How do tidal streams affect sediments on the English Channel seabed?

Tidal streams play a primary role in shaping the distribution of superficial deposits on the English Channel seabed, where such deposits are generally very thin or absent due to the area having remained beyond the reach of Pleistocene glaciers.1

The influence of these streams on sediment is determined by their velocity:

• Strong tidal streams: In areas where currents are powerful, the seabed is typically swept bare, leaving behind only pebbles.1
• Decreasing velocities: As current speeds diminish, the energy is insufficient to keep all material in suspension, leading to the formation of sand and gravel ribbons and waves, the latter of which can reach thicknesses of up to 40 feet.1
• Sheltered areas: In regions with minimal current activity, such as the Gulf of Saint-Malo, the environment allows for the accumulation of thick beds of fine-grained deposits.1

Overall, the current distribution of these sediments represents a complex, ongoing reworking of materials from various geological ages.1