A comprehensive view of sedimentation and erosion processes in small reservoirs: a case study of the Pocheň reservoir, Czech Republic

ABSTRACT This article focuses on the need to improve current knowledge of sedimentation and erosion processes in small reservoirs using the example of the Pocheň reservoir (Czech Republic). We combined data from sediment cores with unmanned aerial vehicle imaging and ground-penetrating radar survey data. The results show a distinct sediment distribution, grain-size gradient, petrophysical properties, and geochemistry. Sediment thickness increases in the proximal-to-distal direction (from the inflow to the dam) with frequent erosion near the inflow, especially during floods. This contributed to the sediment relocation towards distal sites with a tendency towards downstream accretion. After reservoir flushing, sedimentation processes were replaced by drawdown-enhanced erosion. Considerable erosion occurred along a temporary drawdown channel, resulting in headward erosion and channel incision. Lateral erosion resulted in drawdown-channel widening. The most extensive lateral erosion took place in the middle part of the reservoir, where the channel created a complex multichannel-branched system.