Abstract :
The Sankosh river in its lower course is found to have a tendency to meander over floodplains in order to
balance the transport of its water and sediment load. As a result, both the neck and chute cut-offs
develop and are considered to be the main mechanism of abandoned channel formation. The neck cut off
occurs due to the continuous deposition of sediments on the convex bank and sediments curved out of the
concave bend. As a result, the sinuosity of the meander increases, thereby forming a narrow neck. The
convoluted meander bend at the neck remains in the threshold level of instability unless naturally, the
neck disappears due to the crossing of the limit of threshold. Eventually, a straight channel is formed,
creating a cut-off. When the cut off is sealed from the main channel by sediment deposition, an ox-bow
lake is normally formed and left as an abandoned channel. On the other hand, chute cut-off occurs when
successive high flows develop a chute across the inner part of a point bar which starts to flow as straight
channel decreasing the sinuosity of the main river course on that part. Thus, the former sinuous course
becomes detached as an abandoned channel. Thus, channel sinuosity is reduced with increase in
velocity and gradient in flow and discharge through chute and neck leaving cut-offs that lead to the
development of abandoned channels.
Keyword :
Abandoned Channels Chute Cut off Neck Cut off Plug Bar