Sediment carried by longshore transport moves to deep sea through the submarine canyons. The investigation of submarine topography had been conducted by narrow-multi beam echo-sounders system. Detailed bathymetric changes shows the mechanism of sediment transport from beach around coastal structures to submarine canyon. This sediment transport mainly occurs at storms related with several typhoons. Large amount of sediments appear to be migrated by sediment gravity flow at storms submarine topography and distribution pattern of bottom materials have been changed due to this processes.

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Bottom topography change in a harbor due to tsunami was investigated experimentally. Experiments were carried out three times under the same tsunami condition to investigate reproduction of the bottom topography change. Reflected wave of tsunami from the harbor model was sufficiently absorbed. Data sets with high quality were obtained with respect to tsunami water level, velocity, suspended sediment concentration and bottom topography. Vortices generated near a breakwater play an important role in topography change inside the harbor. A heap with mild slope was generated near the center of the harbor due to the vortex.

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Coastal dunes are natural bed forms caused by wind and wave actions. They run parallel to the shoreline close to the beach and thus have an important role to protect land against external force due to tsunami. To evaluate such protective effects of sand dunes, their erodible property must be considered since some part of them might be washed out during tsunami flooding. In this paper, a numericalm odelf or dune deformationi nducedb y tsunami is presented. The model is based on the Boussinesq-type equation coupled with the sediment advection equation and existing empirical formulae of sediment transport rate. The model performanc is confirmed through comparison with available laboratory data. Finally, the dune erosion induced by tsunami is discussed on the basis of the model application.

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We developed a hydrostatic three dimensional numerical model, which was applicable to analyses of tsunami scours and depositions in harbors. The model can explicitly estimate vertical distributions of suspended sediment concentration, which would be important to predict the tsunami deposition precisely. In order to validate the model, we carried out the test simulations; the long-wave propagations over a flat wall, and the development of suspended sediment concentration profiles in a steady homogeneous flow over a sand bed with initially clear water. The numerical simulation of tsunami scour and deposition in an idealized harbor was also carried out, and we compared our numerical results with the laboratory experiment. As a result, we confirmed an agreement among them.

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Authors carried out numerical study on the topography change due to tsunami in the bay of Kesennuma when Chilean Tsunami had occurred. In the site, huge erosion was observed at the narrow strait and devastating sediment transport in the form of suspended sediment according to large tractive force was expected. We proposed some parameters on the topography change model in order to reappear such condition by means of numerical simulation. In comparison with the observed bathymetry, it was verified that the effect of moving bed condition had to be considered in the equivalent roughness coefficient and vertically uniform eddy diffusivity with the turbulence scale around 1.0 to the depth well reproduced horizontally eliminated sediment transport under the tsunami.

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This study investigates relationship between tsunami flooding flow and spatial distribution of tsunami deposits observed after the December 2004 Indian Ocean Tsunami. Authors first carried out field survey on the south-east coast of Sri Lanka and measured the thickness of tsunami deposits at various sampling locations in the tsunami run-up area. While obtained spatial distributions of sand deposits showed some correlation with well-known parameters such asdistance from the shoreline, some of the data clearly did not support these features. Based on the numerical analysis, weshowed that tsunami back-rushing flow, which locally concentrates on lower ground area, has different flow pattern from the on-rushing flow and well explained the observed spatial distributions of tsunami deposits.

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Two laboratory experiments have been conducted to examine the time-space variations and spectral evolutions of sandy beach profiles under tsunami. The beach was exposed to only positive solitary waves. The profile changes were measured with changing the still water depth. Then, the beach recovery and non-recovery processes were examined by exposingt o the solitary waves in combination with three kinds of regular waves. Under depositional regular wave conditions, the beach recovery processes under tsunami were achieved within thirty minutes. Under erosional wave conditions, however, the beach recovery process was not observed. This is partly because the solitary wave does not break in the offshore bar crest but does near the shoreline.

