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This study presents an intercomparison of a SWAN and SWASH wave model and 3D laboratory experiments for an existing navigation channel towards a harbor. Results show that the spectral refraction model SWAN underestimates the wave conditions in the channel and at the lee side of the channel especially -for longer waves travelling under a small angle with the channel -due to the neglect of the effects of wave tunneling by diffraction and evanescent modes. The phase-resolving non-hydrostatic 3D model SWASH does include these effects and performs reasonably well, though computational CPU demands are much higher. A modelling guideline is presented for application to other situations, showing that these effects need to be taken into account in optimizing the (layout) of the harbor; otherwise it may lead to under-or overestimation of the wave conditions and wave penetration into a harbor basin.

Predicting erosion of channel banks and tidal flats due to wind waves in tidal basins involves multiple parameters. These parameters represent the hydrodynamic load onto a bank as well as the stability of a bank against erosion. An efficient method to predict bank erosion in tidal basins is by calculating the sediment stability parameter based on the initiation of motion of sediment particles, because this parameter includes both the oscillatory bed stress and the sediment characteristics. The loading by wind waves on banks and tidal flats can be quantified by the bed shear stress. Wave breaking can be quantified by means of the intensity parameter of energy dissipation by wave breaking. Calculation of the sediment stability parameter gives insight in the locations where erosion or sedimentation may occur in the future.As a case study, the future reintroduction of the tide in Lake Grevelingen, in the Netherlands, is studied. The reintroduction of the tide may be combined with a tidal power plant in the Brouwersdam, between the North Sea and Lake Grevelingen. Reintroduction of the tide will change the wave load on intertidal areas in Lake Grevelingen. The effects of a tidal power plant in the Brouwersdam on erosion and the effectiveness of bank protection in Lake Grevelingen are analysed. The results of this morphological analysis are used as input for an environmental impact assessment. This case study shows that studying the initiation of motion is an efficient method to assess the local risks of (bank) erosion.

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