At the time of beginning of the Meiji era, it was thought that the Japanese couldn't construct modern-style and large-scale harbors. However, Isami HIROI perfectly accomplished the construction of the Otaru port. The factor of his success is requested from the entrepreneurial spirit, and it analyzes it from document to which he did. As a result of the analysis, his knowledge and plan power concerning harbors, pursuit of the economy and efficiency, excellent construction management, and consciousness of limit to nature became clear. Moreover, his spirit to the design introduces from his book “CHIKKOU”.
The HIROI formula, which estimates the wave forces, has been used in breakwater design for many years. As far as the authors know, significant wave height has been used for the HIROI formula in the past. The time when the formula was presented, however, was long before emergence of the concept of significant wave height. We verified the process of derivation of the formula by tracing back to the paper in which Dr. HIROI first presented the formula, studied the changes in wave height used for the formula and investigated the history of changes in the shape of breakwaters. As a result, we found that the highest wave height must be used for the HIROI formula, and that changes in breakwater structure existed behind the use of significant wave height in the formula.
The North Breakwater of Otaru Port which consists of mound and superstructure, was constructed by the sloping-blocks were settled down by an overhanging crane which is well known as Taitan. To ensure the stability of blocks, it is necessary to bond together every block of each separate section. This paper addresses the way and effects of bonding blocks in the North Breakwater of Otaru Port. Detailed investigations have been made on “the Report of Otaru Port Construction Works” written by Dr. Isami Hiroi who focused on researches of sloping-blocks and infrastructure works of the North Breakwater.
During construction of the north breakwater of the port of Otaru, Dr. HIROI conducted tensile strength tests using various types of mortar briquettes. This paper presents material research conducted concerning these tests Dr. HIROI conducted, as well as clarifies the background, place of commencement, purpose and period of testing. We also began to investigate the size, characters on the surface and markings of all the HIROI briquettes (mortar briquettes produced under the guidance of Dr. HIROI) kept at the Otaru Port and Harbour Office. This paper reports on an overview of a comprehensive study concerning the briquette, which was initiated to clarify the details of the tests conducted under the guidance of Dr. HIROI.
North Breakwater of Otaru Port was constructed from 1897 to 1908. Dr.HIROI was the leader of this construction. Sloping block system was applied to construct this upright breakwater. The breakwater has protected Otaru Port and City from waves. However, a result of a series of inspections has shown that these blocks, which are part of the rubble mound, were moved and the rubble mound was eroded by ocean waves. In order to keep the proper function of this breakwater, Otaru port office has investigated the present condition and CERI of Hokkaido has conducted hydraulic model tests on this breakwater. In addition, the design and the way of construction have been studied by reading literatures written at the time of construction. Based on these, repair plans were examined. This report shows the results of the investigation, the hydraulic model test, and the repair plan of this breakwater.
The 2004 Sumatra earthquake, occurred at 00: 58: 53 UTC on December 26, 2004, followed by the Indian oceanic tsunami was the largest earthquake in magnitude of M 9.0 in the world since the 1960 Chilean earthquake. The epicenter was located west off Sumatra Island, but the aftershocks extended through Nicobar to Andaman Islands; the total length is more than 1, 000 km. The number of casualties, death and missing together, is the largest in Indonesia (220, 000), followed by Sri Lanka (35, 000), India (16, 000) and Thailand (8, 300). About 300 fatalities are reported from Somalia, east coast of Africa. In total, nearly 300, 000 lives were lost by the tsunami. The information on the media and the result from the field investigation are introduced in the new disaster's point of view. The frame work to mitigate the tsunami disaster in the future is discussed in the paper.
The great earthquake of M9 was generated in the North Sumatra offing at 7: 58 on December 26th, 2004, and the serious tsunami calamity was produced in every coast of Indian Ocean. We report on the damage survey that we carried out from January 9th to 12th in Thai western coast where typical tsunami damage was produced. (1) The tsunami height of Khoa Lak coast was about 9m on the sea level, and almost all walls and pillars of buildings within 30m of coastal line were toppled. The flood region had reached to lkm or more inland. (2) The tsunami height of Patong beach was about 6m on the sea level, and almost all walls and pillars of buildings within 30m of coastal line were not toppled but the flood depth was about 2m. (3) The tsunami height of Phi Phi island is 6-7m on the sea level at the north side and 3.5-5m on the sea level at the south side.
