This report introduces influences of physical environments on living things on tidal flats and on reef areas. Bottom change and ground temperature on emerging tidal flats understood to be severe conditions to post-larvae of short-necked clams. Next, it was explained that feeding of sea urchinsare controlled by wave motion. From the result to apply them to a site, it understood it to be an important factor that a physical environment decides a distribution of a predator and a prey.
Study results of ecotecnology for coastal development are introduced. The first result is an analysis of relation between annual maximum significant wave height in front of port structures and sessile organisms (sessile animals, motile organisms, and sea algae). The second result is a report of a mesocosm experiment of tidal flat. Ecological environment of the mesocosm and activities of benthos were studied.
A field survey shows that some creatures which lives in rocky shore observed in sandy beach after construction of artificial reef. Furthermore, due to the wave dissipation effect, juvenile of hen calm increased behind the reef. A model in this study is to help better understand the effects of facilities and predict changes in ecology after construction. Data files which contain information on representative kinds of creatures are collected, and individual reaction model, and an ecological model with which one can estimate the direct and indirect effects of shore protection facilities are developed.
To obtain the basic knowledge on marine surface wind, it was investigated that relationship between wind velocity and significant wave parameters and turbulent characteristic of wind by using the data measured from MT station at Osaka bay. Obtained results are as follows: (1) It was confirmed that the measured wind and wave data were satisfied 3/2 power low.(2) Turbulent characteristis of wind velocity was similar to the turbulent boundary layer theory such as open channel flow.
The characteristics of coastal topography, waves and nearshore currents of the coral island in Maldives were investigated through the field observations. U nderwa ter notches were found about 6m below M S L implying that these notches were formed in the past sea level condition lower than the present. N earshore currents induced by wave breaking on coral reef were observed and compared with the numerical simulation. B oth results agreed well.
A mathematical model is established to describe wave-current interaction over uneven sea bottoms. The basic equations of the model are obtained by vertically integrating the continuity equation and the equation of motion for flow over impermeable sea bed of mild slope. Finite difference method is utilized for numerical solutions and the results for a wave-current coexistent field over submerged mound show that the variation of the wave features is fairly significant due to the presence of the current which leads to remarkable drop of the mean water level over the mound and that the waves also affect the mean water level appreciably.
The procedure of wave energy dissipation after breaking have been investigated with trains of the regular wave. To obtain the data for wave breaking and its deformation, experiments have been conducted by utilizing a horizontal step adjoining to a combined slope of 1/20 and 1/10. After breaking, the wave height decreases by dissipation but attains a stable value at some distance from the breaking point. Experimental results show that the stable wave is affected considerably bythe wave period. The study gives the general form of stable wave height. A new one dimensional wave deformation model is proposed, being coupled with an approximated shoaling coefficient before wave breaking and the new energy dissipation term after breaking. It was compared with the experimental data. It predicts well the wave height deformation before and after wave breaking even on the abrupt change of the depth.
Number of people enjoying sailing and cruising is increasing. Acoordingly, number of pleasure boats, especialy illegally moored boats, is increasing. To pre-pare space for mooring of those boats, various marinas or yacht harbors are planned to be constructed. In such planning, full investigation of the harbor tranquility is hardly done and rough waves often cause various troubles in exsiting marinas. Here, the effect of slope of the marina on the harbor tranquility is investigated through numerical and physical model experiment and a procedure for determining the best position of the slope is proposed.
Experiments are carried out in a wind water tunnel. In this paper, wind-waves mean the waves newly generated by wind behind the planting trees. Wind velocity distributions and wave height distributions behind the planting trees are observed. Brushes for chemical washing equipment are used for the planting tree models. Effective tree arrangements for reducing wave height are discussed.
Wave diffraction and radiation around a structure are solved by Green's 3-dimentional theorem. we apply a boundary condition on virtual boundaries which wave diffraction and and radiation are considered. This method reduce computational memory and time, since the virtual boundaries can be locate relatively close to the structure in this method. We analyze the wave field passing over a submerged that plate and obtain the force and moment acting on the structure. the analytical results are compared with experimental data and good agreements are obtained
To prevent water pollution inside a port, a breakwater with piercing slits is developed. The wave transmission of the breakwater should be considered in the computatio of wave transformation in the target port. The proposed simulation model is verified by the model test.
A pendulum-type breakwater partly consisting of peoforated walls was used as a model breakwater. By varying the mooring line constants, peoformance of the breakwater, such as wave transmission and reflection coefficients as well as dynamic displacements, was examined extensively, In order to be able to attenuate long waves, a method of reducing incoming waves through the use of radiation waves was discussed. It was clarified that the pendulum-type breakwater with porous walls is very effective for reducing long waves when the breakwater is moored by comparatively slack tethers.
