Post-mining deformations in the area affected by the former “Siersza” Hard Coal Mine in Trzebinia (southern Poland)

Over the recent years, post-mining terrain deformations have been increasingly frequent around Trzebinia. Sinkholes appearing closer and closer to buildings have become a significant geohazard. The research demonstrated that the problem of post-mining deformation in the area is much more extensive than previously estimated. Identification of the deformations involved analysis of historic aerial photographs, airborne laser scanning data, orthophotomaps and satellite radar data. Moreover, laser scanning of the selected areas using an unmanned aerial vehicle and a terrestrial laser scanner was carried out together with field mapping work. A comprehensive survey of sinkholes, including those previously unknown – located outside built-up areas – allowed an assumption to be made that areas where sinkholes had been remediated in the past were also at significant risk. A number of sinkholes are also located outside areas of shallow mining (up to 100 m below ground level). In the study area, 527 sinkholes and 254 linear-type deformations (post-mining faults) were identified. The use of satellite radar interferometry made it possible to state that continuous deformations also occur in the area of influence of the former "Siersza" Hard Coal Mine. In the past, this was the subsidence of the terrain, and currently an uplift is faced in this area which, in some places, reaches up to 20 mm per year.