Fluvial Imprints in Flysh Valley Bottoms—Topľa and Ondava Valleys

Abstract

The central part of Ondavská vrchovina upland represents a medium-altitude and moderately dissected relief with narrow elongated valleys. The Topľa and Ondava rivers are the main axis of flysch valleys and their flat bottoms are modelled by dynamic river processes acting upon thin layers of Quaternary sediments. They bear a record of all historical changes of the channel pattern, from a wide wandering gravel-bed wild river to a narrow and sinuous channel. Both rivers are characterized by distinct bank erosion, resulting in bank movement and bank retreat within meander bends. From an economic point of view, erosion of arable land and grassland is a negative consequence of channel migration. Vice versa, from an ecological point of view we can consider bank erosion as a natural process that leads to the increase of geo- and bio-diversity of the riparian landscape. Nowadays, ‘green approaches’ are applicable in the river management, aiming to eliminate technical interventions in the river basins and allowing for free channel migration. All these processes create valuable ecosystems with natural flood regime and floodplain forest.