Asset management for infrastructure is systematized activities which manage the infrastructure as a national common property at a long-term viewpoint efficiently and effectively for the improvement in profits of people, which is necessary to be carried out continuously, using synthetically the knowledge in fields, such as engineering, economics, and business administration. While building the management system of physical property, it is important to construct the organizational management system, personnel training and improvement in accountability, and also infrastructure accounts for strategic management.
Tokyo Metropolitan Government manages about 2, 229km road and 1, 238 bridges and 92 tunnels in capital Tokyo. The road assets which Tokyo Metropolitan Government manages have two peak of construction. I think that we must update many of road structure for deterioration ten several years later. However, I think about updating all with impossibility in current financial conditions because extraordinary cost is necessary in replacement of structure. Therefore, The Tokyo Metropolitan Government decided to introduce road asset management early to solve this problem.
This paper attempts to incorporate life cycle management technique in the process to maintain the harbor facilities. Since deterioration will force the pace in many harbor facilities, it is necessary to implement optimal maintenance strategy. Taking steel pipe piles of pile-supported wharves for example, some of the piles need repair because of their severe circumstances against corrosion. It is important to minimize the expected cost during the extended lifespan of the structure to select an appropriate repair method. In this paper we predict the degree of corrosion on steel piles from the result of site inspection and estimate the expected cost to repair the predicted deteriorated area on the piles.
Superannuation of infrastructures has attracted attention to introduction of asset management to infrastructures. This paper summarizes present state of shore protection facilities, a method to evaluate deterioration of coastal dikes, and nationwide urgent check of coastal dikes and revetments, and discusses some points related to asset management of shore protection facilities.
After damage occurs in facilities, the control of maintenance to the infrastructure like the Port and harbor facilities has been executed. Latest information of the investigation, the measurement, and the examination, etc. to understand the current state of the facilities is necessary to execute the control of maintenance of facilities efficiently. Obtained information becomes basic information on the diagnosis of the facilities situation based on the proper procedure. The forecast of the superannuation of facilities becomes extremely important for explaining validity and the priority level of the facilities maintenance. In this paper, a current state of the investigation of the Port and harbor facilities, the measurement, the diagnosis, and the deterioration forecast and technological problems were arranged.
The special session ‘Environment Restoration Project’ in the 30^<th> Symposium on Civil Engineering in the Ocean, JSCE demonstrated that needs of the implementation of ‘Adaptive Management System. ’The five presenters had given various aspects of the adaptive management system, e. g. its need, definition, and background. The system is defined as ‘The adaptive management’, which is a system for implementation of ecosystem and fisheries resource restoration with in unpredictable variation and succession of physical and biological environment. It is enable to build mutual understanding among stake holders, and to match goal, objectives and action in reasonable way. Furthermore, long-term R&D strategies are needed for goal-setting, project-success-criteria and environmental-restoration-techniques, referenced by state-of-the art case studies.
Objective setting for an environmental restoration project and its processes are reviewed to apply adaptive management to the tidal flat at Tokuyama-Kudamatsu Port in the Seto Inland Sea. This project is carried out as one of the leading projects for The Restoration Plan on Marine Environment in the Seto Inland Sea, established by Ministry of Land, Infrastructure and Transport and Fisheries Agency in 2005. In this case study, monitoring and feedback program during and after the project has been proposed. In the program implementation, various stakeholders interested in the project shall share its goal and participate in the program. Since the goal that cannot be evaluated quantitatively is often set conceptually, it is broken down to several clear targets with quantitative success criteria, which are easy to measure and to manage.
How is the adaptive management applied to the implementation of an environmental restoration project and how can the succession/evolution of the project be evaluated? To get the clues of the answer to these questions, the US experiences have been studied. In Poplar Island in Chesapeake Bay and Sonoma Baylands in San Francisco Bay, the large scale environmental restoration projects are carried out by beneficial use of dredged material from harbor development works. An iterative process, where the initial management tools and plans are periodically reviewed through the monitoring, is applied as the management in these projects. The review process is facilitated by concrete success criteria.
