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Dynamique des matériaux en suspension le long de rivières aménagées de montagne. Exemple de l’Arc en Maurienne et de l’Isère

Abstract : (trad auto)One of the ways of managing siltation in the various hydroelectric structures of the Arc in the Maurienne is to carry out annual dam flushing. During these hydraulic hunts, the remobilized sediments from the bottom of the reservoirs are transported several dozen kilometres downstream of the structures to the Isère. The challenge is then to quantify the downstream spread of these suspended solids (SS), in order to understand the impact of dam flushing on the riverbed. In the first part, spatial maps of MES flows generated by the Arc dam chases between 2006 and 2012 are analysed, criticised and completed, and highlight the distribution of deposition and erosion zones. The uncertainty associated with the calculation of these mass balances is quantified, and the dynamics of recovery and deposition are discussed. This method was then applied to other natural flood and debris flow events, pre-sampled from continuous measurement logs. Finally, to better characterize the TSS transported during these hunting episodes, additional measurements of grain size and fall rate were carried out almost in situ during the 2011 and 2012 hunts. The spatial and temporal dynamics of these quantities make it possible to establish a strategy for setting up a digital model. The second part of this thesis work focuses on the 1D hydro-sedimentary numerical modeling. The MASCARET free surface hydraulic calculation code was used to model the flows generated by dam flushing between 2006 and 2012. This hydraulic modelling highlights the role played by the presence of alternating banks of different roughnesses in the riverbed. To take into account the modelling of the transport of TSS in compound beds, a method for estimating an average concentration per bed is proposed based on data from the literature. The new model, implemented in the solid transport module of MASCARET, COURLIS, is compared with the homogeneous model in the section on real cases of flooding (May 2010) and dam flushing (2010, 2011 and 2012). The modelling results show the ability of the new model to reproduce the measured flows in the calculated uncertainty ranges without the need for non-physical calibration of the parameters.
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Guillaume Antoine. Dynamique des matériaux en suspension le long de rivières aménagées de montagne. Exemple de l’Arc en Maurienne et de l’Isère. Sciences de l'environnement. Thèse, Sciences de la Terre, de l’Univers et de l’Environnement, Université Grenoble, 2013. Français. ⟨tel-02599300⟩

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