Okushiri town was attacked by Hokkaido South-West Tsunami on July 12, 1993. Port facilities and residences along the coastal line were seriously damaged by the tsunami. More than two hundred people were killed, and the total amount of damages was estimated to be 6.6 billion yen. In this paper, the damages of Okushiri town are overviewed according to the previous reports, and the restoration process in these ten years is introduced.
With an impending earthquake off the coast of Miyagi Prefecture together with the occurrence of an endangering tsunami, Miyagi Prefecture's important role in control and a model project that is to be considered by a collaboration of residents and government organizations will be presented.
Countermeasure against tsunami in ports has not been taken sufficiently because of giving construction facilities for loading priority, even though ports could be damaged seriously by tsunami. The occurrences of gigantic earthquakes that cause huge tsunami are anticipated in Japanese coastal regions, so tsunami countermeasures in ports have to be one of important matters in the future. In this paper, tsunami disasters in ports are studied by experiences in past, and countermeasures against them are proposed. Real-time tsunami observation offshore by GPS tsunami observation system, construction of breakwaters against tsunami and so on could be proposed as new program for tsunami countermeasures in ports.
This paper introduces the Japanese experience of the offshore tsunami profile observation. For the tsunami profile detection sensors, newly developed two systems are introduced: one is seabed installed Doppler-typed Wave Directional Meter (DWDM), and the other is the GPS Buoy Tsunami Gauge. Plan of the Round-Japanese-Coasts and Round-Indian-Sea Offshore Tsunami Monitoring Network is also introduced in the paper. Real-time data processing will be conducted at the Data Center. Satellite data communication system with self electric energy supply by the coastal wind-power-generators and battery should be applied to keep the continuous data communication without interruption in case where stable electric power is difficult to be obtained.
Adaptive management is a vital concept for enabling effective environmental measures in the ocean development and conservation. Nevertheless, it is unclear what is “the Adaptive Management”, and how we scientists and engineers can tackle with that issue. A special session for the adaptive management will be held in the 30thAnnual Meeting of Civil Engineering in the Ocean, JSCE. The concept, definitions, and related case studies will be presented and discussed in the session.
Japanese governmental efforts to implement the integrated coastal zone management (ICZM) are described. For example, the basic development plan for ports and harbours is set to realize ICZM in the bay wide region from view point of development, use, and conservation. An inter-sectional government working group states importance of 1) collaboration between project managers, 2) strategic project implementation, 3) enhancement of legislative application, 4) integration of legislative action, 5) new action for new use, and 6) information exchange between stakeholders. An action plan for the Tokyo Bay restoration (2004) is one of practical example for implementation of ICZM with adaptive management.
Nitrogen budgets and fauna of benthic organisms were examined at the pond of Osaka Nanko Bird Sanctuary, an artificial tidal flat of Hannan Second District and the natural tidal flat of Wakagawa estuary. These salt marsh and tidal flats, each locates at urban areas, are thought to be a typical ecosystem maintained by artificial environmental manipulation. The introduction of seawater to the salt marsh by sluice pipes and the conveyance of river water from inner tidal flat by pumps are effective methods to preserve the benthic ecosystems at Nanko Bird Sanctuary and Wakagawa Tidal Flat, respectively.
The present state of the tidal zone environment along the coast of the Seto Inland Sea including Hiroshima Bay, Japan are reviewed. The potential and usage of technologies for tidal zone regeneration are discussed. Strategies for adaptive management for tidal zone regeneration are proposed; e.g., 1) unification project from wide area and local area of separated projects, 2) maintenance of necessary conditions for regeneration of the tidal zone, 3) unification of various geographic and biological information into a “Tidal Zone Fundamental Map”, 4) assessment of biological local net work for healthy regeneration, 5) development of cascading and various uses of purified sea water, 6) development of fisheries technology as part of fishing ground management from counter measures against harmful species to develop new resources.
