Insights into a pulsing debris flow

The internal deformation behavior of natural debris flows is of interest for model development and model testing for debris-flow hazard mitigation. The pulsing nature of debris flows can increase the runout length by remobilization of deposited material. Up to now, only a view attempts were made to measure internal deformation behavior in natural debris-flow surges due to the low predictability and high destructive power of these flows.  In this contribution we present recent advances of measuring in-situ velocity profiles together with flow parameters like flow height, basal normal stress, and pore fluid pressure. For that a fin-shaped monitoring barrier was constructed in the Gadria creek (IT), laterally carrying an array of paired conductivity sensors. We present results from a debris-flow event in 2019 with 20 surges and flow heights up to 2 m. We observe changing velocity profiles during the passage of the surges and identify deposition and remobilization domains in the flow. The flows exhibited significant longitudinal changes of flow properties like flow height and density. The liquefaction ratios reached values up to unity in some sections of the flows. Between surges, the lower levels of the flow deposited and were subsequently overridden by the next surge and reactivated. These measurements gain new insights of the dynamics of surges of a real-scale debris flow.