Interplay between input hydrograph and flow resistance within the open-source debris-flow framework DebrisFrame

Debris flows are mountain hazard processes, that are among the most devastating natural disasters in the alpine region. Therefore, reliable simulation tools are indispensable for identifying areas affected by debris flows and for developing and evaluating mitigation measures. In engineering practice, the use of depth averaged single-phase models for debris-flow hazard assessment is challenged by the question of the optimal representation of flow resistance and erosion, the respective uncertainty of model parameters and unknown starting conditions. Open-source availability and documentation, including a database of case studies, pose further challenges. The DebrisFrame project (opennhm.org/about_debrisframe) is a collaborative, open-source, Python-based framework for depth-averaged single-phase debris-flow simulations. It offers a user-friendly, modular, and extensible architecture that allows for the flexible configuration of initial conditions, flow resistance, and erosion formulations. Here we present the first results of a sensitivity analysis that quantifies how different types of input hydrographs and friction models influence deposition behavior. To estimate uncertainties, stochastic approaches and scenario analyses are applied. First, simplified, synthetic topographies are used. Subsequently, real-world case studies from the Austrian Alps are employed, while accounting for variable input data and model parameters. Future studies will focus on the role of erosion and its interaction with initial conditions and flow resistance in controlling debris-flow dynamics. The results of our work will help practitioners to better understand how the choice of input data and parameters affects debris-flow runout simulation.