Practical aspects of ADCP data use for quantification of mean river flow characteristics; Part 1: moving-vessel measurements

Acoustic Doppler Current Profiler (ADCP) measurements have gained considerable popularity because of their capabilities to efficiently measure discharges from boats moving across river transects. The accuracy of the estimated discharges is relatively good compared with the existing measurement alternatives. Currently, there is an increased demand for measurement of the mean velocity field in rivers for applications where mean and turbulence quantities play important roles. Given the good estimates for discharges, it can be inferred that velocity profiles collected during transects can be potentially used for characterization of the average mean velocity field. Instrument and operational limitations, as well as environmental factors result in large scattering of the instantaneous velocity profiles collected from moving boats during transects, making it difficult to readily use the collected data for reporting mean velocities and turbulence parameters across the depth or in cross-sections. The paper presents several methods for enhancing the significance of the ADCP velocity distribution profiles collected from moving boats and proposes complementary software to further process and visualize the ADCP data for better support of hydraulic investigation requirements. The paper analyzes first the assumptions and error sources involved in the measurement process. The appearance of the velocity profiles collected with ADCP operated from moving vessels and post-processing algorithms for data conditioning and smoothing are tested and evaluated next. The relevance of data collected from moving vessels along transects for description of the mean velocity profiles is inferred by comparison with data obtained with the same ADCP system and settings, collected from fixed locations along the transect route. Velocities enhanced using the optimum tested post-processing algorithms are used to further determine depth-averaged velocities, velocity components in river coordinates, and river discharge estimates. (C) 2003 Elsevier Ltd. All rights reserved.