Illgraben bedrock erosion samples

Erosion marks on marble and granite bed samples in the Illgraben Torrent (2006-2007). When studying bedrock erosion by a debris flows event, rarely do we know the detailed initial topography of the bedrock channel. This makes it impossible to measure the volume loss due to single debris flow events. To overcome this challenge, we placed initially flat stone samples of marble and granite in the Illgraben torrent, Switzerland, a location frequently scoured by natural debris flows. At the Illgraben, there are typically several events per year, due to the high availability of source material in the upper catchment that fail during summer rain storms (e.g. McArdell et al., 2007; Badoux et al., 2009, Berger, 2011). The stone samples captured groove and impact marks on the stone samples caused by the debris flows.