Centurial changes in channel processes and their contribution to the sediment budget of a lowland river: The influence of river regulations

The Tisza River in Central Europe has experienced significant changes in its sediment budget since the mid-19th century due to engineering works. The aim of the research is to reconstruct the sediment budget and to assess the effects of various river training works. The analysis of historical maps and channel cross-sections from 1838, 1890, 1929, 1976, and 2017 revealed that channel mobility was high until the early 20th century, after which it gradually declined to one-tenth of its original rate. Lateral erosion and deposition played a crucial role in sediment flux, contributing up to 38–92 % to the sediment flux in some units. Artificial meander cut-offs mobilised large amounts of sediment from the pilot channels that were mainly deposited downstream. By the early 20th century, the sediment budget had reached a state of quasi-equilibrium. However, the increased construction of revetments in the mid-20th century led to an increase in in-channel sediment deposition. The dam and reservoir constructions of the 1970s transformed the river section into a sediment source. Thus, the sediment budget of the Tisza has had significant spatiotemporal variations from net sediment balance to net deposition and finally to net erosion across the centennial scale. • Artificial cut-offs increase the sediment flux of rivers by erosion of pilot channels. • Pilot channels are sediment sources and cut off channels are sediment sinks. • Revetments increase lateral accumulation and sediment trap behaviour of a river. • The modern sediment flux of the Tisza River is one tenth of the 19th century's. • Lateral erosion and accumulation overwhelmed vertical processes throughout centuries.