[A-CG43] Water and sediment dynamics from land to coastal zones

[ACG43-P06] Estimating sand, silt, and clay transport at the Abukuma River estuary for a comprehensive understanding of suspended sediment dynamics from the watershed to the pacific ocean

*Sheikh Hefzul Bari¹, Mayu Tateno¹, Yoshiyuki Yokoo² (1.Graduate Student, Graduate School of Symbiotic Systems Science and Technology, Fukushima University, 2.Professor, Graduate School of Symbiotic Systems Science and Technology, Fukushima University)

Keywords:Suspended Sediment, Abukuma River, Sediment Dynamics, Suspended Sediment Yield

A precise understanding of sediment dynamics plays a vital role in comprehensive sediment management. Based on suspended sediment observation at the estuarine area, this study aimed to elucidate the temporal and spatial variations in sediment dynamics of the Abukuma River, the 6th longest river in Japan. First, we conducted flow velocity and flow rate observations using the acoustic doppler current profiler (ADCP) and electro-magnetic current meter to confirm the accuracy of the observed flow velocity and the observed flow rate by the Ministry of Land, Infrastructure, Transport, and Tourism in Japan. In addition, we measured turbidity, suspended sediment concentration, distribution of particle size, and rock composition by collecting grabbed samples from the river during flooding and non-flooding conditions. Grabbed samples were collected from nine sampling points during the non-flooding condition in the bathymetric and horizontal directions to investigate the spatial distribution of suspended sediment. This revealed the mean and variations in sediment concentration across the river cross-section to compare with the concentration of surface water. By measuring the turbidity of the grabbed samples using a multiple water quality meter (EXO-2, Xylem Japan), we developed a relationship between suspended sediment concentration and turbidity. We also created sediment rating curves for different particle size ranges. X-ray fluorescence analysis revealed the types and percentages of constituting rock compositions in the suspended sediments of water samples. The results showed that rock composition was consistent across sampling points and sampling periods, and that the sediment samples most likely originated from the granitic rocks of the Abukuma Mountains on the right-bank of the Abukuma River.