CHARACTERIZING VOID SPACES AND HYDROLOGICAL FEATURES ASSOCIATED WITH A KARSTIC SWALE AT GRAND CAVERNS, VA USING RESISTIVITY

Electrical resistivity (ER) surveys conducted in karstic environments are well suited for the detection and characterization of void spaces, sediment-filled collapsed features, and water in the subsurface. For this study, we collected several lines of resistivity data (using an AGI Supersting R1 resistivity meter) in the vicinity of a swale feature on top of Cave Hill, approximately 800 m south of, and 60 m above the Grand Caverns commercial cave in Grottoes, VA. This data was combined with surface and structural data using local strike and dip as well as GPS.

The data was processed (using AGI's Earthimager 2D software) and several resistivity profiles were generated. We were able to detect both open-air and collapsed, sediment filled spaces associated with the swale, as well as areas of porous bedrock. We were also able to identify the areas where the water infiltrates and collects in the subsurface, and correlate this to the surface features as well.

Our results will help us understand the establishment and evolution of surficial features in karstic environments, which will benefit further geophysical studies and hazard assessment in the region.