The Osaka bay is one of the typical enclosed seas in Japan. “The action plan to regeneration of Osaka bay” was enacted in 2004 for the environmental improvement by the Promotion Committee of Osaka bay regeneration which is composed with government bodies and related municipalities. Adaptive management has been facilitated for the implementation of the plan. Enhancement of public-private partnership and development of environmental countermeasures are twofold major issues in the management. Some related activities are introduced as case studies.
We report a series of adaptive management approach to a tidal flat constructed in Port of Amagasaki. The management goal setting was to realize a tidal flat rich in bivalve Ruditapes philippinarum. Continuous monitoring after the construction revealed that the achievement of the initial goal was violated by the mat formation of Musculista senhousia. Less turbulence was suggested to cause the mat formation, from the analysis based on the field monitoring and numeric calculation. Therefore, as the countermeasure, structures promoting the turbulence were set up on the sediment surface. It succeeded in a decline of the abundance of M. senhousiaaround the structures. However, the number of Mytilus galloprovincialisthat favors hard substrate has increased around the structures, whereas the number of R. philippinarumwas not necessarily increased. Simultaneous use of other techniques such as mechanical agitation of sediment might be necessary to increase the number of R. philippinarumin the future.
Development of benthic communities were investigated at the Han-Nan 2nd. constructed tidal flat constructed by use of muddy dredged materials in Kishiwada city Osaka prefecture. In this paper, we compared a natural muddy tidal flat with constructed tidal flat about the succession of benthic communities. As the result, benthic communities adapted to muddy substratum were estimated in these experiments. The observed benthic communities resemble to those of natural muddy tidal flat. However, a problem is left unresolved in the use of dredged materials constructed tidal flat in terms of stability of sediment under influence of high waves.
The total design of the nature restoration in Takegashima underwater park was planned out on the basis of investigation for about 3 years. The summary of this design and main enlightenment activities of 3 years from 2003 to 2005 were described. The effectiveness of enlightenment activities was examined by using the questionnaire surveys that had executed in 2003 and 2005. It has been understood that our enlightenment activities is not enough for improving an environmental consideration in the community.
This paper summarizes the special session “Coastal Disaster Prevention -- Rehabilitation and Disaster Preventing City Against Tsunamis--. ” This session has been planned to understand the tsunami disasters and there rehabilitations. Presentations include the experiences in Okushiri Island which had severe damages in the 1993 Hokkaido Nanseioki Earthquake Tsunami and the 2004 Indian Ocean Tsunami. Also, countermeasures against huge tsunami disaster have been introduced by Miyagi Prefecture and Ministry of Land, Infrastructure and Transportations. After presentations, the countermeasures against tsunami disasters have been discussed. Throughout the presentations and discussions, many important issues have been pointed out.
The velocity integration method was applied to measure a wave information using buoys, which can measure a precise velocity for movable body without a reference station on land. In this experiment buoys equipped with GPS were moored in the observational sea area. As 3D movements of the buoys depend on the movement of seawater particle, the velocity integration method to get the precise velocity information of the buoys was used and the measured velocity was applied to estimate the position of the buoys. As experimental result, the wave directions (wave period is 14 seconds) according to the horizontal displacement of the buoys with the 3D buoy movement analysis are measured precisely and reliably.
Ocean wave information is indispensable for a coastal activity and service of ship to be carried out safely and economically. A low-cost wave height and direction sensor was developed by Japan Aerospace Exploration Agency and Japan Weather Association. The purpose of this study is to examine observation accuracy of wave height, period, and direction on the light buoy of Japan Coast Guard. Then, we installed a low-cost wave height and direction sensor on the light buoy and observed ocean wave in the sea. And, we compared data observed by light buoy with data observed by NOWPHAS (Nationwide Ocean Wave information network for Port and HArbourS). Our results show that observation accuracy on the light buoy is high.
We develop a real-time wave information and analysis system on the basis of a data assimilation technique, the optimum interpolation method, applied for wave observation data and forecasted data. The system can provide nowcast wave information for the sea area where there is no wave observation point. In the system, first, the initial estimate (nowcast) is computed in real-time with the observation data and forecasted information, and then the estimate is corrected after 12 hours with more accurate forecasted wave information. Finally, the corrected data is stored in the wave information database for analysis. We investigate the characteristics of the nowcast wave data and confirmed that the accuracy of the data is high enough for practical applications.
