Electrical survey for detailed characterizing of underground karst: Example from Iskar River (Western Bulgaria)

The study was done using the method of Vertical Electrical Sounding (VES) for determination of the space characteristics of the underground karst in the gorge area along Iskar River in Western Balkan Mountain (Bulgaria). The method is very flexible to be use for measurements on difficult terrains, where is not possible to make the standard drilling. For the present investigation the computer program IPI2WIN has been used. One of the advantages of IPI2WIN software is the possibility to export as a file for 2D processing and interpretation the VES records from sites along a profile. In this manner the interpretation using the software RES2DINV can be done. The results obtained by the geophysical studies have confirmed the hypothesis for the existence of karst cavities that are not known and not discovered on the relelef.