A hybrid modelling approach to debris flow modelling combining physical and numerical simulations

Debris flows pose a significant threat to human life and infrastructure due to the extreme forces they bring into play. In order to prevent and mitigate the effect of such events, a fundamental understanding of processes related to debris flows is required. To this end, we used a hybrid modelling approach combining physical and numerical modelling to simulate debris flows

The physical model that served as the basis for the numerical one was a seesaw-like plexiglass flume with a hinge in the middle and sediment reservoirs at the two extreme ends. The hinge enabled the movement of the debris flow back and forth between the reservoirs when the flume was tipped, thus providing reproducible initial (sediment composition) and boundary (slope, roughness) conditions for each run. The physical model was 0.3 m wide and 4 m long, in addition to 0.5 m at each end (lengthwise) working as sediment reservoirs.  Velocity and flow height data were recorded at four points along the flume.

We used the mass flow modelling software r.avaflow to reproduce the physical model runs with varying slopes (20, 25, and 30 degrees) and solid contents (40, 50, and 60 %). The model included simulations with both multiphase flow (unique processes for solids and fluids) and a Voellmy-type mixture model (mass represented as one homogenous block). The present study shows the preliminary findings of the research, but the long-term goal is to utilize a hybrid modelling approach to combine the advantages of real data from physical modelling with the increased potential for data extraction and number of model runs that we get from numerical modelling to perform detailed sensitivity and uncertainty analyses with probabilistic simulations in future work.