Sedimentation control behind a multipurpose tidal hydropower dam on the Rance river estuary The World Association for Waterborne Transport Infrastructure Presentation by Mr Geoffroy CAUDE Permanent member of the French High Council for Environment and Sustainable Development 1

Summary of the presentation 1- The river Rance tidal hydropower dam and the way it has been operated 2- Analysis of the sedimentation process 3- Recommendations produced by the mission to the stakeholders

The hydraulic optimization of the tidal dam

The increasing sedimentation process in the estuary

The Rance estuary ‘s sedimentation between 1889, 1956 and 1982

The type of deposited sediments along the Rance estuary ( from C The type of deposited sediments along the Rance estuary ( from C. Bonnot-Courtois-1982)

The existing water levels behind the dam before 1966 and after

The CEREMA study’s main conclusions impossibility to produce a global sediment balance in the estuary since the building of the dam impossibility to simulate through a numerical model the effects of the dam upon the sedimentation process the essentially marine origine nature of the deposited sediments themselves - the sedimentation creates obstacles to the development of some navigation activities

The ongoing sedimentation management process in the Rance estuary 1- Flushing at Le Chatelier dam 2- Dredging operations 3- Other hydraulic operations 4- Other possible techniques

Flushing operations between 1996 and 2015

Recommendations produced by the mission to the stakeholders A full sedimentation management programm with three combined components : a short term mud pit operation called Lyvet 3 a 5 years experimental program of sediment management including alternative techniques - a R and D associated program to improve numerical modelling with stable bathymetry measures in order to progress in the scientifical understanding of the sedimentation process, which would require a scientific committee with international experts

Territory project under discussion

See you at our next PIANC World Congress 34rd PIANC WORLD CONGRESS Panama in May 2018 See you at our next PIANC-SMART Rivers Conference PIANC-SMART Rivers Conference Lyon, France in September 2019 See you at the next PIANC-COPEDEC Conference PIANC-COPEDEC X Tehran, Iran in 2020

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