In order to develop the fish place around Okinotori-Shima, it has been required that the fertilization of ocean by the nutrient-rich deep seawater. In this proposal, the upwelling method by perpetual salt fountain has been investigated. When the upwelling pipe is moored at the bottom of the ocean, it has a possibility of gradient of the upwelling of pipe. In this study, to moor the upwelling pipe at Okinotori-Shima, the method which spread the streamline upwelling pipe by using container is proposed. To establish this method, the spreading condition of upwelling upwelling pipe was designed and the availability of spreading method of pipe using container was evaluated. The gradient of pipe was modeled with drag coefficient measured by drag force measurement experiment and the buoyancy of the buoy to moor the streamline upwelling pipe at the bottom of the ocean was calculated. And also, the experiment of spreading of the 25 m upwelling pipe was conducted and the spreading of the pipe and the movement of dropping of container were observed. Using this experimental result, dropping movement of container at Okinotori-shima was evaluated.

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 Characteristics of wave absorption and wave forces on a low-crested detached breakwater composed of slit walls and filling was studied by CADMAS-SURF. Four types of the breakwaters which have various slit walls were calculated. In the results, the largest wave energy loss was got by a type of all slit walls (three vertical walls and two horizontal walls). Wave forces on this structure were reduced and the reduction factors for horizontal and vertical wave forces were treated as modified Goda's formula. Moreover, designed cross section was practical for required safety factors of sliding and overturning.

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 A three-dimensional numerical wave tank ‘CADMAS-SURF/3D’ was improved so as to deal with the interaction between waves and movable objects using a volume-force type of immersed boundary method. The improved ‘CADMAS-SURF/3D’ was applied to enforced moving object tests in order to verify the validity and utility of the model. In a wavemaker test, regular waves were generated with a vertical plate in piston-type and flap-type motions. As a result, a reasonable agreement between numerical and theoretical results based on the small amplitude wave theory was found in terms of water surface fluctuation and flow velocity. From the dam-break test, it was demonstrated that the improved ‘CADMAS-SURF/3D’ was able to predict water motion accurately by considering the rapid upward movement of a gate.

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 The study aims to clarify the effects of a new revetment irregularly placed stones on seaweed bed formation and gathering of marine organisms. We compared the seaweed bed and gathering of marine organisms at the new revetment off Iwakuni with those(beds on masonry revetment of the mainland side and beds on rock reef or masonry revetment of island side) at the Hiroshima Bay on the basis of environmental factors such as salinity, wave height. Environment factors of the new revetment were characterized by shallow water, low wave height (H_1/3), low salinity, and high water temperature. These environmental factors were more similar to those of seaweed beds at the mainland side more than they were for the island side. Seaweed biomass (wet weight) and species number of the new revetment tend to be higher than that of the seaweed beds at the mainland side. However, the biomass and the species number are equal to the level of the intertidal seaweed beds of island side. Vertical seaweed distribution and community were slightly different from those of seaweeds of island side, but they were similar to those of seaweeds beds of the mainland side. Marine organisms found at the new revetment had many species in common with seaweed beds of the mainland and island sides. Averaged densities of the new revetment showed almost higher values than that for the seaweed beds of the mainland side. These results suggest that irregularly placed stones of size 0.5–1.0 m have a higher effect on seaweed bed formation and gathering of marine organisms compared with seaweed beds on the mainland side. The method of promoting seaweed bed formation and gathering of marine organisms by arranging stones is applicable in shallow water environments, similar to those found at the Iwakuni coast.

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 This paper introduced observation data of proto-type GPS buoy's mooring chain at 3 years and 7 months after the installation, in order to provide information for practical design of future safer and more economical design of the mooring system. Following findings may be important for the future GPS buoy design. (1) Mooring chains stayed in good performance even after 3 years and 7 months of severe ocean field conditions, although they were covered by large amount of sea plants like shells and several studs disappeared from some of the chains located at frequently suffering from landing and dis-landing action by the buoy motion. (2) The quantity of real frictional wear was considerably smaller than assumed one at all the part of the mooring system. (3) Maximum real frictional wear was observed at chains located at frequently suffering from landing and dis-landing action by the buoy motion.

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