In this paper, the characteristics Of the flexible sheet with many springs on both sides for wave control on offshore were investigated using two-dimensional wave flame. Many experiments for 8 kinds of initial tension were carried out and coefficients of passing wave and reflected wave were measured. In this experiments, when the initial tension added to the sheet increases, coefficient of passing wave becomes small or of reflected wave large. But in the case of rigidiron plate, opposite result was obtained. Accordingly, it is expected that the best initial tension added to flexible sheet exists. In the experimental results, firstly, the best initial tension was found experimentally and secondly, it was discussed that the difference of phase between oscillation of the incident wave and the sheet regarded with wave control.
Several wave absorbing systems are tested in a wave flume. They are two types of pneumatic breakwaters, two types of hydraulic breakwaters and two types of waveabsorbingsystem with sand liquefaction, all of which use electric power to dissipate waves. The hydraulic breakwaters and pneumatic breakwaters are not effective to reduce waves effectively. However, the wave-absorbing system with liquefied sand seems to be promising.
This paper aims at investigating, experimentally as well as theoretically, the local scouring alea alound two lalge circular cylinders under wave action. The lateral extent of the local scouring area adjacent to two large cylinders is wider than that for one large cylinder which is less than about 0.1L (L is the wavelength) from cylinder surface. Maximum scouring depth along cylinders has a strong correlation with d50/L (d50 is the median diameter of sand), that is, as d50/L increases, non-dimensional scouring depth (Δh/HI;HI is the incident wave height) increases. Finally, the local scouring area around two large circular cylinders is shown to be well predicted theoretically with the spatial gradient of mass transport velocity based on diffraction theory.
Characteristic of topographic change around a single fence caused by currents isinvestigated through movable bed experiments. The maximum depth of local scouringunder the fence is determined by Shields' number and the width of the local scouring is 4 to 7 times larger than the maximum scouring depth. This types of fence has been constructed in the field with various plane arrangement. Based on the results obtained by from the single fence experiment, topographic changes around various plane arrangement of fences such as +shape are also examined. The depth and width of the maximum scouring hole is found to be almost the same as those of the single fence.
The annual variation of monthly mean sea level caused by Kuroshio meandering is investigated using observational data around the Ise bay area. The effect of Kuroshio meandering is to increase sea level departure from normal near the coast. The maximum value is about 50cm for daily average level at Atsumi peninsula. It is shown that the occurrence time corresponds to the warm water approaching which is the initial stage of Kuroshio meandering by remote sensing data.
If man-made islands are constructed in an inner bay, the tidal currents are changed and the rate of sea-water exchange is decreased, which often cause water pollution. In this study, model experiment and numerical analyses are carried out in order to investigate the effects of tidal currents and the rate of seawater exchange; furthermore, two methods for the improvement of seawater properties are proposed and examined by model experiments. Circulating flows around the man-made islands are observed in both the model experiments and numerical simulation.
As a new method for water exchange, the installation of the water chamber in front of the crenellated breakwater was proposed, to raise the mean water level, and to create a current from the open sea into the harbor. A series of hydraulic model test was executed to prove the method to be useful for water exchange and to present an appropriate design of such a sturcuture. The water exchange method proposed here applied to a strucuture at Samani Fishing Port.
Laboratory experiments were performed to study entrainment properties of round bubble plumes in linearly stratified environments. It is shown that stratified ambients decrease the liquid volume flux of bubble plumes, compared with the homogeneous, and an empirical foimula of the volume flux was derived. With fitting between this formula and numerical analysis of one dimensional model, entrainment coefficient was estimated, and an empirical foimula of entrainment coefficient in stratified environments was obtained in the form of adjustment from that in the homogeneous.
There are so much reclamation ares in Nagasaki city. Now, a new reclamation work of the foreshore on Nagaski harbour is being planed consideration. Because of this plan, there is a strong suspention that the natural purification of sea water pollution in this area. In this paper, a change with passage of time from 1984 to 1991 of the sea water transparancy on Nagasaki harbour was checked by remote sensing technique using LANDSAT-TM satellite data. And a new active remote sensing technique was tested by digital camera in combination with conventional remote sensing techniques. As a result of this research, a secular change of transparancy in Nagasaki harbour have not appeared from 1984 to 1991. And It is clear that the new active technique by digital camera will become a useful technique.
