流砂観測への時間領域反射測定法(TDR)活用の検討

Toward a novel approach of bedload monitoring in mountainous streams, we attempted to measure height and porosity of sediment layer below water surface by applying TDR. A column experiment was conducted to validate accuracies of estimated sediment height and porosity for a probe (0.75 mm in length). The probe was inserted into a container filled with water and, then, TDR waveforms were measured during a procedure of supplying the sand until the probe was totally covered by sediment layer. TDR waveforms were analyzed and used for calculating height and porosity of sediment layers. Experimental results show good agreements of calculated heights of sediment layer. Calculated porosities ranged from 0.32 to 0.46, which were consistent with general porosity of deposited sand (about 0.4). Comparisons between calculated and observed cumulative sediment volumes suggested that the method proposed in this study is applicable of monitoring sediment in water and bedload in the field.