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.
