This paper is concerning about underwater concrete method using concrete pumping and casing pipe. This method is reliable and popular in the field of construction of port and fishery harbor facilities. Most essential code i. e. mix proportion, the way of placement and so on, is declared at “STANDARD SPECIFICATION FOR CONCRETE STRUCTURES-2002, Materials and Construction”edited by JSCE, and “MANNUAL FOR UNDER SEAWATER CONCRETE”supervised by Hokkaido Development Agency. Though the first-setting distance between casing pipe and surface of rabble mound is one of the most important factors to prevent segregation in water, it is not described in them. To clarify the distance, the placing concrete tests using concrete pumping and casing pipe, wewe carried out with good precision.
According to these experiments, the paper addresses that the appropriate distance can be about 6cm.

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In the construction of steel pipe sheet pile foundation, the displacement of the foundation caused by the external force can be reduced by enhancing the shear strength of the pipe junction, because the overall rigidity of the foundation depends heavily on it. Quantity of the steel pipe sheet pile can be reduced at the same time. This paper explains the development of a pipe-junction named “Super Junction”, which has higher shear strength than the commonly used ones.

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At the time being, deterioration in water quality of closed water body has become a serious issue for local fishery and accumulation of mud layer which covers lakebed has been thought as the cause of deterioration. Then, it can be said that maintenance and preservation of the water environment by retrieving those mud layer is one of the most important subjects to enhance and to promote regional economy in the vicinity with preserving precious marine resources.
The authors have proposed a new retrieving method of lakebed mud on site. This method has been developed as an innovative way that requires neither additional chemicals for condensation of the mud nor a temporary yard for desiccation of the mud. After the first phase with indoor model experiment, it was confirmed that the method successfully retrieve the mud and an on-site experiment is now under planning. In this paper, the authors report a study result on the device, especially the shape of retrieving fan, with 3-D flow analysis. Through this study, important knowledge for designing the shape of fan was obtained in order to expect efficient retrieving. Though further experiment is necessary under various mud conditions to improve the efficiency, the method is getting close to a reality.

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Recently, the conduit transport using compressed air is attempted as a transportation method of emulsified oil, high viscosity solution. This transport system would be used in: compound of corpuscle and water such as seabed-dirt with comparatively high water content, crude petroleum that flowed into sea area with increased viscosity, and liquid that mixed algae in a high density of the freshwater lakes. Though the long distance conduit transportation is needed to achieve these transportations, the research of the corresponding long distance is extremely few. In this research, the experiments are set-upped by 620m for the longest length in the horizontal pipe, 38mm for the pipe diameter. We examined the effect of initial pressure of compressed air in long distance conveyance. As the results of the experiment, it was to clarify that the pipe length and initial pressure have the correlation. Prediction formula concerning the initial pressure was able to be required from these data.

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Conventional pipeline sand transportation systems generally consume excessive amount of energy to ensure the system to transport sediments without causing problems such as blockage of the system. These systems are thus economically inefficient although the safety operation factor of the system may be relatively high. On the other hand, some systems aim to utilize clean energy such as water head to transport sediments. While these systems, consuming relatively low energy, may have only small sediment transport rates, the system may be operated for longer duration of time without having significant impacts on the surrounding environment. The ultimate goal of this research is thus to develop such low-energy sand-bypassing systems. This paper especially aims to investigate the sediment transport characteristics in the pipe flow especially when the flow velocity is relatively low.

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The north breakwater at the Otaru Port, constructed from 1897 to 1908, is a part of our civil engineering heritage and widely known as Japan's first authentic open-sea breakwater. Recent research has found that its foot protection concrete blocks have been displaced and the mound has been deformed. Should it be left as it is, the vertical superstructure might collapse due to scouring. It was therefore decided that the structure would be restored. In the restored structure, the foot protection concrete blocks and the mound should be more stable than the existing ones, because they will be subject to raging waves for many years to come. Restoration worked based on the structure's original design, an approach generally taken in renovating historical buildings, is not appropriate in this case. This paper discusses a basic concept for the restoration project of the north breakwater.

