Friday, 23 November 2018

Our research of instream wood in Mediterranean environment

This year, we continued with investigations of the abundance and geomorphic effect of instream wood in Mediterranean fluvial systems. In June, we again visited the Lefka Mts (the highest mountain range in Crete, Greece) to assess predictors of instream wood loads in intermittent and ephemeral streams draining this mountain range. We measured parameters of wood together with channel geometry and riparian forest characteristics in ca. 40 channel reaches. The preliminary results show that the frequency of instream wood has rather a random character, whereas the biomass in riparian forests is important for instream wood volumes in small Mediterranean channels. 

Wood deposited by a previous flood outside the bankfull channel.

Step consisted of instream wood acting as sediment retention element.
During late September, we also investigated characteristics of instream wood in larger intermittent river (the Evrotas) draining the Peloponnese peninsula. Together with colleagues from Hellenic Center of Marine Research (Dr. Vardakas, Prof. Kalogianni) we also tried to find connections between the occurrence of instream wood and local endemic fish species. The examined river is interesting by alterations of hydrologic (dry vs. wet channels) and geomorphic (single thread vs. wandering) patterns. These alterations are reflected in the abundance of instream wood together with the character of riparian trees and occasional removal of instream wood by local people.

Instream wood in a single-thread wet reach.

The stump transported by a previous flood into dry wandering channel.
Now we are processing field data from both studied areas and we are planning to prepare related scientific articles during the first moths of 2019.      

Monday, 12 November 2018

Field excursion about river restoration projects in Upper and Lower Austria

The field excursion trip took place for students of our Department of Physical Geography and Geoecology from 5 to 8th September 2018. The main idea was showing river restoration projects in Lower and Upper Austria, namely on the Danube River and its tributaries, e.g. on the Traun River or the Ybbs River.
On Tuesday 6th of September, the first day of field excursion trip was focused on river restoration projects in urban area of Linz City. Especially, on the restoration of gravel bars on the left-side bank of the Danube River and future vision of river restoration of Danube River, e.g. creating of islands and side-channels in Urfahr District.
The second day of excursion was focused on the river restoration projects in downstream part of the Ybbs River. We visited reaches between Greinsfurth and Winklarn villages where river restoration were realized, e.g. fishpass through Greinsfurth hydropower dam (or weir), distributary of the Ybbs River near Winklarn for increasing of biodiversity and heterogeneity of channel, or restoration of mouth of the Ybbs River to the Danube River.
The third day, we visited hydropower dam in Melk with lock chamber for river navigation on the Danube River. The last stop was close-to-natural fishpass through hydropower dam in Melk.

Restored gravel bars on the left-side bank of the Danube River in Linz.

Fishpass through Greinsfurth hydropower dam.

Greinsfurth hydropower dam.

Presentation of river restoration of distributary near Winklarn.

Crossing through the restored reach Ybbs River near Winklarn.

On the hydropower dam in Melk.

Field Excursion was supported by Moravian-Silesian Region  

Wednesday, 24 October 2018

Effect of hydraulics of regulated and re-naturalized channels on grain-size parameters

With co-operation with our colleague Assoc. Prof. Dr. Zdeněk Máčka from Masaryk University, we published article about effect of hydraulics of regulated and re-naturalized channels on grain-size parameters in Science of the Total Environment multidisciplinary journal.

The grain-size characteristics obtained on 68 gravel bars were confronted with modelled flow hydraulics and information obtained by fluvial-geomorphic mapping along 14.0-km river reach of the Bečva River (Outer Western Carpathian Mts., Czech Republic). The studied channel reach is presently characterized by several distinctive sections: for a long time (ca. 100 years) regulated single channel sections with artificial bank stabilizations incised several meters in the floodplain and by contrast, multi-thread channel patterns of two sections, which have witnessed retrograde development after large floods in 1997 and 2010.
The mapping of sediment (dis)connectivity brought important findings about the character of sediment flux in the studied reach, which were confronted with simulated cross-sectional hydraulics. We demonstrated that in the case of a high occurrence of lateral sediment inputs (tributaries, bank failures) and longitudinal sediment flux disconnectivities (weirs or boulder ramps), the assessment of the longitudinal distance, bar grain size and simulated hydraulics submerging bars did not produce any clear relationships. Although the sections with re-naturalized multi-thread patterns showed distinctive hydraulic variables (i.e., larger wetted width or lower unit stream power), we did not observe direct relationships with their bar sediment sizes. This implies that for complex fluvial systems of multi-thread rivers as the transition reaches connecting mountainous and lowland areas, even those in unconfined valley settings out of the primary sediment sources, additional factors (i.e., effect of bank failures and especially tributaries as sediment inputs, weirs or boulder ramps as sediment flux disconnectivities) beyond local flow hydraulics and distance from the main sediment sources contribute to better explanation of the downstream evolution of grain-size patterns.

View of the Bečva River channelized (managed) single channel sections (A, C, E) and retrogradually developed (re-naturalized) multi-thread channel sections (B, D).

Wednesday, 3 October 2018

River Flow 2018 - Ninth International Conference on Fluvial Hydraulics

We participated on the River Flow 2018 - Ninth International Conference on Fluvial Hydraulics. Conference was held from 5 to 8th September 2018 in Lyon-Villeurbanne (France). It was organized by the IAHR Committee on Fluvial Hydraulics. River Flow Conference is one of the major international conference in river engineering and fluvial hydraulics since 2002. Conference is focused on the latest findings in the field of fluvial hydraulics, addressing fundamental issues related to fluid processes of sediments and pollutants in rivers and practical issues related to river morphodynamics, river restoration, and river interaction with structures.
We participated with oral presentations with focus on problematics of large wood occurence and mobility in contrast (e.g. of Medirranean or Temperate) mountain streams in Europe and problematic of Carpathian river channels transformation and its effect on ecosystems and also on human society.
Scopus indexed proceedings were published. The PDF versions of papers are available via link here and here

Tuesday, 3 July 2018

New project about bedload sediment regime of torrent streams in Czech Republic was received

Within the fund program of the State Forest Service (LCR, s.p.) in Czech Republic, project about bedload sediment regime of Czech Republic torrent streams was received. Main members of Czech-Rivers research group, namely assistant professors RNDr. Václav Škarpich, Ph.D., RNDr. Tomáš Galia, Ph.D. and Associate Professor RNDr. Jan Hradecký, Ph.D. from Department of Physical Geography and Geoecology are participating in project which will be realized within cooperation of Masaryk University in Brno and the lead partner Envicons, s.r.o. from Pardubice (Czech Republic).
The main aim of the project will be focused to bedload sediment regime quantification of torrent streams in the area of the Moravskoslezské Beskydy Mts., Hrubý Jeseník Mts., Orlické hory Mts., České středohoří Mts., etc. Target of activity is to bring the outputs to management practice of bedload sediment material in torrential streams managed by the State Forest Service in Czech Republic.