Coastal encineering problems concerning wind waves and~ell can be solved with the aid of hydraulic or mathematical models, The irregular wave field i.e. the state of the sea surface can be described in a sufficient way for engineering problems either by parameters such as significant wave height and mean wave period, or in the form of power spectrum function and the zero-moment thereof. A semi-empirical method is developed using transfer functions in order to deteruline tX-le boundary coned tions from wave measurements on a limited number of stations in all important points within a shallow sea area. An economical design is usually possible if the probability of occurrence of all parameters concerlled is known. The extrapolation of multidimensional statistical distributions of such parameters is often based on a relatively short period of field observations. The accuracy of the conclusions drawn from these observations influence the methods applied in the modelstudies i:u,ci the reliability of the economiGal decision. In this respect, an analysis of the available data is made with reference to Borne engineering and navigational problems in the South-Eastern part of the North Sea.