From late January to March the sea area along the Okhotsk Sea coast of Hokkaido are covered by ice floes moving south from northern region of the Okhotsk Sea. Ports and fishing ports in the area freeze during winter. Therefore all activity in ports and fishing ports stops completely during icy season. On the other hand, Okhotsk Sea coast of Hokkaido has a lot of good fishing grounds and is rich in marine products such as scallop, crab, and salmon.This paper shows new method to utilize the fishery port effectively during winter season by means of stocking live scallops in its basin.
Bivalves are important fishery resources. For example, surf clam (Pseudocardium sybillae), lives in sandy beaches along the open sea in northern Japan. It has been reported that an increase in young bivalves of surf clams in tranquil areas around newly constructed ports. A large number of young bivalves are often cast onto the shore by high waves in winter. The process of mortality and behavior of young bivalves due to waves must be clarified. In this study, in order to grasp the behavior of bivalves after released out of sand, the behavior of bivalves over sand ripples under oscillatory flow was experimentally investigated.
Most short-neck clams in Hokkaido live in its eastern part. Zostera beds are frequently found around tideland inhabited by short-neck clams. Their habitats are therefore extremely limited. The reclamation of short-neck clams' fishing ground is being promoted accordingly. Fishing ground reclamation is conducted by taking into account the height of ground with high habitat density as that of reclamation ground. This research examined the relationship between the growth of short-neck clams and ground height (tideland emerging time). Results showed that, in the research period, the ground height with better growth of short-neck clams occurred when the tideland emerging time was up to three hours daily on average. When tideland emerging time was longer, growth was less noticeable.
Wire tagged short necked clams (Ruditapes philippinarum) were released to the artificial pocket beach to evaluate possibility of providing a habitat for the clam, in which maycreate an amusement site for clam-gathering. 1000 tagged clams were released to the site by spreading the dams directly to the sand beach where was surrounded by concrete blocks and by placing the dams into net cases. The tagged dams increased an average 3.4mm of shell length after 49 days. However, the tagged dams which were released directly to the sand beach were killed and fed by moon shells, and the recaptured number was zero after 199 days. The artificial beach can provide an event of dam-gathering where the dams are spread occasionally by human work. Low possibility of creating a sustainable habitat for the clams in this pocket beach is considered.
Seaweed forests composed of Eisenia bicyclis Setchell and Eclonia cava Kjellman are widely distributed along the coast of central Honshu Island, Japan, facing the Pacific Ocean. This study aimed to clarify a zonation of these plants and their causes. We measured their stipe arid maximal blade lengths for one year and attaching force of their hold fast to a substratum in a field and a fluid force on them in a laboratory. They grew rapidly from winter to summer, and maturated from summer to fall. We observed intraspecies and inter-species zonation. Attaching force of their hold fast depended on a condition of substratum surface. Under an oscillatory current, the dominant fluid force exerted on the plants was a drag force in a blade part but an inertial force in a stipe part.
The effect of cobble and boulder zone for the juvenile sea urchin (Strongylocentrotus intermedius) in wave environment was experimentally studied. The experiment was observed in oscillation water flow tunnel with 8.9cm-60.0cm diameter columns as models of cobble stones and boulders. The settlement ratio of the juvenile sea urchins in oscillatory flow depended on the size of the column diameter. The bigger diameter column model was lower the settlement ratio. The current velocity in the gap among columns did not increase in spite of accelerating the current velocity on their surface. Even with increased current velocity, the juvenile sea urchins' settlement ratio among the columns was so high that it proved an effective habitat. However, the ratio dropped in increased current velocity for the biggest model of diameter (60.0cm).
Since recently artificial reef have been installed offshore on the seabed having rough wave, the stability of them becomes of crucial importance. However they consists of not only tubular members but also plates and box shape members, the drag and inertia wave force coefficients for stability evaluation are uncertain so that we determined through model testing. Furthermore, this kind of. the artificial reefs are required the function of fish-gathering and propagation by attaching the plates causing upwelling current and pilling up stones on their top. The paper also presets that observations and measurements of the current adjacent to the reef and possible wash out of the stones secured by fence in order to confirm the validity of such devices.
The purpose of this study is to clarify the best habitable conditions for marine organisms in man-made rocky coast. From this viewpoint, the field observations on plane and vertical distributions of marine organisms are carried out in man-made rocky coast facing Osaka Bay. In addition, the rate of seawater How due to wave and current is surveyed by the plaster ball method at several points in the coast. The relationship between topography and living conditions of marine organisms in man-made rocky coast is discussed based on the results of these observations.
