Estimation du transport solide en suspension le long de l'Arc et de l'Isère (France) au cours d'une chasse de barrage

[Departement_IRSTEA]Eaux [TR1_IRSTEA]ARCEAUInternational audienceDam flushing events are conducted regularly on the Arc River (France) to remove sediments from the dam reservoirs. Four field campaigns carried out during dam flushing events in the upper Arc River basin (in June 2006, 2007, 2009 and 2010) in Northern French Alps are analyzed in this paper. All of these events have a similar discharge hydrograph. At twelve sampling sites along the river channel, measurements of suspended sediment concentration (SSC) were performed. A 1D numerical hydraulic model MASCARET (Goutal and Maurel, 2002) was calibrated and used to estimate the instantaneous discharge at any position along the river system. Thus, the data set was completed to estimate the suspended sediment flux at the twelve sites. To quantify errors, the classical error propagation method is used, taking into account both errors from measurement and modelling. A spectral analysis of the SCC signal at each sampling site gave a new approach to quantify SSC estimation errors that may occur during this type of event. After integration at each measurement site, a spatial distribution of the suspended load was obtained along the Arc and Isère rivers. This work enable us to identify specific locations of the river where deposition is accentuated or where the river bed is eroded. Thanks to these five flushing dam events, it appeared that the response of the river is not the same from one year to another