A regional meteorological model RAMS by two way nesting technique was applied to simulate the time variations of meteorological fields over the Kyushu region. Model results were examined with the Japan Meteorological Agency's observation data within Kyushu area. Evaluation of seasonal variation of available wind power indicated high value in the winter due to winter monsoon. Especially remote islands, the coastal regions (along the Sea of Japan and East China Sea), and mountain regions shows the strong annual average wind speed and high potential of available wind energy. Wind power using the Rayleigh distribution was an underestimated the available wind energy compared with simulation results.

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Through hydraulically-field observations more than thirty times in lake Abashiri, we elucidated the all over behaviors of lake-water and compared with numerical simulation. Visualizing technique by use of ultra-sonic fish finder showed the wave-like motion of the internal boundary between the upper and the lower layer caused by strong wind. In order to clarify the phenomena, we introduced the new equations relating to the surface and internal boundary elevation, and analyzed the time-varying behavior of the boundary. We found the different wave motion of the boundary to the well-known pattern of seiche caused by strong wind. Finally, we carried out three dimensional numerical simulation regarding the transient motions of lake-water in strong wind and could make the diagram showing the appearance of Aoshio with respect to wind speed and water depth of the upper layer.

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In order to elucidate the hydraulic behaviors of flash flood-inflow and sweeping out of salt water into or from lake Abashiri, we have been carrying out synthetic field observation more than thirty times and numerical simulation since 1992. Through the field work, we found that the elevation of the boundary between the fresh water of the upper layer and the salt water of the lower one is influenced by inflow and sweeping out of the salt water caused by flash floods. Further, Aoshio, which is the appearance of salt water in the lower layer without dissolved oxygen in the surface of the lake in strong wind, affects the elevation of the boundary and water quality in the upper layer. Remodeling a ultra-sonic fish-finder, we could visualize the shaded patterns of the inflow caused by snow-melt flood and sweeping out of lake-water. Through visualizing the flow patterns in the lake, we found that there are two types of outflow from the lake. One is sweeping out of the lower water by the faster upper layer and the other is entrainment mechanism of the lower water by diffusion.

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It is indispensable for the effective design of the rubble mound weir to understand the destruction mechanism. Interactions between rubble stones are dominant in the destruction process of the rubble mound weir. So, in this paper, the rubble stones (solid phase) are modeled by using the Distinct Element Method which can express the interaction between rubble stones explicitly, and also, the interaction between solid phase and liquid phase is described by Euler-Langrange coupling model. The destruction mechanism of the rubble mound weir is investigated form the driving force acting on the rubble stones, furthermore, the comparison of numerical simulation with experiments are discussed.

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Field measurements were conducted to investigate hydraulic environmental changes caused by destratification systems. The measurements were designed to observe the following three points: 1) spatial distribution of flow field using a ADCP equipped to a boat. 2) time series of current profile at stations near bubblers. 3) water temperature monitoring to observe thermal stratification. These observations revealed interesting behaviors of intrusion. The depth of intrusion responses to diurnal changes of surface water temperature because of the entrainment around water surface. Flow volume of intrusion was influenced by all the bubble plumes and their accompanying current.

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The typhoon No. 18 in 1999 caused serious damage in the coastal facilities in Suo-Nada sea of Yamaguchi prefecture. The storm surges and wave heights became lager than the present defensive standard level in some areas. The typhoon route, atomosheric pressure depth and storm surge anomaly in the standard level were revised on the basis of probabilistic estimation. The new standard employed the typhoon No. 18 as the representative model typhoon in Suo-Nada sea. The newly proposed sea wall level became much higher than the present height in almost areas in Yamaguchi coast.

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