The Role of Internal Sedimentologic and Biotic Structure in Moderating Storm-Induced Dune Erosion

Laboratory studies indicate that the magnitude of coastal foredune erosion during high-energy events is influenced by the belowground biomass and sediment grain size of those dunes. However, the extent to which dune architecture mediates wave-induced erosion in natural settings is largely unknown. Here, we relate the internal sedimentologic and biotic structure of foredunes with pre- and post-storm beach and dune morphology to determine if the presence of a complex internal dune structure can reduce storm erosion. We quantified dune volume change from five moderate-size storms at six proximal dunes characterized by a diversity of internal sedimentologic and ecologic complexity. Dune volume change associated with a single storm ranged from −9.33 to +1.65 m³/m and varied significantly between sites. Results of multiple linear regression indicate that 25%–78% of observed erosion associated with these moderate storms is explained by antecedent beach and dune morphology and hydrodynamic storm conditions. Within the resolution of the available data set, we found that a complex internal structure is unlikely to substantially reduce dune erosion during mild to moderate storm events. Instead, the role of the internal structure could be more apparent during high-energy events when the influence of pre-storm morphology is weakened as the beach profile adjusts to wave conditions. Our findings ultimately enhance our understanding of the controls of dune erosion for varying storm regimes and underscore the pivotal influence of pre-storm profile morphology—more so than intrinsic properties of the dune itself—for mild to moderate storm events.