Describe the Hjulström curve.

The critical erosion velocity line shows the minimum velocity needed to transport and erode a particle. Common sense tells us that the larger the particle, the more energy it needs to pick it up and be eroded, however there is one exception to this rule. Clay particles are microscopic, flat platelets that tend to stick to each other, and thus they need a relatively high velocity to pick them up and erode them. The mean settling velocity or critical deposition velocity line shows the velocity at which a sediment particle drops to the riverbed. In between these two lines show the velocities of where sediment will be transported, thus the lines split the graph into three sections-erosion, transportation and deposition.