Antropogenous Forms as Part of Living Environment in North Bohemian Brown Coal Basin

Abstract

The origin of new antropogenous forms usually hinders the natural geomorphological development of the relief. The latter's character may even be fundamentally changed if the antropogenous forms are too many or cover too large areas. Consequently, it is necessary to study and evaluate the positive as well as the negative influences of the new forms upon the development of the future relief. Careful consideration should be given to the place of their location and to their shape. Knowledge resulting from such experience should serve as basis for the planning of the future artificial transformation of the countryside. A good example is the North Bohemian Brown Coal Basin. In this area deep mine working as well as surface mining have left their traces on the development of the relief. In undermined areas temporary sedimentation basins originated as a result of subsidence. Gradually they have been filled with water-worn materiaL The modern technique of surface mining resulted in piling up new dumps in these places, and thus a new antropogenous inversion of relief took place in which older concave forms became basis for new convex forms. When starting new dumps, apart from operational also economic and technical requirements, i. e. the appropriatness of occupying further agricultural land, the compactness of the substratum, the future possibility of recultivation and agricultural use must be considered. Dumps are usually piled up in two - most recently in three - levels, the height of individual levels being 20-25 m. At the present the surface of dumps is levelled down simultaneously as they are being piled up since it was found more economic from the viewpoint of operation. Older dumps have uneven surfaces showing differences of 10-15 m in height. They may only be recultivated as forests. Also in such cases many difficulties must be overcome caused by the origin of numerous erosion furrows and water-bearing soil in depressions formed between the individual ridges. The ideal form of a dump - from the economic point of view - is a dump pit with a flat, even surface slanting to one side at an agle of 2-5° enabling the natural run-off of the rain water and excluding any harmful effects of erosion. For the reason of making use of as much space of the dumps as passible their slopes become mostly abrupt (35-40°) by which landslides are favoured and recultivation becomes difficult. One of the most reliable methods of stabilising the slopes and incorporating them into the natural environment is to reduce their gradient. Dumps of such shape situated in a flat country or depression rise high above their environment in the form of "table mountains". They are surrounded with belts of wet up to morassic ground. As their weight pushes out the ground water to their fore-land the latter becomes water-laden. Dumps situated on flat summits or slopes of structural ridges disappear more easily in their natural environment. As an example may serve the dump north of Bílina whose scaled down surface passes smoothly into natural slope of a higher structural ridge. The increasing mining activity aimed at a complete mining out of areas in question, requires the opening of new mines and quarries and a subsequent removal of old dumps. At the present it is impossible to discuss the final arrangement of the new antropogenous relief of the whole area of the North Bohemian Brown Coal Basin. The only exception is the environment of Teplice where mining was abandoned completely, the mined out spaces have mostly been refilled and the surface of dumps recultivated. There are some areas where the, traces of the harmful effects of past mining activity have been removed by a proper arrangement of the terrain, for instance, the environment of Most - the arrangement of the south-eastern slope of the Ryzelský ridge, the recultivation of dumps situated along the southern margin of the town, and the construction of an artificial water reservoir in an abandoned quarry near Vtelno. The above exemples show some of the possibilites of recultivating the countryside affected by the mining activities. Proper situating of dumps, dressing and recultivating their surfaces may restore to life a countryside temporarily devastated by mining activities, and enable its further natural development as well as its agricultural exploitation in a new living environment.