Late Holocene evolution of the Bečva River floodplain (Outer Western Carpathians, Czech Republic).

Abstract: To reconstruct the geomorphic imprint of the anthropogenic and natural environmental changes in the Late Holocene, we studied the alluvial record of the Bečva River floodplain (Outer Western Carpathians, Czech Republic). Coring, geophysical sounding and lithological analysis of floodplain deposits supported by AMS (accelerator mass spectrometry) dating enabled the establishment of the primary evolutionary stages of Late Holocene floodplain evolution. During the Late Atlantic and Early Subboreal periods, gravel aggradation and braided environments occurred in the studied floodplain. The Late Subboreal and Early Subatlantic are characterised by overbank sedimentation, and the Middle Subatlantic is marked by the recurrence of gravel aggradation. A major incision phase took place during the Mediaeval Warm Period. The onset of overbank sedimentation in the 15th century correlated with ongoing deforestation of the lower parts of catchment, and colonisation of the mountain ridges during the 16th–17th centuries further accelerated this process. During the 20th century, reforestation of mountains and river-channel training resulted in a significant incision phase. Our data suggest that climate fluctuations were major driving factors for the morpho-sedimentary evolution of the floodplain approximately up to the 12th century, whereas in the latter evolution period, anthropogenic activity superseded natural factors. This transition occurred more than one millennium later than in other Central and Western European catchments. [Copyright &y& Elsevier]