Sediment Control Mechanism of Debris Dam

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This project has been made to analyze the sediment control mechanism of debris dam in terms of sediment hydraulics. Three subjects, which are concerning the data analysis of actual river, the erosion control mechanism of debris dam and the mechanism of sediment transportation upstream and downstream of the dam, are chosen for consideration. The results show(1) Data on bed variation of the Koshibu River, tributary of the Tenryu River, are collected and analyzed, and give a valuable information of bed variations in rivers where debris dams are constructed. Observational study is made in the Ashiarai River, a tributary of the Jintsu River, for the behavior of debris flow in the crib dam, and clarifies the sediment deposition from the flow.(2) The relation between bed variations upstream of dams and sediment discharge rates from dams is discussed experimentally and theoretically in terms of widths of opening and heights of dams. A mathematical model, which is useful for the predictions of bed variation as well as of the ratio of outflowing sediment discharge to the inflowing one, is presented.(3) The mechanisms of debris flow control are discussed in terms of open type debris dams of various kinds, and are clarified.