FLOOD08463

• County: Las Animas
• Community: Las Animas and Vicinity
• Stream Name: Arkansas River
• Basin: Arkansas
• Title: Arkansas River and Tributaries, Las Animas, Colorado, and Vicinity
• Date: 2/18/1964
• Prepared For: CWCB
• Prepared By: COE
• Floodplain - Doc Type: Project

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SYLLABUS

This report comprises the results of an investigation of the
flood and all led problems along the Arkansas River and its tributaries
at and in the vicinity of Las Animas, Colorado. Las Animas is located
on the south bank of the Arkansas River just above its confluence with
the Purgatoire River, a major' tributary which enters from the south.
The flood plain in this area Includes urban and suburban lands and
improvements; irrigated and grazing lands and improvements, highways,
and rai Iroads. A small area of the flood plain also is subject to
inundation from very rare floods on the Purgatoire River. Under
special authorizations during the period from 1950 to 1956, the Corps
of Engineers constructed a pi lot channel and installed bank stabl Ilza-
tion works along the Arkansas River at Las Animas. Several years later,
local interests extended the pilot channel downstream. These works
provide protection against frequent sma I I floods. Flooding of rural
lands begins with a flow of 6,500 c.f.s. and urban areas with flows
of 10,000 c.t.s.

The largest recorded floods on the Arkansas River at Las Animas
occurred in 1921 and 1955 when estimated peak discharges of 187,000
c.f.s. and 44,000 c.f.s., respectively, were reached. Barrier Dam,
constructed In 1924-25 on the Arkansas River about 6 miles above
Pueblo by the Pueblo Conservancy District, would have reduced the
1921 flood to 140,000 c.f.s. Recurrence of the 1921 and 1955 floods
under the ex i st i ng state of deve lopment wou I d cause damages of
$3,135,000 and $275,000, respectively. A multiple-purpose reservoir
project has been authorized for construction by the U.S. Bureau of
Reclamation at the Pueblo dam site on the Arkansas' River at approxi-
mately the same site as the Barrier Dam. This project is an element
of the authorized Fryingpan-Arkansas Project. If the Pueblo Dam had
been In operation, the peak discharge of the 1921 flood would have
been reduced to 108,000 c.f.s. at Las Animas and the 1955 flood would
have been reduced to 38,000 c.f.s. The damages from floods of these
magnitudes under the existing state of development would be $2,490,000
and $152,000, respectively.

During the public hearings, channel straightening and Installation
of steel jetties were suggested as a solution to the flood problem.
However, during subsequent meetings and conferences with local Interests,
they expressed the opinion that channelization alone would not solve
the problem and that levees also would be required to provide adequate
flood contro I .

The water resources problems in the Arkansas River Basin In
Colorado and possible solutions were investigated in a comprehensive
basin study conducted during the period 1950 to 1955 by interested
Federal and State agencies. The report thereon presented a long-range
plan for the development and uti lization of the water and land re-
sources of the Arkansas, White, and Red River Basins. The plan