A central European alluvial river under anthropogenic pressure: The Ohre River, Czechia

Detailed geomorphic evaluation, drill coring, and analysis of floodplain sediments, along with geophysical imaging, were used to study the evolution of the youngest terraces and palaeo-meanders in the lower reach of the Ohre River. Floodplain sediment dating was performed by optically simulated luminescence and via the examination of sediment contamination from historical mining of metals in the river catchment. Two river segments were studied. In the upper segment, the Zatec area, the trunk channel persistently incised from the Early Holocene to ca. 2 ka, and in historical times the meandering channel changed to a low sinuous channel in a narrow channel belt. The terraces and palaeo-meanders in the Zatec area are younger than indicated in the geological maps, by one to two orders of magnitude. In the lower segment, the Pisty area, 60 km downstream, approximately half of the sediments in the floodplain transect are the Early to Middle Holocene age and the other half are younger than approximately 1,000 years, in particular from the last five centuries. The deposits of the current channel belt in the Pisty area are coarser (mostly sandy in the top metre) than in the rest of the floodplain (mostly silty in the top metre), indicating that the river must have undergone a substantial transformation in the last few centuries. We hypothesise that the trigger of this change was upstream channel straightening and lateral stabilisation, which reduced the amount of river-transported materials. Although the river catchment has been subjected to anthropogenic activity (including intense agriculture in the lower reaches), the river does not show enhanced aggradation.

Automated summary

A study on the evolution of terraces and palaeo-meanders in the lower reach of the Ohre River used various methods such as geomorphic evaluation, drill coring, and floodplain sediment analysis, revealing significant changes in the river channel over historical times. The sediment age in the Zatec area was found to be younger than previously thought, while in the Pisty area, there was a substantial transformation in river deposits in the last few centuries.