A theoretical analysis is given to the wave characteristics of a textile sheet structure which is proposed as a submerged flexible breakwater. The analysis is based on a two-dimensional linear potential theory. The numerical results have good agreements with experimental observations. It is found that the flexible type structure is much more effective as abreakwater than the non-flexible one.

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A wavenergy dissipating structure with water cushion was constructed on the 3rd of March at Mitoyo, Kagawa Pleft-lettecture, on land reclaimed along the shore in order to prevent sea wind damage to farm products. This structure is based on the hydraulic model test. Since construction of this structure, I have observed the effect of the wave dissipation-compare with the hydraulic model test. Two new-type structure with water cushion have been constructed as a result of this observation. There are two types of wave-energy dissipating structures made up of trapezoidal sections joined along Mitoyo's shoreline. This thesis discusses five types of structure which displayed the effect of preventing sea wind damage to farm products during typhoons 17 and 19 in 1991.

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Wind fence is useful structure to reduce the heights of waves which are newly generated by wind behind it. This paper presents a simple forecasting method of the reduced wave heights behind wind fence. Forecasting method is required for desingnning the wind fence. This method is obtained from data which are given by experiments carried out in a wind water tunnel.

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Suberged breakwaters, one of the coastal protection works, are usually constructed byrubble stones of relatively small sizeand armor blocks which cover rubble stone. In order todiscuss the stability of submerged breakwaters and the effect of submerged breakwater on wave attenuation, function of armor blocks for controlllng fluld motion and wave force on them have to be fully analyzed.
In this paper, we simplify the armor blocks on the crown of the submerged breakwater by using flat plate with openings.Flow pattern around opening, energy loss on the plate and wave force on the plate are investigated through experiments

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In the Tamamo district of Takamatsu Port, as a part of the Takamatsu Port Redevelopment Project, a high amenity stairway seawall was planned as a place where people could enjoy the water while relaxing. Facing to the pleasure-boat sailing area and locating in front of the green area, it is required to satisfy low wave-left-lettlective and low spray conditions for the structure of this seawall. In order to construct this new type of wave desiperative stairway seawall, the 3rd District Port Construction Bureau has developed a new type of concrete block which has enough wave-desiperative property. This paper reports some main results of hydraulics experiment which was done to examine the hydlaulic property of this new type concrete block.

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South breakwater in Nagasaki fishing port was almost damaged by typhoon 8712. The south breakwater had repaired cautiously with amendment of design wave and improvement of breakwater type. The safety of breakwater was certified by hydraulic model test. But in 1991, three huge typhoones attacked west coast of Kyusyu where Nagasaki fishing port locates. South breakwater have been damaged heavy again.
The process of these damages and repairs suggest many things about safety of breakwater and fluctuation of climate.

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Design criteria of the new-type offshore breakwater to create “Marine Multi-purpose Zone” was studied in a period between 1986 and 1990. Eleven kinds of the new-type offshore breakwaters have been developed by the cooperative research with private sectors. Developed structures are briefly introduced and classified. Contents of Manual for planning of Marine-purpose Zone are summarized.

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The variation of amounts of wave overtopping per wave has been measured in hydraulic model test in order to investigate the characteristics of the biggest or the mean amount of one-third biggest amount of wave overtopping. The biggest amount of wave overtopping is in direct proportion to the significant wave period of deepwater waves and the significant wave height of deepwater waves to three fourth power on condition that the crest height of seawall is designed to keep wave overtopping rate constant. The biggest amount of wave overtopping is in direct proportion to the wave overtopping rate to the one-half power if the significant deepwater wave height and period are constant.

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This paper reports the developement of high amenity/low crown hight type quaywall made of steel cylindrical caisson with effect of decreasing overtopping waves, at Maruyama area in Turuga Port, inner part of Turuga bay. The depth of water of construction is 20meters and the ground foundation is soft clay.

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A new and novel artificial lagoon with pebble beach has been projected, as a place of recreation and relaxation. As there are only a few precedent for such facilities and structures, proposed cross sections of the pebble beach, artificial lagoon and barrier were investigated by hydraulic model tests.
Hydraulic experiments were carried out to predict transmitted wave height in the lagoon, the pebble beach erosin and wave run up of the pebble beach.

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Hokkaido Development Bureau designed and constructed a new type quay wall in kushiro port. This new structure is called 'Underwater Strutted Steel Structure System (Quay Wall type) '. The horisontal deformation and stress distribution of the system against active earth pressure which are acting on the wall are measured and analyzed in this report.

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In this paper, the following two subjects are investigated.
1) Influence to global greenhouse effect on typhoon action.
2) Increase of wave overtopping rate due to the combined effects of mean sea level rise, intensified typhoon, and beach erosion.
The main conclusions obtained are
1) The possibility of intensifying a typhoon due to mean sea level rise can not be neglected in the treatment of greenhouse effect.
2) Coastal profile eroded by magnified waves can be predicted by eqs.(5), (6), and (7).
3) Rate of wave overtopping is considerably increased by the effect of mean sea level rise and is further increased by beach erosion. the effect of intensifying a typhoon on wave overtopping rate is remarkably large.

