This book provides a summary of the state of the art of all facets of debris-flow science and practice and is designed to be a comprehensive technical reference for practitioners and a state-of-the-art research overview for scientists. It is richly illustrated with equations, graphs, photos, and tables. The book allows students, practitioners, and regulators to get a sense of the current state of the art in this science. Currently, there are 2 to 3 papers published every week on some aspects of debris-flow science. This creates a bewildering amount of literature that cannot be captured by a single individual. This book provides a comprehensive overview of all facets to date, including initial hazard assessments, detailed quantitative risk assessments, debris-flow warning systems, debris-flow mitigation structure designs, and failures of mitigation works, as well as new topics such as climate change effects on debris flows.