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The Effect of Hurricane Irma Storm Surge on the Freshwater Lens in Big Pine Key, Florida using Electrical Resistivity Tomography
  • +1
  • Michael Kiflai,
  • Dean Whitman,
  • Danielle Ogurcak,
  • Mike Ross
Michael Kiflai
Florida International University

Corresponding Author:mkifl001@fiu.edu

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Dean Whitman
Florida International University
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Danielle Ogurcak
Florida International University
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Mike Ross
Florida International University
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Abstract

On September 10, 2017, Hurricane Irma made landfall in the Florida Keys as a category 3 storm. Storm surge inundation heights in the lower Keys were in excess of 2m. In this study, we investigate the effect of the Hurricane Irma storm surge on the freshwater lens of Big Pine Key, FL using Electrical Resistivity Tomography (ERT) on three transect lines of 222 m, 250 m and 278 m length. Two transects, B1 and B3, were situated near the shoreline and crossed the lateral boundary of the previously mapped freshwater lens whereas, the third transect, B2, was inland in the interior of the lens. All transects experienced storm surge flooding from Irma. In this paper, we compare ERT imaging results of baseline data collected 6 years before Irma (November 2011) with data collected 3-4 months (November, 2017/January, 2018) and 8 months (May 2018) after the storm. The data were inverted using a difference inversion algorithm which uses the previous inversion results as a starting model. The resistivity models were then converted to salinity by applying an electrical formation factor. For the November 2017/January 2018 data, all profiles showed low resistivity/high salinity zones in the upper 2 m corresponding to saline water emplaced on top of the freshwater lens by the storm surge. The increase in salinity is most pronounced in the low elevation portions of the transects. On transects B1 and B2, the high salinity zones are mostly continuous. However, on the higher elevation sections of transect line B3, the high salinity zone is broken up and appears to be moving downward through the freshwater lens. The nearshore transects, B1 and B3 also show a greater amount of saltwater intrusion adjacent to the shoreline at depths below 5m. The May 2018 data were collected at the end of the climatological dry season but were collected immediately after 2 weeks of intense precipitation. These data show some limited recovery of the freshwater lens. This recovery is most pronounced in the lower elevation portions of the transects where standing water was observed during data collection. This suggests that both the impact of storm surge and the freshwater recovery due to precipitation are most pronounced in low elevation regions where both saline and fresh water can collect at the surface.
Jul 2020Published in Estuaries and Coasts volume 43 issue 5 on pages 1032-1044. 10.1007/s12237-019-00666-3