Look at this doc, it may be helpful for your topic. Good luck.

The velocity of suspended particles in a fluid flow (e.g. sediment particles) is first of all linked to the velocity of the fluid flow by the acting particle drag force. This depends on the relative velocity of the particle. That means, if the particle moves with the same velocity as the surrounding fluid, than the drag force is zero. Otherwise it is not zero and the drag force tries to equalize the velocity of both fluid and particles.

That gives the first answer: the particle velocity is !_not_! independent from the fluid velocity, it is rather very closely linked.

In a typical sediment particle flow, the particles will be most of the time slower than the water velocity due to losses of particle momentum by particle friction and collisions with the river bed. But under certain circumstances, e.g. if a fast sediment particle enters a water recirculation zone with small or adverse fluid velocity, situations are thinkable, where the particle might be faster than the fluid velocity.

If you are referring to the sedimentation velocity of suspended particles, it will be closely related to the particle size.

But if you are referring to the streamwise velocity of the suspended particles, it will most likely lag that of the fluid. Unless your flow is highly turbulent, then as Dr. Frank said, it is possible for the particle to momentarily lead the fluid.

In the river - water and solid and denser particles - system it is most likely that in average the particle velocity will be lower than that of water. Instantaneously one can find also faster than water particles in the streamwise direction, for short periods of time. The vertical velocity is much higher in gravity direction when particles are suspended and settle. Upward velocity is likely to be smaller than the water. Does it answer your question?

The answer is simply - it depends. You first need to quantify the physiochemical properties of the "particles" as well as the water body in question, the concentration of the particles as well as characteristics of the flow field. Not an easy task!

I would suggest beginning by establishing:

1) The research objective / hypothesis.

2) The physical properties of the particles.

3) The length and time scales relevant to your specific research question.

In short - be more specific. Vague terms such as "suspended particles" and "water-current" cover a vast realm of geophysical flows.

Well,

The relation can be detected from the attached figure.

Sincerely