New methods of sea surface current and water quality measurement using video images are introduced. 1) Using the wide images taken by the video installed on top of the high building, the front of the Tokyo bay mouth was observed. The movement of the front is clearly observed by the stack image taken from the video images. From the stack images of the form left by the ship, we can also estimate the velocity at the monitoring site. 2) In order to estimate the water quality, we use the wake (the form) left by the ship. The normalized R/B and G/B ratio were proportional to the concentration of the chlorophyll a measured by the water quality observation system installed on the ferry boat, “Tokyo-wan ferry Kanayamaru”.
The real-time observation system of water levels is required to establish along coastal areas. The on-air acoustic tide gauge is newly developed here. It does not require the installation of the well in the water, so the construction cost is expected to be lower than conventional types. However, the accuracy is not verified in detail at the sea area which has large amplitudes of tides. In this study, tide data is continuously observed at the observation point in the Seto Inland Sea after the installation. At first, the property of temperatures in the steel pipe of the tide guage is analyzed. The unevenness of temperatures is found, so we construct the algorithm of the correction of the acoustic velocity by using calibration bars. Finally, the improvement of the accuracy is confirmed by observed data.
Flow and density structures in Ise Bay are strongly affected by meteorological disturbances because Ise Bay is a typical shallow and semi-enclosed bay. Therefore, it is necessary to take into account the influence of the meteorological disturbances appropriately in a numerical simulation. In this study, an Atmosphere-Ocean-Wave coupled model that can estimate coastal currents under the influence of meteorological disturbances is used to simulate flow and density structures in Ise Bay under various meteorological conditions. The comparison between the numerical and in-situ observation results was performed to verify the coupled model. As a result, it was demonstrated that the coupled model can appropriately simulate the oceanographic and meteorologic phenomena in Ise Bay, such as wind speed, tide level, water temperature, and so on.
This study examined the capability of the GFS-WRF-SWAN system by comparison of predictions with observations. Firstly typhoon courses were estimated from GFS and compared with observed courses together with forecasted ones by Japan Meteorological Agency. Secondly estimated wind fields around the Mutsu Bay, by WRF, were compared with the observations. It was found that GFS's and WRF's predictions showed fairly good agreement for both cases. Finally GFS-WRF-SWAN wave predictions were compared with observations. Concerning with the time series, there can be seen good agreements; however, the predicted wave heights were smaller than observations. It was also found that options of INPUT BY WIND in SWAN and a setting of frequency range affect wave predictions.
The multi-level model for nonlinear dispersive waves, in which vertical profile of horizontal velocity is assumed to be a chain of quadratic portions, was modified to obtain applicability to wave analysis on step-like bathymetry. A change in vertical dividing method brought about satisfactory result, in which the depth of vertical dividing interfaces was changed to have no horizontal distribution. The applicability of the modified model was examined by reproduction of experimental result for wave deformation on submerged dike.
Coastal waves in the Seto Inland Sea were hindcasted using a third generation wave model, WAM. In this paper, we examined the accuracy of the hindcasted wave data in the sea by comparing the measured wave data, and discussed the usefulness of the hindcasted data for practical applications. In addition, we investigated the statistical characteristics of waves in the sea by using a wave hindcasting database and discussed a few examples for utilizing the database.
The spectral width parameters ε and ν defined with spectral moments exercise little influence on the distribution of zero-crossing wave heights. Quasi-applicability of the Rayleigh distribution to wave heights holds for wind waves regardless of the parameter values of ε and ν. The spectral shape parameter κ related to the autocorrelation of wave envelopes is the governing factor for the distributions of wave heights. Various data of numerical simulations and field observations support the significance of the spectral shape parameter κ.
Short-term, seasonal and annual variation characteristics of unusual tides are analyzed using over 30years' sea level data both for southern Kyushu region and Nansei islands region. Effects of atmospheric pressure on the unusual tides are also discussed. The greatest contribution to the unusual tides comes from the atmospheric effects. However, for the short term variation of the unusual tides, longer term fluctuations more than 40days which are considered to be irrelevant to typhoon directly induced motion become dominant for Nansei island region. The sea level fluctuations at Nakanoshima site are found to be closely related to the variations of Kuroshio axis in the Tokara strait.
