sandbars

A sandbar is a depositional landform created by the accumulation of sand-sized sediment transported by waves, currents, and wind. Sandbars may lie underwater or rise above the water surface and are widespread along coastlines, in rivers, and around lakes.

Coastal sandbars typically form from longshore drift and wave action, creating offshore bars, spits, or barrier bars. They can shield lagoons, alter tidal flows, and migrate over time with storms and seasonal wave regimes. Their position relative to sea level determines whether they are emergent (above water) or submergent.

In rivers and lakes, sandbars form in braided or still-water zones where sediment settles out of slower-moving water. River bars can shift with discharge and flood events; they often create safe shallows and channel splits.

Ecology: sandbars provide habitat for birds, invertebrates, and vegetation; but can also be dynamic hazards to navigation and boating; they trap sediments and influence shoreline morphology.

Human interactions: dredging, beach nourishment to replace eroded bars, harbor modifications; management must balance ecological values with navigation safety and tourism.

Climate change impacts: rising sea level and increased storm intensity can reshape sandbars, causing erosion or new formations; their dynamics reflect sediment supply and hydrodynamic conditions.