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Lifecycle management of coastal dikes is required for making their life span as longer as possible. The purpose of this study is to investigate cracks, unevenness and compressive strength of concrete armored coastal dikes constructed more than 40 years ago along Mikawa Bay, by means of field measurement with 30m tape, 30cm steel rule with mm scale, level and Shumitt hammer. The field measurement shows that crackings are classified into seven patterns, and that the probability of crack occurrence on the concrete armored crown is about 0.4, which is higher than those of the seaward and landside slopes of the coastal dikes. The averaged crack-propagating speed per year after construction is found out to be less than 0.32cm/y on the armored crown and less than 0.17cm/y on the armored seaward and landward slopes.

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The rubble foundation for the immersed tunnel under construction in the Bosphorus strait is build by using the tremie pipe and the grader equipment due to the large depth and strong currents in the strait. The rubble-dumping simulator to predict the height distribution of dumped rubble was developed in order to obtain the optimum rubble volume and positions for dumping. In the simulator, the dumped rubble distribution is estimated by two parameters, the dispersion coefficient and the angle of repose of the rubble.
The field test for building the rubble foundation was performed at the construction site. The two parameters of the rubble were examined from the test. Then it was confirmed that the dumped rubble distribution was simulated well by the simulator. And it's succeeded to build the accurate rubble foundation under the sever sea state by the construction technique using the tremie pipe and the grader equipment.

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The Bosphorus tube crossing in Turkey is constructed in the two-layered and very fast current. To ensure the safety and accuracy of the tunnel immersion, the current forecast models have been developed based on the observation results. In this study, these models are systematized and their reliability is estimated. The forecast system consists of two systems, the water level forecast system and the current forecast system. The former includes wind, air pressure astronomical tide and seasonal effect. The latter is calculated from the water level difference between the both sides of the strait considering the stratification effect.
The system is mainly used for the “Go/No go” decision of the immersion work. According to the validation with the past monitoring data, the 90% confidential range, which includes meteorological forecast error and model error, is almost 0.4m/s. In the same period of that monitoring, the “Go” decision went well in 90% using the forecast directly, in 100% considering the 90% confidential range.

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The repair of detached breakwater body is discussed in this paper. In the repair of the detached breakwater body, the use of rubble stones with larger mass than the required mass in the initial design is proposed. Although the estimation of the repair cost depends on the circumstances of the detached breakwater, the effectiveness of such kind of repair method is investigated on the basis of estimation of the expected repair cost. The repair criterion was determined on the basis of transmitted wave height behind the detached breakwater.
The authors show that the repair cost was reduced in several cases where larger rubble stones were used for repairing the detached breakwater body. In other words, the stability of the detached breakwater improved at low repair cost by such kind of repair method in several cases.

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Possible enhancement of nutrient availability in the euphotic zone was challenged by lifting up subsurface nutrient-rich water in a coastal area. Man-made sea-mount was designed to enhance the rate of upwelling on continental shelf area. Since 1995, a project has been carried out for six years to build up a depth of 80m off Nagasaki Prefecture of Kyushu Island. During the research period, the availability of clear data sets of ocean color satellite images was about 4% of all scenes taken in this study area by the SeaWiFS sensors. Patchy areas of higher chlorophyll-a concentrations than the surrounding water were occasionally observed in the square area of about 10km* 10km where the sea-mount was built in summer. The geophysical locations occurring the high chlorophyll a patches corresponded with the area predicted by a mathematical simulation model.

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Artificial marine ridge has gotten the attention recently as a tool to increase fishery resources. Ridge requires thousands of cubic meters of materials; rocks or concrete blocks. In these projects, it should be appropriate to choose recycled materials for the sake of environmental conservation. However conventional cost evaluation method, which is only considering internal cost, has prevented from using those recycled.
In this study, the comprehensive construction cost considering external cost is estimated and the estimation technique is examined in order to promote utilization of recycled materials. The comprehensive cost is estimated using four external cost counting methods about a virtual ridge development with three kinds of materials. AHP is utilized to integrate internal cost and several external costs. DEMATEL is applied to consider the wishes of inhabitants. The estimation using AHP resulted in correspondent to the wishes. It is suggested that this technique make it easy to reflect local feelings in the choice of material via cost.

