Ground-penetrating radar as a tool for mapping the phreatic surface, bedrock profile, and alluvial stratigraphy in the Sabie River, Kruger National Park

ABSTRACT: This study evaluates the effectiveness of ground-penetrating radar (GPR) as a nondestructive, sedimentological tool for mapping the phreatic surface, bedrock profile, and alluvial stratification within a homogeneous, sand-gravel fluvial deposit in the Sabie River, Kruger National Park, South Africa. The bedrock topography was mapped using a 90 MHz center frequency antennae pair, and a 500 MHz center frequency antennae was used to achieve higher resolution for mapping the phreatic surface and alluvial sediments. The phreatic surface and bedrock profiles determined using GPR correlate well with ground-truthing data (R2=0.97 and R2=0.85, respectively). A groundwater monitoring system and physical probing provided the independent estimates of the phreatic surface and bedrock depths, respectively. Dynamic cone penetration (DCP) tests were used to infer interfaces between sediments of different size and composition characteristics. The DCP interfaces assisted with the interpretation of the high-frequency radar imagery, enabling a detailed description of the alluvial stratigraphy.