A model for predicting bathymetric and grain size changes considering equilibrium slopes corresponding to the composition of grain size and each grain size was incorporated with the BG model proposed by Serizawa et al. (2006). The model was applied to the beach changes on Kemigawa Beach. The cross-shore sorting of sand, in which the grain size gradually decreases with increasing depth, and the formation of a gradually changing longitudinal slope were reproduced well. The model was further applied to predict sand accumulation in the navigation channel and their impact to the nearby coast.

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Pickup rate of seabed sand was estimated from the balance of suspended sediment flux obtained by tsunami experiment (Yoshii et al., 2008). Two nondimensional dominant parameters such as 'nondimensional sand grain diameter' and 'nondimensional settling velocity', were newly introduced. And a new pickup rate formula of suspended sand was proposed by using their two parameters and the Shield's number. Generally, the new pickup rate formula could reproduce the experimental results of two sand grain sizes, and pickup rates by the previous tsunami experiment (Takahashi et al., 1999) better than the conventional pickup rate formula. It was showed that the above formula was able to reproduce the experimental seabed topography deformation around a harbor due to tsunami better than the conventional pickup rate formula.

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When the Indian Ocean tsunami attacked in December, 2004, large-scale erosion or large-scale scour was caused in various places. If the coastal scour by the first tsunami wave caused the destruction of a dike or a seawall, it is also considered that the second tsunami wave may generate much more serious damage. Therefore, research on a predicting method of the coastal erosion and scour by tsunami is important. In this research, a numerical model which can predict the coastal erosion and scour in a wide area including land as easily as possible has been built on the basis of Takahashi's et al model. Moreover, predicting methods of the maximum scour depth and its position in the front beach of the seawall are also proposed.

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Sheetflow is the key to predict a beach deformation because massive sediment is transported by a high shear stress. To understand the mechanism of sheetflow dynamics, numerical simulations and experiments have been performed, however, sheetflow is a highly-concentrated particulate flow internal structure of which, so it is difficult to be investigated experimentally. In the present study, numerical simulation of a sheetflow by using of high resolition model the solid-liquid two-phase turbulence flow is performed, and the internal structure of sheetflow layer has been investigated in detail by a high-resolution solution in 1/10 times of particle diameter.

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The purpose of this study is to investigate sediment grain size and morphological change in the swash zone using Image processing technique and wave gages. Although a number of researches have been carried out into sediment transport and morphological change in the swash zone, quantity of sand transport and topography in that area has not been measured directly. It was found that the technique of this study could measure the sediment grain size and bed elevations in the swash zone.

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The movement of sand and gravels under asymmetric oscillatory flow was studied by laboratory and numerical experiments. The experiment under asymmetric oscillatory flow showed that the movement of gravels was drastically restrained because of the contact network between gravels when the ratio of gravels was over 60%. The result of these experiments did not agree with the established formula of the mixed grain sand transport under oscillatory flow. From numerical simulation of filling up of particles with DEM(Discrete Element Method), it was found that 3D-contact networks between gravels drastically developed while the mixing ratio of gravels increased from 40% to 60%. It was found that the movement of sand and gravels was greatly different from the movement of the mixed sand.

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Beneficial use of shell for constitutive materials of beach is proposed instead of its disposal. Since the shape of shell fragment is oblate, the knowledge on littoral drift of sand with spherical shape could not be applied directly for understanding of its behavior under waves. In this study, critical shields number and fall velocity of shell fragment are evaluated changing oblate shapes of the fragments, and the characteristics of bed load transport of shell and shell-mixed sand beds are examined by a movable-bed experiment. From the experiments, the effects of oblateness on the increase of resistance to wave and current are elucidated. It is found that the interaction of sand and shell on their movements has an effect on the bed - load rate changing the height of sand ripples.