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Kelp forest consisting of Eisenia bicyclis and Ecklonia cava is important for production of fishery resources and conservation of marine environment. It is necessary for maintenance-free kelp forest creation to select the suitable place and season for construction of artificial algal substratum. Important factors to select the place are topography, geologies, iso-thickness of sand, distribution of kelp forest and appearance area of young kelp plants. Important factors to select the season are maturation period of adult kelp plants and appearance season of young kelp plants.

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Social needs are changing from the environmental conservation to the enviroment creation. And the local development and the creation of amenity are desired for the coastal development plans. We are studying on a maintenance free technique for kelp bed creation for this purpose. From the results of litelature survey and interviews with the kelp reserchers, we suggested some ideas related to maintenance free kelp bed creation. Based on three presuppositions, kelp bed creation on sandy sea bottom, setting only kelp bed, and maintenance free, we discussed about how to select the suitable site and time, and also the design of the kelp bed structure in this paper.

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The authors have been examining the effectiveness of an artificial foundation for kelp bed at a sandy sea bottom off the west coast of Miura Peninsula, central Japan. This paper aims at showing a structural design method of artificial foundations for kelp bed. In this paper, described are the design wave condition according to wind wave prediction in this sea area, the structure of the artificial substratum foundation based on hydraulic model experiments and surface form of an artificial algal substratum suitable for adhesion of zoospore found out in a sense of tests both in the field and laboratry.

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On view design of port facilities of Kagoshima port and Shimonoseki port, we studied visualization of complete form of structures and change of view caused by changing of view point by using Computer Graphic system.
As a result, it was proved that Computer Graphic system is very effective measure not only for study of view design but also for confirmation of utilization of port facilities when people enter facilities.

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People on seawalls and breakwaters can enjoy very comfortable sea environment. However such places are actually dangerous to the users especially when waves are high.
A fishing park was built in 1984 on a seawall of Tarumi reclaimed land in City. The park has been operated very safely and successfully. The data concerning operation with measured waves are analyzed to investigate safety operation of such amenity-oriented sea structures. A short series of experiments are also conducted to reproduce the wave overtopping on the seawall.

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The tidal flow and exchange processes between rectangular-shaped pocket and tidal channel was investigated experimentally using a flow visualization technique. The spatial structure of the tidal flow field was found to exhibit marked variation through the course of the tidal cycle, with clear evidence of transient eddies and flow separation at the corner of the pocket. Such variation has a strong connection with the tidal exchange through the entrance of the pocket. A simple analysis of tidal exchange was presented and calibrated by experiments.

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“Breakwater with submerged mound”is facilities for purification of water in fishing port basin by driving fresh sea water into it. Authors had already reported this hadrauric scale model on previous proceedings, and it has been builded for the first time on Yokata fishing port in Toyama city. In this paper the outline of the plan, design and construction onit is described. In addition, the resultof investigation of water inlet ability on it by observation and measurement is mentioned.

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A region of “UTSURO of the sea (An area of the sea surrounded byporous body of dikes)” was constructed in a polluted area of the seain order to purify seawater by means of accretive plants which grow inthe hollow. We have investigated the effect of that experiment and the results are reported. The results of an experiment on removing oils by the agency ofcontact oxidation among pieces of the gravel are also reported.

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Remotely sensed depth prediction in Omura Bay, Nagasaki pleft-lettecture, Japan wasperformed using digital data of band 2 of Landsat-5 Thematic Mapper by an indirectmethods (a use of transparency).Models were developed considering the transparencyhave a good relationship with Landsat-5/TM band 2, and the transpatency have agood relationship with water depth too.Transparency model was developed usingnonlinear regression analysis in other to increase accuracy in this paper.Ther.m.s.error using developed method was measured 2.20m a good value to predictedwater depth of Okinawa sea water.The relationship between depth and transparencywas explained.

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This paper deals with the propagation of water pressure fluctuations inaquifers, as a coupled stress-flow problem. A plane-strain formulation in terms of the method of finite elements is made, with due allowance for the compressibility of pore fluid. Closed-form solutions under simplified situations are given also to focus the importance of the drainage condition at the landward end of an aquifer. The predicted performances using those analytical means are shown to compare favourably with what were measured in the laboratory for a sandy aquifer subject to water pressure oscillations from 1.5 s to 205 s.

