EVALUATING THE INFLUENCE OF STORMS ON THE GEOHISTORICAL DEVELOPMENT OF MARCO ISLAND, A BARRIER ISLAND IN SOUTHWEST FLORIDA, USING LIDAR AND GROUND-PENETRATING RADAR TECHNOLOGIES

Barrier islands are vital in protecting the mainland from storms by taking the brunt of wave and storm energy. Consequently, an understanding of their geologic development can inform future management practices in the context of a changing climate. This study focuses on the recent history (~ last 30 years) of Tigertail spit and its associated landforms, located on the northwestern end of Marco Island, a barrier island along the southern Gulf Coast of Southwest Florida (SWFL), as influenced by major tropical storms. Remote sensing (UAV-flown LiDAR), ground-penetrating radar (GPR), and aerial and satellite historic imagery were used to assess the processes causing geomorphologic change and the timing of that change relative to the passage of tropical storms. Hurricane Ian (September, 2022) was the latest major storm to affect Tigertail since the spit's initial development in 1995. A comparison of digital elevation models (DEMs) from a NOAA fixed-wing LiDAR survey in 2018 and our UAV-flown LiDAR in 2023 shows the effects of Hurricane Ian: the loss of vegetation across a multi-dune ridged strandplain; the reduction of dune crest elevations; and overtopped, landward transport of sand due to storm surge. Historic imagery reveals the timing of Tigertail’s strandplain development, and the development of ebb surge channels, created initially during the passage of Hurricane Wilma (October, 2005), that were reinvigorated by Hurricane Ian. Similar erosional channels created by Ian also occur on 3 other barrier islands in SWFL: Sanibel, Fort Myers Beach, and Lover’s Key. GPR surveys run perpendicular to the coast on Tigertail show progradational stratigraphy of accreted strandplain ridges. The historic imagery establishes the relative timing of ridge progradation, book-ended between the passage of major storms. Subsurface stratigraphy also shows the location of dune scarps, which served as initiation sites for new ridge formation, and overtopped, transgressional deposition behind dune crests, both presumably generated by surge from lesser storms. Tigertail’s 30-year history illustrates the complex relationships among storm intensity, erosional versus depositional processes, and the relative vulnerability or resilience of barrier islands.