For a safe and efficient dimensioning of the Eider Evacuation Sluices it was necessary to know the magnitude and probability of the occurring wave forces. To determine those data a model investigation has been carried out in one of the wind flumes of the Delft Hydraulics Laboratory in charge of and in co-operation with the Bundesanstalt fur Wasserbau in Karlsruhe. For this purpose it was necessary to consider all combinations of wave conditions and waterlevels in nature which can lead to important wave forces, taking into account their probability of occurrence. It was on these grounds that the conditions for the model tests were chosen. The results of the model investigation had to be translated into probabilities of exceedance of the wave forces per year. Taking into account the results of the model tests as well as the general knowledge about the distribution of the wave forces, suitable load figures have been determined especially for the dimensioning of the structure. Only this extensive investigation could provide the guarantee of a safe and efficient dimensioning of the structure against the impacts of breaking waves.