Effects Of Possible Land Reclamation Projects OnSiltation In The Rotterdam Harbour Area.A Model Study.

A three-dimensional numerical model system is used to study the effect of a possible large scale land reclamation on the motion of water and suspended sediment in the sea area around the Rhine outlet and in the inland channels and harbours of Rotterdam. The model is tide resolving and includes deposition and resuspension of cohesive sediment. The results of scenario model runs with different land reclamation designs showed, that the shape of the coast line has a major influence on siltation rates in harbours and shipping channels in the Rhine estuary. In one case siltation rates decreased dramatically as a result of a certain land reclamation. In another case, with an extension of the entrance channel to the West, siltation rates increased to more than the double. These differences are caused by changing residual flow patterns. In the first case the natural alongshore flow of sediment was diverted by residual currents in an off shore direction, leading to a decrease of suspended sediment concentrations in the river mouth. In the second case the near bottom flood currents in the river mouth were much stronger and brought more sediment to the inland areas.