In recent years, seawalls coated with wave-dissipating blocks heve been set in front of upright seawalls. However, wave overtopping on this type of seawall is not fully investigated. Therefore, in this paper, characteristics of wave overtopping on upright seawall covered with wave-dissipating blocks was examined experimentally. From the results, it is found that this type of seawall is effective to reduce the wave overtopping rate. The crest height of the seawall is less than the height in upright seawall case to get the same wave overtopping rate. In addition, an easy method to estimate the runup height on the seawall has been suggested.

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At a low crown caisson seawall with a large-size wave overtopping drainage, overtopping water lump collides with a wall of drainage and the resultant return flow falls down to blocks in front of seawall. This falling water can pick blocks up, however, the velocity measurement around the blocks is difficult in a hydraulic experiment. In this study, using the MPS method, which is suitable to analyse wave overtopping process in a complicated setup of seawall, the velocity field was calculated and compared with the critical velocity of blocks based on CERC formula. The pick-up condition of blocks predicted by the MPS method with CERC formula showed good agreement with ones in a hydraulic experiment.

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In order to clarify the particle size of splash that is caused by wave-overtopping at breakwaters and transported by wind, field observations were conducted at Waku fishing port in Yamaguchi prefecture in the winter season from December 2006 to February 2007. The violent wave run-up at a vertical breakwater and the transportation of splash by wind were recorded by 3 digital video cameras. Wind velocity and wind direction were also measured with an anemometer. The splashes were caught with a kind of Litmus paper which reacts to salt water, and the particle sizes of splashes were analyzed by image processing technique. Based on the observed data, we found explicit formula to determine size distributions of splashed water particles as functions of run-up height and wind velocity.

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Damping effects of ship waves by an emergent vegetation community have been investigated with numerical simulations based on Boussinesq-type equations. The resistance due to the emergent vegetation community is modeled by wave forces on a group of vertical cylinders. The applicability of the numerical model is confirmed by comparing with experimental results on the wave damping by a group of vertical cylinders in a laboratory flume and field observation data on the maximum height of ship waves. The numerical simulations demonstrate that ship waves on a sloping bottom are significantly damped by the emergent vegetation community on a shoaling and surf zone.

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A novel method is proposed to control the wave direction incoming to harbors. In this method, navigation channel to the port entrance is deeply dredged in V-shaped cross-section in order to disperse the wave directions. The channel alignment is parallel to the direction of incoming waves so that it has an effect to refract the waves like a concave lens. The typical length, width, and depth of the channel examined in this study are 1, 000 m, 200 m, and 10 m, respectively. The applicability of the method is examined by means of laboratory experiments and numerical simulations. Both the experimental and numerical results have shown the remarkable effect of the proposed method in attenuating the incident waves to the port entrance.

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Tsunami attenuation ability of coastal forests is attributed to the fluid resistance of their elements; such as a trunk, branches and leaves. In order to evaluate the fluid resistance precisely, quantitative relationships among these elements and the characteristics of their forms should be clarified. This study applies findings in the tree morphology to the modeling for coastal forests. The tree crown region is herein modeled as a three dimensional porous structure. Based on the mathematical model developed here, effects of wave and forest properties on the tsunami attenuation rates are discussed.

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We have proposed a new type breakwater supported by piles, which consists of three major parts, i. e., an inclined plate array as a front wall, a vertical rear wall and a submerged plate at the base. It has been confirmed by the two-dimensional experiment that it enables to reduce both reflected and transmitted waves and also induce the mean current about the breakwater. In this study, we have carried out experiments on the performance of this type of breakwater in the three dimensional fields. For the comparisons, conventional breakwaters, such as a curtain-walled breakwater and also a vertical breakwater, were also used as a breakwater model. For the theoretical prediction of nearshore circulation around the harbor, applicability of the numerical analysis based on the Multi-Layered model was extensively examined.

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The risk of wave overtopping and overflowing is increasing in the waterfront of our country, because of the rise of mean sea level by global warming and the rise of the storm surge due to the typhoon scale increasing. In this research, three dimensional fluid analysis model is demonstrated for wave overtopping and inundation in coastal urban facilities facing to the Tokyo Bay, where the sea level rise and the wave height increase in the future is considered. Secondly, the change in inundation depth and flood time by countermeasures such as the recurved parapet and the drain is numerically estimated and the efficiency of such disaster countermeasures is quantitatively discussed. As a result, it is clarified that the recurved parapet and the drain delays the start time of flood in the ground and underground part.

