Decoding Storm Response in Geologically Controlled Coastal Barriers Using XBeach

Abstract Storm-induced morphological changes in coastal barriers are primarily driven by hydrodynamic forcing. However, in rock-fronted coasts the presence of geological features can modulate storm impacts, but the extent to which these non-dynamic variables influence barrier morphological response to storms is still poorly understood. This study explores the influence of intertidal rock platforms on storm-driven morphological changes. Using the process-based XBeach model, dune erosion during an energetic winter storm was simulated across different schematic cross-shore profiles, incorporating variable intertidal rock platform configurations. The schematic profiles are based on existing barrier profiles in the Outer Hebrides, NW Scotland. Calibration of the model involved adjusting friction coefficients of exposed bedrock surfaces to improve the ability to reproduce observed nearshore wave heights and morphological changes in pre- and post-storm profiles. The results show that higher intertidal rock platforms (above mean sea level) are associated with reduced dune erosion, while lower rock platforms are associated with more extensive dune erosion. This highlights the complex interaction between geological control and storm impacts, with implications for improved understanding of coastal resilience and storm-driven morphosedimentary dynamics in rock-fronted barrier systems.