Parameterised Barrier Morphological Evolution for Future Storm Impact Assessment

Abstract Coastal storm impacts are mainly determined by the interaction of extreme water levels with barrier morphology, particularly the height of the foredune. While future projections of storm hydrodynamic forcing, integrating sea level rise, tides, waves and storm surges, are readily available, predicting future barrier morphology at a decadal scale remains a challenge due to uncertainties in modeling morphodynamic processes. This study proposes a simplified model to predict future foredune morphology at decadal scale and determine storm impacts on coastal barriers, focusing on the critical role of foredune morphology. The model identifies three morphological behavior modes based on the nature of the sediment budget and associated shoreline dynamics, distinguishing between: “keep-up mode” for accreting barriers, “catch-up mode” for stable to mildly accreting barriers, and “give-up mode” for eroding barriers. Application to the Portuguese coast, specifically the eroding barrier of Torrão do Lameiro, demonstrates that even with rising sea level and higher total water levels, storm impacts remain within the same regime by 2050. This simplified model offers a practical approach for considering an evolving foredune morphology, which can support first-order assessments of future storm impacts in changing climate.