Combining sediment connectivity and debris-flow hazard assessment in the Roßalpen-Prielgraben catchment (Austrian Alps)

Climate change is altering precipitation regimes and, consequently, debris-flow hazard patterns, increasing uncertainties in hazard assessments. In Europe, the absence of unified guidelines for hazard zone mapping further complicates regional comparability, underlining the need for rapid and standardized methods to identify hazard sources. This study explores a methodological framework combining sediment connectivity analyses with conventional process-based hazard modelling for efficient and transferable debris-flow hazard assessment. The study case was selected within a geologically complex Alpine catchment in Austria, which is affected by debris-flow processes. The methodology combines i) geomorphological mapping with sediment connectivity analyses, specifically, the Effective Catchment Area (ECA) and the Index of Connectivity (IC), to identify sediment sources and pathways, and ii) RAMMS:Debrisflow (RApid Mass Movement Simulation:Debrisflow) simulations implemented by connectivity delineations. Results show that ECA and IC have the potential to identify hazard-prone zones and support the identification of release areas for RAMMS modelling. In addition, statistical analysis reveals a relationship between IC and simulated flow parameters, supporting the identification of areas with more severe flow conditions. While absolute IC values are catchment-specific, the connectivity–hazard relationship can improve the spatial delineation of hazard zones and define a transferable methodological framework at the catchment scale.