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We carried out experiments on the wave decay through the culture net with live laver. The equation of the wave energy dissipation by the net was made from the motion of the net in the wave field. The resistance coefficient of the net for the estimate of the wave energy dissipation was calculated from the wave decay. The coefficient is the same as the resistance coefficient of the net in a steady flow when the KC number is large, and the coefficient becomes large when the KC number becomes small. Moreover, the coefficient becomes large with the growth of the laver.

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Long-period waves are often trapped in a port and harbor, and cause disturbances of cargo handling and damages of mooring ropes for ships. A new type of long-period wave absorption structure which involves two oblique walls and a vertical slit between them has been developed for dissipate the waves. In this paper, through a large eddy computer simulation and visual experimental measurement, flow patterns and vortex structures formed with the proposing structure, depending on a relative structure length with incident wavelength, are investigated. The long-period waves are found to be reduced via a combination of energy exchanges to a pair of circulated flows trapped with in the structure and of energy dissipation due to turbulent jets formed at the slit.

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The effect of Reynolds number on the properties of turbulence generated by a porous media was investigated by a hydraulic experiment. Velocity field inside and around the porous media was measured with a high resolution temporally and spatially using the Super-resolution KC method and a refractive index matching method. It is presented that some properties of turbulence can be normalized by a characteristic velocity and a diameter of the sphere which constitute the porous media.

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Since the artificial reef has a submerged shape near the sea surface, strong shoreward currents are generated over the crown in general. These shoreward currents return offshore as rip currents from the openings of the reef, causing significant local scouring. A new type of artificial reef was developed in this study, preventing the development of shoreward strong currents, rip currents and resulted local scouring on the basis of the hydraulic model tests. The new type of artificial reef has the crown close to the mean sea level, and the offshore slope is protected by concrete armor units to enhance the stability.

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Breaking waves on coastal structures produce impulse pressures that are high in magnitude and short in duration, compared with pressures exerted by non-breaking waves. The present study is concerned with a theoretical approach, which is based on the momentum impulse, to simulate the impact pressures on a vertical wall. The theoretical impact pressures are determined using varied velocity before impact process. The velocity field in the vicinity of structure is calculated by LES model including turbulence. The necessary coefficient λ* to evaluate impulse pressures is tentatively obtained through a comparison between the laboratory tests and the numerical results. The computational results using the coefficient obtained show time-histories of pressure with nonlinearity rather than linearity considered ever.

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Recently, several types of numerical wave flume to simulate the non-linear wave transformation have been developed. In this study, the applicability of CADMAS-SURF which is one of them for calculating the wave pressures upon wave absorbing caisson is discussed. The structure is identified by the slit wall and wave chamber, and it is important to set the values of inertia coefficient, resistance coefficient and permeability coefficient when modeling the slit wall as porous body. Then, the sensitive analysis on those parameters, and the calculation of the wave pressures upon the structure with CADMAS-SURF was conducted. And it is shown that the calculation results have a good agreement with the experimental results in equivalent sliding wave force acting against the wave absorbing caisson.

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In this paper, we present a new numerical wave flume model capable of handling interface problems with complex geometry on a standard regular Cartesian grid, using immersed boundary method. Force terms are incorporated to the momentum equations to represent the interface on a fixed Cartesian grid and they are calculated on a finite number of Lagrangian points distributed over structure-fluid interface. The wave field around a horizontal circular cylinder has been chosen in order to validate applicability of the proposed numerical wave tank model. The calculated wave forces acting on cylinder are compared with previous experimental and numerical results. Results show that the proposed model gives good agreement with experimental results.

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The properties of tsunami wave pressures acting on a coastal dike were studied in a tsunami experimental tank. The results obtained in this experimental study were as follows; 1) the greatest impulsive pressure occurs when a crest of bore-type tsunami just overtops at an upright coastal dike. 2) The greatest continuous pressure of tsunami generally exceeds the value estimated by Tanimoto's formula (1984). 3) An impulsive pressure of tsunami is not so much affected by sea-bottom slope. 4) In addition, an installation of breakwater in the front of a coastal dike is very effective for decrease of wave pressure.

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If a gigantic tsunami attacks in coastal area, most kinds of structures such as residential houses, industrial plant and cargo transporter would be broken down. Since the best way to preserve the human life from the tsunami is that people run away to a higher place as much as possible, a refuge building in coastal region may exert great effect for saving life. In order to evacuate people safety in the buildings, structure of the building must hold against the gigantic tsunami load. Therefore, it is necessary to estimate the tsunami force on the structure accurately. The objective of this study is to investigate tsunami forces on the structures in coastal area. Hydraulic experiment is carried out to clarify the characteristics of tsunami force, especially the relationship to the agreement of houses and the distance from seawall.

