This paper is intended to estimate beach process and wave deformations at the Shitiri-mihama coast in Mie Prefecture. Field investigation by using an aerial photography technique is conducted along the Shitiri-mihama coast from the Kumano river mouth to the Onigashiro cape. It is clear that almost regions occurred beach erosion, especially Udono harbor region located on the left bank of the Kumano river, as the coastal line faced to sea, the beach protection works were struck by strong storms. Based on bottom sounding survey, maximum shoreline retreat was 100 meters for 5 years immediately after extend construction of breakwater around Udono harbor. It is necessary to predict water deformation for erosion control around coastal protection facilities. It is presented a time-depend mild slope equation for estimating wave deformation. Some simple calculations were conducted for modeling breakwater at the worst beach erosion area where located northern Udono harbor. The numerical model has well explanations for generation of partial standing waves, drop of mean sea level behind breakwaters.

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Authors have proposed a non-wave overtopping type seawall (Flaring Shaped Seawall) with deep circular cross section in order to facilitate a safe and excellent use of coastal space for various purposes. The seawall satisfies a non-wave overtopping condition with extremely lower crown height in comparison with conventional upright seawall. In this study, wind field near the seawall, water spray transported behind the seawall and sounds when waves running up were measured in the experiments, and compared with an upright seawall.

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In recent years, large scale structures have been built on offshore for utilization of coastal zone as offshore airport and marine terminals. Those big scale structures, however, may act as significant barriers against wave and severe beach erosion may take place on the coast.
The present study deals nearshore topography change affected by construction of an offshore structure with different distance from the shore. The series of three dimensional movable bed experiments have been examined in detail. Moreover, in order to make clear the relation of nearshore currents and local erosions behind offshore structure, the nearshore currents are calculated by boussinesq equation model with the same scale condition of the experiments.

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This paper is intended to discuss impacts of sea-level rise, which is one of the exposures of the global warming, on coastal zone and provide fundamental data for assemble adaptation technique. Shichiri-mihama coast has been chosen as a coast of case study and present situation of the coast has been investigated. Then, impacts of sea-level rise on this coast have been discussed and evaluated. As a result, it has been found that impacts of sea-level rise are very significant and may cause sever damages. Moreover, it has been confirmed that the beach protection from erosion is very important to reduce the effects of sea level rise.

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In this paper, the results of the field survey on the coastal erosion at Kemigawa beach as the artificial beach are presented, and causes of the erosion are discussed using the sea conditions and the grain-size distribution of sands of the beach. The results of the investigation are summarized as follows:(1) The erosion at Kemigawa beach is intense compared with neighbor artificial beaches that has a characteristic like the Kemigawa beach.(2) The result of the numerical analysis using the cross section of the construction plan shows that the wave conditions of near shore at Kemigawa beach is calmness in the stormy weather.(3) The results of the grain-size analysis of sands show that the small-size sands that flow away from the center of Kemigawa beach maybe deposit at the base of the breakwater.(4) The result of the comparison between d50 of the sands and the gradient of the foreshore about the construction plan of Kemigawa beach shows that the beach has the tendency of the erosion.

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The purpose of this study is to establish the construction technique of the man-made rocky coast aiming at coexistence with marine organisms. From such viewpoint, the field observations on marine organisms and their life environment were carried out in the seven man-made rocky coasts and natural one at Osaka Bay and Tohban Coast.
The result showed that there were most small marine organisms species of the man -made rocky coast in the bay inner part and that it is abounding as a marine organisms species of the man -made rocky coast of the place which separated from the bay inner part. The diversity and prosperity of marine organism in man -made rocky coast are influenced by the seawater motion due to wave and current. The diversity index and prosperity index of marine organism increase as reflection coefficient of the light and surface temperature of construction material are lower.

