Flow behavior of debris flows at different scales

Debris flows are sediment-water mixtures that are often triggered by heavy rainfall, transiting steep torrents as a kind of debris avalanche. In populated regions, these processes represent a natural hazard that can cause major damage to houses, traffic routes or agricultural land. In extreme cases, human lives can also be at risk. A better understanding of the flow behavior of different sediment- water mixtures is necessary to better predict how fast and how far debris flows can travel. In this project we investigate the flow behavior and composition of natural debris flows in the Gadriabach in South Tyrol, Italy. Debris flows occur very frequently in this catchment, which is why the Institute Mountain Risk Engineering at BOKU University, Vienna, operates a field monitoring station with which the most important parameters of debris flows, such as the flow depth or the density of the mixture, can be measured. The measurement of the velocity distribution within a debris flow is particularly important and only possible at this field measuring station worldwide. In addition, laboratory tests with different sediment-water mixtures are carried out in the project. The advantage of laboratory tests is that a large number of tests can be carried out under controllable and known conditions. This makes it possible to relate the flow behavior to the composition of debris flows and then compare this with the measurements of real debris flows in the Gadriabach. Another aspect of the project is the development of a new type of sensor that can be used to measure not only the velocity distribution in debris flows, but also the water content and thus indirectly the sediment concentration. A prototype will first be developed in the laboratory and then tested at the field measuring station. The results of the project will form the basis for the development of better simulation models for debris flows, which can then be used in engineering practice for hazard assessment and hazard zone planning.