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Experiments on tsunami force and pressure acting on oil tanks were carried out with scale factor of 1/40. The tsunami concerned is that due to Tokai, Tonankai and Nankai earthquakes and the maximum water level is about 5 m high. If the tanks of which diameter ranges from 5. 8 m to 48. 6 m and weight from 5.8t to 540t are empty, they can be floated due to the 2-m high tsunami flooding. Pressure acting on tanks surrounded by oil protection walls is not uniform and buckling of side wall is affected by the distribution of pressure around the tank. The lowest level of oil in the tank should be kept to prevent the tanks from floating and buckling.

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This report investigates the relationship between the destruction of structures and surge front tsunami force. Many houses were destroyed by large tsunamis, so it is necessary to investigate what kind of power acted and how houses broke. For this purpose, large model tests with concrete boards and a framework structure were conducted. A concrete board with 100mm thickness was not damaged, but a concrete board with 60mm thickness was destroyed due to impulsive bore load of the surge front tsunami with 1. 8m inundated depth. A framework structure made of steel was deformed due to the impulsive bore load. Therefore, it is necessary to consider not only the sustainable load but also the impulsive load of the tsunami according to the structure.

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This report investigates the impact force of drifting container due to surge front tsunamis. Because the impact force depends on the material and rigidity of the objects, the 1/5 scale model experiments are conducted with container made of steel and concrete wall. First, effect of the material and rigidity, impact force tests in the air are conducted. Then, the velocity of drifting container is checked. Finally, the drifting container impact force tests due to surge front tsunami are conducted. The empirical formula based on Hertz theory is applied to the impact force results. It indicates that this formula can evaluate the impact force under this report condition.

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This study is intended mainly to investigate collision force due to a drifted container by run-up tsunami. Laboratory experiments were conducted to investigate behavior of run-up tsunami and drifting container. Moreover, effect of vertical wall to reduce run-up tsunami was observed. Results show that the vertical wall installed at the leading edge of apron can reduce wave forces acting on container, which may lead to reduce drift of containers. This study also conducted numerical simulation of collision of container with concrete column. It is revealed that the present analyzing method is useful in such simulation.

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The 2004 Indian Ocean tsunami caused large-scale sediment transport, resulting in substantial scour around a huge number of structures. In this study, tsunami-induced local scour around a land-based structure with a rectangular cross-section on a sand foundation was investigated with a series of hydraulic model experiments and numerical simulations. It was, as a result, revealed that local scour around the seaward corner of the structure could be evaluated with not only flow velocities on the sand foundation but effective stresses near the surface of the sand substrate, that is, flow velocities with a large Shields number resulted in a scour hole around the seaward corner of the structure during restricting force between sand particles fell down due to a decrease in effective stresses inside the sand substrate.

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The paper describes damage assessment of structural components such as wall and column in a masonry infilled house due to a tsunami, assessing the damage data of structures in the south coast of Java due to the 2006 Giant Earthquake and Tsunami. The effect of wave loads with failure mode of subject structural components was verified, inversely computing the dominant parameter ‘α’ representing the amplification of tsunami wave pressure against a structural component. It was found that its crack mode might occur when parameter α takes the value ranging from 4 to 5, and that major failure mode such as collapse or shear crack might occur although parameter a takes more than 3 dependent upon tsunami affection.

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In order to predict the behavior of floating body under tsunami flood appropriately, it is significant to evaluate the drag force exerted on the float shape when reproducing the dynamics with drift. So, we prepared the drift simulation model based on the Distinct Element Method (DEM). In the simulation, every flotsam shape was expressed by an assembly of individual sphere elements and current velocity field generated by tsunami was given from the result of the tsunami propagation simulation computed in advance. This paper shows experimental results of car's drag force coefficient as a function of every current angle. And we report the application of the drift simulation method by comparing the drift motion from the experiment in a 2-dimensional plane water tank with that of the simulation result.

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This study aims to develop efficient methods for an estimation of wave pressures under irregular waves by using time series of water surface elevations. Two methods are presented in this study. One is a linear filter approximation method which is extended from an original way to calculate water particle velocities from the water surface elevations. The other one is a local approximation method which is also extended from an original way to obtain non linear water surface elevations by using time series of subsurface pressures. The validity of each method is verified comparing with experimental results for simultaneous measurements of water surface elevations and subsurface pressures under progressive and standing irregular waves in 2-D wave flume.

