Past and present interaction between the catchment and the valley floor: Upper Osoblaha basin, NE Sudetes slope and foreland

The Osoblaha basin includes the north-eastern slope of the Zlatohorska Vrchovina ridge and the north-eastern foreland area of the undulating Głubczyce Plateau. Rainfall ranges from 1000 mm/year in the highlands to 650–700 mm/year on the Głubczyce Plateau.The mountain part of the Osoblaha basin was already penetrated by humans in prehistoric times. Miners extracted gold from the alluvia and later from the slope covers. Their activities have left traces such as extant pits in sediments. Iron and other ores were mined and processed there from the early Middle Ages onwards. In the 12th or 13th century at the latest, settlements and towns were founded for mining (e.g. Janov, Zlate Hory) and by farmers who tilled the land at the foot of the valley slopes.This exploitation of the mountainous part of the basin caused significant clearance of beech forests as the wood was used to manufacture charcoal. The deforestation of the valley slopes or the introduction of spruce forests in lieu of the beech forests changed the circulation of rain and thaw water. Exposed slope covers were prone to erosion or liquefaction and transfer towards the mountain valleys. Flood episodes caused the sedimentation of clayey overbank deposits, which cover the valley floor. The considerable cohesion of these sediments was conducive to the formation of meandering or anastomosing channels which were a typical feature of the Osoblaha valley floor in the area around the confluence of the Zlaty Potok–Prudnik in the second half of the 18th century and in the 19th century.The Głubczyce Plateau is a 30–40 km wide area consisting of undulating plateaux ranging from 320 to 240 m a.s.l. These are dissected by dry valleys and descend gently towards the north. Fertile soils, the abundance of local streams and a climate conducive to farming led to this area being settled by farming and herding communities as early as the Neolithic period, around 7000 BP. This initiated the deforestation process and increased soil erosion, shown by the colluvia accumulated in the valley heads of dry valleys and by alluvial fan sediments close to their mouths where they entered the main valleys. The last stage of farming colonisation of this part of the Osoblaha basin, initiated by Slavs, had already led to the development of a dense network of settlements and considerable deforestation in the Mediaeval Period.