Stream
substrate (
sediment) is the material that rests at the bottom of a
stream. There are several classification guides. One is:
- Mud – silt and clay.
- Sand – Particles between 0.06 and 2 mm in diameter.
- Granule – Between 2 and 4 mm in diameter.
- Pebble – Between 4 – 64 mm in diameter.
- Cobble – between 6.4 and 25.6 cm in diameter
- Boulder – more than 25.6 cm in diameter.