Modeling of residence time in the East Scott Creek Estuary, South Carolina, USA

A numerical modeling study was carried out to compute average residence time in a tide-dominated East Scott Creek Estuary, South Carolina. The East Scott Creek estuary is a long system of meandering tidal creeks and salt marsh between Edisto Island and the Edisto Beach barrier island, in South Carolina. A coupled hydrodynamic and solute transport model was developed. The flow and solute transport models were based on depth-integrated conservation equations. The equations were discretized by using the total variation diminishing (TVD) finite-volume method. The numerical model predictions were verified against a set of field-measured hydrodynamic data, with the model-predicted water elevations and velocities in good agreement with the field measurements. A remnant function method has been used to quantify the transport mechanism for a dissolved substance in a spatially varying situation with multiple sources, using a high-resolution mass-preserving hydrodynamic and mass-transport model. The spatially varying average residence times for a tide-dominated environment were investigated through a series of numerical experiments using a passive dissolved and conservative tracer as a surrogate. The result indicated that the average residence time varies with the tidal amplitude. The average residence time for the whole estuary for spring-tide condition was found to be about 22 h. The corresponding average residence time for a tracer placed at the head of the estuary was about 170 h. These findings provide useful information for understanding the transport process in the East Scott Creek Estuary that can be used to assess the impact of coastal development in and around the estuary.