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This study conducted field observations in terms of the number of blown sand particles and wind velocity in the period of 12-16 Jan 2005 at an open ocean beach in Japan, in order to investigate effects of climate change on the threshold wind friction velocity of blown sand. The data of blown sand number and wind velocity were logged at a frequency of 1Hz and then divided into 5-minute segments to estimate the threshold wind velocity using Time Fraction Equivalence Method (TFEM). Time-series of the threshold wind velocity (estimated using the TFEM) demonstrated that the threshold corresponded with the value estimated using the Bagnold equation and increased notably during rainfall. The threshold decreased as the mean wind velocity increased.

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Blown sand is a serious problem in the district facing the Japan Sea where seasonal wind is very strong in winter. In order to prevent the blown sand, the construction technique using natural vegetations had been developed. The growth of the natural vegetations is encouraged by the improvement of sand ingredients in this method. The effects of the method were investigated by the field survey and observation at the seashore in Kashiwazaki, Niigata Prefecture. As a result, the increase in the ground level by the sedimentary sand, which was caught by the vegetations, was observed in contrast with the natural beach. It was confirmed that this method is effective on the growth of the natural vegetations and the prevention of the blown sand.

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Effectivec ountermeasure is required for the issue of wind-blown sand generated from nourished beach to hinterland in Niigata West Coast. Double-row sand fences on a parallel with coast and wing fences having with the fence height of 2m have installed in 2005. The comparison was made with past observation results after conducting site observations in the winter season (November, 2006 through February, 2007) in this study. As the result, the volume of wind-blown sand reaching to hinterland was decreased to around 1/10, 000 to 1/100, 000 comparing with the volume without fences and it has been confirmed that the countermeasure by double-row sand fences and wing fences are extremely effective. The cheaper countermeasure by reducing the number of fences is to be studied.

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Ebisuhama fishing harbor is located on the east of Hachinohe port. Around the fishing harbor, a wide reef spreads and an offshore breakwater is constructed and planned to be extended. The breakwater extension may affect the environment and predicting the influence in advance is needed. In this study, sounding survey and sediment analysis have been conducted to understand sediment transport characteristics at the site and it is confirmed that sediment transport around the harbor is mainly from east to west. Also, morphology change simulations have been conducted to reproduce the sediment transport features and to predict the influence of the breakwater extension. By applying a model of sediment transport on a hard bottom, the morphology change on the topography with reef has been reproduced.

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An analysis method is developed to evaluate countermeasure options against fairway shoaling for Yubetsu fishing port, which is located on Okhotsk coastal region. According to the field observation results, the discriminating ocean current, which is so-called Soya Current, could affect on the flow field even in the surf zone. In this study, the ocean current is successfully implemented to the existing nearshore current model and the results give a reasonable agreement with the observed flow conditions. Moreover, the suspended sediment transport model is applied and gives better agreement with the observed bathymetric changes especially in evaluating the scours around the port facilities.

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The Hamaju coast, located on the west part of a sandy beach with 11 km length extending west from the mouth of the Kuzuryu River in Fukui Prefecture, has been eroded by various anthropogenic factors in recent years. As a measure against beach erosion, 15 detached breakwaters had been constructed between 1973 and 1994. The shoreline advanced behind the detached breakwaters, showing the conservation effect, but in the offshore zone, water depth has been increasing. This caused damages of subsiding concrete armor units. In this study, beach changes of this coast were investigated, and numerical simulation was carried out, using the contour-line-change model. Measured beach changes were well reproduced by the model.

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Long-term changes in sand bar in Sanbyakken region in Nakatsu tidal flat were investigated through the comparison of the aerial photographs. Great changes have occurred in this sand bar in recent years, as aresult of increase in eastward longshore sand transport since 1998. The reason was studied in terms of change in wave field. Waves with the direction of N70deg E, which was determined from the shape of the sand bars on the tidal flat, were significantly sheltered due to the offshore breakwater of Nakatsu Port. Takingthe refraction effect of these diffracted waves into account, the tip of the sand bar was also sheltered by the waves. It was found that this caused increase in longshore sand transport.