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The paper describes an extension of the computational code LIQSEDFLOW proposed by the authors. The salient features of the code lie in the capabilities to describe the multi-phased physics of subaqueous sediment gravity flows. Specifically, it combines Navier-Stokes/continuity equations and equations for advection and hindered settling of grains for a liquefied soil domain, with a consolidation equation for the underlying, progressively solidifying soil domain, via a transition layer that is characterized by zero effective stress and a small yet discernable stiffness. Evolutions of the flow and solidification surfaces are traced as part of solution by using a volume-of-fluid (VOF) technique. The predicted features of gravity flows of initially fluidized sediments with different concentrations conform to the observed performances in two-dimensional flume tests. The present results demonstrate the crucial role of two-phase physics, particularly solidification, in reproducing the concurrent processes of flow stratification, deceleration, and redeposition in subaqueous sediment gravity flows.

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The motion of wind-blowing sand grains was photographed by a high speed digital imaging camera in a large wind-tunnel under the realistic conditions. Well-sorted sands taken from a natural beach and sieved with median diameter of 0.15, 0.25, 0.52, 0.68 mm were employed. The vertical distribution of wind speed and the horizontal component of flying sand grains velocity were followed by the logarithmic law. Then the vertical distribution of the ratios for the horizontal component and wind speed also followed by logarithmic law and the gradient of curves was almost the same for four kinds of sand. For the sand with median diameter of 0.68 mm, obtained were approximate values of 2.0 m/s and 10-20 degrees for the falling velocity and angle and approximate values of 1.0 m/s and 20-50 degrees for rebound velocity and angle.

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This study conducted field observations in terms of the number of wind-blown sand impacts and wind velocity in the period of 22 September - 2 December 2005 at an open ocean beach in Japan, in order to investigate variation of the wind-blown sand transport rate. Measured transport rate was calculated using the number of wind-blown sand impacts and compared to the rate estimated from the wind velocity using Bagnold's, Kawamura's, and Owen's equations. During the measurement period, the rate estimated using Owen's equation was relatively good agreement with the measured rate and the other equations overestimate the measured rate. The rate estimated using Kawamura's equation from hourly wind data obtained at off-site significantly overestimates the measured rate more than one order. Further knowledge about the actual aeolian sand transport should be accumulated in the field.

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This study demonstrated applicability of Rouse concentration profile in suspension for fluvial sand transport to aeolian sand transport in order to investigate universal system for the sand transports in water and air and to obtain knowledge of vertical profile of aeolian sand transport flux. Comparison of the Rouse concentration profile and wind-tunnel experimental results indicated that the Rouse concentration profiles underestimated the experimental results when the mode of sand particle motion was classified into saltation by Rouse number; however, the Rouse profiles agreed with the experimental results when the mode was suspension during strong wind conditions. It is revealed that the aeolian sand is transported in suspension during strong wind events and the Rouse profile can be applied to the aeolian sand transport.

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On September 6, 2007, storm waves associated with Typhoon 0709 attacked the Chigasaki-naka coast in Sagami Bay. Owing to the effect of rough waves with the longest duration of 18 hours, offshore sand transport occurred in the shallow water zone between the shoreline and a depth of 4 m, and sand was deposited forming a bar and trough in the offshore zone. These beach changes were predicted using the BG model proposed by Serizawa et al. (2006) incorporating Fukuhama et al.'s concept. The 3-D topographic changes around the Chigasaki fishing port and Chigasaki artificial headland were predicted. Predicted results were in good agreement with the measured beach changes.

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On September 6, 2007, the Seisho Bypass extending along the Seisho coast was severely damaged over a length of 1.1 km owing to storm waves associated with Typhoon 0709, resulting in roads being closed to traffic for urgent repairs. During the typhoon, severe beach erosion occurred owing to both strong offshore sand transport and westward longshore sand transport by storm waves, and the foreshore was rapidly narrowed. However, the foreshore was recovered except the damaged area of the highway as a result of the effect of normal waves. These beach changes were predicted using the contour-line-change model incorporating Fukuhama et al.'s concept. The predicted results were in good agreement with the measured beach changes.

