Short message: Protection of gravel bars and floodplain of the Rožnovská Bečva River

Our group with Beskydy Protected Landscape Area institution participated and helped for rescue and protection of floodplain and gravel bars of the Rožnovská Bečva River. Terrain works were realized on 25th of July 2013.

We have attempted research to predict trends in erosion or deposition in local reach of the Rožnovská Bečva River near the Rožnov pod Radhoštěm. Research was realized on the basis of sediment transport modelling and fluvial-geomorphological mapping. We gave prognose of future development of study reach a try.

We started the monitoring of the Bečva River channel processes

Bečva R. is an originally anabranching gravel-bed stream drains the Czech part of the Flysh Carpathian Mts. as a left tributary of the Morava R. The Bečva R. begins by confluence of two source streams, the northern Rožnovská Bečva R. and the southern Vsetínská Bečva R. The drainage area is 1620 km². The mean annual discharge of the river reaches up to 17.3 m³ s^-1 at the Dluhonice gauging station, where the basin area is 1592 km² (data source: Czech Hydrometeorological Institute).

 

Fig. 1: Localization of the Bečva R. basin in the Czech Republic (source: link).

Fig. 2: Bečva R. reach in the locality of Černotín.

We started with monitoring of the Bečva R. channel. First part of research is connected with use of geodetic survey, grain-size analysis and modeling of sediment transport. Main aim of our research is focused on evaluation of transport parameters of selected channel reaches. The set includes single-thread, channelized and incision affected reaches, compared with anabranching renaturated reaches (they were renaturated by flood event in year 1997). Other aim of this research is a sedimentary budget of the channel segment from the point of view of transport parameters.

Fig. 3: Terrain works in the Bečva R. basin

Emeritus Professor Pavel Novak was speaking in Czech Television

Emeritus Professor Pavel Novak was speaking in Czech Television document about Vltava's Dam Cascade and their effect on flood flows (link to document of Czech Television, in czech language)

Novak is an emeritus professor of civil and hydraulic engineering at the University of Newcastle upon Tyne, in the United Kingdom. He has published more than 100 publications, including the five-volume work Developments in Hydraulic Engineering and the book Hydraulic Structures.He has also made important contributions in hydraulic structures research. His research has focused on physical modeling, open channel flow, sediment transport, river training, the hydraulics of dams, and oxygen transfer at structures. His consulting work encompasses spillway designs, water supply works, flood control and drainage schemes, sediment control, and river training.

Link to his last publication: Novak, P., Moffat, A.I.B., Nalluri, C., Narayanan R. (2007): Hydraulic Structures, Fourth Edition. Taylor & Francis Ltd. 700 p.

Report (live from Koblenz): We participated on 6th International Conference on Water Resources and Environment Research in Koblenz, Germany

3rd – 7th June of 2013, Koblenz, Germany
 

We presented results of our research on the 6th International Conference on Water Resources and Environment Research in Koblenz, Germany. The basis task of this conference is overviews on fundamental issues in environmental hydrological problematics of streams in the world. Especially, climate influence of rivers, problematic of sediment processes and polutants of sediments and water in river systems, hydrological modelling and monitoring and problematic of water management linked with contemporary environmental demands are the main focuses of this congress.

High water stage (water stage about 650-700 cm) of the Rhein River in Koblenz (state at 5 p.m., 3rd of June 2013, photo by Galia T.)

 Fountain which represents historical flood water stage on the right bank of the Rhein River in Koblenz (photo by Skarpich V.)

We participated on sessions:
 
UNDERSTANDING SEDIMENT PROCESSES AT CATCHMENT SCALE (session moderate by Peter Heininger)
 

Modelling of potential bedload transport: identification instrument of erosion and accumulation
 

Škarpich, V., Hradecký, J., Galia, T. 

Abstract: Our paper summarizes the results of bedload transport modelling in the Morávka River, Ostravice River and Bečva River basins, conducted with the use the BAGS (Bedload Assessment for Gravelbed Streams) spreadsheet-based program. The presented results show potential rates of bedload transport linked with identification of erosion and accumulation processes in channels. Selected channel cross-sections include preserved gravel-bed reaches with anabranching development as well as transformed reaches with accelerated deep erosion and occurrence of a single bedrock channel. The modelling shows bed load transport trends in relation with the morphology of the channel. Presented results show a potential rate of bed load transport because sediment inputs and barriers were not included in the model. In fact, these results of potential rates of bed load transport can be use for distinguishing of the reaches with erosion or accumulation trends. The modelling on cross-sections with a low rate of fluvial erosion (anabranching channel pattern) shows the decrease in potential bed load transport. It is caused by increasing or decreasing of (dis)connectivity in longitudinal direction of the fluvial (dis)continuum system. It is affected by diversion of flow through sub-channels and decrease in transport capacity. We define this area of active channel as a zone of reduced growth in transport capacity. In contrast, reaches with single channel pattern show higher values of the potential bed load transport caused by absence of this zone of reduced growth in transport capacity. The results may be applied in order as a conceptual scheme to improve the management of the local watersheds.

and
 
MODERN HYDRAULIC STRUCTURES FOR BETTER HYDRODYNAMICS AND HYDROMORPHOLOGY OF STREAMS AND RIVERS (session moderate by Arthur Radecki-Pawlik) 

Sediment transport in headwater streams of the Carpathian Flysch belt: its nature and recent effects of human interventions 

Galia, T., Hradecký, J.

