Georgia Southern University evaluates coastal resilience on Tybee Island
The City of Tybee Island, Georgia, entered a contract with Georgia Southern University in 2020 to monitor the success of a half mile long, eight-foot-tall restored dune.
According to the final report, titled “Monitoring coastal dune resilience,” the goal of the contract was to evaluate the success of the restored dune by comparing it to natural, previously established dunes on the island.
Goals of the project
The project was led by P.I. Dr. Lissa M. Leege of the Georgia Southern University Department of Biology. The project goals were modified in the Fall of 2023 as the previous graduate assistant had to step down for medical reasons. Graduate assistant Skyler Fox joined the project, and the goals were modified to meet Fox’s master’s thesis project.
According to the report, goals included:
- Implement and adapt dune monitoring protocols
- Evaluate impacts of pedestrian traffic on footpaths on dune resilience by:
- Measuring characteristics of dune vegetation, soil and sand accumulation along footpaths and comparing these to nearby undisturbed dune areas
- Measuring the rate and extent of dune recovery following restricted foot traffic
- Measuring the rate and severity of damage to dunes after adding new footpaths
- Creating an ArcGIS Story Map for public viewing showing the impacts of the footpaths
“The goal of our project was to evaluate the success of the restoration by comparing ecological data we collected from Tybee’s restored dune with that of a previously established, natural dune on the island,” said Fox. “Ideally, over time, the restored dune will develop vegetation characteristics and sand accumulation abilities indistinguishable to those in the established dune.”
Results of the project
The final report showed that, 1.5 years after dune restoration, the dunes on Tybee Island accumulated an average of 9.24 cm of sand from Hurricane Ian. The established dune collected 2.4 times more sand than the restored dune.
3.5 years after dune restoration, the report showed that the dunes on Tybee Island accumulated an average of 3.07 cm of sand during Hurricane Helene. The established dune collected 5.4 times more sand than the restored dune.
“As expected, the established dune accumulated more sand than the restored dune during both Hurricane Ian (2022) and Hurricane Helene (2024),” Fox said. “However, the difference in sand accumulation between the dunes was more pronounced during Helene compared to Ian.”
The report concluded that the restored dune crest (the top of the dune) was more at risk than the established dune. Dune height is an important factor for mitigating the risk of storm surge.
The report also showed that, four years after restoration, the restored dune is supporting vegetation to the same extent as the established dune.
“Initially, we anticipated that over time, the restored dune would increasingly resemble the established dune in its ability to accumulate sand,” Fox said. “This discrepancy in accumulation, however, may be partly due to variations in the intensities of the two hurricanes.”
Recommendations
The report closed with recommendations for officials. As well as highlighting some of the data above, the report suggests a continued relationship between the City of Tybee Island and Georgia Southern University to continue monitoring the dunes.
“Right now is the most critical time to be collecting this data,” Fox said. “Significant erosion has occurred at the beach/dune interface in the restored dune since the summer and accelerated as a result of Hurricane Helene.”
The final report stated that since summer 2024, the restored dune has experienced significant erosion. This is important to track because Tybee’s next beach renourishment won’t begin until 2026.
“We need to continue taking measurements to determine if the restored dune can rebound from these hardships and continue to accumulate sand until the next renourishment occurs,” Fox said.
The report also included preliminary research on pedestrian foot traffic. It found that damage to dunes from foot traffic can occur rather quickly but may take more time for recovery to occur. The report also stated that one of the reasons the footpaths aren’t recovering quickly is due to people still using the closed paths.
The full project will be presented as part of Fox’s thesis in 2025. Fox is still gathering data on the footpath study and expects it to be completed in the summer of 2025.
“The most fun part of the project was engaging with community members and students who assisted us with our quarterly data collection,” Fox said. “I loved talking to them about the importance of monitoring Tybee’s dune restoration to ensure its success for the future as well as teaching them proper data collection methods in the dunes. We have now developed a committed group of citizens who consistently assist us during each monitoring event.”
Alex Cossin | Associate Editor
Alex Cossin is the associate editor for Waterworld Magazine, Wastewater Digest and Stormwater Solutions, which compose the Endeavor Business Media Water Group. Cossin graduated from Kent State University in 2018 with a Bachelor of Science in Journalism. Cossin can be reached at [email protected].
