Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering)
Online ISSN : 1883-8944
Print ISSN : 1884-2399
ISSN-L : 1883-8944
Volume 75, Issue 2
Displaying 151-200 of 234 articles from this issue
Paper
  • Masatoshi IKEUCHI, Tokuzo HOSOYAMADA, Kojiro SUZUKI, Naoki TSURUTA
    2019 Volume 75 Issue 2 Pages I_901-I_906
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     The armor blocks expected to keep stability of the coastal structure from tsunami overtopping wave forces may have serious damages by high wave condition that occurs seasonally. To mitigate the overtopping wave forces to the armor blocks, adjustment of position of fall of the overtopping wave is supposed to be effective. A serial laboratory experiments was carried out to estimate the effect quantitatively. In case of non dimensional values of falling position and water depth are larger than 1.3 and 0.8 respectively, the armor blocks keep stability.

     Numerical simulation by high precision particle method shows good agreement with laboratory experiments. And, we confirmed formation of large swirl and the flow of water within the structure that could not be confirmed in the experiments.

     And then, we confirmed that the breakwater with porous structure further increases the stability numerically and experimentally.

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  • Takao OTA, Shinpei TAKASAGO, Sooyoul KIM
    2019 Volume 75 Issue 2 Pages I_907-I_912
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     In this study, the influence of deformation of wave dissipating works and long period swell on wave pressure and force acting on the caisson breakwater is evaluated on the basis of the experiments. The model profiles corresponding to the deformation amount are used and the wave pressures are measured under the conditions including the long period swell in the experiments. Moreover, an artificial neural network (ANN) model is applied to the prediction of the horizontal wave force. When the deformation becomes large, the wave force increases considerably. The possibility that the smaller wave height causes the relatively strong wave force in the case of long period swell is also indicated. The ANN model predicts the horizontal wave force within about 30% and the applicability of the model is confirmed.

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  • Tomohiro SHIMIYA, Akira TATSUMI, Kazuhiro IIJIMA, Ryoukei AZUMA, Takah ...
    2019 Volume 75 Issue 2 Pages I_913-I_918
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     A hydro-plane type movable breakwater has been developed, which lie on sea bottom in still water but is raised by Tsunami actions without any man operations and electric power. It is required that the breakwater against Tsunami has “redundancy and robustness”. It means that even if the breakwater is partially failed, it should carry further load and continue to reduce Tsunami effect. In order to assess such kind of “redundancy and robustness”, collapse behavior of the breakwater should be investigated under extreme load beyond design load.

     In the present study, the static collapse behavior of the hydro-plane type breakwater is simulated by using nonlinear finite element method (FEM) and ultimate strength of global and local structures is assessed. The ratio of the global ultimate strength to the local one may be regarded as one of the indexes to assess “redundancy and robustness” of the breakwater. In addition, based on the knowledge regarding the collapse behavior of the breakwater obtained from the FE analysis, a simplified method to estimate the global ultimate strength of the breakwater is developed, in which the ultimate strength is predicted based on initial yield criteria while considering reduction of effective width of plate panels due to buckling. The proposed method gives a 15% safe-side prediction of ultimate strength compared to the result of FEM.

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  • Eiichirou SUGI, Hisanori YOSHIMURA, Kenta KAKOI, Aoi ENOMOTO, Takanori ...
    2019 Volume 75 Issue 2 Pages I_919-I_924
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     In this study, we considered wave force characteristic by plane hydraulic model experiment in case more than 60 degrees of sharp-angled incident wave against a caisson having breakwater with low crest wave dissipating blocks in the part of the trunk of breakwaters under construction. The main conclusions are as follows. (1) The impulsive wave pressure does not occur by low crest wave dissipating blocks. On the other hand, 1)The wave height increases by growth of meeting wave from upper side area with no wave dissipating blocks. 2)The wave pressure exceeds Goda value in most of the erect part by concentrating wave in the space between the blocks by the low crest wave dissipating works and the caisson wall. (2) The peak wave force which acts on the whole caisson is restrained because the action time of the wave is delayed from upper side to down side. (3) The peak horizontal wave force is restrained when the waves in the front face of caisson and diffracted waves going around to the back face becomes in phase. (4) The peak vertical wave force is restrained because downward wave force by wave overtopping acts on the caisson superstructure during pressure wave.

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  • Daiki SAKAI, Tsuyoshi KANAZAWA, Gozo TSUJIMOTO
    2019 Volume 75 Issue 2 Pages I_925-I_930
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     It is a problem that the rubble mound is damaged if high waves strikes during construction of the rubble mound seawall. However, there is little knowledge about the damage process of rubble mound against wave conditions. In this study, we focused on the construction process and examined the damage process of the rubble under high wave conditions by hydraulic model test.

     In all the experimental cases, the crest dropped rapidly from 1 hour to 3 hours later at the local scale. As for the damaged cross-sectional shape, the change on the offshore side was small, and the shoreside edge extended with time. The crest elevation dropped to about 40% of the initial crest elevation at relative wave height H1/3 / B = 1.17. The damage rate was found to be around 40% at H1/3 / h = 0.36 and 20-30% at H1/3 / h = 0.5. In addition, it was found that the damage speed is slow in the experiment case with a wide crest width, which is important for considering the damage control of the rubble mound.

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  • Takefumi TOMINAGA, Hukuyoshi OKABAYASHI, Satoshi OKAZAKI, Takayuki KUB ...
    2019 Volume 75 Issue 2 Pages I_931-I_936
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     In Nangoku construction section of Kochi coast, the existing artificial reef is planned to be turn into offshore breakwater by installing wave dissipating blocks on the reef, extremely rare structure, in order to increase control function of littoral transport. In this study, hydraulic model experiments were conducted to evaluate the stability of the facility for the purpose of determining the basic profile, such as weight and location of the wave dissipating blocks, which is necessary for the design of the facility.From these results, behaviour of wave around the offshore breakwater and the failure mechanism of the offshore breakwater were clarified under the condition of terrain of Nangoku construction section of Kochi coast and the design wave. Furthermore, it was clarified that the stability of the facility is secured most economically by installing the wave dissipating block on the shore-side part of the crown of the artificial reef. Based on the above results, basic profile of the facility, including the reinforcement of the landward slope of the existing artificial reef, was determined.