Using a U-shape tube, the movement and decline of bivalve by oscillatory flow are studied experimentally. Beginning of bivalve movement from sand beds into water depends on the ratio of that velocity of getting into sand to erosion velosity. Step-length of bivalve is dependent on initial position before a move, its direction and the axis of its rotation. In the case of oscillatory flow (U=58cm/s, T=3.5s), sunray surf clam and surf clam died in three and seven days respectively.
A relationship between the habitat of clams and littoral transport was investigated through the field observation on the Kashimanada coast. It is found that the longshore distribution of the habitat corresponds well with that of calm wave zone produced by the sheltering effect of the harbor breakwater and active habitat exists in the zone composed of coarser bottom materials near the surf zone. The construction of headlands is found to be effective to the formation of the new habitat of clams.
Field survey was conducted in the two rocky beaches facing Osaka Bay. They are artificial-made lagoon and natural one. There is little difference in the water quality on these beaches, but the species and quantity of marine organisms in the natural rocky beach are more rich than those of artificial one.
Artificial water-front in Japan has been improved mainly in the econmical view up to now.But social demands for the natural enviroment and amenities in the water-front are increasing in these days. Then administrations concerned have been introducing some kind of natural-rich structures for the improvement of water-front. In this paper we tried the design of the low crown seawall with the defensive tydal pool atached with the new ferry berth in Tsuruga Port. As a result, we could designed the economical and natural-rich seawall aesthetically.
An artificial neural network is applied to the environmental analysis by using field data obtained in Biwa lake. Twenty eight varibales of on site data are selected as a set of input vectors. Output vectors from the network are compaired with the inspection data obtained from the observations. Finally a procedure of environmental analys is proposed by a successfully learned neural network and shows remarkable effects on the evaluation of the environment variables.
The proposed quantitative evaluation method of the aesthetic measure for the arrangement of harbour structures were confirmed by the extended questionnaire survey. The harbour structures should be arranged by considering the wave and sea bed conditions, and the required function for harbour. The practically designed drawing and its improvements are influenced by the original configurations of coast line and seabed, or those of the former phase. This paper discussed the aesthetic measure on the drawings of each phases in the process of the practical developments, e.g. the Port of Los Angeles and the Port of Tokyo, based on the proposed method. The configurations in the final phase of the port developments show the higher aesthetic measure than those of the former phases. This means that the designers were unconsciously affected by their easthetic feelings on the configurations of the former phases in developing process.
There are so many small comunities located along coastline in Japan. Their economics are in face of a difficult situation to run fishery under the decline of coastal fishery. Most of residents have insufficient income from fishery. They need another income source. They demand the development of fishery harbour area based on the oceanic recreation. In order to obtain planning infommadon for development and improvement of infrastructure in small comunity in a fishery, this paper studied the feasibility on the development of recreational facilities. The questionnaire survey shows the insufficient economical background of residents and difficulties of development for marine recreation. Successful development demands merger of their Fisheries Co-operated Organization as the core of new business.
In planning and designing a marina for a public marine recreation to be involved in waterfront development, it is very important to grasp the significance of the waterfront for the urban residents and reflect it into the environmental consideration by clarifying the processes of variation in their behavior and perception as visitors to the waterfront. From this point of view, a questionnaire survey was conducted and analyzed to investigate the utilization status and the visitors' perception at a public marina called “Shinmoji Marina” in Kitakyushu City. This paper first outlines Shinmoji Marina and the questionnaire survey, followed by the detailed results of the questionnaire survey and its analysis.
Artificial beaches, beach parks or fishing facilities are often constructed along the sea coast close to newly developed coastal zone for marine recreation and restoration of ecosystem. Many deterioration on human health and natural environment such as biological system accompany the developments of coastal zone. The method on restoration of ecosystem was introduced as mitigation. The substitutive procedures such as an artificial beach are not sufficient for restorastion or reservation of ecosystem but for the human preference. This paper discussed the background data on human preference for sea coast, based on the questionnaire survey. Sea coast plays the important role of the taste of human life. Sand beach is the first thing to be required in sea coasts. The artificial beach is suited for the substitution of the natural beach. Many people resident the area within two hours access to the sea coast. They also prefer to live along the coast where the convenience facilities are available.
Armoring concrete blocks on the slope of seawall reach the damage under the processes from the state of repose to the slightvibration, vibration, rocking, movement and dropping-out depending on the intensity of waves. The slightvibration and vibration of armor units is considerably concerned with the compaction of wave breaking works and the settling of armor units into the underside of sand seabed. The vibration of armor unit due to the wave action was measured in laboratory by using the tetrapod-model attached the micro-accelerometer, which is set on the armor layer crossed the still water level. Based on the result analyzed the measured data, the characteristic of vibration is examined.