The Takachi fishing port (Ishina area) made the seaweed bed behind the offing breakwater for the ecosystem. Surface treatment was given so that the seaweed was parasitic in putting on fixed base of seaweed bed and armor concrete blocks which not was easily. Sargassaceae, EckIonia stolonifera, and Undaria pinnatifida were set about the object seaweed. It has been understood that the block with the ditch is effective in the parasitism at the early stage of EckIonia stolonifera this time.The influence of the surface treatment on the parasitism of the seaweed, and its becoming big shape and appearing effective in the parasitism at the early stage of Ecklonia stolonifera was able to be understood.
In the ocean, seaweed has a major influence on marine resources, by providing spawning grounds for fish, breeding grounds for fry and feed for seaweed-eating creatures. Seaweed itself is also a marine food resource. It also plays an important role in conservation of the global environment as it settles carbon dioxide, which is a cause of global warming, by photosynthesis. In the future development of coastal areas, taking into consideration the breeding of seaweed on breakwaters and other coastal structures will be as important as conserving existing seaweed beds. The authors have found two ways for artificial formation of seaweed beds. One is the rear step method, which is a structural improvement to place flat beds behind the sloping breakwater to facilitate the breeding of seaweed. The other is a method to help seaweed adhere by improving materials and structure surface forms. It was found from the research that sloping breakwater with rear step were very effective for the formation of seaweed communities and there was more seaweed on structures with an uneven surface.
The possibility of the conception on an offshore thermal power plant (TEALAND) t hat does not depend on a conventional reclamation method is evaluated here for the purpo se of reducing the cost to supply electric power. The special feature of this concept ion consists in paying attention to the space under the surface of water. In this conception, the sea occupation area of the power plant is reduced as mu ch as possible by arranging the generation equipment into the layered inside box. The n it reduces the construction cost by constructing both the component and the generation equ ipment simultaneously at land and then shortening the construction time. In this study, seismic responses of the softlanding power plant are analyzed wi th total and effective stress methods and the equipment specifications are discussed for pra ctical utility.
Dynamic behavior of a caisson type quay wall resting on pile foundation with exp anded base was numerically evaluated by a liquefaction analysis based on effective stress model during 1995 Hyogo-ken Nanbu Earthquake. The effective stress model used for the liquef action analysis during earthquake motion was a strain space multiple mechanism model. The deformation during the earthquake ground motion induced due to pore water press ure in the soil behind the caisson quay wall. Though the displacement response of the caisson q uay wall with pile foundation was smaller than that of the caisson without pile foundation, the deformation was mainly induced by the increase of pore water pressure.
In reclaiming a wide tract from the sea, the evaluation of the differential sett lement is important problem. As a factor of the differential settlement, the spatial vari ation of soil profiles can be considered. Authors developed a numerical method of the differential settlement. The developed numerical method, which is based on FOSM (First Order Second Moment), can evaluate the reliability of estimating of the spatial variation of soil profiles. In this paper, contents of the numerical method are shown, its utility is examined by applying for a submarine clayey deposit in Iwakuni.
This Paper introduces, as a case study, the new direct measurement way of underg round steel sheet-pile displacement at TOPSHI-WAKASATO Fishery Harbor in Hokkaido. This direct measurement way can conjugate measurement of underground steel shee t-pile displacement deformed by soft ground or earthquake.
As for the construction of circulating water pipeline for Lumut thermal power station in Malaysia, the works was executed under the design/construction lump contract. Therefore, the hydraulic model test was carried out for the intake structure to confirm the hydraulic characteristics to satisfy requirements from the client. And rapi d construction was necessary for circulating water pipeline due to its long exten sion and short construction period. In this paper, we report the result of hydraulic model test for the intake structure and an outline of construction method.
“Inclined levee body type breakwater” is a structure that has inclined reinforced concrete boards supported by steel piles. The principal features are as follows, a) Horizontal wave force and reflection wave are less than curtain wall type breakwater such as caisson. b) Ground improvement for the poor subsoil is not necessary. c) Tidal current is not so much obstructed. This type breakwaters were constructed in some fishing ports, for example Yobito (Hokkaido Pref) and Otsushima (Yamaguchi Pref.), where wave conditions were calm, and poor subsoil were layered. This paper indicates the hydraulic experiments for grasping the characteristics of wave force and the most suitable figure of inclined levee body, to apply for the sea area that the deep water wave effects in, and mentions about the investigation of jacket structure as a support.
The wave height distribution along reflective structures induced by obliquely in cident waves is discussed based on experimental results in a wave basin. The experiment was p erformed with regular and irregular waves. When the waves with small incident angle don't bre a k, the Mach -stem is formed along the wall and the wave height increases progressively alon g the wall. The irregularity has no significant effect on the distribution of wave height.
