Overbank sediments along the middle Wieprza as a record of flood phenomena

Abstract

Today’s fl ood events along the River Wieprza assume a quite characteristic course entailing calm spillovers of water from the bed in places of riverbank lowering and in sections above and below bridges, where a narrowing of the channel is present. The identity of the land inundated relates to morphology, the near-channel part of a fl oodplain may be affected or those parts in depressions that serve as fl ood basins. Riverbank exposures on both sides of the present river channel plus pits reveal the construction of the Wieprza fl oodplain. The sediments that build the fl oodplain represent channel and overbank facies with subfacies of palaeomeander fi lls. Analysed exposures are located along the valley section between Slawsko and Staniewice, mostly in close proximity to the Early Mediaeval fortifi ed site of Wrześnica. The content of the exposures indicates that the uniform cover of overbank sediments across the fl oodplain emerged during the last 1000 years. It is now impossible to say when exactly, so it is unknown what the rank of the extreme fl oods which took place at the end of 19th century was, and what their role in forming the present fl oodplain.