AbstractThe KFKI project BELAWATT used a coupled model system for simulating a 2-years time-series of currents and waves in the Hörnum tidal basin (German Bight, North Sea). This article deals with the model results concerning the effects of waves on currents and water levels and concerning the input of wave energy into the coastline. During a storm event (wind 13 m/s from NW) the wave-generated radiation stress produces an increase of the current velocity of 1 m/s above the tidal ebb delta and it produces a water level increase of more than 20 cm in parts of the tidal basin. The model system calculates the maximum energy input into the coastline during the storm event "Anatol". Relative to the maximum energy input striking the west coast of Sylt island, only 3 % reaches the coastline of the tidal basin. A scenario-run for December 1999 with a water level increased by 50 cm and a wind velocity increased by 10 % shows that the input of wave energy into the west coast of Sylt island increases by 30 % compared to present conditions. With gerard to the forecasted near-future increase of stron surges, the scenario results indicate an increased risk of coastal erosion in the surf zone of Sylt island.