Recently in Japan, many artificial beaches were constructed to reproduce the lost natural beaches especially along the coast of Osaka bay. It is important to study possible difference of ecosystems between natural and artificial beaches to establish the design standard of artificial beach. The water quality and species of appearing algae and animal have been observed in an artificial pebble and rock beach constructed in Seto Inland Sea during 4 years. The beach consists of a deep offshore basin and a shallow onshore pool. The concentration of total and organic nutrient in the shallow pool is higher than in the basin. This is due to the increase of phytoplankton in the pool in summer. The concentration of inorganic nutrient in the beach is higher than outside of the beach in summer.

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To determine habitat feasibility of mudskipper in artificial tidal flat, ecological studies on mudskipper in the site were carried out for 10 years. Number of the spawning burrow was observed yearly as an indicator for evaluating their habitat feasibility. The spawning burrow increased after 5 years surveying (100-200 burrows). The survey results concluded that the artificial tidal flat could be a sustainable habitat space for mudskipper.

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A series of field surveys investigating the stability of natural/manmade tidal flats were conducted from June 2000 to April 2001, i. e., the profile of the seabed and the stiffness and grain-size distribution of sediment were measured. Five natural and seven artificial tidal flats were investigated including one natural and three artificial sand beaches. The terrace of the foreshore region in most natural tidal flats consists of a main flat part and a multiple bar-trough part (multi-bar). The former serves as an important habitat, while the latter is needed to ensure stability of the main flat part against wave actions which occupy the area from the ebb tide shoreline to 200-350m shoreside. Types of forcshorc tidal flats are classified in the condition of the incident wave height and the grain-size of bottom sediments.

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Under the Newly Revised Seacoast Law, the pilot public involvement project on local beach management and construction of shore protection planning has been executed at Kinoppu beach, in Ohata Town, Aomori Prefecture. Citizens of Ohata have passion to join the project for planning of coasts and rivers in their town. Former ordinary system of planning and construction could not follow the local natural, social andcultural context. But new system to involve the public and local knowledge is still immature. Trials of integration ofthoughts and visions of many sectors show many barriers to be changed. Roles of each joining sector were analyzed.

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The Ministry of Land, Infrastructure and Transport and Aichi Prefecture are jointly involved in various environmental rehabilitation and creation projects inside Mikawa Bay. New tidal flats and shallow waters have been created and capping has been conducted through the utilization of high quality dredged sand arose from the development of Nakayama waterway. Results from the monitoring survey showed improvement in sediment quality and disappearance of oxygen depleted water column in the tidal flat of Mito district. Also diversity of bivalves and other benthic organisms have increased in the tidal flat area, suggesting an improvement of the habitat environment. Furthermore, analysis of the nitrogen cycle in the tidal flat suggested that suspension feeders such as bivalves have an important role in the water purification process of tidal flats. Therefore increase in bivalve abundance will likely result in the improvement of water purification ability of the tidal flat area

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Tokyo Port Wild Bird Park, which was originally a part of the reclaimed industrial area, was constructed in 1989 by the request of the local citizens. Since then, the seaside park that includes an artificial lagoon has provided precious opportunities of natural experience for the people in urbanized Tokyo-Bay Area.
For the maintenance and management of the park, volunteer citizens groups have played a crucial role. Since the opening of the park, the highly motivated volunteer groups, in cooperation with members of Wild Bird Society of Japan, have continuously monitored the topographical change of the artificial lagoon and the situation of birds, benthos, and vegetation. In addition, the volunteer groups carriedout some field experiments. For example, they constructed an artificial creek and monitored the growth of thereed around it. They also constructed bamboo fences to check their anti-erosion effect at the shoreline and seabed. These continuous activities help to build better understanding of the environmental management in an artificial lagoon. The authors suggest the need of the involvement of more persons with biological knowledge, in addition to the volunteer group, in order to enhance the quality of the management method.

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Tidal flats are decreasing by the landfill and reclamation in Japan. Tidal flats areimportantfor the conservation of biodiversity, sustainable fishery, water clarification, recreation, andenvironmental education. Many NGOs continue their activities, and are making networks nationally and internationally under the Ramsar Convention. The history of tidal flats NGOs were brieflydescribed. It is necessary for the conservation and restoration of the tidal flats that NGOs, government, contractor, and stakeholders sit at around table to discuss and reach a consensus.

