Coastal acoustic tomography system for monitoring transect suspended sediment discharge of Yangtze river

Abstract

Suspended sediment discharge (SSD) in the Yangtze River (YR) plays a crucial role in transporting nutrients and sediment to the YR estuaries and the East China Sea. In order to gather information on suspended sediment concentration (SSC) and SSD across an entire river cross-section, we investigated a novel method supported by Coastal Acoustic Tomography (CAT). Consequently, two CAT systems were employed to estimate the cross-section averaged SSC and SSD at the Datong (DT) station of the YR over approximately 2.5 years. Low (0.02 kg/m3), high (0.44 kg/m3), and mean (0.10 kg/m3) SSC values were successfully estimated. The SSD was primarily driven by water discharge, exhibiting low values (204 kg/s) during the dry season and a maximum of 36,299 kg/s during flood events, with the mean value of 3,903 kg/s throughout the observation period. The water sample and CAT results demonstrated high consistency, with correlation coefficients (R2) of 0.92 for SSC between the water sample and CAT results, and 0.96 for SSD between the DT result and CAT results. This study established the ability to monitor transect SSC and SSD in the YR using the CAT sound attenuation approach, offering the advantage of continuous real-time monitoring of transect river flow, SSC, and SSD, even during extreme flood events. For the success of this method, factors such as particle size, sound frequency selection, and the measurable distance between instruments must be meticulously considered. This work highlights the potential of CAT for monitoring riverine transect SSC and SSD.