Author(s): Koichi Tsuchida; Masahiro Hashiba
Linked Author(s):
Keywords: MBES; ADCP; Sand wave; Actual river; Bedload
Abstract: Bedload discharge is important to understand the sediment dynamics in the basin and to verify to the numerical analysis of river bed fluctuating. However, it was difficult to install the bedload sampler on the river bed during high flow and there was involved uncertain data. In this study, we conducted the observation of bedload migration and river bed form using two acoustic devices in an actual river which were the ADCP for bedload velocity measurement and Muti-Beam Echo Sounder(MBES) for detail bathymetry measurement. The boat with an acoustic device was moved from downstream to upstream repeatedly every 10 minutes for 1.5 hours. Next, by using measured data which were bed waveforms, bed migration, we evaluated bedload discharge measurement methods in the actual river. The sand waveform estimated by MBES that the average wavelength was 3.5m, the average wave height was 0.2m. Moreover, the MBES data were estimated the moving speed of the sand waves using the space-time image, the result was from 0.03 m/min to 0.11 m/min. Finally, regarding the bedload discharge, we compared two different methods. The first one is the bedform migration which was the function of the wave height and the wave migration speed by MBES proposed by Kikkawa (1985). The second one is the method using the bedload velocity of ADCP proposed by Koseki et al. (2016). As a result, the bedload discharge was close to similar to each other. Therefore, it was shown that it is possible to estimate the bedload discharge using ADCP without directly sampling the bedload.
Year: 2020