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Communities of Algae have disappeared from the shallow waters along the Japan Sea coastline in southwest Hokkaido. There are many studies of relationships between wave-environments and feeding behavior of the Sea Urchin Strongylocentrotus nudus.
We made a study on the effects of wave-environments on characteristics of vertical distribution of kelp Laminaria religiosa using field survey and numerical calculation. Laminaria religiosa was seen in the limited shallow area in the depth of approximately 2-7m. Our estimation explains that wave velocity on the bottom in spring at this area limits the vertical distribution of Laminaria religiosa, and the calculation was fairly coincident with the result of field survey.

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Field observation of natural and artificial spawning sites of horseshoe crab Tachypleus tridentatus was conducted at Sone tidal flat in Kita-Kyushu City. Natural spawning site is located at the sandy beach at the comet tail extending landward from the lee side of Mashima island on tidal flat. Beach profile and grain size distribution of the spawning site were measured. Artificial nourishment was carried out in front of the gently sloping coastal revetment. Spawning of horseshoe crab was confirmed on this nourished beach, but nourished sand on the artificial beach was carried away by longshore sand transport under wave action. In order to create a stable spawning site for horseshoe crab, it is necessary to build groins to stabilize sandy beach.

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Communities of algae have disappeared from the shallow waters along the Japan Sea coastline in southwest Hokkaido. A large number of studies have been made on coralline flats, it has been shown that the feeding of algae by sea urchins is an important factor affecting the formation of coralline flats.Recent investigations have shown that communities of algae form in coralline flats by removing sea urshins.The purpose of this study is to clarify the control mechanism of movement and feeding behavior of sea urchins Strongy locentrotus nudus by a oscillation of artificial algae due to wave action. It's found that sea urchins cannot climb up an artificial algae and feed fixed algae on it when the artificial algae sway an angle of more than twenty degrees.

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Experiments were conducted to assess the application of granulated blast furnace slag to improve the water quality and bottom sediment in coastal sea areas. It measured that pH, COD, DO and H₂S levels in seawaters and observed organisms on the surface and within slag for one year. From our chemical analysis, it was clear that the slag did not influence the chemical compounds of the seawater close to the slag. As for interstitial water in slag, we observed that pH and H₂S levels were slightly high after 4 weeks. However, pH of the interstitial water remained at about 8.5 and H₂S concentration decreased almost to the limit of detection. We also observed that the environment was suitable not only for the creatures which were on the surface of slag but also for benthonic organisms which inhabited within the slag. From these results, it can be seen that granulated blast furnace slag is applicable to the improvement of the bottom sediment.

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Seaweed forests of Eisenia bicyclis Setchell and Ecklonia cava Kjellman are broadly distributed along the rocky coastal area of central Honshu Island, Japan, facing the Pacific Ocean. We aimed to clarify a process of zonation which are consisted of the two plants. We measured attaching force of holdfast to a substratum in a field and fluid forces on them in a laboratory. Attaching force of their holdfast depended on a condition of substratum surface as same as adult plants. Dominant fluid force exerted on juvenile plants was a drag force different from adult plants because of little development of stipe part. For juvenile as well as adlut plants, attaching force of their holdfast was almost higher than maximum fluid force in situ by using model data.

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This paper briefly describes biological and ecological field analysis results of the mudskipper Periophthalmus modestus, inhabits in the mud flat estuarine area, at Edogawa River mouth, Tokyo Bay.

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Scattering and trapping of the higher order free long waves over a submerged step are investigated. As incident waves, two wave components with slightly different frequencies and obliquely incident angles to the step are considered.The forced waves and the free long waves are obtained up to the second order of the perturbation method. Applicability of these solutions are investigated. It is found that depending on the wave and the step conditions, the free long waves of the progressive mode can not exist in the deeper region but can exist in the shallower

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A three dimensional SOLA scheme model has been developed to estimate sea wind over Ise Bay area. RSM-GPV has been interpolated and then adjusted by MASCON model to provide initial and boundary conditions. The wind field after one hour has been estimated for typical events by this model.As a result, it has been confirmed that the model developed in this study can give three dimensional wind field taking landform into account.Moreover, calculated wind vector has been confirmed to agree well with measured one at Kamishima.

