In coastal and harbor developments, a construction of vertical sea walls and breakwaters in the sea is often necessary to make a calm water region. Secondly effects of such a construction on the neighboring coastal and ocean environment must be reduced. High reflection waves from the vertical sea wall of-the new construction area may become one of such concerns. In order to reduce the reflection waves effectively, a floating-type wave attenuator that causes wave energy dissipations due to wave slamming is proposed. Model tests show that the floating attenuator is effective for reducing reflected waves from a vertical sea wall, especially for comparatively short waves. It was recommended that the floating attenuator must be near the anti-node position of standing waves.

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In this paper, characteristics of the wave control for wall-type vertical breakwater were investigated experimentally. In the experiments, the motion of sea surface wave facing a vertical breakwater, reflected wave and transmitted wave were measured.
Relation between water surface displacement and the crown heights were discussed. And the characteristics of inner flow mechanism, velocity and vorticity distribution near by breakwater was examined. It was clearly that the crown height having a good effect on wave control of wall-type vertical breakwater was determined.

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Termination of cargo handling caused by long period waves sometimes occurs in a port.
The estimation method of the rate of effective cargo handling days for long period waves is derived from the characteristics of long period waves observed in Tomakomai-port.
The countermeasures by breakwaters is proposed to improve the rate.

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In recent years, there has been shortage of sites suitable for construction of thermal power plants. Therefor, the power plants have been occasionally located on the site exposed to large waves in the open sea. The reclaimation land must be protected from wave overtopping. And, at the same time they are required to be in harmoney with the surrounding environment. So, they must been equipped seawalls to reduce wave reflection. Hydraulic model test was made to develop block mound seawalls with slit walls on concrete caisson taking the advantages of both block seawalls and perforated caissons.

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Topographic changes associated with beach erosion around the Fujimori and Tochiyama River mouths located on the Suruga coast were investigated by using aerial photographs and beach survey data. Shoreline recession around these river mouths is very severe and high berm closed the river channel to cause water level rise in the upstream of the river. A new method to prevent forming high berm is proposed by installing wave dissipating breakwater in front of the river mouth

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Relation between the function of sluce flood way and beach erosion on its downcoast was investigated through the field observation at Showa sluce flood way located on the Fuji coast facing Suruga Bay. Beach survey data were analyzed to investigate temporal and spatial change in shoreline position around the flood way. Shoreline change was compared with the theoretical results. This flood way was partly destroyed by wave action associated with the beach erosion and scouring. Succesive beach erosion around this structure was made clear by comparison of aerial pictures.

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Field trip to Daytona Beach, Ponce de Leon Inlet and New Symrna Beach in Florida was made in September 1996. Past beach changes and present results of field observation were compared around Ponce de Leon Inlet, where sand bypassing was once carried out. It was revealed thaton the downcoast of this inlet beach erosion is now underway to cause beach scarp along the sandy shoreline. Eroded coast is protected by seawall, but foreshore width is too narrow for recreational usage, implying the necessity of future sand nourishment. Beach access at many coasts in Florida is compared with the situation in Japan and future improvement method in Japan is proposed.

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Formative process of asymmetric river mouth bar was investigated through the case study of the Abe River mouth flowing into Suruga Bay. Aerial photographs and bottom sounding data were analyzed. It was found that the location of the opening of asymmetric river mouth is mainly determined by the location of the main river stream, but the straight shoreline of the river mouth bar and its height strongly relate to the incident waves. Breaker height and breaker angle around a river mouth ar were inversely calculated from the longshore sand transport formula and they well explained the sediment tranbsport mechanism around the protruding river mouth.

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Aerial photographs of the Shcnar and Seisho coasts facing Sagami Bay were read to investigate characteristics of coastal topography. Shoreline features are summarized around Enoshima island, a headland built at the Chigasaki Beach, Chigasaki Fishery habor, Sagami River mouth, Ohiso Port, Ninomiya Fishery harbor and Sakawa River mouth.
It is found that beach erosion is severe at the Sagami River mouth and east of Ninomiya Fishery harbor due to river mouth dredging and the interruption of eastward littoral drift, respectively. Oblique aerial photographing looking at the shoreline direction is strongly recommended to realize shoreline features around various coastal structures.