Hurricane Katrina struck around New Orleans in August 29, 2005, resulting huge flood disaster due to large storm surge. The process of the storm surge has not been revealed because many observatories were failed during the storm. In this paper, we discuss about the process of the storm surge, ocean waves, and wave-setup by numerical simulations. Besides this, influences of the moving velocity of the Hurricane on the storm surge are also discussed.
In many ports, long-period waves decrease the efficiency of cargo handling and sometimes cause break of mooring ropes. One of the most effective ways to reduce the long-period waves in a port is to construct the wave absorption facilities. Then, we proposed a new slit-type long wave adsorption facility whose length is shorter than the other former long-wave absorbers. The facility has the long wave absorption function applying eddy loss effect. The basic performance of the facility has already been examined by the hydraulic experiments. This study estimates optimum configuration of the facility and verifies the characteristics for the actual form by the hydraulic experiments.
Kato et al. (2005) presented formulae to estimate bound wave heights for various Smax. This paper generalized their idea and presented a formula which can estimate bound wave heights for arbitrary Smax. Bound wave heights have been calculated with observed wave data and analysis has been carried out on the relationship between bound waves and total infragravity waves. The result suggests that the ratio of the bound wave height to the total infragravity wave height depends on Ursell number and the water depth.
This paper shows a countermeasure against low frequency motions of a moored ship. It is difficult to decrease the low frequency surge motions of the ship moored by fiber ropes, because breakwater cannot prevent the entrance of low frequency components of ocean waves. Furthermore the very small damping force of surge motion interferes reducing resonance motions in the low frequency range. The shielding structure, which is close to the weather side of the ship, is prevent the flow due to the low frequency waves so it decreases the wave exciting force. Then the effect of the shielding structure is confirmed by the tank tests. Moreover, the effect of the structure, which consists of flame structure and membrane, is also confirmed. This shielding structure effectively decreases the low frequency surge motions of a moored ship.
In recent years, inhabitants are one of stakeholders in planning a public work and their opinions make an important role in the procedure of assessment. Such assessment is also necessary in evaluating existent works executed before the amendment of the Seacoast Law. To investigate the inhabitants' estimation of public work, questionnaire researches on the opinion of inhabitant about public work have been carried out in two coastal zones. The two zones are in Okura coast, Hyogo and Nishikinohama coasts, Osaka, where the Coastal Community Zone works (CCZ work) were done by Japanese government. In this paper, inhabitants' evaluation of the environment improvement work and the participation of inhabitant have been discussed. The results show that the inhabitants appreciate the improvement works, however, they do not recognize the objectives and plan of the works correctly. This means that the advertising the purpose and outline of works to inhabitants is an essential factor to gain the better estimations of them.
Use and coastal environment assessments by surfers along the suburban coast of Sendai City were examined in order to collect basic data for the improvement of the coastal environment. A survey was conducted in four locations used by surfers along the suburban coast of Sendai City. The survey consisted of assessments of surf conditions, a field study, and a questionnaire survey in the field. Results of the surf conditions at the new port site in Sendai revealed that utilization by surfers accounted for approximately 75% of total use. The field study revealed that surfers were primarily fond of playing in breaking wave heights between 1.3m and 1.8m. Surfers that responded to the questionnaire survey stated that the principal changes to the coastal environment in the past several years included a marked increase in the number of surfers, an increase in the amount of litter, deterioration of the waves, and increased seawater pollution. The number of items concerning coast utilization and items related to the coastal environment accounted for 70% and approximately 10%, respectively, of the total requests by surfers regarding surfing locations.
Law on Promoting Green Purchasing was enforced on 2001. This paper studied the existing state of the Green Purchasing associated with the Law, for public works of port and airport construction. Then the key point of the promotion of procurement of eco-friendly goods and materials by the State and other is considered. This paper presents, as a supporting tool for promotion of Green Purchasing, guidebook of eco-friendly goods and materials for port and airport construction use and reported cases of Green Purchasing of eco-friendly goods and materials.
