16-14 Investigating the Aerial Extent and Revegetation of Hurricane Michael Overwash Deposits on St. George Island, Florida

Session: From Thin Section to Outcrop: Exploration of Undergraduate Research (Posters)

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Abstract:

The presence of dunes on barrier islands is particularly critical for mitigating storm surge and coastal inundation; however, they can be damaged by elevated total water level during strong tropical cyclones. On October 10, 2018, Hurricane Michael made landfall on barrier island St. George Island (SGI), Florida, resulting in overwash, significant erosion of dune topography and vegetation, and landward deposition of washover fans. Extensive prior work has examined barrier island dune systems and their recovery after major hurricanes, yet, little research has been done on SGI. Recent advances in drone-based aerial imagery have enabled researchers to measure and detect detailed geomorphic and ecological changes in these low-relief and dynamic environments. Our goal is to conduct an analysis of the rate of revegetation on dunes and overwash deposits since 2018 in two sections of the Dr. Julian G. Bruce St. George Island State Park to quantify the recovery of the dune systems following Hurricane Michael. We compared changes between 2018 orthoimagery from NOAA Digital Coast and orthoimagery created from drone surveys collected in October 2025. We used a Harris H-X8 quadcopter unmanned aerial system (UAS) to collect geotagged images in an eastern and western section of the state park, and used photogrammetry to create orthoimagery which are of resolution 0.8 cm/pixel and area of 0.147 km2, and 1.3 cm/pixel and area of 0.324 km2, respectively. Quantifying revegetation will help signify dune recovery rates, given dune vegetation and dune size are positively correlated. We expect to find some degree of vegetation regrowth both on the dunes and overwash deposits, which will indicate the rate at which these dune systems naturally recover. Our analysis may also offer insights into the lateral evolution of the island’s dune crests based on the change in position of vegetation. With increasing intensity and frequency of storms due to climate change, it is important that dune systems and barrier islands are closely monitored as their ability to protect coastlines may become weakened, especially in locations where storm frequency exceeds dune recovery time scales. As storm frequency increases, barrier islands will remain topographically low and vulnerable to further erosion. Understanding the dune and vegetation dynamics, recovery rates, and susceptibility to change is helpful to effectively restore and protect barrier islands.

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