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Beach changes around Oharai Port facing the Pacific Ocean were investigated using bathymetric survey data collected between 1979 and 2004. Between the south and offshore breakwaters of Oharai Port, 1.50×10⁶ m³ of fine sand deposited between 1979 and 2004, resulting in the annual rate of 6.0×10⁴ m³/yr, which was originally supplied from the Naka River 3 km north of the port. Also in the wave-shelter of the offshore breakwater on the south side, 7.0×10⁶ m³ of fine sand deposited between 1979 and 2004, giving the annual rate of 2.8×10⁵ m3/yr which was transported by the northward longshore sand transport induced from outside to inside the wave-shelter zone of the offshore breakwater.

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Beach changes around an artificial reef with crests on the Kaike coast were investigated through field observations, and compared with the beach changes around the detached breakwaters. Strong shoreward currents were induced due to wave breaking on the reef, resulting in the formation of a tombolo with a scale less than that of the detached breakwater. Also rip currents were generated, and scouring was measured in the opening. These beach changes were predicted using the BG model proposed by Serizawa et al. (2006). Predicted results were in good agreement with the measured.

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A short-term beach profile change model focusing on berm formation and erosion was proposed using a 2.5-year data set of beach profiles and offshore waves. The investigation area was set from the maximum wave run-up position to the shoreline position at the mean tide level. The cross-shore sediment transport rates for berm formation and erosion were modeled with the offshore wave energy flux and the berm height, respectively. The model was applied for the calculation of three months beach profile change, and the results revealed that the model well predicts the beach profile change including the berm formation and erosion in a qualitative sense.

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Very large scale casping feature appears from the beginning of Jan. 2009. Its amplitude and wave length are about 80m and 500m, respectively. The cusp bay and horn locations keep their alongshore positions for one month period. Rip channel developed at the every bay position. Since a standing edge wave may be capable to be a potential force keeping the bay locations (Bowen et al, 1971), relation between the edge wave properties and the cuspate shoreline is investigated. An existence of the edge wave is not detected directly. However some indirect properties such as breaking water depth change are detected. This change can be induced by alongshore standing long period waves. Together with the breaking depth change and a time interval between the breaking events of incident waves show the existence of long period wave.

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Long term topographic evolutions of a tombolo at Chiringa-shima Island, Ibusuki city were investigated by a fixed point camera-observation. The emerging and submerging processes of the tombolo are discussed by referring both wind climate and hindcasted wave climate. Next, numerical simulations on the emerging process of the tombolo were conducted. The wave and near shore current fields were numerically reproduced. Under the obtained external forces on the sediment transport, the transport rates and the resultant bottom changes were calculated. Considering both results from the field observation and the numerical analyses, the reasonable explanation on the evolution process of the tombolo was shown.

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Field data observed continuously with sampling frequency of 5Hz over two years by many wave (and bottom) gages in the swash zone are analyzed. The bottom heights measured by the gages at low tides are used to evaluate the sediment transport rate in the swash zone between the tides. Relationship among the direction of the transport, the bottom profile (the slope in the swash zone) and the waves is studied. When employing offshore wave information given by NOWPHAS, Sunamura's C parameter does not show any tendency but larger wave height is likely to correspond to offshore sand transport. Local waves measured in the inner surf zone do not give any indication for the direction of transport either. Finally, waves measured in the swash zone show that offshore transport is observed for the waves of low wave steepness.

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A monitoring method is applied to Yokosuka Coast in Miyagi Prefecture for understanding short-term topography change induced by wave action. Using images from an automated digital camera installed on the coast, shoreline position is determined after correcting the influence of wave run-up and tidal variation. Observed shoreline on the southern coast shows temporal variation in response to wave motion, whereas in the northern part of the study area, shoreline advancement is predominantly observed due to consistent recovery of the river mouth sand bar. Furthermore, a simple numerical modeling based on linear response function is applied to the present data set to reproduce the measured short-term shoreline variation.