Abstract: As proved our recent research in Beskydian headwater channels, obtained critical values (bed shear stress, unit stream power and unit discharge) for beginning of bedload transport of certain grain diameters were significantly lower than those coming from Alpine and Andine environments. On the other hand, local flysch-based mid-mountain streams contain generally finer sediments when compared to other regions. Simulation of bedload transport in one-dimensional TOMSED model also pointed up on relatively small total amounts of material which can be potentially transported during a single flood event. This fact resulted from supply-limited character of most of local streams with relation to often occurrence of bedrock outcrops in channels. Together with changes in land-use represented by afforestation since the end of 19th century, systematical cleaning of channels from woody debris by local forest management and building of check-dam structures, accelerated incision trends are observed in most of local torrents. One must note, that flysch bedrock structure (alternation of sandstones and claystones) is less geomorphic resistant and more prone to incision and slope deformations than other solid rocks. Thus, check-dam constructions should be viewed as negative interventions in to the local channel segments due to strictly supply-limited conditions in most local basins and predisposition to quick incision in to weak rocks. Also, removing of large woody debris accelerate incision processes expect its function as a significant element of biodiversity in channel. By contrast, many roads cross local headwater streams by under-dimensioned sluices. These sluices acting as a barrier since sediments clogged up inside during some higher magnitude flood events, resulting to accelerated incision trends under these constructions. Extracting of deposited gravels and boulders from upstream segment comes after a flood event. Unfortunately, it is no surprising fact that extracted material captured by sluices or check-dams is not returned in to the channel segment.

Report in czech language on the website of the Department of Physical Geography and Geoecology, University of Ostrava: here

A quick book review: Gravel-bed rivers: Processes, Tools, Environments

A new Willey-Blackwell publication reflects trends and key contributions of the 7th International Gravel bed Rivers Workshop, which was held in September, 2010, at Tadoussac, Quebec. Thus, the publication presents a definitive review of current knowledge of these fluvial systems covering both fundamental and applied topics, divided in to main chapters: secondary flows in rivers, sediment transport, modelling morphodynamics, river restoration and regulation, ecological aspects of gravel-bed rivers, tools for study (including remote sensing, LiDAR, water surface-velocity radars etc.), steep channels, semi-alluvial channels (including bedrock channels), river channel change and ice in gravel-bed rivers.

Each of a chapter is written by leading specialists of a topic. Moreover, discussions after most of chapters are added, presenting some important opinions and comments noted by other experts. Individual chapters are accompanied with many illustrative photos, maps and graphs including color plate sections. We warns that the publication cannot be understood as some educational text, but it provides a comprehensive review of recent trends in fluvial geomorphology and related disciplines. The book also clearly demonstrates a contrast between top world-wide science and a state of fluvial geomorphology research in Czech Republic.

Church, M., Biron, P.M., Roy, A.G. (2012): Gravel-bed Rivers: Processes, Tools, Environments. John Willey & Sons, 580 p. ISBN: 978-0-470-68890-8

Computed stream velocity in Carpathian headwater streams of the flysch belt

Four equations originally developed for high-gradient channels with steep slopes and high hydraulic roughness, were selected to test their suitability in local channels. Power relations of Rickenmann et al. (2006)-RIC: 

v = (1,93g^0,5D^1,5S^0,5)/d₉₀,

and Zimmermann (2010)-ZIM: 

v = 2,3g^0,5D^1,2d₈₄^-0,72S^0,72,  

logarithmic relation of Lee and Fergusson (2002) with introduced roughness parameter by Jarrett (1990)-LFJ:

√(1/f) = 0,35R^0,33.S^-0,38,

and a classic Manning approach with divided roughness parameter in to the grain and form resistance (Rickenmann, 2005; Wong and Parker, 2006)-MAN: 

v = 1/n_totR^0,67.S^0,5; 1/n_r = 23,2/⁶√d₉₀; n_r/n_tot = 0,092S^-0,35(D/d₉₀)^0,33.  

D means hydraulic depth (m), f is Darcy-Weisbach friction factor, g corresponds to 9.81m.s^-2, n_r is grain roughness parameter (grain resistance).

