How do tidal currents transport sediment near estuaries and inlets?

Tidal currents transport sediment primarily in areas where coastal geometry creates a constriction, such as at the mouths of estuaries or within inlets. In these locations, the volume of water forced through the opening during a flood or ebb-tide cycle—known as the tidal prism—can generate current speeds exceeding two metres per second, which are sufficient to move sediment like sand.1

The dynamics of this transport depend on the equilibrium between river discharge and tidal flow. In many open estuaries, there is a recognized net transport of sediment from the sea toward the land. Furthermore, in salt wedge estuaries, inorganic particles that flocculate upon encountering salt water sink to the bottom and are carried upstream by the landward flow of salt water at depth.23

In civil engineering, understanding these processes is critical for managing siltation and scour. Engineers often use hydraulic models to simulate tidal streams and velocities, allowing them to predict how modifications to a harbor or estuary profile will affect sediment movement over time.4