SEDIMENT TRANSPORT IN THE NIBUTANI DAM RESERVOIR AT 2003 FLOOD LF THE SARU RIVER

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