The trench in which a river flows except when it spills out during a flood.

A small river channel. When not in flood, the river flows well below the top of the banks. The ridges on either side of the banks are artificial levees designed to stop all but the worst of winter flooding.

Here you can see the river channel and also the floodplain to either side.

Most of the channel shaping takes place when the channels are full or in flood. This happens about once every two or three years. For the rest of the time little change occurs. Two types of channel are most common: deep, winding or meandering channels, that occur in places where the majority of the material carried is fine sediment such as silt and clay, and shallow, wide braided channels that occur where the material is mainly sand, gravel, or cobbles.