Over one-third of the Earth’s population resides or works within 200 km of the coast. The increasing threat of coastal hazards with predicted climate change will impact many global citizens. Coastal dune systems serve as a natural first line of defense against rising sea levels and coastal storms. This study investigated the volumetric changes of two dune systems on Isle of Palms, South Carolina, USA prior to and following Hurricanes Irma (2017) and Florence (2018), which impacted the island as tropical storms with different characteristics. Irma had relatively high significant wave heights and precipitation, resulting in an average 39% volumetric dune loss. During Florence, a storm where precipitation was low and winds were moderate, net volumetric dune loss averaged 3%. The primary driving force causing dune change during Irma was water (precipitation and storm surge), and during Florence, it was wind (aeolian transport). We suggest that the application of the Saffir-Simpson Hurricane Wind Scale classifications should be reconsidered because different geomorphic responses were measured, despite Irma and Florence both being designated as tropical storms. Site-specific pre- and post-storm studies of the dune morphology and site-specific meteorological measurements of the storm (wind characteristics, storm surge, precipitation) are critically needed.

In many places along the U.S. East and Gulf of Mexico coasts, barrier islands are the first line of defense against extreme weather events threatening our coastlines. The trademark of these barrier islands are sand dunes that are intricately bound, from a sedimentary perspective, to the beach. Coastal storms, such as Hurricanes Matthew (2016), Irma and Maria (2017), and Florence (2018) have devastating impacts on these environments. This study investigated the volumetric changes of an anthropogenic and controlled beach-dune system on Isle of Palms, South Carolina, for approximately one year following Hurricanes Matthew (2016) and Irma (2017). This research reveals that these systems did not recover. The average loss of sand at the beach was -15.5% (nv = -0.89), whereas the dunes gained an average of 13.3% (nv = 0.79), when compared to the already diminished post-storm volumes. When considering the pre-Hurricane Irma to pre-Hurricane Florence temporal period, the recovery percentages for the anthropogenic and control dunes was -15.5% and -40.1%, respectively, suggesting a net loss of sand. Cumulative storms, such as those experienced on the coast of South Carolina and many other coasts, pose a substantial threat to the long-term viability of coastal dune systems. However, recovery at the control site in the form of incipient foredune growth is promising. This paper concludes with a list of influencing factors to dune recovery.

Sand dunes protect the most important economic and ecologically critical landscapes from coastal hazards (storms and high-tide flooding). The characteristics of the dune affect their protective ability. This paper qualitatively and quantitatively assesses the relationships between pre- and post-storm conditions for vegetation and the morphology of an incipient dune system along the South Carolina coast. Field-based dune vegetation and morphology measurements were obtained before and after tropical storm Dorian (2019). Vegetation is assessed with respect to distribution and functional type, and subgroups are introduced to categorize land cover transitions. At the quadrat scale (0.2 m²) following the storm, there was a shift from stabilizer to builder, a decrease of sand (2%), and the vegetation remained consistent at around 61% of the land cover. Transect-level analysis (0.2 m × 1.0 m) revealed distinct variability concerning post-storm morphology change in the extreme study site extents. Dorian resulted in approximately 10% volumetric loss over the entire study site (101 m²). This study demonstrated changes to a dune system following a tropical storm with wind as the dominant forcing factor. This study revealed that vegetation presence is not broadly correlated with reduced levels of post-storm erosion.