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Biological survey was conducted for three artificial tidal flats in Japan. As compared with natural tidal flat, artificial tidal flats are unstable in features, poor in biodiversity, and feeds fewer shorebirds. It is necessary for a principle that active natural tidal flats are strictly conserved, inactive flats are recovered, lost flats are restored, and local people are involved in planing. An environmental impact assessment and mitigation method should be conducted logically and scientifically. Recovery or restoration should be undertaken by the principles and guidelines for wetland restoration. Consensus of the stakeholders are indispensable to the decision making of tidal flat recovery plan.

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Tidal flats were diminished from 1945 to 2000 about 40% by development in Japan. The flat is highly productive and has a purification function. So, we have to protect and keep the flats to future generation. I describe the productive and purification function of the flat first, then recent loss of these function, fmally a direction to reviving the flats.

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Public involvement in planning of seacoast affairs is executed in Ohshinden area, Nakatsu Portin Oita Prefecture. Large well-reserved mud flat spreads around the port. People enjoy its scenery andcreatures, and coastal fishery utilizes the ecosystem. The local government and people organize the meeting to discuss utilization and conservation of the seacoast in this area. Comparative consideration on civil engineering works and medical care in terms of informed consent, and the role of local governmentsand function of these meeting are discussed.

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This paper presents discussions on the historical development of coastal arrangement technologies with nature (nature friendly technologies). Discussions are also extended to the social acceptance of the tidal-flat construction technology. Mesocosmic experiments as well as the accumulation of field/construction experiences gave us gradual understanding of settlement of the benthic biota into new habitats. As construction works along coasts often require as long as 10-20 years, deep considerations for the future use and impacts of the facilities/sites are necessary with the understandings of long-term social trends. Adaptive management with a long-term monitoring system is one of the attractive ways for the regional application of the nature friendly technologies.

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The historical development of the coastal environment policy is overviewed in the field of Ports and Harbours policy. The first large contributions were set in 1973 along the amendment of Ports and Harbour Law. In 1988, “Sea-Blue” Policy was introduced, initially for the sediment quality improvement by the beneficial use of clean dredged materials. In 1994, “Eco-Port” Policy was enacted as a more comprehensive environmental policy for ports. Under the New Governmental Policy of Prime Minister Koizumi in 2001, “Coastal works harmonizing with nature” and “Water quality improvement inside enclosed waters” are intensively promoted by the partnerships among the sectors.

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Practical reuses of soft dredging are presented in this paper. Other than disposal of the dredging into reclamation area, the dredging after proper treatment with cement shows fairly good characteristics, particularly suitable for leakproofpurposes.
An empirical and simple correlation among compressive strength, cement content and water content is proposed and the variance property of compressive strength is interpreted on the basis of this correlation. Aiming to provide a recycled geomaterial with high quality and to reduce construction cost, special working ships have been introduced in practical engineering. Improved dredgings have already found applications in various marine construction projects, and two examples in Nagoya Port are presented in detail. Finally, difficulties are mentioned concerning the reuse of dredging from a practical viewpoint.

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The standard of impervious structure were specified with the law about a disposal site revisedin 1999. However, with the past material and method, it cannot respond enough. Then, we are grappling with development of a impervious material and a impervious method and a impervious structure newer than several year before. This paper explains the new deformation following impervious material and the new impervious structure.

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In case where the bulkheads, which surround a reclamation area for waste disposal, are required to prevent substances contained in waste leaking out to the sea, they are constructed as waterproof structures.
For a caisson-type bulkhead, waterproof sheets are mostly placed in the backfill space for this purpose. Because wave-driven pressure, which propagates through nibbles mound and backfill, acts on thesheet, weight is placed on it to prevent its movement and failure.
In this study, we conducted a laboratory experiment and numerical analysis to clarify the characteristics of the dynamic pressure, which leads to the development of the design method for this kind of structure.

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It is almost impossible to know the reason and timing of the destruction of our nearest seacoast in the local community. Because almost information of the construction schedule, costs paid by the tax, system of management is not cleared enough. In the text for the public accountability, technical terms of governance and management are full. Especially, women do not have enough chance to join the social decision making, they are tend to be isolated to know the situation of their favorite play space in thelocal nature.

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CENTRAIR, the nickname of Central Japan International Airport, is under construction in the sea off Tokoname City, Aichi prefecture. It will open in March 2005, then will be a major air-hub in global network as a gateway of Japan. CENTRAIR is located 35km south of downtown Nagoya and the access time to that is 30 to 40 minutes by rail or car.
In order to construct and operate CENTRAIR, Central Japan International Airport Co., Ltd. was designated as a commissioning entity by Japanese government.
CENTRAIR is on a man-made island. Dredged soil from Nagoya port is unloaded by compressed air to the north part of the island. This system, “Pneumatic Flow Mixing Method”, enable us to prepare a certain strong ground in a short period, through the mixing and kneading of the soil and cement slurry in a pipeline.

