Sandbanks

Sandbanks are elongated accumulations of sand formed by the action of waves, tides, and currents along coastlines, river mouths, and estuaries. They appear as sandbars or shoals that may lie above the surface at low tide or remain submerged. They arise when sediment carried by longshore drift and tidal currents settles in zones of lower energy. Over time, wave action reworks the deposited material, causing the sandbank to migrate, grow, or disappear in response to storms, sea-level changes, and sediment supply. Some sandbanks connect to the shoreline as barrier beaches; others extend offshore as submerged features that influence water depth and navigation. In estuaries, sandbanks can alter flow patterns and create tidal habitats.

Sandbanks have ecological and practical significance. They can provide sheltered waters for small boats and reduce nearshore erosion in some areas, but they also pose navigation hazards and may require dredging or the construction of groynes and breakwaters. The habitats formed on and around sandbanks support diverse communities of birds, invertebrates, and juvenile fish, making them important for coastal ecosystems.

Notable examples include Sandbanks in Dorset, England, a peninsula extending into Poole Harbour known for its extensive sandy beach and high-value real estate. The term also broadly covers similar shoals and bars in other coastlines and in rivers and lakes.