Coastal protection potential of natural dune systems threatened by SLR scenarios

Coastal dunes are key components of nature-based coastal protection, but they face increasing risk from sea-level rise driven by climate change. This study investigates the morphodynamic response of a natural dune system at the German North Sea Coast to five storm surge cases with progressively rising still water levels (SWLs) reflecting local sea level rise (SLR) projections in 1:7 scaled experimental test series. Results reveal a systematic transition in flooding and erosion hazard regimes from localized, collision-induced dune retreat under current standard storm surge levels to major overwash and partial dune breaching under projected SLR projections of up to +1.2 m by 2100. Characteristic dune erosion processes of periodic scarping, notching, slumping, and sediment removal were found to migrate vertically with rising SWLs, progressively relocating the dune crest and increasing risk of breaching. In addition to the total dune erosion volume, the proportion of eroded area above SWL was identified as a sensitive indicator of residual dune protective capacity. The findings highlight the increasing vulnerability of natural dunes in the context of climate change-driven sea-level rise and underscore the urgent need for improved risk assessments and adaptive management strategies to preserve sufficient dune resilience and maintain their coastal protection function.