In an earlier investigation of the behaviour of tracer particles for determination of bed load transport in an alluvial stream (Thomsen 1980), specific records were taken of the particle velocities in the upper bed layer. These data aroused the interest for more detailed investigations.
The result of the measured surface particle velocities with radioactive tracers, performed in five locatities with different hydraulic conditions in natural alluvial rivers, has been used for determination of the relation UG/Uf'vs. √θ'/θ0.
The obtained results have been inserted in the parameters of Engelund and Fredsøe's sediment transport model (1976) and compared with experimental data (Guy et al. 1966).
Some reservations and methods for possible improvements of the sediment transport model are finally discussed.