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  • Kenta KUDAI, Shinji SASSA, Soonbo YANG, Shoya GOTO
    2019 Volume 75 Issue 2 Pages I_937-I_942
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     The process of internal erosion under various hydraulic forces is studied by the large-scale hydraulic experiment for the purpose of enhancing countermeasure against internal erosion. It is clarified that the direction of hydraulic forces affects the process of internal erosion in which a cavity gradually grows in the sand and abrupt ground subsidence is caused by the collapse of the cavity underneath the ground surface. Lowering of suction accompanied by penetration of water is closely related to the collapse of the cavity. This research also studied systematically geotechnical filter’s deterrent effect of internal erosion so as to improve the prevention method. As a result, it is verified that the geotechnical filter keeps sufficient deterrent effect under strong hydraulic forces if its uniformity coefficient is larger than 3.0 and the median particle diameter ratio is less than 20.

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  • Yuya WATANABE, Sota NAKAJO, Takaaki SHIGEMATSU
    2019 Volume 75 Issue 2 Pages I_943-I_948
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Various models of the porous media flow have been proposed to quantitatively examine the heat and mass transfer inside and around porous media, and the stability of the porous structures. In most studies, porous media components are approximated by spheres. However, natural gravel layers or artificial wave dissipating structures are composed by ellipsoids. Actually, the flow passing through an ellipsoidal porous media is unknown. In this study, we performed numerical simulation to study the microscopic flow in the porous media composed by ellipsoids using an immersed boundary method. Simulation results show that macroscopic pressure drop and fluid force acting on the each component of porous media are influenced by the aspect ratio of ellipsoid.

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  • Tatsuya MATSUDA, Kinya MIURA
    2019 Volume 75 Issue 2 Pages I_949-I_954
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     This study uses a wave flume experiment to investigate pore water pressure response to wave action on a sandy seabed. Crushed stone replacement of sandy seabed is done as a countermeasure to sea wave induced liquefaction, but this countermeasure does not suppress wave induced excess pore water pressure generated in the sandy seabed. It is suggested, therefore, that there is risk of liquefaction in sandy seabed due to action of excessive external wave forces. It has suggested the effect of countermeasure that liquefaction resistance increases because initial effective stress in sandy soil increases with crushed stone replacement.

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  • Tatsuya MATSUDA, Kinya MIURA, Rintaro TAKAYANAGI, Keita ANAI
    2019 Volume 75 Issue 2 Pages I_955-I_960
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     This study investigated wave response for a rectangle block under different seabed characteristics in a 1g field test. On sandy soil, wave induced horizontal acceleration response was generated in the block in the offshore direction. As a result of a simplified constant loading test, it was understood that block acceleration response is obtained due to actions of horizontal wave force in the offshore direction and rolling moment in the offshore direction. Scouring around the block did not affect acceleration response. Analysis of external force on the block showed uplift force generated by horizontal wave force in the offshore direction. At the same time, seabed bearing capacity decreased because excess pore water pressure in the seabed increased due to wave action. On sandy soil, therefore, a block may move easily in the offshore direction due to the action of wave force.

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  • Hidetaka KOBAYASHI, Hideo KOYAMA, Shota ABE, Toshimitsu TAKAGI
    2019 Volume 75 Issue 2 Pages I_961-I_966
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Hydraulic characteristics of a bimodal artificial reef were evaluated by using field observation data. The wave transmission coefficient was less than 0.5 for offshore wave height greater than 4m. The wave setup was less than conventional artificial reefs. It was confirmed that the bimodal artificial reef have the necessary protection performance. Current patterns behind the artificial reef varies with the incident wave height. Undertow velocity is generated by surface rollers of breaking waves when incident waves are high. Also, it was presumed that suspended sediments increase with wave height from backscatter intensities of ADCP. The scouring that occurred during artificial reef construction is thought to have been caused by suspended sediment transport due to undertow through an unbuilt section during high wave periods.

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  • Junji MIYAMOTO, Shinji SASSA, Kazuhiro TSURUGASAKI, Hiroko SUMIDA
    2019 Volume 75 Issue 2 Pages I_967-I_972
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     This paper discusses the experimental findings pertaining to the sinking of buried pipeline in association with wave-induced liquefaction in sand beds. The emphasis of the experiments was placed on investigating the relation between the liquefaction process and pipe behaviour. A series of wave tests using a drum centrifuge was performed under centrifugal accelerations of 70 gravities. It was found that the progressive liquefaction and progressive solidification were well reflected in the start of movement of pipeline and the end of sinking. Indeed, the pipe started moving downward upon the liquefaction front passing through the pipe location, and the sinking of pipe terminated, when the lower surface of the pipe met the solidification front advancing upwards.

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  • Tsubasa EBIKO, Makoto MIYATAKE, Ayumi SARUWATARI
    2019 Volume 75 Issue 2 Pages I_973-I_978
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     In exploring the feasibility of small-scale tide and ocean current power generation with the gradual extended diffuser with flanges in the Tsugaru Strait, the shape of the diffuser specialized for the local flow conditions are optimized through model experiments and numerical simulations. The each dimensions of the flange length (h), the opening angle (θ) and the diffuser length (L) are altered experimentaly. The mechanism of increasing the internal passing velocity of the diffuser are verified by comparing with the each dimension cases. The results of experiments from the variation of h and L show that the traction of the negative pressure region due to the generation of the vortex behind the flange is one of factors of the acceleration mechanism, and the variation of θ show that the lifting force working in the direction of the diffuser's outer edge is also the factor of the acceleration. The analysis shows that the increase of the vortex scale and the turbulence behind the diffuser, respectively in case of h and L changes largely and decrease in pressure reduction effect in case of θ changes largely inhibit the development of the accelerating region.

