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<br />4 <br /> <br />surges from distant storms, tsunamis (large waves produced by <br />subterranean earth movements at sea), or by combination of these <br />causes. Especially along freshwater shores, damage is also caused <br />by ice driven ashore by wind or wave action. <br /> <br />Debris Cone Floodplains are areas along the bases of mountains that <br />developed by deposition of debris carried by flows from the mountain <br />streams (see figure 3). Debris cones are also called alluvial cones, <br />alluvial fans, debris slopes, or talus. Due to the manner of its <br />development, a debris cone often has a somewhat semi-circular <br />appearance when seen from above, and has slopes steeper than the <br />land on which it is formed but less steep than the bed of the stream <br />that is the source of the floodwater, sediment, and debris. Under <br />natural conditions, there is no permanent low-flow or main channel, <br />and the path of the next flood flow down the cone is unpredictable. <br />Floods are due to rainstorm or snowmelt runoffs, or to subsurface <br />return flows (rain or snow that soaks into the soil and travels under- <br />ground to a spring or stream) of the stream that developed the cone. <br />Debris cones are sometimes so flat as to be al:rnost indistinguishable <br />from riverine areas. <br />