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In comparatively deep sea, under which soft grounds exist and also comparatively long waves like swells attack, a curtain-walled breakwater has been adopted as a possible structure for simplicity. However, horizontal wave forces on such curtain-walled breakwaters become very large because of deep draft depth. For the economical construction of breakwaters in those deep sea ports, it has been newly proposed that a jacket-type breakwater with water chambers consisting of two vertical walls and one submerged horizontal plate. The effectiveness of a newly proposed breakwater has been examined extensively, especially focusing on the reduction rate of transmitted waves and wave forces.

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We carried out the experiment to examine the wave pressure acting on the breakwaters for composite bottom slope of 1/1.2 to 1/6. Tests were conducted in a long wave flume and in a basin by irregular waves. The volume of fluid (VOF) method was employed in numerical simulation. As a result of both physical model tests and numerical simulation, characteristics of the wave pressure acting on the sloping wall were confirmed. It can be said that the wave pressure acting on the wall shows impulsive at around trough level of incident waves. The value of wave pressure shows higher for steeper wall. It also points out that the compressibility of air should be taken into account.

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Expanded mild-slope equation models (2D and 3D) have been developed and applied to seismic response analysis of semi-submersible-type isolation structure. It was found by the 2D analysis that the wave resonance above the upper deck occurs at specific periods, which influences the horizontal response of the structure, and that the attachment of porous body on the deck is effective to reduce the maximum response. The 3D computation demonstrated the suppression of the wave resonance, which was found in the 2D computations.

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This paper uses reliability analysis to estimate the failure probabilities associated with wave overtopping of both sloping and vertical seawalls. Failure probabilities are obtained for different freeboards and permissible overtopping rates, using Monte Carlo simulation for calculations at Level III and the First Order Reliability Method for Level II calculations. The sensitivity of the performance function to the various external random variables is also investigated inorder to establish the relative importance of these variables in influencing the failure probabilities.

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The design standard of breakwater has been renewed in this year, which adopts the reliability design method and permits sliding. However, the relationship between wave force and sliding distance is not clarified enough so far, constituting a bottleneck in applying new design method. Inthis study, a series of hydraulic model experiments for breakwaters in relatively calm sea area were conducted to elucidate the characteristics of caisson's sliding in various sliding safety factor. Experimental results are expected to be adopted for new breakwater design based on sliding distance.

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While the research on the deformation-based reliability design of composite breakwaters has been carried out for many years, sliding phenomena including rocking motion have not been carefully examined. In this study, hydraulic model experiments were conducted in a wave flume to investigate the characteristics of wave forces and sliding phenomena of the breakwater caisson. The difference of static friction coefficient and dynamic one should be considered in order to improve the estimation accuracy. Numerical simulation (CADMAS-SURF) can reproduce the time series of wave forces more precisely compared to the practical model used in the current calculation method, especially in deep water area.

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The damage of the concrete blocks causes their own settlement together with the sliding of the caisson. The settlement increases wave forces acting on the caisson. The bigger wave forces enlarge the sliding of the caisson. Thus the damage of the concrete blocks is closely related to the sliding of the caisson. The present paper proposes the estimation procedures of expected sliding distance of a caisson affected by the damage of the armored concrete blocks. It concludes that the insufficient weight of the armor blocks causes the damage of the blocks which affects the sliding of the caisson itself and that the necessary width of the caisson which satisfies the selected allowable value of the expected sliding distance becomes larger under the consideration of the armor block damage than under no consideration of the damage.

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The main purpose of the present study is to introduce an optimal procedure to consider the economical as well as stability aspects into the current model of the Level III reliability based design. To achieve this purpose, first the entire breakwater system composed of the upright section and the rubble mound is considered as the target domain, whereas the past studies have mainly focused on the upright section only. Secondly, two new failure modes, bearing capacity and circular slip failure, are incorporated into the previous model to evaluate the failure probabilities within the service lifetime for the entire section of a breakwater. The validity of the procedure proposed was confirmed through trial calculations. It is expected the newly proposed procedure can prevail over current design methods for breakwaters.

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The authors previously proposed a semi-submersible floating structure for offshore wind power generation system, which is mainly composed of three vertical base floaters and horizontal connecting beams. The present study attempts a structural optimization of the draft depth of the connecting beams by a cumulative fatigue damage analysis. Although the wave induced motion was varied according to the draft depth, it does not interfere the operation of wind turbines, however, fatigue damage was much more influenced by the draft depth. The optimum depth of 30 m has been obtained from the viewpoints of structural safety.

