The effects of Holocene barrier-island evolution on water-table elevations, Hatteras Island, North Carolina, USA

On Hatteras Island, North Carolina, USA, complex stratigraphy results from surficial sediments being superimposed on an inherited Pleistocene platform. Numerical simulations used to simulate watertable profiles on the island illustrate the influence that the complex stratigraphy has on water-table elevations. Field data consist of water-table profiles collected from a cross-island transect of wells. These profiles show unusually high water-table elevations in the south-central portion of Hatteras Island. Geophysical data are used to constrain the subsurface stratigraphy. Simple analytical solutions to the groundwater flow equation using laterally varying recharge rates cannot match mean water-table profiles. More complex numerical simulations, which do match the profiles, indicate that the elevated water levels result from a low-permeability unit that extends several kilometers along the longitudinal axis of the island. Island geomorphology and ground-penetrating radar (GPR) data suggest that this unit is a former interdunal wetland that has been buried by a series of parabolic dunes.