Response of channel dynamics to recent meander neck cut-off in a lowland meandering river with artificial training history: the Morava River, Czech Republic

Abstract

One-decade-long observations of post-cut-off channel development and oxbow lake formation are presented to offer insight into the morphological response of the Morava River to neck cut-off. The main objectives were: calculation of the amount of sediment released to the channel by collapse of the meander neck; comparison of floodplain erosion and deposition rates before and after cut-off; and description of the rate and pattern of oxbow lake sedimentation. The amount of sediment released due to cut-off (~35 000 m3) equalled 2–5 years of sediment input by lateral erosion averaged for the past six decades. Bank erosion rates substantially exceeded long-term averages (0.63–6.21 m year−1, post cut-off). Despite a low entrance angle, alluvial plugs in a newly formed oxbow lake were established within a few months. Between 2006 and 2016, sedimentation of the alluvial plugs proceeded at an average rate of 0.55 m year−1, reflecting the time since cut-off and the frequency of overbank flows.