Saltmarsh vegetation affects tidal movements in estuaries. A study in Wales used a computer model to see how marsh plants impact tides and currents in three different estuaries. The results show that marsh vegetation reduces the strength of tides in the estuaries, especially in the middle and upper parts. This can change how sediment moves in the estuary. Understanding these effects can help in deciding how to manage and protect saltmarshes for environmental and economic reasons, as well as for flood and erosion control.