Influence of rheology on landslide-dammed lake impoundment and sediment trapping: Back-analysis of the Hintersee landslide dam

Abstract

Lacustrine deltas that develop upstream of landslide-dammed lakes can trap and store fluvial sediments. The development of these deltas and their size are conditioned by the geometry of the dam, which is in turn influenced by the landslide rheology. In this study, we back-analyze the formation of the Hintersee landslide-dammed lake in southeastern Germany and investigate the impact of landslide rheology on lake volume and sediment trapping capacity. We use the Voellmy rheology, a rheological model defined by two parameters, μ and ξ, and find that landslide rheology strongly influences sediment trapping. The Voellmy dry friction μ shows a non-linear relationship with lake volume and sediment trapping, while the velocity squared drag ξ has less impact. The Hintersee landslide dam presents a sediment trapping capacity of up to three times the volume of the landslide-dammed lake. Thus, the impact of landslide dams on sediment transport is underestimated by up to a factor of 3 when using lake volume as a proxy for sediment trapping capacity. We find that friction exhibits a non-linear relationship with lake volume and sediment trapping, while velocity has a more limited influence.