Stability of step-shaped armor blocks for covering a sloped revetment against wave actions was examined experimentally. Two different types of armor blocks were used as a model, i. e., a step-shaped concrete block with a hole on its center and the one without a hole. Wave pressures on both the front and bottom sides of the armor block were measured in order to examine the effect of the hole on the stability against wave actions.
The stability of armor units for submerged breakwaters is investigated by two dimensional model experiments with irregular waves. According to test results, stability factor of armor units is newly formulated as a function of relative crown depth of submerged breakwaters to the incident wave height. The effect of the specific weight of armor units is also studied with varying specific weights and structural conditions. For specific weights ranging from 2.65 to 3.22, the test results proved that the stability factor of armor units can be calculated by the proposed method.
Recently breakwaters have been constructed in deep seas. For example, a trapezoidal caisson breakwater is under construction in the depth of 60m at Kamaishi Port. Although the design procedures for the upright section are established, the stability of rubble mound foundations is not sufficiently studied for the deep sea conditions. In the present paper, the characteristics of wave-induced flow near the mound are disclosed, and the stability of armor units is investigated by two-dimensional experiments with irregular waves. According to the test results, the minimum necessary weight and covering area of armor units can be estimated for rubble mounds of composite breakwaters in the deep seas.
The exploration on seafloor soil is one of the first things to be carried out when the construction is planned and performed offshore. The data on the grain size distribution obtained by the exploration are imoportant to identify the mechanical properties of seafloor soil. In this paper an accoustic method to obtain the grain size distribution of seafloor soil is shown, where the ultrasonic transducers are used to acquire the frictional sound pressure generated between soil and sledge. Then, the empirical relationship between frictional sound pressure and grain size distribution is proposed. The grain size distribution is calculated by the empirical relation based on the assumption that the grain size distribution may be the logarithmic normal distribution.
A model experiment is conducted in a large wave channel to reproduce the settlement failures of caisson type seawalls. Due to wave overtopping and wave transmission through the rubble mound, the reclamed sand is washed down through the back-fill rubble stones. The pore pressure variation in the rubble stones and reclaimed sand can well explain the through-wash of the sand.
The frequency response of seabed around a suction anchor subjected to a mooring force of floating structure is numerically evaluated by taking the seabed characteristics into consideration. The seabed is assumed to be a fluid-saturated poroelastic medium whose behavior is governed by Biot's theory of wave propagation, and the suction anchor is modeled as a rigid and hollow cylinderwith upper cover. The suction force acts on the surface of upper cover in suction anchor. The effectof the skirt length and of suction anchor on the response of seabed around it is investigated.
The pack ice drifts south along the east coast of Sakhalin and occupies completely the Okhotsk coast of Hokkaido. It is carried along by winds and watercurrents and continually reaches and leaves the shores, dependied on the wind direction. Sand beaches of the Okhotsk coast are the habitat of scallops and surf clam. Also, in some parts of the sea live a lot of littleneck clams. When the sea ice moves toward the shores, it gouges part of sandy sea bottom and transports the shells ashore. In addition, there are many shells that are crushed to death by ice floes. This paper clarified the mechanisms of ice gougingby model test.
This presentation is titled Ice Forces on Pile Structures Due to Changes in Water Level Under Flooding Conditions. In cold offshore regions, changes in water level can induce vertical forces on structures when sea ice cover interacts with the structures. A rise in water level generates an upward force on pile structures; likewise, a drop generates a downward force. In this presentation, I propose a method of calculation that estimates the vertical ice forces on pile structures due to changes in water level under flooding conditions.
In Hokkaido pack ice usually reaches the area along the coast of the sea of Okhotsk from Wakkanai to the north shore of Nemuro peninsula and Cape Erimo on the Pacific Ocean. In this study we report on the experiments concerning the effectiveness of the Sink-and-Float-type Ice Boom (SFIB) on preventing ice floes entering harbors due to wave action. The SFIB structure consists of a number of floating bodies linked by steel cables, with their ends tied to piers. The SFIB sinks to the sea bottom when the floats are the filled with water, but when the floats are filled with air the SFIB floes entering the harbor.
The Okhotsk Sea coast of Hokkaido is covered with drift ice every winter. Pack ice enters the lagoons occasionally. If a large block of pack ice enters a lagoon, it will move around in it and damage scallop, oyster and related culture facilities. Development of technology for preventing intrusion of pack ice into the lagoons is required at all costs to get rid of suchdamage. In this paper, the authors report the experimental results of newly developed Ice Boom used under special conditions. The newly developed Ice Boom is easier to repair and to clean up than new type Ice Boom that we have developed. The ice control effect of the newly developed Iceboom is the same or more effective than new type Ice Boom.
