Hurricanes Along the Southeast Atlantic Coast Build Marsh Resiliency Through Mineral Sedimentation

Abstract Salt marshes worldwide are threatened by sea‐level rise (SLR) and their survival is linked to the production of belowground biomass and mineral sediment deposition. While hurricanes can pose a significant threat to salt‐marsh stability, we show that a single, large magnitude storm can drive deposition surpassing long‐term annual accretion. However, the potential thickness of a single hurricane‐induced depositional layer remains poorly constrained. Here we assess storm sedimentation (geotechnical characteristics, layer thickness) along the border (∼10 off edge) of salt marshes behind four barrier‐island systems (Amelia Island, Sapelo Island, Hilton Head, Cape Romain). Analysis of short cores reveals the presence of Hurricane Irma‐related deposits in 32 of 37 sites (0.5–8.0 cm thick) composed of mud to muddy sand. Thickness of the event layer decreases from south (Amelia Island) to North (Cape Romain), corresponding to a decrease in wind velocity, wave energy, and storm surge due to increasing distance from the hurricane path. We found that marsh sites proximal to tidal inlets contained thicker sediment layers with coarser sand than sheltered sites. The heterogeneity in grain size indicates that localized hydrodynamics strongly influence variability in sediment reworking. Regression analyses showed a weak correlation of thickness with wave energy, sand–mud ratio, and storm inundation duration. However, we found a strong relationship ( R 2 = 0.56) between storm layer thickness and vertical accretion rates at the same sites determined from 210Pb dating Hein et al. (2024), https://doi.org/10.1038/s43247‐024‐01219‐8 . This suggests that hurricanes are important contributors to marsh sedimentation, boosting accretion rates and enhancing their resilience to SLR.