FLOOD10000

• County: Bent
• Community: Las Animas
• Stream Name: Arkansas River
• Basin: Arkansas
• Title: Las Animas Local Protection Project Design Memo Number 1 Hydrology
• Date: 9/1/1967
• Prepared For: Las Animas
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Project

ENG('W~EZ
SUBJECT:

(SWAED-EH, 3 Oct 67) 2p~ Ind
Las Animas Local Pro tee tion Project, Las Animas, Colorado,
and Vicinity, Design Memorandum No.1, Hydrology

DA, CofEngrs, Washington, DC 20315

5 April 1968

TO: Division Engineer, Southwestern

Approved, subject to the comments of the Division .Engineer and the following
comments.

a. As stated in paragraph 7~01, proposed levee heights were deterrr.ined
by routing a flow of 246,000 c.f.s. through the project reach and using t~e
flow~line as the levee grade profile, The discharge of 246,000 c.f.s. would
correspond to a st~ge three feet above the profile of the project design
flood (140,000 c.f.s,) at the downstream end of the project. This procedure
provides a reasonably adequate levee design freeboard of 3 to 4 feet through-
out most of the project; however, between station 238+71 and station 390+00,
the accumulative effect of bridge losses would result in excessive freeboard
allowances on the order of 11 to 12 feet above the project deSign fIced
profile. In order to provide a more balanced plan of levee freeboard
deSign, considerati.on should be given to modifyi.ng the proposed criteria
along the following lines.

(1) Provide a m~n~murn freeboard allowance of three feet above
projec t design flood throughout the project.

.
(2) Provide moderate additional freeboard allowances "here required
to assure that initial overeopping, in the event of a flood exceeding ehe
project design flood, would not occur at the upstream end of the project.
A flood profile derived for the project reach for a discharge corresponding
to a stage slightly (say one foot) above the project design flood profile at
the downstream end of the project would be helpful and should be considered
in defining locatiens where extra freeboard allowances are needed. In this
connection, reference is made to paragraph 3c of Civil Works Engineer
Bulletin 54-14, dated 23 April 1954.

b. References to the "levee design discharge", such as listed under
Pertinent Data and on Plate 19, may be misleading and snould be deleted.

c. The basis for selection of the starting elevation used in the back-
water computations ror the project design flood profile should be presented.
Available information indicates that the project will not be appreciably
affected by sediment accumulation in the John Martin Reservoir pool.

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