How much gravel we need to have in a gravel-bed river?

In the past decades we observe gradual degradation of Czech and Polish Carpathian rivers. Whereas afforestation in Tatra Mts (reducing sediment supply), channelisation works and gravel mining are the main problems in Poland for channel incision (e.g., Zawiejska et al. (2010),  Wyzga et al. (2016),  Hajdukiewicz et al. (in press)), Czech rivers are often affected by the presence of water reservoirs stopping sediments from upstream and we noted more intensive channelisation works owing to the high population density in the Czech Carpathian forefields (e.g. Škarpich et al. (2013), Galia et al. (2016), Škarpich et al. (2016)). Unfortunately, this channel degradation (narrowing of channels, incision up to bedrock, loss of gravel bars) endangers also preserved wandering fluvial system in Skalická Morávka Nature Reserve. 

Presently, large volumes of gravels is stopped in the upstream part of the Morávka basin by a weir in Vyšní Lhoty, by Morávka Reservoir and we should also note the presence of check dams in small tributaries together with increase in forested area during 20th century. Therefore, Nature Conservation Agency of the Czech Republic is preparing a new management plan for the following decade, which includes management of gravels in the nature reserve. We have participated in calculations of missing gravels in the nature reserve, calculations of loss of bar habitats between 1950s and the present and we tried to determine dominant discharges, which would be able to sustain gravel bars and migration of channels in the reserve. It seems that huge volume of gravels (ca. 20 000 - 25 000 meters cubic) are missing in the upper part of the reserve. Much of this incision occurred during 20-50y flood in 2010. We expect that two-years daily discharges as well as large floods are important for preservation of the wandering system, reflecting natural hydrologic regime of streams based in flysch lithology. On the other hand, the river need to carry sufficient amount of gravels (up to several thousands meters cubic) during individual high-flow events to prevent from further incision. Other actions as artificial disturbations of gravel-bar surfaces, artificial flooding and close-to-natural bed stabilisation elements were suggested.       

Partially degraded wandering channel in Skalická Morávka Nature Reserve

Proposal of universal symbology for detailed fluvial geomorphic mapping

With co-operation with cartographer Jan Miklín, we presented a proposal of universal symbology for geomorphic mapping of wadeable streams. The symbology includes individual channel and floodplain forms as well as selected important fluvial processes (i.e., erosion or deposition within a channel), grain-size characteristics of bed sediments or human interventions (e.g., several types of bank stabilisations or grade-control structures). The symbology has been recently published by Journal of maps, when we tested this mapping approach in three different locations (semi-confined valley with the presence of dumps from mining activity, confined high-gradient channel and mountain stream altered by bed sills). Individual symbols (prepared for ESRI ArcGIS) are ready for download  as supplemental material. 

New book: Open Channel Hydraulics, River Hydraulic Structures and Fluvial Geomorphology: For Engineers, Geomorphologists and Physical Geographers

On September 1, 2017 new book with name Open Channel Hydraulics, River Hydraulic Structures and Fluvial Geomorphology: For Engineers, Geomorphologists and Physical Geographers published by CRC Press.

The book presents practical hydraulic and river engineering research along with fluvial geomorphological concepts, and links the theoretical and practical knowledge of people working every day with rivers, streams, and hydraulic structures to fluvial geomorphology. The book also provides material for students to acquire the knowledge and skills to rehabilitate rivers, streams, and waterways.

The book was edited by Artur Radecki-Pawlik, Stefano Pagliara, Jan Hradecky and Erik Hendrickson and consist 508 Pages (20 Color) and about 257 illustrations.

We participated in three chapters with names: (i) Selected Principles of Fluvial Geomorphology (Jan Hradecky and Václav Škarpich), (ii) On Measurements of Fluvial Geomorphology Parameters in The Field (Vaclav Skarpich) and (iii) Geomorphology and Hydraulics in Steep Mountain Channels (Tomas Galia).

New cooperation with colleagues from Masaryk University

In the last week of June, we started research in the Bečva River basin with colleagues from the Department of Geography, Faculty of Science, Masaryk University in Brno. Main topic will be detailed analysis of grain-size composition of Bečva River gravel bars. Study will be focused on surface and subsurface grain-size composition downstream trends of sediments from the confluence of Rožnovská and Vsetínská Bečva Rivers to the mouth to the Morava River. Special thanks belong to bachelor students Tereza Matušková and David Hradil and PhD student Lenka Tlapáková for their help.

