Complex transformation of the geomorphic regime of channels in the forefield of the Moravskoslezské Beskydy Mts.: Case study of the Morávka River (Czech Republic) (link)
Škarpich, V.; Hradecký, J.; Dušek, R.
Abstract: This paper presents a complex analysis of both the contemporary and historic development of the geomorphic regime of the transformed reach of the Morávka River in the Czech Carpathians. The assessment concentrates on the conditions and causes of the channel development in the last c. 200 years compared with the state of European channels, especially those of the Carpathian zone. The Morávka R. pattern has undergone a rapid change in the last 50 years, particularly in connection with the active channel narrowing and massive incision. The original anabranching river pattern has gradually been replaced by a simple, narrowed channel incised into the bedrock. The average width of the Morávka R. active channel changed from 153 m in 1836-1852 and 165 m in 1876-1878 to 44 m in the year 2010. At some parts, the original river bed has lowered as much as 8 m in the last 40 years, which indicates an incision rate of 12-24 cm/year. These changes have been caused by strong anthropogenic impacts in the form of the river-channel control, bank stabilisation, and weir and valley dam construction. Other reasons are related to land cover and land-use changes. A great influence on the contemporary processes is also exerted by the geological predisposition of the Carpathian Flysch lithology in channel bedrock, particularly the occurrence of claystone layers that present little resistance to water erosion. Currently, the deficit of transportable sedimentary material along with the increased transport capacity of the incised riverbed has generated conditions for constantly intensifying erosion processes in the Morávka R. channel.
Report in czech language on the website of the Department of Physical Geography and Geoecology, University of Ostrava: here
Transformation of geomorphic regime of channels in the Moravskoslezské Beskydy Mts forefield (link)
Škarpich, V.; Hradecký, J.; Galia, T.; Dušek, R.
Abstract: In the end of the 19th century, rivers draining the Czech part of the Flysch Carpathians were characterized by anabranching channel pattern in the piedmont zone. Occurrence of this channel type was predisposed by regional geological settings which affected to large sediments supply in to the rivers system. The geomorphic regime of the river channels have been transform over the last 100 years. Main causes of this changes were identified as (i) decrease in sediment supply to the channels (related to the land use and land cover changes in the study area and to the man-made channel bank stabilizations, affecting the lateral connectivity in river system) and (ii) high number of barriers (dams or weirs), influencing the sediment transport through the river system in longitudinal direction. The original anabranching river pattern has gradually been substituted by simple narrowed channels that incised into the bedrock. The highest rate of incision in the study area was recorded in the Morávka River basin – ca. 12-23 cm per year in the last 40-50 years. Mean value of incision in the Ostravice River basin is ca. 5 cm per year and ca. 2 cm per year in the Olše River basin.
Coarse bed sediments in a headwater channel as indicators of fluvial processes and slope-channel coupling: a case study from the Carpathian Mountains (link)
Galia, T.; Škarpich, V.
Abstract: Character of bed sediments usually reflects fluvial processes and dynamics of sediment transport in fluvial systems. Our approach was based on the measurement of the largest boulders located within a bankfull channel and observance of changes in their sizes within the longitudinal profile of a Beskydian headwater stream. Resulting trends of particle-size index reflected the character of sediment delivery into channel segments, and recent development of the channel. The largest boulders were observed in strongly slope-channel coupled parts of the longitudinal profile, whereas weak coarsening occurred in some of the downstream incised channel reaches. By contrast, the fining of bed sediments was significant in the transitional zone between slope-channel coupled reaches and the alluvial cone characterised by a tendency to aggradation.
Link to the abstract (in Czech) here.
Water management of beskydian gravel-bed streams: case study of the Morávka River basin
Škarpich, V.; Hradecký, J.
Abstract: The Morávka River pattern has undergone a rapid changes of development in the last 500 years. These changes have been caused by a strong anthropogenic impact in the form of the river channel control, bank stabilisation, and level, weir and valley dam construction. This paper summarizes historical impact of man on channels in the Morávka River basin in the sense of identifing degree and categorization of interventions in the river management. Log driving, source of kinetic energy, flood and erosion control measures and water supply represent main causes linked with modifications of channels.
Bed sediments and geomorphological processes in high-gradient streams based in flysch of the Moravskoslezské Beskydy Mts.
Galia, T.; Škarpich, V.
Abstract: Lithology of bed sediments in high-gradient streams may affect grain-size parameters and, thus, bed morphology and sediment transport dynamics. Flysch character of bedrock with alternation of resistant sandstones and less-resistant claystones influenced geomorphic processes and bed sediments in Beskydian headwater channels. Generally, claystone members supplied streams by higher amounts of relatively finer clastic material. On the contrary, channels located in sandstone members (e.g., Godula Member) were prone to occurrence of exposed bedrock due to significantly lower sediment supply, except channel-reaches with evidence of debris-flow activity. Obtained trends of evaluated grain-size parameters (d90 and nominal index) in the stream longitudinal profiles pointed up on influence of claystone ratio in bed sediments and a character of sediment inputs. Significant presence of claystones in bed sediments of selected streams led to decrease in d90 percentile and nominal index Dn of bed surface material. On the other hand, sandstone sediment supply in high-gradient streams underlaid by the middle part of the Godula Member did not show downstream coarsening or fining of bed sediments within stream longitudinal profiles and higher values of grain-size parameters were observed.