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The artificial marine ridge is expected on its gathering effect. In this paper, the method of estimation the economic effect of the ridge from the characteristic of fish species and economic point of view.
The shape of the ridge was assumed, and a ratio of gathering quantity with and without the ridge was estimated. Quantity with the ridge is estimated multiplying fish density at planed site by the ratio. An amount of the effort and a total fish catch that satisfied constant CPUE were obtained. It is suggested that estimated catch satisfies expected CPUE.

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In this paper, marine structure off Tomakomai Hokkaido is reported. This area is planed for developing artificial marine ridge. Analyzing the marine structure gives necessary information to examine the possibility of this project. Main results are as follows,
1) Bottom water mass flows faintly but no stasis is seen. 2) Bottom water mass contains comparatively high nutrients to upper water mass. 3) Stratification is seen in autumn, when upper water lacks nutrients and primary production comes down in this area. 4) Period of low primary production period and of thin nutrients are almost correspondent. 5) This observation suggests the possibility of primary production improvement by upwelling current with artificial marine ridge.

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The dumping method of a large amount of rubble is investigated to optimize the construction works of artificial fishing mound for uplifting the eutrophied water with the upwelling current. In this method, bubble placed in a hopper is dumped by split barge. This paper presents the influence of time to open the split barge on deposition configuration of bubble and refers an acceptable dumping method in actual works. As a result, the new method with time control to open the split barge can develop a good deposition configuration.

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A new environmental creation is attempted at an offshore artificial island in Shimonoseki, where an artificial alga habitat was constructed in a part of the outer shore protection facility of 350m extension. A field experiment was carried out at the existing work base according to a basic plan of the project established by examining the past investigation data. An alga habitat creation plan has been examined based on the data obtained during the field experiment. The configuration and layout plan of the concrete block and the transplant plan of the alga were also examined simultaneously. The effects of alga habitat creation have been confirmed by the reproduction of the sea alga of the transplanted species.

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Restoration of sea grass beds and seaweeds is becoming important for civil engineers as for the conservation of marine environments. In particular, in canals surrounded by large cities and connected to coastal waters, it seems to be rather difficult to develop sea grasses and seaweeds because of the shortage of lights. In the present study, we consider the possibility of the development of sea grass beds in these waters using artificial lights. For this purpose we performed indoor experiments to analyze the efficiency of their photosynthesis using LED lights that have been rapidly improved in recent years. We proposed an efficient methodology to apply LED lights to this objective. Currently, the method still seems not to be feasible because of the high cost, the combination with other purposes and technology evolution would lead to the application of the present method.

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The method to add the function of seaweed bed construction has been applied in the offshore breakwater in Uki fishing port, Nagasaki Prefecture. After completion of a part of the offshore breakwater, the monitoring survey to verify the effect of the function of seaweed bed construction was carried out 7 times during 6 years. On the basis of the results for monitoring survey, the effect of the function of seaweed bed construction was verified and evaluated using the distribution of seaweed bed and succession of seaweed community.

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Laboratory experiments were conducted to evaluate moving speed of drifting seaweed that moves on the bottom and to obtain critical velocities for seaweed to start drift due to waves and currents. It was found that moving speed of seaweed approaches to the ambient fluid velocity when the velocity becomes very large, and the critical velocities in uniform currents were about 5cm/s and 10cm/s for smooth bottom and rough bottom, respectively. Critical velocity amplitude under waves on rough bed was somewhere between 7.7 to 9.8cm/s which was equivalent to that for uniform currents.

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The removal plan of the belt conveyer pier is under way in Niigata Prefecture Joetsu City. It is concerned that the KATANORI (Grateloupia divaricata) vegetation surrounding the pier site might be influenced by this plan. G. divaricatais important algae for local fishermen. However, information of the growth conditions ofG. divaricataand influence by construction were little. Therefore, each stakes holder cooperated to reproduce theG. divaricatacolony and the conference for the problem solving was held. In the conference, the field investigation, the examination construction and the execution scheme were executed. As a result, the KATANORI beds was succeeded.

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In Inner bays used as aquaculture grounds water quality is continuously deteriorating. As a remedial measure, a technique has been proposed and examined to cake dredged bottom mud by mixing with caking agents and further utilize some of the caked bodies by placing them in or near the dredged sea region for eelgrass bed formation, which can be expected to improve water quality in the dredged inner bays. A verification test on the technique to reutilize bottom mud as an eelgrass settlement substrate was carried out in an oceanic water region. Bottom mud with a water content of 50% or higher was mixed with a caking agent at 2-5% in wet weight. The caked bodies did not result in re-suspension. Imbedded seeds were observed to germinate out of the caked bodies for settlement and growth on the caked bodies. An observation revealed that the cement caking agent was good for the germination and initial growth and the magnesium caking agent was relatively good at the declining phase.

