In this study, on the basis of observation data of water temperature and salinity at the center of Uranouchi Bay for about one-year, stratification strength and vertical mixing during the stratification period were evaluated in terms of energy amount. Then their energy amounts were examined comparatively with the tidal energy amount of the bay. These results are described as follows : 1) Stratification strength reaches the maximum of 180 Jm^-3 in August. This is equivalent to the energy amount that the tide works on the bay for about two hours. 2) The vertical mixing energy is as much as l/260-1/2600 of the mean tidal power of the bay. 3) The energy amount that increases stratification strength is l/250 of the mean tidal power of the bay.

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On the basis of observation data of water temperature and salinity at the center of Uranouchi Bay throughout nearly one year, it is shown that the Brunt-Vaisala frequency N is not zero or a constant, but the N has an exponential distribution. In this case, intemal waves are described with Bessel's function. On the basis of this result, the flow characteristics of intemal tidal waves are described.

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Improved practical fomulas for evaluating the equilibrium profile of berm breakwater under irregular wave attack have been developed. In the previous paper, it has been found that three parameters of the stability number, the relative berm crest height (ratio of berm crest height and water depth) and the amor grading have significant effects on the equilibrium profile of berm breakwater. For the improvement, the present study was experimentally conducted to find out the conditions of equilibrium profile of bem breakwater due to effects of the wave steepness and the initial seaward slope of berm breakwater. The results show that, the wave steepness only influences significantly horizontal eroded berm width, however it does not significantly influence vertical eroded berm height and toe width. Whereas, the initial seaward slope of berm breakwater influences significantly horizontal eroded berm width and toe width, however it does not influence significantly vertical eroded berm height. Considering those results, the new evaluation fomula, which regards the equilibrium section of seaward slope of berm breakwater, has been proposed. This proposed fomula may be playing an important role in designing a berm breakwater in the actual beach.

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The experiments were conducted using a circulating water chamel in order to clarify the characteristic movement of the trolling depressor. A three component load cell measured the tension of the line from the trolling depressor. The length of the line and the flow speed were changed between 0.5m and 1.4m, and 0.4m/s and 1.6 m/s, respectively. The movement of the trolling depressor was recorded through CCD cameras onto videotapes. The three component displacement of the point where the line was knotted to the trolling depressor was estimated by the tension of the line. The periods of the x and z component's displacement were similar and about 0.4 seconds. The period of the y component's displacement was about 0.8 seconds and twice as long as that of the x and z component's. It was clear that the locus of the point where the trolling depressor was knotted was similar to the number '8' on thexy, yz and xz planes.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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