The purpose of the Seacoast Law revised in 1999 includes improving and conserving coastal environment. Adaptive management is an important concept to perform shore protection works in harmony with coastal environment. Therefore, this paper summarizes adaptive management in shore protection works, introduces‘Eco-coast Works’, one of systems in which adaptive management can be conducted through environmental monitoring, and shows some prospect of shore protection works, especially on environmental conservation.
This paper summarizes the special session “Coastal Disaster Prevention -for huge earthquakes and tsunami hazards-.” This session has been planned to understand the tsunami hazards and current status of countermeasures, simulation technique, measuring system and international network system. In the session, details of each topic have been presented. After presentations, discussions on the countermeasures against tsunami hazards have been done. In the discussions, safety of residents was one of the main topics. Also importance of education for disaster prevention and provision of adequate information have been pointed out.
This paper presents a summary of the special session “Marine Recreation” The aim of the session lies on identifying relationship between marine recreations and tourism industries as well as sustainable management of marine recreational developments. The session consists of two parts: one part is presentation of the papers regarding with marine recreations and the other part is a panel discussion among panelists presenting the papers. Presented are 12 regular papers concerning various aspects of marine recreational activities and four invited papers concerning major marine recreational activities in Okinawa and tourism policies relevant to marine recreations. Among various topics discussed, contribution of marine recreations to tourism industries and management of ecotourism are most discussed.
As to the flap type gate for the protection against storm surge and tsunami, we are advancing the studies on design and construction by considering the hydraulic and hydrodynamic characteristics of the flap type gate. This paper presents the results derived by the hydraulic model tests using the 2-dimennsional channel with wave maker and the model of scale 1: 25, in order to comprehend the characteristics about the amount of wave overtopping and pressure distribution on the flap body in waves.
Recently, the sea level rise due to global warming is apprehensive, and the sea level rise increases vulnerability to inundation in coastal areas due to storm surges and tsunamis. A flap gate is useful as one countermeasure against the storm surges and tsunamis. We are performing the studies for design and construction by considering the hydraulic and hydrodynamic characteristics for the new type flap gate. This paper presents the results derived by the hydraulic model tests using the 2-dimennsional channel with a wave maker and the model of scale 1: 35, in order to investigate the characteristics of the gate behavior during rise and sink and the floodgate effects on hydrodynamics given by various conditions of wave motion and tidal movement.
Buoyancy-driven vertical piling breakwater-a new type of breakwater formed by upper and lower steel pipes rises above sea level by feeding the air into the upper pipe when high waves or tsunamis are imminent, whereas it normally rests inside the lower pile installed below seabed so that navigation is undisturbed. This paper outlines the results of a series of experiments by a large scale physical model and of the numerical analyses with regard to the rising/sinking behavior of the breakwater. The results clearly demonstrate that: 1) The time required for raising the upper pipe is just a few minutes, being rapid enough to prevent tsunamis from attacking harbors; and 2) The numerical model gives good approximation and is fairly applicable.
To reduce the damage of structures caused by tsunamis, it is essential to know the characteristics of tsunami load. In the present study, a three dimensional hydraulic experiment was performed to investigate the spatio-temporal variation of the tsunami wave pressure acting on a land structure. The followings were found out. (1) Wave pressure can be regarded as the sum of the average component and the random component of pressure. (2) The spatial distribution of wave pressure for 3-D experiment case is similar to that of 2D case. (3) Wave pressure distribution depends on not only run-up depth but also water surface steepness. (4) Random component of tsunami wave pressure is impulsive.
The damage of the structures is classified into two types. The one is caused by the direct action of tsunami, and floating bodies such as destroyed facilities and drifting ships and cars cause the other one. The purpose of the present study is to investigate the damage on structures due to the drifting bodies with tsunami. In order to perform the investigation focused on a drifting body, experimental tests are carried out, and a combination method of non-linear long wave theory and DEM is suggested for drifting numerical models. The models are applied to reproduce the experimental tests. As a result, it is confirmed that suggesting method can predict the behavior of drifting bodies due to tsunami.
