Using multi-frequency acoustic attenuation to monitor grain size and concentration of suspended sediment in rivers

Utilisation de l'atténuation multi-fréquentielle pour suivre la granulométrie et la concentration des sédiments en suspension dans les rivières

Moore, S.A. ; Le Coz, J. ; Hurther, D. ; Paquier, A.

Type de document
Article de revue scientifique à comité de lecture
Langue
Anglais
Affiliation de l'auteur
IRSTEA LYON UR HHLY FRA ; IRSTEA LYON UR HHLY FRA ; LEGI GRENOBLE FRA ; IRSTEA LYON UR HHLY FRA
Année
2013
Résumé / Abstract
Multi-frequency acoustic backscatter profiles recorded with side-looking acoustic Doppler current profilers are used to monitor the concentration and size of sedimentary particles suspended in fluvial environments. Data at 300, 600, and 1200 kHz are presented from the Isere River in France where the dominant particles in suspension are silt and clay sizes. The contribution of suspended sediment to the through-water attenuation was determined for three high concentration (>100 mg/ L) events and compared to theoretical values for spherical particles having size distributions that were measured by laser diffraction in water samples. Agreement was good for the 300 kHz data, but it worsened with increasing frequency. A method for the determination of grain size using multi-frequency attenuation data is presented considering models for spherical and oblate spheroidal particles. When the resulting size estimates are used to convert sediment attenuation to concentration, the spheroidal model provides the best agreement with optical estimates of concentration, but the aspect ratio and grain size that provide the best fit differ between events. The acoustic estimates of size were one-third the values from laser grain sizing. This agreement is encouraging considering optical and acoustical instruments measure different parameters.
Source
Journal of the Acoustical Society of America, vol. 133, num. 4, p. 1959 - 1970

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