Morphodynamics of a composite barrier system, Westward Ho!, North Devon, UK

Understanding and predicting the morphodynamic evolution of gravel barrier systems is essential for coastal management, as these features provide natural protection for infrastructure and ecosystems. This study uses the composite gravel barrier system of Westward Ho!, south west England, characterised by a sandy intertidal region and a gravel high tide ridge, to quantify the morphological behaviour of this barrier system and link the dynamics to the external forcing, notably sea-level rise and waves. Since 1887, the barrier has retreated by 97 m, with an average retreat rate of 0.71 m yr−1. Over the period 2007–2024, the system lost approximately 216,000 m3 of sediment, equivalent to 3.6 m3 m−1 yr−1. It is suggested that most of this material was transported to a beach-dune system north of the barrier, across an estuary. Over the past two decades, the retreat rate of the southern section has slowed to 0.18 m yr−1, while the retreat rate of the northern section has increased to 2.39 m yr−1. This suggests segmentation is occurring, with the southern end becoming swash-aligned and the northern end drift-aligned. Morphological changes did not strongly correlate with SLR or wave power (cross-shore or longshore). The low-tide shoreline appears near equilibrium with prevailing wave direction, but the gravel ridge is slightly misaligned, suggesting net northward sediment transport. Given current trends, the barrier is expected to continue retreating and losing sediment for several decades. However, a comprehensive understanding of the system's future behaviour requires development of a mixed-sediment morphodynamic model.