The Rance estuary in France has a big tidal range, and a huge tidal power station was built there in the 1960s. A study looked at how the power station affects the tides in the estuary. They used a computer model to see what would happen without the power station. The results showed that the power station makes the tides smaller and slower in some parts of the estuary. It also changes the direction of the water flow in certain areas. Overall, the estuary has more water coming in than going out, and the tides last longer when they go out than when they come in. This study helps us understand how the power station affects the water flow in the estuary and what it might mean for the sediment in the area.