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A jetty construction at the east side of the entrance of Lake Saroma has been greatly influenced on the morphological characteristics. In this study, the field observations (wave and current measurement, sediment sampling survey, and bathymetric survey) were conducted and the results were analyzed to investigate the mechanism of morphological change after the east jetty construction started. A numerical model is developed based on the sediment transport characteristic and the simulated results give a reasonable agreement with the observed bathymetric data and successfully verify the appropriate performance for the prediction.

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On the Kashimanada coast, fine sand was selectively transported and deposited in the wave-shelter zone behind the offshore breakwater built on both ends of the coastline, whereas beach was eroded in the central part of the coastline. As a measure, artificial headlands have been constructed on this coast, but beach erosion is still severe. The contour-line-change model considering the effect of changes in grain size was applied to this coast, and the effect of the measure was evaluated. The differences between the total accreted and eroded volumes of sand in the condition with/without headlands became 7.4×10⁶ and 8.1×10⁶ m³. Thus, it was found that the movement of approximately 8.0×10⁶ m³ of sand was controlled by headlands.

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A strong low-pressure system traveled along Japanese Main Island in October 2006. High waves and storm surge attacked Kashima Coast resulting huge erosion over the area. This study analyzes sand loss in sub-aerial zone of southern part of the coast, a stretch of 16 km from Kashima Port to Tone River, using airborne laser data measured in October 2005 and November 2006, and X-band radar images captured during the storm. Longshore distribution of cross sectional change has been estimated from the laser data. Eroded volume of sub-aerial zone was estimated as 600, 000 m³. Pattern of erosion was controlled by headlands in the southern section, and by drainages in the northern section. Shoreline position during the storm has been digitized from radar images with locations of scarps read from aerial imagery.

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Beach changes on the Hazaki coast extending between Kashima Port and Hazaki fishing port were investigated. Numerical simulation of beach changes and grain size changes were carried out, using the contour-line-change model considering the change in grain size (Kumada et al, 2005). In this area, fine sand is transported from outside to inside the wave shelter zone of the breakwater with the construction of Hazaki fishing port. Furthermore, 10.6×10⁴ m³/yr of sand has been supplied from the Tone River and part of fine sand deposited inside the port. The mechanism of deposition of fine sand in the fishing port was well explained by the present model.

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A field investigation was conducted for sand movement in the Tenryu-Enshunada watershed. Sediment samples on the coast and the riverbed were collected in a wide area including in the trench excavated at the old riverbed, for which mineral analysis based on magnetism and Optically Stimulated Luminescence measurements were applied. The ratio of magnetic and non-magnetic particles was found to be highly correlated with the geology of surface sediments. The spatial distribution of non-magnetic particles represented by quartz and feldspar enriched in the upstream geology, as well as the similarity in OSL intensities for the present and the past riverbed samples consistently supported a significant decrease in sediment supply from the upstream region of dams.

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Long-term beach changes after the completion of sand-bypassing project in the Tenryu River, which takes 10 years from the present, were predicted using the contour-line-change model. Even if beach nourishment of 5×10⁴m³/yr is continued in front of Nakatajima sand dune, and 3×10⁵m³/yr of sand is additionally supplied to the river mouth as the effect of sand bypassing at the dam reservoir, supplied sand is only effective for recovering the river mouth terrace severely eroded in the past, and newly supplied sand is ineffective to nourish further downcoast. To conserve the Enshu-nada coast, further overall comprehensive management of sand movement is required.

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Measurements of tides, waves, currents and bottom turbidity were carried out off two different river mouths on the Enshu coast, both of which are affected by strong tidal currents exchanging waters with Hamana Lake or Tenryu River. Based on the field data, the characteristics of tidal currents and their effects on turbidity or concentration of suspended sediments were discussed. High turbidity data were obtained under high wave conditions and also at particular phases of the tidal currents. Some properties of tidal currents near the river mouths are shown. Significant effects of the tidal currents on the sediment suspension and the on-offshore fluxes of the suspended sediments are also indicated.

