Recent insights into inter-annual sandbar dynamics

Abstract

Based on model hindcasts of the bar cycle at two locations along the Dutch coast, the dominant processes and mechanisms that govern the bar amplitude growth and decay during net inter-annual offshore migration, the occurrence of bar switches and the inter-site differences in the bar cycle return period (Tr) are identified. Bar growth and decay are closely related to the wave-induced longshore current as it affects the distribution of the cross-shore sediment transport. The modelling results suggest that cross-shore processes may trigger a bar switch in the case of specific antecedent morphological configurations combined with storm conditions. The deceleration of the offshore migration rate as the bar moves to deeper water (the morphodynamic feedback loop) contrasts with the initial enhanced offshore migration behavior of the bar for steeper slopes. The bed slope in the barred zone is the most important parameter governing Tr.