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The artificial beach nourishment method has been accepted as one of the protection works from beach erosions. For the long term coastal management, it is need to estimate the coastal changes in the future using the beach profile model. When the beach nourishment is carried out, the characteristics of the injected sands are often different from those of the local sands. In this study, the N-line model considering the effects of the beach nourishment and sorting of the mixed sand due to longshore and cross-shore sand transport is suggested. The transport of the nourished sand is estimated by solving the two-dimensional advection diffusion equation. The change of content rate of each grain size is calculated, the result of the numerical model is compared with experimental data.

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A model for predicting the formation and deformation of the multiple bars is developed. The model developed by Shimizu et al. (2008), which can predict 2-D formation of the multiple bars applying the contour-line-change model, is further expanded to predict 3-D formation and deformation of the multiple bars. Taking the beach changes around Fukude fishing port, where multiple bars developed before the construction of the breakwater, but it disappeared after the construction of the breakwater obstructing longshore sand transport as an example, numerical simulations were carried out. The formation and deformation of the multiple bars were predicted by the model.

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The development process of the Hamamatsu strand plain was studied by using Optically Stimulated Luminescence (OSL) dating. The temporal and spatial change of Enshu-nada coast line for 6000 years was revealed by the OSL ages of feldspar partides in foreshore sediments under beach ridges. The rate of coastal progradation was estimated at 1.06 m/year within 1500 years. The speed corresponds quantitatively with the estimation of previous studies.

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Investigation on the sediment movement characteristics in a broad area with a 150 kilometer stretch along the Enshunada Coast and the Suruga Bay was conducted based on feldspar thermoluminescence (TL) properties. River sand grains (primary source) present a higher TL signal than beach sand. Along the nearshore area, local TL intensity peaks are observed at the river mouth and the intensity gradually deceases with increasing distance from the river mouth, which indicates longshore transport features. Taking the spatial distribution of TL intensities into account, a quantitative estimation on the longshore sediment flux was carried out based on the total river sand discharge.Identification of coastal sand source was achieved in terms of the profile and magnitude of the measured TL glow curves.

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Short-term topographic changes of the Nakatajima dune, which is located on an eroded beach on the Enshu-Nada coast, have been investigated with continuous field surveys over two years period (2007-2009). Measurements of wind and wind-blown sand transport rate were also carried out several times in winter. Based on the field data, overall properties of the sediment transport on the dune are first described in the paper. Eastward migration of the dune is then indicated with relation to the topographic changes and the distribution of the sediment transport rate. Quantitative estimate of the average volume of transported sand are well predicted by some existing formulae

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A submarine canyon develops offshore of the Morito River mouth on the Seisho coast in Sagami Bay. Previous studies revealed that littoral sand originally supplied from the Sakawa River located 3 km west of the submarine canyon has been lost in this submarine canyon. To study the mechanism of sand discharge into the submarine canyon, beach changes around the canyon were investigated using bathymetric survey data. Then, a model for predicting sand discharge into the submarine canyon was developed using the BG model proposed by Uda et al. (2008). The major causes of offshore sand loss are the presence of very steep slope of 1/6 of the submarine canyon and the change in shoreline orientation at the submarine canyon.

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Several submarine canyons develop offshore of the Aramata region of the Shimoni-ikawa coast in Toyama Bay. The Kurobe River flows into the sea immediately east of this area, and a large amount of sediment has been supplied to this area as a source of westward longshore sand transport. However, after the construction of the detached breakwaters, offshore sand transport was accelerated and beach erosion occurred downcoast. In this study, aerial photographs and bathymetric survey data were analyzed and then, the mechanism of this offshore sand transport was investigated using the BG model proposed by Serizawa et al. (2006).

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Sand movement around the submarine canyon offshore of the Morito River mouth on the Seisho coast was investigated by a tracer test using colored sand. Because the sand movement deeply depends on the grain size of sand, colored sand with the grain size of 0.2, 2.0 and 10 mm were prepared and placed on the shoreline. The subsequent movement of colored sand was traced by sediment sampling. It was found that the colored sand with the grain size of 0.2 mm was quickly diffused and part of sand sank into the submarine canyon, whereas the colored sand with the grain size of 2.0 and 10 mm were very stable, and gradually moved alongshore without offshore movement.