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Causes of increase in artificial coastline associated with the extension of harbor breakwater were studied through the case study of Ohtsu Fishery Habor and Oharai Port both located in Ibaraki Prefecture. Circurating currents with longshore sediment transport toward the lee side of the harbor breakwater were induced after the extension of the breakwater in these areas. Measures were taken after the severe beach erosion to reduce their effect and the natural sandy coastline were transformed into the artificial one. To improve this condition, it is neccesary for related organaizations responsible for coastal protection works to take measures cooperatively.

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The most elementary equilibrium shoreline is that in which there is no net long-term littoral drift. This condition is most closely approached by a pocket beach where there is little or no additional sand being supplied to the beach. The field investigation of 34 pocket beaches was done for the purpose of design of artificial beaches. The plan form of the pocket beach is influenced largely by local geographical features and by the direction of incident waves.

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The number of reformation to coast-preservation structures is increasing because of improvement of their coastal amenities and retention of adequate safety against natural disasters. The authors have surveyed the actual conditions of reformed coast-preservation structures under the jurisdiction of the Ministry of Transport and a total of 452 examples of reformed facilities has been collected. In this paper, the compiled examples of reformed coast-preservation structures are analyzed and the recent trend of the reformation is examined. The reasons to make reformation and evaluation of remaining capacity of existing structures are also discussed.

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Taijima Island is a small upheaval island with an area of almost 15, 000m² which is located in the Mutsu bay at Wakinosawa, Aomori Prf. The outline of Taijima resembles a sea bream. Because the weather is changed abruptly and the coast is consist of rocks. Taijima Island has been faced a serious aeration and erosion due to a strong wind and sea-flow. Furthermore, it is easy to break-down by a strong earthquake. Hence, A study of counterplan keeping the island frim being break-down is conducted.

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An arched beach between capes or harbors becomes to form a stable shore line after repeated erosion and sedimentation for the effect of geographical features.
The arched beach -so called Pocket Beach- which length is approximately 5 kilometers located in Iwanai Town, Hokkaido, is lying between the existing public harbor on the south and the exclusive harbor completed in 1983 for HEPCo.'s Tomari Nuclear Power Plant on the north. The new east breakwater at the public harbor is constructing from 1986. Based on the analysis of beach survey data from 1983 to 1995 on this coast, a numerical model predicting the movement of shore line is modified to ascertain the effect of harbors, and the result of calculation shows the actual movement of shore line.

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There is a flood terrace formed by the flood in 1986 off the Abukuma River mouth. On the terrace, a channel develops year by year, which has an important effect on the sandbarrier development by refracting waves. The cause of the channel development is estimated to be runoffs of the river but the buoyancy effect of seawater is against the erosion. As the first step to study the channel formation, we have searched the condition that the fresh water erode the seawater around the sandbarrier, expecting the effect of wake from the barrier. We get Ri≤0.5 for the erosion from the hydraulic experiments. Then we apply the result to the Abukuma River mouth.

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The Akashi-Ohkura coast rehabilitation program is being implemented to protect urban waterfront area from stormy waves and to create pebble and sandy beaches for recreational use. The remarkable feature of this project is a small pocket beach nourished with sand and protected by breakwaters. It is anticipated to be a promising model for the urban coast characterized with concrete walls and blocks, which plans to be transformed into more accessible and friendly coast. In this paper, an outline of this program is described, and then the results of the field survey are described, which we made in order to study the beach stability and water quality.

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Nakaumi lake is shallow with extensive intertidal sand and mud flats. The eelgrass (Zoesta marina) zone in the lake may function as an important refugee for many resident and transient species, especially where other structural habitats are poor. In this paper, a new method for eelgrass bed creation is introduced and discussed Field observations have been carried out and suitability conditions of eelgrass are evaluated by field data.

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The sea urchin Strongylocentroutus intermedius is very important echinoid in Japan. In recent year, 20million urchin seeds are released in sublittoral zone of Hokkaido. Behavior of the juvenile Strongylocentroutus intermedius was observed on several substrata in oscillatory flow. The adherence rate of sea urchin rises with a increase in the height of substrate.

