Coastal processes and dune stability: Insights from wave transmission and runup modeling.

This article focuses on assessing the stability of coastal dunes under wave action using laboratory experiments combined with numerical modeling. Employing wave flume experiments with high-speed cameras and the XBeach non-hydrostatic model, the study analyzes wave propagation, runup, and sediment transport under collision and overwash regimes. It finds that wave skewness and infragravity wave components are more pronounced in overwash conditions, leading to increased sediment transport and dune erosion, and establishes a linear relationship between shoreline retreat and erosion volume in overwash scenarios. The research validates the Stockdon et al. empirical formula as the most accurate predictor of wave runup in the experimental setting and introduces a dimensionless overwash threshold parameter, Cs, based on wave runup and dune crest elevation, to distinguish between stable (swash or collision) and unstable (overtopping or overwash) dune states. These findings provide useful tools for early detection of coastal erosion and inform coastal management and protection strategies.