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Osaka Bay Phoenix Project aims to render the final disposal of waste generated from the Kinki district through land reclamation in Osaka Bay and also strives to improve port functions utilizing landfills. Osaka Bay Regional Offshore Environmental Improvement Center carries out the project. The planning, operational and technical subjects are introduced in this paper. Especially, those are the importance of local residents' consensus, design of shielding structure based on the concept of fail safe, utilization of the reclamation disposal ground and its field examinations.

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The New Kitakyushu Airport makes good use of the disposal site for sludge generated by port development in Kanmon area. This type of coordinated development results in a substantially lower cost than if the offshore airport were built entirely from scratch. Due to the fact that the New Kitakyushu Airport is being constructed 3km offshore, residential areas will be only slightly affected by airport noise. This will make it possible to provide 24-hour services at the new airport. Construction works are being carried out with advanced civil engineering technology, taking environmental impact assessment, improvement of maritime safety during the construction works into consideration.

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An artificial island off the coast of Shimonoseki is planned as a base of marine transportation mainly by container cargo ships. The island of about 60ha will be reclaimed at the first stage and consist of wharf area, storage area, green area and so on. The design conditions are preservation of the present coast and current and reproduction of sea weed beds around the artificial island. Gentle slope revetments with shallow rubble mounds are planned as sea weed beds. The effects on adhesion of sea weed by the shapes of blocks covering the rubble mounds or by the methods of transplantation are investigated at present by experiments as described in this paper.

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In Japan, the total area of the land which has been reclaimed from the sea since the dawn of history is estimated to be about 1, 900 km², that is 1.5% of the habitable area in our country. Although land reclamation provides us important places to support our social and economic activities, there are problemsto be solved; how to conserve the environment and how to make a consensus among the people when reclamation works are going to be undertaken.
This report classifies the points of view to make a conccnsus among the stakehoders who are concemed to the reclamation, and also introduces technical measures to solve the problems.

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The effect of long period oscillation (LPO) is usually neglected for storm surge prediction because it is hidden behind high waves. We observed a big LPO (amplitude was about 0.5m and period was about 5 minute) at Shimohaya Bay in Wakayama Prefecture in a storm. The LPO in storm surge condition would raise the water level of 0.5m, which causes the increase of wave overtopping and wave force on coastal structures. Power spectra of wind and wave group were compared with that of LPO. Periods of around 5 minutes are predominant in sea wind and wave group, and they are sameas the resonance period of Shimohaya Bay.

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In order to reduce very long waves in a harbor, a combination of two large-sized resonators with different effective ranges of wave frequency is proposed. In order to understand basic properties of the combined resonators, wave transmission characteristic through an infinite array of the combined resonators was first examined theoretically. As an alternative of a rectangular resonator, a detached caisson-type resonator was also adopted to reduce the construction cost. Finally, in order to check the performance of the combined resonators for very long waves, wavesheltering effect by the resonator for a rectangular harbor model was theoretically examined for various wave period conditions, in which the combined resonators were installed at the harbor entrance.

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It is important in berth planning and port operation to be accurately familiar with moored ship motions correctly in especially long period component, especially at ports facing the open sea. The phenomenon of moored ship oscillations has been studied for decades by model experiments, field observations and numerical simulations. This paper shows the comparison of numerical simulation result and field observations to discuss how we get more accurate result by the numerical simulations on ship motions. Major unknown factors for surging in the numerical simulations are the condition of mooring ropes and damping factor. Then, we discuss on the effect of the characteristics of mooring system and surge damping factor.

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Long period waves with period of 30 to 300s causes the troubles in loading and un-loading of large cargo vessels and breaks of mooring ropes. Such damages are amplified by the resonance of mooring system composed of vessel and hawser to long period waves because the natural oscillation period of the system agrees with that of waves. The countermeasures represented by the extension of offshore breakwaters, improvement of mooring system and establishment to warning system have been proposed to prevent the long period wave turbulence.
In the paper, the practical countermeasures employing the extension of offshore breakwater and development of long period wave absorber are proposed. Numerical modeling is carried out to evaluate the effects of countermeasures to reduce long period wave heights in harbor. The simulated results demonstrate that offshore breakwaters extended appropriately may reduce the incident energy of long period waves and may increase the rate of effective handling days and that double slit caisson sea wall is applicable to reduce the energy of reflected long period waves.

