Utilization of engineering geology in geo-tourism: few case studies of subsidence influence on historical churches in Ostrava-Karvina District (Czech Republic)

This article studies a set of historical churches influenced by subsidence induced by underground coal mining in the Karvina part of the Upper Silesian Coal Basin in the Czech Republic. The research made use of engineering geological tools to assess the influence of underground mining on the ground. In the cases of the churches in question, variations in time of the existing subsidence have also been evaluated. The herein applied method in determination of the building site categories transforms the measured (macroscopically) visible vertical tilts of buildings (churches) into horizontal tilts and it is new. Horizontal tilts are important characteristics expressing differential settlement. However, these are not measurable as the building begins in the foundation soil and the foundations would have to be exposed. Building site categories, i.e. categories of hazard to determine the mining influence on buildings, based on horizontal tilt were used to determine the influence of underground mining onto a building. Due to the fact that the churches under observation find themselves at diverse stages of subsidence, we identified a great variability of subsidence and building site categories. This way, the churches become unique landmarks in the cultivated landscape as they frequently remain the only historical buildings in the subsidence trough. Thanks to rehabilitation and repeated repairs churches survive as the memorials of human life in subsidence troughs induced by underground coal mining. For example, in the Ostrava-Karvina Coal District coal has been mined for 200 years. The fundamental argument for the nomination of the church set onto the UNESCO World Heritage List is the fact that historical churches may remain the only traces left by people living in localities affected by underground coal mining. The article would also like to point at the application of engineering geology for other than construction or environmental purposes. Geo-tourism has this scientific and economic potential for the future.