The 24th IAHR-APD Congress (24th IAHR-APD Congress)

405 / 2024-03-13 21:55:46

Unsteady suspended sediment transport flux measurement using ADCP

unsteady flow,suspended sediment,Yangtze River,ADCP

Subtheme 7: Sediment Regulation and Management > Topic 1: Sediments Transport Dynamics

Suspended sediment transport flux is an important indicator for hydrological monitoring. While the estimation of suspended load transport from Acoustic Doppler Current Profilers (ADCPs) has been extensively investigated, the calibration of ADCP backscatter may face challenges, particularly due to variations in specific attenuation. The accurate prediction of specific attenuation success relies primarily on changes in suspended particle size, posing considerable challenges to monitoring unsteady suspended sediment transport. To investigate the characteristics and observation methods of unsteady suspended sediment transport, we conducted continuous monitoring of flow structure and suspended sediment using acoustic instruments and water sampling both upstream and downstream of the confluence between the Yangtze River and Poyang Lake within the Three Gorges Dam regulation period (June 30, 2023 - July 10, 2023). Our findings reveal a nuanced pattern in flow discharge at Jiujiang Station, decreasing from 27000m^3/s to 23800m^3/s initially and then increasing to 26100m^3/s over the observation period. Similarly, suspended sediment concentration and median particle size exhibited an initial increase followed by a subsequent decrease. Notably, the traditional method, which neglects specific attenuation, struggled to accurately estimate suspended sediment concentration. In contrast, the method incorporating the suspended sediment absorption coefficient successfully retrieved the concentration using ADCP backscatter, where the absorption coefficient displayed variations in tandem with particle size changes. This study contributes valuable insights to sediment regulation and management, offering crucial support for decision-making in water resource management.