This paper reviews the past, present and future of the coastal and marine management in China through internet exploring and researcher interviews. The results show that the coastal and marine management in China is rapidly being improved recently despite of its short history of no more than 30 years. The largest characteristics of current coastal and marine management in China are the separation of the ownership and use rights of coastal and marine areas, and implementation of charge for coastal and marine uses that is based on a market mechanism. New trends in coastal and marine management in China lie in administrative collaboration, legal integration, IT application and public participation to reach good governance of coast and marine areas. All that are done in China are regarded good experiences and could provide important clues for integrated coastal and marine management in Japan.
In order to assess the present state of Japanese Coast, pamphlets for public relations issued by the local and the central government agencies were gathered and analyzed. Results of this analysis clearly displayed the characteristics of Japanese Coast. The main issue to deal with on the coast is to prevent coastal disasters such as beach erosion, storm surge and large waves, and tsunami impact. Beach erosion occurs along the entire coastline and extensive countermeasure works have been carried out. The coastal areas where storm surge is a major problem are primarily located on the East China Sea, the Seto Inland Sea and the Southern part of Pacific Ocean Coast. Tsunamis often attack the Pacific Ocean Coast and they are especially serious in the Sanriku Coast. Coastal structures employed as protection works are mainly sea walls, detached breakwaters, jetties and sea dikes. The use of artificial reefs and beach fills for countermeasures are gaining popularity and several plans to execute such measures are scheduled. To recover sandy beaches that have been lost, many small artificial beaches are constructed and additional minor beach fills are planed throughout the coast, especially on Okinawa and along the coastline of the Seto Inland Sea.
Relationship between long-term change in land use and increase in disaster potential of a coast was investigated through the comparison of past photographs, taking Kamogawa Beach as the example. In 1950s, there was a wide sandy beach at Kamogawa, but planting pine trees was carried out to create coastal forest for preventing wind-blown sand as well as the construction of the seawall very close to the shoreline. Towns also advanced in the vicinity of the seawall. The fishing port breakwaters and detached breakwaters were also built, resulting in significant shoreline changes on a pocket beach. Finally, this beach became vulnerable against coastal disaster.
While lots of harbor structures have been constructed, some of them are reaching the ends of design service life. The number of structures at which remedial actions are required will be increasing rapidly. To meet the increasing number of degraded structures, strategic maintenance and repair methods should be implemented to realize life extension and structural performance recovery, resulting in minimization of life-cycle costs. In this paper, the method is proposed to evaluate proper life-cycle scenario of deteriorated open-type wharf from the viewpoint of life-cycle cost. The change in load carrying capacity of RC members due to rebar corrosion is taken into account. Based on the calculated results, life-cycle scenarios with different repair plans were discussed from the viewpoints of recovery of load carrying capacity and the relevant life-cycle cost.
Recently, the citizens have been become more nervous about disaster prevention and reduction, because a lot of natural damages happen frequently and lager-scale all over the world. The questionnaire research was carried out for the residents suffered from the storm surge, the flood and the others at Kumamoto. As result of analysis, the residents living Kumamoto were suffered form disasters more than the whole country, and they hope the hazard map like that the disaster information be able to seen and used easily more. Finally, we propose that hazard map content not only the natural disaster information but also safety life information including daily lives.
Enhancing macrobenthos diversity is an attractive restoration objective for urban coastal area as canals and harbors. To determine constraints of environmental restoration in such enclosed and entrapped water body, survey based approach was taken at Keihin Canal, Japan as a case study. We had sampled water, sediment and macrobenthos from 14 stations at October 2005. The separated sample for short-necked clams were collected from 7 stations in the same period. The constraints are elevation of the site, Chemical Oxygen Demand (COD), and silt-clay fraction for overall macrobenthos abundance while low salinity due effluent from outfall of sewage giving additional constraint for short-necked clam diversity.
