Suspended load is the portion of the sediment that is carried by a fluid flow which settle slowly enough such that it almost never touches the bed. It is maintained in suspension by the turbulence in the flowing water and consists of particles generally of the fine sand, silt and clay size.
The boundary between bed load and suspended load is not straightforward because whether a particle is in suspension or not depends on the flow velocity – it is easy to imagine a particle moving between bed load, part-suspension and full suspension in a fluid with variable flow. Suspended load generally consists of fine sand, silt and clay size particles although larger particles (more coarse sands) may be carried in the lower water column in more intense flows - further blurring the line between bed load and suspended load.
Suspended load is carried within the lower to middle part of the water column and moves at a large fraction of the mean flow velocity of the stream, with a Rouse number between 0.8 and 1.2.
USGS CMG InfoBank: Suspended and Dissolved Loads