IMPROVED METHOD OF PARTICLE SIZE ANALYSIS AND SUSPENDED SEDIMENT CONCENTRATION MEASUREMENT BY ULTRASONIC ATTENUATION SPECTROSCOPY

To investigate sediment transport in rivers, the authors measured suspended sediment by two methods: water sampling and continuous measurement with a flow-cell ultrasonic attenuation spectrometer. Two one-liter samples were taken to measure sediment concentration and particle size distribution, for calibration of the spectrometer. In the Inagawa River, sand particles could not be measured either by sample analysis or by the flow-cell ultrasonic attenuation spectrometer, but the sand bars that formed in the river channel due to sand movement during floods could be observed. To solve this problem, the sample volume was increased from one liter to 18 liters, and the concentration and particle size distribution of the samples were measured by dividing the sample into sand particles and wash load. It is necessary to improve the flow cell so that sand particles pass within the measurement area of an ultrasonic transducer.