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A series of artificial reefs were constructed in the nearshore waters in Akita coast faced on the Japan sea. Each reef was constructed in consecutive years from 1992-1996. This provided the opportunity to investigate settlement and recruitment processes in this area. Using belt transects and quadrats, algal and faunal distributions were identified. By comparison of these distributions on each structure for 5 years, different distributions of marine organisms caused by the passed time were found.

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Surf clam Pseudcardium sybillae which lives in sandy beaches along the open sea is important fishery resources at Tomakomai coast. Characteristics of the distribution and the growth of the clam around harbor structures are studied from field observation. Environments of food and sediment for the clam are investigated. It was found that the Population of young clam increased around Tomakomai-port by its accumulation effects.

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Coastal zones represent the “third sector of the earth” which is neither landnor sea, but a peculiar mix of the two. There is no accurate technical description for this sector.
Studies of salt damage, as an environmental problem of coastal zones, have been conducted for a considerable time. As previously reported, a field measurement of seawater and meteorological information, coastal forms, and the distribution of aerial sea-salt particles near the coast of the Kitakyushu area (within 100 m of the coastline) was conducted to obtain fundamental data for comprehensive, wide-area planning of the development of the coastal zone from an environmental point of view. A field measurement was also conducted of the area within a distance of 7, 500 m from the coastline in the northern Kyushu natural coastal zone.
This paper presents an outline of the field measurement methods employed in surveying distribution of aerial sea-salt particles, and explains the results of measurement and analysis.

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Sea salt particles influence on life environments on coastal regions. And high concentration sea salt particles are influential to the growth of plants.
It is necessary to consider the influences of tne sea salt particles on the woods around the coastal region for the planning of waterways in Tomakomai port (Higashi port).
This paper presents a field measurement shows the horizontal and vertical distributions of the sea salt particles from the beach line to the land area, in the open coastal region which has no buildings near the port. In addition, the numerical simulation of the distribution of the sea salt particles is described.

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This study deals with the fishing village in terms of an eco-social system representing a social mechanism in which natural environment and human society are integrated together, and aims at making its structural clarification.
Rausu Town was selected as subject for this study and the due analysis was conducted based on the available date and the questionnairing. As a result, the following points have been proved and clarified in conclusion;
(1) Recognition that wildlife becoming even an indicator for natural environment conservation is also important in the industry and human life.
(2) Reciprocity among nature, the industry and human life by benefit from nature and regulation of industry and human life.
(3) Reduction of the industry and life of fishing village by ecosystem conservation.
(4) Assessment criteria on the value as reduced by ecosystem conservation to human society, taking into account the clarified solution of above mentioned (3).

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Environmental evaluation to biological and ecological aspects of marine organism is an indispenable step for preserving coastal nature. To develop a new environmental evaluation method, release-recaptured test using marked shortneck clam was conducted at tidal flats in Hiroshima prefecture. The test results clarified ecological characteristics of the clam, in which could not be detected distinctly by analyses of water quality and hydraulic factors. Marked clam release-recaptured test was considered as a efficient method for environmental evaluation.

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Seabathing is a very popular sea activity in Japan. However many people were involved in accidents during bathing, and unfortunately, over one hundred people were killed each year. A series of studies are being conducted to investigate the causes of accidents and to improve the safety of the activity. In this report, waves and currents, and movements of bathing people driven by them are measured in a coast of a small island in the Pacific Ocean.

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Possible reduction of biological production in shallow coastal area due to reclamation by fly-ash produced from coal power plant will be estimated as large as 1, 650 ton dry weight/year per each one mega kw power plant. On the other hand, it will be enhanced net-primary production as large as 516, 000 ton dry weight/year after 30 years due to upwelling by constructing a sea-mount on continental shelf with fly-ash concrete blocks using all fly-ash produced, and, at the same time, above mentioned reduction of biological production can be avoided. After past research and develpment studies, fly-ash concrete block has now been qualified its persistence, safety, economical efficiency and so on for the requirement by the Fisheries Agency of Japan. An actual proof experiment constructing a sea-mount using 5, 000 fly-ash concrete blocks of 1.6 m cube is now being carried out in the vicinity of Kita-Matsuura of Nagasaki Prefecture by the financial support of total 1.2 billion yen from the Fishery Agency of Japan for 6 years since the fiscal year of 1995.