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  • Naru TAKAURA, Yusuke UCHIYAMA, Nizamani ZAFARULLAH, Akihiko NAKAYAMA
    2019 Volume 75 Issue 2 Pages I_979-I_984
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Oceanic forcing on offshore oil platforms deployed ubiquitously in the South China Sea (SCS) was evaluated from the medium-term reanalyses based on the in-house regional HYCOM-ROMS oceanic model and the JMA’s GPV-GSM global atmospheric analysis. An extreme value statistical analysis was conducted for determining the maximum surface currents and winds that may occur with multi-decadal exceedance probability. Wind stresses were most energetic off the eastern shore of the Malay Peninsula due to southwestward winter monsoons, while surface currents were intensified off the northern shore of Borneo Island. We assessed the mechanism behind the latter using a volume flux analysis at several cross-sections around the SCS. It was demonstrated that the remote forcing associated with the Kuroshio and Mindanao Currents triggered changes in the fluxes at the Luzon and Celebes Straits that are indirectly but pronouncedly influential to the coastal currents near the Borneo Strait.

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  • Yoichi SHIMADA, Maki OHWADA, Shogo TAKAGI
    2019 Volume 75 Issue 2 Pages I_985-I_989
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     By observing the movement of a drifting buoy which is affected by leeway and released to the east of the Emperor Seamount Chain, we clarify some of the drifting cases such as a fishing boat that have flowed out due to the Great East Japan Earthquake tsunami.The released drifting buoy moved to the east while meandering, and turned around off the Vancouver Island on the west coast of Canada after 155 days release.The drifting buoy is located closest to the Vancouver Island 175 days after release. The drifting buoy area generally supported the past drifting cases such as a fishing boat. Referring to the observed drifting duration of the drifting buoy from Iwate offshore to the Emperor Seamount Chain in the past study, the drifting buoy traveling duration from offshore Iwate to the west coast of Canada is about one year. The traveling duration suport the past drifting cases such as a fishing boat. The drifting buoy movement velocity has a high correlation with the sea surface wind velocity, and the drifting movement velocity to the east of the Emperor Seamount Chain can be estimated from the sea surface wind velocity.

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  • Naoya MINAMIURA, Soichi YAMAGUCHI
    2019 Volume 75 Issue 2 Pages I_991-I_996
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Color bleaching of Nori by HAB (harmful algal blooms) due to 3 phytoplankton species, Skeletonema spp., Eucampia zodiacus, Asteroplanus karianus, occurs in the inner part of Ariake Sea. This study evaluated the relationship between the growth dynamics of these red tide causing species and physical environments by analysis of weekly field observation data and conducting numerical simulations using unstructured triangular mesh. Red tide index (Number of phytoplankton cells × duration period) was high in the western area of the inner Ariake Sea and has high correlative relationship with the water residence time, which means that the strength of water exchange strongly controls the phytoplankton dynamics. Horizontal distribution of the strength of seawater exchange was determined by the horizontal difference in the strength of density-driven residual current which is strengthened in the eastern part of the inner Ariake Sea by fresh water inflow from 4 large 1st class rivers. Nori aquaculture increased the water residence time, so that the aquaculture formed more favorable environments for phytoplankton growth in terms of physical environment.

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  • Teruhisa OKADA, Masahiro IMAMURA
    2019 Volume 75 Issue 2 Pages I_997-I_1002
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     To reproduce Aoshio (Blue tide) and high turbidity in the middle sea layer at the head of Tokyo Bay, a physical-biogeochemical model including a sulfur cycle is proposed in this study. The sulfur-cycle model comprises anaerobic reduction of sulfate (SO42-) to sulfide (HS-) that occurs in the sediments and in the bottom sea layers, bacterial oxidation of HS- to elemental sulfur (S0), and bacterial oxidation of S0 to SO42--. Appearance and disappearance of the high turbidity in the middle layer, which are caused by upwelling of anoxic water, were reproduced well through distributions of simulated S0. It is observed that the breaking of internal Kelvin waves (as indicated by the propagation of upwelling and counterclockwise circulation in the surface layer) can lead to the mixing of the oxic-anoxic interface. Majority of the high turbidity is caused by the mixing occurring above the anoxic layer because the affected area by the outflow to the middle layer along the Chiba ship channel is limited. Furthermore, by conducting analysis based on the proposed model, it is estimated that at least 50% area of the head of Tokyo Bay is hypoxic during summer.

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  • Muhammad Ali HAFEEZ, Yoshiyuki NAKAMURA, Tetsunori INOUE, Shinya HOSOK ...
    2019 Volume 75 Issue 2 Pages I_1003-I_1008
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     The age of bottom water which indicates the period in which oceanic water stays at the bottom of the inner bay basin after intrusion from the bay mouth was calculated to verify whether the age is a good index for the development of bottom water hypoxia. The spatially distributed water quality data was utilized in this study for three consecutive year in 2012, 2013 and 2014. The data was observed monthly on sixteen monitoring stations by Suzuka fisheries laboratory of Mie prefectural government. To calculate the age of bottom water, a temperature-based age index model was used, the model based on the assumption that bottom water in the Ise Bay originates from the bay mouth (Lower strait water) in the predominate stratified period, i.e., summer season and age of the bottom water is the elapsed time from the beginning of intrusion from the bay mouth. From the analysis of age index model, it was found that the age of bottom water was higher in the center of the bay and water can be of 60 days old whereas near the bay mouth it was much younger and its age varied from 0 to 10 days. In September 2014, the entire basin accounted for younger water mass with a maximum age of 10 days at the center as compared to other years. Overall bottom water age in Ise Bay has also been calculated by taking an average of all stations, and it was found that the maximum average age occurred in June 2013 while the minimum one occurred in September 2014. The bottom water oxygen concentration indicated a high average correlation coefficient (R2 >0·70) with bottom water age in June, July, and August, whereas low average correlation coefficient (R2 <0·30) in September.

