POTENTIAL IMPACTS OF SEA LEVEL RISE ON HILTON HEAD ISLAND, SC

Hilton Head Island, South Carolina is highly vulnerable to land loss from sea level rise and accelerated rates of shoreline erosion due to its low average elevation, low slopes, high tidal fluctuations, and exposure to seasonal storms. The island is a centerpiece of the South Carolina beach-based tourism industry which stands to suffer significant losses to infrastructure and ecosystems unless long-term adaptive planning is implemented. Yet, adequate planning requires high-quality, science-based projections of those areas likely to be impacted by a future rise in sea level.

A 5 ft resolution DEM based on a 2002 LIDAR flight of Beaufort County was used to derive 1 ft contour lines relative to NAVD88. Because MHW at Hilton Head is 3.75 ft, the 6 ft contour interval was used to estimate a sea level rise scenario of around 2.25 ft. Most projections for future sea level indicate that we will experience a rise of at least 2.25 ft by the end of the century. We overlaid low lying areas with parcel data provided by the Beaufort County GIS Office and 30 m LandSat data to categorize loss areas by land cover and zoning. We also overlaid the lost land with the current road network and building footprints to identify problem areas.

Of the 22,927 acres in the 21,860-parcel database maintained by the county, 5,022 acres were submerged more than 50% of the time. The largest land cover classes in areas of loss were dry mixed forest/woodland (1655 acres), marsh/emergent wetland (1182 acres), and grassland/pasture (442 acres). 3080 buildings are contained within or touch the perimeter of land below 6ft NAVD88 and nearly 50 miles of road would be impacted by a 2.25 ft rise in sea level.