The characteristics of the physical coastal system determine the sustainable development of the coastal zone. One important characteristic is the wave climate. The sediment transport of both sandy and muddy particles is very much influenced by the wave climate. Therefore a sustainable coastal morphology has to be in equilibrium with the wave climate. The coastal morphology and the sedimentology are a basis for the ecosystem in the nearshore zone. Thus, indirectly the wave climate has important consequences for the biology in the coastal zone. Several human activities in the coastal zone depend on the wave climate as well. Evidently, to produce “green” electricity from the hydraulic energy in the sea waves can only be a success if the wave climate is known (to estimate possible profits). Likewise for sporters that want to surf the waves. Waves can also be a nuisance for human activities such as shipping and handling goods in coastal harbours, for contractors carrying out coastal engineering works or workability off-shore. To determine the wave climate in a coastal zone it is recommended to combine in situ measurements and wave modelling. Indeed, on the one hand to cover an area is only possible with a wave model, and on the other hand in situ measurements are needed to validate and drive a wave model. This paper presents a way to determine a wave climate, for the case of the Belgian coastal zone. The in situ measurements consist of long time series (more than 10 years) of waves and wind at different locations distributed along the Belgian coastline and in the Belgian coastal waters. The wave modelling is carried out with the state of the art, free software SWAN (Simulating WAves Nearshore).