Tybee Island and Sea Level Rise

Since 1935, a National Oceanic and Atmospheric Administration (NOAA) tide gauge has been in place just over two miles from Tybee Island, GA at the Fort Pulaski National Monument. Long-term data from the gauge show a steady increase in water heights and flooding around Tybee Island. From 2016 to 2021, the rate of flooding events increased by 30 percent, largely due to sea-level rise. Using these data, scientists estimate that sea levels around Tybee Island could rise an additional 1.39 feet by 2050.

Professor Craig Landry has been working with an interdisciplinary team of UGA researchers (Engineering, Environmental Design) to manage flood, storm, and sea-level-rise risk along the marsh shoreline of Tybee Island and other parts of Chatham, Bryan, and Liberty Counties. Using hydraulic modeling, engineering designs, landscape architecture, and economic assessment tools, researchers evaluated alternatives for modifying Tybee’s estuarine shoreline. This project, sponsored by the National Fish and Wildlife Foundation (NFWF), recommends the implementation of several natural and nature-based features, including an estuarine horizontal levee with adjacent living shoreline, redesigning culverts to incorporate natural water flow and green infrastructure, and improving city right-of-ways to include rain gardens and bioswales. These recommendations would capture and filter an estimated 21 percent of the total stormwater runoff, reducing acute and chronic flooding for Tybee Island residents.

“This is a natural next step to improve our coastal resilience," said City of Tybee Island Mayor Shirley Sessions. "We are so pleased with the work done by researchers at the University of Georgia, the Marine Extension and Georgia Sea Grant, and the Skidaway Institute of Oceanography, many of whom have been partners with the City on coastal resilience issues for many years. Just as we did back in 2016 with the adoption of the State's first Sea Level Rise Adaptation Plan, Tybee again leads the State in considering the use of nature-based infrastructure in meeting the challenge of rising seas."

With help from Ph.D. student, Nicholas Bradley, Prof. Landry designed and implemented the Coastal Empire Adaptation Survey to assess individual risk perceptions, preferences, and economic values for gray, natural, and hybrid infrastructure designs for shoreline protection. Their results show that the majority of Coastal Empire residents (64 – 72%) agree or strongly agree that sea level is rising; coastal hazards (flooding, erosion, storms) are getting worse; the coast needs to invest in better hazard mitigation infrastructure (78%), and some buildings and infrastructure may need to retreat from the shoreline (64%).

Survey respondents overwhelmingly preferred natural and hybrid approaches to conventional gray designs (e.g., concrete bulkheads). Despite the fact that gray infrastructure provides the greatest level of flood protection in the short run, these approaches are less adaptable to environmental change, exacerbate wildlife habitat and water quality problems, inhibit ecological functions of coastal marshes, and limit recreation opportunities. The survey provides evidence that Coastal Empire residents value these aspects of natural infrastructure.

The survey evaluated how much households would be willing to pay (WTP) via Special Purpose Local Option Sales Tax (SPLOST) to implement gray, hybrid, and natural infrastructure projects. Hybrid designs exhibited the largest economic value (WTP = $324 per household/year for 10 years), followed by green (WTP = $293) and gray (WTP = $155). Wildlife habitat, recreation benefits, and flood protection were found to be the most important ecosystem services provided by shoreline protection, while reductions in nuisance flooding were less relevant. For example, Coastal Empire households are willing to pay an average of $83 per household/year for 10 years for a 10% reduction in the probability of catastrophic flooding in low-lying areas over 30 years.

The comprehensive engineering and economic analysis is being incorporated into a second phase proposal to NFWF, that seeks funds to finish planning/design and permitting for the projects, targeting a fall 2025 construction start.