Stream substrate is the material that rests at the bottom of a stream

Stream

A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...

. There are several classification guides. One is:

• Mud
  Mud
  Mud is a mixture of water and some combination of soil, silt, and clay. Ancient mud deposits harden over geological time to form sedimentary rock such as shale or mudstone . When geological deposits of mud are formed in estuaries the resultant layers are termed bay muds...
  
   – silt and clay.
• Sand
  Sand
  Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
  
   – Particles between 0.06 and 2 mm in diameter.
• Granule
  Granule (geology)
  A granule is a clast of rock with a particle size of 2 to 4 millimetres based on the Krumbein phi scale of sedimentology. Granules are generally considered to be larger than sand and smaller than pebbles . A rock made predominantly of granules is termed a conglomerate....
  
   – Between 2 and 4 mm in diameter.
• Pebble
  Pebble
  A pebble is a clast of rock with a particle size of 4 to 64 millimetres based on the Krumbein phi scale of sedimentology. Pebbles are generally considered to be larger than granules and smaller than cobbles . A rock made predominantly of pebbles is termed a conglomerate...
  
   – Between 4 – 64 mm in diameter.
• Cobble
  Cobble (geology)
  A cobble is a clast of rock with a particle size of to based on the Krumbein phi scale of sedimentology. Cobbles are generally considered to be larger than pebbles and smaller than boulders . A rock made predominantly of cobbles is termed a conglomerate....
  
   – between 6.4 and 25.6 cm in diameter
• Boulder
  Boulder
  In geology, a boulder is a rock with grain size of usually no less than 256 mm diameter. While a boulder may be small enough to move or roll manually, others are extremely massive....
  
   – more than 25.6 cm in diameter.

Stream substrate can affect the life found within the stream habitat. Muddy streams generally have more sediment in the water, reducing clarity. Clarity is one guide to stream health.

Marine substrate can be classified geologically as well. See Green et al., 1999 for a reference.

See also

• Substrate (biology)
  Substrate (biology)
  In biology a substrate is the surface a plant or animal lives upon and grows on. A substrate can include biotic or abiotic materials and animals. For example, encrusting algae that lives on a rock can be substrate for another animal that lives on top of the algae. See also substrate .-External...
  
  
• Particle size (grain size)
  Particle size (grain size)
  Particle size, also called grain size, refers to the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials. This is different from the crystallite size, which is the size of a single crystal inside the...