COINCIDENCE OF CLIMATIC AND ANTHROPOGENIC FACTORS ACCELERATING THE SOIL EROSION AND FLUVIAL ACTIVITY

The role of climatic factor in the rate of denudation and deposition is discussed in the literature since long time. Generally it prevails the opinion that deforestation, soil cultivation and overgrazing accelerate the soil erosion by 2-4 orders, what documented in dozens of profiles of lake, proluvial and alluvial sediments. But in Holocene sequences of Central Europe we reconstruct much higher frequency of various kinds of heavy rainfalls, reflected not only in higher rate of deposition, but also in glacial advances and debrisflow activity in high mountains, landslide activity in flysch mountains, rise of lake water level, calcareaus tuffa precipitation in limestone plateaus and finally in avulsions of river channel and their tendency to braiding. These phases were dated at 8.5 -8.0, 6.5-6.0, 5.4-4.9, 4.5-4.1, 3.3-3.0, 2.8-2.7, 2.2-1.8 kyr 14C BP and V-VI c.AD, XIc.AD and Little Ice Age. Several phases of increased human activity coincide with above presented, the others not. The transition Atlantic-Subboreal is expressed by high soil erosion due to activity of late Neolithic farmers, replaced by shephards. The Bronze age soil erosion has no expression in the humidity increase. On the contrary humid Roman phase of extensive agriculture is expressed in aggradation going dowmstream upto lower course of the Vistula river. The abundance of farming causes that 5-6 -th century humid phase is not visible in accelerated erosion. Opposite picture we get in 11-th century and especially during the Little Ice Age, when the extensive agriculture is dominating.