The construction of the floodway of Krueng Aceh river mouth in Indonesia decreases the discharge of the river leading to develop a sand spit at the mouth. The sand spit in turn causes river mouth clogging and troubles in navigation. Nears hore current field near the mouth has complex distribution due to complexity of the topography near the mouth. In this paper, the wave deformation and near-shore current to evaluate sedimentation near the mouth was analyzed by means of datacollection, interview and field reconnaissance.
Laminar boundary layer behavior under irregular wave motion has been investigated in this paper through numerical methods. The irregular wave velocity has first been generated and later used for flow computation in the boundary layer through low Reynolds number κ-ε model. The generation of irregular wave velocity shows a satisfactory result when compared with input spectral properties. Obtained k-ε model results have then been utilized for detailed analysis of time variation of bottom shear stress with freestream velocity. Model results show that the bottom shear stress is more dominated by high frequency component waves than that for velocity. It is also very sensitive to freestream velocity variations and does not always respond in the same way to similar velocity conditions. A comparison of irregular wave bottom shear stress with that of monochromatic waves shows that the significant bottom shear stress closely corresponds to that of sinusoidal wave computed with the highest two-third of wave heights (H2/3).
In this paper, the submerged structure for wave control using a flexible sheet with some springs was proposed. To investigate the characteristics of this structure, the ratio of reflected and transmitted waves was calculated in two-dimensional case, using the boundary element method with three cases of 1, 3, and 5 sheets. When the oscillation of sheet was caused by water waves, the phase difference between water waves and motion of sheet occurred according to wave period. Considering this phase difference in numerical analysis, it was found that analyzed result agreed with experimental results.
Installing artificial fish reefs is expected to improve and preserve sea environment as well as fish cultivation. In order to attain such objectives, fish reefs should have adequate function to gather fish. In this research, the wave generated sound from fish reef is considered to be one of the important factors to gather fish. Laboratory experiments were carried out to measure the sound pressure from fish reef models. In the experiments, number of fish reef models and their arrangements were changed and their effects on generated sound pressure were investigated. Numerical analysis was also conducted to calculate flow conditions around them. It was confirmed that the sound pressure in front of structures is more pronounced by installing another structure in far side.
A boundary element method is proposed to analyze the interactions between waves and motions of a floating body. In this method, by use of a Green's function which satisfies the boundary conditions on the water surface and the bottom, the unknown variables are reduced to the amplitudes of motions of the floating body and the velocity potentials on the submerged surface and the breakwaters, if they are exist. these unknown variables can be obtained simultaneously by solving the discretized linear equations. The amplitudes of motions of the floating body are calculated and significant resonance between waves and the motions of body are appeared. The numerical results are confirmed by comparing to the experimental results in two-dimensional cases.
This paper presents a wave response analysis of a box-like Very Large Floating Structure (VLFS) near a breakwater. The program developed utilizes the modal superposition method for both rigid body motions and bending modes of the floating plate. The computation size has been reduced by employing a Higher Order Boundary Element Method (HOBEM) which utilizes quadratic 8-noded panels, and the finite water depth Green's function has been employed. The inclusion of breakwater has also been made in the context of HOBEM; thus the dynamic interaction effect between the breakwater and the floating structure is automatically satisfied in the sense of the linear potential theory. The effect of a breakwater on reducing the wave response is investigated.
Considered herein is a floating bridge for the strait crossing between Kyushu and Shikoku (Houyo strait). The bridge consists of two rows of floating foundations which are semi-submerged type or pontoon type, and they support two box-girders for road traffic. Wave response of the newly proposed floating bridge has been examined based on the linear potential theory and the linear elasticity. Preliminary analysis performed herein have shown the applicability of such a bridge for severe wave conditions, i. e., the significant wave height of 5m and the wave period of 8 second.
The breaking limit of multi-directional random waves is still unknown and is req uested to be formulated numerically from coastal and ocean engineering viewpoint. In this paper, a brea king wave gauge is newly devised to measure the wave breaking inception as accurately as possible. Indoor laboratory experiments have shown that the breaking wave gauge is able to measure the breaking inception an d that the breaking limit of multi-directional random waves becomes smaller than that of the regular wave. T he critical wave steepness of multi-directional random waves is revealed to become smaller as the spreading p arameter Smax increases.