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A new type transplanting block made from two layers structure (asphalt-palm fiber mat) for the eelgrass (Zostera marina) bed restoration was developed. The block has high specific gravity that can stabilize the sea bottom condition, protect eelgrass seedlings transplanted from washing away. Moreover, the block provides surface structure which root bundles of the eelgrass firmly grip. In the site study, the transplanted seedlings into the block grew well and the number of shoots increased. More than 1000 shoots were observed after 19 months transplantation. Therefore, we conclude that the newly developed block is a practical means for improving the eelgrass community formation.

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One of the problems of developing seagrass beds by sowing was the incident that the sediment movement washes the seeds away. Therefore, we suggested the method of developing seagrass that seeds were weighed down and were kept under the sediment by lumps of mud. They were made by blending marine clay with neutral stabilizer.
Formerly, we have originated the germination test of marine clay and the lumps of mud with seagrass seeds, admitted that the lumps of mud were good for the germination. And then, being based on the test, we conducted the field experiment that proved the method to be effective in germinating and growing. The experiment has been made at two different conditions. As the results, at good site, we could not find the difference of germinating rate of the experimental materials. On the other hand, we could suggest that seagrass in the lumps of mud has grown and remained better at the harder site. So, we could admit validities of the lumps of mud.

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By turning attention to the wake area formed behind the blunt shaped object, where the diffusing dyestuff like minute particle pills up in fluid mechanically, we developed a technology to lead Sargassum's embryo to the wake area of 1mm granular substrate in diameter. We generated a steady flow in range of Reynolds number 3.6-75, by using the diameter of the granular substrate as a standing length, and dispersed the embryo. The embryo was lead to the back of the granular substrate, and clinging was comfirmed after 14 days of culturing. After 3 weeks of culturing from the day clinging was seen, the young plant'sattaching force exceeded than the fluid force which effect on the young plant in the ocean. We used ferrite particle as the granular substrate, and magnetized it. If it is scatterd to the algal reef made of steel, it is suggested that the transplanting technology of this style would be available even in the high waved ocean.

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A new seaweed bed called ‘Recosul’, composed of modified-sulfur and recycled inorganic materials, is examined in immigration and growth of seaweed (Laminaria angustata).
Comparison to conventional concrete seaweed bed shows significant difference in several cases with minute measurements on shape of Laminaria angustata but in the number of immigrated individuals.
Recosul is known as not only salt and acid resistance but also abrasion resistance and stability when added high density steel slag.
Recosul is suitable for artificial reef material.

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The Sone tidal flat in Kitakyushu city has a dry flat of about 517ha during ebb tides. It is one of the nicest spots for the wild bird observation through the four seasons. It is also famous as the breeding ground of Horseshoe crab (Tachypleus tridentatus). Although large-scale landfills have been recently constructed around the Sone tidal flat, number of Horseshoe crab breeding pairs laying eggs have been increasing. The aim of this study is to identify changes in wave environments due to the large-scale landfills through a numerical wave model and to understand physical habitat environments of Horseshoe crab larvas through field studies.
A drastic decrease in the wave intensity due to the large-scale landfills is confirmed and may be one of the reasons for increase in number of the breeding pairs. Also, basic physical characteristics of Horseshoe crab larva's habitat environments are identified and discussed.

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The swimming behavior of laval manila clam Ruditapes philippinarum and laval hen clam Pseudocardium sachalinense can be modeled by repeating the rise by a spiral movement and the swim stop generated intermittent settling. The planktonic larva of bottom-clinging stage increases the swimming speed and the diameter and the fall speed of a spiral movement with growth, and the rotation cycle of a spiral movement has decreased. If the particle diameter of the sediment is larger than the shell length, the planktonic larva is caught in the pore of the sediment when reaching bottom by the settling. If the particle size of the sediment is significant small compared with the diameter of a spiral movement, the planktonic larva caught in the sediment pore is gradually opened from the pore while repeating the surface of the sediment and the head-on collision. On the other hand, if the particle size of the sediment is almost equal to a spiral diameter, the planktonic larva keeps being caught in the sediment because a spiral movement becomes possible in the sediment pore. Larva's dispersion process after the bottom-clinging can be formulated by the advection dispersion equation, and can be evaluated by dispersion coefficient.

