Non-Invasive Monitoring of Salt Intrusion in a Coastal Barrier Environment Using Time-Lapse Electrical Resistivity Imaging (ERI)

M. G. Oduwole and L. D. Slater
Department of Earth and Environmental Sciences, Rutgers University 101 Warren St., Newark, New Jersey

The problem of saline water incursions into groundwater supplies in beachfront municipalities have made continuous monitoring of saltwater/freshwater interface in coastal environment very essential. Direct sampling which is commonly used to estimate the interface is invasive, expensive and time-consuming. Consequently, adequate samples are not obtained in order to produce high level of data with spatial variability.

In this study, we have used electrical resistance tomography to noninvasively resolve the geometry of the freshwater/saltwater interface and evaluate the response of this interface to tidal forcings at the Sandy Hook Beach, Central New Jersey. Dipole-dipole electrical resistivity measurements were continuously collected over a 12-hr period along a shore-perpendicular transect allowing the production of high-resolution time-lapse tomograms. During high tide, modeled resistivities observed were the lowest, indicating that the freshened groundwater plume was least developed at this time. Low tide images show highly resistive layers at depth and near the surface indicating the migration of freshened groundwater plume landward.

AAPG Search and Discover Article #90087 © 2008 AAPG/SEG Student Expo, Houston, Texas