There is no doubt that from the beginning of the Neolithic Age through the Bronze Age (approximately 1700 B. C.) and the Iron Age (from about 700 B. C.) till today higher and higher as well as more frequent flood waves have been observed in the river valleys of the East Mid-European Lowland. This phenomenon cannot be justified by climatic and weather changes observed in this period. They were neither big enough nor unidirectional to account for the intensification of floods. In the period under analysis, however, the numbers and population density increased in human communities, inhabiting not only the river valleys, but also other regions of the Mid-European Lowland. At the same time, the area of farming fields as well as the depth of cultivation increased. Regular grazing of cattle on the same meadows and more and more numerous herds contributed to the destruction of the sod. These phenomena were accompanied by more intensive extirpation of forests which were not capable of self-regeneration, particularly in the period of primitive mining and processing of iron ores, which was based on using a cinsiderable amount of timber.Thus it turns out that frequency and height of the flood waves in the river valleys of the eastern part of the Mid-European Lowland is due to anthropogenic factors, to an extent not smaller than to those natural, i.e. climatic, meteorogical and hydrological factors. On account of this considerable contribution of the anthropogenic factor, the contemporary fluviodynamic processes can and should be regarded as engineering-geological processes.