Consequences of a storm surge for aeolian sand transport on a low-gradient beach

Abstract

Wind-blown beach sand is the primary source for the volume growth of the most seaward dune, the foredune. Strong wind events can potentially dominate long-term aeolian supply but in reality do not contribute considerably because they often coincide with a storm surge. The aim of this paper is to further our understanding of how a storm surge prevents or severely restricts aeolian supply. Using field data collected on the 1:50 sloping Egmond beach (Netherlands) in the aftermath of a 1-m storm surge, we show that the ground water in the upper beach rose to well above normal levels during the surge, which resulted in the development of a seepage face during falling tide and hence persistent saturation of the emerging beach. Using a fetch-based model, we predicted aeolian supply during the 2-day surge period to be about 66% of the potential supply. Fetch limitations imposed by the surge-induced inundation and the continuous saturation of the sand on the emerging beach both contributed to the predicted supply limitation. Our results quantitatively support earlier studies that suggested surges to be the primary condition that causes predictions of long-term potential foredune growth to overestimate measured growth.