Debris-Flow Fans

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Debris flows pose a hazard to lives and structures in mountain communities throughout the world. Motivated by the need to enhance prediction and mitigation, research projects, particularly in the U.S. and Japan, have produced wealth of information on initiation and dynamics of debris flows. By comparison, little research has been devoted to understanding debris flows in the environment where their hazard potential is most serious: i.e., on debris-flow fans. Debris-flow fans form a significant portion of the landscape and aside from concerns about hazards, the dearth of rigorous studies of the processes forming debris-flow fans represents a basic lack of scientific knowledge about a major landform of Earth's surface. The proposed research will address the mechanics of formation of debris-flow fans. The study complements on-going debris-flow monitoring programs in this country and in East Asia in that we will develop a methodology for interpreting the vast amounts of information on debris flows and fan formation stored in the debris-flow deposits themselves. Our approach considers the processes of, and controls on, debris-flow initiation, conveyance, and interaction with the channels of the fan surface, starting with the lithologic and climatic conditions in the source area and their influence on flow mobility, volume, and frequency of occurrence. The approach is a general one, applicable in a range of environments, and not limited to the specific conditions in the chosen field study site: Owens Valley, CA. The model will be built around an rheological description of debris-flow dynamics and will be based on field and laboratory data.