Man's Impact on Fluvial Processes in the Polish Western Carpathians

Abstract

The Western Carpathian Mtns of intermediate height are in the temperate zone. They belong to the Alpine mountain system; erodible flysch rocks are dominant.Pleistocene slope processes and the resulting aggradation of alluvia ended at the Pleistocene/Holocene transition, due to the quick succession of forest communities. As a consequence, the Holocene erosion took place in Carpathian valleys. The agricultural colonization which began in pre-historic times intensified in late medieval times, causing marked changes in the land-use pattern. Forest clearing favoured both erosion of the Pleistocene slope covers and deposition of this material in the Holocene valley floors. Since 3000 years B.P., natural levees have developed there.At the beginning of the 20th century, channel correction was undertaken on the major rivers. Both construction and shortening of the channels caused accelerated channel deepening. Rates of incision are still increasing.Large dams and reservoirs impounded in the last decades for hydro-electric purposes have tended to disturb drastically both the natural hydrologic regimen and sediment transport. Disturbances are especially distinct near the reservoirs, just upstream and downstream of the dams.