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A field investigation was conducted on the eroding coast around the river mouth of the Tenryu River, where the coast covered by sand and gravel experienced severe erosion due to the decrease in sand supply from the river. The movement of gravels was monitored in the period from August to December, 2006, when sand and gravels supplied by a flood in July were transported alongshore. The beach surface was found to be mostly covered by sand under moderate waves. Gravels were found to be predominant only in the vicinity of structures, such as detached breakwaters and a jetty. However, gravel layers were found to be present below the surface sand layer. The role of the gravel layer in maintaining the beach topography around the river mouth was discussed

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This study examined the structure of Water-Intake-Works, which can control the inflow of suspended sediment to the inside the fishing port without reducing the amount of introduced water. A section experiment on two dimensions and a numerical calculation were executed in this study. As a result, it is confirmed that reducing the suspended load and controlling the vortex generated in water chamber could reduce the inflow of the suspended sediment to the inside the fishing port. The results also showed that there were several effective methods to reduce the suspended sediment in inflow as following: 1) to enlarge the size of the submerged mound and water chamber, 2) to install the rejection sand entrance, 3) to install the partition wall in water chamber, 4) to make training mouth upward.

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This study examined the structure of Water-Intake-Works, which can control the inflow of suspended sediment to the inside the fishing port without reducing the amount of introduced water. A section experiment on two dimensions and a numerical calculation were executed in this study. As a result, it is confirmed that reducing the suspended load and controlling the vortex generated in water chamber could reduce the inflow of the suspended sediment to the inside the fishing port. The results also showed that there were several effective methods to reduce the suspended sediment in inflow as following: 1) to enlarge the size of the submerged mound and water chamber, 2) to install the rejection sand entrance, 3) to install the partition wall in water chamber, 4) to make training mouth upward.

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When predicting shoreline changes, process-based modeling, which is usually based on the sediment transport process and external forces, is usually applied. Nevertheless, some models which based on the effect of wave and deposit conditions to shoreline changes are also proposed. One of the advantages of these models is short computing time due to not consider sediment transport process. However, lots of empirical coefficients are the problems of these models. In this study, by applying the convolution integral, a model for predicting the response of shoreline has been developed and based on long term survey data, the constant calibration as well as verification of this model has been examined.

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The water depth, flow velocity, salinity and suspended sediment concentration on an intertidal mudflat has been measured since July 2004. The measured time series were analyzed using time averaging to extract the wave components as well as tidal phase averaging to obtain typical variations and variability during the wet cycles. The phase-averaged water fluxes and suspended sediment fluxes were approximately the same as those estimated using the phase-averaged water depth, velocities and concentration. The phase-averaged quantities were used to understandthe temporal variations of the flow and sediment transport during one typical wet cycle, which appeared to be influenced by the local bathymetry and the river discharge.

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The contour-line-change model considering change in grain size proposed by Kumada et al.(2005) was applied to the Chigasaki coast, where beach erosion has taken place due to the effect of decrease in longshore sand supply. Bottom sampling was carried out. Depth distribution in median diameter and longitudinal profiles were measured. The grain size was divided into three dominant grain size populations such as fine sand, medium sand and gravel. The effect of beach nourishment using materials with different grain sizes was predicted. Optimum beach nourishment was the nourishment using materials composed of mixed grain sizes in terms of protection, environment and use of the coast.

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Shoreline changes of the Akiya coast located in Sagami Bay were investigated on the basis of the comparison of aerial photographs. A breakwater of Kuruwa fishing port was extended forming a wave shelter zone. This induced longshore sand transport from outside to inside the wave shelter zone. Sand accumulated inside the wave shelter zone, whereas beach erosion occurred on the nearby coast. Tracer test using sand with various grain sizes was carried out. The contour-line-change model considering change in grain size given by Kumada et al.(2005) was applied to the coast to investigate the effect of beach nourishment using materials with different grain sizes. It is concluded that beach nourishment using sand composed of coarse materials is effective to recover the stable beach without damages to offshore sea grass field.