Two-hundred years long history of direct human impact on Beskydian headwater channels

Two new scientific publications were released from the area of the Moravskoslezské Beskydy Mts, which deal with direct and indirect human impact on local steep channels. Our recent article in Catena describes the geomorphic impact of stream crossings on adjacent channel reaches. Under co-operation with dedrologeomorphologists from Dendroman group, we reconstructed the history of channel incision downstream culverts. We also documented notable changes in channel geometry upstream and downstream these constructions together with the size of bed sediments, which could have a negative effect on local biota. 

The scheme of observed geomorphic effects of culverts. 

The history of direct (torrential works, timber floating, instream wood removal) and indirect (land use changes related to sediment supply) impact on Beskydian streams is now comprehensively presented in the article published in Geografie (in Czech, but with English summary). We documented that although the Moravskoslezské Beskydy Mts were for a quite long period without settlements or extensive medieval mining activity, the indirect impact began at the turn of 15th and 16th in relation to Vallachian and Pastoral colonization. Later in 19th century, many streams were used as transport routes for timber, which is still reflected in their recent cross-sectional geometry. Since 1906, torrential works have been applied and recently, up to 150 km of stream courses is managed by artificial bank stabilization and grade-control structures (check-dams, block ramps).       

Check-dam built in 1920s in the Morávka Basin.

Our participation on the traditional Czech conference of geomorphologists

Between 17th and 19th of May, 2017, we participated the 17th international conference State of geomorphologic research in 2017, which was held this time in Pec pod Sněžkou (Krkonoše Mts). Dr. Galia presented the present stage of instream wood research in Carpathian headwaters, whereas Dr. Škarpich demonstated the relations between the bar grain-sizes and local flow hydraulics in the gravel-bed Bečva River. Moreover, the poster proposing map symbology for small channels was prepared by co-operation with our department colleague Jan Miklín. The conference was also the first occasion to present the research of our new PhD student Tereza Macurová for scientist community. She showed the results of her magister thesis dealing with channel geometry, bed grain-sizes and fluvial processes in the Kobylská Stream (Moravskoslezské Beskydy Mts, Western Carpathians).

• Galia, T., Šilhán K., Ruiz-Villanueva, V., Tichavský R.: Geomorphic function and residence time of instream wood in steep headwater channels: a case study from the Mazák Basin, Moravskoslezské Beskydy Mts.
• Macurová, T., Škarpich, V.: Downstream variation in bed sediments in the Kobylská mountain stream based in flysch geologic structures (Vsetínské vrchy Mts)  
• Miklín, J., Galia, T.: Detailed fluvial-geomorphologic mapping of wadeable streams: a proposal of universal map symbology
• Škarpich, V., Galia, T., Ruman, S., Máčka, Z.: Downstream variations in bar grain sizes in the context of managed and re-naturalized channel reaches of the Bečva River

The conference proceedings with abstracts will be prepared for download here.

   

Václav Škarpich during his presentation.

Instream wood dynamics in Carpathian headwater streams

New results were published from ongoing research of instream wood in Czech Carpathian headwaters. Our recent article in Geomorphology prepared in co-operation with colleagues from the University of Geneve (Dr. Ruiz-Villanueva and Prof. Stoffel) deals with the residence time of typical tree species of Carpathian forests (Norway spruce and European beech) in small channels of Mazácký Grúnik Natural Reserve, Moravskoslezské Beskydy Mts (Fig. 1). We investigated that spruce logs indicated more than two times longer mean and maximal residence times as compared to European beech based on the successful cross-dating of 127 logs (Fig. 2). Maximum obtained residence time in the headwaters was 128 years for spruce and 59 years for beech, whenlog age and log diameter played the most important role in the preservation of wood in the fluvial system.Instream wood creating steps or logs accumulated in jams did not show any differences in residence time as compared to nonfunctional pieces. Shorter residence time was found for hillslope-stabilized wood when compared to unattached wood entirely located in the channel or pieces stabilized by other wood or sediments. We also documented that large flood events recorded by nearby gauging station or by dendogeomorphic methods (dating of exposed roots by channel erosion) were not always responsible for tree mortality and delivering of wood into local channels and thus, another important agents of wood recruitment than lateral erosion (e.g. windthrows, mass movements) should be considered.