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On the northern part of the Shimizu coast in Suruga Bay, beach erosion has been severe because of lack of longshore sand supply and offshore discharge of littoral sand through the steep slope of the coast. On the beach with the foreshore being extremely narrowed the extension of wave dissipating structures placed along the shoreline is planned to reduce wave run-up. In this study, beach changes in this area are investigated using bathymetric survey data and the grain size analysis of seabed material. Then, the optimum arrangement of wave dissipating facilities was studied using the contour-line-change model.

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The river mouth closure of the Okukubi River in Okinawa Prefecture, flowing into the coral reef, was studied. In this area, the shoreline material was extensively excavated after World War II, resulting in the disappearance of sand beach. Since then, coral sand was naturally supplied from the reef edge, resulting in recovering sandy beach. Sand reached the shoreline was then transported by longshore sand transport due to waves, and the river mouth bar was formed. The river mouth closure associated with this sand accumulation was predicted by the BG model proposed by Serizawa et al. (2006). The predicted beach changes are in good agreement with the measured.

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The long-term evolution of the Tenryu River delta associated with the sand bypassing at several dams was investigated using the contour-line-change model considering the change in grain size. The effect of the increase in sediment yield from the river mouth to the nearby coasts was numerically predicted. When the sediment yield is artificially increased, the supplied sediment is mainly deposited around the mouth, resulting in a large shoreline advance, but it takes a longer time for the sandy beach far from the river mouth to recover. Another measure such as the sand bypassing of the coast is required to recover sandy beaches downcoast.

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On the Shonan coast, narrow multi-beam surveys have been carried out once a year between 1999 and 2008. These bathymetric survey data were analyzed to investigate the beach changes. The volume changes in five regions of the coast were analyzed using the bathymetric data in a 5-m mesh. It was found that the terrace offshore of the Sagami River mouth has been reducing owing to the imbalance between the sediment yield from the river and eastward longshore sand transport. The rate of decrease in sand volume in the terrace is 2.5× 10⁴ m³/yr. Because sand supply from the river has already been exhausted, this decrease in sand volume is equal to the eastward longshore sand transport.

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At the entrance of the Tofutsu Lake, which is one of the lagoons located along the Okhotsk Sea in Hokkaido, sand bars have been significantly developed. The objective of this study is to evaluate the sequential sedimentation history of the sand bars by means of MASW (Multi-channel Analysis of Surface Waves) technology. We found out that the sedimentation stratigraphy under the sand bars were significantly different from muddy to sandy, even though the sand bars apparently consisted of the same sandy material. From the shear wave velocity structure obtained in this study, we successfully restored the sequential sedimentation process. Also, the sedimentation history was consistent with an old aerial photograph and memories of local inhabitants.

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Strong low-pressure systems traveled along Japanese Main Island in October 2006. High waves and storm surge attacked Kashima Coast resulting huge erosion over the area. Airborne laser data measured in October 2005 and November 2006 have been analyzed to estimate cross-sectional changes within the subaerial zone. The results indicate that the amount of the erosion of the northern and southern parts decreased toward the south which may be raised due to the activation of longshore sediments. The SWAN wave model was applied to estimate wave condition along the coast during the storm event hours. The longshore component of wave power and run-ups are estimated and showed a correlation with the survey results, especially for the areas without coastal works.

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Mechanism of sediment movement and long-term deformation of sand and gravel beaches in the Hyuganada Sediment Cell, Miyazaki Prefecture, were investigated on the basis of comparisons of shoreline position in old maps and aerial photographs for the period of 200 years. Significant coastal erosion in the northern region and slight shoreline advance in the southern region were identified. Huge amount of sediment retention in reservoirs with a rate of 1.9 million cubic meters per year was considered to decrease the sediment supply to the sea through four major rivers. Physical properties of sand particles, such as particle size and thermo-luminescence intensity, indicated the direction of alongshore sand transport to be southward, which was consistent with macroscopic analyses.

