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<br />44
<br />
<br />FLOODS IN COLORADO
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<br />MAJOR FLOODS--SOUTH PLATTE RIVER
<br />
<br />45
<br />
<br />.SOUTH BOULDJ:o~R CREEK
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<br />total rainfall was 4.42 inches. Phillip Kneale, who was living 2 miles
<br />above Eldorado Springs, in sec. 26, T. 1 S., R. 71 W., stated that the
<br />rain began at 4 p. m., September 2 and was heavy until 10 p. m.,
<br />being succeeded by a "slow" rain that lasted until the morning of
<br />September 4. By means of a bucket in his yard he measured about 6
<br />inches of precipitntion during the entire storm. This storm occurred
<br />after 2 days of rain which at Eldorado Springs amounted to 0.60 inch
<br />on September 1, and 0.80 inch on September 2. That the cloud-
<br />burst was confined to the foothills is indicated by the fact that at
<br />Pinec1iff, 8 miles west" at an elevation of about 8,000 feet nnd about
<br />2,000 feet higher than Eldorado Springs, only a light shower was
<br />reported.
<br />The Geological Survey made an investigation of this flood within a
<br />few days, and computed the peak flow over a dam a quarter of a mile
<br />above Eldorado Spring... The velocity of apprOllCh was determined
<br />by the slope of the water surface above the dam, lIS indicated by high-
<br />. \Vater marks. The peak flow was found to he 8,180 second-feet.
<br />A slope-area measurement made at Eldorado Springs indicated a dis-
<br />charge of 8,540 second-feet.
<br />The State engineer, in cooperation with t.he Geological Survey,
<br />maintains a gaging station 1 X miles ahove Eldorado Springs. L. T.
<br />Burgess, chief hydrographer of Colorado, made a slope-area measure-
<br />ment at the gaging station and found the peak flow at that point to be
<br />7,400 second-fcet. The stages on the recorder chart indicated the
<br />following discharges during the flood:
<br />
<br />Very little precipitation occurred in the upper part of the basin, as at
<br />the Orodell gaging station the peak discharge, which occuned at
<br />midnight September 2, was only 642 second-feet. The effect .of this
<br />rainfall on the streltIll flow WIlS fclt at the gaging station near the
<br />. mouth, where a slope-area measurement made by the office of the
<br />State engineer indicated a peak discharge of 4,410 second-feet. This
<br />peak occurred at noon on September 3. It was caused chiefly by the
<br />flood from South Boulder Creek which, about 10:30 p. m., entcred
<br />Boulder Creek at a point about 18 milcs above the gaging station near
<br />the mouth. The effect of channel storage was indicated by the fact
<br />that the discharge of 8,500 second-feet at Eldorado Springs plus an
<br />undetermined but very considerable flow from Boulder Creek abovo
<br />South Boulder Creek WIlS rednced to a peak of 4,410 second-fcct at tho
<br />gaging station ncar the mouth. The total discharge for the 3-day
<br />period, howevcr, increased from 4,250 acre-feet at the Eldorado Springs
<br />and Orodcll stations to 9,900 acre-feet at the mouth. Prior to 1938
<br />the greatest discharge at the mouth of Boulder Creek' since the
<br />establishment of that stntion in 1927 had been 860 second-feot, on
<br />May 28, 1935. Little or no overflow occurred in Boulder, but at
<br />Erie, below thc mouth of South Bouldcr Creek, the flood reachcd the
<br />town, and many residents left their homes for highcr ground.
<br />
<br />The only recorded flood on South Boulder Creek occurred September
<br />2, 1938. A gaging station hIlS been maintainod on this stream near
<br />Eldorado Springs since 1888, with some lapses, but the eaTlier records
<br />do not indicnte any floods. The station was not in operation during
<br />1894, when floods were prevalent throughout northern Colorado; it is
<br />probable that a flood occurred at that time, but no information regard-
<br />ing it is available.
<br />The eorliest reference to a flood on South Boulder Creek is to the
<br />one in June 1923, causod by the heavy rains of June 7~1O. The rain-
<br />fall at Eldorado Springs was 3.15 inches during that period. The
<br />Boulder Camera of June 9, 1923, stated that, owing to the flood, the
<br />Interurbnn Bridge ncross South Boulder Creek was considered so
<br />dnngerous thnt service between Boulder and Louisville was stopped.
<br />Also, South Boulder Creek had overflowed its bnnks nt VILlmont,
<br />A series of cloudbursts along the foothills of the Front RILnge,
<br />September 2, 1938, cnused a flood on South Boulder Creek at Eldorado
<br />Springs, at the mouth of the Canyon. The Weather Bureau observer
<br />. at that point stated thILt the rain causing the flood storted about 6 :30
<br />p. m., September 2 and was particularly heavy until 2 a. m., September
<br />3, when it lessened materially but continued during that day. The
<br />
<br />Discharge of South Boulder Creek near Eldorado Springs, Sept. 2-3, 1938
<br />
<br />Stcond-
<br />feet
<br />Sept. 2, 7 p. nL_______________ gO
<br />7:30 p. m~____________ 470
<br />8 p. m________________ 970
<br />8:30 p. m_____________ 1,850
<br />9 p. m________________ 3,500
<br />9:30 p. m_______,__ __ 5,500
<br />10 p. m_______________ 7,400
<br />10:30 p. m____,_______ 7,400
<br />11 p. mn_____________ 6,900
<br />
<br />&cond-
<br />I,d
<br />Sept. 2, 11:30 p. m_____,______ 5,800
<br />Midnight_____________ 4,900
<br />Sept. 3, 1 a. m__ __ __ __ _ __ __ __ _ 3, 900
<br />2 s. m_______________, 3,100
<br />3 a. m________________ 2,400
<br />48. m________________ I,800
<br />5 s. moO________,_____ 1,300
<br />7 s. m________________ 1,020
<br />10 s. m_______________ 855
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<br />Eldorado Springs is a summer resort at the mouth of a narrow
<br />canyon. Because of lack of space some of the resort buildings cxtend
<br />over the creek, nnd the flood, by undermining their foundations,
<br />wrecked these buildings. In addition, several residences not over the
<br />creek were carried awny by the flood. The foul' bridges in Eldorado
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<br />755376-47-4
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