Significant oscillations of moored ships with long period are often reported in Tomakomai East Port. This long period oscillation of moored ship is considered to be caused by the long period harbour oscillation or the resonance between harbour oscillation and the mooring system. In the present paper, numerical analyses of the harbour oscillation with BEM are performed. It clarifies what types of harbour oscillation occur in what wave conditions.
It is described in this paper that the classification moving to onoffshore of sand bar relates to the reflection coefficient of waves from shoreline, and the movement of sand bar is decided by the shoreline change rate and the topography change rate between shoreline and stable point not having the remarkable movement of sand near the wave breaking point on beach profile obtained from sounding.
A large number of coastal and port structures, which have been constructed to prevent wave overtopping or beach erosion, have been damaged in Japan by severe marine climates caused by strong monsoons in winter and huge typhoons in summer to autumn. The reports of damaged structures, especially sea walls, for the past five years from 1992 to 1996 are selected from the annual books of damaged facilities edited by Port Bureau of Ministry of Transport in order to investigate the characteristics and causes of their damages. We have made statistical analysis for 197 cases of damaged sea walls. The analytical results show that scoring is a main cause of sea wall damages for each type of sea wall andtherefore the establishment of countermeasures against scoring is of great importance to reduce sea wall damages.
Beach characteristics and Sand fill movement of the Kashiwazaki beach were investigated by using aerial photographs, topographic chart and beach profile chart as well as field observation of the coastline. We proposed the best beach conservation plan for the beach face front of the step-type revetment at the joint of groin A.
An artificial beach has been constructed in coastal region facing to a coral reef. To prevent beach erosion, characteristics of sediment movement on the beach should be investigated in flume experiments. The watervelocity becomes very large with wave breaking zone on the reef. Therefore, the critical amplitudes of velocity on reef should be defined for the promotion of beach protection methods. The-experiment results demonstrate that the critical velocity is related to the shields number.
Formation of scarp associated with offshore dredging is modeled with the assumption of equilibulium profile. Offshore dredged hole is assumed to be refilled by cross-shore sand transport as well as longshore sand transport. The Fukiagehama coast in Kagoshima Prefectrure is considered for an example. Predictive model of the formation of scarp is developed.
In spite of the importance of knowing sediment transport near a river mouth, it has not been well studied because of the complexity of exerting forces and topography. This study has developed an analytical model to reproduce large cuspate topography which has been often observed at the Abukuma River mouth. The velocity field of river flow is evaluated by the two dimensional jet model and the longshore current field by Longuet-Higgins's model. Along stream lines for the superimposed field of the two flows, the continuity equation of sediment is solved. Computational results for several river and wave conditions show that high river discharge is especially effective to form large cuspate topography. Keywords: sediment transport, river flow, longshore current, computation
Beach changes due to the elongation of river mouth jetties around the mouth of the Kinoto-dainichi River in Niigata Prefecture was investigated. Topographic surveys were conducted five times from 1988 to 1997 and sea bottom changes were compared. Southward longshore sand transport prevails at this river mouth. After the extension of jetties south beach was gradually eroded, whereas sand accumulated at the river mouth. The function of an artifical reef being insta Iled off the mouth of the Kinoto-dainichi River to prevent sand deposition inside the river mouth was studied.
River mouth improvement of floodway of Ohya River flowing into the Shizuoka coast was investigated. This river mouth is located at the erosive coast and shoreline has been retreated for a long time. For the measures against beach erosion detached breakwaters have been built. Since northward longshore sand transport is predominant at this river mouth, sand accumulated at the mouth due to the accumulation effect of these detached breakwaters. In order to improve this condition, a method using submerged breakwater installed off the mouth was planed and numerical simulation was carried out to verify the usefulness of this method.
Formation of a group of sand spits on lakeshore was investigated in Lake Saroma in eastern Hokkaido. Several sand spits develop by longshore sand transport generated by wind waves in eastern part of slender shape of this lake. Wild flower park is located in this area, but recently seawalls to protect cycling road against lakeshore erosion were built, which kill scenic beauty of natural lakeshore. The cause is due to the approximation of cycling road to the shoreline, which is changing responding to the movement of sand spits. In order to improve this condition appropriate setback is needed.
A method to consider the causes of beach changes from the limited field data is introduced by taking the Katase-higashi and Shichiriga-hama beachs in Kanagawa Prefecture as the examples. Aerial photographs were read and shoreline changes were studied. Sounding maps taken in different years were compared. Field observation was carried out to investigate present shoreline situation. Based on these limited field data, it is found that seasonal, cyclic beach changes are dominating on the Shichirigahama beach, and net sand loss is caused by wind blown sand.
