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<br />ponding and release of debris dams is a. major source of the flows, the <br /> <br />events probably would have oecurred even U discharge from the upper slopes <br /> <br />had been less. <br /> <br />B. The Flow of Debris <br />Field investigations made shortly after the July 24, 1977, events <br /> <br />revealed the following facts that providE> significant information about <br /> <br />the dynamics of the debris-flow process: <br /> <br />(1) A thick deposit of mud was widespread on the <br />upper fan surfaces. <br /> <br />(2) Boulders of various sizes were imbedded 1n the <br /> <br />mud matrix. <br /> <br />(3) The largest boulders werE> found near the upper <br /> <br />parts of individual debris-flow lobes. <br />(4) Distinct lateral levees were deposited 1n channels <br /> <br />and on parts of the upper fan surfaces, presumably <br /> <br />marking the lateral limits of the flows. <br /> <br />(5) Debris-flow surfaces (as infE>rred from the positions <br /> <br />of levees in channels) were tilted at locations <br /> <br />in channels where the debris were forced to flow <br /> <br />around curves. <br /> <br />(6) Debris-flow cross-section sizes and shapes could be <br /> <br />- 20 - <br />