When armor stones are dumped into water from a hopper above a water surface, a violent motion of water surface may arise from violent entries of stones. These violent behaviors bring a problem of numerical instability even in computation by particle methods. A stability of semi-implicit schemes, such as MPS or ISPH, depends on control of unphysical pressure fluctuations. Hence accurate particle methods are necessary in computation of solid-liquid two-phase flow with violent motion of water surface. In particular, around interface of solid and liquid phases, a pressure fluctuation is apt to be locally high. In this study, the DS (Dynamic Stabilization) scheme is introduced into the DEM-MPS method in order to resolve the problem, and its validity is examined by some numerical benchmark tests through the comparison with results of the previous DEM-MPS method.

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In this paper, a floating tsunami shelter with mooring has been proposed and developed. The shelter is capable of accommodating at least three hundred people to evacuate from run-up tsunami. The floating tsunami shelter can be lifted by buoyancy when tsunami strikes on it. To investigate fluid force on the floating tsunami shelter, impact pressure and its motions such as heave, surge and pitch due to a run-up tsunami, some experiments were conducted and five tsunami shelters with different configurations was examined. The floating tsunami shelter, the type AF and the type B can reduce the tsunami force. The front shape in both types and the floating technique with mooring can avoid the tsunami force and strongly flow due to tsunami wave.

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In the 2011 Off the Pacific Coast of Tohoku Earthquake, the toughness of earth banks against the tsunami could be learned and the sea walls with the toughness will be required for the future tsunami. Because the toughness against the tsunami aren't identified clearly, this paper discusses and proposes the concepts on the toughness of sea walls etc. against the tsunami, and the toughness of earth banks and the methods improving the toughness of them are discussed and clarified based on the earth bank model tests experimentally. As the results, the toughness of earth banks and its improving methods can be shown for applying them similar to the sea walls as one of measures against the tsunami.

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We examined structures for coastal dike with concrete armors resilient to tsunami overflow by conducting large-scale model experiments. Infiltration from the seaward toe raised seepage surface in the embankment soil, increasing air pressure in the space enclosed with concrete armors. Besides this, pressure under the concrete armors rose higher in the saturated part of the embankment soil, and filter layer under the concrete armor would accelerate saturation in the embankment soil. High pressure under the landward slope armor may reduce friction force between the landward slope armor and the embankment soil, resulting damages to the landward slope toe. Sheet piles can mitigate movement of the foundation at the landward toe, and concrete subslab under the landward slope armor can reduce washout of the embankment soil.

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To provide a computational framework for simulating fluid-sediment-seabed interactions, a three-dimensional coupled fluid-sediment-seabed interaction model is developed and applied to seabed response under regular waves and local scouring from tsunami run-up. For the seabed response under regular waves, the computational capability of the model is demonstrated from comparison with analytical solutions in terms of pore-water pressure and the displacement of the seabed skeleton. For the local scouring from tsunami run-up, numerical results show that the model can compute the seabed response during the onset of the local scouring, and suggest that the model is a useful tool for analyzing and evaluating a general complex fluid-sediment-seabed interaction phenomenon in the marine environment.

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A scouring phenomenon in seabed soil under the breakwater due to tsunami flow causes large-scale topographical changes and a decrease in bearing capacity of structure, resulting in serious damage. This study attempts to explain the scouring mechanism focusing on the tractive force and seepage force in the seabed soil with tsunami seepage flow with the different permeability of rubble mound and seabed soil. During a tsunami, the high speed seepage flows into the rubble mound generates a vertically upward hydraulic gradient along in the seabed ground with the tractive force and scouring is facilitated.

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This paper describes calculation method of failure probability for safety factors of existing harbor and coastal facilities from viewpoint of their maintenance that has become of great importance in recent years. Design method by using safety factor had been used until 2007, when “Technical Standards for Harbor Facilities” was revised by which reliability-based design method was employed. Large amount of harbor and coastal facilities designed by using safety factor method, therefore, exist in Japan. Finding out probability density function of the ratio resistant force to acting force, which is equal to safety factor and both of the forces are random valuables, failure provability of their structures can be calculated in discipline of mathematical statistics.

