Averaged indicators of secondary flow in repeated acoustic Doppler current profiler crossings of bends

摘要: [1] Cross-stream velocity was measured in a large river bend at high spatial resolution over three separate survey episodes. A suite of methods for resolving cross-stream distributions tested on data collected using acoustic Doppler current profilers (ADCP) the sand-bedded Sacramento River, California. The surveyed with repeated ADCP crossings eight cross sections during rising limb discharge February 2004 and twice recession March 2004. By translating interpolating to planar grids, ensembles similar positions along irregular boat paths could be averaged. averaging minimized turbulent fluctuations streamwise velocities 1 m/s, enabling weaker (~15-30 cm/s). Secondary-flow influence suspended sediment inferred from lateral region backscatter intensity aligned outward flow point bar. near-bed decrease across pool corresponded inward flow. These suspension indicators were used orient averaged grids unambiguously defining magnitudes. Additional field investigations test whether correlation between patterns results helical recirculation inside bend. measurements, consistent classic recent laboratory studies, show that surveys can provide refined views secondary movement rivers.