In this paper, the characteristics of the tsunami due to Nankaido earthquake and moored ship motions were investigated numerically. Tsunami simulation was carried out by using shallow water wave theory and moored ship motions were evaluated by strip method. The traveling time of the tsunami that from hypocenter to Kobe port was about 2 hours, and tsunami current was parallel to normal direction of quay walls. The moored ship was oscillated several meters to surge and sway direction by incident of tsunami. Reaction force of fenders where located near stem and stern were increased by yaw. Such influence of the tsunami on moored ships to quay walls and countermeasures against tsunami disasters were estimated.
This paper describes two 3D numerical models to simulate tsunami phenomena including runup onto a complex beach. The governing equations are the continuity and Reynolds equations for incompressible fluids in porous media. In the first model water surface displacement is determined by the vertically integrated equation of continuity, while in the second model by the 3D-VOF method. Topography of seabed can be smoothly expressed with the porous model. These two models were applied to reproduce the existing hydraulic-model experiment, which treated the 1993 Hokkaido Nansei-Oki earthquake tsunami in Okushiri Island. The highest runup calculated by the VOF method indicates the full-scale value of about 30.6m.
There is a little time to react until the tsunami arrival in each port in Osaka Bay in case of Nankai Earthquake occurrence. Therefore, it is possible to take precautions against the tsunami if appropriate tsunami information can be obtained. In this study, the real-time tsunami forecast system which can complement the forecast of the Meteorological Agency is examined. The real-time tsunami forecast method which is proposed in this research forecasts the tsunami that reaches in Osaka Bay 1 to 1.5 hours later by using the observed data outside the bay. The Shirahama Observation Tower in Tanabe Bay, Wakayama is considered as one of the offshore tsunami observation facilities. As a result of the examination, the accuracy of this method using the observed data was well and usefulness was confirmed.
The reduction of an inundated water depth and flow velocity by a vertical tide barrier, which is installed in order to higher a crown height of an existing seawall against tsunami attack, was investigated through physical model tests. The inundated water depth and flow velocity behind the barrier were measured with changing a barrier height as well as a tsunami height. An elevated seawall with the vertical tide barrier effectively reduces the inundated water depth, and its efficiency depends on the tsunami height as well as the barrier height. On the other hand, reduction effect on the inundated flow velocity is extremely small compared to the inundated water depth. When the vertical barrier is installed retreated landward position, control functions of the tide barrier on inundated water depth and flow velocity are nearly same as the functions where the barrier is installed at the tip of the seawall, though the run-up height of tsunamis in front of the barrier is extremely reduced.
In order to take countermeasures against tsunami disasters, it is important to understand deformation of tsunami runup on shore, characteristics of flow around structures, and mechanism of tsunami wave force acting on the structures. In this study, we carried out the hydraulic model test and the numerical analysis to clarify characteristics of flow around the oil tank on shore acted by tsunami. Thorough the hydraulic model test, the following findings were obtained. Separation vortexes appeared behind the tank and the fast-flowing area shifted to the rear of the tank as the distance from it was farther. Maximum velocity was close to0.8m/s and there was great possibility of scour of foundation around the tank. It was possible to simulate these characteristics around the oil tank by numerical analysis.
In this study, numerical simulation of tsunami evacuation was conducted for the estimation of the number of casualties by tsunami within a certain area of the bay Kesennuma. The evacuees' action in the simulation was based on the potential model. Walking velocity and limit condition for evacuation under flood situation were decided by the function of the inundation height and velocity of a flow, which we had verified with the results of walking experiments in a water channel with steady flow. Applying this simulation to the bay Kesennuma supposed the tsunami induced by the Keicho-Sanriku earthquake, we obtained the number of casualties under the various conditions such as dispositions of refuges, start time of evacuation, and blockade of roads.
To evaluate the water quality of sea areas around Japan, a new water quality index was proposed using the data released by public organizations. First, to make the water quality index of sea areas, principal component analysis was applied for the data at 6008 observation points where the data of TN (total nitrogen), TP (total phosphorus) and COD (chemical oxygen demand) were gathered for four yearsfrom 1999 to 2002, and the first principal component was considered as the comprehensive index of water quality. Next, the water qualities of sea areas around Japan were compared by the water quality index. The evaluation shows that the water qualities are relatively bad in sea areas near the big cities and in large harbors. And it is found that the value of the water quality index in polluted seaareas with organic substances is less than -1. In addition, the water quality ofthe Hakata bay for 20 years (from 1983 to 2002) was shown by using the proposed index, and the change of the water quality due to various developments was investigated.
