ESTIMATION OF BEDLOAD TRANSPORT IN HEADWATER STREAMS USING A NUMERICAL MODEL (MORAVSKOSLEZKÉ BESKYDY MTS, CZECH REPUBLIC)
The TOMSED numerical model, originally developed for Alpine torrents, was successfully applied on the May, 2010 flood event in headwater streams of the Czech part of the Western Flysch Carpathians. The Manning equation was used together with application of a reduced energy gradient and potential erosion limits. Contributions of form resistance and grain resistance to Manning’s roughness parameter were considered separately. The absence of bedload discharge measurement made it difficult to validate the model for local headwater channels, although channel reaches with recent erosional and depositional trends were recognized fairly well by the simulations. Bedload transport was calculated in the range from 480–1240 m3 for the richly-supplied headwater stream and 380–860 m3 for the stream with limited sediment-supply conditions. It turns out that the channel reaches with higher sediment supply have less developed bedforms (e.g. steps) and thus lower flow resistance resulting in a higher intensity of bedload transport.