Vliv sedimentačního prostředí na magnetickou susceptibilitu přelivových sedimentů nivy Moravy ve Strážnickém Pomoraví

Four profiles in different sedimentary environments - natural levee, proximal floodplain, distal floodplain, oxbow lake - were sampled to obtain magnetic susceptibility (MS), grain size, organic matter content (LOI) and pH. Relationships between selected parameters (χlf, D50, LOI, pH) were analysed by means of statistical analysis (linear regression, PCA, factor analysis). Principal goal was to investigate how character of individual sedimentary environments and their distance from the active river channel is reflected in the magnetic signal of overbank deposits. A decrease in the magnetic signal with increasing distance from the river channel was shown, confirming that fluvial deposition is a major factor of contamination of floodplain sediments by anthropogenic magnetic particles. The base of elevated values of MS (levee: 80 cm, proximal floodplain: 30 cm) probably corresponds to the turn of the 19th and 20th century and the strongest magnetic signal (levee: 32,5 cm, proximal floodplain: 5 cm) belongs to the 1980s. Statistically significant relationships were found between: χlf and LOI (direct dependence), LOI and D50 (indirect dependence), pH and D50 (direct dependence) when data from all profiles were analysed together

MORFOLOGICKÉ A SEDIMENTOLOGICKÉ ÚČINKY ŘÍČNÍHO DŘEVA V KORYTĚ ČERNÉ OPAVY

Woody debris in streams and rivers is an important controlling variable of channel morphology. Morphological and sedimentological effects of individual wood pieces and wood accumulations in two segments of the Černá Opava River were investigated. It can be concluded that live and dead woody vegetation conditioned the origin of river branching after the extreme flood in 1997. Afterwards, woody debris governed the spatial distribution of small erosional bed forms (pools) and also partly enhanced the retention of finer sediments. Woody debris has also local impact on sediment grain size and to a lesser extent on sediment sorting. Bed load samples from fluvial forms which were generated by woody debris show finer and better sorted sediments. However, the difference to samples unaffected by woody debris is statistically insignificant. Nevertheless, it is inferred that the presence of woody debris increased the differences in sediment grain size and sorting on a local scale

Geomorphological and vegetation changes of the Morava River oxbow lake in the locality of Osypané Břehy five years after the cut-off

Ox-bow lake of the Morava River located nearby the locality of Osypané Břehy has undergone significant geomorphological transformation since the cut-off in 2006. Clearly evident is development of two alluvial plugs separating the lake from the active river channel. Maximal depth of alluvial material deposited in the ox-bow lake may reach 4.5 m locally. The slope of concave banks was reduced significantly to the value of 36°; reduction of mean bank slope has reached almost 20° since the cut-off. Vegetation succession began on newly exposed surfaces (alluvial plugs) and on surfaces that are no more disturbed by fluvial processes (steep river banks); prevailing species are willow and poplar.Ox-bow lake of the Morava River located nearby the locality of Osypané Břehy has undergone significant geomorphological transformation since the cut-off in 2006. Clearly evident is development of two alluvial plugs separating the lake from the active river channel. Maximal depth of alluvial material deposited in the ox-bow lake may reach 4.5 m locally. The slope of concave banks was reduced significantly to the value of 36°; reduction of mean bank slope has reached almost 20° since the cut-off. Vegetation succession began on newly exposed surfaces (alluvial plugs) and on surfaces that are no more disturbed by fluvial processes (steep river banks); prevailing species are willow and poplar

Gully network in the Bosonožský Hájek area – unique geomorphological phenomenon westward from Brno

The Bosonožský Hájek area is a unique example of intensive gullying of Pleistocene loess deposits; locally the incision reached even the underlying granitoid bedrock. Four main gully networks are developed. Geometry and topology of gully networks is primarily governed by slope morphology. Gullies are mostly inactive and covered by old-growth forest. Absolute dating of the main phase of gully incision is still opened and debated question.The Bosonožský Hájek area is a unique example of intensive gullying of Pleistocene loess deposits; locally the incision reached even the underlying granitoid bedrock. Four main gully networks are developed. Geometry and topology of gully networks is primarily governed by slope morphology. Gullies are mostly inactive and covered by old-growth forest. Absolute dating of the main phase of gully incision is still opened and debated question