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Two-dimensional tank experiments were conducted to establish a method for assessing the stability of a sand-pack structure on a beach. The results of 89 experimental cases showed that piping out of nourished sand and pulling out of a sand-pack on a slope were typical collapsing processes, and these were caused by the return flow of a wave over topping. Lifting up of the seaward tip of the sand-pack by wave run-up was also observed. The desirable weight of a sand-pack for avoiding these pulling out and lifting up behaviors was investigated. Based on these findings, structures for moderating sand dune erosion were designed, and a field experiment was conducted. Through the one-year-long field experiment, the developed structures were confirmed to endure against even high typhoon-induced waves.

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To understand the characteristics of the bottom boundary layer (BBL), movements of suspended particle material (SPM) and its related radionuclide transport on Jyoban coast, the continuous monitoring of bottom environments using the mooring system and the intensive field survey of BBL with FRA-TRIPOD were performed. The observation results have shown the fundamental characteristics of BBL (vertical distributions of velocities and bottom roughness, etc.) and bottom turbidity variations. The turbidity at the shallow water depth (30m) was strongly influenced by waves and turbid water generated on rough wave conditions was transported by the coastal currents with the several days period. Turbidities at the deeper depths (80m and 130m) were affected by semidiurnal internal tides.

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A detailed oceanic downscaling model (Uchiyama et al., 2012) is utilized to better understand the oceanic initial dispersion of the leaked radionuclides during the accident at the Fukushima Daiichi Nuclear Power Plant (1F). Particular attention is paid to the influences of northward geostrophic coastal jet associated with an alongshore high SSH belt peaked at 50 km offshore, and mesoscale eddies shed by the jet in Sendai Bay and by the Kuroshio near the separation point. A spectral coherence analysis exhibits that alongshore wind stress is highly correlated with alongshore current on the shelf over the periods around 168 hours, suggesting that coastally trapped shelf waves are also responsible for the dispersion of the nuclide.

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Anthropogenic land-derived materials in wastewater have been recognized to influence on the water quality and the marine ecosystem in Osaka Bay and Harima Nada. Towards a rigorous environmental assessment of these two semi-enclosed estuaries, a triple-nested high-resolution oceanic modeling framework based on ROMS is developed to investigate the dispersal and dilution of urban wastewater effluent released from the subsurface nearshore outfall of Tarumi Sewage Treatment Plant near Akashi Strait. The effluent dispersal in the northern Osaka Bay is two-layered and highly reversal in the upper and lower layers due to stratification influenced by freshwater input mainly from Yodo River. The estimated cumulative tracer flux for the four-month period is found to accumulate by about 75% in Osaka Bay.

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A semi-enclosed bay frequently causes water environmental problems such as red tide and hypoxia because it has little exchange with the ocean. Therefore it is important to estimate the exchange time in the bay. In this research, we considered average exposure times using a numerical model in Ise Bay. The average exposure times were calculated by river discharge (river method) and solving a convection-diffusion equation using virtual dyes (dye method). The average exposure times and its seasonal changes of the two methods were significantly different each other. It suggests that the seasonal changes of the average exposure time by river method may lead to a misinterpretation. In addition, it was implied that an estuarine front has an important effect on the seasonal changes in the average exposure time.

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We describe performance of two vertical mixing schemes based on in-situ measured vertical profiles of turbulent mixing in Tokyo Bay. Three-dimensional hydrodynamic simulations using two turbulence closure schemes, the Mellor-Yamada (MY) model and the k-ε (KE) model, were carried out in the period 2011-2012. In almost all the vertical profiles, the difference in the potential density was insignificant between the two schemes although the turbulent mixing predicted by KE was rather stronger than that by MY. Both models well reproduced the observed turbulent energy dissipation and eddy mixing rates in the whole columns during nearly neutral conditions, but significantly underestimated them in the middle and bottom layers during the strongly stratified conditions.

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The flow, salinity and water temperature field of Ise bay from the year 2010 to 2011 was investigated by a 3D-hydrodynamic model that was recently developed by the author. The computed data were compared with the data obtained by the automatic observation stations; those were deployed at three locations around the bay by MLIT (Ministry of Land, Infrastructure, Transport and Tourism) in April 2010. The comparison proved not only the accuracy of the model, but revealed the dynamics of the bay such as the intermittency of intrusion of high saline water from the outer sea to the bay. Other dynamic behaviors such as the seasonal formation of density stratification and the seasonal variation of gravitational circulation of the bay were captured in the observation data and were also well reproduced by the model. In addition, the flow structures in the bay with and without the density stratification computed by the model were evaluated with those reported by previous articles. Finally, the monthly water exchange rate was investigated by the transport calculation of passive scalar quantity, and the cause of its seasonal variation was argued from a view point of the flow structure.

