Study of the evolution of dredged material discharges by means of radioactive tracers

The choice of a dumping area for dredged materials must take into account the general movement of sediments in order to evaluate the risk they represent for the zone itself, harbour works and the coastal area. The use of radioactive tracers allows the study in situ, of transfer properties under tidal currents of fine sediments resuspended during the release, the distribution over the sea bed of coarse particles and their future evolution as affected by currents and waves. In this way, parameters such as transport axis, mean velocity, dispersion, dilution and bed-load transport rates can be determined. Four experiments which took place at Octeville, Antifer (France), Singapore and Zeebrugge (Belgium) during the past ten years illustrate the method. (author). 6 refs, 14 figs, 1 tab