The Upper Rhine River has undergone several anthropogenic modifications since the last two centuries for flood protection, navigation and hydropower generation. Channel rectification, groyne fields and lateral "Grand Canal of Alsace" construction heavily altered the hydro-sedimentary functioning of the 50 km-long "Old Rhine" by-passed between Kembs and Breisach: channel pattern simplification, bed incision, armouring and ecological habitats alterations. Two complementary projects have been initiated to restore the sediment transport and the reach alluvial dynamics. This thesis investigated space-time and experimental geomorphic approaches within the morpho-ecological restoration of a modified fluvial system. The archive and field data-based work aimed at understanding the Old Rhine historical trajectory. The geomorphological monitoring of a gravel input experiment also consisted in evaluating environmental benefits and potential risks for society and proposing physical assessment indicators. Results will help river stakeholders to define strategies to restore morphological processes and associated ecological functions in the Old Rhine.