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  • Msanori ENDO, Jun SASAKI, Syougo SUGAWARA
    2019 Volume 75 Issue 2 Pages I_1009-I_1014
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     In order to clarify the dynamics of blue tides in the Sanbanze shallow water area at the head of Tokyo Bay, water quality measurements and interval photographing were performed in summer and autumn of 2017 and 2018. A couple of blue tides were observed in the Sanbanze fishing ground, having a tendency to occur first in the Funabashi navigation channel and off-Makuhari, and then in the Ichikawa navigation channel and off-Urayasu. This time lag was considered to be due to immediate upwellings of anoxic waters containing sulfide in the bottom layer of the Funabashi channel. A series of laboratory experiments was conducted to examine the influence of marine waters, including blue tides, on hard clams, one of the major fishery products in this fishing ground. Hard clams were found to die within 2 days at a high water temperature of 35 °C. When exposed to anoxic water with hydrogen sulfide, discoloration of their shells were observed.

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  • Sosuke OTANI, Yasunori KOZUKI, Maya MATSUSHIGE, Ryoichi YAMANAKA
    2019 Volume 75 Issue 2 Pages I_1015-I_1020
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     To reveal the relationship between temporal variation of CO2 flux and water quality using eddy correlation method at Omaehama beach in the inner part of Osaka Bay was conducted in this study. During the observation period, the CO2 flux fluctuated between -0.90 and 0.67 mgCO2/m2/s. CO2 was absorbed in all the neap tides, and was emited in spring tides. In addition, CO2 flux at daytime was absorbed about 2.8 times than that at night in the neap tide. There was no strong correlation CO2 flux and the surface water quality. It was thought that CO2 flux in the inner part of Osaka Bay fluctuated with neap and spring tide. Therefore, CO2 flux was effected by tide, but not events such as hypoxia, stratification and occurrence of hydrogen sulfide.

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  • Kentaro NAGAO, Yoshiyuki NAKAMURA, Daiki TSURUSHIMA, Yuto KOYAMA
    2019 Volume 75 Issue 2 Pages I_1021-I_1026
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     This study focuses on nutrient management operation at sewage treatment plants as a measure to improve biological productivity in the sea area. The effectiveness of the nutrient managements was evaluated using a numerical simulation model in Ise-bay where the amount of catch has decreased particularly in recent years. As a results, it was estimated that nutrient management operation could increase primary production, secondary production and clam resource. In order to reduce hypoxia and to regenerate of biological productivity simultaneously, it is necessary to implement conservation and restoration of habitats such as tidal-flats and seaweed-beds in conjunction with nutrient management operation.

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  • Kyeongmin KIM, Kaichi NISHIMURA, Kazuki YOSHIMURA, Tadashi HIBINO
    2019 Volume 75 Issue 2 Pages I_1027-I_1032
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     This study deals with sediment microbial fuel cell (SMFC) as a technique for purifying (reducing suppression) sediment by obtaining electric power from organically-enriched sediment in coastal areas. Other studies have shown that performance of SMFC is strongly dependent on the efficiency of consuming electrons harvested from anode to cathode. In this study, the current acquisition and the increase of the anode potential were evaluated at the local scale by SMFC with sufficient cathode performance. After that, possibility of development of bio-cathode was examined by clarifying change in performance of cathode electrode used in the field via V-I test. As a result, it has been found that the cathode having a high performance can suppress the diffusion of electrons from the sediment layer to efficiently recover electrons, and attached algae onto cathode reduce electrode deterioration at the field.

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  • Manaka OKABE, Hideaki NOHARA, Shinya NAKASHITA, Tadashi HIBINO
    2019 Volume 75 Issue 2 Pages I_1033-I_1038
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Ages sediment (acidification, reduction) inhibits the inhabiting of organisms in the coastal area where minerals are lacking. Effect of combustion ash elute minerals have a very important role in the activity of organisms, and it was possible to confirm reproduction of benthic organisms by scattering GCA (granulated coal ash) on ages sediment. Coal ash (FA) composed of oxides such as amorphous SiO2, Al2O3, CaO, Fe2O3 and bamboo ash (BA) that can elute K+ and Mg2+ are expected to promote coastal ecosystem regeneration. Dissolution characteristics of BA-GCA granulated by FA and BA are evaluated experimentally by dissolution test and combustion test used BA-GCA. And we clarified the basic matters on the development of recycled materials for Environmental purification of reduced soil.

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  • Shuzo NISHIDA, Yusuke NAKATANI, Taiga HIROSE
    2019 Volume 75 Issue 2 Pages I_1039-I_1044
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Reducing the inflow load, improving the sediment quality by dredging and sand capping, and promoting water exchange by artificial flow control are necessary measures for regenerating the water environment in highly enclosed urban coastal areas such as harbors. In this study, field surveys and analyses were conducted in the old port of Sakai to clarify the water and sediment quality characteristics and the water quality fluctuation because of an external disturbance.

     In the summer, hypersaturation and hypoxia were caused in the surface layer and the bottom layer, respectively, by density stratification in the port. Even though high concentrations of organic nitrogen and phosphorus were detected in the surface layer because of the impact of combined sewer overflow during rainfall, a high concentration of inorganic nutrients was observed in the bottom layer under the influence of nutrient elution from the polluted sea mud. During Typhoon No. 21, the water mass of the amount corresponding to the port volume flowed inside from outside the port. The water quality in the port was not completely mixed despite the strong wind and the storm surge. Further, the water environment in this port was observed to be strongly dependent on the bottom sediment. Accordingly, the improvement of the sediment quality is considered to be the most effective methodology for improving the water quality.