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Compaction-process of blocks which is one of the subsidence mechanism of wave dissipating blocks has been investigated by sxperiment and numerical. The experiment was conducted in wave flume with piston-type wave generator. The 1/100 scale model of 80t-type tetrapod _® block was used as wave-dissipating block. On the other hand, numerical simulation was performed under the same experimental condition using the block model based on the three-dimensional distinct element method with the passively-moving-solid model. Influence of the mound topology to the subsidence of the blocks will be described.

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Safety traffic control measures for a temporary bridge, which was constructed with a permeable floor over a road (National Route 229) on a coastal reef, were studied through a hydraulic model experiment and field observation. When the offshore wave height exceeded 4 meters, a large wave force was acted to passing vehicles. It was thus revealed that road closure or other measures would be necessary before the offshore wave height reached 5 meters to ensure the safety of vehicles. It was also found that the wave height could be estimated from the wave pressure measured with wave pressure gauges installed on a bridge pier, and that it would be possible to make full use of such wave pressure data for traffic control on the bridge.

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It is important to evaluate the estimation accuracy of wave pressure appropriately by experiment or field observation result in order to set the partial factors for gravity-type breakwaters. However, there are only a few experimental examples on gravity-type breakwaters with two or more structural features developed in recent years. In this study, taking breakwaters with wave-dissipating blocks having the slant superstructure as an example, we showed the method for evaluating the estimation accuracy of wave pressure of the gravity-type breakwater with two or more structural features by using that of the gravity-type breakwater of each feature. We furthermore proposed the partial factors for breakwaters with wave-dissipating blocks having the slant superstructure by the reliability analysis.

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This research investigates the protection performance against tsunami with the buoyancy- driven vertical breakwater by using the numerical simulations. Macro-Micro scale interlocked tsunami simulator named STOC (Storm surge and Tsunami simulator in Oceans and Coastal areas) has been applied to the series of simulations. Results of comparison of tsunami height in the Wakayama-shimotsu port and Fukura port due to Tokai, Tonankai and Nankai earthquakes indicates that this new breakwater decreases tsunami height and inundation area. Although the dissipating rate is depending on the position of this breakwater, the breakwater with 10% opening brings a 33% decrease in the maximum tsunami height.

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The Bosphorus tube crossing, which is constructed by the immersion tunnel method, is now under construction in Turkey. The current of Bosphorus strait has two-layer current system and it is very variable due to meteorological condition. The immersion process, towing, mooring and lowering, should be executed continuously, so it must be confirmed before towing that the current condition meets the construction limitation among the immersion work. The authors have already developed the current forecast system and it is in operation on the site. In this paper, the verification result and the process making the “go/no go” decision are described.

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The application of geo-textile soil bags flled with recycled dredged material is proposed for the material of submerged dike of man-made tidal flat.The proposed dike is made of apile of soil bags, in which not only sand but soft clayey material is supposed to be filled. In this study, the design method is proposed for the construction of dike of soil bag in the initial stage of placement of soil bags through the final stage of filling material for tida1 flat. Especially, the shape of soil bags at the placement, the required strength of geo-textile material and the deformation of dikealong with consolidation are analyzed in a case study, and the applicability of submerged dike by soil bag is investigated.

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The purpose of this study is to numerically discuss countermeasures against wave overtopping around a coastal revetment in main Okinawa Island using a numericalw ave flume ‘CADMAS-SURFO’. ptimumc rest height and wave overtopping quantity were examined for three types of revetments of an upright seawall with an offshore breakwater, a seawall covered with wave-dissipating blocks and a flaring-shaped seawall. As a result, it was revealed that the countermeasurec an be selected so as to adapt to the characteristics of the region based on the numericalr esults taking into account economy efficiency of construction, landscape and the coastal environment. The numerical wave flume ‘CADMAS-SURF’ was, therefore, found to be useful in the examination of countermeasures against wave overtopping.

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Susumu ARAKI, Gou URAI, Hirotoshi MAKINO, Mamoru ARITA and Ichiro DEGUCHI Expected total repair cost of detached breakwaters is estimated in this study. The criterion for repair is based on the reduction of hydraulic performance of the detached breakwaters. The relationship between incident wave height, deformation of the detached breakwater body and transmitted wave height is measured in experiments. The influences of wave group characteristic of incident waves on the transmitted wave height behind the detached breakwater are taken into account. Wave group characteristics have a great influence on the expected total repair cost because the deformation of the detached breakwater and the transmitted wave height are dependent on the wave group characteristics in a certain range of incident wave height.