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The purpose of this study is to analyze the sediment transport of Miyazaki Coast, especially the dominant longshore direction of sand transport, from the results of recent 3 years sand tracer experiment and of the analysis of currents observed by camera systems during the experiment. The dominant direction obtained by accumulation of longshore sediment transport rate estimated by equation of Kraus et al.(1982), which is based on the breaking wave height and nearshore currents, agrees with the direction of motion of the tracer. In addition, it becomes clear that there is a high correlation between the distance of tracer movement and the longshore sediment transport rate. It is also obvious that sediment transport to south is predominant in the experiment period.

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Three-dimentional Digital photogrammetry and X-ray Computed Tomography (CT) have been applied to investigate a time-space evolution of sediment size and density profile due to beach profile changes in the laboratory wave flume conditions. The time-space variations of grain size distributions were measured using a spatial autocorrelation between pixels in digital images. The sediment density profiles in the collected sediment cores were measured using X-ray CT scanning. Reconstructing three-dimensional images using CT values, the evolution of the low bulk density region were examined. These experiments indicate possible importance of the spatial and temporal variations of sediment grain size and sediment porosity.

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Numerical computations are made for the nearshore currents and morphology around a system of multiple submerged groins. They function in decreasing the speed of longshore currents and controlling beach erosion. Nearshore currents are computed with the PEGBIS model by Goda (2004) for wave transformation and beach morphology is estimated with the suspended sediment transport model by Katayama and Goda (2000). The computation indicates the efficacy of a submerged groin system for beach erosion control.

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A model for predicting bathymetric and grain size changes considering equilibrium slopes corresponding to the composition of grain size and each grain size was applied to predict the beach changes on the Chigasakinaka coast. The cross-shore sorting of sand, in which the grain size gradually decreases with increasing depth, and the formation of a gradually changing longitudinal slope were reproduced well. The diffusion of colored sand with different grain sizes placed on the shoreline and at a depth of 4 m was predicted and compared with the results of a field observation using colored sand on the Chigasakinaka coast. Both results were in good agreement.

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The effect of the beach nourishment on the Yamamoto coast which has been suffering from serious beach erosion was evaluated. From the fluorescent sand survey even medium sand with diameter of about 0.3mm passed over the headland in coming of significant waves higher than 2m. About 80% of sand particles moved out from the injection point within 1 year. According to the Bruun equation, the profile of this beach was identified as the concave and eroded type. Sediment survey showed that sand particles larger than 0.25mm stayed in shallow area with depth less than 2m and remained there for more than 1 year. In addition, Numerical model built to estimate the effectiveness of different grain size on beach nourishment demonstrated availability of gravels for effective nourishment.

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In Niigata west coast, a belt-shaped scour is formed behind the submerged breakwater. The scour is considered as a cause of the loss of filled sand. In this study, field experiments by installation of filled sand and fluorescent tracer were conducted to examine the sand movement around the scour. The result of experiments indicates that the sand on the filled beach is transported in the offshore toward the scour and that the sand settled in the scour is also transported along the submerged breakwater and flows out. These characteristics have become clear, and therefore, basic policy of countermeasures to prevent the loss of filled sand has been suggested.

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In Suruga coast, the sand bypass system has been introduced for the shore protection since 1983. Although the total nourishment sand volume has amounted to about one million cubic meters so far, some beaches have continued to erode. Yaizu section located at the down-drift side have also continued to erode and the overtopping by stormy waves has come to happen in typhoon seasons. The present paper studies the shoreline change near the river-mouth and summarizes detailed features of the sand bypass system. It also proposes the effective usage of sand bypass system as a part of the entire sand management.

