FLOOD02478

• County: Statewide
• Community: State of Colrado
• Stream Name: Arkansas River
• Basin: Arkansas
• Title: Flood Report-Arkansas River Basin Flood of May 1955
• Date: 5/1/1955
• Prepared For: CWCB
• Prepared By: COE
• Floodplain - Doc Type: Flood Documentation Report

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2-03. The upper air circulation at 700 m.b. illustrates. better than
the surf,ce movement, the conditions which caused the extremely heavy pre-
cipitation during the main storm period. On the evening of 15 May a Low
was centered over Idaho with troughs extending to the southwest over
Nevada arid southeast over Wyoming and Colorado. During the evening of
16 May, {he western trough remained stationary and cyclonic circulation
began OVer southeast Colorado and western Kansas. . This circulation spread
over Colqrado, New Mexico, western Kansas and the Texas and Oklahoma Pan-
handle during the 17th and continued until the evening of the 18th, when
the Low ~oved slowly eastward out 6f the area.
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2-04. Storm Rainfall. The stOrm began on the afternoon of 17 May
over the :entire area and continued through thel9th in New Mexico and
Kansas. ,Precipitation ended at most of the Colorado stations during the
afternoon of the 19th. At Lake Maloya, New Mexico, 13.59 inches occurred
in ~8 hoUrs, with 11.28 inches falling in the 2~-hour period ending at
~ p.m. 011 19 May. This was the highest total amount recorded during the'
storm. In Colorado, Rye recorded 9.92 inches and Lake Moraine 7.76 inches
while the two highest amounts in the Kansas area were 8.79 inches at Ulysses
and 7.10:inches at Cimarron. Precipitation of more than 2 inches occurred
over a v~ry large area, as indicated by the isohyetals on plate I. Mass
curves o~ rainfall for representative stations are shown on plates 2-5.
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III FLOOD DATA

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3-01. General. The storm of 17-23 May 1955 produced excessive
flows in:the Arkansas River watershed ,from Pueblo, Colorado, to Great
Bend, Kansas, and in the Canadian River watershed above Conchas Reservoir.
John Martin Reservoir contained the total volume of the flood from above
that point, amounting to 260,000 acre-feet.. Total volume of inflow to .
Conchas Reservoir during the period 18-21 May 1955 was 12~,OOO acre-feet.
No damag$ occurred below Conchas Dam and only minor damages resulted below
John Martin Dam from local inflow. Major flooding occurred ih the Arkansas
River wa~ershed from Pueblo, Colorado, to John Martin Reservoir and in the
entire r~ach of the Purgatoire River from Valdez, Colorado to the mouth.
The flood on the main stem of the Arkansas River was the greatest since
1921, while that of the Purgatoire approached the magnitude of the 1942
flood at:Trinidad, Colorado, and was the greatest of record in its lower
reaches 0 :

3-02. Flood staees and discharees above John Martin Dam. The pattern
of the storm was such that no flooding occurred above Pueblo, Colorado.
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Very little flow resulted from the northern tributaries, except Fountain
Creek, which had a peak discharge of 5,000 cubic feet per second at its
mouth, just below Pueblo. The peak at the Arkansas River station at Pueblo
was 10,900 cubic feet per second and this. flow combined with the flow of
Fountain:Creek produced very little flooding. From the mouth of St. Charles'
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River, which peaked at 20,000 cubio feet per second, to John Martin Reser-
voir, ma~or flooding occurred.

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