MEASUREMENT OF NON-UNIFORM SUSPENDED SEDIMENT TRANSPORT DURING SLUICING AND FLUSHING OPERATIONS AT THE SETO-ISHI DAM ON THE KUMAGAWA RIVER

Abstract

 There were floods of 4 450 m³s⁻¹ at the Seto-ishi Dam on the Kumagawa River in Japan during July 2018. The sluicing and flushing operations were performed for 7 days at Seto-ishi Dam, and suspended sediment concentration and particle size distribution were continuously measured using a flow-cell type ultrasonic attenuation spectrometer, and suspended sediment transport was observed. The main results follow. The amount of suspended sand transport due to sluicing and flushing operations was 490 × 10⁶ kg. This comprised sand content of 64.7 × 10⁶ kg(13.2%), cosrse silt of 145.0 × 10⁶ kg(29.6%), and wash load of 280.5 × 10⁶ kg(57.2%). Sediment of 149 × 10⁶ kg flowed out of the reservoir due to the flushing operation, and suspended sediment flow into reservoir was estimated as 341 × 10⁶ kg.