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Suspended matter was sampled using vacuum pump and plankton net. Dry weight and ignition loss were determined for each class of particles. The size, shape and material of particles were analyzed using digital microscope. Large particles over 425 μm consisted of fibered detritus of plant and zoo plankton. The percent composition of fiber reached 95% of total volume. Particles of 106 - 425 μm was consisted of fiber, floc and mineral. The percent composition of fiber was 30% of total volume, floc was 60% and mineral was 10% respectively.The percentage of sand was 40% in total weight, silt and clay in floc was 30%, organic matter in floc was 20%, fiber was 10% respectively. Floc consists of 40% organic matter by weight, and 95% by volume. The effective density of floc was estimated to be 100 kg/m³.

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We have been conducting monthly sea water sampling to detect particulate/dissolved mercury at three sites in Minamata Bay from 2006. After 2010, LISST-100X was applied for measurement of vertical profile of suspended solid grain size distribution. Also, highly resolved core sampling of bottom sediment at about 100 sites and deposition rate measurement were carried out. As a result, the followings were clarified: i) Correlation between SS grain size characteristics and particulate total mercury concentration was confirmed; ii) Spatial distributions for median grain size and water content of bottom sediment and deposition rate of SS were detected.

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The Amagasaki Canal has been polluted,especially eutrophication and hypoxic condition have occurred significantly yet. To restore the aqueous environment of the canal,a water purifying plant was constructed by Amagasaki Sea Blue Project of Hyogo Prefecture. This study was made to clarify the effect of removing suspended substance by the water improvement aquarium using bivalve (Xenostrobus securis) part of the plant,and method of operation and maintenance. As a result,effect of removing suspended substance,material conversion and necessity of control biomass of bivalve was clarified. Moreover,calculation formula of material conversion for control biomass was found out.

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Water environment of closed water area was influenced by eluting nutrient salt and hydrogen sulfide of clay in the bottom. Those chemical elements were made through organic matter was decomposed. Samples of clay were taken from the bottom in the west part of Lake Sinji, and the ratio of ignition loss, “IL_α°C”, was measured by each 100°C from 300°C to 600°C. It was known that intactness organic matter was burned in low temperature. By using the characteristic of organic matter, ratio of intactness organic matter could be estimated by IL_300°C/IL_600°C. It was suggested that decomposition condition of organic matter and reduced state of clay in the bottom could be estimated by the distribution of ignition loss and IL_300°C/IL_600°C.

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To investigate the water quality in the Great East Japan Earthquake-stricken coastal area, Nagatsura-ura Lagoon, Miyagi, field observations and nutrient analyses were carried out between August 2012 and January 2013. The narrow inlet connecting the sea and the lagoon disappeared by tsunami and subsidence. Salinity distribution measured in August and October 2012 showed that the lagoon has changed from semi-enclosed sea area to open water area. Though the water exchange in the lagoon has changed after the earthquake, DO in the closed-off section of the lagoon was still under 4 mg l-1 in the bottom layer. TN and TP increased in the same area. The dysoxic and eutrophication in this area were also detected before the earthquake, we revealed the changed and unchanged points of water environment in the disaster bay.

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Lake Jusan is a brackish lake located in the down reaches of Iwaki River system and is one of the most famous fishing places of Corbicula japonica in Japan. However, the annual catches of C. japonica have been greatly fluctuated over time, since they are sometimes easily pressured by environmental changes. To maintain sustainable fishery, it is essential to understand the relationship between distribution of the Larvae of C. Japonica and brackish environmental condition in Lake Jusan. In this study, field measurements have been conducted on salinity water temperature, and distribution of the Larvae of C. Japonica. Investigations of spawning seasons were also conducted. From the results, number and distribution of the larvae are greatly affected by those conditions such as water temperature, salinity, and discharge from the rivers.

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In this paper, first the anaerobic digestion processes of biowaste are reviewed, and then changes in the anaerobic digestion processes of sludge after applying a sediment microbial fuel cell (SMFC) are discussed through laboratory experiments. In the experiments, many types of sludges that have different organic conditions were used. The pH, redox potential (ORP) of pore water and the ignition behavior, oxygen consumption of the sludge were measured to understand changes in the digestion processes of the sludge after applying SMFC. It was found that the ignition behavior of the sludge was altered along with a decrease in pH, an increase in ORP, and a decrease in oxygen consumption after applying SMFC. It is clear that the digestion processes of unstable-form organic matter existing in the sludge are greatly enhanced after applying SMFC.

