Hydromorphological restoration of Alpine rivers

More and more efforts are undertaken to restore rivers in a state close to their natural conditions in order to meet the Water Framework Directive requirement. This directive commits EU member states to achieve a good ecological status of all their water bodies. It became thus very important to develop river restoration such as fish passages, bank renaturation, natural bars or meanders. Another important component of river restoration schemes is the decommissioning of man-made structures. These interventions can have significant impact on the river hydrology, hydraulics and morphology, such as bed degradation or aggradation, bank failures. Predicting these impacts of restoration schemes on the river, especially for large scale projects, should rely on detailed numerical studies. To achieve this goal, we develop a methodology to analyse different scenarios of river restoration based on several criteria related to flow, sediment transport and environment. This method is applied to the case of a French alpine river in which five hydropower plants will be replaced by a unique underground hydropower plant on the same section of river.