Event-based sediment loads from Austrian torrent catchments related to process and catchment characteristics

In engineering practice, the export of sediment loads during so-called “torrent events”, i.e. fluvial events or debris-flow events in steep headwater catchment, is of interest for short-term hazard assessment and longer-term sediment management in alpine regions. Several empirical models already exist for this purpose, each with varying degrees of complexity and uncertainty. In this study, a total of 3,642 torrent events in Austria, where information on the associated sediment load is available, were analyzed and related to geomorphological, geological, and hydro-meteorological boundary conditions. Despite of substantial scatter, we find that the type of event – fluvial flows or debris flows – as well as geology and geomorphology have the strongest control on sediment loads, while, interestingly, triggering precipitation show only limited correlations. Based on these results, we derive simple empirical equations to provide a data-driven assessment tool to estimate value ranges for future event sediment loads in torrent catchments in the Austrian Alps.