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<br />THE ARKANSAS RIVER FLOOD OF .JUNE 3-5, 1921.
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<br />:By RoBERT FOLl:.ANSBEE and EDWARD :g, JONES.
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<br />INTRODUC'rION, .
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<br />Between June 2 and June 5, 1921, Iwavy rains of an intensity to
<br />justify the term," cloud-bursts" in the foothill region of the Arkansas
<br />Valley in Colorado caused the severest flood in the valley since its ,
<br />settlement.' Flood conditions prevailed during the entire period, but
<br />there were three distinct floods in the upper valley. The first flood
<br />was caused by heavy rairi'on Dry Creek just above Pueblo on the
<br />night of June2j the second was the main flood, which occurred dur-
<br />ing the night of June 3 jand the third wns that due to the breaking of
<br />the Schaeffer reservoir, 'on' Beaver Creek, on the morning of June 5.
<br />The area consideredin'this report is shown in Plate 1.
<br />The flood was remarkable for the very small area. covered by the
<br />,rainfall that was its chief cause, and for the swift rise of the river
<br />to an unprecedented stage and its almost equally rapid falL" The
<br />swift rise and fall, indicated very great flood discharges of, the
<br />tributary streams, which drain It mountainous country of steep slopes.
<br />The total discharge of the maiii flood was less than 1JiO,000 acre-feet.
<br />I Immediately after the flood the United States Geological Survey
<br />undertook an investigation of its causes llnd results, and the field
<br />work was begun as soon as conditions permitted.' An examination!
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<br />. was made of all the streams within the' area affected by the flood tol
<br />procure data on maximum run-off in the' foothilI region and the'
<br />effect'of this tributary run-off upon the main flood. The maximum
<br />discharge of each stream was determin'ed from the slope shown by
<br />well-defined high-water marks arid from the a veragle of several cross
<br />sections.: "As there are, no' regular ,Veather' Bureau stations in the
<br />area, especial care was taken to obtain from local residents as reliable
<br />statements as possible regarding rainfall and time of flood flows of
<br />each stream. ,From the field data ana from information obtained
<br />from various reliable sources it has been possible to show the canse
<br />of the flood and the cause of its rapid rise and tuIl at Pueblo. In
<br />5
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