We taken bankfull parameters and grain-size distributions from a variety of local channels (n=93), where alluvial and semi-alluvial channel-reach morphologies were accounted (i.e., pool-riffles, rapids, step-rapids, step-pools, cascades and bedrock-cascades). Table 1 shows computed values during bankfull stage for some typical channel-reaches of the studied region. All evaluated channel-reaches are illustrated by Figure 1 together with normalised parameters of the channel roughness, channel gradient and stream velocity.

Table 1.

Stream	Morphology	S [m/m]	D/d90 [m/m]	ZIM [m.s-1]	RIC [m.s-1]	LFJ [m.s-1]	MAN [m.s-1]
Libotínský potok	pool-riffle	0.03	2.69	0.67	1.35	0.54	0.90
Veřmiřovský potok	rapid	0.04	2.21	0.80	1.48	0.73	1.02
Velký Škaredý p.	rapid	0.06	3.67	2.01	3.60	0.95	1.55
Malá Ráztoka	step-rapid	0.06	1.26	0.79	0.95	0.65	0.74
Dížená	step-rapid	0.07	1.85	0.87	1.25	0.52	0.79
Vsetínská Bečva	step-pool	0.07	2.09	1.12	1.60	0.58	0.89
Rybský potok	step-pool	0.07	2.53	1.36	2.14	0.67	1.05
Kněhyňka	cascade	0.22	1.03	1.88	1.52	0.74	0.78
Velký Škaredý p.	cascade	0.32	3.11	6.42	7.29	1.16	1.81
Velký Škaredý p.	bedrock-casc.	0.53	2.99	7.14	8.21	1.09	1.79

Fig. 1

As Fig. 1 and Tab. 1 documented, we computed a wide range of stream velocities in local high gradient channels and so, there cannot be recommended a single equation valid for all evaluated cases. Power relationships (RIC and ZIM) highly overestimate velocities in steep narrow channels with relatively fine bed sediments. In world-wide literature, stream velocities in steep channels are usually lower than 2 m.s^-1. Logarithmic relationship LFJ systematically underestimates velocities even on higher slopes >0.1 m/m. Combined Manning relatioship MAN calculates relatively uniform values for all reaches. Thus there is a possibility of underestimating on higher channel gradients and on the other hand, some overestimating on moderate slopes. Nevertheless, for stepped-bed morphologies with some lower roughness, this equation can be appropriate. For pool-riffles and rapids we recommend some of power-law equation. Probably relationship derived by Rickenmann RIC is more suitable due to the fact, that relationship by Zimmermann ZIM was tested only in a laboratory flume. We hope that one day we will do some direct measurement of stream velocities in local high-gradient channels to test and verify our conclusios.  

Jarrett, R.D., (1990): Hydrologic and hydraulic research in mountain rivers. Water Resoures Bulletin 26 (3), p. 419–429. 

Lee, A. J., Ferguson, R.I., (2002): Velocity and flow resistance in step-pool streams. Geomorphology 46, p. 59–71.

Rickenmann, D., (2005): Geschiebetransport bei steilen Gefällen. Mitteilung 190 der Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie, ETH Zurich, p. 107–119.

Rickenmann, D., Chiari, M., Friedl, K., (2006): SETRAC - A sediment routing model for steep torrent channels. In Ferreira, R., Leal, E.A.J., Cardoso, A. (Eds.): River Flow 2006, Vol. 1, p. 843–852. London, Taylor & Francis.

Wong, M., Parker, G., (2006): Reanalysis and correction of bed-load relation of Meyer-Peter and Müller using their own database. Journal of Hydraulic Engineering 132, 1159 doi:10.1061/(ASCE)0733-9429(2006)132:11(1159).

Zimmermann, A., (2010): Flow resistance in steep streams: An experimental study. Water Resources Research 46, W09536, doi:10.1029/2009WR007913.

Our reaction on the paper of Roušar L. et al. (2012): Evaluation of function nature-inspired river widening on the Morávka R. downstream division structure object Vyšní Lhoty.

We made a reaction on the paper evaluating local channel widening function in the Morávka River lower reach. Local channel widening was constructed for undesirable bed degradation of the Morávka River at downstream reach in 10.7 river km. We answered to the problematic questions and conclusions of this paper. As compared with non-function of the anti-erosive construction with support of data coming out from monitoring of Department of Physical Geography and Geoecology, Faculty of Science, University of Ostrava.

Original article Roušar L., Veselý J., Zachoval Z., Tureček B. (2012): Evaluation of function nature-inspired river widening on the river Morávka downstream division structure object Vyšní Lhoty. Vodní Hospodářství, 11. pp. 352-355, link here, p. 352 in journal, in Czech language with English abstract).

Our reaction original article link here, p. 398 in journal, in Czech language. 

Figure: Morphology of the Morávka River bed at 10.7 r. km regulated within anti-erosion measures; A – state in 2008 (September to October); B – state in 2010 (October to November).