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Ship waves in shallow water are considerably different from those in deep water.They are greatly influenced by the depth Froude number. In the present paper, the numerical method proposed by Tanimoto et al.(1999) has been confirmed to be applicable to predict ship waves in a shallow water by comparing with experimental data by Kurata et al.(1983).Variations of the maximum wave height by the mid ship section coefficient, the distance from the sailing line and the depth Froude number are discussed together with experimental data.The maximum wave height increases as the depth Froude number increases up to the critical speed condition. In the range of super critical speed, the maximum wave height becomes almost constant or slightly decreasing tendency.

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We have observed waves, tide, winds and temperatures at the tower named Tanabe-Nakajima Storm Surge Observation Tower standing at the mouth of Tanabe-Bay in Wakayama Prefecture. After removing many kind of noise in the original data by a special filter, significant wave heights and periods are calculated from Dec. 1994 to Aug. 1999. Comparing between wind and wave conditions, characteristics of seasonal and yearly variations are analyzed. In winter season, wind waves are dominant and there is an upper criterion of wave height restricted from wave slope. In summer season, swell become predominant. Yearly maximum wave heights are generated by typhoons so that the yearly variation is bigger than mean seasonal one.

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There are several papers concluding that the free long waves are generated to compensate the discontinuity of the forced long waves across the harbour (or channel) mouth. But the linear waves should be continuous across the mouth and the forcing terms in the free surface condition also should be continuous. Therefore, there is no reason for the forced waves to have discontinuity across the mouth.
In the present paper, we re-analyze the problem of Bowers (1977) in more exact way and show that the numerical discontinuity of the forced waves comes from the Gibbs phenomenon of the Fourier analysis. Therefore this discontinuity has no physical meaning and do not generate the free long waves.

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The season's 18th typhoon hit Kumamoto Prefecture on September 24, 1999, and 12 people were killed in the town of Shiranui facing Yatsushiro Sea. The storm surges produced abnormal sea level rises and caused heavy damage to Matsuai District. The maximum sea level was marked at 7.0 m above C. D. L., and the anomaly of meteorological tide was estimated to be 3.9 m (5:50 a.m.). It is quite dangerous to believe that even very violent attack of storm surges can be completely prevented by man-made structures. Evacuation to safe areas as soon as possible is the best recourse for the inhabitants before a storm surge attacks.

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Under the new seacoast law, protection of coastal environment became important target of the law.In order to promote protection of coastal environment, understanding of topographic changes of the shore and conditions materializing coastal vegetations is important.This study introduces ergodic reasoning regarding beach changes and its related change in vegetation area, taking the Isewan-Seinan coast as the example.Field observation was made as well as the investigation of aerial photograph of the coast.

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A new corrosion prevention method for offshore steel structure using seawater resistance stainless steel sheets has been developed. The seawater resistance stainless steel sheets are welded to the structures by the indirect seam welding method.
This stainless steel lining was applied to the splash and the tidal zones of the inclined levee body type breakwater. Since the breakwater faces an open sea, the splash and the tidal zones are subjects to corrosion by wind brown salt, damage due to occasional impacts with floating debris and fluctuating stress by wind and wave.The experimental results indicate good corrosion resistance in seawater, good impact resistance and good mechanical properties, therefore this stainless steel lining will give successful and economical corrosion protection of steel structures.

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In Toppusi-Wakasato fishery port lying at Lake Saroma in Hokkaido, the fishery infrastructures have been often built on a soft ground. This situation induced asevere problem of deforming in quay structure including steel sheet-pile. The present study allowed to fully understand the cause of deformation. To take measures to meet this situation, double sheet-pile pier have been designed and constructed. For this investigation, we refer to effect of double sheet-pile pierbased on the analysis FEM model.

