INVESTIGADORES
LATOSINSKI Francisco Guillermo
congresos y reuniones científicas
Título:
Acoustic backscatter and suspended sediment calibration in a large river. Impact of bimodal grain size distribution and fine fraction concentration
Autor/es:
SZUPIANY RICARDO NICOLÁS; LÓPEZ WEIBEL CECILIA; LATOSINSKI FRANCISCO GUILLERMO; GUERRERO MASSIMO; AMSLER MARIO LUIS
Lugar:
Iquitos
Reunión:
Simposio; 9th River Coastal and Estuarine Morphodynamics; 2015
Institución organizadora:
CREAR (Center for researchand education of the Amazonian Rainforest)
Resumen:
Traditional methods currently usedto quantify sediment transport, especially in large rivers characterized bydepths and widths greater than 10 m and 300 m respectively, require that thevessel remains anchored for sediment sampling and flow velocity measurements.These methods entail long measurement times and laboratory processing ofsamples, with a consequent increase in associated costs. Moreover, thesetraditional techniques present low spatial-temporal resolution hinderinga better understanding of the associated variability. On the other hand, thetime consuming of sampling operations may be highly unsafe in a large river characterizedwith high flow velocities, depths and inland navigation. Due to these reasons, during thelast decade, a significant number of surrogate technologies has been proposed (basedon optical, laser and acoustic principles) aimed to meet operational as well asresearch objectives. Regarding acoustic technologies (especiallythe use of the acoustic Doppler current profile instruments, ADCP), they havebeen recognized as potential tools for the quantification of sediment transportin natural streams, that entails the analysis of the echo intensity level (EIL)of the return signal (backscatter) (Dienes, 1999; Thorne and Meral, 2008;Guerrero et al, 2011; Latosinski et al, 2014; among others). Moreover, the ADCPhas important advantages such us: it is not intrusive, it measures flowvelocity simultaneously to EIL and enables suspended sediment fieldinvestigation with high temporal and spatial resolutions.Despite the significant progressmade so far, further analyses are still required regarding the impact of particlesize distributions in a cross section of a river channel that typically combinessuspended sediment from the riverbed (i.e., sand) and washload (i.e., silt andclay). These fractions differently affect the backscatter and corresponding attenuation.Additionally, an accurate and detailed field sampling with high spatialresolution (i.e., point sampling along verticals) is necessary to further validatethe acoustic theory under natural condition.This contribution presents the relationshipsbetween the concentrations of suspended sediment from the riverbed (Css), washload (Cw) and EIL recorded from two ADCPs working at different frequenciesand with changing energy supply. For this purpose, sediment concentrations andgrain size distribution were sampled simultaneously with the two ADCPs in a largesecondary channel of the Parana River, the sixth largest lowland river in theworld