Ongoing monitoring of tagged bed particles

We continue with the monitoring of bed particles marked by pit-tags, which have been installed into stream beds of two contrast small streams (check-dam impacted and close-to-nature pool-riffle stream) with similar catchment areas. The monitoring covered one bankfull event and several close-to-bankfull discharge events in following months. After ca. 21-month period, up to 350 m transport distance was measured for tagged particles in the check-dam managed stream; some of grains passed through four check dams. Similar transport distance (up to 300 m) was obtained in the pool-riffle stream. However, there were large differences in recovery rates of pit-tag-marked grains. We reached up to 65% recovery rate in the check-dam managed streams, but only 20-25% recovery rate prevailled in the pool-riffle stream. This notably low recovery rate is likely caused by higher morphodynamics of the pool-riffle stream, which caused frequent burying of the marked grains into gravel-bed deposits during sediment transport-effective discharges. We are planning to continue this monitoring also in the following year; this will also include a development of rating curves for both studied streams, which will allow us to create direct relations between the critical discharge and transported distance (or size) of tagged particles. 

Monitored check-dam impacted stream

Monitored pool-riffle stream

Abandoned channelization works in Beskydian steep streams

The major part of the Moravskoslezské Beskydy Mts. was unaffected by human activities until the 17^th century. Since that times, local forests started to be managed as sources of timber and first villages have been built the valleys. At the turn of 19^th and 20^th century, the first large flood-protective structures had been constructed, which mainly consisted of long stone embankments and check dams. Some of these structures were later not needed and local authorities did not attempt to repair them after damages caused by flood events. We are still able to find their remains in some headwater parts of the mountains. Nowadays, they can act as disconnectivities in lateral sediment flux by abruption of effective hillslope-channel coupling or by contrast, they can serve as sources of coarse (for the most time except extraordinary floods immovable) sediments into stream channels. Nevertheless, their presence clearly documents past vital activities of local people in relatively inaccessible headwater parts of the mountain valleys.      

Long stone embankment, the Slavíč Stream

Remains of check dam, the Slavíč Stream

Predictors of low instream wood abundance in Cretan steep streams

Our new paper demonstating the role of low tree density in riparian corridors on low abundance of instream wood in steep nonperennial streams was just published in Water Resources Research. Thus, the paper provides deeper understanding of recruitment and retention procecess of instream wood at the reach scale in vulnerable environment of Mediterranean semiarid landscapes, which was based on our detailled measurements in 37 independent channel reaches in Lefka Ori Mts., Crete, Greece. The parameter of elevation controlled mean annual percipitations, which in turn were reflected in the composition of riparian canopy along the steep mountain streams. It is also interesting that the mobilized wood tended to be stored as individual, dispersed pieces rather than in jams, likely due to overall low instream wood abundance which effectively prevented clustering of wood into large jams.

Deposited instream wood in the Kallikratis gorge. 

The study of river restoration potential of the Černá Ostravice River

Human interactions with mountain streams in Czech part of the flysch Western Carpathians has more than 100 years of history. These are represented by indirect impacts since the 16th century linked with an extensive changes in land use, and by direct human interventions connected with control works, check-dam constructions (e.g., due to timber floating, flood protection, sediment regime control). We finished project which was focused on potential restoration measures in the Černá Ostravice River basin in Moravskoslezské Beskydy Mts in Czech Republic. The project was realized in cooperation with the Union for the Morava River. The study proposes potential measures to improve hydromorphological and habitat conditions in the lower reach of the Černá Ostravice River. The main measures were aimed to increase stream connectivity for aquatic communities or sediment flux, increase morphological heterogeneity and occurrence of instream wood as element affected better stream habitat conditions and increase of water retention in floodplain.

Bank stabilization structures protecting road.

Regulated channel (partially due to timber floating).

Check-dam controlled longitudinal profile of the channel.

Carpatho-Balkan-Dinaric Conference on Geomorphology

Our fluvial group presented research on Carpatho-Balkan-Dinaric Conference on Geomorphology. The Conference was held from June 24 to 27, 2019 at Szeged in Hungary. It was focused on rapidly changing world, various environmental hazards which cause considerable damages and loss of life, or their consequences change the rate of geomorphological processes and forms in the Carpatho-Balkan-Dinaric Region. We participated in sessions which were focused on problematics linked with human impact on fluvial processes and systems. Our contributions were dealing with Morphological response of mountain streams to long-term human interventions in the Czech Carpathians presented by Tomas Galia, Fluvial system diversity in relation to confluence hydrodynamic zone – a review study by Lukáš Vaverka, Morphological effects of long-term low sediment inputs – the Elbe River by Jan Hradecký, Public perception of gravel bed rivers. A case study from the Czech Carpathians by Zuzana Poledniková, Possibilities for stopping of further degradation gravel-bed Morávka River by Tereza Macurová, and Conceptual framework for restoration of Czech Carpathian Rivers by Václav Škarpich.

Check dams decrease the channel complexity of intermediate reaches in the Western Carpathians

Our new article published in Science of the Total Environment focuses on potential degradation of mountain channels affected by direct human interventions. We dealt with four channel complexity dimensions (longitudinal, cross-sectional, large wood and bed sediments) of foothill and steep streams treated by check dams. We observed that check dams altered the channel complexity of intermediate reaches (i.e., reaches between subsequent check dams) when compared with reaches of undisturbed streams. A higher degradation was typical for a foothill unconfined stream (S = 0.01-0.02 m/m), where this stream completely lost its vertical bed oscillations because of the transformation of pool-riffles to a uniform plane bed morphology. On the other hand, a steep stream (S = 0.06-0.12 m/m) indicated an increase in sediment homogeneity when compared to an untreated stream, but this management did not heavily affect longitudinal or cross-sectional heterogeneity. Due to the presence of managed riparian corridors, we did not observe differences in instream wood abundance between treated and untreated streams.

Galia, T., Škarpich, V. Ruman, S., Macurová, T. (2019): Check dams decrease the channel complexity of intermediate reaches in the Western Carpathians (Czech Republic). Science of the Total Environment 662, 881-894. doi: 10.1016/j.scitotenv.2019.01.305

Participation on the traditional conference of Czech Association of Geomorphologists

We participated on the traditional conference of Czech Association of Geomorphologists. 19th International Conference "State of geomorphological research in 2019", this year titled „Český ráj ´19” was held in the Bohemian Paradise in Parkhotel Skalní Město near Jičín from 3rd to 5th April 2019. It was organized by the Institute of Rock Structure and Mechanics of the CAS, in cooperation with Bohemian Paradise Geopark.

The conference venue was situated in the geomorphologically attractive area of Bohemian Paradise, near the famous Prachovské skály rock labyrinth. This unique area, formed by sandstone plateaus of Bohemian Cretaceous basin and dominant landmarks of Tertiary neovolcanic intrusions, offers some of the most spectacular landforms.

We participated with oral and poster presentations with focus on problematics of check dams in mountain streams and their effect on channel complexity, effect of instream wood on fluvial processes in the Odra River, perspectives of gravel bars in the sense of planned lock chamber construction in the lower Elbe River, a confluence hydrodynamic zone as integral part of fluvial system diversity and mapping geomorphic (dis)connectivity in the human modified landscape of the Slavíč River valley in the Moravskoslezské Beskydy Mts.

Proceedings were published (here).