Investigating the Stream Network Changes and Landslide Processes in Open Coal Mining Areas Using Remote Sensing Methods

The paper presents integrated database created using as input information ground-based and remote sensing data for studying the changes of the stream network and the development of landslide processes in open coal mining areas. Remote sensing methods and GIS technologies make it possible to identify the areas with strongest manifestation of landslide processes and determine their spatial parameters. The advantage here is that the analysis is performed on an integrated basis, and not separately for the particular landscape components. The changes of the stream network and landslide processes over a 65-year period (1940-2006) on the territories of the land of Novi Iskur, Sofia Municipality, affected by coal mining were investigated. The development of coal mining arouses a number of geoecological problems, contributes to the intensification of erosion and landslide processes in the area and has negative impact on the Kutina Pyramids natural landmark located in its immediate vicinity. The thematic database created for the purpose includes archive panchromatic aerial photographs and high spatial resolution satellite images for various years (prior to, during, and after the exploitation period), large-scale topographic maps, data from terrain studies and GPS measurements, photos, climatic and geologic data, and other types of information. To reveal the changes in the stream network and landslide processes in the open coal mining areas, remote sensing methods in conjunction with geomorphologic and cartographic methods were used. Computer-aided visual deciphering and interpretation of the high spatial resolution aerial photographs and satellite images for the aforementioned years was carried out. It was supplemented by terrain and indoor activities, aimed to highlight the geological structure and precipitation regime and their impact on the development of the stream network and activation of landslide processes. Based on the created thematic database, a number of thematic cartographic models, tables, and graphs were produced. The morphologic and morphometric analyses revealed material changes in the relief structural elements' contours and quantitative parameters. The comparative data analysis makes it possible to identify the state and configuration of the stream network and the time course of landslide processes. As a result of the area's investigation, three stages may be identified. The first stage is related with the territory's natural development course during which the stream network was formed in a natural way and no landslide processes were observed. The second stage is the stage of active coal mining during which the anthropogenic factor played a leading role in the area's development. Dynamic changes in the structure of the stream network were identified (digging of canals, corrections of the riverbed of the Kutinska River), and steep unstable technogenic slopes were formed. The third stage begins after coal mining's termination. During this stage a recultivation of the investigated territory is performed which is still incomplete. It is characterized by the development of periodic landslide processes generating numerous geoecological problems. The created database for the investigated processes may be of use in landscape planning, for the needs of sustainable regional development, or to the local self-governing bodies.