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The contour-line-change model considering change in grain size given by Kumada et al.(2005) was applied to the Enshu-nada coast, where beach erosion has taken place due to the effect of decrease in fluvial sand supply from the Tenryu River. Bottom sampling was carried out in an extensive area of the coast. Depth distribution in median diameter and longitudinal profiles were measured. The grain size was divided into three dominant grain size populations such as fine sand, medium sand and gravel. The effect of beach nourishment using materials of different grain sizes was predicted. Optimum beach nourishment is the nourishment using coarse materials in a zone, where beach erosion is severe and protected by detached breakwaters, and simultaneously, beach nourishment using fine sand on downcoast.

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This study is concerned with a one-line model for predicting shoreline changes after beach nourishments. The behavior of the injected materials was represented using one-dimensional convection diffusion equation in the alongshore direction. The shoreline changes were calculated by solving the fundamental equation for the conservation of bed material, combined with the advection diffusion equation. First, the proposed model was applied to tombolo formation behind offshore structure in the field. Secondly, the performance of the model was investigated by a model test. Finally, the presented model was applied to the sand recycle project at Yumigahama Coast, Japan, in order to investigate the applicability of the model.

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Use of beach fill materials, which have higher stability than the original natural beach sands, is increasing in Japanese beach fill projects. We therefore need more sophisticated methodology to design the beach fill projects. We performed hydraulic physical model tests to examine yield of the beach fill and erosion of the natural beach by the difference of the physical properties of the fill material. It was understood that erosiveness of the natural beach could be lowered when the material with smaller grain size was used. There is relation between erosion of natural beach under fill material and permeability of fill material.

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Continuous shoreline monitoring is necessary for coastal management. It is however difficult to conduct shoreline measurements frequently because of high cost and hard work. In this research, a short term prediction method using the neural network was investigated as a tool of shoreline monitoring for the adaptive coastal management. The neural network could reproduce the measured shoreline position with a high accuracy of 6.2m for a maximum change of 50m. A combination use of the neural network and shoreline measurement is an effective method for the continuous monitoring although the development of the neural network needs field data for the network construction and its performance is affected by quality and quantity of the data.

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Long-term variations of seabed profiles on Mikawa Coast, Japan, have been investigated using a set of field surveys collected over 46 years. The focus is placed on the migration of nearshore bars under the influence of severe erosion. The variation of the cross-shore bar locationi s examinedi n detail.I t is shown that the cross-shore periodicm ovements have been repeated several times with about 10-year cycles. Superimposed on periodical migration, the outer bar position has a clear onshore trend in longer time scale of decades. An attempt has been made to separate the eroding trend and periodic migration of bars by using a time-varying standard profiles. On the basis of the separated results, real type empirical orthogonal function analysis is conducted to effectively capture the characteristics of sand bar migrations

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The present study deals with a short-term change on-offshore sand bar topography along Tottori coast. The observations were made applying ARGUS method. The sand bar shows year around change characteristics. In late autumn, shore line and offshore sand bar are very smooth and straight. In winter, storm waves bring cusping geographical feature and the offshore sand bar shows concavo-convex features with convexity at bay and concave at horn locations on the shoreline. From spring to autumn, these concavo-convex features gradually disappear. The amplitude of these features are relevant to the integrated values of wave energy minus threshold wave energy, which may be necessary to generate rip current with sufficient velocity

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This paper presents the observation method for the current in the surf zone where topography change is intensive, based on images taken from camera of the sea surface near the coast. To predict the current velocity, the images analysis technique proposed by Suzuki et al.(2005) has been used. The observation is carried out for the duration of one year, from January to December 2006, when the erosion process is actualized in Miyazaki coast. The result confirmed that the direction of current around Miyazaki coast is generally southward during the observation period. The short-term change of the shoreline ranges from 30 to 40m (the fluctuation is ±15-20m from the average shoreline Position).

