The motion state of a particle is a crucial aspect in sediment transport
problems. In this paper, we conceptualized three states: stillness,
‘transport’ and ‘non-transport’. Starting from a data set of bed-load
particle tracks obtained from Particle-Tracking-Velocimetry, we removed
the bias from experimental uncertainty and applied one-dimensional,
instantaneous and non-parametric criteria for distinguishing the
different states. We present the distributions of particle velocity for
all the moving states and separating the transport and non-transport
states, fitting a literature model to them. The transport state is
related to isotropic particle vibrations and does not significantly
contribute to the bed-load rate. Vice-versa, the choice of accounting or
not accounting for the non-transport state has major quantitative impact
on the mean number of moving particles and mean particle velocity.
Finally, the non-transport state has non-negligible contribution to the
total kinetic energy of the bed-load particles.