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Carbon dioxide partial pressure (pCO₂) has been continuously measured in surface water in Osaka Bay from June to September and in November, 2012, using a moored-equipment which measures temperature, salinity and pH. pCO₂ have been also measured monthly for two years at 19 stations in eastern Osaka Bay using a ship. Air to sea CO₂ flux were calculated from these data and wind speed measured at Kobe airport. In summer, the CO₂ absorption flux was high in the day and low in the night. CO₂ flux had large diurnal change by daytime photosynthesis and nighttime respiration. Annual mean CO₂ absorption exceeded 0.12 g-C m^-2 d^-1 in off Kobe area, and was less than 0.09 g-C m^-2 d^-1 in off Osaka area. As a whole, eastern Osaka Bay absorbs CO₂ at a rate of 0.1 g-C m^-2 d^-1.

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Recently in the Ariake Sea and Yatsushiro Sea,reduction of benthos has been pointed out. We examined the factor of reduction of Arthropod. As a result, we have suggested that characteristics of Gammaridea with the negative correlation to the rise of mud temperature and remarkable rise of water temperature in summer and autumn are one of the reduction factors of benthos communities in the Ariake Sea and Yatsushiro Sea. In this paper, we first pointed out that the importance of mud temperature as variation factor of benthos communitis in the Ariake Sea and Yatsushiro Sea.

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The deposition and transport of sediments should be managed properly in ports not only for the maintenance of port channels, but also from an environment perspective. Our focus in this study was to create maps of sediment spatial distributions in Tokyo Bay by using chemical composition. We collected sediments from 449 stations in the bay and analyzed particle-size distribution and chemical composition. Sediments were grouped by chemical compositions using k-means clustering and maps of the spatial distribution of sediments were drawn up. These maps enable determination of spatial distributions of sediments from each main river that enters the bay.

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Global warming is thought to affect hypoxia and oxygen-depleted water, which is the serious problem in semi-enclosed bays. This research focuses on the impact of anoxic water variation by global warming in Tokyo Bay, Ise Bay and Osaka Bay which is largest third bay in Japan, using the three-dimensional physical model and lower-trophic ecological model. The results showed that anoxic water decreases by global warming in Ise bay although anoxic water increases at all times in Tokyo Bay and Osaka Bay. These differences among each bays are caused mainly by the geographical feature of the Ise Bay. In addition, the places where the amount of dissolved oxygen especially decreases by global warming were revealed.

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The objective of this study is to reproduce turbid ocean color on the coral reef of Amami-Oshima Island which located in Kagoshima Prefecture, Japan using the bio-optical model in consideration of bottom reflectance. The comparison between the model and in-situ reflectance at the surface water under four kinds of conditions is tested. As a result, the absolute values is different, but the significant correlation (R²>0.80) was acquired. Moreover, ocean color at the time of changing water depth and SS on coral reef was reproduced using CIE color coordinate theory (xyY color coordinate). It was confirmed that the significant correlation between water depth and SS have hue (x, y) and brightness (Y) of ocean color, respectively. This bio-optical model serves as a good tool reproducing ocean color under turbid condition on coral reef.

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In this study, reduced conditions of sea bottom sediment in Yong-Won Bay (Korea) were investigated through field observations and laboratory experiments. In the laboratory experiments, the ignition loss (IL), pH, redox potential (ORP), and oxygen consumption were measured to identify the reduced conditions of the sediment. It was found that the ratio of ignition loss at 300°C to that at 600°C (IL₃₀₀/IL₆₀₀) of the sediment in the western part of the bay was higher than that of the sediment in the central part of the bay. Furthermore, lower ORP and pH, and higher oxygen consumptions were also found in the sediment in the western part of the bay. The results suggested that the reduced conditions of the sediment in the western part of the bay are enhanced because of high contents of unstable form organic matter (high IL₃₀₀/IL₆₀₀).

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The seasonal variation of sediment adsorption of NH₄⁺ in the inner area of the Ariake Bay was investigated during June, 2010-May, 2011. The adsorbed NH₄⁺-N concentration between sampling sites was closely related to the mud content in sediments. The amounts of NH₄⁺-N adsorbed onto the sediment particles were found to account for approximately 80 ? 90% of the total amounts of NH₄⁺-N (dissolved + adsorbed NH₄⁺-N) in sediments throughout the year. The sediment environmental factors that affect the adsorption coefficient (K^*) were determined using a stepwise multiple regression analysis. As a result, we found that redox potential at St1 (muddy sediment) and mud content at St2 (sand-muddy sediment) had an important effect on K^*, respectively.

