Observations on single particle movement in three alpine torrents
During the last years, investigations about sediment transport were made with the method of magnetically tagged tracer particles in three torrents of the Swiss Pre-Alps. Recovery campaigns were carried out at irregular intervals. Five classes of tracers have been used: 0,1 kg rod, 0,1 kg disc, 0,5 kg, 1,4 kg and 3,4 kg stones. The smaller particles (discs and rods) were made of artificial material whereas the other particles were prepared from natural stones. The recovery rate of the tracer stones decreased with the number of flood events but the grain weight distribution of the recovered tracers did not change significantly. Correlations could be established for all torrents between the mean transport distance of the tracer particles and the peak runoff of a period as well as with the effective runoff volume. In general it is found that the mean transport distances are higher in the Erlenbach than in the Rotenbach for similar hydraulic conditions.