Since the extension of the harbour of Zeebrugge (finalised in 1986) a lot of bathymetrical data are available. With these data the evolution around Zeebrugge (including the Western part, area around the harbour breakwaters, Baai van Heist, the beaches of Knokke and the Appelzak gully) can be reconstructed. But also before this extension some data are available, such that the difference pre and post extension can be compared.

Other data and literature are also described, including numerical modelling of currents and morphology, detailed hydrodynamic and sediment transport measuring campaigns and analysis of the sediment composition.

In front of Knokke-Heist the beaches are eroding due to the presence of the Appelzak-gully. The Appelzak shows a long term landward movement. However the movement and development of the gully seems to slow down during the last 10 years. Although confirmation is needed (both based on further trend analysis and numerical modelling), this might suggest that big scale measures to reduce erosion, might be less effective Possibilities for the slow down are the more equilibrium state of the system after the extension of the harbour of Zeebrugge and the influence of the large nourishments in the last decade .