Degradation of multi-thread gravel-bed rivers in medium-high mountain settings: Quantitave analysis and possible solutions

The new article about possible solution of gradually transformed Morávka River channel was published in April 2020. The research was realized with Nature Conservation Agency of the Czech Republic in 2017 (see report here).

The Morávka River was characterised large amount of gravels transported from mountainous area of Beskydy Mts to the forefield. Presently, large volumes of gravels is stopped in the upstream part of the Morávka R. basin by a water reservoir and we should also note the presence of check dams in small tributaries together with increase in forested area during 20th century. A combination of field and laboratory research with modelling of the transport stage and the potential bedload transport to determine the dominant discharge was used to understand the process that is necessary to manage Morávka River system. Artificial disturbance of the vegetation cover (which stabilise gravel material) and the relatively rare high-magnitude floods were identified as important factors that could help to increase and preserve the Morávka River active channel dynamics (in Skalická Morávka nature reserve especially). Because sediment balance of the Morávka River system was negatively affected, the estimation of the sediment material deficit as a tool for support, protection and sustainability of the close-to-natural multi-thread channel reach in the nature reserve was necessary. The estimation of absent sediment volumes during ~1- and 20-year recurrence interval of mean daily discharges based on the analysis of eroded material from repeatedly measured cross sections will help to stop further degradation of other multithread gravel-bed rivers. More about these conclusions are available in article which was published in journal Ecological Engineering.

Schematic showing estimated parameters for eroded material volume calculation of individual segments in the upper part of the nature reserve in the monitored one-year period, showing examples of cross sections at 10.33 r. km; d′i is ½ the length between the given cross section and the adjacent upstream cross section, di is ½ the length between the given cross section and the adjacent downstream cross section, Vi, year is the volume of the eroded/aggraded material of the individual segment in the monitored one-year period, Xi-X'i shows the schematic location of a cross section, (A) Ai, year−1 is the flow area of the channel from the cross section at the beginning of the one-year monitored period in the section where erosion was observed at the end of the monitored period, and (B) Ai, year is the flow area of the channel in the section where erosion was observed from the cross section at the end of the one-year monitored period.

The extension of gravel bars and islands in the active channel of the Morávka River in the nature reserve between 2000 and 2016 and in 1955.