Study of the Evolution of Dredged Material Discharges by Means of Radioactive Tracers

Abstract

The choice of a dumping area for dredged materials must be carried out taking into account the general movement of sediments in order to evaluate the risk they represent for the zone itself, the harbourworks and the coastal area* The use of radioactive tracers allows to study, in situ, 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 due to currents and waves. In this way, parameters such as transport axis, mean velocity, dispersion, dilution and bed-load transport rates are determined- Four experiments which took place at OCTEVILLE, ANTIFER (FRANCE), SINGAPORE and ZEEBRUGGE (BELGIUM) during the ten past years illustrate the method.

Amélioration des connaissances sur les rejets par clapage de type vase

“…Plusieurs auteurs ont décrit le comportement de matériaux rejetés en eaux libres (mer, lac, estuaire) par clapage (Bokuniewicz et al, 1978 ;Brandsma et Divoky, 1976;Gûrdon, 1974 ;Kon et Chang, 1973 ;Krishnappan ,1975 ;Tavolaro, 1984 ;Bokuniewicz et Gûrdon, 1980 ;Truitt, 1986 ;Tala et al, 1987). Ils fondent leurs analyses sur l'observation de différentes opérations en nature.…”