A stream is a body of water that flows across the Earth’s surface and is contained within a narrow channel and banks.  Streams vary in size -- the smallest streams are sometimes called creeks or brooks; the largest streams are called rivers.  Stream order provides information about of the relative size and strength of a stream and provides a very good indication of the number and types of organisms present in a stream of a given size.

A stream is made up of the following features:

Overhead Canopy: Trees and branches overhang the stream and form the overhead canopy, providing food, shade and cover for organisms living in the stream below.

Riparian Zone: The riparian zone is the area immediately surrounding the stream.  Vegetation in this zone holds soil in place during rains and provides a home for insects.

Stream Bed: The composition of the stream bed influences the aquatic plant and animal life.

Large woody debris: When trees die and fall into the stream, they provide a base of large woody debris.

Water: Water may form deep, slow-moving pools or shallow riffles, where water moves quickly over rocks and other barriers. 

Stream Bank: Moving water can carve out the stream bank, moving material downstream as it flows.