Estimating suspended sediment concentrations using a broadband ADCP in Mahshahr tidal channel

Abstract

Data sets of Acoustic Doppler Current Profiler (ADCP) backscatter intensities (ABS) were used to evaluate suspended sediment concentrations (SSC) in the Mahshahr Channel (MC) of the Persian Gulf. Since the echo intensity is closely related to turbidity in water, the ADCP may be a promising tool to monitor the sediment transport. The low susceptibility of the acoustic backscatter to bio-fouling and the ADCP provision of current profiles as well as sediment time series makes this monitoring method more advantageous compared with the traditional methods. Time series of ADCP backscatter intensity profiles were used for improving temporal resolution of SSC estimates. Backscatter and traditional observational data were separated into two segments. The first part was utilized for calibrating the backscatter data and attributing the intensity to suspended particle concentrations and using the second part acoustic intensities were validated. Acoustic based SSC estimates are slightly underestimated in comparison with traditional water sample based SSC values, but still there is good agreement between acoustic SSC and traditional observations. Results illustrate a rather high correlation between lab based and acoustic based particles in suspension (<i>R</i><sup>2</sup> = 88 %). Additionally measurements reveal the domination of a semidiurnal ebb asymmetric system in the MC. Tidal currents provide the main energy source for particle resuspension and transport. Maximum suspended load concentrations are evident in ebb tides, while the currents strengths are enough to refloat loads from the bed. In general spring tides show higher SSC values compared with neap tides in the study area

Comparison of Acoustic to Optical Backscatter Continuous Measurements of Suspended Sediment Concentrations and Their Characterization in an Agriculturally Impacted River

“…There may also be variations of the particles size distribution for higher vs lower SSC. Moreover, the trend of SSC underestimation at smaller size distribution conditions by the acoustic method is often reported in the literature [7,8,17]. Ultimately, the results of this comparison reveal the potential of the acoustic backscatter technique for a non-intrusive monitoring of SSC within rivers with high sediment loads.…”

“…A cost-effective and reliable automated sampling or monitoring strategy for SSC is essential to develop sediment budgets in systems. Optical backscatter sensors (OBS), and more recently acoustic backscatter sensors, are indirect SSC monitoring techniques suitable for continual monitoring that is essential for a highly temporally variable such as SSC [7][8][9]. The technologies of both types of instrument have improved markedly recently and they have been successfully applied to quantifying the suspended sediment transports in many fluvial environments [10][11][12][13][14].…”

Suspended sediment flux at the Rhone River mouth (France) based on ADCP measurements during flood events

“…Efforts to quantify SSF from the SSC distributions measured over the entire vertical flow column and across an entire cross-section of channel have focused on the use of acoustic Doppler Current Profilers (ADCPs; Alvarez and Jones, 2002;Gartner, 2004 ;Kostaschuk et al, 2005;Tessier et al, 2008;Ghaffari et al, 2011;Duclos et al, 2013). ADCPs use the Doppler effect of sound scattered back from particles transported in suspension to measure flow velocity.…”

Quantification and Analysis of Suspended Sediments Concentration Using Mobile and Static Acoustic Doppler Current Profiler Instruments

“…Based on the empirical formula, 1 count of static ADCP Nortek 400 kHz is equivalent to 0.45 dB, and 1 count of SonTek 750 kHz is equivalent to 0.72 dB. In mobile ADCP RDI 307.2 kHz, 1 count is equivalent to 0.43 dB [12][13][14]. This variation of conversion process depends on the instrument frequency.…”