HR: 1340h
AN: H43F-0548 INVITED     [Abstracts]
TI: Applications of Ground Penetrating Radar to Hydrogeological Investigations in Coastal Environments
AU: * Kruse, S
EM: skruse@cas.usf.edu
AF: Dept. of Geology, Univ. of South Florida, 4202 East Fowler Ave., Tampa, FL 33620 United States
AU: Grasmueck, M
EM: mgrasmueck@rsmas.miami.edu
AF: Marine Geology and Geophysics, RSMAS, University of Miami 4600 Rickenbacker Causeway, Miami, FL 33149 United States
AU: Bentley, L
EM: lbentley@ucalgary.ca
AF: Dept. of Geology and Geophysics, University of Calgary , Calgary, AL T2N 1N4 Canada
AU: Guha, S
EM: sguha@mail.usf.edu
AF: Dept. of Geology, Univ. of South Florida, 4202 East Fowler Ave., Tampa, FL 33620 United States
AU: Juster, T
EM: juster@mail.usf.edu
AF: Dept. of Geology, Univ. of South Florida, 4202 East Fowler Ave., Tampa, FL 33620 United States
AB: Ground penetrating radar is sensitive to the porosity and compositional variations common in coastal sands, and hence has become a staple tool for coastal stratigraphers. Under the right circumstances, GPR can also provide useful information on surficial aquifer hydrogeology in coastal zones. Here we present examples of the primary uses for GPR in coastal hydrogeology: (1) to identify depth to the water table; (2) to estimate the depth to the freshwater/saltwater interface; (3) to map hydrostratigraphic units; and (4) to track water flow and changes in water content in surficial aquifers. The water table generally produces a distinct GPR reflection where the capillary zone is thin relative to the radar wavelength. Uncertainties in the water table depth come primarily from uncertainties in the wave velocity and in the thickness of the capillary fringe. The freshwater/saltwater interface is typically too gradational to reflect energy; instead the radar pulse is attenuated. For some GPR instruments, a very shallow freshwater/saltwater interface can cause saturation in pre-amplifiers, resulting in a spurious high-frequency pulse in the record. On a coastal barrier island in the Outer Banks of North Carolina, GPR proved an excellent tool for mapping a muddy marsh layer that serves as a (semi) confining unit for a perched water table. In siliciclastic and carbonate units in Florida, repeated GPR surveying of individual sites has been used for qualitative tracking of unsaturated zone flow, water table migration, and changes in water content.
DE: 0694 Instruments and techniques
DE: 1829 Groundwater hydrology
DE: 1835 Hydrogeophysics
DE: 4217 Coastal processes
SC: Hydrology [H]
MN: Fall Meeting 2005