Relationship between drowning accidents and development of a rip current around a headland was investigated, taking the Chigasaki coast in Kanagawa Prefecture as an example. On this coast, a headland of 200m length was built. After the construction, swimmers and surfers were carried away by a rip current near the headland, causing marine accidents. Numerical simulation of waves and nearshore currents was carried out to obtain maximum velocity of a rip current, while changing the longshore and offshore lengths of the headland. Most dangerous condition with developing a strong rip current is found in relation to the scale of a headland and wave characteristics.
Use of the suburban coast by surfers was examined in Sendai City, Japan as basic data for improving utilization of the coastal area. A total of 4 surfing locations were considered based on surf information, and the popular Sendai New Port site was chosen for the field study. The survey was carried out in 2004, observing once on each day of the week between August 30 and September 19, and involved taking counts of surfer numbers, male and female composition, types of boards used, and weather and surf conditions in a 20 min period every hour on the hour from 5am to 5pm. The survey revealed that only 10% of the surfers are female. Most male surfers use short boards, while most female surfers use body boards. The relationship between the surfer number and each of these factors suggests that the day of the week and the time of day are more important for utilization than the weather or surf conditions.
Structures of sea and land breeze over the Osaka Bay area are complex because of westerly general wind flow and complex topographical conditions. The purpose of this study is to simulate three dimensional structures of realized sea and land breeze over the area by introducing the objective analysis data. Vertical profiles of wind velocity were measured by a Doppler sodar anemometer at the Osaka Nanko area in the 2003 summer. Numerical model simulations were carried out to produce weather conditions which occurred during the measurement. Simulated vertical profiles of horizontal wind velocity vectors agreed quite well with the observed one. However vertical velocity couldn't be simulated accurately. Some modification will be needed for the numerical model to calculate behavior of atmospheric pollutants emitted in the bay area.
Hakata Bay is an enclosing costal sea, whose hinterland is a large urban settlement with the population of about 1.4 millions. Construction of an artificial island has been carrying out at the inner part of the bay. The state of natural environments of Hakata Bay are main issues among the city government, citizen and scientists. The aim of this study is to investigate natural environmental characteristics of Hakata Bay by using data of various observation for water and sediment quality, benthos, marine planktons, and so forth. The multivariate statistical analysis and the proposed the environmental evaluation method are applied for studying natural environmental qualities of Hakata Bay and to verify validity of the proposed evaluation method. It is found that some of the water quality elements like T-P and SS have been constantly improving, although the physical environment is deteriorating due to construction of the artificial island. The proposed evaluation method clearly indicates this trend.
Recently, interest in night landscape has been increasing, and waterfront is one of the most significant spots to enjoy it. In the field of art, expression of night landscape in waterfront has been interested by, for example, Mr. Kiyothika KOBAYASHI, Japanese engraver in 19th century, or Rene Magritte, Belgium painter in the middle of 20th century. This study pointed out the clear reflection of light as significant factor of night landscape in waterfront in their works. In addition, we analyzed contemporary guidebooks of night landscape for Tokyo, Osaka Kobe and Kyoto regions to examine the light sources, their locations and conditions of reflected images. Furthermore, we attempted to manifest the evaluation of night landscape in Biwa-Lake, Shiga, Japan through in-situ questionnaire investigations and proved the property of night landscape evaluation in comparison with daytime.
Artificial beaches are normally used year-round, making the maintenance of such beaches very important.“Inagenohama” in Chiba prefecture was the first artificial beach built in Japan, and a variety of maintenance problems have developed there; beach garbage in particular is one of the most important problems. This paper investigates the characteristics of beach garbage by stochastic analysis and a questionnaire survey. As a result, the sources of the garbage are identified and user consciousness is analyzed.
