Landslide-dammed lakes form when a landslide deposits in a river bed, stopping the flow of water and forming a lake (Fan et al., 2020). Landslides dams exert both an influence in terms of natural hazards and landscape evolution on the upstream and downstream valleys. Indeed, their formation leads to water impoundment and flooding of upstream areas, whereas their failure causes catastrophic mud flows in the downstream valleys. As for stable dams, they act as sediment traps that alter bedload transport in the catchment. In this talk, I will present the results we obtained through the simulation of thousands of landslides across the Austrian Alps, in 8 other mountain ranges world-wide and through the reconstruction of a case-study in the Bavarian Alps. We found that the formation of landslide-dammed lakes is influenced by local topography, the main erosive process and landslide rheology, and that small events are often overlooked in the field. We also discovered that landslide-dammed lakes follow a similar size-frequency scaling to landslides, and that the sediment trapping capacity of landslide-dammed lakes is at least threefold higher than their water impoundment capacity.