# Hjulström curve

Hjulström curve describes the relationships between erosion, transportation, and deposition of sediments. Based on this logarithmic plot, it is possible to determine whether a river will erode, transport, or deposit the sediment depending on the particle size and water velocity.
The upper curve depicts the critical erosion velocity as a function of particle size, which decreases with decreasing particle size down to around 0.1mm. For particles below that size, the critical erosion velocity increases with decreasing grain size in cohesive sediments. The lower curve shows the deposition (settling) velocity as a function of particle size. The critical velocity for deposition, depends on the settling velocity of particles, which decreases with smaller grain sizes.

## Used for

Resuspension Sedimentation

## Procedure

 $$u_{cr} = 2.8 \left( \sqrt{\rho' gd} + 5.25 \frac{v}{d} \right) c$$                               $$v_p = \frac{2}{9} \frac{\rho_r \rho_f}{\mu} gR^2$$ https://www.malvern.com/en/products/technology/dynamic-light-scattering   ISO22412 (2017) Particle size analysis - Dynamic Light Scattering (DLS)

## Contact

Frank von der Kammer

University of Vienna, Austria