Mining and its impact on the earth surface in the Ruhr District (Germany)

The article presents spatial differences in ground level changes in the Ruhr District due to large-scale coal extraction over the past 100 years. Elevation data on historical maps from 1892 was digitised with the help of a Geographic Information System and the interpolated historical surface was intersected with a current Digital Elevation Model, in order to calculate the differences in elevation. As a result, the highest values of subsidence, amounting to more than 25 m, were observed within the coalfields of the former coal mine Zollverein which is distinguished for its long mining history and its World Heritage status. Two examples from the cities of Essen and Dortmund analysed in detail reveal that not only depressions but also elevation features are affected by mining subsidence. These kinds of surface transformations are not visible in the field without a comparison of digital topographical models. The average amount of a net surface lowering was calculated for all maps digitised and analysed, resulting in values between 0.5 m for the map of Kamen, located at the eastern border of the Ruhr District, and 5.2 m for the map of Gelsenkirchen within the central Emscher floodplain with a total area of 128.5 km(2). The mean net surface lowering of the total area under investigation (approximately 2,700 km(2)) amounts to 1.6 m.