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The purpose of this study is to develop a new flattype armor block with large openings aiming at high stability and economical advantage. Wave force measurements were performed to investigate the effect of the size and placement pattern of openings for both horizontal and vertical wave forces. Stability tests were conducted to evaluate the stability number for use in the Hudson formula. Stability test results clearly show that the stability of new flat type armor block has improved drastically in comparison with the existing X-shaped block. New flat type armor block reduced the amount of concrete needed by 25% that of the existing X-shaped block, indicating that it can contribute to an outstanding cost reduction as well.

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The purpose of the study is to propose a stabilization method for seabed subjected to sea wave loading through a series of FEM analyses. The suppression of the wave load is one of the most effective measures to stabilize the seabed, and breakwaters are often applied to reduce the wave impact. Our proposal for the stabilization is the suppression not of the water pressure itself, but of seepage force in the seabed. The seepage force is a kind of body force induced by the gradient of potential water head in the seabed. Thus the unification of potential water head must be effective for the stabilization of seabed. In the method proposed in this paper, the permeable columns are installed in seabed to propagate the water pressure applied to the seabedsurface into the seabed. The efficiency of the method proposed was examined by means of 3-D FEM analysis.

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In order to analyze the variation of current using numerical calculation in the Seto Inland Sea, which formed by several enclosed bay, it is very important to clarify the relation of sea level at boundaries. However, it is required that the method for using sea level at boundaries because of low reliability in T. P. In this study, the standard datum sea level was proposed at Kii and Bunko channels to simulate the current in the Seto Inland Sea and evaluate it' s validity.

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The in-and outflow of water and salt in tidal estuary was estimated by means of the box model modified to adapt to a shallow tidal estuary. The tidal variations of salinity profile were estimated using the tidal variation of depth of the sensors. The tidal variations of the estuary' s volume and longitudinal salinity distribution were also considered in the model. The water inflow from upstream inlet estimated by the box model was verified with the inflow through the up stream water gate. The groundwater discharge may affect on the budget of the water and the geochemical constituent in the Ota River estuary.

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An intensive field survey was carried out in Inohana and Hamana Lakes including a narrow channel to investigate the characteristics of flow and material transport between the two lakes. In the vertical profiles of flow and phosphorus concentration, Inohana Lake has a two-layer structure under stratified conditions; the outward flow and particulate phosphors (PP) in the surface, while the inward flow and dissolved phosphorus (DP) in the middle and bottom. The surface discharge in the channel can be estimated from the wind. Using a simple box model that made use of salinity as a tracer, the horizontal and vertical exchange of waters were calculated and agreed with the observed ones. The vertical transport of salinity was influenced by advection and responded to the density field, i.e. the degree of stratification.

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The erosion behaviour of fine cohesive sediments is not yet well understood by the complexity of its physical and biological property. In order to discuss the effect of biological film formed on the bed mud surface, experimental investigations for erosion are performed by using the annular flume at Fukuoka University. Basis for the comparison of experimental results are as follows. 1) under the biological film formed condition, the erosion rate was decreased. 2) the biological film thickness under the high water temperature was thicker than the low water temperature condition. 3) the thickness of biological film reached 7mm at the maximum.

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It is important to predict the quantitative variation ofNoctiluca and the occurrence of the red tide. The grazing relationship betweenNoctilucaand the prey is modeled by taking account of carbon budget. It presumes that one Noctiluca has to take Heterosigma akashiwo as preys in 2400cells for increase. The model is able to predict the number of Noctiluca at the peak well. Moreover the model expresses the characteristic of Noctiluca's proliferating rapidly in rising period about water temperature in March and April, and decreasing considerably in high water temperature period in May, June and July.

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Horizontal distribution of the organotin compounds in the bottom sediment was examined in the Kaita Bay that is located at the head of Hiroshima Bay. The concentration of the organotin compounds was the highest at the portion in a front sea area of the shipyard and has decreased along with the distance from this portion. This result suggested that the bottom sediment particles that absorb the organotin compounds were transported from the shipyard sea area Moreover, the transportation process of the bottom sediment particles was examined using the transport numerical model of particle. Result of model computation indicated that the horizontal distribution of the organotin compounds is affected by estuarine circulation due to the river inflow.

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