This paper highlights the efficiency and complementarity of a light package of geophysical techniques to
study the structure of karst Unsaturated Zone (UZ) in typical Mediterranean environment where soil cover
is thin or absent. Both selected techniques, 2D Ground Penetrating Radar (GPR) and Electrical Resistivity
Tomography (ERT), are widely used in environmental studies and their application is accessible for a lot of
scientists/engineers. However, GPR or ERT alone is not able to provide an enhanced characterization of
geological features in karst media. In the present study, GPR results supply a near surface high resolution
imaging and thus can provide relevant geological information such as stratifications and fractures. Despite
the quality of the results GPR's investigation depth remains limited to around 12 m. Apparent and inverted
resistivity provided by ERT surveys shows strong lateral and vertical variations. These variations can inform
about general geological structuring and feature orientation. ERT is able to prospect down to 40 m but it's a
low resolution integrative technique. In the study area the investigated limestone is a commonly electrical
resistive formation (more than 2000 Ω.m). However deeper than 5–7 m, the ERT profiles reveal several
zones of moderate resistivity (around 900 Ω.m). In these zones a stratification change corresponding to
slanted bedding is clearly identified by GPR results. The combination of both GPR and ERT results can allow
a well-established geological interpretation. These moderate resistivity zones with slanted beddings can
explain the presence of a perennial water flow point 35 m below the surface of the studied site within the
underground gallery of the Low-Noise Underground Laboratory (LSBB).