Comparing Tropical Cyclone and King Tide Impacts on a South Carolina Coastal Dune System

Abstract

Harris, M.E. and Ellis, J.T., 2021. Comparing tropical cyclone and king tide impacts on a South Carolina coastal dune system. Journal of Coastal Research, 37(5), 923–932. Coconut Creek (Florida), ISSN 0749-0208. Coastal populations face an ever-growing threat as natural hazards increase in frequency and magnitude. In South Carolina, king tides (abnormally high tides) responsible for coastal flooding have increased by 126% between 2014 and 2019. King tides present an evolving threat as sea levels rise, yet the implications for coastal dune response have not been investigated. This study compares the geomorphic impacts from king tides to two tropical cyclones on a South Carolina barrier island during four time periods (TPs): Hurricanes Florence (TP1) and Michael (TP2) and two subsequent periods (TP3 and TP4) with king tides but devoid of tropical cyclone activity. Florence resulted in the greatest average change to the dunes, with normalized volumes (nv) equivalent to –11.6 m3/d. During Michael, the average change rate was nv = –1.5 m3/d. Dune changes during TP3 and TP4 averaged nv = –1.7 m3/d and nv = –2.3 m3/d, respectively. The reduction rate during nonstorm conditions is indicative of the erosive potential of king tides. The erosive potential should be further investigated in conjunction with king tide magnitude and frequency. Smaller, more pervasive coastal hazards, such as king tides, should be more strongly considered, in addition to larger singular events, such as tropical cyclones, when investigating the geomorphic change of coastal dune systems.