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For strategic planning of habitat restoration at Tokyo Bay, a basic data set of habitat had been corrected by field work at March and September, 2006. The targeted species are sessile organisms and macro benthos at seawalls and tidal flats. We found 1) even in the inner part of the bay where over eutrophicated area, tidal flats had kept rich benthos diversity, 2) sessile organisms diversity had been attributed by the spatial structure of water quality such as transparency or salinity. A hypothesis of predominant factors for the spatial distribution of benthos and sessile organisms at Tokyo Bay shore is formulated.

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Yatsu Higata is one of the most significant remaining tidal flats in Japan, and was registered under the Ramsar Convention in 1993. In recent years, Yatsu Higata has witnessed an extraordinary growth of Ulva sp. algae. This paper describes field studies intended to explore the dynamics of the nutrient in Yatsu Higata and Tokyo Bay. As a result, the Ulva sp. flourishes in Yatsu Higata, due to the ready supply of nutrient runoff supplied by the Yatsu River. In the water quality of Yatsu Higata, nitrate nitrogen is high and to be considered to strongly affect the growth of Ulva sp.. The ability of purification of Yatsu Higata reduces in summer and winter because of the existence of Ulva sp..

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The ecological network formation of Uca lactea which is one of the Near Threatened species in Red-data Book published by Japan Environment Agency was considered. Study site is the tidal flats in Awaji Island which is located between Hrima-Nada, Osaka Bey and Kii Channel and around there. In this study, first, to confirm the habitat distribution of Uca lactea in Awaji Island, field observations were carried out. Secondary, to examine the possibility of the ecological network formation of Uca lactea around Awaji Island, the numerical simulations were run. Main results are as follows; 1) The habitats of Uca lactea in Awaji Island distributes on both east and west sides of Awaji Island. 2) In some of the habitats of Uca lactea in Awaji Island, the alternation of generations might be proceeding. 3) There is limited possibility that the movement of Uca lactea's larvae can reach to other habitats which is located across-the-sea neighbor in one month.

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In order to understand bio-production process of fiddler crab (Ilyoplax pusilla) which is a typical benthic organism of sand muddy tidal flat, temperature range of the crab's activities on the substratum, effects of substratum temperature, habitat density and ebb period on the growth were determined indoor using an experimental tidal flat system in which water temperature, tide cycle and light intensity were controlled. Habitat density of the crab in situ was also surveyed every month for a year. The crabs emerge from their burrow for feeding as well as other activities as the surface substratum temperature ranged 13.4-46.5C. There was a high correlation between temperature of the substratum during daytime eddy period and the growth. No increasing in fresh body weight of the crab was detected as the substratum temperature is below 13.7C. The bio-production was calculated with data which were obtained by the indoor experiments as well as the site survey. The bio-production in the summer was 70 times larger than that in the winter. It is implied that temperature of the substratum is a crucial factor of influencing the bio-production of the fiddler crab in tidal flat.

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The Ariake Sea, a typical closed bay on the west coast of Kyushu Island, has been suffered several external impacts. However, the relative contribution of the various factors and processes of such impacts is still unclear. We have conducted field observations inside an artificial tidal flat to model the physical, chemical and ecological attributes of the tidal flat system in effort to preserve and recover the coastal environment of the Ariake Sea. In this study, the ecosystem and habitat of the artificial tidal flat was investigated by field observation over a 4- year period following the construction in October, 2002. Sediment has deposited in sub-tidal zone due to erosion of inter-tidal zone and inflow from outside the pond by rain and wind. Organic substance in the sediment is in proportion to soil content at sea, although it is dependent on eating by Benthos at inter-tidal zone. To use of the “minimum function” which selected the minimum SI could verify the accuracy of the Habitat Suitability Index model.