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Stability performances of composite breakwaters such as deformation against wave actions are investigated considering their probabilistic nature. The mean and 5% exceedance values of the damage rate of concrete blocks of horizontally composite breakwater against design wave are twice and ten times the design value of N⁰=0.3, respectively. The mean value of cumulative damage during 50-year lifetime is 8 times the design value. The mean and 5% exceedance values of the sliding distance against the design wave are 7cm and lm, respectively when a vertical wall of a composite breakwater is designed so that the mean value of the cumulative sliding distance over 50-year lifetime is 30cm. The performance design methods of the breakwaters against wave actions are introduced based on their stability performances.

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A large wave flume named' Large Hydro-Geo Channel' was constructed in March 2000.The flume has a length of 184m, width of 3.5m and depth of 12m with a sandbed of 4m deep in addition to apistontype wave-maker generating 3.5m waves and a current generator with 20m³/s. Large-scale experiments can be conducted with amodel scale of 1/5 to 1/1, without major scale effbct problems. The wave flume is expected to contdbute to promote performance design of madtime structures by large-scale experiments including their failure processes: defbrmation of the structures, breakage of members, scouring and liquefaction of the fbundation. The wave flume should also contribute to reveal the mechanism of sea-seabed interactions.

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The purpose of this research is to investigate effect of compressed secondary air injection and flow resistance in horizontal pipe flow transport system by compressed air. This transport system is very useful for high-density slurry transport because it is easily to separating air from slurry. This paper describe about the mechanism of slurry transporting system using a compressed air in the experimentally. In the experiment, the airliquid two-phase flows have been focused on liquid of low viscosity in long distance pipelines with narrow diameter and discussed the effect of secondary air and relation between air-injection volume and friction loss. As the results of experiments it was shown that the secondary air injection is useful for acceleration of slug velocity in horizontal pipe flow.

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This study describes the design and benefits of a new type of caisson called the “precast form caisson”. Many recently developed caisson construction methods use full-precast plates, whose joints are poor in durability and load bearing capacity. Design and construction methods that compensate for these weaknesses by using full-precast members are very complicated, making them inferior in cost and effectiveness. The authors overcame those drawbacks by using a precast form concrete caisson that has half-precast members and a reinforced concrete composite structure. The caisson is made of H-steel and comprises a high-durability precast form and an RC precast form, which are filled with super-plasticized concrete. In July 1999, we produced a precast form caisson measuring 14m long, 12m wide and 11m high in Tomakomai Port, to verify the method's effectiveness and economic feasibility.

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Harbor structures with suction foundations bring sharp cost reductions over conventional gravity harbor structures consisting of foundation mounds and caissons thanks to their superior structural properties and constructibility.
This report presents an outline of the suction foundation structure, a description of a corroborative field test, and a summary of the results of the primary analysis of measurement data obtained during suction foundation penetration.

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Connection of panels is an important aspect of the design of panel-assembly harbor caissons. PC cables are exclusively installed in the joints and the details concerning the connection such as groove shape, interval etc. should be carefully designed as simple as possible. The strength and aperture of the connecting parts were studied. The quantity of PC installed and the locations of the joints were set so that fully compressive force acts at the connection The mechanical properties of the joint under various limit states have been confirmed by loading tests.
During the application of this technique to a prototype caisson, possible measure was taken to improve panel manufacturing and assembly precision and it was confirmed that the manufacturing precision of this technique is equal to or superior to that of conventional caissons. Panel manufacturing, panel assembly, and grout injection times were also measured to evaluate the effect of this technique on reduction of construction time.

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In recent years, several large-scale earthquake occurred in Japan. Many port structures and fishery harbor structures were damaged.
In the such social background, the-4.0m earthquake proof berth was designed and constructed at Shibetu fishery harbor.“Under water strutted steel structure system that have the piles behind the berth” was adopted for the structural model of the-4.0m earthquake proof berth. The adoption of this structural model is first in Japan.
This paper gave, “the design and construction of -4.0m earthquake Proof berth”, “the details of this structural model adoption”, “The technical characteristics of this structuralmodel”.

