How do tides influence the movement of sediment near a shoreline?

Tides influence the movement of sediment near a shoreline through two primary mechanisms: direct transport via currents and the indirect redistribution of wave energy.1

Direct Sediment Transport

Tidal currents can transport significant quantities of sediment, though this typically occurs only in constricted areas such as inlets, the mouths of estuaries, or barrier island complexes where water flow is forced to accelerate. In these locations, current speeds can exceed two metres per second, effectively moving sand and other materials. Conversely, on open coasts like beaches, tidal currents are generally too weak to transport sediment directly.1

Indirect Influence on Wave Energy

The rise and fall of the tide indirectly affects sediment transport by shifting the position of the shoreline. This movement dictates where waves and longshore currents interact with the coast. In areas with a high tidal range, this process can alter the active zone of sediment transport across a broad area, such as on a gently sloping tidal flat.1

Furthermore, tidal processes are a key factor in the morphology of deltas. In tide-dominated deltas, strong currents create characteristic funnel-shaped configurations with elongated sand bodies that fan out from the coast.2