Flow behaviour of debris flow material in a rotating drum

Geomorphologic processes like debris flows represent a serious hazard in alpine environment. Debris flows are agitated mixtures of mainly water and sediments of various grain sizes, but also woody debris can play an important role in forested watersheds. For debris flow risk assessment and hazard zone mapping often empirical relationships based on geomorphometric data of past flow events or simple `rheologic` simulation models are used in engineering practice. To gain more insight in the flow behaviour and relevant energy dissipation processes of these mixtures, small scaled experiments in a controlled laboratory environment are necessary. During the period of 2004-2006 a series of experiments with granular suspensions and natural debris flow material have been carried out using a (slowly) rotating drum of 2.5 m diameter at the University for Natural Resources and Applied Life Sciences (BOKU) in Vienna, Austria. A similar setup with a drum diameter of 4 m has been developed at the University of California in Berkeley, USA. The main objective of the proposed project is to compare the general flow behavior of debris flow material mixtures flowing in similar laboratory facilities but of different sizes. This will contribute to a better understanding of the quite complex laboratory flows in a rotating drum and will improve the usability of these very special experimental setups to answer future research questions in connection with hazardous mass movements like debris flows, rock avalanches or snow avalanches.