Image-based migration velocity and dune length in clear water rivers.

This work presents a novel way of measuring image-based migration velocity and dune length in clear water rivers. These results, together with empirical formulations, can be used to estimate bedload sediment transport with a high-spatial resolution. Image processing relies on the non-intrusive image-based technique called Space-Time Image Velocimetry (STIV). STIV consists in visualizing pixel intensity variation in time over a defined line. This technique was originally applied to hydraulics in order to characterize streamwise surface velocities in rivers. In this case, STIV is used to measure dune migration velocity and length in a shallow river with clear water in Córdoba Province, Argentina. Image processing procedures are detailed, including pre-processing and rectification. Results are then compared with measurements obtained from Acoustic Doppler Current Profilers. Finally, as an appendix, using the measured data and empirical equations, an estimation of bedload sediment transport is performed using both techniques. • STIV technique allows for an estimation of the mean streamwise migration velocity of sand dunes in clear water flow conditions. • The use of image processing provides accurate estimates of average dune length. • Results obtained from images are compared with results from ADCP. • Bed load sediment transport can be quantified from Space/Time Images and an empirical approach. [ABSTRACT FROM AUTHOR]