The combined use of radio-frequency electromagnetics and radiomagnetotellurics methods in non-ideal field conditions for delineating hydrogeological boundaries and for environmental problems

Radio frequency geophysical methods are known for being very versatile tools in ground- and groundwater investigation at shallow depths. They are fast and easy to use and allow a high density of information over large surfaces, which makes them very suitable for geological mapping sensu lato (faults, lithological contacts, groundwater-bearing structures, vulnerability maps, and contaminant plumes) and for selecting borehole locations. Significant improvement concerning 2D and 3D modelling of the data has occurred in recent decades. However, field surveys are very seldom performed in "ideal conditions"aEuro"the lack of necessary transmitters, in the convenient direction, in order to catch the structures in E- and H-pol for modelling purposes, is not an unusual situation. The present paper shows how the use of RMT and RF-EM is nevertheless of great help and suggests different ways to explore qualitative data in different geological settings.