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Hydraulic tests were conducted on the characteristics of motion of a buoyant caisson put on a semi-submersible lift barge to confirm the validity of a new caisson transporting and launching method by using a semi-submersible lift barge. It was found that the motion of the barge greatly decreases when it is semi-submerged, and that the motion of the buoyant caisson on the deck is influenced by the wave direction against the barge and the location of the caisson on the deck. Using these results, a safe launching method under wavy conditions was presented.

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Dynamic behavior of a caisson type quay wall resting on pilefoundation against the 1995 Hyogo-ken Nanbu Earthquake was numerically evaluated by a liquefaction analysis based on an effective stress model. The effect of liquefaction countermeasures in the reclaimed land on the dynamic behavior of the caisson structure was investigated using some numerical examples. The feasibility of using non-liquefied material and light-weighted material in the reclaimed land was investigated from the viewpoint of deformation control during the earthquake motion. Further, the differences in the connection condition between the caisson structure and the pile foundation are considered in this paper. The application of non-liquefied material and light-weighted material to the reclaimed land behind the caisson structure has a significant effect on the final residual deformation of the caisson structure.

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The shaking table test and the seismic response analysis of the pier with vertical pile which had arranged theisolation system were done as a technology which improved pier with vertical pile's earthquake resistant ability.It has been understood that the earthquake resistant ability of the seismic isolation pier is better compared with theconventional pier. The analytical method on this study was able to forecast the effect of the seismic isolationquantitatively. For future research, we will investigate the earthquake resistant ability of an actual seismic isolationpier in detail in consideration of the influence of the foundation ground based on the result achieved for thisresearch.

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Effect of Reynolds number on model experiment of wave transformation was examined for permeable breakwaters with a precast concrete armour unit in shallow water region.
Transmission coefficient, K_T increases by the increase in Reynolds number, Re and experiment magnification, N at logarithmic.
Then, linearized friction coefficient, f is decreased with the increase in Reynolds number, and transmission coefficient increases.
As a result of examining transmission coefficient in the field using the equation of the authors which is possible to calculation of transmission coefficient. Then, transmission coefficient becomes almost constant at Re>50×10⁴ and it is about 50%.

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The authors developed a wave dissipating caisson breakwater having a function of seawater exchange. Thiscaisson is a permeable slit caisson with a submerged vertical plate in a water chamber. This caisson generates aone-way flow from offshore to harbour. This flow enhances the exchange between contaminated harbour water andclean offshore water. Originally, this caisson was intended for calm sea. However, the function of seawaterexchange came to be required even for outer breakwaters at large harbours facing rough sea. In offshore areas thewidth of a caisson must be extended to resist against strong wave forces. Therefore, the caisson needs to havechannels piercing itself. In order to make clear its hydraulic characteristic, a two-dimensional hydraulic modelexperiment was carried out. It revealed that the channels never spoiled the seawater exchange, even in the conditionof smaller wave height.

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Many types of breakwater have been developed to withstand the emormous wave force of a deepsea area.
However, most have not proven viable in terms of constructability, economy and so on.
The sloping slit caisson is expected to overcome these problems. It acts to dissipate wave energyby a front perforated wall and a wave chamber.The downward force acting on the slope increasesthe caisson's stability.
This study describes the efficiency, design and construction method, and then explains the resultsof actual construction.

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The relaxation of the construction criterion for leveling of armor stones in mound is expected to reduce theconstruction cost of a breakwater covered with wave dissipating blocks in Open Sea. The stability of armor stonesin the “non-leveling” and “heaping up” construction methods is studied in a hydraulic experiment. The result forthese cases is compared with that for the general leveling. Additionally, the diagram giving the critical depth for anallowable damage rate of approximately 3% in the non-leveling method is proposed.

