Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)
Position, extent and volume of slag accumulation in the cave system of the Rudice Sinkhole, a National Nature Monument, studied geophysical methods
Published online: 9 May, 2020Abstract
The Rudické propadání National Nature Monument (The Rudice Sinkhole) has been strongly affected by slag material washed down from the disturbed slag heaps, then transported by intermittent stream and redeposited in the gully called “Ve Struskách” (In slags) located upstream the sinkhole. Slag from a nearby old iron foundry was dumped on the slopes of the gully in the 19th century. During some heavy rainfall events, the slag was occasionally washed down into an episodic stream channel entering the local karst system near the Rudice Sinkhole. There are many similar slag heaps contaminating the Protected Landscape Area of Moravian Karst. The slag drained into the karst system and caves damages mechanically the karst dripstone and sinter decoration and makes difficult the movement of speleologists investigating the caves. One of the major project objectives was to establish the total volume of the deposited slag for the purpose of the management of the Moravian Karst Protected Landscape Area. Exploratory drilling of slag heaps and redeposited slag material is thought to be inappropriately expensive in such a difficult rough topography. Consequently, several geoelectrical methods exploiting differences in resistivities of various geoelectric bodies were selected and used to determine the thickness of different parts of the slag deposition. The considered geophysical model consists of 3 major quasi-homogeneous geoelectric layers: slag accumulation, Quaternary sediments, and the underlying limestone. The results of the applied electrical resistivity tomography (ERT), vertical electrical sounding (VES), and ground penetrating radar (GPR) together with field mapping and test pits provided a sufficient amount of data to establish the areal extent and thickness of the slag material deposited in the area investigated. Moreover, the GIS analyses of local topography, insertion of geophysical measurements together with an overall interpretation of the obtained data gave interesting results leading to a new assessment of the extent and thickness of the deposited slag. On the other hand, if the issue of the old burden related to the distribution and deposition of slag material would be not resolved, it may endanger the major subject of environmental protection of the Moravian Karst Protected Landscape Area as a whole.
