Suspended sediment transport along the Dutch coast near IJmuiden

Abstract

The Rotterdam harbour is to be extended into the North Sea. This changes the outflow of the river Rhine into the North Sea. Measurements with an ADCP were done during 5 months at 1 location in front of the Dutch coast near IJmuiden to investigate whether changes in outflow of the river Rhine could also change suspended sediment transport along the Dutch coast and into the Wadden Sea, which is the main goal of this thesis. Measurements of the hydrodynamics and suspended sediment concentration along the Dutch coast are used to determine the processes involved in suspended sediment transport along the Dutch coast. A conclusion on the effect of the change of the outflow of the Rhine can be given when these processes are known. There is a cross-shore circulation cell in front of the Dutch coast, when turbulence in the water column is small. This could be related to the fresh water input of the river Rhine and a resulting stratification of the water column. With large turbulence, the water column will be mixed and no stratification will be developed. Remarkable is one period when turbulence is large and the cross-shore circulation is observed. This could be related to a large input of fresh water into the North Sea. Suspended sediment transport direction is determined by the residual current direction, which is to a large extent determined by wind direction. The periods with large cross-shore circulation do not contribute to the transport of suspended sediment as turbulence is low during these periods and with low turbulence the concentration will also be low. This concludes that fresh water input by the river Rhine does influence the hydrodynamics along the Dutch coast, but it hardly influences the suspended sediment transport. A change in outflow of the river Rhine into the North Sea does not change the suspended sediment transport along the Dutch coast.