Longitudinal wave power as a proxy for coastal change detection

Abstract. Coastal areas are subject to atmospheric, fluvial and marine hazards that can cause relevant morphological changes. Wave height (Hs) is the most commonly used climate variable to define morphological changes in coastal engineering studies. However, this approach fails to capture directional effects, which are essential for predicting and managing shoreline erosion and associated risks. This work introduces a methodology that identifies relevant morphological changes (morphological events) by using the longitudinal wave power (LWP), after defining an optimized set of Peak Over Threshold (POT) parameters. The morphological evolution of an idealized river mouth was simulated using the Delft3D numerical model and six different wave climate conditions along with tidal and river flow conditions. The optimized LWP approach performed better than Hs in identifying morphological changes, providing a better agreement between climatological and morphological events. The methodology was further validated through its application to two real-world sites along the southern Iberian Peninsula incorporating real wave conditions, variable river discharges, and complete tidal regimes. In these areas, the numerical models had been previously calibrated. The results confirm the robustness and transferability of the methodology beyond idealized conditions. By considering both erosional and accretional processes, this LWP-based methodology offers coastal managers a robust, physics-based tool for predicting morphological responses to wave conditions, supporting the development of early warning systems on inlet-adjacent shorelines.