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Our previous studies show that the tidal flat of the Tokyo Port Wild Bird Park is a sink of nitrogen. Denitrification and anammox can be cited as one of the factors. In the present study, we measured denitrification and anammox rates in tidal flat sediments and investigated about the factors affecting its rates. Results from the study show that (1)the rates of denitrification and anammox affected by DIN concentration and DO concentration, (2)the anammox rates affected by the number of anammox bacteria.

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The relationship burrows of Macrophthalmus japonica and utilization DIN by microphytobenthos in river mouth tidal flat was evaluated. Seasonal variation and temporal variation about DIN for one tide were investigated in the crab burrows. Though dissolved oxygen decreased during ebb tide for respiration by crab and organic decomposition, NH₄⁺-N in the burrows increased for metabolism by crab and elution from wall surface. Burrows supplied DIN for tidal flat area in flood tide and microphytobenthos efficiently assimilated DIN. It found that burrows served DIN for microphytobenthos as fertilizer application.

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Hakodate fishing port is located in the southwest region of Hokkaido, and the north breakwater was built in the 60's and becoming superannuated. There was a problem with the safety mooring of fishing boats and pleasure boats by the overtopping waves. Therefore in order to solve this problem, the improvement work of the north breakwater had implemented in 2010. In terms of the improvement, we adopt the doubly-placed breakwater that put the submerged bank in front of gravity-type composite breakwater and added a feature of artificial formation of seaweed bed because of isoyake is occurring with frequency around the north breakwater, and we set the crest elevation of the submerged bank to D.L.-0.1m in consideration of the flow velocity that could control feeding behavior of sea urchin. In this research, we report a controlled effect of the significant wave's flow velocity around submerged bank by the wave and current observation after building of the submerged bank has been completed.

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Field surveys and laboratory experiments were carried out to prevent the outbreak of green tides at the north pond of Osaka Nanko bird sanctuary. Dense blooms of green algae, Ulva pertusa, Ulva ohnoi and Rhizoclonium riparium were frequently observed in 2005-2012 and the most dominant species gradually changed from Ulva pertusa to Ulva ohnoi, which is partly due to temperature increase and low salinity at a growing season. Laboratory experiments revealed that photosynthesis was inhibited when they were exposed to air for 6 hours at 35°C followed by a low salinity of 20psu. These results suggest the possibility of controlling green tides of Ulva pertusa and Ulva ohnoi by a combination of exposure to air with low salinity in summer

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As a new technique for restoring tidal flats activities were carried out in Ago Bay by opening the floodgates on the concrete dike in 2 coastal fallow fields (Ishibuchi and Niunoike) with different tidal exchange rates. In both coastal fallow fields, before the restoration a few macro faunas were found. After opening of the floodgate, the macro faunas was increased to the similar level of natural tidal flat in Ishibuchi with high tidal exchange rates (80.4%). On the other hands, In Niunoike with low tidal exchange rates (36.6%), the macro faunas was slowly increased and the COD and AVS in sediment were still high. It is supposed that it will take much longer to complete tidal flat restoration. bacause the tidal exchange rates have a huge effect on restoration.

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As a new technique for restoring tidal flats, activities were carried out by introducing seawater into several unused coastal lands behind dike of the inner Ago Bay. After introducing seawater from Ago Bay, flow and water quality simulation was carried out for a selected restoring tidal flat area (Ishibuchi). Thus, average value of the water quality and its variation patterns in Ishibuchi were identified. As a case study, it was found that there is an improvement in seawater in Ishibuchi due to seawater introduction effect. Accordingly, seawater quality in Ishibuchi was improved by increasing dissolved oxygen, decreasing nutrient salts and controlling phytoplankton due to reduced nutrient salts. Moreover, by same manner, the seawater property improvements in another field in same bay area were identified as similar to the results obtained from Ishibuchi.