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This paper introduces Japanese Nationwide Ocean Wave information network for Ports and HArbourS (NOWPHAS) system, which recently improved for the directional and infra-gravity wave observation with continuous data aquisition. New concept of frequency banded expression has been introduced in the data analysis of directional and infra-gravity waves. Examples are demonstrated as the time series and annual statistics forms observed by the Japanese NOWPHAS system.
The NOWPHAS new wave data acquisition and analysis system clarified the characteristics of the long period swells originated from typhoons and low pressures, and the 2001 Peru Earthquake Tsunami.

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Characteristics of generation and propagation of coasatal long waves with periods of several minutes are discussed based on field data obtained at Akabane on the Enshu coast and at Are in Tsushima island. Differences in amplification of the long waves at the two locations are highlighted and discussed in relation with incident wave properties. Field data obtained by other researchers at different locations are used to compare the amplification characterstics. Wave heights of long waves at most locations are linearly proportional to the products of significant wave height and period. Generation of free long waves with large amplitude is indicated on gentle sandy beaches. Propagation of the free long waves in on-offshore and longshore directions are also discussed.

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The development of infragravity waves and their influence on coastal sedimentary processes were described on the basis of laboratory measurements, field data and numerical experiments. The direction of net suspended sand transport was found to be dependent on the amplitude and the phase of infragravity waves, which were modeled by the secondary interaction theory as well as a numerical model based on the shallow water equation. The contribution of infragravity waves to sediment transport was found to change its direction from offshore to onshore as waves approached to the shoreline.

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The long-period waves have been researched in recent years because of its importance in the various problems of coastal engineering, such as long-period oscillation, long-period motions of moored vessels, sediment transport, wave-overtopping and stability of coastal structures. Importance of long period waves have been well recognized, however, its reflection of effects of the long-period waves into design of coastal facilities is not sufficient.
In this paper, we review previous researches on the long period waves and consider the problems in the reflection of effects of long-period waves into design of coastal facilities.

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The utility of ecosystem model was discussed by using three research examples at Ise and Mikawa Bays. The first is about the quantitative evaluation about the feasibility of improving technology to increase the dissolved oxygen content. The second is about the changes of nitrogen budget between sediment and overlying water accompanied by the progress of hypoxia. The third is about the effective selection method of artificial tidal flat area or shallows from the viewpoint of the bivalve larval supply. Some controversial points in the use of these ecosystem models were also appointed.

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This study is for making seaweed forests efficiently. Various factors, such as light condition, shore current, fouling organism, and grazing pressure affect seaweed forests. We thought that the supply of Sargassum eggs influence formation of seaweed forests. Therefore, We performed a field survey and numerous simulations about transportation of Sargassum eggs at Togi fishing port, Ishikawa prefecture. From this result, we came to understand the importance of the position of natural seaweed forests and the shore current's time to grow seaweed forests.

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The purpose of this study is to use HEP (Habitat Evaluation Procedure) for studying rare species on tidal flats and to evaluate the value of tidal flats themselves. In this study, based on the results both of field observations and numerical simulations, SI (Suitability Index) curves for each mud property and physical factors such as friction velocity were plotted. Then, HSI (Habitat Suitability Index) for each tidal flat was calculated by multiplying each SI curves score and comparing the HSI value among the tidal flats. The following results were obtained: 1) The Yoshino River mouth, which is the largest habitat of genus Uca in Shikoku Lsland, had the highest SI score. 2) The suitability of habitation for other kinds of tidal-living crabs may be estimated as the Yoshino River also had the highest score. Using this method, the value of tidal flats could be discussed indirectly, that is, as the HSI score becomes larger, the necessity of tidal flats becomes great.

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Even our nearest beach, we cannot illustrate the detail of underwater landscape, topography and creatures in three-dimensionally. In the field of environmental education and guidance for ecotourism, landscape simulation methodology is very helpful. Underwater landscape simulation generating system assisted with three dimensional computer graphics was made. Perspectives of the system are discussed.

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A new system of gradational breaker index is introduced to facilitate the computation of random wave transformations in shallow water. The parabolic equation is used to compute wave shoaling, refraction, and diffraction. Computation is made with multiple levels of wave heights under the Rayleigh distribution. Wave breaking is assumed to occur when the ratio of wave height to local water depth exceeds the breaking index, which takes the largest value for largest wave height level and gradually decreases as the wave height level goes down.
The new system succeeds in reproducing the random wave breaking diagrams by Goda (1975), and shows good agreements with various experimental results on wave transformations over bar and trough topographies, elliptical shoals, and artificial reef systems.