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In the present paper, the mobile measurement of tidal current was conducted by using the developed system with ADCP and D-GPS over the wide area in Bisanseto fairway. On the basis of the measurement, the sediment transport mechanism and the dynamics of sand wave formation is understood, and then, the fundamental information is obtained for the maintenance of the fairway. In the flood and ebb tides, the amplitude of tidal current in the upper layer is similar to it in the lower layer, but the current direction is slightly different near the deeper part.

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At the beginning of October 2006, an extreme Typhoon 18th hit Yokosuka coast of Japan. There is a big amount of sediment transported and deposited inland after the typhoon. This study is to evaluate of this overwashed sediment volume and the prediction of overwash occurrence. These estimation are significant for coastal authorities and local managers to give evacuation warnings to people who live near the coast, it is useful for planners and engineers to mobilise equipment for cleaning up sediment after a storm. Profile change estimations are useful for planners creating “buffer zones” indicating where it is safe to build houses. And this calculation is also important for evaluating sediment budgets of sand beach or barrier islands, especially where these sand beach or islands are migrating due to overwash.

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A numerical 3D morphodynamic model for predicting beach evolutions around river-mouth, which is based on the quasi-3D nearshore current model, was presented. The morphodynamic model takes into account the sediment transport rate in the run-up region and shoreline changes. The model applied to the formations of sand spits due to wave-induced currents, river-terrace due to river flows and off-shore sand bar in front of river-mouth under stormy wave condition. The computed results were compared with the conventional morphodynmic patterns around river-mouth. It was found that the presented model gave qualitatively agreements with the morphgodynamic patterns in previous studies.

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Topography of beach cusps and grain size sorting was observed at four coasts, as well as the observation of a backwash flow in a bay of a cusp. A movement of sea water flowing obliquely from the apex to the bay was observed, resulting in the generation of a backwash flow. On the basis of this observation, two pairs of sink and source were assumed and three-dimensional cusp topography was predicted, using the contour-line-change model considering the effect of grain size change by Kumada et al.(2005). The formation of a cusp and associated accumulation of coarse materials around the apex were well predicted.

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Cross-shore distributions of longshore sediment transport rate at the Hasaki Coast of Japan for 15 years from 1987 to 2001 were estimated with a one-dimensional numerical model and the cross-shore distribution of the long-term average longshore sediment transport rate was examined. The model was calibrated with longshore current velocities measured with a spherical float once a day at about 50-m intervals along a 427-meter-long pier at the study site. Numerical simulations showed that the average longshore sediment transport rate was northward near the shore, but southward away from the shore.

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Complex principal component analysis (CPCA) was applied to the bottom topographic data surveyed on Ajigaura and Tokai coast in Ibaraki prefecture, in order to detect the features of topographic changes and the correlations between the changes of bottom topography and energy fluxes of the incident waves.The method for incorporating wave data into bottom sounding data was proposed in this study. The results obtained in the study confirmed the applicability of CPCA to analyze the beach topographic changes as well as the effects of wave energy fluxes on the topographic changes.

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Long-term effects of structures on the beach erosion control were investigated in Nankoku Beach, Kochi Coast from the viewpoint of sediment balance. Monobe River is the main sediment source to the beach though three dams decrease the sediment supply. Construction of 52 detached breakwaters was started in 1973 to prevent beach erosion and completed in 1997. One artificial reef was also constructed in 1999. Effects of the structure were analyzed by the profile data. Results show deposition on the landward side and erosion on the seaward side.It is concluded that breakwaters are effective and decrease longshore transport for the prevention of shoreline retreat though the construction started from up-drift side.

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The state of beach erosion of the southern unit of the Romanian Black Sea shore is described with explanation of its mechanism. Beaches in the northern part of the study area are composed of terrigenous sand from the Danube, while the sediment in the southern beaches is made of shell fragments. Shoreline changes over years have been well reproduced with the one-line model and the net sediment transport rate is evaluated at several coastal units.