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CO₂ concentrations were measured with light and dark chambers at an artificial tidal flat of Osaka Nanko bird sanctuary in the spring and summer of 2012 to examine the effect of benthic microalgae, macrobenthos and bacteria. CO₂ emission rate from the sediment was almost constant during a measuring interval in the dark chamber, while its absorption rate markedly decreased with time in the light chamber. The rapid decrease of CO₂ absorption rate was thought to be caused by low CO₂ concentration in the light chamber in accompanied with increasing photosynthetic activity of the benthic microalgae. To measure the absorption of CO₂ with a difference less than 40ppm from the atmosphere level, a ventilation rate of 10L air/min is indispensable for the light chamber along with a bottom area below 450cm².

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Field surveys and indoor experiments were conducted at the north tidal flat of Osaka Nanko bird sanctuary in 2012 in order to measure the amount of discharge of the carbon dioxide (CO₂) which is an index of the amount of organic matter decomposition. The field survey revealed that CO₂ flux increased with decrease of the groundwater level when the bottom sediment emerged. The CO₂ flux in the submerged period showed 0.2-1.2 mgCO₂/m²/min which was less than 1/5 to 1/40 of the emerged period. In addition, the result of field surveys together with indoor experiments suggested that CO₂ flux changed depending on the flood tide or falling tide as well as the groundwater level.

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Mass mortalities of the pen shell Atrina SPP. occurred in the fishing grounds of Ariake Bay. We built up the hypothesis about a cause of mass mortality from long-term viewpoint (function of population) and short-term viewpoint (biological function). This study considered a cause of mass mortality from field survey, metabolism model of the pen shell and seasonal variation of glycogen contents. It was suggested that change of age structure and miniaturization lead to less sustainability of population. It turned out that the amount of food in the period from November to May is important for growth of pen shell. If glycogen content is not fully accumulated in this period, the physical strength of pen shell declines in summer or autumn, and it becomes easy to cause mortality.

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To elucidate the influence of snowmelt flood event on the habitat of juvenile fish of salmon and sandfish, field observation of water quality were conducted in the Mukawa coast, the Pacific Ocean of northern Japan. The MODIS Chl-a showed the Chl-a increased by snowmelt flood after the spring plankton bloom in the Mukawa coast. As same as summer season, the primary productivity in bottom water was limited by scattering of light by suspended sediment of snowmelt flood in spite of sufficient nutrient for the aquatic ecosystem. However, the primary production was still higher than that after summer flood because of vertical mixture by the surface cooling at nighttime. This high primary productivity seemed to bring the increase in zooplankton, which can provide the better food environment for juvenile fish.

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In the eastern Seto Inland Sea, the boat seine fishery for Japanese Sand Lance is flourishing, and appropriate control of fishing operation is important from industrial, cultural and ecological points of view. In this study, surveys on actual condition of the fishery were conducted and a fishing operation simulator was developed, which consisted of a 3-D hydrodynamic model, a fish behavior model and a fishing operation model. Validation analysis showed that the simulator had good reproducibility of temperature and salinity fields, fishing ground distributions and time series of fish catches and sales. Moreover, the simulation results pointed to the particular importance of quantifying vertical migration properties of this species for improving of accuracy of the simulator.

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Trawling is one of the major fisheries in Ise Bay, living field of whose target fish is significantly affected by the marine environmental conditions. In order to revitalize coastal fisheries, simulation tools to evaluate the effects of fishery management schemes will be useful. In the present study, a fishery simulator for Conger myriaster is developed. The simulator predicts the fishing activities of trawling boats based on economic conditions and resource distribution calculated by fish dynamics model. The developed simulator well reproduced the operation and fish catch at major fishing ports. It is also clarified that the control of fishing gear is effective to increase the profit of the target fishery.

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We have developed new techniques to release hatchery-reared juvenile sea cucumbers, Apostichopus japonicus, into the sea, and cultivate them at high density inside the spiral-fibered highly porous media placed on the sea bottom, while reducing the likelihood of being eaten by other marine life. Juvenile sea cucumbers of about 0.02 m in size are least susceptible to their dispersion by waves or currents when discharged. The porous media must be 0.2 m or more in thickness to breed juvenile sea cucumbers inside them while preventing being swept away by waves. This thickness level is also effective in decreasing the chance of juvenile sea cucumbers being eaten by spider crabs, Pugettia quadridens, their predators.

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When fish and shellfishes live and a fishing port water area is regarded as a place (environmental base), a fishing port is a part of reef ecosystem which is located on the coast, has high calm nature compared with an oceanic region, and made the structure the subject. Moreover, it can realize as a part of network of the living space of fish and shellfishes centering on a childish fish. The quantitive evaluation examples from such a viewpoint are few. So, in this research, present condition grasp of the ecosystem structure in a fishing port and a living thing producing function was performed.

