The mechanism of three-dimensional levee breach by overflow (i.e., lateral overflow with consideration of river flow riverside land) has not been clarified in past studies. Elucidation of this mechanism is very important for disaster prevention as well as for the future progress of studies on levee breach by overflow. We conducted experiments of levee breach in three-dimensions by overflow using the Chiyoda Experimental Channel. The results of the experiment are as follows: Until the beginning of levee breach, phenomena near overflow area was similar to one by front overflow. It means that we can apply knowledge from anamnestic levee breach experiment involving front overflow to until the beginning of levee breach. After the beginning of levee breach, it related to unit width discharge and levee breach speed.

Sedimentation in dam reservoirs is a serious matter of great concern with river management works .In general,sediment deposited in the reservoir is hard to move comparing with river bed materials,even if the diamete is equal.Therefore,hydraulic experiments were conducted on the fall velocity of sediment and the entrainment rate of suspended sediment using the material which is deposited in the dam reservoir .It is found that the fall velocity of sediment and the entrainment rate of suspended sediment are smallre then the value currently used conventionally.These results are applied to calculate bed variation of the 2003 flood in the Nibutani Dam resevoir.The calculated results mostly agree with field surveys .

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The flow of an active thermal protection system exploiting subsonic counter-flow jets for wing leading edges of hypersonic vehicles is numerically studied on the basis of the three dimensional Navier-Stokes equations. The coolant air issuing from around the stagnation point as an array of three jets spreads over both the upper and the lower sides of the cylinder surface and about 40 ~ 60% cooling effectiveness is achieved in the range up to 5 degrees angle of attack despite the occurrence of various three-dimensional fluid-dynamic instabilities. The numerical scheme is second order accurate but simple inclusion of high order polynomial approximation in the reconstruction enables the capturing of finer structure of the flow field.