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Effect of energy dissipation from the viewpoint of the Reynolds number to clear the wave dissipation performanceof the permeable breakwater, was experimentally investigated. And, this experiment was carried out for the wavepressure on the upright seawall that was put behind the absorbing works.
Then, the result was the following. At present, m is the ratio of largest wave pressure as there was the absorbingworks, pm and largest wave pressure as there was without the absorbing works, pm₀. And m clearly decrease with therise in the Reynolds number Re and the dimensionless quantity H_I/d′. Now the incident wave height H_I and therepresentative diameter of void, d′. In addition m is found between 0.23 and 0.93.

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The stability of stones for a rubble mound used as a habitat for rocky shore fisheries resourceswas examined by two-dimensional hydraulic model experiment using irregular waves. We examined thescattering characteristics of stone by changing the structure of the mound and the waves conditions. Based on the results we proposed a calculation method of stable weight of stone materials forrubble mound habitat. The stability number Ns was formulated as a function of the ratioof water depth to wave length. We also examined the influence of weight distributionof stone materials on the mound stability.

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A basic study to assess the displacement process of surface particles of rubble-mound-structure armorlayer under normally incident monochromatic waves has been conducted. The present study tries toinvestigate the relation among wave-induced pressures, velocities, and forces acting onto the armor particlesof rubble mound breakwater slope, and accordingly the reaction of the particles against those forces. At thesame time, the relation among wave height, wave period, and slope angle of the structure on the particleinitial movement has been assessed. A two-dimensional numerical reshaping-model of uniform sphereparticles breakwater was developed to study this phenomena. The simulation involved two separate models, i. e. wave model and displacement model, which are linked by iteration.
It was observed that the maximum resultant wave forces always exist close to the water line during waverun-up or run-down and cause considerable displacement of particles at this area.

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In the preservation of sound coastal environment, public understanding of the state of the coasts and various phenomena occurring on the coasts is important. In order to realize this, scientific knowledge of the coast should be popularized as much as possible. Santa Barbara, California, where is the famous marine resort town of high society in West Coast, was investigated in March and August 1999. Santa Barbara is considered as a field museum to exhibit coastal sciences. People can see various natural phenomena with many explanation panels on the coasts. In Santa Barbara, cliff erosion is severe for much personal property above the cliff to be endangered. A wooden pier was built in the central part of the sandy beach to show shore dynamics. Museums also are useful for the understanding of the local coast.

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A new approach to promote coastal works with public agreement was tested experimentally at the Kinoppu coast in Ohata Town in Aomori Prefecture. New seacoast law enforced on April 1, 2000 requests public agreement to initiate new coastal works. In this study, a public hearing method was tested to exchange views on coastal works at the Kinoppu coast. A method to reach consensus between engineersin the administration, consultants, academic people and inhabitants through discussions and field trip wascreated. This procedure is effective for future public agreement.

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In the planning of the improvement works of fishing port, it is important to pay a deep consideration to the surrounding environment in order to keep the fishing ground sustainable as much as possible, since the fishery depends on the natural resources. In this study, ecosystem in the shallow sea around Koshigoe fishing port, where is rich in seaweed, was investigated. In order to reduce the impact of the extension of the breakwater, a method to select optimum location was given, based on the distribution of the seabottom less covered with seaweed.

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Applications of HACCP (Hazard Analysis and Critical Control Point) for safe food are increasing recently. Due to the food poisoning caused by O-157, the sanitary handling of marine products is strongly required. Before the marine products are supplied to consumers, they are handled in fishingports. Therefore, the sanitary handling of them in fishing ports is indispensable. Fisheries Agency hasperformed examination to improve the fishing ports for sanitary handling. It consisted of questionnaire investigation, hearing investigation and field survey. The results showed sanitary problems related tofacilities in many fishing ports. Better structures of port facilities are proposed to improve the sanitary conditions of them. The proposal will be adopted for the next Long-Term Fishing Port Development Planning.

