Román-Rivera, M.A. and Ellis, J.T., 2018. The king tide conundrum. Over the last decade the concept of “king tides” has become a common colloquial term to describe higher than normal high tides. The terminology originated in 2009, when Australia experienced their highest seasonal tides in almost 20 years. In response, a public engagement program, “The King Tides Project,” was formed that has since spread globally. Discrepancies regarding the definition and frequency of king tides can be identified between the different initiatives. This communication analyzes the multifaceted and contradictory meanings of king tides and concludes by providing a holistic and comprehensive definition.

The purpose of this study is to document the geomorphic evolution of a mechanical dune over approximately one year following its installation and compare it to the recovery of a natural dune following the impact of Hurricane Matthew (2016). During the study period, the dunes’ integrity was tested by wave and wind events, including king tides, and a second hurricane (Irma, 2017), at the end of the study period. Prior to the impact of the second hurricane, the volumetric increase of the mechanical and natural dune was 32% and 75%, respectively, suggesting that scraping alone is not the optimal protection method. If scraping is employed, we advocate that the dune should be augmented by planting. Ideally, the storm-impacted dune should naturally recover. Post-storm vegetation regrowth was lower around the mechanical dune, which encouraged aeolian transport and dune deflation. Hurricane Irma, an extreme forcing event, substantially impacted the dunes. The natural dune was scarped and the mechanical dune was overtopped; the system was essentially left homogeneous following the hurricane. The results from this study question the current practice of sand scraping along the South Carolina coast, which occurs post-storm, emplacement along the former primary dune line, and does not include the planting of vegetation.

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.