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Design offshore waves are one of the most important exerting forces for marine structures.Ideally, they may be calculated from reliable observed waves, but there are not enough observation stations. So generally, design offshore waves are calculated from wave hindcasting. Recently, a new wavehindcasting method has been developed. But, in determination of design offshore waves, even with excellent theoretical analysis, there are several practical problems.
In this paper, we report problems and solutions encountered in determination of designoff shore waves for fishing ports in Hokkaido.

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Impulse responses of digital filters for use in separating incident and reflected water waves in a time domain are improved by using a non-linear least square formulation. The applicability and limitations of the method are discussed. Trial computations using a set of analytical examples with known incident and reflected waves demonstrate the validity and usefulness of proposed method.

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This paper is intended to estimate wind field over sea area, which is main cause of wind wave. The Navier-Stokes equation and equation of continuity have been solved numerically with the initial and boundary conditions given by interpolation of GPV. Computed wind field seems to reproduce well the wind field affected by landform. Then computed winds have been compared with measured values obtained at Kamishima Island. It is confirmed that the computed wind variation agrees well with measured wind variation. Moreover, the numerical computations have been applied to estimate wind field in another area including Osaka bay and this technique is found to be applicable to other area without any change other than input data.

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For a circular shoal bathymetry, the conventional wave ray method is comparatively hard to estimate wave height distributions. In order to avoid the difficulty, combined analysis of the vertical line source Green's function method and the regional division method was adopted. Applicability of the method to a circular shoal bathymetry was examined by the comparison between the experimental and computed results. As an extensive case study, a circular shoal bathymetry with a vertical circular caisson at the top was used to know the effect of wave diffraction on the wave refraction by the shoal.

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In 1990's, in the Kyushu coastal areas landed T9119 and T9918 which generated the recorded maximum storm surge level, and large damages were caused in various places along the Kyushu coastal areas. For disaster prevention, it is important to examine vulnerable areas where the storm surge increases remarkably. This research aims to study through a numerical analysis the storm surge amplification characteristics along the coasts of the Suo, Genkai and Hibiki seas by varying typhoon parameters including typhoon tracks, central pressures and forward speeds.

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Numerical calculations are conducted to investigate the characteristics of wave pressure propagation into backfill nibbles of caisson type seawall. The wave pressure in front of the caisson is transmitted directly into the backfill rubble mound when the backfill mound is covered by reclaimed soil. The pressure may cause so-called through-wash or liquefaction of the covering soil and consequently the settlement of the reclaimed occurs. The pressure canbe reduced significantly by putting an air-pressure release opening on the top of the backfill rubble mound.

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The purpose of this study is to clarify the characteristics of wave overtopping on gentle slope-type seawall. Therefore, experiments on wave overtopping by irregular waves were carried out for gentle slope-type seawalls. Using the results, effects of the ratio of the water depth to the wave height, the relative crown height of the seawall, the sea bottom slope and the slope gradient of the seawall on the wave overtopping rate of gentle slope-type seawalls were discussed. And, an optimum combination between slope gradient of the seawalls and sea bottom slope was examined from the wave overtopping prevention of view. In addition, frequency of appearance distribution of wave overtopping rate was also investigated.

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This study investigated deformation of a gentle slope type dike with a step. Stability of armor stones and armor blocks is investigated by hydraulic model tests. Some basic experimental results showed that a sliding of armor blocks occurred due to deformation of a step which was covered by armor stones. To find out the countermeasures, some experiments using armor blocks instead of armor stones were carried out. The experimental results indicated that a filter layer under the armor blocks reduces the lift force which acts to armor blocks. The results were in agreement with Van der Meer's study. A numerical simulation that focused on the deformation of armor stones at a step was also carried out. The simulation methods are DEM and CADMAS-SURF. The simulation indicated the processes of deformation of armor stones. The results had good agreement with experimental results.

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A Flaring Shaped Seawall (FSS), a new type of one, can drastically reduce a crest height and wave overtopping quantity in comparison with a conventional upright one. The FSS will usually be set on a mound from the point of a cost of manufacturing and construction. Thus, in this paper, effects of the mound on hydraulic characteristics of the FSS (a wave overtopping rate, a wave run-up height and a reflection coefficient) are clarified from experiments using a two-dimensional flume. Furthermore a method for the FSS on the mound is proposed, and it is shown that the method is adequate under the condition of experiments in this paper.

