Fluxes of fine sediment along the Dutch coast and the impact of Maasvlakte 2 : A system description

There is concern that land reclamation for the proposed Maasvlakte 2 development (refened to as MV2) will lead to changes in the transport of suspended particulate matter (sru) along the Dutch coast and into the Wadden Sea. This in turn could potentially affect the ecological conditions in the Wadden Sea. This report describes the existing knowledge of the transport of SPM in the southern North Sea in general, and in the Dutch coastal zone in particular. A qualitative description is proposed on the effects of an extension of MV2 on the SPM-fluxes and fate along the Dutch coastal zone (the 'hypotheses'). From the analysis it can be concluded that the major part of marine SPM sterns from the South, partly through erosion of the cliff coasts, partly from import from the Atlantic Ocean, and possibly partly from erosion of the Flemish Banks. However, no consensus exists on the latter source. Although it seems relatively small in comparison to the other sources, erosion of the Flemish Banks and hence sediment import to the Dutch coastal system, must be closely related to storm events in the southem North Sea, more directly than the other sources. The fresh water plume of the River Rhine in particular (the 'coastal river') plays an important role in the transport of SPM along the Dutch coast. Because of the interaction of earth rotation, tide, fresh-saline water-induced density gradients and bed friction, SPM is transported in a narrow band mainly in northem direction. Temporarily some southward transport may occur as well. Because ofbed friction, a near-bed net current towards the coast is generated on top ofthe net northern flow, which brings sediment to the coast. The accumulation of spu in this zone can be observed from in situ and satellite measurements. It is expected that MV2 will not affect the input of srna into the Dutch coastal system nor will it affect the total amount of fresh water delivered to the systern, the overall tidal motion, or the meteorology in the system. The effects of Mv2 are expected to occur at a relatively small scale, as the land reclamation itself is fairly small in comparison to the coastal system. In summary, the following impact of MV2 on the flux of SPM along the Dutch coast towards the Wadden Sea is expected: o A decrease in SPM close to the coast, compensated by larger SPM-concentrations further offshore, o An increase in temporal variations of sptvt because of buffering of SPM in the Haringvliet mouth and larger residence times of Haringvliet fresh water south of MV2.