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<br />; The ",au ",:,:,w, ',,yn~ I'"~ ;::" :,11"'\': "",' srots for flooding in the United States: areas such
<br />as ~he ~O\l\:d.TC~:-, pjcl:,>;-;rlL: If ,e:-".~,-:!, IE-:>;;-:~, ~ne fronl range of the Rockies from New Mexico to
<br />1!lon:ana ar~, ,nE "al[,: ,:w:er ;:a21, "":Jugh, Oklahoma, Kansas, Nebraska, and Iowa, Known
<br />""hot"" Sp01S br thunoerslor,T, fiOCIOS su:n as the northeast Oregon-southwest Washington area,
<br />the cenual Appalachlar: Mountains, and me Missouri River Valley between Kansas City and Sioux
<br />City, are also well represemed
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<br />Historically, the USSR hcs served only lhe 17 Western States. Consequently, the availability of
<br />histOriC data and resources 10 oeiorrr:omparlson studies may be biased in favor of these States,
<br />although an ,,;;empt has been cclade 10 cover all 48 conterminous states, From this study, it is
<br />not possible to conclude that any part of the country is more prone to floods representing large
<br />percentages of the PlViF peaks tnan other areas. Additional studies producing hundreds of com-
<br />parisons would be required to make such a conclusion.
<br />
<br />Historic Flood Events
<br />
<br />The remainder of this discussion describes the 61 individual historic events. Brief histories of the
<br />storm and resulting flooding are paraphrased from the literature, and brief discussions of the
<br />hydrologic parameters used to estimate a PMF peak for each site are presented.
<br />
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<br />1, Eldorado Canyon, Nevada
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<br />"It first looked like a dark heavy cloud of dust. Looked like a solid wall moving d n.
<br />As it came down, every vehicle was pulled into this muck, I saw four to six vehicles In
<br />the debris, The wall of muck appeared to go under the lake when it hit the water, causing
<br />a swell of water at the surface,""
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<br />This was how Lemuel Washington, a weekend fisherman from Las Vegas, described his impression
<br />of the onrushing flash flood of September 14, 1974, at the mouth of Eldorado Canyon [18],
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<br />The devastating flash flood was caused by a thunderstorm that struck Eldorado Canyon, a 22,8
<br />mi' drainage basin in southern Nevada with a history of flash flooding, The severe runoff resulted
<br />from an intense basinwide rain and hailstorm, which produced precipitation at a rate of 3 in per
<br />y, h. The storm is believed to have moved in a downstream direction in the basin and increased
<br />in intensity as the flood wave moved toward the developed area near the mouth of the canyon.
<br />The peak discharge of 76,000 ft3/s just upstream from the developed area was estimated by
<br />slope-area measurements by the USGS [18]
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<br />The flood was a direct result of an intense convective thunderstorm, Rainfall in the upper basin
<br />apparently began about 1 :00 p.m, According to documented reports by local residents, the most
<br />intense rainfall occurred between 1:45 and 2:00 p,m, The total storm duration was believed to
<br />be approximately 1 y, h. Eyewitness accounts describing the arrival of the leading edge of this
<br />very destructive flood wave indicate that it was accompanied by intense rainfall, thunder, and hail
<br />at the canyon mouth about 2:30 p,m, The apparent volume of the total runoff was roughly esti-
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