Suspended-sand budgets estimation are important for hydrologists and river managers. It is required for river restoration and monitoring, river engineering, flood risk evaluation. Suspended-sand budgets are still difficult to establish, due to large uncertainty and scarce data, which does not allow appropriate diagnosis and decision making. Two main modes of sand transport are currently described : bedload and graded suspended load. The moving sand load depends both on the transport capacity of the river reach and on the supply of sand from upstream, river-bed and banks. The main motivation of this thesis is to quantify and reduce suspended-sand fluxes uncertainty in large rivers with a physically based approach. This work looks at the main uncertainty sources in suspended-sand flux data, related to sampling representativeness, sample analysis, and computation in the cross-section. One highlighted concern is that without a sand suitable analysis protocol, the amount of sand can be underestimated. A field measurement protocol and a surrogate method for suspended-sand flux computation in the cross-section are proposed. The method combines point sampling measurements and ADCP (Acoustic Doppler Current Profiler) data. This approach is applied on four large rivers in various morphological and flow conditions : the Colorado, Rhône, Mekong, and Amazon Rivers. Various sand rating curves approaches (physically based or empirical) are studied. The results of suspended sand flux measurements combined with suspended sand rating curve models allow, by a Bayesian approach, to determine continuous suspended-sand load, budgets and their associated uncertainties

Publication

• Dramais, G., Camenen, B., & Le Coz, J. (2018). Comparaison de méthodes pour la mesure des matières en suspension dans les cours d'eau, en présence de sable. La Houille Blanche, (5-6), 96-105.

Communications, Posters, Proceedings

• Dramais, G., Camenen, B., & Le Coz, J. (2017, November) Comparaison de méthodes pour l’analyse des matières en suspension dans les cours d'eau, en présence de sable. Colloque TSMR 2017 Abstracts.
• Dramais, G., Camenen, B., Le Coz, J., Thollet, F., Le Bescond, C., Lagouy, M., & Lacroix, F. (2018, September). Comparison of standardized methods for suspended solid concentration measurements in river samples. In River Flow 2018: 9th International Conference on Fluvial Hydraulics (pp. 8-p).
• Dramais, G., Camenen, B., Le Coz, J., Pierrefeu, G., Peteuil, C., & Fretaud, T. (2018, December). Observation and modeling of sand fluxes in the Rhône River during a flood. In AGU Fall Meeting Abstracts.
• Dramais, G., Camenen, B., Le Coz, Topping, D. Peteuil, C., Pierrefeu, G. (2019, June) A physically based method of combining ADCP velocity data with point samples to compute suspended-sand discharge – Application to the Rhône River, France. SEDHYD proceedings (pp. 13-p)

Cite the thesis

Guillaume Dramais. Observation et modélisation des flux de sable dans les grands cours d’eau. Mécanique des fluides [physics.class-ph]. Université de Lyon, 2020. Français. ⟨NNT : 2020LYSE1230⟩. ⟨tel-03188258⟩

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