Correlation Between Measured Sound Noise Ratio of an ADCP and Suspended Sediment Concentration

Acoustic Doppler Current Profiler (ADCP) Technology has been used in river applications to determine channel flow, bathymetric data and flow field velocity. Based on the Doppler effect an ADCP measures the echo using sound waves scattered back from particles within the water column to determine velocity profiles and flow field. Through an integration process overall channel flow is estimated. River dynamics in Colombia is characterized by significant load in suspended solids. In general characterization of suspended transport would require an extensive sampling protocol over channel depth and width that may be prohibitive in terms of resources and time. Furthermore, such evaluation requires significant laboratory work and analysis. This study strived to establish a correlation between measured SNR quality of an ADCP and actual suspended sediment rate of concentration. It was believed that given a valid implementation protocol ADCP sampling may provide a valuable estimation of total suspended sediment transport in a river. In doing so ADCP calibration would be completed using a limited number of field data samples, thus reducing suspended load sampling requirements. As part of an associated modelling study two field campaigns were completed on January and May 2018 along the Magdalena River in La Dorada, Caldas including topographical and bathymetric surveys using and Sontek River Surveyor ADCP over 5km of the river course. In addition, suspended and river bed samples were retrieved in order to characterize the channel roughness and total sediment transport. Collected SNR ADCP data and suspended sediment transport has been analyzed and correlated over both campaigns. Furthermore, limited laboratory te4stting has been completed to validate the proposed correlation relationship. Results indicate that although the SNR may provide a useful approximation tool it would require a minimum sampling data points to correctly predict suspended sediment transport. Nonetheless the proposed protocol may be sufficient as a preliminary tool and as a first estimation in field campaigns.