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The purpose of this study was to improve the quality of sediment through sand covering and to improve the quality of water through aeration, in order to restore the population of zoobenthos. This study made it possible to verify the consistency of effect that these methods bring about, and what countermeasures may be necessary. The sand covering effects are verified by total sulfide reduction from the sediment and inhabiting benthos. The aerators were set on a constructed tidal flat to reduce the baneful effect of the surrounding hypoxic seawater on zoobenthos. The effect on benthic animals was obtained from the aeration experiment of three years. Long-term monitoring is needed for evaluating the full effect of aeration on zoobenthos. As a result of this study, guideline for the management and countermeasures to be taken in the next construction of tidal flats has been verified by the quality of environmental improving techniques and consistency of effect.

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An adaptive management technique was applied to creation of creature's living place in the municipal river estuary as well as in canal where various creatures lived in formerly. A terrace type embankment which was formed with tide pool and tide land was constructed for Tokyo Bay revival. The adaptive management consists with three phases. Phase 1 is site characterization and goal setting, phase 2 is site rebuilding, and phase 3 is evaluation and management. This study elucidates that necessity of systematization of citizen participation for the evaluation and management, necessity of development of environmental improvement technology including site experiment, as well as necessity of arrangement of crucial points in the mechanism.

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The aim of this study is the development of a method to evaluate a suitable habitat condition of a colony of Acropora tumida which is a kind of stony coral. We improved the HSI model which was often used in a quantitative ecological assessment and suggested the PHSI model which was introduced a probabilistic way of thinking. We can evaluate the optimum habitat condition of coral more precisely than the conventional HSI model by applying the PHSI model to an ecological assessment. We estimated the distribution of a colony of Acropora tumida in 1975 by using the PHSI model in which three physics factors was involved and the estimated distribution well coincided with the observed one. In addition, it was found that the average PHSI value of the object sea area has decreased gradually since 1985. And, the present value was approximately 60% in comparison with that in 1970.

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This paper describes an integrated methodology to evaluate the tidal flat geoenvironments and its application to natural and artificial muddy flats. The proposed methodology enables quantitative assessment of the dynamics of thermal and geophysical environments that were found to vary significantly under given tidal and meteorological conditions. The temporal and spatial variations of suction, void state and surface shear strength of the artificial flat soils were particularly noteworthy, occasionally yielding unfavorable geophysical environments to benthos habitats. The present method may thus provide a rational basis for adaptive geoenvironmental management so as to facilitate the favorable performance of diverse benthos activity.

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Questionnaire survey for Contingent Valuation Method (CVM) was executed in Aichi prefecture, 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 4 type utility functions. They were linear type, logarithmic type, involution type and sigmoid type. Sigmoid type function was derived from assumption that ranges of perception which people can cognize are limited. AIC (Akaike's information criterion) on the distribution curve fitting was calculated on each function type. AIC of sigmoid type had the maximum in the four types. This suggests that the assumption of limited perception is fit to describe mechanism of people's cognition. AIC and WTP (willingness to pay) on logarithmic type was considerably close to ones on sigmoid type. This suggest that using logarithmic type, which has simple structure of function, is practical in CVM.

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The nutrient profiles of NO₃^-, NO₂^-, and SO₄^2- in pore water in Tama intertidal sediment during low tide from May 2003 to September 2004 were investigated to elucidate material cycles and the factors controlling them in that area. Each profile showed intermittent concentration peaks at about 5, 20, and 60 cm depth. Characteristically at this site, increases in concentrations were preserved for a period of a few months. The peaks at 5 and 20cm depth predicted aerobic conditions at those depths, owing to bioturbation at 5cm depth and to the presence of plant rhizomes near 20cm depth, consistent with results of previous studies of the same intertidal flat and those of other intertidal flat sediments. Conditions may also have been aerobic at 60cm depth, reflecting the influence of advection from river side at the sampling site.

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Ariake Sea, a typical closed bay on the west of the Kyushu Island, is a sea area where a vast tidal flat develops. Recently, various environmental degradations are reported occur in Ariake Sea, as red tidal and anoxic water. In this study, the ecosystem formation process by recovery of shore line, the aim in this method is to establish the technology that can artificially restore the tidal flat and the shore line in front of embankment development and to recover and maintain the ecosystem, was investigated in Ariake Sea. One year passed after shore line was constructed; benthos species has increased by the twice or more. The effect in the future can be expected by recovery of shore line.

