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The SWAN (Simulating WAves Nearshore) wave prediction model developed at TU Delft has been a huge international success for many years. This model predicts the distribution of wave heights close to the shore. It was recently expanded to include the SWASH (Simulating WAves till SHore) model, which enables the modelling of wave behaviour right up to the shore, including how they break and overflow.

Over a 1,000 institutes worldwide use the SWAN computer model which is available within the public domain (GNU GPL license, ). This model was recently expanded to include the SWASH (Simulating WAves till SHore) model, which enables the results of the SWAN model to be continued right up to the shore, including how the waves break and overflow.

As this model directly simulates the ocean surface, impressive images and film clips can be generated which are helpful in explaining the complex underlying physics of currents near the shore, and how waves break on the shore. The advent of SWASH means, for instance, that for the first time it is possible to depict how a tsunami flows onto and around an island.

Dr Marcel Zijlema is the developer and point of contact for SWASH: 'In line with the Dutch Flood Defences Act, the Dutch Directorate for Public Works and Water Management needs to ensure that our flood defenses can withstand the type of storm which only occurs once every 10,000 years. The problem is that we have never experienced this type of storm, and we therefore don't know exactly how high the waves will be or how they will behave. A model like SWASH is excellently suited to giving us a better idea of this type of situation. As we can create a better portrait of the complex processes near the shore, we can better estimate the safe height for our flood defences.'