Flow Field and Morphology Mapping Using ADCP and Multibeam Techniques: Survey in the Po River

摘要

An 8-km-long and 250-m-wide reach of the Po River (Italy) was surveyed with two vessels, aiming to investigate the channel morphology and flow field characterizing this major Italian river and to provide data for the calibration of a numerical model. The first vessel was equipped with a multibeam ecosounder (MBES), whereas an acoustic doppler current profiler (ADCP) was located on the second one. Fixed-vessel ADCP measurements were used to preliminarily investigate the turbulence variability affecting the reliability of moving-vessel measurements. To evaluate the friction velocity by using moving-vessel measurements, the vertical variance of velocity profiles as an alternative to logarithmic fitting of ADCP profiles was estimated. An average of 30-m cells of depth-averaged velocity, friction velocity, and surface-bottom velocity angle are presented in maps as the most relevant flow field features. The flow field and channel morphology at bed-form or channel scales showed noticeable correlations (0.9). In particular, a correlation between the friction velocity and small-scale bed forms (4-5 m mean wavelength) was observed.