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Effect of wave history to the beach profile changes due to longshore sand transport is investigated by the numerical simulation by using the contour line change model. The profile changes and wave climate were investigated on the Shimoni-ikawa coast. Wave history in the model simulation was selected as follows; single wave height, two wave heights (low + high and high + low), and gradually decreasing and increasing wave heights. In each case, beach profile changes were compared with the ones observed on the Shimoni-ikawa coast.Qualitative agreement was obtained.

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This study aims to apply the participatory planning method to contribute solving local problems in the fisherysector. Northern Sulawesi, Indonesia was selected as study area. Fish catch had been declining recent ten years and that incident had a serious negative impact not only to fishing operation but also to society. The authors applied the participatory planning methods to analyze problems and attempted to allocate solutions. In many parts the decline of fish catch was suggested by the tremendous increasing fishing effort of foreign fleet as well as non-existence of adequate program for regional fishery management. A Project Design Matrix (PDM) was formed as a trial to solve those issues. The paper also discusses about the lessons learned during the course of participatory workshop.

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Optimum conditions for surf-riding was investigated. They are given by not only wave characteristicsand sea bottom slope, but also wind condition determining roughness of sea surface. Disappearance of past famous surf spot due to the construction of coastal structures was investigated on the Maebara beach in Kamogawa City in Chiba Prefecture by the comparison of past aerial photographs before and after the construction of structures. Surf spot can be recognized by existence of the triangular-shape surf zone as given by the previous study.

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Field observation of movement of nourished gravels was carried out at Kashiwazaki area in Lake Kasumigaura. Beach changes after the nourishment using gravels of median diameter 5.3mm were measured by beach surveys. Aerial photographs were taken by using a model airplane, and shoreline changes were compared. Longshore sediment transport rate was estimated to be around 2.4m³/d (868m³/yr) from July 25, 1997 to October 28 from thecomparison of beach profiles. Nourished gravels mainly moved in the longshore direction whileforming berms.

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Long-term monitoring of beach changes around the port of Hirono Thermal Power Plant in Fukushima Prefecture facing the Pacific Ocean was carried out. Topographic surveys have been conducted around this port since 1972, and beach changes were analyzed by using these data sets. Longshore sand transport rate (Q) wasestimated to be around 8.5×10⁴m³/yr from the change in accumulated sand volume inside the port. This value has the same order of magnitude with 14×10⁴m³/yr predicted by the relation |Q|=780h_c^5/2 given by the author, where (h_c) is the critical depth for beach changes. Measured value is 39% smaller than calculated one. This defference is considered to be due to that a large part of this coast is covered by exposed rock and, therefore, the amount of littoral sediment is small compared with the sandy beach.

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Topographic features of coastal sand dune located very close to the south end of Monterey Bay in California was observed on September 3, 1999. On this sand dune, landward winds formed blowout at many places and they often block traffic in the Highway. Detailed observation of topographic changes caused by blowout was made. Based on the field observation, longitudinal and vertical change of the sand dune associated with the formation of the blowout is summarized in the schematic diagram.

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Cliff erosion was investigated at the coasts around Point Loma in San Diego and Del Mar areas in California. On these coasts, installation of countermeasures against cliff erosion is rare in contrast to the cliff coasts in Japan. On Japanese coasts, concrete armor units are usually installed to protect coastal cliff and this causes decrease in sediment supply from the cliff, which induces beach erosion on the down coast. This gives one of the reasons for extension of artificial coastline in Japan. Overall stability of the sandy beach including cliffy coast as a sand supply source should be deeply considered.

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Beach erosion of the Ventura coast in California was investigated by field observation. On this beach, located on the downcoast of the Ventura River mouth, where eastward longshore sand transport dominates, beach erosion was triggered by the obstruction of continuous sediment supply from the Ventura River by the construction of Matilija Dam. Removal methods of deposited sediment in upstreamregion of this dam, and their effects and influences to the riverbed and the coastline were discussed in Sand Right '99 symposium held in Ventura. This study summarizes the results of this symposium as wellas the results of field observation, and future measures in Japan are discussed through the comparison.

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