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For the prediction of the stability or settlement of the sea floor or any structure founded on it we should determine the kind of parameters to solve each problem. If we restrict our considerations to cohesive sediments, then the soil constants used for the design of coastal structures on them are classified into the two categories during and after cyclic loading, each depending on the magnitude of cyclically induced excess pore pressures and shear strains. Each cateogry is also sub-divided into the ranges of small and large shear strains, respectively. In this paper, comments are made on both the degradation of deformation modulus during cyclic loading which is regarded as in the category of small strains and the changes in deformation and strength after cyclic loading, as pertaining to the category of large strain for cohesive soils.

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A new solution for the seabed response to surface waves, in which the effects ofthe wave-induced bottom shear is taken account for, is derived. The effects of the bottom shear on the shear stress of the solid skeleton is significant in the seabed near the bed surface. For some conditions, the vertical effective stress of the solid skeleton near the bed surface becomes 0 after the wave crest passes. The shear stress takes a negative maximum in this phase. This maximum does not depend on the seabed conditions, but depends only on the wave conditions.

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This paper describes a method of applying the results of cyclic triaxial tests on undisturbed samples of a marine clay to predict the settlement of a breakwater. The stresses and strains beneath the structure are determined using a finite element analysis allowing the determination of shear deformations under undrained cyclic loading and settlements due to post-cyclic volumetric changes. The results of numerical analysis indicate that the cyclic-induced settlements of a lightweight breakwater on seabed clay are mainly influenced by the kind of breakwater, the direction of wave action and the base width of breakwater.

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The aim of this paper is to study numerically the seabed response around the block by the water waves. The excess pore pressure in the seabed is accumulated by the cyclic load of the waves and the block is the danger of the settlement. The method of numerical analysis is solved by the finite element method with using the Biot's two mixture theory and the elasto-plastic theory.
The gradient of the pore pressure and the shear strain generates strongly at the seabed of the block edge. The seabed around the block is stable as the permeability and the specific gravity is large.

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In the analysis of soil-structure interaction problems, the ground is typically modelled by either an elastic or a visco-elastic medium.
It may be more suitable. however, to assume a fluid-filled porous material for seabed.
The frequency response of seabed around an end bearing anchor due to steady-state mooring force is numerically evaluated by assuming the seabed as a fluid-saturated poroelastic halfspace whose behavior is governed by Biot's theory, and depends on the permeability of seabed and the load carrying share of pore fluid to acting force.
In this paper, these effects to frequency response of seabed are investigated through some numerical examples.

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A large part of shoaling of navigation channel surrounded by fine sand is caused by suspended sediment in non-equilibrium state. We develop a numerical model for predicting shoaling of navigation channel where concentration of suspended sediment in such state is accurately simulated.
In this study, effect of channel geometry on the shoaling of thechannel are investigated numerically. A composite slope of navigation channel is also proposed to reduce non-equilibrium property of suspended sediment.It is found that the composite slope can effectively reducenon-equilibrium property of suspended sediment and the amount of sediment deposited in the main channel.

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Soft muddy bottoms have significant effects on damping coefficient of water waveswhich propagate over them. Model tests of wave damping are done for two different mudmaterials (kaolinite mud, bentonite mud) and these results are compared with thetheoretically predicted results. The theoretical damping rates determined by assuminga viscoelastic mud layer agree well with the rates obtained by experiments that kaoriniteis the bottom mud materials. In the case of bentonite mud, the predicted results byviscous fluid model agree well with experimental results.

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Beach nourishment was carried out at Eigashima area on the Toban coast facing the Seto Inland Sea. Sea cliff erosion of this coast was studied first, and beach changes after the sand nourishment were investigated by topographic surveys. It is found that the predominant wave direction is S 24°W from the shoreline indentation, and the characteristicheight of beach changes and critical depth for beach changes are about 2.7m and 1.5m, respectively.

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In the case of very deep-water crossings, conventional bridges and tunnels are expensive. This has lead to the development of alternative concepts for crossings. The mostsignificant concept at the time being is the submerged floating tunnels.This paper reviews the development of design and construction techniques for these tunnels up to the present day.

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Submerged floating tunnels, which consist of buoyant tubes and tension legs, have been expected as one of the most prospective structures for deep-water crossings in the future. In this paper, their dynamic responses due to wave forces were reported. The dynamic motions of submerged floating tunnels were analyzed by a two-dimensional model based on the potential theory. In order to realize their fundamental characteristics, various arrangements of tension legs were taken into consideration as well as the tube weights and water depths. Consequently, the wave forces and displacements were generalized with the natural frequencies.

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A large Submerged floating tunnel is studied at the many projects in the world. But there are many problems for the construction at the real sites.In Japan, investigation on the development of the Submerged floating tunnel technology has been started from 1990. This paper deals with the wave force characteristic to the tunnel with experiments (2-D channel) and numerical calculation by means of boundaly element method. From obtained results, the most important thing is snap force control under the large wave height.And numerical calculation of the wave force to the tunnel is good agreement with the experimental results.

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