It takes longer for the water to travel the same linear distance, and thus the average velocity is lower . When the discharge becomes too high, the stream widens its channel by overtopping its banks and flooding the low-lying areas surrounding the stream. The areas that become flooded are called floodplains . Channel Patterns spectrum of three types Straight Channels Rare, and usually controlled by a linear zone of weakness in the underlying rock, like a fault or joint system. Even in straight channel segments water flows in a sinuous fashion, with the deepest part of the channel varying in position from near one bank to near the other.
Velocity is highest in the zone overlying the deepest part of the stream.
In these areas, sediment is transported readily resulting in pools. Where the velocity of the stream is low, sediment is deposited to form bars . The bank closest to the zone of highest velocity is usually eroded and results in a cutbank . The natural velocity structure of a running water on Earth's surface is a meandering one, especially in streams flowing over low gradients with easily eroded banks - straight channels will eventually erode into meandering channels. Erosion takes place on the outer parts of meander bends where stream velocity is highest.