Ministry of Land, Infrastructure and Transport and Shunan City plan a pilot project to restore a tidal flat for culturing short-necked clams at Oshima area in Tokuyama-Kudamatsu Port, Japan. Developing the plan for this pilot project, we introduce the concept of adaptive management into it. This report reviews the process to break habitation conditions of this tidal flat down into the success criteria for adaptive management and to develop a monitoring & evaluating system.
Ariake Sea, a typical enclosed bay on the west of the Kyushu Island, has been suffered with environmental damages. However it is still unclear which factor and process is dominant. In this study, field observation was conducted inside the artificial tidal flat to model the physical, chemical and ecological system in tidal flat for the preservation or recovery of the coastal environment in Ariake Sea. Three years pass after an artificial tidal flat was constructed; the habitable condition has been influenced with the ground lever, the ground bearing capacity, and the tide. In addition, the existence of tidal pool has been improved the water quality within an artificial pond “Yacho-no-ike”.
An integrated environmental assessment of a coastal wetland will be presented using Awase wetland (N 26° 18.47, E 127° 58.12, Subtropics) as a case study site. Environmental indicators are selected, and the current environmental status for the indicator species (groups) are described by the Habitat Suitability Index (HSI) methodology. Based on the standing stock biomass and its fraction of each species (groups) are used as an indicator of the assessment. Subsequently the impact of a future large-scale landfill development on the wetland was evaluated. Large losses in optimal habitat (>20%) are recorded in large seagrass area, benthic zones IV (Gastropod dominant) and VI (Annelid dominant), and Kubiremidoro (green algae), with significant losses (>10%) in benthic zone V (Annelid and Arthropod dominant). The relative proportion of optimal area for the each species (groups) doesn't change except for a special type of benthic zone IV. This attempt of assessment gives a guideline for integrated coastal ecosystem management of the area.
Questionnaire survey for Contingent Valuation Method was executed in East Mikawa region, West Mikawa region, Chita region and Nagoya city, to measure social utility on development of tidal flats and shallows in Mikawa Bay. From the obtained data, distribution curve was estimated by using Logit model with loglinear type utility function. The median of willingness to pay was estimated to be 2500 (yen/household) from the distribution curve. To supplement the information for decision-making, questions asking recognition on the developments of tidal flats and shallows was attached to the questionnaire. From the result, proportion of people who recognized the bad environmental state of Mikawa Bay was high. Proportion of people who prefer the region image of old times as a target of restoration was kind of higher than proportion of people who prefer the region image of present age. The proportion of people who accept to continue the tidal flats and shallows development projects was high.
PLB (Porous Layer Boundary) method was proposed by Hirayama (2001) for a Boussinesq-type wave transformation model in order to calculate partial reflected waves on both breakwaters and revetments covered with armor blocks. The modeling of horizontal distribution of porosity in porous media is improved in this study. The porosity of improved PLB is estimated by integrating vertical distribution of porosity from sea bottom to water surface, which consists of armor block layer and water layer. This modeling is similar to the definition proposed by Madsen et. al. (1997) or Kennedy et. al. (2000), therefore the newly proposed PLB method can also calculate moving shoreline as the porosity of armor block layer is very small. The calculated reflection coefficients at sea wall covered with armor blocks agree with the results of model experiment very much.
Wave-induced currents in a surf zone have been simulated with Boussinesq-type wave transformation model considering wave breaking and runup. In this paper, two kinds of the averaged current fields estimated by different ways are shown. One is calculated with the gradient of radiation stress given by the distribution of wave height and the other is directly given by momentum flux, simulated in surf zone. Both the averaged current fields estimated by the numerical simulation on a sloping beach or an actual reef agree with the results of model experiments in the flow pattern and velocity. Thus, it is confirmed that the depth-averaged flows in surf zone are calculated by using Boussinesq-type wave transformation model with good accuracy though the vertical distributions of water flow including the undertow are not focused.
Much research has focused on breaking waves, revealing key findings on vortices and turbulence within wave motion; however, the wave motion of breaking waves is strongly affected by the presence of an entrained gas phase. It is essential to explain the wave-breaking mechanism with reference to the fluid mechanics of the gas phase and to examine the velocity distributions in the two phases and vortex structure in the incipient motion of wave-breaking. In this research, time and space-dependent changes in the velocity field of two-phase flow of gas-liquid have been observed in a breaking wave with respect to the changes in water surface profile. The velocity distribution in the gas phase is predominantly influenced by the changes in the water level, while the gas phase forms a circulating flow field near the wave crest.
