CONTROLLING SE IMENT ACCUMULATION BEHIND HE LOCKS OF ZANDVLIET AND BE EN RECH by Edward De Broe Head of the Dredging Department, Port Authority of Antwerp. 20, Siberiastreet, quay 63, B-2030 Antwerp (Belgium). E-mail:
[email protected] Fax: 03/205.24.37. Key words The lower Scheldt is that part of the Scheldt from the roadstead of Antwerp to the Dutch border. Sediment Antwerp, Scheldt, docks, sedimentation pattern, reaches the lower Scheldt from upstream as well as measurement campaign, siltation downstream. The silt tends preferably to settle in the access channels to the locks. Sedimentation-rates of 100 to 350 kg d.s./m2/month (d.s.: dry sediment) were Mots-clefs measured. The lower Scheldt can, in this respect, be regarded as a huge silt reservoir of unconsolidated silt. Anvers, Escaut, dock, modalites de sedimentation, The access channel to the Zandvliet and Berendrecht acquisition de donnees, envasement locks has a surface area of 60 ha and computations proved the quasi-permanent presence of an unconsol 1. DESCRI TION OF idated silt volume of about 2 million m3. THE SEDIMENT SUPPLY Past measurements to identify the sedimentation mechanism at work in the access channel to the locks MECHANISM FROM proved the existence of density flows of salt water laden with silt. The presence of this saline wedge is THE RIVER SCHELDT most emphatic at high tide. The density flows, which are driven by small differences of salinity, may be TO THE DOCKS reinforced by differences in suspension concentra tions and a difference in temperature. Presumably, the same mechanism is at work during lock opera tions due to the contact between imushing water of 1.1 Analysis of historical an average salinity which is always greater than the data one of the less brackish water in the docks.