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Sand movement in the field experiment of beach nourishment offshore of south Kujukuri Beach was numerically simulated using the BG model, given the wave field predicted by an angular spreading method of irregular waves on the basis of wave data measured at Choshi. The effectiveness of the model was confirmed, and then numerical simulation of the recovering effect of sandy beach in full-scale beach nourishment was carried out under the conditions that the artificial headlands have the present shapes, they are half and fully extended. It is found that although the best one is the shape fully extended, significant effect can be expected in artificial headland with a half length.

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As a long-term measure of the northern Kashimanada coast facing the Pacific Ocean, the effect of sand bypassing in which sand originally supplied from the Naka River, one of the main source to this coast, and deposited inside Oharai Port is transported to the southern beach, was investigated using the contour-line-change model considering changes in grain size proposed by Kumada et al. (2007). The effectiveness of beach nourishment using coarse material was also investigated. It was shown that sand bypassing is effective for not only the maintenance of navigation channel but also raising the offshore seabed. In addition, the effectiveness of beach nourishment using coarse sand is also shown.

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Characteristic beach profile change has been observed at the beach with integrated shore protection system by large scale submerged breakwater, jetties and nourishment. In this study the cause of characteristic beach profile change was presumed. Two-dimensional hydraulic model test with movable bed was carried out to verify the presumed result. Through the model test, it was found that the cause of constant shoreline erosion is land subsidence, the beach erosion by storm surges in winter is accumulated because sand transport onshore is not occurred in calm, the flat profile is formed at the depth equal to transferred wave height by submerged breakwater.

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In the Ukishima region in Lake Kasumigaura, beach nourishment has been carried out to recover a sandy beach along with the construction of groins. After the beach nourishment a part of nourishment sand was transported away from the beach over the downcoast groin owing to oblique wave incidence in winter. To enhance the stability of the beach, the groins were extended and a spur dike was constructed. For the design of these structures, the numerical simulation using BG model was carried out, and the optimum shapes were determined under the seasonally-changing wave direction.

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In a tidal inlet, a part of littoral sediment is transported offshore owing to the ebb tidal currents, resulting in permanent loss of nearshore sand. The ordinary sand-bypassing method, in which simply sand deposited upcoast is transported downcoast, is ineffective for preventing this sand loss. In this study, a sand-raise method, in which sand is pumped up from an offshore zone and disposed of on downcoast shoreline, is proposed, taking Imakiri-guchi inlet of Lake Hamana as an example. The effectiveness of the method is numerically investigated using the BG model proposed by Serizawa et al. (2006). It is shown that this method can be a practical tool to prevent offshore sand loss.

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After the completion of beach nourishment using 87,000 m³ of gravel with the grain size between 3 and 15 mm in April 2008 at the Jinkoji coast which faces the Pacific Ocean and is surrounded by artificial headlands, boring test and core sampling on the beach were carried out to investigate the formation of the gravel layers. It was found that gravel is deposited with a slope of 1/8 on foot of the seawall, exhibiting the foot protection effect to the seawall, and the nourishment gravel is stably deposited without offshore discharge.

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Beach nourishment using 87,000 m3 of gravel has been carried out in a shoreline zone bounded by artificial headlands on the Jinkoji coast facing the Pacific Ocean by the end of April in 2008. After the completion of beach nourishment, monitoring surveys have been conducted to investigate the change in volume of nourishment beach and the foot protection effect of the seawall. Due to the change in longitudinal profile, gravel was deposited in front of the seawall for the foreshore slope to keep a steep slope of 1/8, and excellent foot protection effect was observed.

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This paper is concerned with tsunami sedimentation and attempts to promote preparedness against tsunami-induced scour for critical infrastructure. The sub-bottom seismic profiling in Uchinoura cove identified a few distinct reflectors in the seabed, implying the presence of tsunami-related horizons. This was substantiated by retrieval of a continuous sediment core, showing the consequences of past tsunamis. A high-resolution side scan imaging with bathymetry captured a signature of extensive scouring at the constriction of the cove. These findings provide a stimulus for examining stream powers of the past tsunami events, especially the one induced by the 1946 Nankai Earthquake.

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