During last days, we measured topography of the Mazák Stream and installed RFID pit-tags into fifty logs in order to observe their movement during future hydrogeomorphic events (Fig. 3). To compare wood and sediment dynamics, we also added ca. 70 stones with pit-tags (ca. D50 grain-size) on channel bed.

Fig. 1. Cross-dating performed in the headwater channel

Fig. 2. Depletion rate of European beech and Norway spruce in the studied channels

Fig. 3. Geodetic measurements and pit-tags installation

   

New textbook released

The textbook of Fluvial geomorphology designated for students of the Department of Physical Geography and Geoecology of the University of Ostrava (author's affiliation) was released. It is written in Czech language and its aim is to present principal concepts of fluvial geomorphology as same as basics of channel hydraulics, watershed management, river restorations and modelling of morphodynamics and sediment transport. The textbook can be also useful for students of related subjects (general geomorphology, hydrology, environmental sciences, water resources engineering) and other people interested in fluvial systems. It can be ordered via secretariat of the Department (black/white softcover print, 186 pages, price 200 CZK).

Front page

Within the EPSILON programme for the support of applied research and experimental development of the Technology Agency of the Czech Republic, Risks identification and possibility of support of landscape natural functions in landscape protected areas influenced by climate change project was received.

Members of Czech-Rivers research group, namely associate professor RNDR. Jan Hradecký, Ph.D., assistant professors RNDr. Václav Škarpich, Ph.D., RNDr. Tomáš Galia, Ph.D. and Mgr. Stanislav Ruman, from Department of Physical Geography and Geoecology are lead partners of project. Other project partners (i) EKOTOXA  s.r.o. and (ii) T. G. Masaryk Water Research Institute, public research institution are involved in this project.

The main objective of the project is to identify risks arising from the predicted climate change impacts on the landscape and its features in the model area PLA Beskydy. On the basis of the sensitivity and vulnerability of the landscape identifying the main problems and subsequently designing variants of suitable adaptation measures and appropriate management models in order to support the main features of the landscape and thus create conditions for the existence of valuable habitats and species in the changed climate conditions. The project outcomes will be generalized and provide professional support for public administration authorities for decision making and conceptual activities in ensuring the effective conservation of PLA, taking into account climate change.

Channel bed adjustment to over bankfull discharge magnitudes of the flysch gravel-bed stream – case study from the channelized reach of Olše River (Czech Republic)

This research is dealing with the Olše River in the Czech part of the Flysch Carpathians. It summarises the results of the increased kinetic energy of flowing water of contemporary channel based on the analyse of hydraulic parameters of channel. The comparison of geodetic measurements from 1960 and 2003 was used together with the assessment of aerial photos from 1950s and present. The active Olše R. channel was narrowed from 35 m in 1955 to 24 m in 2010 in the studied reach. In some locations, the original river bed has lowered as much as 2.3 m between the years 1960 and 2003. Morphology of the Olše River channel has accelerated these erosion processes. The main reason for this is an adjustment of water flow dynamics. The unit stream power and hydraulic radius values have increased two to three times from 1960 to 2003 for 5, 20, 50 and 100-recurrence interval discharge. Incision of channel greater than 0.10-0.21m in the studied period was affected especially by change in cross-sectional geometry and lower than 0.10-0.21m may reflect other factors such as sediment disruption operating in the basin (e.g. with land-use changes, gravel mining etc.).
 
The paper has been recently published in Zeitschrift für Geomorphologie.

Cross profiles, water level stage and w during the 100 R.I. discharge (the source of discharge data was provided by Povodí Odry Enterprise, R.I. discharges were derived from the Jablunkov-Olše gauging station) in 1960 (grey colour) and 2003 (black colour) in the studied river reach of the Olše R.: a – 56.163 r. km; b – 57.601 r. km; c – 58.604 r. km; d – 59.773 r. km; e – 63.204 r. km; f – 64.932 r. km; g – 66.064 r. km; h – 67.426; i – 69.850 r. km; vertical axes – elevation (in m a.s.l.); horizontal axes – distance (in m).

Comparison of incision and change of ω from 1960 to 2003 of analysed cross-sections in the Olše R. study reach during the 5, 20, 50 and 100 R.I. discharge.