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The experiments on the damage of gentle-slope sea dike were conducted by using the irregular waves. The gentle-slope dikes of 1/3, 1/4 and 1/5 slope were constructed at the shoreline and the offshore side. The mutual relationship between the damage of sea dike and the relative maximum scoring (h_max/Ho) in front of dike was sufficiently estimated from the result of experiments. In the case of l_t/Lo=-0.2, as the value of slope angle increase, the value of h_max/Ho becomes large and damage of dike becomes early. On the other, in the case of l_t/Lo=0.0, as the value of slope angle increase, the value of hmax/Ho becomes small, but the damage of dike did not occurs within the limits of these experiments.
Damage proceeded in the order as follows:(1) vanishing of sands on the slope, (2) damage of foundation works, (3) piping of backfilling stones, (4) subsidence of armor unit. This damage process agreed well with the result of experiments by the regular waves.

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Breakwaters are very important to keep harbors calm. However, they have been severely damaged quite often since they are directly exposed to large waves from open sea. Port and Harbor Research Institute of Ministry of Transport edited four volumes of damged breakwaters, and published them as technical reports. The present paper investigates the characteristics of damaged breakwater referring to the technical reports and statistically derives main factors closely related to the damages. It was founded that aspect ratio of a casson, and horizonal wave force ratio to weight of the casson show close relationship with breakwatars damage modes

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Deformation of submerged breakwater was examined by three-dimensional experiments to investigate theinfluence of the deformation of the head of submerged breakwater on the total damage of the breakwater. The erodedarea at the breakwater heads was larger than that at the breakwater trunk. The rubble stones moved from the upstreamhead of longshore current were accreted within one wave length from the end of the upstream head. Therefore, thereare two types of accretion at the leeside of the submerged breakawter depending on the ratio of the breakwater lengthto wave length. The difference in deformation between two-dimensional and three-dimensional experiments is large, especially at the upstream head of the breakwater.

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The breakwater using the suction foundation has several advantages over conventional composite breakwater, i. e., it has high stability against wave actions, can be constructed without rubble mound foundation, and also need notspecial construction machine, and therefore, the construction period and cost will be reduced compared withcomposite breakwater.
A series of small scale and large scale hydraulic model experiments were conducted to investigate thecharacteristics of the breakwater using the suction foundation, and the calculation method of wave forces acting onthe suction foundation was proposed.

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Mooing systems using piles and roller fenders, or chains are often used for coastal floating structures. Pile mooring system can restrict horizontal motion, but not heaving and rotational motion. In contrast, chain mooring system does not cost much, but can not reduce horizontal motion.
In Europe and America, ship design and operation have been recommended to respond to elderly and disabled persons' needs. Also in Japan, Transportation Accessibility Improvement Law came into force in November 2000. This law will probably require ships and facilities in harbor and costal zone to reduce the responses in waves in the near future. Therefore, motion reduction in waves as well as cost is possible to be more important guidelines.
In the background, the present research attempts at developing a new mooring system reducing heaving and pitching motion in particular, and demonstrates the mooring performance and the feasibility.

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In marinas, a type of floating structure composed by joined floating units is used for a breakwater or pier. Kato et al (2001) discussed the wave control effects by such a structure in the case of normalincident waves.But generally, the incident waves propagate obliquely toward the structure. In this case, the wave force is notuniform along the structure. Therefore the structure elastically vibrate with this un-uniform force. In thepresent paper, we analyze the wave field and the elastic vibration of the floating structure, and discuss thewave control effects and the interaction between the wave field and the motion of structure.

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Floating breakwaters have been adopted in the comparatively deep-sea area with a mild wave climate, such asinland seas. In that area, various aquacultural facilities, such as fishponds, oyster farming facilities and so on, areusually installed. The development of highly dissipative floating bieakwaters has been devoted in that sea area forreducing both transmitted and reflected waves from newly constructed breakwaters. We have already studied a newtype of floating breakwater intending to reduce both the reflected and transmitted waves. The breakwater consists of abundle of horizontal cylinders at the center and rectangular floats at the both ends. Major dissipation mechanism isthe wave slamming loss of the horizontally installed circular cylinders near the water surface. Here, spatialarrangement of such breakwaters is precisely examined for effective reduction of both reflected and transmittedwaves in the real sea. For the comparison, the conventional floating breakwater, such as a pontoon-type floatingbreakwater, is also adopted in the experiment.

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