Hjulström curve

[2] The upper curve shows the critical erosion velocity in cm/s as a function of particle size in mm, while the lower curve shows the deposition velocity as a function of particle size.

The plot shows several key concepts about the relationships between erosion, transportation, and deposition.

The Hjulström curve shows that sand particles of a size around 0.1 mm require the lowest stream velocity to erode.

He significantly improved the level of detail in the cohesive part of the diagram, and added lines for different modes of transportation.

This curve dates back to early 20th century research on river geomorphology and has no more than a historical value nowadays, although its simplicity is still attractive.