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

Abstract

Acoustic Doppler Current Profilers (ADCP) are increasingly used for velocity and discharge measurements in riverine environment capitalizing on operation efficiency and rugged configuration. Part I of the paper investigated the potential of the moving-boat ADCP measurements to appropriately describe mean velocity field in river cross sections. It was concluded that the ADCP data collected during transects for estimation of discharges is not readily usable for estimation of the mean velocity distribution over the depth. Given the increased demand of the latter data for studies such as sediment transport, ecohabitat restoration, and for supporting numerical simulations, measurements with ADCP at fixed locations are evaluated from the same perspective. The paper reviews first general instrument requirements to accurately measure mean and time-resolved characteristics of turbulent river flows and subsequently formulates practical guidelines for conducting measurements of this kind. Next, the paper analyzes a set of ADCP data collected at fixed river locations using long sampling times. The effect of sampling time length on the accuracy of the mean velocities and turbulence intensities profiles is investigated using several statistical criteria. Time-resolved turbulence characteristics, such as autocorrelation and power spectrum, are also analyzed to verify ADCP capabilities to capture finer details of the turbulence in riverine environment. Additionally, the paper reviews the potential of ADCP fixed-location measurements to measure depth and to quantify near-bed layer velocities.