Saturday, 7 March 2015

Significance of the coarsest bed fraction in flysch headwater streams

Boulders in steep headwater streams play an irreplaceable role in hydraulics, sediment transport and bed stability within this part of fluvial net. A few months ago, our new publication  has been released in Geografiska Annaler: Series A, Physical geography dealling with the connectivity of the coarsest fraction in Beskydian steep streams. Also, effects of past disturbances (debris-flows) and present lateral sediment supply was discussed in this paper. Debris-flow affected channels indicated more frequent occurrence of larger boulders in bed sediments and limited adjustments to contemporary fluvial processes (e.g. incision). On the other hand, bed sediments in channels void of past debris-flow activity often reflected lateral sediment inputs (e.g. bank failures) and trends of erosion or deposition. This study directly followed our previous paper published in Moravian Geographical Reports, which described downstream trends of coarse bed sediments and clustering of bed sediments reflecting recent fluvial processes in one of headwater stream. Other paper discussing bedload transport of the coarsest bed fraction in relation to recent geometrical parameters of steep channels and transformation of channel-reach morphology during bankfull and high-magnitude discharge is in review. The study will summarize our bedload transport observations (Q20 flood 2010, bankfull event 2011, Q5 flood 2014), contemporary fluvial processes (incision, aggradation) and connectivity of boulder and cobble fraction in local steep channels.