meanders

Meanders are broad, looping bends in a river or stream, forming a sinuous, winding path through flat or gently sloping terrain. They develop as water erodes the outside of bends where velocity is greatest while depositing sediment on the inside of bends, creating a characteristic procession of curves over time.

The process begins with slight irregularities in the channel bed or floodplain. As flow accelerates along the outer bend, erosion enlarges the curve; in the inner bend, slower flow promotes sediment deposition, forming a point bar. This lateral migration causes the river to shift gradually from one side of the valley to the other, increasing sinuosity—the ratio of the channel length to the valley length. Meanders can migrate, amplify, and rearrange as climate, flow, and sediment supply change.

Common features associated with meanders include oxbow lakes, which form when a meander neck is breached and the river cuts off the loop, leaving a crescent-shaped lake, and meander scars or abandoned bends on floodplains. Rivers with low gradients and abundant sediment are particularly prone to meandering, producing wide, expansive bends in mature stages of development.

Meanders influence hydrology and ecology by altering flow paths, throttling discharge through bends, and creating diverse habitats along the floodplain. Human activities such as river straightening, dam construction, and cutoffs can reduce natural meandering, affecting flood dynamics, sediment transport, and riparian ecosystems. In geology, preserved meanders can indicate ancient river systems and paleogeography.