LOW FREQUENCY OSCILLATIONS ON THE DUTCH COAST

Abstract

During several months in 1981 and 1982/1983 two extensive programs of field measurements were carried out at Egmond on the Dutch North Sea coast, one during the spring of 1981 and the other during the winter of 1982/83. In these programs researchers of the Dutch "Rijkswaterstaat", of The Delft University of Technology and of the Delft Hydraulics Laboratory cooperated in the planning and execution of the measurements and are now involved in data analysis and evaluation of results. During the year 1983 the senior author spent a sabbatical year with the Rijkswaterstaat in the Netherlands and joined the team effort in analyzing the data. Reference is made to other papers presented at this conference, highlighting some aspect of this research program: Van Heteren and Stive (1984), Derks and Stive (1984). The present paper deals with low frequency oscillations in the surfzone and their potential impact on certain aspects of coastal morphology. The conclusions of this paper have to be considered as tentative and should be followed by further study. Its main intention is to point to certain possible relationships regarding coastal morphology so that in future measurements the program can be designed in such a way that certain relationships can clearly and unmistakenly be identified. The programs of measurements carried out in 1981 and 1982/83 were primarily designed to evaluate the usefulness and accuracy of various types of instruments in the surfzone. The measurements were never designed for the use we have made of them and results may therefore not be fully conclusive and thus subject to discussion. Nevertheless the authors found their tentative findings of sufficient interest to share them with their colleagues.