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This study investigated beach deformation in the vicinity of the headlands using yearly bathymetric data from 2002 to 2005 in this area, in order to understand the effects of the headlands on beach stability. Furthermore, to calculate the longshore sediment transport rate, we compared the longshore wave energy flux with the sediment change volume at the breaking point in this area. The results showed that notable sand deposition occurred around the seaward edge of the headlands, and that the proportionality coefficient of the longshore sediment transport was 0.0028 in the vicinity of one of the headlands with a length of 100m.

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This paper describes the evolutions of sea level and unconfined groundwater table in a nourished sand beach that were measured over one year. Careful time-series analyses identified seasonable variations of the sea level and of the groundwater levels at the three observation wells installed. The groundwater levels proved to be consistently higher landwards, indicating the fresh groundwater discharge (FGD) into the sea. The rate of the FGD was evaluated in two steps. First, the transmissivity of the unconfined aquifer was assessed through analyses of the measured fluctuations of the groundwater levels that responded systematically to four major tidal constituents. Then the identified aquifer constant was incorporated into theoretical equations of FGD and of the related seawater intrusion into the beach.

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A stepped seawall with a large drainage is expected to reduce both wave overtopping to coastal land areas and wave reflection toward the offshore direction. For the economical design of such a seawall, it is important to estimate wave overtopping phenomenon as well as the adequate volume of the drainage. This paper aims to investigate wave overtopping process as well as overtopping quantity on the stepped seawall with the drainage by conducting hydraulic experiments and numerical simulations with a numerical wave flume CADMAS-SURF. As a result, it was confirmed that wave overtopping characteristics depend on wave condition and the computational results were in good agreement with the experimental ones. The effect of optimal parameters in the CADMAS-SURF on wave overtopping was also examined.

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A high mound composite seawall, which has a permeable front wall with a dissipation chamber on the superstructure, on a relatively high mound was newly developed as a revetment for reclaimed land or artificial island. Newly developed seawall was constructed in the Mori port of Hokkaido and field observation was conducted to investigate the wave-overtopping characteristics. It is shown that the wave-overtopping rate gives good agreement with empirical prediction methods derived from laboratory test by Kimura et al (1999), but wave run-up height was found to be higher than prediction methods. Furthermore, large-scale model experiments were conducted to clarify the wave-force characteristics of wave splash barrier, which were countermeasures against wave-overtopping.

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Change of wave overtopping rate with increase of wave period is studied experimentally, first, by using sinusoidal incident waves. It is found that the rate does not increase monotonically. The second-order free waves are generated at wave maker when sinusoidal signal is used in shallow water. Phase difference between the primary waves and the second-order free waves at dike varies with wave period, introducing large variation of peak height of waves and overtopping rate accordingly. The rate increases monotonically when cnoidal waves are generated.

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Large wave overtopping due to storms sometimes causes heavy inundation damage in an offshore airport surrounded with the sea. The wave overtopping rate at seawall lines is significantly changed by the local sea bed topography and the type of seawall. In this paper the variation of wave overtopping rate along the seawall line including a corner part is studied in an experimental basin with a directional wave maker. In the later part of the paper, the countermeasures to reduce wave overtopping at the seawall are discussed. A seawall attached with a wave absorbing permeable bed behind it is proposed for the airport seawall and is investigated experimentally. Experimental results demonstrate the wave overtopping rate becomes remarkably small for the new type seawall.

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In this study, laboratory experiments are conducted to investigate the variations of reflection coefficient and volume of overtopped water due to damage progression of a rubble mound breakwater. Furthermore, a time-averaged numerical wave model and semi-empirical overtopping model are applied to computation of wave energy dissipation, reflection coefficient and overtopping rate. The results of the experiments show that reflection coefficient does not change much with damage progression of the breakwater and the variations of overtopping rate have different tendency in each test. The computed reflection coefficient and overtopping rate agree with the measured values.

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