Mechanics-Based Approach Toward the Mitigation of Debris Flow Disasters

This paper, at first, emphasizes the research on the mitigation of debris flow disasters is globally important and urgently needed by referring to Japanese statistics and other countries' recent cases. Then, introducing a chart describing the process of decision-making in coping with debris flow disasters, the discussion makes clear that debris flow mechanics play the core roll in decision-making. In this context, the problems how to identify the debris flow prone ravines and how to predict the onset of a debris flow in such a basin are discussed based oil the mechanical considerations. The fluid mechanical methods to determine a standard design debris flow and to assess the hazards and the risks are outlined, in which debris flows are classified in reference to the grain concentrations and the predominant stresses in flows. The characteristics of debris flow are different depending on the types thus classified, and the resistance and the erosion or the deposition formulae applicable to each type debris flow are introduced. The estimations of debris flow hydrograph and the hazardous area are given by taking a particular debris flow case as an example. The performance design problems of the grid-type debris flow checking dam are also discussed.