Field observation of coastline in Kagawa and Tokushima Prefectures was carried out to investigate natural characteristics of river mouth bar, gravel beach and sand spit. Topographic features of river mouth bar formed by successive action of longshore sand transport were studied at the Yoda and Minato rivers. Beach erosion triggered by wave reflection due to the construction of the breakwater of Komatsujima Port was found at the Katsu-ura river mouth.
Coastal characteristics of the construction site of Hitachi Bypass Road were investigated by using aerial photographs and topographic chart as well as field observation of the coastline. Existing seawall of the reclaimed land, where a new road is constructed, was found to be damaged by wave action because of protrusion of this seawall into the sea. Causes of the failure of this structure were studied to obtain useful information for the planning of the new road.
Causes of damages of seawall due to storm waves on the Hirono coast in Shizuoka Prefecture were investigated. In 1997 high waves were generated by five typhoons in this area. Direct cause of the failure of the seawall is due to the wave action, but gradual decrease of sea bed due to beach erosion is the indirect cause. Beach erosion of this area is deeply connected with the retreat of river mouth bar of the Abe River.
In order to study overall geomorphological features of coastal area of the Nata coast and the bayshore in Moriye Bay in Oita Prefecture, field observation was carried out between April 30 and May 2, 1997. Areal photographs of these areas were also taken in March and October, 1997. A sand spit is formed at the mouth of this bay. This sand spit was formed by sufficient sand supply from upcoasts, but at present this continuous sand supply is totally interrupted at many locations by construction of artificial structures such as harbor breakwaters and detached breakwaters.
In September, 1997 high waves attacked the Shonan coast in Sagami Bay. Due to this wave attack beach was severely eroded and beach cliff erosion occured in wide spread area. Field observation was carried out during and right after storm waves. It was found that sand accumulated on the east side of the various coastal structures and thus beach erosion was caused by westward longshore sand transport induced by easterly incident waves. Particularly this typhoon waves are of characteristics of long period waves.
Field observation was carried out on beach erosion of the Shonan coast caused by Typhoons 9707 and 9709. This coast is located in Sagami Bay and therefore usually relatively calm waves are incident. However in 1997 unusual, high waves and long period waves generated by several typhoons attacked this coast. Beach was eroded away and high scarp was formed by the combination effect of high waves and longshore sand transport induced by obliquely incident waves.
Beach changes around Shinkawa fishery harbor in Niigata Prefecture were investigated by using beach survey data since 1985. At this coast river mouth jetties were built at the Shinkawa River and Shinkawa fishery harbor originally located inside the river mouth was enlarged to widen mooring site. To this purpose new breakwaters of the outer harbor were built. Southward longshore sand transport dominating on this coast was obstructed by these breakwaters to cause beach erosion on the downcoast. In order to solve this problem sand bypassing is required.
Long period waves often cause large surging motion of moored vessels by resonance to naturaloscillation of the mooring system composed of the elastic hawsers and ship body. In order to preventthe amplification of long period waves in harbor by the reflection, the wave absorbing beach isproposed. The artificial beach with mild slope can reduce the reflection coefficient. The appropriateinstallation planning for beaches in harbor is discussed on basis of the results of numericalsimulation.
There are many fishing ports facing the trouble that any plan composed of only the conventhional protective facilites is deemed functionally difficult to cope with long-period waves which generate peculiar flow called “Abiki”(secondary undulation) and so forth. Such secondaryundulation causes collision between the moored fishing bouts in the mooring basin and also cutting-off of the mooring ropes. In constructhion of the breakwater for Ijima fishing port in Anann City of Tokushima Prefecture, the wave-control gate newly developed against long-period waves was taken into consideration as the most effective construction method and thus the study on its concept, advantage and structure was carried out.
Physical model tests and numerical simulations are carried out to obtain characteristics of reflection of long period waves. The results of the physical and numerical tests demonstrate that waveabsorbing materials with enough width can be reduced reflection coefficient for the long period waves in a narrow channel. Especially, the wave-absorbing material has a good effect on reduction of large waves. In harbors where small long period waves are observed, a beach and tidal flat may be applied as practical countermeasures against the long period waves.
The object of this investigation is to estimate viability of coastal protection facilities, fishing port construction and so on against tsunami runup. As the first step, we carried out a hydraulic experiment on a detached breakwaters and with no structure. Detached breakwaters were of permeable, impermeable and continuous impermeable varieties. Offshore distance, slope of runup zone and characteristics of tsunami were varied. As a result of the experiment, it was clarified tsunami runup was mainly influenced by the diffraction and that surface elevation around shoreline was influenced by the detached breakwaters and the slope of runup zone. As a whole, the effects of opening width and overflow were great