35 Wetlands, Springs, and Streams: Hydrologic Studies at the Groundwater-Surface Water Interface

Tuesday, 16 April 2024
8:00 AM - 12:00 PM
Windsor Ballroom Salon B

CHARACTERIZING GROUNDWATER FLOW ACROSS THE BARRIER ISLAND - SALTMARSH INTERFACE

Paper number: 35-5
Program: Theme Sessions
Time: 9:20 AM – 9:40 AM

Authors

Abstract

The groundwaters of barrier islands are exceptionally diverse in their flow and composition. A multitude of factors including evapotranspiration, geologic constraints, tidal forcing, and meteoric inputs influence subterranean flow. These factors create a groundwater salinity gradient throughout the island-marsh setting which directly influences the spatial distribution of dominant vegetation on the island. Rising sea levels and variation in local climate may alter the hydrologic balance on barrier islands, potentially shifting salinity gradients and ecological baselines on short timescales. The intrusion of saltwater in the porewater-groundwater system could result in shifting of these ecotones and potential destabilization of barrier sediments, as well as degradation of water quality used for municipal services.

An interdisciplinary method was adopted to characterize the groundwaters of Waties Island, a barrier island located in northeastern SC. A 150-meter-long study transect located on the landward side of the island encompassed the ecological shift between maritime forest and salt marsh. Three shallow groundwater wells were located along the transect, with a midpoint well in the high marsh where the greatest subterranean mixing was expected. Water level, temperature, and conductivity were recorded in each well at 20-minute intervals. Modal analysis of the data revealed tidal and meteorological drivers of groundwater level across the transect. Time series electrical resistivity (ER) surveys conducted along the transition from forest to marsh revealed horizontal mixing of groundwater within sediment layers of highly permeable material. Vibracores facilitated analyses of the relative permeability of sediments along the transect and augmented the interpretation of ER data. Together, these data resolved the impact tidal and meteoric drivers have upon groundwater level in addition to characterizing resulting subterranean flow given geologic and biotic constraints.

Geological Society of America Abstracts with Programs. Vol. 56, No. 2

doi: 10.1130/abs/2024SE-396984

© Copyright 2024 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.