ABSTRACT:

Shallow coastal groundwater flow in beaches and salt marshes has been widely studied over the past 20 years, but far less is known about groundwater flow dynamics or the configuration of the freshwater-saltwater interface in deeper confined aquifers in coastal environments. We used field observations and numerical models of North Inlet, SC, to investigate groundwater flow and transport at scales reaching from the beach and marsh (nearshore scale) through the first major confined aquifer (embayment scale). Sediment cores were collected in collaboration with the South Carolina Department of Natural Resources. Electrical resisistivity surveys were conducted to estimate the salinity in the subsurface. Three wells were installed to monitor water levels and collect water samples. Numerical models were calibrated to the field observations and used to simulate the formation and migration of freshwater-saltwater interfaces at multiple scales; to assess the independence of flow at different scales; and to investigate the impact of future predicted rates of sea-level rise on this system.