Leveraging Laboratory Experiments of Shoreline Response to Sea‐Level Rise: A Beach Disequilibrium Perspective

Abstract This study analyzes laboratory data of beach response to sea‐level rise (SLR), isolating shoreline changes driven by passive flooding (PF) of the beach and consequent wave‐driven processes. The disequilibrium concept relates shoreline change to instantaneous and equilibrium beach states. While PF shifts the shoreline geometrically, SLR induces disequilibrium that produces wave‐driven changes due to apparent profile changes. For the first time, 24 experiments from wave flumes of different scale (including new high‐low energy cyclic waves experiments) are gathered into a dimensionless data set through a scaling technique to investigate SLR‐induced processes. The data indicate trends (possibly linear) between relative wave power and wave‐driven shoreline changes for a given SLR, highlighting the effects of changing background wave energy. Cyclic wave experiments best represent Bruun model's behavior. Wave‐energy dissipation emerges as a key variable for quantifying SLR‐induced disequilibrium, offering new pathways for future improvements of equilibrium shoreline models under SLR and wave‐climate change.