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Vertical shear strength distributions of the surface cohesive sediments were measured to clarify the sediment transportation in the north Ariake Sea. The extreme wave by the typhoon 200613 re-suspended the sediment of the north Ariake Sea, Japan. After the extreme wave by the typhoon, surface soft cohesive sediment on the mudflat was obviously eroded and showed low Eh. In contrast, soft cohesive sediment was accumulated over 10 cm on the surface of the offshore sediment and it showed high Eh. Simultaneously, large amount of suspended sediment transportation toward offshore was observed by ADCPs when the typhoon hit the north Ariake Sea. These facts show that a sudden great amount of the sediment (5-15 tons/m) was suspended from the mudflat surface by the typhoon hitting, transported toward offshore, and accumulated on the offshore sea bed. The possibility of these sudden accumulation of the sediment may influence the habitat of bivalves.

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To preserve healthy aquatic environment and to continue sustainable developments in coastal zones comprehensive decision support systems for the Integrated Coastal Zone Management (ICZM) have been requierd. Geographic Information System (GIS) is a very powerful tool that can handle numerous various data related to spatial information, water quality, bottom sediment, physical oceanography, ecosystem, terrestrial information, human developed, and so on. In the present study, a GIS-aided database for the aquatic environment in the Ariake Sea was developed. The database was used for an analysis of spatial and temporal characteristics of median grain size, density stratification, transparency, tidal current, and red tide. Also, the interaction among river discharge, stratification, and state of red tide, and the relation between the reduction of tidal currents due to the installed nets for laver cultivation and variation of the transparency were investigated. The results indicate an effectiveness of the GIS-aided database for understanding and solving complicated aquatic environmental problems in a coastal zone, and for making a decision in the coastal management.

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A nearshore zone characterized by coral reef has so much potential for fish habitat, marine activity and other ecological and recreational functions. However, a subaerial survey with high special resolution is still hard to conduct in the nearshore zone yet especially in depths shallower than several meters. Therefore, an aerial photogrammetry method is applied to a nearshore survey at Yoshiwara beach in Ishigakijima Island, Okinawa. The method uses a digital still camera with nearly 8 mega pixels of resolution and a series of aerial photographs of carbonate beach and coral reef which were taken from a Japan Coast Guard (JCG) helicopter. The original digital photograph is then modified to an orthogonal image by using some new techniques. In addition, a set of nearshore topography data surveyed by an aerial laser system had been applied as a reference data. The resulting map shows a typical character of real coral reef topography although there are some inconsistencies. Thus, in general the current method can be applicable to a nearshore survey with good cost performance.

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Physical, biological, and chemical approaches should be comprehensively taken to evaluate the environmental conditions of a sea area with tidal mud flats like the Ariake Sea. In this study, a quantitative echo sounder was used to develop an acoustic method for remote and planimetric on-board observation on the distribution of the sea water and the floating mud layer which contain toxic substances like hydrogen sulfide. Based on the acoustic data, accordingly, material balance in tidal mud flats and underwater environmental conditions were evaluated. Specifically, a correlation between underwater acoustic data and the amount of hydrogen sulfide was established based on the indexes of transducer frequency and echo sounder manufacturer.

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When a new breakwater was constructed in Abashiri Port, there was a strong demand from local fishermen to preserve the coastal environment, including marine organisms.
The impact of the new environmentally-friendly breakwater on the surrounding environment has been studied mainly through the surveying of algae zones by divers. It is, however, difficult to clarify the wide-area distribution by such a survey method, although it is possible to obtain spot and linear information. The conventional method also involves considerable time and financial burden.
To solve these problems, the validity of analysis results was examined in this study by comparing aerial and satellite images with the result of the survey of algae zone distribution by divers. As a result, the distribution of algae zones (Rishiri kelp) formed in shallow waters was found to be almost identical among these analysis results, and it was possible to quantify the distribution accurately by satellite images.

