River Flow 2020 Estimation of the transverse mixing coefficients in shallow gravel-bedded rivers

L. Gond (1, 2, 3) , Emmanuel Mignot (2) , J. Le Coz (4) , L. Kateb (1)

1 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)
2 LMFA - Laboratoire de Mecanique des Fluides et d'Acoustique
3 Riverly - Riverly
4 INRAE - Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement

Transverse mixing coefficients are key parameters for predicting pollutant dispersion in rivers. While most studies deal with river reaches considered homogeneous, the literature review indi-cates that shallow, gravel-bedded rivers with a longitudinally-varied bed morphology are still poorly documented. The motivation of the present work is that the transverse mixing coeffi-cient in rivers with varied hydraulic parameters could be estimated with a succession of coeffi-cients of more homogeneous sub-reaches. This work applies a 1D-diffusion model to estimate these local transverse mixing coefficients from several local injections. Slug injections of Rho-damine WT are performed at various locations of the Durance River, France. Cross-profiles of tracer concentration at selected cross-sections delineating as homogeneous as possible sub-reaches are measured using fluorometers located near the bed. In addition, hydraulic data are derived from ADCP measurements. Best-fitting solutions of the 1D-diffusion model against the measurements suggest substantial variations of the transverse mixing coefficient between con-secutive sub-reaches.

Keywords: River; mixing

Domains: Physics [physics]; Nuclear Theory [nucl-th]; Physics [physics]; Nuclear Experiment [nucl-ex]

L. Gond, Emmanuel Mignot, J. Le Coz, L. Kateb. River Flow 2020 Estimation of the transverse mixing coefficients in shallow gravel-bedded rivers. RIVERFLOW 2020 - 10th Conference on Fluvial Hydraulics, IAHR (International Association for Hydro-Environment Engineering and Research), Jul 2020, DELFT, Netherlands. ⟨cea-02972575⟩