Recently, the purpose of the sea bathing is diversifying. Therefore, it i s apprehensive for the occurrence of the accident in the bathing resort which the user of many purposes is mixed in. From such present condition, it tried to explain the technique that it aimed at the improvement in safety and amenity of the bathing resort from view point of the user. In other words, it tried to explain the method which divided a bathing beach and swimming area into every use purpose of the sea bathing. The example of Zoning-Plan of the bathing resort was proposed in consideration of these results.
In this research, the evaluation of the Nishikinohama park where it is prepared before the Coast Law revision due to the coastal environment improvement is explained by the neighboring inhabitant. Therefore, questionnaire investigation about the evaluation of the coastal environment improvement works targeting the inhabitant of the Nishikinohama park's neighborhood was done. Furthermore, it tried to explain how to carry out coastal environment improvement that an inhabitant participated. So, investigation about the improvement works explanation meeting and the workshop of the coastal environment improvement at the time of the execution was done, too. Then, these results were generalized, and desirable inhabitant participation to the coastal environment improvement was suggested.
Japanese coasts have experienced extensive damage caused by storm surges and high waves which made new high records. The impacts of climate change and sea-level rise are suggested to increase in this century. To address these impacts, as protection by hard structures such as coastal dike and seawall has limited effects, integrated policy for coastal conservation should be introduced, combining hard and soft options. Soft options include land use change/regulation, early warning system and disaster prevention scheme. Trends of national population and financial conditions are another factors for the future policy. This paper examines coastal conservation and management policy against sea-level rise caused by global warming through review of existing policy framework in foreign countries as well as in Japan, options of integrated policy, questionnaire survey of coastal residents' opinion, and quantitative assessment of those options. Through these studies, future direction of coastal management is proposed taking into account the effects of climate change and sea-level rise.
Multi-fan beam data shows detailed bathymetric features off the Miho Peninsula, shizuoka Japan. Comparisons between recently acquired bathymetric data sets and past date collections show systematic differences in sedimentary regime of this area. Northern part of the area is characterized by the deposition on the sea floor and progradation and the southern part by the retrogradation and erosion. Several gravitational sediment flows composed of the deposition swell and down slope sand ridges are clearly delineated by the 3D image from multi-fan beam data along the southern coast where intensive coastal erosion has been taking place since 1983. Benthos fauna is examined on the basis of dredge samples from this area. This study indicates that benthos fauna appears to be related with the sedimentary regime. Drastic decrease in biomass of Macrobenthos from 360.5g in 1971 to 168.0g in 2004 is observed and suggests erosional effect on benthic biological community last 33 years.
It is important in shore protection works to consider how to make it harmonize with the natural environment of coastal areas. It is also pointed out that in coastal management there is a necessity of incorporating a concept of ecosystem. Here we conducted a study about what impact can be expected as a result of constructing shore protection facilities. Based on that study, this paper examines the current survey plan and discusses what aspects to be more focused or intensified in coastal environment survey.
The purpose of this study is to examine the relationship between the distribution of sessile organisms and the environment of water quality, water depth and direction of upright structure, and to evaluate the effectiveness of this new research method with the use of an underwater camera as an observation equipment for sessile organisms in comparison with general methods. The research for sessile organisms was carried out at the upright structures in twenty-one ports and fishing ports in four prefectures (Tokushima, Hyogo, Osaka and Wakayama) around Osaka Bay in the summer of 2002. The results of our research showed the distribution of sessile organisms attributed to water quality, water depth, direction of upright structure, and that this research method for sessile organisms was more effective than general methods. With those results, we suggest that this simple research method for sessile organisms on upright structures is highly effective to carry out studies at many sites in large areas at low cost.
By considering the structure of Scallop's body, density of inorganic suspended particle and dissolved oxygen (DO) are the main factors that influence the environmental tolerance of the Scallop and the ability on purification by filtrating. By building a model of the Scallop's filtration process, using Scallop's soft body mass, and water temperature, salinity, DO density, inorganic suspended particle density, it is possible to decide the Scallop's tolerance against anoxic water and inorganic suspended particle by developing a biological model. Under condition of anoxic water (DO density under 2.0mg/L), the Scallop's subsistence condition would be determined only by the tolerance of DO density and the density of inorganic suspended particle does not affect. When the condition of high turbidity lasts more than a day, and the surrounding water is hypoxia (DO density under 5.0mg/L), Scallop starts to decrease from small individuals by the influence of the inorganic suspended particle. However under condition of saturated oxygen, death will not occur in any level of the inorganic suspended particle density.
