Abstract

In the Nete basin (Flanders, Belgium) chemical precipitates derived from groundwater-associated Fe²⁺ seeping into the overlying surface water significantly contribute to the concentration, fluxes and highly flocculated composition of the suspended sediment. To estimate the degree of contribution of these precipitates, they are modelled by MARS (Model for Authigenic River Sediment) 2.0, and consequently compared with total suspended sediment fluxes observed at Grobbendonk on the Kleine Nete (Belgium).

The total suspended sediment fluxes are determined by continuous concentration and discharge measurements on site in combination with estimations from a site-specific rating curve, generated from log-transformed data for suspended sediment concentration, discharge, baseflow, interflow, and run-off.

MARS 2.0 predicts average annual contributions of authigenic suspended sediment of 64%.

A decrease in discharge and sediment load is observed in 2003. However, in 2004 up to 2006 the transported load continues to decrease, in contrast to the higher annual discharges. The decrease in suspended sediment load is most likely due to consolidation and retention processes on the riverbed as the MARS-modelled sediment accumulation confirms.

Keywords: Suspended sediment transport, Authigenic, Flocculation, Mathematical model