The dataset variables are:
Um - maximum orbital velocity at the bottom
Us006 - is the Shields parameter (non-dimensionalized bottom stress) for grain size diameter 0.06 mm
Us025 - Shields parameter for grain size diameter 0.25 mm
Us050 - Shields parameter for grain size diameter 0.50 mm
Us100 - Shields parameter for grain size diameter 1.00 mm
Us200 - Shields parameter for grain size diameter 2.00 mm

The Shields parameter used is presented in Eq 6 in Jnsson, A  (2006) A model study of suspended sand due to surface waves during a storm in the Baltic Proper, Journal of Marine Systems, 6391-104.