LAUSR

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.