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  • Yuji SAKUNO
    2019 Volume 75 Issue 2 Pages I_1045-I_1050
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     The onjecttive of this study is to investigate the influence on the light environment in the Seto Inland Sea off Hiroshima Prefecture during the heavy rainfall in West Japan that occurred in the beginning of July 2018. Specifically, I tried to understand the transparency distribution characteristics of the Seto Inland Sea and its recovery status using measured transparency data, vertical turbidity data, and satellite data before and after the disaster. As a result, the following main results were obtained. First, based on the measured data, there was a drop in transparency of 68% of the average as a whole, off Hiroshima Prefecture. In addition, the transparency returned to the average value in about one month after the disaster (August 2017). Furthermore, a significant high correlation (R2 = 0.90, p <0.01) was obtained for the "band 3 to band 4 ratio" (offset corrected) of the Landsat-8 reflectance product and transparency. Also, the transparency distribution off Hiroshima Prefecture derived from the Landsat-8 data showed that a large-scale loss of several kilometers occurred at the mouths of the Kurose and Ashida rivers immediately after the disaster.

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  • Katsuyuki ABO, Goh ONITSUKA
    2019 Volume 75 Issue 2 Pages I_1051-I_1056
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Mooring observations and numerical model analysis were conducted to investigate characteristics of currents and behaviors of riverine water discharged into Hiroshima Bay by heavy rainfall in July 2018. The tidal and residual flows obtained by numerical calculation were consistent with the observation results. The calculated values of surface salinity distribution due to the heavy rainfall were also in good agreement with the ocean color satellite imagery. The less saline riverine water moved southward in the western part of the bay and was distributed over ten days throughout the bay. After the heavy rainfall, a strong southward (outflow) residual current from the north along the west coast was calculated in the first layer. In the second layer, however, an inflow current was calculated in the northern part of the bay. The discharged riverine water was considered to outflow through the surface layer. We also discussed the influences of changes in the currents and marine environments caused by the heavy rainfall on seedling collection of Pacific oysters.

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  • Hiroto HIGA, Wataru NAKAMURA, Shogo SUGAHARA, Yoshiyuki NAKAMURA, Taka ...
    2019 Volume 75 Issue 2 Pages I_1057-I_1062
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     In this study, we developed a sulfur estimation model for blue tide distributions using geostationary ocean color imager (GOCI) data. In order to develop the sulfur estimation model, Rrs with blue tides, and light absorption coefficient and backscattering coefficient of sulfur particles were figured out by conducting field observations in Tokyo Bay and laboratory experiments. Based on the measured sulfur optical properties, we developed a bio-optical model which was incorporated sulfur as a variable and then Rrs with fluctuation of sulfur concentrations could be calculated. A sulfur estimation model based on QAA_v6 improved by the results of the calculated Rrs of blue tides was developed. Compared to the estimated sulfur by GOCI data with the measured sulfur, it was possible to estimate sulfur concentrations with high accuracy when the difference between satellite data acquisition time and stating time of sampling in the field was small. Furthermore, it was captured that spatial distributions of sulfur concentration have changed with every 1-hour interval with the change of wind condition.

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  • Narong TOUCH, Kazuki YOSHIMURA, Kaichi NISHIMURA, Tadashi HIBINO
    2019 Volume 75 Issue 2 Pages I_1063-I_1068
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Recently, sediment treatments via electrochemical methods have been paid attention. In this paper, removal mechanisms of nutrient salts and hydrogen sulfide (H2S) via an electrokenetic method, and the factors that impact the performance of electrokenetic method are reviewed. Furthermore, field experiments were conducted to confirm the removal rates of nutrient salts and H2S via our developed electrochemical method, i.e. solar cell-combined electrokenetic method. The combination of solar cell makes it possible to increase the anode potential from the sediment potential to 1.5 V. This can facilitate oxidation reactions at the anode (various oxidations occur), leading to a larger increase in the removal rates of nutrient salts and H2S. From field experiments, high removal rates of nutrient salts and H2S were confirmed, indicating that our deveolpoed method can be used for treating excess accumulated sediment in littoral regions.

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  • Eiji YAUCHI, Kahoko HASHIMOTO, Seiji FUJIWARA, Masateru TAGA, Nobuyuki ...
    2019 Volume 75 Issue 2 Pages I_1069-I_1074
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     The Yatsu Higata tidal flat located in the inner part of Tokyo Bay is one of the most significant tidal flats remaining in Japan. The tidal flat was registered as a Ramsar site in 1993 because of the numerous migratory birds that visit the wetland to breed and feed. However, in recent years, the occurrence of green tides due to the extraordinary growth of Ulva spp. has become problematic and the green tides have severely impacted the ecology of the area. However, the green tides disappeared suddenly in 2017 and no green tides were observed in 2018. In this study, the cause of the disappearance of green tides in the Yatsu Higata tidal flat was examined based on field observation data collected from 2003 to 2018. The findings revealed that, while the water quality remained nutrient levels in the tidal flat remained high, Ulva spp. died due to a lack of light caused by the red and green tides in 2017. In 2018, higher than normal water temperatures were observed for an extended period in Tokyo Bay, and these elevated temperatures contributed to the death of Ulva spp..

