Variations in concentration of suspended matter in the Scheldt estuary

An overall picture of the concentration of suspended matter in the section of the Scheldt estuary between the Rupel mouth and the Ballastplaat is given. The evolution from hour to hour of the concentration of suspended matter during one tide is discussed with the help of 12 figures

Flocculation in the Scheldt Estuary: a case study of intertidal mudflats

The flocculation mechanism dominates the fate of suspended matter in the estuarine environment. As it modifies the texture of suspended matter, flocculation thus affects suspended matter's transport and deposition. In order to understand the complexity of the flocculation mechanism, a case study was performed on two intertidal mudflats in the Scheldt estuary, a freshwater and a brackish water one. A one-year biweekly survey investigated the seasonal variation of flocculation, physical properties of suspended matter, organic matter content and suspended matter deposition in the intertidal area. The flocculation study includes floc’s shape, sphericity and microfabric, which properties are believed to be significant in the suspended matter transport processes in the estuary. This study shows that floc size as well as floc sphericity positively correlates with the change of organic matter. Moreover, it reveals that with increasing organic matter floc expands in a three-dimensional way. It is observed that relatively dense, small and elongated flocs appear in winter and spring periods, while loose, large and spherical flocs occur in summer time. The study also reveals that suspended matter transported as dense and fine-to-medium sand-sized flocs have a greater effect on its short-term deposition than loose and medium-to-coarse sand-sized flocs. As the measured suspended matter deposition is much higher in winter-spring than in summer time, it is deducted here that highly concentrated and relatively dense flocs contribute to fast deposition during winter and spring periods resulting in a compact layer, while loosely formed flocs likely lead to an easier erodible layer in summer time. This study concludes that floc density is a more determining parameter in suspended matter’s transport processes than floc size

Clay fabric as an indicator of cyclic changes in an estuarine palaeo-environment: Lower Pleistocene, northern Campine Area, Belgium

SEM photographs of the Turnhout Member (Lower Pleistocene), reveal a vertical cyclicity of 2 main clay-fabric types: (a) face-to-face domains and (b) edge-to-face domains, each of them indicating the existence of respectively dispersed particles deposited in a salt-water environment, the transition being marked by intermediate clay-fabric types. It is suggested that the sequence corresponds to fluctuations in the position of the fluvial-marine equilibrium, related to important changes in river runoff of tidal amplitude. These observations indicate the utility of applying clay-fabric analyses to achieve a higher resolution in palaeo-environmental interpretations

Note concerning the origin of Scheldt estuary bottom sediments (Belgium, The Netherlands)

The analyses of gravels, shells and foraminifera of bottom sediments in the Scheldt estuary reveal a correlation between these sediments and the substratum. This is particularly so for the foraminifera assemblages. The results indicate on the one hand an erosion of Tertiary and Quaternary deposits and, on the other hand, a prevailing downstream sediment transport between the river Rupel and Antwerp and an up- as a downstream sediment transport as well in the river Western-Scheldt