Author(s): Alejandro Nardin; Ricardo Szupiany; Alejandro Arcelus

Linked Author(s): Alejandro Nardin, Alejandro Arcelus

Keywords: Suspended sediment; Uruguay river; ADCP

Abstract: Sediment transport in fluvial environments is of great interest in many disciplines, from ecology to civil engineering. During the last two decades many efforts have been invested in developing an acoustic-based methodology to estimate the suspended bed sediment transport. Uruguay River Administrative Board (Comisión Administradora del Río Uruguay) bet on this technology and during recent years has developed a methodology for using Sontek M9® ADCP to assess this variable. In this paper suspended bed sediment concentration is estimated using the acoustic inversion technique on a dataset obtained with a Sontek M9® ADCP. A methodology for obtaining not-available ADCP parameters is proposed. Simultaneous data from ADCP Sontek M9® and Teledyne® RDI Río Grande is used to reverse engineer the so-called sonar equation, with a backscatter correction function that depends on measurement cell size and depth. ADCP acoustic frequency and bimodal sediment distribution are taken into account. This methodology is subsequently used to estimate suspended sediment concentration for more than 20 Sontek M9 discharge measurements in a cross section in lower Uruguay River. Solid and liquid discharge rating curves were constructed from this data. Historical water head data was used to obtain liquid and suspended sediment load time series. An average of 890.000 tn/year of suspended sediment load was calculated for the period 1980-2020. Calculated values are in agreement with previous modeling and field efforts but never scientifically tested. It is verified that suspension motion threshold occurs at high hydrological scenarios of less than 10% chance of occurrence. Suspended load time series provided useful information to compare, in future steps, with dredging volumes or OBS/ABS/Turbidity continuous monitoring data for example.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221426

Year: 2022