Flow structure and suspended sediment transport variations of sand along nodes of different morphologies in a large braided river

SZUPIANY, RICARDO; AMSLER, MARIO; PARSONS, DANIEL; BEST, JAMES

Santa Fe, Argentina

Workshop; Workshop on Morphodynamic Processes in Large Lowland Rivers; 2007

Facultad de Ingeniería y Ciencias Hídricas (UNL) - National Center of Earth-Surface Dynamics (Universidad de Minnesota/USA) - Universidad de Illinois (USA)

ABSTRACT. The results of measurements of flow structure and suspended sand performed along four nodes of the main channel of the Paraná River in its middle reach, are presented herein. The records were obtained at several cross sections arranged at each node using an acoustic Doppler profiler (ADP), with the moving-vessel mode following a proper methodology designed to that end. The backscatter signals of the ADP were transformed into sand concentrations by means of a relationship fitted by the first two authors enabling the suspended sand concentration field at each cross section to be known. Morphologically, one of the field sites has a nodes pattern displaying a confluence-diffluence unit. The other three are typical bar-confluence nodes with different junction angles and widths. Based on the results complemented with studies of the flow structure at the same sites reported elsewhere, it is hypothesized that the bar-confluence geometry at large rivers would not have such a significant influence on the flow structure as to perturb the continuity of the suspended sand transport along this type of nodes. But the variations of the channel widths, depths and bed slopes at a confluence-diffluence unit, may be of such a magnitude as to modify markedly the equilibrium of flow-suspended sand transport altering the suspended/bed load material ratio. The results of measurements of flow structure and suspended sand performed along four nodes of the main channel of the Paraná River in its middle reach, are presented herein. The records were obtained at several cross sections arranged at each node using an acoustic Doppler profiler (ADP), with the moving-vessel mode following a proper methodology designed to that end. The backscatter signals of the ADP were transformed into sand concentrations by means of a relationship fitted by the first two authors enabling the suspended sand concentration field at each cross section to be known. Morphologically, one of the field sites has a nodes pattern displaying a confluence-diffluence unit. The other three are typical bar-confluence nodes with different junction angles and widths. Based on the results complemented with studies of the flow structure at the same sites reported elsewhere, it is hypothesized that the bar-confluence geometry at large rivers would not have such a significant influence on the flow structure as to perturb the continuity of the suspended sand transport along this type of nodes. But the variations of the channel widths, depths and bed slopes at a confluence-diffluence unit, may be of such a magnitude as to modify markedly the equilibrium of flow-suspended sand transport altering the suspended/bed load material ratio. The results of measurements of flow structure and suspended sand performed along four nodes of the main channel of the Paraná River in its middle reach, are presented herein. The records were obtained at several cross sections arranged at each node using an acoustic Doppler profiler (ADP), with the moving-vessel mode following a proper methodology designed to that end. The backscatter signals of the ADP were transformed into sand concentrations by means of a relationship fitted by the first two authors enabling the suspended sand concentration field at each cross section to be known. Morphologically, one of the field sites has a nodes pattern displaying a confluence-diffluence unit. The other three are typical bar-confluence nodes with different junction angles and widths. Based on the results complemented with studies of the flow structure at the same sites reported elsewhere, it is hypothesized that the bar-confluence geometry at large rivers would not have such a significant influence on the flow structure as to perturb the continuity of the suspended sand transport along this type of nodes. But the variations of the channel widths, depths and bed slopes at a confluence-diffluence unit, may be of such a magnitude as to modify markedly the equilibrium of flow-suspended sand transport altering the suspended/bed load material ratio.