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  • Maiko AKATSUKA, Yuriko TAKAYAMA, Kazunori ITO, Kenta WATANABE, Tomohir ...
    2019 Volume 75 Issue 2 Pages I_1075-I_1080
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     In order to develop a monitoring method for seagrass beds using environmental DNA, basic characteristics of environmental DNA released from Zostera marina were investigated. For eight months, twice a week, water sampling and DNA analysis were performed for Zostera marina which was grown in a water tank, whose seawater was regularly changed. The biomass of Zostera marina decreased in summer and increased in winter. Similarly, the amount of DNA decreased in summer and increased in winter. Moreover, in the sea survey, the growth conditions (plant height and density) were different from that of Zostera marina field survey in the previous year, and growth retardation was confirmed. The amount of eDNA analyzed at the same time was low, and the variation from the previous year survey was obtained. This result shows that by observing a wide range of seagrass beds through monitoring of sea grass using DNA, it is possible to rapidly acquire information such as loss and distribution change of seagrass.

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  • Soonbo Yang, Shinji SASSA
    2019 Volume 75 Issue 2 Pages I_1081-I_1086
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     We developed an integrated platform to predict and evaluate coastal benthic ecology-geoenvironment, and applied the integrated platform to a field. The platform consistently predicted the changes in the crossshore distributions of three peracarid crustacean species, associated with the storm-induced morphological changes in the sandy beach, and demonstrated its effectiveness.

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  • Yuriko TAKAYAMA, Maiko AKATSUKA, Kazunori ITO, Toshifumi MINAMOTO
    2019 Volume 75 Issue 2 Pages I_1087-I_1092
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     The seagrass bed monitoring method using environmental DNA (eDNA) can be established in the following cases. When sampling water is collected at a fixed point and the time change of the amount of eDNA is acquired, eDNA starting from a specific location does not coexist as eDNA from other starting points at the same time. In this study, we examined this feasibility by particle tracking calculation using simple bay model and the Ago bay model as a real sea. Using 10 types of simple bay models and the Ago bay model, it was confirmed that particles starting from a specific area appeared exclusively at the water sampling point depending on the flow pattern, and it was confirmed that this method might be established depending on the combination of seagrass distribution and flow of the bay.

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  • Haruku MORITA, Kentaro NAGAMA, Takashi MASAOKA, Tadashi HIBINO
    2019 Volume 75 Issue 2 Pages I_1093-I_1098
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     A granulated coal ash (GCA) was scattered onto organically-enriched tidal flats deposited along the Kyobashi River flowing through the center of Hiroshima City. It has been observed that the GCA layer is improving the ecosystem by forming algae that feed on benthic animals. In this study, major microalgae that flourished in the GCA layer were identified to examine the feasibility of establishing a diatomaceous farm in the sea where the decrease of diatoms is concerned. In addition, mesocosm experiment was carried out to quantify such microalgae. The purpose of this study is to investigate the mechanism of microalgae production by GCA under various water quality conditions. In the mesocosm experiment, the relationship between SiO2, nutrients and the amount of chl-a attached onto GCA was analyzed. Results indicated that the contribution of GCA (silica elution and nutrients fixation) was found to promote the growth of attached diatoms and floating plants.

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  • Kazumi TERADA, Kei TSUNODA, Hideya SATO
    2019 Volume 75 Issue 2 Pages I_1099-I_1104
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Multiple measurements of vertical distributions of water qualities (water temperature, salinity, DO and turbidity) and nutrients (NH4-N, NO3-N, PO4-P, TN and TP) were made in the Fukido mangrove river, in Ishigaki island, Japan, from 2007 to 2018. The river currents and nutrients in the groundwater were also measured on a section across the river mouth. Concentrations of NH4-N and PO4-P in the groundwater were 16-18 times higher than in the river water. Net SS and TN fluxes for the rainy day (87 mm/day) were about 3.8 times higher than in the other ordinary day.

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  • Che-Wei CHANG, Nobuhito MORI, Naoki TSURUTA, Kojiro SUZUKI
    2019 Volume 75 Issue 2 Pages I_1105-I_1110
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     An experimental study of water waves through a model mangrove forest is presented in this paper. Instead of using idealized or artificial tree models, 3D-printed mangrove models whose geometric structure was based on a typical mature tree (Rhizophora apiculata) at a scale of 1/7 were adopted in the laboratory experiments. During the experiments, the fluid velocity and forces on the tree model were directly measured, which provided a comprehensive investigation of the wave-induced forces on mangroves under various wave conditions. Comparing the predicted forces by Morison-type formula1) with the experimentally-measured forces, good agreements were observed, indicating the proper estimations of drag and inertia coefficients. To provide a useful tool for the estimation of wave dissipation in the future model developments, the relationships between force (drag/inertia) coefficients and the flow parameters (i.e. Reynolds/Keulegan-Carpenter numbers) are presented.

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  • Daiki TSURUSHIMA, Kentaro NAGAO, Kisaburo NAKATA
    2019 Volume 75 Issue 2 Pages I_1111-I_1116
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     This study verifies the influence of recent decline in food concentration on R. philippinarum in Ise bay based on a newly developed growth model of bivarve. Simulation results indicate that condition index and annual egg production per individual clam decrease after 2010 due to the insufficient food availability. This implies that recent decline in food concentration may cause exhaustion, mortality and weakning of reproductive activity of R. philippinarum. Moreover, the simulated decline of condition index and egg production after 2010 corresponds well with the decline in annual catch of R. philippinarum along Chita Peninsula.

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  • Kentaro NAGAMA, Shinya NAKASHITA, Takayuki HAMAMOTO, Tadashi HIBINO
    2019 Volume 75 Issue 2 Pages I_1117-I_1122
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Global warming and eutrophication caused by human activity and variations in social needs for foods have been deteriorated environments of oyster farm. Various surveys in response to environmental contaminations have not yet been conducted sufficiently, because aquaculture technology has been developed mainly with emphasis on the quality and increased production of oysters. i.e., the cause of mass mortality of oyster has not been elucidated. In this study, we hypothesized the mechanism of oyster mortality on the basis of previous study. In addition, mortality conditions were confirmed by surveys on quality of water and sediment during field experiments. As a result, the mechanism of oyster mortality that we assumed was well consistent with results of filed investigation conducted in oyster farm.

