Linking Debris Flows and Landslides to Large Floods in Gravel-Bed Rivers

Landslides and debris flows are very effective geomorphic agents influencing the evolution of fluvial systems in mountain catchments. The concurrence of landslides, debris flows and floods urges the development of methods that can cope with multiple hazards resulting from the interactions between these processes. This paper presents examples of relationships between landslides (including debris flows) and floods in gravel-bed rivers: the occurrence of a large debris flow in a steep gravel-bed channel caused by the failure of landslide dams in an upstream channel reach, the increase of sediment transport following major floods with widespread landslides, the formation and failure of landslide dams and channel blockages caused by debris-flow deposits, and the supply of large wood due to shallow landslides in forested catchments. The methods for predicting landslides and debris flows at different spatial and temporal scales, with a focus on interactions with floods in the main river channels, are briefly described and reviewed. Finally, some research topics that could open valuable prospects for the advancement of research on these topics are mentioned.