We were involved in 'Novel Approaches to Assess and Rehabilitate Modified Rivers' an international conference on river and stream restoration. Conference followed REFORM - Summer School (see report - link). Main scope and objectives of the conference was to enlarge awareness of the need and appreciation for the benefits of river rehabilitation.
Members of CZECH-RIVERS, Dr. Tomáš Galia and Dr. Václav Škarpich presented information about river restoration projects and monitoring in Czech part of the flysch Carpathians. Namely about: (i) Morávka River channel widening and (ii) Kněhyně torrent restoration project where we involved in the research monitoring.
Time schedule and basic description of presented contributions:
Anti-erosive construction in the Morávka River – problematic approach to management of flysch Carpathian rivers, Czech Republic
Authors: Václav Škarpich, Tomáš Galia, Jan Hradecký, Radek Dušek
June 30, 2015 (17:45 p.m to 19:15 p.m.) - poster presentation
During the last century the Morávka River channel has been transformed from anabranching to single channel river pattern that incised as deep as into the bedrock. These changes have been caused by a strong and inappropriate management (as a bank stabilising, weir and valley dam constructing). Contemporary channel changes have not been evident at reach r. km 7.0 to 10.5 which has partly preserved the original anabranching river pattern with lateral erosion. In order to preserve this anabranching channel reach and the prevention of proceeding backward erosion and protection against destruction Vyšní Lhoty weir at r. km 11.3 anti-erosion construction of local channel widening was constructed at r. km 10.7. However, spring flood in year 2010 accelerated present erosive processes and channel incision to the bedrock and showed that the antierosive construction was not well designed. In some parts, the original river bed has lowered by as many as 2.5 m. The anti-erosion construction itself has also been affected by massive incision. This paper summarizes results of monitoring, processes and function of anti-erosion construction of local channel widening with connection to bad management of Water Authorities in Czech Part of the flysch Carpathian Mts and discuss the problematic management solution of destabilized channel reach and gives proposition of the future management.
Torrent restorations in the flysch mid-mountain environment: The case study of the Kněhyně Torrent, Czech Republic
Authors: Tomáš Galia, Václav Škarpich, Jan Hradecký
July 1, 2015 (11:30 a.m. to 11:45 a.m.) - oral presentation
The occurrence of channel-reach morphologies (e.g., bedrock channels, step-pools, anabranching channels) in mountainous landscape is driven by several internal and external time- and space-variable factors. Especially, the identification of the sediment supply potential related to transport capacity is crucial for later stream management in torrential mountain channels. The contribution deals with theoretical aspects of stream restorations of this part of fluvial net with emphasis on the flysch Western Carpathians on the example of restored anabranching channel-reach of the Kněhyně Torrent. This channel-reach was partly renaturalized by the 100y flood event in 1997, when the single riprap-regulated channel was transformed into anabranching pattern with relatively large gravel deposits. Stabilization elements were added into the channel to preserve that morphology during the restoration project realized in 2003-2004. The field geomorphological mapping shows, that longitudinal disconnectivity in the form of checkdams exists in the stream longitudinal profile and recent potential sediment sources are limited at the watershed scale. These facts make difficult the sustainable preservation of the transport-limited conditions in the Kněhyně. We suppose, that the original anabranching pattern noticed by the 2nd Military survey (half of the 19th century) was resulted from the higher sediment supply caused by different land-use of mountain region and the important role was played by the sediment delivery driven by debris flows under suitable climatic conditions during the LIA. The role of potential sediment supply estimations, bedload transport modelling and dendrogeomorphological approach is discussed in order to better asses relationship between the sediment supply, transport capacity and resulted channel-reach morphology.