Coal Mining Area of Köflach/Voitsberg (Austria) – Assessing Changes in Landscapes

Wolfgang Sulzer1 and Walter Poltnig2

Abstract The main objective of this study/project is to document remote sensing techniques for mapping the environmental impacts caused by a long term mining activity. Orthophotographs were generated in several steps from the beginning of the Fifties up to the end of the last century. Additional information (land use, terrain, etc), provided from topographic maps, were included to visualize and quantify the 2- and 3-dimensional change of the surface mining areas. The GIS based data are needed for further planning purposes (governmental and non governmental) of the closed mining pits.

1. Introduction The beginning industrialization in Styria and in the Austrian Hungarian Empire enlarges a great demand for coal energy during the second half of the 19th Century. With the construction of a new railroad the Köflach-Voitsberg coal mining area got a well developed traffic line into the former Austrian – Hungarian Empire and into the international traffic network. After a short regression (First World War), the produc- tion of coal leaded to a prosperous industry (Köflach becomes 1939 an administrative town status), which developed after the Second World War and had his maximum in the very beginning of the Sixties. From this time on, influenced by the world market and low quality of the coal, a regression started, where the coal mining could only survive with an intensive support of the government. New mining areas were opened (1981) but the big show down could not be avoided. After the exploitation of most of the open mining areas and after cancelling a supply contract with an accompanying coal energy power station, to- day’s mining activity is closed. This development, which could be observed in other European regions, too, has significant influence to the landscape shaping (E. Brunnote et al. 1994). Mining activities will change the relief, housing and following land-use of closed mining areas will have impact of the landscape of the region, significantly (A. Lausch and F. Herzog, 2002). Quantification of the effects that mining activities have on ecosystems is a major issue in sustainable development and resources management. The project is embedded within a project “Ground water changes in Köflach-Bärnbach-Region” (W. Polt- nig et al. 2001) and was financed by the Styrian Government, the Mining Company and three accompanying towns (Köflach, Voitsberg and Bärnbach). The results of the project document these changes in relief and land-use/land-cover an associated environmental features by means of remote sensing tools.

2. Data and Information Sources and Data Processing The study area is located 50 km west of Graz (Austria), within a tertiary valley bordering the Alps in the north. The scattered coal mining areas are located within a densely urbanised built up area (3 towns),

1 Institute for Geography and Regional Sciences, University of Graz, Heinrichstrasse 36, 8010 Graz, Austria 2 Institute of Water Resources Management, Joanneum Research Graz, Elisabethstrasse 16, 8010 Graz, Austria

258 which causes a lot of land-use conflicts. A successful monitoring approach for evaluating surface proc- esses and their dynamics at a regional scale requires observations with frequent temporal coverage over a long period of time in order to investigate changes which are associated with human activities. Changes in the landscape can be investigated with time series analyses of aerial photographs, including a three dimensional aspect. DEM´s of several years has been generated to document and quantify the mining activities. Therefore 6 sets of aerial photographs were used from the beginning of the Fifties until the end of the last Century to map the spatial extent of mining activities. The analyses of topographic maps from the 18th, 19th and 20th Century provide additional information about former surface mining activities. The mappings and provided digital data have been intergraded into a GIS environment.

Year media f (cm) scale As of 1787 1. Österreichische Landesaufnahme - 1:2.880 (Josefinischer Kataster) Middle of 19th C. 2. Österreichische Landesaufnahme - 1:2.880 (Franciscäischer Kataster) As of 1919 Prov. edition of the Austrian Topographic map - 1:25.000 1952 Aerial photograph 21 1:14.000 – 1:23.000 1959 Aerial photograph 11,5 1:5.600 – 1:34.800 1963 Austrian topographic map 1:50.000 1975 Aerial photograph 15 1:14,0-19,0 1983 Aerial photograph 15 33,0 1984 Austrian topographic map 1:50.000 1989 Aerial photograph 15 26,0-39,0 1990 Austrian topographic map - 1:50.000 1996 Orthophotograph - 1m (resolution)

Tab. 1: Aerial photographs and topographic map data base

The aerial photographs and maps were scanned and georeferenced with ERDAS Imagine to provide on the one hand orthophotographs (resolution: 1m) from different years (1952, 1959, 1975, 1983, 1989, 1996) and on the other hand digital topographic maps from 1960, 1984 and 1990. Geometric pre-processing is an essential prerequisite for the combined processing of aerial photographs and diverse satellite images. In order to ensure spatial comparability of the remote sensing data as well as other spatial information (e.g. topographic maps, digital cadastre), to enable their integration into a GIS, all data sources had to be georeferenced to one common map geometry (M. Lepschi et al 2001). The aerial photos were geocoded to a grid size of 1m. For each acquisition year a mosaic was built from the single aerial photos.

3. Case Studies Results of the study are different GIS-based maps with topics, which are related with time changes: landuse/landcover maps and associated information about traffic network (streets and railways), drainage network, technical infrastructure, housing, relief, etc. The following figures are documenting some case studies of the project:

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C 200 m 200 m 1952 1996 200m 200m 200m 200m

Fig. 1: Orthophotographs of the eastern (up) and western (down) mining district

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Copyright © Masaryk University Brno, Brno 2005. ISBN: 80-210-3780-6 Figure 1 shows two orthophotographs of the eastern and western mining district (spatial extent is marked in Figure 3). The produced images have a resolution of 1m, which is sufficient to map significant landscape features of the investigation area. It shows the situation in 1952 (left), where the surface mining activities just have started (marked A), and the situation in 1996 (right) shows the maximum of surface mining activities (upper left region, B) before the shutdown. The former pit of the eastern district (C) is now used as a recreation area and sports ground. A comparable development can be detected within the western mining district. Figure 2 show the landuse maps of the whole investigation area, the legend is generated in respect to the official categories of landuse management plans.

1 km 1 km

Fig. 2: Landuse Maps of the whole investigation area from 1952 (left) and 1996 (right)

Figure 3 shows glimpses from a movie, which represents the 3-dimensional development of the mining areas, provided from analyses of the topographic maps. The arrows mark significant changes. All changes in relief are analysed in their volume changes, each mining district were documented in its height changes within the time series steps.

4. Conclusion The presented paper documents some case studies to map and monitor the surface mining areas by means of remote sensing techniques. Data pre-processing, visual classification approaches are performed on im- age data. A digital classification routine for satellite images which was performed on similar projects in Styria (M. Lepschi et al. 2001). Larger mining areas should be mapped by satellite imageries (Latifovic, R., Fytas, K., Chen, J., Paraszczak, J., 2005), smaller regions (like Köflach-Voitsberg) and the need for time series before the availability of high resolution satellite images can be done by aerial photographs, only. With stereoscopic aerial (and spaceborne high resolution) images it is furthermore possible to map the depth and the volume of mining areas and to generate a digital terrain model of it.

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Copyright © Masaryk University Brno, Brno 2005. ISBN: 80-210-3780-6 The results and developed remote sensing methods will help the government (planning departments) of the Province Styria or other (non)governmental (on the community level) institutions to monitor the development of mining areas– especially in that areas, where no or insufficient conventional (e.g. statistical) information is available; and to provide useful information for post mining landuse structure planning.

1963 1970 1980

1990 1995 1998

Fig. 3: Shaded relief from 1963 to1998 (original DEM resolution: 25m)

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