Wave prediction models based on the energy balance equation are suitable for applications involving a large sea area. Time domain models like the Boussinesq wave model can estimate wave fields in detail for a not so large area. As a first step to link together these models seamlessly, this study presents a time domain analysis of multidirectional random wave transformations, in which the incident wave spectrum are intermittently distributed over the rectilinearity. Multidirectional random wave transformation over a spherical shoal is numerically simulated by a Boussinesq model with the present method which starts calculation from cross sections around the shoal. The results on the significant wave height distributions and wave spectrum are compared to those calculated by an energy balance equation model in the whole area.
A lot of inundation of sea water has arisen at coastal zone in Japan recent years because of attacking larger tidal waves and storm surges than usual. Also there are many examples that a destruction of parapet could cause serious damage by increasing of overtopping to the coastal zone. When seawalls have been damaged, a lot of scrap concrete is generated. In this study, a countermeasure against wave overtopping using these scrap concrete of damaged seawalls is proposed and verified the validity of the facilities and equipments for countermeasures against disaster by hydraulic model tests. Furthermore a method for estimating overtopping over seawalls using CADMAS-SURF has applied to the model test and validated.
At Waku fishing port, facing to Japan Sea, in Yamaguchi prefecture, people are troubled with heavy water spray caused by sever waves and strong winds in winter at a vertical type breakwater constructed in front of the mouth of the port to protect the inside against incoming waves. To reduce the generation of and the damage from the water spray, three different types of countermeasures were proposed: 1) the construction of an artificial reef some distance ahead of the breakwater, 2) the construction of an offshore breakwater some distance ahead of the breakwater, and 3) the covering of the breakwater with wave dissipating blocks. Experiments using a wave flume with a wind tunnel were conducted to study the effects of suppressing the water spray generation. It was found that the countermeasure No. 3 is the most effective means and it can reduce the water spray drastically.
Seaside houses in Kamoenai Village were seriously damaged by Typhoon No. 18 in 2004. The damage patterns were classified according to wave overtopping rate and the distance from the seawall alignment. The wave overtopping rate and wave forces on the houses were reproduced by two dimensional model tests, and the critical condition of seaside houses behind the seawall was shown as the function of offshore wave height and the distance from seawall. Based on the results, the evacuation condition was recommended for the coastal residents in Kamoenai Village. It was also confirmed that the safety of seaside houses can be improved by wave absorbing revetments in front of seawalls.
A Non Wave-Overtopping Type Seawall in deepwater which effectively prevents wave-overtopping by its curved part has been studied. By using this seawall, the crown height can be reduced compared to a conventional seawall, and extremely large wave run-ups which suddenly occur due to the irregularity of the waves can be effectively prevented. However, it may sometimes be requested to use this seawall accepting some amount of wave-overtopping in exchange for lower crown height. Thus, in this study, wave-overtopping characteristics of the Non Wave-Overtopping Type Seawall were examined with numerical calculations and experiments, and the followings have been understood: 1) the relation between the height of the crown and the rate of wave-overtopping, 2) the influence of the shape parameters in section on the rate of wave-overtopping.
The permeable terrace-type seawall is a seawall with a wave chamber filled by wave dissipating materials like stones or concrete blocks between a permeable front wall and an impermeable rear wall. In the present paper, a calculation method of wave overtopping rate on the permeable terrace-type seawall has been proposed on the basis of laboratory experimental results. The performance to reduce wave overtopping is discussed in comparison with conventional vertical seawall and sloping seawall. It is concluded that the permeable terrace-type seawall can reduce wave overtopping effectively with a low crest height and less wave dissipating materials comparing with a sloping seawall. An example of application to the field site at the water depth of 12m including tide demonstrates that the permeable terrace seawall with the crest height of 2.4m and the width of 8.5m satisfies the allowable overtopping rate of 0.01m3/m/s against design waves of 9.05s in the significant wave period and 3.0m in the significant wave height.