COMPARISON OF USGS REGIONAL GROUNDWATER MODELS TO LOCAL SCALE MODELS FOR DECISION MAKING IN BEAUFORT SOUTH CAROLINA

Beaufort County Adapts brought together scientists, residents, and decision-makers to prepare for sea level rise impacts on local groundwater and infrastructure in Beaufort County, South Carolina. Focusing on septic systems, this project developed maps of present day and future depth to groundwater surfaces at a parcel scale. These high-resolution topographically constrained groundwater maps were found to match baseline groundwater elevations, established using shallow monitoring wells, to within 0.5 meters across the county. This study compares the ability of the data sets developed in the USGS’s future coastal hazards along the U.S. North and South Carolina coasts projected water table depths data set with the Beaufort Adapts topographically constrained groundwater maps.

The models were run with a local mean higher-high water (MHHW) marine boundary condition, and with groundwater reaching the land surface removed from the model, simulating loss via natural drainage. Modeled groundwater heads were then subtracted from high-resolution topographic digital elevation model (DEM) data to obtain the water table depths providing maps of groundwater heads / depths for both current and future sea-level rise (SLR) scenarios. This study fucuses on two important outcomes: First, to determine if the USGS regional mapping can be used for helping to understand impacts of groundwater at a scale necessary for septic systems planning and failure potential monitoring. Second, to determine at what scale groundwater maps are necessary for these municipal level decisions.