The settlement rate of the larval Manila clam has increased by 28.9 times compared with still water when the steady flow acts on the infiltration flow at the same time. The settlement rate has increased by 5.1 times as the infiltration flow velocity 0.3cm/s increases from 0.01cm/s. Larval Manila clam accumulates in a high density on the surface of the sediments with comparatively rough particle size to which the tidal circulation of groundwater flow develops. If the distribution density of the larval Manila clam, the particle diameter of the sediments, and the flow condition are understood, the settlement rate can be presumed based on this research.
The quadrat method is a conventional way for resource survey of short necked clam. However, it is considered that this method requires skillful technique in order to get a highly accurate survey result. The current paper introduces a new method using a specific concrete (so-called Paste Concrete). The Paste Concrete is buried into the sediment as a settlement base of the clam, let the clams settle on it naturally and then is collected for the measuring. It is an unique method which well utilizes behavior of the clam.
The applicability of a numerical model calculating waves in partial reflection region is examined. The model used in this research is a Boussinesq-type wave transformation model provided by Port and Airport Research Institute in Japan (NOWT-PARI, Ver4.6 β for short), which has a function of evaluating reflected waves at porous layer boundary. The feature of this model is that the reflected waves are reproduced without adjusting any parameters at the reflection boundaries. Experiments with a large scaling model of Nase harbor, Kagoshima prefecture, were conducted. Experimental results were compared with numerical results. Good agreements were obtained for wave height distribution.
The applicability of the VOF method to wave motions was investigated by using a computation model, ‘CADMAS-SURF’, providcd by Costal Development Institute of Technology. First, simple linear and non-linear regular waves were calculated with several combinations of different sizes of cells and time steps, and the numerical results were compared with theoretical ones. It was found that the reproducibility decreases as the wave height increases. Next, random wave run-ups along a vertical seawall were calculated, and the results were compared with the experimental results obtained by model experiments using two-dimensional wave tank. It was also found that the VOF model can roughly reproduces the wave run-up, but the model cannot reproduce the intense wave run-ups in detail.
The characteristics of wave transformation on coral reefs change complicatedly under the influence of submarine topography. This study investigated the characteristics of wave transformation when topography changes in the alongshore direction by the hydraulic model experiment and inspected the accuracy of the Boussinesq model equation used for calculation of wave transformation on complicated coral reefs. It is found that the wave height changes complicatedly under the influence of the alongshore changes of submarine topography. The spatial distribution of long period constituent is represented by the equation for the amplitude of surf beat. The wave height distribution calculated by the Boussinesq equation gave good agreement with the value from experiment.
This paper presents that major computed flow filed above a boundary layer in a surf zone could be strongly affected by kinds of the boundary conditions (slip, non-slip and shift B.C. based on a log law) imposed at a bottom. The estimated bottom shear stress is also considerably dependent on the boundary conditions, which might cause over- or under- predictions for bed-loads transports in the sur-zone. In order to fill a gap between length-scales of predominant turbulent flows over and within the thin boundary layer, a two layer model (TLM) is applied to the boundary layer flows. TLM is found to give the reasonable boundary layer flows and also major flows over the boundary layer. This model may greatly contribute to practical largescale computations typically involving a significant gap of turbulence properties across the boundary layers.
This paper presents the development of models for predictions of near-shore wave characteristics and the evolution of surface rollers. The wave model is based on the concept of an equivalent linear wave, and nonlinear wave characteristics, if necessary, may be reconstructed from the prediction of the equivalent linear wave characteristics. The surface roller model is based on the energy balance equation that is ideally consistent with the proposed breaking wave energy dissipation model. Since both models are based on simple energy balance equations, the entire model retains flexibility and computational efficiency for practical applications. The waves may be periodic or random waves, the beach profile may be plane or barred. Model predictions are compared and show excellent agreement with experimental observations, none of which were used to calibrate the model.