Recent advances quantifying the large wood dynamics in river basins: New methods and remaining challenges

Citation: Ruiz-Villanueva, V., Piégay, H., Gurnell, A. A., Marston, R. A., & Stoffel, M. (2016). Recent advances quantifying the large wood dynamics in river basins: New methods and remaining challenges. Reviews of Geophysics. doi:10.1002/2015RG000514Large wood is an important physical component of woodland rivers and significantly influences river morphology. It is also a key component of stream ecosystems. However, large wood is also a source of risk for human activities as it may damage infrastructure, block river channels, and induce flooding. Therefore, the analysis and quantification of large wood and its mobility are crucial for understanding and managing wood in rivers. As the amount of large-wood-related studies by researchers, river managers, and stakeholders increases, documentation of commonly used and newly available techniques and their effectiveness has also become increasingly relevant as well. Important data and knowledge have been obtained from the application of very different approaches and have generated a significant body of valuable information representative of different environments. This review brings a comprehensive qualitative and quantitative summary of recent advances regarding the different processes involved in large wood dynamics in fluvial systems including wood budgeting and wood mechanics. First, some key definitions and concepts are introduced. Second, advances in quantifying large wood dynamics are reviewed; in particular, how measurements and modeling can be combined to integrate our understanding of how large wood moves through and is retained within river systems. Throughout, we present a quantitative and integrated meta-analysis compiled from different studies and geographical regions. Finally, we conclude by highlighting areas of particular research importance and their likely future trajectories, and we consider a particularly underresearched area so as to stress the future challenges for large wood research. ©2016. American Geophysical Union

State of geomorphological research in the year 2013

Meetings of not only geomorphologists, but also other Earth science researchers at annual geomorphological conferences State of geomorphological research organized under the auspecies of Czech Association of Geomorphologists have already became a tradition. The geomorphologists and other specialists from universities, research and commercial institutions who met in town of Mikulov presented recent research results on character, genesis and dynamics of landscape, from either of theoretical or applied point of view. The presented papers came all over the central European countries – Czech Republic, Slovakia, Poland, Austria, Hungary, and Slovenia. Abstract proceedings consist from presented lectures, posters as well as excursion guide

Objevování Antarktidy

8

Structural control on drainage network orientation -an example from the Loucka drainage basin, SE margin of the Bohemian Massif (S Moravia, Czech Rep.)

This paper discusses the relationship between geological structure and drainage network orientation at both a meso-scale and local scale. The Loucka Basin, located at the SE margin of the Bohemian Massif (S Moravia, Czech Rep.), has been selected as the model region for these studies. In the Loucka Basin, the bedrock comprises the metamorphic rocks of the Moldanubicum Group, which are arranged in elongated bands and lenses and are fractured with the dense network of faults. There is no extensive cover of unconsolidated younger sediments in the basin, nor any deep weathering regolith. In these respects, the geological setting is extremely favourable for the quantification of structural features and their correlation with drainage orientation. The degree of correspondence between the direction of drainage network segments and the orientation of such structural features as faults, mylonite zones, thrust-fronts and rock lineations was investigated in five study areas. The third-order streams are those most influenced by structure. The higher the order of stream segment, the weaker the correlation, and the more important the overall inclination of the terrain as a controlling factor in stream flow orientation. However, there is a strong structural control of first order streams in the periphery of the Basin. The structural control of streamflow direction in the Loucka Basin, which is built up with Precambrian metamorphic rocks, varies between 30-50% of the rectified channel length; the upper limit is considered to be the maximum conditioned by a local very high density of various linear structural elements