Methods for Estimating Associated Risks of Sinkhole Occurrences: A Demonstration Using Available Data from the Ruhr Valley Region of Germany

Abstract

The generation of sinkholes in the Ruhr valley region in Germany is caused by many centuries of coal mining at various depths and, at the least, by residual underground open spaces that do not stay stable with time. Due to the unknown distribution of underground spaces and their undefined, decreasing stability with time, probability calculations provide a somewhat successful approach in order to obtain information about the risks of sinkhole generation and possible relations to structural, geological, mining, and other influences. In this article, we demonstrate procedures and strategies for probabilistic calculations of sinkhole generation. In order to explain the basic steps of data organization and calculation, we provide an application of some of the quantitative methods, using an example from a local data set (sinkholes from a map of the Muddental region) combined with the corresponding structural geological map. This example illustrates the basic methods and clarifies the application of probabilistic methods. Due to the small database available, it was not possible to develop the results further, and thereby provide a final unequivocal classification of the dominant causes to understand the risks of sinkhole occurrences. Nevertheless, should further information be made accessible by the relevant authorities, one will be able to improve and statistically sharpen the arguments given here using the probabilistic methods, and so more clearly define the best possible correlations for estimation and prediction of sinkhole occurrences. The main point made, even with the limited data available to date, is that the methods provide powerful tools to help describe systematically the causes and risks of sinkhole occurrences. Current information from the Ruhr valley region would indicate that preventative methods are not being used on a routine basis; rather, postsinkhole occurrence filling with cement and renovation of badly damaged structures is the norm. It is to be hoped that the methods given in this article will soon be applied to help control the sinkhole problem and dangers.