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In the eastern part of Hokkaido's Kushiro Subprefecture lies Kiritappu Port, resting across two bays and connecting them with a channel. In recent years, sediments, which have accumulated in Kiritappu Port due to littoral drift, have led to the hindrance of the passage of ships at low tide. Since the accumulation of sediments in the passage will continue under the current conditions, measures against littoral drift are being considered. Such measures, however, must be environmentally friendly because Hokkai shrimp and other economically useful marine species live in and around the port as mentioned before. Under such circumstances, it was considered important to understand the distribution area of eelgrass beds before implementing countermeasures. In this study, the quantification of the distribution area was conducted through the analysis of satellite images, echo sounding, underwater photography and submersible research to gauge two-dimensional distribution. As a result, it was found that satellite images are effective in locating algae zones in shallow sea areas and echo sounding is useful in determining the presence of algae zones in sea areas with turbidity.

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The purpose of this research is to verify whether it should be possible to improve the environment of the fishing ground under flow environment by tilling. This experiment was conducted in the fishing ground of the freshwater clam in the Lake Shinji. The tilling machine used for this experiment moves with the pressure of air. In order to verify this experiment effect, the tilling area and the non-tilling area were set up. The contents of investigation are sediment and the freshwater clam. Investigation was conducted once before the tilling experiment and carried out once after four-month progress of the tilling experiment. The following experiments were checked as a result of comparing a tilling area with a non-tilling area about the contents of investigation. (1) The sediment of the bottom of a river in a tilling area would be in the oxidation state during a fixed period. (2) It came to be soft during a fixed period. (3) It was suggested that growth of the freshwater clam in a tilling area is promoted. The above experiments showed that the environment of the sediment of a fishery had the effect of a certain amount of improvement by tilling.

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The survey for the fish-breeding reef development confirmed un effect of reused rocky soils which were produced by the dredging construction in the sea road of the Hirado Seto. The survey were undertaken three times at Yoshizaemonse of the sea road and at Yokoshima offing from 2006 to 2007.
The result of tidal-current surevy and water-quality survey showed the change of the tidal current which accompanies fish-breeding reef establishment. The three-times-dive- watching observation showed the number of the species and individuals is increasing. Also, in the interview survey for the fisherman, it showed that fishery was already engaged at the fish-breeding reef establishment part. The construction technique was devised in the dredging part of the seabed, that is, it formed the unevenness (trench), and as a result it performs as the fish gathering effect and the biotope of the fish. But the definite effect could not be confirmed. However, a lot of commercial fish were confirmed by the dive watching observation and the interview survey, and it maintained a feature as the crude reef.

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Suaeda japonica Makino belonging to the family Chenopodiaceae is a rare halophyte grown only in the muddy tidal flat of the Ariake Sea.
In this research, since it became impossible to grow Suaeda japonica Makino that's one of the nationally rare halophyte species, researches about the species conservation continued to collect the knowledge for reproducing the tidal flat which can grow the halophyte.
Thereby, when a tidal flat was developed as a growth ground of Suaeda japonica Makino, it became clear that a setup of the amount of soil moisture adjusted by wetting and drying scheme and fine-grained fraction in a germination and sprout stage are most important.

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Since 1980s, various artificial reefs for Japanese spiny lobster Panulirus japonicus resource have been deployed in the coastal waters at Pacific and East China Sea. However, their structural feature was to provide only nest rooms but prey items, considered as another important factor to attract the lobsters. We have developed the new concept reef with waste shell, which cultivate prey organisms efficiently. In this study, we will show the following results of the five-year monitoring after this reef installation. (1) The prey animals increased to 45.0kg m^-3 in total weight on the reefs. (2) Adult lobsters were recorded for the first time in 21st month, and reached to 12.3 indv. m^-3 in 57th month. (3) Egg-brooding adults, Puerulus larvae and juvenile were found in the reef. In conclusion, we are convinced the reef with shells is well suited to the all-stages lobsters for dwelling, feeding and reproducing place. And (4) other valuable species such as top shell, abalone and rockfish were found in the reef. Therefore, it is expected this technique to apply habitats for diverse species is also very effective in creation of the eco-friendly harbor area.

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Recently dumping grounds for dredged materials, especially consist of silt and clay, are much insufficient. Therefor the effective use of dredged silt and clay are strongly required.
Expose experiments in open environment, using dredged silt and clay to make tidal-flat were carried out in Keihin Canal in Tokyo bay and Han-Nan 2nd. in Osaka bay. In this study revealed that dredged silt and clay are suitable substratums for benthic fauna. This fauna were mainly consist of surface organic sediment feeders.

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