During periods of high discharge, the entire stream channel may contain water with the islands covered to become submerged bars. During such high discharge, some of the islands could erode, but the sediment would be re-deposited as the discharge decreases, forming new islands or submerged bars. Islands may become resistant to erosion if they become inhabited by vegetation. Erosion by Streams Streams erode because they have the ability to pick up rock fragments and transport them to a new location. The size of the fragments that can be transported depends on the velocity of the stream and whether the flow is laminar or turbulent.
Turbulent flow can keep fragments in suspension longer than laminar flow.
Streams can also eroded by undercutting their banks resulting in mass-wasting processes like slumps or slides. When the undercut material falls into the stream, the fragments can be transported away by the stream. Streams can cut deeper into their channels if the region is uplifted. As they cut deeper into their channels the stream removes the material that once made up the channel bottom and sides. Stream Deposits Sudden decreases in velocity can result in deposition by streams.