Model experiments for multi conical legged structures (MCLS) were performed. Two types of MCLS, namely UB-MCLS and DB-MCLS were tested in IHI Ice Model Tank. The experiments were performed taking the intrusion angle as a testing parameter and six force components were measured. In the experiments, the ice forces and the ice-induced overturning and twisting moments revealed its maximum at the intrusion angle of 30 deg. And in normalized fashion, the ice force and the ice-induced moments for DB-MCLS were twice as large as those for UB-MCLS. However, the magnitudes of those quantities were approximately the same for both DB-MCLS and UB-MCLS.
The Okhotsk Sea coast of Hokkido is rushed by drift ice every winter. Somtimes aquaculture and fishery resources have been damaged by the movement of drift ice. When the ice concentration is low, ice floes are brought on sloping beach by waves. On the coasts of Omusaro, Monbetu airport and Sanri which are facing to Okhotsk Sea, the authors observed run-up height, size and shape of ice floes on sloping dry beaches. And the position, size, thickness and run-up height of run-up ice floes on sloping beach are clalified
The Okhotsk Sea coast of Hokkaido is covered with drift ice in winter. When ice floe concentration is low, sometimes overtopping of ice floe occur at breakwater due to wave action. Fishing boats and pipelines behind breakwater hava been dameged by the ice floes. It is required that ice control facilities are constructed. In order to design the facilities, we have to know the overtopping velocity of ice floe on breakwater. We report on the systematic experimental results on overtopping of ice floes and its mechanisms.
This paper summarizes systematic experiments on the adfreeze bond strength between sea ice and building materiarus used for offshore structures as steel, concrete, as well as a variety of coating materials. As a result of comparative experiments on various test methods for determining the adfreeze bond strength between ice and different materials, very little difference was observed among the result of those methods . It was also confirmed that a factor affecting the asfreeze bonnd strength depends more on the coarseness of the surface of building materials than the interfacial free energy on that surface.
The tsunami caused by the Hokkaido Nansei-Oki Earthquake (M=7.8) on July 12, 1993 brought severe damages over wide area along the Japan sea. The topical points of the Hokkaido Nansei-Oki Earthquake tsunami are : (1) This tsunami was generated at a location where earthquakes have not been observed before.(2) The runup of this tsunami records maximum height in the recent years.(3) Effects of trapping produced serious devastations at Okushiri Island. This paper aims to present some characteristics of this tsunami with the analysis of field survey, theoretical analysis and the numerical simulation
In order to investigate hindcasting and forecasting of tsunami, a numerical simulation system is developed. This system is constitute three subsystem and data-bases for supporting analysis with the aid of Engineering Work Station and Personal Computer. Basic consept of system is creating of hight quality information with easy operation. With the application of this system to hindcating the Kanto Great Earthquake Tsunami, reliable information can be used to design of maritime construction.
The Omura Bay is situated in the central part of Nagasaki Prefecture, which yields many problems including traffic one between both the northern and southern parts and the eastern and western parts of the Prefecture.In this paper the authors proposed a concept of the Omura Bay Bridge in order to solve these problems, and considered on the concept from engineering point of view. Discussions werefocused on environmental, bathymetric and soil surveys, route location, bridge type and others. As the type of bridge, a pontoon type was considered to be more prominent than the other types owing to its working period and cost shortage, and if this type bridge were built here the Omura Bay Bridge will be welcomed to be a tourist route as the first one in this type in Japan.
Real sea wave is quite random in amplitndes, periods and propagating directions. Offshore sea waves, therefore, have characteristics of “directional randomness”. Directional random waves in the offshore consist of the component waves each propagating in different directions in shallow area. Some coastal structures constructed in deep water area should be designed for directional random waves. The experiment for the directional wave force are done. The target structure is a column, which is the simplest component in coastal structures. The wave force on a column in directional seas is compared with that in uni-directional waves.
In this study, the pertinent characteristics of wave forces acting on vertical circular cylinder in two crossing wave fields are experimentally investigated.The maximum wave force of crossing waves is large in case of crossing angle odegree, compared with the linear vector sum of maximum wave forces of two waves trains. However it is small in case of any crossing angle. As the nonlinearity of two wave trains becomes to be strong, the double-peak occurs in the profile of wave forces.The inertia coefficients determined from the wave-by-wave analysis have the different tendency with the envelope shape of water surface elevation, under prominent inertia forces.