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  • Hideki KOKUBU
    2019 Volume 75 Issue 2 Pages I_1123-I_1128
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Influences of nutrients on fisheries resources in Ise bay were reviewed. Concentlation of the total nitrogen and phosphorous were decreased after peaking in 1980s, In 2015 they were decrease below the environmental standard zone II for water quality (TN:0.3mg/L, TP:0.03mg/L). The chrolophile-a which provides an indication of food environment were also decreased especially in southern bay. The fatty and mature index of short neck clams in Ise bay were decreased with reducing of the chrorophyl-a, and low qualities of Porphyra yezoensis were increased with luck of the nutrient in southern part of Ise bay.

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  • Takaharu HAMADA, Tsukasa YOSHIDA, Hiroshi OKAMURA, Takeshi HARA, Terua ...
    2019 Volume 75 Issue 2 Pages I_1129-I_1134
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Pelagic Fishes are the main target species in the inner bay, and the fluctuation of their catches and the formation of fishing grounds associated with natural and anthropogenic environmental changes are of great concern. In this study, we construct a statistical model to estimate the distribution of floating fishes in the inner bay using Gradient Boosting, which is one on the highly efficient machine learning techniques. Then we estimate catch of anchovy(Engraulis japonicus) in Ise Bay and Mikawa Bay. The model reproduced distribution pattern of anchovy well.

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  • Qingxu WU, Miki TSUCHIYAMA, Jumpei SUZUKI, Masafumi FUJITA
    2019 Volume 75 Issue 2 Pages I_1135-I_1139
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Scope for growth based on carbon mass balance (SFGC) and dehydrogenase (NADH) activity were assessed for brackish water bivalve Corbicula japonica exposed to five times diluted municipal wastewater and its components, assuming an anthropogenic water pollution. The results showed that soluble components of wastewater decreased in SFGC, while particulate components contributed to enhance SFGC, because they were used as food sources. On the other hand, soluble components increased in NADH activity and had more adverse effects in the bivalves with lower population density. There was a negative correlation between SFGC and NADH activity. The result indicated that SFGC was in response to NADH activity.

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  • Tomohiro YASUDA, Asuka HAMA, Takashi NAKANISHI, Hiroshi MATSUSHITA, No ...
    2019 Volume 75 Issue 2 Pages I_1141-I_1146
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     In the coastal area, new breakwaters and seawalls have been constructed and existing structures have been strengthened to ensure safety and security against storm surges, high waves, and tsunamis. Although "disaster prevention" and "environment preservation" have often been regarded as conflict relation, it is desirable for coastal protection projects to be coexistent in the future projects. This study focused on the artificial reef at Hamasaki coast in Motobu town, Okinawa Prefecture, and conducted water quality and coral distribution survey with the purpose of clarifying the factors why coral growth status are better than neighboring structures. As a result of water quality survey, there are little differences in water temperature and salinity between the survey lines and the tide conditions, but DO tended to be higher in the surface layer near the artificial reef. Moreover, the results of analyzing the cover rate according to the type of coral indicated that there is a difference depending on the section, and the cover rate of coral on the southern offshore side is higher than the other sections.

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  • Toko TANAYA, Nobuyuki KINJO, Shunpei IWAMURA, Sohei AOYAMA, Iwao HASEG ...
    2019 Volume 75 Issue 2 Pages I_1147-I_1152
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Enhancing coral growth is important given the current declining trend of coral reef ecosystems. We investigated coral distribution and flow structure around caisson joints and conducted the hydraulic model experiments to estimate the water flow velocity throuth the caisson joint varying with wave conditions, in light of the positive effect of water flow on corals. The coral (especially Acropora spp.) cover of caisson joints was higher than that of the center of caisson in Naha Port. The coral cover increased with increasing width of the caisson joint and become highest around ~1 m. The flow velocity also increased with increasing width of the caisson joint, indicating that water velocity through caisson joints enhanced ambient coral growth.

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  • Fuminori NAKAMURA, Takayuki YAMAGUCHI, Keiichi KANDA, Takumi SHIMOMURA
    2019 Volume 75 Issue 2 Pages I_1153-I_1158
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Sea salt spray, which is transported by wind action to the surface of structures, harms long-term durability of the structures. In this study, experiment of transportation and adhesion of sea salt spray particles to surface of concrete structures was carried out. Distribution and size of particle of sea salt spray particles around surface of structures were also estimated. In those results, it was shown that the adhesion amount and particle size of sea salt spray particles to surface of structures can be estimated by experiment results. The adhesion amount of sea salt spray particles to surface of concrete structures is also affected by shape of structures model.

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  • Hideaki NOHARA, Jun NISHIURA, Takahito OIKAWA, Tadashi HIBINO
    2019 Volume 75 Issue 2 Pages I_1159-I_1164
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     It is confirmed that property of the deposited organic mud on the tidal flat with granulated coal ash (GCA) changes, it is suggested that they are related to microorganisms attached to GCA. However, It is not clarified relationship between GCA and effects. In this study, the relationship between microorganisms and tidal flat sediment environment was verified by carring out microbial flora analysis used GCA and bottom mud in the tidal flat. It was suggested that microorganizms contribute to improvement of sediment environment because photosynthetic bacteria etc, selectively inhabit in the tidal flat with GCA and bottom sediment environment in the tidal flat with GCA is better than river bottom environment. It is considered that the tidal flat with GCA form structure that easilysupplies light, oxygen, etc.

