Sediment is the type of material found on the bottom of a river or stream. It ranges from very fine silt through large boulders (silt - sand - gravel - stones - boulders). You may have any combination of types of sediment, however it is usually determined by the speed of the water.

Sediment Type	What Does it Look Like?	Description
Silt		Very fine particles; feels "squishy"
Sand		Slightly larger particles; feels gritty
Gravel		Up to size of a U.S. quarter
Stones		Up to size of a baseball
Boulders		Anything larger than a stone