Why do rivers meander?
Meanders are the sinuous bends in a river, possibly named after the River Menderes in south-west Turkey. It is thought that turbulent flow, rather than straight flow (also known as laminar flow) is a fundamental characteristic of the movement of fluids. Simulations with flumes (laboratory models of rivers) have shown that, above a critical minimum velocity, meanders will form. Friction with the channel bed and banks causes turbulence in the water flow, which promotes the development of alternating bars of sediment along the channel. A helical flow (corkscrew shaped flow) is established, with the water surface being elevated on the outer bank of each curve, and return currents at depth directing the flow towards the opposite bank. The outer bank is eroded as a result of the higher flow velocity, whereas deposition takes place on the inner bank, and forms a point bar.