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  • Toru ENDO, Hironobu IMAYOSHI, Noriko HARADA
    2019 Volume 75 Issue 2 Pages I_1165-I_1170
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Water quality monitoring surveys were carried out for every season at the mouth of the Yamato river in order to examine the air-water CO2 exchange characteristics in the urban estuarine area. In addition, we obtained a regression equation between the electrical conductivity (EC) and the total alkalinity (TA) based on the relationship between EC and TA of the water sampled at some points of Yamato river in order to estimate the TA required for calculation of the partial pressure of CO2 in water (pCO2) from the monitoring data of EC.

     The pCO2w had large daily fluctuations in summer and fall, but the pCO2w had small values and small daily fluctuations in winter. As a result of multiple regression analysis of pCO2w and the observation items, the air-water CO2 exchange depended on the change in salinity due to the tidal change and the change in pH due to the photosynthesis and the respiration. The averaged air-water CO2 flux was 7.9 ± 0.6 CO2/m2/hr in spring, 2.90 ± 0.7 CO2/m2/hr in summer, 16.2 ± 1.3 CO2/m2/hr in fall, -4.2 ± 0.5 CO2/m2/hr in winter, and the Yamato river estuarine area acted net CO2 sources except in winter.

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  • Satomi KAMIMURA, Sosuke OTANI, Kazuki IWAMI, Yasunori KOZUKI, Naoki TA ...
    2019 Volume 75 Issue 2 Pages I_1171-I_1176
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Fish diversity at at Amagasaki canal in the Inner Part of Osaka Bay were investigated by environmental DNA analysis (eDNA) to clarify whether this method is valuable in eutrophic conditions. A ORP and DO was restored in January in Higashi-bori sampling point and the detected fish species was larger number than the other time. The result suggests that Higashi-bori has a potential for fish habitat with a water quality recovery. The number of detected species and fish fauna suggests that eDNA is efficient in comparison among sampling points which has sharp contrast of environmental factors and monitoring seasonal difference. The eDNA is unable to detected a certain species, but allow to detect larger number of species than the conventional sampling methods. eDNA is most effective when used in conjunction with conventional sampling method for investigation of fish diversity.

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  • Tomoya SHIMURA, Nobuhito MORI
    2019 Volume 75 Issue 2 Pages I_1177-I_1182
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Future projection of wave climate around Japan using high resolution wave model was conducted. Climatology of significant wave heights and mean wave periods around Japan would be decreased in the future climate by 10% and 3%, respectively. Temporal average of wave spectra was analyzed in addition to the bulk wave parameters. Energy decreases all over frequency-direction domain lead to decreases in climatology of wave heights and periods around Japan. In the Japan Sea side, the larger magnitude of energy decreases at clock-wise direction of mean wave direction causes the future anti-clock wise changes in mean wave direction by 3.5◦ . In the Pacific side of east Japan, mean wave direction would be changed clock-wise by 4.5◦ because of future energy decreases at the peak of mean wave spectra. Future changes in wave height, period and direction can be discussed consistently owing to analysis on the mean wave spectra.

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  • Ayano SONODA, Yoshihiko IDE, Masaru YAMASHIRO, Noriaki HASHIMOTO, Kats ...
    2019 Volume 75 Issue 2 Pages I_1183-I_1188
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     Suo-nada Sea has a vulnerability against storm surge, however there are less investigations on storm surge in the sea area comparing with the three major bays or Ariake Sea. Due to sea level rising and more intense typhoons than ever caused by global warming, it is concerned that storm surge disasters can be more severe in the future. Hence, future storm surges in Suo-nada Sea were investigated, and numerical simulations were performed using ocean circulation model. Firstly, the most suitable computational domain size for estimating storm surges in Suo-nada Sea was found and also verified the simulation accuracy depending on the data types of external forces and typhoon tracks. Secondly, the future change of typhoon characteristics around the sea area was evaluated with the large ensemble climate database. Finally, future storm surge in Suo-nada Sea was estimated with more reality, considering that the intensity of the typhoon was weakened according to the time when it was passing through land area. As a result, it was found that there is a risk of storm surge developing more than present in the future especially at inner part of the sea area.

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  • Jun YOSHINO, Kohei YAMAMOTO, Akihiko MURATA, Tomonao KOBAYASHI
    2019 Volume 75 Issue 2 Pages I_1189-I_1194
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     In order to estimate the future change in maximum potential storm surge (MPSS) in Ise Bay, Japan, we conducted track-ensemble experiments of a maximum intensity typhoon approaching to Ise Bay under the present and future climates, based on the dynamical direct downscaling technique. Numerical experiments indcated that the MPSS at the Port of Nagoya was 4.1m in the present climate and was 4.5m in the future climate, suggesting underestimation compared with the previous researches. The moving speed of the future typhoon was about 20 km/h, which was slower than that (about 40 km/h) of the present typhoon. In conclusion, increase of the MPSS in the future climate could be supressed from the balance with the natural oscillation period in the inner part of Ise Bay, and the future risk of storm surge disaster along the coast line of Mie Prefecture could be intensified relatively.

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  • Jinji UMEDA, Sota NAKAJO, Nobuhito MORI
    2019 Volume 75 Issue 2 Pages I_1195-I_1200
    Published: 2019
    Released on J-STAGE: October 17, 2019
    JOURNAL FREE ACCESS

     A global stochastic tropical cyclone model (GSTM) considering time series correlation of tropical cyclone properties has been developed by using large ensemble GCM simulation data (d4PDF). The bias of d4PDF has been corrected by using the information of the average and the standard deviation of tropical cyclone properties comparing with that of IBTrACS. AS a result, we could get accurate correction results at each 3 degree grid. The improvement of the reproducibility of the frequency has been observed at many area by using the joint probability distribution functions (JPDF) of GSTM approximated from the corrected d4PDF data. Especially, this improvement was significant in the area that the tropical cyclone data is insufficient. The simulation results show the variation of the change rate of future tropical cyclone frequency around Japan and the intensification of tropical cyclone depending on the SST scenario.

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