Definition of Terms

There is a lot of technical terms on the Rivers and Streams website. This page is designed to help navigate and define these words and phrases. Use the line below to skip to a certain letter.
substrate particles between 0.062 and 2 mm (0.00003-0.01 in) in diameter.
Fragmented inorganic and organic material that is suspended in, transported, and deposited by water or air.
Action of forming and depositing sediments.
Fine soil that is between 0.004 and 0.062 mm (0.00002-0.0003 in) in diameter.
Settling of fine suspended sediments in water where velocity is reduced.
Ratio of channel length between two points in a channel to the straight line distance between the same two points.
Elevation of a water surface above or below an established reference point.
Natural water course containing flowing water, at least part of the year, that supports living communities within the channel and riparian area.
Stream order:
Hierarchical ordering of streams based on the degree of branching. For example, a first-order stream is an un-forked stream. Two first-order streams flow together to form a second-order stream, etc.
Stream power:
Stream power is the amount of work performed by the stream flow per unit time, which can be expressed relative to a unit of stream bed area or length of channel. Power is traditionally expressed in watts, which ultimately can be expressed as ML2/T3 , where the dimensions include: M = mass, L = length, T = time.


  1. Stream power per unit area [? a (M /T3 -or- watts/L2)] can be defined as a product of the shear stress [t (M/LT2)] and average velocity [V (L/T)]. That is, ? a = t V.
  2. Stream power per unit length of channel [? l (ML / T3 -or- watts/m)] can be defined as a product of the water density[? (M/L3)], acceleration of gravity [g (L/T2)], discharge [Q (L3/T)], and water surface slope [S(L/L)]. That is, ? l = ? g Q S.
Suspended solids:
particles of unfiltered, undissovled solid matter such as soil that are present in water.