Morphodynamic development and preservation of physical sedimentary structures in two prograding recent ridge and runnel beaches along the Dutch coast

Abstract

The two studied beaches both form part of the coastal barrier system which extends along the eastern margin of the southern North Sea. One of them (at Schouwen) is bordered by the coalescing ebb deltas of two major tidal inlets; the other one (at Zandvoort) lies beyond the in influence of inlets. The ridge and runnel beach environment is divided into areas lying relatively sheltered from wave action behind ridge or berm crests and seaward dipping surfaces exposed to the influence of swash and backwash during the tidal cycle. Both of the areas are characterized by a set of sedimentary bedforms and structures, which produce distinctive associations in preserved sediments. Comparison of data on sampled structures from buried sediment layers with information from repeated measurement of beach variation, permitted reconstruction of the location of these associations as preserved during the last few years in sections perpendicular to the coastline. Major differences in the morphodynamics of the two beaches as well as in the location of associated sedimentary structures preserved in these sections, are related to the degree to which the beaches are sheltered from storm waves and to rates of progradation.