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The purpose of this study is to clarify the best habitable conditions for marine organisms in a tide pool. From this view point, field observations on marine organisms andtheir life environment are conducted in the tide pools located at the both natural lagoonand man-made one.
It is found that the number of species of marine organisms in the tide pools located at natural lagoon is larger than that at man-made one. This depends on the roughness of side and bottom, the water depth and total volume of boulders scattered in the tide pool.

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The sand drift at beach has been accelerated in recent years and some structures such as groin, (offshore and submerged) breakwater have been constructed in order to avoid the beach erosion. The method of sand drift control proposed in this paper is focussed on the sand drift in suspention, bed load and saltation by making use of Seaweed Type Textile hydrodynamic resistance in the sea. The materials of Seaweed Type Textile is selected from the view points of the strength, fatigue and biology through the experiments of laboratory and theoretical analysis.
The arrangement of the selected Seaweed Type Textile on the concrete foundation is also proposed in this paper because it strongly effects the stiffeness and sand trap characteristics.

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In constructing an offshore structure in a sea area covered with ice it is necessary to understanding the ice load exerted by drift ice. To determine the adhesive and the shearing strengths, and their relation to the bending strength, we used the first-year ice of Notoro lagoon. To define the stress distribution of shear strength of the test specimen, we employed FEM elastic stress analysis. The adhesive strength test specimen kept outdoors separated at the attached surfaces, yielding an adhesive strength of 50 kPa. The shearing strength test specimen ruptured in bending. The shearing strength was found 0.2-0.3 MPa.

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The proper evaluation of ice load on offshore structure in ice-infested area makes it possible to construct the structure. It is the key to clarify that the scale effect, that indentation ice pressure decreases as an area of structure with ice sheet increases, is caused by the nonsimultaneous failure of ice sheet. Medium scale field indentation tests (MSFIT) in JOIA project had been conducted to evaluate the ice load since 1996 winter, using natural sea ice in Lake Notoro. This paper shows the results of ice indentation tests conducted in 1997 winter.

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The effect of the shape of leading edge of an ice sheet on ice force is investigated through the field ice indentation tests using natural freshwater lake ice. The shape of leading edge of natural sea ice near blaff in the harbour is also measured to know how the roughness of its surface is in the real world. And, the shape of leading edge of natural sea ice after ice indentation test is measured to evaluate the actual contact area of ice with structure, in turn to estimate the nature of subsequent (potential) local failure of ice sheet.

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Ports and fishing ports in cold regions in Hokkaido freeze during winter. Changes in sea level after ice sheets have adfrozen to port facilities, such as floating structures, quays and breakwaters, create vertical ice loads. Floating structures often suffer damage from sea ice, making it important to consider the influence of the sea ice in the design of such structures in cold regions.
In this study, investigations of sea ice conditions were conducted to estimate ice loads, and the distribution of ice thickness and the area range where the ice sheet undergoes flexural failure were clarified.

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Ice sheets in rivers, lakes, lagoons, port in cold regions are used for a variety of purposes. They are used as tracks on the ice, as roads for automobiles, as runways for airplanes, and as footholds for the construction of structures. Knowledge of physical and dynamic characteristics of natural ice sheets and techniques to estimate the hearing capacity of natural ice sheets against vertical loads are required to safety in using ice sheets. In this study, the authors indicate the theoretical values of the bearing capacity and the deflection of ice sheets under the condition of partial flooding, and compare with the experiments values, and made the experiments with the longtime-loads.

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The Okhotsk Sea of Hokkaido is covered with drift ice in winter. Drift ice which rushed into Saroma Lagoon caused heavy damages to scallops and oysters, and its facilities. So the ice boom which prevents the drift ice from rushing into is started constructing in 1994, and is completed its 80%. Especially, ice boom with net that set at the center of lagoon mouth completely shut out the drift ice. However, decrease of the amount of sea water exchange is worried about.
In this paper, the authors make two experiment about movement of ice floe, and prove that quality of water does not become worse because of ice boom construction.