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To understand a water circulation among unconfined groundwater, groundwater of tidal flat, and river water, continuous measurements were conducted in Ota River Delta since 2006 to 2012. Variations in groundwater level in tidal flat influenced not only an infiltration of groundwater from the ground surface but also variations in unconfined groundwater of Delta region. Remarkably, dissolved oxygen of groundwater in flood plain was 5 mg/L until at a depth of 6 m. Moreover, a density diversion occurred at a depth of 4 m and 6 m. From these results, it is considered that three types of groundwater flow were generated in the tide pool and flood plain.

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To examine correlations between SS transport L and river discharge Q in Japan, we develop a database for SS and river discharge in Japan under low- and high-flow conditions by collecting previous field data. In addition, we present a new approach to evaluate a sediment rating curve (L=aQ^b) using the database and statistical analysis. The results indicate that the coefficient b was mostly 1.6 to 2.0 which was slightly lower than previous results (b=2). The SS fluxes in mountain rivers were on the whole larger than those in other rivers, showing appreciable dependence of the L-Q relations on land use of watershed. We confirmed the fundamental validity of the present approach through the comparison with observed data.

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Mitigation of density stratification with jet was evaluated by using visualization experiments. First, we developed a simple and high accuracy image analysis method to estimate the spatial distribution of density of water. Then, we experimented on various types of stratified field changing Froude number of the jet. We verified that entrainment by jet and internal wave breakings are important to consider water mixing in density stratified fields. Furthermore, we defined the practical parameter including both the impact on the field and the potential energy of the field. The parameter has a linear relation to the volume of new layer formed after water mixing.

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A Habitat Suitability Index (HSI) model for corals in ports was developed. Environmental parameters of suitability index models (SI models) were photon, average wave orbital velocity, maximum wave orbital velocity, average flow velocity and residual flow velocity. These parameters were selected to evaluate the effect of depth for coral habitat. Field observations were conducted in Naha Port to take data for designing SI models and for verification of the HSI model. The calculated HSI described well the observed coral cover rate. This reveals that wave orbital velocity, which decreases in depth, is an important environmental parameter for corals.

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We performed field surveys on the amount of the kelp as well as the number of the sea urchins adhering to the culture ropes at 19 ports and harbours around Hokkaido. Relationships between the amount of the kelp and conditions of the waveheight, water depth, water temperature and nutrient concentration were investigated using the field data. Seaweed was found to grow on the ropes even under low waveheight conditions in the ports and harbours without adhering sea urchins. Kelp were found to survive on culture ropes in a barren-ground condition and can be used for recovery from the barren ground.

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Valuing coastal ecosystem service is important for disentangling the complex human society-ecosystem relationships and incorporating the value into public decision-making processes. We developed a new evaluation method to comprehensively and concisely quantify the current status and likely future of shallow coastal environments by an ocean health index (OHI) score. We evaluated the environmental condition of four intertidal flats located in Tokyo Bay using OHI. Our method can provide a tool to explicitly show the strengths and limitations of each coastal ecosystem functioning.

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In this study, the effects of vegetation and elevation on the distribution of the endangered tiger beetle larvae were examined in a sandy shore created for the purpose of mitigation. We found that the following four facts. 1) The habitable area for their larvae has been decreasing year by year. 2) The process of making shore slopes is different depending on the location. 3) Seaside plants newly occurred at the elevation where the larvae prefer. 4) No larva was found at the area with dense vegetation. Therefore, the advancement and overgrowth of coastal vegetation were considered to be the major factors that reduced larval distributions in the created shore. So, we suggest the following two plans for the adaptive management. 1) Removal of seaside vegetation and control of the tip of vegetation. 2) Maintenance of habitat area by raising the ground level.

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A carbon dioxide meter with water-resistant breathable tube was developed in order to measure CO₂ concentration in water. Laboratory experiments were conducted for verification of the effectiveness of this method. After measuring the time variations of CO₂ concentration in water aerating by air pump or adding carbonic water, it was confirmed that this method was useful to evaluate the carbon cycle in coastal zone. Furthermore, the CO₂ production from sediment by decomposition of organic matter was confirmed by measuring the time variations of CO₂ and DO concentrations in the water above sediment at the same time.

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