HOLOCENE STORM-SURGE SIGNATURES IN THE COASTAL DUNES OF THE WESTERN NETHERLANDS

On five different sites along the central Netherlands' coast one or more sequences of shell deposits in the dunes have been observed. They are believed to be the result of storm surge activity on the foreshore, either through swash or overwash action, and of subsequent preservation due to aeolian coverage of a basically sedimentary coastal system. Through their stratigraphical positions and radiocarbon dating of shell material their approximate age was determined. By interpretation of the role of dynamic wave set-up and run-up the associated storm surge elevations relative to contemporary mean sea level are reconstructed. Although our data may not be statistically accurate, an increasing level of storm surge elevations over the recent Holocene is observed with a particular maximum during the Little Ice Age. It is our suggestion that climatic variations on the one hand and foreshore bathymetry on the other hand may be factors of relevance to explain these observations. If these findings are correct this would imply that for a proper analysis of exceedance frequencies of extreme storm surge events it would be relevant to base such an analysis not only on present climate and foreshore bathymetry.