Tidal Patterns and Sediment Dynamics in a Hypertidal Estuary Influenced by a Tidal Power Station

The Rance estuary is a relatively small low-inflow steep-sided ria, located in the Brittany coast of northern France, with a maximum spring tidal range of 13.5 m at the mouth. Taking advantage of this hypertidal regime, the first and largest operational tidal power station in the world was built at the estuary mouth and is in operation since the 1960s. Despite a well-known effect of the plant on the damping of estuarine water levels, little attention has been given to the propagation of the tidal wave along the estuary. Moreover, net siltation has been reported by several observations, but there is no specific knowledge on the role of the plant on sedimentation. In this study, tidal wave patterns and sediment dynamics are analyzed in this particular manengineered system. A numerical model, based on a two-dimensional depth-averaged approach is implemented to predict the tide propagation and tidal currents along the estuary. Numerical results are analyzed and discussed to highlight the role of the plant on the transformation of the tidal wave in the estuary and its possible consequences on sediment dynamics and morphological evolution.