the increase in the number of the observation stations and with the inclusion of the wind speed in training the neural network. From the experiment of forecast times, it is seen that the predictions in the 1 and 2 hour forecasts are more accurate than those in the 3, 4 and 5 hour forecasts.

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 Sea level rise and intensified storm caused by global warming increase inundation risk of storm surge. The auther assessed inundation damage risks of storm surge on many areas, and put them on a map of Japan. The map shows that Three Major Bays, Seto Inland Sea and Ariake - Yatsushiro Sea region have high risk and that risk areas are limited in Hokuriku, Tohoku and Hokkaido region.
 Using the inundation damage model, the author calculated inundation damages as functions of inundation height at various regions. Obtained relationship between damages and inundation height showed that the damages rapidly increase with inundation height up to T. P. 5m in the regions of Tokyo bay, Osaka bay and Seto Island sea, whereas damages are relatively lower and increase up to inundation height of T. P. 10m in the regions of Ibaraki - Kujukurihama and Nankai - Tonankai.

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 In October, 2006, the coastal road of national route No.238 was damaged by storm waves at Sarufutsu Village in Hokkaido. In this research, two-dimensional hydraulic model experiments were conducted to reproduce the damage condition and to examine the temporary countermeasures. At the site of the damage, wave run-up induced by high waves continued for about 12 hours, and the deficit of the road shoulder arose. Based on the test results, tetrapods of two layer with three row should be necessary for the stability of large sand bags and the safety traffic. The applicability of the proposed countermeasures was also confirmed by field observations.

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 In the case of a coastal dike and a seawall in a beach or a shallow area, there are a few of field cases that those are destroyed directly by strong wave force and a lot of field cases that scour in front of them and suction from their bodies caused by the continuing action of waves bring their destruction gradually. Therefore, it is important for us to establish the prediction methods of the scouring rate in front of them and the suction rate from their bodies. In this research, first, the accuracy of the 2-D numerical model of Ca et al. is comfirmed by using field data on the scour. Then, the diagrams to estimate the maximum scour depth are proposed. Next, the experiments of the suction from their bodies in which the grain diameters of back filler are changed are conducted. Then, the formula of effective shear resistance force in which the influence of the grain diameter can be considered is proposed also.

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 Vietnam has a long coastline that stretches from north to south and thus is a country highly susceptible to coastal disasters. However, the southern part of Vietnam has generally been perceived to be less vulnerable to typhoons or storm surges compared to the northern and central parts of the country. The authors tried to understand the actual vulnerability of this southern coastline to coastal disasters, in particular storm surge, through the field surveys and numerical simulations. Through the field survey it was evident that there are a number of settlements at risk, such as a number of houses standing on a severely eroded beach and a village located in a low-lying river bank. The interviews with local residents revealed that people living there were not concerned about typhoons, while a typhoon track analysis shows that a substantial number of typhoons have approached southern Vietnam in the past. The authors estimated that the highest water elevation due to storm surges in the past 6 decades was approximately one meter by performing the numerical simulation. It is feared that these vulnerable local communities could be devastated by a storm surge accompanied by strong waves if the past biggest class typhoon occurs.

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 The purpose of this paper is to clarify the risk of storm surge and tsunami in Tokyo port by using three different numerical simulations, a storm surge simulation, a tsunami simulation and an overland inundation simulation. In the storm surge simulation, storm surge behavior in Tokyo port was calculated by considering many typhoon courses. The model typhoon used in the calculation is the Ise bay typhoon(1959), reproduced by using Myers equation. As a result, the maximum storm surge height in Tokyo port and the typhoon course which occurs are clarified. In the tsunami simulation, tsunami behavior in Tokyo bay is calculated under the consideration of three earthquakes. The target earthquakes are Genroku, Miura Peninsula and Kamogawa and Keicho earthquake. Amongst them, the earthquake which induces the highest tsunami in Tokyo port is the Keicho earthquake. In that case, the tsunami height around Tokyo port is about 1.5m. In the simulation, the initial tsunami heights were calculated by using the model of Manshinha and Smylie(1971). Overland inundation is simulated under the impact of the Keicho earthquake. The results show the western Koto Delta, Southern Koto Delta, East Shinagawa and many other areas outside Tokyo port are under the risk of inundation. For the overland inundation simulation, a 5m mesh topography data was used, which enables the display of micro scale inundation. The overall results show that it is necessary to reconsider disaster management plans in Tokyo, as current counter-measures might not be sufficient to protect certain areas against all foreseeable threats.

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