What is the difference between a stream bed and a stream bank?

A stream bed is the bottom sediment layer of the stream channel which is constantly inundated with water. It is a saturated layer of sediment inhabitated by macroinvertibrates, algae, macrophytes, and microbes. The particle size of the stream bed material (fine clay vs large rock and boulders) is dependent on geologic region, size of the stream, and stream velocity. The stream bank is the adjacent sloping walls that confine the stream on either side. They are typically not wet except in times of high flows. Banks typically can grow more terrestrial vegetation such as reeds, grasses, and trees.