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Judging from the mechanical properties of ice sheet, ice sheet is an elastic-plastic substance, and in high strain region, it is seemed as elastic material. Generally ice load acting on structures and mechanisms of its fracture mode depend on the strain and stress rate. In the case of large moving ice sheet colliding with structure, the decision of deformation area of ice sheet was very difficult. In this paper, therefore the authors clarified the deformation area of ice sheet which collides with pile structures at high speed.

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In the past ten years, there has been a tendency for frozen areas in the Okotsk Sea to become narrow, possible because of global warming. In the winter of 1991 waves broke over the south breakwater at the port of Abasiri and bringing with then ice floes which overtopped the breakwater causing grate damage to the oil pipelines and dolphins behind the breakwater.
In this paper, the authors proposed the facility preventing from overtopping ice floes and design method for the phenomena through the systematic experiments of the impact ice load acting on pile structures and the overtopping velocity of ice floes.

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Ice floes are widely known to abrade surfaces of structures constructed in sea water areas where ice floes move actively. Since both corrosion and abrasion by sea ice cause a decrease in the thickness of the steel of marine structures in frozen sea water areas, differentiating these effects is difficult in practice.
We measured thickness of the steel sheet piles used for the side walls of the channel and for the piers of the bridge built over the channel. From the measurements we found the abrasion of the steel by sea ice movements and developed a technique to estimate the abrasion depth.

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In cold regions, natural ice sheets adfreeze to piles, bridge piers, oil-rigs, etc. constructed in the sea and the ocean. Due to changes in the water level, vertical ice loads act on the structures. These ice loads need to be studied to design pile structures affected by natural ice sheets.
Ice loads acting on pile structures with circular cross-sections have been explained analytically. However, ice loads acting on pile structures with other cross-sections have never been researched. In this report, we study ice loads acting on pile structures with elliptical or rectangular cross-sections theoretically and experimentally.

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Mechanical tests were conducted under around -2°C with small size specimens prepared to obtain compressive and bending strength of the ice sheet facing the indentor, which is one year sea ice. Physical characteristics of the sea ice were summarized using various relationships as follows: density vs. salinity, compressive strength vs. density or salinity, compressive vs. bending strength, compressive strength vs. grain structure and inhomogeneity in compressive strength in the horizontal direction. The test results can be explained well by assuming that both compressive strength and bending strength are proportional to D-1/2 (D: crystal grain size).

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The surface of concrete structures is subject to abrasion when they are constructed in sea water where ice movement is active. Abrasion occurs due to the friction force between ice sheets and the structure caused by the ice force working on the structure.
Over the past ten years we have been conducting experiments with many types of concrete and their possible coating materials to find their characteristics of abrasion due to movements of ice sheets. In this experiment we calculated the abrasion rates (average amount of abrasion per 1km movement of ice sheets) of various kinds of stone needed to estimate the abrasion amount due to movements of ice sheets which contain sand particles or not, and we also clarified the mechanism of abrasion.

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It is cralified that doubly placed submerged break waters reduce the incident wave height effectively where the tidal range is small.
Coastal structures constracted in Ohotuku Sea coast of Hokkaido have been attacked by water waves and drifting ice floes. In this paper, the authors cralified the stability of armor stones on doubly placed submerged breakwaters whitch are attacked by waves and ice floes through systematic experiments.

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It is important to define the relation between the unconfined compressive strength of sea ice and the indentation pressure in estimating the ice force loading on structure. However, as variance the value of the strength of sea ice and the ice force becomes large, it is effective method to use probability and statistics. In this study, the authors, the authors understand between the strength of sea ice and ice force, and relate them. Further, the author study the effect of scale factor to simulate ice pressure corresponding to relation ice strength and ice force.

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Ports and fishing ports in relatively cold i regions in Hokkaido freeze during winter. Controlling freezing in these ports would promote economic activity in winter. Methods to protect ports from freezing have been developed and the effective application of these methods requires classification of characteristics of freezing. This study investigates characteristics of freezing, based on field surveys conducted every winter over 9 years.
It was found that significant increases in frozen area required temperatures of - 15°C or below, and that freezing was accelerated by the presence of sea ice.

