The Lauwerszee was closed in 1969 by a dam and it is nowadays a fresh water lake, Lauwersmeer. Before the closure it was a part of the Frisian Inlet basin, which is divided by the Engelsmanplaat into Zoutkamperlaag and Pinkegat (Fig. E.4). The closure caused a decrease of the basin area of the Frisian Inlet by about one third.
Figure E.5 shows the effects of the closure on the water level, flow velocity and sediment concentration at the centre of the Inlet Zoutkamperlaag as calculated by Wang et al. (1995) using a 2DH model. The closure caused a small increase of the tidal range. However, due to the decrease of the tidal basin area the tidal prism and thereby the magnitude of flow velocity decreased significantly. The tidal asymmetry changed such that it became more flood-dominant favouring sediment import.
Since the closure (1969) the tidal basin of Zoutkamperlaag has been accumulating sediment and the ebb-tidal delta has been eroding (Fig. E.6). The sedimentation in the basin and the erosion of the ebb-tidal delta are more or less in balance. As a consequence the closure has not caused erosion problem of the adjacent coasts, in contradiction to the closure of the Zuiderzee. Although in less extent the closure has also caused movements of tidal divides enlarging the tidal basin of Zoutkamperlaag.
An environmental problem induced by the closure is the erosion of the Engelsmanplaat, the large inter-tidal flat between the Pinkegat and the Zoutkamperlaag. This is due to the fact that the tidal flow in the Zoutkamperlaag channel, which is a building force for the flat, became weaker due to the closure. The eroding force for the flat, the wave action did not change due to the closure.