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Lake Saroma is an inland sea-lake on the Sea of Okhotsk. As the lake's environment is suitable for aquiculture, it is widely used for natural sea farming.
Ice floes usually reach Okhotsk Sea coast of Hokkaido from late January through early February. When ice floes arrived before Lake Saroma had sufficiently frozen up, the inflow of ice into the lake damaged aquiculture facilities. As a countermeasure for this, construction of ice booms to control ice floes began in 1994 and 10 spans out of 13 planned have since been completed.
In this study, the effectiveness of ice booms in controlling ice floes in an actual sea area is confirmed, factoes concerning the tension of the main wire, an important point in design, are analyzed using research results, and the design and actual values are compared.

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A study on ice loads under ice-structure interactions started in 1993 as a Japan Ocean Industries Association (JOIA) project. Medium Scale Field Indentation Tests (MSFIT) was conducted inwinters in 1996 and 1997, which include ice indentation tests, tests on physical properties ofice sheetand measurements ofice sheet deformation.
The paper describes the results of measurements of ice sheet strain using strain gages and theestimation of the strain range under ice -structure interactions obtained at a winter test in 1997.

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The velocity field in a surf zone was experimentally investigated, and the effects of an undertow after wavebreaking on turbulence and wave motion are discussed. In order to reveal the mechanisms of sand suspension overthe bottom, the measurement of velocity distribution of sand transportation was tried by the particle imagevelocimetry.
It is important to understand the reciprocal relationship between turbulence caused by wave breaking anda cross-shore steady flow, such as a rip current or an undertow, as both of these are closely related to sedimentrolling up and cross-shore sediment transport. On the other hand, high-strain turbulent flows that have threedimensionallycoherent eddy structures with oblique vortexes are generated in a surf zone, and the steady flow isstrongly influenced by the three-dimensional vortexes generated at thistime. This study was designed to investigatethe three-dimensional characteristics of the velocity field and bed erosion in a surf zone, and the effects of undertowon them, of undertow on them, in order to clarify the mechanisms of fluid motion and the cross-shore sedimenttransport in this region.

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There are a stable point relating the movement of sand near the wavebreaking point in the beach profile.
It is described in this present paper that the change of beach profileat 17 coasts of Japan is analyzed by using Ursell number (U_r=H_bL_b²/h_b³) in relation to waveheight (H_b), wave length (L_b) and water depth (h_b) at the wave breaking point from the wave observation data, and a stablepoint (h_c) of beach profile is explained by the Ursell number (U_r) andthe wave breaking point (h_b).

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A sand tube has long been applied as riverain, coastal and (fishery) port structures.Its typical damage is the lateral displacement of the part locally rotated by externalforces and scouring. We propose a sand tube with twins. Theoretical and experimental (scale model and prototype) analyses reveal the following results.(1) Eachtube has a cross-section of hydrostatic arch.(2) Typical failure or creep disappears.(3) 2/3-dimensional strengths rise to 1.4 to 2.8 times.(4) Wave force and its momentdecrease to 60% and 25%, respectively.(5) Wave refraction turns erosion into accretion.(6) Breaker impulse is absorved by plastic wave.

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A field observation for the on-offshore topography change and the sand compaction on anartificial beach face was conducted under the high wave condition. The slope of artificialbeach face was set steeper than of the original beach face. The artificial beach face wentback to original beach face such as previous results. However, sediment characteristicsdid not change due to larger external force than it corresponding with sediment grain size.At the points on the artificial beach face, data of sand compaction and ground level changewere obtained.

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To estimate and find the sedimentary sources near and in the fishery port of Hashidate of whichbreakwater arrangement is very complex, the ratio of the geochemcal elements to construct the sand isobtained by the X-ray fluorescent spectrcscopy (abbreviated by XRF). The method of ratio matchinggives the correlation number which is different from the statistical meaning and shows the similaritybetween two sand samplesin geochemical distribution. In a result, the sedimentary sand in the port isfound to besimilar to the sand on Hashidate swiming beach. So the sedimentarysource of the port isconsidered to be sand from Hashidate swiming beach. The comparisons of shoreline changesat Hashidateswimming beach and contour lines near the port show that the result is very reasonable. This proves thatthe method of ratio matching using geochemical elements in the sand is very reliable for finding thesedimentary source.

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